Sacral insufficiency fractures: an unsuspected cause of low back pain [clinical conference]

We describe 10 cases of sacral fractures diagnosed within the rheumatologydepartment at Southend Hospital over the last 5 yr. All presented withsudden-onset low back pain. The majority were elderly, frail, with chronicinflammatory disease (six with rheumatoid arthritis, one with polymyalgiarheumatica, one with vasculitis) and had received steroids. Diagnosis wasdelayed by the inability of plain radiographs to show these fractures andwas ultimately demonstrated by technetium scintigraphy/computed tomographyscan. We feel that this diagnosis should be considered in elderly patientswith rheumatoid arthritis or other risk factors for osteoporosis whopresent with low back pain and sacral tenderness. Further clues may beparasymphyseal tenderness (suggesting associated pubic ramus fracture),elevated alkaline phosphatase and plain radiograph showing pubic ramusfractures or parasymphyseal sclerosis. Patients with this complicationgenerally have a poor prognosis and two of our patients have died. Sevenrequired in-patient stay (mean 20 days; range 14-41). The mortality,morbidity and costs incurred in management may be comparable to those offemoral neck fractures.