Tibial Bone Transport Over an Intramedullary Nail Using Cable and Pulleys
Authors: Bernstein Mitchell , Fragomen Austin , Rozbruch S. Robert 
Published: March 2018

Background:
Massive bone defects (>8 cm) will not unite without an additional intervention. They require a predictable, durable, and efficient method to regrow bone. The Ilizarov method of tension stress, or distraction osteogenesis, first involves a low-energy osteotomy
1–5
. The bone segments are then pulled apart, most often using an external device at a specific rate and rhythm (distraction phase), after which the newly formed bone (the regenerate) requires time for consolidation. The consolidation phase is variable and usually requires a substantially greater amount of time before the external device can be removed. Our technique of tibial bone transport over an intramedullary nail using cable and pulleys combines internal and external fixation, allowing the external fixator to be removed at the end of the distraction phase. This increases the efficiency of limb reconstruction and decreases the external-fixator-associated complications.

Description:
The procedure begins with thorough debridement, orthogonal tibial cuts, osteotomy, and insertion of a custom intramedullary nail. A 1.8-mm steel cable is wrapped around the anterior cortex of the distal end of the transport segment and exits the skin distal to the docking site. Two standard rings are applied at the proximal and distal aspects of the leg, and 2 pulleys are attached to the ring at the ankle. The steel cable is then attached to slotted threaded rods that connect to the compression distraction rods that will pull the cable up and the bone segment down. Two Ilizarov “clickers” that rotate 0.25 mm with each “click” are the motor of the system. Once the bone transport system is removed, a custom interlocking bolt is placed to capture the transport segment. This prevents recoil of the fragment as there is a substantial amount of tension in the system.

Alternatives:
There are no nonsurgical options for reconstruction of massive bone loss. The several alternatives for surgical reconstruction include the inducible membrane Masquelet technique; circular fixation alone with standard Ilizarov bifocal transport, hexapod bifocal transport, or trifocal transport; bone transport and then insertion of an intramedullary nail (Lengthening and Then Nailing, or LATN); and amputation
2–8
.

Rationale:
The standard Ilizarov method for posttraumatic bone loss with external fixation is a well-established surgical procedure with high union rates. However, an external fixator has a high association with pin site infection, and it is cumbersome for the patient. In addition, scarring associated with the wires and half-pins as they progress down the limb is unsightly and painful. The advantage of the cable-pulley system is that the frame is used only in static mode; the cable that pulls the bone transport segment remains at the same exit point of the skin, thus limiting scarring. In addition, as soon as the distraction phase is completed, the external device can be removed. This substantially decreases the time that the external fixator needs to be in place.