[Sacral fracture as a rare early complication of lumbosacral spondylodesis]

A 57 year old patient with secondary cortisone induced osteoporosis war surgically treated by means of posterior lumbar interbody fusion with internal fixation from L4-S1 for symptomatic instability in the level L4/5 after previous dorsal stabilisation L5/S1. After an unapparent initial postoperative phase, the patient complained of severe pain in the low back and gluteal region 9 day after surgery. Radiographs as well as CT-scans showed a horizontal fracture of the sacrum. After a short period of immobilisation the patient was carefully remobilised with an orthesis and the pain gradually subsided. Conventional radiographs one year later showed complete consolidation of the fracture and a good clinical result. There are only two literature reports with together 3 cases of patients attaining an early sacral fracture after spondylodesis. The main cause seems to be the unphysiological biomechanical stress placed on the osteoporotic sacrum after moresegmental spondylodesis. Further risk factors seem to be adipositas, female gender and age. Despite the rarity of sacral fractures after lumbosacral fusion, this complication should at least be considered in the differential diagnosis in patients who complain of persisting or sudden-onset pain after surgery.