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Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing.

ABSTRACT: ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the tensile stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps tensile stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased stiffness female quadriceps (i.e., 33% greater stiffness). Peak AM-ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS™ dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated-measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM-ACL relative strain and 21% reduction in change in flexion when quadriceps tensile stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p?=?0.003). We conclude that increased quadriceps tensile stiffness reduces peak ACL strain during a controlled study simulating a pivot landing.

SUBMITTER: Lipps DB

PROVIDER: S-EPMC6380487 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing.

Lipps David B DB Oh Youkeun K YK Ashton-Miller James A JA Wojtys Edward M EM

Journal of orthopaedic research : official publication of the Orthopaedic Research Society 20131202 3

ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the tensile stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps tensile stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibi ...[more]

PMID: 24302388

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Project description:BACKGROUND:Many factors contributing to anterior cruciate ligament (ACL) injury risk have been investigated. Recently, some ACL-injured individuals have presented with a decreased range of hip internal rotation compared with controls. The pathomechanics of why decreased hip range of motion increases risk of ACL injury have not yet been studied. HYPOTHESIS:Peak relative strain of the anteromedial bundle of the ACL (AM-ACL) during a simulated single-leg pivot landing is inversely related to the available range of internal femoral rotation. STUDY DESIGN:Controlled laboratory study. METHODS:A series of pivot landings were simulated in 10 female and 10 male human knee specimens with a testing apparatus that applied a 2-bodyweight impulsive load, inducing knee compression, flexion moment, and internal tibial torque. The range of internal femoral rotation was (1) locked at ~0°, (2) limited with a hard stop to ~7°, (3) limited with a hard stop to ~11°, or (4) free, with rotation resisted by 2 springs to simulate the resistance of the active hip rotator muscles to stretch. The AM-ACL strain was quantified with a differential variable reluctance transducer. A linear mixed model was used to determine whether a significant linear relation existed between peak AM-ACL relative strain and range of internal femoral rotation. RESULTS:Peak AM-ACL relative strain was inversely related to the available range of internal femoral rotation (R (2) = 0.91; P < .001), with strain increasing 1.3% for every 10° decrease in rotation; this represented a 20% increase in peak relative strain, given an average range of femoral rotation of 15° upon landing in healthy athletes. CONCLUSION:Peak AM-ACL relative strain was inversely proportional to the available range of internal femoral rotation during simulated single-leg pivot landings. CLINICAL RELEVANCE:Decreased range of internal femoral rotation results in greater ACL strain and may therefore increase the susceptibility to ACL rupture with athletic cutting and pivoting activities. Screening for a limited range of hip internal rotation should therefore become a component of not only ACL injury prevention programs but also evaluation protocols for those with ACL injuries and/or reconstructions.

Project description:BACKGROUND:It is not known whether the human anterior cruciate ligament (ACL) is susceptible to fatigue failure as a result of repetitive loading or whether certain knee morphologic characteristics increase that risk. HYPOTHESES:The number of knee loading cycles required to fail an ACL by fatigue failure is unaffected by the magnitude of the external load delivered to the knee joint. Furthermore, sex, ACL cross-sectional area, and lateral tibial slope will not affect the number of loading cycles to ACL failure. STUDY DESIGN:Controlled laboratory study. METHODS:Knee pairs from 10 cadaveric donors (5 female) of similar age, height, and weight were imaged with 3-T magnetic resonance imaging to measure lateral tibial slope and ACL cross-sectional area. One knee from each pair was then subjected to repeated application of a load of 3 times body weight (3*BW), while the other knee was subjected to a 4*BW load, both involving impulsive compression force, knee flexion moment, and internal tibial torque combined with realistic trans-knee muscle forces. The resulting 3-dimensional tibiofemoral kinematics and kinetics were recorded, along with ACL relative strain and quadriceps, hamstring, and gastrocnemius muscle forces. The loading cycle was repeated until the ACL ruptured, a 3-mm increase in cumulative anterior tibial translation occurred, or a minimum of 50 trials was reached. RESULTS:Eight of 10 knees failed under the 4*BW load (mean ± SD cycles to failure, 21 ± 18), while 5 of 10 knees failed under the 3*BW load (mean ± SD cycles to failure, 52 ± 10). Four knees exhibited a 3-mm increase in anterior tibial translation, 7 knees developed partial or complete visible ACL tears, and 2 knees developed complete ACL tibial avulsions. A Cox regression showed that the number of cycles to ACL failure was influenced by the simulated landing force (P = .012) and ACL cross-sectional area (P = .022). Donor sex and lateral tibial slope did not influence the number of cycles to ACL failure. CONCLUSION:The human ACL is susceptible to fatigue failure when pivot landings of 3*BW or more load the knee repeatedly within a short time span. An ACL with a smaller cross-sectional area is at greater risk for this type of failure. CLINICAL RELEVANCE:The results show that the human knee can only withstand a certain number of 3*BW or greater jump loading cycles within a short time period before the ACL will fail. Therefore, limiting the increase in the number and severity of pivot landing maneuvers performed over a week of training would make sense from an injury prevention viewpoint.

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Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing.

Publications

Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing.

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