A Case of Femoral Neck Insufficiency Fracture due to Tumor-Induced Osteomalacia

Abstract

Tumor-induced osteomalacia (TIO) is a rare skeletal disease caused by hypersecretion of fibroblast growth factor 23 (FGF-23) from neoplasms of mesenchymal origin; patients with TIO present with insufficiency fractures, progressive bone pain, and delayed fracture unions. Herein, we report the case of a 48-year-old man with an insufficiency fracture in his left femoral neck associated with TIO. The causative tumor located in the patient’s maxillary sinus had been resected; however, complete resection was impossible due to the location of the tumor. Therefore, the patient’s osteomalacia persisted, and he experienced a left femoral neck fracture in the absence of severe trauma. Because delayed fracture union was anticipated in this patient, we performed an internal fixation using an implant with a lateral plate for angular stability and multiple screws for rotational stability. Although fracture union took 15 months, the patient’s postoperative course was uneventful, and he could walk without any symptoms or assistance at his most recent follow-up 30 months after surgery. In TIO, hypersecretion of FGF-23 leads to increased renal excretion of phosphorus, increased bone resorption of calcium and phosphorus, decreased osteoblastic bone mineralization, and decreased gastrointestinal absorption of calcium and phosphorus, leading to insufficiency fractures and delayed fracture unions. Diagnosis of TIO is often delayed due to its rarity and vague symptoms. Total resection of the causative tumor is the optimal treatment; however, in cases wherein complete tumor resection is impossible, drug therapy may be insufficient, and the underlying TIO pathology, including bone fragility, may persist. Early diagnosis of TIO is important for preventing insufficiency fractures; however, when fractures are unavoidable, the surgical treatment of femoral neck fractures in patients with osteomalacia should account for a longer time frame for complete fracture union and therefore utilize implants with sufficient stability.

Preoperative evaluation and orthopedic surgical strategies for tumor-induced osteomalacia

“…The pathogenic tumor located in the patient's maxillary sinus could not be completely removed. Therefore, the patient's symptoms persisted, and without serious trauma, he experienced a left neck femur fracture [123] . Due to expected delayed fracture healing, the surgeon used implants and multiple screws for internal fixation to achieve better stability [123] .…”

“…Therefore, the patient's symptoms persisted, and without serious trauma, he experienced a left neck femur fracture [123] . Due to expected delayed fracture healing, the surgeon used implants and multiple screws for internal fixation to achieve better stability [123] . During the 30-month follow-up period after surgery, the patient showed no symptoms and was able to achieve independent walking [123] .…”

“…Reducing bone density in osteomalacia leads to fractures and increases the risk of bone non-union or delayed bone healing [122] . Inoue et al [123] reported a 48-year-old male TIO case with left neck femur insufficiency fracture. The pathogenic tumor located in the patient's maxillary sinus could not be completely removed.…”

“…Due to expected delayed fracture healing, the surgeon used implants and multiple screws for internal fixation to achieve better stability [123] . During the 30-month follow-up period after surgery, the patient showed no symptoms and was able to achieve independent walking [123] . The clinical course of TIO is gradual, therefore, early diagnosis is important for preventing bone-related events.…”