Evaluation of iatrogenic hemarthrosis of the metacarpophalangeal joint as a method of induction of temporary reversible lameness in horses

Equine Peripheral Gene Expression Changes in Response to Dose-Dependent Lipopolysaccharide-Induced Synovitis

The use of lipopolysaccharide to induce a localized source of inflammation (acute synovitis) and allow for monitoring of changes in systemic mRNA expression has been recently reported. Here, the goal was to maintain a significant systemic mRNA response while limiting the severity of lameness such that this model can be used to examine the effects of various anti-inflammatory treatment modalities on mRNA expression. Three mixed breeds, four-year-old geldings were utilized for this study. One milliliter of phosphate-buffered saline containing 1,000 ng or less of lipopolysaccharide from E. coli O111:B4 was aseptically injected into alternating radiocarpal joints following washout periods. Blood for complete blood cell count, serum amyloid A concentration, and mRNA analysis via RT-qPCR for 23 different genes were collected before each injection, as well as at multiple times post-injection. Lameness severity was also graded at each time point. Two-way, repeated measures analysis of variance was used for statistical analysis (P < .05). Results largely replicated those previously reported, with multiple genes exhibiting significant expression changes during the acute inflammatory period (including increases in CD14, TLR4, IL-1β, IL1RN, MMP1, and MMP9 expression) while some demonstrated dose-dependent changes; significant increases in complete blood cell count parameters and serum amyloid A concentrations were also noted. Attempts to temper the severity of lameness were not successful as nonweight bearing lameness was noted at doses of 10ng or higher, while a dose of 1ng elicited neither a detectable lameness nor a significant change in mRNA expression.

Tramadol Effects on Lameness Score After Inhibition of P-GP by Ivermectin Administration in Horses: Preliminary Results

This study aimed to evaluate the effects and lameness degree in horses administered tramadol after the P-glycoprotein (P-gp) enteric inhibitor ivermectin. Six horses were randomly distributed into three groups, which received two different doses of tramadol by a nasogastric tube: 1 mg/kg (tramadol group 1(GT1)), 4 mg/kg (tramadol group 4 (GT4)), and tramadol 1 mg/kg combined with ivermectin 0.2 mg/kg PO (ivermectin tramadol group (GT1 + Ive)), with one-week washout interval. Heart rate (HR), respiratory rate (RR), intestinal motility, body temperature, and the degree of lameness were evaluated for 360 minutes. The blood gas parameters were evaluated at 0, 60 minutes, and 120 minutes. There were no differences in HR and the degree of lameness. Hypomotility occurred in GT1 and GT4 only at the end of the evaluation period, and RR increased in all groups. We conclude that inhibition of enteric P-gp by ivermectin did not alter the effects of tramadol, suggesting that tramadol is not a substrate for P-gp. However, future studies should be conducted to assess the interaction between P-gp inhibitors on the pharmacokinetics of tramadol.

Alterations of peripheral gene expression in response to lipopolysaccharide-induced synovitis as a model for inflammation in horses

While the use of lipopolysaccharide (LPS) to induce inflammation has been well described in the horse, the object of this study was to evaluate the effect of repeated intra-articular LPS injections and determine whether this method may be of use to assess changes in gene expression related to inflammation. Six mixed breed horses were utilized for this study, with three horses aged 10-17 years (older group) and three horses aged 3 years (younger group). One milliliter of phosphate-buffered saline containing 3 μg of LPS from Escherichia coli O111:B4 was aseptically injected into either the radiocarpal or front fetlock joint a total of four times, with at least two weeks between each injection and a different joint injected each time. Serum for protein concentration quantification and whole blood for expression analysis of 20 different genes were collected before each injection, as well as at multiple times post-injection. Statistical analysis was performed using analysis of variance (one-way and two-way) (P < 0.05). All horses experienced minimal or non-weight bearing lameness at 4-6 hours post-LPS injection, which generally improved by 24 h and resolved by 48 h. Multiple genes exhibited significantly differential expression when compared to both the pre-injection and sham injection time points, including CD14, TLR4, MMP1, MMP9, IL-1β, IL1RN, IL-10, ALOX5AP, IL-8, TNFα, CCL8, IGF1, and PTGS2. Additionally, multiple genes exhibited increased expression in horses where the radiocarpal joint was injected when compared to the fetlock joint, as well as in younger horses compared to older horses. Serum concentrations of serum amyloid A (SAA) were negative prior to injection while all horses demonstrated an increase by 9 h post-injection, which often remained until at least 144 h. Attempts to measure in vivo serum cytokine levels using a multiplex assay were not successful and believed to be due to the lower limits of detection for the assays. The measurement of mRNA expression of pro- and anti-inflammatory genes provide sensitive and rapid information regarding the inflammatory response to an acute, localized stimulus, although care must be taken when selecting target joints or age groups of horses as the transcriptional response may vary based on these choices.

Clinical findings, synovial fluid cytology and growth factor concentrations after intra-articular use of a platelet-rich product in horses with osteoarthritis

Osteoarthritis is a common cause of lameness in horses, resulting in poor performance. Intra-articular platelet-rich plasma can deliver a collection of bioactive molecules, such as autologous growth factors and proteins involved in the quality of tissue repair. Horses (n=5) with osteoarthritis affecting antebrachiocarpal, middle carpal or metacarpophalangeal joints, and horses (n=5) without osteoarthritis of the corresponding joints (radiographically free of osteoarthritis), were used for the production of platelet-rich plasma which was subsequently injected into selected joints. Clinical and synovial fluid changes after intra-articular injection of platelet-rich plasma as well as synovial platelet-derived growth factor-BB and transforming growth factor-beta 1 concentration changes were evaluated in these joints and compared between normal joints and joints with osteoarthritis. A gravity filtration system produced a moderately concentrated platelet-rich plasma, representing a 4.7-fold increase in baseline platelet concentration. The synovial effusion score was significantly different between the control joints and joints with osteoarthritis on Day 0 with a higher score in the group with osteoarthritis. Within the control group, the synovial effusion score was significantly higher on Days 1 and 2 compared to Day 0. For both groups, the synovial fluid nucleated cell count, predominantly intact neutrophils, was significantly increased on Days 1 and 2, with no significant difference between groups. The mean synovial platelet-derived growth factor-BB and transforming growth factor-beta 1 concentrations were increased for both groups but significantly lowered in the group with osteoarthritis on Day 1 compared to normal joints. Concentrations for platelet-derived growth factor-BB remained unchanged on Day 5, compared to Day 1, with no significant difference between groups. In conclusion, intra-articular treatment with platelet-rich plasma resulted in increased synovial growth factor concentrations in joints but with lower concentrations in joints with osteoarthritis. A transient inflammatory reaction was seen both clinically as an increase in synovial effusion and cytologically in both normal joints and joints with osteoarthritis.

Circumferential hoof clamp method of lameness induction in the horse

A circumferential hoof clamp method to induce controlled and reversible lameness in the forelimbs of eight horses was assessed. Peak vertical forces and vertical impulses were recorded using a force plate to verify induced lameness. Video recordings were used by blinded observers to determine subjective lameness using a 0-5 scale and any residual lameness following clamp loosening. Tightening of clamps resulted in consistent, visible lameness in the selected limbs in all horses. Lameness was confirmed by significant decreases from baseline in the peak vertical force (P <0.01). Lameness was also confirmed subjectively by elevated median scores (0 at baseline and 2 during lameness). Lameness was not immediately reversible after clamp loosening (median score 1.5), but horses were not obviously lame after clamp removal and were no different from initial baseline (median score 0.5) approximately 3 days later.

Agreement between accelerometric symmetry scores and clinical lameness scores during experimentally induced transient distension of the metacarpophalangeal joint in horses

REASONS FOR PERFORMING STUDY

Equine lameness examination is based on subjective visual scoring of lameness. Instrumented objective methods for lameness examinations may be complicated to perform and the equipment is often stationary. Accelerometry has a potential clinical use; however, the reduction and interpretation of equine accelerometric data are not yet routine and the value of accelerometry in equine lameness examination is unclear.

OBJECTIVES

To use accelerometric data to calculate 2 different accelerometric symmetry scores and to evaluate the agreement of these with traditional lameness scores done by experienced equine practitioners.

METHODS

Six sound horses were equipped with a 3 axis 10G piezoresistant accelerometer at the lowest point of the back. Horses were trotted and video recorded at 0, 3, 15, 30, 45 and 60 min after injection of saline into one metacarpophalangeal joint. Video recordings were scored in a blind manner according to the AAEP scale by 2 experienced practitioners. Interobserver agreements and 2 symmetry scores S and A, developed on the basis of Fourier transformation of the obtained accelerometric data, were calculated and regression analysis between AAEP scores and symmetry scores was performed.

RESULTS

Interobserver agreements were 70%. There was a statistically significant relationship between AAEP lameness scores and both symmetry scores.

CONCLUSIONS

Both symmetry scores showed a significant relationship with the AAEP scores and can be a valuable tool in the detection and quantification of lameness. While the S score was able to detect changes in degree of lameness, the A score was capable of detecting the lame diagonal. However, more research is needed for the development of a combined accelerometric score to take advantage of the strengths of each of the symmetry scores.

Continuous peripheral neural blockade to alleviate signs of experimentally induced severe forelimb pain in horses

OBJECTIVE

To investigate the efficacy and safety of a low-volume, single-catheter, continuous peripheral neural blockade (CPNB) technique to locally deliver bupivacaine to alleviate signs of severe forelimb pain resulting from experimentally induced tendonitis in horses.

DESIGN

Randomized controlled experimental trial.

SAMPLE

14 horses and 5 forelimbs from equine cadavers.

PROCEDURES

Horses underwent collagenase-induced superficial digital flexor tendonitis in the midmetacarpal region of 1 forelimb. To deliver analgesia, a closed-tip catheter was placed from lateral to medial, approximately 12 cm distal to the accessory carpal bone, between the suspensory ligament and accessory ligament of the deep digital flexor tendon. Success of catheter placement and anesthetic delivery was documented ex vivo in 5 forelimbs from equine cadavers. Effective analgesia in affected forelimbs of horses from continuous (n = 7) versus intermittent (7) local anesthetic delivery (intermittent peripheral neural blockade; IPNB) was compared over a 3-day period.

RESULTS

Horses that received CPNB in the affected forelimb were less lame than horses that received IPNB. A lower proportion of CPNB-treated horses had behavioral and physiologic signs of pain, compared with IPNB-treated horses. Neither technique completely blocked the sensation of pain or resulted in swelling in the distal portion of the forelimb, vasodilation, or an increase in lameness. After removal, Staphylococcus aureus was cultured from 1 catheter tip.

CONCLUSIONS AND CLINICAL RELEVANCE

For short-term treatment, CPNB was more effective than IPNB for reduction in signs of severe pain in the distal aspect of the forelimb of horses.