CE: When Should You Perform Callus Distraction?

Author(s): 
By Michael S. Downey, DPM

The current use of callus distraction techniques in foot, ankle and lower leg surgery is constantly growing. The limits of callus distraction techniques appear to be those imposed by surgical access and fixation. As techniques and technology continue to improve, even more indications for callus distraction will evolve.
Callus distraction, also commonly referred to as distraction osteogenesis or callostasis, is the lengthening of a bone by manipulation of the bone callus during the healing process. Gavriel A. Ilizarov, a Russian-born physician, is credited with popularizing limb lengthening using callus distraction and external fixation devices in the ‘50s and early ‘60s. The tension-stress effect, first described by Ilizarov, is the governing principle that permits the gradual distraction of osseous and soft tissues to achieve lengthening of the skeletal system.
The foundation of the tension-stress effect holds that if limb lengthening is done correctly with distraction performed at the proper rate, both osseous and soft tissues will proliferate in the area of distraction. When you perform such distraction at the proper rate and area of the bone, the growth in the tissues at the lengthening site is similar to the hormone-mediated growth found in children at their growth plates.
As Ilizarov stated in 1989, a living tissue when subjected to slow, steady traction becomes metabolically activated by synthetic and proliferative pathways, a phenomenon dependent on vascularity and functional use.1,2 The tension-stress effect is directly affected by the rate or frequency of the distraction, the stability of the device you use to assist in the distraction, and the position and type of osteotomy.

Pertinent Preoperative Considerations
You must perform callus distraction at a specific rate. When you perform distraction too quickly, both stretching and traction injuries may occur, and tissues may not proliferate. When distraction is performed too slowly, early strengthening of the bone callus can occur, causing premature cessation of the distraction process. Soft tissues generally respond best to a slow, gradual distraction process.

Osteogenic activity at a distraction site is directly related to the stability of the fixation of the corresponding osseous and soft tissue structures you are lengthening. Excessive mobility can lead to a lack of osseous proliferation or a pseudarthrosis.

Vascular tissues, nerve tissues, skeletal muscles and ligaments, and epidermis can all respond positively to proper mechanical distraction. Keep in mind that these soft tissue structures show signs of stretching during the distraction process, but typically return to a normal appearance after you’ve ceased the distraction.

The position or level of the osteotomy is a factor in any callus distraction technique. Potential sites may include the proximal metaphysis, diaphysis, distal metaphysis and the growth plate (if it is still present). Today, most surgeons prefer to perform the osteotomy in metaphyseal bone due to its increased vascularity and greater osteogenic potential. However, the early literature advocated performing the osteotomy in the diaphysis and this area often allows easier positioning of external fixation devices and easier dissection for the osteotomy.
When choosing the optimal site for the level of the osteotomy, you should consider the following factors:
• the level of the deformity you are correcting;
• the amount of length and angulation needed for correction;
• the size and extent of the blood supply in the area;
• the amount of soft tissue coverage in the area;
• the technical ease with which you can perform the osteotomy; and
• the access and ability to apply a fixation device.
The osteotomy technique or corticotomy, and the amount of medullary canal and periosteal damage directly affect the distraction process. There is still some debate as to whether a corticotomy or osteotomy is preferable for initiating the process of callus distraction.
A corticotomy is a procedure in which you cut the outer cortex of a bone but preserve the medullary bone. An osteotomy involves making a complete cut through the bone including both the cortex and endosteum. In both instances, preserving nutrient arteries to the bone is preferred.

Comments

Surgical Board Questions were taken from here. Good Article!
Todd Allain DPM

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