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. Seven Principles Of Callus Distraction Ilizarov identified seven principles of callus distraction which he felt were important to the proper formation of new bone in the distraction gap.3 These include: 1) maximum preservation of marrow and periosseous blood supply; 2) stable external skeletal fixation; 3) a latency before commencing distraction; 4) a distraction rate of 1 mm/day; 5) distraction in small, frequent steps; 6) a period of neutral fixation after distraction; and 7) normal physiological use of the elongated limb.3 These principles form the foundation of callus distraction techniques currently in use. Close adherence to these principles is preferred, but some minor modifications are often necessary. A Procedure With A Growing Number Of Indications In the foot, congenital brachymetatarsia is the most common indication for callus distraction. A slow, gradual lengthening technique is particularly suited for this deformity as it is always associated with coexistent soft tissue contractures and deformities. Successful use of callus distraction for brachymetatarsia has been described by several authors.4 Another indication for callus distraction in the foot is a short metatarsal in which the resultant metatarsal shortening is due to iatrogenic, traumatic, neoplastic or metabolic causes. Callus distraction is often a viable means of achieving improved metatarsal length and function in these instances. However, you must carefully evaluate the associated soft tissues and vascularity of the area. If the soft tissues are of poor quality (e.g., significant scarring) or if the vascularity to the area has been compromised, callus distraction may be ineffective and even hazardous. In the foot, callus distraction has been used in lieu of a bone graft during an Evans calcaneal osteotomy for pes valgo planus correction. Surgeons have also used the technique in medial column lengthening procedures, in which they lengthen one of the bones in the medial column to assist in the correction of metatarsus adductus. In the ankle, callus distraction techniques are typically employed as adjuncts in the correction of severe, complex deformities such as residual clubfoot deformities, neuromuscular deformities and arthrogyposis. Surgeons have also used these techniques to restore or salvage bone length after traumatic, infectious or neoplastic bone loss. In the lower leg, callus distraction techniques have been used to lengthen a short tibia and/or fibula. This shortening may have resulted for a variety of reasons, including congenital, traumatic, neoplastic, infectious or metabolic. You can also correct angular deformities of the tibia and/or fibula via callus distraction. Key Surgical Insights On Callus Distraction Be aware the methodology and parameters surgeons use in performing callus distraction vary significantly, although they generally adhere to the seven aforementioned principles espoused by Ilizarov. Typically, you would use an external fixation device capable of creating distraction and apply it to the area where callus distraction is desired. Proceed to place the pins for the external fixator proximal and distal to the area of the osteotomy/corticotomy. Keep in mind that you wouldn’t necessarily place them within the bone to be lengthened. Then dissect the osteotomy/corticotomy site, ensuring as little trauma to the periosteum and local vasculature as possible. The osteotomy or corticotomy is then created. Intraoperative fluoroscopy is helpful in aiding pin placement and guiding osteotomy/corticotomy placement. Then you would proceed to close the wound. Typically, you wouldn’t start distraction until five or more days after surgery. Once you begin callus distraction, continue the procedure at a rate of approximately 1 mm/day until you’ve achieved the desired length of the bone. Once you’ve reached this goal, lock or neutralize the fixator (i.e., no further distraction is attempted), and maintain the fixation for another three to eight weeks. Patients should demonstrate a progressive return to weightbearing throughout the postoperative course. You should obtain serial radiographs to assess bone formation and healing. Keep in mind that adjustments in the rate and frequency of callus distraction are common based upon both the clinical and radiographic findings during the postoperative course. Specific Pointers On Treating Brachymetatarsia For the distraction of brachymetatarsia, differences in the level of the osteotomy/corticotomy, latency before initiating distraction, and the rate and frequency of distraction have been described. Employing a mini-external fixation device capable of gradual distraction in small increments at the gap site is optimal for fixation of the bone segments. I prefer to perform a corticotomy or minimally traumatic osteotomy in the proximal metaphysis of the short metatarsal when possible. In some instances, this will not be possible and you can use a diaphyseal or distalmetaphyseal corticotomy/osteotomy. In the literature, distraction has been started as quickly as seven days after surgery or delayed for as long as three weeks.4 I prefer to initiate distraction after five to seven days when I’ve performed the osteotomy/corticotomy in metaphyseal bone, and after 14 days if I’ve performed the osteotomy/corticotomy in diaphyseal bone. You would start distraction sooner in children than adults due to the increased rate of healing in the younger population. In the literature, the rate and frequency have varied from 0.25 mm every 12 hours to 0.25 mm every six hours.4 I prefer to achieve 1 mm of lengthening per day, as advocated by Ilizarov, and typically you can achieve this by lengthening 0.25 mm every six hours. After you’ve accomplished adequate lengthening, maintain the frame without further distraction for approximately three to eight weeks. Make sure the patient remains non-weightbearing throughout this period. Once radiographic findings indicate sufficient bone healing, the patient can initiate weightbearing. Once further radiographs demonstrate continued adequate healing, you can remove the pins and fixator. Subsequently, you can allow the patient back into a Cam-walker or shoe and gradually return him or her to full weightbearing. In general, it takes at least three months for a patient who undergoes callus distraction of a lesser metatarsal to return to unrestricted, full weightbearing status. Addressing Potential Complications As with any method of bone lengthening, callus distraction has a significant potential for postoperative complications. Of these complications, delayed union or nonunion of bone healing are common. These can occur for a variety of reasons including: • the technique employed by the surgeon; • poor vascular supply to bone or other host factors (e.g., smoking); • patient non-compliance; • too short a latency period before the initiation of distraction; • too rapid a rate of distraction; • too frequent distraction; • inadequate or unstable fixation or; • an inadequate neutralization period following callus distraction. Several authors have advocated using electrical bone stimulation during callus distraction, but there are no published prospective studies showing improved outcomes with bone stimulation during the distraction period. Malunions and angulation deformities can result from any callus distraction technique. Both can result from a variety of causes including inaccurate osteotomy/corticotomy design; poor fixation placement and direction of callus distraction; loosening of fixation; and a variety of other factors. Premature consolidation may occur and can compromise any callus distraction procedure. Too long a latency period, too slow a rate and/or frequency of distraction, patient noncompliance, and, simply, rapid patient healing are the most common reasons for early osseous healing. Soft tissue and joint contractures, loss of joint motion and new deformities can result from callus distraction techniques. These problems are more common in the lower leg, ankle and rearfoot, but can be seen in the forefoot as well when one attempts significant lengthening. Distractions of less than 10 percent of the initial length of the bone rarely result in any soft tissue or joint problems. Neurovascular compromise can occur and typically manifests itself as neurapraxia and prolonged edema. In cases of lengthening of a metatarsal, neurovascular compromise of the corresponding toe is a potential problem. Finally, pin tract infections are an inherent risk of any external fixation device. Educating the patient on proper pin care and maintenance of a local clean environment in the area of the fixation frame are mandatory. In Conclusion Callus distraction has proven to be a viable technique for lengthening of bone in the foot, ankle and lower leg. The technique works best in long bones of the lower extremity and in younger patients with good soft tissue, bone quality and vascularity. The approaches typically minimize surgical dissection, but still require significant surgical skill and technique to properly apply and administer the external fixation device used for distraction. When it is used for the right indications, callus distraction can obviate the need for autogenous or allogenous bone grafting, and can result in excellent bone formation with a functional result. Future advancements in fixation and surgical techniques will most likely increase the use of callus distraction as a tool for the foot and ankle surgeon. Dr. Downey is Chief of the Division of Podiatric Surgery at the Presbyterian Medical Center in Philadelphia. He is a Fellow of the American College of Foot and Ankle Surgeons and is on the faculty of the Podiatry Institute. He practices privately in Philadelphia, Radnor and Doylestown, Pa. CE Exam #104 Choose the single best response to each question listed below: 1. The tension-stress effect, first described by Ilizarov, is directly affected by: a) the rate or frequency of the distraction b) the stability of the device you use to assist in the distraction c) the position and type of the osteotomy d) all of the above e) none of the above 2. When one performs callus distraction too quickly: a) both stretching and traction injuries may occur b) early strengthening of the bone callus may occur c) tissues may not proliferate d) a and c e) a, b and c 3. When choosing the optimal site for the level of the osteotomy, you should consider the following factors: a) the amount of length and angulation needed for correction b) the amount of soft tissue coverage in the area c) the technical ease with which you can perform the osteotomy d) the size and extent of the blood supply in the area e) all of the above 4. Ilizarov described seven principles of callus distraction. Which of the following principles is incorrect? a) stable external skeletal fixation b) a period of neutral fixation after distraction c) a distraction rate of 2 mm/day d) a latency before commencing distraction e) none of the above 5. Which of the following is the most common indication for callus distraction in the foot? a) a short metatarsal due to iatrogenic causes b) in lieu of a bone graft during an Evans calcaneal osteotomy c) congenital brachymetatarsia d) medial column lengthening procedures e) none of the above 6. Callus distraction has a significant potential for postoperative complications. These complications may be caused by: a) poor vascular supply to bone b) too rapid a rate of distraction c) inadequate or unstable fixation d) patient non-compliance e) all of the above 7. In general, for patients to return to full weightbearing status after undergoing callus distraction of a lesser metatarsal, it takes at least: a) three months b) seven weeks c) one month d) two months e) none of the above 8. In the ankle, callus distraction techniques are typically used as adjuncts in correcting: a) residual clubfoot deformities b) neuromuscular deformities c) arthrogyposis d) all of the above e) none of the above 9. According to the literature, distraction of brachymetatarsia has been: a) started as quickly as three days after surgery b) started as quickly as seven days after surgery c) delayed for as long as three weeks d) b and c e) a and c Instructions for Submitting Exams Fill out the postage-paid card that appears on the following page or log on to www.podiatrytoday.com and respond electronically. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam. Responses will be accepted up to 12 months from the publication date.
References 1. Ilizarov GA: The tension-stress effect on the genesis and growth of tissues. Part I. The influence of stability of fixation and soft-tissue preservation. Clin Orthop 238:249-281, 1989. 2. Ilizarov GA: The tension-effect on the genesis and growth of tissues. Part II. The influence of the rate and frequency of distraction. Clin Orthop 239:263-285, 1989. 3. Ilizarov GA: Clinical application of the tension-effect for limb lengthening. Clin Orthop 250:8-26, 1990. 4. Martin DE: Callus distraction: Principles and indications. In Banks AS, Downey MS, Martin DE, Miller SJ (eds.): McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery, 3rd ed., Vol. 2. Lippincott, Williams & Wilkins, Philadelphia, pp. 2097-2117, 2001.