Preferential loading of the ACL compared with the MCL during landing: a novel in sim approach yields the multiplanar mechanism of dynamic valgus during ACL injuries.
Level 5 - mechanism / opinion, no new human data
Cadaveric biomechanical simulation and finite element modeling (bench/in vitro research).
PubMed 24124198 · doi:10.1177/0363546513506558
What was done
Seventeen human cadaveric lower extremities (mean age 45 ± 7 years; 9 female, 8 male) were evaluated in a dynamic jump-landing simulator at 25° of knee flexion under varying combinations of anterior tibial shear force, knee abduction, and internal tibial rotation. Ligament strains in the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) were measured using differential variable reluctance transducers and analyzed alongside a detailed finite element model.
What was found
ACL failure occurred in 15 of 17 specimens (88%). Under all single-planar and multiplanar loading conditions, the ACL:MCL strain ratio remained greater than 1.7, and relative ACL strain was significantly higher than relative MCL strain (P < .01). Increases in anterior tibial shear force, knee abduction, and internal tibial rotation moments resulted in significantly higher ACL:MCL strain ratios (P < .05). Combined multiplanar loading produced significantly greater relative ACL strain changes than isolated anterior tibial shear force (P = .016), knee abduction (P = .018), or internal tibial rotation (P < .0005) moments alone.
Why it matters
This study resolves the clinical paradox of isolated ACL tears occurring during dynamic valgus collapse, demonstrating biomechanically that physiological multiplanar forces load the ACL to failure before reaching thresholds that compromise MCL integrity.
Limits
Testing was performed on middle-aged cadaveric specimens (mean age 45 years), which may have different tissue properties than young athletic cohorts. The experimental design simulated landings at a fixed knee flexion angle (25°) and lacked dynamic active muscular contractions and neuromuscular feedback.
Cited by
- supports Women experience greater medial shear forces at the knee during movement due to pelvic anatomy, putting them at elevated risk for ACL injuries.