Lag-screw fixation

Partial articular (shearing) fractures require anatomical reduction. Noncomminuted fractures may be fixed with lag screws.

The reduction can be assisted with arthroscopy if skill and equipment are available.

The joint may collapse if there is impaction or comminution while the lag screw is tightened. In this case, plate fixation should be considered for chondral support.

This fracture type may be associated with metacarpophalangeal (MCP) joint dislocation. In this case, the dislocation must be manipulated, and any interposed soft-tissue structures removed.

Percutaneous reduction and fixation may be performed.

The advantages are:

• Shorter operation time
• Less soft-tissue damage
• Faster mobilization

This treatment option needs some skills and experience and special reduction forceps to avoid impingement of swollen soft tissue (atraumatic technique).

These reduction forceps allow to hold the reduction at the planned screw placement, and drilling and screw insertion. There is no need for additional K-wire fixation or reduction forceps placement.

If a percutaneous reduction is not achievable, the treatment can be changed to an open surgery.

Place the patient supine with the arm on a radiolucent hand table.

For this procedure, a dorsal approach to the metacarpophalangeal joint is typically used.

Dislocation usually occurs as an extension deformity.

This can be reduced by increasing the deformity with some dorsally applied pressure on the proximal phalanges to reduce the joint. This keeps the volar structures in tension and reduced the risk of soft-tissue interposition.

Often, the fracture can be reduced by applying traction via finger traps.

For more accurate reduction, use small pointed reduction forceps gently to manipulate the fracture. Application of excessive force can result in fragmentation.

Confirm reduction with an image intensifier.

Preliminarily fix the fragments by inserting a K-wire. Be careful to place it so it will not conflict with later screw placement.

Confirm reduction with an image intensifier and check the joint stability by flexion and extension. This should show congruent movement compared with the adjacent joints.

Each lag screw must be inserted perpendicularly to the fracture plane.

Do not insert screws too close to the fracture apex or the subchondral bone. A minimal distance from the fracture line, equal to the screw head diameter, must be observed.

The screw length needs to be adequate for the screw to penetrate and purchase in the opposite (trans) cortex.

Alternatively, two smaller screws may be used proximally.

The exact size of the diameter of the screws used will be determined by the fragment size and the fracture configuration.

The various gliding and thread hole drill sizes for different screws are illustrated here.

Insert the proximal screw first.

• Cortical lag-screw insertion

Alternate tightening of the two lag screws helps avoid tilting the fragment and applies even compression forces across the fracture surface.

Confirm anatomical reduction and fixation with an image intensifier. Check alignment of the finger by flexing the metacarpophalangeal joint and comparing the orientation of the nail with the contralateral side and the neighbouring fingers.

This case shows the final lag screw fixation and healing in progress of partial articular fractures of the 2nd proximal phalangeal proximal end segment (base) and the distal end segment (the head) of the metacarpal.

The aftercare can be divided into four phases of healing:

• Inflammatory phase (week 1–3)
• Early repair phase (week 4–6)
• Late repair and early tissue remodeling phase (week 7–12)
• Remodeling and reintegration phase (week 13 onwards)

Full details on each phase can be found here.

If there is swelling or joint instability, the hand is immobilized with a dorsal splint for a week. This would allow for finger movement. The arm should be actively elevated to help reduce the swelling.

The hand should be immobilized in an intrinsic plus (Edinburgh) position:

• Neutral wrist position or up to 15° extension
• MCP joint in 90° flexion
• PIP joint in extension

The reason for splinting the MCP joint in flexion is to maintain its collateral ligament at maximal length, avoiding scar contraction.

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

After subsided swelling, protect the digit with buddy strapping to a neighboring finger to neutralize lateral forces on the finger.

To prevent joint stiffness, the patient should be instructed to begin active motion (flexion and extension) immediately after surgery.

See the patient after 5 and 10 days of surgery.

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

In case of joint stiffness or tendon adhesion restricting finger movement, arthrolysis or tenolysis may become necessary. In these circumstances, the implants can be removed at the same time.