Intertrochanteric Osteotomy for Femoral Neck Nonunion: Does "Undercorrection" Result in an Acceptable Rate of Femoral Neck Union?

Objectives: To analyze the radiographic outcomes of intertrochanteric osteotomy for the treatment of femoral neck nonunion with "undercorrection" of the Pauwels angle and relative preservation of the proximal femoral anatomy. Design: Retrospective cohort study. Setting: Level-1 trauma center. Patients: Thirty-two patients with established femoral neck nonunions that had been treated with intertrochanteric osteotomy were retrospectively identified through Current Procedural Terminology codes. Seven patients were treated with 30 degree closing wedge osteotomy and 25 with a 20 degree or smaller osteotomy. Intervention: Valgus-producing intertrochanteric osteotomy with a blade plate. Main Outcome Measurements: Femoral neck and intertrochanteric osteotomy osseous union. Results: Thirty-one of 32 patients (97%) went on to osseous union of the femoral neck and all intertrochanteric osteotomies healed. There was no significant difference in the rate of union of the femoral neck between those patients treated with 30 versus 20 degree or less osteotomies. After osteotomy, the mean Pauwels angle decreased from 71 degrees (range 52-95 degrees) to 47 degrees (range 23-67 degrees) and the mean proximal femoral offset decreased by 11 mm (range 0-23 mm). Seven patients developed radiographic signs of avascular necrosis after osteotomy (22%). Three patients of these patients were converted to total hip arthro-plasty (9%). Patients treated with a 30 degree osteotomy were more likely to develop avascular necrosis (67% vs. 12%, P-value = 0.014). Conclusions: Valgus-producing intertrochanteric osteotomy with a smaller degree of correction than has been traditionally described leads to an excellent rate of radiographic union while preserving more of the native proximal femoral anatomy.