The effect of cyanoacrylate on knot elongation in three sutures used for prosthetic laryngoplasty in the horse.

OBJECTIVE: This study investigated the elongation following cyclic loading on square knots of 5 USP multifilament long-chain ultra-high molecular weight polyethylene core (UHMWPE), 2 mm woven UHMWPE tape, and 5 USP braided polyester, with and without cyanoacrylate glue. STUDY DESIGN: Experimental study. SAMPLE POPULATION: n = 4. METHODS: Three conditions (suture without knot, suture with knot, suture with knot + cyanoacrylate) were evaluated for each suture material on a mechanical test stand by measuring the increased length of the construct after cycling from 25 to 50N for 1000 repetitions at 20 mm/second. Knot elongation was determined by subtracting the length of the control suture from the suture with knot or suture with knot + cyanoacrylate. The data were analyzed with a linear regression model with robust estimation of variance. Post-hoc analysis determined the model adjusted differences (square knot vs. cyanoacrylate) as a difference from control. t-tests were conducted to identify the significant findings. RESULTS: Total elongation of polyester (6.2-7.8 mm) was greater than multifilament UHMWPE (3.4-6.4 mm) and UHMWPE tape (2-3.7 mm) for all conditions. Polyester had the lowest knot elongation (1.6 mm) and the addition of cyanoacrylate decreased knot elongation for polyester by 1 mm. CONCLUSIONS: Polyester had the most total construct elongation followed by multifilament UHMWPE and UHMWPE tape. Polyester showed the least knot elongation and cyanoacrylate decreased this knot elongation. CLINICAL SIGNIFICANCE: Total construct and knot elongation should be considered as contributing factors to loss of arytenoid abduction following prosthetic laryngoplasty when using polyester, multifilament UHMWPE, or UHMWPE tape. Addition of cyanoacrylate to polyester knots should be explored to limit elongation.

Percutaneous doxycycline sclerotherapy in a horse with a mandibular aneurysmal bone cyst.

OBJECTIVE: To describe the use and outcome of sclerotherapy with intralesional doxycycline foam in a horse with a mandibular aneurysmal bone cyst. STUDY DESIGN: Case report. ANIMALS: Client-owned 1 year old Standardbred filly. METHODS: The horse presented for progressive mandibular swelling. A 10 mg/mL doxycycline foam was prepared for intralesional injection. Three doses were injected into the lesion under computed tomographic guidance at 6 and 15 weeks after initial treatment. Volume reduction was monitored after each treatment with 3D volumetric rendering and region of interest segmentation using commercially available software. RESULTS: The volume of the lesion decreased from 458.7455 cm3 before treatment, to 363.3101 cm3 at 6 weeks, 273.5855 cm3 at 15 weeks, and 247.2316 cm3 6 months later, resulting in a total reduction of 54% of the initial volume. Bone formation was noted in the lesion. No adverse effects related to doxycycline foam injections were noted. The mandibular swelling was resolved after treatment. CONCLUSION: Intralesional doxycycline sclerotherapy was shown to be efficacious in reducing the volume of the aneurysmal bone cyst in the horse presented in this report. There was complete resolution of mandibular swelling with no side effects related to the intralesional injections.

Epiglottopexy for the treatment of epiglottic retroversion in 2 horses.

OBJECTIVE: To report an epiglottopexy technique for the treatment of epiglottic retroversion (ER) in 2 horses. STUDY DESIGN: Case report. ANIMALS: A 2-year-old thoroughbred gelding and a 6-year-old standardbred gelding, both with ER. METHODS: Epiglottic retroversion was diagnosed via exercising endoscopic examination in both horses. Epiglottopexy technique was performed in both cases. RESULTS: Both horses returned to previous racing class within 1 year after surgery. Repeat exercising endoscopy of 1 horse 6 months postoperatively revealed resolution of the ER. CONCLUSION: Epiglottopexy should be considered for treatment of ER in the equine athlete. CLINICAL SIGNIFICANCE: Previously reported surgical techniques for ER in the equine athlete have not resulted in horses returning to previous performance level. The technique reported here resulted in both horses achieving athletic status.

Using quarterly earnings to assess racing performance in 66 thoroughbreds after transendoscopic laser surgery for treatment of epiglottic entrapment.

OBJECTIVE: To assess the outcome of transendoscopic laser surgery for the treatment of epiglottic entrapment (EE) and determine the influence of preoperative morphological characteristics on outcomes. STUDY DESIGN: Retrospective cohort study. ANIMALS: Thoroughbred racehorses treated with transendoscopic laser surgery (n = 66) and untreated cohorts (n = 132). METHODS: Medical, surgical, and race records of 66 horses treated with transendoscopic laser surgery were compared with untreated cohorts randomly selected from their last race presurgery. Postsurgery data were collated as number of starts and race winnings for each quarter after the date of surgery. RESULTS: Treated horses performed worse (P = .002) than their untreated cohorts in their last race presurgery. Although treated horses raced fewer times (P < .001) and earned less money (P < .001) in the first quarter after surgery compared with untreated horses, quarterly earnings or starts did not differ between groups after the first quarter. Among variables tested, subepiglottic membrane resection was the only prognostic factor; horses requiring this resection raced fewer times (P = .001) but without a significant difference in earnings. CONCLUSION: Horses treated for EE via transendoscopic laser surgery returned to a performance standard comparable to their untreated cohorts by the second quarter postsurgery. Horses with entrapments requiring resection raced fewer times postoperatively than the untreated cohorts. CLINICAL SIGNIFICANCE: Treated horses can be expected to perform equivocally to that of untreated cohorts in all but the first quarter following surgery except in those cases where resection of the entrapping membranes is required.

Upper Airway Conditions Affecting the Equine Athlete.

Many abnormalities of the upper airway that can inhibit performance are determined on a critical resting endoscopic evaluation. Some dynamic abnormalities can only be seen during an exercising endoscopic evaluation, which should be performed whenever the history of abnormal noise or performance limitations is not completely consistent with the resting endoscopic findings. Head and neck position may play a critical role in the evaluation process and the exact position during performance should be reproduced during the clinical examination to definitively define the abnormality. Treatments and prognoses are presented.

Prosthetic Mesh for Obliteration of the Nephrosplenic Space in Horses: 26 Clinical Cases.

OBJECTIVE: To report surgical complications, occurrence of post-obliteration colic, long term outcome, and return to previous function for horses treated with prosthetic mesh obliteration of the nephrosplenic space. STUDY DESIGN: Retrospective study. ANIMALS: Horses (n = 26) having nephrosplenic space obliteration using prosthetic mesh. METHODS: Horses undergoing mesh obliteration between January 2006 and May 2013 were included. A Proxplast™ mesh was secured to the nephrosplenic space with titanium helical coils in standing horses using laparoscopic technique. Perioperative data were obtained from the medical record and by telephone followup. Tests of proportion were used to compare the study population to the hospital colic population. Occurrence of colic within 1 year of obliteration was compared between horses where the diagnosis was confirmed at laparotomy and those diagnosed by abdominal palpation per rectum using a Fisher's exact test. RESULTS: All 26 horses undergoing mesh obliteration during the study period survived to discharge. Long term followup was available for 25 horses, with 23 returning to their previous level of function, and 21 alive at the time of followup. Cause of death was not associated with the surgical procedure in any case. Geldings and Warmbloods were overrepresented compared to the hospital colic population. Ten horses (38%) demonstrated colic after mesh obliteration. All 10 horses were examined by a veterinarian and none were diagnosed with recurrence of nephrosplenic entrapment. CONCLUSION: Mesh obliteration of the nephrosplenic space is an effective alternative to suture closure for preventing nephrosplenic entrapment of the large colon in horses. No complications related to mesh obliteration were reported in our study population.

Headshaking in 5 horses after paranasal sinus surgery.

OBJECTIVE: To report headshaking and presumptive trigeminal neuritis as a potential complication after paranasal sinus surgery in horses. STUDY DESIGN: Retrospective case series. ANIMALS: Horses (n = 5) that developed headshaking within 45 days of paranasal sinus surgery. METHODS: Medical records (2007-2010) of horses that had been evaluated for headshaking after paranasal sinus surgery were reviewed. RESULTS: Of 5 horses that developed headshaking within 45 days of paranasal sinus surgery, resolution occurred after treatment in 2 horses. One horse was euthanatized because clinical signs associated with headshaking could not be controlled. Headshaking persisted in the other 2 horses but was either adequately controlled with analgesics or was considered infrequent and transient enough to not warrant therapeutic intervention. Only 2 of 5 horses returned to full work after development of headshaking. CONCLUSIONS: Headshaking because of presumptive trigeminal neuritis is a possible career-ending or fatal complication of paranasal sinus surgery in horses.

Standing hand-assisted laparoscopic ovariohysterectomy to treat chronic pyometra in a mare.

OBJECTIVE: To describe a standing hand-assisted laparoscopic ovariohysterectomy in a mare. ANIMAL: A 15-year-old maiden Oldenburg mare. CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES: The mare was presented for evaluation of bucking under saddle and uncharacteristic aggressive behavior. Evaluation of a 24-hour video of the mare in a stall showed behavior consistent with caudal visceral abdominal discomfort. Reproductive evaluation revealed a pyometra secondary to complete transluminal cervical adhesions. The mare was initially managed medically with disruption of the adhesions and uterine lavage, but the adhesions reformed within 6 weeks and could not be manually disrupted. TREATMENT AND OUTCOME: To eliminate the recurrence of pyometra, the mare underwent standing hand-assisted laparoscopic ovariohysterectomy through bilateral flank incisions. The only complication was a seroma at 1 flank incision that resolved after drainage. CLINICAL RELEVANCE: Complete ovariohysterectomy in the mare is a challenging procedure and has previously been performed under general anesthesia. This is the first report of the procedure being performed completely in the standing mare without inversion of the uterus through the cervix.

Using quarterly earnings to assess racing performance in 70 thoroughbreds after modified laryngoplasty for treatment of recurrent laryngeal neuropathy.

OBJECTIVE: To validate and then use quarterly earnings to assess racing performance of Thoroughbreds after modified laryngoplasty for treatment of recurrent laryngeal neuropathy STUDY DESIGN: Retrospective cohort study. ANIMALS: Thoroughbred racehorses after modified laryngoplasty (N = 70), and untreated cohorts (N = 210). METHODS: Medical (2005-2008) and race records of 70 Thoroughbred racehorses treated by modified laryngoplasty were reviewed. Postsurgery data were collated as the number of starts and the dollar race winnings for each quarter after the date of surgery. Comparisons were made to an untreated cohort population. Initial comparisons were made between subgroups of the untreated cohort to ensure that one randomly selected group of untreated horses would not differ significantly from another untreated group. RESULTS: In the last race before surgery, treated horses performed significantly (P < .001) worse than untreated horses. When data were examined by quarter, with the exception of the first quarter after surgery, there were no significant differences in race starts or dollars earned between treated horses and untreated cohorts. All treated horses had at least 1 race after surgery and there was no difference in cumulative survival up to 40 races after surgery between treated and untreated groups CONCLUSIONS: Quarterly earnings can be used to provide a more detailed longitudinal assessment of a racehorse's performance. Horses treated by modified laryngoplasty for recurrent laryngeal neuropathy return to similar level of performance as their untreated cohorts by the second quarter after surgery, and continue to compete as long as their cohorts.

In vitro mechanical testing of an alternate laryngoplasty system (ALPS) for horses.

OBJECTIVE: Mechanical evaluation of a novel alternate laryngoplasty system (ALPS). STUDY DESIGN: Experimental. ANIMAL POPULATION: Cadaveric horse larynges (n = 10). METHODS: Arytenoid and cricoid cartilages were embedded for testing. A novel laryngoplasty system consisting of a metallic anchor, 2 stands of #2 suture material, and a metallic button were evaluated. A traditional laryngoplasty using a single strand of #5 Ethibond was evaluated in parallel. Constructs were evaluated in cyclic testing oscillating from 30 to 50 N for 3600 cycles. Constructs subsequently underwent a single cycle to failure. Distraction during cyclic testing was recorded. Load at failure and stiffness were calculated from single-cycle failure testing. RESULTS: There was no difference in mean arytenoid single-cycle load-to-failure for the Ethibond (206.9 ± 13.1 N) constructs compared with ALPS (220.6 ±17.1 N) constructs (P = .486). In the cricoid under single-cycle testing, the ALPS (236.0 ± 23.4 N) constructs were significantly stronger than the Ethibond (161.5 ± 12.2 N) constructs (P = .013). The combined distraction was significantly greater for Ethibond (6.29 ± 1.24 mm) constructs compared to the ALPS (3.43 ± 0.28 mm) constructs (P = .033). CONCLUSIONS: The ALPS construct was stiffer and at least as strong as the traditional laryngoplasty construct in single cycle failure in both the arytenoid and cricoid cartilages. Combined distraction was significantly reduced using the ALPS compared to the traditional laryngoplasty in vitro under cyclic testing.

A modified laryngoplasty approach promoting ankylosis of the cricoarytenoid joint.

OBJECTIVE: To perform a modification to the standard laryngoplasty procedure in vivo that would result in ankylosis of the cricoarytenoid (CA) joint, and determine the stability provided to the abducted arytenoid in vitro. STUDY DESIGN: Experimental study. ANIMALS: Horses (n=8). METHODS: Horses were assigned to either control laryngoplasty (n=3) or modified laryngoplasty (5) procedure. Endoscopic upper airway evaluations were used to measure right:left quotients 1 day and 3 months postoperatively to assess maintenance of abduction. Horses were euthanatized 3 months after surgery and larynges collected for measurement of translaryngeal impedance and histologic evaluation of CA joint ankylosis. Each specimen was exposed to increasing negative pressure with the sutures intact or cut while translaryngeal impedance was recorded. Data were analyzed using ANOVA with significance set at P<.05. RESULTS: Loss of left arytenoid cartilage abduction at 3 months was greater in the control laryngoplasty group. Overall, impedance was significantly lower for the modified laryngoplasty group compared with the control laryngoplasty group and lower with the sutures intact than cut. Histologic evaluation of the joints confirmed fibrous bridging of the left CA joints of the modified laryngoplasty group. CONCLUSIONS: A modified laryngoplasty approach promotes ankylosis of the CA joint and decreases the loss of abduction of the arytenoid.

Laser vaporization of the dorsal turbinate as an alternative method of accessing and evaluating the paranasal sinuses.

OBJECTIVE: To report a technique for stoma creation into the conchofrontal sinus (CFS) through the dorsal turbinate and to evaluate stoma as a site for sinoscopy. STUDY DESIGN: Prospective experimental study. ANIMALS: Cadaveric equine heads (n=2) and normal adult horses (5). METHODS: Technique feasibility was established on 2 cadaver heads. A diode laser fiber with a contact probe was passed into the nasal passage through a custom built, laser introducer rod (LIR). A videoendoscope was passed ventral to the LIR. A site on the caudal, medial aspect of the turbinate overlying the dorsal conchal sinus (DCS) was identified. A stoma to facilitate endoscope passage was created through the turbinate and sinoscopy performed to identify structures within the CFS and caudal maxillary sinus (CMS) and to evaluate the quality of the approach. The procedure was then performed in standing, sedated horses. Time required, laser energy used and complications were recorded. Endoscopy was performed ≥5 weeks postoperatively to assess stoma size and long-term effects of the procedure. RESULTS: A stoma was successfully created through the turbinate in both cadaveric skulls and in 4 horses; the stoma persisted for ≥5 weeks. The location of the stoma in 1 horse precluded sinoscopy. CONCLUSIONS: Laser vaporization of the dorsal turbinate through the nasal passage creates a stoma that lasts for at least 5 weeks providing a portal to the paranasal sinuses. Based on experience in 1 horse stoma location is critical to ensure adequate endoscope manipulation and sinoscopy. CLINICAL RELEVANCE: Standing endoscopic sinusotomy within the nasal cavity through the DCS is an alternative to more invasive sinusotomy techniques with fewer potential complications and a cosmetic result.

Mechanical evaluation of the equine laryngoplasty.

OBJECTIVES: Mechanical evaluation of the equine laryngoplasty. STUDY DESIGN: Experimental. ANIMAL POPULATION: Cadaveric cricoid (n=36) and arytenoid (46) cartilages. METHODS: Arytenoid and cricoid cartilage specimens were embedded for testing. Suture material (2 Ethilon, 5 Ethibond, or 5 Fiberwire) was inserted simulating laryngoplasty procedures. Constructs were evaluated in single or cyclic loading. Single cycle tests recorded load at failure and stiffness. Cyclical tests recorded displacement after 10,000 cycles. ANOVA and t-tests were used (significance P<.05). RESULTS: The arytenoid Ethibond (241.10+/-47.67 N) constructs were stronger in single cycle than Ethilon (133.85+/-27.89 N) and Fiberwire (142.67+/-32.40 N). The cricoid Ethibond (220.39+/-49.11 N) constructs were stronger than Ethilon (171.93+/-21.19). The stiffness of Ethilon constructs was lower in both the arytenoid and cricoid compared with Ethibond and Fiberwire. The arytenoids failed at a lower load than the cricoids for Ethilon and Fiberwire but not Ethibond constructs. In cyclic testing complete failure of either cartilage did not occur. Arytenoid Ethibond constructs (0.43+/-0.21 mm) had less distraction than Ethilon (0.92+/-0.41 mm) and a trend for less compared with Fiberwire (0.83+/-0.43 mm; P=.0513). Cricoid Ethibond constructs (0.45+/-0.18 mm) had less distraction compared with Ethilon (1.04+/-0.30 mm) and Fiberwire (0.97+/-0.45 mm). CONCLUSIONS: Ethibond was superior to Ethilon and Fiberwire constructs in vitro. CLINICAL RELEVANCE: Abduction loss after laryngoplasty is a common complication. The results of this study suggest that the use of Ethibond should minimize abduction loss after surgery relative to the other materials tested.

Extraluminal, C shaped polyethylene prostheses in two ponies with tracheal collapse.

OBJECTIVE: To describe the surgical technique, complications, and outcome after use of extraluminal prostheses in 2 ponies with severe tracheal collapse. STUDY DESIGN: Clinical report. ANIMALS: Ponies (n=2) with severe tracheal collapse. METHODS: A ventral median approach was used to expose the trachea from the larynx to the manubrium. Extraluminal, high-density polyethylene, C-shaped prostheses were sutured to the dorsal tracheal membrane and tracheal rings to provide external tracheal support. RESULTS: The surgical approach provided good tracheal access and placement of the rings was uncomplicated. Initial estimates of the tracheal diameter from preoperative radiographs resulted in prostheses that were too small at surgery requiring a 2nd surgical procedure in 1 pony. Postoperative complications were coughing, right laryngeal hemiplegia, seroma formation, and antimicrobial induced colitis. Both ponies had marked resolution of clinical abnormalities after surgery. Recurrent esophageal obstruction resulted in euthanasia of 1 pony 3.5 years after surgery. The other pony was doing well 1 year after surgery. CONCLUSIONS: Extraluminal support of the trachea resulted in rapid resolution of clinical signs in 2 ponies with tracheal collapse. CLINICAL RELEVANCE: Extraluminal tracheal prostheses can resolve clinical abnormalities in ponies with severe tracheal collapse.

Exercising videoendoscopic evaluation of 45 horses with respiratory noise and/or poor performance after laryngoplasty.

OBJECTIVE: To (1) assess upper airway function by videoendoscopy in horses performing poorly after laryngoplasty and (2) establish whether dynamic collapse of the left arytenoid can be predicted by the degree of resting postsurgical abduction. STUDY DESIGN: Case series. ANIMALS: Horses that had left laryngoplasty (n=45). METHODS: Medical records (June 1993-December 2007) of horses evaluated for abnormal respiratory noise and/or poor performance after laryngoplasty were reviewed. Horses with video recordings of resting and exercising upper airway endoscopy were included and postsurgical abduction categorized. Horses with immediate postoperative endoscopy recordings were also evaluated and postsurgical abduction categorized. Relationships between resting postsurgical abduction and historical information with exercising endoscopic findings were examined. RESULTS: Dynamic collapse of the left arytenoid cartilage was probable in horses with no postsurgical abduction and could not be predicted in horses with grade 3 or 4 postsurgical abduction. Respiratory noise was associated with upper airway obstruction but was not specific for arytenoid collapse. Most horses with a left vocal fold had billowing of the fold during exercise. Other forms of dynamic collapse involved the right vocal fold, aryepiglottic folds, corniculate process of left arytenoid cartilage, dorsal displacement of soft palate, and pharyngeal collapse. Complex obstructions were observed in most examinations and in all horses with exercising collapse of the left arytenoid cartilage. CONCLUSIONS: There was no relationship between exercising collapse of the left arytenoid cartilage and grade 3 or 4 postsurgical abduction but was likely in horses with no abduction.

An atypical equine gastrointestinal stromal tumor.

A 17-year-old, gelded Quarter Horse cross was found to have a large, intra-abdominal mass. Clinical signs included infrequent mild colic, weight loss, and chronic anemia. Surgery revealed a very large, discrete, hemorrhagic, multilobular mass with vascular attachments to the transverse colon, mesocolon, jejunal mesentery, and omentum; the site of origin was the transverse colon. Histologic examination demonstrated dense sheets, fascicles, palisades, and interconnecting streams of neoplastic spindle cells with lesser numbers of admixed multinucleated giant cells. Based on morphology alone, this neoplasm might have been misdiagnosed as a peripheral nerve sheath tumor because many of the morphologic features were suggestive of neural differentiation. Neoplastic cells expressed cluster of differentiation (CD)117 (c-kit), vimentin, desmin, smooth muscle actin, neuron-specific enolase, and S-100 protein and did not express cytokeratin. Based predominantly on the immunohistochemical profile, especially the CD117 positivity, this neoplasm was diagnosed as a gastrointestinal stromal tumor with both myogenic and neurogenic differentiation. The morphology and immunohistochemical profile of this neoplasm were different from published cases of equine gastrointestinal stromal tumors. Unusual aspects included the large size of this neoplasm, the neuroid rather than myxomatous morphology, the presence of multinucleated giant cells, and the expression of desmin.

Surgical complications of the equine upper respiratory tract.

Upper respiratory abnormalities are common performance-limiting problems in horses. The complications of various treatment methods, including laryngoplasty surgery, sinus surgery, intermittent dorsal displacement of the soft palate, laser surgery, and tracheal disorders, are discussed.

Use of successive dynamic videoendoscopic evaluations to identify progression of recurrent laryngeal neuropathy in three horses.

CASE DESCRIPTION: 3 racehorses were evaluated because of poor performance or abnormal noise originating from the upper portion of the respiratory tract. CLINICAL FINDINGS: During maximal exercise, initial dynamic videoendoscopy of the upper respiratory tract revealed complete arytenoid cartilage abduction in 2 horses and incomplete but adequate abduction of the left arytenoid cartilage in 1 horse. Subsequent exercising endoscopic evaluation revealed severe dynamic collapse of the left arytenoid cartilage and vocal fold in all 3 horses. TREATMENT AND OUTCOME: 2 horses were treated with prosthetic left laryngoplasty and raced successfully. One horse was retired from racing. CLINICAL RELEVANCE: Idiopathic laryngeal hemiplegia can be a progressive disease. Successive dynamic videoendoscopic upper airway evaluations were used to confirm progression of left laryngeal hemiplegia in these 3 horses. Videoendoscopy of the upper respiratory tract during exercise should be considered as part of the clinical evaluation of horses with signs of upper respiratory tract dysfunction.

Management of bilateral choanal atresia in a foal.

CASE DESCRIPTION: A 1-day-old Standardbred foal with a history of extreme respiratory distress after birth consistent with upper airway obstruction was evaluated. A temporary tracheostomy tube was placed by the referring veterinarian. CLINICAL FINDINGS: On initial examination, there was evidence of hypoxic-ischemic syndrome, secondary to perinatal asphyxia. Endoscopy revealed obstruction of both nares at the level of the choanae; a diagnosis of bilateral choanal atresia was made. TREATMENT AND OUTCOME: The foal was anesthetized and underwent transendoscopic laser fenestration of the buccopharyngeal membranes. Three weeks after surgery, cicatricial narrowing of the choanae was apparent and further transendoscopic ablation was performed. Recurrent stenosis necessitated revision surgeries involving a combination of laser ablation with topical administration of mitomycin and, subsequently, a combination of radial incisions into the stenotic tissue and repeated bougienage with a cuffed endotracheal tube. The degree of stenosis decreased, and at 1 year of age, the horse was an appropriate size for its age, had choanae that were almost maximally open (> 85%), and had entered training. Mild stenosis was still evident when the horse was reexamined the following year, although there was no evidence of exercise intolerance or respiratory compromise. CLINICAL RELEVANCE: Bilateral choanal atresia in a foal can be successfully treated via transendoscopic fenestration of the buccopharyngeal membranes, enabling the horse to subsequently participate in athletic activities. Secondary problems resulting from initial asphyxia and recurrent stenosis at the surgical site can be overcome but may require prolonged and extensive treatment.

Rupture of the gastrocnemius muscle in six foals.

Rupture of the gastrocnemius muscle and subsequent disruption of the reciprocal mechanism of the hind limb was diagnosed in 6 foals examined at 7 hours to 3 weeks of age. In 2 foals, the musculoskeletal injury was detected as an ancillary finding to clinical signs of neurologic dysfunction ascribed to hypoxic ischemic insult during delivery, whereas in the other 4 foals, musculoskeletal injury, manifested as inability to rise or stand unsupported, was the chief complaint at admission. Five foals had a history of dystocia and assisted delivery. Common clinical signs were inability to rise, disruption of the reciprocal mechanism, swelling in the caudal aspect of the thigh, instability of the stifle joint, and stifle joint effusion. For mild gastrocnemius injury, exercise restriction via forced recumbency, with minimal or no bandaging, may be sufficient treatment. For more severe disruption of the muscle, limb stabilization via splinting and intensive nursing and monitoring are necessary. Four foals had important concurrent problems, including musculoskeletal deformations (joint contractures), hypoxic ischemic disease, and failure of passive transfer and associated problems (ie, sepsis, polyarthritis, and pneumonia). Moderate to severe gastrocnemius muscle injury is difficult to treat successfully, and the long-term prognosis for athletic function should be regarded as guarded.