Comparative Biomechanical Evaluation of Cement Augmentation Techniques for Pedicle Screw Fixation in Osteoporotic Vertebrae: A Cadaveric Study

Abstract

Pedicle screw fixation is widely used in spinal surgery to achieve mechanical stability. However, in osteoporotic bone, reduced bone mineral density compromises screw anchorage, increasing the risk of loosening and failure. The main objective of the study was to compare the biomechanical performance, including pull-out force, torque, and displacement, of two polymethylmethacrylate (PMMA) augmentation techniques versus non-augmented pedicle screw fixation in osteoporotic vertebrae. A cadaveric biomechanical study was conducted on thoracolumbar vertebrae (D10–L3) from nine osteoporotic cadavers (>55 years). Each cadaver served as its own control across three groups: (i) solid screws without augmentation; (ii) fenestrated screws with PMMA injection; (iii) kyphoplasty-assisted PMMA augmentation. Pull-out strength, torque, and vertical displacement were measured using a calibrated apparatus. Repeated-measures analysis of variance was applied. Mean pull-out strength was highest in Group 3 (1167 N), followed by Group 2 (828 N) and Group 1 (428 N). Mean torque values were 5838.3 ± 79.2 N mm, 4141.1 ± 145.9 N mm, and 2144.4 ± 146.1 N mm for Groups 3, 2, and 1, respectively ( P < 0.05). Kyphoplasty augmentation significantly had reduced vertical displacement. Cement augmentation substantially improves pedicle screw fixation in osteoporotic spines. Kyphoplasty-assisted PMMA augmentation demonstrated superior biomechanical stability compared to fenestrated screw injection and non-augmented fixation.