Evaluation of safety and pharmacokinetics of vancomycin after intraosseous regional limb perfusion and comparison of results with those obtained after intravenous regional limb perfusion in horses

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). ANIMALS: 6 horses. 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 microg/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.     

Medullary plasma pharmacokinetics of vancomycin after intravenous and intraosseous perfusion of the proximal phalanx in horses

OBJECTIVE: To study the pharmacokinetics of vancomycin in plasma obtained from the medullary sinusoids of the proximal phalanx (P1) after intravenous (IV) and intraosseous (IO) regional limb perfusion (RLP). STUDY DESIGN: Experimental study. ANIMALS: Twelve horses. METHODS: IV and IO RLP were performed in 2 groups (n = 6) of horses. Vancomycin hydrochloride (300 mg in 60 mL 0.9% NaCl) was randomly infused in 1 front limb, with the contralateral limb as control (60 mL 0.9% NaCl). A hole was drilled in the lateral cortex of P1, and blood samples from the medullary sinusoids of P1 were collected before infusion, and 15, 30, 45, 65, and 90 minutes after beginning infusion. Samples were centrifuged and plasma vancomycin concentrations determined. Vancomycin concentrations were compared over time and between routes using a 2-way repeated measures ANOVA. Pharmacokinetic variables were compared with a Kolmogorov-Smirnov test. Significance was set at P<.05. RESULTS: No vancomycin-induced clinical side effects such as lameness or swelling were observed. Both techniques, IV and IO, produced high vancomycin concentrations in the sinusoidal plasma of the P1, which remained above the minimum inhibitory concentration value for methicillin-resistant Staphylococcus aureus (MRSA) during the 90 minutes study. Concentrations and pharmacokinetic variables were not significantly different comparing both routes. CONCLUSIONS: IV and IO routes produced similar antimicrobial perfusion of the medullary cavity of P1. CLINICAL RELEVANCE: Either IV or IO routes for perfusion are likely to be equally selected when planning RLP with vancomycin.     

Lameness and poor performance in horses used for team roping: 118 cases (2000-2003)

OBJECTIVE: To determine the types of musculoskeletal problems that result in lameness or poor performance in horses used for team roping and determine whether these problems are different in horses used for heading versus heeling. DESIGN: Retrospective study. ANIMALS: 118 horses. PROCEDURE: Medical records of team roping horses that were evaluated because of lameness or poor performance were reviewed to obtain information regarding signalment, primary use (ie, head horse or heel horse), history, results of physical and lameness examinations, diagnostic tests performed, final diagnosis, and treatment. RESULTS: Among horses evaluated by lameness clinicians, the proportion with lameness or poor performance was significantly greater in horses used for heading (74/118) and lower in horses used for heeling (44/118) than would be expected under the null hypothesis. Most horses examined for poor performance were lame. A significantly greater proportion of horses used for heading had right forelimb lameness (26/74 [35%]), compared with horses used for heeling (7/44 [16%]). Horses used for heading had more bilateral forelimb lameness (18/74 [24%]), compared with horses used for heeling (4/44 [9%]). Horses used for heeling had more bilateral hind limb lameness (3/44 [7%]), compared with horses used for heading (0%). The most common musculoskeletal problems in horses used for heading were signs of pain limited to the distal sesamoid (navicular) area, signs of pain in the navicular area plus osteoarthritis of the distal tarsal joints, and soft tissue injury in the forelimb proximal phalangeal (pastern) region. Heeling horses most commonly had signs of pain in the navicular area, osteoarthritis of the metatarsophalangeal joints, and osteoarthritis of the distal tarsal joints. CONCLUSIONS AND CLINICAL RELEVANCE: Horses used for heading were most commonly affected by lameness in the right forelimb. Horses used for heeling had more bilateral hind limb lameness than horses used for heading.     

Comparison of two indirect techniques for local delivery of a high dose of an antimicrobial in the distal portion of forelimbs of horses

OBJECTIVE: To compare isolated limb retrograde venous injection (ILRVI) and isolated limb infusion (ILI) for delivery of amikacin to the synovial fluid of the distal interphalangeal and metacarpophalangeal joints and to evaluate the efficacy of use of an Esmarch tourniquet in standing horses. ANIMALS: 6 healthy adult horses. PROCEDURES: Horses were randomly assigned in a crossover design. In ILRVI, the injection consisted of 1 g of amikacin diluted to a total volume of 60 mL administered during a 3-minute period. In ILI, the infusion consisted of 1 g of amikacin diluted to 40 mL administered during a 3-minute period followed by administration of boluses of diluent (82 mL total) to maintain vascular pressure. During ILI, the infusate and blood were circulated from the venous to the arterial circulation in 5-mL aliquots. Synovial fluid and serum samples were obtained to determine maximum amikacin concentrations and tourniquet leakage, respectively. RESULTS: Both techniques yielded synovial concentrations of amikacin > 10 times the minimum inhibitory concentration (MIC) for 90% of isolates (80 microg/mL) and > 10 times the MIC breakpoint (160 microg/mL) of amikacin-susceptible bacteria reported to cause septic arthritis in horses. These values were attained for both joints for both techniques. Esmarch tourniquets prevented detectable loss of amikacin to the systemic circulation for both techniques. CONCLUSIONS AND CLINICAL RELEVANCE: Both techniques reliably achieved synovial fluid concentrations of amikacin consistent with concentration-dependent killing for bacteria commonly encountered in horses with septic arthritis. Esmarch tourniquets were effective for both delivery techniques in standing horses.     

Regional limb perfusion for antibiotic treatment of experimentally induced septic arthritis.

Septic arthritis was induced in one antebrachiocarpal joint of seven horses by the intra-articular injection of 1 mL Staphylococcus aureus suspension containing a mean of 10(5) colony-forming units. Twenty-four hours after inoculation, four horses were treated by regional perfusion with 1 g of gentamicin sulfate, and three horses received 2.2 mg/kg gentamicin sulfate intravenously (IV) every 6 hours. Synovial fluid was collected for culture and cytology at regular intervals, and the synovial membranes were collected for culture and histologic examination at euthanasia 24 hours after the first treatment. Gentamicin concentration in the septic synovial fluid after three successful perfusions was 221.2 +/- 71.4 (SD) micrograms/mL; after gentamicin IV, it was 7.6 +/- 1.6 (SD) micrograms/mL. The mean leukocyte count in the inoculated joints decreased significantly by hour 24 in the successfully perfused joints. Terminal bacterial cultures of synovial fluid and synovial membranes were negative in two horses with successfully perfused joints. S. aureus was isolated from the infected joints in all three horses treated with gentamicin IV.     

Effects of intra-articular administration of dimethylsulfoxide on chemically induced synovitis in immature horses

The effects of intra-articular administration of dimethylsulfoxide (DMSO) on chemically induced synovitis in the middle carpal joint of 6 weanling horses were evaluated. Following aseptic collection of synovial fluid, the middle carpal joint of each forelimb was injected with 50 mg of Na-monoiodoacetate to induce synovitis. Eight days after injection, synovial fluid was obtained and the right middle carpal joints were injected with 2 ml of 40% DMSO in lactated Ringer solution. The corresponding joints of the left limb (control) were injected with 2 ml of lactated Ringer solution. Sampling and treatments were repeated on post-injection days 11 and 14, for a total of 3 treatments. Horses were visually evaluated daily for lameness and joint effusion. Synovial fluid was evaluated for color and clarity, differential and total WBC count, total protein content, and hyaluronic acid concentration. The Kaegi gait analysis system provided an objective assessment of lameness prior to inducing synovitis, again on day 7, and on day 17. At necropsy (day 17), synovial fluid, synovial membrane, and articular cartilage specimens were collected. Joint effusion was evident 12 hours after injection of Na-monoiodoacetate in all joints. Mild lameness was evident at 24 hours; however, the lameness resolved by 72 hours. Objective assessment of lameness did not reveal significant differences between treatment or control limbs. Hyaluronic acid concentrations increased significantly (P = 0.023) above baseline values in most joints over the study period. Synovial fluid WBC counts increased significantly (P = 0.002) following Na-monoiodoacetate injection and remained significantly (P = 0.002) above baseline values throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Desmitis of the straight sesamoidean ligament in horses: 9 cases (1995-1997)

OBJECTIVE: To determine clinical signs, diagnostic findings, and outcome for horses with desmitis of the straight sesamoidean ligament (SSL) near its insertion on the middle phalanx. DESIGN: Retrospective study. ANIMALS: 9 horses. PROCEDURE: Medical records were reviewed, and information on signalment, history, clinical signs, diagnostic findings, and treatment was obtained. Follow-up information was obtained through telephone conversations with owners. RESULTS: In all horses, the diagnosis was made by use of high-resolution ultrasonography. Seven horses had moderate lameness on initial examination; lameness was exacerbated in 6 horses following flexion of the distal limb joints. The cause of lameness could not be determined on the basis of clinical signs, and diagnostic local anesthesia was necessary to localize the source of lameness to the distal portion of the limb. Five horses had forelimb involvement (1 bilateral), and 4 had hind limb involvement (1 bilateral). Treatment consisted primarily of a 6-month rest and rehabilitation program. Six of the 9 horses were able to return to their intended use. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that injury to the SSL proximal to its insertion on the middle phalanx should be considered as a possible cause of lameness in horses, particularly performance horses, with lameness localized to the distal portion of the forelimb or hind limb that do not have any radiographic abnormalities. High-resolution ultrasonography was necessary to make the diagnosis. Horses with an acute injury appeared to have a reasonable chance of responding to treatment and returning to their intended use.     

Musculoskeletal problems associated with lameness and poor performance among horses used for barrel racing: 118 cases (2000-2003)

OBJECTIVE: To identify types of musculoskeletal problems associated with lameness or poor performance in horses used for barrel racing. DESIGN: Retrospective case series. ANIMALS: 118 horses. PROCEDURE: Medical records were reviewed for information on signalment, history, physical and lameness examination findings, diagnostic tests performed, diagnosis, and treatment. RESULTS: Most horses were examined because of lameness (n = 72 [61%]) rather than poor performance (46 [39%]), but owner complaint was not significantly associated with age or body weight of the horse. The most common performance change was refusal or failure to turn properly around the first barrel (19/46 [41%]). The right forelimb (n = 57 [48%]) was most commonly affected, followed by the left forelimb (51 [43%]), the left hind limb (31 [26%]), and the right hind limb (25 [21%]). In 31 horses (26%), both forelimbs were affected, and in 6 (5%), both hind limbs were affected. The most common musculoskeletal problems were forelimb foot pain only (n = 39 [33%]), osteoarthritis of the distal tarsal joints (17 [14%]), suspensory ligament desmitis (15 [13%]), forelimb foot pain with distal tarsal joint osteoarthritis (11 [9%]), and bruised feet (10 [8.5%]). In 81 (69%) horses, the affected joint was treated with intra-articular medications. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in horses used for barrel racing that are examined because of lameness or poor performance, the forelimbs are more likely to be affected than the hind limbs, with forelimb foot pain and osteoarthritis of the distal tarsal joints being the most common underlying abnormalities.     

Effect of induced unilateral synovitis of distal intertarsal and tarsometatarsal joints on sagittal plane kinematics and kinetics of trotting horses

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. CONCLUSION 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.     

Intraosseous gentamicin perfusion of the distal metacarpus in standing horses

OBJECTIVE: To report tissue gentamicin concentrations after intraosseous (IO) perfusion in standing horses. STUDY DESIGN: In vivo study. ANIMALS OR SAMPLE POPULATION: Twelve horses. METHODS: Sedated horses had a cannulated cortical bone screw inserted into the dorsolateral aspect of the treated metacarpus and a tourniquet applied proximally. Gentamicin (2.2 mg/kg) diluted in sterile saline solution (0.1 mL/kg) was infused through the screw. Two horses were euthanatized at each time interval: 0, 2, 6, 12, 24, and 36 hours. Synovial fluid and bone samples were collected distal to the screw from both forelimbs. Gentamicin concentrations were measured using fluorescence polarization immunoassay. RESULTS: The highest synovial fluid gentamicin concentrations were 385+/-273 microg/mL (mean+/-SD) in the metacarpophalangeal joint, 225+/-205 microg/mL in the proximal interphalangeal joint, 215+/-205 microg/mL in the distal interphalangeal joint, 382+/-195 microg/mL in the digital flexor tendon sheath, and 206+/-161 microg/mL in the navicular bursa. The highest bone concentrations of gentamicin were 55+/-30 microg/g in the distal metacarpus, 34+/-27 microg/g in the proximal, 16+/-15 microg/g in the middle, and 16+/-2.2 microg/g in the distal phalanges, and 27+/-17 microg/g in the proximal and 24+/-11 microg/g in the distal sesamoid bones. CONCLUSION: Standing IO perfusion of gentamicin resulted in local antibiotic concentrations in the synovial structures and bones of the distal aspect of the limb that exceed the reported minimum inhibitory concentration of pathogens commonly implicated in equine orthopedic infections. CLINICAL RELEVANCE: Standing IO perfusion of gentamicin in the distal aspect of the limb should be considered for treatment of orthopedic infections of this region in horses.     

Pharmacokinetics and pharmacodynamics of enrofloxacin and a low dose of amikacin administered via regional intravenous limb perfusion in standing horses

OBJECTIVE: To evaluate the pharmacokinetic-pharmacodynamic parameters of enrofloxacin and a low dose of amikacin administered via regional IV limb perfusion (RILP) in standing horses. ANIMALS: 14 adult horses. PROCEDURES: Standing horses (7 horses/group) received either enrofloxacin (1.5 mg/kg) or amikacin (250 mg) via RILP (involving tourniquet application) in 1 forelimb. Samples of interstitial fluid (collected via implanted capillary ultrafiltration devices) from the bone marrow (BMIF) of the third metacarpal bone and overlying subcutaneous tissues (STIF), blood, and synovial fluid of the radiocarpal joint were collected prior to (time 0) and at intervals after tourniquet release for determination of drug concentrations. For pharmacokinetic-pharmacodynamic analyses, minimum inhibitory concentrations (MICs) of 16 microg/mL (amikacin) and 0.5 microg/mL (enrofloxacin) were applied. RESULTS: After RILP with enrofloxacin, 3 horses developed vasculitis. The highest synovial fluid concentrations of enrofloxacin and amikacin were detected at time 0; median values (range) were 13.22 microg/mL (0.254 to 167.9 microg/mL) and 26.2 microg/mL (5.78 to 50.0 microg/mL), respectively. Enrofloxacin concentrations exceeded MIC for approximately 24 hours in STIF and synovial fluid and for 36 hours in BMIF. After perfusion of amikacin, concentrations greater than the MIC were not detected in any samples. Effective therapeutic concentrations of enrofloxacin were attained in all samples. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with orthopedic infections, RILP of enrofloxacin (1.5 mg/kg) should be considered as a treatment option. However, care must be taken during administration. A dose of amikacin > 250 mg is recommended to attain effective tissue concentrations via RILP in standing horses.     

Comparison of 2 techniques for regional antibiotic delivery to the equine forelimb: intraosseous perfusion vs. intravenous perfusion

The purpose of this study was to compare the synovial fluid concentrations and pharmacokinetics of amikacin in the equine limb distal to the carpus following intraosseous and intravenous regional perfusion. The front limbs of 6 horses were randomly assigned to either intraosseous or intravenous perfusion. A tourniquet was placed distal to each carpus and the limb perfused with 500 mg of amikacin. Systemic blood samples and synovial fluid samples were collected over 70 min from the distal interphalangeal (DIP) joint, metacarpophalangeal joint, and digital flexor sheath. The tourniquet was removed following the 30 min sample collection. The mean peak amikacin concentration for the DIP joint was significantly higher with intravenous perfusion. There were no significant differences in time to peak concentration or elimination half-life between methods at each synovial structure. Each technique produced mean peak concentrations ranging from 5 to 50 times that of recommended peak serum concentrations for therapeutic efficacy.     

Comparison of intraosseous or intravenous infusion for delivery of amikacin sulfate to the tibiotarsal joint of horses

OBJECTIVE: To establish the route of infusion (IV or intraosseous) that results in the highest concentration of amikacin in the synovial fluid of the tibiotarsal joint and determine the duration of peak concentrations. ANIMALS: 21 horses. PROCEDURE: Regional perfusion of a limb on 15 horses was performed. Amikacin sulfate was infused into the saphenous vein or via intraosseous infusion into the distal portion of the tibia (1 g in 56 ml of lactated Ringer's solution) or proximal portion of the metatarsus (1 g of amikacin in 26 ml of lactated Ringer's solution). Amikacin concentrations were measured in sequential samples from tibiotarsal joint synovial fluid and serum. Samples were obtained immediately prior to release of the tourniquet and 0.5, 1, 4, 8, 12, and 24 hours after the tourniquet was released. Radiographic contrast material was infused into the same locations as the antibiotic perfusate to evaluate distribution in 6 other horses. RESULTS: Infusion into the saphenous vein produced the highest concentration of amikacin in the tibiotarsal joint, compared with the distal portion of the tibia (mean +/- SE, 701.8 +/- 366.8 vs 203.8 +/- 64.5 microg/ml, respectively). Use of a lower volume of diluent in the proximal portion of the metatarsus produced a peak value of 72.2 +/- 23.4 microg/ml. CONCLUSIONS AND CLINICAL RELEVANCE: For regional perfusion of the tarsus, IV infusion is preferred to intraosseous infusion, because higher concentrations are achieved in the synovial fluid, and the procedure is easier to perform.     

Determination of synovial fluid and serum concentrations, and morphologic effects of intraarticular ceftiofur sodium in horses

OBJECTIVES: To determine the serum and synovial fluid concentrations of ceftiofur sodium after intraarticular (IA) and intravenous (IV) administration and to evaluate the morphologic changes after intraarticular ceftiofur sodium administration. STUDY DESIGN: Strip plot design for the ceftiofur sodium serum and synovial fluid concentrations and a split plot design for the cytologic and histopathologic evaluation. ANIMALS: Six healthy adult horses without lameness. METHODS: Stage 1: Ceftiofur sodium (2.2 mg/kg) was administered IV. Stage 2: 150 mg (3 mL) of ceftiofur sodium (pHavg 6.57) was administered IA into 1 antebrachiocarpal joint. The ceftiofur sodium was reconstituted with sterile sodium chloride solution (pH 6.35). The contralateral joint was injected with 3 mL of 0.9% sterile sodium chloride solution (pH 6.35). Serum and synovial fluid samples were obtained from each horse during each stage. For a given stage, each type of sample (serum or synovial fluid) was collected once before injection and 12 times after injection over a 24-hour period. All horses were killed at 24 hours, and microscopic evaluation of the cartilage and synovium was performed. Serum and synovial fluid concentrations of ceftiofur sodium were measured by using a microbiologic assay, and pharmacokinetic variables were calculated. Synovial fluid was collected from the active joints treated during stage 2 at preinjection and postinjection hours (PIH) 0 (taken immediately after injection of either the ceftiofur sodium or sodium chloride), 12, and 24, and evaluated for differential cellular counts, pH, total protein concentration, and mucin precipitate quality. RESULTS: Concentrations of ceftiofur in synovial fluid after IA administration were significantly higher (P = .0001) than synovial fluid concentrations obtained after IV administration. Mean peak synovial fluid concentrations of ceftiofur after IA and IV administration were 5825.08 microg/mL at PIH .25 and 7.31 microg/mL at PIH 4, respectively. Mean synovial fluid ceftiofur concentrations at PIH 24 after IA and IV administration were 4.94 microg/mL and .12 microg/mL, respectively. Cytologic characteristics of synovial fluid after IA administration did not differ from cytologic characteristics after IA saline solution administration. White blood cell counts after IA ceftiofur administration were < or =3,400 cells/ML. The mean synovial pH of ceftiofur treated and control joints was 7.32 (range, 7.08-7.5) and 7.37 (range, 7.31-7.42), respectively. Grossly, there were minimal changes in synovium or cartilage, and no microscopic differences were detected (P = .5147) between ceftiofur-treated joints and saline-treated joints. The synovial half-life of ceftiofur sodium after IA administration joint was 5.1 hours. CONCLUSIONS: Synovial concentrations after intraarticular administration of 150 mg of ceftiofur sodium remained elevated above minimal inhibitory concentration (MIC90) over 24 hours. After 2.2 mg/kg IV, the synovial fluid ceftiofur concentration remained above MIC no longer than 8 hours. CLINICAL RELEVANCE: Ceftiofur sodium may be an acceptable broad spectrum antimicrobial to administer IA in septic arthritic equine joints.     

The influence of perfusate volume on antimicrobial concentration in synovial fluid following intravenous regional limb perfusion in the standing horse

This study investigated the influence of perfusate volume on antimicrobial concentration in synovial fluid following intravenous regional limb perfusion (IVRLP) and assessed the efficacy of low volume IVRLP. The front limbs of 9 horses were randomly assigned to 1 of 3 volume groups: 10 mL (Group 1), 30 mL (Group 2), or 60 mL (Group 3). A tourniquet was applied distal to the carpus and the limbs were perfused with 500 mg genta-micin diluted to the assigned volume via a catheter placed in the lateral palmar digital vein at the level of the proximal sesamoid bones. Synovial fluid samples were collected from the metacarpophalangeal joint at 30 minutes, followed by removal of the tourniquet. Gentamicin concentration in synovial fluid was detected using a fluorescence polarization immunoassay. There were no statistically significant differences among gentamicin concentrations in synovial fluid among perfusate volume groups. Mean gentamicin concentration in Group 1 (125.9 μg/mL) was higher than Group 2 (82.7 μg/mL) and Group 3 (56.1 μg/mL).     

Efficacy of three tourniquet types for intravenous antimicrobial regional limb perfusion in standing horses

Objective: To determine (1) if clinically useful concentrations of amikacin sulfate can be obtained in synovial fluid during regional limb perfusion (RLP) performed above the carpus in standing sedated horses and (2) to determine the efficacy of 3 tourniquet types (narrow rubber [NR], wide rubber [WR], pneumatic [PN]). Animals: Horses (n=9). Methods: Bilateral forelimb RLP with amikacin sulfate (2.5 g) were administered through the cephalic vein in standing sedated horses. Limbs were randomly assigned to the 3 tourniquet types (NR, WR, PN) applied above the carpus. Metacarpophalangeal synovial fluid was obtained 0.5 hour after perfusion. Amikacin concentration in the synovial fluid was detected using fluorescence polarization immunoassay. Results: Mean synovial concentrations of amikacin in the PN (mean 236 μg/mL; range 23–913 μg/mL) and WR (mean 64.2 μg/mL; range 7–315 μg/mL) were significantly higher (P=.000 and .032, respectively) than the NR tourniquet (mean 2.1 μg/mL; range 0.9–3.3 μg/mL). Conclusions: The PN tourniquet resulted in the highest synovial fluid amikacin concentrations in all horses, although administration with PN and WR tourniquets achieved adequate amikacin concentrations. NR tourniquet is ineffective and should not be used for RLP above the carpus in the standing horse.     

Computer-assisted kinematic evaluation of induced compensatory movements resembling lameness in horses trotting on a treadmill

OBJECTIVE: To characterize compensatory movements of the head and pelvis that resemble lameness in horses. ANIMALS: 17 adult horses. PROCEDURE: Kinematic evaluations were performed while horses trotted on a treadmill before and after shoe-induced lameness. Lameness was quantified and the affected limb determined by algorithms that measured asymmetry in vertical movement of the head and pelvis. Induced primary lameness and compensatory movements resembling lameness were assessed by the Friedman test. Association between induced lameness and compensatory movements was examined by regression analysis. RESULTS: Compensatory movements resembling lameness in the ipsilateral forelimb were seen with induced lameness of a hind limb. There was less downward and less upward head movement during and after the stance phase of the ipsilateral forelimb. Doubling the severity of lameness in the hind limb increased severity of the compensatory movements in the ipsilateral forelimb by 50%. Compensatory movements resembling lameness of the hind limb were seen after induced lameness in a forelimb. There was less upward movement of the pelvis after the stance phase of the contralateral hind limb and, to a lesser extent, less downward movement of the pelvis during the stance phase of the ipsilateral hind limb. Doubling the severity of lameness in the forelimb increased compensatory movements of the contralateral hind limb by 5%. CONCLUSIONS AND CLINICAL RELEVANCE: Induced lameness in a hind limb causes prominent compensatory movements resembling lameness in the ipsilateral forelimb. Induced lameness in a forelimb causes slight compensatory movements resembling lameness in the ipsilateral and contralateral hind limbs.     

Comparison of Synovial Fluid in Middle Carpal Joints Undergoing Needle Aspiration, Infusion with Saline, and Infusion with a Combination of N-Acetyl-d-Glucosamine, Hyaluronic Acid, and Sodium Chondroitin Sulfate

Synovial fluid white blood cell (WBC) count and total protein (TP) concentration were evaluated in the midcarpal joints of horses to not only determine the effects of needle aspiration, infusion with saline, and infusion with a combination of N-acetyl-d-glucosamine, hyaluronan, and sodium chondroitin sulfate (GHCS) at two different doses to evaluate the latter for safety, but to also provide information on saline injection as a control in joints. The midcarpal joints from 24 horses were used for this study. One midcarpal joint served as an untreated control, in which only synovial fluid was aspirated, whereas the opposite joint received either 2.5 mL isotonic saline (n = 8 horses), 2.5 mL of GHCS (n = 8 horses), or 7.5 mL of GHCS (n = 8 horses). Synovial fluid WBC and TP concentration were measured on days 1, 3, 5, 7, 14, and 21. Needle aspiration caused a transient increase in synovial fluid WBC and TP levels after 1 day. Instillation of fluid (2.5 mL), whether saline or GHCS, caused significantly higher WBC and TP concentrations. GHCS at a dose of 7.5 mL created an elevation in TP level for an additional 48 hours; however, after 48 hours, WBC and TP were at concentrations that were not statistically different from controls. Even though an increase in WBC and TP concentrations occurred because of intra-articular saline and GHCS administration, these results were transient demonstrating that GHCS is no different than saline on synovial fluid, WBC, and TP parameters and that as previously described short-term elevation in synovial fluid inflammatory parameters should be expected when saline is used as a control.     

Arthroscopically assisted arthrodesis of the distal interphalangeal joint with transarticular screws inserted through a dorsal hoof wall approach in a horse

CASE DESCRIPTION: A 16-year-old Thoroughbred gelding was examined because of chronic right forelimb lameness. CLINICAL FINDINGS: On radiographs of the right front foot, the distal interphalangeal (DIP) joint space was narrow, and osteophytes and periarticular bony proliferation indicative of severe osteoarthritis were seen. Arthrodesis of the right DIP joint was recommended to improve the horse's comfort on the limb. TREATMENT AND OUTCOME: The horse was anesthetized, and palmar and dorsal arthroscopic approaches were used to remove as much of the articular cartilage as was accessible. Holes were then drilled through the dorsal aspect of the hoof wall, and 3 transarticular, 5.5-mm cortical screws were placed in lag fashion through these holes across the distal phalanx and into the middle phalanx. Defects in the hoof wall were filled with gentamicin-impregnated polymethyl methacrylate plugs and sealed with cyanoacrylate. Eight months after surgery, fusion of the DIP joint was evident radiographically and the horse was sound at a walk. CLINICAL RELEVANCE: Transarticular placement of cortical screws through a dorsal hoof wall approach combined with arthroscopically guided cartilage removal can result in fusion of the DIP joint in horses.     

Detection of lameness and determination of the affected forelimb in horses by use of continuous wavelet transformation and neural network classification of kinematic data

OBJECTIVE: To investigate continuous wavelet transformation and neural network classification of gait data for detecting forelimb lameness in horses. ANIMALS: 12 adult horses with mild forelimb lameness. PROCEDURE: Position of the head and right forelimb foot, metacarpophalangeal (ie, fetlock), carpal, and elbow joints was determined by use of kinematic analysis before and after palmar digital nerve blocks. We obtained 8 recordings from horses without lameness, 8 with right forelimb lameness, and 8 with left forelimb lameness. Vertical and horizontal position of the head and vertical position of the foot, fetlock, carpal, and elbow joints were processed by continuous wavelet transformation. Feature vectors were created from the transformed signals and a neural network trained with data from 6 horses, which was then tested on the remaining 2 horses for each category until each horse was used twice for training and testing. Correct classification percentage (CCP) was calculated for each combination of gait signals tested. RESULTS: Wavelet-transformed vertical position of the head and right forelimb foot had greater CCP (85%) than untransformed data (21%). Adding data from the fetlock, carpal, or elbow joints did not improve CCP over that for the head and foot alone. CONCLUSIONS AND CLINICAL RELEVANCE: Wavelet transformation of gait data extracts information that is important for the detection and differentiation of forelimb lameness of horses. All of the necessary information to detect lameness and differentiate the side of lameness can be obtained by observation of vertical head movement in concert with movement of the foot of 1 forelimb.