EFFECT OF HAMSTRING TENDON AUTOGRAFT FOR ACL RECONSTRUCTION ON KNEE EXTENSION/FLEXION STRENGTH DEFICITS AND KNEE FUNCTION

Abstract

INTRODUCTION Regaining full rehabilitation of the quadriceps (Q) and hamstring (H) muscles following ACL reconstruction is a major contributing factor to athletes returning to pre-injury activity levelsl. A current technique of ACL reconstruction involves harvesting the ,H tendons which are used as a graft to replace the ruptured ACL. However, H tendon harvesting has been shown to result in Q and H muscle strength deficits2. It was the purpose of this study to determine knee extension/flexion strength deficits following H tendon harvesting from the ACL injured compared to the uninjured Limb. A secondary purpose was to determine if there was any relationship between lower limb strength deficits and subjective ratings of knee function. METHODS Thirty unilateral, isolated subacute ACL deficient athletes (mean age = 24.7 4.9 years) who were patients of the North Sydney Orthopaedic and Sports Medicine Centre were randomly assigned to an experimental (E) and a control (C) group. Experimental subjects had the H tendon graft to reconstruct their ACL harvested from their uninjured limb whereas control subjects had the H tendon graft harvested from the ACL injured limb. Using the protocol of Kannus et al.3, H and Q strength for each subject was assessed using a CybexII+ isokinetic dynamometer pre-surgery and at 12 weeks and 6 months post-surgery. Strength deficits were then calculated using the Strength Scoring Scale3. Subjective ratings of knee function were collected using the International Knee Documentation Committee Form (IKDC) at the same three testing sessions. RESULTS ' h o way repeated ANOVA results indicated a significant main effect of test week on total strength deficits (F2,46 = 15.625, p < 0.0001). Post hoc analysis indicated mean strength deficit scores at 12 week post-surgery testing (27.4) were significantly less than pre-surgery (37.5) or 6 months (5 1.15) with 6 months scores being significantly higher than pre-surgery scores. ANOVA on ranks revealed a main effect of test week on IKDC scores (E: H2 = 20.724, p d.001; C: H2 = 26.808, p < 0.001) where both subject groups rated their knee function significantly higher at 12 weeks and 6 months post-surgery compared to pre-surgery. A significant negative correlation was found between strength score and IKDC score (r = -0.28; p = 0.01); ie, lower strength deficits were associated with higher ratings of knee function. CONCLUSIONS Strength deficits following H tendon harvesting are evident, irrespective of whether the graft is harvested from the ACL injured or uninjured limb, with lower strength deficits being associated with better knee function ratings. Whether minimizing strength deficits in the ACL reconstructed limb by taking the graft from the contralateral limb provides greater protection for the new H graft is yet to be determined. REFERENCES Shelbourne KD & Rowdon GA (1994). Sports Med 17(2): 132- 140. Marder R et al. (1991). Am J Sports Med 19(5): 187-194. Kannus Petal. (1987). Scand J Sports Sci 9(1): 9-13.