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Elbow Septic Arthritis

elbow septic arthritis osteomyelitis

Introduction

Septic arthritis is inflammation of the joints secondary to an infectious etiology such as bacterial, fungal, mycobacterial, viral, or other pathogens.1 Septic arthritis is usually monoarticular involving one large joint such as the hip or knee. The elbow ranks as the third most frequent site of joint infection, accounting for 10-15% of all septic arthritis cases, behind only the knee and hip joints.1 Though uncommon, septic arthritis is an orthopedic emergency that can cause significant joint damage leading to increased morbidity and mortality. Several conditions increase the risk of developing septic arthritis, including:1,2

Rheumatoid arthritis
Diabetes mellitus
Systemic lupus erythematosus
Intravenous drug use
Corticosteroid therapy
HIV infection
Cancer
Elderly age

Bacteria can infiltrate the elbow joint through three primary mechanisms:1,2

Hematogenous spread (via bloodstream), commonly seen in IV drug users
Direct introduction through traumatic injury
Spread from nearby infections, such as cellulitis, abscesses, or infected bursae

While numerous microorganisms can cause septic arthritis, the joint damage stems primarily from the body's own inflammatory response. The release of proteolytic enzymes and interleukin-1 triggers destructive changes to the joint cartilage. This damage can begin within just 8 hours of infection onset, highlighting the critical importance of rapid diagnosis and treatment to preserve joint function.

Epidemiology

Reported incidence of septic arthritis varies by population. In the general population in western Europe, there are 4-10 proven and probable cases per 100,000 person-years, while this increases to 30-100 cases per 100,000 person-years in patients with risk factors such as rheumatoid arthritis, prosthetic joint, older age, or immunocompromised. 1,3

The prevalence is notably higher in patients who have undergone specific procedures:4 860-1,100 cases per 100,000 total knee arthroplasties, 500 cases per 100,000 patients on hemodialysis, 300-1,400 cases per 100,000 hip arthroplasties, 140 cases per 100,000 postarthroscopic procedures, and 40 cases per 100,000 post joint injections of corticosteroids, according to the American Family Physician 2011 publication.

Regarding HIV patients specifically, studies show varying incidence: in the Netherlands, 23 cases of osteoarticular infection were identified among 1,515 patients with HIV infection between 1983 and 2003 (Acta Orthop 2007), while in Italy, 14 cases of bacterial osteoarticular infection were identified among 4,023 patients with HIV infection between 1985 and 1996.5

Risk Factors

Risk factors for septic arthritis can be categorized by their mechanism of infection:1,2

Hematogenous spread risk factors include diabetes mellitus, HIV, gout and pseudogout, systemic lupus erythematosus, cirrhosis, end-stage renal disease, immunosuppressive medication, IV drug abuse, osteoarthritis, other causes of sepsis, prosthetic joints (typically > 24 months after placement, but may occur earlier), rheumatoid arthritis (associated with 4 to 15-fold increase in risk), sexual activity (gonococcal arthritis), skin lesions or infections near prior joint surgery, vascular compromise (arterial or venous), and lymphedema and associated risk of cellulitis.
Direct introduction risk factors involve skin infection or ulcers, previous intra-articular injection, trauma, prosthetic joints (< 24 months after placement), joint surgery, human bite, and animal bite or scratch.
Contiguous spread can occur from skin infections, cutaneous ulcers, psoriasis, and eczema.
Additional risk factors include age > 80 years, low economic status, and alcoholism.

Etiology

Almost any organism can cause joint infection.6 Most infections are monomicrobial. Polymicrobial infection is less common and may be seen in penetrating injuries, contiguous spread from adjacent soft tissue infection or polymicrobial blood infection (rare).
Gram-positive bacteria are the most common causative organisms:6,7,8

Staphylococcus aureus

Most common cause, reported to account for up to 50% of cases. Usually associated with hematogenous spread, although can also extend to joints from soft tissue infection. Accounts for 60%-75% of joint infection in patients with rheumatoid arthritis.

Streptococci

Second most common cause of nongonococcal septic arthritis. Infections typically hematogenous, and often associated with gastrointestinal pathologies. Group A, B, C, or G streptococci may cause infection. Peptostreptococcus infections associated with dental surgery.

Gram-negative bacteria is reported as a causative agent in 5%-20% of patients.

Neisseria gonorrhoeae

Suspect as causative agent in patients who are young, healthy, and sexually active.

Pseudomonas aeruginosa

Usually healthcare associated bloodstream infections in both native and prosthetic joints. May occur after invasive procedures, such as prostate resection or urologic surgery, anterior cruciate ligament surgery or intra-articular injection of knee. May also be associated with IV drug abuse.

Meningococcal disease

Results in 14% incidence of arthritis.

Other causative pathogens, particularly after invasive procedures, include:

Burkholderia cepacia
Acinetobacter baumannii
Cutibacterium acnes (formerly Propionibacterium acnes )
Borrelia burgdorferi
Fungal infections
Mycobacterial infection
Viral infections

Pathogenesis

Septic arthritis infections can be transmitted to joints through multiple pathways, with hematogenous spread being the most prevalent mechanism.1,3 This route allows organisms to enter the joint due to the absence of a limiting basement plate in synovial tissues. While direct hematogenous transmission is primary, other routes of infection include direct inoculation, which typically occurs following invasive medical procedures, traumatic injuries, or urinary catheterization.1,3 Contiguous spread represents another potential pathway, often emerging from proximal skin infections or cutaneous ulcers near the joint.1,3

Once a microorganism is deposited into the synovial membrane, an inflammatory response is rapidly initiated.2 The subsequent cascade of inflammatory mediators, combined with increased pressure from substantial joint effusions, leads to progressive and destructive consequences. This inflammatory process ultimately results in significant damage to both cartilage and bone structures within the infected joint, potentially causing severe and long-lasting articular impairment.2

Clinical Presentation

Pain serves as a critical diagnostic signal in septic arthritis of the elbow, characterized by a deep, imprecisely localized discomfort that intensifies dramatically with any attempt to move the joint.1,3 The severity of the condition often renders the affected upper extremity essentially non-functional, with patients experiencing significant difficulty bearing weight or executing even minimal movements. Systemic involvement is frequently evident through the presence of fever, which suggests the infection's potential to extend beyond the localized joint space. As the infection progresses, patients may develop a distinctly unwell appearance, presenting with a toxic clinical demeanor that reflects the serious nature of the underlying inflammatory process.

Physical Exam

During physical examination, the infected elbow presents a constellation of distinctive clinical signs. The joint appears visibly inflamed, characterized by pronounced warmth, reddened skin (erythema), and extreme tenderness upon palpation. Clinicians should carefully assess for any accompanying cellulitis or abscess in the surrounding soft tissues. Significant swelling is evident, often accompanied by a notable joint effusion that further contributes to the joint's distorted appearance. Movement becomes severely restricted, with patients experiencing intense pain during attempted flexion, extension, and rotational movements of the elbow. The range of motion is dramatically compromised, reflecting the profound inflammatory process underlying the septic arthritis.

Imaging Studies for Elbow Septic Arthritis

Radiographic Evaluation⁹

Standard radiographs should include anteroposterior, lateral, and oblique views of the elbow. These images may reveal joint space widening or the presence of an effusion. A key diagnostic indicator is the displacement of fat pads, with the posterior fat pad sign being particularly sensitive for joint inflammation.

Ultrasonography

While not a standard part of the diagnostic process, ultrasound offers value in confirming joint effusion and providing guidance for aspiration procedures.

Magnetic Resonance Imaging¹⁰

MRI remains the gold standard for detailed evaluation of soft tissue and early inflammatory changes such as septic arthritis. MRI can detect several important findings including:

Joint Effusion and Synovial Changes

Moderate to large joint effusion with hyperintense signal on T2-weighted images
Marked synovial thickening and enhancement following contrast administration
Synovial proliferation with villous projections in more advanced cases
Increased signal intensity of synovial fluid on fluid-sensitive sequences

Cartilage and Bone Changes

Early cartilage thinning or erosions, best visualized on gradient echo sequences
Subchondral bone marrow edema appearing as high signal on T2/STIR images
Subchondral bone erosions in later stages
Periosteal edema and enhancement along the distal humerus, proximal ulna, or radial head

Surrounding Soft Tissue Findings

Periarticular soft tissue edema appearing hyperintense on T2-weighted images
Muscle edema in the surrounding flexor and extensor muscle groups
Enhancement of surrounding soft tissues after contrast administration
Reactive olecranon or radial bursitis

Advanced or Complicated Findings

Intraosseous abscess formation presenting as rim-enhancing fluid collections
Sinus tract formation extending from the joint to the skin surface
Osteomyelitis with medullary high signal on T2-weighted images and enhancement patterns
Cortical bone destruction in later stages
Loss of normal low signal intensity of cortical bone
Possible adjacent myositis or fasciitis in aggressive infections

MRI is particularly valuable in differentiating septic arthritis from inflammatory arthropathies, crystalline arthropathy, or hemarthrosis, though clinical correlation with laboratory findings and joint aspiration remains essential for definitive diagnosis.

CT Scan^9,11

CT scanning may be indicated in elbow septic arthritis cases:

When MRI is contraindicated (pacemakers, metal implants, severe claustrophobia)
To evaluate complex fractures that may be associated with infection
To assess for osteomyelitis extending from the joint infection
For pre-surgical planning when significant bony involvement is suspected
To guide aspiration or drainage procedures in difficult cases
To evaluate for foreign bodies that may have introduced infection
When prosthetic joint components are present and hardware-related complications need assessment
To identify periarticular abscesses or sinus tracts
When radiographs are inconclusive but clinical suspicion remains high

When a CT scan is performed for suspected septic elbow arthritis, findings may include:

Joint effusion with increased density of fluid within the elbow capsule
Soft tissue swelling and edema surrounding the elbow joint
Distention of the joint capsule
Loss of normally defined fat planes around the joint
Periosteal reaction of the distal humerus, proximal ulna, or radial head
Erosive changes along articular surfaces
Gas within the joint space (in cases of gas-forming organisms)
Early signs of cartilage destruction (joint space narrowing)
Adjacent osteomyelitis with medullary changes in the humerus, radius, or ulna
Periarticular abscesses or fluid collections
Cortical bone destruction in advanced cases
Post-traumatic changes that may have predisposed to infection

While MRI remains the gold standard for detailed evaluation of soft tissue and early inflammatory changes, CT provides excellent bony detail and is particularly useful when hardware is present or when complex bony involvement needs assessment.

Laboratory Workup

Blood Work

Blood work is the first step which may reveal elevated WBC (> 10,000), ESR (> 30), and CRP (> 5).12 Blood cultures should also be obtained. It is important to note that actual threshold values may vary depending on the laboratory standards. WBC will have a left shift. Inflammatory markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), can be elevated but nonspecific.12 ESR rises after 2 days of infection, normalizes 3 – 4 weeks after the initiation of appropriate treatment. CRP rises within hours after infection, normalizes after 1 week. CRP is the more sensitive indicator. ESR and serum WBC are poor standalone predictors. Serial CRP monitoring helps track treatment response.

Joint Aspiration ^2,9

The gold standard for diagnosing joint infection. Aspirate should be sent for WBC count with differential, gram stain, culture (aerobic and anaerobic), crystal analysis, and acid-fast staining.

A septic elbow aspirate is purulent or cloudy. Cell count and differential for WBC > 50,000 – 80,000, PMNs > 75% in a native septic elbow. Gram stain identifies the bacteria and culture confirms the pathogens (but may fail if antibiotics were administered prior to testing). It is also important to check for crystal results to assess for gout (monosodium urate) and pseudogout (calcium pyrophosphate), as gouty attacks present similarly to a septic joint.

Nonoperative Management ^1,2,3

Non-operative management for elbow septic arthritis is seldom appropriate as a standalone treatment due to potential complications including joint destruction and advancing osteomyelitis, which may result in significant pain and functional limitations. This conservative approach is typically reserved for patients whose substantial comorbidities make surgery too risky.

Empirical antibiotics are initiated immediately after synovial fluid analysis, tailored to suspected pathogens. Later transitioning to targeted antibiotics based on culture and sensitivity results from the aspirate. Antibiotic therapy generally continues for 2-6 weeks .Common regimens include:

Clindamycin-based therapy combined with fluoroquinolones, which allows direct conversion from IV to oral treatment.
Vancomycin or daptomycin for methicillin-resistant Staphylococcus aureus (MRSA) risk factors.

Operative Management ^{1,2,3,14,15,16,17}

Given its destructive nature, septic arthritis of the elbow is considered an orthopaedic emergency and should be managed surgically. Options include open or arthroscopic irrigation and debridement of the elbow. In the setting of an infected elbow replacement, consideration should be made towards removal of the prosthesis with placement of an antibiotic spacer.

The operative technique involves irrigation and drainage of the joint, which can be performed open or arthroscopically depending on the joint. During the procedure, all purulent fluid is removed and the joint is thoroughly irrigated. Synovectomy can be performed as needed for appropriate debridement, and joint fluid and tissue samples must be obtained for culture.

Several pitfalls should be avoided during surgery. It is essential not to forget intra-operative fluid and tissue cultures, as these results can guide treatment even if antibiotics have already been initiated. Aggressive suctioning should be avoided to prevent neurovascular injury, and fluid pressures must be carefully monitored during arthroscopic surgery to minimize fluid extravasation and compartment syndrome.

Potential complications include persistent elbow joint infection possibly leading to osteomyelitis due to inadequate irrigation and debridement or inappropriate antibiotics. Neurovascular injury during surgical treatment may affect structures such as the radial nerve, PIN, or recurrent branch of the radial artery. Other complications include elbow stiffness, articular cartilage injury, synovial fistula formation, and breakage of instruments.

Post-operative rehabilitation may include placing the patient in a long-arm posterior slab splint for comfort. Passive and active range of motion exercises for the elbow (flexion, extension, supination, pronation) should be initiated promptly with weight-bearing as tolerated to avoid stiffness. Following irrigation and debridement with antibiotic initiation, WBC count, ESR, and CRP levels should be monitored to assess the response to therapy.

Outcomes for surgical management of septic arthritis of the elbow show promising results in primary infections treated arthroscopically, with studies reporting 97.9% pain-free outcomes. However, delayed cases demonstrate significantly poorer results, with a 30% failure rate requiring reoperation. Mortality remains concerningly high at 11.9%, largely attributable to the frequent presence of significant comorbidities in affected patients.

Arthroscopic management of elbow septic arthritis should ideally be performed within 24 hours of joint aspiration and antibiotic initiation to optimize outcomes. For best results, arthroscopic lavage should be combined with synovectomy to ensure thorough removal of infectious debris. Collaboration with infectious disease specialists is strongly recommended to guide appropriate antibiotic selection and duration. This comprehensive treatment approach effectively balances infection eradication with preservation of joint function, though it should be noted that outcomes remain significantly dependent on both surgical timing and individual patient factors.

References

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