Summary

MOWHTO without bone graft achieved at least 90% bone healing and had no loss in correction 2 years postoperatively. The present findings suggest that the routine use of bone filler is not required in MOWHTO with the use of a locking plate.

Abstract

Purpose

:To prospectively investigate osteotomy gap filling rates on serial plain radiographs, and to evaluate whether alignment correction is maintained after medial opening wedge high tibial osteotomy (MOWHTO)using a locking plate without bone graft.

Methods

Between March 2014 and June 2017, MOWHTO was performed without bone graft regardless of gap size. Radiographs were taken preoperatively, postoperatively, at 1, 3, 6, 12, 18, and 24 months after surgery. Radiographic examinations included a weight bearing long-standing anteroposterior (AP) view of the whole lower extremity, as well as, the AP, lateral, and both oblique views of the knee. Bone healing was measured on the medial oblique view of the knee. The postoperative alignment correction and its maintenance were assessed using the three radiologic parameters of the weight-bearing line (WBL) ratio, the hip–knee–ankle angle (HKAA), and the medial proximal tibial angle (MPTA) on the weight-bearing longstanding AP view of the lower extremity.

Results

Fifty-two consecutive patients underwent MOWHTO, but three patients failed to follow-up for more than 24 months. A total of 49 patients were assessed in this study. The median opening gap height was 10.0 mm (IQR, 8.0–12.0; range,7–20). On immediate post-operative radiographs, the mean gap filling was 31.4 ± 3.6%. After 1, 3, 6, 12, 18, and 24 months, the mean gap filling rates increased to 38.7 ± 4.4%, 51.4 ± 6.6%, 66.5 ± 5.1%, 84.8 ± 7.0%, 92.4 ± 5.6%, and 97.8 ± 2.3%,respectively. Statistical differences were observed between all the follow-up evaluations (P < 0.001). Statistical differences in the WBL ratio, HKAA, and MPTA were observed between preoperatively and 1 month after surgery (P < 0.001). The mean PTSA increased significantly from preoperatively to postoperatively (P < 0.001). However, no statistical differences were found between the post-operative follow-up radiographs performed for these four values.

Conclusion

MOWHTO using a locking plate without bone graft achieved at least 90% bone healing and had no loss in correction at 2 years postoperatively.