A 35-year-old male laborer from Mumbai presents with chronic wrist pain and clicking sensation 8 weeks after sustaining a scaphoid fracture that was treated with a thumb spica cast for 12 weeks. Repeat radiographs now show a fracture line still visible at the waist of the scaphoid with slight separation of fragments. He has persistent snuffbox tenderness and reduced grip strength. What is the most likely complication, and what is the next step in management?

Explanation

## Diagnosis & Management of Scaphoid Non-Union **Key Point:** Persistent fracture line with fragment separation after 12 weeks of immobilization indicates **scaphoid non-union**, not delayed union. Non-union requires surgical intervention. ### Clinical Features of Non-Union **High-Yield:** Non-union is defined as: - Fracture line still visible on imaging **after 12–16 weeks of immobilization** - Absence of callus bridging - Persistent symptoms (pain, clicking, weakness) - Scaphoid waist fractures have higher non-union risk (10–15%) than tubercle fractures (< 5%) ### Risk Factors for Non-Union | Factor | Mechanism | |--------|----------| | Waist/proximal pole fracture | Poor blood supply (retrograde flow) | | Non-displaced fracture | Minimal periosteal stripping; less callus | | Delayed diagnosis | Occult fracture; inadequate early immobilization | | Smoking | Impaired osteoblast function | | Non-compliance | Inadequate immobilization | | Comminution | Increased fracture surface area | **Clinical Pearl:** The scaphoid has a **retrograde blood supply** entering at the waist and distal pole. Proximal pole fractures are at risk of avascular necrosis (AVN), but this patient's fracture is at the waist with persistent vascularity, making non-union more likely than AVN. ### Management Algorithm for Scaphoid Non-Union ```mermaid flowchart TD A[Scaphoid fracture + 12 weeks immobilization]:::outcome --> B{Imaging findings?}:::decision B -->|Fracture line visible + no callus| C[Non-union]:::outcome B -->|Partial callus bridging| D[Delayed union]:::outcome C --> E{Proximal pole involved?}:::decision E -->|No| F[Percutaneous screw fixation]:::action E -->|Yes| G[Assess vascularity with MRI]:::action G --> H{AVN present?}:::decision H -->|Yes| I[Vascularized bone graft + screw]:::action H -->|No| J[Percutaneous screw fixation]:::action D --> K[Continue immobilization 4-6 weeks]:::action K --> L{Union achieved?}:::decision L -->|Yes| M[Discharge]:::outcome L -->|No| N[Proceed to surgery]:::action ``` ### Surgical Options for Non-Union | Procedure | Indication | Success Rate | |-----------|-----------|---------------| | Percutaneous screw fixation | Non-union without AVN, adequate vascularity | 85–95% | | Open reduction + screw + bone graft | Comminuted, displaced, or with AVN | 80–90% | | Vascularized bone graft (e.g., 1,2-ICSRA) | Proximal pole AVN, failed prior surgery | 75–85% | | Wrist fusion (4-corner, STT) | Chronic non-union with SLAC wrist | 70–80% | **High-Yield:** Percutaneous screw fixation is the **gold standard** for uncomplicated scaphoid non-union (waist fracture, no AVN). It provides rigid fixation, allows early mobilization, and has high union rates (85–95%). ### Why NOT the Other Options? - **Delayed union:** Delayed union shows **partial callus bridging** and may resolve with continued immobilization. This patient has a persistent fracture line with no callus—this is non-union, not delayed union. - **Malunion with secondary OA:** Malunion occurs when the fracture heals in an abnormal position. This patient has a visible fracture line (non-union), not a healed fracture in bad position. Conservative treatment is inadequate for symptomatic non-union. - **AVN of proximal pole:** While AVN is a risk with proximal pole fractures, this is a **waist fracture** with persistent vascularity (evidenced by lack of sclerosis on X-ray). AVN would require vascularized bone graft, not simple screw fixation. **Mnemonic:** **WAIST NON-UNION = SCREW; PROXIMAL AVN = VASCULARIZED GRAFT**