Background

High tibial osteotomy (HTO) is used as an effective treatment for varus knee osteoarthritis (OA). However, the biomechanical relationship between the hip, knee and ankle is important. An observation was made by the senior author of this paper that patients reported a change in their hip function after a medial opening high tibial osteotomy (MOHTO). The effect of a MOHTO on the hip joint has not been well documented. Therefore, we analysed coronal alignment changes at the hip after MOHTO.

Purpose

The purpose of our study was to evaluate the change in alignment of the knee and the ipsilateral hip after MOHTO. We hypothesised that increased valgus alignment of the knee would lead to changes in coronal alignment of the hip, which may lead to hip symptoms after surgery.

Methods

We retrospectively analysed 31 lower limbs from 29 patients who underwent MOHTO for varus OA. Pre-operative and follow up standing bilateral full leg length anteroposterior radiographs were taken. The medial proximal tibial angle (MPTA) and mechanical axis deviation (MAD) were measured to assess the coronal alignment of the knee. The coronal alignment of the hip was evaluated using the mechanical greater trochanter angle (MGTA).

Results

Findings from the MOHTO’s performed demonstrated a statistically significant positive correlation between the change in MPTA and the change MGTA, as well as a statically significant positive correlation between MAD and the change in MGTA. The change in the MGTA had a stronger correlation with the MAD than with the change in MPTA (r = 0.749 vs 0.589). It was found that age, weight, height and BMI had little influence on these correlations.

Conclusion

This study has highlighted that an important change in coronal alignment occurs at the hip joint after medial opening high tibial osteotomy. The study showed that increased correction by the MOHTO lead to increased change in the MGTA at the hip. We suggest these changes are likely to result in an alteration in the weight bearing portion of the femoral head and the function of the abductors, however the clinical significance of these changes are not yet apparent.