The key recognition of FAI is that even minor abnormalities of the proximal end of the femur but also  abnormal orientation and depth  of the acetabulum can become difficult for motion and may lead to impingement within the well constraint hip joint ¹. Internal rotation in flexion is the most critical movement. G.Preiser speculated already in 1911 about reduced internal rotation and later development of osteoarthritis ², however the impingement concept was only formulated  a decade ago ³. High speed movement is more destructive than impingement with slow motion.

Morphological abnormalities are not necessarily visible on standard ap-radiographs of  the hip and pelvis. Lateral views more often reveal a nonspherical extension of the antero-lateral head contour. Although a silent slip produces a similar impingement with its prominent metaphysis, the majority of such nonspherical extensions is covered with hyaline cartilage and therefore part of the epiphysis ⁴. The abutment from femoral causes ( idiopathic, SCFE, posttraumatic retrotilt of the head, head deformation from Perthes disease or AVN) is called cam impingement. The out of round sector of the head or the head-neck junction is jammed into the socket and leads to  outside-in abrasion or even avulsion of the joint  cartilage, while the labrum in the first instance remains intact. With time  middle section and  basis of the disconnected labrum degenerate, while the tip region continues to keeps its normal texture over a long period ⁵, allowing its use for  refixation ⁶. Successful refixation has been proven repeatedly by MR arthrography and by arthroscopy. The cartilage covering the spherical part of the femoral head remains intact over a long time, while the cartilage of the nonsperical zone shows increasing signs of damage. The area of maximum impingement is in about 30% of the more chronic cases characterized by an impingement cyst ⁷, which often has been erroneously  interpreted as osteoid osteoma.

Impingement from acetabular causes ( idiopathic and other retroversion, coxa profunda , protrusio) is called pincer impingement .Idiopathic retroversion is less an acetabular and more a pelvic pathomorphology ^8,9. Pincer impingement is  produced by a linear impact between the head-neck junction and the area of overcoverage of the acetabular rim. The squeezing of the labrum and the fact that the labrum contains nerve endings ¹⁰ ,  may explain why  this, mainly female type of impingement, is  clearly more painful than the cam impingement. With chronic impingement  the labrum shows degeneration and  intrasubstance ganglion formation .The chronic mechanical irritation initiates bony rim apposition , which by continuous growing, leads to expansion and  thinning of the overlying labrum until the involved sector shows a complete bony rim; as such it increases the overcoverage and therefore the impingement. The bony rim is rarely the result of an intra substance ossification of the labrum. Although more painful, pincer impingement  leads to less and slower destruction of the joint cartilage , ending rather late in the full picture of  typical posteromedial osteoarthritis of the hip.

1.        Ganz R, Leunig M, Leunig-Ganz K, Harris WH: The etiology of osteoarthritis of the hip. An integrated mechanical concept.  Clin Orthop Relat Res. in press

2.        Preiser G.: Statische Gelenkerkrankungen. Enke, Stuttgart 1911,p.78

3.        Ganz R, Parvizi J, Beck M, Leunig M, Nötzli H, Siebenrock KA: Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003; 417: 112-120.

4.        Wagner S, Hofstetter W, Chiquet M, Mainil-Varlet P, Stauffer E, Ganz R, Siebenrock KA: Early osteoarthritic changes of human femoral head  cartilage subsequent to Femoroacetabular impingement. Osteoarthritis Cartilage. 2003; 11: 508-518.

5.        Ito K, Leunig M, Ganz R: Histopathologic features of the acetabular labrum in femoroacetabular impingement. Clin Orthop Relat Res. 2004;429:262-271

6.        Espinosa N, Rothenfluh DA, Beck M, Ganz R, Leunig M: Treatment of femoro-acetabular impingement: Preliminary results of labral refixation. J Bone Joint Surg Am. 2006; 88:925-935.

7.        Leunig M, Beck M, Kalhor M, Kim YJ, Werlen S, Ganz R: Fibrocystic changes at anterosuperior femoral neck: Prevalence in hips with femoroacetabular impingement. Radiology. 2005; 236: 237-246

8.        Jamali AA, Mladenov K, Meyer DC,Martinez A, Beck M, Ganz R, Leunig M: Antero-posterior pelvic radiographs to assess acetabular retroversion: High validity of the „ cross-over-sign“. ; JOR  2007; DOI 10.1002/jor. 20380

9.        Kalberer F, Sierra RJ, Madan SS, Ganz R, Leunig M: Ischial spine projection into the pelvis. A new sign for acetabular retroversion. Clin Orthop Relat Res 2007; DOI 10.1007/ s 11999-007-0058-6

10.     Kim YT,Azuma H: The nerve endings of the acetabular labrum. Clin Orthop Relat Res. 1995; 320: 176-181

Discuss the rationale, patient selection criteria, and surgical techniques of hip arthroscopy and limited open osteochondroplasty for the treatment of anterior femoroacetabular impingement disorders.

Structural hip disease is recognized as a cause of early hip dysfunction, articular degeneration and eventual secondary osteoarthritis. With heightened awareness of femoroacetabular impingement disorders, early diagnosis and joint preservation surgical treatment is becoming more commonplace. Various surgical techniques have evolved for the treatment of femoroacetabular impingement, and include periacetabular osteotomy, surgical hip dislocation, arthroscopy with limited open osteochondroplasty and arthroscopic techniques alone. Surgical treatment is focused upon comprehensive deformity correction and concurrent management of intraarticular disease. The optimal surgical technique may vary depending upon the distinct pattern of impingement disease and the expertise and technical preferences of the surgeon. In this presentation, the rationale, patient selection criteria, and surgical techniques of hip arthroscopy and limited anterior exposure for the treatment of femoroacetabular impingement will be discussed.

-          femoral deformities (aspherical femoral head, reduced head-neck offset) as the  major source of repetitive impingement

-          acetabular deformities- overcoverage due to retroversion, profunda, protrusio

-          articular cartilage delamination/chondromalacia

-          labral tear/detachment

-          posterior articular disease/osteophyte

-          progressive secondary OA

Indications

- symptomatic AFI, patients < 55 years (physiologic)

- focal disease patterns best candidates for less-invasive techniques

- no or mild secondary OA (Tonnis I)

Contraindications

- age > 55 years (physiologic)

- advanced DJD

- circumferential or complex disease patterns (relative contraindication)

- severe obesity

- disease pattern better suited for open procedure (surgeon dependent)

- understand the osseous deformities and associated intraarticular disease

- plan osseous and soft tissue aspects of the procedure

- know limitations of the different surgical techniques

                - supine or lateral position, traction to access joint

                - anterior, anterolateral, posterolateral, and accessory portals

                - labrum, acetabular articular cartilage, synovitis, counter lesion

- partial labral resection leaving stable labral remnant or labral repair if healthy tissue

- partial synovectomy

                - chondroplasty/microfracture as needed

-acetabular rim trimming or femoral osteochondroplasty if scope only technique

                - limited Smith-Peterson/Heuter interval

                - incision straight distal from ASIS or translate 2-3cm lateral

                - develop TFL/Sartorius interval

                - rectus release optional (commonly release reflected head)

                - expose anterior hip capsule

-capsulotomy and inspection of femoral head-neck junction and acetabular rim

- osteochondroplasty with anteromedial head-neck junction, articular cartilage discoloration and “trough” at head or head-neck junction as “guides” to resection

- after initial resection assess impingement with visualization, palpation in flexion/internal rotation

- also assess fluoroscopically (“frog lateral”/Dunn views helpful to visualize anterolateral head-neck junction”)

- capsular closure

Advantages

                - precise (arthroscopic) management of intraarticular disease

                - joint assessment prior to open procedure

-excellent visualization of anterolateral head-neck junction for recontouring

- capsular closure (not resection)

                - technically straightforward

- technically time efficient

- less invasive than surgical dislocation (avoid troch osteotomy/dislocation)

- technically feasible for suboptimal candidates (obese, DJD, muscular)

- surgeon “learns” the disease characteristics

- “bridge” from open to arthroscopic treatment

- early clinical results favorable

Disadvantages

- access limited to anterolateral head-neck junction

- most appropriate for cam impingement

- acetabular rim osteoplasty technically difficult

- LFC nerve at risk

-inadequate for severe/complex deformities,

- early clinical follow-up only

- more “invasive” than arthroscopic techniques

1.        Beck M, Leunig M, Parvizi J, Boutier V, Wyss D, Ganz R.  Anterior femoroacetabular   impingement: part II.  Midterm results of surgical treatment.  Clin Orthop Relat Res  2004 (418):67-73.

2.        Burnett RS, Della Rocca GJ, Prather H, Curry M, Maloney WJ, Clohisy JC. Clinical presentation of patients with tears of the acetabular labrum. J Bone Joint Surg Am 2006;88(7):1448-57.

3.        Clohisy JC, Keeney JA, Schoenecker PL.  Preliminary assessment and treatment guidelines for hip disorders in young adults.  Clin Orthop Relat Res 2005;441:168-79.

4.        Clohisy JC, McClure JT.  Treatment of anterior femoroacetabular impingement with  combined hip arthroscopy and limited anterior decompression.  Iowa Orthop J  2005:25:164-71.

5.        Clohisy JC, Zebala L, Hinkle S, McClure T, Robison JF. Combined Hip Arthroscopy and Limited Open Osteochondroplasty for Treating Impingement Disease. Annual Meeting of the American Academy of Orthopaedic Surgeons, San Diego, CA, February, 2007.

6.        Ganz R, Gill TJ, Gautier E, Ganz K, Krugel N, Berlemann U.  Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis.  J Bone Joint Surg Br 2001;83(8):1119-24.

7.        Ganz R, Parvizi J, Beck M, Leunig M, Notzli H, Siebenrock KA. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res  2003(417):112-20

8.        Guanche CA, Bare AA.  Arthroscopic treatment of femoroacetabular impingement.  Arthroscopy 2006;22(1):95-106.

9.        Lavigne M, Parvizi J, Beck M, Siebenrock KA, Ganz R, Leunig M.  Anterior Femoroacetabular impingement: part I.  Techniques of joint preserving surgery.  Clin  Orthop Relat Res 2004(418):61-6.

10.     McCarthy JC, Noble PC, Schuck MR, Wright J, Lee J. The Otto E. Aufranc Award:The role of labral lesions to development of early degenerative hip disease. Clin Orthop Relat Res 2001(393):25-37.

11.     Philippon MJ, et al. Arthroscopic Management of Femoroacetabular Impingement AJSM, 2007.

Femoro-acetabular impingement (FAI) has been shown to cause labral and/or articular cartilage damage and ultimately lead to osteoarthritis of the hip.  Surgical treatment of FAI is directed at alleviating femoral abutment against the acetabular rim with improvement of head-neck offset or acetabular rim resection.  Labrum and articular cartilage lesions can be addressed with repair and/or resection. Surgical dislocation and osteochondroplasty (SDO) has proven to be a safe and effective approach to accomplish treatment of lesions associated with FAI.

SDO is performed utilizing a lateral incision with greater trochanteric flip osteotomy with the patient in the lateral position.  A Z-shaped anterior capsulotomy is performed and the femoral head is dislocated anteriorly.  The femoral head-neck area is assessed for reduction in femoral head-neck offset and articular cartilage damage. Loss of the normal concave transition between the normally spherical femoral articular surface and the more elliptical femoral neck, with chondro-osseous overgrowth, is debrided with a chisel, osteotome and high-speed rotating burr. 

Full exposure of the acetabulum allows an assessment of labral and articular cartilage damage.  Delaminated or damaged articular cartilage subjacent to a normal capsular labral margin is frequently encountered.  Damaged articular cartilage is addressed with resection and labral advancement. Isolated or combined labral lesions or ossified labrum can be treated with repair or resection.

The approach is utilitarian and can be used for relative femoral neck lengthening, femoral neck osteotomy, treatment of femoral head fracture, osteonecrosis, and resurfacing.

From 2001-2007 95 surgical dislocations were performed for a variety of indications.  Of 80 hips performed for treatment of FAI (average age 28, range 15-50), 75 have survived at average follow-up of 2.5 years.  The average surgical time was 105 minutes (range 65-150), average EBL was 344 cc, and average hospital stay was 2 days (range 1-3 days).  The average time to unsupported ambulation was 6 weeks.  The Harris hip score improved from 70 to 87 post-operatively.  There have been no major perioperative complications or trochanteric nonunions.  We continue to utilize this approach commonly for the treatment of young adults with hip pain due to FAI and other conditions.

Retroversion of the acetabulum is defined in reference to the sagittal plane as a posterolaterally directed opening at its proximal extent.¹⁶ It has been described in hip dysplasia,^{6,10,12-14,16} other childhood hip disorders,^4-6,22 post-traumatic deformity,³ and in otherwise normal appearing hips.^16,17 Since first being described by Tönnis in 1984¹,  it has been increasingly recognized as a cause of hip pain on the basis of femoro-acetabular impingement (FAI) and has been linked to osteoarthritis of the hip.^{2,6-8,11,16,18}  It has also been linked to acetabular labral tears as part of the spectrum of FAI.^7,9,21  The anatomic variation in cases of acetabular retroversion fall along a spectrum and this has caused some confusion in the literature.²⁰ The analysis of retroversion on a single AP radiograph of the pelvis is subject to the influences of rotation and lordosis of the pelvis on the relative positions of the anterior and posterior acetabular margins. It has not been scientifically established that all retroverted hips are posterolaterally deficient. Some retroverted hips have adequate posterolateral femoral head coverage while others are deficient posterolaterally.¹⁷  Torsion and deficiency are separate considerations. Every case is unique and treatment must be individualized according to the anatomy.  Redirectional acetabular osteotomy is more likely to benefit those patients with associated lateral coverage deficiency dysplasia. Rim trimming procedures are better for otherwise normal hips that happen to be retroverted or hips with coxa profunda or protrusio¹⁷.  Understanding the changes on the femoral side also weigh in on the surgical decision, as cam lesions may co-exist^15,17 as well as abnormalities in femoral version.^18,19 Both surgical dislocation for rim trimming and redirectional osteotomy are major surgical procedures and should not be undertaken without respect for the magnitude of the surgery, the length of recovery and the potential for complications.

1.        Banks, K. P., and Grayson, D. E.: Acetabular retroversion as a rare cause of chronic hip pain: recognition of the "figure-eight" sign. Skeletal Radiol, 36 Suppl 1: S108-11, 2007.

2.        Beck, M.; Kalhor, M.; Leunig, M.; and Ganz, R.: Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br, 87(7): 1012-8, 2005.

3.        Dora, C.; Zurbach, J.; Hersche, O.; and Ganz, R.: Pathomorphologic characteristics of posttraumatic acetabular dysplasia. J Orthop Trauma, 14(7): 483-9, 2000.

4.        Eijer, H.: Towards a better understanding of the aetiology of Legg-Calve-Perthes' disease: acetabular retroversion may cause abnormal loading of dorsal femoral head-neck junction with restricted blood supply to the femoral epiphysis. Med Hypotheses, 68(5): 995-7, 2007.

5.        Eijer, H.; Berg, R. P.; Haverkamp, D.; and Pecasse, G. A.: Hip deformity in symptomatic adult Perthes' disease. Acta Orthop Belg, 72(6): 683-92, 2006.

6.        Ezoe, M.; Naito, M.; and Inoue, T.: The prevalence of acetabular retroversion among various disorders of the hip. J Bone Joint Surg Am, 88(2): 372-9, 2006.

7.        Ganz, R.; Parvizi, J.; Beck, M.; Leunig, M.; Notzli, H.; and Siebenrock, K. A.: Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res, (417): 112­20, 2003.

8.        Giori, N. J., and Trousdale, R. T.: Acetabular retroversion is associated with osteoarthritis of the hip. Clin Orthop Relat Res, (417): 263-9, 2003.

9.        Guevara, C. J.; Pietrobon, R.; Carothers, J. T.; Olson, S. A.; and Vail, T. P.: Comprehensive morphologic evaluation of the hip in patients with symptomatic labral tear. Clin Orthop Relat Res, 453: 277-85, 2006.

10.      Kim, S. S.; Frick, S. L.; and Wenger, D. R.: Anteversion of the acetabulum in developmental dysplasia of the hip: analysis with computed tomography. J Pediatr Orthop, 19(4): 438-42, 1999.

11.      Kim, W. Y.; Hutchinson, C. E.; Andrew, J. G.; and Allen, P. D.: The relationship between acetabular retroversion and osteoarthritis of the hip. J Bone Joint Surg Br, 88(6): 727­9, 2006.

12.      Li, P. L., and Ganz, R.: Morphologic features of congenital acetabular dysplasia: one in six is retroverted. Clin Orthop Relat Res, (416): 245-53, 2003.

13.      Mast, J. W.; Brunner, R. L.; and Zebrack, J.: Recognizing acetabular version in the radiographic presentation of hip dysplasia. Clin Orthop Relat Res, (418): 48-53, 2004.

14.      Murphy, S. B.; Kijewski, P. K.; Millis, M. B.; and Harless, A.: Acetabular dysplasia in the adolescent and young adult. Clin Orthop Relat Res, (261): 214-23, 1990.

15.      Peters, C. L., and Erickson, J. A.: Treatment of femoroacetabular impingement with surgical dislocation and debridement in young adults. J Bone Joint Surg Am, 88(8): 1735-41, 2006.

16.      Reynolds, D.; Lucas, J.; and Klaue, K.: Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br, 81(2): 281-8, 1999.

17.      Siebenrock, K. A.; Schoeniger, R.; and Ganz, R.: Anterior femoroacetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am, 85-A(2): 278-86, 2003.

18.      Tonnis, D., and Heinecke, A.: Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am, 81(12): 1747-70, 1999.