In vitro analysis of stabilization forces applied through a dynamic spring ACL brace compared to a static one, examined through a range of knee tests

Introduction: Anterior circuit ligament (ACL) tears are one of the most serious injuries in sport, yet regular bracing may not reduce risk of injury. The purpose of the present study is to compare the stabilization forces applied to knee joint between a novel dynamic spring ACL brace and a traditional static one. Methods: Nine healthy males (mean age=23.4±3.4yrs; height=1.8±0.3m; body-mass= 81.1±6.3kg) underwent two sets of seven tests, once wearing the dynamic brace and once with a traditional one. Tests included Lachman (LT); pivot shift test (PST); single-leg squat (SLS), Thessaly (TT); drop jump (DJ), crossover hop test (CH); and 90° rotational hop (RH). During all tests, force measurement sensors were placed under the brace: three under the upper femoral strap and three under the lower tibia strap. Measurements included peak changes in stabilization forces (total and posterior), knee joint internal rotation (IR) and knee joint external rotation (ER), and time-to-peak force. Results: Total peak force was significantly higher in the dynamic brace (LT=69±5, PVT=154±8; SLS=140±8; TT=138±6; DJ=120±5; CH=136±8; and RH=128±4 g/cm2; and LT=15±3; PVT51±7; SLS14±2; TT =13±4; DJ18±4; CO=15±3; and RH16±3 g/cm2, respectively, p<0.001). And higher posterior forces measured in the dynamic brace than in the static one (LT=31±4g/cm; PS=30±2g/cm; SLS=65±6g/cm; TT=52+3; DJ=55±5; CH=50±4; RH=67±5g/cm; and LT=4.7±2; PS=5±3; SLS=3±1.8; TT=8±3; DJ=5±3; CH=7±3g/cm2, respectively, P<.001) Additionally, in some tests (IR) stabilization forces was significantly higher in the l dynamic brace than in the static one (PS=82±5; TT=44±3; DJ=39±5; CH=57±3; RH=50±6g/cm2; and PS=30±3; TT=4±1; DJ=6±3; CH=3±1; RH=4±2g/cm2, respectively, P<.001). Time-to-peak force was significantly shorter in the dynamic spring brace than in the static one for three functional tests (DJ=330±6; CH=26O±5; RH=290±5 ms) compared to the standing SLS test (77O±8 ms p<0.01). Conclusion: These finding demonstrate that the novel dynamic ACL brace presented in this research applies greater stabilization forces than traditional static