Computed tomographic imaging of the equine head.

The head from three horses euthanized due to diseases unrelated to the head and neck was imaged using computed tomography (CT). Gross cross-sectional slices of equine head #1 and skeleton of equine head #2 were compared with the CT images of the three equine heads to identify normal structures of the cranium, brain, paranasal sinuses, nasal cavity, and teeth. Labeled transverse CT images of the equine head are presented sequentially as a reference for normal anatomy.

Removal of large fragments of the extensor process of the distal phalanx via arthrotomy in horses: 14 cases (1992-1998).

OBJECTIVE: To evaluate the outcome of horses with large fragments of the extensor process of the distal phalanx that were removed by use of arthrotomy. DESIGN: Retrospective study. ANIMALS: 14 horses with large fragments of the extensor process of the distal phalanx. PROCEDURE: Medical records for horses with large fragments of the extensor process that were removed by use of arthrotomy were reviewed. Data retrieved from medical records included signalment, use of horse, affected limb, lameness history, lameness examination findings, radiographic findings, surgical technique, and outcome. Follow-up evaluation was obtained by telephone interview. RESULTS: Most affected horses were < 5 years old and had a history of chronic lameness. Lameness grade ranged from 1/5 to 4/5. Fragments involved 20 to 45% of the dorsopalmar articular surface of the distal phalanx. Eight of 14 horses had a successful outcome. Outcome was not associated with age, duration or severity of lameness, or fragment size. CONCLUSIONS AND CLINICAL RELEVANCE: Despite involvement of a large portion of the articular surface and use of arthrotomy, joint instability and permanent soft tissue injury was not a problem in most horses. Outcome may be improved by selection of horses with lameness of < 2 years' duration and careful management after surgery. A fair prognosis may be anticipated for removal of large fragments of the extensor process via arthrotomy.

Idiopathic focal eosinophilic enteritis associated with small intestinal obstruction in 6 horses.

OBJECTIVE: To report the history, clinical findings, and outcome of horses with idiopathic focal eosinophilic enteritis associated with acute small intestinal obstruction. STUDY DESIGN: Retrospective study. ANIMALS: Six horses with idiopathic focal eosinophilic enteritis. METHODS: Retrospective review of medical records of horses with idiopathic focal eosinophilic enteritis, with acute abdominal pain and small intestinal obstruction, associated with a focal region of eosinophilic enteritis of unknown cause. Information retrieved from the medical records included signalment, physical examination, laboratory findings, surgical procedure, histologic diagnosis, and postoperative management. Outcome was determined by telephone communication with owners. RESULTS: Six horses met the selection criteria. Horses had persistent pain, distended small intestine, and nasogastric reflux. Idiopathic focal eosinophilic enteritis lesions associated with a small intestinal obstruction were treated surgically by intestinal resection and anastomosis or wedge resection. There were no observed complications associated with extension of the disease from the lesion site. Five horses were alive at follow-up 5 to 60 months after surgery. CONCLUSIONS: Although the cause of these focal eosinophilic enteritis lesions is unknown, the long-term outcome after lesion resection was favorable. CLINICAL RELEVANCE: Small intestinal obstruction associated with a focal eosinophilic enteritis lesion may be a cause of acute abdominal pain in horses. Horses apparently have a good prognosis after lesion resection.

Desmotomy of the accessory ligament of the superficial digital flexor tendon in the horse with use of a tenoscopic approach to the carpal sheath.

OBJECTIVE: To describe a tenoscopic approach to the carpal sheath for desmotomy of the accessory ligament of the superficial digital flexor tendon. STUDY DESIGN: The surgical procedure was developed with use of normal forelimbs from equine cadavers and experimental horses. ANIMALS OR SAMPLE POPULATION: Twelve equine cadaveric forelimbs, 4 forelimbs from 2 horses anesthetized for terminal surgical laboratories, and 10 forelimbs from five experimental horses were used. METHODS: The limbs were positioned lateral side up with the carpus slightly flexed. After distention of the carpal sheath, a portal was made approximately 2 cm proximal to the distal radial physis for arthroscope insertion. An instrument portal was made approximately 0.2 cm proximal to the distal radial physis. After flexion of the limb to 90 degrees, the accessory ligament of the superficial digital flexor tendon was palpated and desmotomy was performed. Cadaveric limbs were dissected to confirm complete desmotomy. Experimental horses were monitored for short- (perioperative) and long- (4 weeks) term postoperative complications. RESULTS: A tenoscopic approach to the carpal sheath provided adequate surgical access to the accessory ligament of the superficial digital flexor tendon for desmotomy. Most of the accessory ligament of the superficial digital flexor tendon could be easily seen within the sheath, except for the proximal 2 cm that could be readily palpated and subsequently transected. Important technical considerations were location of the arthroscope portal, adequate sheath distention, limb flexion to 90 degrees, and desmotomy location. It was beneficial, but apparently not essential, to avoid the proximal perforating vessel. Postoperatively, some horses had swelling but were not lame and had normal range of motion of the carpus. CONCLUSIONS: Desmotomy of the accessory ligament of the superficial digital flexor tendon could be performed by using a lateral tenoscopic approach to the carpal sheath. CLINICAL RELEVANCE: Desmotomy of the accessory ligament of the superficial digital flexor tendon by using a tenoscopic approach to the carpal sheath is an alternative technique to the medial incisional approach.

Tenoscopic anatomy of the equine carpal flexor synovial sheath.

OBJECTIVE: To describe the tenoscopic anatomy of the carpal sheath of the flexor tendons (carpal sheath) viewed from a lateral approach. STUDY DESIGN: Tenoscopic observation of structures within the carpal sheath subsequently confirmed by dissection. ANIMALS OR SAMPLE POPULATION: 12 equine cadaveric forelimbs. METHODS: The limbs were positioned lateral side up with the carpus slightly flexed. After distention of the carpal sheath, a portal for the arthroscope was made approximately 3 cm proximal to the distal radial physis and 2.5 cm caudal to the radius between the tendons of the ulnaris lateralis and lateral digital extensor muscles. RESULTS: A lateral tenoscopic approach was adequate to identify all structures within the carpal sheath. From proximal to distal, structures identified using this approach were the radial head of the deep digital flexor muscle, accessory ligament of the tendon of the superficial digital flexor muscle, distal radial physis, tendons of the superficial and deep digital flexor muscles, accessory carpal bone, antebrachiocarpal and middle carpal joints, and vincula of the tendon of the deep digital flexor muscle. CONCLUSIONS: A lateral tenoscopic approach offered an easy, repeatable entry into the carpal sheath and allowed good observation of all structures within the sheath except for the medial borders of the tendons of the deep and superficial digital flexor muscles. CLINICAL RELEVANCE: Applications of a lateral tenoscopic approach to the carpal sheath include diagnostic procedures, lavage and synovial resection for septic tenosynovitis, desmotomy of the accessory ligament of the tendon of the superficial digital flexor muscle for flexural deformity or tendinitis, and removal of osteochondromas from the distal radial metaphysis.

Lateral approach for endoscopic removal of solitary osteochondromas from the distal radial metaphysis in three horses.

A lateral approach to the carpal sheath was used for endoscopic removal of osteochondromas from the distal aspect of the radius in 3 horses. Previously osteochondromas have been removed through an incision into the carpal sheath; however, endoscopy is less invasive, requires less surgery and convalescence time, provides better cosmetic results, is associated with a lower risk of infection, and allows better examination of structures within the sheath. A medial approach for endoscopic removal has been described previously; however, the lateral approach was advantageous, because it avoided the median vein, artery, and nerve and because the sheath was more easily distended from the lateral approach. Therefore, this approach may be an alternative for removal of osteochondromas from the distal aspect of the radius in horses.

Bacterial culturing of ventral median celiotomies for prediction of postoperative incisional complications in horses.

OBJECTIVE: The purpose of this study was to determine whether detection of bacterial contamination of ventral midline incisions was predictive of postoperative incisional complications in horses undergoing exploratory celiotomy for colic. STUDY DESIGN: Prospective study. ANIMAL OR SAMPLE POPULATION: Horses that had ventral median celiotomies for colic at Colorado State University between May 1, 1991 and April 30, 1993 were studied prospectively. Complete information was obtained on 66 horses. METHODS: Bacterial cultures were obtained from ventral midline incisions at surgery. Information regarding the type of surgery performed (celiotomy vs celiotomy plus enterotomy or enterectomy), preoperative total nucleated cells and presence of a left shift, postoperative fever (> 38.5 degrees C), incisional drainage, incisional herniation, and outcome were obtained from medical records. Additional information concerning incisional drainage, herniation, and survival was obtained at a minimum of 18 months after surgery. RESULTS: Examination of odds ratio (ORs) and confidence intervals (CIs) revealed that a celiotomy plus enterotomy or enterectomy was positively, but not significantly, associated (OR > 1) with positive culture results, presence of incisional drainage and incisional herniation. A significant association between incisional drainage and hernia formation was found; odds of incisional herniation were 62.5 times greater in horses that had incisional drainage. Incisional drainage and herniation were negatively associated with patient survival. The later association was significant (OR = 0.18, P = .04). CONCLUSIONS: This study indicated that detection of bacterial contamination at incisional closure by the swab culture technique was not beneficial in the prediction of postoperative incisional problems in horses undergoing colic surgery. Incisional drainage or infection appeared to be associated with hernia formation. CLINICAL RELEVANCE: Immediate treatment of incisional drainage or method to prevent incisional infections may decrease hernia formation.

Abnormalities in oxygenation, coagulation, and fibrinolysis in colonic blood of horses with experimentally induced strangulation obstruction.

OBJECTIVE: To measure arterial and venous blood gas, coagulation, and fibrinolysis variables in blood from isolated segments of control and ischemic large colons for the purpose of identifying variables for rapid, indirect assessment of colonic mucosal injury. DESIGN: Variables were determined at specific intervals during the 4-hour study (3 hours of ischemia and 1 hour of reperfusion). ANIMALS: Seven clinically normal horses between 2 and 15 years old. PROCEDURES: Horses underwent laparotomy and occlusion of the lumen and vasculature of the mid-portion of the pelvic flexure of the large colon. During ischemia of 1 randomly-chosen colonic segment, variables were measured to determine colonic mucosal damage and were compared with histologic scores of colonic biopsy specimens. RESULTS: Significant (P < 0.05) differences from control values were observed over time for venous pH, PCO2, PO2, oxygen saturation, oxygen content, arteriovenous oxygen difference, and lactate and glucose concentrations. Mean histologic scores of biopsy specimens obtained from ischemic colons were significantly (P < 0.05) greater (indicating greater damage) than those from control colons, and increased significantly (P < 0.05) with duration of ischemia. CONCLUSIONS: Venous lactate, oxygen saturation, and PO2 values were the most significant predictors of the severity of histologic damage within the ischemic colons (R2 = 0.661). CLINICAL RELEVANCE: Venous blood gas and lactate values in the large colon are good predictors of the amount of intestinal damage incurred during 3 hours of ischemia, and may be clinically useful for the rapid determination of colonic viability.

Evaluation of occlusive dressings for management of full-thickness excisional wounds on the distal portion of the limbs of horses.

Two 2.5-cm2 full-thickness skin wounds were created surgically over the lateral aspect of the cannon bone of each limb of 6 horses (n = 48 wounds). Dressings evaluated were a nonadherent gauze pad (group 1); a synthetic semiocclusive dressing, (group 2); equine amnion (group 3); and a synthetic fully occlusive dressing (group 4). Wounds were assessed subjectively at each dressing change, and total wound area, area of granulation tissue, and area of epithelium in each wound were determined by computerized digital analysis of photographs of the wounds. Complete healing time (wound covered by epithelium) also was determined for each wound. Statistical comparisons were made, using Kruskal-Wallis analysis and a Mann-Whitney U test. Median time to complete healing was: group 1, 53 days; group 2, 71 days; group 3, 63 days; and group 4, 113 days. Time to complete healing was significantly longer for wounds of group-4 horses than all other groups, and wounds of group-1 horses healed faster than did those of group-2 horses (P < 0.05). Wounds in group-4 horses required significantly (P < or = 0.05) more excisions of granulation tissue (median, 11.5 times) than did those in group-1 (median, 3.5), group-2 (median, 5.5) or group-3 (median, 2.5) horses. Epithelial tissue was detected later in wounds of group-4 horses (median, 27 days) than in wounds of horses in groups 1, 2 or 3 (median, 17 days); however, this difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Reconstructive surgery of selected injuries of the head.

Traumatic injuries to the head region of the horse are a common presenting complaint. Because of a copious blood supply, these wounds typically exhibit a tremendous capability for healing. By following the basic principles of wound management and employing a few techniques unique for specific injuries, the healing of these wounds can result in a satisfactory outcome.

Intestinal fibrosis with partial obstruction in five horses and two ponies.

Fibrosis of the small intestine led to recurrent colic and weight loss in 2 ponies and 5 horses. There was a reduction in the length of the small intestine to one-half normal in horses 4 to 7. Histologic examination revealed substantial small intestinal submucosal fibrosis and arteriole sclerosis. The cause was not determined, but an environmental factor was suspected because 3 horses were from the same farm and the other animals were from within a 10-mile radius of the farm. The submucosal fibrosis appeared to be secondary to sclerosis of arterioles in the submucosa and mesentery, with low blood flow state or altered vessel permeability.

Respiratory stridor associated with polymyopathy suspected to be hyperkalemic periodic paralysis in four quarter horse foals.

Four Quarter Horse foals ranging in age from 6 days to 2 months were determined to have upper airway stridor secondary to polymyopathy suspected to be hyperkalemic periodic paralysis. Electromyography revealed spontaneous muscle activity in all muscles examined. Electromyographic findings were similar in the dams of 3 foals (No. 1, 3 and 4). Hyperkalemia was found in foals 1 and 4. Endoscopically, the upper airway stridor in foals 1 and 3 was confirmed to be attributable to laryngeal and pharyngeal collapse or spasm. Foals 1, 2, and 3 were treated with acetazolamide. Foal 4 was not treated, at the owner's request. Foals 2 and 3 improved with treatment, foal 4's condition was static, and foal 1 required a tracheostomy and laryngeal surgery to manage its upper airway stridor.

Multivariable prediction model for the need for surgery in horses with colic.

A survey of 1,965 equine colic cases was conducted from August 1985 to July 1986 at 10 equine referral centers located throughout the United States. The purpose of this study was to develop and validate a multivariable model for the need for surgery. Two-thirds of the cases were randomly selected for model development (1,336), whereas the remaining cases (629) were used only for subsequent validation of the model. If a lesion requiring surgical correction was found at either surgery or necropsy, the case for the horse was classified as surgical, otherwise the case was classified as medical. Only variables that were significant (P less than 0.05) in an initial bivariable screening procedure were considered in the model development. Because of the large number of missing values in the data set, only variables for which there were less than 400 missing values were considered in the multivariable analysis. A multivariable logistic regression model was constructed by use of a stepwise algorithm. The model used 640 cases and included variables: rectal findings, signs of abdominal pain, peripheral pulse strength, and abdominal sounds. The likelihood ratio for surgery was calculated for each horse in the validation data set, using the logistic regression equation. Using Bayes theorem, the posttest probability was calculated, using the likelihood ratio as the test odds and the prevalence of surgery cases (at each institution) as an estimate of the pretest odds. A Hosmer-Lemeshow goodness-of-fit chi 2 statistic indicated that the model fit the validation data set poorly, as demonstrated by the large chi 2 value of 26.7 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Traumatic injuries involving tendons of the distal limbs in horses: a retrospective study of 55 cases.

Fifty-five horses were presented to Colorado State University Veterinary Teaching Hospital between 1st of January 1980 and 31st of December 1989 for treatment of distal limb lacerations involving flexor tendons (n = 35) or extensor tendons (n = 20). Of the 35 flexor tendon lacerations, 11 horses were killed without treatment and 24 horses were treated. Twenty-two horses were included in determining outcome. Four (18 per cent) returned to their original level of use, nine (41 per cent) returned to limited riding, seven (32 per cent) returned to breeding or pasture soundness and two (9 per cent) were killed. Eighteen of the 20 horses with extensor tendon lacerations underwent treatment and 15 had sufficient follow-up to determine outcome. Seven (47 per cent) returned to their original or intended use, five (33 per cent) returned to limited use, one (7 per cent) was used for breeding and two (13 per cent) were killed. Results for horses with extensor tendon lacerations support previous reports that these injuries can be treated successfully. Results for horses having flexor tendon lacerations were better than in previous reports.

Alteration in intestinal morphologic features associated with extensive large-colon resection in horses.

Light microscopy, morphometry, and scanning electron microscopy were used to examine the mucosal morphologic features of 7 intestinal specimens (3 from the small intestine; 4 from the large intestine) from each of 8 horses 1 year after sham operation (group 1; n = 3) or extensive large-colon resection (group 2; n = 5). Qualitative light microscopic examination did not reveal differences between groups, but morphometry revealed significantly (P less than 0.05) greater intercrypt area and distance in horses with colon resection and this was most pronounced in the cecum and remaining right ventral and dorsal colon. Crypt area and depth were similar for horses with colon resection and sham operation (P greater than 0.05). Qualitative evaluation of the scanning electron micrographs revealed more prominent crypt orifices in the large intestine of horses with colon resection. The larger intercrypt distance in the colon of horses with resection was not an obvious feature of the qualitative evaluation of the surface with scanning electron microscopy. Small intestinal morphologic features were variable and significant differences were not detected between horses with sham operation and colon resection. Horses adapted to extensive large-colon resection within 1 year by increasing the absorptive (intercrypt) surface area of the remaining large intestine.

Alteration of intestinal enzyme activities associated with extensive large-colon resection in horses.

Lactase, maltase, sucrase, and alkaline phosphatase activities were determined in the intestinal mucosa from 3 locations in the small intestine and 4 locations in the large intestine 1 year after extensive large-colon resection (group 1; n = 5) and 1 year after sham operation (group 2; n = 3) in horses. Lactase, maltase, and sucrase activities were similar (P greater than 0.05) between group-1 and group-2 horses in all locations measured in the intestinal tract. Alkaline phosphatase activity in the remaining large colon of group-1 horses was significantly (P less than 0.05) greater than the activity in the large colon of group-2 horses. Decreased apparent digestion of phosphorus and a negative phosphorus balance are persistent features of large-colon resection in horses. Increases in alkaline phosphatase activity in the remaining colon of horses with extensive large-colon resection may be a specific functional adaptive mechanism that attempts to counteract the derangements in phosphorus metabolism.

A comparison of repair methods for gap healing in equine flexor tendon.

In nine horses (18 forelimbs), a 3 cm section of superficial digital flexor tendon was removed and the tendons were repaired with immobilization for 6 weeks and (1) no suture (n = 6); (2) a double locking loop tenorrhaphy with carbon fiber (n = 6); or (3) a double locking loop tenorrhaphy with size 2 nylon suture (n = 6). Clinical assessment, gross evaluation, morphometry, histology, and mechanical testing were performed on two limbs from each treatment group at weeks 6, 12, and 24. At weeks 6 and 12, the unsutured tissue was less mature than the tissue sutured with nylon. By week 24, the carbon fiber repair had breaking stress (mean, 12.5 M Pa) similar to the unsutured repair (mean, 10.6 M Pa). There was necrosis and a granulomatous foreign body reaction around the carbon fiber. The nylon suture repair had significantly greater strength per unit area (mean breaking stress, 20.4 M Pa) because of a smaller area of repair tissue in the gap (mean, 3.6 cm2). At week 24, the nylon suture repair tissue was the most mature with the least inflammation of the three repair methods. A nylon double locking loop suture was the preferred method for equine flexor tenorrhaphy of a tendon gap because of greater breaking stress, histologic maturity, biocompatibility, and the adequate functional and cosmetic outcome.

Failure to demonstrate reperfusion injury following ischaemia of the equine large colon using dimethyl sulphoxide.

A study was undertaken to evaluate the significance and mechanism of reperfusion injury in the equine large colon following 1 h of haemorrhagic strangulation obstruction (HSO) or ischaemic strangulation obstruction (ISO) and to assess the effect of treatment with dimethyl sulphoxide (DMSO). ISO or HSO were created 40 cm from the pelvic flexure and maintained for 60 mins under general anaesthesia. Normal saline or 20 per cent DMSO (1 g/kg bodyweight) was administered intravenously 10 mins prior to the end of the ischaemic period. Four groups of four horses in a 2 x 2 factorial design were used. Treatments of HSO or ISO and DMSO given (yes or no) were utilised. Intestinal wall biopsies and right colic arterial and venous blood samples were taken at 0, 60, 90 and 120 mins following initiation of the obstructions. Histological evaluation of the intestine using haematoxylin and eosin stained sections and immunohistochemical staining for albumin were performed. Mucosal and serum reduced glutathione (GSH) and oxidised glutathione (GSSG) levels and the amount of lymphatic dilatation with albumin and submucosal pooling of albumin were used as indirect measures of oxygen free radical production. Histopathological changes were minimal after 1 h of either type of ischaemia. Progressive changes during the post ischaemic period were minimal for ISO and moderate for HSO. Serum GSH and GSSG levels were not detectable. There was no demonstrable benefit of DMSO treatment as assessed by histology, immunohistochemistry or preservation of GSH levels in the mucosa. In conclusion, a reperfusion injury following 60 mins of ischaemia could not be detected in this study.

Mechanical properties of four suture patterns for transected equine tendon repair.

Thirty-six superficial digital flexor tendons from nine fresh equine cadavers were transected and sutured with size 2 monofilament nylon. Nine tendons were repaired with each of four suture patterns: single-locking loop, double-locking loop, triple-locking loop, or three-loop pulley. The times required for application, tensile strengths, resistance to distraction (gap), and modes of failure were analyzed. The mean times required were: single-locking loop, 3 mins, 15 secs; double-locking loop, 4 mins, 15 secs; triple-locking loop, 10 mins, 50 secs; and three-loop pulley, 4 mins. The double-locking loop, triple-locking loop, and three-loop pulley suture patterns were stronger than the single-locking loop. The triple-locking loop and three-loop pulley patterns were close in strength and only the triple-locking loop was stronger than the double-locking loop. The three-loop pulley had the greatest resistance to gap formation and its mode of failure was different from the others. The three-locking loop suture patterns failed by suture breakage but the three-loop pulley failed first by suture pull-out and then by suture breakage.