Prevalence and clinical outcomes of hip fractures and subchondral insufficiency fractures of the femoral head in patients with tumour-induced osteomalacia.

Abstract

Tumour-induced osteomalacia (TIO) is a rare paraneoplastic syndrome usually caused by phosphaturic mesenchymal tumours, leading to great distress due to bone pain and affecting quality of life (QoL). This study aimed to investigate the prevalence and clinical outcomes of hip fractures and subchondral insufficiency fractures (SIF) of the femoral head. Twelve TIO patients were treated between January 2000 and December 2016 at our hospital. All underwent surgery for the tumour causing TIO, and complete removal of the tumour was accomplished in nine of 12 cases. Plain radiographs of the hip were obtained in all cases, and magnetic resonance imaging (MRI) was obtained from 15 hips representing eight patients before tumour removal. We evaluated the prevalence of hip fractures or SIF and their clinical outcomes. Hip fractures were observed in six of 12 cases, and the total number of fractures was nine, of which five were femoral neck, two were intertrochanteric and two were subtrochanteric fractures. Conservative treatment, regardless of complete remission of TIO, was successful except in one case with impending subtrochanteric fracture. SIFs were observed in 11 of 24 hips. Seven of 11 hips with SIF showed progression after surgery for tumour resection. Hip fractures and SIF are highly prevalent in TIO patients. Surgical and medical treatment for TIO is sufficient for treating hip fractures conservatively. However, SIF tends to show progression of femoral head collapse, serving as the main cause of pain after successful TIO treatment.