Electromyographic comparison of the mid-vastus and sub-vastus approaches to total knee arthroplasty

Abstract

Background: To date there has been no study using robust surface electromyographic methods to compare the effect of sub-vastus and mid-vastus approaches to total knee arthroplasty on quadriceps activity. This study was done to ascertain if the sub-vastus technique would result in greater postoperative muscle activity than a vastus splitting approach as measured by electromyography and an earlier achievement of a straight leg raise. Methods: This was a prospective comparative study of the sub-vastus and mid-vastus approaches on vastus medialis and vastus lateralis muscle activity measured by electromyography and time to straight leg raise in 18 patients (7 men and 11 women) after a primary total knee arthroplasty. Results: A statistically significant difference in the number of days taken to achieve straight leg was noted between the mid-vastus and sub-vastus groups (mid-vastus = 2.0 days, 95% CI, 1.43 to 2.56; sub-vastus = 1.25 days, 95% CI, 0.93 to 1.57; P = 0.045). There were no statistical differences (P > 0.05) between the two techniques in electromyography or any of the secondary outcomes at 5 days, 6 weeks and 3 months after surgery. There was no significant correlation (P > 0.05) between the earlier return of straight leg raise in the sub-vastus technique and increased quadriceps activation. Conclusions: This study did not find any statistically significant differences in electromyographic data between the two approaches, suggesting no evidence of denervation of the vastus medialis, although the sub-vastus technique led to an earlier single-leg raise. (C) 2009 Lippincott Williams & Wilkins, Inc