Differences in wound contraction between horses and ponies: the in vitro contraction capacity of fibroblasts

The contribution of wound contraction to wound closure determines the speed of second intention wound healing and it has been shown that significant differences exist with regard to both contraction and inflammatory response between horses and ponies and between various areas of the body. In this study, the contraction capacity of fibroblasts from limbs and buttocks of 4 Dutch Warmblood horses and 4 Shetland ponies was studied in vitro, in order to determine whether differences in wound contraction are due to differences in the inherent contraction capacity of the fibroblasts or to differences in tissue environmental factors, such as the inflammatory response. Fibroblasts were harvested from subcutaneous tissue, cultured and then suspended in both floating and anchored collagen gels. Contraction capacity was assessed by measuring the decrease in area of the floating gels and by measuring the microforces generated in the anchored gels using a custom-built measuring device. In the floating gels, no difference existed in the contraction capacity of fibroblasts from horses and ponies, or from limbs and buttocks. In the anchored gels, no differences existed between horse and pony fibroblasts, but the fibroblasts from the limbs started to contract significantly sooner and produced significantly higher forces than those from the buttocks. It is concluded that the in vivo differences in wound contraction between horses and ponies and between different sites of the body are not caused by differences in the inherent contraction capacity of fibroblasts. The in vitro differences between fibroblasts from limbs and buttocks are thought to be due to the lower proliferation rate and the longer culture time of the fibroblasts originating from the limbs, because mature fibroblasts can develop higher contraction forces than immature fibroblasts. This means that tissue environmental factors, such as cytokine profiles during the inflammatory response, determine the extent of contraction during wound healing. Further research should be directed towards the role of the inflammatory response in wound healing.     

Strangulating obstruction caused by intestinal herniation through the proximal aspect of the cecocolic fold in 9 horses

OBJECTIVE: To report the clinical and surgical findings and outcome for horses with strangulating obstruction caused by herniation through the proximal aspect of the cecocolic fold. STUDY DESIGN: Retrospective study. ANIMALS: Nine horses. METHODS: Medical records were reviewed for clinical signs, surgical findings and technique, and outcome. Cadaver ponies and necropsy specimens were also used to study the regional anatomy of the cecocolic fold. RESULTS: The ileum and distal jejunum were strangulated in 8 horses, whereas in 1 horse the small intestine and the left ascending colons were incarcerated in a rent in the cecocolic fold. Two horses were euthanatized at surgery, 6 horses had a small intestinal resection (mean length, 3 m; range, 1.5-6.4 m) and an end-to-side jejunocecostomy, and the entrapment was reduced without resection in the horse that had small intestine and ascending colon incarceration; cecocolic fold defects were not closed. One horse was euthanatized 36 hours after surgery because of endotoxemia. Six horses were discharged; 4 were available for long-term follow-up, of which 2 were euthanatized, and 2 were euthanatized 12 and 18 months after surgery because of colic signs. Variations in thickness of the cecocolic fold were observed in specimens obtained from necropsy of other horses and ponies. CONCLUSIONS: Reasons for this defect are unknown, although observed anatomic differences in cecocolic fold thickness may contribute to the development of defects. CLINICAL RELEVANCE: Reduction of the entrapped bowel is easiest when traction is placed on the bowel at a 90 degrees to the base of the cecum. Intestinal incarceration through rents within the proximal part of the cecocolic fold should be considered as a differential diagnosis for strangulating obstruction in horses.     

Repair of Fractures of the Distal Aspect of the Radius in Two Horses

Fractures of the distal radius in two horses were repaired by open reduction and interfragmentary compression using screws placed in a lag fashion. One horse had a complete oblique fracture of the medial aspect of the epiphysis of the distal radius and was sound for riding 32 months after surgery. The other horse had an open spiral comminuted fracture with medial displacement of the distal radial fragment. Laminitis developed in the contralateral limb and this horse was euthanatized 5 weeks after surgery. © Copyright 1994 by The American College of Veterinary Surgeons     

IDENTIFICATION OF AN OSSICLE ASSOCIATED WITH THE PALMAR ASPECT OF THE CARPUS IN THE HORSE

An ossicle associated with the palmar aspect of the carpus is described in five horses. The size of the ossicle varied from 3 x 4 mm to approximately 12 x 10 mm. The ossicles were located at the junction of the proximal and distal rows of carpal bones, between the palmaromedial aspect of the fourth carpal bone and the ulnar carpal bone. In 3 horses they were bilateral, in one horse unilateral, and only one limb was examined in the remaining horse. In all horses it was an incidental finding and not regarded to be a pathologic entity.     

Effect of Betamethasone and Exercise on Equine Carpal Joints With Osteochondral Fragments

Osteochondral fragments were created arthroscopically on the distal aspect of both radial carpal bones in 12 horses. On day 14 after surgery, one middle carpal joint of each horse was injected with 2.5 mL Betavet Soluspan (3.9 mg betamethasone sodium phosphate and 12 mg betamethasone acetate per milliliter) and the contralateral joint was injected with 2.5 mL saline as a control. Intra-articular treatments were repeated on day 35. On day 17, six horses began exercising 5 days per week on a high-speed treadmill. The other six horses were kept in box stalls throughout the study as nonexercised controls. On day 56, all horses were examined clinically and radiographically and then were euthanatized. Samples were obtained for histological, his-tochemical, and biochemical evaluation. Mild lameness was observed in five of the six exercised horses at day 56; four horses were lame in the control limb and one horse was lame in the treated limb. Of the five nonexercised horses evaluated for lameness, two were lame in the control limb, two were lame in the treated limb, and one was lame in both the control and the treated limb. No differences were noted on radiographs or palpation of steroid treated limbs versus control limbs. Firm reattachment of the osteochondral fragment to the radial carpal bone occurred in all but three joints. Gross cartilage damage was not different between steroid-treated joints and joints injected with saline. Histologically, there were no significant detrimental effects of betamethasone with or without exercise, but there was a tendency for more pathological change in treated joints. There was a trend toward decreased glycosaminoglycan staining in steroid treated joints of rested horses, whereas exercised horses had similar glycosaminoglycan staining in treated and control joints. No significant difference in the water content or uronic acid concentration was detected between treated and control joints. Intra-articular betamethasone administration in this carpal chip model was not associated with any significant detrimental effects in either rested or exercised horses.     

The Bacteria Isolated from the Skin of 20 Horses at a Veterinary Teaching Hospital

The objective of this study was to isolate bacteria on the skin of the proximal to distal equine limb to guide the practitioner in the selection of prophylactic antimicrobial protocols. This prospective study involved 20 client-owned horses that were admitted to the Veterinary Teaching Hospital for routine elective surgery. Each horse spent between 12 and 36 hours at our hospital before sampling. Samples were collected from the skin of the left mid-thorax and the dorsal aspect of nine joints on the left side of each horse: front and hind coffin and fetlock joints, carpi, elbows, shoulders, hocks, and stifles. Samples were cultured aerobically and speciated when possible. When evaluating bacterial composition by location, a 40% difference was considered clinically significant. When comparing proximal sites above the fetlock to distal sites, the odds of isolating gram-positive bacteria were 1.23 times (P = .0124) higher at proximal sites; the odds of isolating coliform bacteria were 1.32 times (P = .023) higher at distal sites; and the odds of isolating a common septic arthritis pathogen were 1.16 times (P = .018) higher at distal sites. Coagulase-positive Staphylococcus was not isolated in this study. All comparisons between sites and between the proximal and distal limb were <40%, and thus were not considered clinically significant. No coagulase-positive Staphylococcus was isolated from any of the 200 sites in this study, suggesting that iatrogenic infections by that organism may not be because of preexisting flora. These data suggest that antibiotic prophylaxis targeting preexisting normal flora should be similar regardless of the area of interest on the limb.     

Ultrastructural and immunocytochemical evaluation of the effects of extracorporeal shock wave treatment in the hind limbs of horses with experimentally induced suspensory ligament desmitis

OBJECTIVE: To evaluate the effects of extracorporeal shock wave therapy (ESWT) on affected ligaments in the hind limbs of horses with experimentally induced suspensory ligament desmitis by use of ultrasonographic, ultrastructural, and immunocytochemical techniques. ANIMALS: 10 horses. PROCEDURE: Suspensory ligament desmitis was induced in both hind limbs of each horse by use of 2 collagenase injections (administered 2 weeks apart) in each suspensory ligament. Two weeks after the second injection, the right hind limb of each horse was treated with ESWT (3 treatments at 3-week intervals); the left hind limb was not treated (control limb). Periodically during the study, the healing process was monitored ultrasonographically and the proportions of ligaments affected with lesions were assessed. Four weeks after the last ESWT treatment, biopsy specimens were collected from all ligaments for ultrastructural evaluation and immunocytochemical analysis of transforming growth factor beta-1. RESULTS: The difference in the proportion of the lesion-affected ligament between ESWT-treated and control limbs was significant (P < 0.05) from 3 weeks after the second ESWT treatment to the end of the study. Compared with control ligaments, ESWT-treated ligaments had more small, newly formed collagen fibrils and greater expression of transforming growth factor beta-1 4 weeks after the last ESWT treatment was administered. CONCLUSIONS AND CLINICAL RELEVANCE: Results have indicated that ESWT appears to facilitate the healing process in horses with experimentally induced hind limb suspensory ligament desmitis.     

Effects of 25% propylene glycol hydrogel (Solugel) on second intention wound healing in horses

OBJECTIVE: To evaluate the effect of a commercially available 25% propylene glycol hydrogel preparation (Solugel; Johnson and Johnson Medical, North Ryde, Australia) on healing of full-thickness skin wounds on the distal aspect of the limb in horses. STUDY DESIGN: Experimental. ANIMALS: Eight Standardbred horses. METHODS: Standardized (2.5 x 2.5 cm) full-thickness skin wounds were created over the mid-dorsomedial aspect of both metacarpi in 8 horses. One wound in each horse was dressed with saline solution (0.9% NaCl) soaked gauze, and one was treated with Solugel under dry regular gauze; wounds were then bandaged with gauze-coated cotton wool and elastic adhesive bandages. Wounds were videorecorded and rebandaged twice weekly until healed. Wound healing variables were measured from the videorecordings using a computer software package and analyzed as a randomized complete block design with repeated measures. Where necessary variables were made positive for analysis; significance was set at P <.05. RESULTS: The area of the wound at the first bandage change did not vary between treated and untreated wounds. Treatment had no effect on the total rate of healing, rate of healing during the retraction phase of healing, rate of healing after the retraction phase was complete, or the amount the wounds retracted. CONCLUSIONS: Using this model of wound healing, Solugel had no effect on second intention healing of distal limb wounds in horses. CLINICAL RELEVANCE: Solugel does not appear to have any beneficial effect on healing of small full-thickness skin wounds to the distal limb of horses.     

Lameness attributable to osteochondral fragmentation of the plantar aspect of the proximal phalanx in horses: 19 cases (1981-1985)

Osteochondral fragmentation of the plantar aspect of the proximal phalanx was diagnosed as a cause of hind limb lameness in 19 horses. The lameness was evident at the upper levels of the horses' performance capabilities, and was isolated to the metatarsophalangeal joints by use of intra-articular or regional anesthesia. Fragments were surgically removed from 10 horses that later returned to full use. Seven horses were treated intra-articularly with polysulfated glycosaminoglycans or corticosteroids; only one horse was able to return to full use. One horse was retired from work at the time of diagnosis. Surgery appeared to be the most effective treatment for osteochondral fragmentation of the plantar aspect of the proximal phalanx, although medical treatment combined with a decrease in the horses' expected performance also was believed to be useful.     

Behavioral responses to two intranasal vaccine applicators in horses and ponies

OBJECTIVE: To evaluate behavioral compliance of horses and ponies with simulated intranasal vaccination and assess development of generalized aversion to veterinary manipulations. DESIGN: Clinical trial. ANIMALS: 28 light horse mares, 3 pony geldings, 2 light horse stallions, and 3 pony stallions that had a history of compliance with veterinary procedures. PROCEDURE: Behavioral compliance with 2 intranasal vaccine applicators was assessed. Compliance with standard physical examination procedures was assessed before and after a single experience with either of the applicators or a control manipulation to evaluate development of generalized aversion to veterinary manipulation. RESULTS: In all 30 horses, simulated intranasal vaccination or the control manipulation could be performed without problematic avoidance behavior, and simulated intranasal vaccination did not have any significant effect on duration of or compliance with a standardized physical examination that included manipulation of the ears, nose, and mouth. Results were similar for the 2 intranasal vaccine applicators, and no difference in compliance was seen between horses in which warm versus cold applicators were used. For 3 of the 6 ponies, substantial avoidance behavior was observed in association with simulated intranasal vaccination, and compliance with physical examination procedures decreased after simulated intranasal vaccination. CONCLUSIONS AND CLINICAL RELEVANCE: Although some compliance problems were seen with ponies, neither problems with compliance with simulated intranasal vaccination nor adverse effects on subsequent physical examination were identified in any of the horses. Further study is needed to understand factors involved in practitioner reports of aversion developing in association with intranasal vaccination.     

A RADIOGRAPHIC STUDY OF THE DISTAL INTERPHALANGEAL JOINT AND NAVICULAR BURSA OF THE HORSE

Radiographic contrast studies were used in 50 forelimbs from 13 live horses and 12 fresh adult cadavers to determine the frequency of communication between the navicular bursa and the distal interphalangeal joint. Injections of contrast medium were made into the dorsal aspect of the distal interphalangeal joint of one limb and into the navicular bursa of the other forelimb of each horse. In 25 limbs in which contrast medium was injected into the distal interphalangeal joint, no communication was demonstrated between the joint and the navicular bursa. In 20 of the 25 limbs in which injection was made into the navicular bursa, no communication between joint and bursa was seen. In five horses, contrast medium was visible in both the distal interphalangeal joint and the navicular bursa. However, in four of five horses the communication was clearly iatrogenic. In both limbs of one horse, contrast medium was seen to enter the digital flexor tendon sheath after injection into the navicular bursa.
There is probably no naturally occurring communication between the navicular bursa and distal interphalangeal joint in the horse.     

Standing placement of transphyseal screw in the distal radius in 8 Thoroughbred yearlings

This retrospective study describes placement of distal radial transphyseal screws in Thoroughbred yearlings with carpal varus deformities while standing, and identifes short- and long-term complications following the procedure. Data gathered from 2009 to 2013 identified 8 yearlings that met the inclusion criteria. Horses were sedated intravenously and a single 4.5-mm cortical screw was placed in the distal lateral radial physis following application of local anesthetic and surgical preparation of a pre-placed hole. All horses were evaluated weekly after surgery and screw removal was performed standing and under sedation when correction of the angular limb deformity was achieved. The mean time for screw removal was 46 days. No short- or long-term complications were identified. Findings indicate that placing a single transphyseal screw in the lateral aspect of the distal radial physis with the horse standing is a viable option to treat varus angular limb deformity of the carpus in horses.     

Pharmacokinetics of phenolsulfonphthalein in horse and pony mares

Pharmacokinetics of phenolsulfonphthalein (PSP) in horse and pony mares was determined after injection of 1 mg/kg of body weight, IV. A plasma PSP concentration vs time curve was described adequately in horses and ponies by an open, 2-compartment model. There were significant differences in the elimination phase parameters, apparent volume of distribution at steady state, and apparent volume of distribution of horses and ponies. The harmonic mean elimination half-life of PSP in horses was significantly longer (P less than 0.001) than that in the ponies (16.4 and 10.0 minutes, respectively). The mean plasma clearance of PSP in horses was significantly (P less than 0.05) less than that in ponies (0.00554 and 0.00701 L/min/kg, respectively). There was no difference between horses and ponies in the metabolic clearance of PSP. The fraction of the administered dose of PSP excreted in the urine in the first 15 minutes was not significantly different between horses and ponies.     

Production of patellar lesions by medial patellar desmotomy in normal horses

Medial patellar desmotomy was performed on one (treated) hindlimb, and a sham operation on the other (control) hindlimb, of 12 normal horses. The horses were examined for lameness before medial patellar desmotomy and at months 1, 2, and 3. The femoropatellar joints were examined radiographically and arthroscopically at month 3. All horses were lame on the treated limb at months 1, 2, or 3. Radiographic changes, including fragment formation at the distal aspect of the patella and bone production at the attachment of the middle patellar ligament on the patella, were present in 11 horses at month 3. Articular cartilage fibrillation or detachment was seen arthroscopically on the patellas of all treated limbs. In six horses, loosely attached fragments of bone and cartilage were removed arthroscopically from the distal aspect of the patella of the treated limb. The control limbs were clinically, radiographically, and arthroscopically normal throughout the study. Medial patellar desmotomy results in pathologic changes in the articular cartilage of the patella and adjacent soft tissues. Use of this surgical procedure should be reserved for persistent and confirmed cases of upward fixation of the patella.     

Production of Patellar Lesions by Medial Patellar Desmotomy in Normal Horses

Medial patellar desmotomy was performed on one (treated) hindlimb, and a sham operation on the other (control) hindlimb, of 12 normal horses. The horses were examined for lameness before medial patellar desmotomy and at months 1, 2, and 3. The femoropatellar joints were examined radiographically and arthroscopically at month 3. All horses were lame on the treated limb at months 1, 2, or 3. Radiographic changes, including fragment formation at the distal aspect of the patella and bone production at the attachment of the middle patellar ligament on the patella, were present in 11 horses at month 3. Articular cartilage fibrillation or detachment was seen arthroscopically on the patellas of all treated limbs. In six horses, loosely attached fragments of bone and cartilage were removed arthroscopically from the distal aspect of the patella of the treated limb. The control limbs were clinically, radiographically, and arthroscopically normal throughout the study. Medial patellar desmotomy results in pathologic changes in the articular cartilage of the patella and adjacent soft tissues. Use of this surgical procedure should be reserved for persistent and confirmed cases of upward fixation of the patella.     

A new modified live equine influenza virus vaccine: phenotypic stability, restricted spread and efficacy against heterologous virus challenge.

Flu Avert IN vaccine is a new, live attenuated virus vaccine for equine influenza. We tested this vaccine in vivo to ascertain 1) its safety and stability when subjected to serial horse to horse passage, 2) whether it spread spontaneously from horse to horse and 3) its ability to protect against heterologous equine influenza challenge viruses of epidemiological relevance. For the stability study, the vaccine was administered to 5 ponies. Nasal swabs were collected and pooled fluids administered directly to 4 successive groups of na?ve ponies by intranasal inoculation. Viruses isolated from the last group retained the vaccine's full attenuation phenotype, with no reversion to the wild-type virus phenotype or production of clinical influenza disease. The vaccine virus spread spontaneously to only 1 of 13 nonvaccinated horses/ponies when these were comingled with 39 vaccinates in the same field. For the heterologous protection study, a challenge model system was utilised in which vaccinated or na?ve control horses and ponies were exposed to the challenge virus by inhalation of virus-containing aerosols. Challenge viruses included influenza A/equine-2/Kentucky/98, a recent representative of the 'American' lineage of equine-2 influenza viruses; and A/equine-2/Saskatoon/90, representative of the 'Eurasian' lineage. Clinical signs among challenged animals were recorded daily using a standardised scoring protocol. With both challenge viruses, control animals reliably contracted clinical signs of influenza, whereas vaccinated animals were reliably protected from clinical disease. These results demonstrate that Flu Avert IN vaccine is safe and phenotypically stable, has low spontaneous transmissibility and is effective in protecting horses against challenge viruses representative of those in circulation worldwide.     

Septic Arthritis of the Distal Interphalangeal Joint in 12 Horses

The medical records of 12 horses with septic arthritis of a distal interphalangeal joint were reviewed to determine clinical features and response to treatment. Sepsis was caused by trauma or an injection that resulted in an open or contaminated distal interphalangeal joint. All horses were severely lame. Treatment included broad-spectrum parenterally administered antimicrobial drugs (ten horses), percutaneous through-and-through joint lavage (eight horses), indwelling drains (three horses), immobilization of the limb in a cast (three horses), intraarticular injection of sodium hyaluronate (one horse), intraarticular injection of antimicrobial drugs (five horses), curettage of the distal phalanx (one horse), and cancellous bone grafting to promote fusion (one horse). Five horses were euthanatized. Ankylosis of the affected joint developed in five horses, four of which are pasture sound. Two horses treated medically are sound although one underwent subsequent palmar digital neurectomy for treatment of navicular syndrome.     

Use of a hydro-pool system to recover horses after general anesthesia: 60 cases

OBJECTIVE: To report complications observed using a hydro-pool recovery system after general anesthesia in horses. STUDY DESIGN: Retrospective study. ANIMALS: Sixty horses. METHODS: Retrospective review of the medical records and quality of recovery from anesthesia of 60 horses that had surgical or diagnostic procedures under general anesthesia. RESULTS: Mean total anesthesia time was 182 minutes (range, 25 to 390 minutes). Mean time in the hydro-pool was 108 minutes (range, 20 to 270 minutes). One horse that had bilateral rear limb extensor weakness while recovering in a padded recovery stall was moved to the hydro-pool and maintained for 12 hours. Ten horses developed some pulmonary edema; in 3 horses, the signs of pulmonary edema were severe; and 1 horse died from related complications. One horse developed septic arthritis of an operated stifle joint, and 2 horses developed incisional infections. Two horses incurred multiple skin abrasions on the distal aspect of their limbs during violent attempts to leave the pool. CONCLUSIONS: A hydro-pool system was useful for recovering horses from general anesthesia when difficult recoveries were anticipated because of the horse's injury, size, demeanor, duration of anesthesia, or risk of further injury. Recovery using the hydro-pool was more time and labor intensive than a standard stall recovery. Pulmonary edema that required treatment was a serious complication that occurred in 17% of the horses. Careful closure of the skin with cyanoacrylate glue and pressure from bandages were used to prevent postoperative incisional infections. CLINICAL RELEVANCE: A hydro-pool system is a useful method for recovering horses from general anesthesia when difficult recoveries are anticipated.     

Comparison of equine amnion and a nonadherent wound dressing material for bandaging pinch-grafted wounds in ponies

OBJECTIVE: To evaluate healing of pinch-grafted wounds on the distal aspect of the limbs of ponies bandaged with equine amnion or a standard nonadherent wound dressing material. ANIMALS: 6 ponies. PROCEDURE: A 2.5x2.5-cm full-thickness section of skin was removed from the dorsal aspect of each limb at the midpoint of the metacarpus or metatarsus. Six days later, wounds were grafted with partial-thickness pinch grafts. Half the wounds were bandaged with amnion, and the other half were bandaged with a nonadherent dressing. Bandages were changed every 3 days until wound healing was complete. At each bandage change, numbers of grafts lost were recorded, and wounds were measured. RESULTS: Percentage of grafts lost from wounds bandaged with amnion was not significantly different from percentage lost from wounds bandaged with the nonadherent dressing. Median healing time for wounds bandaged with amnion (30 days) was significantly less than median healing time for wounds bandaged with the nonadherent dressing (39 days). All wounds were healed by day 45. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that amnion can be used for bandaging pinch-grafted wounds on the distal aspect of the limbs of ponies.     

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).