Summary
The currently used cut-offs for determining readiness to safely RTS after ACL reconstruction cannot discriminate athletes who go on to suffer a second ACL injury from athletes who do not.
Abstract
Purpose
We aimed to discriminate athletes who sustain a second ACL injury from athletes who do not by 1) identifying the best discriminating LSI cut-offs, 2) evaluating pre-defined LSI cut-offs, 3) assessing an 1% increment in LSI, 4) identifying the best discriminating LSI cut-offs for the deviation from 100% symmetry, and 5) assessing 1% increment in LSI in deviation from symmetry, and their association with second ACL injury within 2 years from RTS, based on 2 strength tests and 3 hop tests.
Methods
This prospective cohort study included athletes between 15-30 years old at the time of ACL reconstruction, had a pre-injury Tegner activity level =6, and had returned to their pre-injury activity level. Endpoint was set to second ACL injury or 2 years survival from RTS. Logistic regression analyses were performed and presented with odds ratio (OR) to determine the association between results/passing from muscle function testing and second ACL injury. In addition, the Receiver Operating Characteristic (ROC), the Area Under the Curve (AUC), specificity and sensitivity were analysed.
Results
Out of the total 233 included patients 51.1% were women. Newly determined cut-offs for all muscle function tests were not able to discriminate between patients who sustain a second ACL injury or not (Youden index 0.06-0.24 and AUC 0.48-0.60). Patients who had an LSI <85% or an LSI <80% had significantly higher odds for not sustaining a second ACL injury (OR=0.38 (0.17-0.82) and OR=0.31 (0.12-0.85) respectively), although the AUC showed poor discriminability, 0.60-0.61. There was no significant difference in odds for not sustaining a second ACL injury from every 1% unit increase in LSI or deviation from symmetry was seen up to 2 years after RTS for either of the muscle function tests included in the test battery.
Conclusion
The currently used cut-offs for determining readiness to safely RTS after ACL reconstruction cannot discriminate athletes who go on to suffer a second ACL injury from athletes who do not. Lower LSI values might increase odds for not sustaining a second ACL injury. Clinicians are advised to look beyond recovery of symmetrical strength and hop performance to inform decision-making on safe RTS.