Enhancing prosthesis stability at the cricoid cartilage in equine laryngoplasty using 3-D-printed laryngeal clamps: An ex vivo model study.

OBJECTIVE: To assess a three-dimensional (3-D)-printed laryngeal clamp (LC) designed to enhance the anchoring of laryngeal prostheses at the cricoid cartilage. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: A total of 22 equine larynges. METHODS: Two experimental groups included larynges with standard prosthetic laryngoplasty (PL; n = 10) and larynges with prosthetic laryngoplasty modified with laryngeal clamps (PLLC; n = 10). All constructs underwent 3000 cycles of tension loading and a single tension to failure. Recorded biomechanical parameters included maximum load, actuator displacement, and construct failure. Finite element analysis (FEA) was performed on one PL and one PLLC construct. RESULTS: The maximum load at single tension to failure was 183.7 ± 46.8 N for the PL construct and 292.7 ± 82.3 N for the PLLC construct (p = .003). Actuator displacement at 30 N was 1.7 ± 0.5 mm and 2.7 ± 0.7 mm for the PL and PLLC constructs, respectively (p = .011). The cause of PL constructs failure was mostly tearing through the cartilage whereas the PLLC constructs failed through fracture of the cricoid cartilage (p = .000). FEA revealed an 11-fold reduction in the maximum equivalent plastic strain, a four-fold reduction in maximum compressive stress, and a two-fold increase in the volume of engaged cartilage in PLLC constructs. CONCLUSION: The PLLC constructs demonstrated superior performance in biomechanical testing and FEA compared to standard PL constructs. CLINICAL SIGNIFICANCE: The use of 3-D-printed laryngeal clamps may enhance the outcomes of laryngoplasty in horses. In vivo studies are necessary to determine the feasibility of performing laryngoplasty using the laryngeal clamp in horses.

Leveraging MRI characterization of longitudinal tears of the deep digital flexor tendon in horses using machine learning.

While MRI is the modality of choice for the diagnosis of longitudinal tears (LTs) of the deep digital flexor tendon (DDFT) of horses, differentiating between various grades of tears based on imaging characteristics is challenging due to overlapping imaging features. In this retrospective, exploratory, diagnostic accuracy study, a machine learning (ML) scheme was applied to link quantitative features and qualitative descriptors to leverage MRI characteristics of different grades of tearing of the DDFT of horses. A qualitative MRI characteristic scheme, combining tendon morphologic features, altered signal intensity, and synovial sheath distention, was used for LT classification with an excellent diagnostic accuracy of the high-grade tears but more limited accuracy for the detection of low-grade tears. A quantitative ML approach was followed to measure the contribution of 30 quantitative phenotypic features for characterizing and classifying tendinous tears. Among the 30 imaging features, boundary curvature represented by the standard deviation and maximum had the most significant discriminatory power (P < 0.05) between normal and abnormal tendons and could be used as an aid for classifying the different grades of LTs of DDFTs. Imaging analysis-based 3D interactive surface plot supports qualitative characterization of different grades of LTs of the DDFT through clearer visualization of the tendon in three dimensions and simple integration of two perspectives features (i.e., margin/distribution and intensity/distribution). A systematic approach combining quantitative features with qualitative analyses using ML was diagnostically beneficial in MRI characterization and in discriminating between different grades of LTs of the DDFT of horses.

Determining Direction of Axonal Flow in the Equine Ramus Communicans by Ultrastructural Examination of the Plantar Nerves 2 Months after Transecting the Ramus.

The ramus communicans, neural connection between medial and lateral plantar nerves of the horse, was transected to determine the degree to which medial and lateral plantar nerves contribute to the plantar ramus. After 2 months, sections of plantar nerves immediately proximal and distal to the communicating branch were collected and processed for electron microscopy. All examined nerves had undergone Wallerian degeneration and contained regenerating and mature fibers. Layers of the myelin sheath were separated by spaces and vacuoles, indicating demyelination of medial and lateral plantar nerves. Shrunken axons varied in diameter and were surrounded by an irregular axolemma. Shrunken axoplasm of both myelinated and non-myelinated fibers contained ruptured mitochondria and cristae, disintegrating cytoskeleton, and vacuoles of various sizes. The cytoplasm of neurolemmocytes contained various-sized vesicles, ruptured mitochondria within a fragile basal lamina and myelin whorls of multilayered structures indicative of Wallerian degeneration. These ultrastructural changes, found proximal and distal to the ramus in medial and lateral plantar nerves, suggest that axonal flow is bi-directional through the ramus communicans of the pelvic limbs of horses, a previously unreported finding. As well, maturity of nerves proximal and distal to the ramus indicates that all nerve fibers do not pass through the ramus.

Prosthetic mesh repair of abdominal wall hernias in horses.

Repair of hernias of the abdominal wall of horses is often augmented by inserting a prosthetic mesh. In this review, we describe the various characteristics of prosthetic meshes used for hernia repair and present 2 systems that are used by surgeons in the human medical field to classify techniques of prosthetic mesh herniorrhaphy. Both of these classification systems distinguish between onlay, inlay, sublay, and underlay placements of mesh, based on the location within the abdominal wall in which the prosthetic mesh is inserted. We separate the published techniques of prosthetic mesh herniorrhaphy of horses using this classification system, ascribing names to the techniques of herniorrhaphy where none existed, and report the success rates and complications associated with each technique. By introducing a classification system widely used in the human medical field and illustrating each technique in a figure, we hope to clarify inconsistent nomenclature associated with prosthetic mesh herniorrhaphy performed by veterinary surgeons.

Perineural Injection of the Ethmoidal Nerve of Horses.

OBJECTIVE: To describe the anatomical location of the ethmoidal nerve in the equine periorbital region and to determine the accuracy of a technique used to deposit local anesthetic solution adjacent to the nerve. STUDY DESIGN: Prospective experimental study. ANIMALS: Adult equine cadaver heads (n=6 for preliminary dissection; n=15 [30 nerve sites] for evaluation of injection technique). METHODS: Preliminary dissections were performed to identify landmarks for injection of local anesthetic adjacent to the ethmoidal nerve. For evaluation of the injection technique a 20 gauge 6 cm spinal needle was inserted into the rostromedial aspect of the supraorbital fossa, where the caudal aspect of the zygomatic process emerges from the frontal bone caudal and medial to the globe. The needle was inserted to its hub at an angle of 110° to the long axis of the head using a protractor, in both a sagittal plane and a transverse plane, and 0.5 mL of new methylene blue dye was injected as a marker. The ethmoidal nerve was identified by dissection immediately after each injection and inspected for proximity of the dye. RESULTS: Dye was observed surrounding the nerve in 27 of 30 sites (90%) or lying within 5 mm of the nerve at the other 3 sites. CONCLUSION: The described technique of perineural injection of the ethmoidal nerve proved reliable and simple. Anesthetizing the ethmoidal nerve may be helpful in desensitizing portions of the ipsilateral paranasal sinuses and nasal cavity innervated by the nerve when sinonasal surgery is performed in the standing horse.

Urogenital surgery performed with the mare standing.

Many urogenital procedures of the mare are commonly performed with the mare standing. Ovariectomy via colpotomy was described as early as 1903, and the Caslick vulvoplasty was first described in 1937. As knowledge expands and instruments become more specialized, techniques will improve. With the introduction of laparoscopy, clinicians have not only been able to improve the previously described urogenital procedures but also to devise new procedures. This article describes multiple surgeries of the female urogenital tract, all of which can be performed with the mare standing, and describes a variety of approaches to some portions of the female urogenital tract.

Hypospadias in a Friesian gelding.

OBJECTIVE: To report clinical signs and management of hypospadias in a horse. STUDY DESIGN: Clinical report. ANIMAL: A 6-year-old, Friesian gelding. METHODS: Partial phallectomy was performed to resolve contact dermatitis of the pelvic limbs and abnormal behavior during urination. Subsequent urethral meatal stenosis was treated by revision. RESULTS: Hypospadias and chordee caused altered direction of urine flow, contact dermatitis of the pelvic limbs, and abnormal behavior. Partial phallectomy and subsequent revision after meatal stenosis resolved urine direction, flow and abnormal behavior. CONCLUSIONS: Abnormalities of the urinary tract associated with hypospadias can result in urine-induced, contact dermatitis and distress during urination, but these complications can be resolved by partial phallectomy.

Repair of an incompetent urethral sphincter in a mare.

OBJECTIVE: To describe successful surgical treatment of urinary incontinence caused by a ruptured and/or transected urethral sphincter in a mare. STUDY DESIGN: Clinical report. ANIMAL: A 7-year-old, Swedish Warmblood mare with urinary incontinence. METHODS: The urethral sphincter, which had been damaged during removal of a cystic urolith, was repaired by apposing the ends of the disrupted urethralis muscle and tunica muscularis. RESULTS: The mare was no longer incontinent after repair of the defect by apposition of the ends of the urethralis muscle and tunica muscularis. CONCLUSIONS: Transection and/or rupture of the urethral sphincter of a mare may result in urinary incontinence. CLINICAL RELEVANCE: Apposition of the ends of the ruptured or transected urethralis muscle and tunica muscularis can correct urinary incontinence caused by this defect.

Evaluation of four techniques for injecting the trochanteric bursa of horses.

OBJECTIVE: To describe the anatomic features of the equine trochanteric bursa and to evaluate 4 techniques for bursa centesis. STUDY DESIGN: Prospective, randomized design. ANIMALS: Equine cadavers (n=2) and 20 live horses. METHODS: The trochanteric bursae of 2 equine cadavers were injected with latex to identify the boundaries of the bursae. Four techniques for centesis of the trochanteric bursa were evaluated by attempting to inject dye into both trochanteric bursae of 20 live horses. Techniques included injection of the bursa with the limb-bearing weight and injection with the limb nonweight bearing and supported on a block, with or without ultrasonographic guidance of the needle. Ultrasonographic guidance of the needle was performed with or without the use of a guide channel attached to the ultrasound probe. Each of the 4 techniques was used to inject 10 bursae. The region of the bursa was dissected after horses were euthanatized to determine the location of the dye. RESULTS: The trochanteric bursa was most successfully injected with the limb positioned caudally with the foot on a block, even though topographic landmarks for centesis were more difficult to identify when the limb was in this position. The highest incidence of success was achieved when the needle was inserted using ultrasonographic guidance with the foot in a Hickman block. CONCLUSION: Positioning the limb caudally with the foot nonweight bearing and on a block facilitated centesis of the trochanteric bursa.

In vitro effect of ventriculocordectomy before laryngoplasty on abduction of the equine arytenoid cartilage.

OBJECTIVE: To determine whether ventriculocordectomy (VCE) performed before prosthetic laryngoplasty (PL) results in increased rima glottidis size compared with PL alone. STUDY DESIGN: Experimental study. ANIMALS: Equine cadaver larynges (n=13). METHODS: Right arytenoid cartilages were maximally abducted using a standard PL technique. Standard PLs were then performed on the left side and the force required to maximally abduct the left arytenoid cartilage recorded (F(max) ). Photographs were taken of the rima glottidis at zero force and at five equal levels of force up to F(max) . The force applied was released, left VCE performed, and photographs repeated. Arytenoid left:right angle quotients (LRQ) and glottic cross-sectional area ratios (CSAR) were calculated at each force level in each condition (PL and VCE-PL). RESULTS: Mean LRQ and CSAR for both PL and VCE-PL increased with increasing force, initially rapidly before plateauing at ~50% of F(max) . LRQ and CSAR were significantly greater for VCE-PL than for PL (P<.001). When VCE was performed before PL, 12% less force was required to achieve an LRQ of 0.8, and 45% less for a CSAR of 0.8. CONCLUSIONS: In vitro, VCE performed before PL enables the arytenoid cartilage to be abducted to a greater degree for a given PL suture force.

Implications of the neuroanatomy of the equine thoracolumbar vertebral column with regional anaesthesia and complications following desmotomy of the interspinous ligament.

Impinging/overriding dorsal spinous processes (DSPs) of the thoracolumbar vertebrae are a common cause of poor performance in horses. In the last five decades, numerous surgical treatments have been reported on, from transverse transection of the affected DSPs, and endoscopic resection of the affected DSPs, to transection of the interspinous ligament. Until recently, cosmetic outcomes have been reported as good to excellent in studies. However, a previously unreported complication of neurogenic atrophy of the contralateral epaxial muscle following desmotomy of the interspinous ligament has been recently reported. The authors hypothesised that this was because of a more lateral approach than previously described, resulting in the scissors being too far across midline and transecting a nerve in the region. Considering this finding, we have reviewed the literature on the neuroanatomy of the thoracolumbar region in the horse. Literature on the neuroanatomy of the horse is lacking when compared with that of humans and companion animals, with most of the work extrapolated from companion animals. Based on the current literature, we hypothesise that transection of an intermediate branch of the dorsal spinal nerve supplying the m. longissimus is potentially the cause of the post-operative neurogenic atrophy. The lack of detailed knowledge of the neural anatomy of the equine back has resulted in the role of local anaesthesia in localising pain in the equine back being poorly understood. The wide variation in techniques used for localising back pain may explain why some horses suffering from poor performance or an abnormal gait because of back pain improve to local anaesthesia of the back while others do not. This review article highlights a lack of anatomical knowledge regarding the equine thoracolumbar region in the literature despite diagnostic local anaesthesia, medication, and surgery in this area being relatively common.

Full-thickness skin grafting to cover equine wounds caused by laceration or tumor resection.

OBJECTIVE: To describe and evaluate full-thickness skin grafting of equine wounds. STUDY DESIGN: Case series. ANIMALS: Adult horses (n=6). METHODS: A full-thickness graft was harvested from the pectoral region with the horse anesthetized or standing and sedated after local anesthetic infiltration. Grafts were attached to the cutaneous margin of the wound with staples and/or sutures if the horse was anesthetized or if the recipient site was desensitized. Cyanoacrylate glue was used to attach the grafts to the cutaneous margin of the wound of 3 horses. Medical records were reviewed for history, physical examination findings, grafting technique, postoperative complications, and outcome. RESULTS: Three horses had full-thickness skin grafting to cover a fresh defect created by excision of a cutaneous neoplasm, and 3 horses had full-thickness skin grafting to cover a fresh or granulating laceration. Grafts were completely accepted in 5 horses. The superficial layers of all grafts sloughed, but the final cosmetic appearance of accepted grafts was good. CONCLUSIONS: Full-thickness skin grafting can be performed in standing sedated horses with good cosmesis, especially when the meshed graft is expanded minimally. CLINICAL RELEVANCE: Good acceptance of a full-thickness graft can be expected, regardless of whether the graft is applied to a fresh or granulating wound.

Bone and Cartilage Interfaces With Orthopedic Implants: A Literature Review.

The interface between a surgical implant and tissue consists of a complex and dynamic environment characterized by mechanical and biological interactions between the implant and surrounding tissue. The implantation process leads to injury which needs to heal over time and the rapidity of this process as well as the property of restored tissue impact directly the strength of the interface. Bleeding is the first and most relevant step of the healing process because blood provides growth factors and cellular material necessary for tissue repair. Integration of the implants placed in poorly vascularized tissue such as articular cartilage is, therefore, more challenging than compared with the implants placed in well-vascularized tissues such as bone. Bleeding is followed by the establishment of a provisional matrix that is gradually transformed into the native tissue. The ultimate goal of implantation is to obtain a complete integration between the implant and tissue resulting in long-term stability. The stability of the implant has been defined as primary (mechanical) and secondary (biological integration) stability. Successful integration of an implant within the tissue depends on both stabilities and is vital for short- and long-term surgical outcomes. Advances in research aim to improve implant integration resulting in enhanced implant and tissue interface. Numerous methods have been employed to improve the process of modifying both stability types. This review provides a comprehensive discussion of current knowledge regarding implant-tissue interfaces within bone and cartilage as well as novel approaches to strengthen the implant-tissue interface. Furthermore, it gives an insight into the current state-of-art biomechanical testing of the stability of the implants. Current knowledge reveals that the design of the implants closely mimicking the native structure is more likely to become well integrated. The literature provides however several other techniques such as coating with a bioactive compound that will stimulate the integration and successful outcome for the patient.

Successful treatment of a sinonasal cryptococcal granuloma in a horse.

CASE DESCRIPTION: A 12-year-old 500-kg (1,100-lb) American Quarter Horse mare was evaluated because of chronic mucopurulent, bloody discharge from the left nostril, inspiratory dyspnea, and respiratory noise. CLINICAL FINDINGS: The horse had severe inspiratory dyspnea and stertorous respiration with no airflow from the left nostril. A temporary tracheostomy was performed. Endoscopy revealed a tan mass protruding from the left middle nasal meatus into the left common nasal meatus; it extended caudally into the nasopharynx and around the caudal edge of the nasal septum into the right nasal cavity. Radiographically, a soft tissue opacity was evident in most of the left nasal cavity and left paranasal sinuses. Cytologic examination of mass tissue revealed evidence of pyogranulomatous rhinitis; thickly encapsulated, budding yeast typical of Cryptococcus neoformans were detected. TREATMENT AND OUTCOME: While the horse was sedated and in a standing position, the fungal granuloma was removed from the paranasal sinuses. Treatment with fluconazole (5 mg/kg [2.27 mg/lb], PO, q 24 h for 4 weeks) was initiated; enilconazole (50 mL of a 10% solution) was instilled into the paranasal sinuses every other day (7 lavages). Six weeks after surgery, infection had not recurred and epithelialization appeared normal in the left paranasal sinuses. CLINICAL RELEVANCE: In horses with cryptococcosis of the paranasal sinuses, surgical removal of granulomatous lesions and systemic and topical administrations of antifungal drugs may be curative. Successful surgery may be performed in standing horses. Concommitant removal of a large portion of the conchae allows follow-up rhinoscopic evaluation of the paranasal sinuses.

Effects of extracorporeal shock wave therapy on wounds of the distal portion of the limbs in horses.

OBJECTIVE: To evaluate the effects of focused, extracorporeal shock wave therapy (ESWT) on the healing of wounds of the distal portion of the limbs in horses. DESIGN: Randomized controlled trial. ANIMALS: 6 healthy adult horses. PROCEDURES: In each horse, a 4-cm-diameter full-thickness wound that included underlying periosteum was created on the dorsomedial aspect of each metacarpus and two 3-cm-diameter full-thickness wounds that included underlying periosteum were created on the dorsomedial aspect of each metatarsus. One randomly selected metacarpal wound and a randomly selected pair of metatarsal wounds were treated once weekly with ESWT at an energy flux density of 0.11 mJ/mm(2). For metacarpal wounds, swab specimens were collected for bacterial culture on days 1, 2, and 3 and area of epithelialization and extent of wound contraction were measured at 3- to 4-day intervals. Metatarsal wounds were biopsied after 2 and 4 weeks, and immunohistochemical staining for vascular endothelial growth factor, transforming growth factor-beta1, and insulin-like growth factor-1 was performed. RESULTS: Results of bacterial culture, area of epithelialization, and percentage of wound contraction did not differ between treated and untreated wounds; however, healing time for treated wounds (mean, 76 days) was significantly shorter than healing time for untreated wounds (90 days). Staining intensity of growth factors did not differ significantly between treated and untreated wounds. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that ESWT may stimulate healing of wounds of the distal portion of the limbs in horses, although the mechanism by which healing was stimulated could not be identified.

Comparison of sinoscopic techniques for examining the rostral maxillary and ventral conchal sinuses of horses.

OBJECTIVE: To develop a reliable technique for sinoscopic examination of the ventral conchal (VCS) and rostral maxillary sinuses (RMS) of horses STUDY DESIGN: Descriptive study ANIMALS: Cadaveric equine heads (n=40) METHODS: The VCS and RMS were examined endoscopically using: (1) rostral trephination of the RMS (rostral RMS approach); (2) caudal trephination of the RMS (caudal RMS approach); (3) conchofrontal sinus (CFS) trephination followed by RMS trephination at a site identified by endoscopic transillumination of the maxillary bone at the most rostral aspect of the caudal maxillary sinus (CMS) (light-indicated RMS approach); (4) CFS trephination with fenestration of the ventral conchal bulla (VCB; frontal VCB approach); (5) CMS trephination with VCB fenestration (caudal VCB approach); and (6) CFS and CMS trephination with VCB fenestration (combined VCB approach). RESULTS: Success in observing the rostral and caudal aspects of the VCS and RMS with each approach were: (1) rostral RMS approach (0 horses; 16 horses [40%]); (2) caudal RMS approach (0 horses; 11 horses [28%]); (3) light-indicated RMS approach (3 horses [8%]; 24 horses [60%]); (4) frontal VCB approach (24 horses [60%]; 29 horses [73%] respectively); (5) caudal VCB approach (16 horses [40%] both structures); and (6) combined VCB approach (27 horses [68%]; 35 horses [88%]). CONCLUSIONS: Trephination into the CFS coupled with fenestration of the VCB provided consistent access to both the rostral and caudal aspects of the RMS and VCS. A trephine hole into the RMS provided poor access to the VCS, and placed the reserve crowns of the maxillary cheek teeth at risk of damage. CLINICAL RELEVANCE: The RMS and VCS can be best examined endoscopically using approaches with fenestration of the VCB.

Effects of hyperbaric oxygen on full-thickness meshed sheet skin grafts applied to fresh and granulating wounds in horses.

OBJECTIVE: To determine the effects of hyperbaric oxygen therapy (HBOT) on full-thickness skin grafts applied to fresh and granulating wounds of horses. ANIMALS: 6 horses. PROCEDURES: On day 0, two 4-cm-diameter circular sections of full-thickness skin were removed from each of 2 randomly selected limbs of each horse, and two 4-cm-diameter circular skin grafts were harvested from the pectoral region. A skin graft was applied to 1 randomly selected wound on each limb, leaving the 2 nongrafted wounds to heal by second intention. On day 7, 2 grafts were harvested from the pectoral region and applied to the granulating wounds, and wounds grafted on day 0 were biopsied. On day 14, 1 wound was created on each of the 2 unwounded limbs, and the wounds that were grafted on day 7 were biopsied. All 4 ungrafted wounds (ie, 2 fresh wounds and 2 wounds with 1-week-old granulation beds) were grafted. The horses then received HBOT for 1 hour daily at 23 PSI for 7 days. On day 21, the grafts applied on day 14 were biopsied. RESULTS: Histologic examination of biopsy specimens revealed that grafts treated with HBOT developed less granulation tissue, edema, and neovascularization, but more inflammation. The superficial portion of the graft was also less viable than the superficial portion of those not treated with HBOT. CONCLUSIONS AND CLINICAL RELEVANCE: The use of HBOT after full-thickness skin grafting of uncompromised fresh and granulating wounds of horses is not indicated.

Surgical correction of wry nose in four horses.

OBJECTIVE: To describe surgical techniques used for correction of congenital nasal deviation (wry nose) in horses (wry nose) and to report outcome. STUDY DESIGN: Retrospective study. ANIMALS: Horses (n=4), 5-17 months old with wry nose. METHODS: Nasal deviation was corrected by transecting the premaxillae/maxillae and nasal bones at their site of maximum curvature and realigning and stabilizing the bones in a more normal alignment using internal fixation. The nasal septum was removed during the same anesthetic period. RESULTS: For each horse, physical appearance was improved and respiratory stridor eliminated. CONCLUSIONS: Wry nose can be corrected by transecting the premaxillae/maxillae and nasal bones and stabilizing the transected bones in a more normal alignment; the nasal septum can be removed concurrently. CLINICAL RELEVANCE: Surgical correction of wry nose may provide a good functional and cosmetic outcome.

Compressive damage to the deep branch of the lateral plantar nerve associated with lameness caused by proximal suspensory desmitis.

OBJECTIVE: To describe pathologic changes in the deep branch of the lateral plantar nerve (DBLPN) of horses determined to be lame because of proximal suspensory desmitis (PSD), and to report the outcome after treatment by excision of a segment of the horses' DBLPN. STUDY DESIGN: Retrospective case series. ANIMALS: Adult horses (n=16). METHODS: Horses determined to be lame on one or both pelvic limbs because of PSD were treated by excision of a segment of the DBLPN, and 30 nerves were examined histologically. Owners were contacted to obtain information about the horses >or=6 months after surgery. RESULTS: Histologic changes suggestive of chronic nerve compression were identified in both nerves of 11 bilaterally lame horses and in the lame limb of 5 unilaterally lame horses. The nerve of the sound limb of 2 of 3 unilaterally lame horses that had bilateral nerve resection also had histologic changes compatible with nerve compression. Ten of 16 horses (62.5%) with follow-up information returned to soundness after excision of the DBLPN. CONCLUSIONS: Pathologic changes of the DBLPN associated with compression may complicate PSD of the pelvic limbs. Excision of the nerve may resolve lameness caused by PSD. CLINICAL RELEVANCE: Horses lame because of PSD of the pelvic limb may remain lame after desmitis has resolved because of compression of the DBLPN. Excising a portion of this nerve may resolve lameness.

Effects of stacked wedge pads and chains applied to the forefeet of Tennessee Walking Horses for a five-day period on behavioral and biochemical indicators of pain, stress, and inflammation.

OBJECTIVE To determine the effects of stacked wedge pads and chains applied to the forefeet of Tennessee Walking Horses on behavioral and biochemical indicators of pain, stress, and inflamation. ANIMALS 20 Tennessee Walking Horses. PROCEDURES Horses were randomly assigned to 2 treatment groups: keg shoes (control; n = 10) or stacked wedge pads and exercise with chains (10). Ten days before treatment application, an accelerometer was attached at the left metatarsus of each horse to record daily activity. Horses were exercised for 20 minutes daily, beginning on day -7. On day 0, exercise ceased, the forefeet were trimmed, and the assigned treatment was applied. From days 1 through 5, horses were exercised as before. Blood samples for measurement of plasma cortisol, substance P, and fibrinogen concentrations were collected on days -5, 1, and 5 before and after exercise and every 30 minutes thereafter for 6 hours. RESULTS No significant differences in plasma concentrations of cortisol, substance P, and fibrinogen were detected between groups. Although lying behaviors changed after shoes were applied, these behaviors did not differ significantly between groups. Shoeing appeared to have altered behavior to a greater extent than did the type of treatment applied. CONCLUSIONS AND CLINICAL RELEVANCE Application of stacked wedge pads and chains to the forefeet of horses for a 5-day period as performed in this study evoked no acute or subacute stress or nociceptive response as measured. Although these findings should not be extrapolated to the long-term use of such devices in Tennessee Walking Horses performing the running walk, the data should be considered when making evidence-based decisions relating to animal welfare and the use of stacked wedge pads and chains.