A Novel Finding of Type V Osteogenesis Imperfecta: A Distinctive Pattern of Hip Dysfunction

Abstract

Introduction: In 2000, Glorieux et al. described a novel type of osteogenesis imperfecta (OI). Albeit resemblance with type IV in terms of severity, distinguishing radiological features including post-fracture hyperplastic callus (HPC), calcification of interosseous membrane (CIM) and radial head dislocation (RHD) were present. This clinical presentation was therefore termed type V OI. Additional patterns of clinical and radiological features were noticed over the years. This study aims to describe these findings which might influence the management of this rare condition. Method: Patients admitted for inpatient care at The Hong Kong University-Shenzhen Hospital and Duchess of Kent Children Hospital between January 2006 and May 2018 with a diagnosis of type V OI (6 diagnosed clinically or 13 diagnosed genetically with the IFITM5 c.-14C>T mutation) were recruited, with a total of 19 patients. Results: A novel finding is spontaneous autofusion of the hip in type V patients (22.22%). Prevalence of type V radiological features were comparable to that reported in previous literatures (HPC: 72.22%, CIM: 82.35%, RHD:100%). HPCs were located at femur (86.35%), tibia (9.09%) and humerus (4.04%). With peri-operative use of indomethacin, 25.00% patients develop HPC postoperatively. Comparatively, 60.00% patients who did not receive indomethacin developed HPC. Patients with hip autofusion and large HPC located near the joints significantly influenced the neighbouring joint motion. Discussion: This is the first paper presenting the functional impairment resulting from hip autofusion in OI type V patients. The underlying mechanism of hip autofusion is not yet known. There is a high prevalence of HPC developing in the femur as compare with other locations. An important observation is the low incidence of HPCs after surgical intervention to bones in patients with peri-operative use of indomethacin. The effectiveness of indomethacin in prevention of hyperplastic formation is yet to be confirmed with controlled study.