There are different methods for improving the quality of regenerate during the consolidation phase; and removing the external fixators after the end of distraction phase during segment transfer.
Technical variations on the conventional Ilizarov method have been developed with the goal of reducing the duration of external fixation or eliminating its use. New techniques include: segment transport over an intramedullary (IM) nail; segment transport followed by nailing; hemicorticotomy; tibiofibular synostosis; and fibular transport. These techniques are not without risk, and they may not be appropriate in patients with a history of local infection. Although these methods decrease the external fixation index, protect against refracture, and promote faster rehabilitation, they have not been shown to improve the bone healing index consistently. Other disadvantages include: the possibility of IM infection; the potential for customized instrumentation; increased surgical time, and excessive blood loss; additional surgery for removal of deep hardware; added cost; and a steep learning curve.
Hemicorticotomy: After primary management which comprises debridement, excision of the sinus in the incision, and removal of the anterior half of the tibial cortex and any sequestrum, leaving the posterior cortex intact in its vascular muscle bed. Later, when the condition of the surgical wound allows, a partial corticotomy is performed of the anterior aspect of the tibia adjacent to the area from which bone has been removed. The hemi-corticotomy starts with a skin incision allowing a posteromedial approach to the tibia. The incision is deepened to expose the anteromedial surface of the tibia. The tibial periosteum is incised 1 cm anterior to the posterior tibial cortex, and periosteal stripping is avoided, multiple drill holes in an L-shaped configuration are then made, connected using an osteotome to separate the anterior half of the tibia from the posterior half (Figure 1), the hemicorticotomy is secured by using half pins, wires or both (Figure 2), and then gradual segment transfer is made to fill the defect.
Figure 1 Radiograph shows the hemicorticotomy tibia after surgery.
Figure 2 Radiograph shows the transfer of a hemicorticotomy segment.
Hemicorticotomy is indicated in chronic osteomyelitis involving the anterior tibial cortex with intact and healthy posterior cortex, and contraindicated in diffuse osteomyelitis involving both anterior and posterior tibial cortices.
In our study of twenty patients with chronic osteomyelitis of the tibia hemicorticotomy and transfer by Ilizarov was performed. Of these patients 19 had complete healing of infection and the discharging sinus. Radiography confirmed consolidation of the new bone. The external fixator remained in place in 11 patients until full maturation of the new bone (average duration was 38 wk). Nine patients asked for removal of the frame immediately after segment transfer had been completed followed by a below knee cast for average period of 18 wk (Figure 3).
Figure 3 Radiograph shows after finishing segment transfer and removal of external fixation.
The technique did not work in one patient, whose sinus continued to discharge for 8 wk after surgery. As this was thought due to persistent infection related to insufficient removal of infected dead bone, segment transfer was discontinued and the transferred segment was returned to its original site. This was followed by another operation with complete excision of the segment with the suspected infection and classic segment transfer.
Ilizarov external fixation and then nailing: The plan consists of: segment transfer to reconstruct the defect resulting from the radical debridement; achievement of limb length equality, and deformity correction; use of Ilizarov external fixator frame; corticotomy of the tibia is performed in relatively normal bone; postoperative intravenous antibiotics, specific for culture and sensitivity, are given for 6 wk.
Removal of the external fixator and intramedullary fixation is done at 4th wk after finishing segment transfer. The 4 wk gap between finishing segment transfer and removal of the external fixator is to: (1) give a chance for the irritated skin at the pin site of segment transfer to heal; and (2) the docking site being compressed for some time to avoid gapping and decrease risk of regenerate spring-back after removal of the external fixator.
During nailing, the guide wire for the nail is passed gently through the proximal tibia, the soft distraction callus and the transferred bony segment to the distal tibial segment, followed by insertion of the nail. The statically locked nail fixes both the corticotomy distraction and the docking site while maintaining the length.
Ilizarov fixator followed by intramedullary nailing is indicated in infected nonunion of the tibial shaft, and contraindicated in prior intramedullary tibial nail insertion (to decrease risk of infection recurring after nail insertion, because any hidden infected focus along the medullary canal away from the fracture site could be missed in the debridement), as well as pin track infection during segment transfer.
In a study we had 33 patients with infected nonunion of the tibia managed with segment transfer using an Ilizarov fixator; in 17 patients the fixator was replaced by nailing after segment transfer was completed.
The average duration of infected nonunion was 12.6 mo, in the patients who continued in the fixator where the average duration of the fixator was 8.5 mo; in the patients with nailing, the average duration of the fixator was 3.1 mo.
In the 17 patients with nailing, 15 had complete healing at the docking site and the corticotomy site with no residual infection. In one patient the nail was broken at the docking site level after seven weeks; in another there was recurrence of infection over the intramedullary nail.
Segment transfer over an intramedullary nail: The technique described involves radical debridement, application of a polymethylmethacrylate spacer with a monoplanar external fixator, followed by segment transfer using the Ilizarov technique over an intramedullary nail.
This method is indicated in Cierny-Mader Type IVA or IVB chronic osteomyelitis of the femoral and tibial metaphysis and diaphysis, and contraindicated in Cierny-Mader type IVC chronic osteomyelitis of the femoral and tibial metaphysis and diaphysis, Cierny-Mader Type I, II, or III chronic osteomyelitis of the femoral and tibial metaphysis and diaphysis.
In this method there are pitfalls such as: failure to achieve radical debridement of all dead tissue until the observation of the so-called paprika sign (live cortical bone); failure to determine debridement levels, decision-making which is assisted by intravenous contrast-enhanced magnetic resonance imaging of the whole long bone, which displays all necrotic tissues and skipped abscesses; failure to achieve good soft-tissue coverage of the debridement area which is managed by local or distant soft-tissue flaps; failure to include culture-specific, heat-stable antibiotics into the polymethylmethacrylate; failure to determine precisely the length and diameter of the intramedullary nail to be inserted and the level and number of custom locking holes which can be avoided by preoperative use of templates and standing orthoradiographs; failure to overream the medullary canal 1.5 mm larger than the diameter of the intramedullary nail to ensure easy gliding of bone segments over the nail; failure to ensure that the inserted Schanz screws or Kirschner wires are at least 1 mm away from the nail and failure to place the external fixator parallel to the intramedullary nail in both the frontal and sagittal planes.
In a study done by Eralp et al, this technique was used for 13 patients, the mean size of the defect was 7 cm, mean time of union at the docking site was 9 mo. Excellent results, in terms of both bone and functional assessment, were achieved for 11 patients, 2 patients had recurrence of infection which necessitated removal of the nail and revision with Ilizarov.
Fibular transport: The technique is a gradual ipsilateral fibular transport using a stable external fixator based on the Ilizarov principles. Proximal and distal fibular osteotomies are performed to allow medial translation of the central portion of the fibula. Olive wires with olives placed on the lateral aspect of the ipsilateral fibula are used to perform the medial fibular translation. This technique is indicated in patients with scarce bone regenerate obtained with the standard Ilizarov technique to replace the massive tibial loss as well as recurrence of osteomyelitis.
Catagni et al used this technique in one patient with massive tibial bone loss and previous failed segment transfer. The Ilizarov ring fixation time to achieve fibular transport and bone union was 11 mo, the patient underwent additional multiple bone debridement with insertion of antibiotic beads. Using fibular transport, full replacement of tibial bone loss was obtained.
Two distinct forms of physical forces have been used to enhance DO: LIPU and PEMFs.
Low-intensity pulsed ultrasound: Low intensity pulsed ultrasound delivers high-frequency, low intensity pressure waves to the maturing distraction regenerate. An ultrasound transducer placed on the skin enhances endochondral ossification and callus formation, especially in acute fractures of the distal radius and tibial shaft managed with a cast. Most authors recommend Low intensity pulsed ultrasound over the healing fracture site for 20 min/d. The role of low intensity pulsed ultrasound in distraction osteogenesis is less well defined and is considered a physician-directed (off-label) application.
In a study of 20 young adults with segmental tibial defects who underwent distraction osteogenesis using external fixation, 10 underwent low intensity pulsed ultrasound applied to the distraction site during the consolidation phase[20,26]. The mean healing index was 30 d per centimeter in the ultrasound group compared with 48 d per centimeter in patients treated with rigid fixation (range, 27 to 36 d/cm and 42 to 75 d/cm, respectively).
Pulsed electromagnetic field: Electromagnetic stimulation is a noninvasive modality that has long been used to enhance fracture healing; however, a recent meta-analysis of randomized controlled trials revealed inconsistent outcomes[20,27].
A small double blind study of adolescent patients who underwent limb lengthening did not demonstrate a difference in the rate or amount of new bone formation in patients treated with an active pulsed electromagnetic field coil during distraction compared with control patients treated with an inactive coil. However, when dual-energy X-ray absorptiometry was used to measure bone density, patients treated with pulsed electromagnetic field were found to have less bone loss adjacent to the distraction gap.
Growth factors and stem cells
A variety of Bone morphogenic proteins (BMPs) play an active role in osteogenesis, including recruitment of stem cells, cellular proliferation and differentiation, and bone formation. Recombinant BMP-2 and BMP-7 have been used primarily in adults as an autograft-substitute for single-level spine fusions and certain open tibial shaft fractures and nonunions.
Currently, limited information exists on the clinical use of BMPs for distraction osteogenesis in humans.
In 2008, Burkhart et al reported a case study of a 19-year-old woman with insufficient bone regeneration following tibial transport over an intramedullary nail. The patient was successfully treated with exchange reamed nailing and intramedullary application of recombinant BMP-7 mixed with reamed debris at the site of the atrophic regenerate. However, several simultaneous interventions were used in this case; thus, the role of BMPs in distraction osteogenesis remains unclear and needs further study.
Platelet-rich plasma contains a variety of osteoinductive growth factors that may play a role in the proliferation and differentiation of osteoprogenitor cells and thereby enhances new bone formation during distraction osteogenesis. In a case series, three adolescent patients who underwent lower limb lengthening received an injection of culture-expanded bone marrow cells and platelet-rich plasma at the site of lengthening during the distraction and consolidation phases. The healing index was 23 days per centimeter, with no untoward effects. The same group of investigators applied a similar protocol in the treatment of a group of teenagers of short stature secondary to achondroplasia and hypochondroplasia who underwent lower limb lengthening. Eleven patients (24 bones) were treated with transplantation of culture-expanded bone marrow cells and platelet-rich plasma during distraction osteogenesis.
These patients had a significantly lower average healing index compared with nine patients (32 bones) in the control group (27.1 ± 6.89 d/cm vs 36.2 ± 10.4 d/cm, respectively, P = 0.0005). The osteogenic effect was more pronounced with femoral lengthening than with tibial lengthening.
Although the initial results of injection of culture-expanded bone marrow cells and platelet-rich plasma (PRP) at the lengthening site seem encouraging, this treatment option requires additional visits to the operating room and special equipment, as well as additional training to harvest the stem cells. This technique must be studied in other patient populations, especially those with typically prolonged healing times, to evaluate whether these results can be duplicated.