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Operative Treatment

Diagnosis and Treatment of Femoroacetabular Impingement in Legg-Calve´-Perthes Disease

Kim, Young-Jo MD, PhD; Novais, Eduardo N. MD

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Journal of Pediatric Orthopaedics: September 2011 - Volume 31 - Issue - p S235-S240
doi: 10.1097/BPO.0b013e3182260252
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Legg-Calvé-Perthes disease (LCPD) is a pediatric form of osteonecrosis that ultimately heal but will cause femoral head and acetabular deformities. The deformities can be quite complex and may cause hip instability, femoroacetabular impingement (FAI), or combinations of both and may ultimately lead to degenerative joint disease and early osteoarthritis (OA) of the hip. In the long-term follow-up of LCPD, OA is reported to be a direct function of femoral head sphericity and congruency of the joint.1–3

The normal hip is a multi-axial highly congruent ball and socket joint that requires inherent stability to protect and maintain long-lasting articular cartilage function.4 In addition, it should provide ample and free range of motion required during everyday activities. Instability of the hip in LCPD is a result of secondary acetabular dysplasia that is often caused by remodeling of the acetabulum in response to the aspherical head. FAI involves abnormal contact between the anterior femoral head and head-neck junction against the anterior aspect of the acetabular rim and has been linked to the onset of early OA of the hip.5–8 Although in the unstable dysplastic hip, the femoral head can subluxate out of the acetabulum, in FAI the femoral head remains well centered, however free range of motion is limited.9 These 2 mechanical problems of the hip are polar opposites and usually do not present in the same hip. However in LCPD, a hip may be unstable in upright activities and yet still impinge in hip flexion owing to the aspherical femoral head. FAI in LCPD can obviously be caused by the aspherical femoral head (“cam” FAI) but also may be secondary to acetabular overcoverage owing to a retroverted acetabulum (“pincer” FAI) and functional retroversion caused by the retroverted position of the articulating portion of the femoral head.8

We describe the pathophysiology, clinical presentation, imaging findings, and the management of FAI in patients with LCPD.


In LCPD, resultant femoral head shape, growth disturbance of the proximal femoral physis, and secondary remodeling of the acetabulum can create complex deformities that may lead to abnormal mechanical function of the hip. Instability of the hip in LCPD is due to secondary acetabular remodeling in response to an aspherical head. Both lateral and anterior undercoverage may be present but often anterior undercoverage may be more severe. Impingement in LCPD is most often owing to intra-articular impingement from the aspherical femoral head.6,10,11 However, intra-articular impingement may additionally be due to acetabular retroversion that is often present in LCPD12,13 or secondary to innominate osteotomy or shelf procedure.14 In addition, intra-articular impingement may be due to functional retroversion of the proximal femur secondary to the retroverted position of the articulating femoral head or secondary to prior femoral osteotomy.15 Just as important, extra-articular impingement may be caused by trochanteric overgrowth or rarely owing to the proximal position of the lesser trochanter because of the short femoral neck. All these deformities need to be recognized and its contribution to the patient's symptoms understood.

Clinical Presentation and Imaging

Symptoms owing to mechanical abnormalities may develop in the residual phase of LCPD and may cause hip pain in adolescents and young adults who were diagnosed and treated for LCPD as a child.6 Typically the patient will present with groin pain that is aggravated by physical activities and sitting for long periods. Instability symptoms may present with groin pain after upright activities such as walking and running. Impingement symptoms are more common in positions of hip flexion and internal rotation. Early on, symptoms may be more characterized as stiffness and limitation of motion rather than pain.

Initial imaging should include an appropriate anteroposterior (AP) pelvic plain radiograph that can be obtained with the patient standing or supine. Quantitative measurements of acetabular coverage on the AP pelvis include the lateral center-edge angle of Wiberg16 and the acetabular index of Tönnis17 (Fig. 2). The presence of a break in Shenton's line greater than 5 mm characterizes joint subluxation and is a sign of mechanical instability of the hip. Acetabular retroversion can be identified by the presence of a cross-over sign18 and the projection of the ischial spine into the pelvis.19 The depth of the acetabulum can be evaluated using the ilioischial line as a reference: if the floor of the fossa acetabuli touches or is medial to the ilioischial line, the hip is classified as coxa profunda and if the medial aspect of the femoral head is medial to the ilioischial line it is classified as protrusio acetabuli.20 In general, coxa profunda is rare in LCPD. Careful technique and analysis of the AP pelvis radiograph is important as increased spino-pelvic lordosis and pelvic rotation may falsely make the acetabulum appear retroverted.21,22 In LCPD, hip flexion contractures may be present, which may make the pelvis appear rotated or in a more lordotic position; therefore, interpretation of acetabular retroversion often needs to be interpreted with caution in LCPD. In addition to the pelvic radiograph, a false profile view of the acetabulum should be obtained to look for anterior undercoverage of the femoral head23.

A, Anteroposterior pelvic radiograph. The acetabular index of Tönnis17 (TA) is the angle between the line that connects the most lateral aspect of the sourcil and a line that passes through the inferior aspect of the sourcil (B) and is parallel to the line that connects both femoral heads. The lateral center edge angle of Wiberg16 (LCEA) is the angle between a line that connects the most lateral edge of the sourcil and the center of the femoral head with a perpendicular line to the line that connects both femoral heads. B, Acetabular retroversion on the right hip. Retroversion is revealed by the crossover sign: the anterior wall (light gray line) intersects the posterior wall (dark black line). The ischial spine (arrow) is projected in the pelvis.
A 13-year-old-girl with FAI secondary to LCPD on the left hip. A, Anteroposterior supine radiograph of the pelvis reveals an enlarged femoral head with a short neck. B, Frog-leg lateral demonstrates the cam impingement. C, Reduced head-neck offset is evident on an axial CT scan. D, MRI arthrogram reveals a labral tear. The aspherical portion of the femoral head to be resected involves the epiphysis (arrow). This patient underwent an arthroscopic labral debridement performed elsewhere that failed to relieve her symptoms. E to F, Radiographic aspect after surgical dislocation of the hip and osteochondroplasty demonstrates correction of the femoral head-neck offset. CT indicates computerized tomography; MRI, magnetic resonance imaging.

A lateral view of the proximal femur (cross-table lateral,24 frog-leg lateral,25 or a Dunn view26) should also be obtained. The lateral view of the proximal femur adds information about the sphericity of the femoral head and the reduced head-neck offset. Quantitative evaluation of the head-neck junction includes measuring the alpha angle27 and the head-neck offset ratio.28 Functional radiographs, with or without an arthrogram can provide additional information regarding the indication of a realignment femoral osteotomy in nonspherical hips.

Accurate measurement of acetabular and femoral version can be important information needed in the treatment planning of LCPD and may require advanced imaging modalities such as computerized tomography (CT) scan and magnetic resonance imaging (MRI).29 In LCPD, the anterolateral extrusion of the enlarged femoral head is believed to block internal rotation, whereas the posteromedial superior portion of the head that truly articulates in the acetabulum is retroverted and may functionally cause retroversion of the proximal femur.15 CT scan helps in quantifying the femoral head-neck concavity and has the advantage of 3-dimensional reconstruction, however, it requires a higher dose of radiation. MR arthrography with radial cuts rotating around the femoral neck axis allows assessment of the femoral head-neck junction shape and the labrum in its entire circumference.30,31 Recently dGEMRIC has allowed direct assessment of cartilage matrix and understanding of the complex damage pattern of hip joint cartilage and labrum after LCPD.29

Surgical Treatment

Successful treatment of LCPD patients with residual disease requires identification of individual deformities that contribute to the patient's symptoms. In this instance, the most challenging aspect is to differentiate those patients with isolated FAI from patients with secondary acetabular dysplasia and instability and association of both. In addition, it is important to understand the source of the conflict between the femoral head-neck and the acetabulum rim (femoral vs. acetabular or combined; intra-articular vs. extra-articular) to design the surgical plan.

The most common treatment options on the femoral side of the hip joint include intertrochanteric osteotomy,32 relative neck lengthening,33 true femoral neck lengthening,34 and osteochondroplasty of the head-neck junction.8 Recently, a femoral head reduction osteotomy has been described for correction of the enlarged femoral head.35 On the acetabular side, extra-articular procedures include acetabular augmentation osteotomy36 and redirectional osteotomies.37 Complex deformities of both femur and acetabulum leading to instability and FAI usually require a combined approach.38,39 Intra-articular procedures include acetabular trimming with labral refixation40 and possible microfracture for cartilage loss. The rather complex mismatch between the enlarged femoral head and the misshapen acetabulum limits the role for arthroscopic approach.41,42

The ultimate goal in the management of adolescents with FAI secondary to LCPD is to improve impingement-free range of motion and restore joint congruency and stability. The recently described surgical dislocation of the hip allows full inspection of the joint and dynamic assessment of femoroacetabular contact during hip motion.43 Through this approach, reshaping of the proximal femur through head-neck osteoplasty with or without a proximal femoral osteotomy or a relative neck lengthening when indicated can be performed.35 In addition, it allows correction of acetabular overcoverage (pincer impingement) by an acetabular osteoplasty and full access to the acetabular labrum and cartilage.40

Surgical management therefore should start with correction of the femoral deformity first through a surgical dislocation approach. We carefully evaluate the causes of impingement preoperatively. If the enlarged femoral head with reduced head-neck offset is thought to be the isolated cause, then an osteochondroplasty of the head-neck junction is performed. In these complex deformities, the aspherical portion of the femoral head to be resected by osteochondroplasty most often involves the epiphysis requiring complete assessment of the femoral head-neck junction intraoperative. Even though a labral tear may be present, it should not be treated without correction of the cam deformity (Fig. 2). The indication to perform a relative neck lengthening osteotomy after the osteochondroplasty is to correct extra-articular impingement owing to a high-riding greater trochanter and a short wide neck (Fig. 3). When the osteoplasty is not enough to correct the FAI, then a femoral osteotomy is added to the procedure. The osteotomy should be performed at the intertrochanteric level and the final decision on the type of osteotomy to be performed is based on preoperative evaluation of hip range of motion, functional radiographs, and radially reconstructed MRI or CT. Finally, a perioperative assessment of the dynamic of the femoroacetabular contact during hip motion is done after the surgical dislocation of the hip. A flexion osteotomy is indicated when the anterolateral impingement area is too large to be completely removed. When the articulating portion of the femoral head is retroverted and functional retroversion of the proximal femur is present, a flexion-internal rotation osteotomy may be necessary to realign the lower extremity and reestablish a more functional arc of motion (Fig. 4). After correction of the femoral deformity, it is crucial to evaluate the acetabulum, which may be dysplastic with undercoverage of the femoral head. In this situation, symptoms related to mechanical instability may persist and may be improved by a redirectional periacetabular osteotomy (Fig. 5). In some patients with previous shelf augmentation of the acetabulum and pincer-type impingement, the overcoverage may be corrected by an osteoplasty of the acetabular rim with labrum refixation. Our preliminary results on 15 patients who underwent an Surgical Dislocation of the Hip for the management of FAI secondary to LCPD revealed that the Western Ontario and McMaster Universities Osteoarthritis Index scores reduced from a preoperative score of 9.6 to a postoperative score of 5.1.44

Osteochondroplasty with relative femoral neck lengthening in an 18-year-old-girl with FAI secondary to previous LCPD on the right hip. A, Anteroposterior standing radiograph of the pelvis reveals an enlarged aspherical femoral head with a short neck and an overriding greater trochanter. B, An abduction view reveals the possible extra-articular impingement of the greater trochanter. C, MRI delineates the deformity and is useful in for the surgical planning. D and E, Anteroposterior and lateral postoperative radiographs shows that the articulo-trochanteric and the head-neck offset are improved. FAI indicates femoroacetabular impingement; LCPD, Legg-Calve´-Perthes disease; MRI, magnetic resonance imaging.
A 12-year-old-boy with bilateral Legg-Calve´-Perthes disease. A, Anteroposterior radiographic of the pelvis reveals a severe deformity of the left femoral head. B, The enlarged femoral head extrusion impinging on the acetabulum rim. C, Axial CT scan demonstrates that the round portion of the femoral head was posteromedial—functional retroversion. D and E, Radiographic aspect 3 years after a surgical dislocation of the hip with femoral head-neck osteoplasty and a flexion intertrochanteric osteotomy. CT indicates computerized tomography.
Combined hip instability and impingement in a 15-year-old-male with residual deformity of the right femoral head after LCPD (A) AP radiograph of the pelvis. B, False profile of the right hip. C, AP of the pelvis following surgical dislocation of the hip, osteochondroplasty of the femoral head/neck junction and relative lengthening of the femoral neck. The patient had persisted pain mainly with standing activities. D, Von Rosen view reveals better joint congruency with abduction, flexion and internal rotation. E to F, Radiographs after a Bernese-type periacetabular osteotomy was performed to correct mechanical instability demonstrate improved joint congruency and anterolateral coverage of the femoral head. AP indicates anteroposterior; LCPD, Legg-Calve´-Perthes disease.

We believe that following careful preoperative planning, including accurate measurement of hip range of motion and radiographs (AP pelvis, false profile, and lateral hip) associated with MRI (radial sequences), a surgical dislocation of the hip allows a safe approach to correct the femoral and acetabular deformities responsible for FAI secondary to LCPD in adolescents.


1. Weinstein SL. Legg-Calve-Perthes disease: results of long-term follow-up Hip.. 1985:28–37
2. Stulberg SD, Cooperman DR, Wallensten R. The natural history of Legg-Calve-Perthes disease J Bone Joint Surg Am.. 1981;63:1095–1108
3. Mose K, Hjorth L, Ulfeldt M, et al. Legg Calve Perthes disease. The late occurence of coxarthrosis Acta Orthop Scand Suppl.. 1977;169:1–39
4. Bombelli R, Santore RF, Poss R. Mechanics of the normal and osteoarthritic hip. A new perspective Clin Orthop Relat Res.. 1984;182:69–78
5. Beaule PE, Allen DJ, Clohisy JC, et al. The young adult with hip impingement: deciding on the optimal intervention Instr Course Lect.. 2009;58:213–222
6. Eijer H, Podeszwa DA, Ganz R, et al. Evaluation and treatment of young adults with femoro-acetabular impingement secondary to Perthes' disease Hip Int.. 2006;16:273–280
7. 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;87:1012–1018
8. Ganz R, Parvizi J, Beck M, et al. Femoroacetabular impingement: a cause for osteoarthritis of the hip Clin Orthop Relat Res.. 2003;417:112–120
9. Leunig M, Beaule PE, Ganz R. The concept of femoroacetabular impingement: current status and future perspectives Clin Orthop Relat Res.. 2009;467:616–622
10. Snow SW, Keret D, Scarangella S, et al. Anterior impingement of the femoral head: a late phenomenon of Legg-Calve-Perthes' disease J Pediatr Orthop.. 1993;13:286–289
11. Yoo WJ, Choi IH, Chung CY, et al. Valgus femoral osteotomy for hinge abduction in Perthes' disease. Decision-Demaking and outcomes J Bone Joint Surg Br.. 2004;86:726–730
12. Ezoe M, Naito M, Inoue T. The prevalence of acetabular retroversion among various disorders of the hip J Bone Joint Surg Am.. 2006;88:372–379
13. Sankar WN, Flynn JM. The development of acetabular retroversion in children with Legg-Calve-Perthes disease J Pediatr Orthop.. 2008;28:440–443
14. Dora C, Mascard E, Mladenov K, et al. Retroversion of the acetabular dome after Salter and triple pelvic osteotomy for congenital dislocation of the hip J Pediatr Orthop B.. 2002;11:34–40
15. Kim HT, Wenger DR. “Functional retroversion” of the femoral head in Legg-Calve-Perthes disease and epiphyseal dysplasia: analysis of head-neck deformity and its effect on limb position using three-dimensional computed tomography J Pediatr Orthop.. 1997;17:240–246
16. Wiberg G. Studies on dysplastic acetabula and congenital subluxation of the hip joint. With special reference to the complication of osteoarthritis Acta Chir Scand.. 1939;83(suppl 58):28–38
17. Tönnis D Congenital dysplasia and dislocation of the hip in children and adults. 1987 New York, NY Springer
18. Jamali AA, Mladenov K, Meyer DC, et al. Anteroposterior pelvic radiographs to assess acetabular retroversion: high validity of the “cross-over-sign” J Orthop Res.. 2007;25:758–765
19. Kalberer F, Sierra RJ, Madan SS, et al. Ischial spine projection into the pelvis: a new sign for acetabular retroversion Clin Orthop Relat Res.. 2008;466:677–683
20. Clohisy JC, Carlisle JC, Beaule PE, et al. A systematic approach to the plain radiographic evaluation of the young adult hip J Bone Joint Surg Am.. 2008;90(suppl 4):47–66
21. Clohisy JC, Carlisle JC, Trousdale R, et al. Radiographic evaluation of the hip has limited reliability Clin Orthop Relat Res.. 2009;467:666–675
22. Tannast M, Zheng G, Anderegg C, et al. Tilt and rotation correction of acetabular version on pelvic radiographs Clin Orthop Relat Res.. 2005;438:182–190
23. Lequesne M, de Sèze S. Le faux profil du bassin: nouvelle incidence radiographique pour l'etude de la hanche. Son utilité dans les dysplasies et les differentes coxopathies Rev Rhum Mal Osteoartic. 1961;28:643–652
24. Eijer H, Leunig M, Mahomed M, et al. Cross-table lateral radiograph for screening of anterior femoral head-neck offset in patients with femoroacetabular impingement Hip Int.. 2001;11:37–41
25. Clohisy JC, Nunley RM, Otto RJ, et al. The frog-leg lateral radiograph accurately visualized hip cam impingement abnormalities Clin Orthop Relat Res.. 2007;462:115–121
26. Dunn DM. Anteversion of the neck of the femur; a method of measurement J Bone Joint Surg Br.. 1952;34-B:181–186
27. Murphy SB, Ganz R, Muller ME. The prognosis in untreated dysplasia of the hip. A study of radiographic factors that predict the outcome J Bone Joint Surg Am.. 1995;77:985–989
28. 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
29. Zilkens C, Holstein A, Bittersohl B, et al. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage in the long-term follow-up after Perthes disease J Pediatr Orthop.. 2010;30:147–153
30. Horii M, Kubo T, Hirasawa Y. Radial MRI of the hip with moderate osteoarthritis J Bone Joint Surg Br.. 2000;82:364–368
31. Locher S, Werlen S, Leunig M, et al. MR-Arthrography with radial sequences for visualization of early hip pathology not visible on plain radiographs Z Orthop Ihre Grenzgeb.. 2002;140:52–57
32. Millis MB, Murphy SB, Poss R. Osteotomies about the hip for the prevention and treatment of osteoarthrosis Instr Course Lect.. 1996;45:209–226
33. Ganz R, Huff TW, Leunig M. Extended retinacular soft-tissue flap for intra-articular hip surgery: surgical technique, indications, and results of application Instr Course Lect.. 2009;58:241–255
34. Hefti F, Morscher E. The femoral neck lengthening osteotomy Orthopedics and Traumatology.. 1993;2:144–151
35. Ganz R, Horowitz K, Leunig M. Algorithm for Femoral and Periacetabular Osteotomies in Complex Hip Deformities. Clin Orthop Relat Res [epub ahead of print] 2010. Available at Accessed November 2, 2010
36. Chiari K. History and present indications for corrective surgery of the acetabulum in hip dysplasia (author's transl) Arch Orthop Unfallchir.. 1976;86:67–76
37. Ganz R, Klaue K, Vinh TS, et al. A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results Clin Orthop Relat Res.. 1988;232:26–36
38. Millis MB, Kim YJ. Rationale of osteotomy and related procedures for hip preservation: a review Clin Orthop Relat Res.. 2002;405:108–121
39. Clohisy JC, Nunley RM, Curry MC, et al. Periacetabular osteotomy for the treatment of acetabular dysplasia associated with major aspherical femoral head deformities J Bone Joint Surg Am.. 2007;89:1417–1423
40. Espinosa N, Beck M, Rothenfluh DA, et al. Treatment of femoro-acetabular impingement: preliminary results of labral refixation. Surgical technique J Bone Joint Surg Am.. 2007;89(suppl):36–53
41. Kocher MS, Kim YJ, Millis MB, et al. Hip arthroscopy in children and adolescents J Pediatr Orthop.. 2005;25:680–686
42. Roy DR. Arthroscopic findings of the hip in new onset hip pain in adolescents with previous Legg-Calve-Perthes disease J Pediatr Orthop B.. 2005;14:151–155
43. 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;83:1119–1124
44. Rebello G, Spencer S, Millis MB, et al. Surgical dislocation in the management of pediatric and adolescent hip deformity Clin Orthop Relat Res.. 2009;467:724–731
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