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- Author or Editor: John A. Stick x
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Abstract
Objective—To describe a single-portal cranial arthroscopic approach to the stifle joint in horses and to determine the clinical outcome in horses with femorotibial joint disease in which this approach was used.
Design—Retrospective study.
Animals—23 adult horses.
Procedure—Medical records were reviewed to obtain information on clinical outcome in horses in which the single-portal cranial arthroscopic approach was used.
Results—Twenty-nine stifle joints of 23 horses were examined arthroscopically, using the described approach. Subchondral bone cysts were treated in 19 medial femoral condyles of 12 horses. Unilateral cruciate ligament desmitis (4 horses), meniscal tearing (3), or both (2) were identified in 9 horses. Evidence of degenerative joint disease without cystic lesions or soft tissue trauma was found in 2 horses. Information on clinical outcome was obtained for 21 of 23 horses. A successful outcome was obtained in 15 of 21 horses and was defined as return to sound performance at a degree equal to or better than that prior to injury and lameness. Eight of 12 horses treated for medial femoral condylar cysts had a successful outcome. Four show horses treated for cruciate ligament lesions alone successfully returned to showing activity. None of the 3 horses with meniscal tearing were able to perform successfully.
Conclusions and Clinical Relevance—The femorotibial joint was evaluated through a single-portal cranial arthroscopic approach, using the femoropatellar joint as the point of access. This approach was easy to perform, allowed controlled access to the femorotibial joint, avoided accidental damage to articular structures, and required fewer access portals. (J Am Vet Med Assoc 2002;220: 1046–1052)
Abstract
Objective—To evaluate changes in strain patterns in normal equine hooves following 4-point trimming, using photoelastic stress analysis.
Sample Population—15 equine front limbs with normal hoof configuration.
Procedure—Limbs were disarticulated at the carpometacarpal joint. Weight-bearing surfaces of each hoof were trimmed level to ensure 100% ground contact. Hoof walls were coated with a custom-made strain-sensitive plastic, and limbs were loaded to a third of body weight. Using a polariscope, strain distribution, magnitudes, and directions were evaluated in level hooves as well as before and after standardized 4-point trimming. Repeated-measures ANOVA was used to compare strain magnitudes and directions before and after trimming.
Results—In leveled specimens, strain fields were symmetrically distributed above the heels and at quarter-toe junctions along a line between the middle and distal thirds of the hoof wall. After 4-point trimming, strain epicenters localized above the contact points, whereas strain magnitudes significantly increased by approximately 50%. Decreasing contact area by 50% resulted in an additional significant increase (32%) in strain magnitude. Trimming did not have a significant effect on strain orientations.
Conclusion and Clinical Relevance—This study documents that 4-point trimming results in strain concentration above the hoof contact points and that strain magnitude is dependent on contact area. (Am J Vet Res 2001;62:467–473)
Abstract
Objective—To demonstrate myofibroblasts in the accessory ligament of the deep digital flexor tendon (ie, distal check ligament) and deep digital flexor tendon of clinically normal foals.
Sample Population—Tissue specimens from 25 foals that were necropsied for reasons unrelated to this study and unrelated to musculoskeletal disease.
Procedure—The distal check ligament and deep digital flexor tendon of both forelimbs were examined histologically. Myofibroblasts were identified by immunohistochemical staining specific for alphasmooth muscle actin (α-SMA).
Results—Most of the cells in the distal check ligament and deep digital flexor tendon of all foals stained positive for α-SMA.
Conclusion and Clinical Relevance—Myofibroblasts made up most of the cells in the distal check ligament and deep digital flexor tendon of clinically normal foals. These cells have contractile ability and therefore, may play a role in flexure contracture of these tendons. The ability of tetracycline to chelate calcium or decrease the expression of the contractile protein α-smooth muscle actin could inhibit the myofibroblasts' ability to contract, thus providing a rationale for tetracycline administration as a treatment of distal interphalangeal joint flexor deformity in foals. (Am J Vet Res 2001;62:823–827)
Abstract
Objective—To determine the microvascular anatomy of the suspensory ligament of the forelimb of horses.
Sample—17 cadaveric forelimbs from 9 adult horses with no known history of forelimb lameness.
Procedures—The median artery of the forelimb was cannulated proximal to the antebrachiocarpal joint and injected with contrast medium for CT evaluation of the gross vasculature (n = 2) or India ink to evaluate the microvasculature (12). Routine histologic evaluation was performed on an additional 3 forelimbs to confirm the microvascular anatomy.
Results—The vascular supply of the suspensory ligament of the forelimb originated from branches of the medial and lateral palmar and palmar metacarpal vessels as well as the proximal and distal deep palmar arches. An abundant, longitudinally oriented microvascular supply was evident throughout the length of the suspensory ligament without distinct variation among the proximal, midbody, and distal regions. The intraligamentous blood supply originated from a periligamentous vascular plexus that surrounded the suspensory ligament throughout its length. Histologic findings indicated the presence of a periligamentous connective tissue plexus, which contained vessels that penetrated and anastomosed with an extensive network of intraligamentous vessels throughout the length of the suspensory ligament.
Conclusions and Clinical Relevance—The suspensory ligament of the equine forelimb had an abundant intraligamentous microvascular supply throughout its entire length. The absence of an obvious hypovascular area suggested that regional variations in healing rates of the suspensory ligament are not associated with the microvascular anatomy.
Abstract
Case Description—3 foals were referred for treatment of tympany of the auditory tube diverticulum (guttural pouch).
Clinical Findings—Bilateral guttural pouch tympany was diagnosed in all 3 foals on the basis of clinical signs and results of radiographic and endoscopic evaluations and gutturocentesis. In each foal, previous medical or surgical interventions or both had failed to correct the problem.
Treatment and Outcome—Bilateral surgical resection of the plica salpingopharyngeus was performed. Follow-up telephone interviews with owners 8 months to 3 years after surgery revealed that long-term resolution of the tympany had been achieved in each foal, with few to no postsurgical complications.
Clinical Relevance—Surgical correction of refractory bilateral guttural pouch tympany can be accomplished by resection of the plica salpingopharyngeus within the pharyngeal opening of the Eustachian tube. In the foals of this report, permanent resolution of tympany was apparently achieved without interfering with upper airway function, providing support for the use of surgical resection of the plica salpingopharyngeus in the treatment of bilateral guttural pouch tympany.
Abstract
Objective—To evaluate the safety and efficacy of thoracoscopically guided pulmonary wedge resection in horses.
Animals—10 horses (5 control horses and 5 horses affected with recurrent airway obstruction [ie, heaves]).
Procedure—Each horse underwent a thoracoscopically guided pulmonary wedge resection. Before, during, and after surgery, heart rate, respiratory rate, arterial blood gases, and systemic and pulmonary arterial pressures were measured. Physical examination, CBC, and thoracic radiography and ultrasonography were performed 24 hours before and 2 and 48 hours after surgery. Pulmonary specimens were assessed by histologic examination. A second thoracoscopic procedure 14 days later was used to evaluate the resection site.
Results—The technique provided excellent specimens for histologic evaluation of the lung. Heart and respiratory rates decreased significantly after horses were administered sedatives. A significant transient decrease in PaO2 was detected immediately after pulmonary wedge resection, but we did not detect significant effects on arterial pH, Paco2, or mean arterial and pulmonary arterial pressures. All horses except 1 were clinically normal after thoracoscopic surgery; that horse developed hemothorax attributable to iatrogenic injury to the diaphragm. The second thoracoscopy revealed minimal inflammation, and there were no adhesions.
Conclusion and Clinical Relevance—Thoracoscopically guided pulmonary wedge resection provides a minimally invasive method for use in obtaining specimens of lung tissues from healthy horses and those with lung disease. This technique may be useful for the diagnosis of diseases of the lungs and thoracic cavity. (Am J Vet Res 2002;63:1232–1240)
Abstract
Objective—To compare endoscopic findings of the upper portion of the respiratory tract in Thoroughbred yearlings with their subsequent race records to determine whether subjective assessment of airway function may be used as a predictor of future racing performance.
Design—Retrospective study.
Animals—427 Thoroughbred yearlings.
Procedures—Endoscopic examination findings were obtained from the medical records and the videoendoscopic repository of the Keeneland 1996 September yearling sales. Racing records were requested for the yearlings through the end of their 4-year-old racing season (1997–2000). Twenty-nine measures of racing performance were correlated with endoscopic findings. Subjective arytenoid cartilage movement grades were determined, using a 4-point grading scale (grade 1 = symmetrical synchronous abduction of the arytenoid cartilages; grade 4 = no substantial movement of the left arytenoid cartilage).
Results—Of the 427 Thoroughbred yearlings included in this study, 364 established race records, and 63 did not. Opinions regarding suitability for purchase, meeting conditions of the sale, and the presence of epiglottic abnormalities had no significant association with racing performance. Arytenoid cartilage movement grades were significantly associated with many of the dependent variables. However, palatine abnormalities were not predictive of inferior racing performance.
Conclusions and Clinical Relevance—Thoroughbred yearlings with grade-1 and -2 arytenoid cartilage movements had significantly better racing performance as adults, compared with yearlings with grade- 3 arytenoid cartilage movements. In contrast, epiglottic and palatine abnormalities were not predictive of inferior racing performance. Therefore, evaluation of laryngeal function, but not epiglottic or palatine abnormalities, using the 4-point grading system, should be the major factor in developing recommendations for prospective buyers. (J Am Vet Med Assoc 2001;219: xxx–xxx)
Abstract
Objective—To record respiratory sounds in exercising horses and determine whether spectrum analysis could be use to identify sounds specific for laryngeal hemiplegia (LH) and dorsal displacement of the soft palate (DDSP).
Animals—5 Standardbred horses.
Procedure—Respiratory sounds were recorded and pharyngeal pressure and stride frequency were measured while horses exercised at speeds corresponding to maximum heart rate, before and after induction of LH and DDSP.
Results—When airway function was normal, expiratory sounds predominated and lasted throughout exhalation. After induction of LH, expiratory sounds were unaffected; however, all horses produced inspiratory sounds characterized by 3 frequency bands centered at approximately 0.3, 1.6, and 3.8 kHz. After induction of DDSP, inspiratory sounds were unaffected, but a broad-frequency expiratory sound, characterized by rapid periodicity (rattling) was heard throughout expiration. This sound was not consistently detected in all horses.
Conclusions and Clinical Relevance—The technique used to record respiratory sounds was well tolerated by the horses, easy, and inexpensive. Spectrum analysis of respiratory sounds from exercising horses after experimental induction of LH or DDSP revealed unique sound patterns. If other conditions causing airway obstruction are also associated with unique sound patterns, spectrum analysis of respiratory sounds may prove to be useful in the diagnosis of airway abnormalities in horses. (Am J Vet Res 2001;62:659–664)
Abstract
Objective—To determine the effects of oxytetracycline on matrix metalloproteinase-1 (MMP-1) mRNA expression and collagen gel contraction by equine myofibroblasts in an effort to explain the mechanistic basis for the pharmacologic treatment of flexural deformities in foals.
Sample Population—Cultured myofibroblasts from the accessory ligament (distal check ligament) of 6 foals.
Procedure—Collagen gel scaffolds seeded with equine myofibroblasts were cultured in individual culture dishes containing complete media (Dulbecco's modified Eagle medium with 10% fetal bovine serum) and oxytetracycline (0, 12.5, 25, or 75 µg/mL) for 48 hours. After 24 hours, the gels were released from the bottom of the culture plate and allowed to contract. Photographs were taken at 0, 1, 2, 4, 6, 8, and 24 hours after release to assess the degree of collagen gel contraction. Additional gels were harvested at 2 hours after release for RNA isolation and reverse transcriptase-polymerase chain reaction assessment of the degree of MMP-1 mRNA expression.
Results—Oxytetracycline induced a dose-dependent inhibition of collagen gel contraction by equine myofibroblasts. Oxytetracycline also induced a dose-dependent decrease in MMP-1 mRNA expression by equine myofibroblasts.
Conclusions and Clinical Relevance—Results of this study indicate that oxytetracycline inhibits tractional structuring of collagen fibrils by equine myofibroblasts through an MMP-1 mediated mechanism. In young foals, oxytetracycline administration may make the developing ligaments and tendons more susceptible to elongation during normal weight-bearing. Inhibition of normal collagen organization may provide the mechanistic explanation for the results seen following the pharmacologic treatment of flexural deformities in foals by oxytetracycline administration. (Am J Vet Res 2004;65:491–496)
