The stability of internal fixation in the proximal phalanx.

A biomechanical study was performed to assess quantitative differences in the stability obtained with five commonly used types of internal fixation used in proximal phalangeal fractures. The techniques included dorsal plating, dorsal plating combined with an interfragmentary lag screw, two interfragmentary lag screws, tension-band technique, and crossed Kirschner wires. Rigidity and strength in apex palmar bending were determined after oblique osteotomy and fixation of the proximal phalanx. The failure modes for each fixation technique were also observed and described. The results showed that both of the techniques that used interfragmentary lag screws across the oblique osteotomies provided significantly more rigidity than did dorsal plating alone or the wired configurations but that measurements of strength were similar between all techniques tested. Dorsal plates were at a mechanical disadvantage on the compression surface in our apex palmar bend test and consequently provided no more rigidity and strength than did the wired techniques. The tension band technique represented a combination of stiff and flexible intraosseous wires without strict application of tension band principles and provided intermediate rigidity and strength. Rigidity and strength in intact proximal phalanges in the controls were significantly greater than in all techniques tested.