Comparison of the use of intramedullary telescopic system and titanium elastic rods in children with osteogenesis imperfecta I and III types

Osteogenesis imperfecta (OI) is a rare disease characterized by frequent fractures and deformities of the bone skeleton due to collagen abnormalities. Clinically, OI is heterogeneous in its features and varies in severity. Frequent fractures as a result of brittle bones lead to malunion and deformity, which increases the risk of refraction. Surgical treatment of children with imperfect osteogenesis is aimed at reducing the number of fractures, the formation of deformities and improving the quality of life of the child. According to the literature, two main methods of intramedullary osteosynthesis in the surgical treatment of children with OI can be distinguished: static rods and a “growing” metal structure.

Aim. To compare the frequency of revisions and complications when using titanium elastic rods (TEN) and the Fassier-Duval telescopic system (FD) in the treatment of fractures and deformities of long bones in children with OI type I (mild disease) and type III (severe disease).

Materials and methods. A retrospective and prospective analysis of the results of surgical treatment in 38 children with OI using two different methods of intramedullary osteosynthesis was carried out. Among them, 26 children (68% of all studied patients) were of type III and 12 (32%) children of type I. The mean age of the patients was 7.8 years [5.2, 10.8]. The 1st study group (retrospective) included 17 patients (45% of all patients) who underwent surgical treatment with the installation of titanium elastic rods (TEN). A total of 46 surgical interventions were performed. Surgical treatment with the installation of titanium elastic rods (TEN) for patients was carried out in other medical institutions before hospitalization at the National Medical Research Center for Children's Health. The 2nd study group (prospective) included 21 patients (55% of the total number of patients in the study), who were implanted with FD telescopic rods, 53 surgical interventions were performed. Patients of the prospective group received surgical treatment on the basis of the neuroorthopedic department of the National Research Center for Children's Health. The study groups were structured as follows: Study Group 1 consisted of 2 subgroups. Subgroup A included 6 patients with OI type I, subgroup B included 11 patients with OI type III; The 2nd study group was represented by two subgroups. Subgroup C included 6 patients with OI type I, and subgroup D included 15 patients with OI type III. A total of 228 segments of the upper and lower extremities (humerus, femur and tibia) were examined. Surgical treatment using intramedullary osteosynthesis was performed on 99 segments. The average period of postoperative follow-up was 20 months (from 16.5 to 24.5 months), the data collection of the retrospective group was carried out in the period from 2015–2022, the prospective group from 2017–2022. Analysis of the results of surgical treatment according to the following criteria: the frequency of migration of metal structures, the formation of bone deformities, the number of bone fractures with an installed metal fixator in two different methods of osteosynthesis, as well as the number of revisions in OI types I and III. The results of motor activity in the retrospective and prospective groups were assessed using two scales (the Hoffer–Bullock scale, the Gillette Functional Assessment Questionnaire score scale), before the start of surgical treatment and after 20 months. The statistical analysis was performed using the Matplotlib, SciPy, Pandas и NumPy modules in Python 3.8. In all cases, the distribution was different from normal. The comparison of the independent groups was carried out using the Mann–Whitney test (in the case of comparing two samples), while the comparison of the dependent groups was carried out using the Wilcoxon test. To compare the distribution of the categorical features, the Pearson chi-square test and Fisher's exact test (with the number of observations in one of the cells in the table $2\times 2\le 5$) for the independent groups, and McNemar’s test for the dependent groups were used. In all cases, when the multiple comparisons were made, the level of the significance of p was recalculated using the Bonferroni correction. Hypothesis testing was two-sided; the values of p<0.05 were considered statistically significant.

Results. According to the comparison of two subgroups of the 1st study group, it was noted that fractures in two subgroups after the installation of static intramedullary nails occurred with an equal frequency (p-value>0.999). Among patients with OI type I, migration was observed in 13% of cases (2 segments), with OI type III in 48%. Deformity in type I OI was formed in 13% of cases, in type III in 39%. Revisions in children with type I OI were required in 13% of cases, in children with type III in 32%. According to the comparison of two subgroups of the 2nd study group, it was noted that fractures and migrations in two subgroups after the installation of a telescopic metal structure occurred with equal frequency (p-value>0.999). Deformity in type I OI was not formed, in type III it was 18%. Revisions in children with type I OI were required in 7.7% of cases, in children with type III in 15%. A comparative analysis of the results of surgical treatment of children with type I OI who underwent TEN osteosynthesis and children with type III OI who used a telescopic metal fixator demonstrates the absence of statistically significant differences in deformities, migrations, and revisions (p-value>0.999). Also, in the group of children with OI type III, osteosynthesis of which was performed by FD, there is a decrease in the risk of re-fracture by 10%, in comparison with the group of children with OI type I, osteosynthesis of which was performed by TEN. Also, according to the data of statistical processing, surgical treatment of children with OI type III using an intramedullary telescopic system makes it possible to achieve a level of motor activity comparable to the group of patients with OI type I (p-value=0.344), where osteosynthesis was performed using TEN.

Conclusion. The TEN method is a reliable method of treatment in children with OI type I, it is comparable to the method of telescopic metal construction in children with OI type I in terms of the frequency of migrations (p-value>0.999). However, the risk of repeated surgical interventions is increased by 5.3% compared with FD, the frequency of fractures is higher by 12.3%, the formation of deformities by 13%. The use of “growing” hardware in children with type III reduces the risk of possible refracture by 9%, migration by 36%, deformity by 21% and the number of revisions by 17% compared with static rods. Patients who underwent FD osteosynthesis showed higher results of motor activity than patients who underwent TEN osteosynthesis. The results of the frequency of complications and revisions in the group of patients with OI type III, in which osteosynthesis was performed by the telescopic FD system, are comparable with the group of patients with OI type I, in which osteosynthesis was performed with TEN static rods. The quality of life and motor activity of children in the group with a severe course, whose osteosynthesis was carried out with a “growing” metal structure, reaches the level of patients with a mild course of the disease, whose osteosynthesis was performed using TEN (p-value=0.344). The method of choice in the surgical treatment of children with OI, both in type I and type III, is a “growing” intramedullary metal structure. The use of static rods is acceptable in OI type I, however, it should be taken into account that this metal structure is effective for the first 12 months, later, due to the inability to reinforce the bone throughout its entire length, the risk of possible complications increases.