The most important finding of this study was that the duration of the bone union in external fixation was significantly shortened for the femur group compared to the tibia group. In addition, the between-group differences for both bone and functional results were also significant. With this effect size and the number of patients we included, our study was adequately powered (using P < 0.05) to detect between-group differences using prior analysis. Generally, the femur group has a physiologically better bone healing response, and lower limb function recovery. The total number of complications per patient was significantly greater in the femur group compared to the tibia group. These findings could be explained as soft tissues and fruitful blood vessels in the thigh have better quality than in the tibia, and this allows for better postoperative rehabilitation and faster bone healing. In turn, the favorable influence of these physiological characteristics brought about comorbidities simultaneously, such as pin tract infection, axial deviation, which increased the number of operations potentially and prolonged the rehabilitation time. Thus, timely and effective detection and management of complications by internet follow-up applications are beneficial for bone healing. This study investigated the clinical efficacy preliminarily of trifocal bone transport in femoral and tibial infected bone defects, recorded and compared the distribution of postoperative complications, and provided the reference for treating infected defects of lower limbs.
Critical bone defects caused by osteomyelitis or trauma are an insurmountable challenge for both patients and orthopedic clinicians, and limb salvage with any technique can be disappointing [14, 16, 18–20]. Masquelet techniques are spacer filling, induced membrane formation, bone grafting, and fixation. It has been reported in the literature about its efficacy in controlling infection and treating nonunion, but this technique requires fruitful coverage of soft tissue at the bone defect site and has poor ability in correcting the deformity. Despite less psychological stress and better acceptance of internal fixation, both plate and intramedullary nailing require operation time to address the problem of suitability and stability of fixation devices and bone. The utilization of automatic intramedullary lengthening devices for lower limb bones is still in the experimental animal stage, and more evidence is needed to support its clinical efficacy.
Based on the spectrum of multi-focal osteosyntheses of the Ilizarov technique, external fixation uses distraction osteogenesis to regenerate bone defects caused by complex etiologies to smooth the way for limb reconstruction and rehabilitation . The reconstruction of soft tissue loss can be resolved effectively by this technique, while addressing bone defects and allows the patient to mobilize on the second postoperative day, accelerating bone mineralization dynamically. Critically, this method allows radiographic and histological analysis easier, whilst standardize the mechanical stability of the defect precisely. Via a recent study [14–16, 21, 22], multi-level bone transport was developed to resolve the reconstruction of the critical bone defects (> 6cm), which enriches the traditional Ilizarov technique. In bone defects, the critical tibia defect caused by trauma has been treated successfully by trifocal bone transport with an external fixator, which could eliminate infection and reconstruct bone and soft tissue defects simultaneously. The main theoretical advantage of trifocal bone transport is to eliminate infection, reconstruct bone and soft tissue defects simultaneously, and connect across the original area of bone loss with the expectation of decreased the whole treatment period [12, 13]. The external fixators are divided into circular fixators and unilateral fixators commonly. The application of a circular external fixator in the treatment of bone defects caused by an infection often has an impact on daily life, nursing, and adjacent joint's range of motion. Besides, the hydroxyapatite-coated screws decrease the risk of pin tract infection, have been used for the treatment of open fracture or osteomyelitis . In this study, all patients were treated by unilateral fixators to minimize external-fixator-nature complications. Bone healing was received in 39 patients (100%), and the rate of excellent and good bone and function was 74.3% and 87.1% respectively.
For the operative procedure, the principles of the Ilizarov technique of percutaneous osteotomy should be followed to conserves the periosteum. The osteotomy was conducted minimally along with the predesigned bone cutting position (the bone cutting position should be considered in combination with the factors away from the lesion, metaphysis, skin, and soft tissue conditions, etc.), and low-speed drill, low-energy, subperiosteal bone cutting are used to reduce the incidence of iatrogenic fracture nonunion. Trifocal osteotomy was given the meaning of dividing the residual large segmental bone defect into two segments for stretching into the bone and reducing the length of each distraction area. Thereby, it could double the distraction speed because two-level osteotomies divided lengthening (and healing) into two locations. In our cohort, an earlier start to distraction (7 days after surgery) at the rate of 2 mm per day was achieved in all patients by the above surgical method. However, the operating time and surgical bleeding volume were significantly different between femur and tibia, which illustrated that the multilayered physiological anatomy and thicker subcutaneous superficial fascia of the thigh adds significantly to the difficulty of the procedure and increases the risk of postoperative complications, such as pin tract infection and axial deviation. Despite it seems like an elegant solution for the management of bone defects, there is a great problem for clinicians to manage postoperative care, including pin tract care, radiographic follow-up. In this study, 39 bone defects were salvaged and the docking site was connected. Some complications occurred inevitably during the bone transport period. The rate of complications was 0.84 per patient (0.67 of minor and 0.17 of major). Pin tract infection was a common complication in the process of bone transport [23–26], the rate varied from 6–70%. In our study, seven patients (17.9%) had different symptoms of pin tract infection, including four cases in the femur group (22.2%) and three cases in the tibia group (14.2%). Similarly, the complications related to the rich soft tissue of the thigh, especially muscle contractures were also in higher occurrence than the calf.
Another significant observation from this study is the high incidence of delayed or non-union of the docking site in the tibia group. There were delayed unions in 5 cases (23.8%) in the tibia group, compared to the delayed union in one case (5.5%) in the femur group. There was also a significant difference between the two groups about the complications per patient (minor 0.44 vs 0.23, major 0.06 vs 0.11, P < 0.05). One of the similarities in these delayed unions was that the bone defects were greater than 8 cm and at least four previous surgical procedures were conducted before bone transport surgery. In our consideration, previous surgeries and invasive osteotomies may disturb the vascular capacity of the affected limb, and give a negative impact on bone regeneration. And the tibia anatomical structure changes in the middle and lower third , which results in fewer nutrient vessels here, increasing the risk of delayed union or even nonunion. The basis for the greater incidence of these is also likely related to a temporary imbalance between bone resorption and apposition at a time when loading rapidly increases due to bone transport, which causes few cortical layers to bridge the middle regenerate zone in the consolidation stage. The same phenomenon was noticed by Borzunov et al.[27, 28], they recommended using imaging to monitor the status of regenerated bone and adjust the distraction rate timely to avoid bone ischemia. Thus, the chief surgeon should fully understand the anatomical structure of the lower extremities and make a correct approach for the protection of the periosteum at the osteotomy site before the operation to reduce the probability of delayed union. Besides, the method was recommended by scholars that autologous cancellous bone grafting of the docking site at the end of distraction do a favor to avoid the occurrence of delayed union[6, 29–31]. In our study, the patients with delayed union managed with additional surgery of bone grafting and walking with the help of a walking aid after removal of the external clamps to achieve dynamization to promote bone healing. Finally, bone union was obtained.
Some surgical methods [27, 28, 32–36], which can prevent its potential complications and bring about better clinical outcomes have been proposed to reduce the external fixation index. For example, bone transport using the unilateral fixator and locking plate/intramedullary nail to fix simultaneously to avoid prolonged wearing of external fixators. However, these methods require additional surgery, which is no doubt to leave a worse psychologic pressure and monetary burden for patients, given their multiple failed previous surgeries. Fortunately, it is universally accepted that the trifocal bone transport is born to shorten the external fixation index and reduce the complications during the implementation of distraction osteogenesis [12, 21, 37], which requires a less surgical procedure. Trifocal bone transport can partition the distraction gap and perform bone distraction in segments, which reduces the tensile stimulation to the middle of regenerated bone and avoid the occurrence of bone ischemia. In this study, satisfactory results of this technique were obtained in the treatment of lower limb infected bone defects. The patients in the femur group had shorter bone transport time (40.41 ± 8.67 vs 45.45 ± 5.75 days), shorter consolidation time (231.54 ± 3.31 vs 250.46 ± 2.99 days), shorter bone union time (323.72 ± 5.66 vs 344.25 ± 3.69 days), shorter external fixation time (334.49 ± 8.54 vs 344.64 ± 3.64 days), and smaller external fixation index (55.96 ± 2.96 vs 65.02 ± 1.29 days/cm). Trifocal bone transport in femurs was associated with significantly shortened external fixation time, and higher quality of bone healing (excellent/good/fair/poor, 3/11/3/1 vs 2/13/4/2), and recovery of limb function (excellent/good/fair/poor, 3/14/1/0 vs 4/13/3/1) than the tibia group, but this was accompanied by an increased complication rate (femur vs tibia, 94.4% vs 76.2%). According to our observation, more attention should be paid to the situation of the timely management of complications associated with abundant soft tissue during femoral bone transport. At the same time, alertness needs to be paid for the prompt response to the bone ischemia (hourglass-like or thin central cylinder showed by X-ray), which often occurred in the tibia during the process of bone transport and led to delayed union or nonunion. If nonunion occurred, the mechanic solutions published by Borzunov et al. maybe a practical way to salvage the limb.
There are some limitations to this study. First of all, it was conducted retrospectively rather than as a randomized controlled trial, and the chart review process is possibly subject to assessor bias. Secondly, as our data represent the experience of one group of surgeons at a single institution, the potential for selection and information bias exists and our results are subject to the influence of surgeon experience, and patient selection preferences. Thirdly, long-term follow-up is required to assess the eventual efficacy of this strategy to enable better tailoring of the treatment strategy for individual patients.