Delayed bone union is one of the common complications in closing wedge distal femoral osteotomy (DFO). However, the detail of the progression of bone union after DFO was not fully examined. In addition, there has been no established method to evaluate bone union after DFO. The purpose of this study was to examine bone union after medial closing wedge distal femoral osteotomy (MCWDFO) in comparison with that after lateral closing wedge distal femoral osteotomy (LCWDFO) in double-level osteotomy (DLO) using a newly developed scoring system.
Material And Methods
Twenty-nine patients who received biplanar MCWDFO for valgus knee were retrospectively examined (MCWDFO group). For comparison, 19 patients who received biplanar LCWDFO in DLO for the treatment of varus knee OA were examined (DLO group). Patient demographic data and operation data including wedge size of the resected bone were analyzed. The progression of bone union of the transverse osteotomy plane in the femur was assessed by a newly developed scoring system (Total 0-6 pts, higher score means better union) using radiographs taken immediately after, 3 and 6 months after surgery. The scoring was performed by 3 examiners who were blind to the patient information. Inter-class correlation coefficients (ICC) were calculated using a two-way mixed effect model with absolute agreement to assess the interobserver reliability. The incidence of hinge fracture was assessed using CT images and the presence of reoperation was examined on the medical record.
ICC for the union score were 0.69, 0.89 and 0.97 for MCWDFO and 0.63, 0.93 and 0.85 for LCWDFO in DLO immediately after, 3 and 6 months after surgery respectively. The mean patient age in the MCWDFO group was significantly younger than that in the DLO group (46.5 ± 10.8 y.o. vs 58.4 ± 8.5 y,o., P <0.01) while the mean wedge size of the resected bone in the DFO group was significantly larger than that in the DLO group (8.1 ± 2.4 mm vs 5.8 ± 1.4 mm, P < 0.01). The mean bone union score was significantly lower in the MCWDFO group compared with the DLO group 3 and 6 months after surgery (2.1 ± 1.9 vs 3.7 ± 1.7, P < 0.01. 3.8 ± 2.0 vs 4.9 ± 1.5, P < 0.03 respectively). The incidence ratio of hinge fracture was significantly higher in the MCWDFO group than that in the DLO group (72.4% vs 31.6%, P < 0.01). Two patients in the MCWDFO group received re-operation for delayed bone union or non-union.
Progression of bone union was slower and hinge fracture was more frequently observed after MCWDFO than LCWDFO in DLO. The results of this study suggest that MCWDFO is technically challenging and care must be taken during and after surgery.