Summary
Older age, poor preoperative quadriceps muscle strength, and residual pain are risk factors for poorer quadriceps muscle strength recovery at one year after anterior cruciate ligament reconstruction
Abstract
Background
Poor postoperative quadriceps muscle strength recovery after anterior cruciate ligament reconstruction (ACLR) causes delayed return to sports and lowers patient satisfaction. In previous studies, several factors, such as age, preoperative quadriceps muscle strength, sex, graft type, and pain, reportedly affect quadriceps muscle strength recovery after ACLR. However, confounding factors were not sufficiently adjusted, and the sample sizes were not large enough. This study aimed to examine factors that affect quadriceps muscle strength one year after ACLR surgery using cases from the Tokyo Medical and Dental University multicenter study (TMDU MAKS study). We hypothesized that older age, poor preoperative quadriceps muscle strength, and residual pain would be risk factors for poor quadriceps muscle strength recovery one year after ACLR.
Methods
This study included patients with primary ACLR using autologous hamstring tendon grafts between August 2013 and March 2018, who were followed up for one year with data extracted from a multicenter database. Patients were divided into two groups with muscle strength > 80% and < 80% the contralateral leg. Multivariate logistic regression analysis was performed to investigate the factors influencing quadriceps muscle strength one year postoperatively. Explanatory variables in demographic, preoperative, and intraoperative items included age, gender, preoperative Tegner activity scale, preoperative quadriceps muscle strength, reconstruction method (single or double bundle), meniscal procedure (excision or repair/lateral or medial meniscus), and operation time. Explanatory variables one year after surgery were extension and flexion ranges of motion, Lachman test, Pivot shift test, side-to-side KT1000 measures and KOOS pain score. Additionally, a categorical analysis was conducted based on factors extracted by the multivariate logistic regression analysis. The sample size of this study was estimated. Based on a previous study, the quadriceps strength one year after ACLR standard deviation was fixed at approximately 18.5%. Given that a 10% difference in preoperative quadriceps muscle strength is clinically significant, 156 patients were required as the minimum sample size to obtain an aof 0.05 and a ßof 0.80.
Results
Four-hundred and two patients were included in this study. Multivariate logistic regression analysis revealed that age at surgery (OR=1.04, 95%CI=1.01-1.07, P= 0.02), preoperative quadriceps muscle strength (OR=0.98, 95%CI=0.96-0.99, P= 0.01), and the postoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) pain score (OR=0.94, 95%CI=0.91-0.98, P<0.01) were associated with quadriceps muscle strength at one year postoperatively. The odds ratios for poor muscle recovery by the categorical analysis were 5.0-fold higher for those aged over 40 than for those aged under 20, 4.2-fold higher for those with preoperative quadriceps muscle index < 60% than for those with this index of > 80%, and 7.7-fold higher for those with a postoperative KOOS pain score of < 85 points than for those with a KOOS score of 100 points.
Conclusion
Older age, poor preoperative quadriceps muscle strength, and low postoperative KOOS pain score were risk factors for poor quadriceps muscle strength one year after primary ACLR. Surgical indications, including age, preoperative active rehabilitation, and pain control, should be considered for optimization of postoperative quadriceps muscle strength recovery.