What is the appropriate management for a patient with hip pain and elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)?

From the Guidelines

Management of a patient with hip pain and elevated inflammatory markers (ESR or CRP) should begin with prompt evaluation for septic arthritis, as this represents a medical emergency requiring immediate intervention. The initial approach includes joint aspiration for synovial fluid analysis, blood cultures, and appropriate imaging such as plain radiographs and possibly MRI 1.

Key Considerations

• If septic arthritis is confirmed or strongly suspected, urgent surgical consultation for joint drainage and debridement is necessary, along with empiric intravenous antibiotics (typically vancomycin 15-20 mg/kg IV every 8-12 hours plus ceftriaxone 2g IV daily or cefepime 2g IV every 8 hours) pending culture results 1.
• Antibiotics should be tailored based on culture results and continued for 4-6 weeks.
• If septic arthritis is ruled out, other inflammatory conditions should be considered, including rheumatoid arthritis, reactive arthritis, or crystalline arthropathy.
• Management then depends on the specific diagnosis, potentially involving NSAIDs, disease-modifying antirheumatic drugs, or colchicine for gout.

Diagnostic Approach

• Laboratory findings such as ESR and CRP can be useful in diagnosing infection, but they are not specific and can be elevated in other conditions as well 1.
• Synovial fluid analysis, including cell count and differential, culture for aerobic and anaerobic organisms, and alpha-defensin testing, can be helpful in diagnosing prosthetic joint infection 1.
• Imaging studies such as plain radiographs, MRI, and CT scans can also be useful in evaluating hip pain and suspected infection 1.

Prioritization of Tests

• The American Academy of Orthopaedic Surgeons (AAOS) guidelines strongly recommend the use of ESR, CRP, and serum interleukin-6 testing for patients being assessed for peri-prosthetic joint infection 1.
• The combination of abnormal results for at least 2 of 3 tests (CRP, ESR, and fibrinogen) can lead to accurate results for the diagnosis of infection 1.

From the Research

Interpretation of Elevated ESR or CRP in Hip Pain

• Elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) in a patient with hip pain may indicate an underlying inflammatory condition, such as septic arthritis or osteoarthritis 2, 3, 4.
• In patients with total hip arthroplasty, elevated ESR and CRP levels can indicate septic loosening, while mechanical loosening may have variable ESR and normal CRP levels 3.
• CRP is more informative and sensitive than ESR for detecting complications and monitoring the effects of treatment in patients with total hip arthroplasty 3.
• ESR and CRP can be used complementarily to diagnose and monitor inflammatory conditions, with ESR being helpful in monitoring chronic inflammatory conditions and CRP being more useful in diagnosis and monitoring responses to therapy in acute inflammatory conditions 4.

Clinical Decision-Making

• In children with hip pain, investigation based on hip ultrasound, body temperature, ESR, and CRP can help select cases for hip joint aspiration and reduce the number of radiographs and hospital admissions 2.
• In adults with hip pain, radiography of the hip and pelvis should be the initial imaging test, and ultrasound-guided anesthetic injections can aid in the diagnosis of an intra-articular cause of pain 5.
• Monitoring CRP and ESR levels after total hip or knee arthroplasty can help make an early diagnosis of periprosthetic joint infections (PJI) 6.

Laboratory Tests

• ESR and CRP are markers of inflammatory conditions and should be used in conjunction with good history taking and physical examination to diagnose and monitor inflammatory conditions 4.
• Many factors can result in falsely high or low ESR and CRP levels, and it is essential to consider these factors when interpreting test results 4.