BackgroundThe purpose of this study was to investigate the initial union rate, refracture rate and residual deformities of congenital pseudarthrosis of the tibia (CPT), using combined surgery including pseudarthrosis resection, intramedullary rodding, autogenous iliac bone grafting and Ilizarov’s fixator, with a mean 5.2 years follow-up.MethodsWe retrospectively reviewed the records and diagrams of patients with Crawford type IV congenital pseudarthrosis of the tibia between February 2007 and March 2010. Patients managed by pseudarthrosis resection, intramedullary rod of the tibia, wrapping autogenous iliac bone grafting and Ilizarov’s fixator were enrolled. We evaluated the bone union rate, tibial alignment, limb length discrepancy (LLD), valgus deformity of the ankle and the frequencies of refracture during period of follow-up.ResultsThere were 56 cases enrolled in the study, with a mean follow-up 5.2 years (range, 3 to 6.7 years). The mean age of the patients at surgery was 3.5 years (range, 1.5 to 12.4 years). Fifty (89.2 %) of the 56 patients had primary bone union at site of pseudarthrosis, while 5 obtained union after second surgery and 1 failed. The average time spent to obtain pseudarthrosis initial union was 4.5 months (range, 3.0 to 10.0 months) and mean duration of Ilizarov treatment was 4.7 months (range, 3.2 to 10.4 months). Eleven (19.6 %) patients had proximal tibial valgus with a mean angle of 9.5° (range, 5 to 24°), while 10 (17.9 %) patients had ankle valgus deformities with a mean of 12.3° (range, 6 to 21°). Sixteen (28.6 %) patients had an average 2.2 cm LLD (range, 1.5–4.2 cm). Of the 50 cases who obtained initial bone union of pseudarthrosis, 13 (26.0 %) had refracture which need cast immobilization or secondary surgery.ConclusionsThis combined surgery obtained initial union rate of 89.2 % at primary surgery while the refracture rate is 26.0 %. However, residual deformities such as proximal tibial valgus, LLD and ankle valgus were also existed which should be pay more attention to and dealt with.Trial registrationThis study was registered in ClinicalTrials.gov under the name “The Effect of Combined Surgery in Management of Congenital Pseudarthrosis of Tibia” (NCT02640040), which was released on August 31, 2015.

Background: Re-fracture is the most serious complication in congenital pseudarthrosis of the tibia (CPT). There are reports that children with small cross-sectional areas in the sections of the pseudarthrosis are more prone to refracture. Presently, preventing complications is a challenge. Increasing the cross-sectional area in healed segments may reduce the incidence of re-fracture. Purpose: To elucidate the indications, surgical technique, and outcomes of combined surgery and 3-in-1 osteosynthesis in CPT with intact fibula. Methods: We retrospectively assessed 17 patients with Crawford Type IV CPT with intact fibula (Type A) who were treated with combined surgical technique and 3-in-1 osteosynthesis between March 2014 and August 2015. The average age of the patients at the time of surgery was 3 years. Incidence of re-fracture, ankle valgus, proximal tibial valgus, and limb length discrepancy (LLD) were investigated over an average follow-up time of 47 months. Results: Primary union was achieved in all patients. The average time for primary union was 4.9 months. Fifteen (88%) cases showed LLD with an average limb length of 1.6 cm; 6 (35%) cases exhibited tibial valgus with an average tibial valgus deformity of 7.8°; 2 cases had ankle valgus, wherein the ankle valgus deformity was 12°in one and 17°in another; and the cross-sectional area of the bone graft was enlarged to 1.74 times that of the tibia shaft. No case had re-fracture during the follow-up period. Movement of the ankle joint was restored in 16 patients with an average dorsiflexion of 22°and an average plantar flexion of 41°; the function of the ankle joint was normal. One patient had plantar flexion of 20°but did not have dorsiflexion. Conclusion: Combined surgical technique with 3-in-1 osteosynthesis, which is primarily considered for bone union with a large cross-sectional area, results in a high primary union rate. This can provide satisfactory results in shortterm follow-up when treating CPT with intact fibula (Type A).

Background Congenital pseudarthrosis of the tibia (CPT) is a rare disease. Some patients present neurofibromatosis type 1 (NF1), while some others do not manifest NF1 (non-NF1). The etiology of CPT, particularly non-NF1 CPT, is not well understood. Here we screened germline variants of 75 CPT cases, including 55 NF1 and 20 non-NF1. Clinical data were classified and analyzed based on NF1 gene variations to investigate the genotype-phenotype relations of the two types of patients. Results Using whole-exome sequencing and Multiplex Ligation-Dependent Probe Amplification, 44 out of 55 NF1 CPT patients (80.0%) were identified as carrying pathogenic variants of the NF1 gene. Twenty-five variants were novel; 53.5% of variants were de novo, and a higher proportion of their carriers presented bone fractures compared to inherited variant carriers. No NF1 pathogenic variants were found in all 20 non-NF1 patients. Clinical features comparing NF1 CPT to non-NF1 CPT did not show significant differences in bowing or fracture onset, lateralization, tissue pathogenical results, abnormality of the proximal tibial epiphysis, and follow-up tibial union after surgery. A considerably higher proportion of non-NF1 patients have cystic lesion (Crawford type III) and used braces after surgery. Conclusions We analyzed a large cohort of non-NF1 and NF1 CPT patients and provided a new perspective for genotype-phenotype features related to germline NF1 variants. Non-NF1 CPT in general had similar clinical features of the tibia as NF1 CPT. Germline NF1 pathogenic variants could differentiate NF1 from non-NF1 CPT but could not explain the CPT heterogeneity of NF1 patients. Our results suggested that non-NF1 CPT was probably not caused by germline NF1 pathogenic variants. In addition to NF1, other genetic variants could also contribute to CPT pathogenesis. Our findings would facilitate the interpretation of NF1 pathogenic variants in CPT genetic counseling.