Although Paget's disease of the bone is a relatively common disease in Australia, New Zealand, North America and most European countries, but it has a low incidence in Scandinavia, and is extremely rare in the Japanese population, with a prevalence of 0.15/100000; in patients aged 55 years of more, the proportion reaches 0.41/100000 [1–4, 6]. The characteristic feature of Paget's disease is excessive bone resorption coupled with increased and disorganized bone formation. The affected bone is enlarged, disorganized in structure, and weakened. Pathological fractures are the most common complication of Paget's disease, and the treatment of such fractures is challenging. An increased rate of complications including delayed union, non-union, and malunion in pagetic bone fracture has been reported [8–10]. Open reduction and internal fixation of fractures has been recommended to prevent such complications. However, plate and screw fixation requires extensive exposure, and in the present patient this was not possible because of her poor medical condition. Recently, there have been some reports of good fracture healing with the use of intramedullary nailing [11, 12]. However, the latter is available only for mild bowing deformities. In the present patient, we decided to use an external fixator to fix this pathological fracture because of the above situation. However, after 6 months of treatment, the external fixator had to be removed due to pin site infection, even though fracture union had not been obtained. We then had no alternative but to apply a functional brace for delayed union of the femur fracture with the aim of allowing the patient to walk on crutches, although, to the best of our knowledge, no familial cases were found in the reported cases. Fortunately, in this case, fracture union was obtained 6 months after application of the functional brace. This treatment period is comparable to that reported by others using functional brace in the treatment of delayed union of the tibia [13–15]. We speculate that this treatment was advantageous because the external fixator and functional bracing did not violate the fracture site, allowing vascular regeneration and eliminating further damage to the peripheral and intramedullary blood supply which occurs during plate and screw fixation and intramedullary nailing. The success of this treatment suggests that functional bracing, a biological fracture treatment, may be a viable alternative for the treatment of fracture, delayed union, and non-union resulting from Paget's disease of the bone. This would be especially useful in the elderly and those considered at high risk from major corrective surgery. In recent years, the concept of biological osteosynthesis has gained a reputation in fracture treatment. Minimally invasive plate osteosynthesis (MIPO) techniques minimize the extent of soft tissue trauma to the injury zone, theoretically maintaining a better blood supply around the fracture area. Treatment of fractures secondary to Paget's disease using MIPO techniques might avoid the significant complications associated with more commonly used techniques of internal fixation.
This unusual case of delayed union of the femur fracture associated with Paget's disease of the bone for which functional bracing was ultimately successful illustrates the usefulness of biological fracture treatment in patients with this potentially refractory condition.