After malignant tumor cells reach the bone marrow with the blood flow, they interact with osteoblasts, osteoclasts and bone stromal cells to destroy bone tissue, release a variety of growth factors stored in bone tissue, and proliferate tumor cells and form metastatic lesions. The presence of bone metastatic disease destroys the normal structure of the bone and can lead to pathological fractures. Among them, bone metastasis can be divided into three types: lytic, osteogenesis and mixed. For example, the metastasis of breast and lung cancer is predominantly osteolytic, and the metastasis of prostate cancer is predominantly osteogenesis.
In 1989, Mirelsr proposed a risk scoring system for pathological fractures of limbs, which consisted of four variables: lesion location (upper extremity, lower extremity, and around the trochanter); pain (mild, moderate, severe); lesion type (lytic, osteogenesis, mixed); and cortical destruction (< 1/3, 1/3 to 2/3, >2/3). (Figure 1) Mirels scored a total of 12 points, with a ≤ of 7 points indicating a low risk of pathological fractures, a fracture risk of 15% at 8 minutes, and a fracture risk of 33% at 9 minutes. Prophylactic fixation should be performed when the score > 9.
Clinically, it is necessary to pay close attention to pathological fractures, because this affects the quality of life, affects the patient's ability to move, and if necessary, requires surgical treatment. Previous studies have shown that pathological fractures reduce survival, while patients who avoid fractures through prophylactic fixation have less bleeding and lower incidence of postoperative complications than patients treated urgently after fractures. Therefore, it is important to predict the risk of pathological fractures and perform preventive fixation.
