Insufficiency fractures (IF) occur when normal or physiological muscular activity stresses a bone that is deficient in mineral or elastic resistance. IF of the tibia and fibula are probably less common than IF of the ribs, vertebrae, hip, pelvis, and distal ulna, and therefore they are frequently underrecognized and mistaken for other conditions. Our aim was to analyze the main features and outcome of IF of the tibia and fibula in patients attending our Rheumatology Service.
IF was considered when occurring spontaneously or with minimal trauma. Between January 1984 and July 1997, 25 patients were diagnosed as having IF of the tibia and fibula. The main predisposing factors, clinical features, therapy, and outcome were retrospectively reviewed.
All the patients except four were women (mean age, 66+/-12 years). Three cases were diagnosed between 1984 and 1990 (0.42 cases/year) and 22 between 1991 and 1997 (three cases/year). Eighteen patients had an underlying condition: rheumatoid arthritis (RA, 13 cases), psoriatic arthritis (2), systemic lupus erythematosus (SLE) (1), kidney transplant (1), and Crohn's disease (1). Eleven patients had osteoporotic fractures in other locations. Risk factors for osteoporosis were corticosteroids (13 cases), prolonged immobilization (10), early menopause (2), and methotrexate therapy (10). All patients had pain on weight bearing and marked functional impairment, 16 had local inflammatory signs, and 10 had deformity. In only five patients the diagnosis of IF was considered at the first examination. The diagnostic delay was 76+/-117 days (median, 21). The initial radiograph was diagnostic in 20 patients, and in the remaining the diagnosis was made by computed tomography (CT) scan (three cases), magnetic resonance imaging (MRI) (1), and bone scan (1). IF were located as follows: tibia (10 cases), fibula (seven), tibia and fibula (eight). Nineteen patients were treated with conservative management, four received no specific treatment, and two required surgery. Sixteen patients were hospitalized for a mean period of 12+/-8 days. Most patients had complete recovery. The high frequency of IF seen in RA patients is probably due to the severe disease in patients treated by our Service and that such patients have a higher risk for osteoporosis and its complications.
IF of the tibia and fibula are probably more common than previously thought. They usually occur in patients with underlying rheumatic diseases, mainly RA, and are frequently mistaken for other joint and bone conditions. Despite a frequent delay in diagnosis, they have a good prognosis with conservative management. Nonetheless, a higher index of suspicion may avoid unnecessary investigations and treatments.