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THE HIP SOCIETY |
MEETING OF THE HIP SOCIETY Thirtieth Open Scientific Meeting The Eighth Combined Open Meeting Hip Society and AAHKS Dallas, Texas February 16, 2002 PROGRAM CHAIRMEN Joseph McCarthy, M.D. and Richard White, M.D. CONTENTS: COURSE DESCRIPTION: This course is divided into seven sections. The first three sections deal with several aspects of DJD. The fourth section presents the three Hip Society award papers. Symposium five discusses head size, bearing surface and wear. The sixth section communicates late sequelae of hip joint trauma. In the final symposium the speakers will reveal some new views in THR. COURSE OBJECTIVE: The Objective of this Open Meeting of the Hip Society will be to convey information on important management decisions regarding hip surgery in the older, middle aged and the younger patient with osteoarthritis. In addition the Basic Science issues and controversies regarding head size, the bearing surface and wear will be addressed. There will be a symposium on the late joint effects on hip trauma. Finally, there will be a look ahead at upcoming techniques and technology in total hip reconstruction. INTENDED AUDIENCE: Orthopaedic surgeons and orthopaedic residents. 8:00
a.m. Opening Remarks President Hip Society -
Benjamin Bierbaum, M.D. President AAHKS- John
Callaghan, M.D. SYMPOSIUM I: THE OLDER
PATIENT WITH DJD (75 YEARS OR OLDER): ISSUES OF BONE QUALITY AND STABILITYModerators: Richard
Coutts, M.D., San Diego, CA Richard Welch, M.D., San Francisco, CA 8:05 a.m. Basic Science: Osteoarthritis In The Elderly How The Older Patient Is
Different Miguel Cabanella, M.D. Rochester, MN 8:15 a.m. Surgical Approach and THA Dislocation: A Critical Review of the Literature Robert Bourne, M.D. London, Ontario 8:25 a.m. Hip
Implant Selection for Total Hip Arthroplasty In Elderly Patients William L.
Healy, M.D. Burlington, MA 8:35 a.m. Bearing
Surface Variations to Improve Stability Paul Lachiewicz, M.D. Chapel Hill, NC 8:45 a.m. DISCUSSION
SYMPOSIUM II: THE MIDDLE AGED
PATIENT WITH DJD (45 YRS OR OLDER): ISSUES OF
FIXATION , THE BEARING SURFACE AND OSTEOLYSIS Moderators: Richard
White, M.D., Albuquerque, NM Ken Krackow, M.D., Buffalo, NY 8:55 a.m. Basic Science: Fixation:
Lessons Learned from Analysis of Long-Term Cemented Human Retrievals. William Maloney, M.D. St. Louis, MO 9:05 a.m. What We’ve Learned About
Long-Term Cementless Fixation From Autopsy Retrievals Charles Engh, M.D. Arlington, VA 9:15 a.m. The
Case For Proximally Coated Stems. William Capello, M.D. Indianapolis, IN 9:25 a.m. The Case For Extensively Coated Stems In
Middle Aged Patients. Wayne Paprosky, M.D. Winfield, IL 9:35 a.m. Cement
Versus Cementless Fixation In THR. Eduardo Salvati, M.D. New York, NY 9:45 a.m. DISCUSSION 9:55 a.m. BREAK 10:10 a.m. Presidential
Guest Speaker Introduction –
Benjamin Bierbaum, M.D. 10:15 a.m. Guest
Speaker: Philippe Hernigou, M.D.
Creteil, France Treatment Of Osteonecrosis With Autologous Bone Marrow Grafting (From Research To Treatment) SYMPOSIUM III: THE YOUNG PATIENT WITH DDH/EARLY DJDModerators: Richard
Rothman, M.D. Philadelphia, PA Lester Borden, M.D.
Cleveland, OH 10:45 a.m. Basic Science: Natural History of DDH and its effect on
Hip Bio-Mechanics. Stuart Weinstein, M.D. Iowa City, IA 10:55 a.m. Alternative
Treatment for Osteoarthritis of the Hip.
David S. Hungerford, M.D. Baltimore, MD 11:05 a.m. Rationale
And Results Of Osteotomy And Related Procedures For Hip Joint Preservation. Michael Millis,
M.D. Boston, MA 11:15 a.m. The Rationale and Results of Hip
Arthroscopy. Joseph McCarthy, M.D. Boston, MA 11:25 a.m. The Rationale and Results of Surface
Replacement (AVN, DJD) Michael Mont, M.D. Baltimore, MD 11:35 a.m. Rationale, Technique and Results of THR The Young Patient with DDH/Early
DJD.
James D'Antonio,
M.D. Moon Township, PA 11:45 a.m. DISCUSSION 12:00 a.m. LUNCH SYMPOSIUM IV: THE HIP SOCIETY
AWARDS Moderators: Benjamin
Bierbaum, M.D., Boston, MA Joseph McCarthy, M.D.,
Boston, MA 1:00 p.m. OTTO AUFRANC AWARD The Relative Contributions of Surface Chemistry and Topography To the Osseointegration of HA Coated Implants S.A. Hacking Montreal, Quebec 1:15 p.m. JOHN
CHARNLEY AWARD Metal on Metal Versus Metal on Polyethylene Liners in Total Hip Arthroplasty: Clinical and Metal Ion Results of a Prospective Randomized Clinical Trial S.J. MacDonald, M.D. London, Ontario 1:30 p.m. FRANK
STINCHFIELD AWARD Viscosity Effects on Cement Pressurization and
Trabecular Bone Cement Intrusion.
Michael R. Dayton, M.D.
Burlington, VT
SYMPOSIUM V: HEAD SIZE, THE
BEARING SURFACE AND WEAR Moderators: Cecil
Rorabeck, M.D., London, Ontario Merrill Ritter, M.D., Mooresville, IN 1:45 p.m. Basic Science: Fundamental relationships among bearing material,
ball diameter, penetration rate, Volumetric wear, debris morphology and the
incidences of dislocation and osteolysis. Harry McKellop, Ph.D. Los Angeles, CA 1:55 p.m. Osteolysis: A Disease of Access to Fixation Interfaces. Michael Manley, Ph.D. Franklin Lakes, NJ 2:05 p.m. Particles
and Peri-Implant Bone Resorption. Thomas Bauer, Ph.D. Cleveland, OH 2:15 p.m. Intra-Articular
Pressure Differences In Total Hip Arthroplasty. William Lanzer, M.D. Seattle, WA 2:25 p.m. All
Heads Should Be 28 Millimeter or Less: Rationale & Results. John Callaghan, M.D. Iowa City, IA 2:35 p.m. All Heads Can Be 32-mm or Greater with Highly Crosslinked Poly: Rationale and Results. Harry Rubash, M.D. Boston, MA 2:45 p.m. The Bearing Surface Should be
Metal-on-Metal. Lawrence Dorr, M.D. Los Angeles, CA 2:55 p.m. Ceramic On Ceramic Bearings In Total Hip
Arthroplasty. Benjamin Bierbaum,
M.D. Boston, MA 3:05 p.m. DISCUSSION 3:20 p.m. BREAK SYMPOSIUM VI: LATE SEQUELAE OF HIP JOINT TRAUMAModerators: Leo
Whiteside, M.D., St. Louis, MO Clive Duncan, M.D.,
Vancouver, BC 3:35 p.m. Basic Science: Articular
And Bony Changes Following Acetabular Fracture. Marvin Tile, M.D. Toronto, Ontario 3:45 p.m. Anatomic Joint Fracture Fixation and Long
Term Results. Joel Matta, M.D. Los Angeles, CA 3:55 p.m. Total Hip
Arthroplasty For Post-Traumatic Arthritis Following Acetabular Fracture. Daniel Berry, M.D. Rochester, MN 4:05 p.m. DISCUSSION SYMPOSIUM VII: A VIEW AHEAD IN THR (VIDEO VIGNETTES) Moderators: Douglas Dennis, M.D., Denver, CO Clifford Colwell, M.D., LaJolla, CA 4:15 p.m. New Developments from the O.R.S. Richard Coutts, M.D. San Diego, CA 4:25 p.m. Mini-Incision
For Total Hip Replacement. Thomas P. Sculco, M.D. New York, NY 4:31 p.m. Pre-operative Assessment of Hip Dysplasia: Prognosis for Outcome After Periacetabular
Osteotomy Stephen Murphy, M.D. Brookline, MA 4:37 p.m. Surgical Navigation for Hip Surgery. Anthony DiGioia, M.D. Pittsburgh, PA 4:43 p.m. Virtual
Reality of the Hip. Jay Mabrey, M.D. San Antonio, TX 4:49 p.m. DISCUSSION 5:00 p.m. ADJOURN 8:05 a.m. Osteoarthritis
In The Elderly How The Older
Patient Is Different Miguel
E. Cabanela, M.D. As
the longevity of the population increases the number of elderly patients with
coxarthrosis that requires hip replacement continues to increase. Our
trends of utilization of THA in the patient older than 75 years will be
shown. Three
general issues that are of obvious importance in the elderly patient
contemplating a THA need to be addressed: 1)
GENERAL HEALTH Under this heading, hypertension, diabetes and
obesity can affect immediate outcome and need to be evaluated and their
control optimized prior to surgery. Incidence of medical complications in
this group of patients will be contrasted with the general population. Also under this heading neurologic disease, such as
Parkinson’s or prior CVA can influence outcome. In the case of Parkinson with
a shown increase incidence of postoperative pulmonary or urinary tract
infections, but also with a higher risk of postoperative dislocation, a risk
also present with previous CVA. Incidence of general and orthopedic
complications in these situations will be presented. 2)
COGNITIVE Patients in this age range are more likely to
develop postoperative confusion. This is particularly common in patients
afflicted with Parkinson’s disease. Therefore cooperation can not be
anticipated to be as reliable as with younger patients with issues of
positioning in bed or seating and one can not predict how such patient will
be able to ambulate with protected weight bearing. Thus component position
and fixation will have to be optimized in the operating room, expecting a
relatively limited postoperative cooperation. Statistics to support this will
be included extracted from our Joint Registry. 3)
MUSCULOSKELETAL SYSTEM Issues of decreased muscle
and bone mass will influence both our choice of implant (large patulous
femoral canal, osteoporotic pelvis) and our choice of fixation. We still use
occasionally cemented all polyethilene sockets in this aged patients and our
results continue to justify this choice. Cemented fixation of the femoral
stem is also preferred. Decreased muscle mass can
slow down the patient’s functional recovery, but also can be a contributory
factor to increased joint instability (decreased myofascial tension) making
it at times necessary to deliberately elongate the extremity to maximize soft
tissue tension. The alternative, to advance the greater trochanter, is not
desirable in this group of patients. Despite these issues, with proper preoperative preparation, attention to surgical technique and careful postoperative support these elderly patient do tolerate the procedure very well and the results are not different in quality than those obtained in the general population 8:15 a.m. Surgical
Approach and THA Dislocation: A Critical
Review of the Literature John L. Masonis, M.D., Robert Bourne, F.R.C.S.C. Dislocation is the leading
early complication of total hip arthroplasty. The effect of surgical approach
on instability and abductor function remains a controversial topic. A comprehensive
literature review was performed to evaluate the correlation of surgical
approach and primary THA dislocation. 260 clinical studies were identified
between 1970 and 2001. Three prospective studies were identified but
individually contained insufficient power to reach statistical significance
regarding dislocation. 15 studies involving 13,381 primary THA met inclusion
criteria based on variables previously demonstrated to affect stability.
These studies were evaluated with respect to surgical approach and
dislocation. The combined dislocation rate for these studies was 1.46% for
the transtrochanteric approach, 0.72% for the lateral approach, and 3.35% for
the posterior approach. The quality of literature regarding surgical
approach, dislocation rates, and abductor function is limited. Larger
controlled prospective studies are needed to investigate the potential
benefits of the posterior approach in lieu of a dislocation rate almost five
times higher than the lateral approach for total hip arthroplasty. 8:25 a.m. Hip Implant Selection for Total Hip
Arthroplasty In Elderly Patients William L. Healy, M.D. The
population of the United States is increasing and aging, according to the
2000 United States census. The life
expectancy of 75-year-old men and women in the United States is 9.6 years and
12.2 years respectively. The
prevalence of total hip arthroplasty (THA) is likely to increase in the next
decade, and a successful hip replacement in a patient greater than 75 years
of age should relieve pain and improve function for at least ten years. Considerations
regarding hip implant selection for THA in the elderly include: bone quality,
bone morphology, implant fixation, bearing surface wear, and implant
cost. The importance of bone quality
to implant fixation is not clear.
Satisfactory implant fixation in the elderly has been achieved with
both cemented and cementless THA implants, and cementless implants have
demonstrated predictable fixation in octogenarians and in patients with
osteopenic bone. Bone morphology can
affect implant fixation, and femoral shape is more important when selecting
cementless femoral components than cemented implants. Cemented
THA and cementless THA can be successful in the elderly. Following cemented
THA in patients over eighty years old, implant loosening has been reported as
4.2% (3 of 71) at 5 years, 3.7% (6 of 162) at 1 year; and 0 % (0 of 76) at 5
years. Following cementless THA in
patients over 65 years old, implant loosening has been reported as 3% (4 of
135) at 5 years or death, and in patients over 80 years old as 0% (0 of 78)
at 5 years. Bearing surface wear is
generally not a major problem in the elderly due to lower activity levels and
a shorter life span. Conventional
polyethylene articulating with polished cobalt chromium provides a
predictable bearing surface for the elderly patient. Implant
cost is an important issue for hospitals.
In general, hospitals are reimbursed for hip replacement operations by
case price reimbursement. For
Medicare patients the hospital payment for hip replacement is determined by
the Diagnosis Related Group payment system (DRG 209). On January 1, 2002, DRG 209 payment to
hospitals decreased 1.8% to $9,057.
During the 1990's the cost of hip implants became a point of contention
between hip surgeons and hospitals.
Hospitals were in a difficult position of paying for a surgical supply
item selected by a surgeon who had no economic accountability for implant
selection. Hip
surgeons are committed to giving their patients the "best result
possible" from THA. Hip surgeons
should not have to consider implant cost in the operating room. In 2002, the cost of hip implants should
be evaluated, negotiated, and determined in the Board Room, rather than the
operating room. We have had success
with a Single Price/Case Price Hip Implant Purchasing Program. Using a competitive bid process, the
hospital and the hip surgeons selected one implant manufacturer to provide
all hip implants for one single price for each primary THA operation (CPT
27130). The Single Price/Case Price Hip Implant Purchasing Program allowed
the hospital to reduce its cost for hip implant replacement operations and it
allowed surgeons to use any implants they desire within that implant vendor's
inventory for the same price. Consideration
regarding selection of hip implants for THA operations in elderly patients
include: bone quality, bone morphology, implant fixation, bearing surface
wear and implant cost. The goal of
THA in the elderly is to relieve pain and improve function for the rest of
the patient's life. This goal can be
successfully achieved with cemented and cementless implants, which are
inserted with precise, accurate surgical technique. In my practice in 2002, I use a modular, porous coated titanium
alloy acetabular shell with screw fixation and a conventional polyethylene
acetabular liner. I use a modular,
flat tapered femoral component without a collar with proximal circumferential
porous coating made of cobalt chromium, or titanium and a polished 28-mm.
femoral head made of cobalt chromium.
The price of the implants is negotiated through a Single Price/Case
Price Implant Purchasing Program so I do not have to consider implant cost in
the operating room. 8:35
a.m. Bearing Surface Variations to Improve
Stability Paul F. Lachiewicz, M.D. Increasing patient age is a known risk factor for dislocation of total hip arthroplasty, with rates of 1 to 10% reported in the older population. Dislocation has been reported in 8.7% of hips with cemented all-poly acetabular components in patients ≥ 75 years with osteoarthritis and in 1-5% of hips with modular cementless acetabular components The use of bipolar arthroplasty in this population has a lower rate of dislocation (1.5%), but there are problems with residual pain and high rates of reoperation, wear and osteolysis. Bipolar arthroplasty may be a useful salvage for recurrent dislocation. Constrained components may be indicated in the older patient for recurrent dislocation associated with dementia, trochanteric non-union - abductor insufficiency or failure of modular revision. The reported rate of failure of these devices ranges from 4% (tripolar) to 9-29% (snap-fit, locking ring). Larger (36, 38 and 40 mm) femoral heads may be implanted with highly cross-linked acetabular liners, which have greatly decreased in-vitro wear even with larger femoral heads. Although these components will allow greater range of motion before dislocation, there is no clinical data yet available. The author has performed 146
primary total hip arthroplasties in patients ≥ 75 years. Of 140 with a minimum 1-year follow-up,
there were 100 in females and 40 in males and the preoperative diagnosis was
osteoarthritis in 82%. The mean follow-up time was four years. The acetabular
component was modular-cementless in 121 hips and cemented in 19. There were
five dislocations (3.5%), but only two were recurrent, and successfully
treated by modular exchange. In our study of 17 modular revisions for
recurrent dislocation, the procedure was successful in 82%.
Modular-cementless acetabular components appear to be preferable for total
hip arthroplasty in patients ≥ 75 years. A 28 or 32 mm femoral head is used, but larger heads should be
considered in fracture patients and in the treatment of recurrent
dislocation. Modular exchange has a reasonable rate of success for recurrent
dislocation if acetabular component position is satisfactory. 8:55 a.m. Fixation:
Lessons Learned from Analysis of Long-Term Cemented Human Retrievals William
J. Maloney, M.D., Thomas Schmalzried, M.D. and William H. Harris, M.D. A detailed biomechanical, histological and histomorphometric analysis
of autopsy specimens from patients who had previously undergone cemented
total hip arthroplasty have help to elucidate the skeletal response to
cemented components. Bone cement has
the capacity to provide long-term implant stability. However, the biological response to
polyethylene wear debris has a more critical effect on destabilization of
cemented acetabular stability when compared to the femoral side. In contrast, mechanical events tend to
predominated the early mode of destabilization of cemented femoral components
with debonding at the metal-cement interface as well as fracture in the
cement itself. Fractures predominate
in cement mantles less than 1 millimeter thick and are associated with mantle
defects, debonded interfaces and sharp corners of the implants. Correlation of the histologic findings at
the cement-bone interface with radiolucencies found on clinical radiographs
demonstrate that on the acetabular side radiolucencies represent
interposition of a soft tissue membrane that represents the biologic response
to polyethylene debris. In contrast,
on the femoral side, most radiolucencies were as a result of skeletal
remodeling. Quantification of the
adaptive remodeling process in the femur demonstrates that remodeling is a
diffuse process that occurs over the entire fixation surface. The most profound disuse osteoporosis
occurred in the proximal medial quadrant however when one takes into account
all four quadrants, anterior, posterior, medial and lateral, the most severe
osteoporosis actually occurred at the midpoint of the stem. Overall, the degree of bone remodeling
correlates the bone-metal density of the contralateral femur. The less dense the bone is before hip
replacement, the greater the extent of bone loss after replacement. 9:05
a.m. What We’ve
Learned About Long-Term Cementless Fixation From Autopsy Retrievals Christi J. Sychterz, M.S.,
Alexandra M. Claus, M.D., PhD., Charles A. Engh, M.D. This paper
summarizes insights gained from the authors’ experience studying uncemented
porous-coated femoral and acetabular hip replacement components retrieved at
autopsy. For femoral components, autopsy studies demonstrated that
osseointegration occurs over an average 35% of the porous surface with the
most predictable ingrowth occurring near the termination of the porous
coating. The bone ingrowth pattern
causes a predictable bone remodeling pattern: an overall decrease in bone
mineral content (mean 23% loss) occurring on a gradient with most loss
proximally and the least distally. This pattern occurs regardless of the
implant’s level of coating, mirrors the gradient of strain reduction, and
because it is easily recognized, can be used by orthopaedists to identify
bone ingrown components on standard radiographs. Studies have also shown that
femoral bone loss is more related to the characteristics of the implanted
femur than any other variable. Histologic evidence demonstrated that
circumferential porous coating protects against the migration of polyethylene
wear debris to distal locations along the length of the femur and around
acetabular components. On the acetabular side, bone ingrowth is more
unpredictable and occurs randomly. Although the amount of bone ingrowth
averaged 32%, it ranged from 3 to 84%. Unfortunately, a consistent pelvic
remodeling pattern has not been associated with an implanted porous-coated
uncemented cup. Consequently, orthopaedists cannot determine radiographically
whether an acetabular component is truly bone ingrown. Overall, autopsy
studies have contributed to a basic understanding of the histological and
resultant radiographic appearance of osteointegrated porous-coated implants,
and confirmed the durability of this three-dimensional fixation even in the
presence of osteolysis. 9:15
a.m. The Case for
Proximally Coated Stems William N. Capello, M.D. The
aim of research in total hip arthroplasty (THA) is to extend the longevity of
implants in situ. Pertinent issues
are implant design, fixation, and reduction of wear debris and subsequent
osteolysis. Total hip arthroplasties
are being performed in older and younger age groups than were done a decade
ago, however the preponderance of those undergoing THA remains the middle
aged individual (45 years and older) with DJD. This report will focus on clinical and radiographic results of
a prospective, multicenter study of a proximally hydroxyapatite (HA) coated
femoral component (Omnifit-HA stem, Osteonics Corporation, Allendale,
NJ). Within this large study group,
229 hips in 201 patients were implanted in patients aged 45 years and older,
have a diagnosis of DJD, and have a minimum ten-year follow-up. Average age of this subgroup of patients
is 56 years (range, 45 - 73), and 53% are male. Clinically,
the average Harris Hip Score is 91 with 95% reporting no or mild hip pain and
no cases of activity-limiting thigh pain.
Four stems have been revised, one each due to aseptic loosening, pain,
deep joint infection, and one well-fixed done in conjunction with cup
revision. There are no
radiographically loose stems.
Proximal femoral osteolysis confined to zones one or seven is seen in
38% of cases with no cases of intramedullary osteolysis. Thirty-one cups have been revised, 19 due
to aseptic loosening, nine due to excessive polyethylene wear and/or
osteolysis, and one each for recurrent dislocation, pain, and deep joint infection. In
summary, this proximally HA coated stem has provided excellent long-term
stability with a mechanical failure rate of 0.4% at 10 to 14 years
post-implantation. This implant seals
the femoral canal from distal egress of wear particles, but polyethylene wear
remains a threat to the integrity of the greater and lesser trochanters and
the acetabulum. As a result, we are
currently involved in a large, multicenter FDA study pairing this stem with
an alumina ceramic-on alumina ceramic bearing surface. At two-year minimum follow-up, there have
been no complications with regard to the ceramic bearing surface, no cortical
erosions, and no stems revised for aseptic loosening. If this stem performs as it has in the
long-term study and the alumina ceramic-on- alumina ceramic bearing surface
reduces wear as has been shown in laboratory and earlier clinical studies,
the issue of implant longevity may be no longer be a primary concern in THA. 9:25
a.m. The Case For Extensively Coated Stems In Middle Aged Patients Wayne G. Paprosky, M.D.,
F.A.C.S. Cemented total
hip arthroplasty in patients under 45 years of age in the long term has shown
high revision rates at long-term follow-up. Cementless acetabular and femoral
fixation in this age group has been very successful with 0 to 4.0% loosening
rates. However, an increased incidence of osteolysis has been associated with
these implants (8-28%). Most patients under 45 have bone quality conducive to
cementless fixation. We have looked at cementless femoral fixation,
osteolysis and bearing surfaces in the middle-aged group using extensively
coated femoral components. This
study examines a consecutive series of patients between 45 and 65 years of age
who underwent total hip arthroplasty with various designs of acetabular
components combined with a cementless extensively coated femoral component. A
retrospective analysis was undertaken of 164 patients who underwent 186
consecutive primary cementless total hip arthroplasties between 1984 and
1989. Ten patients were lost to
follow-up leaving 174 hips in 154 patients. The average age at the time of
surgery was 57 years old. There were
56% females and 44% males. From 1984 to 1985, non-modular AML's were used
with 32mm heads (N=84). From 1986 to 1989 modular heads were used. Thirty-two
stems had 32mm. diameter heads (26 cobalt chrome and 6 ceramic). The rest
were 28mm. heads (27 chrome cobalt and 31 ceramic). The different acetabular
designs were assessed as well as polyethylene thickness. The overall
pain and walking scores improved significantly using a modified D'Aubigne and
Postel score. The results were 83% excellent, 11% good, 4% fair and 2% poor.
Thigh pain was noted in 6-8% of the patients. There were 15% revisions of the
acetabulum for dislocation, lysis or loosening. According to Engh's criteria,
93% of the stems had bony ingrowth and there were 2.9% stable fibrous and
0.8% were loose. The loose stem was infected. There were 19.6% with acetabular
and femoral lysis noted. There
does not seem to be any effect of age or bone type on femoral fixation using
fully porous coated stems. There is a higher acetabular failure rate and more
osteolysis with 32mm. heads. There does not seem to be any difference in
wears pattern and osteolysis between 28mm. ceramic or chrome cobalt heads. We
highly recommend the use of extensively coated stems in the middle age group. 9:35
a.m. Cement Versus Cementless Fixation In THR Eduardo A. Salvati, M.D. The table demonstrates the approximate number of primary total hip replacements (THR) and
the variation every five years in the percentage of cemented, cementless and
hybrid fixation utilized at The Hospital for Special Surgery, from 1985 to
2001. Senior surgeons prefer hybrid fixation, while a few of the younger
surgeons favor cementless fixation, particularly for the young, active
patient. HSS 1985 1990 1995 2001 THRs
(#) 800 1100 1400 1600 Cemented
(%) 100 50 25 5 Cementless
(%) 0 20 15 15 Hybrid
(%) 0 30 60 80 CEMENT FIXATION A properly designed and
well-fixed cemented cup and stem will have a long-lasting successful result.
We implanted our first Charnley THR at The Hospital for Special Surgery in
1968. Callaghan et al.(1) reported the 25 year minimum follow-up
of 327 Charnley THRs in a population whose average age at the time of surgery
was 65 years: 90% retained both prosthetic components until last follow-up or
death. Of the 25 year survivors (62 hips), 77 % retained the original prosthesis. A common factor of the long-term survivors was the
low average linear wear (0.1mm/year), suggesting ideal tribology. The thick
polyethylene and the 22 mm head contributed to the long-term success.
However, young, active, males demonstrated a 0.3 mm/yr linear wear and
required earlier revision surgery.
Likewise, patients with hypoplastic acetabulae (congenital dislocation
or dysplasia) only accepted a thin poly cup and experienced a higher failure
rate.(2) In
the 1980s, metal-back cups were introduced based on finite element studies
that predicted a better transfer of load. However, the clinical experience
demonstrated a 37% increase in mean polyethylene wear and a higher incidence
of loosening, in comparison to all poly cups.(3) Reduced linear wear was
also observed with molded poly in comparison with machined poly (0.05 vs 0.11 mm/yr).(4) UNCEMENTED
CUPS Our experience with modular, uncemented cups
started in the mid 1980s. The press-fit fixation, obtained under-reaming by 2
mm, is consistently good and long lasting. While we used adjuvant screw
fixation during our early experience, during the last decade we have limited
screws to special situations such as dysplastic acetabulum with insufficient
superolateral coverage, protrusio with a deficient medial wall, markedly
cystic acetabulae and postraumatic deformities. Our main concern with cementless modular cups is
the increasing incidence of osteolysis, which varies from 10 to 20% at 10
year follow-up. This complication, due to the generation of particulate
debris from both the articulating and non-articulating surface of the
polyethylene,(5) is not limited to a particular design as we have
observed it with multiple types of modular cups. It is a clinically “silent”
process and by the time the hip becomes symptomatic it is usually evident
radiographically. MRI can further define the location and extent of the
osteolysis and periprosthetic soft tissue swelling.(6), which are
usually more severe than conventional radiographs demonstrate. Another complication we have observed at
intermediate follow-up is the dislodgment of the plastic liner due to the
failure of the locking mechanism and/or plastic deformation and wear of the
polyethylene liner. (7) Overall, the linear wear of modular cups is
higher than that observed with all-poly cemented cups (0.2 vs 0.1mm/yr,
respectively). The plastic liner is thinner in modular uncemented
cups to accommodate the thickness of the metallic shell. Thus, we recommend
selecting smaller heads to maintain a minimum plastic thickness of 8 mm. We
also prefer cups with no holes to increase the surface for bone ingrowth and
the contact area between the backside of the liner and the metallic shell.
Furthermore, cups with no holes prevent the access of particulate debris from
the non-articulating surface to the acetabulum, via the holes.(5)
The backside of the liner must be congruent with the metal shell and the
metallic surface should be polished to minimize abrasion and generation of
particulate debris. The importance of an adequate locking mechanism cannot be
overemphasized.(7,8) Most of the problems outlined are inherent to the
first generation of modular uncemented cups. While it is conceivable that the
second generation will fare better, a report by Sychterz, et al.(9) demonstrated no
improvement in the rate of linear wear between first and second generation
modular cups at mid-term follow up. The detrimental effect of third body wear
is recognized.(10,11) Reference: 1.
Callaghan,
JJ, Albright, JC, Goetz, DD, et al: Charnley total hip arthroplasty with
cement. J.
Bone Joint Surg. 82A:487-497, 2000 2.
DiFazio,
F, Shon, WY, Salvati, EA, Wilson, PDJr. Long-term results of total hip
arthroplasty with a cemented custom-designed swan-neck femoral component for
congenital dislocation or severe dysplasia. J.
Bone Joint Surg. 84A:204-7, 2002 3.
Cates,
HE, Faris, PM, Keating, M., Ritter, MA.:
Polyethylene wear in cemented metal-backed acetabular cups. J. Bone Joint Surg.
75B:249-253, 1993 4.
Bankston,
AB, Keating, ME, Ranawat, C., et al: Comparison of polyethylene wear in
machined versus molded polyethylene. Clin. Orthop 317:37-43, 1995 5.
Huk,
O., Bansal, M., Betts, F., Rimnac, CM, Lieberman, JR, Huo, MH, Salvati,
EA: Polyethylene and metal debris
generated by non-articulating surfaces of modular acetabular components. J. Bone Joint Surg. 76B568-574, 1994 6.
Potter,
HG, Sofka, CM, Peters LE, Nestor, BJ, Salvati, EA: MRI in total hip
replacement. Paper 231, AAOS, Dallas, Feb. 2002 7.
Della
Valle, A., Salvati, EA: Dislodgment of Polyethylene Liners in First and
Second-Generation Harris-Galante Acetabular Components. J.
Bone Joint Surg. 83-A,553-559, 2001 8.
Chen,
PC, Mead, EH, Pinto, JG, Colwell, C: Polyethylene wear debris in modular
acetabular prostheses. Clin. Orthop.
317:44-56, 1995 9.
Sychterz,
CJ, Engh, CA, Jr, Yang, A., et al:
Analysis of temporal wear patterns of porous-coated acetabular
components: Distinguishing between true wear and so-called bedding-in. J. Bone Joint Surg. 81A:(6):821-830, 1999 10.
Hop,
JD, Callaghan, JJ, Olejniczak, JP, et al: Contribution of cable debris
generation to accelerated polyethylene wear.
Clin. Orthop. 344:20-32, 1997 11. Morscher, EW, Hefti, A.,
Aebi, U: Severe osteolysis after
third-body wear due to hydroxyapatite particles from acetabular cup
coating. J.
Bone Joint Surg. 80B:267-272, 1998 10:15
a.m. Treatment Of Osteonecrosis With Autologous
Bone Marrow Grafting (From Research To Treatment) Philippe Hernigou, M.D. Association of
core decompression with addition of bone graft is frequent and many different
techniques have been described. In this series grafting was done with
autologous bone marrow obtained from the iliac crest of patients operated for
hips osteonecrosis. The results of a prospective study of 189 hips in 116
patients treated with core decompression and autologous bone marrow grafting
are reported in this study. Patients were followed up from 5 to 10 years. The
outcome was determined by the changes in the Harris hip score, by progression
in radiographic stages and by the need of hip replacement. The
bone marrow was harvested under general anaesthesia. The usual sites were the
anterior iliac crests. A bevelled metal trocar of 6 - 8 cm length and a bore
of 1.5 mm was pushed deep into the cancellous bone. A 10 mL syringe that has
been flushed with heparin is used to aspirate the marrow. Once the needle has
been inserted to the desired depth, the tip is swept around a full circle in
45° steps, with the bevel pointing in different directions at each step. Bone
marrow is withdrawn at each of these points. Once this 360° aspiration has
been performed at one site, the needle is brought out and reinserted at a
different site, where the 360° sweep in 45° steps is repeated. This procedure
is continued until a sufficient quantity of bone marrow has been harvested
(150 mL). The same percutaneous tract may be used for multiple punctures of
the iliac crest. All the marrow aspirated is discharged into a plastic
collection bag containing ACD (acid citrate dextrose) anticoagulant solution.
It is then filtered, to remove fat aggregates and clots. The aspirated marrow
was reduced in volume by concentration and injected in the femoral head after
core decompression with a small trocar. When patients were operated on before
collapse (stage I and II), hip replacement was performed in 9 of the 145
hips. THR was necessary in 25 hips among the 44 hips operated after collapse
(stage III and stage IV). To
measure the number of progenitor cells transplanted, we used the fibroblast colony
forming unit as an indicator of the stroma cell activity and performed in
vitro cultures of the fibroblast progenitor cells. The average volume of bone
marrow aspiration was 147 mL ± 12 mL per hip. The number of progenitor cells
was average 12.4 ± 3.4 per 106 bone marrow nucleated cells and the
number of nucleated cells was estimated to be 16.4 millions cells per mL of
bone marrow. Patients who had the greater number of progenitor cells
transplanted in their hips had the better outcome. While
fundamental research and clinical studies have shown that dead bone may be
repaired by living bone, the reparative osteogenic potential is slight in
osteonecrosis. At this time using progenitor cells may be one of the
solutions to improve this reparative process. 10:45
a.m. The Natural
History of DDH and it Effect on Hip Biomechanics. Stuart L. Weinstein, M.D. For normal
development of the hip joint to occur, there must be a delicate, genetically
determined balance between growth of the acetabular and triradiate cartilages
and a well-centered femoral head.
This balance may be profoundly affected by the intrauterine
environment. Without treatment, it is
uncertain how many dysplastic, unstable hips will retain their dysplastic
features throughout life. The natural
history of untreated complete dislocation varies considerably and is affected
by societal considerations. There may
be little, if any, functional disability in many cases. Significant roentgenographic degenerative
disease and poor clinical results, however, may develop in completely
dislocated hips with well developed false acetabulae. In unilateral cases, ipsilateral knee
deformity and pain may develop.
Congenital subluxations have a particularly poor long-term
outcome. A significant percentage of
these patients have roentgenographic degenerative joint disease and clinical
disability. The age of symptom onset
and roentgenographic degenerative joint disease is related to the amount of
subluxation and dysplasia. The
natural history of acetabular dysplasia in the absence of subluxation is
difficult to predict. Physical signs
may be absent, and the diagnosis only established with symptom onset or as an
incidental roentgenographic finding.
While degenerative joint disease may ensue, current roentgenographic
parameters are not predictive. The reasons for degenerative changes in
dysplastic hips are probably mechanical in nature and related to increased
contact stresses with time. A certain "over pressure" may correlate
with long term outcomes with aspherical heads having even worse outcomes.
Degenerative joint disease in hip dysplasia correlates with the magnitude of
the "over pressure" and the length of exposure. 10:55 a.m. Alternative Treatment for
Osteoarthritis of the Hip
David
S. Hungerford, M.D. Many
of our most important pharmaceuticals have their origin in plants, such as
digoxin, penicillin, and coumadin. However, many physicians are deeply
skeptical about the use of natural remedies. This skepticism is based on the
concerns about patient self-diagnosis and treatment as well as the lack of
scientific testing of claims. Nonetheless, a new class has emerged called
nutraceuticals - nutritional supplements with pharmaceutical properties.
Because these substances are relatively unregulated there is no requirement
for rigorous scientific testing prior to marketing. This lack of regulation
also poses problems with purity and quality control. Even so, patients are being
bombarded with, and responding to, claims of the results of the use of herbs,
nutraceuticals, and nutritional supplements. Glucosamine and chondroitin sulfate sales alone in the
U.S. are estimated at $600 million. Sales of all nutraceuticals and vitamin
supplements in the U.S. exceeded 12 billion dollars in 1999. Many physicians
took offense at the title of the book by Theodosakis et al., The Arthritis
Cure, because they know no cure exists. That offense translated into
discounting the very reasonable recommendations in the book. Patients, on the
other hand, pushed sales of the book to the bestseller list. Moreover, glucosamine and
chondroitin sulfate have been widely studied in tissue culture, animal models
of arthritis, veterinary clinical trials, and human comparative or placebo
controlled trials. No published study has failed to show a positive effect
and no trial has shown significant side effects. These nutraceuticals have
become our first line of treatment for osteoarthritis. 11:05
a.m. Rationale And
Results Of Osteotomy And Related Procedures For Hip Joint Preservation Michael B. Millis, M.D. Most
osteoarthrosis of the hip results from chronic abnormal hip mechanics, often
associated with instability, impingement, or combinations of instability and
impingement The site of earliest articular damage usually is the acetabular
rim, as noted first by Ganz and co-workers.
The etiology of the mechanical problem in many hips is a surgically
treatable anatomic abnormality, often a developmental deformity (DDH, Perthes
disease, slipped epiphysis, or femoral/acetabular retroversion). The rationale of
mechanically-based measures to prevent osteoarthrosis assumes that there is
an initial stage of primary deformity during which there is mechanical overload
of the joint which would, if not corrected in timely fashion, would lead to
OA. Correction of the primary
deformity, to a degree that brings joint contact pressures within tolerable
limits and eliminates instability and impingement before irreversible
articular damage has occurred, seems to accomplish this goal in congruous
acetabular dysplasia and in slipped capital femoral epiphysis. An important step in
preventing and effectively treating arthrosis-producing hip conditions lies
in understanding the pathomechanics of each particular deformity. In DDH, acetabular
obliquity and instability create shearing forces and chronic overload of the
anterior and anterolateral acetabular rim, which leads to frequent fatigue
failure in the third or fourth decade of the labrum or the bony acetabular
rim. In SCFE, impingement of the
anterior metaphyseal prominence at the head-neck junction can cause a variety
of impingement lesions of the anterior acetabular labrum, bony rim, and
adjacent anterior acetabular articular cartilage. In Perthes disease and
osteonecrosis, somewhat similar impingement syndromes are frequently found. In males, many hips with
less-than-normal femoral and acetabular anteversion, often with a reduced
femoral head-neck offset, develop stiffness and arthrosis in the fourth
decade of life. Anterior impingement
seems to be the mechanical lesion in these hips, too. Correction of the
mechanical hip problem before the development of arthrosis is the goal of the
joint-preserving surgeon, since the results in published series of joint preserving
operations confirms that the quality of long-term results correlates
inversely with the amount of arthrosis present at the time of the
intervention. In acetabular dysplasia,
where OA will occur in almost every hip left untreated with a C-E angle of
less than 20 degrees, the best long-term result requires the establishment of
a stable joint, without impingement, usually achieved best by acetabular or
periacetabular osteotomy A congruous articulation, intraoperative flexion of
at least 90 degrees, and a horizontal sourcil are desirable. In such hips where preop arthrosis is
grade 0 or 1, 10 year good-excellent results are at least 85-90%. In slipped epiphysis, there
has been incomplete historical understanding of the importance that
impingement plays in the development of arthrosis. Until the recent development of new generation MR cartilage
imaging techniques (radial sequences), impingement has been difficult to diagnose.
In addition, safe and surgical methods to relieve impingement have only
recently become known, as Ganz and others have refined the technique of surgical
dislocation to allow precise osteoplasty, intraarticular debridement, and
proximal femoral realignment with minimal risk of osteonecrosis. In
the non-SCFE
retroversion syndromes relief of impingement also is the essence of
joint-preserving treatment.
Osteoplasty, joint debridement, and osteotomy-alone and in
combination-are accomplishing maintenance and recovery of joint function
never seen before. In
each of the
mechanical hip conditions predisposing to OA, the most important factor
limiting the quality of the joint-preserving procedures continues to be
relatively late diagnosis. As
awareness increases and early diagnosis becomes more common, many more hips
can be saved−most, hopefully, by early measures much less dramatic than
PAO or surgical
dislocation. 11:15
a.m. The Rationale and Results of Hip Arthroscopy
Joseph C. McCarthy, M.D.,
Jo-ann Lee, R.N. Introduction: In
hip dysplasia conventional radiographs, including high-contrast
gadolinium-enhanced MRI, are not always sensitive enough to diagnose a labral
tear or chondral pathology. This
study examines the relationship between mild acetabular dysplasia, labral and
acetabular cartilage injury and development of early osteoarthritis. Materials
& Methods: Between
1989 and 2000, 170 hips in 163 patients with mild acetabular dysplasia
underwent arthroscopic evaluation of their hip. Surgical findings were classified by location and by severity
of the chondral lesions of the femoral head, acetabulum and labrum. Results: Of
the 170 hips with dysplasia, 122 of these had labral tears (72%) at the
free-margin articular surface and 113 were anterior (66%). One hundred hips (59%) had anterior
acetabular chondral lesions. Among
the 113 patients who had anterior labral tears, 78 hips (69%) had anterior
acetabular chondral defects, and 44 hips (39%) had anterior femoral head
chondral lesions. Conclusion: Even
in mild dysplasia uncovering of the anterior femoral head subjects the labrum
to increased load and potential susceptibility to tearing. Labral tears may contribute to or can
occur in association with articular cartilage lesions of the contiguous
femoral head or acetabulum. Findings
in this study support the concept that labral disruption is frequently part
of the continuum of degenerative joint disease. 11:25
a.m. The Rationale
and Results of Surface Replacement (AVN, DJD) Michael A. Mont,
M.D., Zohair Alam, M.D., Gracia
Etienne, M.D., Ph.D. and Amar D. Rajadhyaksha, M.D. The use of
resurfacing hip arthroplasty is not a new concept, having been used by hip
arthroplasty surgeons for over 30 years.
These devices have often been targeted for young patients and have gone
through a series of evolutions that include various interfaces from ceramic
to vitallium, various metals, as well as metal and polyethylene. Metal on polyethylene interfaces for
resurfacing fell out of favor in the 1980’s because of consequences of severe
osteolysis and problems with fixation.
More recently, several devices of metal-on-metal interfaces have been
used. These have met with some
success and enthusiasm because of better machining methods to reduce wear
rates of these prostheses, as well as better methods of fixation. The use of limited femoral resurfacing of
just the femoral head (metal on articular cartilage) has met with some
success for later stages of osteonecrosis when the acetabulum is minimally or
not involved. This talk will describe
the present use and results of limited resurfacing arthroplasty for
osteonecrosis of the femoral head, as well as the use of metal on metal
resurfacing total hip arthroplasty for various arthritic diagnoses. 11:35
a.m. Rationale, Technique and
Results of THR The Young Patient with
DDH/Early DJD James A. D’Antonio, M.D.
and William N, Capello, M.D. The
average age of patients undergoing THR has decreased as implant technology
has improved. New research must continue to aim towards increasing the longevity
of implants in situ, and solving the problems related to wear and
osteolysis. No one implant system,
fixation type, or treatment modality may provide the single answer or
solution particularly with anatomic abnormalities. The indication for THR in the very young is disabling pain
without any other viable option. It would be remiss not to address
non-arthroplasty procedures.
Osteotomy can be successful in delaying or preventing the need for
arthroplasty in DDH patients.
Hemi-resurfacing of the femoral head has yielded promising results in
young AVN patients. Hip fusion remains an option in select young males. Perhaps additional research should focus
on earlier intervention to delay the need for THR in the very young. The
technique for THR in most instances is similar for both young and old
patients. Every effort in the young patient should be made for bone
preservation and restoration of biomechanics. For a patient with anatomic
variations (DDH), unique implant selection, bone grafting, or combined
osteotomy may be necessary. For example, with excessive femoral anteversion
(DDH) a subtrochanteric derotation osteotomy to restore hip biomechanics is
desirable. The results of THR in the
young patient have historically been a challenge in terms of long-term
fixation and prevention of wear and osteolysis(2,5). Modern cement technique has improved fixation on
the femoral side(7) and cementless fixation has grown
in popularity because of encouraging 10+ years fixation results.(1,6). The major problem with cementless fixation
in the young has been on the acetabular side where wear, osteolysis and
loosening have been a problem. In a
multi-center study involving 237 patients, 36 (41 hips) were under the age of
45 at the time of the implant surgery(4). All patients had 10-14 yr. follow-up, a diagnosis of
DJD, and received a tapered Ti HA femoral stem and a cementless socket. The
results on the femoral side have been very encouraging with one aseptic
loosening (2.4%) and no endosteal osteolysis. However, on the acetabular side there have been 7 revisions for
aseptic loosening (17%) and 6 additional liner exchanges for osteolysis
(14.5%). In a personal series of 235
consecutive cementless THR’s (HA stems), 48 patients (54 hips) were under the
age of 50 (avg. age 38) (8). With
100% follow-up at 8-13 yrs. there has been no stem revisions, no endosteal
osteolysis, and all of the femoral stems are bony stable. There have been 8 socket revisions
(14.8%): 6 (8%) for socket loosening associated with osteolysis; and 2 (3.7%)
revisions for liner and femoral head exchange because of lysis. In
summary the HA coated femoral stem have provided outstanding stable fixation
in young patients out now to 14 years.
Issues of wear, osteolysis, and loosening on the socket side have now
led us to study the use of alternative bearing surfaces. Our current choice
for the young patient with DJD who has no alternative to THR, is a tapered HA
femoral stem, an ingrowth socket, and an Al-on-Al ceramic bearing surface(3). Long-term data will be necessary to determine if the issues of
wear, lysis, and socket loosening are diminished or resolved with this
combination. References: 1.
Capello WN, D’Antonio JA, Feinberg JR, et al:
Hydroxyapatite-coated total hip femoral components in patients less than
fifty years old. Clinical and radiographic results after five to eight years
of follow-up. Journal Bone Joint Surg
Am 79:1023-1029, 1997. 2.
Collis DK: Cemented total hip arthroplasty in
patients who are less than fifty years old.
Journal Bone Joint Surg Am 66:353-359, 1984. 3.
D’Antonio JA, Capello WN, Manley MT, Bierbaum B: A
New experience with alumina/alumina ceramic bearings for total hip
arthroplasty. In press, Journal
Arthroplasty, 2002. 4.
D’Antonio JA, Capello WN, Manley MT, Geesink R:
Hydroxyapatite femoral stems for total hip arthroplasty: 10-13-year
follow-up. Clinical Orthop and
Related Research, December 2001. 5.
Dorr, LD, Kane III TJ, Conaty JP: Long-term
results of cemented total hip arthroplasty in patients 45 years old or
younger. Journal Arthroplasty
9:453-456, 1994. 6.
Kronick JL, Barba ML, Paprosky WG: Extensively
coated femoral components in young patients.
Clin Orthop 344:263-274, 1997. 7.
Smith SE, Estok II DM, Harris WH: 20-year experience
with cemented primary and conversion total hip arthroplasty using so-called
second generation cementing techniques in patients aged 50 years or
younger. Journal Arthroplasty
15:263-273, 2000. 8.
D’Antonio JA, Thomas SJ, Bischak TL:
Hydroxyapatite: A noncemented fiction? Orthopedics 24:857-858, 2001. 1:00
p.m. The Otto Aufranc Award: The Relative
Contributions of Surface
Chemistry and Topography To the Osseointegration of HA Coated
Implants S.A. Hacking, M. Tanzer, E.J. Harvey, J.J. Krygier
and J.D. Bobyn
The
positive effect of HA coatings on osseointegration has been attributed to its
chemistry and its ability to increase the concentration of calcium and
phosphate in the microenvironment, immediately adjacent to the implant. The
bone response to grit blasted titanium (GB Ti) surfaces can be remarkably
similar to that which occurs with calcium-phosphate-coated implants. While
the topographies of these metallic and ceramic surfaces are similar the
surface chemistries are very different. The purpose of this study was to ascertain
the relative contributions of surface chemistry and topography to the bone
forming tissue response to HA coated implants using an in vivo canine implant
model. A canine femoral
intramedullary implant model was used to compare the osseous response to
identical c.p. titanium (Ti) implants that were either polished, grit
blasted, plasma sprayed with hydroxyapatite (HA) or HA coated and covered
with a thin layer of c.p. Ti by plasma vapor deposition (PVD-masked). The PVD-masked the
chemistry of the underlying HA layer without changing its surface topography.
Bone apposition averaged 3% for the polished implants and 23% for the grit
blasted implants. Bone apposition to the HA-coated rods averaged 74% while
bone apposition to the PVD-masked rods averaged 59%. These results clearly
illustrate that topography is the dominant factor governing bone apposition.
This is not to suggest that HA chemistry is irrelevant to the osseous
response, but that it is of relatively minor benefit. The implications of
this finding are wide ranging with respect to basic research and implant
design. 1:15
p.m. The John Charnley Award: Metal on Metal Versus Metal on Polyethylene
Liners in Total Hip Arthroplasty: Clinical and Metal Ion Results of a Prospective
Randomized Clinical Trial S.J. MacDonald, M.D., F.R.C.S.C., R.W. McCalden, M.D., F.R.C.S.C.,
D.G. Chess, M.D., F.R.C.S.C., R.B. Bourne, M.D., F.R.C.S.C., C.H. Rorabeck, M.D., F.R.C.S.C., D.
Cleland, B.Sc.N., F. Leung, Ph.D., F.C.A.C.B. Polyethylene wear
continues to be the most significant issue following total hip arthroplasty leading
to the current increase in use of alternative bearing surfaces. We performed a prospective, randomized,
blinded clinical trial to evaluate polyethylene versus metal bearing surfaces
following total hip replacement.
Forty-one patients meeting eligibility criteria were randomized to
receive either a metal (23 patients) or a polyethylene (18 patients) insert. The femoral and acetabular components were
identical in all patients with the acetabular insert being the only variable.
All patients were assessed pre-operatively and post-operatively
utilizing radiographs, multiple outcome measures (WOMAC, Harris Hip Score,
SF-12), erythrocyte metal ion analysis (cobalt, chromium, titanium) and urine
metal ion analysis (cobalt, chromium, titanium). All patients were
followed for a minimum of 2 years (mean 2.9 years, range 2.0 – 3.6) with the
exception of one patient who died prior to the 2-year fol1ow-up evaluation.
There were no differences in radiographic outcomes with no patients
demonstrating measurable liner wear or osteolysis. There were no differences in outcome measures between patients
receiving metal on metal versus metal on polyethylene inserts (WOMAC: 19.9
vs. 28.8 p>.05, Harris Hip Score 92.8 vs. 88.5 p>.05, and SFl2
(physical): 47.1 vs. 44.3 p>.05, SF12 (mental): 55.5 vs. 53.8 p>.05).
There were significant differences in metal concentrations measured in both
the red blood cells and urine of patients with a metal on metal compared to
those with a metal on polyethylene articulation. (Mean erythrocyte cobalt:
3.46 μg/l vs 0.18 μg/1, p< .001, mean erythrocyte
chromium: 3.03 μg/l vs. 1.88 μg/1, p> .05, mean
erythrocyte titanium: 2.11 μg/1 vs. 1.54 μg/1, p> .05,
mean urine cobalt: 50.57 μg/day vs. 0.28 μg/day,
p< .001, mean urine chromium: 11.82 μg/day vs. 0.28 μg/day,
p< .001,
mean urine titanium: 0.63 μg/day vs. 0.36 μg/day, p< .016). Despite
equal clinical and radiographic outcomes at a minimum 2-year follow-up,
patients with a metal on metal articulation had significantly elevated serum
and urine metal ions compared with those receiving a polyethylene
insert. Compared with their
preoperative evaluations, the metal on metal group had on average a 24-fold increase
in erythrocyte cobalt, a 2-fold increase in erythrocyte chromium, no change
in erythrocyte titanium, a 103-fold increase in urine cobalt, a 29-fold
increase in urine chromium and a 3-fold increase in urine titanium at 2 years
follow-up. In contrast, those receiving a polyethylene insert had no change
in erythrocyte cobalt, erythrocyte titanium urine cobalt or urine chromium
and a 2-fold increase in both erythrocyte chromium and urine titanium. The
markedly elevated erythrocyte and urine metal ions seen in patients receiving
a metal on metal total hip arthroplasty is concerning. As well, despite
previous reports of diminishing ion release over time, 41%of these patients
had still increasing metal ion levels at the time of latest follow-up. The
long-term affects, if any, of such metal ion elevations are unknown at
present. 1:30
p.m. The Frank Stinchfield
Award: Viscosity Effects on Cement
Pressurization and Trabecular Bone Cement Intrusion
Michael R. Dayton, M.D., David L. Churchill,
Ph.D., Stephen J. Incavo, M.D., Jonathan A. Uroskie, M.D.
and Bruce D. Beynnon, Ph.D. Authors
have previously advocated femoral stem placement into early stage (low
viscosity) cement. We contend that superior cement-cancellous bone intrusion
can be achieved with cement in the late stage (high viscosity) of the curing
cycle. Five stems each were inserted in early vs. late stage cement in
distally plugged femoral canal models. Canal-mounted transducers measured
cement pressure at four regions, and compared between early and late stage
groups. Separately, nine paired human cadaveric femora underwent prosthetic
stem replacement into early or late stage cement, and were then
underwent radiographic study for analysis. Radiolucency was quantified at the
cement-bone interface and analyzed between the two groups in the four
regions. Insertion into late stage
cement generated significantly higher pressures at all levels vs. early stage
cement (p<0.05). In the cadaveric
femora significantly less radiolucency was observed in the middle zone region
(zones 2 and 6) for late stage vs. early stage (p=0.0117). The data suggest that femoral stem
insertion into the late cure stage of cement leads to higher intramedullary canal
pressures, and greater cement-bone contact.
The results show that cement cure stage at stem insertion may be a
clinically useful variable to maximize cement-bone interdigitation. 1:45
p.m. Fundamental relationships
among bearing material, ball diameter, penetration rate, Volumetric wear, debris morphology and the incidences of
dislocation and osteolysis. Harry A. McKellop, Ph.D. Based
on simple mechanics, the likelihood of dislocation is greater with a smaller
diameter femoral ball (i.e., for a smaller head to neck ratio), but this
trend may have been obscured in some clinical studies due to a large number
of confounding variables. All other factors equal, increasing the ball
diameter increases the contact area and reduces the contact stress at the
bearing surface, tending to decrease the depth rate of wear. However,
this is approximately offset by the greater area being worn, giving the same
volume of wear per unit sliding distance. Nevertheless, since the sliding
distance per walking step increases linearly with the ball diameter, so does
the volume of wear per step. For example, the volume of polyethylene wear
with a 32 mm ball should be about 50% greater than with a 22 mm ball. This
relationship has been demonstrated in several hip simulator studies and in
some clinical reviews. However, the trend for increased volumetric wear with
a larger diameter may be of no clinical significance if the baseline wear
rate is low enough, as with a crosslinked polyethylene, or it may be
substantially offset if there is increased fluid film separation of the
bearing surfaces, as might occur with hard-on-hard bearings. For
historical, gamma-air sterilized polyethylene cups, osteolysis has been rare
if the radiographic penetration rate was less than about 0.1 mm per year. The
wear rate of polyethylene can be reduced by about 85% or more for
crosslinking doses of 5 Mrads or more, such that the wear should be well
below the clinical threshold for osteolysis in even the most active patients.
At present, there is considerable disagreement among investigators regarding
the magnitude and potential biological significance of any systematic
differences in the morphology of the wear particles between the historical
and new polyethylenes. Similarly,
under usual clinical conditions, the volumetric wear rates of metal-metal and
ceramic-ceramic bearings are well below the threshold for osteolysis even in
very active patients. Under adverse conditions, sufficient metallic or
ceramic wear debris can be generated to induce osteolysis as severe as that
with excessive polyethylene. In addition, there is concern regarding the
potential systemic effects of increased levels of metal ions from metal-metal
implants, and ceramic bearings are subject to catastrophic fracture that
usually is rare, but can increase substantially with improperly fabricated
components, or due to mechanical impingement or dislocation. The choice of an
optimal bearing material and ball diameter requires quantitative comparison
of the benefit-to-risk ratios for each option. 1:55
p.m. Osteolysis: A Disease of Access to Fixation Interfaces Michael T. Manley, Ph.D. Long-term
clinical studies of total hip replacement suggest a direct relationship
between bearing wear and periprosthetic osteolysis, particularly if
polyethylene wear is greater than a threshold value of 0.1mm/year. Present clinical trend to crosslinked
polyethylene and hard/hard bearings attempts to ensure that bearing wear
remains below this threshold. Fluid
pressure generated in the hip joint during patient activity has also been
implicated in the formation of periprosthetic lesions. Pressure fluctuation measured during
manipulation of the hip at revision, or the identification of modular
components that pump fluid during loading, suggest cyclic pressure may be a
causative factor in bone resorption.
Animal studies show the adverse effect of direct pressure on
osteocytes. At more than ten years
follow-up, the low incidence of osteolytic lesions in retrospective reviews
of successful cemented and cementless implant designs suggest that osteolysis
is not an inevitable consequence of particle or pressure generation in the
hip. If the quality of implant
fixation prohibits fluid access to the surrounding bone, the rate of
osteolysis is minimal. It is evident
that whether the active factor in osteolysis is pressure, wear particles, or
both, adverse effects can be minimized if access to the fixation interfaces
in the hip is denied. 2:05 p.m. Particles
and Peri-Implant Bone Resorption Thomas W. Bauer M.D.,
Ph.D. Studies
from many investigators have provided compelling evidence that the most
important factor in late peri-prosthetic bone resorption is an inflammatory
reaction to particles of debris. Evidence has been derived from clinical
observations, qualitative and quantitative studies of tissues around
successful and failed implants, and from studies in which cells have been
incubated with particles. Based on studies from different laboratories, it
seems likely that opsonized particles interact with macrophage membranes,
activating the NF-kB system of signal transduction. This leads to expression
of genes in macrophages that encode cytokines, of which TNF-a is the most important.
Secreted TNF-a appears to interact with specific receptors on osteoblasts,
fibroblasts and on osteoclast precursors. In osteoblasts, TNF-a leads to release of IL-6,
GM-CSF, and PGE-2, which in turn recruit inflammatory cells, macrophages and
osteoclast precursors to the site, and promote the differentiation of
precursors into cells committed to osteoclast lineage. In fibroblasts TNF-a influences the expression
of tissue metalloproteinases that are involved in bone resorption. TNF-a also induces expression
of c-src in mononuclear cells that have been committed to the osteoclast cell
line. This proto-oncogene must be expressed for osteoclast maturation and
bone resorption. Phagocytosis of debris directly by osteoblasts appears to
cause reduced synthesis of type-1 and type-3 collagen, while phagocytosis of
particles by fibroblasts may induce the release of chemokines that attract
more macrophages and other inflammatory cells. Bone has been at least
partially protected from particle-induced resorption in animals that are
without TNF-a receptors, have defective TNF-a signaling, or that are deficient in NF-kB
signaling, or with the use of a soluble TNF-a inhibitor. Many aspects
of this inflammatory reaction require clarification, including identifying
the factors that influence variability among individual patients, but the
fundamental importance of particles in most cases of aseptic loosening seems
certain. 2:15
p.m. Intra-Articular
Pressure Differences In Total Hip Arthroplasty William L. Lanzer, M.D.,
Christopher J. Drinkwater, M.B., B.S., F.R.A.C.S., James V. Rogers, III, M.D.
and Robert W. Eberle Introduction: We
hypothesize that there is a relationship between the stiffness of the
secondary hip joint capsule; high intra-articular pressures and
peri-prosthetic circulation of wear debris and subsequent aseptic loosening
in THA. Thus, we investigated intra-articular pressure/volume relationships
by means of pressure arthrography in those patients with pain following THA. Methods: Eighty
patients with 88 painful THA's were included for review. In all cases, an IRB
reviewed informed consent was obtained from the patient. All patients had
complaints of activity-related pain at a level 5 or greater on a standard
visual-analogue scale. The average patient age was 59 years (range: 29- 88
years). Forty-eight right hips and 40 left hips were examined. Average time
to follow-up was 63 months. Following joint aspiration, pressure/volume data
was corrected and digital subtraction arthrography performed. Results: With
10cc normal saline, mean intra-articular pressures are 292 mmHg for patients
with non-loose implants and 135 mmHg for patients with loose implants as
defined by radiographic and arthrographic criteria. Mean pseudocapsular
compliance was 0.031 cc/mmHg for the group with non-loose implants,
and 0.070 cc/mmHg for those with loose implants. The differences are
statistically significant. Discussion and Conclusion: Patients with
non-loose total hip arthroplasties have stiffer, non-compliant
pseudocapsules, and thus, the potential for higher intra-articular pressures.
The authors believe, then, that low pseudo capsular compliance and high fluid
pressures are significant in the mechanism of osteolysis and aseptic
loosening through particle transport, biochemical and biomechanical effects
of secondary joint fluid. High pressures can cause capsular distention and
pain with, or without associated loosening. 2:25
p.m. All Heads Should Be 28 Millimeter or Less: Rationale & Results John J. Callaghan, M.D. Charnley championed small head sizes in total hip replacement because
of their low frictional torque around the acetabular implant. Mueller championed larger head sizes
because of the larger surface area of contact provided at the bearing surface
when larger heads were utilized. Initial wear data of intermediate term follow-up radiographs demonstrated higher volumetric wear in cases with 32-millimeter head components and higher linear wear in cases with 22-millimeter head components. The volume of the particulates from polyethylene wear are now known to be the most important factor in producing osteolysis in the total hip arthroplasty construct. The recent implant retrieval data demonstrates an increase in volumetric wear with increasing head size. In addition computational finite element analysis confirms these studies. Finally wear simulator studies are in agreement with these findings. The reason for the decrease in wear with smaller head sizes is related to the decrease in sliding distance of a smaller head compared to a larger head throughout the gait cycle. Although the wear rates are lower with hyper crosslinked polyethylene wear, the rate with these materials still increases with head size in wear hip simulators. Our long-term data for both cemented and cementless implants demonstrate a lower volumetric wear rate in implants with smaller head sizes. The concern with smaller head sizes is their property for instability
and dislocation especially in the modular component era because of the
relatively smaller femoral head to neck ratio created by the modular tapers. However the manufacturers are addressing
this concern with dislocation friendly designs of femoral tapers and
acetabular component chamfers. The
surgeon should also be aware that although cup impingement is greater with
smaller head sizes, bony impingement is greater with larger head sizes. 2:35
p.m. All heads can be 32-mm or greater with highly crosslinked poly:Rationale and results Brian Burroughs, M.S.,
Harry E. Rubash, M.D. and William H. Harris, M.D. The
modern, highly-crosslinked polyethylenes produced by e-beam irradiation and
melt amealing and approved for use in total hip arthroplasty have three
special characteristics based on extensive "in vitro" testing. 1)
Very low wear rates and extremely low particulate burden 2)
No free radicals in the substrate 3)
Low wear rates that are independent of head size The first
property predicts less wear and importantly less osteolysis. The second
property predicts no oxidation or "white banding" in the subsurface.
The third property predicts that larger heads can be used without the higher
wear rates that previously were seen
with when 32-mm heads articulated against conventional poly. Data
showing wear rates below detectable limits come from five independent
laboratories using three different hip simulators. 1-3 Data showing wear rates that are
independent of head size cover 11 million cycles of simulated wear. Data from
46-mm heads in the face of massive third body alumina particles show marked
reduction in wear even in the face of heavy third body debris compared to
conventional poly. Large
heads are more anatomic, more physiologic, have greater ROM, less
impingement, greater stability, less risk of dislocation and should provide
greater activities of daily living. The
clinical results are a work in progress to date without any negative
reports. In our center we are
currently performing a prospective randomized IRB approved study of
conventional versus highly crosslinked polyethylene using both clinical
outcome measures, radiographic, and RSA analysis. References: 1.
D’Lima DD, Hermida J, Chen PC, Coldwell, Jr. CW:
Polyethylene cross-linking methods and acetabular liner wear rates.
Presented at Harvard Hip Course, Oct. 3 thru 6, 2001 2.
Muratoglu OK, Bragdon CR, O'Connor AS, Jasty M, Harris
WH: Anovel method of cross-linking ultra-high molecular-weight
polyethylene to improve wearm reduce oxidationm, and retain mechanical
properties. J. Arthoplasty, 16, 149-160, 2001. 3.
Muratoglu OK, Bragdon C.R., O’Connor DO, Perinchief
RS, Estok DM, Jasty M, and Harris WH: Larger diameter femoral heads used in
conjunction with highly cross-linked ultra-high molecular weight
polyethylene. A new concept. (In Press)
J. Arthroplasty. 2:45
p.m. The Bearing Surface Should be Metal-on-Metal Lawrence D. Dorr, M.D. Metasul should be the
bearing surface because: 1)
Wear is reduced to
average 25 microns in each of the first two years and 5 microns per year
thereafter in retrieval implants. 2)
The bearing surface always
remains congruent. 3)
Loosening of the cup
with Metasul is no longer a failure mechanism as it was with McKee-Farrar! 4)
Osteolysis is not
prevalent - and not a failure mechanism - in the first 5-10 years with Metasul
bearings. 5)
There is a 13 year
experience with the same bearing surface. 6)
Patients have confidence in their hip. 7)
There is no evidence
of cancer or systemic disease in epidemiological studies or in the current
150,000 implants since 1988 even though increased ion levels have been
measured in blood and urine. 2:55
p.m. Ceramic On Ceramic Bearings In Total Hip Arthroplasty Benjamin E. Bierbaum,
M.D., Jim Nairus, M.D., Dan Kuesis, M.D., J. Craig Morrison, M.D.
and Daniel Ward, M.D. The ideal
bearing surface for total hip arthroplasty is still being sought. This
bearing would be durable, cost effective, easy to implant, inert, and produce
minimal wear debris. Ceramic on
ceramic bearings have continued to evolve and enjoy success in many European
centers throughout the past three decades. A limited number of early US
reports discouraged widespread acceptance and use of ceramic on ceramic total
hip arthroplasty. Once critically
analyzed most of the failures from the early reports are attributable to
design specific and material specific flaws. Vast improvements have been made
in ceramic manufacturing leading to even more superior wear characteristics
and exponentially higher burst strengths. The case for alumina on alumina
ceramic bearings is becoming stronger as data accumulates both clinically and
in vitro. In
a multicenter, prospective and randomized study, an alumina-on-alumina
ceramic bearing is compared to a cobalt chrome-on-polyethylene bearing. At
follow-up as long as 60 months there has been no significant difference in
clinical performance between the two study groups. No ceramic head fracture
or ceramic bearing failure has occurred. Therefore, this new
alumina-on-alumina ceramic bearing is a safe option for total hip
arthroplasty and may provide a more durable prosthesis especially in young
and active patients. 3:35
p.m. Articular And Bony Changes Following Acetabular Fracture Marvin Tile, M.D. Most fractures involving articular
cartilage are produced by a combination of compression and shear forces. Because of the particular anatomical configuration
of the hip joint the head of the femur may be thought of as a hammer, the
injury being produced by the head of the femur striking the articular surface
of the acetabulum. In this
circumstance compression forces predominate.
The particular pattern of injury produced depends on the position of
the femoral head at the moment of impact whether it be in abduction or
adduction, flexion or extension, internal or external rotation. All of these positions produce acetabular
fractures of different anatomic types. Also the biologic factors are
important especially the strength of the underlying bone. There are two peaks of incidence of these
injuries, the first the usual trauma population, young males, but the second
and growing peak is the fracture in the older age group often with less
traumatic force but with similar consequences because of the osteopenia
present. The resultant forces may
have the following effects. On the hip joint the forces may produce
fractures of the acetabular wall and dislocation, either anterior or
posterior with accompanying impaction of articular cartilage fragments. Forces directed medially produce “central
dislocation of the hip” the old word for acetabular fracture, usually a
transverse or T pattern where both columns may be fractured through the joint
or above the joint, and the columns may be separated from each other. On
the macro level these bony injuries have lead to the accepted anatomical
classifications ( Judet-Letournel, AO-ABC)
into fractures of the wall, the column, both columns (transverse) or
both columns separated (T).
The direct forces on the acetabulum may produce a devastating effect
on the articular cartilage. The articular fractures may mirror the
underlying bony injury but in both demographic populations, may also involve
comminution of the articular surface of both the acetabulum and the femoral
head, often with avascular fragments, marginally impacted fragments with
minimal bone attachment and finally bruising of articular cartilage. With the advent of MRI, bruising is seen
commonly in articular fractures and articular injuries. All of these factors may have a long term
effect on the articular surface. The accepted principles of treatment
include anatomic reduction, stable internal fixation and early motion which
give the patient the best opportunity for an excellent long term result. However, even in the hands of experts, and
even if the above is achieved there are a small number of patients who do
poorly early because of the above factors and another group who may exhibit
degenerative post traumatic arthritis three to four decades after the initial
insult. Other treatment modalities,
therefore, such as, total hip arthroplasty, are being evaluated in a select
group of patients, as an alternative to O.R.I.F. 3:45
p.m. Anatomic Joint Fracture Fixation and Long Term Results Joel Matta, M.D. Acetabular
Fractures occur in adults of all ages and compromise the functional viability
of the hip. In younger patients they result almost exclusively from
high-energy trauma. In older patients
these fractures can result from a simple fall as well as high-energy
trauma. Open reduction and internal
fixation of the fracture with anatomic reduction of the fractured inominate
bone and acetabulum is the preferred treatment for the great majority of
fractures. The most effective and
best proven surgical approach is to operate through a single surgical
approach with the patient positioned appropriately on the fracture table:
prone for the Kocher-Langenbeck (KL) approach, supine for the ilioinguinal
(II) approach, or Lateral for the extended iliofemoral (EIF) approach. A small percentage of fractures are
operated through successive KL and II approaches From
July 1980 through December 2000 the author operated 890 acetabular fractures
including acute fractures operated prior to three weeks from the time of
injury 88% and old fractures (over three weeks) 12%. The distribution of
operative approaches was: KL 44%, II 35%, EIF 19% and KL+II 1%. For year 2000, 67 fractures were operated
and the approach distribution was: KL 52%, II 42%, EIF 7%, and KL+II 3%. Reductions
of the acetabulum were rated anatomic 71%, imperfect 20%, poor 7% and
surgical secondary congruence 3%. Clinical results in patients with minimum
2-year follow-up were rated excellent in 40%, good in 36%, fair in 8% and
poor in 16%. Anatomic reduction correlated with an excellent or good clinical
result (p= .002). Surgical complications included 3% infection and 2% nerve
injury. Osteonecrosis for the femoral head occurred in 3% and wear of the
head in 5%. Subsequent surgeries
included total hip replacement in 6%, arthrodesis in 2% and excision of
ectopic bone in 5%. The
goal of surgery for acetabular fractures remains preservation of a mobile and
painless hip for the rest of the patient's life. Long term follow-ups up to 20 years in this series and 30 years
for the series of Letournel indicate that in the majority of cases the hip
can be preserved and prosthetic replacement avoided. The surgeon's challenges
remain: achieving an anatomic reduction and avoidance of complications. The fracture table,
specialized reduction instruments and the surgeon's experience maximize the
capability for reduction through the KL or II approach used alone and thereby
minimize the surgical trauma by limiting the number of cases for which the
EIF or KL+II approaches are indicated. 3:55
p.m. Total Hip Arthroplasty For Post-Traumatic Arthritis Following Acetabular Fracture Daniel J. Berry, M.D.,
Michael Halasy Challenges
in performing total hip arthroplasty following acetabular fracture include:
acetabular bone loss, pelvic deformity, ununited bone, poor or sclerotic bone
quality, previously placed internal fixation devices, heterotopic bone, and
scar tissue. The durability of
cemented acetabular components in this patient population is suboptimal,
mostly due to implant loosening. For
this reason uncemented porous coated sockets have been advocated, and
mid-term results have been reported to be favorable. The
purpose of this paper was to evaluate the longer-term results of uncemented
sockets inserted for arthritis following an acetabular fracture. Thirty-four
total hip arthroplasties using uncemented porous coated titanium acetabular
components were performed in 33 patients (26 male, 7 female; mean age 48.6,
range 19-77) from 1984 through 1990 following acetabular fracture. Three were
lost and 5 died at less than 10 years, all with their implants intact. The remaining patients were followed until
death, revision or for a minimum of 10 years (mean 11.6, range10-16). There were 7 socket or liner
revisions: 3 for wear and osteolysis,
1 for loosening and osteolysis, 1 for liner dissociation, and 2 for
dislocation. Radiographs in unrevised
hips showed no loose sockets, but two hips had marked osteolysis Conclusions: Uncemented sockets provided dramatic
long-term improvements in cup fixation compared to reports of cemented cups
for this challenging diagnosis.
However, in this mostly young male cohort with unilateral hip disease,
polyethylene wear and osteolysis were the major problems of uncemented cups
placed in the 1980s. Hopefully the
improved fixation provided by uncemented cups combined with improved bearing
surfaces will further improve arthroplasty durability in these patients in
the future. 4:15
p.m New
Developments from the O.R.S. Richard Coutts, M.D. Seven
to ten key papers related to the hip that were presented at this year's
Orthopaedic Research Society meeting will be presented in abstract format
with commentary on their significance. 4:25
p.m. Mini-Incision
For Total Hip Replacement Thomas P. Sculco, M.D. Total
hip replacement may be performed through incisions from 7-10 centimeters
which allow adequate exposure for proper placement of components. The video
will illustrate this technique. It has now been used in over 1,000 total hip
replacements. This approach results in less dissection, bleeding and
operative time and facilitates rapid patient recovery and discharge from the
hospital. Custom retractors have been developed for this procedure which
simplifies the exposure. A monoblock cup is used routinely, which makes
acetabular component insertion easier. Patient selection is important and in
obese patients or heavy male patients larger exposures are necessary but
these are rarely greater than 12-15 centimeters. A randomized prospective
trial has demonstrated reduction in recovery time without added morbidity. 4:31
p.m. Pre-operative
Assessment of Hip Dysplasia: Prognosis for
Outcome After Periacetabular Osteotomy Stephen B. Murphy. M.D. Introduction: This
study was conducted to determine if pre-operative clinical and radiographic
parameters could be used to predict outcome following periacetabular
osteotomy. Methods: Clinical
and radiographic information was prospectively acquired on 110 consecutive
patients treated by peri-acetabular osteotomy from 1992 to 2000. Data include pre- and post-operative hip
scores, AP pelvis and false-profile radiographs. Pre-operative AP pelvis views in abduction, false profile views
in flexion, and dynamic fluoroscopic evaluation were performed in patients
with hips that were either incongruous or moderately osteoarthritic.
Variables were correlated with clinical outcome to determine predictive factors. Results
and Conclusion: All
patients with concentric dysplastic joints and grade 0 to 2 osteoarthrosis
did well without progressive osteoarthrosis or clinical deterioration for up
to 9 years post-operatively. While
most patients with moderate osteoarthrosis, incongruity, or uncorrected
femoral deformity also did well post-operatively, all failures were in hips
of these subtypes. Outcome following periacetabular osteotomy in low risk
hips is predictably good. Outcome in
high-risk patients is also usually good, and factors predictive of failure
can usually, but not always be identified pre-operatively. 4:37
p.m. Surgical Navigation for Hip Surgery Anthony M. DiGioia III,
M.D. Accurate
implant alignment during total hip replacement surgery (THR) is critical to
optimize patient outcomes. Computer-based surgical navigation systems allow
measurement and guidance of implant alignment. This study reports on the use
of a navigation system to intraoperatively measure and align acetabular
components. A computer assisted navigation system (HipNav) was used to
measure acetabular implant alignment and pelvic orientation while providing
continuous measurement of cup abduction and flexion angles. These angles were
recorded as the acetabular component was placed during and after
pressfitting, and after the placement of supplementary screws when needed. A
sequential series of 150 cases of THR using HipNav are reported. Alignment
results were available in 138 cases. Surgical navigation during THR improved
the accuracy and reliability of acetabular alignment. The final cup alignment
using computer-assisted navigation was within 3° (SD 3°, range 0° to 10°) of
abduction and 4° (SD 3°, range 0° to 16°) of flexion when compared to the
planned pre-operative alignment. The process of pressfitting the cup and
supplementary screw fixation also influenced the final cup orientation and
these changes were not always easily detected visually. Using surgical
navigation technologies, acetabular alignment can be measured during surgery
leading to more reliable and accurate cup orientation compared to mechanical
guides. 4:43
p.m. Virtual
Reality of the Hip Jay D. Mabrey, M.D. The
increasing power of microprocessors opens new vistas for the orthopaedic
surgeon toward understanding the complex three dimensional anatomy about the
hip, planning complex hip procedures, designing custom implants, and finally
executing the procedure with unheralded precision. Data from the Visible Human Project enables virtual environment
designers to build anatomically precise models of not only the bony tissues
about the hip, but all of the soft tissues as well. From here, the physician visualizes the structures in three
dimensions utilizing the DataDesk – a large format 3D display. This device allows the physician to
interact with the virtual models in real time and explore the anatomy before
entering the operating room.
Individual CT data allows the surgeon to design custom implants for
challenging cases and have them manufactured quickly. Similar CT data is used for the
preoperative planning for even routine cases with the software suggesting not
only the size, but the ideal position of the implants. The range of motion of
the reconstructed hip is demonstrated first on the computer well before the
operation, alerting the orthopaedist to potential pitfalls. Finally, this data is taken into the
operating room where the surgeon employs intraoperative guidance techniques
to ensure accurate placement of the prosthesis. President: 1st
Vice President: 2nd
Vice President: Secretary-Treasurer: Chairman
of the Education Committee: Member-at-Large, Board of Directors: President: First
Vice-President: Second
Vice-President: Third
Vice President: Secretary: Treasurer: Members-At-Large: Immediate
Past President: Educational
Committee Chair: Membership
Committee Chair: |
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