Leiomyoma of the Small Colon in a Horse

A leiomyoma of the small colon was discovered incidentally in a 4-year-old Thoroughbred gelding during colic surgery to correct large colon displacement. The mass and 20 cm of small colon were resected, and an end-to-end anastomosis was performed. A postoperative fecal impaction proximal to the anastomosis responded after 5 days to administration of intravenous fluids, analgesics, and stool softeners.     

Force Plate Analysis of Triple Pelvic Osteotomy for the Treatment of Canine Hip Dysplasia

Triple pelvic osteotomy was performed in 15 dogs with bilateral hip dysplasia. Ten dogs were treated bilaterally and five dogs were treated unilaterally. Ten untreated dogs with normal hips served as controls. Force plate analysis, lameness evaluation, and radiography were performed before surgery and at weeks 5, 10, 15, and 28. Three dogs treated unilaterally were euthanatized and the hips were examined grossly and microscopically. Force plate data indicated that young dysplastic dogs transmitted significantly less vertical force through the hip joints than normal dogs. The force transmitted through treated hips reached or approached control levels by week 28 and was significantly greater than the force transmitted through untreated hips. Clinical lameness resolved in 92% of limbs and progression of radiographically detectable degenerative joint disease was minimal. Gross and microscopic degenerative changes in the articular cartilage were similar in the treated and untreated hips. The synovial membrane was less reactive in treated hips.     

Hemodynamic Responses of Horses to Anesthesia and Surgery, Before and After Administration of a Low Dose of Endotoxin

Seven horses, which were part of an investigation of the effect of endotoxin administration on vascular reactivity, were anesthetized on two separate occasions for surgical excision of 4-cm sections of palmar digital artery and vein. On the first occasion, the horses were given an infusion of 1 L 0.9% NaCl solution intravenously (IV) just before induction of anesthesia (control); on the second occasion, the horses received an infusion of 1 L 0.9% NaCl containing Escherichia coli endotoxin, 0.1 μg/kg (endotoxin). On both occasions, anesthesia was induced with xylazine, guaifenesin, and ketamine, and maintained with halothane in oxygen. Hemodynamic measurements were made with the horses under anesthesia immediately before beginning surgery (period 1), during skin incision (period 2), during dissection and excision of the vessels (period 3), during skin suturing (period 4), and after completion of surgery during bandaging (period 5). Hemoglobin concentration and mixed venous oxygen content were greater at all periods in horses that received endotoxin. Otherwise, there were no significant differences in hemodynamic parameters between control horses and horses administered endotoxin before beginning surgery (period 1). During surgery and bandaging, horses administered endotoxin had significantly higher heart rate (periods 3, 4, and 5), cardiac index (periods 3, 4, and 5), and oxygen delivery (periods 2, 3, 4, and 5) than did control horses, and mean arterial blood pressure (period 2) and systemic vascular resistance (periods 2, 3, 4, and 5) were less than in control horses. Compared with period 1, surgical stimulation in control horses was associated with increased mean arterial blood pressure and systemic vascular resistance (periods 2, 3, 4, and 5), but cardiac index and oxygen delivery were decreased (periods 3, 4, and 5). In contrast, horses administered endotoxin responded to surgical stimulation with increased mean arterial blood pressure (periods 2, 3, 4, and 5) and vascular resistance (periods 4 and 5), as well as a heart rate-induced increase in cardiac index (periods 2, 3, 4, and 5) compared with period 1; oxygen delivery also increased (periods 2, 3, 4, and 5) during surgery in the endotoxin group. This study documents some of the differences in the response to anesthesia and surgery between normal horses and those that have received endotoxin.     

Effects of Three Intramedullary Pinning Techniques on Proximal Pin Location and Articular Damage in the Canine Tibia

The effects of three different techniques of intramedullary (IM) pin placement on pin location and incidence of stifle joint injury were evaluated using 70 cadaver canine tibiae after middisphyseal osteotomy. In 50 tibiae, pins were placed retrograde in either a nondirected (group A) or a craniomedially directed fashion (group B) with 25 tibiae in each group. Pins were driven normograde (group N) in 20 tibiae. All the stifles were dissected to qualitatively evaluate pin interference with different joint structures. End-on radiographs of the tibial plateaus were used to quantitatively evaluate pin location. Interference with the caudal cruciate ligament, medial meniscus, lateral meniscus, or meniscal ligaments was not observed in any group. There was a significant association between pinning technique and incidence of involvement of the cranial cruciate ligament ( P < .005), patella ( P < .001), patellar ligament ( P < .005), and femoral condyle ( P < .01). Pin location for group A was significantly different from either other group in a cranial-caudal direction ( P = .003), and was significantly different from group N in a medial-lateral direction ( P = .005). No significant difference was observed between pin location for groups B and N in either plane. It was concluded that although nondirected retrograde pinning cannot be recommended, retrograde pins directed craniomedially may be an acceptable technique for the repair of proximal to mid-diaphyseal tibial fractures if care is taken to properly seat the pins.     

Evaluation of an Autologous Tendon Graft Repair Method for Gap Healing of the Deep Digital Flexor Tendon in Horses

A sutured tenorrhaphy technique that incorporated an autologous tendon graft was compared mechanically and histologically with a sutured tenorrhaphy at 6, 12, and 24 weeks after repair. Tenorrhaphy was performed in the forelimb tendon of the deep digital flexor muscle and the graft was taken from the hindlimb tendon of the lateral digital extensor muscle; one forelimb site included the graft, whereas the other forelimb site was not grafted. Tenotomies were made immediately proximal to the insertion of the accessory ligament into the tendon of the deep digital flexor muscle. Grafted and nongrafted tenorrhaphies were sutured with 2 polydioxanone in a modified double locking-loop pattern. Limbs were supported with a bandage and an extended elevated heel shoe that maintained the dorsal hoof wall angle at 70° to 75°; this support was removed at 12 weeks and dorsal hoof wall angle was maintained at 40° to 45° for the remainder of the study. Gap formation (2.5 ±.3 cm) was evident at all tenorrhaphy sites at 3 days on ultrasound examination. In grafted repairs, the breaking stress was increased ( P <.001) between 6 weeks (2.56 ±.44 MPa) and 12 weeks (17.69 ± 7.68 MPa), with grafted tendon having a greater breaking stress than nongrafted tendon (8.77 ± 2.5 MPa; P <.05). No differences in breaking stress were evident at 24 weeks. At 12 weeks, repair tissue in grafted tendon was histologically more mature, had less cellularity, better fibroblast orientation and more homogeneous collagen matrix than nongrafted tendon. Polydioxanone suture was still evident histologically at 24 weeks and was associated with minimal cellular reaction. Incorporation of an autologous tendon graft improved the mechanical properties and histological quality of the repair tissue in equine flexor tenorrhaphies at 12 weeks but not at 24 weeks after repair.     

Development of Parenchymal Abdominal Organ Models for Use in Teaching Veterinary Soft Tissue Surgery

Models of the canine spleen, kidney, and liver were made from soft plastic to simulate the organs of the live animal as closely as possible in appearance and tissue handling properties. Each organ model was independently evaluated by five small animal surgeons who performed several common surgical procedures on each model. All models had a realistic appearance and, with the exception of one tissue handling problem with the kidney model, and one with the liver model, tissue handling properties of the models were comparable to those of the organs in the live animal. All models were useful for teaching each of the procedures evaluated.     

Complete Excision of a Fractured Fourth Metatarsal Bone in Eight Horses

Proximal open comminuted fractures of the fourth metatarsal bone (Mt IV) in eight horses were treated by complete removal of the affected bone and antimicrobial therapy. Two horses had concurrent septic arthritis of the tarsocrural or distal tarsal articulations, and five horses had radiographic evidence of osteomyelitis and sequestration of the affected bone. Five horses became athletically sound for their intended use, two horses with septic arthritis had residual lameness but were pasture sound, and one horse was lost to follow-up. Excision of the entire bone appears to be an acceptable treatment of open comminuted fractures of the proximal one-third of Mt IV that do not respond to more conservative modes of therapy.     

Healing Characteristics of Free and Pedicle Fat Grafts after Dorsal Laminectomy and Durotomy in Dogs

Dorsal laminectomy and durotomy were performed at thoracic vertebrae 12 and 13 (T12-T13) and lumbar vertebrae 1 and 2 (L1-L2) in 12 normal dogs. A free fat graft harvested from subcutaneous tissue adjacent to the incision was placed over the T12-T13 laminectomy site. A 75 X 25 X 5 mm pedicle fat graft harvested from a similar location was placed over the L1-L2 laminectomy site. Three dogs each were euthanatized at weeks 2, 4, 8, and 16. With both types of fat grafts, an initial inflammatory stage reduced the size of the graft approximately 50%. Axonal degeneration and demyelination of the spinal cord resolved by week 16. At week 16, the durotomy sites had healed, but the dura mater was adhered to the spinal cord. No difference between the grafts could be demonstrated by antemortem myelography and cerebrospinal fluid analysis. There was no demonstrable advantage to the use of pedicle fat grafts.     

Closed System Delivery of Halothane and Isoflurane with a Vaporizer in the Anesthetic Circle

Forty-four healthy dogs undergoing elective ovariohysterectomy were anesthetized with halothane or isoflurane delivered with an in-circuit vaporizer with closed system flow rates or an out-of-circuit vaporizer with semi-closed system flow rates. When dogs were anesthetized with halothane, there were no differences in heart rate, blood pressure, body temperature, respiratory rate, or lingual venous pH, PCO2, or PO2 during induction and maintenance. Lingual venous PO2 was significantly less but still within a clinically acceptable range when isoflurane was used in an in-circuit vaporizer. Recovery times tended to be longer with in-circuit vaporizers. The amount of anesthetic used was not affected by vaporizer location. In-circuit vaporizers were suitable for delivery of halothane or isoflurane to healthy dogs.