Percutaneous Pinning of the Fifth Carpometacarpal Joint

Traditional treatment of unstable fifth carpometacarpal joint injuries is closed reduction and pinning. The aim of this study was to determine the safest corridor for pinning of fifth carpometacarpal joint to prevent the iatrogenic injury to the ulnar nerve and tendons. In the first phase of study، three fresh cadaver samples were dissected and the safest directions of kirschner wire insertion in coronal and sagittal planes were determined to the base of the fifth metacarpal. The second phase evaluated the accuracy of data obtained in previous phase. Therefore k-wires were inserted in combination of maximum angles in different planes determined previously. After taking X-rays، the ulnar nerve branches and tendons were explored to detect any possible damage. In the third phase، four fresh carpometacarpal joints were fixed with directions outside the range of defined angl es. The safe direction determined in the first phase was 20° to 30° coronal plane angle in regard to body of the fifth metacarpal bone and between 10° volar to dorsal to 20° dorsal to volar angle in sagittal plane. Insertion of k-wires in the second phase could fix the fifth carpometacarpal joint firmly. All inserted k-wires outside the defined range resulted in injuries to nerve or tendons or infirm fixation The safest corridor for pinning the unstable fifth carpometacarpal injuries is two centimeters distal to the joint with 20° to 30° in coronal plane and from 10° volar to dorsal to 20° dorsal to volar direction in sagittal plane.