[Bilateral pathological sub-trochanteric fracture in a long-term biphosphonate user]

The number of papers reporting the occurrence of specific pathological fractures in long-term biphosphonate users has recently increased. They refer to the forms of stress fracture probably resulting from an extreme decrease in bone turnover, which may involve sub-trochanteric or isolated transverse fractures, or short transverse fractures with a unicortical beak in an area of cortical hypertrophy. At the time of prodromal signs and symptoms, cortical bone at the site of impeding fracture appears rougher on radiographs. Gradually, an incomplete fracture develops, with a subsequent complete fracture often sustained without any mechanism of injury noted. The occurrence of such fractures is reported in the range of 2 to 8 years from the start of biphosphonate use. The fractures are often bilateral and, at the time the first occurs, it is often possible to diagnose contralateral pathological changes similar to those before the first fracture. The paper presents the case of a female patient who sustained a bilateral pathological sub-trochanteric fracture; the first fracture occurred after 5 and the other after 9 years of Rizendronat use. She was followed up for unilateral incomplete sub-trochanteric fracture from the fourth year of its use. In that period, magnetic resonance imaging showed a pathological finding in the contralateral extremity. She had already had prodromal signs manifested as lasting hip pain before the first fracture. Both fractures were surgically treated. Thirty-three months later she had to undergo repeat surgery for pseudoarthrosis at the site of the first fracture. The pseudoarthrosis healed without complications. However, in the second fracture non-union was still present at 7 months after surgery. The patient took Rizendronat during the whole treatment period and thereafter. In the discussion, certain aspects of long-term biphosphonate use are addressed, as well as some preventive, diagnostic and therapeutic procedures related to this rare complication.