Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

94. Treatment of Anterior Femoroacetabular Impingement Through an Anterior Incision

John C. Clohisy

DEFINITION

images Anterior femoroacetabular impingement encompasses a category of structural hip disorders that are characterized by abnormal abutment of the anterolateral femoral head–neck junction against the acetabular rim–labral complex.

images Repetitive anterolateral impingement produces acetabular articular cartilage delamination, labral disease, and, eventually, secondary osteoarthritis.

ANATOMY

images Understanding the pathoanatomy of hip impingement disorders is essential to establishing an accurate diagnosis and selecting an optimal surgical treatment strategy.

images Structural impingement disease can be primarily femoralbased (ie, “cam” impingement) or primarily acetabular-based (ie, “pincer” impingement) (FIG 1).2,12,17

images Combined cam and pincer impingement deformities are common,2 and are characterized by abnormal anatomy of both the proximal femur and the acetabulum.

images Deformities of the proximal femur that produce impingement disease include reduced femoral head–neck offset, an aspherical femoral head, slipped capital femoral epiphysis, Perthes abnormalities, and femoral neck malunion.

images The common impingement deformities on the acetabular side include acetabular retroversion, coxa profunda, and protrusio acetabulum.

PATHOGENESIS

images Impingement deformities of the proximal femur or acetabulum, or both, produce an abnormal mechanical environment that initiates and sustains hip joint degeneration.12,17,22

images Mechanical impingement is most pronounced with hip flexion alone or hip flexion and combined internal rotation.

images Recurrent impingement of the anterolateral femoral head–neck junction with the acetabular rim–labral complex initiates a detrimental cascade of biologic events.

images Osseous impingement leads variously to delamination of the articular cartilage of the acetabular rim, labral degeneration, posteroinferior acetabular articular disease (due to levering of the femoral head from anterior impingement), and anterolateral femoral head–neck junction chondral disease.

images This constellation of intra-articular disease worsens with time and is a common cause of secondary osteoarthritis.12,17,22

NATURAL HISTORY

images The natural history of anterior femoroacetabular impingement has not been clearly defined.

images Radiographic studies have demonstrated an association between structural impingement deformities and secondary osteoarthritis,1,15,22 but authentic natural history data are lacking.

images The consensus is that the prognosis of symptomatic impingement disorders is poor, and that these diseases commonly result in secondary osteoarthritis.

images Future natural history studies will add substantially to improved understanding of these disorders.

PATIENT HISTORY AND PHYSICAL FINDINGS

images Patients with anterior femoroacetabular impingement commonly present with activity-related anterior inguinal (groin) pain. Associated lateral and posterior hip pain are common.

images Symptoms are variable and may include a combination of aching pain with intermittent episodes of sharp or stabbing pain.

images

FIG 1  Patterns of anterior femoroacetabular impingement disease. The reduced clearance during joint motion leads to repetitive abutment between the proximal femur and the anterior acetabular rim. Cam impingement is caused by reduced femoral head and neck offset, pincer impingement by overcoverage of the femoral head by the acetabulum, and combined cam and pincer impingement by both reduced head and neck offset and excessive anterior overcoverage.

images Mechanical symptoms of locking and catching also may be problematic, presumably from labral disease or unstable articular cartilage flaps.4

images Difficulty with daily activities, including prolonged walking, prolonged sitting, raising from a seated position, and pivoting, is common.

images High-demand athletic activities, including running, cutting, pivoting, and repetitive hip flexion (eg, soccer), often exacerabate symptoms.

images Any history of hip trauma, childhood hip disease, previous surgeries, and previous treatments should be determined.

images The patient's age, activity level, and overall health, and the impact of hip dysfunction on his or her quality of life are obtained.

images Physical examination should include assessment of overall health, conditioning, and body habitus.

images Previous surgical scars are inspected to clarify the nature of previous procedures and to facilitate preoperative planning.

images Observation of sitting posture, gait, palpation of the hip, abductor strength testing, careful hip range of motion assessment, and specific provocative tests are performed.

images Anterior femoroacetabular impingement commonly elicits discomfort in an erect sitting position.

images A level pelvis in the single-legged stance is normal. Dropping of the contralateral hemipelvis indicates abductor weakness of the symptomatic hip. Abductor weakness is common in patients with early intra-articular hip disease and impingement.

images Hip flexion commonly is restricted to 100 degrees or less in impingement disorders. Internal rotation in flexion is frequently restricted to 0 to 10 degrees.

images The gait pattern over short distances and abductor strength usually are normal in early stages of disease.

images A limp and mild abductor weakness may develop as labral disease and joint degeneration progress.

images Hip range-of-motion testing should be performed carefully with stabilization of the pelvis to accurately define motion endpoints. Passive hip flexion motion and internal rotation at 90 degrees of flexion are restricted. Hip discomfort often is reproduced at the endpoints of passive motion.

images The anterior impingement test and Patrick's test are sensitive maneuvers to detect intrinsic hip disease and usually reproduce hip symptoms in patients with anterior femoroacetabular impingement.

IMAGING AND OTHER DIAGNOSTIC STUDIES

images Plain radiographs include a supine anteroposterior (AP) view of the pelvis, cross-table lateral view with the extremity in 15 degrees of internal rotation, and a frog-leg lateral view.9,18,20

images The structural parameters of the hip are assessed on all radiographic views.

images The acetabular inclination, femoral head coverage, and acetabular version (FIG 2C–E) are determined from the AP view of the pelvis. Joint space narrowing, periarticular cysts, and labral ossification also are noted.

images The lateral views are examined to assess femoral head sphericity and femoral head–neck offset.

images These projections best visualize the anterior and anterolateral femoral head–neck deformity that characterizes cam impingement disease.

images

FIG 2  Radiographic assessment of acetabular version. A. Drawing of an AP view of the hemipelvis showing a hip with normal version. Note the near parallel orientation of the anterior and posterior (dashed line) acetabular walls. There is no crossover, and the lines converge at the superolateral aspect of the acetabulum. B. Drawing of a hip with acetabular retroversion. The “crossover” sign, which has been previously described as an indicator of acetabular retroversion, is present. The anterior aspect of the acetabular rim projects lateral to the posterior aspect of the rim (dashed line) at the most proximal aspect of the acetabulum. C–E. Preoperative radiographs from a 19-year-old football player with left hip pain and cam impingement. C. In this case, the patient has relatively normal acetabular version, femoral head coverage, and acetabular inclination on AP view. D. On the frog-leg lateral view, an anterolateral prominence is noted at the femoral head–neck junction (arrow). E. On the cross-table lateral view, there is a mild decreased offset from the anterior aspect of the femoral head to the anterior aspect of the femoral neck (arrow). (A,B: Adapted from Espinosa N, et al. Treatment of femoro-acetabular impingement: preliminary results of labral fixation. J Bone Joint Surg Am 2006;88A:925–935.)

images An MR arthrogram (MRA) of the hip is obtained on all patients with suspected impingement and associated intraarticular disease.

images The contour of the femoral head–neck junction,16 labral disease, and associated articular cartilage disease are all inspected.

images The MRI also facilitates exclusion of other uncommon disorders, including stress fracture, osteonecrosis of the femoral head, neoplasm, and infection.

images CT scanning of the hip can be useful in identifying and characterizing the extent of osseous impingement lesions.

images The contour of the femoral head–neck junction and the extent of femoral-sided disease can be appreciated in detail.

images Version of the acetabulum and associated osseous abnormalities of the acetabular rim also can be assessed in detail.

images The CT scan complements other imaging modalities and can impact surgical decision making.

DIFFERENTIAL DIAGNOSIS

images Isolated intra-articular hip disease (eg, synovitis, labral tear, chondral disease, loose body) in the abscence of an impingement disorder4

images Mild hip dysplasia (joint instability)

images Extra-articular disorders (eg, lumbar spine disease, bursitis, inguinal hernia)

NONOPERATIVE MANAGEMENT

images Nonoperative management for the treatment of anterior femoroacetabular impingement has not been rigorously investigated or documented in the literature.

images Consensus is developing that hip impingement disease is common, and that definitive treatment should address the underlying pathomechanics of the joint.

images The benefit of nonoperative treatment has not been established for joints that are relatively healthy with no or mild degenerative changes.

images Activity restrictions, physical therapy, anti-inflammatory medicines, and intra-articular cortisone injections can be considered as potential nonoperative treatment options. Nevertheless, the efficacy of these treatment modalities over time has not been proven.

images Physical therapy should not emphasize improving hip range of motion and should avoid aggressive maneuvers to gain hip flexion and internal rotation motion, because these will irritate the hip.

images Anti-inflammatory medicines may reduce discomfort derived from labral disease and structural impingement.

images Activity restriction may alleviate symptoms in some patients. Athletes involved in repetitive hip flexion activities may experience significant relief of discomfort if they refrain from their sport.

images Patients with symptomatic femoroacetabular impingement who desire to maintain high activity levels often fail nonoperative management and desire surgical intervention.

images For patients with moderate to advanced degenerative disease, the nonoperative modalities listed can be considered as temporizing therapies before joint arthroplasty.

SURGICAL MANAGEMENT

images Surgical management of hip impingement disease continues to evolve, and various surgical techniques are now available for joint reconstruction,6 including surgical dislocation of the hip,11 combined hip arthroscopy and limited open decompression,7 and purely arthoscopic decompression techniques.14

images The fundamental goal of surgery, independent of the technique selected, is to address the structural impingement lesions and the associated intra-articular disease elements (eg, labrum, articular cartilage).

images We prefer surgical dislocation of the hip for cases with nonfocal impingement problems or severe deformities and for those cases requiring acetabular rim trimming with labral repair, eg, hips with a nonfocal femoral head deformity or circumferential pincer impingement.

images For hips with focal, cam-type anterior femoroacetabular impingement, the less-invasive surgical techniques may have distinct advantages. In such cases, we use hip arthroscopy to precisely address the intra-articular disease (eg, labrum, articular cartilage), followed by a limited open osteochondroplasty to correct the femoral-sided impingement deformity.

Preoperative Planning

images The patient history and physical examination findings are reviewed.

images All preoperative radiographs plus the MRA and CT scan (if obtained) are evaluated. The size and location of the impingement lesion or lesions is determined. The status of the acetabular labrum and articular cartilage should be assessed on the MRA.

images Restriction of hip flexion motion and internal rotation in flexion is noted, because these clinical parameters should be improved with recontouring of the anterolateral femoral head–neck junction.

images It is very important that the surgeon determine whether the impingement lesion is a cam, pincer, or a combined campincer deformity, because the characteristics of the specific deformity will impact the surgical planning and treatment.

images In our practice, hip arthroscopy and limited open osteochondroplasty of the femoral head–neck junction are used primarily for the treatment of cam-type impingement and associated intra-articular disease.

Positioning

images Spinal or general anesthesia with muscle relaxation is preferred.

images The patient is positioned supine on a radiolucent fracture table with lower-extremity traction attachments (FIG 3).5

images The feet and ankles are well padded and firmly stabilized within the traction boots. The perineal post is heavily padded to prevent pudendal nerve palsy.

images

FIG 3  Surgical positioning and operating room set-up. The patient is positioned supine on a radiolucent fracture table. The hip arthroscopy is performed first followed by the limited open osteochondroplasty of the femoral head–neck junction.

images The operative hip initially is positioned in neutral flexion– extension and slight (0 to 10 degrees) abduction. The operative lower extremity is internally rotated 15 to 20 degrees.

images The contralateral hip is flexed about 15 degrees and abducted 10 to 20 degrees, and minor traction is applied to stabilize the pelvis.

images The ipsilateral upper extremity is positioned over the chest.

images Traction is applied to the operative hip to achieve 8 to 10 mm of joint distraction, which is confirmed with fluoroscopy. Traction is released during preparation and draping of the hip.

TECHNIQUES

HIP ARTHROSCOPY PORTALS

images Hip arthroscopy is perfomed via the anterior, anterolateral, and posterolateral portals with the patient in the supine position5 (TECH FIG 1A). The limited open osteochondroplasty of the femoral head–neck junction also is performed in the supine position. This surgical incision uses the Smith-Peterson interval to access the anterior hip joint.19

images The open incision is 8 to 10 cm long and extends from the anterosuperior iliac spine distally to incorporate the anterior arthroscopic portal (TECH FIG 1B).

images A cannulated hip arthroscopy system is used for portal placement.

images The anterolateral portal is established first with fluoroscopic guidance.

images The joint is entered distal to the labrum and superior to the femoral head. A 70-degree arthroscopic lens is inserted and used to directly visualize placement of the anterior and posterolateral portals (TECH FIG 1C, D).

images The anterior portal should be established with specific care to avoid injury to the lateral femoral cutaneous nerve.

images A superficial skin incision is made, and the soft tissues are then spread with a hemostat down to the hip capsule.

images The cannula sheath is advanced through the subcutaneous tissue to the hip capsule, and the trocar is advanced into the joint.

images Diagnostic evaluation of the central compartment is performed with both a 70- and 30-degree arthroscope. This enables excellent visualization of the femoral head and acetabulum.

images Most arthroscopy is done with the arthroscope in the anterolateral portal, but the anterior and posterolateral portals are used for comprehensive joint inspection.

images

TECH FIG 1  A. The anterior, anterolateral, and posterolateral arthroscopic portal positions are demonstrated with respect to the greater trochanter and anterior superior iliac spine (ASIS). B. The hip joint is distracted 8 to 10 mm, and the anterolateral portal is established first. C,D. The posterolateral (C) and anterior portals are then placed under direct visualization with a 70-degree arthroscope positioned in the anterolateral portal (D).

HIP ARTHROSCOPY FOR LABRAL AND CHONDRAL DISEASE

images The anterior and superolateral labrum is carefully inspected and probed (TECH FIG 2A).

images  If a labral tear is identified, the labrum is débrided back to the stable labral remnant.

images The débridement is performed with a combination of an arthroscopic shaver and radio-frequency chisel.

images Care is taken to be conservative in not resecting excessive labral tissue.

images In most cases, the capsular attachment of the labrum remains stable and should not be excised.

images  Labral repair is an option in selected cases, but our initial experience has focused on partial labral resection (TECH FIG 2B).

images  The articular cartilage is assessed, specifically along the anterior and superolateral rim of the acetabulum.

images Unstable flaps of articular cartilage should be removed with a mechanical shaver.

images If full-thickness delaminated flaps are present, they are débrided back to a stable articular cartilage remnant (TECH FIG 2C). Care is taken to avoid central propagation of the delaminated articular flaps.

images

TECH FIG 2  Arthroscopic treatment of intra-articular disease. A. The anterior and superolateral labrum are inspected and probed. Labral disease commonly involves this region of the acetabular rim and often includes a degenerative, intraarticular tear with an intact capsular attachment. B. Partial labral resection is performed, and the adjacent articular cartilage is examined. C–E. Unstable articular cartilage flaps are débrided (C), and exposed subchondral bone is treated with a microfracture technique (D,E).

images  When subchondral bone is exposed, microfracture treatment is performed (TECH FIG 2D,E).

images  Associated synovitis is ablated.

images  When arthroscopic evaluation and treatment of intraarticular disease is completed, the instruments are removed and the traction is released.

LIMITED OPEN OSTOECHONDROPLASTY

Surgical Approach

images  The patient is maintained in a supine position and an 8- to 10-cm incision is made extending from the lateral aspect of the anterior superior iliac spine distally to incorporate the anterior arthroscopic portal incision (TECH FIG 3A).

images  The dissection is carried through the subcutaneous tissue to the fascia of the tensor fascia lata muscle (TECH FIG 3B). Care is taken to bring the subcutaneous dissection slightly lateral to avoid the lateral femoral cutaneous nerve.

images  The fascia of the tensor muscle is incised over the muscle belly, and the tensor fascia muscle is reflected laterally. The medial soft tissue flap, including the sartorius, is reflected medially. The underlying rectus tendon is identified.

images  The direct and indirect heads of the rectus are released and reflected distally to allow wide access to the hip and wide exposure of the femoral head–neck junction (TECH FIG 3C, D).

images

TECH FIG 3  Osteochondroplasty surgical approach. A. The anterior incision (8–10 cm) is started at the lateral aspect of the anterosuperior spine and extended distally to incorporate the anterior arthroscopic portal incision. B. The dissection is carried through the subcutaneous tissue to the underlying fascia of the tensor fascia lata (TFL) muscle. The fascia is incised, and the tensor muscle belly is reflected laterally. The sartorius is reflected medially. C. This enables exposure of the direct (pictured) and indirect heads of the rectus femoris tendon. D. Both heads of the rectus tendon are released, exposing the underlying iliocapsularis muscle over the anterior hip joint capsule. The iliocapsularis is reflected distally and medially. The plane between the hip capsule and overlying iliopsoas muscle is developed medially.

images

TECH FIG 3  E. The anterior hip capsule is then identified and a capital I–type arthrotomy made. F. The retractors are placed intraarticularly, and exposure of the anterolateral head-neck junction is obtained.

images  After release of the rectus, the soft tissue and iliocapsularis muscle fibers are stripped from the anterior hip capsule. A cobra retractor is placed medially between the psoas muscle and the anterior hip capsule, and a right angle narrow-deep retractor is placed laterally.

images  A capital “I”-shaped arthrotomy is made, and the retractors are moved intra-articularly to displace the medial and lateral capsular flaps and provide access to the femoral head and neck (TECH FIG 3E, F).

images  The foot is then removed from traction and positioned on the radiolucent table to allow unrestricted motion of the lower extremity and wide access to the femoral head–neck junction.

images  The joint is inspected with specific attention to the femoral head–neck junction.

Femoral Head–Neck Recontouring

images  The lower extremity is brought up into a figure 4 position, which enables excellent visualization of the anteromedial head–neck junction.

images This region of the proximal femur commonly has normal offset in the face of reduced anterolateral head–neck junction offset. Thus, the anteromedial neck contour may be used as a template for the anterolateral osteochondral resection.

images  Articular cartilage discoloration, the presence of chondromalacia, or evidence of an impingement trough (indentation) also is observed at the anterolateral femoral head–neck junction (TECH FIG 4A). The osteochondroplasty is started proximal to the area of suspected impingement.

images  A combination of ½- and ¼-inch curved osteotomes is used to perform the recontrouring of the femoral head and neck (TECH FIG 4B). The osteochondroplasty is beveled inferiorly to prevent delamination of the preserved femoral head articular cartilage.

images  The depth of the osteochondroplasty ranges from 5 to 10 mm, depending on the severity of the deformity. The resection usually involves the majority of the anterolateral femoral head–neck junction, and may expand to cover more than 180 degrees of the femoral head–neck circumference.

images  Lower extremity positioning with internal and external rotation greatly enhances the extent of visualization and allows safe recontouring under direct vision.

images  Care is taken not to extend into the posterolateral femoral neck, because this area contains the terminal branches of the deep branch of the medial femoral circumflex artery.13

images  After the femoral head has been recontoured, the resection is assessed by direct visualization and palpation through the arthrotomy. Anterior femoroacetabular impingement is examined dynamically by palpation through the arthrotomy while moving the hip into flexion and combined flexion–internal rotation.

images  If palpation identifies residual impingement, then the resection is refined to remove the impinging structures at the femoral head–neck junction or the femoral neck.

images

TECH FIG 4  Femoral head–neck recontouring. The anterolateral femoral head–neck junction is inspected. A. Care is taken to observe any irregularity in the articular catilage, discoloration of the articular cartilage, and impingement trough or indentation. B. The osteochondroplasty and recontouring of the anterolateral femoral head–neck junction are performed using ½- and ¼-inch curved osteotomes. C. After the osteochondroplasty is completed and inspected by direct physical examination and fluoroscopy, the osteochondroplasty bony bed is treated with bone wax.

images  Fluoroscopic examination is performed after completion of femoral head recontouring to confirm sphericity and adequate osteochondral resection. The head is visualized in extension with neutral rotation and external rotation. The hip is then examined in a frog-leg lateral position to better visualize the anterolateral head–neck junction. Varying degrees of flexion and internal–external rotation permit excellent assessment of the osteochondroplasty.

images  After recontouring of the femoral head–neck junction is complete, the osteochondroplasty bed is treated with bone wax (TECH FIG 4C).

CLOSURE

images  The longitudinal capsulotomy incision is approximated with absorbable suture. The superomedial and superolateral capsular flaps are also reapproximated. The inferior capsular flaps do not require repair.

images  The direct and indirect heads of the rectus tendon are repaired with nonabsorbable sutures (TECH FIG 5).

images  The fascia, subcutaneous tissue, and skin are closed in standard fashion.

images

TECH FIG 5  The hip joint capsule and overlying rectus tendons are repaired.

images

images

FIG 4  AP pelvis and frog-leg lateral views after hip arthroscopy and limited anterior osteochondroplaty of the femoral head–neck junction. A. The AP pelvis view shows enhanced offset at the lateral femoral head–neck junction (arrow). B. The frog-leg lateral view clearly shows improved femoral head–neck offset (arrow) anteriorly and improved sphericity of the femoral head compared to preoperative x-rays (see Fig 2C–E). At 2-year follow-up, this patient had no symptoms and no activity restrictions.

POSTOPERATIVE CARE

images Postoperative radiographs are obtained to verify the recontouring of the femoral head–neck junction and to document the integrity of the proximal femur (FIG 4).

images Patients are treated with one aspirin two times a day for 6 weeks for deep venous thrombosis prophylaxis, and with indomethacin, 75 mg per day for 6 weeks, to prevent heterotopic ossification.

images Patients are toe-touch weight bearing for 4 weeks and then progress to full weight bearing. Gentle physical therapy is started the day after surgery. Therapy focuses on gentle range of motion and progressive strengthening within the patient's comfort zone.

images Continous passive motion is used for 4 to 6 hours per day for 2 to 4 weeks.

images The patient may return to normal daily activities as tolerated 4 weeks after surgery and may return to contact sports or running 6 months after surgery.

OUTCOMES

images Documentation of clinical outcomes for surgical treatment of hip impingement disease is limited.3,8,10,14,21

images Early to mid-term results are now available for treament with surgical dislocation of the hip and are encouraging for most patients.3,10,21

images Reported clinical outcomes with less invasive impingement techniques are limited.8,14

images Our experience with hip arthroscopy and combined limited open osteochondroplasty has been encouraging. Analysis of our first 23 consecutive cases demonstrated good or excellent clinical results in 22 of the 23 hips at a mean 18 months of follow-up.8

COMPLICATIONS

images Neurovascular injury

images Deep venous thrombosis

images Heterotopic ossification

images Femoral neck fracture

images Infection

images Articular cartilage scuffing

images Arthroscopic instrument breakage

REFERENCES

1. Aronson J. Osteoarthritis of the young adult hip: etiology and treatment. Instr Course Lect 1986;35:119–128.

2. Beck M, Kalhor M, Leunig M, et al. 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 2005;87B:1012–1018.

3. Beck M, Leunig M, Parvizi J, et al. Anterior femoroacetabular impingement: part II. Midterm results of surgical treatment. Clin Orthop Relat Res 2004;418:67–73.

4. Burnett RS, Della Rocca GJ, Prather H, et al. Clinical presentation of patients with tears of the acetabular labrum. J Bone Joint Surg Am 2006;88A:1448–1457.

5. Byrd JW. Hip arthroscopy in the supine position. Oper Tech Sports Med 2002;10:184–195.

6. Clohisy JC, Keeney JA, Schoenecker PL. Preliminary assessment and treatment guidelines for hip disorders in young adults. Clin Orthop Relat Res 2005;441:168–179.

7. Clohisy JC, McClure JT. Treatment of anterior femoroacetabular impingement with combined hip arthroscopy and limited anterior decompression. Iowa Orthop J 2005;25:164–171.

8. Clohisy JC, Zebala L, Hinkle SN, et al. Combined hip arthroscopy and limited open osteochondroplasty for treating impingement disease. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, San Diego, CA, February 14–17, 2007.

9. Eijer H, Leunig M, Mohamed M, et al. Cross-table lateral radiographs for screening of anterior femoral head-neck offset in patients with femoroacetabular impingement. Hip International 2001;11:37–41.

10.         Espinosa N, Rothenfluh DA, Beck M, et al. Treatment of femoro-acetabular impingement: preliminary results of labral fixation. J Bone Joint Surg Am 2006;88A:925–935.

11.         Ganz R, Gill TJ, Gautier E, et al. 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;83B: 1119–1124.

12.         Ganz R, Parvizi J, Beck M, et al. Femoro-acetabular impingement. An important cause of early osteoarthritis of the hip. Clin Orthop Relat Res 2003;417:112–120.

13.         Gautier E, Ganz K, Krugel N, et al. Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg Br 2000;82B:679–683.

14.         Guanche CA, Bare AA. Arthroscopic treatment of femoroacetabular impingement. Arthroscopy 2006;22:95–106.

15.         Harris WH. Etiology of osteoarthritis of the hip. Clin Orthop Relat Res 1986;213:20–33.

16.         Ito K, Minka MA II, Leunig M, et al. Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br 2001;83B:171–176.

17.         Lavigne M, Parvizi J, Beck M, et al. Anterior femoroacetabular impingement: part I. Techniques of joint preserving surgery. Clin Orthop Relat Res 2004;418:61–66.

18.         Meyer DC, Beck M, Ellis T, et al. Comparison of six radiographic projections to assess femoral head/neck asphericity. Clin Orthop Relat Res 2006;445:181–185.

19.         O'Brien RM. The technic for insertion of femoral head prosthesis by the straight anterior or Hueter approach. Clin Orthop 1955;6:22–26.

20.         Peelle MW, Della Rocca GJ, Maloney WJ, et al. Acetabular and femoral radiographic abnormalities associated with labral tears. Clin Orthop Relat Res 2005;441:327–333.

21.         Peters CL, Erickson JA. Treatment of femoro-acetabular impingement with surgical dislocation and debridement in young adults. J Bone Joint Surg Am 2006;88:1735–1741.

22.         Tanzer M, Noiseux N. Osseous abnormalities and early osteoarthritis: the role of hip impingement. Clin Orthop Relat Res 2004;429: 170–177.



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