Recovery of muscle strength after high tibial osteotomy.

To assess muscle strength after high tibial osteotomy (HTO) using percutaneous drilling, we prospectively evaluated the isometric and isokinetic muscle torque of the thigh before operation and after operation over time. We evaluated 27 joints of 26 patients with a mean age of 66 years. The muscle torque/weight ratio was seen to decrease, and the hamstrings/quadriceps (H/Q) ratio increased at 3 months after HTO; both ratios showed no significant difference at 6 months. Improved muscle strength appeared at isometric extensor of 50 degrees, not 80 degrees, and at slow isokinetic speeds of 30 degrees /s, not 90 degrees /s. There was no significant difference in terms of the age of patients regarding the recovery of muscle strength. We also compared patients with a varus angle of >/=5 degrees and those with a varus angle <5 degrees before the operation. In terms of extension, the group with varus angles <5 degrees showed a greater postoperative increase in isometric torque at 80 degrees flexion of the knee and isokinetic torque at 90 degrees /s than did the group with varus angles of >/=5 degrees.