Subclinical slipped capital femoral epiphysis. Relationship to osteoarthrosis of the hip.

We examined the femora of 2665 adult human skeletons from an osteological collection to determine the prevalence of post-slip morphology termed femoral head-tilt deformity by Murray and pistol-grip deformity by Stulberg et al. The hypothesis was that primary osteoarthrosis of the hip is a secondary manifestation of a subclinical developmental disorder of the hip. The prevalence of post-slip morphology was 8 per cent (215 of 2665 skeletons). Severe osteoarthrosis was more prevalent in association with postslip morphology (116 [38 per cent] of 306 hips) than in the matched controls (seventy-nine [26 per cent] of 306 hips) (p < 0.005). In the skeletons that had unilateral post-slip morphology, severe osteoarthrosis was more prevalent in the involved hips (thirty-one [37 per cent] of eighty-three) than in the contralateral, normal hips (eighteen [22 per cent] of eighty-three) (p < 0.05). Post-slip morphology, which was unrelated to age, was found to be a major risk factor for the development of high-grade osteoarthrosis. We noted evidence of high-grade osteoarthrosis in sixty-three (68 per cent) of the ninety-three hips with minimum post-slip morphology in skeletons from individuals who had been fifty-six years old or more at the time of death compared with forty-five (48 per cent) of the ninety-three control hips. With the numbers available, this difference was not found to be significant (p < 0.025). The osteoarthrosis in the hips with post-slip morphology was distinctly characterized by anterior flattening of the acetabulum, cystic degeneration in the anterior metaphyseal-epiphyseal region, and progression to global osteoarthrosis of the hip. Osteoarthrosis is second only to cardiovascular disease as a cause of severe chronic disability, and it affects more than 60 per cent of the population who are sixty-five years old or more (11,402 of 14,032 in one study). This disease leads to the expenditure of billions of dollars for medication, operations, and days lost from work. In 1977, the direct economic cost for the treat*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study. tDepartment of Orthopedics, University Hospitals of Cleveland, 11100 Euclid Avenue, Cleveland, Ohio 44106. Please address requests for reprints to Dr. Goodman. ment of arthritis was 7.7 billion dollars and the indirect cost (lost income of both wage earners and homemakers) was 918 million dollars-. Osteoarthrosis can be classified as primary or secondary. The secondary causes include trauma, metabolic disorders, vascular disease, congenital dysplasia of the hip, slipped capital femoral epiphysis, and Legg-CalvePerthes disease. Osteoarthrosis without evidence of pre-existing disease is classified as primary or idiopathic. Lloyd-Roberts found that 59 per cent of 124 hips in 117 patients had evidence of osteoarthrosis with no apparent etiology. Some authors believe that idiopathic osteoarthrosis of the hip is the result of an as yet undetermined systemic metabolic or genetic abnormality of cartilage or subchondral bone, whereas others believe that most cases of primary osteoarthrosis of the hip are secondary to subclinical acetabular dysplasia, slipped capital femoral epiphysis, or Legg-CalvePerthes disease-". We evaluated the femoral heads of adult human skeletons to determine the epidemiology of post-slip morphological changes and their relationship, if any, to osteoarthrosis of the hip. Materials and Methods We obtained 2972 complete human disarticulated skeletons from the Hamann-Todd osteological collection at the Cleveland Museum of Natural History that had been gathered from the unclaimed dead at the Cleveland city morgue between 1893 and 1938. There were 2457 skeletons from men (837 of whom had been black) and 515 skeletons from women (287 of whom had been black). The average age of the individuals at the time of death was forty-five years (range, one to ninety-six years). Forty-four of the skeletons were from individuals who had been less than twelve years old. A skeleton was excluded from the study if it had an open physis; the pelvis and femora were not intact; part or all of the lower extremity was missing; or there was evidence of osteomyelitis, Paget disease, ankylosing spondylitis, rheumatological disease, fracture of the femur or acetabulum, dysplasia of the hip, or Legg-Calv6-Perthes disease. Fifty-two skeletons were excluded because they were skeletally immature; sixty-one, because they were incomplete; and 194, because they had evidence of another disease. Thus, 2665 skeletons (2227 from men and 438 from women) were included in this study. Complete clinical information was not available for these skeletons. The dissections had been performed by medical students, the soft tissue had been removed by boiling, and the bone had then been cleaned with brushes. In 1985, all of the bones were degreased with trichloroethane. The femora were examined visually for evidence of post-slip morphology by two examiners who were blinded with regard to the VOL. 79-A, NO. 10. OCTOBER 1997 1489 1490 D. A. GOODMAN ET AL. age, gender, and race of the individual. Post-slip morphology was characterized by loss of the normal concavity of the anterosuperior region of the head-neck junction, increased concavity of the posteroinferior region of the head-neck junction, location of the fovea posterior to a line through the axis of the neck, posterior tilt of the edge of the articular surface in reference to the perpendicular of a line through the axis of the neck, and a roughened surface of exposed metaphyseal bone located anteriorly between the apparent original position of the epiphysis and its displaced position (Figs. 1-A through 2-D). The skeletons were divided according to age at the time of death: forty years or less, forty-one to fifty-five years, and fifty-six years or more. We compared the degree of osteoarthrosis in the hips with post-slip morphology with that in control hips and then repeated the comparison after the two groups had been subdivided in terms of age. Statistical analysis was performed with the chi-square method. The degree of maximum posterior tilt of the head in relation to the axis of the neck was measured with a goniometer. The findings were graded as minimum (an angle of 30 degrees or less), moderate (an angle of 31 to 45 degrees), and severe (an angle of 46 degrees or more). The posterior angulation for the femora with post-slip morphology ranged from 5 to 78 degrees, whereas the angulation for the controls ranged from -5 to +3 degrees. The absence of any overlap between these ranges validated our visual scoring system. We selected a group of 215 femora without a deformity that were matched for age, gender, and race of the donor with those of the 215 skeletons with a deformity. The two groups were graded for osteoarthrosis on the basis of the presence of osteophytes, erosions, and flattening or exposure of trabecular bone. Lipping of the femoral fovea was considered normal. The acetabulum was graded first, by an examiner who did not know the morphology of the corresponding femur; then the femur was graded, and a total hip score was calculated on the basis of these two grades. According to the osteoarthrosis