Bilateral pedicle stress fracture after instrumented posterolateral lumbar fusion: a case report.

Methods: A case of bilateral pedicle stress fracture is reported, and the literature is reviewed. Objective: To report the rare case of bilateral pedicle stress fracture after instrumented posterolateral fusion, and to investigate the contributing factors.

Background: A 62-year-old man underwent revision spinal surgery for adjacent-segment degeneration. Decompression and instrumented posterolateral fusion from L1 to L3 were performed after removal of the previously inserted pedicular screws. In the patient's history, he had undergone L3-L5 instrumented posterolateral fusion for spinal stenosis 6 years previously. At 1 year after the revision surgery, he presented with severe progressive low back pain. Computer-assisted tomogram and bone scan demonstrated bilateral L4 pedicle stress fracture. To the best of the authors' knowledge, only two cases of pedicle stress fracture after lumbar posterolateral fusion have been reported.

Methods: This study reviewed the reported patient's medical record, his imaging studies, and related literature. The possible factors contributing to bilateral pedicle stress fractures were investigated.

Results: In the reported case, the features of radiographic studies confirmed bilateral pedicle stress fracture. The involved vertebra was L4. In all three cases reported so far, including the current case, the site of the pedicle stress fracture was at the junction of the pedicle and vertebral bodies.

Conclusions: Bilateral pedicle stress fracture occurs as a complication of posterolateral lumbar fusion. Pedicle weakening by prior inserted screws and persistent anterior motion after posterolateral fusion are the contributing factors.