Sandwich vertebral fracture in the study of adjacent-level fracture after vertebral cement augmentation.

The literature is inconclusive on the development of adjacent-level vertebral fracture after initial cement augmentation. A preliminary hypotheses is that cement injection exaggerates force transmission to the adjacent vertebral bodies, thereby predisposing those levels to future fractures. A sandwich vertebra is an intact vertebral body located between 2 previously cemented vertebrae. The purpose of this study was to determine whether the risk of adjacent-level fracture increased due to load shift after a cement injection procedure. The authors retrospectively investigated the rate of adjacent-level fracture after sandwiching compared with conservative treatment and determined the potential causative factors of sandwich vertebral fracture. Age, sex, weight, height, body mass index, follow-up period, and location of sandwich level (T10-L2 or nonT10-L2 junction) were assessed. Surgical variables, including surgical procedure (vertebroplasty or balloon kyphoplasty), surgical approach (through uni- or bilateral pedicle), volume of cement injected into the painful vertebrae, cement leakage into the intervertebral disk, cumulative number of treated levels, and pre- and postoperative kyphotic angulation of the sandwich region, were also analyzed. Nine of 42 sandwiched levels developed fatigue fractures, whereas 11 of 71 patients treated with conservative therapy sustained new vertebral fractures adjacent to the treated levels. Only preoperative kyphotic angulation was the variable positively associated with sandwich vertebral fracture at follow-up (P=.021). Although subjected to double load shifts, the sandwich vertebra was not prone to structural failure. Thus, cement augmentation protocol does not increase the incidence of adjacent vertebral fracture.