Reliability of 3-Dimensional Measures of Single-Leg Cross Drop Landing Across 3 Different Institutions: Implications for Multicenter Biomechanical and Epidemiological Research on ACL Injury Prevention

Sports-related injuries to the anterior cruciate ligament (ACL) affect approximately 1% to 3% of the athletic population on average10,23,24; however, when they do occur, these injuries are devastating physically,21 psychologically,20 and economically.2,8,10,18 Investigations on relatively rare phenomena such as this require large-scale studies to adequately power results. Because of the low incidence rate for ACL injury, the number of subjects needed to prospectively study the noncontact ACL injury phenomena total in the hundreds, if not thousands. Furthermore, data collection and risk assessment of relatively rare events, like ACL injuries, typically require costly technologies and trained personnel to reliably collect prospective data from a large subject pool, which is challenging for even an adequately staffed research laboratory. Multicenter collaborative studies allow researchers to share responsibilities and resources while vastly increasing the available subject pool. They can also increase the generalizability of prospective risk assessment for ACL injury by improving the ability to include additional populations of interest into prospective studies. Moreover, increased subject pools allow for the opportunity to achieve adequate statistical power through an increased sample size. Thus, use of a multicenter approach is likely the most feasible method to execute prospective, coupled biomechanical-epidemiological studies. Specific risk factors for ACL injury include increased dynamic knee abduction (caused by increased hip internal rotation and/or adduction, which contribute to knee joint movement toward the midline), decreased knee flexion, elevated ground reaction force during landing, and asymmetrical landing patterns.13 In general, these factors are observed in subjects performing sports-related tasks, such as landing from a jump,22 which directly affects knee alignment and load transmission through the knee.12,14,25 Furthermore, 2-dimensional video analyses have indicated that female athletes with a noncontact ACL injury had greater lateral trunk flexion along with increased peak knee abduction during landing compared with both female and male control athletes.15 With regard to trunk motion, there is a link between lateral trunk flexion and ACL injury whereby aberrant lateral trunk motion perturbs the center of mass and directly affects proximal knee loading.17,30 While many risk factor studies have effectively included analyses of landing maneuvers, including drop vertical jumps4,13 and single-leg jump landings,5 these maneuvers perhaps may not adequately challenge trunk control for assessment of deficits that influence lower extremity biomechanics. Given the extensive negative health consequences of ACL injury and the low incidence rate of these injuries, collaboration between multiple research laboratories is necessary to increase sample size and enhance generalizability. An important step in the establishment of such an approach is to determine whether the tasks can be reliably studied between institutions. The purpose of this project was to determine the reliability and consistency of kinematic and kinetic measures collected during a single-leg cross drop task (SCD) using 3-dimensional motion analysis across 3 different institutions.