1 Principles topenlarge
Comminuted fractures often result from crushing or high-energy injuries and may include several metacarpals. Compartment syndrome may occur with these types of injuries, and fasciotomy may therefore be necessary. These fractures are very unstable.
Bridge plating uses the plate as an extramedullary splint fixed to the two main fragments, while the complex fracture zone is bridged. The dissection required for anatomical reduction of all fragments would risk disturbing their blood supply and is not necessary. If the soft-tissue attachments of these fragments are preserved, and they are relatively well aligned, healing is predictable. Occasionally, a larger wedge fragment can be fixed to one of the main fragments using a lag screw. However, it is important
to restore axial alignment, length and correct rotational alignment of the main shaft fragments.
Relative mechanical stability, provided by the bridging plate, leads to healing by callus formation.
Multiple metacarpal fractures
When multiple metacarpals are injured, restoration of length and rotation is difficult. If one of the finger metacarpals is intact, the fixation is started on the adjacent metacarpal, and then continued sequentially.
If all four metacarpals are fractured, fixation is started with the least comminuted, and then the adjacent metacarpals are fixed. With one incision it is possible to fix two metacarpals.
2 Reduction topenlarge
The fracture is reduced by using longitudinal traction on the finger, manually, using a finger trap, or with pointed reduction forceps. Additional pressure can be exerted on the metacarpal head from the palmar aspect.
Restoration of length
Length should be restored in relation to the neighboring intact metacarpals so that their heads form a gentle arc with its apex over the third metacarpal.
Check for correct rotation
Correct rotation has to be checked with the metacarpophalangeal (MCP) joints flexed to detect any overlapping of the fingers.
Flexing the MCP joints whilst preventing overlap of the fingers will reduce a rotational displacement.
Under general anesthesia, the tenodesis effect can be used, the surgeon fully flexing the wrist to produce extension of the fingers, and fully extending the wrist to cause flexion of the fingers.
Alternatively, the surgeon can exert pressure against the muscle bellies of the proximal forearm to cause passive flexion of the fingers.
3 Plate selection & preparation topenlarge
The plate should be long enough to allow for 2 screws in each main fragment.
Usually, 2 mm plates are used for the fixation of the metacarpals. For comminuted fractures, 2.4 mm plates may be indicated.
As these fractures are very unstable, more stable fixation devices may be preferable, such as the Locking Compression Plate (LCP).
If the fracture zone extends far distally or proximally, a T-plate, or minicondylar plate, may be indicated.
Bending and contouring the plate
The plate is placed dorsally onto the metacarpal.
The plate is contoured to conform with the normal shape of the metacarpal.
As there is to be no axial compression, overbending is not necessary and would result in a flexion deformity.
4 Fixation topenlarge
The plate is applied dorsally onto the metacarpal in its long axis. Correct rotational alignment of the distal main fragment may be difficult to achieve but is essential.
Ensure that at least 2 screw holes come to lie over each of the main fragments.
Using a drill guide, the first hole is drilled in the proximal fragment close to the fracture zone.
Make sure that the screw does not enter the fracture zone.
Option: Using an LCP
If an LCP is used with locking screws, a drill sleeve with centering thread must be used for drilling. The screw direction is strictly perpendicular to the plate.
Use a depth gauge to determine screw length.
Insert the first screw. Ensure that it engages the far cortex. Failure to take accurate measurement of the required screw length risks not engaging the far cortex, thereby weakening the fixation and creating the risk of implant failure.
Insert second screw
Make sure that the plate is correctly aligned in the longitudinal axis of the metacarpal. Insert a second neutral screw into the distal main fragment after the same fashion as above.
Confirm correct axial alignment and length using image intensification. Check correct rotation by flexing all fingers at the MCP joints.
Drill for the third and fourth screws. Measure for screw length, and insert the screws in neutral position.
If an LCP is used with locking head screws, the centering thread drill guide must be used.
Option: Approximate large fragments with a screw
If a large intermediate fragment is present, it can be approximated to the plate with a single screw.