Comparison of radiographic and computed tomographic measurement of pedicle and vertebral body dimensions in Koreans: the ratio of pedicle transverse diameter to vertebral body transverse diameter

Morphology and Composition of Lumbar Intervertebral Discs: Comparative Analyses of Manual Measurement and Computer-Assisted Algorithms

BACKGROUND

The morphology and internal composition, particularly the nucleus-to-cross sectional area (NP-to-CSA) ratio of the lumbar intervertebral discs (IVDs), is important information for finite element models (FEMs) of spinal loadings and biomechanical behaviors, and, yet, this has not been well investigated and reported.

METHODS

Anonymized MRI scans were retrieved from a previously established database, including a total of 400 lumbar IVDs from 123 subjects (58 F and 65 M). Measurements were conducted manually by a spine surgeon and using two computer-assisted segmentation algorithms, i.e., fuzzy C-means (FCM) and region growing (RG). The respective results were compared. The influence of gender and spinal level was also investigated.

RESULTS

Ratios derived from manual measurements and the two computer-assisted algorithms (FCM and RG) were 46%, 39%, and 38%, respectively. Ratios derived manually were significantly larger.

CONCLUSIONS

Computer-assisted methods provide reliable outcomes that are traditionally difficult for the manual measurement of internal composition. FEMs should consider the variability of NP-to-CSA ratios when studying the biomechanical behavior of the spine.

Do the benefits of hook-hybrid construct justify their use over all-pedicle screws constructs in maintaining postoperative curve correction for adolescent idiopathic scoliosis patients from an Asian population?

STUDY DESIGN

Retrospective study.

OBJECTIVE

(1) Compare outcomes of all-pedicle screws (PS) and hook-hybrid (H) constructs in adolescent idiopathic scoliosis (AIS) patients; and (2) investigate whether BMI, height or pedicle size may modify the effect of the type of surgical construct on the extent of curve decompensation.

METHODS

AIS patients who underwent surgical fixation with H or PS constructs at a single tertiary institution were reviewed. Patients with implant density of at least 70% and 2-year follow-up were included. Demographic and perioperative data collected were age, sex, height, BMI, implant density and pedicle diameter. Cobb's angles and curve correction were compared preoperatively, postoperatively and at follow-up.

RESULTS

In total, 59 patients were included. H group had a lower pedicle size at the highest level of construct and at T4 compared to PS group. Postoperatively, H group (30.2° ± 11.7°) and PS group (32.1° ± 10.4°) had similar correction (mean diff. 2.0°, p = 0.516). At 2-year follow-up, H group (1.6° ± 3.5°) and PS group (0.1° ± 2.8°) had similar curve deterioration (mean diff. 1.5°, p = 0.079). Uni- and multivariate analyses revealed that BMI and height were not associated with curve deterioration at 2-year follow-up among the H and PS groups.

CONCLUSION

H constructs provided similar maintenance of curve correction at 2-year follow-up compared to PS constructs. BMI and Stature did not modify curve deterioration between both groups at follow-up. This study supports the use of H constructs when faced with difficult pedicle morphology associated with shorter stature as it provides comparable and satisfactory long-term maintenance of curve correction.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

MRI-based synthetic CT of the lumbar spine: Geometric measurements for surgery planning in comparison with CT

PURPOSE

MRI is the imaging modality of choice for soft tissue-related spine disease. However, CT is superior to MRI in providing clear visualization of bony morphology. The purpose of this study is to test equivalency of MRI-based synthetic CT to conventional CT in quantitatively assessing bony morphology of the lumbar spine.

METHOD

A prospective study with an equivalency design was performed. Adult patients who had undergone MRI and CT of the lumbar spine were included. Synthetic CT images were generated from MRI using a deep learning-based image synthesis method. Two readers independently measured pedicle width, spinal canal width, neuroforamen length, anterior and posterior vertebral body height, superior and inferior vertebral body length, superior and inferior vertebral body width, maximal disc height, lumbar curvature and spinous process length on synthetic CT and CT. The agreement among CT and synthetic CT was evaluated using equivalency statistical testing.

RESULTS

Thirty participants were included (14 men and 16 women, range 20-60 years). The measurements performed on synthetic CT of pedicle width, spinal canal width, vertebral body height, vertebral body width, vertebral body length and spinous process length were statistically equivalent to CT measurements at the considered margins. Excellent inter- and intra-reader reliability was found for both synthetic CT and CT.

CONCLUSIONS

Equivalency of MRI-based synthetic CT to CT was demonstrated on geometrical measurements in the lumbar spine. In combination with the soft tissue information of the conventional MRI, this provides new possibilities in diagnosis and surgical planning without ionizing radiation.

Spinal Pedicle Morphometry using Multidetector CT—An experience from the Indian Subcontinent

Introduction For safe pedicle screws placement, knowledge of pedicle morphometry is essential, because an inconsistency between pedicle width and the screw diameter may lead to severe complications like nerve, vessel or visceral injuries.

Objectives To study the spinal pedicle width and height of lumbar spine, using multidetector CT (MDCT), among the Indian population.  To study the spinal pedicle angulation of lumbar spine, using MDCT, among the Indian population.

Method The study was conducted at a tertiary care multispecialty hospital. In the present study, a total of 321 patients were included, who underwent MDCT scan without contrast at our institution, over a period of 2 years, from May 2017 to May 2019. The study population (n = 321) was divided into different subgroups on the basis of the age. The data was taken from the workstation. Comparison was made separately between each subgroup.

Results In our subset of population, the 10 to 90 years age group, pedicle dimensions are as follow: The pedicle diameter from L1 to L5 is 4.46 to 11.92 mm. The pedicle height from L1 to L5 is 7.38 to 11.01 mm. The pedicle axial angulation from L1 to L5 is 22.27 to 36.08 degree. The pedicle lateral angulation from L1 to L5 is 16.12 to 22.47 degree.

Conclusion Knowledge of the pedicle morphometry (pedicle width, height and angulation) of lumbar spine will help the neurosurgeons standardize the size of pedicle screws which is required for spinal fixation surgery at various lumbar vertebra levels.

Computed Tomographic Morphometry of Lumbar Spine in Indian Population

Purpose Several studies have been conducted to determine morphometry of lumbar vertebrae, mostly in western population and data on other populations is relatively sparse. Most of these studies have been carried out using fresh cadavers or osteological collections and several of them having limitations such as a small sample size and lack of demographic information. We conducted morphometric analysis of the lumbar vertebrae in a relatively large number of Indian patients using computed tomography scan. Vertebral body and pedicle dimensions of lumbar spinal elements were documented in Indian population and compared with other studies from the subcontinent as well as from other parts of the world. The morphometric data thus compiled may help in the development of new spinal implants for transpedicular screw fixations.

Methods An observational study was conducted and a total of 302 patients were evaluated. Thin section computed tomographic images of the 12th thoracic vertebra (D12) to 1st sacral vertebra (S1) were acquired and various dimensions of vertebral body and pedicle were recorded and analyzed.

Results Generally, the lumbar vertebral and pedicle dimensions were found to be greater in male patients. Comparison of dimensions in different populations revealed statistically significant differences in pedicle dimensions between Indian population and others.

Conclusion Morphometric analysis of lumbar vertebrae using computed tomography scan provides measurements of different vertebral dimensions. This will help in development of spinal implants in future to meet the specific needs of the studied population.

Prediction of Incidental Osteoporotic Fractures at Vertebral-Specific Level Using 3D Non-Linear Finite Element Parameters Derived from Routine Abdominal MDCT

To investigate whether finite element (FE) analysis of the spine in routine thoracic/abdominal multi-detector computed tomography (MDCT) can predict incidental osteoporotic fractures at vertebral-specific level; Baseline routine thoracic/abdominal MDCT scans of 16 subjects (8(m), mean age: 66.1 ± 8.2 years and 8(f), mean age: 64.3 ± 9.5 years) who sustained incidental osteoporotic vertebral fractures as confirmed in follow-up MDCTs were included in the current study. Thoracic and lumbar vertebrae (T5-L5) were automatically segmented, and bone mineral density (BMD), finite element (FE)-based failure-load, and failure-displacement were determined. These values of individual vertebrae were normalized globally (g), by dividing the absolute value with the average of L1-3 and locally by dividing the absolute value with the average of T5-12 and L1-5 for thoracic and lumbar vertebrae, respectively. Mean-BMD of L1-3 was determined as reference. Receiver operating characteristics (ROC) and area under the curve (AUC) were calculated for different normalized FE (Kload, Kdisplacement,K(load)g, and K(displacement)g) and BMD (KBMD, and K(BMD)g) ratio parameter combinations for identifying incidental fractures. Kload, K(load)g, KBMD, and K(BMD)g showed significantly higher discriminative power compared to standard mean BMD of L1-3 (BMDStandard) (AUC = 0.67 for Kload; 0.64 for K(load)g; 0.64 for KBMD; 0.61 for K(BMD)g vs. 0.54 for BMDStandard). The combination of Kload, Kdisplacement, and KBMD increased the AUC further up to 0.77 (p < 0.001). The combination of FE with BMD measurements derived from routine thoracic/abdominal MDCT allowed an improved prediction of incidental fractures at vertebral-specific level.

Lumbar Canal Diameter Evaluation by CT Morphometry-Study of Indian Population

STUDY DESIGN

A cross-sectional study.

BACKGROUND

To document dimensions of the lumbar vertebrae and bony canal in an Indian population and to compare with other studies from the subcontinent as well as from other parts of world.

METHODS

An observational study was conducted on the basis of a review of thin-cut (3 mm) computed tomographic images of lumbar vertebrae. A total of 302 patients were studied, and various dimensions were analyzed.

RESULTS

In general, the vertebral and bony spinal canal dimensions were found to be greater in male patients. Comparison of populations revealed statistically significant differences in the spinal canal between an Indian population and others.

OVERVIEW OF LITERATURE

Lumbar canal stenosis is a condition in which the anteroposterior and lateral dimensions of the bony spinal canal are less than normal for corresponding age and sex. Numerous studies have been conducted to determine morphometry of the lumbar vertebrae and spinal canal, mostly in western populations, using fresh cadaver or osteologic specimens. These studies did not mention the difference between the vertebral parameters in men and women. Moreover, many of these studies have limitations such as a small sample size and lack of demographic data including race, age, and sex. In this study, we have conducted morphometric analysis of the lumbar vertebrae in a relatively large number of Indian patients by using computed tomography scan. The morphometric data thus compiled may provide a baseline of body and canal dimensions that could guide clinical experts in their practice.

CONCLUSIONS

The dimensions of the lumbar vertebrae and bony canal thus obtained shall provide a baseline normative data for evaluation of patients presenting with low backache and lumbar canal stenosis in an Indian population.

Depression of the Thoracolumbar Posterior Vertebral Body on the Estimation of Cement Leakage in Vertebroplasty and Kyphoplasty Operations

Background:

The cross-section of thoracolumbar vertebral body is kidney-shaped with depressed posterior boundary. The anterior wall of the vertebral canal is separated from the posterior wall of the vertebral body on the lateral X-ray image. This study was designed to determine the sagittal distance between the anterior border of the vertebral canal and the posterior border of the vertebral body (DBCV) and to analyze the potential role of DBCV in the estimation of cement leakage during percutaneous vertebroplasty (PVP) or percutaneous kyphoplasty (PKP).

Methods:

We retrospectively recruited 233 patients who had osteoporotic vertebral compression fractures and were treated with PVP or PKP. Computed tomography images of T11–L2 normal vertebrae were measured to obtain DBCV. The distance from cement to the posterior wall of the vertebral body (DCPW) of thoracolumbar vertebrae was measured from C-arm images. The selected vertebrae were divided into two groups according to DCPW, with the fracture levels, fracture grades and leakage rates of the two groups compared. A relative operating characteristic (ROC) curve was applied to determine whether the DCPW difference can be used to estimate the degree of cement leakage. The data were processed by statistical software SPSS version 21.0 using independent sample t-test and Chi-square tests.

Results:

The maximum DBCV was 6.40 mm and the average DBCV was 3.74 ± 0.95 mm. DBCV appeared to be longer in males than in females, but the difference was not statistically significant. The average DCPW of type-B leakage vertebrae (2.59 ± 1.20 mm) was shorter than that of other vertebrae (7.83 ± 2.38 mm, P < 0.001). The leakage rate of group DCPW ≤6.40 mm was lower than that of group DCPW >6.40 mm for type-C and type-S, but much higher for type-B. ROC curve revealed that DCPW only has a predictive value for type-B leakage (area under the curve: 0.98, 95% confidence interval: 0.95–0.99, P < 0.001), and when the cut-off value was 4.05 mm, the diagnostic sensitivity and the specificity were 94.87% and 93.02%, respectively.

Conclusions:

Depression of the thoracolumbar posterior vertebral body may be informative for the estimation of cement location on C-arm images. To reduce type-B leakage, DCPW should be made longer than DBCV on C-arm images for safety during PVP or PKP.

Development of an integrated CAD-FEA system for patient-specific design of spinal cages

Spinal cages are used to create a suitable mechanical environment for interbody fusion in cases of degenerative spinal instability. Due to individual variations in bone structures and pathological conditions, patient-specific cages can provide optimal biomechanical conditions for fusion, strengthening patient recovery. Finite element analysis (FEA) is a valuable tool in the biomechanical evaluation of patient-specific cage designs, but the time- and labor-intensive process of modeling limits its clinical application. In an effort to facilitate the design and analysis of patient-specific spinal cages, an integrated CAD-FEA system (CASCaDeS, comprehensive analytical spinal cage design system) was developed. This system produces a biomechanical-based patient-specific design of spinal cages and is capable of rapid implementation of finite element modeling. By comparison with commercial software, this system was validated and proven to be both accurate and efficient. CASCaDeS can be used to design patient-specific cages with a superior biomechanical performance to commercial spinal cages.