• 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.