Specific considerations for the wrist are given below.
In joint-spanning external fixation of the wrist, the 4 mm (small) external fixator system is commonly used and may be combined with the 8 mm (medium) system. They are applied as described in the basic technique for the 11 mm (large) system.
There are several other external fixation systems available.
AO teaching video: Distal Radius - Small External Fixator: Wrist-spanning Frame
Larger surgical incisions (1 cm over the second metacarpal, longer incision over the radius), instead of stab incisions
Blunt dissection to the bone
Predrilling prior to insertion of the pins
Landmarks for pin insertion into the second metacarpal
The distal pin should be inserted proximal to the transition of the metacarpal head into the shaft.
The more proximal pin is inserted distal to transition of the shaft into the metacarpal base.
The pins should obtain a good hold in both cortices.
Pitfall: Eccentric pin positioning An eccentric position of a pin may weaken the metacarpal, leading to fracture.
The extensor tendon hood must not be transfixed with the distal metacarpal screw.
To avoid this complication, the index metacarpophalangeal (MCP) joint should be passively flexed 90° so that the extensor hood moves slightly distally, and the tendons are pulled in an ulnar direction.
In the frontal plane, the pins should be inserted at an angle of 30°-40° in relation to the sagittal plane to avoid transfixing the extensor tendon/hood.
Landmarks for pin insertion in the radial shaft
The proximal two pins should be inserted proximal to the muscle bellies of abductor pollicis longus (APL) and extensor pollicis brevis (EPB), and should not penetrate them.
These muscles are usually easy to identify. Proximal to these muscles, the radial shaft can be palpated through the skin between the bellies of the extensor digitorum communis (EDC) and extensor carpi radialis longus/brevis (ECRL/ ECRB) over 3-4 cm. This is the preferred area for proximal pin insertion in the radial shaft.
The pins are inserted perpendicular to the transverse section of the radius.
5. Frame construction / reduction and fixation (wrist)
Reduction and fixation
Longitudinal traction is applied on the thumb and index finger or the distal partial frame to reduce the fracture. Additional maneuvers may be necessary depending on the specific fracture pattern. Pressure from the dorsal side of the carpus may be helpful to restore volar tilt of the distal radius joint surface.
In multifragmentary fractures, additional K-wires may be inserted percutaneously, if the external fixator is used as a definitive treatment.
For details of K-wire insertion see the corresponding treatment option for the specific fracture type.
6. Aftercare following external fixation
Immediately postoperatively, the patient should be encouraged to elevate the limb and mobilize the digits, elbow and shoulder.
If necessary, functional exercises can be under the supervision of a hand therapist.
If external fixation is used for definitive treatment, the fixator (and K-wires if used) is usually left in place for six weeks.
The timing of removal may be influenced by various factors. These include the specific details of the fracture and patient, and the radiological appearance of the healing fracture.