A computed tomography morphometric study of occipital bone and C2 pedicle anatomy for occipital-cervical fusion (original) (raw)
Related papers
Journal of Spine, 2016
Background: Occipital cervical fixation (OCF) is an important and difficult technic and has certain risks due to its relation with adjacent special anatomic features. One of specific areas to perform screw fixation and to prevent technical failures is the thickness of the occipital bone which require detailed morphological anatomical knowledge. To our knowledge, no published study has provided thicknesses of occiput in African Continent. Objective: The aim of this study was to evaluate occipital bony thickness in Moroccan population in order to determine the variability of the occipital bone thickness and to assess the feasibility and safety of hook and screw placement in these patients. Patients and methods: We evaluated occipital bony thickness using computed tomography (CT) imaging in 100 patients (30 females and 70 males; age range, 18-70; mean, 36.2 ± 11.9 years). Axial CT cutting was made at 1.25 mm intervals. CT measurements were performed on the bone windows at two levels starting at 1 cm under the external occipital protuberance (EOP) and 1 cm inferior to this level. Three measurements were performed both sides at 1 cm interval. We acquired 14 values. Results: The mean thickness of occipital bones varied between 10.003 to 13.964 mm in the left and 10.747 to 13.715 mm in the right (± 2.8) and between 9.845 to 11.478 mm in the left and 9.903 to 11.371 in the right (± 2.5) at 1 cm and 2 cm above EOP respectively. The thickest point was in the midline with 17.366 mm and 12.579 mm at 1 cm and 2 cm above EOP respectively, Intra-individual and inter-individual discrepancies are found between left and right sides (p<0.05) but not between age and sex at two levels in our adult patients. Conclusion: Our radiological study findings suggest that there were significant differences between individuals and ethnics. The preoperative CT scans of occipital bony thickness as the pedicle size should be thoroughly analysed of patients undergoing occipital cervical fixation. These are essential for successful intraoperative fusion and to further decrease the risk of occipito-cervical fusion.
The cervical end of an occipitocervical fusion: a biomechanical evaluation of 3 constructs
Journal of Neurosurgery: Spine, 2008
Object Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link. Methods Ten intact human cadaveric spines (Oc–C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested. Results All constructs demonstrated a significant increase in stiffness...
Densitometric comparison of 3 occipital regions for suitability of fixation
Journal of Neurosurgery: Spine, 2016
OBJECTIVE Atlantooccipital fixation is an important technique in the treatment of upper cervical spine instability. Important considerations for implant devices are obtrusiveness and propagation of torque through the device caused by cervical rotation. The authors evaluated the feasibility of 3 regions of the occiput as sites for occipitocervical fixation by examining bone mineral density at these locations. METHODS Unembalmed occiputs of 9 male and 4 female cadavers were used (mean age at time of death was 61.6 years, range 36–68 years). Studies were undertaken using caliper measurements and dual-energy x-ray absorptiometry of the superior nuchal line (SNL), the external occipital protuberance (EOP), and the inferior nuchal line (INL). RESULTS Data indicate that the bone at the INL has a similar volumetric bone density as the bone at the SNL, despite having half the thickness. Also, the volumetric bone density increases laterally along the nuchal lines. CONCLUSIONS Most hardware fi...
Clinical Biomechanics, 2020
Background: Occipito-cervical fusion can be necessary in case of cranio-cervical junction instability. Proximal stabilisation is usually ensured by bi-cortical occipital screws implanted through one median or two lateral occipital plate(s). Bone thickness variability as well as the proximity of vasculo-nervous elements can induce substantial morbidity. The choice of site and implant type remains difficult for surgeons and is often empirically based. Given this challenge, implants with smaller pitch to increase bone interfacing are being developed, as is a surgical technique consisting in inverted occipital hook clamps, a potential alternative to plate/screws association. We present here a biomechanical comparison of the different occipito-cervical fusion devices. Methods: We have developed a 3D mark tracking technique to measure experimental mechanical data on implants and occipital bone. Biomechanical tests were performed to study the mechanical stiffness of the occipitocervical instrumentation on human skulls. Four occipital implant systems were analysed: lateral plates+large pitch screws, lateral plates+hooks, lateral plates+small pitch screws and median plate+small pitch screws. Mechanical responses were analysed using 3D displacement field measurements from optical methods and compared with an analytical model. Findings: Paradoxical mechanical responses were observed among the four types of fixations. Lateral plates +small pitch screws appear to show the best accordance of displacement field between bone/implant/system interface providing higher stiffness and an average maximum moment around 50 N.m before fracture. Interpretation: Stability of occipito-cervical fixation depends not only on the site of screws implantation and occipital bone thickness but is also directly influenced by the type of occipital implant.
Asian Spine Journal, 2018
Study DesignComputed tomographic (CT) morphometric analysis.PurposeTo assess the feasibility and safety of occipital condyle (OC)-based occipitocervical fixation (OCF) in Indians and to define anatomical zones and screw lengths for safe screw placement.Overview of LiteratureLimitations of occipital squama-based OCF has led to development of two novel OC-based OCF techniques.MethodsMorphometric analysis was performed on the OCs of 70 Indian adults. The feasibility of placing a 3.5-mm-diameter screw into OCs was investigated. Safe trajectories and screw lengths for OC screws and C0–C1 transarticular screws without hypoglossal canal or atlantooccipital joint compromise were estimated.ResultsThe average screw length and safe sagittal and medial angulations for OC screws were 19.9±2.3 mm, ≤6.4°±2.4° cranially, and 31.1°±3° medially, respectively. An OC screw could not be accommodated by 27% of the population. The safe sagittal angles and screw lengths for C0–C1 transarticular screw inser...
The role of imaging in the pre- and postoperative evaluation of posterior occipito-cervical fusion
La Radiologia medica, 2011
PURPOSE: Occipitocervical fusion is required when the occipitoatlantal joint is unstable. The purpose of this paper is to discuss the role of imaging in the pre- and postoperative evaluation of posterior occipitocervical fusion (POCF), focusing on contoured loop fixation by Hartshill and Songer instrumentation. MATERIALS AND METHODS: We studied 21 patients (eight males, 12 females; age range 6-70 years; mean age 32.6 years) with craniocervical instability who underwent POCF with Hartshill U-shaped rod and Songer sublaminar wires. Pre- and postoperative radiographic, computed tomography (CT) and magnetic resonance (MR) imaging examinations were performed in all patients. A 3-to 6-month period of external orthosis with halo vest, sterno-occipitalmandibular immobiliser (SOMI) brace or Philadelphia collar followed surgery. Follow-up was 12-96 (mean 53.1) months. RESULTS: Clinical assessment using the Frankel scale revealed improvement or deterioration arrest in all but two patients: one...
Biomechanical evaluation of occipitocervicothoracic fusion: impact of partial or sequential fixation
The spine journal : official journal of the North American Spine Society
Surgical instrumentation used for posterior craniocervical instability has evolved from simple wiring techniques to sophisticated implant systems that incorporate multiple means of rigid fixation for the cervical spine. Polyaxial screws and lamina hooks in conjunction with occipital plating and transitional rods for caudal fixation theoretically allow for fixation points at each vertebra along the posterior aspect of the cervical spine. However, the potential for anatomical constraints to prevent intraoperative instrumentation at the desired vertebral level exists. The biomechanical implications of such "skipped segments" have not been well documented. The purpose of this study was to determine the biomechanical effects of partial three-point fixation versus sequential fixation at all levels of the cervical spine from the occiput to T1. Fresh frozen human cadaveric cervical spines from the occiput (CO) to T1 were prepared and mounted on a spine simulator. Motion was assess...
Journal of Orthopaedic Research, 2021
Our primary study aim investigated volumetric BMD (vBMD) of the trabecular table at the EOP and the upper cervical vertebrae. Our secondary aim identified age-and sex-related differences in vBMD values at these locations. Given the structural differences between occipital and load-bearing cervical bone, we hypothesized that the trabecular table at the EOP has a higher vBMD than at the upper cervical levels that is less prone to age-related changes. Occipitocervical fixation commonly includes the use of occipital plates, and bone screws of at least 8 mm length are recommended for adequate screw purchase. 1-3 The occipital bone reaches its maximum thickness at the external occipital protuberance (EOP). 4,5 Biomechanical studies showed that unicortical screw fixation at the EOP is as strong as bicortical fixation in other locations, 6 possibly highlighting the influence of the trabecular table on pull-out strength. However, studies that reliably quantify trabecular bone mineral density (BMD) in this area and the upper cervical spine are lacking.
Asian spine journal, 2017
A retrospective computed tomography (CT)-based morphometric study of 82 occipital condyles in the Indian population, focusing on critical morphometric dimensions with relation to placing condylar screws. This study focused on determining the feasibility of placing occipital condylar screws in an Indian population using CT anatomical morphometric data. The occipital condylar screw is a novel technique being explored as one of the options in occipitocervical stabilization. Sex and ethnic variations in anatomical structures may restrict the feasibility of this technique in some populations. To the best of our knowledge, there are no CT-based data on an Indian population that assess the feasibility of occipital condylar screws. We measured the dimensions of 82 occipital condyles in 41 adults on coronal, sagittal, and axial reconstructed CT images. The differences were noted between the right and left sides and also between males and females. Statistical analysis was performed using the ...
MORPHOMETRIC CERVICAL ANALYSIS
Background. Any abnormalities in subaxial typical cervical vertebrae could cause functional disorder and/or instability. Instrumentation can be applied to overcome the instability, such as pedicle screw insertion. Pedicle screw insertion in typical subaxial cervical spine is technically demanding due to its pedicle dimension. This study is designed to measure the anatomical morphometric of typical subaxial cervical pedicle in Hasan Sadikin hospital as a pre operative evaluation to avoid the complication in that procedure.