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Pancarpal arthrodesis with a circular or hybrid external skeletal fixator

Use of a circular or hybrid external skeletal fixator (ESF) for arthrodesis of a nonreconstructable joint fracture. A hybrid ESF combines fixation half- (and occasionally full-) pins coupled to connector rods proximally and diverging K-wires coupled to full or partial rings distally.

The placement of hybrid ESF is facilitated by fluoroscopy, allowing a minimally invasive approach to fracture fixation.

$Pancarpal arthrodesis with a circular or hybrid external skeletal fixator for arthrodesis of a nonreconstructable joint fracture$

The patient is placed in dorsal recumbency at the end of the operating table. The affected limb is aseptically prepared using a hanging-limb technique.

A minimally invasive approach is used when closed reduction can be achieved. Alternatively, a mini-open craniomedial approach to the radius and carpal joint can be used to reduce the fracture and prepare the joint surfaces before applying the hybrid ESF.

Patient in dorsal recumbency for a minimally invasive approach when closed reduction can be achieved

Arthrodesis principles

The joint levels spanned by the implants are prepared by removal of the cartilage with a high-speed burr.

Preparation of the joint levels by removing the cartilage with a high-speed burr

To promote bone fusion, autogenous or synthetic bone graft should be applied. Bone graft needs to be well distributed in each aspect of the antebrachiocarpal joint; this may require placement of bone graft after the radiocarpal screw is inserted.

Note: Once collected, autogenous bone graft should be stored carefully and kept moist.

Distributing bone graft well in each aspect of the antebrachiocarpal joint

The fracture fragments cannot be anatomically reconstructed to add to construct stability. Therefore, functional alignment of the limb (ie, antebrachium and foot) should be maintained during stabilization.

Maintaining functional alignment of the limb during stabilization

Ring fixator application

One or two appropriately sized rings are placed on the limb proximal to the carpal joint.

Using a surgical drill, a K-wire is driven parallel and immediately proximal to the joint in the distal segment. This K-wire should be placed in a craniolateral to caudomedial direction. The exact direction of the K-wires is dictated by avoiding fracture fragments.

The K-wire is secured to the distal side of the ring with the limb centered in the ring. The ring axis is positioned perpendicular to the long axis of the bone.

Read more about general principles for ESF.

Ring fixator with an appropriately sized ring placed on the limb and a K-wire placed in a craniolateral to caudomedial direction

A second K-wire is placed on the proximal side of the ring, driven with a surgical drill in a craniomedial to caudolateral direction with the surgical drill, and secured to the ring. When placing the second wire, caution should be exercised to maintain the ring's plane perpendicular to the tibia's long axis.

Ring fixator with second K-wire placed on the proximal side of the ring in a craniomedial to caudolateral direction

Additional ring(s) are added distally below the carpus.

Ring fixator with additional ring(s) distally below the carpus

Assembly of the hybrid external skeletal fixator

A hybrid connector rod is coupled to the ring on the medial side, and three to four clamps are placed on the connector rod.

The rod is aligned with the long axis of the radius, and an appropriately sized threaded half-pin is used to secure the connector rod to the bone, starting proximally. The half-pin should be placed through an appropriately sized pilot hole.

Ring fixator with a hybrid connector rod coupled to the ring on the medial side and three to four clamps placed on the connector rod

A second threaded half-pin is placed through the clamp closest to the fracture line, approximately one bone diameter proximal to the fracture line.

$A second threaded half-pin placed through the clamp closest to the fracture line$

The remaining one to two half-pins are equally distributed between the first two pins. Any skin tension against a fixation pin is released with a scalpel.

Equal distribution of the remaining one to two half-pins between the first two pins

The K-wires are cut and bent over the ring.

Cutting of the K-wires and bending of the ends over the ring

Note: For these highly unstable comminuted fractures, adding a craniocaudal connector bar with two to three threaded half-pins in the proximal segment to create a IB frame design may be required for additional stability.

Adding a craniocaudal connector bar with two to three threaded half-pins in the proximal segment may be required for additional stability

Pitfall: Threaded full pins often cause significant soft-tissue morbidity and should therefore only be used when the need for mechanical stability outweighs the anticipated soft-tissue morbidity.

Threaded full pins should only be used when the need for mechanical stability outweighs the anticipated soft-tissue morbidity

Phase 1: 1–2 days after surgery

An Elizabethan collar (E-collar) must be worn until all bandages have been removed and the skin incision completely healed (approximately 10–14 days). Crate confinement and leash walking are critical.

Dry surgical scrub brush sponges should be placed between the skin and the bars to create gentle skin compression. A Robert Jones bandage can be used to help prevent postoperative swelling for the first 3–5 days after surgery. The aim is to reduce edema, inflammation, and pain. Following removal of the Robert Jones, bandaging can be limited to covering the frame with loose-weaved gauze and self-adhesive wrap.

Analgesics, including nonsteroidal anti-inflammatory medications and opioids, are recommended.

The pin-skin interface should be cleaned and adequately protected with a nonadherent bandage and triple antibiotic ointment.

Phase 2: Day 3–fracture healing

The aim is to resolve hematoma and edema and control pain. Nonsteroid anti-inflammatory medications may still be needed for the first 7–10 days.

The progress of incision healing can be assessed 10–14 days after surgery, and the sutures, if present, are removed.

The use of an E-collar can be discontinued once the incision has healed.

On day 3, the bandage and sponges are removed, and the pin-skin interface is inspected for drainage and cleaned with an antiseptic solution.

If edema still exists, the pin-skin interface is covered with a nonadherent bandage, surgical scrub brush sponges are placed between the skin and the bar, and the frame is wrapped with a compression bandage. In addition, a triple antibiotic ointment is applied on the edges of the skin. This process is repeated every 2–3 days (depending on the degree of drainage) until the edema has resolved. Once the edema has resolved and the pin-skin interface incisions have begun to granulate, the frame can simply be covered by compression bandage.

Clamp tightness should be checked weekly.

The skin-pin tract interface should be cleaned regularly until no discharge is noted.

Crate confinement and leash walking with sling support should continue. However, walks can slowly be increased to 5–10 minutes per week.

No high-impact activities, including running, jumping, or playing, should occur until the fracture is healed.

A radiographic assessment is performed every 4–8 weeks until confirmed bone healing.

Note: If the patient becomes lame, the frame should be carefully inspected for loose or broken components. If no external cause can be identified, x-rays should be made to identify broken pins or wires and pin-bone interface loosening.