Minicondylar bridge plate fixation

When vertical compression forces, created by axial load, are applied to the finger, comminuted, intraarticular, compression fractures may result. These fractures are very unstable.
Typically, they occur in two configurations:

• as centrally impacted, comminuted fractures, or
• with a T- or Y-type fracture geometry.

It is desirable to obtain stable fixation to allow early motion and to minimize the risk of degenerative joint disease.

For this procedure a dorsal approach to the MCP joint is normally used.

Compression fractures are not reducible by ligamentotaxis, as the centrally impacted fragments are devoid of soft-tissue attachments.
Direct reduction is therefore necessary.
The key to fixing compression fractures is restoring the joint surface to as close as normal as possible, and supporting the reduction with bone graft and internal fixation.

Using a K-wire, or dental pick, the fragments are disimpacted and pushed towards the head of the metacarpal, which is used as a template to ensure congruity of the articular surface of the phalanx.
If a cartilage step-off greater than 1 mm remains, degenerative joint disease may follow.

Since the metaphyseal cancellous bone is impacted, a void may be created by its disimpaction.
This jeopardizes the fracture in two ways:

• this is a very unstable situation in which the fragments may easily redisplace (collapse)
• the healing process is delayed.

Cancellous autograft, or very occasionally bone substitutes (e.g. hydroxyapatite, tricalcium phosphate) will be necessary to support the articular fragments and fill the impaction void. The graft will also enhance the healing process.

Cancellous bone is harvested from the distal radius or the iliac crest. It is then chopped into tiny pieces and filled into a syringe.

Impact the bone graft using a mallet to compress the syringe plunger. This results in a high concentration of bone cells, increasing the potential for bone regeneration and healing.

The bottom of the syringe is cut off using a scalpel.
Insert the compacted bone graft into the cavity by pressure on the plunger.

Using a blunt dissector, impact the bone graft and fill the whole fracture cavity.

Two types of plate are available for treatment of this fracture:

• 1.5 Minicondylar plate
• 1.3 or 1.5 T-plate (adaption plate)

Select a plate according to fragment size, fracture geometry, and surgeon‘s preference.

Measure the length of the drill hole using a measuring device.
Cut the blade to the determined length, so that it just fills the drill hole.

Pitfall
Avoid protrusion from the opposite cortex, as friction during movement and eventual ligament injury may result.

Adapt the plate length to fit the length of the proximal phalanx. Avoid sharp edges which may be injurious to the tendons. There should be at least 3 plate holes distal to the fracture available for fixation in the diaphysis. At least two screws need to be inserted into the diaphysis.

Pearl: Cut the blade transversely
If you cut the blade on the flat, it will compress and widen very slightly as it is cut. This makes its maximal width very slightly larger than 1.5 mm. It may not fit in the 1.5 mm hole that you have drilled.
Therefore, cut the blade on edge (to deform it through its narrower dimension) to the correct length. The resultant tip is somewhat arrow-shaped.

Use pliers to contour the plate so that it fits exactly the anatomy of the base of the proximal phalanx.
The plate was designed for condylar fractures and is precontoured to fit around a condyle. It has to be adapted for the less curved shape of the base of the proximal phalanx.

In order to determine the position of the first drill hole, it can be very helpful to turn the plate over and use it as a template ...

... as shown in this clinical photo.

Drill a 1.5 mm transverse hole through the base of the proximal phalanx adjacent to the joint surface as a track for the blade of the plate.

The drill hole needs to be dorsal enough as to leave enough space for the plate’s most proximal screw hole.

Introduce the blade into the drill hole. Gently push with the thumb until the plate is fully seated.

Before inserting the first (distal) screw, ensure that the plate is in line with the phalangeal diaphysis in the sagittal plane by rotating it around the axis of the blade.

Use a 1.1 mm drill bit to prepare the first neutral screw hole at the distal end of the plate.

Measure for screw length and insert a self-tapping 1.5 mm screw.

The proximal screw is inserted next, in the same fashion.
The screws should just engage the far cortex. This proximal screw functions as a position screw only.
Do not exert compression through this screw, as this may compromise the reduction of the comminuted zone.

Note
Be careful to avoid protrusion of the proximal screw through the far (trans) cortex, as ligament injury may result from friction during movement.

Insert further screws into the diaphyseal holes in a neutral position to finalize fixation.

Immobilize the hand in a safe position for at least 3 weeks. This may not be necessary in the case of large fragments when the lag screw fixation is judged at operation to be absolutely stable. In that case, buddy strapping is applied immediately postoperatively.

See patient 5 days after surgery to check the wound, clean and change the dressing. After 10 days, remove the sutures. Check x-rays.

Remove the splint at 3 weeks, and apply buddy strapping.

Then begin with active motion exercises.