What is the diagnosis and treatment for swelling of the metacarpal after a twisting motion?

Metacarpal Swelling After Twisting Motion

The most likely diagnosis is a carpometacarpal (CMC) joint sprain or dislocation, and initial management requires standard 3-view radiographs (PA, lateral, and oblique) to rule out fracture or dislocation before proceeding with treatment.

Diagnostic Approach

Initial Imaging

• Obtain a minimum of 3-view radiographic examination including posteroanterior, lateral, and 45° semipronated oblique views to properly visualize metacarpal injuries 1, 2
• An internally rotated oblique projection in addition to the standard externally rotated oblique increases diagnostic yield for metacarpal fractures 1, 2
• Common pitfall: Relying on only 2 views is inadequate and may lead to missed diagnosis 3

Key Physical Examination Findings

• Point tenderness directly over the carpometacarpal joint is the most frequent finding in CMC sprains 4
• Palpable joint laxity and crepitus with manipulation suggest chronic sprain 4
• Severe swelling over the carpometacarpal area with tenderness and weakness suggests acute sprain 4
• Painful swelling on the dorsal side of the hand after twisting injury should raise suspicion for CMC dislocation 5

Differential Diagnosis Based on Mechanism

CMC Joint Injuries (Most Likely)

• Twisting mechanisms commonly cause CMC joint sprains, subluxations, or dislocations 4
• The second and third CMC joints are more susceptible to injury in palmar flexion than dorsiflexion 4
• CMC dislocations represent less than 1% of hand injuries but are frequently missed due to difficulty in diagnosis 5
• Critical point: Severe swelling without significant radiographic findings is suggestive of acute CMC sprain 4

Metacarpal Fractures

• Spiral fractures can occur from twisting mechanisms 2
• Most metacarpal fractures are managed non-operatively 6

Floating Metacarpal (Rare)

• Concurrent bipolar dislocation at both CMC and MCP joints is rare but carries high risk of missed diagnosis 7

Treatment Algorithm

If Radiographs Show Dislocation

• Perform closed reduction to anatomical position in the emergency department 5
• For acute dislocations with minimal swelling, closed reduction and cast immobilization may be sufficient 7
• For delayed presentation or significant swelling, open reduction is the favorable choice 7

If Radiographs Show Fracture

• Most metacarpal fractures can be treated successfully by closed reduction and cast or splint immobilization 8
• Unstable fractures require internal fixation 8
• CT imaging is typically not indicated unless there is concern for complex articular involvement 2

If Radiographs Are Negative (Acute Sprain)

• Acute CMC sprains generally respond to immobilization 4
• Diagnostic injection of 0.5 ml lidocaine directly into the joint offers dramatic relief and confirms diagnosis 4
• Place patient in splint and repeat radiographs in 10-14 days if clinical suspicion remains high 3
• Alternatively, proceed to MRI without IV contrast if high clinical suspicion persists, as it can detect occult fractures and ligament injuries 1, 3

If Conservative Measures Fail (Chronic Sprain)

• Arthrodesis of the CMC joint is relatively simple, symptomatically reliable, and functionally uncompromising, especially for the second and third rays 4

Post-Treatment Management

Early Mobilization

• Initiate active finger motion exercises immediately following diagnosis and treatment to prevent stiffness 2
• Early mobilization is critical to prevent stiffness and restore function 6
• Finger stiffness is the most common functionally disabling complication 2

Monitoring

• Consider vitamin C supplementation for prevention of disproportionate pain 2
• When external fixation is used, limit duration to reduce complications 2

Critical Pitfalls to Avoid

• Delayed diagnosis: CMC dislocations are frequently missed, leading to ongoing pain and loss of function 5
• Inadequate imaging: Failure to obtain all 3 standard views may result in missed fractures or dislocations 3
• Overlooking chronic sprains: These are often misdiagnosed; look specifically for point tenderness, laxity, and crepitus 4
• Delayed mobilization: Failure to initiate early finger motion leads to functionally disabling stiffness 2, 6