Distal interphalangeal joint arthrodesis comparing tension-band wire and Herbert screw: a biomechanical and dimensional analysis.

Thirty cadaveric distal interphalangeal joints (15 male and 15 female joints) were prepared with either a Herbert screw or a tension-band wire technique to simulate an arthrodesis. To elucidate mechanical differences between these constructs, the strength of the specimens was determined for three-point anteroposterior and lateral bending and for axial torsion. The Herbert screw demonstrated significantly greater anteroposterior bending strength and greater torsional rigidity when compared to the tension-band wire technique. For dimensional analysis, the height and width of each distal phalanx was measured prior to fixation, 4 mm from the distal tip of the bone (the region that must accommodate the large-diameter threads of the Herbert screw). Results indicated that the mean height of the distal phalanx (3.55 mm) is smaller than the diameter of the screw (3.90 mm). Fracture or thread penetration at the tip of the distal phalanx during screw placement occurred in 25 of the specimens overall and in all the female phalanges, often resulting in stretching or violation of the nail bed. Despite fracture or screw penetration, the Herbert screw appears to offer additional strength that may be clinically important for joint arthrodesis.