Purpose: The purpose of this prospective study was to describe the variability in leg muscle power and hop performance up to 2 years among patients following ACL reconstruction and specifically to illustrate the effects of various criteria for an acceptable level of muscle function.
Methods: Eighty-two patients (56 men and 26 women)with a mean age of 28 years, who underwent ACL reconstruction using either hamstring tendons (n = 46) or a patellar tendon (n = 36), were assessed pre-operatively and 3, 6, 12 and 24 months post-surgery with a battery of three lower extremity muscle power tests and a battery of three hop tests.
Results: Leg symmetry index (LSI) values at group level ranged between 73 and 100% at all follow-ups. When the tests were evaluated individually, patients reached an average LSI of ≥ 90% at 24 months. The success rate at 24 months for the muscle power test battery, that is,patients with an LSI of ≥ 90% in all three tests, was 48 and 44% for the hop test battery. The success rate at 24 months for both test batteries on all six muscle function tests was 22%. The criterion of an LSI of ≥ 80% resulted in 53% of the patients having an acceptable level on all six tests,while with a criterion of an LSI of ≥ 100%, none of the patients reached an acceptable level.
Conclusion: At group level and in single muscle function tests, the muscle function outcome 1 and 2 years after ACL reconstruction is satisfactory in the present study and on a par with the results presented in the literature. However,when using more demanding criteria for a successful muscle function outcome, using batteries of tests or increasing the acceptable LSI level from ≥ 90% to ≥ 95%or ≥ 100%, the results are considered to be poor. It is suggested that this should be taken into consideration when presenting results after ACL rehabilitation, deciding on the criteria for a safe return to sports, or designing rehabilitation programmes after ACL reconstruction.
Level of evidence: Prognostic prospective cohort study, Level I.