Anterior Cervical Plate Fixation: A Biomechanical Study to Evaluate the Effects of Plate Design, Endplate Preparation, and Bone Mineral Density

Object Among the various ways to optimize the fixation of bone implants is to use bone cement, for example, in a total hip prosthesis. No data exist, however, concerning the effectiveness of cemented rescue screws for anterior cervical plate fixation. The aim of this study was to investigate whether cemented rescue screws increase fixation strength in comparison with uncemented standard screws. Methods Six cervical spine segments (C4–7) were explanted during routine autopsy studies from fresh human cadavers. Bone mineral density (BMD) was measured for each vertebral body (VB) using quantitative computerized tomography scanning, and 24 VBs were dissected from the segments. Two initial pilot holes were drilled into each VB parallel to the sagittal plane. Based on their BMD, the specimens were assigned to one of two groups in which torque and pullout force were tested. The test was begun with standard screws and was repeated with cannulated slotted rescue screws into which bone cement was injected. The mean values of peak torque and pullout forces resulting from the left and right measurements were used for statistical analysis. A t-test was performed to determine the effect of screw type on peak torque and pullout force. Moment correlation coefficients were calculated to determine the effect of BMD on peak torque and pullout force for each type of screw. The mean insertional peak torque was 67.1 N/cm for the standard screw and 102.6 N/cm for the cemented screw (p < 0.05). The mean pullout force was 526.9 N for standard osteoporosis screws and 531.5 N for cemented screws (p > 0.05). The effect of increased holding strength as measured by peak torque and pullout force was more pronounced in the presence of low bone density. Conclusions Cemented rescue screws that have been inserted into a fatigued pilot hole in the cervical VB strengthen the screw–bone interface compared with the strength initially conferred by a standard screw.

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Effects of long-term plate fixation with different fixation modes on the radial cortical bone in dogs

PLoS ONE ◽

10.1371/journal.pone.0247410 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0247410

Author(s):

Norihiro Muroi ◽

Hiroki Ochi ◽

Masakazu Shimada ◽

Yoshinori Asou ◽

Yasushi Hara

Keyword(s):

Bone Mineral Density ◽

Bone Mineral ◽

Histological Analysis ◽

Locking Plate ◽

Plate Fixation ◽

Control Group ◽

Mineral Density ◽

Plate Group ◽

Necrosis Factor

The aim of this study was to examine the effect of long-term locking plate fixation on the cortical bone of the canine radius. Locking compression plates were fixed to the left and right radius in dogs (n = 3). The left radius was fixed with a locking head screw (Locking Plate group, LP). The locking compression plate was compressed periosteally in the right radius using a cortex screw (Compression Plate group, CP). Radial bones from dogs that were euthanized for other purposes were collected as an untreated control group (Control group). After euthanasia at 36 weeks following plate fixation, radial bones were evaluated for bone mineral density and underwent histological analysis. Bone metabolic markers were analyzed by quantitative polymerase chain reaction (qPCR). Statistical analyses were performed for comparisons between groups. The LP group showed no significant difference in bone mineral density after plate fixation, whereas the CP group showed significantly lower bone mineral density. Histological analysis indicated that the number of osteoclasts and rate of empty lacunae increased significantly in the CP group relative to the Control and LP groups. qPCR analysis indicated increased expression of inflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-6, and tumor necrosis factor ligand superfamily member 11 in the CP group, whereas Runt-related transcription factor 2, an osteoblast marker, was similar in all groups. The expression of hypoxia-inducible factor-1α in the CP group was also increased relative to that in the Control and LP groups. Thus, locking plate fixation is a biologically superior fixation method that does not cause implant-induced osteoporosis in the bone in the long term.

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