What is the appropriate management for persistent right hip pain in a patient with a history of right total hip replacement, now presenting after right total knee replacement surgery?

Management of Right Hip Pain After Right Total Knee Replacement in a Patient with Prior Right Total Hip Replacement

Begin with plain radiographs of the right hip as the first-line imaging study to assess for component loosening, wear, osteolysis, or periprosthetic fracture, followed by targeted advanced imaging based on initial findings. 1

Initial Diagnostic Approach

Clinical Assessment

• Characterize the pain pattern carefully: Night pain or pain at rest strongly suggests infection, while pain predominantly on weight-bearing indicates mechanical issues such as aseptic loosening or component wear 1, 2, 3
• Assess for infection signs: Warmth, erythema, fever, or systemic symptoms warrant immediate infection workup, as periprosthetic joint infection is the most serious complication requiring urgent management 4
• Temporal relationship matters: Determine if hip pain began immediately after the knee surgery (suggesting referred pain or positioning injury) versus gradual onset (suggesting progressive hip prosthesis failure) 5

First-Line Imaging

• Obtain comparison radiographs of the right hip to evaluate for component migration, progressive lucencies, osteolysis, or periprosthetic fracture 1
• Key radiographic findings to assess: Component position, presence of lucencies >2mm, progressive osteolysis, heterotopic ossification, or greater trochanter abnormalities suggesting abductor tendon pathology 1

Algorithmic Management Based on Clinical Suspicion

If Infection is Suspected (Night Pain, Systemic Symptoms)

• Proceed directly to image-guided hip aspiration for synovial fluid analysis with cell count, differential, culture, and sensitivity—this remains the most useful test for confirming or excluding infection 1, 4
• Laboratory markers: Obtain ESR and CRP, though these have limited specificity; CRP >13.5 mg/L has 73-91% sensitivity for infection 3
• If aspiration is positive or highly suspicious: Combined WBC scan and sulfur colloid scan has high specificity (88-100%) for periprosthetic hip infection 1

If Infection is Excluded (Mechanical Pain Pattern)

• CT hip without IV contrast is usually appropriate as the next imaging study, with sensitivity of 84.85% for component loosening (versus only 33-52% for radiographs) and superior detection of osteolysis 1
• MRI hip without IV contrast is an equivalent alternative to CT, particularly useful for detecting soft tissue abnormalities including abductor tendon tears, bursitis, or pseudotumors that may cause lateral hip pain 1
• Bone SPECT/CT changed management in 68% of patients with painful hip prostheses when conventional imaging failed to identify the pain source, including identifying non-hip causes such as spine pathology 1

If Trochanteric/Lateral Hip Pain Predominates

• Ultrasound or MRI are equivalent first choices for evaluating abductor tendon tears, trochanteric bursitis, or iliopsoas tendinopathy 1
• Radiographic clue: Greater trochanter surface irregularities >2mm correlate with abductor pathology on MRI, though specificity is only 25.7% 1

Critical Considerations and Pitfalls

Referred Pain from Recent Knee Surgery

• The temporal relationship to recent TKR is crucial: Hip pain beginning immediately post-TKR may represent positioning injury, referred pain, or exacerbation of pre-existing hip pathology rather than new prosthesis failure 5
• Consider non-arthroplasty causes: Lumbar spine pathology, vascular claudication, or soft tissue injury from surgical positioning should be excluded 1

Advanced Imaging Selection

• CT advantages: Superior for quantifying osteolysis, assessing bone-implant interface, detecting liner wear, and evaluating component loosening with metal artifact reduction algorithms 1
• MRI advantages: Better for soft tissue evaluation (sensitivity 95.4% vs 74.7% for CT in detecting osteolysis), can identify 21 soft tissue abnormalities including tendon tears and bursitis that SPECT/CT misses 1
• Avoid planar bone scans: Insufficient evidence supports their use when infection is excluded, as they cannot differentiate aseptic loosening from other causes of pain 1

Management Implications

• If imaging reveals aseptic loosening or significant wear: Orthopedic surgery referral for revision consideration is appropriate 1
• If imaging is negative but pain persists: Bone SPECT/CT should be considered to identify alternative pain sources including spine pathology 1
• Multimodal pain management: NSAIDs as first-line, avoid long-term opioids, and consider physical therapy focusing on core strengthening and hip stabilization 2, 6