Introduction:  While internal fixation is recommended for most nondisplaced fractures of the femoral neck, the optimal treatment for displaced fractures of the femoral neck is controversial.  Options for operative treatment include: internal fixation, unipolar hemiarthroplasty, bipolar hemiarthroplasty, and total hip arthroplasty. 

Materials & Methods:  One hundred eighty-six displaced fractures of the femoral neck in elderly patients were treated surgically with internal fixation (120), hemiarthroplasty (43), and total hip arthroplasty (23).  One hundred twenty fractures treated with internal fixation were compared with 66 fractures treated with arthroplasty.  Criteria for comparison were re-operation, mortality, hospital discharge disposition, functional outcome living status, and cost effectiveness.

Results:  There was no difference in rates of re-operation or mortality, between groups; however, arthroplasty produced a longer interval to re-operation or death.  Arthroplasty was associated with more independent living, and arthroplasty was more cost-effective than internal fixation.

Conclusion:  Total hip arthroplasty was the best treatment for displaced fractures of the femoral neck in elderly patients in this series.  We treat displaced fractures of the femoral neck in elderly patients with total hip arthroplasty.

Total hip replacement is rarely indicated in the management of acute intertrochanteric fractures of the femur.  Pathological fractures with involvement of the head and/or peri-acetabular pelvis may represent one such indication; rheumatoid arthritis with or without radiographic involvement of the joint space or end-stage osteoarthritis with significant hip symptoms prior to fracture may represent other indications.  Total hip replacement is generally reserved for the management of complications such as non-union or avascular necrosis of the femoral head.

Failed hip fracture treatment leads to profound disability hence effective salvage methods are essential.  For physiologically young patients with adequate remaining bone and a preserved hip joint space, joint preserving operations are preferred.  However, for older patients, particularly those with poor remaining bone stock and a damaged joint, the most reliable treatment and most expeditious means of regaining mobility often is arthroplasty. 

For failed femoral neck fractures, the main controversy is whether to convert to hemiarthroplasty or total hip arthroplasty.  Total hip arthroplasty is preferred if the joint is damaged.  Most series demonstrate total hip arthroplasty provides very consistent pain relief but historically has had a high rate of instability.

Arthroplasty for a failed intertrochanteric fracture has technical challenges including retained broken hardware, proximal bone loss that often requires head and neck prostheses, and proximal bone deformity.  Management of the greater trochanter, which often impedes access to the femoral canal is problematic and may require greater trochanteric osteotomy or a slide through a nonunion.  Despite technical challenges, we found good clinical results and surprisingly few orthopedic complications in 60 patients treated with hip arthroplasty for this problem (JBJS 85A:899, 2003).

Total hip arthroplasty in patients who have previously undergone open reduction and internal fixation of an acetabular fracture may be made necessary by posttraumatic degenerative changes, persistent malunion or nonunion, or occasionally avascular necrosis and destruction of the femoral head.  Problems that may be encountered during these procedures include: prior scarring and soft tissue injury complicating exposure, presence of heterotopic ossification, and occasionally pre-existent nerve palsy from the original fracture or subsequent osteosynthesis.  Retained hardware can present significant challenges and frequently is left in place unless intraarticular in location or immediately adjacent to the acetabulum such that it prevents preparation of the acetabular cavity or results in impingement against the acetabular component.  Additional challenges that may be encountered in this patient subgroup include residual deformity and malunion, persistent pelvic dissociation or nonunion of fracture fragments, cavitary or segmental bone loss from displaced or resorbed bone fragments, and occasionally, an occult deep infection.  Preoperative assessment and planning should include careful consideration of the most appropriate surgical approach, which may be impacted by the need for hardware removal. Screening laboratory studies and occasionally aspiration of the hip may prove helpful in excluding associated infection.  Intraoperative sciatic nerve monitoring may be of assistance in patients with partial residual nerve deficits or where extensive posterior exposure for hardware removal or excision of heterotopic ossification is anticipated.  Metal cutting tools to allow partial removal of long plates and adjunctive equipment for removal of broken or stripped screws should be routinely available during these cases.  Careful preoperative planning regarding implant and reconstructive options can also ensure availability of proper implants and equipment and will allow the surgeon to anticipate the potential need for techniques developed for revision surgery for management of major bone deficiencies.  Reported results suggest that surgery is frequently prolonged, can be associated with greater blood loss and may result in increased risk of post-arthroplasty heterotopic ossification when compared to routine primary procedures, but bone stock may be better than that encountered following nonoperative treatment of major displaced acetabular fractures (1, 3).  Available long-term results relate to older fixation and implant options with noncemented cups appearing to provide more durable results with lower rates of aseptic loosening than those reported for cemented acetabular components (1-6).  These patients are at higher risk of revision and failure than patients undergoing THA for osteoarthritis (1, 3), though initial short-term results are comparable to conventional hip arthroplasty patients (2), as long as wound healing problems and deep infection can be avoided (4).  Significant interest exists in the application of newer methods for management of acetabular bone deficiency to this challenging subset of primary arthroplasty patients. 

The enduring success of the low friction arthroplasty first advanced by Sir John Charnley as a solution for severe hip arthritic problems may be appreciated from the fact that in 2002 over 340,000 primary and revision hip arthroplasties were performed in the United States, a number easily doubled on a global basis. Despite the obvious success of this solution, ultra-high molecular weight polyethylene (UHMWPE) wear is an inescapable consequence of in vivo articulation and is a first-step in the sequela leading to osteolytic response. In this regard, a number of alternative bearing material couples, some with distinct historical track records, are gaining popularity in contemporary orthopaedic hip surgery.

The purpose of this discussion is to briefly set out a series of questions that informed clinicians should be asking when considering the use of alternative bearing technologies.

• Evidentiary materials defining the problems of current bearing couples should be scrutinized and compared to those describing new bearing couple performance. The extent of the problem may not warrant a change.

• Patient profiling is an important part of the selection process. It is not always necessary to choose the latest and greatest bearing solution for all patient populations.

• Marketing briefs, pre-clinical and clinical reports are important in assessing the safety and effectiveness of these couples. Surgeon awareness in these regards is an imperative.

• Historical failures and early clinical use are important antecedents in defining problems that the contemporary solution must address.

• The surgeon must consider the learning curve of optimal surgical implantation when system changes are considered. This is particularly important if the proposed alternative bearing couple is not compatible with the current system.

Results: Liners sterilized by gamma-irradiation wore 0.09 mm/yr less than those that were sterilized by gas-plasma, a non-crosslinking chemical surface treatment.  For every additional year of age at the time of surgery, the wear rate decreased by 0.003 mm/yr.  For each additional year that gamma-irradiated-in-air Hylamer liners were stored prior to implantation, the wear rate increased by 0.05 mm/yr.  Other factors associated with an increased wear rate included male gender and a pre-operative diagnosis of osteoarthritis.  Increased body mass index, a ceramic head, use of a Duraloc 1200 cup and barrier packaging of gamma-irradiated liners decreased wear rates.  Cup abduction, polyethylene thickness, use of a lateralized liner, Hylamer polyethylene, femoral head diameter, surgeon and approach did not have a significant influence on linear wear rates.

Discussion and Conclusion: While the homogeneous surgical techniques employed at our institute limited our ability to examine the effects of surgeon-related variables, it improved our ability to discern the effects of implant and patient-related factors.  The substantially decreased wear rate associated with gamma-irradiation was attributed to the sterilization-induced polyethylene crosslinking.

Like metal-on-metal articulations and ceramic-on-ceramic articulations for total hip arthroplasty highly crosslinked polyethylenes have been used for the articulation for total hip replacement covering sixteen to twenty-five years.  The excellent result of these previous, longstanding uses provides one of the three strong elements in the support for the use of highly crosslinked polyethylenes today. 

The second extremely strong element is the extensive, detailed, and imaginative in vitro testing that preceded the introduction of the current versions of highly crosslinked polyethylenes, taking into full account the remarkable new information about polyethylene that has been generated in the past two decades.

The third and fulfilling element is the in vivo assessment of both wear and oxidation of selected contemporary highly crosslinked polyethylenes.  A prospective and randomized RSA study of electron-beam crosslinked polyethylene versus gamma in  nitrogen polyethylene shows at just three years a highly statistically significant reduction in wear by the electron-beam treatment.  In fact, after the first year, which included the bedding in issues, no further penetration of the femoral head into the polyethylene could be detected.

Another prospective randomized bilateral simultaneous RSA study of electron-beam highly crosslinked polyethylene against gamma in nitrogen polyethylene done as a bilateral simultaneous study, shows that at just two years there is a statistically significant reduction in wear of the electron-beam crosslinked polyethylene, despite the fact that at the end of one year (the bedding in period) no difference could be determined.  Again, between the first and second year, no further penetration of the femoral head into the polyethylene could be measured.

In a study contrasting gamma in air polyethylene versus electron-beam polyethylene using the Martel method, it has been shown that the steady state penetration rate (after the bedding in period) for the gamma in air material was 136 micra per year.

In contrast the penetration rate for the electron-beam crosslinked material was 8 micra per year, a remarkable and highly statistically significant difference.

Retrieval studies have confirmed the absence of oxidation in the highly crosslinked melted ultra high molecular weight polyethylenes after in vivo use..

The penetration rate in vivo from these three studies, of three different patient populations, using two different measuring techniques, have shown wear rates that are virtually identical with wear rates of metal-on-metal and ceramic-on-ceramic.

Since there is no advantage of metal-on-metal or ceramic-on-ceramic in terms of wear or oxidation, the decision amongst these three alternate bearing surfaces hinges on a multiplicity of other factors.

The highly crosslinked, melted polyethylene articulation has major advantages in terms of familiarity (no learning curve, no special techniques, no increased demands for higher surgical precision).  It also has marked advantages in terms of adaptability.  One can use extended lip liners, offset liners, eccentric liners, and constrained liners. None of these are possible with the hard on hard bearings.

Forgiveness is also a remarkable advantage.  Impingement is far more benign with the polyethylene.  There is no striped wear, as occurs with hard on hard bearings.  Micro-separation reduces material damage for polyethylene but accelerates for metal-on-metal and for ceramic-on-ceramic.  Slight degrees additional abduction of the acetabular component is far less harmful for polyethylene than for ceramic-on-ceramic or metal-on-metal.

Finally, cost is a major factor.  The hard on hard bearings are substantially more expensive.

Thus, the case for metal on polyethylene articulations for total hip arthroplasty is extremely strong.

Within the subset of contemporary polyethylenes, the prediction that about 10 M Rad of radiation would produce better wear characteristics than 5 M Rad has been confirmed in the hip simulator.

The concerns about the high level of free radicals in those contemporary polyethylenes which have not been melted after radiation have also been confirmed by retrieval of specimens after in vivo use that show unusually high degrees of oxidation and white banding at less than three years following insertion.

Concerns about scuffing of the surface of the highly crosslinked polyethylene have been unfounded.  This is a process that exists in all polyethylenes and has for the conventional polyethylene for forty years.  It does not accelerate wear and is not adverse.

Concerns about micro cracks in the highly crosslinked polyethylenes are also unfounded.  These micro cracks are ubiquitous for all polyethylenes and were published by Charnley on gamma in air polyethylene thirty years ago.

In summary the case for the use of highly crosslinked (approximately 10 M Rad), melted ultra high molecular weight polyethylene in total hip replacement surgery is extremely strong.  

A higher degree of crosslinking has been shown to improve wear properties of ultra-high molecular weight polyethylene (UHMWPE) in laboratory studies.  However, crosslinking can also affect the mechanical properties of UHMWPE.  Fatigue crack propagation resistance was determined for electron beam crosslinked UHMWPE and compared to gamma irradiation crosslinked and non-crosslinked polyethylene fatigue specimens.  Crosslinking was performed with different dosages of irradiation followed by melting.  For one irradiation dose (50 kilogray) both extrusion and molding processes were compared. A fracture mechanics approach was used to determine how the degree of crosslinking affects resistance to crack propagation in UHMWPE.  Fatigue crack propagation resistance was reduced in proportion to the irradiation dose.  The type of irradiation (gamma or electron beam) or manufacturing method (extrusion or molding) did not affect fatigue crack propagation resistance.  The reduced fatigue strength of highly crosslinked UHMWPE could lead to mechanical failure under conditions which are associated with cyclic local tensile stresses.

Ceramic components have been an option in total joint arthroplasty for many decades. A recent resurgence in popularity has occurred within this country with these bearings, especially in the face of arthroplasty concerns such as wear related osteolysis. Newer more technologically advanced products have made ceramic on ceramic bearings an attractive choice in the quest for a more durable and longer lasting arthroplasty. Ceramics have already had an excellent track record when it comes to wear resistance. Data reveal significantly lower volumetric wear compared to other available bearings, and it is also noted that particle size is in the same range as polyethylene particles. These qualities along with potential for less bio-reactivity make for less wear and more importantly potentially less osteolysis. Improvements in alumina ceramics namely Biolox Forte and newer work with “Delta” alumina has spawned a tougher material that is highly wetable and has a low coefficient of friction. These characteristics along with improvements in taper tolerances have provided an extremely strong and durable product. Strength improvements in these materials allow for thinner liners in comparison to traditional metal on polyethylene bearings, and thus an increase in range of motion can be accomplished due to the larger femoral head sizes. Alumina on alumina bearings also have a resistance to separation during the gait cycle, possibly related to their enhanced wetability. Bearing separation during the gait cycle has been associated with increased wear of the bearing; minimizing this can possibly lead to lower wear rates in-vivo. Ongoing clinical studies of ceramic on ceramic bearings, some with built in controls thus far suggest less osteolysis at three to six years than is seen with traditional metal/poly articulations. Therefore, alumina on alumina bearings demonstrate both experimentally and clinically a high resistance to wear and few complications and thus currently are a viable option in our younger and more active patients.

Currently available ceramic materials are superior to those originally utilized in total hip arthroplasty, which should translate into a much lower complication rate then previously reported.  In spite of this, a number of concerns persist.  The ceramic-ceramic articulation is not immune to wear and surface damage.  Conditions associated with ceramic wear include vertical cup position, femoral neck impingement, and femoral head separation.  A unique pattern of  “stripe wear” has been described as resulting from microseparation during gait.  Catastrophic failure, although rare, continues to be a concern and not all fractures can be predicted by proof testing.  Revisions necessitated by ceramic fractures can be extensive and the results of the revision procedure can be compromised by the presence of retained highly abrasive particulate debris.  Other concerns include generation of debris from modular interfaces, neck damage and debris generation from impingement of some designs, inability to utilize a ceramic head a second time on a metal trunion, and the dramatic loss of head and liner options intraoperatively.  While ceramics show great promise as a lower wear articulation, manufacturing and design modifications and improvements will continue in an attempt to address the substantial concerns that persist.

The metal-on-metal bearing couple is enjoying a resurgence in clinical applications seen in both total hip and hip resurfacing technologies.  The most significant advantage of a metal-on-metal implant is the improved wear characteristics seen both in vitro on wear simulators and in vivo with retrieved implants.  All bearings have disadvantages and a metal-on-metal bearing is no exception.  Concerns exist regarding the generation of metal ions seen in both the blood and urine of patients with metal-on-metal implants.  These elevated metal ions have theoretical, although not proven, risks related to carcinogenic and biological concerns.  In addition, concerns exist regarding hypersensitivity, increased incidence of instability and increased costs.  As well, specific patient selection issues arise with metal-on-metal implants and with the current generation of implants only early and mid-term results are available with no long-term series yet published.  Therefore, while a metal-on-metal bearing may be considered a viable alternative to either polyethylene or ceramic implants, outstanding and unresolved issues continue to exist.

Rare it is in the long annals of the history of human medicine to generate a brand- new, never previously encountered, unique human disease, identify its clinical manifestations, define the underlying mechanism, elaborate the molecular biologic sequence, establish the origin of the pathogen, understand the mechanism of the creations of the pathogen and correct the pathology, all within one lifetime.

Thus is the story of periprosthetic osteolysis.

It is a unique disease because it requires the elaboration of micron and submicron particles within the body over many years.  It never existed prior to the last half of the Twentieth Century, because such a mechanism required the invention and widespread application of total joint replacement surgery, a phenomena of the last fifty years.

Its alarming clinical manifestations, namely, massive local lysis of bone, was initially overlooked, initially misunderstood, and initially attributed to alternate explanations.

With the establishment that the fibrous membrane around failed total hip implants had the capacity to generate PGE II and collagenase, the stage was set for the unroofing of the molecular biologic sequence involved, which ultimately leads to the stimulation of the osteoclast.

With the identification for the underlying pathogen being micron and submicron particles, mainly ultra high molecular weight polyethylene particles but also PMMA, metal, ceramic and others, it then became clear what the solution needed to be.

With the insightful establishment that the specific mechanism by which micron and submicron particles were generated, as being related to the surface deformation of the polyethylene, it became possible to hypothesize the process of preparing ultra high molecular weight polyethylene to eliminate this mechanism.

The hypothesis has proven correct.  It is now possible to both crosslink the polyethylene to severely reduce wear and melt it to eliminate detectable free radicals and thus eliminate oxidation.

The longstanding in vitro data from prior crosslinked polyethylene experiences now combines the extensive and sophisticated contemporary in vitro hip simulator data on current crosslinked polyethylenes and now the in vivo data confirming the low wear and absence of oxidation in the contemporary polyethylenes. This powerful array of support portends the cure of this unique, never previously encountered, complex biologic response and thus, the elimination or near elimination of a worldwide scourge, periprosthetic osteolysis.

The frequency of dislocation after total hip arthroplasty varies widely in different series in part because most series report prevalence figures, which are dependent on the incidence of the complication and the length of time patients are followed for this complication.  To learn more about the chronology of the problem, we studied the long term cumulative risk of dislocation in 6621 primary Charnley total hip arthroplasties (JBJS-A, 2004, in press).  The incidence of first-time dislocation was highest in the first month (cumulative risk 1%), still high in the first year (cumulative risk 1.8%), then continued at an incidence of about 0.2% per year for the life of the arthroplasty.  By 25 years postoperatively for living unrevised patients, the cumulative risk was 7%.  In multivariate analysis the risk of dislocation for females was 2.1 times that of males, and for patients 70 or over at arthroplasty was 1.3 times that of patients less than 70.  Patients with osteonecrosis of the femoral head, previous hip fracture, and inflammatory arthritis all had statistically increased dislocation risk compared to osteoarthritis.  The etiology of late dislocations appears to be multifactorial and includes new episodes of trauma, new neurologic conditions, component loosening and position change, and also probably polyethylene wear and soft tissue stretching (JBJS 84A: 1949, 2002). 

Operative approach and femoral head size also have an important effect on dislocation risk.  In a multivariate analysis of 22,174 primary total hip arthroplasty, the hazard ratio for posterior approach was 2.1 compared to the anterolateral or transtrochanteric approach.  The hazard ratio for 22-mm head size was 1.8 (compared to 32-mm) and for 28-mm was 1.3 (compared to 32-mm).  The increased cumulative dislocation prevalence for posterior approach and smaller head sizes was mostly due to higher dislocation incidence in the first five years after arthroplasty (AAOS 2003). 

Reviewing the outcome of over 23,000 hip replacements reveals a 3.3% (range 1-6%) incidence of hip prosthetic instability.  The predisposing features and circumstances associated with hip dislocation have been well recognized.  However, emotional impact of this complication as well as the financial implications to the patient and society has been less appreciated.  Based on a review of over 10,500 procedures at the Mayo Clinic, approximately one-third of the 330 who sustained a dislocation will require a surgical procedure to render the hip stable. (Woo)  Based on these data, which may be rather conservative, we assessed the actual costs at this institution for 18 dislocations.  Twelve were treated by closed reduction and six were treated by open revision.  At our institution the mean cost of closed reduction of the 12 patients was 10% of the initial procedure.  The mean cost of the open revision for the six patients was 150% of the cost of the index procedure.  Assuming approximately 250,000 hips are replaced each year in the United States, and again based on Mayo actual cost data, a conservative estimate of a societal cost impact of this complication is approximately 75 million dollars.  Considering the above information it is not surprising then that there have been numerous reports discussing the management of this problem. 

Herein we will review the effectiveness of surgical intervention principally directed to the management of the unstable hip arthroplasty.  The discussion is largely based on our published analysis of approximately 10,500 primary cases (Woo) and on our experience with approximately 2500 hips using elevated cup liners (Cobb); with 95 reoperations for primary hip instability (Daly); 78 procedures using a constrained articulation (Schrader), 22 procedures using a bipolar implant (Parvizi) and 115 operations for instability following revision hip procedures (Albertson). 

The options for surgical intervention may be logically discussed in three categories:  first, non-revision procedures -- these include 1) eliminating impingement; 2) trochanteric osteotomy; and 3) allograft soft tissue augmentation.  The second category of intervention is revision, focusing on 1) the head size 2) the orientation of the cup or 3) the use of an elevated rim acetabular component.  Finally, the use and value of a constrained acetabular articulation will be reviewed. 

The stability and durability of total hip reconstruction is dependent on many factors that include the design and anatomic orientation of prosthetic components.  An analysis of femoral component head size and acetabular component orientation demonstrates an interdependency of these variables and joint stability.  Increased femoral component head size can increase hip stability by increasing the prosthetic impingement-free range of hip motion and by increasing the inferior head displacement required before hip dislocation.  Increasing the femoral head size from 22 mm to 40 mm increases the required displacement for dislocation by about 5 mm with the acetabular component at 45° of abduction; however, increasing acetabular component abduction greatly diminishes this stability advantage of larger femoral heads.  Vertical acetabular component orientation and femoral component head subluxation are each predicted to more than double the tensile stress with acetabular component polyethylene compared to components at 45° of abduction.  With a desirable acetabular component orientation, the use of larger femoral heads may result in improved joint stability and durable use of polyethylene.  With high abduction acetabular component orientation, the use of larger femoral heads contributes little to joint stability and contributes to elevated stress within the polyethylene that may result in implant failure.

Methods: 140 hips in 135 patients had a total hip replacement using femoral heads at least 36 millimeters in diameter (average 40.9mm, range 36 to 52).  The average age was 61.6 years old (range 16 to 95).  The patients were grouped in three different categories depending on their diagnoses: recurrent dislocators from previous THR (group 1 - 29 hips), revision surgeries not including revisions for dislocations (group 2 - 54 hips), and primary surgeries (group 3 - 57 hips).

Results:  Average follow-up was 5.5 years (range 1 to 17). A total of 16 hips were revised:, 6 for instability, 4 for fracture or disassociation of conventional polyethylene liner which had been sterilized in air, 3 for aseptic loosening of the socket and for sepsis. One additional hip from group 1 dislocated at 12.5 years post surgery, was treated with closed reduction and has been non-recurrent since. University of California Los Angeles hip scores for pain, walking, function and activity improved significantly (p<0.001) from 4.8 to 8.8, 5.4 to 7.7, 4.8 to 6.7, and 3.9 to 4.9, respectively.  The prevalence of dislocation varied among the 3 groups with 13.7% (4 out of 29) for group1, 1.8% (1 out of 54) for group 2, and 3.5% (2 out of 57) for group 3. In group 2 and group 3, all dislocations occurred in hips reconstructed with a head size less than 40mm.  The cause of failure in the six cases which required revision was due to poor socket orientation. All of the hips became stable after revision. Four additional hips required revision because of liner fracture or dissociation. All were conventional polyethylene sterilized in air. None of the hips that dislocated had to be revised with a constrained acetabular liner.

Conclusions:  Large diameter femoral heads provide additional stability without compromising range of motion not only for recurrent dislocators, but also for patients undergoing revision. The low wear of cross-linked polyethylene and especially metal on metal now enables the surgeon to extend the use of big femoral heads to primary total hip arthroplasty although longer follow-up will be necessary to evaluate any negative wear consequences. The occurrence of liner fractures or disassociation from the acetabular shell added to the thickness of polyethylene bearings suggest that metal on metal is the ideal material of choice for a bone-conserving reconstruction with the largest femoral head.

Constrained acetabular liners have been available for close to two decades.  Two basic types of liners are available.  The type first developed by Joint Medical Products was the SROM constrained liner that captured the femoral head with a locking ring in the polyethylene.  These liners may have better results with larger head sizes because the hip can be taken through a larger range of motion (with larger head sizes) before the locking ring is stressed.  The second type of constraining liner was developed by Osteonics.  It consisted of a tripolar replacement that is constrained by a locking ring in the outer polyethylene of the device.  Indications for constrained liners include patients undergoing primary arthroplasty who are low demand and have dementia or hip muscle weakness or spasticity.  Indications for constrained liners in the revision situation include cases with previously failed operations for instability, elderly low demand patients with instability, cases with poor or absent hip musculature, and cases with well positioned acetabular and femoral components and with hip instability.  In this last scenario we cement the liners into fixed shells.

Our results at average 10-year follow-up in 101 hips, demonstrate a 6 percent failure of the device.  Four hips were revised for acetabular loosening and four hips for femoral loosening.  One additional hip was revised for acetabular osteolysis.  Considering the difficulty of the cases we consider these results to be quite encouraging.  At average 3.9 year follow-up of 31 cases where the liner was cemented into the secure shell only one case failed by dislodgement of the liner and one case by fracture of the locking mechanism.

Our experience has led to the following technical recommendation:  (1) if cementing the component score the liner and make sure it is contained within the shell (2) avoid inserting the liner into a grossly malpositioned shell (3) avoid positioning the elevated rim of the liner into a position where impingement might occur and (4) avoid placing the shell and constrained liner in cases with massive acetabular allografts unless additional fixation, i.e. cages, are utilized.

Osteonecrosis (ON) of the femoral head accounts for approximately 10% of all total hip replacements.  That the average age of these patients is 40, with many in their 20’s gives the problem an importance greater than the numbers. There is little consensus about ON, not the pathogenesis, not the natural history, not the treatment.  With only ~20,000 new cases a year, no single surgeon or center has the kind of experience that allows the most important questions to be answered. The answer to the title question is: it depends. To treat implies that untreated, the lesions will progress, first to symptoms and then to collapse.  To treat also implies that treatment will alter the otherwise progressive nature of the disease.  Acknowledging the controversy that exists in the literature, and on the basis of our experience with over 1500 cases treated at the Johns Hopkins Center for Osteonecrosis Research and Education, we believe that moderate sized lesions (15- 30% of the femoral head) should be treated by CORE decompression and bone grafting. Properly done, this procedure has low morbidity and no impact on any subsequent procedure that might become necessary. Lesions smaller than 15% have a higher likelihood of not progressing, and larger lesions are less likely to be influenced by any preservative measure, so that prophylactic intervention is probably not indicated. The authors point out however, that the literature is so diverse, that any position can be chosen, to treat or not to treat, and support can be found.

Osteonecrosis is a disease with a wide ranging etiology and poorly understood pathogenesis seen commonly in young patients.  Core decompression has historically been utilized in patients with small or medium sized, pre-collapse lesions.  Typically, an 8 to 10 millimeter large cannula trephine is used to perform the core decompression.  The authors report a new technique using multiple small drillings with a 3 millimeter Steinman pin to effectuate a core decompression.  In this report there were 32 of 45 hips (71%) with a successful clinical result at a mean follow-up of 2 years (range, 20 to 39 months).  Twenty-four of 30 Stage I hips (80%) had successful outcomes compared to 8 of 15 Stage II hips (57%) with no surgical complications occurring with this technique. 

Core decompression has been utilized as a method to attempt to forestall the need for hip replacement in patients with pre-collapse lesions.  It is postulated that this procedure reduces intraosseous pressure in the femoral head.  The authors believe that this minimally invasive technique can effectuate this reduction in pressure and relieve the symptoms and achieve success with less morbidity than previous approaches for core decompression.

Osteonecrosis (ON) of the hip is a disease of impaired blood flow to the femoral head. The ultimate goal of treatment of ON is preservation of the femoral head but establishing definitive treatment modalities has been difficult because neither the etiology nor the natural history of ON have been defined and a number of different diseases are associated with this condition.  Core decompression of the hip and osteotomy have been two of the most common forms of treatment of osteonecrosis of the femoral head. However, over the past decade, there has been increased interest in combining core decompression with biologic approaches that may enhance the body’s inherent ability to repair dead bone.  These approaches include vascularized and non-vascularized bone grafts, bone marrow cells and demineralized bone matrix.

The goal of the free vascularized fibular graft (FVFG) is to decompress the femoral head, remove the necrotic bone and provide revascularization and osteogenesis of the femoral head.  Urbaniak et al have reported on the treatment of 119 femoral heads without collapse with 5-year follow-up. Only 11% required conversion to a total hip arthroplasty.  However, the FVFG is an extensive procedure and 10-15% of patients have ankle problems post-operatively.  In a more recent study, evaluating treatment of femoral heads that have collapsed, conversion of total hip arthroplasty was necessary in approximately 33% of hips at two-year follow-up.

Other investigators have used autologous bone graft, DBMs or bone marrow cells combined with core decompression of the femoral head or a cortical window in the femoral neck.  No large randomized trial has been performed to compare the efficacy of these different surgical procedures.  Most authors report approximately 80-90% success in pre-collapse hips.  Core decompression does not seem to be effective for hips that have already collapsed.  In general, surgeons believe that the use of autologous bone graft or bone graft substitutes such as bone morphogenetic proteins should enhance the results of core decompression because these agents have osteoinductive potential.  However, there is limited data to support this strategy. 

There remains no consensus regarding the best way to preserve the femoral head with osteonecrosis.  Different types of core decompressions, vascularized fibular grafts and osteotomy have all been used with variable success rates.  Clearly this is a heterogenous population of patients and the underlying disease will influence outcome.  In addition, the extent of femoral head involvement and the proportion of the weight bearing area that is involved will clearly have an impact on the results of surgical treatment.  In general, once the hip is collapsed core decompression has limited success.  The efficacy of growth factors and cytokines combined with traditional strategies needs to be assessed in randomized trials.

Hemi-resurfacing of the femoral head for treatment of osteonecrosis has been proposed as a reasonable alternative to total hip arthroplasty.  The results of 59 patients with Ficat stage III osteonecrosis performed by a single surgeon are reviewed.  At average 4.5-year follow-up, 16 patients were considered failures, defined as conversion to total hip arthroplasty, or significant groin pain requiring medication.  Failure did not correlate with age, body mass index, pre-operative length of symptoms, acetabular articular cartilage status at the time of surgery, or etiology of the underlying disease.  The only statistically significant factor associated with failure was lower pre-operative Harris Hip Score.  Conversion of the failed implants to total hip arthroplasty was straight forward, confirming the conservative nature of the procedure.  However, pain relief and recovery following resurfacing are less reliable and slower than that associated with total hip replacement.  It is suggested that this procedure be reserved for patients under age 30 until greater long term experience with alternative bearing surfaces in total hip replacement or resurfacing are available, and that the patient be realistically counseled with regard to expectations.

With the resurgence of metal-metal bearings, there is renewed interest in total hip resurfacing.  A cementless acetabular resurfacing component with a wall thickness of less than 5mm is comparable in size to acetabular components used for total hip replacement.  The fixation of a porous ingrowth acetabular resurfacing component has been demonstrated to be reliable and durable.  There are few clinical reports of total hip resurfacing that stratify results by diagnosis.  However, available evidence indicates that the pain relief, function and activity following total hip resurfacing for osteonecrosis are superior to that reported for hemi-resurfacing and similar to the results of total hip replacement.  Femoral side failure is the issue and is higher than that of hemi-resurfacing.  Refined patient selection and surgical technique can improve the outcomes and durability of total hip resurfacing.

The annual wear rate in polyethylene articulations should be 0.1 mm or less to avoid future osteolysis.  Highly Crosslinked polyethylene demonstrates 80-90% wear reduction in simulator testing, but the clinical documentation of this new polyethylene is still inadequate.  We evaluated the highly crosslinked PE in two prospective randomized clinical studies.  Thirty-two patients (12 male, 20 female, 64 hips) with a median age of 48 years (range, 29-70 years) with bilateral primary or secondary arthrosis of the hip received hybrid THA with liners made of highly crosslinked on one side and conventional PE on the other one.  Twenty-seven patients in this study have passed two years follow up.  Further sixty patients (61 hips) with a median age of 55 years (range, 35-70 years) were randomized to receive either highly crosslinked or conventional cemented all PE of the same design.  Forty-nine patients have been followed for three years.  In both studies all patients received Spectron stems with 28mm cobalt-chromium head.  Radiostereometric examinations with the patient supine or standing were done at regular intervals.  Wear was measured in the supine position from the postoperative week, whereas standing examinations were initiated three months after the operation.  The penetration rate was almost identical in the study and control groups in six months after the operation.  Thereafter the penetration rate leveled out in the two groups with highly crosslinked PE.  At two years the highly crosslinked PE liner showed 62% lower proximal penetration and 31% lower total (three dimensional) penetration when the patients were examined in supine position.  The highly crosslinked all PE cups showed significantly lower proximal penetration in both positions.  The better wear performance of highly crosslinked PE could increase the implant longevity.  Longer follow up is needed to evaluate if this new material is associated with less occurrence of osteolysis.

The effect of joint fluid on the Tribology (i.e., lubrication, friction and wear) of total hip arthroplasty has not yet been adequately investigated.  In the current study, a friction assay was used to assess the effect of human joint fluid and its principal components on the articulation of cobalt-chromium alloy (Co-Cr)-on-polyethylene (PE).  Joint fluid samples from some patients enabled very low friction similar to, and in selected cases lower than, that of bovine serum, which is generally used as the lubricant in joint simulator wear studies.  Joint fluid samples from other patients remarkably increased friction over that of saline.  These findings suggested that a component of the joint fluid in some patients serves as a better boundary lubricant than can be found in bovine serum, thus alleviating conditions favoring wear, in other individuals joint fluid contains components that may interfere with the lubricating effect of water, thus placing the articulation at higher risk of wear than if water alone were the lubricant.  Related studies demonstrated that hyaluronic acid, phospholipids, albumin and γ-globulin were not acting as boundary lubricants, but that one or more other proteins (as yet unidentified) were responsible for reducing friction in this couple.  Associated investigations demonstrated that significantly lower friction occurs with oxidized zirconium alloy-on-PE articulation when compared to the Co-Cr-PE couple.  The present study demonstrated that joint fluid is a patient factor that influences the Tribology of metal-on-PE arthroplasty.

Despite immense improvements, periprosthetic infection continues to compromise the result of otherwise successful joint arthroplasty.  There are various limitations in the management of periprosthetic infection, the most important of which is the inability to deliver antibiotics to the local tissue without the need for intravenous administration.

We have, in a novel manner, utilized the process of chemisorption to covalently tether vancomycin to metal (Titanium) surface that exhibits effective bactericidal activity.  The covalent bonding of vancomycin is designed to be acid-labile, and hence only selectively cleave in the presence of microorganisms.  Furthermore, the covalent bonding was modulated to allow precise control of the antibiotic cleavage.  The chemical synthesis process does not affect the biological activity of the biofactors being attached to the metal surface.  This technology holds a great promise for the manufacturing of ‘smart’ implants that can be self-protective against periprosthetic infection or be used for the treatment of periprosthetic infections when they occur.

The importance of minimally invasive techniques to visualize and treat hip joint disease has been given further credence by a wide age range of patients with high physical demand who present with debilitating hip problems. Advancement in diagnostic and therapeutic applications for hip arthroscopy have lead to safe visualization and instrumentation of the hip joint which has further clarified our understanding of earlier stages of hip disease.  This evolving body of knowledge has dispelled several previously believed myths.  Arthroscopic clinical findings have dispelled previous myths that included:

• Acetabular labral tears do not occur

• Acetabular chondral lesions cannot occur due to the geometry of the joint, the ligament and muscular strength, and the negative pressure in the joint.
• Radiographic studies identify and stage hip disease.
• Acetabular cysts, in the absence of advanced degenerative joint disease, have no significance in joint pathophysiology.
• Hip arthroscopy can and should be done without distraction.
• Indications for hip arthroscopy are limited to labral lesions and calcified loose bodies.
• The outcome of arthroscopy for labral lesions is related to the size and pattern of the lesion.

For many years patients presenting with disabling hip symptoms with non-specific x-ray and bone scan findings were assumed to have groin strains or synovitis, both of which would resolve.  For those with unremitting pain, surgeons were reluctant to perform arthrotomy because of the risk of infection, blood clots, and osteonecrosis.  Thus many labral, chondral, and synovial injuries went unnoticed.  The advent of arthroscopic hip surgery required development of distraction techniques and specialized tools and their successful application has led to the recognition of numerous hip lesions, heretofore, undiagnosed.

The optimal imaging modality for diagnosing intraarticular hip pathology continues to be debated.   In this study, we have compared MR arthrography results with hip arthroscopy findings to better define the diagnostic value of this imaging technique in evaluating acetabular labral tears and concurrent articular hip pathology.

One hundred and one consecutive patients (102 hips) with a mean age of 37.6 years (range, 16-64) were evaluated for persistent hip pain with history and examination findings suggestive of acetabular labral pathology.  All patients failed nonoperative treatment, were assessed with MR arthrography and underwent subsequent hip arthroscopy.  MR arthrograms and hip arthroscopy findings were assessed. 

MR arthrography detected 71 (76 percent) of 93 acetabular labral tears, yet failed to detect 22 tears (24 percent). Five hips (4.9 percent) had a false positive study for labral tear.  Articular findings diagnosed by MR arthrography were confirmed by arthroscopy in 64 cases (62.7 percent).   However, MR arthrography failed to identify major articular defects in 9 patients (8.8 percent) and minor articular defects (focal cartilage defects smaller than 1 cm diameter or Grade 1-2 chondromalacia) in an additional 23 patients (22.5 percent).  In comparison with findings at arthroscopy for labral pathology, MR arthrography had a sensitivity of 71 percent, positive predictive value of 93 percent, negative predictive value of 13 percent and accuracy of 69 percent.   With respect to articular cartilage pathology, MR arthrography had a sensitivity of 47 percent, specificity of 89 percent, positive predictive value of 84 percent, negative predictive value of 59 percent and accuracy of 67 percent.

We conclude that MR arthrography is an excellent positive predictor in diagnosing acetabular labral tears and articular cartilage abnormalities, but has limited sensitivity. A negative imaging study does not exclude significant intraarticular hip pathology that can be identified and treated arthroscopically.

Primary or idiopathic arthritis remains the most common cause of hip arthritis.  There is increasing evidence that all idiopathic hip arthritis may be secondary to subtle, previously underestimated or unrecognized femoral or acetabular pathology.  This study looks at the relationship between anterior hip impingement, from a pistol grip deformity, and hip disease.  This study clearly establishes that anterior hip impingement, secondary to an anterior femoral offset deficiency from a pistol-grip deformity, is a common and poorly recognized cause of hip disease manifested by a spectrum of hip disease ranging from anterior hip pain, labral tears, damage to the acetabular articular cartilage and idiopathic arthritis.  Hip impingement secondary to a pistol-grip deformity was felt to be the underlying etiology in 97% of the patients undergoing arthroscopy for a labral tear and 100% of the patients diagnosed with “idiopathic” osteoarthritis.  The identification of anterior hip impingement as a cause of labral tears and idiopathic arthritis may allow surgeons to correct it early in its natural history and delay or prevent end-stage arthritis.

Surgical debridement of the adult hip, including full dislocation as necessary, can be safely performed without causing osteonecrosis of the femoral head.  The primary indication is for the relief of femoro-acetabular impingement due to abnormalities of femoral or acetabular development.  Femoral deformities causing impingement include pistol grip and “slip-like” configurations with poor anterior head-neck offset and/or posterior tilting of the femoral head.  Femoral sources of impingement can be relieved by debriding the aspherical peripheral portion of the femoral head and the adjacent femoral neck.  Acetabular deformities causing impingement usually consist of relative acetabular retroversion and excessive anterior coverage.  The acetabular causes of impingement can be relieved by debridement of the anterior rim.

Full surgical dislocation can be achieved using a trochanteric slide/peripheral capsulotomy exposure.  Using this technique, the greater trochanter, medius, minimus, and capsular iliacus can be mobilized anteriorly while leaving the capsule and short external rotators intact.  The capsule can be incised along the acetabular rim and along the psoas sheath to allow full anterior dislocation of the hip while preserving the vascular supply to the femoral head.  Debridement of the periphery of the femoral head and/or acetabulum can be performed to relieve the impingment.  More discretely localized impingement can be addressed with less extensive exposures including the limited iliofemoral exposure and the modified direct lateral/peripheral capsulotomy exposure.  Less extensive bony debridement can be performed arthroscopically.

In the current study, 21 hips treated by debridement for impingement were followed from 2 to more than 10 years.  20 were treated by full surgical dislocation and one was treated by relief of impingement without dislocation.  Diagnoses included primary femoro-acetabular impingement in 10, prior trauma in 5,  a combination of dysplasia and impingement in 4, SCFE in 1, and LCPD in 1.  In addition to surgical dislocation and debridement, 3 hips were treated by intertrochanteric osteotomy and 2 hips were treated by periacetabular osteotomy. 

Ten of the hips were in females and 11 were in males.  Patients had a mean age of 34.6 +/- 8.6 years (range, 17.3-54.0 years).  Mean follow-up was 6.0 +/- 2.8 years (range, 2.2 to 11.1 years). 15 have had no further surgery and 6 have been converted to total hip arthroplasty.   Two of the failures had both impingement and instability and only the impingement was treated. One had arthrosis that was simply too advanced.  Three had an extended period of good function and then were converted to THR at 6 years 5 months, 9 years 1 month, and 10 years 6 months from surgery.  None developed osteonecrosis. 

The current study demonstrates that hips affected by primary or secondary femoro-acetabular impingement can be effectively treated by surgical relief of the impingement.  Indications and contraindications have become clearer over the past decade.  Hips at greatest risk of failure have advanced arthrosis or a combination of impingement and instability preoperatively. 

Acetabular osteotomy is the treatment of choice for young patients with symptomatic structural acetabular abnormalities in the absence of severe secondary degenerative changes.  These disorders can include hip instability from classic developmental dysplasia or post-traumatic acetabular dysplasia, hip impingement from retrotorsional acetabular deformities, or rarely post-traumatic problems.  Over the last fifteen years, various techniques of acetabular reorientation have evolved making the procedure reliable, reproducible and durable.  This paper will discuss the present indications and results of acetabular osteotomy in patients with symptomatic acetabular structural problems.

The purpose of this study was to determine the indications for revision hip surgery in a consecutive series of patients.  We retrospectively reviewed the clinical records and radiographs of 439 revision hip surgeries performed between 1996 and 2003.  55% of the surgeries were for aseptic loosening, 14% for instability, 13% for osteolysis around a well-fixed implant, 7% for infection, 5% for periprosthetic fracture, 3% for conversion of a hemiarthroplasty, 1% for psoas impingement, 1% for loose recalled implants, and 1% for implant fracture.  As expected, aseptic loosening was the most common reason for revision surgery.  Instability was a common reason for early revision while revision for osteolysis around a well-fixed implant was a more common reason for late revision.

Methods: Fourteen hemipelves containing cementless modular acetabular components with localized periacetabular bone loss of unknown cause were selected from the autopsy retrieval program of the senior author’s institution. All hemipelves had been retrieved from individuals with well-functioning total hip arthroplasties. All acetabular components were porous-coated and had been implanted by the senior author. Bone defects were identified on CT of the retrieved specimens after orientation markers had been inserted. Each specimen was embedded and cut into thin slices in the coronal plane of the pelvis. Slab radiographs were made of each slice and analyzed to identify any bony lesions. All bony lesions were graded according to the presence or absence of four criteria: trabecular bone, sclerotic border, joint space communication, and cortical erosion. Each lesion was in turn examined histologically to confirm the presence or absence of osteolysis.

Results: Twenty “osteolytic” lesions were identified in nine hemipelves that had no pre-existing bony lesions on pre-operative radiographs. All twenty lesions (100%) had absence of trabecular bone, eighteen (90%) had a sclerotic border, seventeen (85%) had clear communication with the joint space, and ten (50%) had cortical erosion. Five “cystic” lesions were identified in five hemipelves that had pre-existing cysts or relative areas of osteopenia on pre-operative radiographs. All five lesions (100%) had absence of trabecular bone, two (40%) had a sclerotic border, one (20%) had communication with the joint space, and one (20%) had cortical erosion.

Conclusion: Autopsy retrieval studies provide unique information to researchers and clinicians regarding patterns of bone loss and remodeling around retrieved components. Periacetabular osteolytic lesions are observed frequently and can be characterized as areas devoid of trabecular bone with a sclerotic border and communication with the joint space.

Managing large segmental acetabular defects that comprise greater than 50% of the acetabulum, is one of the most difficult challenges in revision arthroplasty of the hip.  One of the surgical options is a structural acetabular allograft.  Unless these allografts are protected by a cage that extends from ilium to ischium, there is an unacceptable incidence of graft fracture, non-union, resorption and cup failure.

The cage has certain advantages.  It allows reconstruction at the correct anatomic level.  It provides a scaffold for bone grafting (structural and morsellized).  The cage is a cementless device because the cement that is used to stabilize the cup in the cage makes contact primarily with the cage and to the surface of the bone graft, but not against host bone.  The use of cement to stabilize the cup allows the surgeon to adjust the cup position independent of the cage, and also to deliver local antibiotics.  A constrained cup can be used with a cage.

The cage has certain disadvantages.  The present generation of cages do not provide biological fixation and therefore with time may loosen or fracture.  If the bone graft has united and remodelled by the time the cage fails, the re-revision can be carried out with an uncemented cup, (made of trabecular metal if necessary).  The cage must be well supported by bone or it will fail early.

Our results with large structural allografts protected by a cage will be presented.  At an average follow-up of five years in a series of 61 cases, there were fractured flanges in 5 cases and loosening of the cage in 3.  Defining success as a stable reconstruction with no further revision of the acetabular component and incorporation of the acetabular bone graft, the success rate was 42 of 55 or 76%.  Another 4 cases had revision of the cup only for recurrent dislocation bringing the success rate for the cage and bone graft to 84%.

The next generation of cages will be made of a material that allows biological fixation.  We have had recent experience in combining a trabecular metal cup with a cage (cup-cage).  The trabecular metal cup provides a better environment for bone graft union and remodelling, and the cage protects the trabecular metal cup until biological fixation occurs.  A composite trabecular metal cup and cage is being designed.

Most revision acetabular procedures can be performed with an uncemented hemispherical acetabular device. Cases requiring alternative treatment options typically include those with insufficient host bone coverage. Options include bipolar hemiarthroplasty, acetabular impaction bone grafting techniques, acetabular reconstruction cages, bilobed acetabular components, and custom triflanged acetabular components. An approach using modular porous metal augments combined with an uncemented cup has been developed to simultaneously achieve biologic fixation and provide cup coverage.

Between Sept 2000 and Dec 2001, modular acetabular augments were implanted in 16 patients in whom it was deemed necessary to provide support for the use of an uncemented hemispherical acetabular component during revision acetabular reconstruction. These patients included 12 women and four men whose mean age at the time of the revision procedure was 64.6 years (range, 34 to 86 years). According to the Paprosky acetabular bone loss classification, there were 1-2A, 3-2B, 1-2C, 5-3A, 5-3B, and 1-3C defects. The patients had had an average of 2.8 previous operations. The primary indication for acetabular revision operation was aseptic loosening of a hemispherical acetabular component in 11, mechanical failure of a cage in 2, one aseptic loosening of a bilobed acetabular component, one failed endoprosthesis, and one infected tripolar arthroplasty. Patients were followed up a mean of 31.5 months (range 24-39 months) after surgery. No patients were lost to follow-up.

The preoperative hip center location radiographs improved from an average horizontal distance of 18.6 mm (range, -3 to 46 mm) to an average horizontal distance of 10.4 mm (range, 1 to 25 mm) postoperatively. Preoperatively, the vertical hip center averaged 27.6 mm (range, -16 to 52 mm) as compared with an average vertical distance of 7.4 mm (range, -15 to 25 mm) postoperatively. The diameters of the hemispherical shells ranged from 52 mm to 70 mm (mean 59 mm). The median augment size was 15.6 mm (range, 10 to 30 mm) and the average number of augments used was 1.2 (range, 1 to 2 augments). No bulk structural acetabular bone grafts were used. Particulate bone grafting was used in all sixteen hips to fill remaining cavitary bone deficiencies and fenestrations inside the acetabular augments.

Three patients had partial progressive radiolucent lines, measuring less than one millimeter at the latest follow-up, one in zone I around the modular augment, one in zone II around an augment and the third in zone III around the acetabular shell. None of the other cups or augments had radiolucent lines. None of the implants migrated. One patient underwent revision surgery for persistent pelvic discontinuity 15 months after the index revision. Three patients had a postoperative dislocation, and one patient had a postoperative partial sciatic palsy. There were no infections.

The use of these acetabular augments with a cup achieves the goals of cementless acetabular fixation and has facilitated adjustment of the hip center without the use of structural allografts in difficult revision acetabular procedures that precluded the routine use of a cementless hemispherical cup. At early clinical follow-up, this modular acetabular system appears to be a new and useful resource for acetabular reconstruction with severe bone loss.

Difficulty persists in consistently managing massive acetabular defects in revision total hip arthroplasty.  A relatively new treatment option for these complex cases is a custom triflanged acetabular component (CTAC) created from anatomic data derived from a CT scan of the pelvis.  The CTAC achieves fixation on the remaining ilium, ischium and pubis with multiple fixation screws while the acetabular defect is filled with cancellous allograft bone.  A retrospective review of 26 cases with massive periacetabular bone loss (Paprosky type 3B) reconstructed with a CTAC was performed.  Twenty-three of 26 cases (88.5%) were considered clinically successful at short-term follow-up (average 54 months, maximum 85 months), with stable fixation and reconstruction of periacetabular bone.  Three failures occurred from loss of ischial fixation in two patients with a preoperative pelvic discontinuity and one with severe osteopenia.  Presently, these devices should be used with caution in cases with a preoperative pelvic discontinuity, unless additional column plating is performed.

One option for dealing with significant femoral bone deficiency at revision surgery is the use of extensively porous coated cylindrical stems. Review of results at the Anderson Orthopedic Research Institute and from other centers has shown this to be a reliable, technically straightforward technique, which can be applied to all but the most severe femoral structural defects. Very high rates of osseointegration and durability of fixation are obtained when simple principles are followed. Survivorship with loosening or revision as the endpoint has been 93.8% or better overall. The key to success is obtaining initial endosteal diaphyseal fixation over 4-5 cm. To achieve this, adequate exposure and accurate bone preparation are essential.

 The limitations of this technique relate directly to the severity of bone loss, which can be easily predicted on plain preoperative radiographs. For Paprosky 3B and 4 defects, which by definition are deficiencies which disrupt the integrity of the diaphysis, other options such as allograft prosthetic composites, impaction grafting, or alternate modes of distal fixation should be considered.

Clinical results of revision total hip arthroplasty using fully porous-coated tapered titanium stems to treat severe proximal femoral bone loss were evaluated in a retrospective review of 39 patients (45 hips).  The bone was reinforced with cables in 39 hips, and in 14 hips strut allografts were added.  Fixation was successful in 44 hips, and one hip required revision to treat undetected fracture and migration of the stem.  Three patients (three hips) had mild thigh pain, but the others had no pain related to the femoral component.  Eight hips dislocated; one resolved and seven had recurrent dislocation that was treated with a constrained acetabular component, capsulorrhaphy, or liner reorientation.  Ten patients (12 hips) used a walker and 10 patients (12 hips) used a cane at the last postoperative visit.  Whereas fixation was successful with this surgical technique, complications related to deficiency of the soft tissue structures were common.

Significant femoral bone loss can be encountered in the multiply revised patient.  Deficient proximal bone requires either a bulk allograft or a femoral component that allows stable distal fixation.  Extensively coated stems have shown excellent results for many revisions, but have shown higher rates of failure among patients with femoral remodeling in retroversion, an enlarged endosteal diameter or an ecstatic canal.  A modular tapered implant provides axial and rotational stability through the use of distal splines while the proximal body segments can allow independent adjustment of leg length, offset and anteversion.

Introduction:  Recently there has been increased interest in THA via small incisions.  One such technique is the two-incision approach, initially developed by Dana Mears’ group. Zimmer (Warsaw, IN) oversaw further development and refinement of the procedure based on surgeon suggestions and the results of a multi-center IRB approved pilot study.  Zimmer then developed a training program for surgeons interested in performing the MIS™ Two-Incision™ Hip Procedure.  An “index case” study was then initiated and included 89 surgeons who completed such training and reported on their first 10 two-incision hip replacements.  The purpose of this report is to present the data available from this index case study regarding the process of developing fluency with the two-incision minimally invasive total hip replacement. 

Methods:  Eighty-nine surgeons underwent corporate-sponsored training in the techniques and instrumentation needed to perform two-incision, minimally invasive total hip replacement.  All surgeons were required to report surgical details and perioperative complications to the company on their first 10 two-incision hip replacements.  Between October 2002 and September 2003 the initial 89 surgeons reported on 423 procedures.  For each case, the operative surgeon reported patient demographics, intra-operative data, and complications. 

Results:  Of these 423 patients were 48% females, 52% males.  The mean age was 60 years and the mean weight was 170 pounds.  Mean operative time decreased from a mean of 160.6 minutes for the first case to 126.7 min. for the tenth case (p<0.05).  Fluoroscopy time decreased from a mean of 146 seconds during the first case to 71 seconds during the tenth case (p<0.05).  Complication rates for the total 423 cases included a 6.7% risk of intraoperative femoral fracture (calcar (4.7%), trochanter (1.4%) and femoral shaft fracture (0.5%)), a 1.4% incidence of nerve injury, a 1.2% incidence of superficial and deep infection, and a 0.2% dislocation rate at early follow up.  There were 4 early revisions (0.9%) (one for instability, one for infection, one for femoral fracture, and one for fracture with stem subsidence).  We found no significant change in the incidence of key complications (fractures, dislocations, and nerve injuries) as a function of case number one through ten or surgeon volume.

Discussion:  The purpose of this report is to present the data available to date regarding the process of developing fluency with the two-incision minimally invasive total hip replacement.  We found a significant decrease in the mean operative time and fluoroscopy time from the first to tenth case.   Key complications did not decrease as a function of case number for the first ten cases.  Clarification of the entire learning curve for this technique requires further investigation but appears to last beyond case ten for most surgeons.  The evolution of minimally invasive joint replacement is clearly in its infancy.  These complications and the demonstrated learning curve will be altered by changes in the training and surgical technique as it is refined.  These changes will most certainly involve technology that will result in a reduced requirement for direct visual feedback such as computer-assisted surgery.

The adoption of minimally invasive surgical techniques in total joint arthroplasty has made postoperative patient management and rehabilitation protocols among the major limiting factors to a more rapid patient recovery.  To assess the potential recovery rate of total hip arthroplasty using a minimally invasive approach, an accelerated rehabilitation protocol was developed which encouraged rapid return to all activities.  This accelerated rehabilitation protocol was implemented along with a minimally invasive total hip replacement technique in which no muscle or tendon is violated.  Both patients and physical therapists were encouraged to advance to normal activity as quickly as possible.  One hundred consecutive patients who met criteria for enrollment in this IRB approved, prospective study were followed for 3 months. No patient was lost to follow-up. This protocol included the use of oral analgesics and ambulation with weight bearing as tolerated on the day of surgery.  Ninety-seven patients (97%) met all the inpatient physical therapy goals required for discharge to home on the day of surgery; 100% of patients achieved these goals within 23 hours of surgery. Nine patients started outpatient physical therapy immediately; the remainder initially started home physical therapy. Outpatient physical therapy was initiated in 62% of patients by one week postoperatively and the remainder by two weeks. The mean time to discontinue the use of crutches, discontinue narcotic pain medications and start driving was 6 day postoperatively. The mean time to return to work was 8 days, the mean time to discontinue the use of any assist device was 9 days, and the mean time to resumption of all activities of daily living was 10 days.  Finally the mean time to walk 1/2 mile was 16 days. There have been no readmissions, no dislocations, and no reoperations.  This study demonstrates that a rapid rehabilitation protocol used in conjunction with a minimally invasive surgical technique is safe and fulfills the potential benefits of a rapid recovery with minimally invasive total hip arthroplasty.

1.        Less morbidity, faster rehabilitation, reduced length of stay, patient satisfaction

2.        Must not compromise arthroplasty

1.        Arthroplasty experience, patient selection, customized instrumentation, experienced  assistant/s

2.        Thin patient, monoblock socket, epidural hypotensive anesthesia

1.        Severely obese patients, heavy muscular patients, complex revision surgery

1.        Standard posterolateral incision

2.        Posterior trapezoidal capsulotomy

3.        Custom acetabular retractors for exposure

4.        Anterior capsular release

5.        Femoral retractor to elevate femur

6.        Capsular repair through trochanter

1.        Group 1 22 patients: 8 cm incision

2.        Group 2 24 patients: 15 cm incision

3.        Demographics similar for two groups

4.        BMI 25.2

5.        Significantly reduced blood loss in Group I

6.        More rapid rehabilitation in Group I

7.        Radiographic evaluation  Group I

a.        Abduction angle 36.4 degrees

b.       Cement Grade: 93% A or B

1.        Average follow-up 2.8 years (1-5.4)

2.        Average skin incision: 8.2 cm (6-10cm)

3.        Radiographic Evaluation

a.        Lateral abduction angle:  42.4 degrees (28-59)

b.       Cement Grade (Barrack): 95% A or B

c.        Femoral alignment: 93% neutral

4.        Dislocation: 4

5.        Femoral Fracture: 1

6.        Neuropraxia: 2

a.        Must reduce posterior retraction

b.       Extend incision in excessive posterior retraction

c.        Release quadratus, gluteus maximus tendon if needed

d.       Hip extension whenever possible

7.        Wound complications

a.        Hematoma 2

b.       Infection 0

Minimally invasive total hip replacement seeks to eliminate some of the complications of traditional extensile exposure and also attempts to facilitate more rapid rehabilitation of patients after surgery.  Different surgical approaches have been historically used to perform hip replacement surgery.  Anterior or antero-lateral approaches have often been selected to decrease the risk of posterior dislocation.  Traditional antero-lateral approaches have divided the anterior portion of the gluteus medius and minimus and potentially jeopardized the superior gluteal nerve.  These disadvantages have been associated with abductor weakness, prolonged limp and decreased patient satisfaction.  To overcome these problems a new minimally invasive approach was developed, using the intermuscular plane between the gluteus medius and the tensor fascia lata.  This intermuscular interval through a small incision provides good exposure for total hip replacement and preserves muscle integrity so that rehabilitation can be rapid and the posterior capsule remains intact so that posterior dislocation is less of an issue.  The surgical technique for this new innovative approach is described in this article.