Objective—To determine the anisotropic characteristics of the microarchitecture of the subchondral bone (SCB) plate and trabecular bone (TBB) of the distopalmar aspect of the metacarpal condyles in horses with different stages of SCB disease.
Sample Population—12 third metacarpal bone pairs from racing Thoroughbreds euthanized for diverse reasons.
Procedures—Both metacarpi were collected from horses with SCB changes that were mild (sclerosis and focal radiolucencies; n = 6) or severe (multifocal radiolucencies and articular surface defects; 6). Sample blocks of SCB plate and TBB were collected from the distopalmar aspect of both condyles and the sagittal ridge and examined via 3-D micro-computed tomography at 45-?m isotropic voxel resolution. For each sample, the angle between the principal orientation of trabeculae and the sagittal plane and the degree of anisotropy (DA) were calculated from mean intercept length measurements.
Results—Condylar samples had significantly lower angle (mean, 8.9°; range, 73° to 10.9°) than sagittal ridge samples (mean, 40.7°; range, 33.6° to 49.2°), TBB had significantly higher DA (mean ± SE, 1.75 ± 0.04) than SCB plate (1.29 ± 0.04), and mildly diseased TBB had higher DA (1.85 ± 0.06) than severely diseased TBB (1.65 ± 0.06).
Conclusions and Clinical Relevance—The highly ordered appearance of trabeculae within the condyles supports the concept that joint loading is primarily transmitted through the condyles and not the sagittal ridge. The sharp changes in the trajectories of the SCB trabeculae at the condylar grooves may be indicative of hypothetical tensile forces at this location contributing to the pathogenesis of condylar fractures. (Am J Vet Res 2010;71:1148—1153)
Objective—To describe the clinical use of regional limb perfusion with antimicrobials (A-RLP), complications, and outcome in a large series of patients.
Design—Retrospective case series.
Procedures—Medical records of horses treated with A-RLP between 1999 and 2009 were reviewed. Signalment, primary complaint, horse use, etiology, duration of clinical signs, previous treatment, structures involved, concurrent conditions, A-RLP characteristics, additional treatments, complications, and outcome were recorded. At long-term follow-up, 2 outcomes were investigated: survival rate and return to previous use at the same or higher level. Univariate and multivariate logistic regression analyses were conducted.
Results—Group 1 (96 horses) included septic synovitis. Group 2 (50 horses) included extrasynovial lacerations (23 horses) and fresh, minimally contaminated intrasynovial lacerations without evidence of established synovial infection (27 horses). Group 3 (28 horses) included miscellaneous other conditions. Only minor complications were reported in 12.26% of horses that received IV (n = 155) and 33% of horses that received intraosseous (27) A-RLP. Horses with septic synovitis had a lower survival rate (53.43%) than did horses with lacerations (91.89%). Within group 2, no significant differences in short- or long-term outcomes were found between horses with extrasynovial and fresh, minimally contaminated intrasynovial lacerations. For the horses returning to previous use, 80% of horses with septic synovitis and 72.72% of horses with lacerations were performing at the same or higher level at the time of follow-up.
Conclusions and Clinical Relevance—The results of the present study indicated that A-RLP is a safe technique with minimal adverse effects. The IV route presented fewer complications than intraosseous injection. Horses with infection of synovial structures had a lower survival rate than did those with acute, minimally contaminated intrasynovial lacerations. The latter had a similar prognosis for horses with extrasynovial lacerations treated with A-RLP.
Case Description—A 4.6-month-old pot-bellied pig was evaluated because of non–weight-bearing lameness (grade 5/5) in the right forelimb of 4 days' duration.
Clinical Findings—Clinical and radiographic examination revealed a closed, lateral luxation of the right shoulder joint.
Treatment and Outcome—Initial attempts at closed reduction failed to provide adequate stability of the shoulder joint. Open reduction and internal fixation by placement of 2 lateral tension sutures with a system designed for canine cranial cruciate ligament repair provided adequate joint stability and a successful outcome.
Conclusions and Clinical Relevance—Stabilization of the shoulder joint with lateral tension sutures after open reduction should be considered for management of lateral shoulder luxation in pot-bellied pigs.
Objective—To characterize the microstructure of subchondral bone (SCB) plate and trabecular bone (TBB) of the distopalmar aspect of the condyles of third metacarpal bones (MC3s) from Thoroughbred racehorses at 2 different stages of SCB disease via micro–computed tomography (CT).
Sample Population—12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons.
Procedures—MC3s were collected from horses with mild (n = 6) or severe (6) SCB disease, as determined via micro-CT. Cubic (6 × 6 × 6-cm) specimens of SCB plate and TBB were cut from the palmar aspect of condyles and sagittal ridges and examined with 3-dimensional micro-CT. For each specimen, apparent bone mineral density (aBMD), true BMD (tBMD), bone volume fraction (BVF), trabecular thickness (TBT), trabecular separation (TBS), and connectivity (CN) were calculated.
Results—Condyles had higher aBMD, tBMD, BVF, and TBT and lower TBS than did the sagittal ridge. In bone specimens with mild SCB changes, SCB plate had higher aBMD, TBT, and CN and lower TBS than did TBB. In bone specimens with severe SCB disease, TBB had higher aBMD and TMD and lower TBS than it did in bone specimens with mild disease, and values were similar to those for SCB plate in bone specimens with severe disease.
Conclusions and Clinical Relevance—The microstructure of SCB of the distopalmar aspect of metacarpal condyles of horses varied according to the severity of changes identified via micro-CT. With mild SCB disease, sclerosis existed in the SCB plate of the condyles; with severe disease, sclerosis also invaded condylar TBB.
Objective—To characterize the mechanical properties of subchondral bone (SCB) of the distopalmar aspect of the condyles of the third metacarpal bone (MC3) and their correlations with structural aspects of MC3s in Thoroughbred racehorses.
Sample Population—12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons.
Procedures—MC3s were collected from horses with mild (n = 6) and with severe (6) SCB changes, as determined by micro–computed tomography (CT). Specimens of SCB plate and trabecular bone were cut from the distopalmar aspect of condyles and sagittal ridge and examined with 3-dimensional micro-CT. Specimens were tested in compression, and elastic modulus, yield stress, yield strain, and toughness were calculated. Apparent and true bone mineral density, bone volume fraction, trabecular thickness, trabecular separation, and connectivity were also calculated. Differences in mechanical properties among various classifications of bone were evaluated. Correlations between structural and mechanical variables were also assessed.
Results—No differences were detected between left and right forelimbs. Specimens from condyles had higher values for elastic modulus, yield stress, and toughness than did specimens of sagittal ridge. In SCB with severe changes attributable to SCB disease, SCB plate was weaker and trabecular bone was stronger than in SCB with mild changes. Microstructural and mechanical properties were significantly correlated.
Conclusions and Clinical Relevance—A marked gradient in mechanical properties of SCB from horses, which could be involved in the pathogenesis of condylar fractures, was detected. Mechanical properties of SCB from the distal aspect of MC3s can be predicted to some extent via micro-CT.
Objective—To evaluate clinical variables, regional
concentrations, and pharmacokinetics of vancomycin
in the synovial fluid of distal forelimb joints of horses
after IV regional limb perfusion.
Procedure—Vancomycin was administered via IV
regional limb perfusion to the distal portion of the
forelimbs of anesthetized horses. Drug (300 mg of
vancomycin hydrochloride in 60 mL of saline [0.9%
NaCl] solution) was infused into 1 forelimb, whereas
the contralateral limb served as a control and was perfused
with 60 mL of saline solution. Solutions were
injected into the lateral digital vein after digital exsanguination.
Synovial fluid from the metacarpophalangeal
(MTCP) and distal interphalangeal (DIP) joints
and systemic blood were collected prior to perfusion
and 15, 30, 45, 65, and 90 minutes after initiation of
the infusion. Synovial fluid from the MTCP joint and
blood were also obtained at 4, 8, 12, and 24 hours
after infusion. Plasma urea and creatinine concentrations,
degree of lameness, and certain clinical variables
involving the MTCP joint and infusion site were
assessed for 7 days. Results were compared
between the vancomycin treatment and control
Results—No complications or significant differences
in renal function, lameness, or clinical variables were
observed between groups. Vancomycin concentrations
exceeded 4 µg/mL in MTCP joints for approximately
20 hours. Higher concentrations were reached
in DIP joints than in MTCP joints.
Conclusions and Clinical Relevance—IV regional
limb perfusion with 300 mg of vancomycin as a 0.5%
solution was safe and may be useful in horses as
treatment for distal limb infections. (Am J Vet Res
Objective—To evaluate the clinical effects and pharmacokinetics of vancomycin in plasma and synovial fluid after intraosseous regional limb perfusion (IORLP) in horses and to compare results with those obtained after IV regional limb perfusion (IVRLP).
Procedures—1 forelimb of each horse received vancomycin hydrochloride (300 mg in 60 mL of saline [0.9% NaCl] solution) via IORLP; the contralateral limb received 60 mL of saline solution (control). Solutions were injected into the medullary cavity of the distal portion of the third metacarpal bone. Synovial fluid from the metacarpophalangeal (MTCP) and distal interphalangeal (DIP) joints and blood were collected prior to perfusion and 15, 30, 45, 65, and 90 minutes after beginning IORLP, and synovial fluid from the MTCP joint only and blood were collected 4, 8, 12, and 24 hours after beginning IORLP. Plasma urea and creatinine concentrations and clinical appearance of the MTCP joint region and infusion sites were determined daily for 7 days. Results were compared with those of a separate IVRLP study.
Results—Clinical complications were not observed after IORLP. Mean vancomycin concentration in the MTCP joint was 4 μg/mL for 24 hours after IORLP. Compared with IORLP, higher vancomycin concentrations were detected in the DIP joint after IVRLP. Compared with IVRLP, higher vancomycin concentrations were detected in the MTCP joint for a longer duration after IORLP.
Conclusions and Clinical Relevance—IORLP with 300 mg of vancomycin in a 0.5% solution was safe and may be clinically useful in horses. Intravenous and intraosseous routes may be better indicated for infectious processes in the DIP and MTCP joints, respectively.
Case Description—A 3-year-old male alpaca was evaluated because of non–weight-bearing lameness (grade 5/5) in the left hind limb.
Clinical Findings—Clinical and radiographic examination revealed a closed, comminuted, nonarticular, displaced diaphyseal fracture of the left third and fourth metatarsal bones.
Treatment and Outcome—Initial attempts at treatment via reduction of the fracture under traction and subsequent application of a cast were unsuccessful, and more stable fracture fixation was pursued. The alpaca underwent closed reduction of the fracture, which was stabilized by the application of a 3-ring circular external skeletal fixator (CESF). Improved weight bearing on the affected limb was evident soon after surgery and gradually increased; full weight bearing was evident by the seventh day after discharge from the hospital (day 20 after application of the CESF). Lameness was hardly noticeable during walking at that time. After 3 months, complete fracture healing was evident and the CESF was removed; mild outward rotation of the distal fragment and metatarsophalangeal joint was present. A Robert Jones bandage was applied to the limb, and the alpaca was kept in a stall for another 4 weeks. Eleven months after CESF application, the owners and referring veterinarian reported that the alpaca was healthy, not lame, and serving as a stallion without apparent impediment.
Clinical Relevance—Although mostly restricted to small animals, application of a CESF can be a viable alternative for management of long bone fractures in South American camelids.