Eric G. Meyer

Publications (31) View all

• Article: Characterization of Occupant Lower Extremity Behavior During Moderate-to-High Speed Rear Impacts

  Steven Rundell, Allison Guiang, Brian Weaver, Eric G. Meyer
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  ABSTRACT: Injury potential to the neck has been studied extensively for rear-end impacts. The capacity for injury to other body regions, such as the lower extremities, has not been previously explored. The objective of the current study was to characterize the forces and motions experienced in the lower extremities during moderate-to-high speed rear-end impacts. The current study utilized publicly available rear-end crash tests. Forty-two 50 km/hour, 20% offset, 180° barrier rear-end impacts were used. The occupant lower extremity behavior was analyzed for 63 ATDs, and included 42 driver's seats, 8 front passenger seats, and 13 right-rear seat scenarios. Three consistent events were identified during each test, in the following sequence; 1. initial compressive femur force, 2. secondary tensile femur force, and 3. rearward pelvis acceleration peak. In addition to pelvic contact with the seatback, in some cases the loading in the femur was influenced by contact between the seat pan and the back of the tibia just below the knee. The larger, male occupants experienced higher magnitudes of femur compression as the vehicle was impacted from the rear. The smaller, female occupants experienced predominately femur tension. Pelvic acceleration data corroborated these findings. Femur forces were consistent between both legs, indicating that there was little torsion applied to ATDs during the rear-end crash tests. The current study indicates that occupant anthropometry and seat pan geometry play a significant role in loading of the lower extremity in a rear-end impact.
  SAE International. 04/2013; 2013(01):0222.
• Source

  Available from: Yohei Shimokochi

  Article: Changing sagittal plane body position during single-leg landings influences the risk of non-contact anterior cruciate ligament injury.

  Yohei Shimokochi, Jatin P Ambegaonkar, Eric G Meyer, Sae Yong Lee, Sandra J Shultz
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  ABSTRACT: PURPOSE: To examine the effects of different sagittal plane body positions during single-leg landings on biomechanics and muscle activation parameters associated with risk for anterior cruciate ligament (ACL) injury. METHODS: Twenty participants performed single-leg drop landings onto a force plate using the following landing styles: self-selected, leaning forward (LFL) and upright (URL). Lower extremity and trunk 3D biomechanics and lower extremity muscle activities were recorded using motion analysis and surface electromyography, respectively. Differences in landing styles were examined using 2-way Repeated-measures ANOVAs (sex × landing conditions) followed by Bonferroni pairwise comparisons. RESULTS: Participants demonstrated greater peak vertical ground reaction force, greater peak knee extensor moment, lesser plantar flexion, lesser or no hip extensor moments, and lesser medial and lateral gastrocnemius and lateral quadriceps muscle activations during URL than during LFL. These modifications of lower extremity biomechanics across landing conditions were similar between men and women. CONCLUSIONS: Leaning forward while landing appears to protect the ACL by increasing the shock absorption capacity and knee flexion angles and decreasing anterior shear force due to the knee joint compression force and quadriceps muscle activation. Conversely, landing upright appears to be ACL harmful by increasing the post-impact force of landing and quadriceps muscle activity while decreasing knee flexion angles, all of which lead to a greater tibial anterior shear force and ACL loading. ACL injury prevention programmes should include exercise regimens to improve sagittal plane body position control during landing motions.
  Knee Surgery Sports Traumatology Arthroscopy 04/2012; · 2.21 Impact Factor
• Article: Eversion during external rotation of the human cadaver foot produces high ankle sprains.

  Feng Wei, Joel M Post, Jerrod E Braman, Eric G Meyer, John W Powell, Roger C Haut
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  ABSTRACT: While high ankle sprains are often clinically ascribed to excessive external foot rotation, no experimental study documents isolated anterior tibiofibular ligament (ATiFL) injury under this loading. We hypothesized that external rotation of a highly everted foot would generate ATiFL injury, in contrast to deltoid ligament injury from external rotation of a neutral foot. Twelve (six pairs) male cadaveric lower extremity limbs underwent external foot rotation until gross failure. All limbs were positioned in 20° of dorsiflexion and restrained with elastic athletic tape. Right limbs were in neutral while left limbs were everted 20°. Talus motion relative to the tibia was measured using motion capture. Rotation at failure for everted limbs (46.8 ± 6.1°) was significantly greater than for neutral limbs (37.7 ± 5.4°). Everted limbs showed ATiFL injury only, while neutral limbs mostly demonstrated deltoid ligament failure. This is the first biomechanical study to produce isolated ATiFL injury under external foot rotation. Eversion of the axially loaded foot predisposes the ATiFL to injury, forming a basis for high ankle sprain. The study helps clarify a mechanism of high ankle sprain and may heighten clinical awareness of isolated ATiFL injury in cases of foot eversion prior to external rotation. It may also provide guidance to investigate the effect of prophylactic measures for this injury.
  Journal of Orthopaedic Research 02/2012; 30(9):1423-9. · 2.81 Impact Factor
• Article: Temporal and spatial changes in cartilage-matrix-specific gene expression in mesenchymal stem cells in response to dynamic compression.

  Matthew G Haugh, Eric G Meyer, Stephen D Thorpe, Tatiana Vinardell, Garry P Duffy, Daniel J Kelly
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  ABSTRACT: Various forms of mechanical stimulation have been shown to enhance chondrogenesis of mesenchymal stem cells (MSCs). However, the response of MSCs undergoing chondrogenesis to such signals has been shown to depend on the temporal application of loading. The objective of this study was to determine the effect of dynamic compression on cartilage-matrix-specific gene expression and to relate this response to the local biochemical environment and cell phenotype at the time of loading. At 0, 7, 14, and 21 days extracellular matrix (ECM) deposition within MSC-seeded agarose hydrogels due to transforming growth factor-β3 stimulation was determined biochemically and histologically, and then reverse transcription-polymerase chain reaction was used to examine the effects of dynamic compression on cartilage-matrix-specific gene expression. The results of these experiments show that the local environment in the core of the constructs is more favorable for chondrogenesis in comparison to the annulus, as evident from both ECM synthesis and gene expression. Additionally, we found that the response of the cells to mechanical stimulus varied with both the spatial region within the constructs and the temporal application of loading. Dynamic compression applied at day 21 was found to enhance levels of cartilage matrix gene expression following a peak in expression levels at day 14 in free swelling constructs, suggesting that mechanical signals play a key role in the maintenance of a chondrogenic phenotype. The application of mechanical stimulus to enhance cartilage ECM synthesis may be an important tool in regenerative medicine-based cartilage repair. The results of this study suggest that a chondrogenic phenotype and/or a well-developed pericellular matrix must first be established before dynamic compression can have a positive effect on cartilage-matrix-specific gene expression.
  Tissue Engineering Part A 08/2011; 17(23-24):3085-93. · 4.64 Impact Factor
• Article: Pure passive hyperextension of the human cadaver knee generates simultaneous bicruciate ligament rupture.

  Eric G Meyer, Timothy G Baumer, Roger C Haut
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  ABSTRACT: Knee hyperextension has been described as a mechanism of isolated anterior cruciate ligament (ACL) tears, but clinical and experimental studies have produced contradictory results for the ligament injuries and the injury sequence caused by the hyperextension loading mechanism. The hypothesis of this study was that bicruciate ligament injuries would occur as a result of knee hyperextension by producing high tibio-femoral (TF) compressive forces that would cause anterior translation of the tibia to rupture the ACL, while joint extension would simultaneously induce rupture of the posterior cruciate ligament (PCL). Six human knees were loaded in hyperextension until gross injury, while bending moments and motions were recorded. Pressure sensitive film documented the magnitude and location of TF compressive forces. The peak bending moment at failure was 108 N m±46 N m at a total extension angle of 33.6 deg±11 deg. All joints failed by simultaneous ACL and PCL damages at the time of a sudden drop in the bending moment. High compressive forces were measured in the anterior compartments of the knee and likely produced the anterior tibial subluxation, which contributed to excessive tension in the ACL. The injury to the PCL at the same time may have been due to excessive extension of the joint. These data, and the comparisons with previous experimental studies, may help explain the mechanisms of knee ligament injury during hyperextension. Knowledge of forces and constraints that occur clinically could then help diagnose primary and secondary joint injuries following hyperextension of the human knee.
  Journal of Biomechanical Engineering 01/2011; 133(1):011012. · 1.90 Impact Factor