SPINAL METASTATIC DISEASE

Abstract

Objective: In 1989 Mirels published a scoring system for identifying impending pathological fractures in long bones, and it is now standard practice that long bones with metastases at risk of fracture are treated with prophylactic internal fixation. The spine is the most common site of skeletal metastases, with spinal metastases present in up to 36% of patients with terminal cancer. A pathological fracture through a vertebral body can result in paralysis, incontinence and severe pain. However, there is no equivalent of the Mirels’ scoring system to aid the spinal surgeon in determining the probability of an impending spinal fracture.

A weighted scoring system is proposed to quantify the risk of sustaining a pathological fracture through a metastatic lesion in a vertebral body. This system analyzes and combines four magnetic resonance (MR) risk factors into a single score.

Methods: A retrospective analysis of 100 vertebral body metastatic lesions was carried out. The original MR scans were scored, and the subsequent imaging was used to identify which vertebral body lesions fractured. Patients with no subsequent imaging within 12 months were excluded.

Results: Twenty of the 100 lesions fractured within 12 months. A mean score of 0.64 was identified in the non-fracture group, where as the fracture group had a mean score of 6.80. The percentage risk of a lesion sustaining a pathological fracture was calculated for any given score. As the score increased above 3, so did the percentage risk of fracture (sensitivity 90%, specificity 91%).

Conclusions: The authors propose that all painful vertebral body metastatic lesions be evaluated by MR scanning. Lesions with a score of 2 or less can be left untreated, while lesions with scores of 3 or higher should be considered for prophylactic balloon kyphoplasty.