Degree and location of metacarpal angulations

Abstract

Aim: Fractures of metacarpals are commonly encountered in hand surgery. For adequate fixation, a thorough knowledge about the anatomy is essential. While fixing the metacarpals with plates and screws, plates are bent to contour the dorsal surface. However, there are no reference values in literature for the location and degree of angulation. The authors studied the dorsal surface of metacarpals in cadavers to gather data regarding the location and degree of angulation of the dorsal cortex.

Methods: Cadaveric dissections of 118 metacarpals from 30 hands were performed. A true lateral view of each metacarpal was taken using fluoroscopy. These pictures were analyzed using Image J software. The dorsal cortex angle was measured in each image, and the center of rotation of angulation (CORA) was identified. The distance from the CORA to the base of metacarpal was measured and calculated as a percentage of the metacarpal length.

Results: The average dorsal angle of the metacarpals was 11.5°. The average angles for each metacarpal were as follows: 2nd metacarpal = 13° (range, 6-26°; SD, 4.73), 3rd = 10° (range, 1-25°; SD, 5.28), 4th = 11° (range, 1-20°; SD, 4.45), 5th = 12° (range, 2-24°; SD, 5.11). The average location of the CORA from the base of the metacarpal as a percentage of the metacarpal length was identified as follows: 53.5% for the index finger, 52.1% for the long finger, 48.3% for the ring finger and 50.3% for the small finger.

Conclusion: These measurements are able to serve as reference values for plate bending while operating on a metacarpal fracture or metacarpal corrective osteotomy.

Keywords

Metacarpals / plate fixation / anatomy

References

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