Effect of different designs of interspinous process devices on the instrumented and adjacent levels after double-level lumbar decompression surgery: A finite element analysis

• Published in: PloS one 2020-12, Vol.15 (12), p.e0244571-e0244571
• Main Authors: Lo, Hao-Ju, Chen, Hung-Ming, Kuo, Yi-Jie, Yang, Sai-Wei
• Format: Article
• Language: English
• Subjects: Biology and Life Sciences; Biomechanical Phenomena; Biomechanics; Biomedical engineering; Bone surgery; Contact force; Contact stresses; Decompression; Decompression, Surgical - instrumentation; Degeneration; Engineering and Technology; Finite Element Analysis; Finite element method; Hospitals; Humans; Implants; Intervertebral discs; Ligaments; Lumbar Vertebrae - physiopathology; Lumbar Vertebrae - surgery; Medicine and Health Sciences; Numerical analysis; Orthopedics; Patients; Pedicle screws; Physical Sciences; Physiology; Range of Motion, Articular; Segments; Spinal canal; Spinal stenosis; Spinal Stenosis - physiopathology; Spinal Stenosis - surgery; Spine; Stenosis; Stiffness; Stress; Surgery; Vertebra; Vertebrae
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0244571

Recently, various designs and material manufactured interspinous process devices (IPDs) are on the market in managing symptomatic lumbar spinal stenosis (LSS). However, atraumatic fracture of the intervening spinous process has been reported in patients, particularly, double or multiple level lumbar decompression surgery with IPDs. This study aimed to biomechanically investigate the effects of few commercial IPDs, namely DIAMTM, CoflexTM, and M-PEEK, which were implanted into the L2-3, L3-4 double-level lumbar spinal processes. A validated finite element model of musculoskeletal intact lumbar spinal column was modified to accommodate the numerical analysis of different implants. The range of motion (ROM) between each vertebra, stiffness of the implanted level, intra stress on the intervertebral discs and facet joints, and the contact forces on spinous processes were compared. Among the three implants, the Coflex system showed the largest ROM restriction in extension and caused the highest stress over the disc annulus at the adjacent levels, as well as the sandwich phenomenon on the spinous process at the instrumented levels. Further, the DIAM device provided a superior loading-sharing between the two bridge supports, and the M-PEEK system offered a superior load-sharing from the superior spinous process to the lower pedicle screw. The limited motion at the instrumented segments were compensated by the upper and lower adjacent functional units, however, this increasing ROM and stress would accelerate the degeneration of un-instrumented segments.