Knee Abduction Affects Greater Magnitude of Change in ACL and MCL Strains Than Matched Internal Tibial Rotation In Vitro

Abstract

Background Anterior cruciate ligament (ACL) injures incur over USD 2 billion in annual medical costs and prevention has become a topic of interest in biomechanics. However, literature conflicts persist over how knee rotations contribute to ACL strain and ligament injury. To maximize the efficacy of ACL injury prevention, the effects of underlying mechanics need to be better understood. Questions/purposes We applied robotically controlled, in vivo-derived kinematic stimuli to the knee to assess ligament biomechanics in a cadaver model. We asked: (1) Does the application of abduction rotation increase ACL and medial collateral ligament (MCL) strain relative to the normal condition? (2) Does the application of internal tibial rotation impact ACL strain relative to the neutral condition? (3) Does combined abduction and internal tibial rotation increase ligament strain more than either individual contribution?Methods A six-degree-of-freedom robotic manipulator was used to position 17 cadaveric specimens free from knee pathology outside of low-grade osteoarthritis (age, 47 ± 8 years; 13 males, four females) into orientations that mimic initial contact recorded from in vivo male and female drop vertical jump and sidestep cutting activities. Four-degree rotational perturbations were applied in both directions from the neutral alignment position (creating an 8°range) for each frontal, transverse, and combined planes while ACL and MCL strains were continuously recorded with DVRT strain gauges implanted directly on each ligament. Analysis of variance models with least significant difference post hoc analysis were used to assess differences in ligament strain and joint loading between sex, ligament condition, or motion task and rotation type. Results For the female drop vertical jump simulation in the intact knee, isolated abduction and combined abduction/internal rotational stimuli produced the greatest This work was supported by National Institutes of Health/NIAMS Grants #R01-AR049735 (TEH), #R01-AR055563 (TEH), #R01-AR056660 (JTS), and #R01-AR056259 (TEH -017-5367-9 Clinical Orthopaedics and Related Research ® A Publication of The Association of Bone and Joint Surgeons® change in strain from the neutral position as compared with all other stimuli within the ACL (1.5% ± 1.0%, p B 0.035; 1.8% ± 1.3%, p B 0.005) and MCL (1.8% ± 1.0%, p \ 0.001; 1.6% ± 1.3%, p \ 0.001) compared with all other applied stimuli. There were no differences in mean peak ACL strain between any rotational stimuli (largest mean difference = 2.0%; 95% confidence interval [CI], À0.9% to 5.0%; p = 0.070). These trends were consistent for all four simulated tasks. Peak ACL strain in the intact knee was larger than peak MCL strain for all applied rotational stimuli in the drop vertical jump simulations (smallest mean difference = 2.1%; 95% CI, À0.4% to 4.5%; p = 0.047). Conclusions Kinematically constrained cadaveric knee models using peak strain as an outcome variable require greater than 4°rotational perturbations to elicit changes in intraa...

External loads associated with anterior cruciate ligament injuries increase the correlation between tibial slope and ligament strain during in vitro simulations of in vivo landings

“…29 However, limited magnitudes of isolated rotational stimuli applied to a knee joint have failed to produce statistically significant changes in ACL strain as compared to the baseline knee orientation. 8 Accordingly, the present findings that MPTS and LPTS were potentially predictive factors for ACL strain, but only in simulated conditions with high KAM loading, corroborated the existing literature.…”

“…The largest R-squared values reported presently were typically found when the combinatorial loads of KAM, ATS, and ITR were at or above the 90 th percentile recorded from the in vivo . These three external loading mechanisms couple together straining the ACL as ITR predisposes valgus orientation through slight superior and inferior translation of the medial and lateral femoral condyles, respectively, 34 which is compounded by KAM that effects greater change in strain on the ACL than any other isolated knee rotation, 8 and is further exacerbated by anterior tibial translation introduced from ATS. Individually, very high KAM (200 th percentile) demonstrated the most consistent association with tibial slope r-squared values being above the predictive threshold of 0.2.…”

Dynamic knee control and movement strategies in athletes and non‐athletes in side hops: Implications for knee injury

“…Using the knee helical motion, interval of 10° to provide the FHA inclination angles is considered a strength since it evaluates the relative knee motion between the motion planes, which is relevant for non-contact knee injuries such as ACL injury. [8][9][10] If we instead would have used knee flexion intervals of 10° or specific time intervals, we might miss important spatial information due to a loss in the relation between knee movement planes. Consequences include a decreased representation of dynamic knee stability and robustness with relevance to non-contact knee injuries.…”

“…It remains undetermined whether high athletic training leads to definite gains in dynamic knee robustness or altered task execution. Since the combination of knee frontal and transversal plane loading (specifically abduction and internal rotation) strains the ACL more than either specific loading alone; dynamic knee robustness in relation to ACL injury and re‐injury risk should optimally be evaluated under such conditions. An appropriate method may be to describe the 3D joint motion as an instantaneous rotation about an axis as performed using finite helical axis (FHA) methods .…”

“…Such dynamic knee stability is maintained during dynamically challenging tasks when frontal and transversal plane motions are minimal. 6,7 These movements have indeed shown to decrease the strain placed on the ACL, [8][9][10] with obvious implications for injury prevention.…”