Synovial fluid parameters following acute articular fracture in the horse

The objective was to investigate synovial sample appearance, total nucleated cell count (TNCC), total protein concentration (TP), and neutrophil percentage in horses with acute articular fractures to aid decision making in acutely lame horses.

Retrospective case series.

Synovial fluid samples (n = 55).

Synovial fluid records were analyzed over an 11 year period from horses undergoing lag screw fixation or arthroscopic fragment removal of intra-articular fractures within 48 h of occurrence. Horses were excluded when presented with wounds close to the joint or when treatment was delayed by 48 h or more. The TNCC was compared between two groups according to time from occurrence (<8 and >8 h).

A total of 54 horses met inclusion criteria yielding 55 synovial samples obtained from either the metacarpo/tarsophalangeal (n = 49) or intercarpal joints (n = 6). The median TNCC for all samples was 20.6 × 10⁹/L (range 0.1-76.1 × 10⁹/L). The TNCC was greater than 30 × 10⁹/L in 17 cases (30.9%). The highest median TNCC was recorded in the earlier group (<8 h). The median TP concentration was 40 g/L (n = 48, range 4-76 g/L) and median neutrophil percentage was 83.0% (n = 27, range 0% to 93%). No differences were observed in samples from different joints or different fracture configurations. Hemarthrosis was present in 94.6% of cases where gross appearance was described (n = 35).

Acute intra-articular fracture in the horse had the potential to elevate synovial fluid parameters above values considered diagnostic for septic arthritis. Limitations of this study include the small sample size and the absence of serial samples to assess temporal variations.

The findings demonstrate that there can be overlap in synovial fluid parameters between cases of acute intra-articular fracture and septic arthritis.