Timing sequence of multi-planar knee kinematics revealed by physiologic cadaveric simulation of landing: implications for ACL injury mechanism

Abstract

Background: Challenges in accurate, in vivo quantification of multi-planar knee kinematics and relevant timing sequence during high-risk injurious tasks pose challenges in understanding the relative contributions of joint loads in non-contact injury mechanisms. Biomechanical testing on human cadaveric tissue, if properly designed, offers a practical means to evaluate joint biomechanics and injury mechanisms. This study seeks to investigate the detailed interactions between tibiofemoral joint multi-planar kinematics and anterior cruciate ligament strain in a cadaveric model of landing using a validated physiologic drop-stand apparatus.

Methods: Sixteen instrumented cadaveric legs, mean 45(SD 7) years (8 female and 8 male) were tested. Event timing sequence, change in tibiofemoral kinematics (position, angular velocity and linear acceleration) and change in anterior cruciate ligament strain were quantified.

Findings: The proposed cadaveric model demonstrated similar tibiofemoral kinematics/kinetics as reported measurements obtained from in vivo studies. While knee flexion, anterior tibial translation, knee abduction and increased anterior cruciate ligament strain initiated and reached maximum values almost simultaneously, internal tibial rotation initiated and peaked significantly later (P<0.015 for all comparisons). Further, internal tibial rotation reached mean 1.8(SD 2.5)°, almost 63% of its maximum value, at the time that peak anterior cruciate ligament strain occurred, while both anterior tibial translation and knee abduction had already reached their peaks.

Interpretation: Together, these findings indicate that although internal tibial rotation contributes to increased anterior cruciate ligament strain, it is secondary to knee abduction and anterior tibial translation in its effect on anterior cruciate ligament strain and potential risk of injury.

Keywords: Anterior cruciate ligament; Biomechanics; Cadaveric experiments; Injury; Landing.

Figure 1

Custom designed drop-stand testing apparatus.

Figure 2

Cable-pulley system used for application of the simulated muscle loads (left). External fixation frame with the embedded cable-pulley system used for application of external loads.

Figure 3

DVRT insertion on the AM-bundle of the ACL.

Figure 4

Time-history graph of the normalized generated axial impact, tibiofemoral kinematics and ACL strain for a typical specimen during simulated landing. (+) Demonstrating significant delay (~30ms) in occurrence of the peak anterior tibial translation, knee abduction, ACL strain and internal tibial rotation following peak axial impact load (p<0.013). (*) Shows significant delay (~40ms) in occurrence of the peak internal tibial rotation subsequent to the concurrent peak anterior tibial translation, knee abduction and ACL strain (p<0.015).