12.1 | Septic arthritis |
- About: infected joint can become a permanently painful and destroyed joint. Involve orthopaedic team and microbiology immediately.
- Aetiology: destruction of cartilage begins within 48 h due to pressure, proteases and cytokines from macrophages, bacteria and inflammatory cells.
- Microbiology: Staph. aureus, streptococci, gonococci, Gram negatives, Lyme disease, salmonella (sickle cell). Viral – hepatitis B, parvovirus B19, and lymphocytic choriomeningitis viruses. Propionibacterium acnes can cause post-op shoulder septic arthritis.
- Risks: immunosuppressed, RA, age >80, prosthetic joints, recent steroid joint injections, diabetes. Sickle cell, IV drug user, gonococcus, cellulitis, ulcers.
- Clinical: new joint pain/swelling or increase in usual pain, erythema. Immobility (held in maximal position of comfort), systemic fever. Knee 50%, hip 22% and shoulder. Also ankles, wrists, elbow, and PIPs and DIPs. Also sternoclavicular and sacroiliac joints in generally decreasing frequency. Note that concurrent immunosuppression can dampen clinical findings.
- Differential: gout, pseudogout, fracture, reactive arthritis, osteoarthritis. RA itself does not give this presentation but it can have secondary infection. Crystal deposition uncommon in RA affected joints. Gonococcus – rash, sexually active. Lyme disease affects knee. Polyarticular – Haemophilus, gonococcus, meningococcus.
- Investigations: FBC: ↑WCC, ↑ESR, ↑CRP, U&E, LFT, bone, urate, glucose, blood culture, CXR. Joint aspiration: relieves pressure and pain in a tense effusion. Turbid pus with ↑WBC, predominantly neutrophils. Send aspirate for Gram stain, microscopy for crystals and culture. Consider urethral culture for gonococcus or skin lesion if STD likely. Plain X-rays to look for bony changes. Ultrasonography: can detect effusions and synovial changes. MRI can show bone and joint destruction and osteomyelitis. Radionuclide leucocyte scans can detect inflammation.
- Management: urgent consult with orthopaedics as requires joint aspiration especially if prosthesis. This will relieve pressure and pain and provide microbiological information. FLUCLOXACILLIN IV. MRSA positive consider VANCOMYCIN or TEICOPLANIN IV penicillin allergic. Add GENTAMICIN IV if coliforms are likely. If N. gonorrhoea then CEFTRIAXONE IV/IM OD. High risk MRSA consider VANCOMYCIN IV (adjusted to renal function).
- Contact consultant microbiologist if risk factors for, or evidence of, MRSA colonisation or infection or HIV positive patient. Orthopaedic review as arthroscopy or open surgery may be required. Prosthetic joint infections: needs urgent microbiologist and orthopaedic review. Empirical therapy is usually not indicated unless patient is septic. Later physiotherapy and rehabilitation may be required.
12.2 | Osteomyelitis |
- About: infection of bone which can rapidly lead to pain, deformity and chronic disease if not treated. Differing picture in adults and children. Association with sickle cell disease and salmonella infection. Infection either haematogenous or direct from local wound sepsis.
- Adult disease: 60% are due to Staph. aureus, enterobacter or streptococcus. In older adults the vertebral bodies are more likely to be infected, due to changes in blood flow with spinal osteomyelitis. TB still remains prevalent in certain groups. Risks: open fractures, prostheses, diabetes, diabetic foot, alcoholism, AIDS, immunosuppression. Sickle cell, IV drug abuse – blood spread to vertebrae, chronic steroids.
- Clinical: toxic, febrile and rigors, localised bone pain – long bone or spine, foot, tenderness, warmth and swelling. Children can have just vague symptoms for weeks.
- Investigations: plain X-ray: unreliable (will take 2–4 weeks for demineralization of bone). CT or MRI or USS or three-phase bone scan. MRI modality of choice and will show early oedema. Blood cultures +positive in 50% of cases of acute osteomyelitis. FBC: ↑ESR, ↑WCC, ↑CRP. Obtain pus by open surgery or needle aspiration. Bone biopsy for culture and histology.
- Differential: synovitis, trauma and fracture, bone cancer, sickle cell crisis.
- Management: rapid diagnosis and orthopaedic and microbiology liaison to choose optimal antimicrobial therapy. Acute osteomyelitis: FLUCLOXACILLIN IV +/− FUSIDIC ACID PO. Penicillin allergy: TEICOPLANIN IV + FUSIDIC ACID PO. Duration of therapy: usually 4–6 weeks (minimum 2 weeks IV). High risk of MRSA add VANCOMYCIN IV. Discuss with microbiology. Surgical: debridement and removal of necrotic tissue and drainage of any abscess or collections. Replacement of dead space with tissue flaps or bone grafts. Internal/external fixation. Amputation may be needed. Sickle cell disease: Staph. aureus and salmonella often involved organisms.
- Adult disease: 60% are due to Staph. aureus, enterobacter or streptococcus. In older adults the vertebral bodies are more likely to be infected, due to changes in blood flow with spinal osteomyelitis. TB still remains prevalent in certain groups. Risks: open fractures, prostheses, diabetes, diabetic foot, alcoholism, AIDS, immunosuppression. Sickle cell, IV drug abuse – blood spread to vertebrae, chronic steroids.
12.3 | Reactive arthritis |
- About: inflamed joint but sterile joint aspirate. Infection may be a trigger.
- Aetiology: salmonella, chlamydial, shigella, campylobacter. Others may be post viral e.g. hepatitis B, parvovirus B19, hepatitis C, rubella, HIV, EBV. Post streptococcal with glomerulonephritis and vasculitis.
- Clinical: co-existing urethritis, conjunctivitis, diarrhoeal illness, males > females. Balanitis, keratoderma blennorrhagica (soles of feet). Large joints, knee, sacroiliitis, fever, malaise.
- Investigations: joint aspirate excludes infection and crystals. ↑WCC, ↑ESR, ↑CRP. Urethral swab. Stool for culture. Consider HIV test.
- Management: rest joint, NSAIDs, intra-articular steroids. Treat urethritis. Rheumatology review.
12.4 | Acute gout and pseudogout |
Always aspirate any red hot painful joint to exclude septic arthritis, send Gram stain, culture and microscopy for crystals.
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