Comparative Analysis of Serial Union Patterns After Opening-Wedge High Tibial Osteotomy with and without Bone-Void Fillers

Background: Opening-wedge high tibial osteotomy produces opening gaps; however, there is little consensus on bone graft necessity and the material that would produce a superior union. The purposes of the present study were (1) to compare the serial union patterns associated with various bone-void fillers, (2) to determine whether bone-void filler is necessary to achieve bone union of the opening gap, and (3) to determine whether bone union is different according to the correction degree during opening-wedge high tibial osteotomy. Methods: In this retrospective study, 97 knees were randomly assigned to treatment with hydroxyapatite chip bone (Group A), allogenic chip bone (Group B), or no bone graft (Group C) and were analyzed after a minimum 1-year follow-up. To compare the bone union pattern, the area of callus filling located at the most medial side on an anteroposterior radiograph of the knee was recorded, and a modified van Hemert scoring system was used in the mediolaterally divided 5 zones. The correlations between the correction degree and bone union scores were evaluated. Results: There were no significant differences in the extent of mediolateral bone-healing at 6 weeks or 3 months postoperatively (p = 0.172 and p = 0.228). However, Group C showed more prominent progression of the gap filling to the medial side compared with Groups A and B at 6 months postoperatively (p = 0.002). Group C showed slow progression of bone union up to 6 weeks but surpassed the other groups at 6 months. The union pattern was not different between Groups A and B, and the correction degree was not correlated with bone union beyond 3 months postoperatively. Conclusions: Despite the different gap-healing patterns, opening-wedge high tibial osteotomy without bone graft achieved bone union comparable with allogenic and synthetic graft materials. Group C (no bone graft) showed slower progression of bone union but surpassed the other groups at around 6 months. Based on the union pattern, there was no difference depending on the correction degree and the use of bone-void fillers. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.