Factors Associated with Excellent 6 Month Functional and Isokinetic Test Results Following ACL Reconstruction

OBJECTIVES: Following ACL reconstruction, objective measurements of function and isokinetic testing are often used to guide decision-making regarding clearance for return to sport. However, there is currently no data analyzing potential causes for differences in regaining early function in this setting. The purpose of this study was to identify patient, concomitant injury, and surgical characteristics associated with excellent functional and isokinetic testing results at six months following ACL reconstruction surgery. METHODS: Patients that underwent ACL reconstruction by a single surgeon from 1998 to 2005 had isokinetic and functional testing performed at 6 months following surgery. Excellent 6 month outcome included patients that scored greater than 85% in isokinetic strength and 90% in functional tests in 6 of 7 categories (excellent 6 month group). This group was then compared to the remaining group of patients (delayed 6 month group). Patient, concomitant injury, and surgical factors were then analyzed in univariate and multivariate statistical models to assess which characteristics were significant between patients in the excellent 6 month group versus delayed 6 month group. RESULTS: The 224 patients included 93 males and 131 females, with mean age of 26 (range 12-59) years, BMI 25.8 (range 17-44), and mean pre-injury Tegner activity score of 6.7 (range 2-10). Fifty-two patients (23.2%) were included in the excellent 6 month group, while 172 patients (76.8%) were in the delayed 6 month group. In univariate analysis, favorable factors with the excellent 6 month outcome group were younger age (24.1 vs 27.1; p=0.01), lower BMI (24.5 vs 26.2; p=0.03), and minimal articular cartilage damage (71% vs 56%; p = 0.048). In multivariate analysis, a significant negative effect was observed for patients older than 30 years that had ACL reconstruction with autograft (p = 0.0004). CONCLUSION: In conclusion, factors significantly associated with excellent 6 month functional and isokinetic test results following ACL reconstruction included younger age, lower BMI, and minimal cartilage degeneration. The use of allograft was associated with improved excellent functional and strength testing after ACL reconstruction in patients over 30 years of age.