Injury to Synovial Structures

Diagnostic Imaging and Cytological Analysis Aid the Clinical Investigation of Long Digital Extensor Tendon Subtendinous Bursitis in a Horse

The fetlock joint is a high mobility structure that accommodates enormous loading during locomotion. An injury of the superficial constituent such as subtendinous bursitis may occur due to repeated trauma. An 8-year old school riding horse was presented with dorsomedial distension in the left hindlimb fetlock region. The lesion was noted following routine exercise. The horse demonstrated no lameness and a negative response to the fetlock flexion test. Radiographic findings revealed a smooth surface cortical thickening on the medial aspect of the distal third metatarsal bone. Furthermore, the ultrasonography showed synovial thickening and proliferation, fibrous thickening with an irregular border in the inner synovial lining, and local protuberance of the fibrous layer within the bursa beneath the long digital extensor tendon. Cytological examination of the fluid from the distended lesion discovered multiple nucleated cells, including synoviocytes, nondegenerate neutrophils, lymphocytes, and macrophages. Eventually, the horse suffered subtendinous bursitis of long digital extensor tendon in the left hindlimb fetlock region. Intrabursa administration of 10 mg triamcinolone acetate alongside 25 mg hyaluronan (HA) and subsequent pressure bandaging were performed in the affected fetlock area. The distension was substantially reduced after the 4-week recovery period post medical administration. In summary, the horse was diagnosed with long digital extensor subtendinous bursitis that can occur accidentally. The diagnostic imaging and cytological analysis of accumulated fluid benefited a critical evaluation and facilitated the selection of the appropriate therapeutic plan for this defect.

Effect of experimentally induced synovitis on amikacin concentrations after intravenous regional limb perfusion

OBJECTIVES

To determine the effects of experimentally induced synovitis of the radiocarpal joint on the intra-articular pharmacokinetics and pharmacodynamics of amikacin after intravenous regional limb perfusion (IVRLP).

STUDY DESIGN

Randomized crossover experimental design.

ANIMALS

Adult horses (n = 8).

METHODS

Horses were randomly assigned into 2 trials: synovitis and no-synovitis. Radiocarpal joint synovitis was induced with lipopolysaccharide 6 hours before IVRLP. IVRLP (5-mg/kg amikacin qs 60 mL) was performed with a pneumatic tourniquet under general anesthesia. Synovial fluid was obtained before and 0.5, 1, 3, 5, 12, 24, 48 hours after IVRLP. Amikacin concentrations at each time point and pharmacokinetic values were compared between synovitis and no-synovitis trials with Student's t-test.

RESULTS

Amikacin synovial fluid concentrations indicated suspected tourniquet failure on 3 occasions (2 synovitis, 1 no-synovitis) on 3 different horses. Data from both trials in these 3 horses were excluded from further analysis. Observed time to maximal concentration (T(max); mean ± SD = 54 ± 13.42 min) was reached earlier in synovitis joints (5/5, 30 min) than in no-synovitis joints (1/5, 30 min and 4/5, 1 h; P = .0476) (P = .0161). Mean observed maximal concentration (C(max)) was higher in synovitis joints (144.48 ± 43.17 μg/mL) than in no-synovitis joints (60.02 ± 28.81 μg/mL; P = .0301). The recommended C(max): minimum inhibitory concentration ratio of 8 was achieved in 3/5 of the successfully perfused joints with induced synovitis, but this ratio was not achieved in any of the clinically normal joints.

CONCLUSION

Synovitis of the radiocarpal joint resulted in an earlier observed T(max) and higher observed C(max) of intra-articular amikacin after IVRLP compared with normal joints.