Dean W. Richardson

Suspensory Ligament Desmitis

The gross and functional anatomy of the suspensory ligament (SL) and its ultrasonographic variability are described. Injuries of the suspensory apparatus are divided into lesions confined to the proximal one third of the metacarpus or metatarsus (proximal suspensory desmitis and avulsion fractures), lesions of the body, and branch lesions. Complete breakdown injuries are also discussed. In view of the close association of the SL, the second, third, and fourth metacarpal or metatarsal bones, and the proximal sesamoid bones, associated bony lesions are also considered.

Dose-dependent effects of corticosteroids on the expression of matrix- related genes in normal and cytokine-treated articular chondrocytes

Abstract:Objective and Design: To assess the effects of glucocorticoids on the expression of multiple matrix-related genes in normal and cytokine-treated cultured equine articular chondrocytes in a phenotypically correct suspension culture.¶Material or Subjects: Articular cartilage harvested from the joints of 15 foals, 7 yearling horses, and 16 adult horses.¶Treatment: Glucocorticoids (dexamethasone, prednisolone, triamcinolone) at 10–10 to 10–4 M.¶Methods: Equine articular chondrocytes maintained in suspension cultures were treated with glucocorticoids with and without human recombinant interleukin 1-β (IL1-β) and tumor necrosis factor-α (TNF-α). Northern blots of total RNA from the treated cells were probed with equine specific cDNA probes for a number of cartilage matrix-related genes. Zymography, Western blotting, and fluorography were also performed to study the effects on protein synthesis. Results: The glucocorticoids, dexamethasone, triamcinolone, and prednisolone, markedly decreased MMP1, MMP3, MMP13, TIMP1, and ferritin steady-state mRNA levels. There were no qualitative differences seen among the tested corticosteroids although dexamethasone and triamcinolone appeared to be slightly more potent than prednisolone. The effects of the glucocorticoids on MMP transcription occurred consistently at lower doses than those required to similarly downregulate type II collagen and aggrecan. Link protein and fibronectin mRNA were increased by the glucocorticoids, and biglycan and decorin were minimally affected. Fluorography of [14-C] proline-labeled media demonstrated that the decrease in type II collagen transcription (mRNA levels) was paralleled at the protein level. Zymography and Western blotting confirmed the decrease in functional metalloproteinases found in chondrocyte cultures following glucocorticoid treatment.¶Conclusions: The effects of glucocorticoids are complex inasmuch as they differentially affect numerous genes involved in the composition of cartilage matrix and the degradation of that matrix. This study provides new insight into the effects of glucocorticoids on the regulation of extracellular matrix and matrix-related genes by demonstrating that low doses of glucocorticoids can inhibit the degradative metalloproteinases with minimal negative effects on the transcription of extracellular matrix genes.

Vancomycin-Modified Implant Surface Inhibits Biofilm Formation and Supports Bone-Healing in an Infected Osteotomy Model in Sheep: A Proof-of-Concept Study

BACKGROUND Implant-associated infections contribute to patient morbidity and health care costs. We hypothesized that surface modification of titanium fracture hardware with vancomycin would support bone-healing and prevent bacterial colonization of the implant in a large-animal model. METHODS A unilateral transverse mid-diaphyseal tibial osteotomy was performed and repaired with a titanium locking compression plate in nine sheep. Four control animals were treated with an unmodified plate and five experimental animals were treated with a vancomycin-modified plate. The osteotomy was inoculated with 2.5 × 106 colony-forming units of Staphylococcus aureus. The animals were killed at three months postoperatively, and implants were retrieved aseptically. Microbiologic and histologic analyses, scanning electron and confocal microscopy, and microcomputed tomography were performed. RESULTS All animals completed the study. Compared with the treatment cohort, control animals exhibited protracted lameness in the operatively treated leg. Gross findings during necropsy were consistent with an infected osteotomy accompanied by a florid and lytic callus. Microcomputed tomography and histologic analysis of the tibiae further supported the presence of septic osteomyelitis in the control cohort. Thick biofilms were also evident, and bacterial cultures were positive for Staphylococcus aureus in three of four control animals. In contrast, animals treated with vancomycin-treated plates exhibited a healed osteotomy site with homogenous remodeling, there was no evidence of biofilm formation on the retrieved plate, and bacterial cultures from only one of five animals were positive for Staphylococcus aureus. CONCLUSIONS Vancomycin-derivatized plate surfaces inhibited implant colonization with Staphylococcus aureus and supported bone-healing in an infected large-animal model.

Efficacy of Three Tourniquet Types for Intravenous Antimicrobial Regional Limb Perfusion in Standing Horses

OBJECTIVE To determine (1) if clinically useful concentrations of amikacin sulfate can be obtained in synovial fluid during regional limb perfusion (RLP) performed above the carpus in standing sedated horses and (2) to determine the efficacy of 3 tourniquet types (narrow rubber [NR], wide rubber [WR], pneumatic [PN]). ANIMALS Horses (n=9). METHODS Bilateral forelimb RLP with amikacin sulfate (2.5 g) were administered through the cephalic vein in standing sedated horses. Limbs were randomly assigned to the 3 tourniquet types (NR, WR, PN) applied above the carpus. Metacarpophalangeal synovial fluid was obtained 0.5 hour after perfusion. Amikacin concentration in the synovial fluid was detected using fluorescence polarization immunoassay. RESULTS Mean synovial concentrations of amikacin in the PN (mean 236 μg/mL; range 23-913 μg/mL) and WR (mean 64.2 μg/mL; range 7-315 μg/mL) were significantly higher (P=.000 and .032, respectively) than the NR tourniquet (mean 2.1 μg/mL; range 0.9-3.3 μg/mL). CONCLUSIONS The PN tourniquet resulted in the highest synovial fluid amikacin concentrations in all horses, although administration with PN and WR tourniquets achieved adequate amikacin concentrations. NR tourniquet is ineffective and should not be used for RLP above the carpus in the standing horse.

Clinical use of the locking compression plate (LCP) in horses : a retrospective study of 31 cases (2004-2006)

REASONS FOR PERFORMING STUDY Fracture repair and arthrodesis in horses require rigid fixation in order to achieve early post operative comfort. The locking compression plate (LCP) was designed to allow greater stability and less periosteal disruption than conventional plates. OBJECTIVE To describe a series of clinical cases in which the LCP was used for fracture stabilisation or arthrodesis. METHODS Medical records, radiographs and follow-up for 31 horses having fracture stabilisation or arthrodesis with the LCP were reviewed. Reasons for treatment included fracture of the olecranon (n = 2), metatarsal III (n = 2), ilial shaft (n = 1), femur (n = 2), radius (n = 2), medial condylar (n = 5) and complex lateral condylar (n = 1); or arthrodesis of the metacarpophalangeal joint (n = 8), proximal interphalangeal joint (n = 8) and carpus (n = 2). RESULTS Of the 31 horses, 27 were discharged from the hospital. Complications included incisional infection (32%), implant infection (19%), implant loosening/ breakage (22%), contralateral limb laminitis (16%), colic (3%) and diarrhoea (3%). Follow-up was available on all horses with at least 6 weeks of follow-up ranging up to 25 months. Of the 31 horses, 25 are sound for intended purpose, one is lame and 5 were subjected to euthanasia for complications associated with the original injury. CONCLUSIONS The LCP is an acceptable means of fracture stabilisation and arthrodesis in the horse. POTENTIAL RELEVANCE The LCP should be considered for difficult fracture configurations and arthrodeses, especially when increased stability of the fixation is needed.

Minimally invasive plate fixation of lower limb injury in horses : 32 cases (1999-2003)

REASONS FOR PERFORMING STUDY Complications of osteosynthesis including superficial and deep infections continue to affect adversely outcome in equine surgery of the lower limb. OBJECTIVE To describe a technique for minimally invasive plate fixation in horses and evaluate clinical results of the technique. HYPOTHESIS Lower complication rates would occur in horses treated with a minimally invasive approach compared with conventional techniques. METHODS Cases of minimally invasive plate fixation from January 1999 to December 2003 were evaluated. Case records, radiographs and race records for horses that sustained distal third metacarpal/metatarsal (Mc/tIII) condylar fractures were assessed. Follow-up information was obtained and results analysed. In addition, results for horses that received arthrodesis by a conventional, open approach during the same period were evaluated and statistical analysis was performed. RESULTS Thirty-two cases of minimally invasive plate fixation were identified (22 incomplete distal Mc/tIII condylar fractures with a spiralling or diaphyseal component, 10 metacarpophalangeal arthrodeses and 4 pastern arthrodeses). For both types of arthrodesis, surgery times and infection rates were lower and survival rates higher in the minimally invasive group, but no statistical difference was found. Spiralling condylar fractures were successfully managed, without catastrophic fracture. CONCLUSIONS AND POTENTIAL RELEVANCE Minimally invasive percutaneous plate osteosynthesis (MIPPO) can be successfully used for select applications in horses, and may reduce morbidity and mortality in equine fracture repair.

Long-Term Outcome in 44 Horses with Stifle Lameness After Arthroscopic Exploration and Debridement

OBJECTIVE To (1) examine the outcome in horses with osteoarthritis or intra-articular soft tissue injuries of the stifle after arthroscopic exploration and debridement and (2) to determine any imaging or surgical findings that may influence prognosis. DESIGN Case series. ANIMALS Horses (n=44) with lameness referable to the stifle, diagnosed with osteoarthritis, meniscal tears, or other intra-articular soft tissue injuries based on arthroscopic examination. METHODS Medical records of horses with stifle lameness that had arthroscopic exploration were reviewed. Horses with osteochondrosis lesions, intra-articular fractures, or osseous cyst-like lesions were excluded. Pertinent case information was analyzed and short- and long-term outcome was assessed. RESULTS There was no association between radiographic score and surgery score. Diagnostic ultrasound had a sensitivity of 79% and a specificity of 56% for identifying meniscal injuries. Follow-up information was available for 35 horses; 23 horses (60%) improved after surgery, 16 (46%) became sound, and 13 (37%) returned to their previous level of function. A negative association was observed between age and degree of preoperative lameness and outcome. More severe changes observed on preoperative radiographs were also negatively associated with prognosis. No horses with grade 3 meniscal tears improved postoperatively and increasing meniscal pathology was negatively associated with return to previous function. A weak association between surgery grade and outcome was also observed. Degree of chondral damage, location of primary pathology, and microfracture techniques had no effect on outcome. CONCLUSIONS Advanced horse age, severe lameness and preoperative radiographic changes, and presence of large meniscal tears are associated with a negative postoperative outcome for horses with stifle lameness. Appearance of the articular surface at surgery appears to be an inconsistent prognostic indicator. CLINICAL RELEVANCE Some horses with extensive cartilage damage may return to athletic function after arthroscopic debridement and lavage. A more pessimistic prognosis may be given to older horses, those with more severe preoperative lameness, and those with severe radiographic changes or large meniscal tears.

Hemangiosarcoma in 11 Young Horses

Hemangiosarcoma is a rare neoplasm of horses and hemangiosarcoma in young horses might behave differently than in mature horses. The purpose of this study was to identify the characteristics of hemangiosarcoma occurring in horses < or = 3 years of age. Medical records from 1982 to 2004 were searched for horses < or = 3 years of age with a histopathologic diagnosis of hemangiosarcoma. Eleven records were identified. Thoroughbred and Thoroughbred crosses predominated. Age ranged from 9 days to 3 years. All horses presented with cutaneous or leg swellings or joint effusion. Physical examination findings included tachycardia, fever, and depression. Laboratory abnormalities included anemia (5/11), hyperfibrinogenemia (4/11), hypofibrinogenemia (3/11), thrombocytopenia (2/11), and neutrophilic leukocytosis (1/11). Ultrasonographic and radiographic evaluation was not diagnostic in any case. Antemortem histopathologic diagnosis was obtained in 10 cases. Six of 11 horses were euthanized. Surgical resection was performed in 5 horses, 2 of which were later euthanized. Diagnosis was confirmed histologically at postmortem examination in all euthanized horses. Two cases resolved spontaneously. Early histopathologic diagnosis may allow cure if the mass is localized and amenable to surgical resection. In cases where the horse is medically stable, and masses are not interfering with quality of life, a period of observation may be warranted.

Orthopedic Infections in Equine Long Bone Fractures and Arthrodeses Treated by Internal Fixation: 192 Cases (1990–2006)

OBJECTIVE To determine the rate of postoperative infection (POI) for internal fixation repaired equine long bone fractures and arthrodeses and identify associated risk factors. STUDY DESIGN Case series. ANIMALS Horses (n=192) with fracture repair of the third metacarpal and metatarsal bones, radius, ulna, humerus, tibia, and femur, or arthrodesis with internal fixation. METHODS Medical records (1990-2006) were reviewed for signalment, anatomic location, fracture classification and method of repair, technique and surgical duration, bacterial species isolated, postoperative care, onset of POI, and outcome. RESULTS Of 192 horses (171 [89%] closed, 21 [11%] open fractures), 157 (82%) were discharged from the hospital. Infection occurred in 53 (28% horses), of which 31 (59%) were discharged. Repairs without POI were 7.25 times more likely to be discharged from the hospital. Closed fractures were 4.23 times more likely to remain uninfected and 4.59 times more likely to be discharged from the hospital compared with open fractures. Closed reduction and internal fixation was associated with a 2.5-fold reduction in rate of POI and a 5.9 times greater chance for discharge from the hospital compared with open reduction and internal fixation. Females had a strong trend for increased POI when compared with colts and stallion but not geldings. CONCLUSIONS Overall rate of POI was 28%. Fracture classification, method of repair, gender, and surgical duration were significant risk factors.

Urogenital Problems in the Neonatal Foal

The common conditions affecting the urogenital tract of the neonatal foal and their medical and surgical management are described. Early recognition and treatment of serious abnormalities are necessary for a successful outcome in the equine neonate.