A 58-year-old woman with osteoporosis is admitted 3 days after a fall with a displaced fracture of the right proximal humerus. Intraoperative fixation with open reduction and internal fixation (ORIF) was performed. On postoperative day 2, she develops severe pain in the hand, swelling of the fingers, skin mottling, and a skin temperature drop of 3–4°C compared to the left hand. Radial and ulnar pulses are palpable. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Complex Regional Pain Syndrome (CRPS) Type I **Key Point:** CRPS Type I (formerly reflex sympathetic dystrophy) is a post-traumatic pain syndrome characterized by disproportionate pain, edema, skin changes (mottling, color changes), temperature asymmetry, and functional impairment. Critically, **pulses remain intact** — distinguishing it from vascular occlusion. It occurs in 5–10% of fracture patients, especially after proximal humerus fractures. **High-Yield:** CRPS diagnostic criteria (Budapest criteria) require: 1. Continuing pain disproportionate to the injury 2. At least 3 of 4 categories of symptoms (sensory, vasomotor, sudomotor, motor) 3. At least 2 of 4 signs on examination 4. Exclusion of other diagnoses In this case: severe pain + swelling + skin mottling + temperature asymmetry (vasomotor signs) + intact pulses = CRPS Type I. **Clinical Pearl:** The intact pulses are the key discriminator. CRPS is a **neurogenic inflammatory** condition, not a vascular occlusion. The pathophysiology involves: - Sympathetic nervous system dysregulation - Neurogenic inflammation (substance P, CGRP release) - Microvascular dysfunction (not macrovascular occlusion) - Central sensitization and pain amplification **Mnemonic: VASOMOTOR** — Vasomotor changes (mottling, color), Autonomic dysfunction, Swelling, Mottled skin, Onset post-trauma, Temperature asymmetry, Oedema, Reduced function ### Distinguishing CRPS from Vascular Complications | Feature | CRPS Type I | Acute Compartment Syndrome | Arterial Thrombosis | |---------|-------------|---------------------------|---------------------| | Pulses | **Intact** | Intact (early) | **Absent/diminished** | | Pain severity | Disproportionate to injury | Severe, with passive stretch | Severe, acute onset | | Skin color | Mottled, cyanotic | Pale, tense | Pale, pulseless | | Temperature | Decreased 2–4°C | Normal/elevated | Cold, pale | | Edema | Diffuse, soft | Firm, compartmental | Minimal | | Onset | Days to weeks | Hours (post-injury) | Immediate to hours | | CK/Myoglobin | Normal | Elevated | Normal | ### Diagnostic Approach ```mermaid flowchart TD A[Post-fracture pain +<br/>swelling + skin changes]:::outcome --> B{Pulses present?}:::decision B -->|No| C[Vascular occlusion]:::urgent C --> D[Arterial duplex/CTA]:::action B -->|Yes| E{Pain disproportionate<br/>to injury?}:::decision E -->|Yes| F[CRPS Type I likely]:::outcome E -->|No| G[Compartment syndrome<br/>or local inflammation]:::outcome F --> H[Clinical diagnosis<br/>+ exclusion imaging]:::action H --> I[Early PT/OT,<br/>sympathetic blocks]:::action ``` ### Management of CRPS Type I 1. **Early recognition** — critical for prognosis 2. **Physical/occupational therapy** — graded exposure, desensitization 3. **Pharmacotherapy:** - Bisphosphonates (alendronate) — reduce bone turnover - Topical agents (lidocaine patches, capsaicin) - Neuropathic pain agents (gabapentin, pregabalin) 4. **Sympathetic nerve blocks** — diagnostic and therapeutic (stellate ganglion block for upper limb) 5. **Avoid immobilization** — perpetuates dysfunction **Prognosis:** Early diagnosis and aggressive therapy improve outcomes. Delayed recognition leads to chronic disability, contractures, and psychological morbidity. [cite:Rockwood & Green's Fractures in Adults Ch 1; Harrison 21e Ch 389]