As previously stated, dynamic forces result in distraction or tension across the fracture site. Wire loops can be placed to reduce these distraction forces and encourage bony union.3 For metacarpal fractures, placing perpendicular interosseous wires with the transverse wire dorsal to the midaxis of the fracture may provide a tension band to limit dorsal cortical distraction. We have also used this perpendicular technique in more distal replants with good results, even though creating an adequate tension band wire may be controversial. Combining wire loops, both intra- and extra-osseous, with K-wires may also help to reduce distraction forces.

A modification of the intraosseous technique by John Cassel uses a tetrahedral wire to provide compression and reduce rotation. Although our early experience with this method has been limited, when it is applied to transverse shaft fractures, frequent bony shifts have occurred. This method, however, may be useful in intra- or periarticular fractures because it allows the inclusion of ligament insertions in the transverse component (Fig. 32-2). Because wire tension depends on wire length and the angles transversed, we are investigating a modification of the tetrahedral wire using two shorter wires tightened independently (Fig. 32-3).

SCREW AND PLATE FIXATION

The principles of the Argeitsgemeinschauft fur Osteosynthesefragen/Association for the Study of Internal Fixation (ASO/ASIF) are applied to the hand through the use of the plate and screw implants of the small fragment set. These achieve rigid bony fixation that can be combined with compression of either static or dynamic nature. Rules and techniques for application are well outlined in many texts,2,17 articles, 15,16,21 and instructional courses, and only general principles are discussed here.

The basic implant of the rigid fixation technique is the screw itself. To use the screw effectively alone, the threaded portion of the screw must be separated from the head by a zone with no matrix contact. This allows the force created on the distant bone by the threads to be transferred to the plane of the head by the "lag screw" principle. This gliding zone can be created by overdrilling of the first cortex. Its value can be heightened by the use of compression plates with the screw, causing the force created by the distal threads to extend along the plate and into the opposite fracture fragment.

FIG. 32-02. The Cassel technique.

FIG. 32-03. Double-wire pyramidal technique.

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