Techniques and fixation of metacarpal fractures

Rotational deformity

Even small amounts of rotational deformity (10 degrees; Fig. 14.1 ) can cause overlap (“scissoring”) of the digits; therefore this deformity must be corrected to preserve proper hand function.

Angular deformity

Angular deformity is typically apex-dorsal ( Fig. 14.2 ). Because of compensatory motion at the carpometacarpal (CMC) joints, residual angulation of metacarpal fractures is tolerated better in the thumb, ring, and small fingers than in the index and middle fingers.

In particular, the small finger metacarpal neck fracture (often called a “boxer’s fracture”) is a common fracture that typically heals with negligible morbidity, despite significant residual angulation, as long as there is no rotational deformity.

Surgical correction should be considered for shaft angulation of:

• Index and middle: More than 5 to 10 degrees

• Ring: More than 20 degrees

• Small: More than 30 degrees

• Thumb: More than 30 degrees

Surgical correction should be considered for neck angulation of:

• Index and middle: More than 10 to 15 degrees

• Ring: More than 20 to 30 degrees

• Small: More than 40 to 70 degrees (wide variation in recommendations)

Shortening

Shortening is better tolerated than angular and rotational deformity, but loss of more than 5 mm of length may cause symptoms of pain, weakness, and a noticeable extension lag.

Multiple fractures

If adjacent metacarpals are injured, fracture instability is dramatically increased beyond what is seen for a single fracture, owing to loss of additional supporting structures.

Open fractures

Percutaneous Kirschner wire (K-wire) fixation may be preferable for open fractures with contamination or soft tissue defects requiring supplementary coverage to avoid exposure of hardware in an open wound.

• Metacarpal neck fractures can also be treated with intramedullary fixation (see “Percutaneous Intramedullary Fixation of Metacarpal Head and Neck Fractures”).

• Long oblique or spiral metacarpal shaft fractures may be more easily treated with lag screws (see “Open Reduction and Internal Fixation of Metacarpal Shaft Fractures”).

Contraindications

• Note that most metacarpal fractures do not require operative treatment. Nondisplaced fractures or minimally displaced fractures without clinical deformity that meet acceptable radiographic parameters can be treated with a brief period of immobilization and early motion. Stable displaced fractures with satisfactory alignment after closed reduction can also be treated nonoperatively.

• General contraindications for surgery:

  • Medically unfit: Highly comorbid patients or patients with active hemodynamic compromise or systemic infections should have medical issues addressed before considering operative treatment.

  • Patient preference: Low-demand patients can have satisfactory functional results even with substantial deformity and may prefer to be treated nonoperatively.

• Specific contraindications for closed reduction and K-wire fixation include:

  • Comminution: K-wire fixation may not adequately maintain length and rotational stability in fractures with long comminuted segments, which can be better treated with bridge plating constructs (see Open Reduction and Internal Fixation of Metacarpal Shaft Fractures).

  • Bone loss: Fractures with segmental bone loss also require a lengthy and rotationally stable construct and can be better treated with bridge plating.

  • Early return to athletic activity: Exposed pins can migrate or cause infection and are not ideal for athletes seeking to return to early vigorous activity.

  • Noncompliance: Because of concerns for pin site infection, patients who will not reliably return for follow-up should be treated with other means.

Step 1

• Longitudinal traction, plus external pressure at the fracture site, can reduce most metacarpal shaft fractures, which typically have an apex-dorsal configuration.

• The Jahss maneuver ( Fig. 14.7 ) can help with reduction of metacarpal neck fractures intraoperatively. This maneuver uses dorsally-directed force applied to the flexed proximal interphalangeal (PIP) joint to reduce an apex-dorsal metacarpal neck fracture. Alternatively, this maneuver can be performed with the PIP joint extended to relax the intrinsic muscles and further facilitate reduction.

  

Step 2

• Fixation is usually performed with 0.045-inch (1.1-mm) K-wires. Two configurations of wires can be used: longitudinal or transverse.

• Longitudinal K-wires:

  • They are typically placed from distal to proximal ( Fig. 14.8A–D ).

    

  • Wires may be left exposed distally or advanced to exit the skin proximally.

  • At least two wires are required for rotational stability.

  • Alternatively, a single longitudinal wire can be used to prevent angular displacement, and postoperative buddy-straps can be used to control rotational displacement in stable fracture patterns.

• Transverse K-wires:

  • They are typically placed from index-to-middle or small-to-ring metacarpals ( Fig. 14.9 ).

    

  • Uses a healthy neighboring metacarpal as a stable foundation to immobilize the adjacent fracture indirectly.

Step 3

• K-wires are cut to an appropriate length to accommodate a pin cap (a protective covering for the end of the wire).

• Alternatively, K-wires can be cut beneath the surface of the skin and removed with a minor procedure at a later date (not common).

• A protective splint is applied, with ample padding around the K-wire exit sites. This initial splint is typically a forearm-based intrinsic-plus splint for the operative digit and at least one neighboring digit.