What is the assessment and management plan for a patient with acute unilateral leg pain and swelling on post-operative day 5 after hip arthroplasty?

Assessment and Management Plan for Acute Unilateral Leg Pain and Swelling Post-Operative Day 5 After Hip Arthroplasty

This patient requires immediate evaluation for deep vein thrombosis (DVT) and periprosthetic infection, as sudden increases in pain and swelling on postoperative day 5 are harbingers of serious complications that demand urgent comprehensive assessment. 1

Immediate Diagnostic Priorities

Primary Differential Diagnosis

The two most critical diagnoses to rule out are:

• Deep vein thrombosis - DVT incidence ranges from 1.1% for pulmonary embolism to over 70% for infrapopliteal DVT following hip arthroplasty 2
• Periprosthetic infection - Sudden pain increase with associated tachycardia, hypotension, or hyperthermia suggests postoperative complications including infection 1

Essential Clinical Assessment Points

Look specifically for:

• Vital signs: Tachycardia, hypotension, and hyperthermia indicate potential infection or other serious complications 1
• Wound examination: Assess for significant swelling, erythema, drainage, or warmth - these indicate infection requiring immediate intervention 3
• Suture/staple status: Document whether sutures/staples remain in place, as wound healing typically requires ~14 days 3
• Unilateral vs bilateral presentation: Unilateral swelling narrows the differential significantly 4, 5

Diagnostic Algorithm

First-Line Imaging and Laboratory Studies

For suspected DVT:

• Obtain duplex ultrasound of the affected lower extremity immediately 2
• This is the standard initial diagnostic test for DVT evaluation

For suspected infection:

• Image-guided hip aspiration with synovial fluid analysis is the most useful test for confirming or excluding periprosthetic infection 6
• Send aspirate for cell count with differential, gram stain, and culture
• Obtain inflammatory markers (ESR, CRP), though ESR alone should not be relied upon as it remains elevated for months after uncomplicated surgery with poor specificity 6

Advanced Imaging Considerations

If initial workup is inconclusive:

• MRI with metal artifact reduction can demonstrate inflammatory synovitis, soft tissue edema, lymphadenopathy, fluid collections, and bone marrow edema associated with infection 6
• Enlarged lymph nodes on MRI comparing affected to unaffected hip can identify infected implants with up to 93.1% accuracy 6
• Ultrasound can identify soft tissue complications including iliopsoas bursitis causing venous compression 4, 5, 7

Tests to Avoid

• Do not rely on ESR alone - it has poor specificity in the postoperative period 6
• Do not order bone scan alone - sensitivity ranges only 29-88% and specificity 50-92% for periprosthetic infection 6
• Do not interpret FDG-PET positive results as definitive - false-positive rates reach up to 77% due to aseptic inflammation 6

Management Based on Diagnosis

If DVT Confirmed

• Initiate anticoagulation immediately per institutional protocol
• Consider vascular surgery consultation for extensive thrombosis
• Monitor for pulmonary embolism symptoms

If Infection Confirmed

• Obtain orthopedic surgery consultation immediately
• Initiate broad-spectrum antibiotics after cultures obtained
• Surgical debridement may be required depending on infection depth and severity 8
• Do not restart any biologic therapy (if patient was on such medications) until wound shows complete healing, all sutures/staples are out, there is no significant swelling, erythema, or drainage, and there is no clinical evidence of surgical or non-surgical site infections 3

If Iliopsoas Bursitis with Venous Compression

• This rare complication presents as unilateral leg swelling from femoral vein compression 4, 5
• Ultrasound-guided aspiration can provide transient relief 4
• Definitive treatment requires surgical excision 4, 5
• Consider revision surgery if polyethylene wear debris is the underlying cause 5

Pain Management During Evaluation

While diagnostic workup proceeds, provide appropriate analgesia:

• Continue paracetamol and NSAIDs/COX-2 inhibitors as basic analgesia unless contraindicated 1
• Add opioid rescue medication as needed for breakthrough pain 1
• Reassess pain levels regularly - worsening pain despite adequate analgesia mandates reevaluation for complications 1

Critical Pitfalls to Avoid

• Do not dismiss unilateral swelling as "normal postoperative edema" at day 5 - this timing and presentation demands investigation 4, 5
• Do not delay aspiration if infection is suspected - early diagnosis and treatment significantly impact outcomes 6
• Do not restart biologic medications (if applicable) until wound healing is complete and infection is definitively excluded 3
• Do not attribute symptoms to pain alone without ruling out DVT and infection first 1, 2