Joint Moment Arms Research Articles

Effect of six degrees of freedom knee kinematics on ligament length and moment arm in an intact knee model.

Biomechanics studies can help improve athletic performance. However, the biomechanics of knee joint ligament length changes and moment arms over six degrees of freedom (DOF) have yet to be established. To construct a knee model to investigate the length and moment arm changes of the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). Six DOF joint modeling and analysis were performed using specialized modeling software. The length of all ligaments varied with tibiofemoral flexion angle, contributed to joint motion, and restrained the joint in different positions. The ACL, MCL, and LCL lengths decreased, the PCL increased, the posterior tibial translation increased, the MCL moment arm increased, and the LCL moment arm decreased between 0° and 90°. The primary ligament restraints were the PCL (0° to 30°), MCL (30° to 60°), and PCL (60° to 90°). The restraining function of each ligament during motion can be modeled based on changes in ligament lengths during tibial translations and rotations during flexion. Understanding the correlations between ligament lengths and moment arm changes over a wide range of motion will help improve our understanding of joint kinematics and may be useful for the diagnosis and treatment of sports injury.

Stride frequency in relation to allometric growth in ghost crabs

AbstractBody size has significant impacts on fundamental processes of locomotion, including the operational frequency of skeletal muscle contraction, which declines systematically with increasing size. Although this shift in operation frequency and contractile kinetics is well documented in the literature, the mechanisms responsible for these changes are still incompletely understood. One important factor is that the mechanical properties of the musculoskeletal system possess resonant properties that favor higher frequencies in small animals. Another significant element is the physiological properties of the skeletal muscles, which may be tuned for faster contractions in smaller animals. These two components are interrelated, but precisely how muscle physiology and musculoskeletal mechanics interact to shape patterns of locomotion is complex. Ghost crabs Ocypode quadrata present an interesting model to study these processes because they are proficient runners that exhibit systematic changes in stride frequency as they grow. In the current study, we focused on anatomical changes that might occur with allometric growth in ghost crabs to test the hypothesis that changes in mechanical parameters contribute to the slowing of stride frequency. We paired basic anatomical measurements with kinematic analyses of crabs running at top speeds on a treadmill and experimentally weighted crabs to determine if the relative mass of larger crabs affects running frequency. We found that biologically relevant mechanics of the leg joints do not change with growth, as mechanical advantage and muscle fiber length relative to joint moment arm were unaffected by body size. Loading crabs had similar effects on stride frequency in both large and small animals alike. In contrast, muscle shortening velocity, estimated directly from angular velocity of the leg joints, decreased significantly with increasing body size. These data suggest that fundamental changes to the contractile properties of skeletal muscles during growth are primarily responsible for the changes in stride frequency observed in ghost crabs.

Biomechanical comparison of frontal plane knee joint moment arms during normal and Tai Chi walking

[Purpose] Medial knee osteoarthritis, a degenerative joint disease, affects adults. The external knee adduction moment, a surrogate knee-loading measure, has clinical implications for knee osteoarthritis patients. Tai Chi is a promising intervention for pain alleviation in knee osteoarthritis; however, the characteristics of external knee adduction moment during Tai Chi have not been established. [Subjects and Methods] During normal and Tai Chi walking, a gait analysis was performed to compare the external knee adduction moment moment-arm characteristics and paired t-tests to compare moment-arm magnitudes. [Results] A significant difference was observed in the average lateral direction of moment-arm magnitude during Tai Chi walking (−0.0239 ± 0.011 m) compared to that during normal walking (−0.0057 ± 0.004 m). No significant difference was found between conditions in average medial direction of moment-arm magnitude (normal walking: 0.0143 ± 0.010 m; Tai Chi walking: 0.0098 ± 0.014 m). [Conclusion] Tai Chi walking produced a larger peak lateral moment-arm value than normal walking during the stance phase, whereas Tai Chi walking and normal walking peak medial moment-arm values were similar, suggesting that medial knee joint loading may be avoided during Tai Chi walking.

Effects of Shoeing on Breakover Forces in Icelandic Horses at Walk, Tölt and Trot

IntroductionTo enhance expressiveness and regularity of the tölt, Icelandic horses are commonly shod with excessively high and long hooves. The aim of this study was to objectively assess the effect of shoeing on distal interphalangeal (DIP) joint moments of the left forelimb during break‐over at walk, tölt and trot.MethodsTwelve sound Icelandic horses accustomed to exercise with a rider on a treadmill were assessed with hooves trimmed and shod according to the standards of normal shoeing and with long and high front hooves; besides the 20 x 8 mm steel shoes, this condition included pads and packing material used in competition. Vertical ground reaction forces (GRFz) were measured with an instrumented treadmill. Time of break‐over was determined kinematically. Measuring systems were started synchronously; sampling frequency was 480 Hz. Measurements were taken at 1.34 ± 0.04 m/s (walk), 3.89 ± 0.10 m/s (tölt), and 3.90 ± 0.10 m/s (trot). The DIP joint moment arm was determined on size‐calibrated latero‐medial radiographs of the left front hoof. Differences were tested using a t‐test (walk) or repeated measures ANOVA (tölt, trot).ResultsIn the condition with the long and high hooves, DIP joint moment was increased by 18.5% at walk (P<0.001), 17.3% at tölt (P<0.001) and 13.4% at trot (P = 0.017) although vertical GRFz at break‐over was not statistically different between the two shoeing conditions. The increase could be attributed to the 22.7% increase of the lever arm.ConclusionsHigh hooves with long toes may have negative implications for the health of the palmar structures of the distal foot.Ethical Animal ResearchThe experiment was carried out with the approval of the Animal Health and Welfare Commission of the Canton of Zurich (No. 206/2010). Owners gave informed written consent. Sources of funding: Stiftung Forschung für das Pferd, the Haldimann Stiftung, the Swiss Metall Union, the Stiftung Temperatio, the Swiss Veterinary Office (FVO) and the Islandpferde‐Vereinigung Schweiz. Competing interests: none.

Comparison of the iemg activity elicited during an isometric contraction using manual resistance and mechanical resistance

Introduction: Quantification of muscle strength is an essential component of assessment and treatment in rehabilitation. Considering the measurement of the muscle strength, mostly two methods are used. They are qualitative and quantitative measures. Maximum voluntary isometric contraction (MVIC), measured using dynamometer and manual muscle testing (MMT) are the most common measurement techniques used in the clinical and research setting. Objectives: This study's aim was to observe, if greater activity is produced using mechanical instruments for torque measurements (since the resistance is adjusted to subject's maximum capacity) or if tests, position of MMT, and resistance offered by trained physiotherapist are effective. We compared the IEMG (Integrated electromyography) output between manual and mechanical testing during maximal voluntary isometric contraction. Subjects and Methods: Forty normal healthy subjects including 20 males and 20 females were selected for the study. The measuring system comprises an EMG (Noraxon USA, INC, Scottsdale, Arizona) and ®HUR 5340 (Kokkola, Finland) leg extension/curl computer controlled machine for isometric evaluating peak torque. MVIC of the Vastus medialis oblique (VMO), Vastus lateralis (VL), Rectus femoris (RF), Semitendinosis (ST) and Biceps Femoris (BF) were measured from dominant leg using SEMG and then subjects were seated on HUR with hip flexed and chest, pelvis, thigh stabilized. The axis of rotation of HUR aligned with the joint axis and moment arm is fixed for every subject. Each subject performed maximal contraction of 10sec at 60°of test angle to get the peak torque and myoelectrical activity are also recorded while performing the same. Result: Paired t-test analysis were used to see the difference between MMT and HUR IEMG amplitude and the results show significance difference(p< .05) for each muscle when comparing between the EMG amplitude between MMT and HUR. Conclusion: HUR system has very good reliability in measuring muscle strength of the knee extensors and flexors as compared to the MMT, suggesting that it will be useful in clinical applications, especially for professional athletes or physically powerful populations.

腱骨格モデルを用いたつまみやすさの生体力学的解析

In this paper, we analyze a human pinching motion based on biomechanics for the quantification system of a product usability. We compare three experimental results to analyze the relationship between the deep sensation and subjective pinching effort. First, the surface EMG and the pinching force were measured during the pinching motion by a human. Questionnaire results show that subjects feel easy to pinch a cylinder of 60[mm] length. Experimental results show the profile of the surface EMGs reflects the human subjective pinching effort. Second, the pinching motion was simulated using the tendon skeletal model that mimics the variation of human joint moment arm. Simulation results show that the profile of the tendon forces has similar characteristics to that of the human muscle activity. These result suggest the finger posture influences the subjective pinching effort. Furthermore, a tendon-driven robot hand was developed as a sensing hand prototype. The motor torques and the human muscle activity were compared in a pinching experiment using the tendon-driven robot hand. Experimental results show the profile of the motor torques mirrors the human muscle activity. These results show that the tendon force is a useful index for the evaluation of the subjective pinching effort, and it can be used for the quantitative evaluation instead of EMGs.

A Neuro-Muscular Elasto-Dynamic Model of the Human Arm Part 2: Musculotendon Dynamics and Related Stress Effects

In this paper we develop an elasto-dynamic model of the human arm that includes effects of neuro-muscular control upon elastic deformation in the limb. The elasto-dynamic model of the arm is based on hybrid parameter multiple body system variational projection principles presented in the companion paper. Though the technique is suitable for detailed bone and joint modeling, we present simulations for simplified geometry of the bones, discretized as Rayleigh beams with elongation, while allowing for large deflections. Motion of the upper extremity is simulated by incorporating muscle forces derived from a Hill-type model of musculotendon dynamics. The effects of muscle force are modeled in two ways. In one approach, an effective joint torque is calculated by multiplying the muscle force by a joint moment arm. A second approach models the muscle as acting along a straight line between the origin and insertion sites of the tendon. Simple arm motion is simulated by utilizing neural feedback and feedforward control. Simulations illustrate the combined effects of neural control strategies, models of muscle force inclusion, and elastic assumptions on joint trajectories and stress and strain development in the bone and tendon.

Muscle architecture of the common chimpanzee (Pan troglodytes): perspectives for investigating chimpanzee behavior

Thorpe et al. (Am J Phys Anthropol 110:179-199, 1999) quantified chimpanzee (Pan troglodytes) muscle architecture and joint moment arms to determine whether they functionally compensated for structural differences between chimpanzees and humans. They observed enough distinction to conclude that musculoskeletal properties were not compensatory and suggested that chimpanzees and humans do not exhibit dynamically similar movements. These investigators based their assessment on unilateral limb musculatures from three male chimpanzees, of which they called one non-adult representative. Factors such as age, sex, and behavioral lateralization may be responsible for variation in chimpanzee muscle architecture, but this is presently unknown. While the full extent of variation in chimpanzee muscle architecture due to such factors cannot be evaluated with data presently available, the present study expands the chimpanzee dataset and provides a preliminary glimpse of the potential relevance of these factors. Thirty-seven forelimb and 36 hind limb muscles were assessed in two chimpanzee cadavers: one unilaterally (right limbs), and one bilaterally. Mass, fiber length, and physiological cross-sectional area (PCSA) are reported for individual muscles and muscle groups. The musculature of an adult female is more similar in architectural patterns to a young male chimpanzee than to humans, particularly when comparing muscle groups. Age- and sex-related intraspecific differences do not obscure chimpanzee-human interspecific differences. Side asymmetry in one chimpanzee, despite consistent forelimb directional asymmetry, also does not exceed the magnitude of chimpanzee-human differences. Left forelimb muscles, on average, usually had higher masses and longer fiber lengths than right, while right forelimb muscles, on average, usually had greater PCSAs than left. Most muscle groups from the left forelimb exhibited greater masses than right groups, but group asymmetry was significant only for the manual digital muscles. The hind limb exhibited less asymmetry than the forelimb in most comparisons. Examination of additional chimpanzees would clarify the full range of inter- and intra-individual variation.

Maxillo-facial surgery simulation with a simple patient specific material model

In this paper we develop an elasto-dynamic model of the human arm that includes effects of neuro-muscular control upon elastic deformation in the limb. The elasto-dynamic model of the arm is based on hybrid parameter multiple body system variational projection principles presented in the companion paper. Though the technique is suitable for detailed bone and joint modeling, we present simulations for simplified geometry of the bones, discretized as Rayleigh beams with elongation, while allowing for large deflections. Motion of the upper extremity is simulated by incorporating muscle forces derived from a Hill-type model of musculotendon dynamics. The effects of muscle force are modeled in two ways. In one approach, an effective joint torque is calculated by multiplying the muscle force by a joint moment arm. A second approach models the muscle as acting along a straight line between the origin and insertion sites of the tendon. Simple arm motion is simulated by utilizing neural feedback and feedforward control. Simulations illustrate the combined effects of neural control strategies, models of muscle force inclusion, and elastic assumptions on joint trajectories and stress and strain development in the bone and tendon.

Investigation of the validity of modeling the Achilles tendon as having a single insertion site

Objective. To assess the propriety of modeling the Achilles tendon insertion on the calcaneus as a single point when musculoskeletal models are used to predict subtalar joint moment arms. Design. The sensitivity of model-predicted subtalar joint moment arms to insertion site position was investigated and measurements of Achilles tendon function were made in cadaver specimens. Background. The insertion site of the Achilles tendon is typically modeled as having a single-point insertion. A more sophisticated representation may be required, however, when subtalar joint function is considered. Methods. Achilles tendon moment arms about the subtalar joint axis were assessed using a computer model in which a single-point insertion was systematically displaced. The effective insertion site was located at three positions in three cadaver specimens using a six-degree-of-freedom load cell. Results. Model-predicted moment arms of the Achilles tendon about the subtalar joint axis were substantially affected by medial–lateral displacement of the insertion site. The medial–lateral location of the effective insertion site varied linearly with subtalar joint angle in cadaver specimens, shifting medially when the foot was everted and laterally when the foot was inverted. Conclusions. More sophisticated representations of the Achilles tendon are needed when the subtalar joint is of interest. A single-segment tendon with an insertion that is fixed throughout subtalar joint motion may not permit accurate predictions of moment arms about the subtalar joint. Relevance Accurate prediction of the large moments produced by the triceps surae when simulating movement or investigating the effects of orthopaedic surgeries requires a realistic representation of the Achilles tendon insertion.

UNCHANGED MECHANICAL PROPERTIES AND DIMENSIONS OF THE HUMAN ACHILLES TENDON-APONEUROSIS COMPLEX WITH ENDURANCE TRAINING

Whether running results in altered mechanical properties and dimensions of the human Achilles tendon-aponeurosis remains unknown. PURPOSE To examine the effects of running on the cross-sectional area (CSA) and the mechanical properties of the Achilles tendon-aponeurosis complex. METHODS Ten untrained subjects completed a 9 month running regimen. Data was obtained twice with a one-week hiatus prior to training (tests 1&2) and after training (test 3). Axial MR-images of the Achilles tendon at three different levels (48, 60 and 72 mm) above the inferior calcaneal margin were analyzed with software for automatic recognition of tendon outline and calculation of CSA. Syncronous ultrasonographic displacement was obtained during 10-s graded isometric plantarflexion trials. Tendon force was obtained from maximal isometric joint moment and MRI moment arm data. Tendinous stiffness (N/mm) was calculated from force and displacement data corresponding to the least common 90% maximal force for all contractions. RESULTS (mean±sem) Total training duration was 44±1 hrs within 34±2 wks (2.4±0.2 sessions/wk). Maximal oxygen consumption increased (Δ0.31±0.06 1 min−1, P < 0.01). Tendon-aponeurosis displacement was similar for test 1 (5.8±0.7 mm), test 2 (5.5±0.5 mm) and test 3 (5.7±0.6 mm). Structural stiffness was also comparable for test 1 (266±36 N/mm), test 2 (255±24 N/mm) and test 3 (237±27 N/mm). Coefficient of variation (CV) for repeated tests (test 1&2) yielded 11.5% for stiffness and 10.1% for displacement. Tendon CSA (mm2) was unchanged: Level 1 (test 1; 34.5±1.7, test 2; 34.0±1.7 and test 3; 34.2±1.7). Level 2 (test 1; 35.1±2.9, test 2; 34.3±2.9 and test 3; 34.6±2.6). Level 3: (test 1; 33.1±2.8, test 2; 33.4±2.7 and test 3; 32.7±2.7). CV for repeated tests (test 1&2) was 4.9–8.2%. CONCLUSIONS Long term running (34 wks) did not induce detectable alterations of the in vivo mechanical properties and gross morphology of the human Achilles tendon-aponeurosis complex.

Load-displacement properties of the human triceps surae aponeurosis and tendon in runners and non-runners.

The load-displacement and stress-strain characteristics of the human triceps surae tendon and aponeurosis, in vivo, was examined during graded maximal voluntary plantarflexion efforts in runners who trained 80 km/ week or more and age-matched non-runners. Synchronous real-time ultrasonography of triceps surae tendon and aponeurosis displacement, electromyography of the gastrocnemius, soleus and dorsiflexor muscles, and joint angular rotation were obtained. Tendon cross-sectional area and ankle joint moment arm were obtained from magnetic resonance imaging. Tensile tendon force was calculated from the joint moments and tendon moment arm and stress was obtained by dividing force by cross-sectional area. Strain was obtained from the displacements normalized to tendon length. Antagonist coactivation and small amounts of ankle joint rotation significantly affected tensile tendon force and aponeurosis and tendon displacement, respectively (P < 0.01). Plantarflexion moment was similar in runners (138 +/- 27 Nm, mean +/- SEM) and non-runners (142 +/- 17 Nm). Tendon moment arm was alike in non-runner (58.3 +/- 0.2 mm) and runners (55.1 +/- 0.1 mm). Similarly, there was no difference in tendon tensile force between runners (2633 +/- 465 N) and non-runners (2556 +/- 401 N). The cross-sectional area of the Achilles tendon was larger in runners (95 +/- 3 mm2) than non-runners (73 +/- 3 mm(2)) (P < 0.01). The load-deformation data yielded similar stiffness (runners 306 +/- 61 N/mm, non-runners 319 +/- 42 N/mm). The maximal strain and stress was 4.9 +/- 0.8% and 38.2 +/- 9.8 MPa in non-runners and 4.1 +/- 0.8% and 26.3 +/- 5.1 MPa in runners. The larger tendon cross-sectional area in trained runners suggests that chronic exposure to repetitive loading has resulted in a tissue adaptation.

Changes in muscle moment arms following split tendon transfer of tibialis anterior and tibialis posterior.

Moment arms of tibialis anterior (TA) and tibialis posterior (TP) about the subtalar and talocrural joint axes were measured in anatomic specimens both before and after split tendon transfers. These procedures are commonly performed to correct hindfoot varus, a gait deformity that is often seen in patients with cerebral palsy, stroke, and brain injury. Split tendon transfer significantly reduced the inversion moment arms of tibialis anterior and tibialis posterior at all subtalar joint angles except for the most everted position in the case of TA. Changes in subtalar joint moment arms produced by split tendon transfer, especially those seen in TA, were variable, suggesting that the procedure may be susceptible to technical errors, especially related to balancing tensions in the medial and lateral tendon halves. Talocrural joint moment arms of both muscles were preserved following split tendon transfer. This study presents the first measurements of the moment arms of split transferred muscles. These characterizations of the mechanics of split tendon transfer will aid in the planning and assessment of these procedures.

Muscle fiber length and moment arm coordination during dorsi- and plantarflexion in the mouse hindlimb.

The purpose of this study was to test the hypothesis that muscle fiber length and joint moment arm are combined in such a way that maximum muscle force is produced during locomotion. Plantarflexor (soleus, SOL and medial gastrocnemius, MG) and dorsiflexor (extensor digitorum longus, EDL and tibialis anterior, TA) muscle architecture in the mouse was measured along with their associated moment arms. Fiber length varied significantly between muscles ranging from 5.7 +/- 0.2 mm (MG) to 7.6 +/- 0.2 mm (TA). Plantarflexor moment arms were over twice as large as dorsiflexor moment arms (1.88 +/- 0.06 mm vs. 0.84 +/- 0.03 mm) suggesting a greater muscle length change with joint angle for plantarflexors compared to dorsiflexors. Using a simple muscle-joint model, the active sarcomere length range in these muscle groups was calculated and proved to be quite similar between functional groups. The active range for dorsiflexors was 2.2-2.4 microns, while the active range for plantarflexors was 2.2-2.5 microns, indicating that both muscle groups operate primarily near the plateau of their length tension-relation. Finally, when calculating force produced by muscles during locomotion, the combination of moment arm and fiber length measured in all muscle groups yielded muscle-joint systems that produced near maximal forces at the velocities modeled. These data indicate that fiber length and moment arm appear to be coordinated to yield the greatest possible force production during locomotion.

Load redistribution after desmotomy of the accessory ligament of the deep digital flexor tendon in adult horses

Summary An analysis of joint moments was used to study the biomechanical implications, load redistribution and kinematic pattern following desmotomy of the accessory ligament of the deep digital flexor tendon (AL) in adult horses. Recordings of 6 sound horses were made before and 10 days after desmotomy of the AL of the right forelimb at the walk and the trot. Kinematic recordings of the right forelimb and the left distal forelimb were made using the CODA-3 system. Kinetic recordings of the ground reaction forces in both forelimbs were made using a Kistler force plate simultaneously with the kinematic recordings. Radiographic localisation of the CODA-3 markers in both distal limbs allowed an analysis of coffin and fetlock joint moments, moment arms and forces in the digital flexor tendons. No transfer of load from the operated to the contralateral limb was found. In the operated limb the total joint moment of the coffin joint decreased substantially due to a reduced moment arm of the vertical ground reaction force component during the entire stance phase, while the fetlock joint moment decreased only slightly. To compensate for the loss of AL function, the superficial digital flexor tendon (SDFT) took a higher load during midstance, while at the end of the stance phase, the deep digital flexor tendon (DDFT) carried a higher load with a marked load peak just before heel off. While the compensation was adequate during midstance (no changes in maximal hyperextension of the fetlock joint), a prolonged hyperextension of the fetlock joint together with a rapid flexion at the start of the swing phase indicated that the DDFT was unable to compensate completely for the loss of AL function. It was concluded that the changes in total joint moments and increases in loading of the SDFT and DDFT allow locomotion without serious overloading of the compensating tendons following AL desmotomy.