Jun 8, 2016

Intraoperative biomechanics of pedicle screw loosening in the lumbar spine

BioRxiv : the Preprint Server for Biology
Hope B PearsonJames L Chappuis


Pedicle screw loosening has been implicated in recurrent back pain after lumbar spinal fusion, but the degree of loosening has not been systematically quantified in patients. Instrumentation removal is an option for patients with successful arthrodesis, but remains controversial. This study measured pedicle screw insertion and/or removal torques in one hundred and eight patients (age 47 ± 11 years) who experienced pain recurrence despite successful fusion after posterior lumbar interbody fusion (L2-S1). Between implantation and removal, pedicle screw torque was reduced by 58%, indicating significant loosening over time. Extent of loosening correlated with screw placement as measured by EMG stimulus threshold, and an analytical stress analysis revealed increased local stresses in pedicles with decreased pedicle-screw clearance. Loosening was greatest in vertebrae at the extremities of the fused segment, with reduced biomechanical stability. Instrumentation removal also significantly reduced patient pain. These data indicate that pedicle screws can loosen significantly in patients with recurrent back pain, which may be ameliorated by instrumentation removal following successful arthrodesis.

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Mentioned in this Paper

General Adaptation Syndrome
Recurrent Malignant Neoplasm
Blastocyst Implantation, Natural
Lumbar Spinal Fusion
Limb Structure
Lumbar Region

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