Author(s): RIEDER, F., HÖLBE, M., SCHULZE, C., Institution: PARACELSUS MEDICAL UNIVERSITY SALZBURG, Country: AUSTRIA, Abstract-ID: 339

INTRODUCTION:
Knee injuries such as anterior cruciate ligament (ACL) or meniscus tears are everyday challenges in sports medicine and rehabilitation and often followed by persistent quadriceps weakness (Holder-Powell & Rutherford 2001). The limb asymmetry index (LSI) is frequently used as return to activity clearance, whereby athletes should achieve strength differences of less than 10% (Zwolski et al. 2016). However, there are limited studies that examine this area years after injury and the role of body weight for the calculation is often underestimated (Holder-Powell & Rutherford 2001).
METHODS:
In this retrospective data analysis of n=29 patients (13 female, 16 male; age 37±12 years, mean weight 73±17 kg) with chronic (86±71 months) unilateral ACL and/or meniscus injuries, we compared strength values of the injured to the healthy leg and have also put the values into perspective relative to body weight. Strength tests were performed on an isokinetic dynamometer (BIODEX system pro, Schnaittach, Germany) with testing velocities of 60°/s, 180°/s and 240°/s for each leg separately. Strength differences between legs were analysed using the student´s t-test for independent samples using SPSS (IBM statistics, New York, USA). P-values of<.05 were set to be significant.
RESULTS:
Twenty-one patients had an ACL and eight a meniscus injury. There were no significant side differences for absolute maximum torque (diff. = 18±11Nm (11%); p =.117), absolute mean torque (diff. = 21±11Nm (13%), p =.061), absolute maximum work (diff. = 22±13 J (12%), p = .083), absolute mean work (diff. = 20±12J (11%), p = .107) or maximum power (diff. = 11±8W (11%), p = .145) at 60°/s. All values relative to body weight showed significant leg differences (maximum torque: diff. = 0.2±0.1Nm/kg (24%), p = .041; mean torque: diff. = 0.3±0.1Nm/kg (26%), p = .014; maximum work: diff. = 0.3±0.1J/kg (28%), p = .021; mean work: diff. = 0.3±0.1J/kg (25%), p = .037) with a weaker injured leg, except maximum power (diff. = 0.1±0.1W/kg (14%), p = .069). There were no significant and relevant differences for the other velocities.
CONCLUSION:
Besides limitations due to the small and heterogenous sample size, this study shows that relevant persistent strength deficits exist even years after injury, especially when accounting for body weight and tested with a velocity (60°/s) which enables maximum force production. These differences are also far above the 10% LSI border (Zwolksi et al. 2016). Return to activity decisions should therefore also rely on strength values relative to body weight.