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

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.

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

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.

Endplate Changes with Polyetheretherketone Cages in Posterior Lumbar Interbody Fusion

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.

Spontaneous hyphema in an infant with Christmas disease

A 4-month-old boy presented with an apparently spontaneous uniocular hyphema as the initial manifestation of Christmas disease (hemophilia B). Although it is uncommon for patients with hemophilia to experience major bleeds in infancy, and the ocular involvement is usually limited to periocular hemorrhages, we recommend that a coagulation profile be obtained in all patients with intraocular hemorrhage to rule out this disease.

Medical and socio-economic aspects of long term therapy of open angle glaucoma

Hundred patients of open angle glaucoma (OAG) who were on any one of the three drugs pilocarpine, timolol and epinephrine--for an average period of 3.3 years were chosen. Proforma regarding socio-economic status and the patients' reaction to long-term medication were recorded. Though the objective and subjective effects of long term medication were negligible the financial constraints were considerable. More than 70% patient would prefer laser's and surgery because of the cumbersome schedule and financial burden. The visit to the clinic was a time consuming process suggesting a lack of adequate glaucoma follow-up at the peripheral level. The study reflects a need for reorientation of glaucoma management.

Leiomyoma of the orbit

A rare case of leiomyoma located anteroinferiorly in the orbit of a 39-year-old male patient is reported. The histopathogenesis and management is discussed.

Modified split level lid resection in ptosis

10 patients of congenital simple ptosis having 3 to 5 mm of ptosis with variable levator action were operated. All the patients showed a good response of lid lift after instillation of phenyl ephrine drops showing the activity of Muller's muscle. With this technique the lagophthalmos was minimal and good lid folds were formed in all cases. The skin muscle lamina was not excised and was utilized for formation of lid folds which were equal in depth and dynamic in nature. However, the lid lag which is an unavoidable complication of any ptosis surgery was present in the present technique also.

Proximate principle and energy content of human milk in well-nourished urban mother

Milk samples from 54 well-nourished urban mothers between the age of 18-36 years were studied. The birth weight of infants ranged between 2.5 to 3.9 kg at full term. The mean (g or Cal/100 ml) lactose (6.51), protein (1.08), fat (4.48) and energy contents (74.83) of milk was on par with the well-nourished mothers of developed countries. The milk fat content observed was higher than that reported in under nourished mothers from developing countries.