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.

Sensory nerve conduction velocity of the caudal cutaneous sural and medial cutaneous antebrachial nerves of adult horses.

Maximal conduction velocities of compound action potentials evoked by stimuli of 2 times threshold in the caudal cutaneous sural (CCSN) and medial cutaneous antebrachial (MCAN) nerves were determined by averaging potentials evoked and recorded through percutaneous needle electrodes. Mean maximal conduction velocities of compound action potentials were: CCSN = 61.3 +/- 2.0 meters/second (m/s) and MCAN = 56.4 +/- 2.8 m/s. To confirm accuracy of our percutaneous recordings, compound action potentials were recorded through bipolar chlorided silver electrodes from the exposed surfaces of fascicles of the CCSN and the MCAN. The maximal conduction velocities of these potentials were in agreement with the conduction velocities of compound action potentials that were evoked and recorded through percutaneous needle electrodes. The specificity of stimulating and recording sites was verified by recording before and after section of the nerves. Stimuli from 3 to 5 times threshold evoked a second, longer latency, compound action potential that consisted of a variable number of components in the CCSN and MCAN. The configurations and conduction velocities of the shorter latency potentials were the same as those of the single compound action potentials evoked by stimuli of 2 times threshold. Mean conduction velocities of the longer latency potentials were: CCSN = 24.4 +/- 2.6 m/s and MCAN = 24.5 +/- 2.2 m/s. Needle electrode and direct stimulation of either the CCSN or the MCAN at 3 to 5 times threshold failed to evoke contractions of limb muscles. Therefore, action potentials that contributed to the evoked compound potentials recorded in these horses arose, most likely, from afferent nerve fibers.

Clinical anatomy of the equine head.

This topical presentation emphasizes the structures most likely to be encountered in the diagnosis and treatment of diseases of the equine head. Most of the approaches are from superficial to deep. Anatomic variations associated with aging are described. The larynx and guttural pouches are not included in this article.

Effect of dietary fat and aging on adipose tissue cellularity in mice differing in genetic predisposition to obesity.

A line of mice had been developed which became obese when fed a commercial mouse breeder chow. This obese line was compared to a non-obese line at various ages to determine whether the type or amount of dietary fat would affect adipocyte size and number. Experimental diets containing beef tallow (38% of calories as beef fat and 2% as corn oil), corn oil (40% corn oil) or low fat (2% corn oil) were provided ad libitum at the time of weaning. Dorsoscapular subcutaneous fat pads were removed at 5, 6, 7, and 8 weeks and at 3, 6, 9, 12, 15, 18, and 21 months of age. Adipocyte size and number were determined histologically. Obese mice had enhanced adipocyte hyperplasia compared to the non-obese line. Only when eating the low fat diet did the obese mice have life-long elevated hypertrophy compared with their non-obese counterparts since non-obese mice responded to high fat feeding with a dramatic increase in adipocyte volume, regardless of type of fat. Body weight was greater in the obese line at all ages studied; however, some overlap in body weight was encountered between non-obese mice fed the high fat diets and genetically obese mice. Non-obese mice fed the low fat diet were smaller than mice in all other treatment groups throughout the study. Weight of the dorsoscapular subcutaneous adipose tissue was consistently greater in the obese line; however, high fat feeding greatly increased fat pad weight in non-obese mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Anatomical and functional communications between the synovial sacs of the equine stifle joint.

The anatomical and functional communications of the synovial sacs of the equine stifle joint were evaluated in 50 stifle joints of 25 horses. Femoropatellar joint (FPJ) sacs were injected with 50 ml of gelatin-based dye and horses were then walked for 50 m. Horses were subsequently killed, the stifle joints dissected and the location of the dye recorded. Twenty-three horses (46 joints) had clinically normal stifle joints and in this group, anatomical communications of the stifle joints were bilaterally symmetrical in each horse. In 15 of these 23 horses (65 per cent), direct anatomical communication between the FPJ sac and the medial sac of the femorotibial joint (FTJ) was demonstrated. The FPJ sac communicated with both the medial and lateral sacs of the FTJ in four of these 23 horses (17.5 per cent). There were no anatomical communications between the FPJ sac and either sac of the FTJ in the remaining four horses (17.5 per cent). Functional communication, which was established by finding dye in the FTJ sacs were anatomical communication with the FPJ sac existed, was demonstrated in 14 of 19 horses (74 per cent). Two horses were affected with degenerative joint disease of one stifle joint. In both of these joints the FPJ sac communicated with both the medial and lateral FTJ sacs. This distribution was different from that of the contralateral joint. When performing intra-articular anaesthesia of equine stifle joints, each synovial sac needs to be injected separately to ensure that anaesthesia of the appropriate synovial sac is obtained.

Morphologic measurements of the external horizontal ear canal of dogs.

Microscopic anatomy of the horizontal part of the external ear canal was evaluated in 24 dogs. Sixteen dogs were from breeds known to have a predisposition to otitis externa. The remaining 8 dogs were from breeds that do not have a predisposition to otitis externa. Dogs were separated into groups according to predisposition to otitis externa: group 1-predisposed dogs without otic inflammation, group 2-predisposed dogs with otic inflammation, and group 3-nonpredisposed dogs without otic inflammation. Qualitative microscopic evaluation of distribution of hair follicles revealed hair within proximal, middle, and distal regions of the horizontal ear canal in all breeds. The degree of keratinization was directly proportional to the presence of otic inflammation and was excessive in group-2 dogs. Quality of sebaceous glands within the horizontal ear canal was similar among dogs with and without otitis externa, whereas the quantity of apocrine tubular glands was significantly increased (P less than 0.05) in dogs with otitis. Quantity of apocrine tubular glands was also greater in group-1 dogs than in group-3 dogs. Thickness of the soft tissue in the external ear canal increased in direct proportion to the progression of disease and was greatest in the proximal region of the affected ear canal. Soft tissue located caudally between nonopposing ends of the annular cartilage, within the proximal region of the horizontal ear canal, contained few glands and hair follicles in dogs without otitis externa. In dogs with otitis externa, this region was infiltrated by distended apocrine tubular glands.

Clinical anatomy of the equine foot.

A review of investigations of the functional anatomy of the equine foot is presented. Emphasis is placed on the relationships of structures involved in the major diseases of the foot.

Host response to bovine ocular squamous cell carcinoma.

Specific humoral and cellular immunologic responses to autologous and heterologous tumors were evaluated in 35 Hereford cows with ocular squamous cell tumors and in 6 healthy cows. Sera from 5 healthy cows and 23 ocular tumor-bearing cows were evaluated for antibody to tumor, using radioimmunoassay, passive hemagglutination, agglutination, and microagglutination assays with various soluble tumor antigen and whole tumor cell preparations. Antibody to tumor was detected in only 2 cows. Using the microagglutination assay, antibody to autologous and heterologous tumor cells was found in the sera of 2 cows inoculated intraocularly with purified, viable autologous tumor cells. Twenty-eight tumor-bearing cows and 3 healthy cows were evaluated for delayed-type hypersensitivity responses, using 5 tumor preparations; positive skin test responses were not observed.

Current concepts in the treatment of bovine ocular squamous cell tumors.

Usually 10 per cent or fewer of the ocular squamous cell tumors in a Hereford cow herd are true carcinomas. Around 30 per cent of the benign tumors regress spontaneously, and squamous cell carcinomas may arise ab initio without progressing from a grossly visible "precursor" lesion. Differential gross and cytologic features assist in making accurate diagnoses of the disease and determining the treatment. Radiation therapy, immunotherapy, surgery, and, in particular, cryosurgery have been employed successfully in the treatment of bovine ocular squamous cell tumors. RF current-induced hyperthermia is an easily performed, highly effective method for treating small squamous cell tumors, causing regression in over 90 per cent of the cases; surgical removal of similar tumors causes regression in only 46 per cent of the cases. A management protocol for controlling losses due to ocular squamous cell tumors in a Hereford or Simmental cow herd includes: Periodic observation of all susceptible cattle. Hyperthermic treatment of all small tumors; orbital exenteration in cases of large, noninvasive carcinomas on the globe or palpebrae; shipment to slaughter of animals with invasive or metastatic disease. Genetic control through careful record keeping and culling.

Autotransplantation of bovine ocular squamous cell carcinoma and effects on primary tumor growth.

Autologous transplantation of ocular squamous cell carcinoma was done in 7 Hereford cows in 17 trials. Three preparations of tumor were used in orthotopic transplantation to 5 sites on the eye and eyelid. None of the transplants was successful. However, in 2 of 5 cows given autografts of a pure, viable tumor cell suspension, marked regression of the primary tumor was observed after transplantation.

Reaction of normal equine eyes to radio-frequency current-induced hyperthermia.

In the main study, hyperthermia was induced by radio-frequency current to obtain a single, central, corneal lesion in the right eye and 2 separate limbal lesions in the left eye of 13 light horses and 8 ponies. Intracorneal and intralimbal temperature profiles for the procedure were obtained in a separate study from the eyes of a horse and a pony treated in the same manner. After treatment of the principal eyes and 6 sham-treated eyes, clinical observations were conducted for up to 6 months, using indirect ophthalmoscopy, biomicroscopy, and fluorescein staining. Immediately after hyperthermic treatment of the eyes, dense opaque imprints of the electrodes of the localized current field device were present. Ulcerative keratitis persisted variably from day 2 through day 6 after treatment; anterior uveitis was present from day 3 through day 7. A mucopurulent discharge occurred infrequently, and conjunctival hyperemia was variable. Depigmentation resulted from hyperthermic treatment at pigmented limbal sites. Small scars persisted at 1 central site and 6 limbal sites where the electrodes were positioned vertically. Vision was not compromised in any of the horses permitted to live beyond a week. Microscopically, denudation and subsequent repair of the corneal epithelium correlated with the presence and then the absence of fluorescein staining. Stromal inflammation, edema, disorganization of collagenous fibers, and temporary disruption of corneal endothelium contributed to transitory corneal opacity. Time required for repair of corneal tissues varied, but all layers were integral 8 days after exposure to hyperthermia. Later changes included choroidal hydrops, vascular damage in conjunctival vessels, stromal neovascularization, and corneal fibroplasia.

Morphophysiologic bases for the predisposition of the bovine lung to bronchial pneumonia.

The susceptibility of the bovine lung to pneumonia may be attributed to the following morphophysiologic features: 1. The large, rugose, nonciliated surface of the pharyngeal tonsil; retrograde drainage from the pharynx during inflammation; gravitational effects on the predominant ventral parts of the pulmonary lobes. 3. Limited compliance due to abundant interstitial connective tissue. 3. Relatively small lungs for the mass of the animal with low tidal volume and functional residual capacity; lower capacity for diffusion of oxygen across the air-blood barrier than in most mammals. 4. Sensitivity of the bovine respiratory tract to marked alterations in ambient environmental temperatures. 5. Normally high pulmonary arterial pressure.

Hyperthermia for treatment of ocular squamous cell tumors in cattle.

Fifty-six benign ocular squamous cell tumors and 20 squamous cell carcinomas were subjected to hyperthermia (50 C for 30 sec/cm2 of tumor surface) created by radio-frequency current from an electrothermal device. Of the 76 tumors, 60 (49 benign and 11 malignant) regressed completely following a single treatment. Among the remaining 16 tumors, 7 benign tumors and 2 squamous cell carcinomas regressed completely following a second treatment, whereas 5 carcinomas regressed partially and 2 carcinomas failed to respond after the second treatment, whereas 5 carcinomas regressed partially and 2 carcinomas failed to respond after the second treatment. Thus, 90.8% of the tumors regressed completely, and all of these sites were free of visible lesions 5 1/2 months after the initial treatment. Of 69 sites that were tumor-free at 5 1/2 months, 42 were available for observation at 1 year; all 42 sites were free of tumor. Squamous cell tumors developed subsequently at other ocular or adnexa

Regression of bovine ocular carcinoma by treatment with a mycobacterial vaccine.

Hereford cows with naturally occurring ocular squamous cell carcinoma were treated by injection of BCG cell-wall vaccine into the tumor. Regression or arrest of disease was observed in 71% of treated animals. The disease progressed in all untreated animals and animals treated with improperly compounded vaccine. At autopsy, most animals with progressive disease had lymph node metastases.