Lag-screw fixation with a neutralization plate for Simple oblique fracture of the diaphysis

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Principles

In short oblique fractures, only one lag screw can be inserted. This is insufficient to produce enough stability, and the lag screw must be protected by a plate. A neutralization plate may also be indicated if screw fixation alone is not providing sufficient stability, eg, in poor quality bone.

As the screw should be inserted perpendicularly to the fracture plane, in most cases, it has to be inserted independently of the plate.

$Lag screw fixation with neutralization plate of an oblique metacarpal fracture$

Plate selection

Select a plate (1.5–2.0 mm) according to the size of the bone, fracture geometry, and surgeon’s preference.

The plate length should allow for at least two screws in each main fragment.

The plate is available as a conventional compression plate or with variable-angle (VA) locking-head screws.

$Plate options for plating metacarpal shaft fractures$

AO teaching video

Metacarpal III–Short oblique fracture–Fixation with a 2.0 mm lag screw and 2.0 mm Variable Angle Adaption plate

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

Patient positioned supine with the arm on a radiolucent hand table

For this procedure, the following approaches may be used:

Dorsal approach to the metacarpals

In the 2nd metacarpal, a radial approach may be used. In the 5th metacarpal, an ulnar approach may be used.

Indirect reduction by traction

Reduce the fracture with longitudinal traction on the finger and pressure from a periosteal elevator or a dental pick.

$Reduction of an oblique metacarpal fracture$

Direct reduction

Secure the reduction with pointed reduction forceps and confirm reduction with an image intensifier. Ensure the reduction forceps do not conflict with the planned screw position.

It is essential to confirm that the apex of each fracture fragment has been properly reduced.

$Reduction of an oblique metacarpal fracture with reduction$

Alternatively, special reduction forceps designed for percutaneous fixation may be used.

$Reduction of an oblique metacarpal fracture with reduction forceps designed for percutaneous screw insertion$

Identifying malrotation

At this stage, it is advisable to check the alignment and rotational correction by moving the finger through a range of motion.

Rotational alignment can only be judged with flexed metacarpophalangeal (MCP) joints. The fingertips should all point to the scaphoid.

Malrotation may manifest by an overlap of the flexed finger over its neighbor. Subtle rotational malalignments can often be judged by a tilt of the leading edge of the fingernail when the fingers are viewed end-on.

If the patient is conscious and the regional anesthesia still allows active movement, the patient can be asked to extend and flex the finger.

Any malrotation is corrected by direct manipulation and later fixed. Flexing the MCP joints while preventing overlap of the fingers will reduce rotational displacement.

Fingertips of flexed fingers should point to the scaphoid. Malrotation manifests by overlap of a flexed finger over its neighbors.

Using the tenodesis effect when under anesthesia

Under general anesthesia, the tenodesis effect is used, with the surgeon fully flexing the wrist to produce extension of the fingers and fully extending the wrist to cause flexion of the fingers.

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.

Surgeon exerting pressure against the muscle bellies of the proximal forearm to cause passive flexion of the fingers

Insertion of the lag screw

Insert the lag screw in the center of the fracture and perpendicular to the fracture plane. Carefully tighten the screw.

Cortical lag-screw insertion

The fracture is now compressed. The reduction forceps may now be removed.

Confirm reduction and correct screw position with an image intensifier.

Note: Countersinking in the diaphysis should be performed with care as it risks iatrogenic fractures.

$Lag screw fixation with neutralization plate of an oblique metacarpal fracture – lag screw insertion$

Screw size selection

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.

Screw sizes of the diameters and thread hole drill sizes

Screw length pitfalls

Ensure that a screw of the correct length is used.

Too short screws do not have enough threads to engage the far cortex properly. This problem increases when self-tapping screws are used due to the geometry of their tips.
Too long screws endanger the soft tissues, especially tendons and neurovascular structures. With self-tapping screws, the sharp cutting flutes are especially dangerous, and great care has to be taken that the flutes do not protrude beyond the cortical surface.

$Correct screw length for fracture fixation means screws should not be too long or too short.$

Pitfall: screw too close to the fracture

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

$Lag screw fixation with neutralization plate of an oblique metacarpal fracture – screw distance to the fracture line$

Pitfall: beware of fissure lines

Often there are short fissure lines that are not apparent on the x-rays. Check for these under direct vision and ensure the screw is not inserted through these fissure lines.

$Lag screw fixation with neutralization plate of an oblique metacarpal fracture – fissure lines$

Apply the neutralization plate dorsally.

Insert at least two screws proximally and distally to the fracture in neutral mode.

Cover the plate with periosteum to avoid adhesion between the tendon and the implant leading to limited finger movement.

$Lag screw fixation with neutralization plate of an oblique metacarpal fracture – order of screw placement$

Confirm correct rotational alignment by clinical examination.

Confirm anatomical reduction and correct placement of implants in AP, lateral, and oblique views.

$Lag screw fixation with neutralization plate of an oblique metacarpal fracture – case$

Postoperative phases

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.

Postoperative treatment

If there is swelling, the hand is supported with a dorsal splint for a week. This would allow for finger movement and help with pain and edema control. The arm should be actively elevated to help reduce the swelling.

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

Neutral wrist position or up to 15° extension
Metacarpophalangeal (MCP) joint in 90° flexion
Proximal interphalangeal (PIP) joint in extension

Dorsal splint to treat a dislocation of the proximal interphalangeal joint

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.

The metacarpophalangeal joint in flexion maintains the collateral ligament at maximal length and the proximal interphalangeal in extension 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.

Buddy strapping avoiding direct skin contact with adjacent fingers as conservative treatment

Functional exercises

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

Follow-up

See the patient after 5 and 10 days of surgery.

Implant removal

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.