Lateral numbness in the lower leg: An underestimated complication following medial open-wedge high tibial osteotomy.

BACKGROUND

This study aimed to investigate the incidence, degree, and natural course of lateral numbness following medial open-wedge high tibial osteotomy (MOWHTO). It also evaluated which predisposing factors would affect lateral numbness following MOWHTO.

METHODS

One-hundred and sixty-nine knees that underwent MOWHTO for treatment of varus osteoarthritis with a minimum follow-up of three years were enrolled. Lateral numbness in the lower leg was assessed with the light-touch method using a cotton wool ball and compared with the contralateral leg. Patients were classified into groups based on a scale according to grading of sensation to light touch. To assess the improvement of lateral numbness, lower leg sensation was investigated using a sensory score compared with the contralateral leg. The predisposing factors that would affect lateral numbness were assessed.

RESULTS

Lateral numbness was observed in 87 knees (51.5%) at six weeks postoperatively. Although 69 knees improved over time, 18 knees showed no improvement to the latest follow-up. The level of skin incision showed a significant association with lateral numbness on univariate and multivariate analyses: the higher the level of skin incision, the greater the degree of estimated numbness.

CONCLUSIONS

About half the patients reported postoperative lateral numbness in the lower leg following MOWHTO. Of the patients with lateral numbness, approximately one-fifth remained symptom until the last follow-up. The level of skin incision might be a risk factor for lateral numbness. Pre-operative patient education concerning the likelihood of lateral numbness is recommended.

LEVEL OF EVIDENCE: Level IV, case series.