Statistical analyses were performed with StatView software (version 5.0; SAS Institute, Cary, North Carolina). We used the chi-square test to compare the frequency rate of acetabular retroversion between each pair of groups. A difference was considered to be significant when the p value was <0.05.
In the normal group, all fifty-six subjects (112 hips) had Grade-0 osteoarthritis according to the Tönnis classification system (Table II). The prevalence of acetabular retroversion was 6% (seven hips). Acetabular retroversion was slightly more frequent among male subjects, occurring in three (7%) of the forty-four hips in male subjects and four (6%) of the sixty-eight hips in the female subjects. The difference was not significant. The posterior wall sign was present in five of the seven hips with acetabular retroversion.
In the osteoarthritis group (sixty-six patients; seventy hips), no hip had Grade-0 osteoarthritis; two had Grade-1, thirty-four had Grade-2, and thirty-four had Grade-3 osteoarthritis according to the Tönnis classification system. The prevalence of acetabular retroversion was 20% (fourteen hips), a significantly higher prevalence than that in the normal group (p = 0.0047) (Table III). Two of the nine hips in the male patients and twelve (20%) of the sixty-one hips in the female patients demonstrated acetabular retroversion; the difference was not significant. The posterior wall sign was noted in ten of the fourteen hips with acetabular retroversion. Of the fourteen hips with acetabular retroversion, six had Grade-2 osteoarthritis and eight had Grade-3 osteoarthritis according to the Tönnis classification system. No significant association was detected between the prevalence of acetabular retroversion and the Tönnis classification.
In the dysplasia group (sixty-four patients; seventy-four hips), thirty-five hips had Grade-0 osteoarthritis according to the Tönnis classification system, thirty-three had Grade 1, six had Grade 2, and no hip had Grade 3. The prevalence of acetabular retroversion was 18% (thirteen hips), which was significantly higher than that in the normal group (6%; p = 0.0147) (Fig. 3). The prevalence of acetabular retroversion was higher for male patients (two of eight hips) than for female patients (17%; eleven of sixty-six hips) (p = 0.559). The posterior wall sign was seen in all thirteen hips with acetabular retroversion.
The prevalence of acetabular retroversion in the osteonecrosis group was 6% (two of thirty-six hips). No significant difference was detected between this group and the normal group or between male and female patients. Acetabular retroversion occurred in one (5%) of the twenty hips in male patients and in one of the sixteen hips in the female patients. The posterior wall sign was present in one of these two hips. A collapsed femoral head was seen in twenty-four hips in twenty patients.
In the Legg-Calvé-Perthes group (thirty-four patients; fifty hips), thirteen hips had Grade-0 osteoarthritis according to the Tönnis classification system, twenty-three had Grade 1, fourteen had Grade 2, and no hip had Grade 3. The prevalence of acetabular retroversion was 42% (twenty-one hips), a significantly higher frequency than in the normal group (p < 0.0001). Acetabular retroversion was more frequent among male patients; it occurred in eleven (46%) of twenty-four hips in male patients and in ten (38%) of the twenty-six hips in female patients (p = 0.598). The posterior wall sign was observed in nineteen of the twenty-one hips with acetabular retroversion.
The Legg-Calvé-Perthes group was divided according to the Stulberg classification of femoral head and acetabular deformities12. The acetabular retroversion occurred in one of eight class-I hips, three of seventeen class-II hips, nine of thirteen class-III hips, six of nine class-IV hips, and two of three class-V hips.
In the Legg-Calvé-Perthes group, we also compared the prevalence of acetabular retroversion in the hips with spherical femoral heads (Stulberg classes I and II [the spherical group]) and the hips with Stulberg class-III, IV, and V involvement (the nonspherical group). Seventeen (68%) of twenty-five hips in the nonspherical group had acetabular retroversion compared with only four (16%) of twenty-five hips in the spherical group (p = 0.0002) (Fig. 4).
No significant association was seen in the Legg-Calvé-Perthes group between the prevalence of acetabular retroversion and the Tönnis classification.
The posterior aspect of the acetabulum is subjected to high loads during the activities of daily living15-17. With acetabular retroversion, theoretically greater unit loads are imposed on the available posterior cartilage. These increased unit loads may be responsible for the development of osteoarthritis of the hip.
A proper determination of acetabular retroversion requires that the orientation of the pelvis be taken into consideration. The cross-over sign can be easily influenced by the inclination or rotation of the pelvis9,14,18,19. Siebenrock et al.9 suggested that the cross-over sign is influenced by the inclination of the pelvis. They measured the distance between the pubic symphysis and the sacrococcygeal joint in healthy subjects and reported a mean value of 32.3 mm for males and 47.3 mm for females. The values we obtained were slightly larger than those, although the difference might reflect lifestyle and skeletal differences between Asian and white populations. If pelvic inclination and rotation are overlooked, some normal images may be misdiagnosed as acetabular retroversion.
In a review of the literature, Li and Ganz reported that acetabular retroversion was found in forty (17.2%) of 232 hips with developmental dysplasia20. This prevalence is almost identical to our findings (18%). In contrast, Mast et al. reported that acetabular retroversion was found in eighty-seven (37%) of 235 hips with developmental dysplasia21. However, they used different criteria to evaluate pelvic tilt. Their study excluded patients in whom the tip of the coccyx was >2 cm from the superior border of the pubic symphysis, which they considered excessive inclination of the pelvis, whereas we used the pelvic tilt evaluation criteria of Siebenrock et al.9,13. Mast et al. also reported that a smaller lateral center-edge angle is closely related not only to acetabular anteversion but also to acetabular retroversion21.
Malformations of the acetabulum, such as those seen in developmental dysplasia, slipped capital femoral epiphysis, and Legg-Calvé-Perthes disease are thought to be of etiologic importance to the development of osteoarthritis of the hip2,22,23. The dysplasia group in our study had a higher prevalence of acetabular retroversion than the normal group, and the posterior wall sign was recognized in all dysplastic hips with retroversion. These results indicate that retroversion in developmental dysplasia is more common than previously thought. Murphy et al. found heterogeneous patterns of developmental dysplasia1. Of twenty dysplastic hips, seven had anterolateral deficiency, six had posterolateral deficiency, and seven had symmetric, global deficiency. This heterogeneity has important implications for corrective surgery because the type of acetabular insufficiency must be evaluated preoperatively so that appropriate reorientation of the acetabulum is performed.
Adult-onset osteonecrosis and the resulting collapse and deformity of the femoral head generally occur after the completion of acetabular growth. The prevalence of acetabular retroversion in the osteonecrosis group was 6%, and no significant difference was observed between this group and the normal group. Therefore, it appears that osteonecrosis is a problem exclusively of the femoral head, and acetabular retroversion is not a contributing factor to the osteoarthritis that ensues.
In contrast, the prevalence of acetabular retroversion in patients with so-called idiopathic osteoarthritis was 20%. Harris postulated that most instances of so-called idiopathic osteoarthritis were secondary to preexisting developmental deformities2. While we did not examine these patients or hips to elucidate possible developmental abnormalities, we believe that this group of patients deserves further study to determine why the prevalence of retroversion is so high.
Recent reports have examined the relationship between femoroacetabular impingement attributable to acetabular retroversion and osteoarthritis of the hip5-7,9. For hips with acetabular retroversion but without the posterior wall sign, it is possible that acetabular retroversion might have resulted from excessive coverage of the anterior wall. We suspect that, in the four hips with acetabular retroversion but without the posterior wall sign in the osteoarthritis group, the deformity might have been caused by excessive coverage of the anterior acetabular wall rather than by deficiency of the posterior wall. We further presume that excessive coverage of the anterior acetabular wall might lead to femoroacetabular impingement5-7,9.
Legg-Calvé-Perthes disease is an idiopathic osteonecrosis of the femoral head in children. Although the age at onset ranges from two to thirteen years, the majority of our patients were between four and seven years of age when it developed. The prevalence of acetabular retroversion in the Legg-Calvé-Perthes group was 42%, which was significantly higher than that in the normal group. In addition, within the Legg-Calvé-Perthes group, the frequency of acetabular retroversion was significantly higher in the nonspherical group than in the spherical group. It is unclear whether acetabular retroversion is a cause or effect of the femoral head deformities in these patients. The significantly higher frequency of acetabular retroversion in the nonspherical group compared with the spherical group suggests that the magnitude of femoral head deformity during growth is related to the development of acetabular retroversion in patients with Legg-Calvé-Perthes disease.
We perform periacetabular osteotomy as surgical treatment for developmental dysplasia24. The presence of acetabular retroversion influences the reorientation of the acetabulum during surgery. When dysplasia of the lateral and anterior aspect of the acetabulum is found, we transfer the osteotomized acetabulum anterolaterally to obtain sufficient coverage of the femoral head. However, when we perform a periacetabular osteotomy for a patient with lateral developmental dysplasia and acetabular retroversion, we transfer the osteotomized acetabulum only in a lateral direction while simultaneously moving the femoral head medially, to avoid transferring the acetabulum anteriorly and thus cause an insufficiency in the posterior wall and a possible exacerbation of femoroacetabular impingement25,26.
When we perform a total hip arthroplasty on a patient with acetabular retroversion, we pay careful attention not to align the acetabular component with an insufficient posterior wall and thereby orient the cup in retroversion.
In conclusion, we investigated the prevalence of acetabular retroversion in normal subjects and in patients with osteoarthritis of the hip, developmental dysplasia, osteonecrosis of the femoral head, and residual deformity resulting from Legg-Calvé-Perthes disease, by examining standard anteroposterior radiographs of the pelvis. Acetabular retroversion occurred at a significantly higher rate in patients with osteoarthritis of the hip, developmental dysplasia, and Legg-Calvé-Perthes disease compared with that in subjects in the normal group. Within the Legg-Calvé-Perthes group, the frequency of acetabular retroversion was significantly higher in the nonspherical group than in the spherical group. Acetabular retroversion is more common than has been previously noted, and it appears in a variety of diseases of the hip. Its relationship to the subsequent development of degenerative arthritis in these entities deserves further study. ▪
The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Department of Orthopaedic Surgery, Fukuoka University School of Medicine, Fukuoka, Japan
1. , Kijewski PK, Millis MB, Harless A. Acetabular dysplasia in the adolescent and young adult. Clin Orthop Relat Res. 1990;261: 214-23.
2. . Etiology of osteoarthritis of the hip. Clin Orthop Relat Res. 1986; 213: 20-33.
3. . Patterns of osteoarthritis of the hip. J Bone Joint Surg Br. 1976; 58: 176-83.
4. . Studies on dysplastic acetabula and congenital subluxation of the hip joint. With special reference to the complication of osteoarthritis. Acta Chir Scand. 1939; 83(Supplementum 58).
5. , Leunig M, Parvizi J, Boutier V, Wyss D, Ganz R. Anterior femoroacetabular impingement: part II. Midterm results of surgical treatment. Clin Orthop Relat Res. 2004;418: 67-73.
6. , Parvizi J, Beck M, Siebenrock KA, Ganz R, Leunig M. Anterior femoroacetabular impingement: part I. Techniques of joint preserving surgery. Clin Orthop Relat Res. 2004;418: 61-6.
7. , Parvizi J, Beck M, Leunig M, Notzli H, Siebenrock KA. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003;417: 112-20.
8. , Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br. 1999;81: 281-8.
9. , Schoeniger R, Ganz R. Anterior femoro-acetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am. 2003;85: 278-86.
10. , Heinecke A. Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 1999;81: 1747-70.
11. , Trousdale RT. Acetabular retroversion is associated with osteoarthritis of the hip. Clin Orthop Relat Res. 2003;417: 263-9.
12. , Cooperman DR, Wallensten R. The natural history of Legg-Calve-Perthes disease. J Bone Joint Surg Am. 1981;63: 1095-108.
13. , Kalbermatten DF, Ganz R. Effect of pelvic tilt on acetabular retroversion: a study of pelves from cadavers. Clin Orthop Relat Res. 2003;407: 241-8.
14. . Congenital dysplasia and dislocation of the hip in children and adults. Berlin: Springer Verlag; 1987. p 167.
15. , Carlson KL, Fijan RS, Burgess RG, Riley PO, Harris WH, Mann RW. Contact pressures from an instrumented hip endoprosthesis. J Bone Joint Surg Am. 1989;71: 1378-86.
16. , Brand RA, Davy DT. Pelvic muscle and acetabular contact forces during gait. J Biomech. 1997;30: 959-65.
17. , Eckstein F, Recknagel S. A calculation of the forces acting on the human acetabulum during walking. Based on in vivo force measurements, kinematic analysis and morphometry. Acta Anat (Basel). 1997;160: 269-80.
18. , Svenningsen S, Grontvedt T, Benum P. Pelvic inclination and spatial orientation of the acetabulum. A radiographic, computed tomographic and clinical investigation. Acta Radiol. 1990;31: 389-94.
19. , Nakagawa T, Tohkura A. Simulation of acetabular coverage of femoral head using anteroposterior pelvic radiographs. Arch Orthop Trauma Surg. 1998;117: 330-6.
20. , Ganz R. Morphologic features of congenital acetabular dysplasia: one in six is retroverted. Clin Orthop Relat Res. 2003;416: 245-53.
21. , Brunner RL, Zebrack J. Recognizing acetabular version in the radiographic presentation of hip dysplasia. Clin Orthop Relat Res. 2004;418: 48-53.
22. , Feighan JE, Smith AD, Latimer B, Buly RL, Cooperman DR. Subclinical slipped capital femoral epiphysis. Relationship to osteoarthrosis of the hip. J Bone Joint Surg Am. 1997;79: 1489-97. Erratum in: J Bone Joint Surg Am. 1999;81:592.
23. , Bjerkreim I, Kolbenstvedt A. Anteversion of the acetabulum and femoral neck in normals and in patients with osteoarthritis of the hip. Acta Orthop Scand. 1983;54: 18-23.
24. , Shiramizu K, Akiyoshi Y, Ezoe M, Nakamura Y. Curved periacetabular osteotomy for treatment of dysplastic hip. Clin Orthop Relat Res. 2005; 433: 129-35.
25. , Buhler M, Stover MD, Mahomed MN, Ganz R. Morphologic characteristics of acetabular dysplasia in proximal femoral focal deficiency. J Pediatr Orthop B. 2004;13: 81-7.
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26. , Mascard E, Mladenov K, Seringe R. 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.