J Am Acad Orthop Surg, Vol 12, No 1, January/February 2004, 28-38.
© 2004 the American Academy of Orthopaedic Surgeons
Management of Posttraumatic Segmental Bone Defects
Thomas A. DeCoster, MD,
Rick J. Gehlert, MD,
Elizabeth A. Mikola, MD and
Miguel A. Pirela-Cruz, MD
Dr. DeCoster is Professor and Vice Chair, Department of Orthopedics and Rehabilitation, University of New Mexico, Albuquerque, NM. Dr. Gehlert is Assistant Professor, Department of Orthopedics and Rehabilitation, University of New Mexico. Dr. Mikola is Assistant Professor, Department of Orthopedics and Rehabilitation, University of New Mexico. Dr. Pirela-Cruz is Associate Professor, Department of Orthopedics, Texas Tech University–El Paso, El Paso, TX.
Reprint requests: Dr. DeCoster, University of New Mexico, 2ACC, 2211 Lomas Boulevard NE, Al-buquerque, NM 87131-5296.
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Abstract
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Because of difficulty in managing posttraumatic segmental bone defects and the resultant poor outcomes, amputation historically was the preferred treatment. Massive cancellous bone autograft has been the principal alternative to amputation. Primary shortening or use of the adjacent fibula as a graft also has been used to attempt limb salvage. Of more recent methods of management, bone transport with distraction osteogenesis has been suggested as the leading option for defects of 2 to 10 cm, but problems include delayed union at the docking site and prolonged treatment time. Free vascularized bone transfer has been suggested as the leading option for defects of 5 to 12 cm, but hypertrophy of the graft is unreliable and late fracture, common. Bone graft substitutes continue to be developed, but they have not yet reached clinical efficacy for posttraumatic segmental bone defects. Although each of the new techniques has shown some limited success, complications remain common.
Posttraumatic segmental bone defects (PTSBDs) resulting from injuries of the extremities can have severe negative long-term impact on patients’ lives and present complex treatment challenges. Although standard management options have been refined, new developments have expanded the breadth of therapeutic options. Special skills are required to perform many of these new techniques effectively. However, despite these advances, treatment courses remain prolonged and fraught with frequent complications. Determining the optimal management strategy may be difficult. At horough knowledge of the alternatives, their respective complications and outcomes, and their relative applications can help with decision-making.
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Overview
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Massive cancellous bone autograft became the primary alternative to amputation during World War II.1,2 Shortening of the limb or using the adjacent fibula to create a one-bone leg (fibula pro tibia) also was used to achieve limb salvage.3 However, the fibula transmits only about 15% of the weight-bearing load of the leg and does not reproduce the mechanical function of the tibia well.4 These treatments left patients with problems, including prolonged time of treatment, nonunion, infection, refracture, and poor functional results.1,5 Overly aggressive débridement of bone has resulted in unreconstructable bone defects and thus potentially avoidable amputations. Even with a more cautious approach to bone débridement and despite technologic advances, reconstruction of PTSBDs presents formidable obstacles.
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Etiology
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PTSBDs result from acute trauma with loss of bone substance, acute trauma with bone loss from surgical débridement, chronic infection requiring bone resection, or chronic nonunions with segmental bone defects. The defects can occur in any of the four long bone segments. The most common clinical situation is open fracture of the tibial shaft (Fig. 1,A
). Open fractures always have some degree of comminution, and the surgeon is faced with deciding how much bone to remove. Aggressive débridement of bone fragments does help reduce the risk of infection, but it also may create a PTSBD (Fig. 1, B and C). Most authors recommend removal of bone fragments that are contaminated and devoid of soft-tissue attachment1,6,7 (Fig. 1, B). Inadequate resection of contaminated tissue, specifically bone, increases the risk of chronic infection because this contaminated devitalized tissue is an excellent medium for infection, and the injured blood supply limits the body’s local resistance to infection (Fig. 1, C).
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Figure 1 A, Anteroposterior radiograph of an open tibial shaft fracture in an 11-year-old boy who was in a dirt bike wreck. There were two main segments of tibial diaphyseal comminution with extensive stripping. He had good arterial and nerve function to the foot and no other injuries. B, Initial treatment included irrigation and débridement of the wound. The 9-cm distal segment was débrided. The 11-cm proximal segment had some soft-tissue attachment and was cleansed and preserved. The limb was stabilized with a unilateral external fixator. C, Gross infection required wound débridement (including removal of the 11-cm segment) and use of antibiotic-impregnated beads, which resulted in resolution of infection but left a 20-cm PTSBD of the tibia. Systemic antibiotic treatment with vancomycin was complicated by red man syndrome and diffuse exfoliation. D, The patient underwent shortening of the limb and transference of the fibula segment into the medullary canal of the remaining tibia proximally and distally, with skeletal stabilization with a ring fixator. The 15-cm fibula segment was overlapped with the tibia by 1 cm proximally and distally, and the limb was shortened 7 cm (15 – 2 = 13 cm; 20 – 13 = 7 cm). This shortening allowed relaxation of soft-tissue tension and split-thickness skin grafting.
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Larger bone defects are associated with more difficult reconstructions and less certain long-term outcomes (Fig. 2). The risk of infection must be balanced against the problems associated with increasingly large skeletal defects. Some fractures that initially do not have segmental bone loss become complicated by chronic infections, and resection of bone often is necessary to control the infection. Determination of the appropriate amount of bone to remove in the presence of chronic infection also is difficult. Vital staining, laser Doppler flowmetry, imaging, computed tomography scanning, and direct surgical observation can help determine the appropriate extent of bone débridement, but they rarely provide a definitive solution.8
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Figure 2 Same patient as Figure 1 . Postoperative anteroposterior (A) and lateral (B) radiographs at 14 months demonstrating that length was regained by proximal corticotomy of the tibia and lengthening of the limb by 7 cm. Regenerate bone was formed and consolidated. The fibula healed to the distal tibia, but there was delayed union of the fibula to the proximal tibia, which healed with cancellous bone grafting. The patient was left with a salvaged limb but small-diameter bone (fibula transfer) and uncertain growth potential at 14 months postinjury. Anteroposterior (C) and lateral (D) radiographs at 3.5-year follow-up (patient age, 15 years 3 months) demonstrating that the patient has grown 15 cm and has only a 2-mm limb length discrepancy. The regenerate bone and fibula have remodeled. The patient returned to normal activities, including soccer and basketball.
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Limb Salvage Versus Amputation
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Bone defects frequently occur as a result of attempted salvage of mangled extremities. Early amputation often is superior to prolonged attempts at salvage that can leave the patient destitute, disabled, divorced, or depressed.9 Cierny et al10 have emphasized the importance of patient factors in determining the risk of infection and the probability for acceptable function. These factors include age, immune system status, wound-healing capacity, and general medical condition. Amputation should be discussed with every patient with a PTSBD, both as an alternative for treatment and as a potential result of failure of other alternatives.
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Management Alternatives for Posttraumatic Segmental Bone Defects
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Established methods of managing PTSBDs to restore limb function include limb shortening, autologous nonvascularized cancellous bone graft, bone transport distraction osteogenesis, and free vascularized bone transfer. In the presence of tibial defects, various treatments make use of the fibula. The major advantages and disadvantages of each method are given in Table 1.
Acute Limb Shortening
Limb shortening is a reasonable option for the management of PTS-BDs in certain situations. Of the available options, it has the shortest treatment times and results in the least complications.1 Acute limb shortening allows fracture healing to begin immediately, improves stability (compared with leaving a gap), and relaxes tension on the soft tissues. This technique also may improve vascularity, reduce neurogenic pain, and allow primary closure or coverage. However, excessive soft-tissue swelling and redundancy may be an undesired consequence.
Shortening is better tolerated in the humerus than in other bones because in the upper extremity, equality of limb length is less important functionally. Also, shortening is better tolerated in one-bone segments (ie, the upper arm and thigh) than in two-bone segments (ie, the forearm and lower leg). Femoral shortening often can be managed effectively by compensatory shortening of the contralateral femur, especially in patients of above-average height.11 When limited to a bone defect of <3 cm and associated with fibular comminution, shortening often is the most effective treatment for PTSBDs of the tibial shaft. Resulting limb function is comparable to or better than that with many alternative treatments.
Autologous Nonvascularized Cancellous Bone Graft
Autologous nonvascularized cancellous bone graft remains a common method of managing PTSBDs. Skeletal stabilization with external fixation, intramedullary rods, or plates may be done at normal length or with some shortening. The timing of the bone graft procedure is important. Delaying it 6 weeks after a free-tissue transfer allows complete epithelialization of the flap and therefore decreases bacterial contamination of the surgical site with skin flora.12 Healing of the flap to the surrounding native soft tissues also is ensured. Even when tissue transfer is not required, autologous bone graft should be delayed for 6 weeks to allow wound healing and revascularization of marginally viable tissues.12,13
Several surgical approaches are available for grafting in the tibia. The posterolateral approach described by Harmon14 in 1945 avoids the anteromedial soft tissues that frequently are compromised by open wounds and are unforgiving with regard to closure. The patient may be positioned prone, which allows surgical access to both the posterior iliac crest and the posterior leg. Harmon described placing the bone graft on the interosseous membrane to obtain a long synostosis with the fibula spanning the tibial defect14 (Fig. 3). With the advent of free-tissue transfer for wound management, use of an approach between the flap and the anterior compartment musculature has gained favor. If the flap pedicle is to the posterior tibial artery, the approach is anterolateral. If the vascular pedicle of the flap is anastomosed to the anterior tibial artery, the approach should be posteromedial.15 Using this direct approach, the graft can be more easily placed directly in the tibial defect. This approach also has been shown to be reliable and technically less demanding than the posterolateral approach. The Harmon approach is more hazardous in a limb with blood supply only from the posterior tibial artery. Posterolateral grafting generally is not used for proximal tibial fractures because of the proximity of the neurovascular bundle.15
Cancellous autograft remains the best graft material for stimulating new bone formation, possessing unsurpassed osteoconductivity and osteoinductivity. Although the metaphyseal region of most long bones can be a source for bone graft, the posterior ilium is the best source in the management of PTSBDs. Each posterior iliac crest contains enough harvestable bone for a 4-cm tibial defect.16,17
Incorporation of a bone graft is improved by a host bed with stable vascularity. To improve the local blood supply around a diaphyseal defect at the time of graft implantation, all avascular scar tissue is débrided from the surrounding soft tissues. Another method is to recanalize the medullary canal that typically is sealed by callus on both ends of the recipient bone; doing so reestablishes the medullary blood supply. Vascular in-growth from surrounding tissue may be stimulated by making multiple small drill holes in local avascular cortical bone or abrading the local cortex with a fine burr.8 The bone graft mass then is packed firmly and contoured into the defect, overlapping the cortical ends by at least 1 cm. In general, the patient is kept partial weight bearing until radiographic consolidation of the graft occurs.8
Autologous bone grafting generally is applicable to manage PTSBDs, does not require special instrumentation or expertise, and ultimately allows reasonable restoration of function.6 However, graft incorporation typically is slow and sometimes unreliable, contributing to nonunion, re-fracture, or poor limb function. The technique may not be appropriate for large bone defects.
Bone Transport Distraction Osteogenesis
The technique of distraction osteogenesis has been used to effectively treat PTSBDs. Originally, Ilizarov and others stabilized the limb with a circular external fixator, and the bone transport segment was produced by osteotomy of the metaphysis17,18 (Fig. 4). After a 5-day latent period, this segment can be transported approximately 1 mm per day to eliminate the diaphyseal segmental bone defect and create a new defect at the osteotomy site. This defect fills with new bone by the process of distraction osteogenesis. The docking site heals in compression by fracture callus. Two to 3 days of consolidation are required for each day of distraction. Bone graft typically is applied to the docking site, and the ends of the bone may be freshened to stimulate healing.18–20
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Figure 4 Bone transport distraction osteogenesis with a circular frame and proximal corticotomy. The middle segment is transported distally (arrows).
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An alternative technique for PTSBDs involves acute limb shortening with subsequent lengthening of the limb21,22 (Figs. 1, D and 2, A and B). This technique has the theoretic advantage of faster healing of the traumatic fracture because it does not require waiting until docking is achieved to begin callous healing. Another advantage is that shortening assists with closure of traumatic soft-tissue defects. However, acute shortening of large defects may cause soft-tissue redundancy and swelling. The greater the injury to the fibula, the greater the benefit of acute shortening of the leg.21
Other refinements of bone transport have been reported. Unilateral rail external fixator systems are reported to decrease the soft-tissue problems of transfixation wires.23,24 These rail fixators have multiple pin-holding clamps that slide along rails to achieve bone transport or lengthening. They are particularly useful when angular correction is not required. Distraction over a nail is reported to reduce time in a fixator, allow earlier return of function, and minimize the incidence of malalignment.25 The potential disadvantages include disruption of the regenerate by the nail and risk of medullary infection from contamination of the nail by pin tracts.
Successful treatment of PTSBDs with the Ilizarov technique has been reported by many authors.1,16–18,20–27 Very large defects (up to 30 cm) can be treated in both adults and children, while concomitant deformity and soft-tissue problems can be addressed in all portions of the extremity. This technique requires specialized training and equipment as well as long treatment duration, and it is associated with frequent complications. Despite these problems, some form of distraction osteogenesis is probably the most commonly used method of managing intermediate and large PTSBDs.
Free Vascularized Bone Transfer
Vascularized bone transplantation can be done with rib, fibula, or iliac crest. Free vascularized bone grafting was developed as an extension of new microsurgical methods in the 1970s.28 The technique involves isolation of a segment of the contralateral fibula with attached nutrient artery and veins. This segment is transferred to the tibial defect, and skeletal fixation is followed by vascular anastamoses (Fig. 5). The length of the graft is 4 cm more than the tibial defect to allow 2 cm of overlap at the proximal and distal ends. Five centimeters of distal fibula must be left at the donor site to avoid ankle problems, and 7 cm of proximal fibula usually is left to avoid knee and peroneal nerve problems. Average time to union is from 3 to 6 months.28,29 In posttraumatic reconstruction, this technique has a union rate of up to 90%.29
Vail and Urbaniak30 reported a 19% incidence of donor site morbidity in their series of 247 vascularized fibula grafts. Objective motor weakness, subjective discomfort in the ankle and other sites in the leg, and sensory abnormalities were documented. Other isolated findings of wound cellulitis, peroneal palsy, and thromboembolic complication also were noted.30 Fracture through the graft has been reported in 25% of vascularized fibula transfers and is most common when the graft does not hypertrophy.31,32 Most of these fractures occur within 1 year of union and are thought to be secondary to mechanical fatigue because adequate bone hypertrophy requires at least 2 years.31
Watson et al1 reported frequent failure of free vascularized fibula bone transfer in the management of bone loss in tibial shaft fractures and abandoned the technique in favor of bone transport or bone graft. They noted that good results were reported in patients with long-standing segmental nonunions and suggested the technique might be more efficacious in that setting. Free vascularized fibula requires a recipient artery that is not essential to the survival of the limb, although this may not be available in some patients with PTSBDs.
The vascularized fibula bone transfer technique is applicable to large defects, and bone can be transferred to the radius, ulna, humerus, femur, or tibia. Living autograft tissue with good strength and immediate stability and resistance to infection is transferred, and healing generally is rapid. In spite of the improved reliability of microvascular techniques, the procedure still is technically difficult and requires specialty services.32 In addition, donor site morbidity particularly is problematic in patients with PTSBDs whose contralateral leg is placed under high functional demand. The technique perhaps is best indicated in very large defects in which the advantages of immediate restoration of skeletal continuity outweigh the disadvantages.
Management of the Associated Soft-Tissue Defect
Most open fractures with PTSBDs are associated with soft-tissue defects. Regardless of the technique used to manage the skeletal deficiency, treatment of the soft-tissue defect is necessary. Early soft-tissue coverage with vascularized muscle flaps has been beneficial in these patients. This method now is one of the central tenets in the management of soft tissue in PTSBDs.7,33 The success of a free-tissue transfer is improved by performing the reconstruction before wound colonization has occurred, usually within 1 week of injury.34 Unfortunately, there is virtually no blood flow from the undersurface of the flap to the tissue beneath it in the bone gap, and therefore there is no direct stimulation of new bone formation.33 Free-tissue transfer provides coverage that allows safer use of other techniques to replace the bone defect. Lowenberg et al,35 Spiro et al,36 and Jupiter et al37 reported enhanced outcomes using Ilizarov techniques combined with free-tissue transfers compared to Ilizarov techniques alone.
Antibiotic-impregnated beads also are very useful in the management of dead space in PTSBDs.38 The strong local concentration of antibiotic in the region of high bacterial contamination and low blood flow is superior to intravenous administration of antibiotic. The beads occupy dead space and pre-vent accumulation of hematoma or scar tissue that otherwise would be conducive to infection and make subsequent bone replacement more difficult. Free flaps placed over the beads contour much better and are much easier to elevate subsequently compared with other coverage techniques. Each of the techniques for replacement of the bone defect (bone transport, autologous nonvascularized cancellous graft, free vascularized bone transfer) is enhanced by initial dead space management with antibiotic-impregnated beads38 (Figs. 1, C and 6).
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Figure 6 Anteroposterior radiograph of a PTSBD of the tibial shaft, with antibiotic-impregnated beads filling the defect.
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Other techniques of soft-tissue coverage include rotational muscle flaps, local fasciocutaneous flaps, and free-skin grafts. High complication rates with muscular rotation flaps for tibial fractures have been reported, and some authors have moved almost entirely to free flaps in acute injuries.34 The energy that causes segmental bone and soft-tissue loss typically injures surrounding tissue. This tissue at the margin of the débrided open wound may be viable if left in place, but it may be unsuitable and nonviable after rotation.34
Bone transport distraction osteogenesis also has been reported to pull and stretch soft tissue for sufficient closure or coverage and to obviate the need for free-tissue transfer.19 Soft tissue and bone are pulled into the defect site, and new tissue histogenesis occurs at the distraction site.21
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Techniques for Specific Anatomic Sites
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The most common anatomic site for a PTSBD is the tibial shaft (Fig. 1, A). The tibia is devoid of muscle coverage on its anteromedial surface, which both increases the risk of bone loss and complicates treatment. Muscle facilitates blood flow to the bone and healing of incisions. Most other long bones have a more substantial muscular envelope compared with the tibia. Tibial defects potentially benefit from the presence of the fibula. The fibula serves as a strut to help maintain limb length and alignment as well as muscle attachment. The fibula has good healing properties, and fibular shaft fractures often unite without fixation early in the course of treatment. The fibula can be used in a variety of ways to create a one-bone leg. The posterolateral synostosis technique allows the forces of weight bearing to be passed from the ankle and distal tibia across the distal synostosis to the fibula, carried by the fibula that spans the tibial defect, then passed back across the proximal synostosis to the proximal tibia and knee.14 Huntington3 described a technique that involves a double osteotomy of the fibular shaft, transferring it to the lateral side of the tibia to span the tibial defect. The transferred fibula can be either attached to the tibia with screws or placed within the medullary canal of the tibia and maintains vascularity through muscular attachment and nutrient artery39 (Fig. 7). Subsequent hypertrophy to normal tibial diameter is particularly common in children40 (Figs. 1, D and 2).
The presence of the fibula also is helpful in other techniques. Astraight fibula facilitates bone transport by providing a strut to prevent the bone transport from translating or angulating, two problems commonly encountered in single-bone anatomic sites, such as the thigh or brachium.24 For all of the management methods, the presence of the fibula adds significantly to solid muscle attachment, leg stability, and the ability of the patient to bear weight early in the course of treatment.
PTSBDs of the femoral shaft are more difficult mechanically than those of the tibia. Injuries that cause segmental femoral defects typically involve more force. The femur is more proximal and supports greater load and more muscle mass than the tibia does, so segmental femoral defects create greater mechanical instability. External fixation of the femur is more difficult to achieve because of both the greater forces involved and the extensive soft-tissue envelope, which makes placement of the pins difficult. Small femoral defects heal more rapidly and reliably than tibial defects do. Defects of 1 to 3 cm that would likely require extensive reconstruction in the tibia often heal spontaneously with placement of an intramedullary nail in the femur.41
The humerus is similar to the femur in that its extensive soft-tissue envelope can reduce the frequency of PTSBDs but also increase the complexity of the placement of external fixation. Humeral bone defects, however, behave much like those in the tibia in that they often are not associated with spontaneous healing. Even small gaps present after plating or nailing often are associated with nonunions. Segmental defects of the internally fixed humeral shaft rarely heal without adjunctive treatment. Cancellous grafting,12 vascularized fibula transfer,42 and bone transport15 all have been performed successfully for PTSBDs of the humeral shaft. Muscle adjustment to a shortened humerus is typically rapid, so acute shortening of up to 5 cm generally is associated with good function and is an attractive option.
Just as the fibula is used to help reconstruct the tibia, so isolated radial or ulnar segmental defects benefit from the presence of the other bone.43 Shortening of the forearm is not as well tolerated as that of the humerus because of the loss of pro-nation and supination that usually occurs and because of the interference with good hand motor function that results from shortening the muscle tendon units. The ulna has a subcutaneous border that is similar to the tibia in accepting external fixation. The muscle coverage is better for the radius than the ulna, but the ulna still has relatively better muscle coverage than the tibia. Wound healing typically is better in the forearm than in the tibia, and free soft-tissue flaps are less commonly required to obtain sufficient soft-tissue coverage.43 Cancellous grafting,43 vascularized fibula,42 and bone transport44 all have been reported as techniques for managing segmental defects of the forearm.
The volume of bone loss per centimeter of defect varies by anatomic site because of the difference in diameter of the long bones. Defects of the tibia and femur require a much greater volume of bone graft than do defects of the radius or ulna. The volume of bone graft available from the adult male pelvis typically will fill a 10-cm femoral defect, a 15-cm tibial defect, or a 20-cm humeral defect.16 Considerably less bone graft from the pelvis is available from children and women.16 Bone transport is not affected by required volume of bone. In terms of size and strength, the vascularized fibula transfer is closer to the normal humerus than to either the tibia or femur.45
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Management Based on Defect Size
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Some authors have promoted management protocols based on the length of the PTSBD16,24,27 (Table 2). Others have gained sufficient familiarity and dexterity with a preferred technique to apply it across a wider range of segmental defects.1,6,18 Some authors consider factors other than length of the defect to be so important that they do not base the treatment primarily on the size of the segmental defect1,6,17,24,45 (Figs. 1 and 2, A and B).
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Duration of Treatment
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All methods for treatment of PTSBDs require a long time. For most techniques, time in treatment is related directly to the length of the defect, with approximately 1.5 months needed for every centimeter of defect, in addition to the usual time for the fracture to heal. A tibial shaft fracture (basic healing time, 4 months) with a 5-cm defect (5 x 1.5 = 7.5 months) will require approximately 1 year (4 + 7.5 = 11.5 months) of treatment.1 Most patients are not aware of the likely time of treatment at the initial injury, so this should be discussed early. Prolonged time in treatment prevents the patient from engaging in normal activities and causes disuse atrophy, loss of income, and psychological stress.9
Watson et al1 reported equivalent treatment times (total treatment time and time to osseous union) in patients with tibial shaft fractures with bone loss who were treated with either un-reamed nails (average, 43 weeks) or external fixators (average, 45 weeks). Green16 also found no difference in treatment time in his comparison of bone transport and bone graft for segmental skeletal defects. Cierny and Zorn27 found no difference in treatment time when bone graft and bone transport were compared in patients with infections that caused segmental bone defects. Marsh et al23 reported the same treatment time for bone transport and bone graft in patients with chronic infected tibial nonunions with bone loss.
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Direct Financial Cost
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All techniques for treatment of PTSBDs require significant direct financial cost, approximately $100,000 per case.46 Williams46 reported a cost comparison of limb salvage with the Ilizarov technique versus amputation. Acute treatment was $30,000 for amputation (without prosthesis cost) and $60,000 for limb salvage with distraction osteogenesis. With amputation plus prosthesis for the life expectancy of the patient, the cost increased to $400,000 (with inflation adjustment) or $180,000 (without inflation adjustment). Others have estimated the lifetime prosthesis cost of young amputees at a range of $250,000 to $1.5 million.3 Cierny and Zorn27 compared distraction osteogenesis and autologous bone graft in patients with segmental tibial defects; the former cost nearly $30,000 less than the latter ($85,000 versus $113,000, which included surgical fees, hospital bills, and outpatient therapy).
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Complications
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All techniques for management of PTSBDs are associated with a myriad of problems and complications.1,6,9,23,24,31,34 Complications are so frequent that nearly all patients require at least one surgical procedure that was not specifically planned initially.23 Failure to obtain healing of the segmental bone defect (nonunion) is always a risk. Other common complications include deep infection, superficial infection, pin track problems, implant failure, flap failure, antibiotic toxicity, vascular injury, malalignment, weakness, donor site morbidity, dysfunctional limb, unplanned surgical procedures, and psychological problems.1,6,9,24,31,34
In a comparison of bone transport and bone graft techniques, Green16 reported that both shared complications associated with external fixation. Also, each had its own unique set of complications. The bone graft group (15 patients) exhibited limited graft availability, donor site morbidity (20%), and refracture (13%). The bone transport group (17 patients) exhibited delayed union at the docking site (41%) and joint contracture (41%). Bone transport was applicable to gaps >5 cm, whereas bone grafting was not.16
Cierny and Zorn27 compared conventional (bone graft, 23 patients) and Ilizarov (bone transport, 21 patients) techniques for segmental tibial defects and concluded that successful management was achieved after the first treatment in 70% of both groups. The overall success rate was 95% in both groups. The Ilizarov group had a higher rate of complication (60% versus 33%); however, it also had a higher percentage of compromised hosts. The Ilizarov group showed benefits over the conventional bone graft group, including fewer hospital days, fewer months of disability (17 versus 22), less time in the surgical department, and lower cost. Cierny and Zorn27 had a lower incidence of docking site nonunion (10%) than did Green16 (41%) but had a higher rate of delayed consolidation of the regenerate (20% versus 6%). Cierny and Zorn27 found bifocal transport advantageous at speeding consolidation of large defects, whereas other authors have reported an excessive increase in complications with this technique.22
Marsh et al23 reported equivalent complication rates for bone transport and bone graft treatments for patients with chronic infected tibial nonunions with bone loss, including malunion, recurrence of infection, number of surgical procedures, and number of complications. After completion of treatment, some patients had residual limb length discrepancy, but this problem was significantly (P < 0.01) less common with bone transport (0.4 cm) than bone graft (2.0 cm).23
Watson et al1 reported on a series of tibial shaft fractures with bone loss and found malunion to be greater with posterolateral autologous graft (80%) compared with direct grafting (34%) and bone transport (<5%). Subsequently, Watson8 further refined the bone transport technique.
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Other Management Techniques
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Other techniques for managing PTSBDs may be applicable, but they have not been accepted routinely. Structural allograft has been used to restore bone stock in patients with revision arthroplasty or tumor resection, but it has failed in most PTSBDs because of infections, slow and incomplete remodeling, and high rate of fracture.47 Titanium cages containing bone graft material recently have been reported for management of PTSBDs, with reasonable success.48 The data are preliminary, but risk of infection and difficulty with removal of the cage are concerns.
Synthetic bone graft substitutes have been successful as bone fillers but do not provide the long-term load-bearing function required in PTSBDs. Ehrnberg et al49 found uniformly poor results with demineralized bone matrix in segmental defects. Other synthetic and biologic scaffolds will become available and will be tested on PTSBDs.
Bone morphogenic protein (BMP) and other osteoinductive growth factors (eg, transforming growth factor beta, platelet-derived growth factors, insulin-like growth factors, fibroblast growth factors), osteoconductive matrices (scaffolds), and osteoprogenitor stem cells offer considerable promise but remain unproven.50,51 The proteins BMP-2 and BMP-7 have been effective in animal PTSBD models, and BMP-4 and BMP-7 (osteogenetic protein 1 [OP-1]) are now available for limited clinical use in humans.50,52,53 The most promising technique is use of a local carrier or scaffold introduced surgically into the defect. The carrier is laced with biologically active agents that can be serially injected to maintain effective levels as healing progresses.54 Gene therapy initially has been evaluated, but areas of concern remain, such as the production of safe vectors for gene therapy and the assurance that the altered cells will be subject to normal control mechanisms and not create undesired consequences.
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Summary
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PTSBDs remain a difficult clinical challenge. Initial treatment and patient selection for limb-salvage techniques are important. The historical standard of massive cancellous grafting, using current modifications, remains a viable treatment alternative. The use of free flaps for improved coverage, antibiotic-impregnated beads for the management of dead space and infection control, direct placement of graft in the defect site, and stable fixation during consolidation have improved clinical outcomes. New techniques of distraction osteogenesis and vascularized fibula transfer offer some benefits. Other techniques offer promise for the future. Bone is precious, and reconstructing PTSBDs is a long, challenging process for the patient as well as the treating surgeon.
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Footnotes
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Dr. DeCoster or the department with which he is affiliated has received research or institutional support from EBI, Smith & Nephew, and Howmedica. None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Gehlert, Dr. Mikola, and Dr. Pirela-Cruz.
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References
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