An In Vitro Biomechanical Investigation of Compression Plating with Cable Cerclage for Repair of Oblique Osteotomies in Foal Femurs

Long oblique diaphyseal osteotomies were created in 14 pairs of femurs from cadaver foals less than six months of age. One bone from each pair was repaired using two dynamic compression plates (DP), and the other was repaired using a dynamic compression plate with cable cerclage (CC). Seven pairs were tested in compression and seven pairs in craniolateral-caudomedial (CrL-CdM) three-point bending.

A difference was not found in mean (± SD) breaking strength in compression between the DP (7257.19 ± 2004.08 N) and CC (7761.41 ± 2552.91 N) techniques. Nor was there a difference in mean stiffness in compression between the DP (2533.83 ± 1777.38 N/mm) and CC (3177.98 ± 1694.70 N/mm) techniques. There was no difference in mean stiffness in three-point bending between the DP (244.60 ± 60.80 N/mm) and CC (195.50 ± 80.90 N/mm) techniques. The mean bending breaking strength and bending moment for the DP technique (2839.36 ± 199.46 N and 124,932.00 ± 8776.38 N mm) was significantly (P = 0.02) greater than the CC technique (1940.39 ± 732.80 N and 85,377.72 ± 32243.34 N mm).

The CC system was inferior to the DP technique in CrL-CdM three-point bending strength and moment, but provided equal bending stiffness and equal compressive strength and stiffness.

The use of compression plating with cable cerclage was compared to double plating for repair of long oblique osteotomies in foal femurs. The repairs were tested in compression and 3-point bending. The compression plate with cable cerclage was inferior to double plating in bending strength and moment, but provided equal compressive strength and stiffness.

Head and pelvic movement asymmetry during lungeing in horses with symmetrical movement on the straight

Reasons for performing study

Lungeing is commonly used as part of standard lameness examinations in horses. Knowledge of how lungeing influences motion symmetry in sound horses is needed.

Objectives

The aim of this study was to objectively evaluate the symmetry of vertical head and pelvic motion during lungeing in a large number of horses with symmetric motion during straight line evaluation.

Study design

Cross‐sectional prospective study.

Methods

A pool of 201 riding horses, all functioning well and considered sound by their owners, were evaluated in trot on a straight line and during lungeing to the left and right. From this pool, horses with symmetric vertical head and pelvic movement during the straight line trot (n = 94) were retained for analysis. Vertical head and pelvic movements were measured with body mounted uniaxial accelerometers. Differences between vertical maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) heights between left and right forelimb and hindlimb stances were compared between straight line trot and lungeing in either direction.

Results

Vertical head and pelvic movements during lungeing were more asymmetric than during trot on a straight line. Common asymmetric patterns seen in the head were more upward movement during push‐off of the outside forelimb and less downward movement during impact of the inside limb. Common asymmetric patterns seen in the pelvis were less upward movement during push‐off of the outside hindlimb and less downward movement of the pelvis during impact of the inside hindlimb. Asymmetric patterns in one lunge direction were frequently not the same as in the opposite direction.

Conclusions

Lungeing induces systematic asymmetries in vertical head and pelvic motion patterns in horses that may not be the same in both directions. These asymmetries may mask or mimic fore‐ or hindlimb lameness.

Comparison of an inertial sensor system of lameness quantification with subjective lameness evaluation

REASONS FOR PERFORMING STUDY

Subjective evaluation of mild lameness has been shown to have poor interobserver reliability. Traditional methods of objective lameness evaluation require specialised conditions and equipment. Wireless inertial sensor systems have been developed to allow for simple, rapid, objective lameness detection in horses trotted over ground.

OBJECTIVE

The purpose of this study was to compare the sensitivities of an inertial sensor system and subjective evaluation performed by experienced equine practitioners at detecting lameness in horses. We hypothesised that the inertial sensor system would identify lameness at a lower level of sole pressure than a consensus of 3 experienced equine veterinarians.

METHODS

Fifteen horses were fitted with special shoes that allowed for lameness induction via sole pressure. Horses were simultaneously evaluated by 3 equine veterinarians and a wireless inertial sensor system. Horses were subjected to multiple trials: 1) before inserting the screw; 2) after inserting the screw to just touch the sole; and 3) after tightening the screw in half turn increments. The number of screw turns required for lameness identification in the correct limb by the inertial sensors and by consensus of 3 equine veterinarians was compared using the Wilcoxon test.

RESULTS

The inertial sensor system selected the limb with the induced lameness after fewer screw turns than did the 3 veterinarians (P<0.0001). The inertial sensor system selected the correct limb before the 3 veterinarians in 35 trials (58.33%), the evaluators selected the correct limb before the inertial sensors in 5 trials (8.33%), and in 20 trials (33.33%) they selected the correct limb at the same time.

POTENTIAL RELEVANCE

The inertial sensor system was able to identify lameness at a lower level of sole pressure than the consensus of 3 equine veterinarians. The inertial sensor system may be an effective aid to lameness localisation in clinical cases.

Repeatability of subjective evaluation of lameness in horses

REASONS FOR PERFORMING STUDY

Previous studies have suggested that agreement between equine veterinarians subjectively evaluating lameness in horses is low. These studies were limited to small numbers of horses, evaluating movement on the treadmill or to evaluating previously-recorded videotape.

OBJECTIVES

To estimate agreement between equine practitioners performing lameness evaluations in horses in the live, over ground setting.

METHODS

131 mature horses were evaluated for lameness by 2-5 clinicians (mean 3.2) with a weighted-average of 18.7 years of experience. Clinicians graded each limb using the AAEP lameness scale by first watching the horse trot in a straight line only and then after full lameness evaluation. Agreement was estimated by calculation of Fleiss' (kappa). Evaluators agreed if they picked the same limb as lame or not lame regardless of the severity of perceived lameness.

RESULTS

After only evaluating the horse trot in a straight line clinicians agreed whether a limb was lame or not 76.6% of the time (kappa= 0.44). After full lameness evaluation clinicians agreed whether a limb was lame or not 72.9% of the time (kappa= 0.45). Agreement on forelimb lameness was slightly higher than on hindlimb lameness. When the mean AAEP lameness score was >1.5 clinicians agreed whether or not a limb was lame 93.1% of the time (kappa= 0.86), but when the mean score was < or = 1.5 they agreed 61.9% (kappa= 0.23) of the time. When given the task of picking whether or not the horse was lame and picking the worst limb after full lameness evaluation, clinicians agreed 51.6% (kappa= 0.37) of the time.

CONCLUSIONS

For horses with mild lameness subjective evaluation of lameness is not very reliable.

POTENTIAL RELEVANCE

A search for and the development of more objective and reliable methods of lameness evaluation is justified and should be encouraged and supported.

Detection of spinal ataxia in horses using fuzzy clustering of body position uncertainty

REASONS FOR PERFORMING STUDY

Subjective neurological evaluation in horses is prone to bias. An objective method of spinal ataxia detection is not subject to these limitations and could be of use in equine practice and research.

HYPOTHESIS

Kinematic data in the walking horse can differentiate normal and spinal ataxic horses.

METHODS

Twelve normal and 12 spinal ataxic horses were evaluated by kinematic analysis walking on a treadmill. Each body position signal was reduced to a scalar measure of uncertainty then fuzzy clustered into normal or ataxic groups. Correct classification percentage (CCP) was then calculated using membership values of each horse in the 2 groups. Subsequently, a guided search for measure combinations with high CCP was performed.

RESULTS

Eight measures of body position resulted in CCP > or = 70%. Several combinations of 4-5 measures resulted in 100% CCP. All combinations with 100% CCP could be obtained with one body marker on the back measuring vertical and horizontal movement and one body marker each on the right fore- and hindlimb measuring vertical movement.

CONCLUSIONS AND POTENTIAL RELEVANCE

Kinematic gait analysis using simple body marker combinations can be used objectively to detect spinal ataxia in horses.

Signal decomposition method of evaluating head movement to measure induced forelimb lameness in horses trotting on a treadmill

In horses at a trot, the head moves up and down twice in one stride. In horses with unilateral forelimb lameness this movement is asymmetric. Computer-assisted kinematic analysis of vertical head movement can be used to quantify objectively lameness in horses in clinical trials. However, in mild lameness, absolute measurements of vertical head height may not be sensitive enough to detect small differences in lameness, and extraneous head movement by the horse due to curiosity, excitement or nervousness interferes with the accurate measurement of vertical head movement asymmetry. We describe a simple, signal-decompensation method of evaluating vertical head movement using a model of induced mild foot lameness in 9 horses. The technique assumes that the vertical head movement pattern can be broken down into 3 components; the vertical head movement caused by forelimb lameness (A1), the amplitude of the natural biphasic vertical head movement (A2) and extraneous head movement. Extraneous head movement is mathematically removed from the vertical head movement pattern. A1 and A2 are then calculated. After induction of lameness, mean A1 increased by 1.63 cm (range 0.10-3.33 cm, P = 0:005). Mean A2 did not significantly change after lameness induction. Error in reproduction of the original head movement pattern was 0.3-0.5%. We calculated that a hypothetical clinical trial would require 12 subjects for testing to be 80% certain that this difference would be successfully detected using this method of lameness evaluation.

Kinematics of the hind limb in trotting horses after induced lameness of the distal intertarsal and tarsometatarsal joints and intra-articular administration of anesthetic

OBJECTIVE

To identify hind limb and pelvic kinematic variables that change in trotting horses after induced lameness of the distal intertarsal and tarsometatarsal joints and after subsequent intra-articular administration of anesthetic.

ANIMALS

8 clinically normal adult horses.

PROCEDURE

Kinematic measurements were made before and after transient endotoxin-induced lameness of the distal intertarsal and tarsometatarsal joints and after intra-articular administration of anesthetic. Fourteen displacement and joint angle (metatarsophalangeal [fetlock] and tarsal joints) measurements were made on the right hind limb, sacrum, and the right and left tubera coxae. Kinematic measurements were compared by general linear models, using a repeated measures ANOVA. Post hoc multiple comparisons between treatments were evaluated with a Fisher least squared difference test at alpha = 0.05.

RESULTS

After lameness induction, fetlock and tarsal joint extension during stance decreased, fetlock joint flexion and hoof height during swing increased, limb protraction decreased, and vertical excursion of the tubera coxae became more asymmetric. After intra-articular administration of anesthetic, limb protraction returned to the degree seen before lameness, and vertical excursion of the tubera coxae became more symmetric.

CONCLUSIONS AND CLINICAL RELEVANCE

Increased length of hind limb protraction and symmetry of tubera coxae vertical excursion are sensitive indicators of improvement in tarsal joint lameness. When evaluating changes in tarsal joint lameness, evaluating the horse from the side (to assess limb protraction) is as important as evaluating from the rear (to assess pelvic symmetry).

A curve-fitting technique for evaluating head movement to measure forelimb lameness in horses

Evaluation of the asymmetry of vertical head movement is used during kinematic evaluation of forelimb lameness in horses. For mild lameness, absolute translational measurements are not sensitive enough to detect small differences in the asymmetry of vertical head movement. Also, conscious movement of the head by the horse, not associated with lameness, interferes with accurate measurement. We describe an improved method of evaluating vertical head movement as a measure of lameness, using an model of induced lameness in 9 horses and a time-domain processing technique of curve-fitting. The technique assumes that vertical head movement can be broken down into 3 components; the natural inertially-driven vertical head movement, the alteration of vertical head movement caused by forelimb lameness, and extraneous head movement. The technique uses data from several contiguous strides, eliminates the natural inertially-driven and extraneous head movements, and quantifies lameness as a single value. The technique is shown to more sensitive to change in lameness than absolute measurement of head height translation and to be more accurate than a previously reported frequency-domain technique.

Changes in kinematic variables observed during pressure-induced forelimb lameness in adult horses trotting on a treadmill

OBJECTIVE

To determine whether kinematic changes induced by heel pressure in horses differ from those induced by toe pressure.

ANIMALS

10 adult Quarter Horses.

PROCEDURE

A shoe that applied pressure on the cuneus ungulae (frog) or on the toe was used. Kinematic analyses were performed before and after 2 levels of frog pressure and after 1 level of toe pressure. Values for stride displacement and time and joint angles were determined from horses trotting on a treadmill.

RESULTS

The first level of frog pressure caused decreases in metacarpophalangeal (fetlock) joint extension during stance and increases in head vertical movement and asymmetry. The second level of frog pressure caused these changes but also caused decreases in stride duration and carpal joint extension during stance as well as increases in relative stance duration. Toe pressure caused changes in these same variables but also caused maximum extension of the fetlock joint to occur before midstance, maximum hoof height to be closer to midswing, and forelimb protraction to increase.

CONCLUSION AND CLINICAL RELEVANCE

Decreased fetlock joint extension during stance and increased head vertical movement and asymmetry are sensitive indicators of forelimb lameness. Decreased stride duration, increased relative stance duration, and decreased carpal joint extension during stance are general but insensitive indicators of forelimb lameness. Increased forelimb protraction, hoof flight pattern with maximum hoof height near midswing, and maximum fetlock joint extension in cranial stance may be specific indicators of lameness in the toe region. Observation of forelimb movement may enable clinicians to differentiate lameness of the heel from lameness of the toe.

Gastric impaction and obstruction of the small intestine associated with persimmon phytobezoar in a horse

Signs of mild colic, intermittent lethargy, and weight loss of 6 weeks' duration in a 2-year-old Quarter Horse gelding were attributed to persimmon (Diospyros virginiana) phytobezoar formation. Diagnosis of the phytobezoar was facilitated by gastric endoscopy. Signs of gastrointestinal tract obstruction were associated with a large phytobezoar in the lumen of the stomach, gastric ulceration, and obstruction of the small intestine (as a consequence of fragmentation of the primary bezoar). Conservative treatment, using mineral oil and dioctyl sodium sulfosuccinate, was unsuccessful. A celiotomy was performed, and gastric impaction and partial obstruction of the small intestine associated with phytobezoar formation and fragmentation were identified. The horse made a complete recovery following removal of all phytobezoars. Persimmon phytobezoar should be considered in the fall and winter as a possible cause of lethargy, colic, and weight loss in horses allowed access to persimmon fruit.

Growth characteristics of fibroblasts isolated from the trunk and distal aspect of the limb of horses and ponies

OBJECTIVE

To determine if there is a difference in in vitro growth of fibroblasts isolated from the trunk and distal aspect of the limb of horses and ponies. To determine the effects of a corticosteroid and monokine on in vitro growth of fibroblasts isolated from the trunk and distal aspect of the limb of horses and ponies.

STUDY DESIGN

Growth of fibroblasts from tissues harvested from the trunk and limb were compared from horse and pony samples grown in control media and control media with triamcinolone or monokine added.

ANIMALS OR SAMPLE POPULATION

Dermal and subcutaneous tissue from 22 horses and 17 ponies of various ages and breeds.

METHODS

Fibroblast growth was assessed by tritiated thymidine uptake using standard cell culture techniques. The effect of a monokine or triamcinolone plus control media were compared with control media for fibroblast growth.

RESULTS

Fibroblast growth from tissues isolated from the horse limb was significantly less than growth from the horse trunk and the limb and trunk of ponies. Monokine was more effective than triamcinolone in suppressing fibroblast growth from tissues isolated from the trunk and limb in both horses and ponies.

CONCLUSIONS

There are growth differences in fibroblasts isolated from the limb of horses compared with those isolated from the trunk and from the limb and trunk of ponies.

CLINICAL RELEVANCE

The difference in fibroblast growth from tissues isolated from the trunk and limb of horses and ponies may provide evidence for the difference reported in the healing characteristics of limb wounds in horses and ponies. Influencing fibroblast growth may provide a key to controlling the development of exuberant granulation tissue in horses and ponies.

An in vitro biomechanical comparison of two fixation methods for transverse osteotomies of the medial proximal forelimb sesamoid bones in horses

OBJECTIVE

This study compared the mechanical properties of the normal intact suspensory apparatus and two methods of fixation for repair of transverse, midbody fractures of the proximal sesamoid bones of adult horses: transfixation wiring (TW) and screws placed in lag fashion (LS).

STUDY DESIGN

An in vitro, paired study using equine cadaver limbs mounted in a loading apparatus was used to test the mechanical properties of TW and LS.

ANIMAL OR SAMPLE POPULATION

Seventeen paired (13 repaired, 4 normal) equine cadaver limbs consisting of the suspensory apparatus third metacarpal bone, and first and second phalanges.

METHOD

The two methods of repair and normal intact specimens were evaluated in single cycle-to-failure loading. Yield failure was defined to occur at the first notable discontinuity (>50 N) in the load-displacement curve, the first visible failure as evident on the videotape, or a change in the slope of the moment-fetlock angle curve. Ultimate failure was defined to occur at the highest load resisted by the specimen. Corresponding resultant force and force per kg of body weight on the suspensory apparatus, fetlock joint moment, and angle of fetlock dorsiflexion were calculated by use of specimen dimensions and applied load. These were compared along with specimen stiffness, and ram displacement.

RESULTS

Load on the suspensory apparatus, load on the suspensory apparatus per kg of body weight, moment, applied load, and angle of fetlock dorsiflexion at yield failure were significantly greater for the TW-repaired than for the LS-repaired specimens. A 3 to 5 mm gap was observed before yield failure in most TW-repaired osteotomies.

CONCLUSIONS

Transfixation wiring provided greater strength to yield failure than screws placed in lag fashion in single cycle load-to-failure mechanical testing of repaired transverse osteotomized specimens of the medial proximal forelimb sesamoid bone.

Evaluation of mild lameness in horses trotting on a treadmill by clinicians and interns or residents and correlation of their assessments with kinematic gait analysis

OBJECTIVE

To estimate sensitivity and accuracy of subjective evaluation of mild lameness in horses during treadmill locomotion and to correlate subjective evaluation with kinematic analysis.

ANIMALS

19 lame and 5 clinically normal horses.

PROCEDURE

Lameness was evaluated by subjective score and kinematic analysis before and after palmar digital nerve block (PDNB). Evaluations were made by 6 clinicians and 7 interns or residents. Within- and between-observer agreement analyses (kappa values) were calculated and compared, using a Student's t-test. Pearson's product-moment correlation coefficients were calculated between clinician's change in score and the change in kinematic variables after PDNB.

RESULTS

Within-observer agreement was within the range expected for conditions of moderate diagnostic difficulty. Within-observer agreement was higher for clinicians than for interns or residents. Between-observer agreement was acceptable for scores within 1 value of each other. Between-observer agreement of change in lameness score after PDNB was poor. When kinematic variables were ranked with each clinician's subjective change in score, only 2 were among the top 3 for the majority of clinicians. Asymmetry of vertical head movement between contralateral forelimb stance phases and the point of maximum hoof height during swing decreased as lameness subjectively improved.

CONCLUSION

Mild lameness may be difficult to evaluate during treadmill locomotion. Although clinicians were more repeatable in their subjective evaluation of lameness than interns or residents, they were not more reliable at detecting the true state of lameness.

CLINICAL RELEVANCE

Lack of agreement between clinician scoring of mild lameness emphasizes the need to use more objective measures for quantifying lameness.

Effects of anesthesia of the palmar digital nerves on kinematic gait analysis in horses with and without navicular disease

OBJECTIVE

To determine the effect of local anesthesia of the palmar digital nerves on forelimb kinematics in Quarter Horses with and without navicular disease.

ANIMALS

12 adult Quarter Horses; 5 clinically normal (sound) and 7 with navicular disease.

PROCEDURE

Kinematic measurements were made on adult horses trotting on a treadmill, before and after palmar digital nerve block (PDNB). Twenty-three displacement, joint angle, and temporal gait measurements of the right forelimb and head were made for 5 strides in each horse. Initial (before local anesthesia) right forelimb measurements were obtained after a left forelimb PDNB. Kinematic measurements were compared before and after PDNB of the right forelimb by multiple ANOVA with an alpha = 0.05, adjusted for posthoc comparisons by Bonferroni correction.

RESULTS

In sound horses, the only significant change in kinematic measurements after PDNB nerve block was in the maximum extension of the metacarpophalangeal joint at mid-stance, which was decreased by an angle of 2 degrees. In horses with navicular disease, mean maximum extension of the metacarpophalangeal joint during stance phase and maximum flexion of the carpal joint during swing phase were significantly increased after PDNB. Also, total stance phase, cranial stance phase, and break-over durations were significantly shorter. In horses with navicular disease, differences between minimum head heights during stance phase of each forelimb and total vertical head excursion during a complete stride were significantly smaller after PDNB.

CONCLUSION

Several kinematic measurements of gait can be used to determine improvement of lameness in horses with navicular disease after PDNB block while trotting on a treadmill.

In vitro and in vivo effects of activated macrophage supernatant on distal limb wounds of ponies

OBJECTIVE

To determine whether monokines produced by activated rabbit peritoneal macrophages can inhibit development of exuberant granulation tissue formation in distal limb wounds in ponies.

DESIGN

Randomized block.

ANIMALS

5 castrated male ponies, 2 to 6 years old and weighing 140 to 190 kg.

PROCEDURE

In vitro activity of cell-free rabbit peritoneal macrophage supernatant was determined after incubation of fibroblasts from the flank and the distal portion of limbs of horses and ponies. Tritiated thymidine was then added, and after reincubation, radioactivity was measured. After creation of a 4-cm2, full-thickness wound on the mid dorsal aspect of each metacarpus and metatarsus of each pony, in vivo activity of the macrophage supernatant was evaluated. Biopsy specimens were collected at random sites near a border of each wound at 4, 6, and 10 weeks after creation of the wounds. Treatment effects were evaluated on the basis of presence of exuberant granulation tissue requiring excision, number of times that excision was required, total area of the wound, epithelialized area, area of granulation bed, and histologic evaluation of the biopsy specimens.

RESULTS

The macrophage supernatant effectively inhibited proliferation of equine fibroblasts in vitro. No significant in vivo treatment effects were found among the 4 treatment groups.

CONCLUSION AND CLINICAL RELEVANCE

Monokines from stimulated rabbit peritoneal macrophages may have potential for improving wound healing in horses and ponies because of their effective inhibition in vitro of equine fibroblast proliferation.

Scintigraphic evaluation of 99mTc-methylene diphosphonate uptake in the navicular area of horses with lameness isolated to the foot by anesthesia of the palmar digital nerves

OBJECTIVE

To evaluate distribution and intensity of 99mTc-methylene diphosphonate (99mTc-MDP) uptake in the navicular area in horses with forelimb lameness isolated to the palmar aspect of the foot.

DESIGN

Prospective, case-controlled study.

ANIMALS

7 horses with clinical signs of navicular syndrome and 7 control horses.

PROCEDURE

Palmar view, soft tissue-phase scintigraphic images of the foot were obtained between 7 and 12 minutes after injection of 120 to 170 mCi of 99mTc-MDP. Lateral and palmar view, bone-phase images were obtained at 30 minutes and 1, 2, and 4 hours after injection. Palmar views were evaluated by determining the ratio of image density in the navicular area to mean image density in the distal phalangeal area. Palmar and lateral view, bone-phase images were also scored on the basis of navicular area intensity (intense = 3, moderate = 2, mild = 1, and no uptake = 0). Density ratios and mean scores were evaluated as a three-way ANOVA.

RESULTS

Mean navicular-to-distal phalangeal density ratio for affected horses (1.77) was significantly (P = 0.003) greater than that for control horses (0.97). The mean subjective score for affected horses when evaluating palmar views only (1.85) and when evaluating palmar and lateral view pairs together (1.99) was significantly (P < 0.01) higher than scores for control horses (0.51, 0.62). Images obtained 1 hour after injection were as good at differentiating affected from control horses as images obtained between 2 to 4 hours after injection.

CONCLUSION

A substantial number of horses with palmar foot pain have increased scintigraphic uptake within the navicular bone 1 to 4 hours after injection of 99mTc-MDP. Lateral view, bone-phase images are less sensitive than palmar view, bone-phase images in revealing navicular area uptake.

CLINICAL RELEVANCE

A combination of lateral and palmar view scintigraphic images obtained between 1 and 4 hours after injection of 99mTc-MDP is a useful diagnostic aid in evaluating navicular bone involvement in horses with forelimb lameness isolated to the palmar aspect of the foot.

Local distribution of mepivacaine after distal interphalangeal joint injection in horses

OBJECTIVE

To evaluate the distribution of mepivacaine hydrochloride after distal interphalangeal (DIP) joint injection in horses.

DESIGN

Prospective, uncontrolled study.

ANIMALS

10 adult horses.

PROCEDURE

30 minutes before euthanasia, 8 ml of 2% mepivacaine hydrochloride was injected into the dorsal pouch of a forelimb DIP joint. Synovial tissue from the DIP joint and podotrochlear (navicular) bursa and bone tissue from the medullary cavity of the distal sesamoid (navicular) bone were taken from both forelimbs immediately after death. All synovial and bone specimens were analyzed for tissue concentration of mepivacaine by high-performance liquid chromatography. Synovial tissue and bone specimen concentrations from the injected forelimb were compared with corresponding specimens from the noninjected forelimb. All synovial tissue and bone specimen concentrations were compared with an estimated effective tissue concentration of mepivacaine (0.3 microgram/mg) for local anesthesia.

RESULTS

Specimen concentrations of mepivacaine from the injected forelimb were significantly greater (P < 0.05) than those in the corresponding tissues of the contralateral noninjected forelimb. All DIP joint and navicular bursa synovial tissue specimens from the injected forelimb had greater than the estimated effective tissue concentration of mepivacaine for local anesthesia. Of the 10 navicular bone specimens from the injected forelimb, 4 were higher and 2 were within 20% of the estimated effective tissue concentration of mepivacaine for local anesthesia.

CONCLUSIONS

Mepivacaine hydrochloride deposited into the DIP joint should anesthetize pain arising from navicular bursa synovia and may decrease pain arising from the medullary cavity of the navicular bone.

CLINICAL RELEVANCE

DIP joint injection of mepivacaine hydrochloride is not specific for DIP joint pain.

Effects of tendon grip technique (frozen versus unfrozen) on in vitro surface strain measurements of the equine deep digital flexor tendon

OBJECTIVE

To determine effects of tendon grip technique on in vitro surface strain measurements of equine deep digital flexor tendon (DDFT) when loaded in tension.

SAMPLE POPULATION

12 hind limb DDFT from 8 adult horses (mean age, 9.8 years [range, 4.5 to 17 years]; mean body weight, 472 kg [range, 450 to 509 kg]), with no clinical evidence of hind limb lameness.

DESIGN AND PROCEDURE

After calibration, liquid mercury strain gauges were sutured to plantar surfaces of the tendons at distal (position 1), middle (position 2), and proximal (position 3) metatarsal regions. Each tendon was affixed to a materials testing machine (distally by the distal phalanx, and proximally by a metal clamp), and loaded once in tension, at a strain rate of 2.8 to 3.0%/s, to 3% clamp displacement. Liquid nitrogen was used to freeze the proximal ends of 6 tendons before placement in the clamp. Proximal ends of the remaining 6 tendons were left unfrozen. Surface strains were determined with the aid of low-resistance bridge circuits. Data were analyzed at time points corresponding to 1, 2, and 3% clamp displacement.

RESULTS

Mean surface strains of tendons with frozen ends were significantly greater than those for tendons with unfrozen ends, and closer to strain measured by clamp displacement, at 1 and 2% clamp displacement. This difference was present but not significant at 3% clamp displacement. Mean local surface strain was not significantly different between the 3 gauge positions.

CONCLUSIONS

Freezing tendon ends is a useful technique to increase measured surface strains in equine DDFT, thereby making them closer to universal strain as measured by clamp displacement, and, thus, more likely to represent true surface strain.

Bilateral tibial metaphyseal stress fractures associated with physitis in a foal

A 7-month-old Appaloosa foal had bilateral hind limb lameness and was unable to rise from recumbency without assistance. Lameness could be exacerbated by tarsal flexion and a firm swelling at the distomedial aspect of the tibias was associated with a marked pain response when palpated. Radiography revealed enlargement of the distal tibial metaphysis physis (compared with normal), and radiolucent fissure lines extending proximally from the physis into the metaphysis at its medial aspect. Treatment included rest and dietary adjustment. Although clinical signs initially resolved following treatment, the problem recurred when the foal was 14 months old. Further treatment included 7 months of pasture rest without forced exercise, after which the foal was reported to be clinically normal.

Scintigraphic evaluation of fractures of the distal phalanx in horses: 27 cases (1979-1988)

Retrospective radiographic and scintigraphic analyses were performed on 27 fractures of the distal phalanx in 25 horses. Location of 99mtechnetium methylene diphosphonate (99mTc-MDP) uptake was compared with fracture line location as seen on radiography. Intensity (intense, moderate, mild) and pattern (focal, diffuse) of 99mTc-MDP uptake was recorded and compared with duration of fracture. Nine horses were monitored during convalescence by obtaining additional scintigraphic views 3 to 68 months after injury. Palmar scintigraphic views had evidence of focal areas of increased 99mTc-MDP uptake that corresponded to fracture line location as seen on radiography. Lateral scintigraphic views had evidence of diffuse increased uptake. There was a significant (P < 0.01) association between duration of fracture and intensity of uptake, with fractures < 3 months in duration more likely to have intense focal uptake. All fractures < 10 days in duration had intense focal uptake. As fracture age increased, 99mTc-MDP uptake became less intense and more diffuse. Three fractures not evident on radiography had evidence of 99mTc-MDP uptake on scintigraphy. Stall rest resulted in decreased 99mTc-MDP uptake in 6 of 9 horses, but increased uptake was still visible in all horses between 4 and 25 months after injury. The only scintigraphic view without evidence of increased uptake was that obtained from a horse reexamined 68 months after injury.

Evaluation of support bandaging during measurement of proximal sesamoidean ligament strain in horses by use of a mercury strain gauge

Liquid mercury strain gauges were implanted in the forelimb proximal sesamoidean ligaments (PSL) of 8 adult horses. The gauges measured PSL strain while horses were standing with or without external support. In 6 of the horses, the gauges also measured PSL strain in horses at a walk, with or without external support. Gauges were enclosed within sliding polypropylene tubes to prevent nonaxial deformation. Each gauge was placed in 1 arm of a low-resistance half-bridge circuit. To provide temperature compensation, a dummy gauge was placed in the adjacent arm of the bridge circuit and was implanted next to the active gauge in the surrounding fascial tissue. External support included fiberglass cast support (CAST), dorsal fetlock splint support (DFS), support wraps of 3 bandage materials (SW1, SW2, and SW3), and support wrap with caudal splint (SW4). The cast was applied, with the fetlock and foot in weightbearing position, from the proximal portion of the metacarpus distal to and including the foot. The DFS was applied by placing the cranial half of the fiberglass cast on the dorsal aspect of the instrumented limb. The SW1, SW2, and SW3 were applied in a figure-8 pattern around the fetlock, using 50% of the linear stretch capacity of the bandage material, with the horse standing squarely on all 4 limbs. The SW4 was applied identically to the other support wraps, with the exception of addition of a flexible caudal splint incorporated in the support wrap. Mean maximal strain while standing (epsilon S) without external support for 8 horses was 6.0% (range, 3.8 to 7.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Cimetidine for treatment of melanomas in three horses

Cimetidine, an H2 histamine antagonist, was used in the clinical management of progressive, multifocal melanomatosis in 3 adult gray horses. Prior to treatment, the tumors had increased rapidly in size and number in 2 horses (duration of 6 and 27 months, respectively) and slowly in the third horse (duration of 48 months). All 3 horses were treated with cimetidine (2.5 mg/kg of body weight, PO, q 8 h) for 2 months to 1 year. During treatment, the number and size of the melanomas decreased substantially (50 to 90%). The progression of the disease was halted in 2 horses and controlled in the third horse, which is still being treated with cimetidine (1.6 mg/kg, PO, q 24 h). The horses in which treatment was terminated have not been treated for 31 and 41 months, respectively, during which time the melanomas have not increased in number or size.

Monthly prevalence (in 1986) of antibody titers against equine monocytic ehrlichiosis in apparently healthy horses in Illinois

The seroprevalence and seasonal trend of antibody titers against equine monocytic ehrlichiosis (Potomac horse fever) were determined in apparently healthy horses in selected areas of Illinois in 1986. Sera from 1,367 horses (6 months to 29 years old) were evaluated for the presence of antibodies against Ehrlichia risticii with indirect immunofluorescence. The majority (88%) of the horses were Thoroughbred or Standardbred racehorses. The number of horses with antibodies against E risticii was 229/1,367 (16.75%). The titers in these horses ranged from 1:10 to 1:640. As the year progressed, the number of seropositive horses (titers greater than or equal to 1:10) and the magnitude of the titers increased significantly, both reaching a maximum in July and August, respectively (P less than 0.05). A relationship between seropositivity and gender was not detected. In the year prior to sampling, 56.8% of the seropositive horses had not been ill, whereas 0.8% had diarrhea, an episode of acute abdominal pain, or laminitis. It was concluded that a large number of horses in Illinois are exposed to E risticii, that maximal exposure occurs in July, and that the most common form of the disease in Illinois is not associated with clinical signs.