High prevalence of coxa vara in patients with severe osteogenesis imperfecta.

The purpose of this study was to determine the incidence and clinical presentation of coxa vara in 283 patients with osteogenesis imperfecta (OI). The charts and X-rays of 150 girls and 133 boys with OI were reviewed. The patients were classified according to the Sillence classification modified by Glorieux: 94 type I, 90 type IV, 67 type III, 18 type V, 10 type VI, and 4 type VII. The mean age was 9.4 years (range 0.3-23.3). Twenty-nine patients (10.2%) had coxa vara (23 left and 20 right). Fifty-five percent of them were type III, 24% type IV, 13.8% type VI, and 3.4% each of types V and VII. The incidence of coxa vara was 6% in type V, 8% in type IV, 24% in type III, 25% in type VII, and 40% in type VI (P < 0.001 for difference between types I, III, and IV). The mean neck-shaft angle was 99 degrees (range 80-110 degrees), the average head-shaft angle was 104 degrees (range 90-120 degrees), and the mean Hilgenreiner-epiphyseal angle was 68 degrees (range 40-90 degrees). Twenty-five patients (36 hips) had previous femoral rodding before diagnosis and seven hips (all type III) had no history of rodding. Abduction and internal rotation of the hip joints were restricted in all patients with this deformity. All children with coxa vara had a Trendelenburg gait. In conclusion, coxa vara in OI is not rare, especially in severe forms of the disease. Regular clinical and radiologic follow-up is indicated in children with previous femoral rodding and in severely affected children, particularly those with OI type III.