Understanding Metacarpal Morphology and Practical Surgical Applications

Area of Science:

• Orthopedic surgery
• Human anatomy
• Biomechanical engineering

Background:

• Metacarpal morphology, specifically its curvature, is not well-understood.
• Understanding the radius of curvature (ROC) is crucial for assessing hand biomechanics, joint alignment, and stability.

Purpose of the Study:

• To quantify the dorsal and volar radius of curvature (ROC) of the metacarpals.
• To measure metacarpal canal and isthmus diameters.
• To compare these measurements across the five metacarpals.

Main Methods:

• Utilized 105 computed tomography scans of cadaver hands.
• Measured volar and dorsal ROC, canal diameters, and isthmus dimensions for all metacarpals.
• Confirmed high interrater and intrarater reliability (ICCs > 0.95).

Main Results:

• All metacarpals exhibited a smaller, more curved volar ROC compared to the dorsal ROC.
• The index metacarpal had the largest ROC, while the small finger metacarpal had the smallest.
• The thumb metacarpal showed the largest intramedullary diameter; the fourth had the smallest.

Conclusions:

• The smaller volar ROC in thumb and small finger metacarpals may relate to grasping and opposition functions.
• The dorsal surface is relatively straight with a large ROC.
• Surgeons can use the dorsal cortex as a guide for intramedullary fixation; volar ROC variations necessitate consideration in fracture fixation.