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- Author or Editor: Joel L. Lanovaz x
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Objective—To test the sensitivity to measurement and modeling errors of a method for noninvasive calculation of flexor tendon forces in the equine forelimb and to calculate tendon forces for Dutch Warmblood horses during trotting.
Sample Population—A normative set of kinematic and ground-reaction force (GRF) data obtained from horses during trotting in another study.
Procedure—Forces in the flexor tendons were calculated from the data set before and after addition of fixed relative and absolute errors. Amount of error was based on normal accuracy of the variables. A similar analysis was performed for a measure of strain of the accessory ligament of the deep digital flexor tendon.
Results—The only errors that had a substantial influence on accuracy were modeling errors in the mechanical properties of the suspensory ligament and measurement errors in the point of application of the GRF and position of the marker on the distal interphalangeal joint. Influence of the measurement errors could be minimized by applying usual correction methods.
Conclusion and Clinical Relevance—After correction of measurement errors, the method can be used to calculate mean tendon forces for a group of horses and to evaluate the influence of factors such as surface properties, type of shoe, speed, and fatigue on tendon forces. The method could become an important tool for use in research on the cause, prevention, and treatment of tendon injuries in horses. (Am J Vet Res 2001;62:1594–1598)
Objective—To measure the effect of subject velocity on hind limb ground reaction force variables at the walk and to use the data to predict the force variables at different walking velocities in horses.
Animals—5 clinically normal horses.
Procedure—Kinematic and force data were collected simultaneously. Each horse was led over a force plate at a range of walking velocities. Stance duration and force data were recorded for the right hind limb. To avoid the effect of horse size on the outcome variables, the 8 force variables were standardized to body mass and height at the shoulders. Velocity was standardized to height at the shoulders and expressed as velocity in dimensionless units (VDU). Stance duration was also expressed in dimensionless units (SDU). Simple regression analysis was performed, using stance duration and force variables as dependent variables and VDU as the independent variable.
Results—Fifty-six trials were recorded with velocities ranging from 0.24 to 0.45 VDU (0.90 to 1.72 m/s). Simple regression models between measured variables and VDU were significant (R 2 > 0.69) for SDU, first peak of vertical force, dip between the 2 vertical force peaks, vertical impulse, and timing of second peak of vertical force.
Conclusion and Clinical Relevance—Subject velocity affects vertical force components only. In the future, differences between the forces measured in lame horses and the expected forces calculated for the same velocity will be studied to determine whether the equations can be used as diagnostic criteria. (Am J Vet Res 2001;62:901–906)
Objective—To develop a method of measuring 3-dimensional kinematics of the temporomandibular joint (TMJ) in horses chewing sweet feed.
Animals—4 mature horses that had good dental health.
Procedure—Markers attached to the skin over the skull and mandible were tracked by an optical tracking system. Movements of the mandible relative to the skull were described in terms of 3 rotations and 3 translations. A virtual marker was created on the midline between the rami of the mandibles at the level of the rostral end of the facial crest to facilitate observation of mandibular movements.
Results—During the opening stroke, the virtual midline mandibular marker moved ventrally, laterally toward the chewing side, and slightly caudally. During the closing stroke, the marker moved dorsally, medially, and slightly rostrally. During the power stroke, the mandible slid medially and dorsally as the mandibular cheek teeth moved across the occlusal surface of the maxillary cheek teeth. The 4 horses had similar chewing patterns, but the amplitudes varied among horses.
Conclusions and Clinical Relevance—The TMJ allows considerable mobility of the mandible relative to the skull during chewing. The method presented in this report can be used to compare the range of motion of the TMJ among horses with TMJ disease or dental irregularities or within an individual horse before and after dental procedures.
Objective—To calculate forces in the flexor tendons and the influence of heel wedges in affected and contralateral (compensating) forelimbs of horses with experimentally induced unilateral tendinitis of the superficial digital flexor (SDF) tendon.
Animals—5 Warmblood horses.
Procedure—Ground reaction force and kinematic data were obtained during a previous study while horses were trotting before and after induction of tendinitis in 1 forelimb SDF and after application of 6° heel wedges to both forehooves. Forces in the SDF, deep digital flexor (DDF), and the suspensory ligament (SL) and strain in the accessory ligament (AL) of the DDF were calculated, using an in vitro model of the distal region of the forelimb.
Results—After induction of tendinitis, trotting speed slowed, and forces decreased in most tendons. In the affected limb, SL force decreased more than SDF and DDF forces. In the compensating limb, SDF force increased, and the other forces decreased. After application of heel wedges, SDF force in both limbs increased but not significantly. Furthermore, there was a decrease in DDF force and AL strain.
Conclusions and Clinical Relevance—The increase in SDF force in the compensating forelimb of horses with unilateral SDF tendinitis may explain the high secondary injury rate in this tendon. The lack of decrease of SDF force in either limb after application of heel wedges suggests that heel wedges are not beneficial in horses with SDF tendinitis. Instead, heel wedges may exacerbate the existing lesion. (Am J Vet Res 2002;63:432–437)
Objective—To assess the reliability of the center-ofpressure (COP) values obtained from a force platform for analysis of postural sway in horses.
Animals—Six 2-year-old horses that were free from lameness and neurologic disease.
Procedure—Horses stood stationary with all 4 hooves on a force platform; COP data were collected at 1,000 Hz and 3-dimensional kinematics collected at 60 Hz for 10 seconds. Five trials were recorded at each of 3 time periods (15-minute intervals) or at 1 time period on 3 separate days. Mean values for each set of 5 trials and actual, normalized, and relative COP variables were calculated. The reliability was quantified by use of agreement boundary.
Results—The COP results within and across days were similar and provided small agreement boundary limits (eg, across days, in order of least relative reliability: area, ± 62 mm2; mediolateral range, ± 8 mm; radius, ± 2 mm; craniocaudal range, ± 4 mm; and velocity, ± 3 mm/s). Head height possessed the greatest relative intraday reliability (12%) but a high agreement boundary limit (± 0.15 m).
Conclusions and Clinical Relevance—The use of a force platform to analyze postural sway in a group of young healthy horses was found to produce reliable results and may provide a simple and sensitive measure for assessing balance deficiencies in horses. Agreement boundaries provide 95% confidence intervals for use as limits of error and variability in measurements that, if exceeded, may signify meaningful effects. (Am J Vet Res 2003;64:1354–1359)
Objective—To measure respiratory motion of the thoracic wall region in dogs using a real-time motion tracking system and compare the amount of respiratory motion between dogs positioned with and without a vacuum-formable cushion.
Animals—8 healthy adult mixed-breed dogs (median weight, 23 kg).
Procedures—Dogs were anesthetized and positioned in sternal and dorsal recumbency with and without a vacuum-formable cushion. Three-dimensional movement of anatomic landmarks was measured with a real-time motion capture system that tracked the locations of infrared light–emitting diodes attached externally to the dorsal or ventral and lateral aspects of the thoracic wall.
Results—Dogs positioned in sternal recumbency had significantly less cranial-to-caudal and left-to-right respiratory motion at the lateral aspect of the thoracic wall, compared with dogs positioned in dorsal recumbency, whether or not a cushion was used. For dogs treated in sternal recumbency, use of a cushion significantly increased the peak displacement vector (overall movement in 3-D space) for 3 of 4 marker locations on the dorsal thoracic wall. As respiratory rate increased, respiratory motion at the lateral and ventral aspects of the thoracic wall decreased when data for all dogs in dorsal recumbency were evaluated together.
Conclusions and Clinical Relevance—Associations between respiratory rate and respiratory motion suggested that the use of rapid, shallow ventilation may be beneficial for dogs undergoing highly conformal radiation treatment. These results provide a basis for further research on respiratory motion in anesthetized dogs.
Objective—To study the effect of unilateral synovitis in the distal intertarsal and tarsometatarsal joints on locomotion, including the compensating effects within and between limbs.
Animals—4 clinically normal horses.
Procedure—Gait analyses including kinematics, force plate, and inverse dynamic analysis were performed at the trot before lameness, after which synovitis was induced by injecting endotoxin into the right distal intertarsal and tarsometatarsal joints. Gait analyses were repeated 24 to 30 hours later during lameness. Differences between the stride variables during the 2 conditions (lame and sound) were identified.
Results—Tarsal joint range of motion, peak vertical force, and vertical impulse were decreased during lameness. Mechanical deficits included a decrease in negative work performed by the tarsal extensors during the early stance phase and a decrease in positive work by the tarsal extensors during push off. No compensatory changes in work were performed by other joints within the lame hind limb during the stance phase. Vertical impulse in the diagonal forelimb decreased, but there were no significant changes in forces or impulses in the ipsilateral forelimb or contralateral hind limb.
Conclusions and Clinical Relevance—Results indicate that horses are able to manage mild, unilateral hind limb lameness by reducing the airborne phase of the stride rather than by increased loading of the compensating limbs. (Am J Vet Res 2003;64:1491–1495)
Objective—To measure and correlate kinematic and ground reaction force (GRF) data in horses with superficial digital flexor tendinitis.
Animals—6 sound horses.
Procedure—Horses were evaluated before (sound evaluation) and after (lame evaluation) induction of superficial digital flexor tendinitis in 1 forelimb (randomized) by injection of collagenase. As each horse trotted, kinematic data were collected by use of an optoelectronic system, and GRF data were measured by use of a force plate. Three-dimensional kinematic and GRF data were projected onto a 2-dimensional sagittal plane.
Results—Lame limbs had significantly lower peak vertical GRF, less flexion of the distal interphalangeal joint, and less extension of the metacarpophalangeal joint, compared with compensating limbs. Carpal joint kinematics did not change. Compensating limbs had a more protracted orientation throughout the stance phase and higher braking longitudinal force and impulse; however, total range of rotation from ground contact to lift off did not change. Transfer of body weight from lame to compensating limbs was smooth, without elevation of the body mass into a suspension phase. Propulsive components of longitudinal GRF did not differ between limbs.
Conclusions and Clinical Relevance—In horses with experimentally induced superficial digital flexor tendinitis, changes in vertical GRF were reflected in angular excursions of the distal interphalangeal and metacarpophalangeal joints, whereas changes in longitudinal GRF were associated with alterations in the protraction-retraction angle of the entire limb. (Am J Vet Res 2000;61:191–196)
Objective—To determine whether analysis of net joint moments and joint powers is a suitable technique for evaluation of mechanics and energetics of lameness in horses and to measure effects of superficial digital flexor tendinitis.
Animals—6 sound horses.
Procedure—Horses were evaluated before (sound evaluation) and after (lame evaluation) induction of superficial digital flexor tendinitis in 1 forelimb by injection of collagenase. Recordings were made with an optoelectronic system and a force plate as horses trotted. Net joint moments and joint powers in the sagittal plane at each joint in the forelimbs during the stance phase were determined. Peak values were determined, and mechanical energy absorbed and generated at each joint was calculated. Comparisons were made between contralateral limbs during sound and lame evaluations.
Results—Lame limbs had significant reductions in peak values for net joint moments on the palmar aspect of metacarpophalangeal (fetlock), carpal, and humeroulnar joints. Total energy absorbed was significantly lower at every joint in lame limbs, compared with compensating limbs.
Conclusions and Clinical Relevance—Horses with superficial digital flexor tendinitis had significant differences between lame and compensating limbs for net joint moments and joint powers at all joints, indicating that the gait of horses with superficial digital flexor tendinitis is energetically inefficient. Assessment of net joint moments and joint powers is a useful tool in evaluating equine lameness. (Am J Vet Res 2000;61:197–201)
Objective—To assess the safety and efficacy of alcohol-facilitated ankylosis of the distal intertarsal (DIT) and tarsometatarsal (TMT) joints in horses with osteoarthritis (bone spavin).
Design—Prospective clinical trial.
Animals—21 horses with DIT or TMT joint-associated hind limb lameness and 5 nonlame horses.
Procedures—11 horses (group 1) underwent lameness, force-plate, and radiographic examinations; following intra-articular analgesia, lameness and force-plate examinations were repeated. Nonlame horses were used for force-plate data acquisition only. Following localization of lameness to the DIT and TMT joints, contrast arthrographic evaluation was performed; when communication with the tibiotarsal joint was not evident or suspected, 70% ethyl alcohol (3 mL) was injected. Group 1 horses underwent lameness, force-plate, and radiographic examinations every 3 months for 1 year. Ten other horses (group 2) underwent lameness and radiographic examinations followed by joint injection with alcohol; follow-up information was obtained from owners or via clinical examination.
Results—Significant postinjection reduction in lameness (after 3 days to 3 months) was evident for all treated horses. Twelve months after injection, 10 of 11 group 1 horses were not lame; lameness grade was 0.5 in 1 horse. Follow-up information was available for 9 of 10 group 2 horses; 7 were not lame, and 2 remained mildly lame (1 had a concurrent problem in the injected limb, and the other had DIT joint collapse that precluded needle entry).
Conclusions and Clinical Relevance—Intra-articular alcohol injection in horses with bone spavin resulted in a rapid (usually within 3 months) reduction in lameness and joint space collapse.