Muscle torque in total knee arthroplasty: comparison of subvastus and midvastus approaches

The subvastus and midvastus approaches are two of the most commonly performed quadriceps preserving approaches for total knee arthroplasty (TKA), which can hasten functional recovery and rehabilitation. However, there has not been sufficient investigation with respect to a quantitative comparison between the two approaches in terms of muscle strength. To compare outcomes with respect to muscle strength between these two approaches, quadriceps and hamstring muscle torques of 20 patients who underwent primary TKA with the subvastus (SV) approach and 10 patients who received the midvastus (MV) approach were measured after surgery. The median age of patients in the SV group (68 years, range 53-77 years) was significantly different that the median age of patients in the MV group (61 years, range 50-73 years) (P = 0.0141). There was no significant difference in patient weight, height, or postoperative duration before muscle testing between the SV and MV groups. There were no significant differences in peak muscle torque or hamstring/quadriceps (H/Q) ratio between the groups. We thus conclude peak muscle torque and H/Q ratios were not statistically different with the SV or MV approach, therefore functional outcome is comparable.