Genomic loci associated with performance limiting equine overriding spinous processes (kissing spines).

Commonly known as "Kissing Spines" (KS), the pathological mechanisms underlying impingement and overriding of spinous processes (ORSPs) in horses are poorly understood. Thoroughbreds, Warmbloods, and stock-type breeds, including Paint Horses and Quarter Horses are at increased risk for developing clinical signs of KS. A total of 155 stock-type and Warmblood horses presented at collaborating veterinary clinics and hospitals were examined using a strict clinical and radiographical phenotyping scheme to grade each horse from 0 for unaffected controls to 4 for severe KS. Following genotyping with the Illumina Equine SNP70 array (Illumina, Inc.) a Genome Wide Association Study (GWAS) using 61,229 filtered individual Single Nucleotide Polymorphisms (SNPs) was performed to the KS grade phenotype. Two significantly associated SNPs (BIEC2-668062 and BIEC2-668013) on chromosome 25 defined a ~1.4 Gb candidate region containing approximately 17 coding genes (EquCab3) and 195 ENSEMBL annotated variants. Investigation of the best associated SNP (BIEC2-668062) on chr25 demonstrates a significant correlation with an increase in one KS grade, on average, per A allele in this population. A significant effect of breed group, age, height or sex was not observed in this population. These preliminary results demonstrate the potential for KS diagnosis and preventative measures for WB/ST individuals supported by increased genetic risk for more severe KS grade. We propose further research including other affected breeds and evaluating causative variants, as well as the effect of BIEC2-668062 in these populations.

Results of plate fixation of type 5 olecranon fractures in 20 horses.

REASONS FOR PERFORMING STUDY: Previous olecranon fracture reports contain a small proportion of type 5 fractures, mostly treated with conservative therapy. OBJECTIVES: To evaluate the clinical details and outcome of type 5 olecranon fractures in a large group of horses treated by tension band plate fixation and to compare results with other treatment methods. METHODS: Medical records of 97 cases, including 32 (33%) classified as type 5, were reviewed. Subject details, history, radiographic findings, treatment and follow-up results (2-146 months post operatively) were recorded. RESULTS: Treatment included open reduction and internal fixation using a narrow or broad dynamic compression plate (n = 20), conservative therapy (n = 7) and euthanasia (n = 5). Long-term follow-up was available in 15 cases treated surgically, of which 2 were sound and in training, 11 sound and performing athletically and 2 unsound. Distal semilunar notch involvement, comminution or open status did not appear to affect prognosis. CONCLUSIONS: Internal plate fixation provides an excellent prognosis for an animal to be capable of athletic performance. POTENTIAL RELEVANCE: Describing tension band plate fixation and results offers a method of fracture repair that should improve treatment and prognosis for type 5 olecranon fractures.

Results of plate fixation of type 1b olecranon fractures in 24 horses.

REASONS FOR PERFORMING STUDY: Previous olecranon fracture reports contain a small proportion of type 1b fractures, with only a few repaired by tension band plate fixation. OBJECTIVES: To evaluate subject details, history, clinical findings and outcome of type 1b olecranon fractures in a large group of horses treated by tension band plate fixation. METHODS: Medical records of 77 horses diagnosed with an olecranon fracture were reviewed. Twenty-four horses (31%) were classified as having type 1b olecranon fractures. Clinical details and follow-up results (4-128 months post operatively) were recorded. RESULTS: Treatment included open reduction and internal fixation using a narrow dynamic compression plate (n = 20), conservative therapy (n = 2) and euthanasia (n = 2). Long-term follow-up was available for 16 plated horses. Four were sound and in training and 9 were sound and performing athletically. Articular surface involvement, comminution, open status or removal of anconeal process fragments did not appear to affect prognosis or soundness. CONCLUSIONS: Internal plate fixation provides an excellent prognosis for an animal capable of athletic performance. POTENTIAL RELEVANCE: Describing tension band plate fixation and results offers a method of fracture repair that will improve the treatment and prognosis for type 1b olecranon fractures.

Osteomyelitis of the sustentaculum tali in horses: 10 cases (1992-1998).

OBJECTIVE: To determine outcome of horses with osteomyelitis of the sustentaculum tali (ST), with or without associated tarsal sheath tenosynovitis, following surgical debridement and lavage. DESIGN: Retrospective study. ANIMALS: 10 horses in which a diagnosis of osteomyelitis of the ST had been made on the basis of history, physical examination findings, and results of radiography. PROCEDURE: Information on results of diagnostic testing, surgical findings, postoperative treatment, and short-term outcome was obtained from the medical records. Long-term follow-up information was obtained through reevaluation of horses at the teaching hospital and telephone conversations with referring veterinarians, owners, and trainers. RESULTS: Treatment consisted of surgical debridement, intra- and postoperative lavage, and long-term antimicrobial and anti-inflammatory treatment. Eight horses had evidence of involvement of the tarsal sheath. One horse was euthanatized after surgery because of a lack of response to treatment; the other 9 were discharged from the hospital. Severity of lameness had improved, but all still had grade-1 or -2 lameness at the time of discharge. One horse was euthanatized after discharge because of contralateral hind limb laminitis, and another horse was lost to follow-up. Of the remaining 7 horses, 6 returned to their previous use, and 1 was sound but retired for breeding for unrelated reasons. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that horses with osteomyelitis of the ST, with or without concomitant tarsal sheath tenosynovitis, can have an excellent to good outcome and may return to their previous use after surgical debridement of affected tissues and lavage of the tarsal sheath.

Osteitis of the axial border of the proximal sesamoid bones in horses: eight cases (1993-1999).

OBJECTIVE: To determine clinical, radiographic, and scintigraphic abnormalities in and outcome of horses with septic or nonseptic osteitis of the axial border of the proximal sesamoid bones. DESIGN: Retrospective study. ANIMALS: 8 horses. PROCEDURE: Data collected from medical records included signalment; history; horse use; severity and duration of lameness; results of perineural anesthesia, radiography, ultrasonography, and scintigraphy; and outcome following surgery. RESULTS: Five horses did not have any evidence of sepsis; the other 3 had sepsis of the metacarpophalangeal or metatarsophalangeal joint or the digital synovial sheath. All horses had a history of chronic unilateral lameness. Three of 5 horses improved after diagnostic anesthesia of the metacarpophalangeal or metatarsophalangeal joint; the other 2 improved only after diagnostic anesthesia of the digital synovial sheath. Nuclear scintigraphy was beneficial in localizing the source of the lameness to the proximal sesamoid bones in 4 horses. Arthroscopy of the palmar or plantar pouch of the joint or of the digital synovial sheath revealed intersesamoidean ligament damage and osteomalacia of the axial border of the proximal sesamoid bones in all horses. All 5 horses without sepsis and 1 horse with sepsis returned to their previous uses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that osteitis of the axial border of the proximal sesamoid bones is a distinct entity in horses that typically is associated with inflammation of the associated metacarpointersesamoidean or metatarsointersesamoidean ligament and may be a result of sepsis or nonseptic inflammation. Arthroscopic debridement may allow horses without evidence of sepsis to return to their previous level of performance.

A multicenter, matched case-control study of risk factors for equine laminitis.

Risk factors for equine laminitis were examined in a prospective case-control study of the 258 cases seen at six collaborating veterinary teaching hospitals over a 32-month period. Case-control pairs were matched on institution, clinician, and season of diagnosis. The 90% of case-control pairs (78 acute, 155 chronic) that had complete data for age, gender, and breed were used in separate conditional logistic-regression models for acute and chronic laminitis. There was an increase in risk for horses with acute laminitis from 5 to 7 years of age (OR 4.7, 95% CI 1.3-16) and from 13 to 31 years of age (OR 3.9, 95% CI 1.3-12) (both compared to <5 years); risk was increased for chronic laminitis from 10 to 14 years (OR 3, 95% CI 1.4-6.8) and from 15 to 38 years (OR 2.9, 95% CI 1.4-6.1) (both compared to <6 years). Mares - but not stallions - were more likely than geldings to develop acute laminitis (OR 2.6, 95% CI 1.1-6.2) and chronic laminitis (OR 2.0, 95% CI 1.1-3.6). In the small acute-laminitis data set, the breed variable was collapsed into three categories: Thoroughbred (THB, reference), the Quarter Horse (QH), and other (non-QH-THB). The non-QH-THB group was at increased risk of acute laminitis (OR 3.8, 95% CI 1.2-11.8). For the seven breed-group categories used in the chronic-laminitis model, however, all non-THB breed groups appeared significantly at risk as compared to the THB, with odds ratios ranging from 3.3 (95% CI 1.3-8.30) for the QH to 9.1 (95% CI 2.1-39.3) for ponies.

Treatment response and athletic outcome of foals with tarsal valgus deformities: 39 cases (1988-1997).

OBJECTIVE: To evaluate the response to various treatments and long-term outcome of foals with tarsal valgus deformities. DESIGN: Retrospective study. ANIMALS: 39 foals with tarsal valgus deformities. PROCEDURE: Data collected from medical records, included signalment, history, reason for admission, and clinical findings. Radiographic views of the tarsus were evaluated for incomplete ossification of tarsal bones and were classified as normal in appearance, type-I incomplete ossification, or type-II incomplete ossification. Treatment and athletic outcome were documented for each foal. RESULTS: Radiographic assessment revealed that 22 of 39 foals (56%) had concomitant tarsal valgus deformities and incomplete ossification of the tarsal bones. Eight of 19 foals with tarsal valgus deformities that were treated with periosteal stripping responded favorably. Foals < or = 60 days old were significantly more likely to respond to periosteal stripping than older foals. Five of 8 foals with tarsal valgus deformities that were treated with growth plate retardation responded favorably. Eleven of 21 foals with long-term follow-up performed as intended. Compared with foals with type-II incomplete ossification, foals with tarsal bones that had a normal radiographic appearance or type-I incomplete ossification were significantly more likely to perform as intended. CONCLUSIONS AND CLINICAL RELEVANCE: Foals with tarsal valgus deformities should have lateromedial radiographic views of the tarsus obtained to assess the tarsal bones for incomplete ossification, which will affect athletic outcome. Because foals with type-II incomplete ossification of the tarsal bones respond poorly to periosteal stripping alone, treatment by growth-plate retardation is recommended.

Nonsurgical treatment of suprascapular nerve injury in horses: 8 cases (1988-1998).

OBJECTIVE: To determine the outcome of horses with suprascapular nerve injury treated with stall rest alone. DESIGN: Retrospective case series. ANIMALS: 8 horses. PROCEDURE: Information on signalment, history, limbs affected, severity of lameness, degree of muscle atrophy, gait abnormalities, and results of radiography and electromyography was obtained from medical records. All horses were treated with stall rest. Follow-up information on severity of lameness, gait abnormalities, degree of muscle atrophy, time between injury and resolution of gait abnormalities, and outcome was obtained during reexamination at the hospital or through telephone conversations with owners. RESULTS: In 4 horses, the injury was a result of trauma; in the other 4, the injury was suspected to be a result of trauma. All horses had pronounced instability of the shoulder joint during the weight-bearing phase. Follow-up information was available for 7 horses. Shoulder joint instability resolved in all 7 horses within 3 to 12 months (mean, 7.4 months) after the original injury. Two horses had complete return of the supraspinatus and infraspinatus muscle mass 15 and 18 months after the injury. Two horses used as broodmares before the injury and 4 of 5 horses used for riding or in race training before the injury were able to return to preinjury activities. CLINICAL IMPLICATIONS: Horses with suprascapular nerve injury treated with stall rest alone have a good prognosis for recovery of normal gait and return to performance; however, the recovery period may be prolonged.

Deep digital flexor tenotomy as a treatment for chronic laminitis in horses: 35 cases (1988-1997)

OBJECTIVE: To determine long-term prognosis for horses with laminitis treated by deep digital flexor (DDF) tenotomy and to identify factors affecting success of the surgical procedure. DESIGN: Retrospective study. ANIMALS: 35 horses with laminitis treated by DDF tenotomy between 1988 and 1997. PROCEDURE: Information was obtained from individual medical records and follow-up telephone interviews with owners and referring veterinarians. Cumulative proportions of horses that survived 6 months and 2 years after tenotomy were determined. Effect of Obel grade of lameness on 6-month and 2-year survival and effect of distal phalangeal rotation on survival and future performance were evaluated by chi 2 analysis. Body weights of horses that survived > or = 2 years were compared with those of horses that survived < 2 years by ANOVA. RESULTS: 27 of the 35 (77%) horses survived > or = 6 months, and 19 of 32 (59%) survived > 2 years. Obel grade of lameness and body weight at time of surgery had no effect on 6-month or 2-year survival. Degree of distal phalangeal rotation had no effect on 2-year survival or the ability of horses to be used for light riding. Twenty-two of the 30 (73%) owners interviewed indicated they would have the procedure repeated on their horses given similar circumstances. CLINICAL IMPLICATIONS: DDF tenotomy is a viable alternative for horses with laminitis refractory to conventional medical treatment. In some instances, the procedure may be effective in returning horses to light athletic use.

Incomplete ossification of the tarsal bones in foals: 22 cases (1988-1996).

OBJECTIVE: To determine outcome for foals with incomplete ossification of the tarsal bones and to determine whether clinical and radiographic abnormalities at the time of initial examination were associated with outcome. DESIGN: Retrospective study. ANIMALS: 22 foals. PROCEDURE: Information on signalment, history, owner's initial complaint, clinical findings, whether tarsus valgus was evident, and radiographic abnormalities was obtained from medical records. Radiographic lesions were classified as type I (i.e., incomplete ossification with < 30% collapse of the affected bones) or type II (incomplete ossification with > 30% collapse and pinching or fragmentation of the affected bones). Follow-up information was obtained via telephone conversations with owners. RESULTS: Foals were between 1 day and 10 months old when first examined. Eleven were premature (i.e., < 320 days of gestation) or were twins. Sixteen had tarsus valgus. Severity of radiographic lesions was associated with outcome; 4 of 6 foals with type-I incomplete ossification of the tarsal bones performed as intended, but only 3 of 16 foals with type-II incomplete ossification of the tarsal bones performed as intended. CLINICAL IMPLICATIONS: For foals with incomplete ossification of the tarsal bones, severity of the radiographic lesions was associated with outcome. Foals with type-II incomplete ossification of the tarsal bones have a guarded prognosis for athletic soundness.

Traumatic dental disease and soft tissue injuries of the oral cavity.

Trauma to the oral cavity can result in an array of injuries affecting teeth, bone, and soft tissue. A thorough examination of the oral cavity is often facilitated by employing a full-mouth speculum after the horse has been tranquilized. Identification of broken, loose, or split teeth; fractures of the premaxilla or mandible; and avulsion or laceration of soft tissue structures such as the lips or tongue is usually straightforward. Treatment options vary depending on the structure involved; however, appropriate treatment generally results in a functional and cosmetically acceptable end result.

Transendoscopic chemical ablation of progressive ethmoidal hematomas in standing horses.

OBJECTIVE: To examine the response of horses with progressive ethmoidal hematoma (PEH) to intralesional injection of 4% formaldehyde solution. STUDY DESIGN: Nasal passages of horses affected with PEH were examined endoscopically at different intervals to determine the effects of intralesional injection of formaldehyde solution. ANIMALS: 21 horses with PEH. METHODS: PEHs were injected transendoscopically with 4% formaldehyde solution. Horses were examined endoscopically and retreated at different intervals until the PEH was eliminated or was so small that reinjection was not possible. RESULTS: Lesions diminished significantly in size or were eliminated after 1 to 18 injections (median, 5; mean, 7.0 +/- 5.62). Seventeen lesions (60.7%) resolved completely after 1 to 18 injections (median, 5; mean, 7.2 +/- 5.71). Five lesions decreased markedly in size but did not resolve after receiving 1 to 18 injections (median, 5; mean, 7.6 +/- 6.66). Injection of these lesions was discontinued 4.0 to 25.1 months (median, 9.5; mean, 11.02 +/- 8.446) after the first injection. The PEH of one horse was removed surgically after one injection. Three horses, one with bilateral PEH, were lost to follow-up. One horse developed signs of laminitis. No other complications were observed. CONCLUSIONS: Horses with a PEH can be treated effectively by transendoscopic, intralesional injection of 4% formaldehyde solution. CLINICAL RELEVANCE: Ablation of PEH using formaldehyde solution avoids general anesthesia and problems associated with ablation by conventional surgery or laser.

Evaluation of postoperative peritoneal lavage in standing horses for prevention of experimentally induced abdominal adhesions.

OBJECTIVE: To evaluate the postoperative use of peritoneal lavage for prevention of experimentally induced intraabdominal adhesions in horses. STUDY DESIGN: Areas of serosal abrasion were created on the jejunum of 12 horses. Postoperatively, six horses had peritoneal lavage, and six horses did not (controls). The number of adhesions was determined at necropsy 2 weeks after surgery. ANIMALS OR SAMPLE POPULATION: 12 horses. METHODS: Five sites of jejunal serosal abrasion were created in each horse. A 32 French thoracic catheter was placed into the right ventral aspect of the abdomen before closure of the abdominal incision. Treated horses had abdominal lavage with 10 L of lactated Ringer's solution on four occasions, then catheters were removed from all horses 34 hours after celiotomy. Horses were necropsied at 2 weeks to quantify the number of intraabdominal adhesions. RESULTS: All control horses and one treated horse developed intraabdominal adhesions. The number of adhesions was significantly less (P < .0293) in treated horses. No adverse inflammatory reactions appeared to be associated with repeated peritoneal lavage using lactated Ringer's solution or use of an abdominal drain. CONCLUSIONS: Peritoneal lavage reduced the frequency of intraabdominal adhesions. CLINICAL RELEVANCE: When postoperative adhesions are likely to develop, postoperative peritoneal lavage may decrease the frequency of adhesion formation.

Surgical treatment of subchondral cystic lesions of the third metacarpal bone: results in 15 horses (1986-1994).

Subchondral cystic lesions (SCLs) in the condyle of the third metacarpal bone (MCIII) were surgically treated in 15 horses. The median age at presentation was 18 months (range 10 months-12 years) with 10 of 15 horses less than age 2 years. The SCLs were confined to the front limbs in all cases with 2 horses having bilateral lesions. Lesions were isolated to the medial condyle(s) of MCIII in 13 of 15 horses; a cystic lesion occurred in the lateral condyle in one horse and in the sagittal ridge in one horse. One horse with bilateral lesions had an additional cystic lesion located in the right medial femoral condyle. Fourteen of 15 horses had a history of moderate lameness attributable to the metacarpophalangeal joint; the lesion was an incidental finding in one horse. Duration of lameness ranged from 4 weeks to 8 months and was either acute in onset, or occurred intermittently and was associated with exercise. Fetlock flexion significantly exacerbated the lameness in all cases. Synovial effusion was absent in 8 (53%) cases. Cystic lesions were curetted arthroscopically in 12 horses, and through a dorsal pouch arthrotomy in 3 horses. Concurrent osteostixis of the cystic cavity was performed in 7 horses. Two horses were treated arthroscopically for osteochondral fragmentation of the proximodorsal aspect of the proximal phalanx one year following surgical curettage of the SCL. Twelve of 15 horses (80%) were sound for intended use following surgical treatment. Two horses did not regain soundness and follow-up information was unavailable for one horse. Total period of follow-up was 1-6 years. Follow-up radiographic examinations were available for 9 horses. Mild periarticular osteophyte formation and enthesiophyte formation at the dorsal joint capsular attachments was present in 5 of the 9 horses. Bony ingrowth of the cystic lesion was detectable in 8 horses and enlargement of the cystic cavity was observed in one horse. Based on the information gained from this study, it would appear that surgical treatment of SCLs in the distal metacarpus can result in a favourable outcome for athletic use.

Effects of postoperative peritoneal lavage on pharmacokinetics of gentamicin in horses after celiotomy.

OBJECTIVE: To evaluate the effect of peritoneal lavage on pharmacokinetics of gentamicin sulfate in healthy horses after experimental celiotomy. ANIMALS: 13 clinically normal horses. PROCEDURE: Horses were randomly assigned to control or experimental groups. All horses received gentamicin (6.6 mg/kg of body weight, IV, q 24 h) before surgery, underwent experimental abdominal surgery, and had abdominal drains placed percutaneously. Horses of the experimental group received postoperative peritoneal lavage; horses of the control group did not receive peritoneal lavage. The day after surgery, 24 hours after the preoperative dose of gentamicin, a second dose of gentamicin was administered. Three and 15 hours after this second dose of gentamicin, horses of the experimental group received peritoneal lavage. Venous blood was obtained, for determination of concentration of gentamicin, immediately before and at specified intervals during the 24-hour period after the second dose of gentamicin. RESULTS: There were no differences in any of the pharmacokinetic values of gentamicin between horses of the control and experimental groups. CONCLUSIONS: Peritoneal lavage had no effect on pharmacokinetics of gentamicin in healthy horses after abdominal surgery, in which localized nonseptic peritonitis was induced. CLINICAL RELEVANCE: Peritoneal lavage in horses with localized nonseptic peritonitis or for the prevention of intra-abdominal adhesions should not necessitate alteration of the dosage of gentamicin to maintain predictable serum concentrations.

Racing-related factors and results of prerace physical inspection and their association with musculoskeletal injuries incurred in thoroughbreds during races.

OBJECTIVE: To describe and compare data from Thoroughbreds that sustained musculoskeletal injuries while racing with data from matched control horses. DESIGN: Matched case-control study. ANIMALS: 216 Thoroughbreds that sustained a musculoskeletal injury while racing and 532 horses from the same races that were not injured. PROCEDURE: Data regarding racing history, race-entrant characteristics, racing events determined by analysis of videotapes of races, and results of prerace physical inspections were determined for all horses. Injured horses were compared with control horses by using conditional logistic regression. RESULTS: Results of prerace inspection by regulatory veterinarians were significantly associated with injury. Odds of musculoskeletal injury, injury of the suspensory apparatus of the forelimb, and injury of the tendon of the superficial digital flexor muscle of the forelimb were 5.5 to 13.5 times greater among horses assessed to be at increased risk of injury by regulatory veterinarians on the basis of results of prerace inspection than for horses not considered to be at increased risk of injury. Odds of an abnormal finding in the suspensory ligament during prerace inspection were 3.4 times greater among horses that injured the suspensory apparatus than among control horses, and odds of an abnormal finding in the tendon of the superficial digital flexor muscle during prerace inspection were 15 times greater among horses that injured the tendon than among control horses. CLINICAL IMPLICATIONS: Regulatory veterinarians can identify horses during prerace physical inspection that have an increased risk of injury during races. Prerace physical inspections could be used to reduce the risk of injury to Thoroughbreds during races.

Evaluation of skin bacterial flora before and after aseptic preparation of clipped and nonclipped arthrocentesis sites in horses.

OBJECTIVE: This study evaluates skin bacterial flora before and after aseptic preparation of clipped and nonclipped arthrocentesis sites in horses. STUDY DESIGN: The hair over one midcarpal joint and one distal interphalangeal joint on each horse was clipped. The contralateral joint served as the nonclipped comparison. ANIMALS OR SAMPLE POPULATION: Twelve adult horses. METHODS: A prescrub sample for microbial culture was taken from the dorsal surface of all four joints for each horse. Each site was aseptically prepared with povidone iodine and 70% alcohol, followed by postscrub sampling for microbial culture. Colony forming units (CFUs) were determined for each sample, 24 hours after inoculation of blood agar plates. RESULTS: There was no significant difference (P > .05) in number of postscrub CFUs between clipped and nonclipped skin over the midcarpal or distal interphalangeal joints. Percent bacterial reduction (mean +/- SD%) after aseptic preparation differed significantly (P = .02) between clipped (99.8 +/- .003%) and nonclipped (96.2 +/- .05%) skin at the midcarpal joint, but not at the distal interphalangeal joint (clipped, 98.5 +/- .03% and nonclipped, 97.8 +/- 0.21%). There was a significant difference (P = .009) in number of prescrub CFUs obtained from clipped and nonclipped skin for the midcarpal joint. There was no significant difference in number of prescrub CFUs between clipped and nonclipped skin at the distal interphalangeal joint. Bacteria isolated from both clipped and nonclipped skin sampled postscrub included Bacillus sp, nonhemolytic Staphylococcus sp, and Micrococcus sp. CONCLUSIONS: The presence of hair over the midcarpal and distal interphalangeal joints does not appear to inhibit the ability of antiseptics to effectively reduce bacterial flora to an acceptable level for arthrocentesis. CLINICAL RELEVANCE: Aseptic preparation of the skin over the midcarpal and distal interphalangeal joints can be accomplished without hair removal in horses.