The Concept of Lamina–Pedicle Perpendicularity: Part 1. Lumbar Spine

Elfiky Tarek Anwar,Patil Nirmal Dhananjay,Luk Keith DK,Faheem Mohamed Esam,Samartzis Dino 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.1

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.

The Concept of Lamina–Pedicle Perpendicularity: Part 2: Thoracic Spine

Elfiky Tarek Anwar,Patil Nirmal Dhananjay,Luk Keith DK,Faheem Mohamed Esam,Samartzis Dino 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.2

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.

Oxford Cobbometer Versus Computer Assisted-Software for Measurement of Cobb Angle in Adolescent Idiopathic Scoliosis

Tarek Elfiky,Nirmal Patil,Mohamed Shawky,Ahmed Siam,Raafat Ragab,Yasser Allam 대한척추신경외과학회 2020 Neurospine Vol.17 No.1

Objective: The objective was to compare Cobb angle measurements performed using an Oxford Cobbmeter and digital computer software (Surgimap) in a series of 83 adolescent idiopathic scoliosis (AIS) patients. Methods: Two independent observers measured the Cobb angles for 123 curves on 83 consecutive long radiographs of patients with AIS using both Oxford Cobbmeter and digital computer software (Surgimap). The measurements were repeated a week. Curves were classified according to the severity into mild, moderate, and severe. The results were statistically analyzed for intraobserver and interobserver reliability Results: The mean Cobb angle was 48.12°±19.75° (range, 10.54°–110.76°). Globally the results of curve measurements were comparable between and within both observers using both methods, with small mean differences. According to intraclass correlation coefficient, there was high inter- and intraobserver high agreement for both methods. All readings were >0.9. There was a good interobserver (κ=0.745, 0.693) and a very good interobserver agreement (κ=0.810, 0.804) for both methods for curve classification. However, poor agreement was observed as regards to the measurement time, being less with Oxford Cobbometer. Conclusion: The results of this study indicate that the Surgimap digital computer software measurement is an equivalent measuring tool to the Oxford Cobbmeter in Cobb angle measurement. Both have high intra and interobserver agreement for measurement and for curve classification, with small measurement differences. Oxford Cobbmeter is advantageous in being quicker, and therefore it is the method of choice for manual measurement, where PACS (patient archiving and communication system) or digital system is not available.

Endplate Changes with Polyetheretherketone Cages in Posterior Lumbar Interbody Fusion

Tarek Anwar Elfiky,Nirmal Dhananjay Patil,Yasser Allam,Raafat Ragab 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.2

Study Design: A retrospective radiographic analysis. Purpose: The aim of the current study is to assess endplate changes after the use of polyetheretherketone (PEEK) cages in posterior lumbar interbody fusion (PLIF). Overview of Literature: A few recent reports had revealed endplate abnormalities due to PEEK cages, which may lead to nonunions. Methods: A retrospective computed tomography (CT)-based analysis of the endplate cavities and fusion status following PLIFs with PEEK cages was conducted by two independent observers. The term “cavity” was used to describe the endplate changes. The vertebral endplate cavities were assessed according to the size, multiplicity, location, and presence or absence of sclerosis. Results: There were 86 fixed levels in 65 consecutive patients, with a mean age of 35.44±19.60 years. The mean follow-up was 16.5±10.1 months (range, 6–57 months). Definite fusion was seen in 56 levels (65.12%) by observer 1 versus 44 levels (51.16) by observer 2. The strength of agreement was moderate. Endplate cavities were observed in 42 levels (48.84%) by observer 1 versus 47 levels (54.65%) by observer 2, with fair agreement. The strengths of agreement for the locations, multiplicity, and size were moderate, fair, and poor, respectively. Neither age, sex, etiology, levels, nor follow-up period was significantly associated with the presence of cavities. With regard to fusions, the nonunions detected by observer 1 were significantly associated with the presence of cavities (p<0.0001). However, those detected by observer 2 were nearly significant (p=0.05). Conclusions: There was a high rate of unfavorable radiographic findings in the form of endplate cavities in PLIF cases with PEEK cages. A more comprehensive classification for the assessment of fusions and endplate cavities should be formulated. We strongly recommend further CT-based studies with larger sample size and longer follow-up periods.