Isolated Proximal Femoral Valgus Osteotomy for Hinge Abduction Improves Femoroacetabular Relationship in Patients With Perthes Disease

Background Proximal femoral valgus osteotomy is a recognized salvage procedure for managing hinge abduction in Perthes disease. Although proximal femoral valgus osteotomy aims to improve joint congruency, previous studies have been limited by heterogeneous methodologies and concomitant procedures, making it difficult to determine its isolated effect. Furthermore, no study of which we are aware has specifically examined how proximal femoral valgus osteotomy influences acetabular development or lower limb alignment over time. Questions/purposes (1) Is isolated proximal femoral valgus osteotomy associated with improvements in femoral sphericity and proximal femur development at skeletal maturity? (2) Is it associated with promotion of acetabular development? (3) Is it associated with changes in the lower limb mechanical axis? Methods Between November 2000 and December 2020, we treated 33 patients using proximal femoral valgus osteotomy for painful hinge abduction deformity associated with Perthes disease, which was initially suspected through serial clinical examinations and confirmed during examination under anesthesia combined with arthrographic findings. All 33 patients who met diagnostic criteria during the study period were treated with the same operation (except as specified below), and all were accounted for at a minimum of 5 years of follow-up and considered potentially eligible for study here. Of these, eight patients were excluded for prespecified reasons (bilateral surgery, use of shelf procedure or limb lengthening procedure, or skeletal immaturity at the most recent follow-up), leaving 25 patients, with a mean ± SD follow-up of 13 ± 5 years; two of those patients had not been evaluated within the past 5 years, although both had achieved skeletal maturity at their most recent follow-up (19 and 20 years of age, respectively). The mean ± SD age was 9 ± 2 years at the time of surgery and 22 ± 5 years at the most recent follow-up. Femoral head morphology was assessed using the sphericity deviation score, a continuous measure that quantifies the shape of the femoral head, with values < 10 considered spherical. Proximal femoral alignment was evaluated using the neck-shaft angle and the articulotrochanteric distance, with higher neck-shaft angles indicating coxa valga, lower angles indicating coxa vara, and reduced articulotrochanteric distances indicating relative overgrowth or proximal migration of the greater trochanter. Acetabular development was assessed using the center-edge angle and the Sharp angle, with lower center-edge angles and higher Sharp angles associated with acetabular dysplasia. The alignment of the lower limb was assessed at the most recent follow-up. The hip shape at the most recent follow-up was assessed using both the Stulberg classification and the head-acetabulum-trochanter (HAT) system. The Stulberg classification categorizes hips at skeletal maturity as from Class I (a normal hip) to Class V (a flattened femoral head with a normal neck and acetabulum). The HAT classification assesses the femoral head, acetabulum, and greater trochanter, with higher scores indicating greater residual deformity (≤ 3 is considered a “good” outcome). Pain was assessed using the VAS during activities of daily living. Hip ROM was measured at the most recent follow-up. Results Proximal femoral valgus osteotomy was associated with improvement in femoral head sphericity, as the mean ± SD sphericity deviation score improved from 62 ± 19 before surgery to 34 ± 22 at the most recent follow-up (mean difference 28 95% confidence interval (CI) 16 to 41; p < 0.001). The neck-shaft angle increased postoperatively but partially remodeled, while the articulotrochanteric distance returned toward preoperative levels. Proximal femoral valgus osteotomy was also associated with improvements in acetabular development, as the center-edge angle progressively increased and the Sharp angle decreased. The Stulberg classification was Class II in three hips, Class III in 15, Class IV in three, and Class V in four, while 13 hips had a HAT score of ≤ 3, representing a good outcome on that parameter. The mechanical lateral distal femoral angle was 84° ± 2° on the affected side and 86° ± 2° on the contralateral side (mean difference -2° 95% CI -3° to -1°; p = 0.001), whereas no differences were observed in the other mechanical angles. On the VAS, preoperative scores ranged from 6 to 10, whereas scores at the most recent follow-up ranged from 0 to 2. The overall hip ROM was within normal limits, with internal rotation demonstrating a slight reduction. Conclusion Isolated proximal femoral valgus osteotomy for hinge abduction deformities was associated with improvements in femoral head sphericity and acetabular development in patients with Perthes disease. We recommend a paradigm shift in which proximal femoral valgus osteotomy may be regarded more as a joint preservation procedure than as a salvage operation. Future research is warranted to evaluate the potential influence of patient age and disease stage on outcomes and to further define the indications for additional acetabular procedures in hinge abduction deformities. Level of Evidence Level IV, therapeutic study.