Characteristics of regional bone quality in cervical vertebrae considering BMD: Determining a safe trajectory for cervical pedicle screw fixation

Abstract

This study aimed to report the mechanical strength and characteristics of the lateral mass and pedicle considering BMD for the safe insertion of pedicle screws in the subaxial cervical level. We evaluated BMD and Hounsfield unit (HU) values of cortical bones at the lateral mass and pedicle of C3-7 from CT images in 99 patients. Patients were divided into three groups (Group A, T-score ≥ -1; Group B, -2.5 < T-score < -1.0; Group C, T-score ≤ -2.5). The HU numbers of cortical bone in the vertebral canal (medial wall of the lateral mass; cHU), posterior wall of the transverse foramen (fHU), and medial wall, lateral wall, and trabecular area of the pedicle (mHU, lHU, and pHU, respectively) were measured on the CT images in the middle of the pedicle. A mechanical study was also performed to measure cortical bone strength using 10 fresh cadavers. The cHU and mHU values in Group C were higher than lHU and fHU in Groups A and B, and there was a wide gap between the pHU value and other areas. The penetrating force also had a close correlation with HU number. The mean penetrating force of the medial wall of the lateral mass and the posterior wall of the transverse foramen were 210.08 ± 110.46 and 50.51 ± 46.09 N, respectively. The cortical bones in the vertebral canal and medial wall of the pedicle were stronger than the lateral wall and the trabecular area. The cHU and mHU in the osteoporotic group were higher than fHU and pHU in the normal group. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:217-223, 2018.

A Novel Semi‐Cannulated Screw Enhanced Bone Cement Augmentation and Pullout Strength in Posterior Cervical Lateral Mass Screw Fixations: An In Vitro Biomechanical and Morphological Study

“…Several additional aspects were addressed in the present study. Studies demonstrated the strong influence of bone quality on the binding strength of the bone–screw interface, which is a crucial factor in stabilizing thoracolumbar implants 28,29 . However, few studies have focused on evaluating the relationship between pull‐out strength and local bone quality in the lateral mass of cervical segments.…”

“…Studies demonstrated the strong influence of bone quality on the binding strength of the bone-screw interface, which is a crucial factor in stabilizing thoracolumbar implants. 28,29 However, few studies have focused on evaluating the relationship between pull-out strength and local bone quality in the lateral mass of cervical segments. DEXA (Dual-energy X-ray absorptiometry), a two-dimensional technique, has been the most commonly used method to assess bone quality in studies.…”

A new anatomical approach of cervical lateral mass for cervical pedicle screw and paravertebral foramen screw insertion

“…They did not explain why contact of the medial wall of the lateral mass is important for finding the opening of the pedicle. Recently, only one study evaluated the strength of the medial cortex of the lateral mass [30]. Studies on the complications of CPS provided further indications on the proper screwing of the cervical pedicle; that is, major misplacements of CPS involving the transverse foramen occurred in the lateral part of the pedicle, but involvement of medial wall was relatively rare.…”

Versatile Usage of the Modified Lateral Mass Screw as an Alternative to Cervical Pedicle Screw Fixation

“…The medial wall of the lateral mass is stronger than the trabecular bones and other cortices of the nearby structures. 19 If the trajectory is chosen correctly, the surgeon feels the resistance of the medial cortex of the lateral mass, if introducing the probe. The tip of the mLMS should stop 1 to 2 mm anterior to the posterior wall of the vertebral body as seen on lateral fluoroscopic image ( Fig.…”