A 30-month prospective observational cohort study was led to assess the prevalence of and describe the clinical features of spontaneous long bone insufficiency fractures (LBIF) in the 'oldest old' patients of long-term nursing homes (LTNH). The study was conducted in 30 LTNH in northeast France, which represented 3052 beds. Subjects aged 65 and more showing LBIF were included in the present study. Clinical data and outcome were collected. Fifty-five LBIF were found. The prevalence of LBIF calculated on the basis of the number of patients consecutively admitted in LTNH was 1%. The mean age of the subjects was 85+/-7 years. The LBIF sites were as follows (1) hip fractures in 15 subjects (27%); (2) femoral shaft fractures in 13 subjects (24%); (3) tibia and/or fibula fractures in 14 subjects (25%); (4) humerus fractures in 11 subjects (20%); (5) cubitus in 2 subjects. The global mortality at 2 months was 24%. The poorest outcome was observed in the group with femoral shaft fracture who showed mortality of 54% at 2 months. The dramatic repercussions in outcome and quality of life in bedridden patients show that the detection of LBIF should not be neglected in nursing homes. There is no consensus for a preventive pharmacological treatment in these patients. Educational programs for 'proper handling' by the nursing staff are highly recommended.