Computed tomographic analysis of the internal structure of the metacarpals and its implications for hand use, pathology, and surgical intervention.
The variation of bone structure and biomechanics between the metacarpals is not well characterized. It was hypothesized that their structure would reflect their common patterns of use (i.e., patterns of hand grip), specifically that trabecular bone density would be greater on the volar aspect of all metacarpal bases, that this would be most pronounced in the thumb, and that the thumb diaphysis would have the greatest bending strength. Cross-sections at basal and mid-diaphyseal locations of 50 metacarpals from 10 human hands were obtained by peripheral quantitative computed tomography. The volar and dorsal trabecular densities of each base were measured and characterized using the volar/dorsal density ratio. The polar stress-strain index (SSIp), a surrogate measure of torsional/bending strength, was measured for each diaphysis and standardized for bone length and mass. Comparisons were made using mixed-model analyses of variance (ANOVAs) and post hoc tests. Volar/dorsal trabecular density ratios showed even distribution in all metacarpal bases except for the thumb, which showed greater values on the volar aspect. The thumb, second, and third metacarpals all had high bending strength (SSIp), but the thumb's SSIp relative to its length and trabecular mass was much higher than those of the other metacarpals. Trabecular density of the metacarpal bases was evenly distributed except in the thumb, which also showed higher bending strength relative to its length and mass. Understanding of how these indicators of strength differ across metacarpals may improve both fracture diagnosis and treatment and lays the groundwork for investigating changes with age, hand dominance, and occupation.
Center for Bioengineering Innovation and Design, Johns Hopkins University, 3400 N. Charles Street, Clark Hall, Suite 200, Baltimore, MD, 21218, USA. alison.wong@dal.ca.|Division of Plastic and Reconstructive Surgery, Dalhousie University, Room 4714 Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada. alison.wong@dal.ca.
Alison L
AL
Wong
The Curtis National Hand Center, MedStar Union Memorial Hospital, 3333 North Calvert Street, Baltimore, MD, 21218, USA.
Clifton G
CG
Meals
Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, 1830 E. Monument Street, Room 302, Baltimore, MD, 21205, USA.
Christopher B
CB
Ruff
D015519:Bone Density; D006225:Hand / Q000502:physiology*; D018737:Hand Strength; D006801:Humans; D050279:Metacarpal Bones / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013933:Thumb / Q000502:physiology; D014057:Tomography, X-Ray Computed
Biomechanical; Bone; Computed tomography; Metacarpals; Morphology