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  • Author or Editor: David M. Nunamaker x
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Abstract

Objective—To determine the degree to which components of the training program of 2-year-old Thoroughbred racehorses influence their susceptibility to fatigue injury of the third metacarpal bone (bucked shins).

Animals—226 two-year-old Thoroughbred racehorses.

Procedure—Daily training information and health reports on 2-year-old Thoroughbreds were compiled from records provided from 5 commercial stables. For each horse, data (exercise variables) were collected that comprised distance jogged (approx speed of 5 m/s), galloped (approx 11 m/s), and breezed (approx 15 to 16 m/s) until a single instance of bucked shins was reported. Data were coded for analysis using cross-tabulation, graphic, and survival techniques.

Results—Of 226 horses, 56 had bucked shins, 9 completed the observation period without bucked shins, and 161 were lost to follow-up. Distinct training strategies were used at stables resulting in significantly different survival profiles among stables. Mean (± SD) allocation of exercise to breezing was 0.15 ± 0.13 miles/wk (maximum, 0.64 miles/wk), to galloping was 4.47 ± 1.52 miles/wk (maximum, 9.56 miles/wk), and to jogging was 2.34 ± 1.70 miles/wk (maximum, 8.53 miles/wk). Survival (ie, lack of bucked shins during 1 year of monitoring) was found to be significantly reduced by exercise allocation to breezing, significantly increased by exercise allocation to galloping, and uninfluenced by exercise allocation to jogging. The log of the hazard ratio was reduced by 4.2 ± 1.5/mile breezed and increased by 0.3 ± 0.1/mile galloped.

Conclusions and Clinical Relevance—Relationships between different gaits and speeds in the training regimen influence the incidence of bucked shins. To reduce the incidence of bucked shins, trainers should consider allocating more training effort to regular short-distance breezing and less to long-distance galloping. (Am J Vet Res 2000;61:602–608)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate stiffness and bone-pin interface stress for a transcortical tapered-sleeve pin (TSP) that incorporates bilateral tapered sleeves over a transcortical pin.

Sample Population—14 third metacarpal bones (MCIII) collected from adult horses of various breeds.

Procedure—Each MCIII was cut in half to provide 2 test specimens. Pins (conventional and TSP) of 3 diameters (6.35, 7.94, and 9.50 mm) were inserted in specimens (3 specimens for each diameter and each type of pin). The test fixture simulated a typical sidebar- span skeletal fixation device for horses. Single cycle load-deflection tests were performed. Cyclic fatigue tests of TSP were performed to evaluate fatigue characteristics and stress conditions at the bone-pin interface. Maximum stress and strain were calculated, and results were compared with existing data on fatigue characteristics of bone.

Results—Significant increases in stiffness (loaddeflection) and higher loads at yield point were detected for the TSP (stiffness for conventional 9.50- mm pins, 4,500 N/mm; stiffness for TSP, 19,988 N/mm). Results of cyclic tests revealed a close correlation with existing data on fatigue characteristics.

Conclusions and Clinical Relevance—The TSP described here is stiffer than conventional transcortical pins, and stress across the bone-pin interface is more evenly distributed. Use of this TSP should minimize major problems encountered during external fixation associated with the transcortical pin and bone-pin interface (ie, bone necrosis, infection of the pin track, pin loosening, and bone failure). ( Am J Vet Res 2001;62:955–960)

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in American Journal of Veterinary Research

Abstract

Objective—To report the outcome of surgical treatment of comminuted fractures of the proximal phalanx in horses.

Design—Retrospective study.

Animals—64 horses.

Procedure—Medical records and radiographs were reviewed to obtain information regarding signalment, fracture classification, and treatment. Follow-up information was obtained by telephone conversation or evaluation of production records.

Results—Thirty-eight horses had moderately comminuted fractures of the proximal phalanx. Two horses were euthanatized immediately. Fractures of the proximal phalanx in 36 horses were repaired with open reduction and internal fixation with a successful outcome in 33 (92%) horses. Reconstruction of the fracture was performed in most horses by use of a long curved incision, transection of the collateral ligament of the metacarpophalangeal or metatarsophalangeal joint, and open exposure of the proximal articular surface of the proximal phalanx. Twenty-six horses had severely comminuted fractures of the proximal phalanx. Six horses were euthanatized immediately. One horse was euthanatized after 9 days of treatment with a cast alone. Severely comminuted fractures of the proximal phalanx in 13 horses were treated with an external skeletal fixation device, and fractures healed in 8 of those horses. Six horses with severely comminuted fractures of the proximal phalanx were treated with transfixation pins incorporated into a fiberglass cast, and fractures healed in 4 horses.

Conclusions and Clinical Relevance—Moderately comminuted fractures of the proximal phalanx can be successfully repaired; however, fractures that are too severe to permit accurate reconstruction of the fragments remain difficult to treat and horses have only a fair prognosis for survival. (J Am Vet Med Assoc 2004; 224:254–263)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To describe the pool-raft recovery system protocol and to evaluate the clinical outcome inhorses that underwent recovery from general anes-thesia using this system.

Design—Retrospective study.

Animals—393 horses that underwent recovery fromgeneral anesthesia in the pool-raft system.

Procedure—Anesthetic records were examined fromhorses recovered from anesthesia in the pool-raft sys-tem between January 1984 and December 2000.Complete medical records of horses were examinedwhen available. Information regarding the anestheticand recovery period was recorded. Horses first recov-ered from general anesthesia in the pool-raft and,once awake, were transported to a recovery stall andlowered to the floor in a standing position.

Results—351 horses underwent 1 pool-raft recovery,and 42 horses underwent multiple pool-raft recover-ies. Most horses were recovered from general anes-thesia within the pool-raft system to safeguard repairof a major orthopedic injury. During 471 pool-raftrecoveries, 34 (7%) horses had complications withinthe recovery pool and 62 (13%) had complicationswithin the recovery stall. Deaths resulted from complete failure of internal fixation, pulmonary dysfunc-tion, or a combination of pulmonary dysfunction andfixation failure in 2% (10/471) of horses that under-went pool-raft recoveries.

Conclusions and Clinical Relevance—The pool-raftsystem is a good option for recovery from generalanesthesia. Although not a fail-safe system, itappears to decrease the complications of recoveringhorses in a high-risk category. Potential disadvan-tages of this system are added expense and man-power necessary in building, maintenance, andusage, as well as size limitations of the raft itself. (J Am Vet Med Assoc 2002;221:1014–1018)

Full access
in Journal of the American Veterinary Medical Association