Ectopic bone formation around the poly-L-lactide screw head in rotational acetabular osteotomy for hip dysplasia

Ectopic bone formation around the poly-L-lactide (PLLA) screw head in eccentric rotational acetabular osteotomy for hip dysplasia was investigated. A total of 174 hips in 165 patients with hip dysplasia were consecutively treated with eccentric rotational acetabular osteotomy. Average age at the time of operation was 37 years. Acetabular fragments of 123 patients (132 hips) were fixed by Kirschner wires (K-wire group), and 42 hips in 42 patients were fixed with PLLA screws (PLLA group). There was no statistically significant difference between the backgrounds of the two groups. All patients were evaluated clinically and radiologically. In the K-wire group, ectopic bone formation of class 2 was observed in only 1 hip. In the PLLA group, ectopic bone formation of class 3 in 1 hip and class 2 in 3 hips was observed around the screw head 3 months postoperatively, and all hips but 1 showed class 2 at final follow-up. One hip with class 3 at 1 year developed marked reduction of range of motion, and this patient complained of moderate hip pain and stiffness. PLLA screws significantly enhanced ectopic bone formation around the screw head in eccentric rotational acetabular osteotomy.