Cervical extraforaminal ligaments: an anatomical study

A comparative study of the anatomy and MRI images of the lumbar foraminal ligaments at the L1-L5 levels

PURPOSE

The purpose of this study was to evaluate the ability of MRI images to reveal foraminal ligaments at levels L1-L5 by comparing the results with those of anatomical studies.

METHODS

Eighty lumbar foramina were studied. First, the best MRI scanning parameters were selected, and the transverse and sagittal axes of each lumbar foramina were scanned to identify and record the ligament-like structures in each lumbar foramen. Then, the cadaveric specimens were anatomically studied, and all ligament structures in the lumbar foramina were retained. The number, morphology and distribution of ligaments under anatomical and MRI scanning were observed. Histological staining of the dissected ligament structures was performed to confirm that they were ligamentous tissues. Finally, the accuracy of ligament recognition in MRI images was statistically analyzed.

RESULTS

A total of 233 foraminal ligaments were identified in 80 lumbar intervertebral foramina through cadaveric anatomy. The radiating ligaments (176, 75.5%) were found to be attached from the nerve root to the surrounding osseous structures, while the transforaminal ligaments (57, 24.5%) traversed the intervertebral foramina without any connection to the nerve roots. A total of 42 transforaminal ligament signals and 100 radiating ligament signals were detected in the MRI images of the 80 intervertebral foramina.

CONCLUSION

The MRI can identify the lumbar foraminal ligament, and the recognition rate of the transforaminal ligament is higher than that of the radiating ligament. This study provides a new method for the clinical diagnosis of the relationship between the lumbar foraminal ligament and radicular pain.

US-Guided Transforaminal Cervical Nerve Root Block: A Novel Lateral in-Plane Approach

OBJECTIVE

The aim of the present study was to investigate the effectiveness and safety of a novel lateral in-plane approach for ultrasound-guided transforaminal cervical nerve root block (US-guided TF-CNRB) in the treatment of cervical radiculopathic pain.

DESIGN

The design of the present study consisted of an institutional, retrospective case series.

SETTING

The present study was conducted at a university hospital.

SUBJECTS

Thirty-two patients with cervical radiculopathy who were resistant to conservative therapies and regular US-guided CNRB were included as participants.

METHODS

The included patients were treated with US-guided TF-CNRB. During the treatments, using real-time fluoroscopy, we monitored the spreading patterns of a contrast medium and double confirmed the positions of needle tips. Pain numeric rating scales (NRS) and symptom relief grades were determined via telephone interviews at one, four, and 12 weeks after the procedures.

RESULTS

US-guided TF-CNRB was performed at the C5 level in six patients, the C6 level in 18 patients, and the C7 level in eight patients. Compared with NRS at baseline, pain scores decreased throughout the observation period. Symptom relief rates of US-guided TF-CNRB at one, four, and 12 weeks were 72%, 69%, and 63%, respectively. Venous blood was aspirated during the procedures in two patients, and the needle tips were corrected. No intravascular injections or neurologic injuries were observed.

CONCLUSION

US-guided TF-CNRB produced circumferential spreading around the involved cervical nerve root and showed significant clinical effectiveness in patients resistant to regular US-guided CNRB.

Fibrous Connection Between Cervical Nerve and Zygapophysial Joint and Implication of the Cervical Spondylotic Radiculopathy: An Anatomic Cadaveric Study

STUDY DESIGN

Observational, anatomical, cadaveric study.

OBJECTIVE

We anatomically investigated the fibrous connection between the cervical nerves and the zygapophysial joint capsules.

SUMMARY OF BACKGROUND DATA

Cervical spondylotic radiculopathy is caused by the compression of the cervical nerves as the static factor and head and neck movements as the dynamic factor. To understand the dynamic pathology of cervical spondylotic radiculopathy, the anatomic relationship between the cervical nerves and the zygapophysial joints needs to be investigated in detail.

METHODS

In 11 cadavers, we dissected both sides from the C5 to C7. For macroscopic examination, we observed structures connecting the cervical nerves and the zygapophysial joints in 18 cervical nerves from three cadavers. In 14 sides of eight cadavers, we histologically analyzed the fibrous structures and their attachments.

RESULTS

Macroscopically, the fibrous band connected the cranial surface of the cervical nerve to the lateral and inferior aspects of the transverse process. In four of 18 nerves, the fibrous bands were divided into two fascicles by loose connective tissues. In addition, the fibrous bands extended along the dorsal aspect of the posterior tubercle of the transverse process and attached to the zygapophysial joint capsule. Histologically, densely stained fibrous tissues overlaid the zygapophysial joint capsule and extended to the recess between the posterior tubercle and inferior articular process on the cranial vertebral body.

CONCLUSION

We macroscopically and histologically clarified the fibrous bands connecting the cervical nerve to the zygapophysial joint capsule. The fibrous bands may help clarify the pathology of cervical spondylotic radiculopathy associated with the zygapophysial joints as dynamic factors.Level of Evidence: N/A.

C5 Palsy After Cervical Spine Decompression: Topographic Correlation With C6 Chassaignac Tubercle?: A Fresh-Cadaveric Study of the Cervical Spine and Rediscussion of Etiological Hypotheses

STUDY DESIGN

Cadaveric study on fresh unprocessed, nonpreserved, undyed specimens, which has not previously been reported.

OBJECTIVE

Our aim was to explore the possible topographic correlation of the C5 nerve root with regards to its course and regional relation to C6 Chassaignac tubercle.

SUMMARY OF BACKGROUND DATA

C5 palsy is reported amongst the most frequent postoperative complications of cervical spinal procedures. We hypothesized that etiologic mechanisms proposed thus far in the current literature, although with some plausible explanation, still cannot explain why the C5 nerve root and not any other level suffer a postoperative palsy.

METHODS

Six fresh cadavers had extensive layer by layer dissection performed by two surgeons (one of whom has experience as an anatomy demonstrator and dissector). Roots of brachial plexus were exposed in relation to cervical transverse processes. Photographs were taken at each stage of the exposure.

RESULTS

We observed a close relation of the path of the C5 nerve root with the C6 tubercle bilaterally. Moreover, we noted a steeper descent of C5 in comparison with the other adjacent roots.

CONCLUSION

Steeper angle of the C5 nerve root and close proximity to C6 Chassaignac tubercle may play a role in predisposing it to neuropraxia. Detailed anatomical photographs on fresh unprocessed cadaveric specimens are novel. Peculiar anatomical features and recent experimental evidence discussed do highlight a postganglionic extraforaminal etiology corresponding well to the demographic meta-analysis data on clinical features of postoperative C5 palsy. Exploring an alternative unified "neurophysiologic stress and critical tipping point" etiological model that encompasses current theories and correlates known metanalyses observations, we believe further studies would be prudent to ascertain/refute these findings.

LEVEL OF EVIDENCE

3.

Foraminal Ligaments Tether Upper Cervical Nerve Roots: A Potential Cause of Postoperative C5 Palsy

Background  Nerve root tethering upon dorsal spinal cord (SC) migration has been proposed as a potential mechanism for postoperative C5 palsy (C5P). To our knowledge, this is the first study to investigate this relationship by anatomically comparing C5–C6 nerve root translation before and after root untethering by cutting the cervical foraminal ligaments (FL).

Objective  The aim of this study is to determine if C5 root untethering through FL cutting results in increased root translation.

Methods  Six cadaveric dissections were performed. Nerve roots were exposed via C4–C6 corpectomies and supraclavicular brachial plexus exposure. Pins were inserted into the C5–C6 roots and adjacent foraminal tubercle. Translation was measured as the distance between pins after the SC was dorsally displaced 5 mm before and after FL cutting. Clinical feasibility of FL release was examined by comparing root translation between standard and extended (complete foraminal decompression) foraminotomies. Translation of root levels before and after FL cutting was compared by two-way repeated measures analysis of variance. Statistical significance was set at 0.05.

Results  Significantly more nerve root translation was observed if the FL was cut versus not-cut, p  = 0.001; no difference was seen between levels, p  = 0.33. Performing an extended cervical foraminotomy was technically feasible allowing complete FL release and root untethering, whereas a standard foraminotomy did not.

Conclusion  FL tether upper cervical nerve roots in their foramina; cutting these ligaments untethers the root and increases translation suggesting they could be harmful in the context of C5P. Further investigation is required examining the value of root untethering in the context of C5P.

Factors Associated With C5 Palsy Following Cervical Spine Surgery: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

C5 palsy (C5P) is a not uncommon and disabling postoperative complication with a reported incidence varying between 0% and 30%. Among others, one explanation for its occurrence includes foraminal nerve root tethering. Although different risk factors have been reported, controversy about its causation and prevention persists. Inconsistent study findings contribute to the persistent ambiguity leading to an assumption of a multifactorial nature of the underlying C5P pathophysiology. Here, we report the results of a systematic review on C5P with narrow inclusion criteria in the hope of elucidating risk factors for C5P due to a common pathophysiological mechanism.

METHODS

Electronic databases from inception to March 9, 2019 and references of articles were searched. Narrow inclusion criteria were applied to identify studies investigating demographic, clinical, surgical, and radiographic factors associated with postoperative C5P.

RESULTS

Sixteen studies were included after initial screening of 122 studies. Eighty-four risk factors were analyzed; 27 in ≥2 studies and 57 in single studies. The pooled prevalence of C5P was 6.0% (range: 4.2%-24.1%) with no consistent evidence that C5P was associated with demographic, clinical, or specific surgical factors. Of the radiographic factors assessed, specifically decreased foraminal diameter and preoperative cord rotation were identified as risk factors for C5P.

CONCLUSION

Although risk factors for C5P have been reported, ambiguity remains due to potentially multifactorial pathophysiology and study heterogeneity. We found foraminal diameter and cord rotation to be associated with postoperative C5P occurrence in our meta-analysis. These findings support the notion that factors contributing to, and acting synergistically with foraminal stenosis increase the risk of postoperative C5P.

The relationship between density variations of transverse ligament tubercles on multidetector computed tomography (MDCT) and age, gender, or laterality in a large cohort

BACKGROUND

Transverse ligament tubercles are unique structures that maintain the stability of the upper cervical spine. However, the density variations of tubercles in different clinical contexts or populations have not been carefully studied through multidetector computed tomography (MDCT).

PURPOSE

This study aimed to evaluate the relationship between density variations in the transverse ligament tubercles, as measured through multidetector computed tomography (MDCT), with age, gender, or laterality.

METHODS

A cohort of 339 Chinese patients that underwent MDCT in the head or neck were recruited. The patients were divided into eight age groups. The densities of the bilateral transverse ligament tubercles were classified through MDCT, and the potential relationship between the density of the tubercles and the age, gender, or laterality was analyzed.

RESULTS

Based on MDCT findings, four different density types of tubercles were identified (type 0-III). Our data suggest that the density of tubercles increased with age (χ² = 637.7, p < 0.05). However, the density of tubercles did not correlate with laterality (male: t = 0.217, p > 0.05, female: t = 1.448, p > 0.05) or gender (χ² = 5.706, p > 0.05).

CONCLUSIONS

The density of the transverse ligament tubercles, as measured through MDCT, shows a stereotyped dynamic pattern, i.e., it apparently increases with age, but neither gender nor laterality significantly contribute to these changes.