Tibial Bone Transport Over an Intramedullary Nail Using Cable and Pulleys

Overview

Introduction

Use of a cable-pulley system over an intramedullary nail for posttraumatic bone loss mitigates many of the disadvantages of classic Ilizarov bone transpot with external fixation alone; the following description of the procedure is for a distal tibial diaphyseal defect with the transport from proximal to distal (anterograde).

Indications & Contraindications

Step 1: Debridement

The local environment requires thorough debridement.

Step 2: Proximal Tibial Osteotomy for Lengthening

In the planned location, perform the tibial osteotomy prior to insertion of the intramedullary nail ( Fig. 4 ) .

Step 3: Insertion of the Intramedullary Nail

Prepare the nail path by reaming the medullary canal of the tibia.

Step 4: Wrapping the Steel Cable Around the End of the Tibia ( Fig. 6)

Wrap a 1.8-mm Ilizarov threaded cable around the end of the anterior aspect of the tibia.

Step 5: Passing the Cable from the Tibia to the Pulley ( Fig. 7)

Bring the threaded cable out of the leg at the planned level of the pulleys.

Step 6: Wound Closure

Close the surgical wounds prior to mounting the circular frame.

Step 7: Mounting a 2-Ring Circular Frame

Mount a 2-ring circular fixator to the top and bottom parts of the tibia.

Step 8: Mounting the Pulleys

Mount pulleys to the distal ring (in cases in which the transporting bone segment is moving from the top of the leg down to the ankle).

Step 9: Connecting the Steel Cable to the Frame

Wrap the steel cable around the pulley and connect it to a slotted threaded rod.

Step 10: Bone Transport ( Fig. 8)

Initiate the Ilizarov method of distraction osteogenesis.

Step 11: Fixation of the Transported Segment with an Interlocking Bolt in the Custom Hole ( Fig. 10)

Place an interlocking bolt into the bone transport segment.

Step 12: Postoperative Management

Postoperative management consists of range-of-motion and strengthening exercises with limited weight-bearing initially.

Results

In comparison with classic bone transport (using external fixation alone), our technique involves a similar number of surgical procedures to complete the tibial reconstruction as well as a similar prevalence of unplanned surgical procedures.

Pitfalls & Challenges

Abstract

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.