Gait, hip strength and functional outcomes after a Ganz periacetabular osteotomy for adolescent hip dysplasia

The Ganz (Bernese) periacetabular osteotomy was first described for the treatment of adult patients with hip dysplasia; however, it has also been used for adolescent patients. Its effectiveness in improving patients in the short term has not been fully established and no studies, to our knowledge, have analyzed gait and functional outcome in patients with adolescent hip dysplasia.

An Institutional Review Board-approved prospective study of a consecutive series of patients undergoing a Ganz (Bernese) periacetabular osteotomy for adolescent hip dysplasia was carried out. Standard radiographic parameters were analyzed. Harris hip scores, gait analysis, hip abductor, and flexion strength testing preoperatively and at 6 months and 1 year postoperatively were performed. Statistical analysis compared the 6-month and 1-year data to the preoperative values and a second analysis was performed comparing the patients with hip dysplasia to normative data of similarly aged patients.

Twenty-one patients (24 hips) underwent a Ganz periacetabular osteotomy at an average age of 16.1 years for a primary diagnosis of hip dysplasia and pain. There was a significant improvement in all radiographic parameters from preoperation to 1 year in lateral center edge angle (5.5 to 33.0 degrees) (P<0.05), acetabular index of the weight-bearing zone (29.0 to 10.5 degrees) (P<0.05), ventral center edge angle (-1.1 to 32.5 degrees) (P<0.05), and medialization of the joint center relative to the contralateral side (1.12 to 1.05) (P<0.05). Isokinetic abductor strength decreased initially from 62 Nm/kg preoperatively to 58 Nm/kg at 6 months but was improved to 64 Nm/kg at 1 year. Flexion strength decreased from 92 Nm/kg preoperatively to 58 Nm/kg at 6 months but improved to 69 Nm/kg at 1 year. Abductor impulse decreased from 0.26 Nm/kg-s preoperatively to 0.23 Nm/kg-s at 6 months but improved to 0.29 Nm/kg-s at 1 year. Flexion pull-off power decreased from 1.35 Watts/kg to 1.27 Watts/kg and then improved to 1.29 Watts/kg. The Harris hip scores improved from 64.6 at the preoperative evaluation to 74.5 at the 1-year evaluation (Max 89).

The Bernese periacetabular osteotomy is effective in significantly improving radiographic parameters for adolescent hip dysplasia with improvement in functional outcome. Because the osteotomy allows for medialization of the hip joint center and limited abductor muscle dissection the abductor strength improved at follow-up, however, the hip flexion pull-off was decreased. Strategies to improve hip flexion power preoperatively and postoperatively in the future are necessary.

Level IV.