Lag screw fixation

These are rare unicondylar fractures that occur in the coronal plane and are associated with palmar, or dorsal, dislocations.
If the PIP joint is dislocated dorsally, a coronal dorsal fracture is present. If the PIP joint is dislocated palmarly, a coronal palmar fracture is associated.

Typically these fractures are the results of sports injuries, occurring as a result of axial loading associated with hyperflexion or hyperextension.
Condylar fractures tend to be very unstable and should usually be treated operatively. If conservative treatment is attempted, secondary displacement leads to angulation of the finger.

Caveat
These fractures are rare, but difficult to treat. There is an increased risk of joint stiffness resulting from these fractures.
It is wise to use magnifying loupes in these procedures. Gentle and precise handling throughout the procedure is mandatory.

For this procedure a dorsal approach to the IP joint of the thumb is normally used.

Articular fractures must be reduced anatomically, otherwise, the articular cartilage may be damaged, leading to painful degenerative joint disease and digital deformities.
This illustration shows how displacement may lead to abrasion and shearing of the articular cartilage, and also to instability.

Dorsal dislocation
Apply traction to the finger with the PIP joint in partial flexion, and exert dorsal pressure on the displaced condyle in order to reduce the dislocation.

Palmar dislocation
Apply traction to the finger with the PIP joint in extension and exert palmar pressure on the displaced condyle in order to reduce the dislocation.

In dorsal fragments, part of the fracture line on the lateral aspect of the head is covered by the collateral ligament.
Flexing the PIP joint will draw back the collateral ligament, which can be further retracted with a hook to expose the dorsal fragment.

In palmar dislocations, the collateral ligament complex is torn or partially torn. In most cases, the remnant of the collateral ligament can be retracted gently to reveal the palmar condylar fracture line.

In order to gain better visualization of the fracture, use a syringe to clear out blood clot with a jet of Ringer lactate.
Gently reduce the fragment with a dental pick. Be careful to avoid fragmentation.

The opposite joint surface of the middle phalanx can be used as a template for reduction.

Small dorsal articular defect
If a small articular fragment is present, it can be excised. This will not compromise stability or flexion of the PIP joint.

Small palmar articular incongruency
Any incongruency on the palmar side is critical and can impede movement. It must be anatomically reduced and fixed.

On the lateral intraarticular aspects of the condyles, there is a small ridge on each side. These are uniquely suited for screw placement, as the screws can be buried deep to the edge of the cartilage without violating the joint surface and avoiding causing irritation.

Drill a gliding hole as perpendicularly to the fracture plane as possible, using a 1.0 mm drill bit for a 1.0 mm screw.
Use a 0.8 mm drill bit to drill a thread hole in the opposite fragment, just through the far (trans) cortex.

Dorsal fragment
In a dorsal fragment, fixation is from dorsal to palmar.

Palmar fragment
In a palmar fragment, fixation is from palmar to dorsal.

Insert the lag screw. Carefully tighten the screw to achieve interfragmentary compression.

While the patient is in bed, use pillows to keep the hand elevated above the level of the heart to reduce swelling.

In cases of dorsal fracture dislocation with intact collateral ligaments, an Edinburgh splint is not necessary, and buddy strapping is applied postoperatively.

In cases of palmar fracture dislocation associated with collateral ligament tearing, a removable splint is applied at the end of the operation, with the hand in an intrinsic plus position (“safe” or “Edinburgh” position).

Immobilize the hand in a safe position for 3 weeks.

The reason of immobilization of the MP joint in flexion is to maintain its collateral ligament at maximal length, avoiding scar contraction.

PIP joint extension in this position also maintains length of the volar plate.

Begin with active motion exercises as soon as patient comfort permits.

Instruct the patient to lift the hand regularly overhead, in order to mobilize the shoulder and elbow joints.

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

The implants may need to be removed in cases of soft-tissue irritation.

In case of joint stiffness, or tendon adhesion’s restricting finger movement, tenolysis, or arthrolysis become necessary. In these circumstances, take the opportunity to remove the implants.