|Microsurgery: Transplantation and Replantation by Harry J. Buncke, MD, et al.|
| In the small fragment set, screws are available in three sizes, 1.3, 2.0, and 2.7 mm in diameter. Screw length selection is done by matching a depth-gauge measurement of the fracture and cortical thickness, allowing for adequate bony contact without impinging on surrounding soft tissue. Using the lag principle, the screw alone can be used to provide excellent fixation, but it has limited ability to control rotatory or bending forces. Screws should be either placed at an oblique angle to the fracture axis or used in combination with other screws or fixation methods. Although the method is often not applicable to the digit replant, associated injuries metacarpal fractures, small avulsive fractures) can be managed well in this manner.
We have also used a single screw for fixation in elective toe-to-hand transplantation, particularly for the great toe. The recipient first metacarpal shaft is trimmed to create a bone peg, over which the drilled-out medulla cavity of the transferred toe metatarsal is fitted. A single large, lagged screw is placed perpendicular to the bony shafts, contacting all four shaft cortices. This method has been excellent in reducing rotational deformities and has allowed early motion.
Plate fixation can satisfy a variety of splinting functions that apply to other sites as well as the hand: 1. Neutralization - correction of axial forces without using compression
| 2. Buttressing - supporting multiple fragments or metaphyseal fractures
3. Bridging - stabilizing in areas of cortical loss
4. Compression - directly impacting fracture fragments by plate contouring, screw offset or compression plating.
Familiarity with the equipment is essential to correct choice and application of the plates; of particular importance are screw selection, drilling, and tapping. Plates come in a variety of shapes and sizes and are matched to the appropriate screw size. Placement is with at least two holes with three or more cortices of screw contact on each side of the fracture. If the bony edges can be contoured for good contact, compression plating may be an added feature. Furthermore, if the plate can be positioned along the tension cortex, dynamic compression of the opposing cortex will occur with mobilization. Soft tissue dissection and plate fixation are usually prolonged compared with other methods; moreover, the hazards of a retained foreign body remain. Reoperation may be necessary to remove the implant because of bulk, osteopenia or pain. This may be done concurrently with secondary soft tissue reconstruction. These may be acceptable tradeoffs for the benefits of rigid fixation and available compression.
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