Three-Dimensional Analysis of Metacarpal Head Articular Defects Created by Headless Screws

Objectives: Headless screw fixation used to treat metacarpal neck and metacarpal shaft fractures is gaining popularity. The aim of the study is to determine the proportion of the metacarpal head articular surface that is compromised during retrograde insertion of headless screws. Methods: Metacarpal screw fixation through a metacarpal head starting point was performed using fluoroscopic guidance on ۱۴ metacarpals. Headless compression screws, with a tail diameter of ۳.۶mm, were used. The specimens were subsequently skeletonized and digitized using a ۳-dimensional surface scanner. The articular surface defects created by the screws were then determined using computer software. Screw position in the dorsal aspect of the metacarpal head was expressed as a percentage of the total volar-to-distal distance. Results: The ۱۴ metacarpals studied consisted of ۲ index, ۴ long, ۴ ring and ۴ small metacarpals, taken from ۴ hands. The average total metacarpal head surface area was ۲۸۴.۶ mm۲ (range, ۱۵۱.۰-۴۶۲.۲ mm۲); the average screw footprint in the metacarpal head was ۱۳.۳ mm۲ (range, ۱۰.۳-۱۷.۴ mm۲), which compromised a mean of ۵.۰% (۳.۰-۷.۸%) of the total cartilaginous metacarpal head surface area. In the sagittal plane, screw placement was found to lie in the dorsal ۳۷.۴% of the metacarpal head (range, ۲۰.۷-۵۸.۶%). Conclusion: The proportion of the articular surface area injured with retrograde insertion of headless compression screws into the metacarpal head is ۵.۰%. Screw placement is generally in the dorsal ۳۷% of the metacarpal head. Level of evidence: V