Radiologic simulation of leg length change after double level osteotomy in preoperative surgical planning

BACKGROUND: To evaluate the expected postoperative total leg length change using preoperative radiographs during surgical planning of four different methods of double level osteotomy (DLO). METHODS: This study included 34 patients (44 knees) who underwent DLO for varus knee osteoarthritis. Surgical planning was performed so that the postoperative weight bearing line ratio was 62.5%. In DLO, lateral closed or medial open wedge distal femoral osteotomy (LCWDFO, MOWDFO) was performed so that the postoperative mechanical lateral distal femoral angle was 85°, and residual deformity was corrected with medial open or lateral closed wedge high tibial osteotomy (MOWHTO, LCWHTO). Pre- and surgical planning X-rays in the one-leg standing position were compared to assess the change in leg length, and the factors affecting it, in the various surgical groups. The proportion of cases in which Δ total leg length was greater than 6 mm (symptomatic change) was investigated. RESULTS: The mean postoperative total leg length increased significantly with LCWDFO + MOWHTO, MOWDFO + MOWHTO, and MOWDFO + LCWHTO, while it decreased with LCWDFO + LCWHTO. The proportion of cases with a postoperative total leg length change > 6 mm was 72.7%, 2.3%, 100%, and 6.8% in LCWDFO + MOWHTO, LCWDFO + LCWHTO, MOWDFO + MOWHTO, and MOWDFO + LCWHTO, respectively. In addition, the preoperative hip-knee-ankle angle correlated negatively with the postoperative total leg length change in LCWDFO + MOWHTO, MOWDFO + MOWHTO, and MOWDFO + LCWHTO, but not in LCWDFO + LCWHTO. CONCLUSIONS: MOWDFO + MOWHTO had the largest postoperative leg length change and MOWDFO + LCWHTO had the smallest. Symptomatic leg length change (> 6 mm) should be considered in MOWDFO + MOWHTO and LCWDFO + MOWHTO.