Risk Factors for Nonunion After Femoral Rotational Osteotomy for Idiopathic Anteversion and Retroversion in Adolescents

BACKGROUND: Lower extremity rotational abnormalities can cause difficulty with ambulation, patellofemoral pain and instability, hip and ankle pain, as well as differences in self-image in children and adolescents. Rotational osteotomies of the femur to correct these torsional differences have been shown to improve function, pain, and self-image. There are no studies to date evaluating risk factors for nonunion after femoral rotational osteotomies in children and adolescents. METHODS: Patients 10 to 18 years old treated with femoral rotational osteotomy fixed with intramedullary nailing for idiopathic anteversion and retroversion over a 15-year period were included. Charts and radiographs were reviewed for patient characteristics, laterality, concomitant tibia osteotomy, nail material, interlocking screw construct, and radiographic measurements, including osteotomy location and canal fit. Patients with nonunion were compared with those who fully healed. RESULTS: In this study of 203 femoral rotational osteotomies in 118 adolescent patients, the total incidence of nonunion was 10/203 for a rate of 4.9%. Overall complication rate was 6.9%. Univariate analysis of patient factors revealed that patients who were older, had a higher weight, and higher BMI were at higher risk of nonunion. The use of static interlocking screws and a lower canal fit ratio were also associated significantly with nonunion. Multivariate stepwise linear regression found relative canal fit ( P = 0.003) and interlock configuration ( P = 0.003) to be significant, and causal modeling identified significant factors related to nonunion as older age, static interlock type, and lower canal fit. CONCLUSIONS: Nonunion after femoral osteotomy is associated with higher age, weight, and BMI as well as use of static interlocking screws and lower canal fit ratio. Surgeons can use this information to risk stratify and counsel patients undergoing this procedure. Surgical techniques to minimize the chance of nonunion include use of dynamic interlocking screws and maximizing the canal fit ratio. LEVEL OF EVIDENCE: Therapeutic level III-case-control study.