BONE-DISEASE IN AFRICAN CHILDREN WITH SLIPPED CAPITAL FEMORAL EPIPHYSIS - HISTOMORPHOMETRY OF ILIAC CREST BIOPSIES

African teenagers with slipped capital femoral epiphysis (SCFE) not in frequently also have genu valgum (knockknee). Because we had previousl y demonstrated metabolic bone disease attributable to dietary calcium deficiency in black teenagers with genu valgum, we examined 29 black t eenagers (15 male, 14 female) with SCFE for metabolic bone disease. Ea ch patient had an iliac crest bone biopsy taken (after double tetracyc line labeling) for routine histomorphometry, and blood and urine sampl es for bone biochemistry. Spinal bone mineral density was measured in 13 patients. Compared to reported data, we found our patients to be se xually more immature, older, at least as obese, and to have more sever e and more frequently bilateral hip disease. Eighty percent of the chi ldren took dairy products only once or twice a week or less frequently , and 37.9 % had genu valgum. Compared with race-and age-matched South Africans, bone biopsies in our patients showed lower bone volume (BV/ TV, p = 0.0003), wall thickness (p = 0.0002), and trabecular thickness (Tb.Th, p = 0.0002), and a tendency to greater trabecular spacing (Tb .Sp,p = 0.053). Lower osteoid volume (OV/BV, p = 0.0001), osteoid surf ace (OS/BS, p = 0.0001), osteoid thickness (O.Th, p = 0.0002), double labeled surface (dLS/BS, p = 0.029), and bone formation rate (BFR/BS, p 0.037) suggested poorer bone forming capacity in our patients. No ev idence of hyperparathyroid bone disease or osteomalacia was found. BV/ TV was below the reference range (14.2%) in 65.5% of cases; these pati ents had lower values for Tb.Th (p = 0.037) and Tb.N (p = 0.0003), gre ater Tb.Sp (p = 0.0002), a tendency to lower adjusted apposition rate (Aj.AR, p = 0.057), and had had less frequent intake of dairy products than those with normal BV/TV (p = 0.024). Furthermore, months since m enarche correlated with histomorphometric variables BV/TV (I = 0.667, p = 0.009), Tb.Th (r = 0.745, p = 0.002), Tb.Sp (r = -0.549, p = 0.042 ), O.Th (r = 0.784, p = 0.0009), and Aj.AR (r = 0.549, p = 0.042). The correlation between Tb.Th and spinal bone mineral content (r = 0.656, p = 0.015) suggests that the reduced trabecular thickness reflected a generalized bone condition. A greater than normal proportion of patie nts had spinal bone mineral density values below -1 standard deviation (SD) of the mean (osteopenia) (p = 0.001). Patients tested for parath yroid hormone and 25-hydroxyvitamin D levels were found to have normal values. Parathyroid hormone correlated with Aj.AR (r = 0.661, p = 0.0 38) and serum phosphorus (r= -0.764, p = 0.010). We conclude that sexu al immaturity and possibly past dietary calcium deficiency contributed to osteopenia, and that this, together with obesity, led to the devel opment of more severe and more frequently bilateral SCFE in our patien ts than in reported series of black and white children. (C) 1998 by El sevier Science Inc. All rights reserved.