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- Author or Editor: Mont Hubbard x
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Abstract
Objective—To determine the relative contributions of the muscles, tendons, and accessory ligaments to the passive force-length properties of the superficial (SDF) and deep digital flexor (DDF) myotendinous complexes.
Sample Population—8 cadaveric forelimbs from 6 adult Thoroughbreds.
Procedure—In vitro, limb configurations during slack position and myotendinous lengths during subsequent axial loading of forelimbs were recorded before and after transection of accessory ligaments. Expressions were derived to describe the forcelength behavior of each muscle, tendon, and accessory ligament-tendon unit; linear stiffness was computed for these components. The elastic modulus was established for the SDF and DDF tendons.
Results—Linear stiffness was 2.80 ± 0.38 kN/cm for the SDF muscle, 3.47 ± 0.66 kN/cm for the DDF muscle, 2.73 ± 0.18 kN/cm for the SDF tendon, 3.22 ± 0.20 kN/cm for the DDF tendon, 6.46 ± 0.85 kN/cm for the SDF accessory ligament, 1.93 ± 0.11 kN/cm for the SDF accessory ligament-tendon unit, and 2.47 ± 0.11 kN/cm for the DDF accessory ligament-tendon unit. The elastic modulus for the SDF and DDF tendons was 920 ± 77 and 843 ± 56 MPa, respectively.
Conclusions and Clinical Relevance—Both the muscle-tendon and ligament-tendon portions of SDF and DDF myotendinous complexes had important roles in supporting the forelimb of horses. Although muscle tension can be enhanced by elbow joint flexion and active contraction, the accessory ligaments transmitted more force to the distal tendons than did the muscles under the conditions tested. (Am J Vet Res 2004;65:188–197)
Abstract
Objective—To calculate normative joint angle, intersegmental forces, moment of force, and mechanical power at elbow, antebrachiocarpal, and metacarpophalangeal joints of dogs at a walk.
Animals—6 clinically normal mixed-breed dogs.
Procedure—Kinetic data were collected via a force platform, and kinematic data were collected from forelimbs by use of 3-dimensional videography. Length, location of the center of mass, total mass, and mass moment of inertia about the center of mass were determined for each of 4 segments of the forelimb. Kinematic data and inertial properties were combined with vertical and craniocaudal ground reaction forces to calculate sagittal plane forces and moments across joints of interest throughout stance phase. Mechanical power was calculated as the product of net joint moment and the angular velocity. Joint angles were calculated directly from kinematic data.
Results—All joint intersegmental forces were similar to ground reaction forces, with a decrease in magnitude the more proximal the location of each joint. Flexor moments were observed at metacarpophalangeal and antebrachiocarpal joints, and extensor moments were observed at elbow and shoulder joints, which provided a net extensor support moment for the forelimb. Typical profiles of work existed for each joint.
Conclusions and Clinical Relevance—For clinically normal dogs of a similar size at a walk, inverse dynamic calculation of intersegmental forces, moments of force, and mechanical power for forelimb joints yielded values of consistent patterns and magnitudes. These values may be used for comparison in evaluations of gait in other studies and in treatment of dogs with forelimb musculoskeletal disease. (Am J Vet Res 2003;64:609–617)
Abstract
Objective—To compare hoof acceleration and ground reaction force (GRF) data among dirt, synthetic, and turf surfaces in Thoroughbred racehorses.
Animals—3 healthy Thoroughbred racehorses.
Procedures—Forelimb hoof accelerations and GRFs were measured with an accelerometer and a dynamometric horseshoe during trot and canter on dirt, synthetic, and turf track surfaces at a racecourse. Maxima, minima, temporal components, and a measure of vibration were extracted from the data. Acceleration and GRF variables were compared statistically among surfaces.
Results—The synthetic surface often had the lowest peak accelerations, mean vibration, and peak GRFs. Peak acceleration during hoof landing was significantly smaller for the synthetic surface (mean ± SE, 28.5g ± 2.9g) than for the turf surface (42.9g ± 3.8g). Hoof vibrations during hoof landing for the synthetic surface were < 70% of those for the dirt and turf surfaces. Peak GRF for the synthetic surface (11.5 ± 0.4 N/kg) was 83% and 71% of those for the dirt (13.8 ± 0.3 N/kg) and turf surfaces (16.1 ± 0.7 N/kg), respectively.
Conclusions and Clinical Relevance—The relatively low hoof accelerations, vibrations, and peak GRFs associated with the synthetic surface evaluated in the present study indicated that synthetic surfaces have potential for injury reduction in Thoroughbred racehorses. However, because of the unique material properties and different nature of individual dirt, synthetic, and turf racetrack surfaces, extending the results of this study to encompass all track surfaces should be done with caution.
