Ultrasonographic diagnosis of septic arthritis of the distal interphalangeal joint in cattle

Abstract

Diagnosis of septic arthritis in the distal interphalangeal joint (SADIJ) is often difficult, particularly when arthrocentesis or probing of the joint space are inconclusive. The aim of this prospective study was to investigate the usefulness of ultrasonography in reinforcing a tentative clinical diagnosis of SADIJ in 60 Holstein–Friesian cows with septic arthritis in one distal interphalangeal joint (DIJ). The diagnosis of septic arthritis was based on the results of clinical examination and radiographic images, as well as surgical findings. The DIJ of the partner claw of the same foot and the normal DIJs of 18 healthy Holstein–Friesian cows were used as controls. Visualisation, echogenicity and flow phenomena of the synovial fluid were assessed ultrasonographically. The size of the dorsal pouch of the distal interphalangeal joint (DPDIJ) was determined by measuring two defined distances.

The DPDIJ could be imaged in all cows with SADIJ, although the quality of the image varied from good (63%) or moderate (30%) to poor (7%). The echogenicity of the synovial fluid in joints with SADIJ did not differ from those of the partner claws. Flow phenomena were seen in only 30% of the DPDIJs with septic arthritis and in none of the DPDIJs of the partner claws. The DPDIJ was larger in DIJs with septic arthritis than in those of the partner claws and controls (P < 0.05). The dorsopalmar/plantar distance of the DPDIJ indicated a suitable sensitivity (0.97) and specificity (1.0) for the diagnosis of septic arthritis when a threshold value of 6 mm was used. Ultrasonographic examination of the DIJ appeared to be a reliable method for confirming a tentative clinical diagnosis of septic arthritis in cattle.

Introduction

Lameness is the third most common reason for culling dairy cows, after reproductive problems and mastitis (Seegers et al., 1998), and is attributable to claw disease in >90% of cases (Hernandez et al., 2002, Manske et al., 2002). Septic arthritis of the distal interphalangeal joint (SADIJ) is a common complication and, in severe cases, digital amputation or resection of the distal interphalangeal joint (DIJ) is the only effective treatment (Fessl, 1975, Funk, 1977, Köstlin and Nuss, 1988, Starke et al., 2006).

SADIJ is usually associated with a diffuse inflammatory swelling of the foot (Starke et al., 2007), although a definitive diagnosis and differentiation of the affected structures is often difficult (Kofler, 1995). In the clinical examination, stress tests that include flexion, extension and rotation of the joint can be used to reach a tentative diagnosis. In cases with a penetrating joint injury, the diagnosis can be confirmed by passing a probe along the tract into the joint space. Arthrocentesis and evaluation of the synovial fluid is an additional diagnostic technique. Cloudy synovial fluid with at least 10,000 nucleated cells/μL and >90% neutrophils is indicative of purulent arthritis (Dirksen, 1990, Meier, 1997). Rohde et al. (2000) reported that >25,000 nucleated cells/μL with >80% neutrophils was diagnostic for infectious arthritis. In contrast, fibrinous arthritis cannot always be diagnosed by arthrocentesis (Nuss, 2000). Septic arthritis of the DIJ should be suspected on radiographic images when there is narrowing or widening of the joint space, subchondral bone lysis and periarticular bone proliferation. However, in the acute stages of SADIJ, radiography reveals only non-specific soft tissue swelling and bone lysis does not appear until the lesion is at least 14 days old (Verschooten and De Moor, 1974, Bailey, 1985, Ebeid, 1992, Stanek and Kofler, 1995, Desrochers et al., 2001).

In cases where SADIJ cannot be conclusively diagnosed by clinical examination, arthrocentesis or radiography, ultrasonography may be helpful. The normal ultrasonographic appearance of the DIJ (Kofler, 1994) and ultrasonographic findings of SADIJ in cattle have been described (Kofler and Edinger, 1995). Ultrasonographic evaluation of the joint content allows early detection of the disease and stage determination of the septic process (Kofler, 1995, Kofler, 1996, Kofler, 1997, Nuss, 2000).

We hypothesised that SADIJ is characterised by specific ultrasonographic findings, primarily the distension of the joint pouch. The goal of the present study was to evaluate the usefulness of ultrasonography in confirming a tentative clinical diagnosis of SADIJ in the early stages of infection.