5 results on '"Keith DK Luk"'
Search Results
2. The Concept of Lamina–Pedicle Perpendicularity: Part 2: Thoracic Spine
- Author
-
Tarek Anwar Elfiky, Nirmal Dhananjay Patil, Keith DK Luk, Mohamed Esam Faheem, and Dino Samartzis
- Subjects
thoracic ,lamina ,pedicle ,sagittal ,orthogonal ,Medicine - Abstract
Study Design Retrospective radiographic study. Purpose The hypothesis of this study was that the pedicle axis (PA) is almost perpendicular to the interlaminar line (ILL) in the sagittal plane of the thoracic vertebrae. The objective of the current study was to define the thoracic lamina–PA inclination in order to verify the right-angle concept and to estimate the safety zones for sagittal inclination during pedicle screw insertion. The authors, to the best of their knowledge, are unaware of previous similar studies. Overview of Literature Based on the study’s observations of different spinal disorders, including deformities, it was noted that following a sagittal cranial–caudal trajectory perpendicular to the ILL and joining the two adjacent thoracic vertebrae would work well at most vertebral levels. Methods This was a retrospective study on the computed tomography (CT) chest scans of patients with no spinal pathologies. The ILL–PA, superior and inferior safe angles of the pedicle screw trajectories, and the exit zone of the screw perpendicular to the ILL were reviewed by two observers via three-dimensional multiplanar reconstruction mode of the Horos DICOM software (https://horosproject.org/ ). Results The CT chest images of 30 consecutive patients (20 males and 10 females) with a mean age of 49.87±15.48 years (range, 24–74 years) were evaluated. The mean ILL–PA angle was almost orthogonal for all levels. This angle ranged between 86.21°±3.01° at D5 and 90.59°±2.72° at D10. The safety zones of the sagittal inclination of the pedicle screws were demonstrated. The results revealed that the least safe angle was when the screw was directed cranially along the middle part of the pedicle between 4.43°±0.75° at D8 and 6.94°±1.19° at D11. Conclusions The results of this study confirmed the ILL–PA angle perpendicularity in the thoracic spine at all levels. The ILL is a useful guide for pedicle screw sagittal inclination.
- Published
- 2021
- Full Text
- View/download PDF
3. The Concept of Lamina–Pedicle Perpendicularity: Part 1. Lumbar Spine
- Author
-
Tarek Anwar Elfiky, Nirmal Dhananjay Patil, Keith DK Luk, Mohamed Esam Faheem, and Dino Samartzis
- Subjects
lumbar ,lamina ,pedicle ,sagittal ,orthogonal ,Medicine - Abstract
Study Design Retrospective radiographic study. Purpose We hypothesized that the pedicle is almost perpendicular to the interlaminar line in the sagittal plane of the lumbar vertebrae. The current study aimed to define the lumbar lamina–pedicle inclination to verify the right-angle concept and to estimate the safety zones of sagittal inclination during pedicle screw insertion. To the best of our knowledge there are no previous similar studies. Overview of Literature Based on our observations in different spinal disorders including deformities, we noted that following a sagittal (cranial–caudal) trajectory perpendicular to the interlaminar line joining the two adjacent vertebrae would work well in most of the vertebral levels. Methods This was a retrospective study on normal lumbar spine lateral radiographs of patients who presented with low back pain and were reviewed by two observers. Different inclination angles were constructed to estimate the safety zones of the pedicle screws’ sagittal inclination. Results Radiographs of 30 consecutive patients, 25 females and five males, with a mean age of 39.43±11.18 years, were studied. The mean angle of the interlaminar line and the pedicle axis was almost orthogonal at all the levels, with a range of 89.16°–94.63°, which was not affected by the lumbar sagittal profile. The safety zones of the pedicle screws were measured, and they revealed a safe sagittal range of 19.73°–24.40° if the screw was inserted from the pedicle axis, 21.03°–22.59° if inserted from the most cephalic part, and 13.31°–17.03° if inserted from the most caudal part. Conclusions Our results confirmed the perpendicularity of the interlaminar line with the pedicle axis in the lumbar spine at all the levels. The interlaminar line is a useful guide for pedicle screw sagittal inclination.
- Published
- 2021
- Full Text
- View/download PDF
4. Amplitude of Low Frequency Fluctuation (ALFF) in the Cervical Spinal Cord with Stenosis: A Resting State fMRI Study.
- Author
-
Xiaojia Liu, Wenshu Qian, Richu Jin, Xiang Li, Keith Dk Luk, Ed X Wu, and Yong Hu
- Subjects
Medicine ,Science - Abstract
Cervical spondylotic myelopathy (CSM) is a common spinal cord dysfunction disease with complex symptoms in clinical presentation. Resting state fMRI (rsfMRI) has been introduced to study the mechanism of neural development of CSM. However, most of those studies focused on intrinsic functional connectivity rather than intrinsic regional neural activity level which is also frequently analyzed in rsfMRI studies. Thus, this study aims to explore whether the level of neural activity changes on the myelopathic cervical cord and evaluate the possible relationship between this change and clinical symptoms through amplitude of low frequency fluctuation (ALFF). Eighteen CSM patients and twenty five healthy subjects participated in rsfMRI scanning. ALFF was investigated on each patient and subject. The results suggested that ALFF values were higher in the CSM patients at all cervical segments, compared to the healthy controls. The severity of myelopathy was associated with the increase of ALFF. This finding would enrich our understanding on the neural development mechanism of CSM.
- Published
- 2016
- Full Text
- View/download PDF
5. The Use of a Modified Fulcrum for Fulcrum Bending Radiographs: A Technical Note
- Author
-
Kenneth MC Cheung, Josephine WN Lam, Dino Samartzis, William W Lu, and Keith DK Luk
- Subjects
Orthopedic surgery ,RD701-811 - Abstract
We describe a modified fulcrum design to overcome limitations of a traditional fulcrum. The modified fulcrum is a triangular prism–shaped foam with rounded and padded edges. The 3 faces of the fulcrum represent 3 different heights (17.0 cm, 17.5 cm, and 21.0 cm). For fulcrum bending radiographs of the thoracic curve, the patient is placed on an X-ray table in a lateral decubitus position over the fulcrum. The apex of the appropriate height of the fulcrum is positioned under the rib corresponding to the apex of the curve, such that the ipsilateral shoulder is lifted off the X-ray table for maximum passive bending force to the curve. For fulcrum bending radiographs of the lumbar curve, the fulcrum is positioned directly under the apex of the curve such that the ipsilateral iliac crest is lifted off the X-ray table.
- Published
- 2014
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.