Septic arthritis (SA) is an infection of the joint space and is considered to be a joint-threatening emergency owing to substantial morbidity and mortality.1 It can affect any joint and is relatively uncommon in the hand and wrist; however, there are unique aspects of these cases that distinguish them from cases involving other joints. Septic arthritis is most commonly caused by a penetrating trauma or spread of an infection from contiguous structures, and like other closed-space infections, bacterial toxins and the local inflammatory response result in damage to the affected joint.2 Because SA can rapidly lead to articular destruction and eventually osteomyelitis, it requires urgent treatment that includes intravenous (IV) antibiotics, immediate irrigation, and debridement, followed by early mobilization.1,3
Pathophysiology
- SA of the hand or wrist is typically caused by direct joint penetration (eg, human or animal bite) or the extension of an infection through contiguous or hematogenous spread;4 direct spread of an infection can also occur in phalangeal joints from a felon, paronychia, or pyogenic flexor tenosynovitis5
- Spontaneous SA in is generally uncommon, but there have been occasional reports cases in the wrist without a definable etiology6
- The most common organisms that cause SA are beta-hemolytic Staphylococcus aureus and Streptococcus organisms7
- Eikenella corrodens: commonly found in SA of the metacarpophalangeal joints from a clenched-fist injury due to direct inoculation or from a human bite5
- Neisseria gonorrhoeae: should be considered in sexually active patients or young adults with monarticular, nontraumatic SA8
- Haemophilus influenza: should be considered in young, unvaccinated children2
- Pasteurella multocida: may be responsible in patients that are bitten by a cat or dog9
- Pseudomonas aeruginosa: may be responsible in patients with a history of IV drug abuse10
- Hand and wrist joints are prone to local trauma that predispose them to unusual microbiologic infections (eg, anaerobic and mycobacterial infections) that require antimicrobial management substantially different from that for Staphylococcus aureus9
- Like other close-space infections, cartilage destruction results from bacterial toxins, proteolytic enzymes, and other associated enzymes that are released during the joint infection; with time, direct damage to cartilage ensues, which can ultimately lead to osteomyelitis2,4
- Predisposing factors for SA include infancy, immunosuppressive therapy, alcoholism, drug abuse, some immunoglobulin deficiencies, phagocytic cell dysfunction, chronic arthritis, previous joint damage, previous joint surgery, and a history of intra-articular glucocorticoid injections6
Related Anatomy
- There are several unique aspects of SA of the hand and wrist that distinguish it from SA of other joints:
- By virtue of the small joint size, the infectious burden in any single septic wrist or finger joint is much smaller than it is in larger septic joints
- Although the hands typically have a very good blood supply, circulation may be compromised in some patients with comorbid medical problems
- The small joint size limits serial aspiration as a practical option for drainage9
- In severe infections, purulence can exit the wrist joint and extend into the carpal tunnel and subcutaneous tissues11
Incidence and Related Conditions
- The incidence of SA is estimated to be 2–5/100,000/year in the general population, and rates depend on population variables and pre-existing structural joint abnormalities1,10
- Incidence rates are higher, 28–38/100,000 individuals with rheumatoid arthritis (RA) and 40–68/100,000 individuals with a prosthetic joint1
- The incidence of SA of the wrist is not known, but it occurs less frequently than in other large joints and is considered rare; ~25% of upper extremity cases affect the wrist1
- In one of the largest series available, only 29 cases of SA of the wrist were identified over a 10-year period12
Differential Diagnosis
- Septic bursitis
- Cellulitis
- Gout
- Pseudogout
- Transient synovitis
- Osteomyelitis
- Abscess
- Rheumatoid arthritis
Laboratory Workup
- Key diagnostic test is synovial fluid analysis
- Gram stain, culture, white blood cell count and differential, and polarizing microscopy for crystals11
- Unfortunately, bacterial Gram stain and culture—is not consistently positive in an acute septic joint, and the culture might become positive only after several days
- Gonococcal SA is notorious for being culture negative in ~50% of cases11
- Fluid findings characteristic of SA include:
- A friable mucin clot
- A white blood cell count >50,000 with greater than 75% are polymorphonuclear leukocytes
- A glucose level 40mg less than the fasting blood glucose level2,8
