Fred J. Caldwell

Proximal interphalangeal joint arthrodesis in a one-month-old foal for superficial digital flexor tendon and straight sesamoidean ligament disruption

Proximal interphalangeal joint (PIJ) arthrodesis is typically performed in skeletally mature horses to alleviate pain associated with osteoarthritis or as part of intra-articular fracture fixation (Watkins 1999; Auer 2006). There have been 3 previous reports of PIJ arthrodesis in 3-month-old foals, the first being undertaken for a proximal phalangeal fracture, the second for an unreported reason, and the third for a congenital malformation of the pastern joint (Steenhaut et al. 1985; Schneider et al. 1987; Caron et al. 1990). However, there are no reports of PIJ arthrodesis in a foal of less than 3 months of age, nor are there reports of arthrodesis in a foal for traumatic injury to the soft tissue support structures of the pastern joint. Here, we describe the clinical findings associated with a case of acute, unilateral palmar subluxation of the PIJ joint in a onemonth-old foal, and the resulting surgical repair using internal fixation to arthrodese the PIJ joint. In the case reported here, the subluxation was unilateral at presentation; however, it became bilateral at 4 months of age, 3 months after the original injury. The second injury was successfully treated with external cast coaptation. There are 2 reports of bilateral pastern subluxation or luxation occurring in foals. The treatment of one foal was not reported and in the other euthanasia was carried out (Harrison and May 1992; Stashak 2002). This case report describes successful surgical management in one forelimb at one month of age and successful medical management in the second forelimb at 4 months of age, of a foal with bilateral PIJ subluxation.

Use of a Barbed Knotless Suture for Laparoscopic Ablation of the Nephrosplenic Space in 8 Horses

OBJECTIVE To evaluate use of a knotless suture for laparoscopic closure of the equine nephrosplenic space. STUDY DESIGN Experimental in vivo study. ANIMALS Normal horses without previous history of abdominal surgery (n=8). METHODS The nephrosplenic space was closed under laparoscopic visualization using a unidirectional, barbed 0 metric absorbable suture (copolymer of glycolic acid and trimethylene carbonate). Intracorporeal suturing of the nephrosplenic space was performed in a cranial-to-caudal direction in a simple continuous fashion. Repeat evaluation was performed laparoscopically in 2 horses and by necropsy in 6 horses. The length of closure was measured and nature of the healed tissue was evaluate grossly. RESULTS Total surgery time was 65-167 minutes (mean ± SD, 89.6 ± 22.6). Suturing time was 30-65 minutes (40.4 ± 16.3). Second laparoscopy in 2 horses was performed at days 198 and 227. Necropsy was performed at day 69-229 postoperatively (132.7 ± 63.0) in 6 horses. The closure measured 12-14 cm in length (13 ± 1) and consisted of mature fibrous tissue bridging the splenic capsule and the nephrosplenic ligament. No residual suture material was identified grossly in any horses. The procedure was easily performed; extracorporeal suture management to hold it taut was unnecessary since the barbs had excellent purchase in the apposed tissues, and intracorporeal knot tying was not required. CONCLUSION The barbed knotless suture appears to be a valid alternative to facilitate laparoscopic closure of the nephrosplenic space in normal horses; however, further work is necessary to investigate its suitability in clinically affected horses.

DISTAL BORDER FRAGMENTS OF THE EQUINE NAVICULAR BONE: ASSOCIATION BETWEEN MAGNETIC RESONANCE IMAGING CHARACTERISTICS AND CLINICAL LAMENESS

Distal border fragments of the navicular bone are increasingly being detected due to the improved capabilities of magnetic resonance imaging (MRI), but their clinical significance remains unclear. The purpose of this retrospective study was to describe the location, size, and frequency of fragments in a cohort of horses presented for MRI of the foot and to compare MRI findings with severity of lameness. Archived MRI studies and medical records were searched from March 2006 to June 2008. Horses were included if a distal border fragment of the navicular bone was visible in MRI scans. Confidence interval comparisons and linear regression analyses were used to test hypotheses that fragments were associated with lameness and lameness severity was positively correlated with fragment volume and biaxial location. A total of 453 horses (874 limbs) were included. Fragments were identified in 60 horses (13.25%) and 90 limbs (10.3%). Fifty percent of the horses had unilateral fragments and 50% had bilateral fragments. Fragments were located at the lateral (62.2%), medial (8.89%), or medial and lateral (28.9%) angles of the distal border of the navicular bone. There was no increased probability of being categorized as lame if a fragment was present. There was no significant difference in fragment volume across lameness severity categorizations. Confidence intervals indicated a slightly increased probability of being classified as lame if both medial and lateral fragments were present. Findings indicated that distal border fragments of the navicular bone in equine MRI studies are unlikely to be related to existing lameness.

Evaluation of a Tenoscopic Approach for Desmotomy of the Accessory Ligament of the Deep Digital Flexor Tendon in Horses

OBJECTIVE To develop a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT) in horses. STUDY DESIGN Experimental. ANIMALS Cadaveric forelimbs (n=10) and 4 forelimbs from 2 horses anesthetized for terminal teaching procedures, and 12 forelimbs of 6 experimental horses. METHODS Saline distention of the carpal flexor sheath facilitated insertion of an arthroscope into the distal medial aspect of the sheath between the AL-DDFT and deep digital flexor tendon (DDFT). Location of an instrument portal on the lateral aspect of the metacarpus was identified with a needle. The lateral aspect of the AL-DDFT was transected and the arthroscope and instrument were switched to transect the remaining fibers on the medial aspect. Cadaveric specimens were dissected for evaluation. Experimental horses were monitored for 30 days postoperatively. RESULTS Minor complications including incomplete division of the AL-DDFT and shallow incision into the suspensory ligament were observed in some cadaver specimens. The AL-DDFT was completely transected in all experimental horses with no suspensory ligament damage. Mean±SD surgical time (incision to skin closure) was 28.3±11.8 minutes. On ultrasonographic examination, transection of the AL-DDFT was complete in all experimental horses. Minor DDFT fiber disruption was noted in 1 limb during ultrasound examination at day 30. CONCLUSIONS A tenoscopic approach through the carpal flexor sheath provided adequate access for desmotomy of the AL-DDFT.Objective: To develop a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT) in horses. Study Design: Experimental. Animals: Cadaveric forelimbs (n=10) and 4 forelimbs from 2 horses anesthetized for terminal teaching procedures, and 12 forelimbs of 6 experimental horses. Methods: Saline distention of the carpal flexor sheath facilitated insertion of an arthroscope into the distal medial aspect of the sheath between the AL-DDFT and deep digital flexor tendon (DDFT). Location of an instrument portal on the lateral aspect of the metacarpus was identified with a needle. The lateral aspect of the AL-DDFT was transected and the arthroscope and instrument were switched to transect the remaining fibers on the medial aspect. Cadaveric specimens were dissected for evaluation. Experimental horses were monitored for 30 days postoperatively. Results: Minor complications including incomplete division of the AL-DDFT and shallow incision into the suspensory ligament were observed in some cadaver specimens. The AL-DDFT was completely transected in all experimental horses with no suspensory ligament damage. Mean±SD surgical time (incision to skin closure) was 28.3±11.8 minutes. On ultrasonographic examination, transection of the AL-DDFT was complete in all experimental horses. Minor DDFT fiber disruption was noted in 1 limb during ultrasound examination at day 30. Conclusions: A tenoscopic approach through the carpal flexor sheath provided adequate access for desmotomy of the AL-DDFT.

Review of glucocorticoid therapy in horses. Part 1: Pharmacology

Summary This article is the first in a three part review series examining glucocorticoid use in treatment of medical conditions and musculoskeletal disorders of the horse. This article provides a review of the structure and function of corticosteroids together with a summary of the available literature pertaining to the pharmacodynamics, pharmacokinetics and indications for use of, and adverse effects associated with, glucocorticoids currently available for use by equine veterinarians.

Management of enterocutaneous fistula associated with an umbilical hernia in a two-year-old horse

Enterocutaneous fistula (ECF) occurs when there is open communication between the lumen of intestine and the skin. This report describes a two-year-old, American Quarter Horse filly presented with an acute ECF involving the ileum entrapped within an umbilical hernia. After four days of conservative therapy and worsening of hydration status and electrolyte and acid-base imbalances, surgical correction of the ECF was performed. The filly was stable 24 hours after surgery and eventually made a full recovery.

Review of glucocorticoid therapy in horses. Part 2: Clinical use of systemic glucocorticoids in horses

Summary This article is the second in a review series about the use of glucocorticoids to treat medical and musculoskeletal conditions in horses. This segment in the series summarises reported dosages, methods of administration and the efficacy of glucocorticoids for various systemic diseases in equids. The most common use of systemic glucocorticoids reported in the literature for management and treatment of alterations of the respiratory, integumentary, immune and neurological systems are included.

Encapsulation of equine ECFCs in highly uniform, injectable hydrogel microspheres for local cell delivery

A common challenge in cell therapy is the inability to routinely maintain survival and localization of injected therapeutic cells. Delivering cells by direct injection increases the flexibility of clinical applications, but may cause low cell viability and retention rates due to the high shear forces in the needle and mechanical wash out. In this study, we encapsulated endothelial colony forming cells (ECFCs) in poly(ethylene glycol)-fibrinogen (PF) hydrogel microspheres using a custom-built microfluidic device; this system supports rapid encapsulation of high cell concentrations (10 million cells per mL) and resulting cell-laden microspheres are highly uniform in shape and size. The encapsulated ECFCs were shown to have >95% viability and continued to rapidly proliferate. Expression of cell markers (von Willebrand factor, CD105, and CD14), the ability to form tubules on basement membrane matrix, and the ability to take up low-density lipoprotein were similar between pre- and post-encapsulated cells. Viability of encapsulated ECFCs was maintained after shear through 18-23-gauge needles. Ex vivo and in vivo cell delivery studies were performed by encapsulating and injecting autologous equine ECFCs subcutaneously into distal limb full-thickness wounds of adult horses. Injected ECFCs were visualized by labeling with fluorescent nanodots before encapsulation. One week after injection, confocal microscopy analysis of biopsies of the leading edges of the wounds showed that the encapsulated ECFCs migrated into the surrounding host tissue indicating successful retention and survival of the delivered ECFCs. Rapid, scalable cell encapsulation into PF microspheres was demonstrated to be practical for use in large animal cell therapy and is a clinically relevant method to maintain cell retention and survival after local injection.

Reconstruction of a Complicated Orbital Depression Fracture with Medial Wall and Globe Repositioning in a Horse: A Collaboration Across Disciplines and Specialties.

OBJECTIVE To report the surgical reconstruction of a complicated orbital depression fracture in a horse with emphasis on medial wall and globe repositioning. STUDY DESIGN Clinical report. ANIMALS A 6 year old Irish Sport Horse gelding. METHODS The eventer presented with acute, severe orbital trauma and globe displacement. After initial elevation of the depression fractures of the facial bones and reconstruction of the orbit, the globe was recessed secondary to displacement of the medial wall and floor of the orbit within the conchofrontal sinus. A three-dimensional model of the fracture configuration was used for presurgical planning to reposition the globe. During a subsequent surgical procedure, a resorbable plate was placed in the floor of the orbit and the medial orbital wall and globe were repositioned using a sinoscopic approach and stabilized with the placement of tissue expanders within the conchofrontal sinus. The tissue expanders were subsequently removed after 3 weeks under standing sedation. RESULTS The right globe was successfully repositioned in a more correct anatomical orientation and the horse resumed work 3 months postoperatively, and successfully competed at its previous level 5 months postoperatively. No visual deficits have been reported by the owners. CONCLUSION Efforts to restore the medial wall and/or floor of the orbit with concurrent globe repositioning should be considered in horses with severe orbital depression fractures that result in abnormal globe position.