In osteogenesis imperfecta (OI) because of bone fragility, deformities in load bearing regions of the body such as femoral neck and proximal femur are expected. The purpose of this study was to determine the prevalence and clinical presentation of coxa vara in two hundred and ninety-two patients with different types of OI. More than half of the patients were OI type III (55%) and the highest prevalence of coxa vara was seen in OI type VI (44,5%). The children suffering from coxa vara had also a significant limitation of range of motion in their hips.
The charts and x-rays of one hundred and fifty-four girls and one hundred and thirty-eight boys with OI were reviewed. The patients were classified according to the Sillence classification modified by Glorieux: eighty-seven Type I, sixty-nine Type IV, sixty-two Type III, eighteen Type V, nine type VI, four types VII, and forty-three unclassified. The mean age was nine, four years (0, 3–23, 3).
Twenty-nine patients (9, 9%) had coxa vara (twenty-three left, twenty right). 55% of them were type III, 17% type IV, 13, 8% type VI and three, 4% each of types I, V, VII and unclassified OI. The prevalence of coxa vara was 1% in type I, 5,5% in type V, 7 % in type IV, 25% in type VII , 26% in type III and 44,5% in type VI (p<0,001 for difference between types I, III and IV). Coxa vara was less frequent in patients with blue sclera (p=0,007). The mean neck-shaft angle was 99° (80°–110°) and the mean Hilgenreiner-epiphyseal angle was 68° (40°–90°). Twenty-five of coxa vara patients (thirty-six hips) had femoral rodding before diagnosis and six hips (all type III) had no history of rodding; however, 26 % of five hundred and thirty-one hips without coxa vara, had previous history of femoral rodding (p=0,004).
Abduction, extension and internal rotation were restricted in the hips with deformity. The abductors and extensors of the hips were weak in some that resulted in limping and Trendelenburg gait.
Special attention including clinical and radiological follow-up should be given to type III and VI patients particularly in the presence of previous femoral rodding.
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada