A pilot study to determine the optimal dose of scAAVIL-1ra in a large animal model of post-traumatic osteoarthritis.

Gene therapy approaches using adeno-associated viral vectors have been successfully tested in the equine post-traumatic osteoarthritis (PTOA) model. Owing to differences in the levels of transgene expression and adverse tissue reactions observed in published studies, we sought to identify a safe therapeutic dose of scAAVIL-1ra in an inflamed and injured joint that would result in improved functional outcomes without any adverse events. scAAVIL-1ra was delivered intra-articularly over a 100-fold range, and horses were evaluated throughout and at the end of the 10-week study. A dose-related increase in IL-1ra levels with a decrease in PGE2 levels was observed, with the peak IL-1ra concentration being observed 7 days post-treatment in all groups. Perivascular infiltration with mononuclear cells was observed within the synovial membrane of the joint treated with the highest viral dose of 5 × 1012 vg, but this was absent in the lower-dosed joints. The second-highest dose of scAAVeqIL-1ra 5 × 1011 vg demonstrated elevated IL-1ra levels without any cellular response in the synovium. Taken together, the data suggest that the 10-fold lower dose of 5 × 1011vg scAAVIL-1ra would be a safe therapeutic dose in an equine model of PTOA.

Comparison of lameness outcomes in horses with acute or chronic digital lameness that underwent magnetic resonance imaging.

Aims: To compare the outcome, in terms of lameness score or return to athletic function, of horses with acute vs. chronic digital lameness that underwent magnetic resonance imaging (MRI) of the distal limb and to compare the proportion of horses that received intra-articular therapy of the distal interphalangeal (DIP) joint and pattern of diagnostic analgesia in these groups. Methods: This is a retrospective study of horses (n = 95) with acute (≤12 weeks; n = 46) or chronic (>12 weeks; n = 49) digital lameness that underwent MRI of the distal limb from 2009-2016, at two equine referral centres in the USA. Criteria for inclusion in the study were that a majority of lameness localised distal to the fetlock, and that lameness assessments for ≥12 months following MRI could be obtained from the medical record or the owner could be interviewed regarding their horse's athletic function. Outcome was characterised by an improvement score where 2 = return to work at a previous or higher level or lameness improved by one grade or more, 1 = return to work at a lower level or lameness improved by less than one grade, and 0 = did not return to work or lameness grade worsened. Whether horses had received intra-articular therapy of the DIP joint and the pattern of diagnostic analgesia prior to MRI was also obtained from medical records or by interviewing the owner. Results: There was a difference (p = 0.004) in the proportion of horses assigned to improvement scores of 0, 1 and 2 between horses with acute or chronic lameness. There was no evidence of a difference in the likelihood of having received intra-articular therapy of the DIP joint prior to MRI between horses with chronic or acute lameness (p = 0.085). Similarly, there was no evidence of a difference in the pattern of diagnostic analgesia prior to MRI between the two groups (p = 0.94). Eighty-two percent of owners of horses with acute and 62% of those with horses with chronic lameness had a positive opinion of the utility of MRI as a diagnostic modality. Conclusion: In a population of horses with digital lameness undergoing MRI, a difference in the outcome, in terms of lameness score or return to athletic function was identified between horses with acute lameness compared to those with chronic lameness. Clinical relevance: Horses with digital lameness that undergo MRI when the lameness is acute may have an improved prognosis due to accurate diagnosis and earlier application of appropriate therapy.

Allogeneic vs. autologous intra-articular mesenchymal stem cell injection within normal horses: Clinical and cytological comparisons suggest safety.

BACKGROUND: Allogeneic bone marrow-derived mesenchymal stem cells (BMDMSCs) could provide multiple advantages over autologous BMDMSCs, including creating an 'off-the-shelf' treatment together with the ability to control for donor variation. OBJECTIVES: The objective of the study was to compare the clinical and synovial fluid response of the normal equine joint to autologous and pooled-allogeneic BMDMSCs while controlling for individual variation and joint variations in response to intra-articular injections. We hypothesised that, by controlling for individual animal and joint variation, we could identify differences between allogeneic vs. autologous BMDMSCs in noninflamed joints. STUDY DESIGN: Randomised-controlled experiment. METHODS: Bone marrow was harvested from eight horses. Autologous BMDMSCs were culture expanded, cryopreserved and thawed immediately prior to administration. For allogeneic BMDMSC treatments, four horses' BMDMSCs were culture expanded, pooled, cryopreserved and thawed immediately prior to use. Ten million (autologous or pooled-allogeneic) BMDMSCs were administered into contralateral forelimb metacarpophalangeal joints so that every autologous and allogeneic injection could be compared within the same animal. Clinical parameters included subjective lameness, objective lameness (Lameness Locator™), response to flexion, joint circumference and joint effusion. Arthrocentesis was performed for assessment of the nucleated cell count, differential cell count, total protein, and synovial concentrations of prostaglandin E2 (PGE2) and c-reactive protein (CRP). All parameters were measured at baseline, 6, 12, 24, 72, 168 and 336 h post-injection. RESULTS: No difference was detected in any parameters between forelimb metacarpophalangeal joints administered autologous or pooled-allogeneic BMDMSCs. MAIN LIMITATIONS: This study did not attempt to measure efficacy of BMDMSCs for musculoskeletal disease and should be followed by properly controlled efficacy trials. CONCLUSIONS: The study did not identify any clinical or cytological differences in the normal joint response to allogeneic or autologous BMDMSCs. A larger study to prove equivalence is warranted as allogeneic BMDMSCs may be a feasible alternative to autologous BMDMSCs.

Evaluation of equine articular cartilage degeneration after mechanical impact injury using cationic contrast-enhanced computed tomography.

OBJECTIVE: Cationic agent contrast-enhanced computed tomography (cationic CECT) characterizes articular cartilage ex vivo, however, its capacity to detect post-traumatic injury is unknown. The study objectives were to correlate cationic CECT attenuation with biochemical, mechanical and histological properties of cartilage and morphologic computed tomography (CT) measures of bone, and to determine the ability of cationic CECT to distinguish subtly damaged from normal cartilage in an in vivo equine model. DESIGN: Mechanical impact injury was initiated in equine femoropatellar joints in vivo to establish subtle cartilage degeneration with site-matched controls. Cationic CECT was performed in vivo (clinical) and postmortem (microCT). Articular cartilage was characterized by glycosaminoglycan (GAG) content, biochemical moduli and histological scores. Bone was characterized by volume density (BV/TV) and trabecular number (Tb.N.), thickness (Tb.Th.) and spacing (Tb.Sp.). RESULTS: Cationic CECT attenuation (microCT) of cartilage correlated with GAG (r = 0.74, P < 0.0001), compressive modulus (Eeq) (r = 0.79, P < 0.0001) and safranin-O histological score (r = -0.66, P < 0.0001) of cartilage, and correlated with BV/TV (r = 0.37, P = 0.0005), Tb.N. (r = 0.39, P = 0.0003), Tb.Th. (r = 0.28, P = 0.0095) and Tb.Sp. (r = -0.44, P < 0.0001) of bone. Mean [95% CI] cationic CECT attenuation at the impact site (2215 [1987, 2443] Hounsfield Units [HUs]) was lower than site-matched controls (2836 [2490, 3182] HUs, P = 0.036). Clinical cationic CECT attenuation correlated with GAG (r = 0.23, P = 0.049), Eeq (r = 0.26, P = 0.025) and safranin-O histology score (r = -0.32, P = 0.0046). CONCLUSIONS: Cationic CECT (microCT) reflects articular cartilage properties enabling segregation of subtly degenerated from healthy tissue and also reflects bone morphometric properties on CT. Cationic CECT is capable of characterizing articular cartilage in clinical scanners.

Recent advances in articular cartilage evaluation using computed tomography and magnetic resonance imaging.

Articular cartilage is a critical joint tissue and its evaluation remains a diagnostic challenge in horses. Coupled with a poor capacity for healing, early degenerative changes in articular cartilage are difficult to characterise using routine diagnostic imaging evaluations. Both computed tomography (CT) and magnetic resonance imaging (MRI) provide volumetric joint assessment and highlight morphological and quantitative properties of articular cartilage, improving assessment of this essential tissue. While the use of CT and MRI for joint evaluation is not new, there still remains a shortage of literature and scientific studies on the ability of these methods to evaluate articular cartilage in the horse. This review article summarises current CT and MRI techniques capable of characterising equine articular cartilage, highlights recent advances in these techniques and discusses the numerous methods studied in human subjects that have been minimally investigated in horses. Imaging techniques are presented in terms of their capabilities of offering morphological and quantitative evaluation along with a discussion of their benefits and limitations. Finally, it summarises the current state-of-the-art approaches and identifies unmet clinical imaging needs to propel the advancement of articular cartilage and joint imaging in the horse.

Use of contrast media in computed tomography and magnetic resonance imaging in horses: Techniques, adverse events and opportunities.

The use of contrast media in computed tomography (CT) and magnetic resonance imaging (MRI) is increasing in horses. These contrast-enhanced imaging techniques provide improved tissue delineation and evaluation, thereby expanding diagnostic capabilities. While generally considered safe, not all contrast media exhibit the same safety profiles. The safety of contrast media use and descriptions of adverse events occurring in horses are sparsely reported. This review summarises the reported evidence of contrast media use and adverse events that occur in horses, with added contribution from other veterinary species and studies in man for comparison. This comprehensive data set empowers equine clinicians to develop use and monitoring strategies when working with contrast media. Finally, it summarises the current state-of-the-art and highlights the potential applications of contrast-enhanced CT and MRI for assessment of diseased or injured equine tissues, as well as (patho)physiological processes.

Radiographic localisation of the entheses of the equine stifle.

REASON FOR PERFORMING STUDY: Injury to the tendons and ligaments of the equine stifle is a common cause of lameness in horses. Individual radiographic localisation of each tendon and ligament of the stifle has not been previously reported or demonstrated in multiple radiographic projections. OBJECTIVE: To create a series of radiographs identifying the origins and/or insertions of the tendons and ligaments of the equine stifle. STUDY DESIGN: Descriptive study of radiographic anatomy. METHODS: The location of all entheses were determined by gross dissection. The proximal tibia and fibula, distal femur, patella and menisci were isolated from one horse and used as a template. A series of 4 radiographs was obtained with each enthesis identified with barium paste. The radiographic landmarks for each enthesis were described and the best projection(s) for evaluation of each structure of interest identified. RESULTS: Forty-eight radiographic images were produced that demonstrated the best radiographic projections to define each enthesis. CONCLUSIONS: Radiography is the imaging modality most frequently used to evaluate the equine stifle. The images presented here will serve as a guide for evaluating radiographs of the equine stifle, particularly identifying avulsions and enthesopathies of ligamentous and tendinous origins and insertions.

A comparison of arthroscopy to ultrasonography for identification of pathology of the equine stifle.

REASONS FOR PERFORMING STUDY: To evaluate and compare the diagnostic capability of arthroscopy and ultrasonography for the detection of pathological change in equine stifle joints. Although descriptions of the arthroscopic and ultrasonographic boundaries of the normal femorotibial joint exist, there are few examples in the literature comparing the pathological changes observed with each imaging modality. OBJECTIVES: To evaluate and compare arthroscopic and ultrasonographic examinations for characterising pathological change in the stifle joint. To describe how the results of arthroscopic and ultrasonographic examinations may differ in characterising the severity of lesions and to evaluate which lesions are best assessed with each modality. STUDY DESIGN: Retrospective review of ultrasonographic and arthroscopic examinations. METHODS: The structures of the stifle joint were evaluated and graded for pathological change by scoring arthroscopic and ultrasonographic examinations. The presence and severity of the lesions were then compared between each modality. RESULTS: Medial meniscal lesions were detected more often with ultrasonography than with arthroscopy. Conversely, arthroscopy was better for detection of cranial medial meniscotibial ligament (CrMMTL) tearing. Articular cartilage defects were best detected with arthroscopy and periarticular osteophytes of the medial femoral condyle with ultrasonography. Four cases had defects within one of the patellar ligaments, all of which were only characterised with ultrasonography. CONCLUSIONS: Ultrasonography and arthroscopy should be combined to best evaluate pathology of the stifle, since each modality has its own limitations depending on the location and type of lesion.

Adeno-associated virus gene therapy vector scAAVIGF-I for transduction of equine articular chondrocytes and RNA-seq analysis.

OBJECTIVE: IGF-I is one of several anabolic factors being investigated for the treatment of osteoarthritis (OA). Due to the short biological half-life, extended administration is required for more robust cartilage healing. Here we create a self-complimentary adeno-associated virus (AAV) gene therapy vector utilizing the transgene for IGF-I. DESIGN: Various biochemical assays were performed to investigate the cellular response to scAAVIGF-I treatment vs an scAAVGFP positive transduction control and a negative for transduction control culture. RNA-sequencing analysis was also performed to establish a differential regulation profile of scAAVIGF-I transduced chondrocytes. RESULTS: Biochemical analyses indicated an average media IGF-I concentration of 608 ng/ml in the scAAVIGF-I transduced chondrocytes. This increase in IGF-I led to increased expression of collagen type II and aggrecan and increased protein concentrations of cellular collagen type II and media glycosaminoglycan vs both controls. RNA-seq revealed a global regulatory pattern consisting of 113 differentially regulated GO categories including those for chondrocyte and cartilage development and regulation of apoptosis. CONCLUSIONS: This research substantiates that scAAVIGF-I gene therapy vector increased production of IGF-I to clinically relevant levels with a biological response by chondrocytes conducive to increased cartilage healing. The RNA-seq further established a set of differentially expressed genes and gene ontologies induced by the scAAVIGF-I vector while controlling for AAV infection. This dataset provides a static representation of the cellular transcriptome that, while only consisting of one time point, will allow for further gene expression analyses to compare additional cartilage healing therapeutics or a transient cellular response.

An optimised injection technique for the navicular bursa that avoids the deep digital flexor tendon.

REASONS FOR PERFORMING STUDY: Injection of the navicular bursa is commonly performed from the palmar aspect of the limb, which results in penetration of the deep digital flexor tendon (DDFT). OBJECTIVES: To report a radiographic guided injection from the lateral aspect of the limb that avoids puncture of the DDFT and to assess synovial and soft tissue penetration by the needle. STUDY DESIGN: Prospective clinical and cadaveric study. METHODS: Prospective analysis of cadaver limbs and clinical cases in which the navicular bursa was injected from the lateral aspect. Cadaver limbs were placed in a stand to simulate weight bearing and injection was performed in limbs without synovial distension or with distension of either the distal interphalangeal (DIP) joint, digital flexor tendon sheath (DFTS) or navicular bursa. In cadaver and clinical limbs, contrast was injected and the needle position assessed with radiographs. Cadaver (but not clinical) limbs were also examined using magnetic resonance imaging with the needle in situ. RESULTS: Successful navicular bursal injection was achieved in all limbs (n = 71). Relative risk of DIP joint puncture was 19 times higher (95% confidence interval 1.3-285.4, P<0.001) when the DIP joint was distended (9 of 10 limbs) than in normal limbs (0 of 10 limbs). Relative risk of DFTS puncture was 2.7 times higher (95% confidence interval 1.0-7.2, P = 0.06) when the DFTS was distended (8 of 10 limbs) than in normal limbs (3 of 7 limbs). Synovial fluid was aspirated from 47% of bursae from clinical cases. CONCLUSIONS: The lateral injection technique for the navicular bursa avoids penetration of the DDFT, although risk of synovial penetration must be considered when there is potential DIP joint or DFTS infection.

Comparison of subjective lameness evaluation, force platforms and an inertial-sensor system to identify mild lameness in an equine osteoarthritis model.

When mild lameness exists, agreement between clinicians is often controversial due to its subjective nature. The goal of the study was to compare subjective and objective methods to identify the presence of mild lameness using an established model of osteoarthritis (OA) in which OA was induced by creating a unilateral carpal osteochondral fragment (OCF) in the middle carpal joint of 16 horses. Subjective lameness evaluations (blinded and unblinded), force platforms (FP), and an inertial-sensor system (ISS) were used to detect forelimb lameness at four time points. Limbs identified as lame by each method were compared as well as compared with the OCF limb at each time point. Spearman correlations were calculated between all outcome parameters. Independent of time, blinded subjective evaluation (54%) and the ISS (60%) identified a higher percentage of horses as lame in the OCF limb compared to FP (40%). Blinded subjective evaluation and the ISS agreed which forelimb was lame more often (50%) compared with blinded subjective evaluation and the FP (38%). Induction of mild lameness within the OCF limb was supported by an increase in the frequency of horses considered lame by both subjective evaluations the ISS and a decrease (3.6%) in mean (among all horses) peak vertical force from baseline to post OCF induction. The percentage of horses identified as lame in the OCF limb, independent of time, was highest with the ISS (60%) followed by blinded subjective evaluation (51%) and the FP (42%). It was concluded that the best agreement was between subjective evaluation and the inertial-sensor system.

scAAVIL-1ra dosing trial in a large animal model and validation of long-term expression with repeat administration for osteoarthritis therapy.

A gene therapeutic approach to treat osteoarthritis (OA) appears to be on the horizon for millions of people who suffer from this disease. Previously we described optimization of a scAAVIL-1ra gene therapeutic vector and initially tested this in an equine model verifying long-term intrasynovial IL-1ra protein at therapeutic levels. Using this vector, we carried out a dosing trial in six horses to verify protein levels and establish a dose that would express relevant levels of therapeutic protein for extended periods of time (8 months). A novel arthroscopic procedure used to detect green fluorescence protein (GFP) fluorescence intrasynovially confirmed successful transduction of the scAAVGFP vector in both the synovial and cartilage tissues. No evidence of intra-articular toxicity was detected. Immune responses to vector revealed development of neutralizing antibodies (Nabs) within 2 weeks of administration, which persisted for the duration of the study but did not lower protein expression intra-articularly. Re-dosing with a different serotype to attain therapeutic levels of protein confirmed establishment of successful transduction. This is the first study in an equine model to establish a dosing/redosing protocol, as well as examine the Nab response to capsid and supports further clinical investigation to determine the clinical efficacy of scAAVIL-1ra to treat OA.

Dynamic compression plate (DCP) fixation of propagating medial condylar fractures of the third metacarpal/metatarsal bone in 30 racehorses: retrospective analysis (1990-2005).

REASONS FOR PERFORMING STUDY: An in-depth review of dynamic compression plate (DCP) fixation of propagating medial condyle fractures of the third metacarpus or metatarsus has not been previously reported. OBJECTIVES: To describe the technique, evaluate short-term outcome and long-term race performance of racehorses that underwent DCP fixation for repair of propagating or spiralling medial condylar fractures of the third metacarpal (McIII) or metatarsal (MtIII) bone. STUDY DESIGN: Retrospective case series. METHODS: The surgical case records of 30 horses with propagating fractures of the medial condyle of McIII or MtIII were reviewed. Medical information included: age, breed, sex, presentation, how injury occurred (racing or training), surgical treatment and post operative complications. Racing information included: starts, top 3 placing and career earnings. RESULTS: Long propagating fractures of the medial condyle of Mc/tIII were identified in 23 Thoroughbred (TB) and 7 Standardbred (STB) racehorses. The fracture spiralled proximally in 22 of 30 cases (73%). Standardbreds had a higher propensity for hindlimb involvement (71%), whereas TBs tended to have more front limb involvement (61%). Twelve of 30 (40%) horses raced post surgery. Career earnings were significantly lower for TB horses with medial condylar fractures; $34,916 when compared with the national average of $60,841 (P≤0.03). Overall, horses having DCP fixation for medial condylar fractures had less starts post surgery (3.1 TBs and 5.8 STBs) compared with the national average (7 TBs and 17.3 STBs) and decreased lifetime starts 13.4 (TBs) compared with 17.3 nationally. CONCLUSIONS: Propagating medial condyle fractures can be repaired with plate fixation to potentially lessen the risk of catastrophic fracture destabilisation and return to racing can be expected in 40% of horses. Further prospective studies are warranted comparing lag screw fixation with DCP fixation for repair of severe medial condylar fractures of the metacarpus/metatarsus.

Equine bone marrow-derived mesenchymal stromal cells (BMDMSCs) from the ilium and sternum: are there differences?

REASONS FOR PERFORMING STUDY: The 2 sites of bone marrow harvest for isolation of mesenchymal stromal cells (MSC) in the horse are the sternum and ilium. The technical procedure is based on practitioner preference, but no studies have compared MSC concentrations and growth rates between the sites in horses aged 2-5 years. OBJECTIVES: The objective of this study was to compare nucleated cell counts and growth rates between the sternum and ilium and between consecutive 5 ml bone marrow aspirates. We hypothesised that there would be a higher concentration of MSCs in the sternum than the ilium, and that the first sequential aspirate from either site would yield the greatest concentration of MSCs. We hypothesised that growth rates of cells from each site would not differ. METHODS: Seven horses, aged 2 to 5 years, had 2 sequential 5 ml marrow aspirates taken from the sternum and ilium. Nucleated cell counts (NCCs) were obtained before and after marrow processing. Cells were expanded in culture for 3 passages and growth rate characteristics compared for all aspirates. RESULTS: The NCCs of the first 5 ml aspirate were higher than those of the second 5 ml aspirate for both sites (P<0.05). There was no difference between growth rates for any of the groups (P>0.05). CONCLUSIONS: The NCCs and growth rates of progenitor cells in the ilium and sternum are similar for horses in the 2-5 year age category. The first 5 ml bone marrow aspirate has a higher concentration of NCCs and resulting bone marrow-derived MSC population than subsequent aspirates. POTENTIAL RELEVANCE: The first 5 ml aspirates from the sternum and ilium offer a rich supply of bone marrow-derived MSCs with similar growth rate characteristics. The harvesting procedure of only a 5 ml draw from either the sternum or ilium should result in adequate numbers of MSCs.

Use of a radiofrequency probe for tenoscopic-guided annular ligament desmotomy.

REASONS FOR PERFORMING STUDY: Annular ligament desmotomy is commonly performed in horses with chronic tenosynovitis. Previously reported tenoscopic techniques have limitations related to haemorrhage and awkward instrumentation. Radiofrequency (RF) energy affords precision and excellent haemostasis and may be a good alternative to sharp transection of the annular ligament in horses. OBJECTIVE: To describe a technique for using a RF probe for tenoscopic-guided annular ligament desmotomy and to report the clinical outcome of horses in which it was performed. METHODS: Cadaver specimens (n = 14) and live horses undergoing unrelated terminal procedures (n = 2) were used to optimise the tenoscopic-guided RF annular ligament desmotomy technique. Records were examined for all horses undergoing annular ligament desmotomy with an RF probe from 2003 to 2008 for which follow-up of >1 year post operatively was available. RESULTS: The annular ligament was successfully transected in the cadaver and live horse model limbs using 2 different commercially available RF probes. Complete transection was achieved with practice and confirmed on gross dissection. Histopathology did not reveal any collateral damage to surrounding tissue. Follow-up of >1 year was available for 6 of 7 clinical cases. Four of 6 horses returned to work. Owners were satisfied with the outcome in all cases. CONCLUSIONS: Desmotomy using a RF probe allows precise tissue transection under tenoscopic guidance without damage to surrounding structures or haemorrhage. With experience, it is an easily performed technique. In clinical patients, an acceptable outcome may be expected. POTENTIAL RELEVANCE: Tenoscopic-guided RF annular ligament desmotomy offers advantages, including reliable haemostasis and precise tissue transection, over previously reported techniques and is a viable surgical alternative for treating horses with annular ligament desmitis and other complex pathology within the tendon sheath.

Incidence of support limb laminitis in horses treated with half limb, full limb or transfixation pin casts: a retrospective study of 113 horses (2000-2009).

REASONS FOR PERFORMING STUDY: To determine the incidence of support limb laminitis among horses treated with half limb, full limb or transfixation pin casts and determine potential risk factors. METHODS: Medical records of 113 horses treated with half limb, full limb or transfixation pin casts at an equine referral hospital from 2000 to 2009 were reviewed. Associations between potential risk factors and development of support limb laminitis were evaluated by bivariable and multivariable logistic regression analyses. RESULTS: Of the 113 horses that received casts, 14 (12%) developed confirmed support limb laminitis. The bodyweight of the horse and duration of casting in weeks were significantly associated with support limb laminitis. Horses requiring full limb casts or transfixation pin casts were more likely to develop this complication than horses requiring half limb casts. There were no significant associations between developing support limb laminitis and weightbearing capacity on presentation to the hospital, the limb affected (fore- or hind), whether there was a fracture present or breed of horse. CONCLUSIONS: Support limb laminitis is a relatively common complication among horses treated with half limb, full limb and transfixation pin casts. Greater durations of casting and higher bodyweights increase the likelihood of developing this complication. POTENTIAL RELEVANCE: Support limb laminitis may occur secondary to any painful unilateral lameness and is not necessarily more likely to develop in horses with severe orthopaedic conditions such as fractures. However, heavier horses, those requiring casts for longer periods of time and those that require a full limb or transfixation pin cast as opposed to a half limb cast should be considered to have an increased risk for developing support limb laminitis post operatively.

Antimicrobial delivery by intrasynovial catheterisation with systemic administration for equine synovial trauma and sepsis.

OBJECTIVE: To present the technique for intra-articular catheter placement and report the clinical outcomes of 38 cases of equine synovial trauma and/or infection treated with broad-spectrum antimicrobials administered via an intrasynovial catheter (ISC). DESIGN: Retrospective study. PROCEDURE: Medical records of 38 horses treated for synovial trauma and sepsis with frequent antimicrobial administration through an ISC from 1995 to 2008 were reviewed. Follow-up information was obtained via clinical re-evaluation or telephone contact with the owners. RESULTS: The majority of horses (84%) received amikacin and Timentin(R) four times daily. In addition, synovial lavage through the ISC was carried out in 27 horses (71%). Only radiological evidence of osteolysis had a significant negative impact on both lameness at the time of hospital discharge and the long-term outcome. In total, 92% of horses treated with frequent antimicrobial administration through an ISC had clinical resolution of infection. Catheter obstruction occurred in three cases, necessitating replacement or removal, and two synovial fistulae developed at sites of open drainage. The majority of horses treated had a favourable outcome, with 86% being at least pasture sound and 43% returned to riding. CONCLUSION: Septic synovial structures treated with frequent antimicrobial administration through an ISC had a good prognosis for survival and 43% returned to riding, which is consistent with the results of other studies. The use of a simple ISC should be considered when broad-spectrum intrasynovial antimicrobial administration and lavage of a septic synovial structure are indicated.

Concurrent or sequential development of medial meniscal and subchondral cystic lesions within the medial femorotibial joint in horses (1996-2006).

UNLABELLED: Summary Reasons for performing study: Medial meniscal injuries and subchondral cystic lesions (SCL) are known to occur independently within the medial femorotibial (MFT) joint in horses. However, there are no reports of a potential clinical relationship between these 2 types of lesions. OBJECTIVES: To: 1) document the concurrent presence or sequential development of medial meniscal and SCL of the medial femoral condyle within the MFT joint; and 2) determine the prognosis with both types of lesions. METHODS: Retrospective case series of horses with both a medial meniscal and SCL of the medial femoral condyle identified concurrently or sequentially by radiography, arthroscopy or post mortem examination. Case records and radiographs were reviewed, and a telephone survey of referring veterinarians, owners and trainers was conducted. RESULTS: Twenty-one horses (9.1% of all horses undergoing MFT joint arthroscopy) were identified to have both a medial meniscal injury and SCL of the medial femoral condyle. Thirteen horses had both abnormalities identified concurrently, 6 developed a meniscal lesion subsequent to SCL debridement, and 2 developed a SCL subsequent to a medial meniscal injury. Only 4/19 horses were classified as successful and returned to their intended use. The severity of the meniscal injury was significantly associated with the severity of lameness but not with outcome. CONCLUSIONS: A low percentage of horses may develop both a meniscal injury and SCL of the medial femoral condyle within the MFT joint and have a poor prognosis. POTENTIAL RELEVANCE: Trauma to the MFT joint may lead to both meniscal and subchondral bone damage of the medial femoral condyle that may be recognised concurrently or sequentially.

Ex vivo serotype-specific transduction of equine joint tissue by self-complementary adeno-associated viral vectors.

Cell transplantation for the treatment of joint disease is an important clinical tool. Genetic modification of cells before transplantation has shown enhanced healing. Ex vivo genetic modification of joint tissue cells with various adeno-associated virus (AAV) serotypes has not been investigated. The transduction efficiencies of self-complementary AAV serotypes (1-6 and 8) were determined in joint tissue containing chondrocytes and synoviocytes isolated from equine models. When comparing scAAV serotypes for efficient transduction ex vivo, in chondrocytes versus synoviocytes, serotypes 6 and 2, and serotypes 3 and 2, respectively, appeared superior for gene expression. Unlike adenoviral vectors, no upregulation of inflammatory markers, such as matrix metalloproteinases and aggrecanase, was seen on treatment of joint tissue with AAV vectors ex vivo. Our findings also corroborate that ex vivo transduction of joint tissue can result in high transgene protein levels over time, and transplantation modalities might be feasible using AAV vectors in the treatment of joint-related diseases.

Arthroscopic injection of corticosteroids into the fibrous tissue of subchondral cystic lesions of the medial femoral condyle in horses: a retrospective study of 52 cases (2001-2006).

REASONS FOR PERFORMING STUDY: There are no published results of subchondral cystic lesions (SCLs) in the medial femoral condyle (MFC) treated with arthroscopic injection of corticosteroids into the lining of the cyst. OBJECTIVES: 1) To determine the success rate for treatment of SCLs in the MFC with arthroscopic injection of the fibrous tissue of the cyst with corticosteroids. 2) To identify any factors that may predict outcome. HYPOTHESES: Injection of the fibrous tissue of SCLs of the MFC with corticosteroids utilising arthroscopic guidance yields a similar or higher chance for intended performance than does arthroscopic debridement as previously reported; this technique will be effective for treating SCLs in older horses. METHODS: Horses with clinical and radiographic evidence of a SCL in the MFC were injected with corticosteroids under arthroscopic guidance, and case records and radiographs were reviewed retrospectively. A telephone survey of referring veterinarians, owners and trainers was conducted. RESULTS: Thirty-five of 52 (67%) cases were classified as successful involving 73 SCLs of which 56 (77%) were classified as successful. There was no significant association between age group (age3 years) and outcome, or cyst configuration and outcome. Significantly more unilateral SCLs (28/31 [90%] SCLs) were classified as successful than bilateral (28/42: 67%). There were significant differences in outcome based on the surgeon operating the case and an association between pre-existing radiographic findings of osteophytes and negative outcome. CONCLUSIONS: Injection of SCLs utilising arthroscopic guidance is an effective alternative method of surgical treatment of SCL. POTENTIAL RELEVANCE: This technique offers a similar chance of success as has been reported with debridement and may allow for a shorter period of convalescence. If unsuccessful, the option remains to debride the cyst in a second surgery.