Pedicle fracture after instrumented posterolateral lumbar fusion: a case report

STUDY DESIGN: The case report of a 60-year-old man with late onset back pain after lumbar spine fusion is presented. OBJECTIVE: To report the rare complication of bilateral pedicle stress fractures after instrumented posterolateral lumbar fusion. SUMMARY OF BACKGROUND DATA: A 56-year-old man underwent revision spinal surgery for ongoing back pain secondary to pseudoarthroses. A posterolateral L4-S1 instrumented fusion using pedicle screws was performed. Autologous bone graft was applied to the decorticated lateral masses. The internal fixation was removed 2 years later, at which time plain radiographs showed that the fusion mass was solid. At the age of 60 years, the man presented with worsening back pain. Plain radiographs and computed tomographic scans demonstrated bilateral L4 pedicle stress fractures. A bone scan indicated that these were recent in origin. METHOD: The clinical assessment was undertaken by the senior author and surgeon. Investigations included plain radiography, computer tomography, and scintographic imaging. A systematic literature review of the relevant publications was performed. RESULTS: In the reported patient, bilateral pedicle stress fractures developed 2 years after pedicle screw removal from an L4-S1 instrumented posterolateral lumbar spine fusion. This occurred at the uppermost level of the fusion mass. CONCLUSIONS: The pedicle is the weakest point in the neural arch after posterolateral fusion. Although movement continues at the level of the disc space anteriorly, the pedicle is susceptible to fracture. Pedicle fracture is a rare late complication of posterolateral lumbar spine fusion.