A 58-year-old woman with osteoporosis sustains a fall at home and fractures her right proximal humerus (2-part fracture). She is treated conservatively with a sling and early passive range-of-motion exercises. At 3 months follow-up, X-rays show good fracture union, but she complains of severe pain, swelling, and stiffness in the shoulder. On examination, the shoulder is warm, swollen, and there is marked limitation of both active and passive motion. Skin over the shoulder appears shiny and smooth. Laboratory tests show elevated inflammatory markers. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Complex Regional Pain Syndrome Type 1 This patient presents with the classic features of **Complex Regional Pain Syndrome (CRPS) Type 1**, a severe post-traumatic pain disorder that develops after fracture. ### Diagnostic Criteria for CRPS Type 1 **High-Yield:** CRPS Type 1 (formerly Reflex Sympathetic Dystrophy) is diagnosed using the **Budapest Criteria**, which require: 1. **Continuing pain disproportionate to the inciting event** ✓ (severe pain despite good fracture union) 2. **Signs of regional inflammation** ✓ (swelling, warmth, elevated inflammatory markers) 3. **Evidence of edema, changes in skin blood flow, or abnormal sudomotor activity** ✓ (shiny, smooth skin; swelling) 4. **No other diagnosis explains the signs and symptoms** ✓ (fracture healed, no infection) ### Key Distinguishing Features ```mermaid flowchart TD A[Post-fracture shoulder pain at 3 months]:::outcome --> B{Fracture healed?}:::decision B -->|Yes| C{Pain disproportionate to healing?}:::decision C -->|Yes| D{Signs of inflammation + skin changes?}:::decision D -->|Yes + Swelling + Warmth + Shiny skin| E[CRPS Type 1]:::urgent D -->|No inflammation signs| F[Adhesive Capsulitis]:::outcome B -->|No| G[Avascular Necrosis]:::outcome ``` ### Comparison: CRPS vs. Adhesive Capsulitis vs. AVN | Feature | CRPS Type 1 | Adhesive Capsulitis | AVN | Rotator Cuff Tear | |---------|---|---|---|---| | **Pain character** | Burning, disproportionate | Dull, progressive stiffness | Deep ache | Sharp, worse with activity | | **Skin findings** | Shiny, smooth, color changes | Normal skin | Normal skin | Normal skin | | **Swelling** | Marked, with warmth | Mild | No | No | | **Inflammatory markers** | Elevated | Normal | Normal | Normal | | **Fracture union** | Good | Good | May show collapse | Good | | **Passive ROM** | Limited (pain-limited) | Limited (capsular) | Limited (pain) | Limited (weakness) | | **Imaging** | Osteoporosis, soft tissue edema | Normal bone | Crescent sign, collapse | Tear on MRI | **Key Point:** The **combination of good fracture healing + severe disproportionate pain + skin inflammation + elevated inflammatory markers** is pathognomonic for CRPS Type 1, not simple stiffness. ### Pathophysiology CRPS Type 1 involves: 1. **Peripheral sensitization** — nociceptor hyperexcitability 2. **Central sensitization** — spinal cord wind-up 3. **Sympathetic dysfunction** — abnormal vasomotor and sudomotor responses 4. **Neuroinflammation** — glial activation and cytokine release **Clinical Pearl:** CRPS is a diagnosis of **inclusion** (meets Budapest Criteria) rather than exclusion. Early recognition is critical because delayed treatment leads to irreversible disability. ### Management Approach 1. **Multimodal therapy** — physical therapy, pharmacotherapy, psychological support 2. **Sympathetic blockade** — stellate ganglion block (diagnostic and therapeutic) 3. **Medications** — bisphosphonates, corticosteroids, gabapentin 4. **Avoid immobilization** — early mobilization is essential **Warning:** Prolonged immobilization (sling use) may have contributed to CRPS development. Early passive ROM should have been more aggressive.