Changes in knee joint line orientation after high tibial osteotomy are the result of adaptation of the lower limb to the new alignment.

BACKGROUND

Changes in knee joint line orientation (KJLO) resulting in excessive joint line obliquity are a well-known consequence of high tibial osteotomy (HTO) procedures and could lead to degenerative changes. The precise effect of the correction on final KJLO changes is poorly understood. The goal of this study was to identify radiographical parameters that could help to explain the size of KJLO changes after HTO surgery.

METHODS

A total 117 HTO patients were radiographically examined preoperatively and three months postoperatively. Radiographic parameters were KJLO, medial proximal tibial angle (MPTA), hip-knee angle (HKA), mechanical lateral distal femoral angle (mLDFA), lateral distal tibial angle (LDTA), knee joint line congruence angle (KJLCA), ankle joint line congruence angle (AJLCA) and ankle joint line orientation (AJLO). Four new radiographic parameters were introduced to describe knee and foot position on long-leg X-ray: malleolar distance to midline (MDTM), intermalleolar distance (IMD), condylar distance to midline (CDTM) and intercondylar distance (ICD). Correlations of these parameters and changes in KJLO were assessed.

RESULTS

Strong correlations are found between KJLO changes and MDTM (r = 0.709), IMD (r = 0.691), CDTM (r = 0.711) and ICDM (r = 0.702), in contrast to weak correlations between changes in KJLO and MPTA (r = -0.342). These results suggest an important impact of foot and knee position changes on the final alteration of KJLO after HTO.

CONCLUSIONS

The final change of KJLO after HTO is the effect of adaptation of the lower limb, which is driven by the (maximum) alterations of foot and knee position rather than the size of correction of the procedure.