Metacarpal Bony Dimensions Related to Headless Compression Screw Sizes

Area of Science:

• Orthopedic surgery
• Radiology
• Biomedical engineering

Background:

• Accurate fracture fixation relies on appropriate implant sizing.
• Headless compression screws are commonly used for metacarpal fractures.
• Understanding metacarpal dimensions is crucial for optimal screw selection.

Purpose of the Study:

• To determine the radiographic dimensions of the index, long, ring, and small metacarpals.
• To compare these dimensions with commercially available headless compression screws.
• To identify potential screw-bone size mismatches in metacarpal fracture fixation.

Main Methods:

• Computed tomography (CT) scans of 223 metacarpals from 57 patients were analyzed.
• Key measurements included metacarpal length, isthmus-to-head distance, and intramedullary isthmus diameter.
• Dimensions were compared against 33 types of commercially available headless screws.

Main Results:

• Index metacarpals were longest (mean 67.6 mm).
• Mean isthmus diameters were 2.6 mm (index), 2.7 mm (long), 2.3 mm (ring), and 3 mm (small).
• Only 27% of tested screws reached the index metacarpal isthmus, with higher percentages for other metacarpals.

Conclusions:

• The index and long metacarpals exhibit a higher risk of screw mismatch.
• This mismatch is attributed to their relatively long lengths and narrow isthmus diameters.
• Findings highlight the need for careful screw selection in metacarpal fracture fixation.