Patients
This retrospectively study included 282 patients who underwent bone transport procedures in lower extremity using the Ilizarov method at our institution from Jan 2007 to June 2017, including 243 male and 39 females with a mean age of 40 years (range 18-65 years). Patients older than 18 years with bone defect more than 3 cm in the lower extremity and received bone transport procedure using the Ilizarov method were included. Patients with bone defect caused by pathological fractures, associated vascular and nerve injury, age >65 years, poor compliance, and any other illness that can affect bone healing (such as diabetes, hypertension, osteoporosis, kidney disease, etc.) were excluded. This study was approved by the Ethical Committee of our institution.
Surgical technique
Surgical treatment started by radical debridement. We resected the devitalized or infected bone segments by using an oscillating saw according to the limit of healthy bleeding bone. Cortical bleeding with the tourniquet deflated, described as the so-called paprika sign, was accepted as an indication of vital tissue20. In addition, the infected or necrotic soft tissues, especially the sinus tracts, were all debrided adequately. The debridement of bone and soft tissues might perform several times if needed, just keep the residual bony ends flat for better healing. At least 6 samples were taken to culture during operation for all patients. If there was a soft tissue defect, surgical intervention was performed with flap transfer or free skin grafting after infection controlled.
Bone transport was performed when clinical manifestations and laboratory indicators showed there is no infection. Preoperative anteroposterior and lateral X-rays were used to evaluate the defect size and plan the construction of the external fixator. The type of external fixator was comprehensive determined by the location of bone defect and patients’ opinion. We conducted bone transport by a minimally invasive osteotomy at the proper site using Gigli saw technique and care was given to preserving as much periosteum as possible. Bone defect which larger than 8 cm or exceeded 40% of the injured bone underwent a double level bone transport21-23 procedure. All the procedures were conducted by the same surgical team.
Data collection
The demographic data include age, sex, weight and height (BMI = weight (kg) /height (m2)), injured bone, location of bone defect (proximal, middle and distal), defect size(DS), type of external fixation (circular (TrueLok Ring Fixation System, Orthofix, Verona, Italy) or monolateral (Limb Reconstruction System, LRS, Orthofix, Verona, Italy)), type of bone transport (single level and double level), direction of bone transport(from proximal to distal or distal to proximal in single level and converging or “twin” transport in double level) were collected.
Postoperative data were recorded which include distraction regenerate length (DRL), docking time (DT), regenerate consolidation time (CT), external fixation time (EFT), external fixation index (EFI) and type of difficulties occurred during and after bone transport procedure. The EFT referred to the time spend on before removal of the external fixator. The EFI was defined as the ratio of the days of EFT to the DRL (centimeters). Radiographic evaluation was conducted every 2 weeks during the bone transport period and every month in the consolidation phase. All patients were closely followed up at minimum of two years after the removal of external fixator (EF).
According to Paley24, difficulties that occur during limb lengthening were subclassified into problems, obstacles and complications. Problems represented difficulties that required no operative intervention to resolve, while obstacles represented difficulties that required an operative intervention. All intraoperative injuries were considered true complications, and all problems during limb lengthening that were not resolved before the end of treatment were considered true complications. True complications were subclassified as minor and major complications. Minor complications did not affect the final result or required nonoperative or a minor operative intervention, while major complications required a more complex and unplanned operative intervention or resulted in permanent sequelae. The bone and functional results were assessed by ASAMI21 at the last clinical visit.
Postoperative management
All patients were encouraged to do isometric muscle and joint range of motion (ROM) exercise within the tolerance of pain on the second day after surgery. Antibiotics that are suitable according to the results of cultures and antibiotic susceptibility tests are applied intravenously for at least 3 weeks or until the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels return to normal limits.
According to the reference data25, 26, after latency period of 7 to 10 days, bone transport started at a rate of 1mm (single level) or 2 mm (double level) daily, 4 times a day. The rate of bone transport was adjusted according to patients’ tolerance and the quality of the regenerate. The procedure of bone transport continued for 4 or 5 days to compress the docking site after the docking. The external fixator was dynamized before removal. And removal of the external fixator was conducted when the standard orthogonal radiographs showed sufficient consolidation of the distraction zone (dense bone formation) and solid docking site union (corticalization in 3 of 4 cortices). Additionally, all patients were put on the functional brace for 4-6 weeks for the protection of refracture
Statistical analysis
Statistical analysis was performed with the SPSS 22.0 (IBM Corp, USA) and R Studio (Version 1.2.5001) with rms, ROCR, gplots and forest plot packages. Continuous variables were analyzed by Independent-samples T tests and expressed as the mean and standard deviation. And the count variables were analyzed by the Chi-square or Fisher’s test, expressing as number. Statistically significant difference was set at P < 0.05.
Variables with P < 0.05 were identified in the univariate logistic regression analysis (ULRA). And the variables with P < 0.1 in the ULRA were included in the multivariate logistic regression analysis (MLRA), then variables with P < 0.05 were screened out by the stepwise method and these variables were used to construct the nomograms. Finally, the ability of nomograms to distinguish the models was evaluated by the area under the curve (AUC) of the receiver operating characteristic (ROC) curve.