34th Annual Scientific Meeting proceedings

Introduction
Septic arthritis (SA) is the most common joint disease in ruminants.

Bacteria are the most common causes of septic arthritis. Hematogenous spread is the most common route of infection in adult cattle and calves, followed by indirect infection from a nearby focus and direct infection through trauma or arthrocentesis.

Although the hematogenous spread of infection is common, only one joint is usually infected in adult cattle. Polyarthritis is more common in calves.

Bacteria directly damage cartilage, synovial membrane, and synovia. Subsequently, severe articular degeneration is caused by an immunological response.

Diagnosis
Early diagnosis is essential for successful treatment of septic arthritis.

The diagnosis based on the results of clinical examination, ultrasound, radiography, and synovial fluid analysis. In addition to the orthopedic examination, the origin of septic arthritis should be investigated. Ultrasound is superior to radiography for the evaluation of soft tissues. The surrounding connective tissues and synovial fluid can be evaluated, which can help in choosing an ideal treatment.

Radiographic evaluation of the joint space and osseous changes helps determine the stage of the disease and its prognosis.

Arthrocentesis is performed after clipping and strict aseptic preparation of the site. The aspirated synovial fluid is examined macroscopically and microscopically and sent for bacterial culture and sensitivity testing. Commonly isolated bacteria in ruminants include Trueperella pyogenes, Streptococcus spp., Staphylococcus spp., Escherichia coli and Mycoplasma bovis. Positive bacteriological cultures are reported in 50-70% of cases. In calves, an additional PCR examination for Mycoplasma bovis is recommended [1, 2] .       

Treatment
The goals of treatment are to control infection, remove abnormal joint fluid, control inflammation, and restore joint function.

Whenever possible, primary disease should be identified and treated as aggressively as possible.

Antibiotics should be administered immediately when septic arthritis is suspected. Broad-spectrum antibiotics should be used until the results of microbiological culture are available[3]. If animals on a farm show signs of pneumonia, otitis, or mastitis, the chosen antibiotic should be effective against Mycoplasma spp. Most antibiotics diffuse into healthy joints. However, the pharmacokinetics of antibiotics differ in the septic joint because of higher intrasynovial pressure, periarticular edema, the presence of fibrin, and a lower pH. Additional options for antibiotic treatment are intra-articular injection, regional intravenous limb perfusion, or antibiotics incorporated in a slow-release medium. Clinicians must be aware that the intra-articular administration of antibiotics constitutes extra-label use. Systemic antibiotics should be administered for 2–3 weeks after clinical signs improve.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a good choice for the management of pain and inflammation in cattle. If prolonged NSAID administration is necessary, the risk of abomasal ulcers must be considered, especially in calves[2, 4].

Joint lavage
Techniques used to remove debris and abnormal fluid from the joint include distension lavage, through-and-through lavage, and arthroscopy. With either form of irrigation, the joint is flushed until the returning fluid becomes clear. The procedures require knowledge of the anatomy of the affected joint, adequate local anesthesia, and restraint or general anesthesia[2, 5].

Arthroscopy requires general anesthesia, but allows visual monitoring of joint lavage, provides an opportunity for evaluation of the soft tissues and cartilage, as well as removal of fibrin clots.

Arthrotomy
The approaches to the joint for arthrotomy and arthroscopy are the same; however, a longer incision is made for arthrotomy to allow digital and visual exploration. Arthrotomy can be performed under local anaesthesia (nerve blocks, retrograde intravenous anaesthesia) in joints distal to the elbow/stifle. After arthrotomy, the incision sites can be closed or left to heal by second intention to provide drainage of the joint.

To decide whether a patient should undergo conservative (joint lavage) or surgical (arthrotomy) treatment, the stage of arthritis must be considered. In advanced arthritis with fibrinous or purulent joint contents, the outcome is better with surgical treatment. The success of initial therapy determines whether further therapeutic steps are required. The clinical signs (lameness) should improve within 2–3 days after joint lavage, and the total nucleated cell count of the synovial fluid should decrease.

When clinical signs do not improve after lavage, the total nucleated cell count of the synovial fluid does not decrease after two lavages, or the needles become blocked with fibrin, the patient should undergo surgery.

Postoperatively, exercise should be restricted because the cartilage of the affected joint is prone to injury, especially on the weight-bearing surface. In patients with septic arthritis of the joints distal to the elbow and stifle, thick bandages, splints, or casts can be applied to minimize motion and support healing. The benefits and risks of fixation should also be considered[4, 5].

Complications and Prognosis
The prognosis depends on the time between the onset of infection and treatment, number of joints involved, and extent of bony lesions. The main reasons for an unsuccessful outcome are chronic septic arthritis, failure to eliminate infection, or failure to break the vicious circle of cartilage destruction.

References

1. Constant, C., et al., Clinical findings and diagnostic test results for calves with septic arthritis: 64 cases (2009-2014). J Am Vet Med Assoc, 2018. 252(8): p. 995–1005.
2. Desrochers, A. and D. Francoz, Clinical management of septic arthritis in cattle. Vet Clin North Am Food Anim Pract, 2014. 30(1): p. 177–203, vii.
3. House, J.K., et al., Antimicrobial prescribing guidelines for dairy cattle. Aust Vet J, 2024. 102(4): p. 143–186.
4. Nuss, K., Stadienorientierte Sequenztherapie der septischen Monarthritis beim Rind. 2000.
5. Mulon, P.Y., A. Desrochers, and D. Francoz, Surgical Management of Septic Arthritis. Vet Clin North Am Food Anim Pract, 2016. 32(3): p. 777–795.