Arthroscopy of the Coxofemoral Joint of Foals

An arthroscopic procedure for examination of the coxofemoral joint was developed in nine foals (four cadavers, five anesthetized) to determine if access was sufficient for evaluation and surgical treatment of intra-articular lesions. The joint was distended and the arthroscope inserted through the notch (incisura trochanterica) between the cranial and caudal parts of the greater trochanter. This portal allowed examination of the cranial, lateral, and caudal aspects of the joint. Mechanical distraction of the joint through an instrument portal located 2 to 4 cm cranial and 1 to 2 cm ventral to the arthroscope portal allowed examination of the ligament of the head of the femur, the femoral head, and articular and nonarticular surfaces of the acetabulum. Adduction and rotation of the limb improved visualization of the craniomedial and caudomedial portions of the femoral head. Traction applied to the distal limb allowed visualization of the same structures that were observed when mechanical distraction was used. Traction also created space for placement of surgical instruments into the joint through the instrument portal. Access to most regions of the joint was adequate, but access to the caudal and medial aspects of the joint was limited. Three foals were killed while they were anesthetized, and their coxofemoral joints were dissected. Two foals were allowed to recover from anesthesia and were observed for 30 days after surgery. One foal was mildly lame for 2 days after surgery. The other foal was not lame after surgery. The incisions healed, and the coxofemoral joints were radiographically normal by postoperative day 30.     

Cardiorespiratory Effects of Combined Midazolam and Butorphanol in Isoflurane-anesthetized Cats

The cardiorespiratory effects of midazolam (0.1 mg/kg) and butorphanol (0.4 mg/kg) were evaluated in seven cats. Cats were induced in a chamber, removed and intubated, and maintained with isoflurane in 100% oxygen. Cardiorespiratory data were recorded before and 3, 10,20,30,40,50, and 60 minutes after intravenous injection of midazolam-butorphanol. Heart rate, mean arterial pressure, and respiration rate were significantly (p < .05) decreased below baseline at various times throughout the study. Tidal volume and minute ventilation were unchanged. End-tidal carbon dioxide was significantly (p < .05) increased above baseline for 30 minutes. Midazolam-butorphanol administered intravenously induced significant alterations in several cardiorespiratory parameters in isoflurane-anesthetized cats.     

Instrumentation of Exercising Thoroughbreds to Determine Blood Gas Tensions and Acid-base Status

A device was constructed of easily obtained medical supplies, and hardware and could be used to obtain multiple arterial samples when manually triggered. The right carotid arteries in five normal horses were surgically elevated, thereby permitting percutaneous cannulation. Each horse was galloped on a 1.6-km test track at approximately 500 m/min, and the rider triggered the mechanism at each 0.4-km mark. Each horse underwent 10 test gallops, and a mean and standard error was determined for each sampling mark including preexercise and postexercise samples. The results indicated that horses ridden under the aforementioned conditions became acidemic and hypoxic.     

In Vitro Loss of Tensile Strength and Elasticity of Five Absorbable Suture Materials in Sterile and Infected Canine Urine

The loss of breaking strength and elasticity of five absorbable suture materials (polydioxanone [PDS-II], polyglycolic acid [PGA], polyglactin 910 [PG-910], polyglyconate [GTMC], and chromic gut) after in vitro incubation in sterile, Escherichia coli- and Proteus mirab/tfs-inoculated canine urine was studied. Biomechanical testing, in a controlled environment, was performed during the 28-day study period. Polydioxanone and chromic gut retained greater than 90% of their original strengths after 28 days of incubation in sterile urine and 87% of original strengths in E. co//-inoculated urine. Polyglyconate retained 24% and 18% of original strength, respectively, after incubation in sterile and E. co/i-inoculated urine for 28 days. Polyglycolic acid and PG-910 retained less than 30% of original strength in sterile urine and only 7% in E. co/i-inoculated urine after 21 days of incubation. In P. m/rabi/is-inoculated urine, loss of tensile strength and elongation was significant for all suture materials. Polyglycolic acid and PG-910 lost all strength after 24 hours of incubation. Polydioxanone lost all strength after 7 days of incubation, whereas GTMC retained 19% at day 7. Chromic gut retained 78% at day 7 and 16% after 21 days of incubation, however, the absence of normal phagocytic destruction of chromic gut in this in vitro study may have artificially elevated these values. In sterile urine with chemically modified pH, loss of strength and elongation was greater in alkaline urine than in neutral or acidic urine for all types of suture materials.     

Evaluation of Thoracic Duct Healing After Experimental Laceration and Transection

Healing of the thoracic duct (TD) was evaluated clinically and histologically in six healthy dogs. A 2.5 cm longitudinal laceration of the caudal TD was created in three dogs and the caudal TD was completely transected in three other dogs. The site of the defect was identified by placing one 4-0 stainless steel suture in the tissue adjacent to the TD defect. All dogs developed a chylous effusion confirmed by biochemical analysis. By five days after surgery in dogs with TD lacerations, and by 10 days after surgery in dogs with TD transections, thoracic effusion had ceased. Lymphangiography, performed seven days after resolution of thoracic effusion, showed TD patency only in the dogs with TD lacerations. The TD did not appear to be patent in dogs with TD transections. Histologically, in dogs with TD lacerations, one moderately dilated lymphatic vessel was seen at the surgical site in one animal and the thoracic duct and other lymphatics in the two other dogs appeared normal. Minimal perivascular accumulations of neutrophils, macrophages, and lymphocytes were present adjacent to two lymphatics in one animal. A mild increase in fibrous connective tissue and neovascularization was present in the adjacent subpleura. In dogs with complete transections, three to six dilated lymphatics were present at the transection site. Mild thickening of the tunica media was present in one thoracic duct, associated with a "J"-shaped area of condensed collagen, presumed to be a collapsed thoracic duct in one animal. Mild to moderate accumulations of macrophages, lymphocytes, and moderate neovascularization was present in the surrounding tissue, separating it from the underlying connective tissue. Healed TDs could not be differentiated histologically from normal TDs.     

Controlled Tissue Expansion in the Distal Extremities of Dogs

Controlled tissue expansion using a 100 cc rectangular silicone elastomer expander was performed in the mid-antebrachium and mid-crus of eight adult mixed-breed dogs. Two expander inflation schedules were followed. Group 1 dogs (n = 4) underwent expander inflation using 10 cc sterile saline every other day, and group 2 dogs (n = 4) underwent expander inflation using 15 cc sterile saline every other day until the nominal volume (100 cc) was attained. Significant mean postexpansion increases in skin surface area of 94.1 cm² (35.9%) and 108.9 cm² (37.3%) were measured in the antebrachium and crus, respectively (p < .05). In a second procedure, the expanders were removed and skin flaps were developed from the redundant tissue generated during the expansion process. Single pedicle advancement flaps and transposition flaps were used to cover surgically created defects measuring 5 times 10 cm in the antebrachium and cms. Single pedicle advancement flaps consistently measured 10 × 10 cm and could be advanced to cover defects involving one third of the mid-antebrachial or mid-crural circumference. Transposition flaps were rotated up to 170 and the donor site defects were easily closed under minimal or no tension. Complications included an abscess in one dog and seroma formation in four dogs. Differences in success or complication rates between group 1 dogs and group 2 dogs were not observed; an accelerated inflation schedule using 15 cc sterile saline every other day was recommended.     

Progression of Femoropatellar Osteochondrosis in Nine Young Horses Clinical, Radiographic and Arthroscopic Findings

The clinical and radiographic progression, and arthroscopic findings for nine young horses (<1 year of age) with femoropatellar osteochondrosis (OCD) are presented. Horses had a 2 to 12 week history of bilateral (8 horses) or unilateral (1 horse) hindlimb lameness. The most consistent clinical signs included femoropatellar joint distention and bilateral hindlimb lameness. At the onset of clinical signs, radiographic lesions were not present (4 horses) or subtle (5 horses), but were easily identified on radiographs taken 4 to 24 weeks later. Arthroscopic surgery was delayed until radiographic changes became obvious. Surgical findings in 20 femoropatellar joints were most commonly osteochondral "flaps" located on the proximal lateral trochlear ridge of the femur and were larger than had been indicated by the radiographs. Eight horses were being used for their intended purpose, which was racing (3 horses were racing and 3 were in race training), dressage (1 horse) or pleasure riding (1 horse). One horse required a second surgery when similar lesions developed in the opposite stifle, and was euthanatized 2 months later because of persistent lameness. Once clinical signs are observed, osteochondrosis lesions of the distal femur can progress in foals younger than 9 months of age and the full extent of the radiographic lesion may take several weeks to develop.     

Cystourethropexy to Correct Refractory Urinary Incontinence Due to Urethral Sphincter Mechanism Incompetence Preliminary Results in Ten Bitches

Cystourethropexy was performed in 10 bitches with refractory urinary incontinence due to urethral sphincter mechanism incompetence. All animals had an abnormally shaped vesico-urethral junction. The bladder neck was located in the pelvic canal in nine dogs (pelvic bladder). Surgery alone restored urinary continence in two cases and markedly improved incontinence in two cases. Surgery combined with medical therapy (phenylpropanolamine, 1.5 mg/kg orally once or twice a day, using a sustained-action preparation) restored urinary continence in four cases and markedly improved continence in one case. Surgery, with medical therapy, was completely ineffective in one case. No major complications were encountered in any dogs. In four cases, histopathologic evaluation of the dorsal bladder wall and neck revealed the presence of a single, perinuclear, clear vacuole in the cytoplasm of smooth muscle fibers. Electron microscopic examination showed that the vacuoles represented a dilatation of normal membrane organelles. Such abnormalities have the potential to alter the smooth muscle motility. This study indicates that cystourethropexy alone restored urinary continence only temporarily in the majority of the patients. The significance and frequency of the histopathologic findings requires further investigation.     

Clinical and Pathologic Effects of a Modified Technique for Application of Spiral Prostheses to the Cervical Trachea of Dogs

A modified surgical technique for application of extraluminal polypropylene spiral prostheses (PSP) to the trachea was developed. A portion of the segmental blood supply to the collapsed segment of trachea was maintained by fenestrating rather than completely dissecting the right lateral pedicle. Polypropylene spiral prostheses were applied to the cervical trachea of 12 dogs (group I) via the modified technique and to 12 dogs (group II) with the identical surgical dissection but without PSP applied. Clinical abnormalities included mild coughing in group I dogs and swelling of the incisions in both groups. Limited necrosis and moderate degeneration and inflammation were observed histologically in both groups. Pathologic changes were worse in the caudal cervical segment of the trachea. Mucosal regeneration was present on day 10 in both groups. Transmural tracheal necrosis was not observed. The modified technique for application of PSP is recommended by the authors because it provides adequate surgical exposure and the blood supply preserved by segmentally dissecting the right lateral pedicle is adequate to maintain tracheal viability.     

Quantitative Ingrowth Analysis of a Porous-coated Acetabular Component in a Canine Model

Histomorphometric analysis of bone ingrowth into a porous-coated acetabular component was evaluated in a canine model. A total of nine prostheses were evaluated, 3 at 6 months, 3 at 12 months, and 3 at 24 months after implantation. All implants were grossly stable at the time of retrieval. The mean percentage of bone ingrowth was 12% at 6 months, 24% at 12 months, and 24% at 24 months. Narrow radiolucent lines noted on microradiographs were more evident at the 6 month time period than at the 12 or 24 month time periods. Bone ingrowth into a porous-coated acetabular component in a weight-bearing model may continue beyond the 6 month time period, and early evaluation of bone ingrowth may underestimate final bone ingrowth.