Treatment of adolescent tibia vara with hemiepiphysiodesis: risk factors for failure

Lateral tibial hemiepiphysiodesis is an accepted surgical treatment for skeletally immature patients with adolescent tibia vara. However, the results of this procedure are unpredictable. This study was conducted to identify the risk factors associated with failure of hemiepiphysiodesis.

We studied patients with adolescent tibia vara who were at least ten years of age, had open physes, had been treated with a lateral hemiepiphysiodesis, and had been followed for at least two years. The mechanical axis deviation, medial proximal tibial angle, and lateral distal femoral angle were measured on radiographs preoperatively, at six months postoperatively, and at the time of final follow-up. Failure was defined as a residual varus deformity requiring osteotomy or a mechanical axis deviation exceeding 40 mm (moderate or severe varus) at the time of final follow-up.

Forty-nine patients (forty-six male) with a total of sixty-four involved extremities met the inclusion criteria. The average age was 13.4 years, the average body mass index was 40.7 kg/m(2), and the average duration of follow-up was 3.3 years. The lateral hemiepiphysiodesis was unsuccessful in 66% of the patients. In a multivariate Cox proportional hazards regression analysis, the variables associated with a higher risk of failure included an age of fourteen years or more (hazard ratio = 3.9, p = 0.0009) and a body mass index of > or =45 kg/m(2) (hazard ratio = 2.8, p = 0.01). Greater deformity at baseline as indicated by a smaller medial proximal tibial angle was also found to be a significant factor in the multivariate analysis (p = 0.03).

Lateral hemiepiphysiodesis may be a valuable treatment option for non-morbidly obese patients with less severe adolescent tibia vara, but it is likely to fail in older adolescents with a high body mass index and greater deformity.