Effect of high-grade pre-operative knee laxity on outcomes of anterior cruciate ligament reconstruction

Objectives: Knee laxity in the setting of suspected anterior cruciate ligament (ACL) injury is frequently assessed through physical examination using the Lachman, pivot-shift, and anterior drawer tests. The degree of laxity noted on these examinations may influence treatment decisions and prognosis. We hypothesized that increased pre-operative knee laxity (Grade 3+ pivot-shift, Lachman > 10mm, or anterior drawer greater than 10mm) are associated with increased risk of revision ACL reconstruction and poorer patient-reported outcomes at two years post-operative. Methods: From an ongoing prospective cohort study, 1394 patients that underwent primary isolated ACL reconstruction within 3 months of injury with autograft tissue without medial collateral, lateral collateral, or posterior cruciate injury requiring treatment or prior contralateral ACL injury were identified. Demographic data, physical examination findings under anesthesia at the time of ACL reconstruction, information regarding meniscus status and treatment, and pre-operative and 2 year post-operative International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Outcome Score Knee Related Quality of Life subscale (KOOS-QOL), and Marx activity scores were collected. Patients reported by the operating surgeons as having a Lachman or anterior drawer examination at least 10mm greater than the contralateral side were classified as having a high grade Lachman or anterior drawer respectively. Patients reported by the operating surgeon as having a 3+ pivot-shift were classified as having a high-grade pivot-shift. Patients demonstrating high-grade laxity on any of these examinations were classified as having high-grade preoperative knee laxity. Multiple logistic regression modeling was used to evaluate whether having high-grade pre-operative laxity was associated with increased odds of undergoing revision ACL reconstruction within 2 years of the index procedure, controlling for patient age, sex, activity level, and graft type. Multiple linear regression modeling was used to evaluate whether having high-grade pre-operative laxity was associated with poorer IKDC or KOOS-QOL scores at 2 years post-operative, controlling for patient age, sex, BMI, and smoking status, baseline score, activity level, graft type, and the presence and treatment of meniscal tears. Results: Two year revision data were available for 1333 patients (95.4%) and patient-reported outcomes were available for 1205 patients (86.4%). High-grade pre-operative laxity was noted in 395 patients (29.6%), including high grade pivot-shift in 24.9%, high-grade Lachman in 11.5%, and high-grade anterior drawer in 8.1%. ACL graft revision was performed in 59 patients (4.4%). The mean post-operative IKDC score was 84.1 ± 14.4 and the mean KOOS-QOL score was 75.1 ± 20.4. The presence of high grade prelaxity was not associated with increased odds of ACL graft revision (OR=1.47, 95% CI: 0.85 - 2.55, p = 0.17). Similarly, the presence of high-grade pre-laxity was not associated with any difference in postoperative IKDC (β = -0.33, p = 0.71) or KOOS-QOL (β = -0.51, p = 0.70). Conclusion: The presence of high-grade pre-operative knee laxity as assessed by physical examination under anesthesia (Grade 3+ pivot-shift, Lachman > 10mm, or anterior drawer greater than 10mm) is not associated increased odds of revision ACL surgery or poorer patient-reported outcome scores at 2 years following ACL reconstruction.