SEPTIC ARTHRITIS/SEPTIC PHYSITIS

SEPTIC ARTHRITIS/SEPTIC PHYSITIS

Presented by: Erika Little, DVM, MBA, MS, Dipl. ACVS

RELEVANT READING MATERIAL

  • Chapter 86, Synovial and Osseous Infection

  • Pages 1458 - 1470, Auer & Stick Equine Surgery, Fifth Edition

OVERVIEW

  • Causes

    • Pathogenesis

    • Foals

    • Adults

    • Consequences

    • Treatments

OVERVIEW - CAUSES

  • Naturally Occurring Causes:

    • Hematogenous (originating from blood)

    • Traumatic (caused by injury)

    • Iatrogenic (caused by medical treatment)

    • Examples:

    • Arthroscopy

    • Arthrocentesis

    • Fracture repair

  • Common Infectious Agents:

    • Typically bacterial

    • Rarely viral, mycobacterial, or fungal

PATHOGENESIS

  • Initial Responses:

    • Synovitis and capsulitis (inflammation of the synovial membrane and capsule)

    • Fibrin deposition

    • Cellular infiltrates (migration of immune cells into tissues)

  • Enzymatic Activity:

    • Release of degradative enzymes such as collagenase, stromelysin, and metalloproteinases (MMP)

    • Cytokines involved: Interleukin-1 (IL-1), Interleukin-6 (IL-6), and Tumor Necrosis Factor (TNF)

    • This contributes to a cycle of cartilage matrix destruction

ACTIVATORS

  • Cells Involved:

    • Synoviocytes

    • Fibroblasts

    • Neutrophils

    • Macrophages

  • Key Factors:

    • Trauma and inflammation activate IL-1 and TNFα

    • Additional contributors include:

    • Metalloproteinases

    • Collagenase

    • Gelatinase

    • Stromelysin

    • Free radicals

    • Prostaglandins

    • Wear particles

    • Hyaluronate degradation

Impact on Articular Cartilage

  • Damage results from

    • Physical damage

    • Inflammatory mediators such as IL-1 and TNFα

    • Compromise in subchondral bone integrity and subsequent resorption

RISK FACTORS - FOALS

  • Factors similar to foal septicemia

  • Failure of Passive Transfer (FPT) increases risk of bacteremia leading to localized infection

  • Types of septic arthritis in foals include:

    • S-type

    • E-type

    • P-type

S-TYPE SEPSIS

  • Description:

    • Affects synovial membrane and fluid

  • Age Range:

    • Less than 1 week

  • Common Joints Involved:

    • Larger joints: stifle (knee) and tibiotarsal (hock)

    • Multiple joints are often affected

  • Clinical Signs:

    • Acute, severe lameness

    • Joint effusion (swelling due to fluid accumulation)

E-TYPE SEPSIS

  • Description:

    • Affects bone adjacent to articular cartilage and epiphysis

  • Age Range:

    • Weeks old

  • History:

    • Associated with FPT or other diseases such as pneumonia and diarrhea

  • Commonly Affected Joints:

    • Distal femur, talus, tibia, radius

  • Clinical Signs:

    • Mild lameness, possibly fever, followed by exacerbation with effusion

P-TYPE SEPSIS

  • Description:

    • Common in foals aged weeks to months

    • Often has a history of prior diseases

  • Common Sites Affected:

    • Distal physis of MCIII/MTIII (metacarpus/metatarsus), radius, tibia

  • Clinical Signs:

    • Initial lameness followed by a sudden acute severe lameness and swelling

    • Periarticular swelling usually without effusion

P-TYPE: DIAGNOSIS

  • Diagnostic Techniques:

    • Radiographs (X-rays)

    • Aspiration of physis (joint fluid extraction)

    • Possible bone biopsy

    • Critical Note:

    • Do NOT debride to avoid damaging the physis, which could lead to premature closure of growth plates

SEPTIC ARTHRITIS IN FOALS

  • Symptoms:

    • Presenting signs include lameness, joint effusion, potential fever

  • Diagnostic Procedures:

    • Radiographs

    • Synovial fluid analysis should show:

    • Cell count > 50,000 cells/mL

    • > 90% polymorphonuclear cells (PMNs)

    • Color may range from normal to cloudy, red, orange, or pink

  • Blood Work Findings:

    • Potential leukocytosis

    • Fibrinogen levels usually exceed 900 mg/dL when bone is involved

  • Ultrasound Findings:

    • Hypercellular fluid observed

FOALS: JOINT EVALUATION

  • Must identify all joints involved

    • U/S evaluation of umbilicus is critical

  • Prognosis:

    • Approximately 77% survival rate

RISK FACTORS - ADULTS

  • Iatrogenic Causes:

    • Risk associated with

    • Synovial surgeries

    • Fracture repairs

    • Arthrocentesis

    • Reported risk is 1 per 1279 injections (Aust Vet J 2013)

    • Staphylococcus spp. is most common (34.3% from retrospective of 206 cases, 2010)

  • Trauma:

    • Various causes can lead to infection

    • Enterobacteriaceae are more common after trauma, along with Staphylococcus, Pseudomonas, and fungi

    • Bacteremia is rare in adults

TRAUMA IN ADULTS

  • Key Note:

    • An open joint is an infected joint

SEPTIC ARTHRITIS IN ADULTS - CLINICAL SIGNS

  • Present similarly to foals

  • Key Symptoms:

    • Acute onset of severe lameness

    • Synovial effusion observed

    • Peri-articular heat and swelling

    • Potential fever

SEPTIC ARTHRITIS - DIAGNOSIS

  • Microbiology Techniques:

    • Gold Standard: Microbiology assessment

    • Gross Examination:

    • Evaluation of color, clarity, and viscosity of joint fluid

    • Clinicopathological Evaluation Includes:

    • Total protein

    • Cell count and differential

    • Staining of smears

DIAGNOSIS PROCEDURES

  • Cultural Techniques:

    • Culture and sensitivity tests should be performed early

    • Enrichment/blood culture media should be used for better yield

    • Fungal cultures should be submitted if needed

    • Repeat cultures if the initial sample comes back negative

    • In foals: aspirate the physis if physitis is suspected

DIAGNOSIS - CYTOLOGY

  • Fluid Color Assessments:

    • Normal = Pale yellow

    • Abnormal = Serosanguinous, orange, or turbid

  • Cell Count & Clarity:

    • Normal clarity = clear

    • Normal WBC < 500 cells/dL

    • Normal < 10% of neutrophils

  • Total Protein Assessment:

    • Normal total protein < 2.0 g/dL

SEPTIC ARTHRITIS - DIAGNOSIS

  • Most Common Isolate:

    • Staphylococcus spp. (34.3% from Equine Vet J 2010)

  • Must culture before initiating antibiotics

  • Technique Note: Tap away from the wound to avoid contamination

IMAGING TECHNIQUES

  • Imaging Modalities:

    • Radiographs:

    • Marked effusion

    • Associated soft tissue swelling

    • Osseous involvement if present

    • Ultrasound:

    • Assists in fluid aspiration and analysis

    • Hypercellular fluid assessment

    • For foals, check umbilicus

    • Nuclear Scintigraphy:

    • Applicable to fetlock joint and tarsocrural joint evaluation

TREATMENT

  • Critical Note:

    • To be successful, rapid disease recognition and immediate aggressive treatment are required

  • Therapeutic Innovations:

    • Intensive local therapies such as lavage, local antibiotics, and effective drainage

TREATMENT - GOALS

  • Objective is to

    • Return cartilage to a normal environment

    • Eradicate infection

    • Eliminate inflammation

    • Minimize matrix loss and cartilage damage

  • Consequences of Failure:

    • Irreversible structural damage

    • Decreased prognosis

    • Possible contralateral limb laminitis (inflammation of the hoof)

TREATMENT - AFTER SAMPLE ACQUISITION

  • Antibiotic Management:

    • Begin broad-spectrum antibiotics (e.g., Penicillin/Gentamicin) as foundational treatment

  • Lavage Technique:

    • Conduct lavage as early and often as possible

    • Use large volumes (5-10 liters) for optimal impact

TREATMENT - LAVAGE

  • Approach:

    • Arthroscopic techniques are best for rapid and accurate delivery

    • Aims to remove fibrin clots and perform targeted debridement

    • Needle lavage (through-and-through) for acute infections

    • Use large gauge needles (14, 16, 18g)

    • Place needles in all compartments of the joint

TREATMENT - LAVAGE UNDER ANESTHESIA

  • Sedation and Local Anesthesia

    • 2% Mepivacaine may be used in joint

    • General anesthesia options include arthroscopy or arthrotomy

TREATMENT - LAVAGE SOLUTIONS

  • Recommended Solutions:

    • Balanced Electrolyte Solutions like Lactated Ringer's Solution

  • Prohibitions:

    • Do NOT add chlorhexidine or povidone-iodine due to tissue irritation and harm

  • Considerations:

    • +/- DMSO (Dimethyl sulfoxide) as an adjunct

TREATMENT - LAVAGE FREQUENCY

  • Conduct lavage every other day

  • Endpoint for Treatment:

    • Stop when lameness resolves, effusion and swelling normalize, and WBC levels in synovial fluid return to normal

TREATMENT - ANTIBIOTIC STRATEGY

  • General Approach:

    • Utilize broad-spectrum antibiotics initially, then switch to targeted therapy based on culture/sensitivity

    • Local Administration is Vital:

    • Encourages high local concentrations of antibiotics compared to systemic treatment

  • Duration of Antibiotics:

    • Minimum 2 weeks beyond resolution of clinical signs

TREATMENT - LOCAL ANTIBIOTICS

  • Administration Routes:

    • Intra-articular (IA), regional limb perfusion (RLP), intra-osseous (IO), or antibiotic-impregnated biomaterials

    • Continuous rate infusion (CRI) vs intermittent bolus administration

  • Targeted Approach:

    • Follow culture/sensitivity for specific pathogens

INTRA-ARTICULAR ADMINISTRATION OF ANTIBIOTICS

  • Technique Details:

    • Administer AFTER lavage is complete

    • Achieves high concentration of drug at the site (10-100x systemic levels)

    • 500 mg Amikacin can maintain therapeutic levels for >72 hours for most common pathogens

    • Caution:

    • Avoid exceeding daily total systemic dose when treating multiple joints

REGIONAL LIMB PERFUSION

  • Procedure Steps:

    • Performed every other day (QOD)

    • Requires sedation and local anesthesia

    • Use of an Esmarch tourniquet (or pneumatic) for accessibility

    • Proper tourniquet placement is crucial

    • Inject slowly (over 5-10 minutes)

    • Keep tourniquet on for 30 minutes

    • Option for topical Surpass® application

REGIONAL LIMB PERFUSION - DOSAGE

  • Rule of Thumb:

    • Use 1/3 of systemic antibiotic dose

    • Dilute to 30 mL for the distal limb, or 60 mL for above carpus/tarsus

    • In CATTLE: Utilize RLP with Florfenicol for effective tissue concentrations against common pathogens

    • Caution:

    • Do NOT exceed total daily systemic dose

INTRA-OSSEOUS ANTIBIOTIC ADMINISTRATION

  • Technique Overview:

    • Requires sedation/local anesthesia

    • Drill a 4mm hole for access

    • Employ Esmarch tourniquet for the procedure

    • Inject antibiotics slowly

    • Leave the tourniquet in place for 30 minutes

ANALGESIA

  • Pain Management Considerations:

    • Patients experience excruciating pain, eventual contralateral limb laminitis may occur

    • Excessive time in recumbency can lead to further complications such as decubital ulcers, respiratory disease, gastrointestinal issues, and weight loss

ANALGESIA - STRATEGIES

  • Use of non-steroidal anti-inflammatory drugs (NSAIDs) requires monitoring for toxicity

  • Utilize GI protectants such as

    • Omeprazole AND Sucralfate

  • Options includes opiates and continuous rate infusion (CRI) of

    • Lidocaine, Ketamine, and hind limb epidural catheters for enhanced analgesia

RESPONSE TO TREATMENT

  • Clinical Assessment:

    • Clinical lameness is the most reliable measure for response to treatment

  • Caution: NSAIDs and analgesics may mask pain, leading to false impressions of treatment success

  • Recommendation:

    • Do not discontinue any antibiotics or lavage until a full evaluation post-analgesics is conducted

ADJUNCT TREATMENT

  • Treatment Goals:

    • Aim to

    • Eradicate infection

    • Eliminate inflammation

    • Return cartilage to its normal environment

    • Options include intra-articular administration of Hyaluronic Acid (HA), Autologous Conditioned Serum (ACS), or Platelet-Rich Plasma (PRP)

    • Hyaluronic Acid (HA) is considered the most plausible option for effective recovery