These fractures tend to be unstable, and bone healing is often prolonged. Internal fixation allows for anatomical reduction, early active motion and shorter rehabilitation. In transverse fractures, an interfragmentary lag screw can not be used. Absolute stability is achieved using compression plate principles.
AO teaching video: Transverse Fracture of metacarpal II - fixation with 2.0/5-hole LC-DCP
For this procedure the following approaches may be used:
Two pointed reduction forceps can be used for direct reduction. As most of these fractures have a flexion deformity, indirect reduction can be performed by pressure on the metacarpal head from the palmar aspect.
Pearl: flex finger
Alternatively, maximally flex the finger at the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints and use the proximal phalanx to push up the metacarpal head. If all the fingers are flexed at the MCP joints, this automatically ensures correct rotational alignment.
Preliminary fixation in unstable situations
In very unstable situations, insert a K-wire across the fracture plane for provisional stabilization. Be aware that the cortical bone in the metacarpals is dense and thick, so the tip of the K-wire gets very hot. Irrigation during insertion of the K-wire is essential to avoid thermal necrosis of the bone around the wire track.
4. Fixation: Compression plate
Bending and contouring the plate
The plate is placed dorsally onto the metacarpal; usually 2 mm plates are used. The plate has to be slightly overbent in order to compress the far cortex when axial compression is produced by tightening the screws. If the plate is not overbent, tightening the screws will result in a gap in the opposite cortex.
Depending on the fracture configuration, a 4- or 5-hole plate is used. When using a 5-hole plate, the middle hole is centered over the fracture. When a 4-hole plate is used, ensure that the screw position will not interfere with the fracture line.
If the plate is not properly centered on the dorsal surface of the metacarpal, the screws may not penetrate the medullary canal and may not have sufficient purchase. Secondary fractures may result.
Using a drill guide, the first hole is drilled with a 1.5 mm drill bit close to the fracture line. Make sure that the screw does not enter the fracture plane. When a 4-hole plate is positioned, take care that the corresponding plate hole on the other fragment is not too close to the fracture.
Use a depth gauge to determine screw length.
Insert the first screw but do not fully tighten. 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
Pull the plate towards the second fragment so that the first screw comes to occupy an eccentric load position. Ensure that the plate is lying in the long axis of the metacarpal shaft. Insert the second screw as a load screw. Tighten the screws alternately to produce interfragmentary axial compression. Before final tightening, any provisional K-wire should be extracted.
Check rotational alignment
Before inserting the remaining screws, check rotational alignment.
The remaining screws are inserted in neutral positions.
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.
6. Postoperative splint
A removable splint may be applied at the end of the operation, with the hand in an intrinsic plus (Edinburgh) position. In compliant patients with stable internal fixation the splint can be removed after any swelling has receded. It may be worn at night for a longer period as this may increase patient comfort.
While the patient is in bed, use pillows to keep the hand elevated above the level of the heart, in order to reduce swelling.
For ambulant patients, put the arm in a sling and elevate to heart level.
Instruct the patient to lift his hand regularly above the head, in order to mobilize the shoulder and elbow joints.
See the patient after 2 days for a dressing change. After 10-12 days, remove the sutures and confirm radiologically that no secondary displacement has occurred. Additional x-rays are taken 4 weeks after internal fixation. Usually, the fracture line will still be visible. X-rays are repeated after 8 weeks to assess union. Strengthening exercises and manual work are allowed according to clinical and radiological evidence of bone healing.
As pain and swelling recede, early, active, controlled digital range of motion exercises gently progress. The importance of mobilization must be emphasized to the patient and rehabilitation should be supervised by a physical therapist.