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Background: Osteogenesis imperfecta (OI) is a genetic connective tissue disorder affecting quantity and integrity of collagen type I, which is integral for the strength of osseus tissue. OI has a heterogenous molecular inheritance pattern – divided into four major subgroups (I-IV). Defects in collagen protein products lead to poor development of skeletal structures and increased fracture rates. Children with OI suffer from multiple fractures and bone deformities often requiring surgical intervention with osteotomies and intramedullary telescoping rods, most often with Fassier-Duval (FD) rods. Our study–updated cohort from 2018 paper Azzam et al.–looked at the relationship between initial and reoperation indications for femur and tibia FD rodding surgeries based on age, bone, and OI type.

Methods: Retrospective chart review of initial surgeries included 197 bones (femurs and tibias) from 58 patients. Reoperations included 140 bones from 45 patients. Variables included age at first operation (0-24, 24.1-48, 48.1+ months), time to reoperation, operation indications, bone, and OI type. Spearman correlations were used separately for each bone-type to assess associations between age at first surgery and total number of surgeries. To assess dichotomous outcomes (i.e. specific indication), generalized estimating equations were utilized and adjusted for bone-type and side. Hazard ratios and associated 95% confidence intervals were derived from frailty survival models for the time to first reoperation outcome. Kaplan-Meier curves were generated to display time to reoperation, stratified by age at first operation and bone-type. Data was collected from 2003-2018. Analyses were performed using SAS software v9.4.

Results: There was a statistically significant correlation between age at first surgery and indication (bowing and fracture) for initial (p<0.0001, p=0.01) and reoperation surgeries (p=0.004, p=0.03), respectively. All bones, except left tibias, showed significant negative correlation between age at first surgery and total number of surgeries. Both older age at first surgery groups (24.1-48, 48.1+ months) had significantly lower risks of needing reoperation relative to the 0-24 months group (p=0.0003, p=0.0004). Descriptive analyses suggest median survival of FD rods in OI type III was decreased relative to type IV, XV or unknown when initial surgery was between 0-24 months.

Conclusion: Bowing and fractures are the most common causes for initial and reoperation surgeries in children with OI. Patients in older age groups at first surgery need fewer reoperation surgeries. Median survival probabilities of FD rods increased when age at first surgery was after 48.1+ months. OI type may impact median survival of FD rods.

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Femoral and Tibial Indications for Initial and Reoperation Surgeries with Fassier-Duval Intramedullary Rods for Children with Osteogenesis Imperfecta

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