[Clinical study of Cross-Union surgery for treatment of pseudarthrosis of tibia with neurofibromatosis type 1 in children].

Objective: To evaluate the effectiveness of Cross-Union surgery for the treatment of pseudarthrosis of the tibia (PT) with neurofibromatosis type 1 (NF1).

Methods: The clinical data of 8 children of PT with NF1 who met the selection criteria between January 2018 and December 2023 was retrospectively analyzed. There were 5 boys and 3 girls, and the operative age ranged from 1.8 to 13.3 years with a median age of 3.5 years. According to Paley classification, there were 2 cases of type 2a, 2 cases of type 3, 2 cases of type 4a, and 2 cases of type 4c. There were 5 cases of first operation and 3 cases of re-fracture after previous operation. Six cases had leg length discrepancy before operation, and 2 of them had shortening over 2.0 cm. Except for 1 case of ankle fusion, the other 7 cases had ankle valgus. Preoperative coronal/sagittal angulation was recorded. Postoperative pseudarthrosis healing and refracture were observed. Leg length discrepancy and tibiotalar angle were measured and recorded before operation and at last follow-up. Inan imaging evaluation criteria was used to evaluate the imaging effect.

Results: All patients were followed up 12-37 months (mean, 23.5 months). One pseudarthrosis failed to heal at 12 months after operation and healed at 3 months after reoperation, while the other pseudarthrosis healed with a healing rate of 87.5% and a healing time of 4-8 months (mean, 5.3 months). No refracture occurred during the follow-up. At last follow-up, there were 2 new cases with leg length discrepancy, which were 0.7 cm and 1.3 cm, respectively. In 2 cases with the leg length discrepancy more than 2.0 cm before operation, the improvement was from 4.1 cm and 12.6 cm to 2.1 cm and 9.0 cm, respectively. There was no significant difference in leg length discrepancy between pre- and post-operation in 8 cases ( P>0.05). At last follow-up, 6 patients still had ankle valgus, and there was no significant difference in the tibiotalar angle between pre- and post-operation ( P>0.05); the tibial coronal/sagittal angulation significantly improved when compared with that before operation ( P<0.05). According to Inan imaging evaluation criteria, 1 case was good, 6 cases were fair, and 1 case was poor.

Conclusion: Cross-Union surgery is an effective method for the treatment of PT with NF1 in children, can achieve good bone healing results with a low risk of re-fracture. The surgery may not have significant effects on leg length discrepancy and ankle valgus, and further treatment may be required.