Intra‐articular pressure, elastance and range of motion in healthy and injured racehorse metacarpophalangeal joints

Abstract

The objective of this study was to determine if intraarticular pressure, elastance of the soft tissue forming the dorsal pouch, and range of motion in flexion measurements are significantly different in Thoroughbred metacarpophalangeal joints with clinical evidence of idiopathic synovitis, primary synovitis, synovitis/ capsulitis, or osteoarthritis relative to clinically normal joints. Forty-two metacarpophalangeal joints, in 25 active or retired Thoroughbred racehorses, were categorised by palpation and visual inspection of the palmar pouch into one of 4 increasing grades of distention. Intra-articular pressures were then measured using 2 pressure transducers attached to 22-gauge needles from both the dorsal and palmar pouches simultaneously while the horses stood squarely under mild sedation. After obtaining baseline pressure measurements, a third needle was inserted into the dorsal pouch, and 0.5 ml increments of saline solution were added every 10 s to perform a pressure/volume (elastance) study of the dorsal pouch. The elastance study for each joint ended when leakage into the palmar pouch was detected by the pressure transducer placed in that region. A lateral radiographic view was taken of each metacarpophalangeal joint in maximal flexion. The maximum angle of flexion was measured from the radiograph, and this angle was subtracted from 180" to acquire the range of motion in flexion.In this study, all Thoroughbreds with clinical evidence of lameness and/or sensitivity to flexion, referable to the metacarpophalangeal joint region, had fluid distention of the palmar pouch (grade 2 or 3 distention). The 16 metacarpophalangeal joints with no clinical abnormalities had a mean palmar pouch pressure of -1.25 mmHg. Joints afflicted with synovitislcapsulitis had the highest intraarticular pressures (mean +51.00 mmHg); however, joints with idiopathic synovitis (mean +15.71 mmHg), primary synovitis (mean +28.33 mmHg) and osteoarthritis (mean +26.20 mmHg) also had significantly elevated intraarticular pressures relative to the clinically normal group. Thoroughbred metacarpophalangeal joints diagnosed with *Present address: Department of Large Animal Surgery, Norwegian Veterinary College, Postbox 8146 Dep. 0033 Oslo, Norway. synovitis/capsulitis, or osteoarthritis, had significantly increased elastance (stiffness) of the soft tissue forming the dorsal pouch relative to the normal group and, probably, as a result significantly decreased range of motion in flexion. The presence of primary synovitis alone did not have a significant immediate effect on elastance of the dorsal pouch and range of motion in flexion. The 16 Thoroughbred metacarpophalangeal joints assessed as having no clinical abnormalities had a mean range of motion in flexion of 60.81". The mean range of motion in flexion of Thoroughbred metacarpophalangeal joints with a clinical diagnosis of primary synovitis was 53.67"; idiopathic synovitis 52.14'; synovitislcapsulitis 44.20'; and those with radiographic evidence of moderate to marked osteoarthritis 30.80'....

Which anatomical region determines a positive flexion test of the distal aspect of a forelimb in a nonlame horse?

“…This may be related to the high force (200 N) that was applied during this experiment. Studies have shown that the flexion test induces an increased intra‐articular pressure of the metacarpophalangeal joint and increased intraosseous pressure (Stolk and Firth 1994; Strand et al. 1998).…”

Anti-inflammatory and analgesic effects of intra-articular injection of triamcinolone acetonide, mepivacaine hydrochloride, or both on lipopolysaccharide-induced lameness in horses

“…38 Peak reduc- tion in range of motion, corresponding to increased joint pain, was evident 12 hours after the first LPS injection. 38 Peak reduc- tion in range of motion, corresponding to increased joint pain, was evident 12 hours after the first LPS injection.…”

“…35 A handheld goniometer g was positioned so that the center of the rotation was over the center of rotation of the MCP joint. 38,39 Synovial fluid analysis-Two to 6 mL of synovial fluid was collected from MCP joints into EDTA and heparinized tubes. 37 Metacarpophalangeal joint swelling (edema score and joint circumference)-Forelimbs were palpated by 2 investigators (DMB and ALB), who were unaware of the treatment horses had received.…”

Which joint is most important for the positive outcome of a flexion test of the distal forelimb of a sound horse?

“…Joint pain is thought to be related to increasing tension and pressure on structures located on the extension and flexion sides of the joint, respectively (Verschooten and Verbeeck 1997), increased intraarticular pressure (IAP) (Stolk and Firth 1994) and/or intra-osseous pressure (IOP) (Strand et al 1998). Therefore, the conclusion seems warranted that a positive flexion test in a clinically sound horse is probably caused by pain originating from the MCP joint and related structures.…”

“…Joint pain is thought to be related to increasing tension and pressure on structures located on the extension and flexion sides of the joint, respectively (Verschooten and Verbeeck 1997), increased intraarticular pressure (IAP) (Stolk and Firth 1994) and/or intra-osseous pressure (IOP) (Strand et al 1998). In fact, this is one of the suggested mechanisms through which joint disorders are thought to lead to an increase in response to the flexion test (Strand et al 1998). Mechanoreceptors located in the joint capsules react promptly to the nonphysiological loading during the flexion test.…”