Hardware Failure¶

Overview¶

Spinal hardware failure encompasses screw loosening, screw breakage, rod fracture, cage migration, and plate/screw pullout. Hardware failure is often associated with pseudarthrosis (failure of fusion) because the hardware is subjected to persistent cyclic loading without the stress-sharing of solid bone fusion.

Types¶

Screw Loosening¶

CT finding — Lucent halo (>2 mm) around the screw
Often at the most cranial or caudal screws (junction screws)
Causes: pseudarthrosis, poor bone quality (osteoporosis), infection

Screw Breakage¶

Fracture through the screw shaft, typically at the screw-rod junction
Best seen on CT

Rod Fracture¶

Break in the connecting rod, usually at the level of pseudarthrosis
Indicates ongoing motion at the non-fused segment

Cage Migration/Subsidence¶

Anterior, posterior, or lateral migration of an interbody cage
Subsidence (sinking) into the endplate — loss of disc height
Posterior migration into the spinal canal is a surgical emergency

Plate Pullout (Cervical)¶

Anterior cervical plate and screws backing out
Can impinge on the esophagus (dysphagia) or airway
Lateral radiograph shows increased distance between plate and vertebral body

Clinical Pearl

Rod fracture is a reliable indicator of pseudarthrosis — the rod breaks because it is bearing all the load at a segment that has failed to fuse. When you see a rod fracture, always evaluate that level for pseudarthrosis (absence of bridging bone on CT).

Key Points¶

Hardware failure is often associated with pseudarthrosis
Screw lucency >2 mm = loosening
Rod fracture suggests pseudarthrosis at that level
Cage retropulsion into the canal is a surgical emergency
CT is the best modality for hardware assessment
Always correlate hardware findings with fusion status

References¶

Young PM, Berquist TH, Bancroft LW, Peterson JJ. Complications of spinal instrumentation. RadioGraphics. 2007;27(3):775-789. https://pubs.rsna.org/doi/full/10.1148/rg.273065055
Wuertzer SD, Pohl EC, Stevens EA, Geer CP. Spinal fusion: role of perioperative radiography. RadioGraphics. 2023;43(4):e220061. https://pubmed.ncbi.nlm.nih.gov/36893053/
Corona-Cedillo R, Saavedra-Navarrete MT, Espinoza-Garcia JJ, Mendoza-Aguilar AN, Ternovoy SK, Roldan-Valadez E. Imaging assessment of the postoperative spine: an updated pictorial review of selected complications. BioMed Res Int. 2021;2021:9940001. https://pmc.ncbi.nlm.nih.gov/articles/PMC8154286/
Mohi Eldin MM, Ali AMA. Lumbar transpedicular implant failure: a clinical and surgical challenge and its radiological assessment. Asian Spine J. 2014;8(3):281-297. https://pmc.ncbi.nlm.nih.gov/articles/PMC4068848/
Wu X, Shi J, Wu J, et al. Pedicle screw loosening: the value of radiological imagings and the identification of risk factors assessed by extraction torque during screw removal surgery. J Orthop Surg Res. 2019;14(1):6. https://pmc.ncbi.nlm.nih.gov/articles/PMC6322238/
Peters MJM, Bastiaenen CHG, Brans BT, Weijers RE, Willems PC. The diagnostic accuracy of imaging modalities to detect pseudarthrosis after spinal fusion—a systematic review and meta-analysis of the literature. Skeletal Radiol. 2019;48(10):1499-1510. https://pmc.ncbi.nlm.nih.gov/articles/PMC6702186/
Hardware failure. Radiopaedia. https://radiopaedia.org/articles/hardware-failure-2