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Combined Arthroscopic and Modified Open Approach for Cam Femoroacetabular Impingement: A Preliminary Experience
Combined Arthroscopic and Modified Open Approach for Cam Femoroacetabular Impingement: A Preliminary Experience Max Lincoln, M.D., Kelly Johnston, M.D., Michael Muldoon, M.D., and Richard Santore, M.D.
Purpose: We report our case series of patients undergoing surgical treatment (femoral osteoplasty) for symptomatic cam femoroacetabular impingement (FAI). Clinical results using a modified Heuter anterior approach combined with adjunctive hip arthroscopy are presented. Methods: A chart review of 16 hips (14 consecutive patients) was conducted. Radiographic parameters (␣ angle, head-neck offset, and Tönnis grade) were compared preoperatively and postoperatively. Clinical features (range of motion, provocative testing, and Harris hip score) were assessed. Results: At 2.0 years, mean hip flexion improved from 94.1° to 110.0° (P ⬍ .01) and internal rotation from 7.1° to 12.3° (P ⫽ .02). The mean ␣ angle improved from 64.5° to 43.3° (P ⬍ .01), whereas the mean femoral head-neck offset improved from 1.9 to 9.6 mm (P ⬍ .01). The mean Harris hip score improved from 63.8 to 76.1 (P ⫽ .01). No deterioration in overall radiographic Tönnis grades was present at last follow-up. Conclusions: The combination of hip arthroscopy with a limited anterior approach (Heuter) is a useful technique for patients with cam or cam-dominant FAI lesions. We believe the limited anterior approach with open osteoplasty presents a reasonable alternative to arthroscopic methods of osteoplasty with minimal drawbacks in the event that total hip arthroplasty is indicated in the future. Level of Evidence: Level IV, therapeutic case series. Key Words: Femoroacetabular impingement— Labral tear—Osteoarthritis—Hip arthroscopy—Osteoplasty—Acetabular retroversion.
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nderstanding of the factors that predispose patients to osteoarthritis of the hip continues to evolve.1-3 The premature conflict during flexion between the femoral neck and the acetabular rim has been termed femoroacetabular impingement (FAI). Three variations of hip impingement have been described: cam, pincer, and combined (cam and pincer) FAI.4 Cam impingement is the result of an increased radius of curvature of the femoral head segment that converges on the acetabular rim during motion. Diminished femoral anteversion has also been impli-
From Orthopedic Medical Group, San Diego, California, U.S.A. The authors report no conflict of interest. Received June 1, 2008; accepted December 1, 2008. Address correspondence and reprint requests to Richard Santore, M.D., Orthopedic Medical Group, 7910 Frost St, Suite 200, San Diego, CA 92123, U.S.A. E-mail: [email protected] © 2009 by the Arthroscopy Association of North America 0749-8063/09/2504-8303$36.00/0 doi:10.1016/j.arthro.2008.12.002
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cated. Intrusion of this cam into the native acetabulum results in an internally directed shearing force that damages the anterosuperior labrum and adjacent articular cartilage.5,6 Conditions including malunited femoral neck fracture,7 residual Legg-Calvé-Perthes disease,8 and sequelae of slipped capital femoral epiphysis9 have been associated with cam impingement. This impingement results in degeneration of the cartilage architecture and has been linked to the onset of osteoarthritis.10-12 Distinct from this mechanism is pincer impingement. In this case the femoral anatomy is often normal whereas acetabular overcoverage restricts range of motion of the hip. The overcoverage may be focal, as in acetabular retroversion,13 or global, as in either coxa profunda or protrusio.14 The labrum is affected more diffusely, whereas a “contrecoup” lesion can be found on the posteroinferior cartilage of the femoral head and acetabulum as a result of constraint during flexion.1 Symptoms of hip impingement include deep groin pain with flexion and adduction of the hip, which is
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 25, No 4 (April), 2009: pp 392-399
CAM FEMOROACETABULAR IMPINGEMENT elicited clinically with the impingement test. Such pain is believed to be caused by nociceptive fibers in the labrum itself.1 “Giving way” and intra-articular catching symptoms may herald an associated labral tear. Surgical treatment of FAI is designed to address the pathoanatomy. Pincer impingement can be addressed with acetabular rim trimming with labral reattachment via surgical dislocation or hip arthroscopy. Reverse periacetabular osteotomy may be warranted in selected cases in which retroversion coexists with frontal plane dysplasia of the acetabulum.15-17 The optimal management of cam impingement lesions is a matter for discussion. The problem is addressed on the femoral side by osteoplasty, which restores normal sphericity to the femoral head. Authors from the University of Bern, Switzerland, have described a safe method of surgical hip dislocation that allows for complete visualization of the entire head-neck junction.18 Although clinical results have been good with this technique, it does necessitate trochanteric osteotomy, extensive surgical dissection, and protracted recovery.18 Others have advocated allarthroscopic techniques, although achieving appropriate decompression comparable to open methods may be difficult.19-21 An intermediate solution for cam impingement has been proposed.22 This involves using hip arthroscopy followed by an open anterior approach to provide enhanced visualization for femoral osteoplasty.23 Performing arthroscopy provides an excellent means of assessing the articular cartilage of the hip joint, as well as a means of managing intra-articular pathology.24 The purpose of this study was to describe our clinical results using a modified anterior rectus- and tensorsparing approach combined with adjunctive arthroscopy. We hypothesized that this surgical method would provide clinical outcomes for cam FAI similar to those in the literature without the necessity for trochanteric osteotomy (surgical hip dislocation) and with improved visualization in comparison with allarthroscopic methods. METHODS With institutional review board approval, a retrospective case series of patients presenting to our office between October 2004 and August 2006 was reviewed. Inclusion criteria consisted of symptomatic (predominantly cam) FAI as determined from clinical examination and radiographic criteria. Exclusion criteria included significant arthritic change on radiogra-
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phy (Tönnis grade III or higher), advanced age, or inability to provide informed consent. All consecutive patients who met the criteria during the study period were offered the surgery described later. In all, 19 hips (17 patients) were selected, but 3 were considered to be inappropriate for this study. Two patients had previously undergone surgery on the affected hip; one had a valgus-extension osteotomy and arthroscopy, and one had a varus intertrochanteric osteotomy for childhood Legg-Calvé-Perthes disease. These 2 patients were therefore excluded, along with a third patient who had a staged procedure (hip arthroscopy followed by open osteoplasty 9 months later). The remaining 16 hips (14 patients) were deemed appropriate for inclusion in this study. The study group included 10 male patients (11 hips) and 4 female patients (5 hips). One female patient and one male patient had bilateral staged procedures. The group included 8 right and 8 left hips. One patient had bilateral precollapse osteonecrosis of the femoral head (Ficat stage II) due to steroid treatment for lupus (Fig 1). The mean age in this series was 37 years (range, 17 to 51 years). Follow-up in these patients averaged 2.0 years (range, 1.3 to 3.0 years). Clinical Data Patients underwent clinical testing of active and passive range of motion and provocative testing for anterolateral FAI and labral pathology. This testing was completed by a single examiner preoperatively and postoperatively. The impingement test was performed at 90° of flexion (or maximal flexion in patients unable to achieve 90°) combined with adduction and internal rotation. This was uniformly positive in all patients preoperatively. We also performed the McCarthy test for labral pathology (with both hips fully flexed, the patient’s pain is reproduced by extending the affected hip, first in external rotation and then in internal rotation).25 These were documented and compared at the time of last follow-up (mean, 2.0 years). Radiographs (anteroposterior [AP] pelvis) from the preoperative period and those obtained at last follow-up were evaluated by 1 observer for evidence of osteoarthritis using the grading system of Tönnis.26 ␣ Angles and femoral head-neck offset were measured preoperatively and postoperatively by 1 observer.6 These measurements were taken from frog lateral radiographs, readily available postoperatively and shown to provide optimal intraobserver and interobserver reliability.27 We also evaluated AP pelvis ra-
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FIGURE 1. (A) Preoperative frog lateral radiographs of a patient with bilateral symptomatic cam FAI. Excess bone was present at the head-neck junction, as shown by the arrows. A proximal crossover sign is seen bilaterally on the AP pelvis. This sign, made by the abnormal crossover of the anterior and posterior wall on standardized AP pelvis radiographs, can be indicative of either anterior overcoverage or acetabular retroversion, although a concomitant posterior wall sign is typically found with the latter.37 The predominant structural hip problem for this patient was cam pathology; therefore combined hip arthroscopy and open anterior osteoplasty were performed, as described previously. Femoral head-neck offset in the right (B) and left (C) hips was restored after osteoplasty.
diographs, as well as magnetic resonance (MR) angiograms in 8 of 16 hips, to determine whether cam or pincer impingement was present. In all, 10 hips were considered to have cam FAI only and 6 had combined (cam and pincer) FAI. Harris hip scores in all 16 hips were collected preoperatively and compared with those at the time of last follow-up. Clinical records were also used to determine time to return to work.
was assessed individually with attention to the quality of tissue and potential of repair and was either repaired arthroscopically or debrided (Fig 2). At the end of the arthroscopy, the wounds were closed and the patient positioned supine for the open arthrotomy part of the procedure.
Surgery Patients underwent arthroscopic examination with careful attention to intra-articular pathology. This was done in the lateral position with the leg in 10° to 20° of flexion, 15° to 30° of abduction, and neutral rotation. A lateral hip distractor (Innomed, Savannah, GA) was used. Anterior and posterior peritrochanteric portals were established bluntly over flexible guidewires (Smith & Nephew Endoscopy, Andover, MA). Initially, a diagnostic arthroscopy was conducted, with the Outerbridge grade of the femoral and acetabular articular surfaces being noted. When a focal area of degeneration was identified, microfracture was performed with an arthroscopic awl. Labral pathology
FIGURE 2. Intra-articular pathology was reliably addressed arthroscopically after first visualizing the entire joint. A labral tear (top) is seen in this view from the posterolateral portal of the right hip.
CAM FEMOROACETABULAR IMPINGEMENT The modified anterior approach with osteochondroplasty was then completed. In brief, a linear incision beginning at the anterior-superior iliac spine extending distally was made. Care was taken to stay well lateral to the sartorius–tensor fascia lata interval to avoid injury to the lateral femoral cutaneous nerve (LFCN) (Fig 3). The fascia of the tensor muscle was opened, and a subfascial approach to the interval between the tensor and sartorius was developed. The rectus muscle was then accessed laterally and posteriorly and elevated from the hip capsule sharply. With a retractor under the rectus and over the pelvic brim, the reflected head of the rectus was placed under tension and transected. After capsulotomy, the impingement lesion was identified. Care was taken to avoid any posterolateral dissection on the femoral neck. A combination of osteotomes, motorized burs, and rasps was used to contour the head-neck junction. In all cases the adequacy of decompression was assessed through observation dynamically and by use of fluoroscopy. Pre- and post-ostectomy fluoroscopic images were compared to ensure adequate and appropriate resection of the impingement lesion. The arthrotomy was then closed and the reflected head of the
FIGURE 3. (A) An anterolateral incision extending approximately 10 cm distal and lateral to the anterior-superior iliac spine was made. (B) The LFCN was protected by splitting the fascia of tensor fascia lata (TFL) lateral to the interval with the sartorius (SRT). (C) After retraction of the rectus femoris anteriorly, the reflected head of the rectus femoris (RHRF) was transected and repaired later, to provide access for osteoplasty. (D) An osteotome (OST) was used at the junction of the femoral head (H) and neck (N), under direct vision.
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rectus repaired. The tensor fascia was left open to lower the risk of damage to the LFCN, and an otherwise routine closure was performed. Surgical drains were not used. Rehabilitation Patients were either discharged the day of surgery or on the first postoperative day. All patients were instructed to use crutches with protected weight bearing for the first few days until able to walk without a limp, as well as to avoid any rigorous activities for 6 weeks. In cases in which microfracture was performed, patients continued protected weight bearing for the entire period of 6 weeks. Otherwise, light duties including return to work were permitted by 2 weeks postoperatively. A representative clinical case is shown (Fig 1). Statistics Statistical analysis in this series was completed with the R version 2.6.1 (Windows), shareware, cran.rproject.org. The Wilcoxon signed rank test was used in comparing preoperative and postoperative medians
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M. LINCOLN ET AL. TABLE 1.
Patient No.
Outerbridge Grade
1 2 3 4 5 6 7 7 8 9 10 10 11 12 13 14
IV IV IV II IV IV III I IV II IV IV IV II IV III
Results of Arthroscopy 2
Area of Debridement (cm )
No No
No No
1 ⬎2 2 ⬍1 1 ⬎2 1 debridement ⬎2 debridement ⬎2 1 2 debridement ⬍1 debridement
of outcome measures. For non-normative data, the McNemar test for the paired preoperative and postoperative proportions was used. In comparing correlations between variables, we used the Wilcoxon rank sum test. RESULTS At the time of arthroscopy, labral tears were observed in 13 patients (81%). The quality of tissue and tear pattern were considered to require debridement to stable margins in all but 1 of those patients. Significant focal chondral injury (Outerbridge grade IV) was present in 10 cases (62%). The chondral flap was of sufficient size to necessitate debridement in 10 cases. Microfracture was performed in 3 patients (19%). These data are summarized in Table 1. A significant difference was present between the mean Harris hip score preoperatively and that at last follow-up (improving from 63.8 to 76.1, P ⫽ .01) (Table 2). Mean range of motion in flexion was similarly improved, from 94.1° to 110.0° (P ⬍ .01), whereas internal rotation improved from 7.1° to 12.3°
TABLE 2.
Clinical and Radiographic Results
Flexion (°) Internal rotation (°) ␣ Angle (°) Head-neck offset (mm) Harris hip score
Preoperative
Postoperative
P Value
94.1 ⫾ 3.0 7.1 ⫾ 1.8 64.5 ⫾ 2.3 1.9 ⫾ 0.6 63.8 ⫾ 5.1
110.0 ⫾ 11.9 12.3 ⫾ 2.0 43.3 ⫾ 1.6 9.6 ⫾ 1.2 76.1 ⫾ 4.8
⬍.01 .02 ⬍.01 ⬍.01 .01
Microfracture Done
Labral Tear Observed
Labral Tear Debrided
No No No No Yes Yes No No No No No No Yes No No No
Yes Yes No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes No Yes
Yes Yes No Yes Yes Yes Yes Yes Yes No Yes Yes Yes No No Yes
(P ⫽ .02). A significant decrease in the number of patients with a positive impingement sign was seen, from 11 of 16 positive preoperatively to 2 of 16 postoperatively (P ⬍ .01). There was a decrease in the number of patients with a positive McCarthy test, from 9 of 16 preoperatively to 4 of 16 postoperatively, but this did not reach statistical significance. At the time of last follow-up, we found a significant improvement in mean ␣ angle, from 64.5° to 43.3° (P ⬍ .01), and a favorable increase in femoral headneck offset, from 1.9 to 9.6 mm (P ⬍ .01). At the time of last follow-up, 1 patient had progressed from Tönnis grade I arthritis to grade II on AP pelvis views and 1 improved from Tönnis grade II to I. The Tönnis grades in the remainder were unchanged. Thus there was no deterioration in overall Tönnis grades at the time of last follow-up in comparison with preoperative grades (data not shown). One patient had transient anesthesia in the perineum, thought to be related to hip distraction. The symptoms were entirely resolved at 2 weeks’ follow-up. Six patients had transient anesthesia in the proximal-lateral area of innervation of the LFCN. The symptoms were resolved in all patients at 3 months’ follow-up. One patient underwent total hip arthroplasty (THA) at 1.5 years postoperatively for persistent groin pain. This 51-year-old male Workers’ Compensation patient had Tönnis grade II changes preoperatively and a large (⬎2 cm2) chondral flap requiring debridement at the time of arthroscopy. One patient underwent repeat arthroscopy at 1.5 years because of the return of mechanical symptoms. Clinical data before these sub-
CAM FEMOROACETABULAR IMPINGEMENT sequent procedures in all 3 patients were used for the purposes of this study. DISCUSSION The management of both cam and pincer FAI focuses on correcting the underlying pathoanatomy. On the femoral side, the pathology consists of an asphericity of the head-neck junction. Patients with these anomalies have impingement at the anterolateral acetabulum earlier during hip flexion than do healthy subjects. This is believed to be primarily due to bony impingement.28 We have presented our results using a combined anterior approach and hip arthroscopy for the treatment of cam FAI. A similar approach has been advocated previously by Loude (personal communication) and more recently by Clohisy et al.22,27 Several key advantages are present with this strategy in addressing cam-dominant pathology. The surgical approach described is directed anatomically toward the site of anterolateral pathology at the femoral head-neck junction found in cam lesions. Furthermore, the limited dissection required does allow for a much shorter length of stay and much earlier patient recovery than those of surgical dislocation,18 given that trochanteric union is not required in our method before weight bearing. Another advantage is the addition of arthroscopy as a diagnostic and therapeutic tool before open osteoplasty (Table 1). At present, the sensitivity of detecting chondral injury of the hip by MR arthrogram is very technique sensitive,29 which poses difficulty in deciding whether to proceed with joint-preserving surgery. Peters and Erickson30 have reported on a series of 30 patients who underwent surgical hip dislocation for FAI. Eighteen of these patients had significantly worse articular pathology than had been expected based on preoperative radiographs and MR arthrography, whereas four were believed to require THA during the study period. Beck et al.31 and Murphy et al.32 have similarly observed clinical failure in surgical hip dislocation patients with significant articular defects seen at the time of surgery. Although we have had 1 patient who required conversion to THA during our study period, we now use arthroscopy as a second opportunity for surgical decision making. We presently no longer proceed with osteoplasty in patients of advanced age or in patients who present with significant articular pathology at the time of arthroscopy or who have Tönnis grade II arthritis at the time of presentation.
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In this series patients had only a modest improvement in Harris hip scores. We believe that this was largely because of patient selection, which has changed since the study period. Specifically, 3 patients in this series had final Harris hip scores lower than 72. One of these had a preoperative Harris hip score of 26 and had previously undergone failed hip arthroscopy and valgus osteotomy. Surgery was offered because of the patient’s age of 32 years, though in hindsight, delayed THA would have been more helpful. The second patient had a preoperative Tönnis grade of II and grade IV chondral flap greater than 2 cm2 in size at the time of arthroscopy. The third patient has been described in the “Results” section and ultimately required conversion to THA because of failure of treatment. The potential for failure of FAI surgery with subsequent conversion to THA is important in deciding on a treatment strategy. Patients with symptomatic FAI may represent challenging candidates for THA because of the underlying pathoanatomy, which may include acetabular retroversion, coxa profunda, or other abnormalities. At the University of Bern and other centers, the rate of conversion to THA after surgical dislocation has been reported at 26% to 30%.31,32 The avoidance of trochanteric osteotomy with the anterior approach advocated here is advantageous, because it allows for unviolated posterolateral access for primary hip arthroplasty in these patients. Recently, there has been much enthusiasm for allarthroscopic management of FAI, because it carries the potential for minimal soft-tissue trauma with the potential for more rapid recovery.19,33-36 As with open treatment strategies for FAI, the available clinical literature on arthroscopic management is sparse. With regard to the management of cam pathology, we have found arthroscopic-only management problematic in comparison with the method described here. The ability to contour the femoral head-neck junction and confirm appropriate resection is enhanced with open visualization. We do not favor arthroscopic management of pincer-dominant lesions because of the technical challenges with current methods. There were of course definite weaknesses of this case series. Most apparently, the treatment we advocate here is directed only at cam impingement. From the literature, we know that combined (cam and pincer) impingement is seen more commonly than either type in isolation.1 The treatment of pincer impingement through the methods we describe here is only possible through arthroscopic rim trimming, which may be challenging when labral takedown and reat-
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tachment are necessary. In our experience, however, the quality of the labrum in the region of the overcoverage is often degenerative, and debridement only may be the most appropriate measure. A second major weakness lies in the fact that our study group contained only 16 consecutive hips, which is lower than the numbers reported in larger series.19,28 The radiographic interpretation of results is further limited because the observer was not blinded. Future studies with more extensive follow-up and larger patient populations will better assess whether the natural history of FAI is actually changed by the treatment we advocate here. CONCLUSIONS The combination of hip arthroscopy with a limited anterior approach (Heuter) is a useful technique for patients with cam or cam-dominant FAI lesions. We believe the limited anterior surgical approach with open osteoplasty provides a reasonable means of treating cam pathoanatomy with minimal drawbacks in the event that THA is indicated in the future. Acknowledgment: The authors thank Robert M. Healey for his assistance with preparation of the figures. REFERENCES 1. Beck M, Kalhor M, Leunig M, 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 2005;87:1012-1018. 2. Tanzer M, Noiseux N. Osseous abnormalities and early osteoarthritis: The role of hip impingement. Clin Orthop Relat Res 2004:170-177. 3. Tönnis D, Heinecke A. Acetabular and femoral anteversion: Relationship with osteoarthritis of the hip. J Bone Joint Surg Am 1999;81:1747-1770. 4. 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 2003:112-120. 5. Ito K, Minka MA II, Leunig M, Werlen S, Ganz R. Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br 2001;83:171-176. 6. Nötzli HP, Wyss TF, Stoecklin CH, Schmid MR, Treiber K, Hodler J. The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement. J Bone Joint Surg Br 2002;84:556-560. 7. Eijer H, Myers SR, Ganz R. Anterior femoroacetabular impingement after femoral neck fractures. J Orthop Trauma 2001;15:475-481. 8. Eijer H, Berg RP, Haverkamp D, Pécasse GA. Hip deformity in symptomatic adult Perthes’ disease. Acta Orthop Belg 2006; 72:683-692. 9. Schai PA, Exner GU. Indication for and results of intertrochanteric osteotomy in slipped capital femoral epiphysis. Orthopade 2002;31:900-907 (in German).
10. Leunig M, Podeszwa D, Beck M, Werlen S, Ganz R. Magnetic resonance arthrography of labral disorders in hips with dysplasia and impingement. Clin Orthop Relat Res 2004:74-80. 11. Ferguson SJ, Bryant JT, Ganz R, Ito K. An in vitro investigation of the acetabular labral seal in hip joint mechanics. J Biomech 2003;36:171-178. 12. Harris WH. Etiology of osteoarthritis of the hip. Clin Orthop Relat Res 1986:20-33. 13. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br 1999;81:281288. 14. Ganz R, Leunig M, Leunig-Ganz K, Harris W. The etiology of osteoarthritis of the hip: An integrated mechanical concept. Clin Orthop Relat Res 2008;466:264-272. 15. Espinosa N, Beck M, Rothenfluh DA, Ganz R, Leunig M. Treatment of femoro-acetabular impingement: Preliminary results of labral refixation. Surgical technique. J Bone Joint Surg Am 2007;89:36-53 (suppl 2, pt 1). 16. 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. 17. Siebenrock KA, Schoeniger R, Ganz R. Anterior femoroacetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am 2003;85:278-286. 18. Ganz R, Gill TJ, Gautier E, Ganz K, Krügel 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;83:1119-1124. 19. Philippon M, Schenker M, Briggs K, Kuppersmith D. Femoroacetabular impingement in 45 professional athletes: Associated pathologies and return to sport following arthroscopic decompression. Knee Surg Sports Traumatol Arthrosc 2007; 15:908-914. 20. Stähelin L, Stähelin T, Jolles BM, Herzog RF. Arthroscopic offset restoration in femoroacetabular cam impingement: Accuracy and early clinical outcome. Arthroscopy 2008;24: 51.e1-51.e8. Available online at www.arthroscopyjournal.org. 21. Sampson T. Arthroscopic treatment of femoroacetabular impingement. Tech Orthop 2005;20:56-62. 22. Clohisy JC, McClure JT. Treatment of anterior femoroacetabular impingement with combined hip arthroscopy and limited anterior decompression. Iowa Orthop J 2005;25:164-171. 23. Pierannunzii L, d’Imporzano M. Treatment of femoroacetabular impingement: A modified resection osteoplasty technique through an anterior approach. Orthopedics 2007;30:96-102. 24. Larson CM, Giveans MR. Arthroscopic management of femoroacetabular impingement: Early outcomes measures. Arthroscopy 2008;24:540-546. 25. McCarthy JC, Lee JA. Acetabular dysplasia: A paradigm of arthroscopic examination of chondral injuries. Clin Orthop Relat Res 2002:122-128. 26. Tönnis D. Normal values of the hip joint for the evaluation of X-rays in children and adults. Clin Orthop Relat Res 1975: 39-42. 27. Clohisy JC, Nunley RM, Otto RJ, Schoenecker PL. The frogleg lateral radiograph accurately visualized hip cam impingement abnormalities. Clin Orthop Relat Res 2007;462:115-121. 28. Wyss TF, Clark JM, Weishaupt D, Nötzli HP. Correlation between internal rotation and bony anatomy in the hip. Clin Orthop Relat Res 2007;460:152-158. 29. Knuesel PR, Pfirrmann CW, Noetzli HP, et al. MR arthrography of the hip: Diagnostic performance of a dedicated waterexcitation 3D double-echo steady-state sequence to detect cartilage lesions. AJR Am J Roentgenol 2004;183:1729-1735. 30. 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. 31. Beck M, Leunig M, Parvizi J, Boutier V, Wyss D, Ganz R.
CAM FEMOROACETABULAR IMPINGEMENT Anterior femoroacetabular impingement: Part II. Midterm results of surgical treatment. Clin Orthop Relat Res 2004:67-73. 32. Murphy S, Tannast M, Kim YJ, Buly R, Millis MB. Debridement of the adult hip for femoroacetabular impingement: Indications and preliminary clinical results. Clin Orthop Relat Res 2004:178-181. 33. Sampson TG. Arthroscopic treatment of femoroacetabular impingement: A proposed technique with clinical experience. Instr Course Lect 2006;55:337-346.
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34. Khanduja V, Villar RN. The arthroscopic management of femoroacetabular impingement. Knee Surg Sports Traumatol Arthrosc 2007;15:1035-1040. 35. Byrd JW. Hip arthroscopy: Surgical indications. Arthroscopy 2006;22:1260-1262. 36. Guanche CA, Bare AA. Arthroscopic treatment of femoroacetabular impingement. Arthroscopy 2006;22:95-106. 37. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br 1999;81:281288.
Purpose: We report our case series of patients undergoing surgical treatment (femoral osteoplasty) for symptomatic cam femoroacetabular impingement (FAI). Clinical results using a modified Heuter anterior approach combined with adjunctive hip arthroscopy are presented. Methods: A chart review of 16 hips (14 consecutive patients) was conducted. Radiographic parameters (␣ angle, head-neck offset, and Tönnis grade) were compared preoperatively and postoperatively. Clinical features (range of motion, provocative testing, and Harris hip score) were assessed. Results: At 2.0 years, mean hip flexion improved from 94.1° to 110.0° (P ⬍ .01) and internal rotation from 7.1° to 12.3° (P ⫽ .02). The mean ␣ angle improved from 64.5° to 43.3° (P ⬍ .01), whereas the mean femoral head-neck offset improved from 1.9 to 9.6 mm (P ⬍ .01). The mean Harris hip score improved from 63.8 to 76.1 (P ⫽ .01). No deterioration in overall radiographic Tönnis grades was present at last follow-up. Conclusions: The combination of hip arthroscopy with a limited anterior approach (Heuter) is a useful technique for patients with cam or cam-dominant FAI lesions. We believe the limited anterior approach with open osteoplasty presents a reasonable alternative to arthroscopic methods of osteoplasty with minimal drawbacks in the event that total hip arthroplasty is indicated in the future. Level of Evidence: Level IV, therapeutic case series. Key Words: Femoroacetabular impingement— Labral tear—Osteoarthritis—Hip arthroscopy—Osteoplasty—Acetabular retroversion.
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nderstanding of the factors that predispose patients to osteoarthritis of the hip continues to evolve.1-3 The premature conflict during flexion between the femoral neck and the acetabular rim has been termed femoroacetabular impingement (FAI). Three variations of hip impingement have been described: cam, pincer, and combined (cam and pincer) FAI.4 Cam impingement is the result of an increased radius of curvature of the femoral head segment that converges on the acetabular rim during motion. Diminished femoral anteversion has also been impli-
From Orthopedic Medical Group, San Diego, California, U.S.A. The authors report no conflict of interest. Received June 1, 2008; accepted December 1, 2008. Address correspondence and reprint requests to Richard Santore, M.D., Orthopedic Medical Group, 7910 Frost St, Suite 200, San Diego, CA 92123, U.S.A. E-mail: [email protected] © 2009 by the Arthroscopy Association of North America 0749-8063/09/2504-8303$36.00/0 doi:10.1016/j.arthro.2008.12.002
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cated. Intrusion of this cam into the native acetabulum results in an internally directed shearing force that damages the anterosuperior labrum and adjacent articular cartilage.5,6 Conditions including malunited femoral neck fracture,7 residual Legg-Calvé-Perthes disease,8 and sequelae of slipped capital femoral epiphysis9 have been associated with cam impingement. This impingement results in degeneration of the cartilage architecture and has been linked to the onset of osteoarthritis.10-12 Distinct from this mechanism is pincer impingement. In this case the femoral anatomy is often normal whereas acetabular overcoverage restricts range of motion of the hip. The overcoverage may be focal, as in acetabular retroversion,13 or global, as in either coxa profunda or protrusio.14 The labrum is affected more diffusely, whereas a “contrecoup” lesion can be found on the posteroinferior cartilage of the femoral head and acetabulum as a result of constraint during flexion.1 Symptoms of hip impingement include deep groin pain with flexion and adduction of the hip, which is
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CAM FEMOROACETABULAR IMPINGEMENT elicited clinically with the impingement test. Such pain is believed to be caused by nociceptive fibers in the labrum itself.1 “Giving way” and intra-articular catching symptoms may herald an associated labral tear. Surgical treatment of FAI is designed to address the pathoanatomy. Pincer impingement can be addressed with acetabular rim trimming with labral reattachment via surgical dislocation or hip arthroscopy. Reverse periacetabular osteotomy may be warranted in selected cases in which retroversion coexists with frontal plane dysplasia of the acetabulum.15-17 The optimal management of cam impingement lesions is a matter for discussion. The problem is addressed on the femoral side by osteoplasty, which restores normal sphericity to the femoral head. Authors from the University of Bern, Switzerland, have described a safe method of surgical hip dislocation that allows for complete visualization of the entire head-neck junction.18 Although clinical results have been good with this technique, it does necessitate trochanteric osteotomy, extensive surgical dissection, and protracted recovery.18 Others have advocated allarthroscopic techniques, although achieving appropriate decompression comparable to open methods may be difficult.19-21 An intermediate solution for cam impingement has been proposed.22 This involves using hip arthroscopy followed by an open anterior approach to provide enhanced visualization for femoral osteoplasty.23 Performing arthroscopy provides an excellent means of assessing the articular cartilage of the hip joint, as well as a means of managing intra-articular pathology.24 The purpose of this study was to describe our clinical results using a modified anterior rectus- and tensorsparing approach combined with adjunctive arthroscopy. We hypothesized that this surgical method would provide clinical outcomes for cam FAI similar to those in the literature without the necessity for trochanteric osteotomy (surgical hip dislocation) and with improved visualization in comparison with allarthroscopic methods. METHODS With institutional review board approval, a retrospective case series of patients presenting to our office between October 2004 and August 2006 was reviewed. Inclusion criteria consisted of symptomatic (predominantly cam) FAI as determined from clinical examination and radiographic criteria. Exclusion criteria included significant arthritic change on radiogra-
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phy (Tönnis grade III or higher), advanced age, or inability to provide informed consent. All consecutive patients who met the criteria during the study period were offered the surgery described later. In all, 19 hips (17 patients) were selected, but 3 were considered to be inappropriate for this study. Two patients had previously undergone surgery on the affected hip; one had a valgus-extension osteotomy and arthroscopy, and one had a varus intertrochanteric osteotomy for childhood Legg-Calvé-Perthes disease. These 2 patients were therefore excluded, along with a third patient who had a staged procedure (hip arthroscopy followed by open osteoplasty 9 months later). The remaining 16 hips (14 patients) were deemed appropriate for inclusion in this study. The study group included 10 male patients (11 hips) and 4 female patients (5 hips). One female patient and one male patient had bilateral staged procedures. The group included 8 right and 8 left hips. One patient had bilateral precollapse osteonecrosis of the femoral head (Ficat stage II) due to steroid treatment for lupus (Fig 1). The mean age in this series was 37 years (range, 17 to 51 years). Follow-up in these patients averaged 2.0 years (range, 1.3 to 3.0 years). Clinical Data Patients underwent clinical testing of active and passive range of motion and provocative testing for anterolateral FAI and labral pathology. This testing was completed by a single examiner preoperatively and postoperatively. The impingement test was performed at 90° of flexion (or maximal flexion in patients unable to achieve 90°) combined with adduction and internal rotation. This was uniformly positive in all patients preoperatively. We also performed the McCarthy test for labral pathology (with both hips fully flexed, the patient’s pain is reproduced by extending the affected hip, first in external rotation and then in internal rotation).25 These were documented and compared at the time of last follow-up (mean, 2.0 years). Radiographs (anteroposterior [AP] pelvis) from the preoperative period and those obtained at last follow-up were evaluated by 1 observer for evidence of osteoarthritis using the grading system of Tönnis.26 ␣ Angles and femoral head-neck offset were measured preoperatively and postoperatively by 1 observer.6 These measurements were taken from frog lateral radiographs, readily available postoperatively and shown to provide optimal intraobserver and interobserver reliability.27 We also evaluated AP pelvis ra-
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FIGURE 1. (A) Preoperative frog lateral radiographs of a patient with bilateral symptomatic cam FAI. Excess bone was present at the head-neck junction, as shown by the arrows. A proximal crossover sign is seen bilaterally on the AP pelvis. This sign, made by the abnormal crossover of the anterior and posterior wall on standardized AP pelvis radiographs, can be indicative of either anterior overcoverage or acetabular retroversion, although a concomitant posterior wall sign is typically found with the latter.37 The predominant structural hip problem for this patient was cam pathology; therefore combined hip arthroscopy and open anterior osteoplasty were performed, as described previously. Femoral head-neck offset in the right (B) and left (C) hips was restored after osteoplasty.
diographs, as well as magnetic resonance (MR) angiograms in 8 of 16 hips, to determine whether cam or pincer impingement was present. In all, 10 hips were considered to have cam FAI only and 6 had combined (cam and pincer) FAI. Harris hip scores in all 16 hips were collected preoperatively and compared with those at the time of last follow-up. Clinical records were also used to determine time to return to work.
was assessed individually with attention to the quality of tissue and potential of repair and was either repaired arthroscopically or debrided (Fig 2). At the end of the arthroscopy, the wounds were closed and the patient positioned supine for the open arthrotomy part of the procedure.
Surgery Patients underwent arthroscopic examination with careful attention to intra-articular pathology. This was done in the lateral position with the leg in 10° to 20° of flexion, 15° to 30° of abduction, and neutral rotation. A lateral hip distractor (Innomed, Savannah, GA) was used. Anterior and posterior peritrochanteric portals were established bluntly over flexible guidewires (Smith & Nephew Endoscopy, Andover, MA). Initially, a diagnostic arthroscopy was conducted, with the Outerbridge grade of the femoral and acetabular articular surfaces being noted. When a focal area of degeneration was identified, microfracture was performed with an arthroscopic awl. Labral pathology
FIGURE 2. Intra-articular pathology was reliably addressed arthroscopically after first visualizing the entire joint. A labral tear (top) is seen in this view from the posterolateral portal of the right hip.
CAM FEMOROACETABULAR IMPINGEMENT The modified anterior approach with osteochondroplasty was then completed. In brief, a linear incision beginning at the anterior-superior iliac spine extending distally was made. Care was taken to stay well lateral to the sartorius–tensor fascia lata interval to avoid injury to the lateral femoral cutaneous nerve (LFCN) (Fig 3). The fascia of the tensor muscle was opened, and a subfascial approach to the interval between the tensor and sartorius was developed. The rectus muscle was then accessed laterally and posteriorly and elevated from the hip capsule sharply. With a retractor under the rectus and over the pelvic brim, the reflected head of the rectus was placed under tension and transected. After capsulotomy, the impingement lesion was identified. Care was taken to avoid any posterolateral dissection on the femoral neck. A combination of osteotomes, motorized burs, and rasps was used to contour the head-neck junction. In all cases the adequacy of decompression was assessed through observation dynamically and by use of fluoroscopy. Pre- and post-ostectomy fluoroscopic images were compared to ensure adequate and appropriate resection of the impingement lesion. The arthrotomy was then closed and the reflected head of the
FIGURE 3. (A) An anterolateral incision extending approximately 10 cm distal and lateral to the anterior-superior iliac spine was made. (B) The LFCN was protected by splitting the fascia of tensor fascia lata (TFL) lateral to the interval with the sartorius (SRT). (C) After retraction of the rectus femoris anteriorly, the reflected head of the rectus femoris (RHRF) was transected and repaired later, to provide access for osteoplasty. (D) An osteotome (OST) was used at the junction of the femoral head (H) and neck (N), under direct vision.
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rectus repaired. The tensor fascia was left open to lower the risk of damage to the LFCN, and an otherwise routine closure was performed. Surgical drains were not used. Rehabilitation Patients were either discharged the day of surgery or on the first postoperative day. All patients were instructed to use crutches with protected weight bearing for the first few days until able to walk without a limp, as well as to avoid any rigorous activities for 6 weeks. In cases in which microfracture was performed, patients continued protected weight bearing for the entire period of 6 weeks. Otherwise, light duties including return to work were permitted by 2 weeks postoperatively. A representative clinical case is shown (Fig 1). Statistics Statistical analysis in this series was completed with the R version 2.6.1 (Windows), shareware, cran.rproject.org. The Wilcoxon signed rank test was used in comparing preoperative and postoperative medians
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M. LINCOLN ET AL. TABLE 1.
Patient No.
Outerbridge Grade
1 2 3 4 5 6 7 7 8 9 10 10 11 12 13 14
IV IV IV II IV IV III I IV II IV IV IV II IV III
Results of Arthroscopy 2
Area of Debridement (cm )
No No
No No
1 ⬎2 2 ⬍1 1 ⬎2 1 debridement ⬎2 debridement ⬎2 1 2 debridement ⬍1 debridement
of outcome measures. For non-normative data, the McNemar test for the paired preoperative and postoperative proportions was used. In comparing correlations between variables, we used the Wilcoxon rank sum test. RESULTS At the time of arthroscopy, labral tears were observed in 13 patients (81%). The quality of tissue and tear pattern were considered to require debridement to stable margins in all but 1 of those patients. Significant focal chondral injury (Outerbridge grade IV) was present in 10 cases (62%). The chondral flap was of sufficient size to necessitate debridement in 10 cases. Microfracture was performed in 3 patients (19%). These data are summarized in Table 1. A significant difference was present between the mean Harris hip score preoperatively and that at last follow-up (improving from 63.8 to 76.1, P ⫽ .01) (Table 2). Mean range of motion in flexion was similarly improved, from 94.1° to 110.0° (P ⬍ .01), whereas internal rotation improved from 7.1° to 12.3°
TABLE 2.
Clinical and Radiographic Results
Flexion (°) Internal rotation (°) ␣ Angle (°) Head-neck offset (mm) Harris hip score
Preoperative
Postoperative
P Value
94.1 ⫾ 3.0 7.1 ⫾ 1.8 64.5 ⫾ 2.3 1.9 ⫾ 0.6 63.8 ⫾ 5.1
110.0 ⫾ 11.9 12.3 ⫾ 2.0 43.3 ⫾ 1.6 9.6 ⫾ 1.2 76.1 ⫾ 4.8
⬍.01 .02 ⬍.01 ⬍.01 .01
Microfracture Done
Labral Tear Observed
Labral Tear Debrided
No No No No Yes Yes No No No No No No Yes No No No
Yes Yes No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes No Yes
Yes Yes No Yes Yes Yes Yes Yes Yes No Yes Yes Yes No No Yes
(P ⫽ .02). A significant decrease in the number of patients with a positive impingement sign was seen, from 11 of 16 positive preoperatively to 2 of 16 postoperatively (P ⬍ .01). There was a decrease in the number of patients with a positive McCarthy test, from 9 of 16 preoperatively to 4 of 16 postoperatively, but this did not reach statistical significance. At the time of last follow-up, we found a significant improvement in mean ␣ angle, from 64.5° to 43.3° (P ⬍ .01), and a favorable increase in femoral headneck offset, from 1.9 to 9.6 mm (P ⬍ .01). At the time of last follow-up, 1 patient had progressed from Tönnis grade I arthritis to grade II on AP pelvis views and 1 improved from Tönnis grade II to I. The Tönnis grades in the remainder were unchanged. Thus there was no deterioration in overall Tönnis grades at the time of last follow-up in comparison with preoperative grades (data not shown). One patient had transient anesthesia in the perineum, thought to be related to hip distraction. The symptoms were entirely resolved at 2 weeks’ follow-up. Six patients had transient anesthesia in the proximal-lateral area of innervation of the LFCN. The symptoms were resolved in all patients at 3 months’ follow-up. One patient underwent total hip arthroplasty (THA) at 1.5 years postoperatively for persistent groin pain. This 51-year-old male Workers’ Compensation patient had Tönnis grade II changes preoperatively and a large (⬎2 cm2) chondral flap requiring debridement at the time of arthroscopy. One patient underwent repeat arthroscopy at 1.5 years because of the return of mechanical symptoms. Clinical data before these sub-
CAM FEMOROACETABULAR IMPINGEMENT sequent procedures in all 3 patients were used for the purposes of this study. DISCUSSION The management of both cam and pincer FAI focuses on correcting the underlying pathoanatomy. On the femoral side, the pathology consists of an asphericity of the head-neck junction. Patients with these anomalies have impingement at the anterolateral acetabulum earlier during hip flexion than do healthy subjects. This is believed to be primarily due to bony impingement.28 We have presented our results using a combined anterior approach and hip arthroscopy for the treatment of cam FAI. A similar approach has been advocated previously by Loude (personal communication) and more recently by Clohisy et al.22,27 Several key advantages are present with this strategy in addressing cam-dominant pathology. The surgical approach described is directed anatomically toward the site of anterolateral pathology at the femoral head-neck junction found in cam lesions. Furthermore, the limited dissection required does allow for a much shorter length of stay and much earlier patient recovery than those of surgical dislocation,18 given that trochanteric union is not required in our method before weight bearing. Another advantage is the addition of arthroscopy as a diagnostic and therapeutic tool before open osteoplasty (Table 1). At present, the sensitivity of detecting chondral injury of the hip by MR arthrogram is very technique sensitive,29 which poses difficulty in deciding whether to proceed with joint-preserving surgery. Peters and Erickson30 have reported on a series of 30 patients who underwent surgical hip dislocation for FAI. Eighteen of these patients had significantly worse articular pathology than had been expected based on preoperative radiographs and MR arthrography, whereas four were believed to require THA during the study period. Beck et al.31 and Murphy et al.32 have similarly observed clinical failure in surgical hip dislocation patients with significant articular defects seen at the time of surgery. Although we have had 1 patient who required conversion to THA during our study period, we now use arthroscopy as a second opportunity for surgical decision making. We presently no longer proceed with osteoplasty in patients of advanced age or in patients who present with significant articular pathology at the time of arthroscopy or who have Tönnis grade II arthritis at the time of presentation.
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In this series patients had only a modest improvement in Harris hip scores. We believe that this was largely because of patient selection, which has changed since the study period. Specifically, 3 patients in this series had final Harris hip scores lower than 72. One of these had a preoperative Harris hip score of 26 and had previously undergone failed hip arthroscopy and valgus osteotomy. Surgery was offered because of the patient’s age of 32 years, though in hindsight, delayed THA would have been more helpful. The second patient had a preoperative Tönnis grade of II and grade IV chondral flap greater than 2 cm2 in size at the time of arthroscopy. The third patient has been described in the “Results” section and ultimately required conversion to THA because of failure of treatment. The potential for failure of FAI surgery with subsequent conversion to THA is important in deciding on a treatment strategy. Patients with symptomatic FAI may represent challenging candidates for THA because of the underlying pathoanatomy, which may include acetabular retroversion, coxa profunda, or other abnormalities. At the University of Bern and other centers, the rate of conversion to THA after surgical dislocation has been reported at 26% to 30%.31,32 The avoidance of trochanteric osteotomy with the anterior approach advocated here is advantageous, because it allows for unviolated posterolateral access for primary hip arthroplasty in these patients. Recently, there has been much enthusiasm for allarthroscopic management of FAI, because it carries the potential for minimal soft-tissue trauma with the potential for more rapid recovery.19,33-36 As with open treatment strategies for FAI, the available clinical literature on arthroscopic management is sparse. With regard to the management of cam pathology, we have found arthroscopic-only management problematic in comparison with the method described here. The ability to contour the femoral head-neck junction and confirm appropriate resection is enhanced with open visualization. We do not favor arthroscopic management of pincer-dominant lesions because of the technical challenges with current methods. There were of course definite weaknesses of this case series. Most apparently, the treatment we advocate here is directed only at cam impingement. From the literature, we know that combined (cam and pincer) impingement is seen more commonly than either type in isolation.1 The treatment of pincer impingement through the methods we describe here is only possible through arthroscopic rim trimming, which may be challenging when labral takedown and reat-
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tachment are necessary. In our experience, however, the quality of the labrum in the region of the overcoverage is often degenerative, and debridement only may be the most appropriate measure. A second major weakness lies in the fact that our study group contained only 16 consecutive hips, which is lower than the numbers reported in larger series.19,28 The radiographic interpretation of results is further limited because the observer was not blinded. Future studies with more extensive follow-up and larger patient populations will better assess whether the natural history of FAI is actually changed by the treatment we advocate here. CONCLUSIONS The combination of hip arthroscopy with a limited anterior approach (Heuter) is a useful technique for patients with cam or cam-dominant FAI lesions. We believe the limited anterior surgical approach with open osteoplasty provides a reasonable means of treating cam pathoanatomy with minimal drawbacks in the event that THA is indicated in the future. Acknowledgment: The authors thank Robert M. Healey for his assistance with preparation of the figures. REFERENCES 1. Beck M, Kalhor M, Leunig M, 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 2005;87:1012-1018. 2. Tanzer M, Noiseux N. Osseous abnormalities and early osteoarthritis: The role of hip impingement. Clin Orthop Relat Res 2004:170-177. 3. Tönnis D, Heinecke A. Acetabular and femoral anteversion: Relationship with osteoarthritis of the hip. J Bone Joint Surg Am 1999;81:1747-1770. 4. 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 2003:112-120. 5. Ito K, Minka MA II, Leunig M, Werlen S, Ganz R. Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br 2001;83:171-176. 6. Nötzli HP, Wyss TF, Stoecklin CH, Schmid MR, Treiber K, Hodler J. The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement. J Bone Joint Surg Br 2002;84:556-560. 7. Eijer H, Myers SR, Ganz R. Anterior femoroacetabular impingement after femoral neck fractures. J Orthop Trauma 2001;15:475-481. 8. Eijer H, Berg RP, Haverkamp D, Pécasse GA. Hip deformity in symptomatic adult Perthes’ disease. Acta Orthop Belg 2006; 72:683-692. 9. Schai PA, Exner GU. Indication for and results of intertrochanteric osteotomy in slipped capital femoral epiphysis. Orthopade 2002;31:900-907 (in German).
10. Leunig M, Podeszwa D, Beck M, Werlen S, Ganz R. Magnetic resonance arthrography of labral disorders in hips with dysplasia and impingement. Clin Orthop Relat Res 2004:74-80. 11. Ferguson SJ, Bryant JT, Ganz R, Ito K. An in vitro investigation of the acetabular labral seal in hip joint mechanics. J Biomech 2003;36:171-178. 12. Harris WH. Etiology of osteoarthritis of the hip. Clin Orthop Relat Res 1986:20-33. 13. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br 1999;81:281288. 14. Ganz R, Leunig M, Leunig-Ganz K, Harris W. The etiology of osteoarthritis of the hip: An integrated mechanical concept. Clin Orthop Relat Res 2008;466:264-272. 15. Espinosa N, Beck M, Rothenfluh DA, Ganz R, Leunig M. Treatment of femoro-acetabular impingement: Preliminary results of labral refixation. Surgical technique. J Bone Joint Surg Am 2007;89:36-53 (suppl 2, pt 1). 16. 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. 17. Siebenrock KA, Schoeniger R, Ganz R. Anterior femoroacetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am 2003;85:278-286. 18. Ganz R, Gill TJ, Gautier E, Ganz K, Krügel 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;83:1119-1124. 19. Philippon M, Schenker M, Briggs K, Kuppersmith D. Femoroacetabular impingement in 45 professional athletes: Associated pathologies and return to sport following arthroscopic decompression. Knee Surg Sports Traumatol Arthrosc 2007; 15:908-914. 20. Stähelin L, Stähelin T, Jolles BM, Herzog RF. Arthroscopic offset restoration in femoroacetabular cam impingement: Accuracy and early clinical outcome. Arthroscopy 2008;24: 51.e1-51.e8. Available online at www.arthroscopyjournal.org. 21. Sampson T. Arthroscopic treatment of femoroacetabular impingement. Tech Orthop 2005;20:56-62. 22. Clohisy JC, McClure JT. Treatment of anterior femoroacetabular impingement with combined hip arthroscopy and limited anterior decompression. Iowa Orthop J 2005;25:164-171. 23. Pierannunzii L, d’Imporzano M. Treatment of femoroacetabular impingement: A modified resection osteoplasty technique through an anterior approach. Orthopedics 2007;30:96-102. 24. Larson CM, Giveans MR. Arthroscopic management of femoroacetabular impingement: Early outcomes measures. Arthroscopy 2008;24:540-546. 25. McCarthy JC, Lee JA. Acetabular dysplasia: A paradigm of arthroscopic examination of chondral injuries. Clin Orthop Relat Res 2002:122-128. 26. Tönnis D. Normal values of the hip joint for the evaluation of X-rays in children and adults. Clin Orthop Relat Res 1975: 39-42. 27. Clohisy JC, Nunley RM, Otto RJ, Schoenecker PL. The frogleg lateral radiograph accurately visualized hip cam impingement abnormalities. Clin Orthop Relat Res 2007;462:115-121. 28. Wyss TF, Clark JM, Weishaupt D, Nötzli HP. Correlation between internal rotation and bony anatomy in the hip. Clin Orthop Relat Res 2007;460:152-158. 29. Knuesel PR, Pfirrmann CW, Noetzli HP, et al. MR arthrography of the hip: Diagnostic performance of a dedicated waterexcitation 3D double-echo steady-state sequence to detect cartilage lesions. AJR Am J Roentgenol 2004;183:1729-1735. 30. 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. 31. Beck M, Leunig M, Parvizi J, Boutier V, Wyss D, Ganz R.
CAM FEMOROACETABULAR IMPINGEMENT Anterior femoroacetabular impingement: Part II. Midterm results of surgical treatment. Clin Orthop Relat Res 2004:67-73. 32. Murphy S, Tannast M, Kim YJ, Buly R, Millis MB. Debridement of the adult hip for femoroacetabular impingement: Indications and preliminary clinical results. Clin Orthop Relat Res 2004:178-181. 33. Sampson TG. Arthroscopic treatment of femoroacetabular impingement: A proposed technique with clinical experience. Instr Course Lect 2006;55:337-346.
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34. Khanduja V, Villar RN. The arthroscopic management of femoroacetabular impingement. Knee Surg Sports Traumatol Arthrosc 2007;15:1035-1040. 35. Byrd JW. Hip arthroscopy: Surgical indications. Arthroscopy 2006;22:1260-1262. 36. Guanche CA, Bare AA. Arthroscopic treatment of femoroacetabular impingement. Arthroscopy 2006;22:95-106. 37. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br 1999;81:281288.