A 19-year-old boxer strikes an opponent and sustains a fracture of the neck of the fifth metacarpal with volar angulation of the distal fragment. Closed manipulation and cast treatment is planned. The reason the degree of acceptable volar angulation is greatest in this particular metacarpal is:

• A It has no tendinous insertion on its base, so remodeling forces act freely
• B Its collateral ligaments prevent any residual rotation from affecting function
• C It remodels faster because it lies entirely within the growth plate zone
• D Its carpometacarpal joint has the greatest mobility, compensating for residual deformity ✓

Explanation

The fourth and especially the fifth carpometacarpal joints are mobile saddle-type articulations allowing significant flexion, so residual volar angulation at a fifth metacarpal neck fracture is functionally well compensated, and large angulations are tolerated in closed treatment. By contrast, the index and middle CMC joints are nearly immobile, so their deformities cannot be compensated. The metacarpal base receives insertions including the extensor carpi ulnaris nearby, making option A false.

Reference: Green's Operative Hand Surgery, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.