Does the treatment approach change for an injury to the third metacarpal?

Third Metacarpal Injury: Treatment Approach

The treatment approach for third metacarpal injuries does not fundamentally differ from other metacarpal fractures, but the third metacarpal's unique anatomical position and stability characteristics require specific attention to carpometacarpal (CMC) joint involvement and rotational deformity. 1

Key Anatomical Considerations

The third metacarpal occupies a central position in the hand and has distinct characteristics that influence management:

• The third CMC joint is highly stable due to strong ligamentous attachments and limited mobility, making isolated dislocations rare but potentially easy to miss on initial evaluation 2, 3
• CMC joint injuries at the third metacarpal are frequently missed on initial presentation due to soft tissue swelling and require high clinical suspicion 2
• Point tenderness over the third CMC joint should prompt consideration of occult joint pathology, which can be confirmed with local anesthetic injection (1% lidocaine) providing complete pain relief 2

Imaging Protocol

Standard imaging for third metacarpal injuries requires:

• Obtain minimum 3-view radiographs (posteroanterior, lateral, and 45° semipronated oblique) as 2-view examination is inadequate 4, 5
• Add an internally rotated oblique projection in addition to standard externally rotated oblique to increase diagnostic yield for metacarpal fractures 4, 5
• Lateral and oblique views are essential for detecting CMC dislocations, which are easily missed on anteroposterior views alone 3
• CT imaging is usually not indicated during acute injury unless there is concern for complex articular involvement 5
• MRI without IV contrast is ideal for evaluating tendon injuries and surgical planning when radiographs are negative but clinical suspicion remains high 6, 4

Treatment Decision Algorithm

For Metacarpal Shaft and Neck Fractures:

• Metacarpal neck fractures are usually stable and do not require surgical intervention in most cases 1
• Shaft fractures can be treated surgically or nonsurgically depending on displacement, angulation, and rotational deformity 1
• Assess for rotational malalignment carefully as the central position of the third metacarpal makes rotational deformity particularly problematic for hand function

For CMC Joint Involvement:

• CMC fracture-dislocations require prompt surgical management to avoid long-term complications 1, 3
• Third CMC joint injuries with persistent pain despite conservative treatment should undergo arthrodesis with inverted triangular graft from the metacarpal base, which provides predictable and lasting relief 2
• Reduction should be performed urgently when dislocation is identified, as these injuries are associated with concomitant metacarpal fractures in the majority of cases 3

For Intra-articular Fractures:

• Metacarpal head fractures often require surgical treatment to restore the joint surface 1
• Operative fixation is necessary when there is >2 mm of residual articular surface step-off to prevent long-term osteoarthritis 7

Post-Treatment Management

Critical elements of post-operative care include:

• Initiate active finger motion exercises immediately following diagnosis and treatment to prevent stiffness, which is the most common functionally disabling complication 5
• Wrist motion does not need early mobilization following stable fracture fixation 5
• Consider vitamin C supplementation for prevention of disproportionate pain 5
• Limit duration of external fixation when used to reduce complications 5

Common Pitfalls

• Failure to obtain adequate radiographic views (minimum 3 views with both oblique projections) leads to missed CMC dislocations 4, 3
• Universal missed diagnosis of third CMC joint pathology occurs when clinicians fail to maintain suspicion based on mechanism of injury and point tenderness 2
• Delayed diagnosis due to negative initial radiographs can lead to functional impairment; consider repeat radiographs in 10-14 days or proceed to MRI if clinical suspicion remains high 4
• Overlooking subtle CMC subluxations on plain films due to overlapping joints requires careful scrutiny of lateral views 3