The quantitative anatomy of the cervical nerve root groove and the intervertebral foramen

Morphometric analysis of cervical neuroforaminal dimensions from C2-T1 using computed tomography of 1,000 patients

BACKGROUND

Race and sex differences are not consistently reported in the literature. Fundamentally, anatomical differences of cervical neuroforaminal dimensions (CNFD) amongst these groups would be important to know.

PURPOSE

To establish normative radiographic morphometric measurements of CNFD and uncover the influence of patient sex, race, and ethnicity while also considering anthropometric characteristics.

STUDY DESIGN

Retrospective radiographic morphometric study.

PATIENT SAMPLE

A total of 1,000 patients between 18 and 35 years of age who were free of spinal pathology.

OUTCOME MEASURES

Foraminal height, axial width, and area of cervical neural foramen.

METHODS

Cervical CTs were reviewed to measure CNFD, defined as follows: foraminal height, axial width, and area. Statistical analyses were performed to assess associations between CNFD, and patient height, weight, sex, race, and ethnicity.

RESULTS

CNFD measurements followed a bimodal distribution pattern moving caudally from C2-T1. Irrespective of disc level, cervical CNFD were as follows: left and right widths of 6.6±1.5 and 6.6±1.5 mm, heights of 9.4±2.4 and 9.4±3.2 mm, and areas of 60.0±19.5 and 60.6±20.7 mm2. Left and right foraminal width were highest at C2-C3 and lowest at C3-C4. Left and right foraminal height were highest at C7-T1 and C6-C7, respectively and lowest at C3-C4. Left and right foraminal areas were highest at C2-C3 and lowest at C3-C4. Significant differences were observed for all CNFD measurements across disc levels. CNFD did not vary based on laterality. Significant CNFD differences were observed with respect to patient sex, race, and ethnicity. Male height and area were larger compared to females. In contrast, female foraminal width was larger compared to males. The Asian cohort demonstrated the largest foraminal widths. White and Hispanic patients demonstrated the largest foraminal heights and areas. Black patients demonstrated the smallest foraminal widths, heights, and areas. Patient height and weight were only weakly correlated with CNFD measurements across all levels from C2-T1.

CONCLUSIONS

This study describes 36,000 normative measurements of 12,000 foramina from C2-T1. CNFD measurements vary based on disc level, but not laterality. Contrasting left- versus right-sided neuroforamina of the same level may aid in determining the presence of unilateral stenosis. Patient sex, race, and ethnicity are associated with CNFD, while patient anthropometric factors are weakly correlated with CNFD.

Best Practices for Dorsal Root Ganglion Stimulation for Chronic Pain: Guidelines from the American Society of Pain and Neuroscience

With continued innovations in neuromodulation comes the need for evolving reviews of best practices. Dorsal root ganglion stimulation (DRG-S) has significantly improved the treatment of complex regional pain syndrome (CRPS), and it has broad applicability across a wide range of other conditions. Through funding and organizational leadership by the American Society for Pain and Neuroscience (ASPN), this best practices consensus document has been developed for the selection, implantation, and use of DRG stimulation for the treatment of chronic pain syndromes. This document is composed of a comprehensive narrative literature review that has been performed regarding the role of the DRG in chronic pain and the clinical evidence for DRG-S as a treatment for multiple pain etiologies. Best practice recommendations encompass safety management, implantation techniques, and mitigation of the potential complications reported in the literature. Looking to the future of neuromodulation, DRG-S holds promise as a robust intervention for otherwise intractable pain.

Tomodensitometric bone anatomy of the intervertebral foramen of the lower cervical spine: measurements and comparison of foraminal volume in healthy individuals and patients suffering from cervicobrachial neuralgia due to foraminal stenosis

PURPOSE

Degenerative foraminal stenosis of the cervical spine can lead to cervicobrachial neuralgias. Computed tomography (CT)-scan assists in the diagnosis and evaluation of foraminal stenosis. The main objective of this study is to determine the bony dimensions of the cervical intervertebral foramen and to identify which foraminal measurements are most affected by degenerative disorders of the cervical spine. These data could be applied to the surgical treatment of this pathology, helping surgeons to focus on specific areas during decompression procedures.

METHODS

A descriptive study was conducted between two groups: an asymptomatic one (young people with no evidence of degenerative cervical spine disorders) and a symptomatic one (experiencing cervicobrachial neuralgia due to degenerative foraminal stenosis). Using CT scans, we determined a method allowing measurements of the following foraminal dimensions: foraminal height (FH), foraminal length (FL), foraminal width in its lateral part ((UWPP, MWPP and IWPP (respectively Upper, Medial and Inferior Width of Pedicle Part)) and medial part (UWMP, MWMP and IWMP (respectively Upper, Medial and Inferior Width of Medial Part)), and disk height (DH). Foraminal volume (FV) was calculated considering the above data. Mean volumes were measured in the asymptomatic group and compared to the values obtained in the symptomatic group.

RESULTS

Both groups were made up of 10 patients, and a total of 50 intervertebral discs (100 intervertebral foramina) were analyzed in each group. Comparison of C4C5, C5C6 and C6C7 levels between both groups showed several significant decreases in foraminal dimensions (p < 0.05) as well as in foraminal volume (p < 0.001) in the symptomatic group. The most affected dimensions were UWPP, MWPP, UWMP, MWMP and FV. The most stenotic foraminal areas were the top of the uncus and the posterior edge of the lower plate of the overlying vertebra.

CONCLUSION

Using a new protocol for measuring foraminal volume, the present study refines the current knowledge of the normal and pathological anatomy of the lower cervical spine and allows us to understand the foraminal sites most affected by degenerative stenosis. Those findings can be applied to foraminal stenosis surgeries. According to our results, decompression of the foramen in regard of both uncus osteophytic spurs and inferior plate of the overlying vertebra might be an important step for spinal nerves release.

Anatomical Evaluation of Spinal Nerve and Cervical Intervertebral Foramina in Anterior Controllable Antedisplacement and Fusion Surgery: A Cadaveric and Radiologic Study

Objective

To achieve the anatomical evaluation of spinal nerve and cervical intervertebral foramina in anterior controllable antedisplacement and fusion (ACAF) surgery, a novel surgical technique with the wider decompression, through a cadaveric and radiologic study.

Methods

Radiographic data of consecutive 47 patients (21 by ACAF and 26 by anterior cervical corpectomy and fusion [ACCF]) who have accepted surgery for treatment of cervical ossification of the posterior longitudinal ligament(OPLL) and stenosis from March 2017 to March 2018 were retrospectively reviewed and compared between an ACAF group and ACCF group. Three postoperative radiographic parameters were evaluated: the decompression width and the satisfaction rate of decompression at the entrance zone of intervertebral foramina on computed tomography (CT), and the transverse diameter of spinal cord in the decompression levels on magnetic resonance imaging (MRI). In the anatomic study, three fresh cadaveric spines (death within 3 months) undergoing ACAF surgery were also studied. Four anatomic parameters were evaluated: the width of groove, the distance between the bilateral origins of ventral rootlets, the length of ventral rootlet from their origin to the intervertebral foramina, the descending angle of ventral rootlet.

Results

The groove created in ACAF surgery included the bilateral origins of ventral rootlets. The rootlets tended to be vertical from the rostral to the caudal direction as their takeoff points from the central thecal sac became higher and farther away from their corresponding intervertebral foramina gradually. No differences were identified between left and right in terms of the length of ventral rootlet from the origin to the intervertebral foramina and the descending angle of ventral rootlet. The decompression width was significantly greater in ACAF group (19.2 ± 1.2 vs 14.7 ± 1.2, 21.3 ± 2.2 vs 15.4 ± 0.9, 21.5 ± 2.1 vs 15.7 ± 1.0, 21.9 ± 1.6 vs 15.9 ± 0.8, from C₃ to C₆). The satisfactory rate of decompression at the entrance zone of intervertebral foramina tended to be better in the left side in ACAF group (significant differences were identified in the left side at C_3/4, C_4/5, C_6/7 level, and in the right side at C_4/5 level when compared with ACCF). And decompression width was significantly greater than the transverse diameter of spinal cord in ACAF group. Comparatively, there existed no significant difference in the ACCF group besides the C₅ level.

Conclusion

ACAF can decompress the entrance zone of intervertebral foramina effectively and its decompression width includes the origins and massive running part of bilateral ventral rootlets. Due to its wider decompression range, ACAF can be used as a revision strategy for the patients with failed ACCF.

Intervertebral Foramen Width Is an Important Factor in Deciding Additional Uncinate Process Resection in ACDF-a Retrospective Study

Background: Anterior cervical discectomy and fusion (ACDF) has been established as a classic procedure for the management of cervical radiculopathy. However, it is unclear whether combined uncinate process resection (UPR) is necessary for treating cervical radiculopathy. Here, we investigated the clinical outcome of ACDF combined with UPR compared to ACDF alone to determine the necessity of UPR in treating cervical radiculopathy. Hypothesis: Uncinate process resection may be necessary in certain patients along with ACDF to achieve better clinical outcomes of cervical radiculopathy. Patients and Methods: Fifty-five patients underwent ACDF with UPR, and 126 patients without UPR were reviewed. The width and height of the intervertebral foramen were measured by 45° oblique X-rays. We also measured the Japanese Orthopedic Association (JOA) score and visual analog scale (VAS) score. C2-C7 Cobb angles were obtained from all patients pre- and post-operatively. Meanwhile, linear regression analysis was used to evaluate the relationship between the clinical outcomes and the intervertebral foramen width before surgery. Results: Linear regression analysis indicated that the improvement in the JOA and VAS scores was irrelevant to both the pre-operative width of the intervertebral foramen (wIVF) and the height of the intervertebral foramen (hIVF) in the ACDF+UPR group. However, pre-operative wIVF was associated with post-operative JOA and VAS scores in the ACDF alone group. Those with pre-operative wIVF <3 mm in the ACDF group had the least improvement in post-operative clinical symptoms due to the change in wIVF (P > 0.05). The ACDF group whose wIVF was over 3 mm showed similar clinical outcomes to the ACDF + UPR group, and wIVF significantly increased post-operatively (P < 0.05). The fusion rate and C2-C7 Cobb angles did not show significant differences between the two groups (P > 0.05). Discussion: Our current findings suggest that UPR should be considered when wIVF is <3 mm pre-operatively. However, there is no need to sacrifice the uncovertebral joint in ACDF when the pre-operative wIVF is over 3 mm. Level of Evidence: Level III.

Change in the postoperative intervertebral space height and its impact on clinical and radiological outcomes after ACDF surgery using a zero-profile device: a single-Centre retrospective study of 138 cases

BACKGROUND

The effects of postoperative intervertebral height (IH) changes on the clinical and radiological outcomes after anterior cervical decompression and fusion (ACDF) surgery using a zero-profile device remain unclear.

METHODS

We retrospectively reviewed patients who had undergone ACDF using a zero-profile device from March 2012 to February 2016 at our institution. Based on the postoperative IH variation, the patients were divided into group A with postoperative IH 0 to 2 mm, group B with postoperative IH 2 to 4 mm, and group C with postoperative IH greater than 4 mm. Clinical efficacy was evaluated using JOA, VAS, and NDI scores in the groups. Imaging parameters including the IH, cervical lordosis, fusion rate, intervertebral foramen (IVF) diameter and complications such as subsidence, dysphagia, and ASD were also compared across the three groups.

RESULTS

The average IH increased significantly from 6.72 mm preoperatively to 10.46 mm 1 week after surgery, and then gradually decreased to 7.48 mm at the final follow-up. The fusion rate was 61.90% in group A, 63.23% in group B, 53.57% in group C at 3 months, 73.81% in group A, 79.41% in group B, 67.86% in group C at 6 months, 90.48% in group A, 95.59% in group B, 92.86% in group C 1 year after surgery, and at the last follow-up, the fusion rate of three groups was all 100%. The IVF diameter was 6.52 ± 1.80 mm in group A, 9.55 ± 2.36 mm in group B, and 9.34 ± 1.62 mm in group C. ASD at the superior and inferior levels affected 11.90 and 16.67% patients in group A, 5.88 and 7.38% in group B, and 14.28 and 10.71% in group C. Regarding the 3 groups, the subsidence rates were 7.14, 4.41, and 14.29%, respectively.

CONCLUSIONS

No clear correlation was found between IH changes and clinical efficacy within a year of surgery. However, the IH may affect various complications after ACDF. If postoperative IH changes are maintained at 2 to 4 mm after a year, a satisfactory imaging parameters and relatively low complications may be achieved after ACDF surgery using a zero-profile device.

Intradural Neuroanatomy in the Cervical Spinal Canal: Importance of a New Anatomic Zone Division and Accurate Assessment of Neural Compression in Myeloradiculopathy Patients

This study defined different anatomic zones within the cervical spinal canal and provides detailed anatomical quantitative data for an accurate diagnosis of cervical spondylosis and a safe and effective anterior decompression surgery.

Effect of Changes in Postoperative Intervertebral Space Height on Clinical and Radiological Outcomes After Cervical Disc Replacement

BACKGROUND

Narrowing of intervertebral space height (ISH) is an important pathological change in degenerative spinal disease, and ideal intraoperative distraction and postoperative intervertebral space maintenance is one of the most expectant goals pursued by spinal surgeons. The effect of postoperative ISH changing on the clinical and radiological outcomes after cervical disc replacement is not fully understood, however.

METHODS

In this study, the height variation and general trend of postoperative ISH in all patients were analyzed. The patients were divided into 3 groups based on the change of postoperative intervertebral space height (ISH)-group A (ISH <2 mm), group B (ISH 2-4 mm), and group C (ISH >4mm)-and the clinical and radiographic results compared among the 3 groups.

RESULTS

A total of 120 consecutive patients with symptomatic cervical disc disease were included in this study. The results showed that the mean ISH increased significantly from 0.729 mm before surgery to 1.143 mm at 1 week, then gradually decreased to 1.032 mm at 3 months, 0.980 mm at 6 months, 0.760 mm at one year, and 0.750 mm at the final follow-up. The average postoperative Neck Disability Index (NDI) was 19.73 ± 0.81, 13.74 ± 4.94, 17.19 ± 4.22, respectively, in the 3 groups at 1 year after surgery and the average range of motion (ROM) was 5.44° ± 3.85° in group A, 9.34° ± 4.38° in group B, and 6.51° ± 4.38° in group C. The mean diameter of the intervertebral foramen was 6.54 ± 1.86 mm in group A, 9.63 ± 2.38 mm in group B, and 9.31 ± 1.68 mm in group C. Degeneration at the superiorly adjacent disc level was observed in 13.51% patients in group A, 9.37% in group B, and 21.05% in group C. Degeneration at the inferiorly adjacent level was radiographically identified in 21.62% in group A, 14.06% in group B, and 26.32% in group C.

CONCLUSIONS

This study revealed that cervical disc replacement cannot maintain the intervertebral disc height obtained immediately after surgery. There is no obvious correlation between the change in intervertebral space height and clinical efficacy in the early postoperative stage. Nonetheless, the intervertebral disc height may affect the NDI index 1 year after surgery. If the postoperative intervertebral space height change can be maintained at 2-4 mm at 1 year, satisfactory ROM, intervertebral foramen diameter, and relatively low adjacent segment degeneration may be obtained after cervical disc replacement.

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.

The Neural Sulcus of the Cervical Vertebrae: A Review of Its Anatomy and Surgical Perspectives

The neural sulcus is a bony channel that spans the transverse process in the subaxial cervical spine. It is located between the anterior and posterior tubercles on either side of the transverse foramen, housing the spinal nerve as it passes through the intervertebral foramina. Although numerous studies have evaluated the anatomy of the cervical spine, very little data on detailed anatomy of the neural sulcus and its implication in cervical spine surgery exist. Here, we review the anatomy of the neural sulcus and surgical considerations. The neural sulcus has important surgical implications, and knowledge of its anatomy is important in considering and planning posterior cervical segmented instrumentation. This increases the ability of the neurosurgeon to choose the best suitable surgical approach to the subaxial cervical spine, allowing good outcomes for the patient.

Dimensions of the Subaxial Lateral Mass: A Systematic Review of Anatomic (Morphometric) Measurement Studies

STUDY DESIGN

This was a systematic review.

OBJECTIVE

To review and synthesize information on subaxial lateral mass dimensions in order to determine the ideal starting point, trajectory, and size of a lateral mass screw.

SUMMARY OF BACKGROUND DATA

The use of lateral mass instrumentation for posterior cervical decompression and fusion has become routine as these constructs have increased rigidity and fusion rates.

METHODS

A systematic search of Medline and EMBASE was conducted. Studies that provided subaxial cervical lateral mass measurements, distance to the facet, vertebral artery and neuroforamen and facet angle made either directly (eg, cadaver specimen) or from patient imaging were considered for inclusion. Pooled estimates of mean dimensions were reported with corresponding 95% confidence intervals. Stratified analysis based on level, sex, imaging plane, source (cadaver or imaging), and measurement method was done.

RESULTS

Of the 194 citations identified, 12 cadaver and 10 imaging studies were included. Pooled estimates for C3-C6 were generally consistent for lateral mass height (12.1 mm), width (12.0 mm), depth (10.8 mm), distance to the transverse foramen (11.8 mm), and distance to the nerve. C7 dimensions were most variable. Small sex-based differences in dimensions were noted for height (1.2 mm), width (1.3 mm), depth (0.43 mm), transverse foramen distance (0.9 mm), and nerve distance (0.3-0.8 mm). No firm conclusions regarding differences between measurements made on cadavers and those based on patient computed tomographic images are possible; findings were not consistent across dimensions. The overall strength of evidence is considered very low for all findings.

CONCLUSIONS

Although estimates of height, width, and depth were generally consistent for C3-C6, C7 dimensions were variable. Small sex differences in dimensions may suggest that surgeons should use a slightly smaller screw in female patients. Firm conclusions regarding facet angulation, source of measurement, and method of measurement were not possible.

Differences in Cross-Sectional Intervertebral Foraminal Area From C3 to C7

STUDY DESIGN

Anatomical comparative study.

OBJECTIVES

Few studies have evaluated foraminal areas in the cervical spine without degenerative changes. The purpose of this study was to determine and compare the mean cross-sectional foraminal areas between the C3/4, C4/5, C5/6, and C6/7 levels while also analyzing specimens for differences between sexes and races.

METHODS

We performed an anatomic study of the intervertebral foramen at 4 levels (C3/4, C4/5, C5/6, C6/7) in 100 skeletally mature osseous specimens. Specimens were selected to obtain equal number of African American and Caucasian males and females (n = 25/group) aged 20 to 40 years at time of death. Foramina were photographed bilaterally with and without a silicone rubber disc. The maximal vertical height and mid-sagittal width of each foramen were digitally measured and the areas were calculated using an ellipse as a model.

RESULTS

The average age at death for all specimens was 30 ± 6 years. The mean cross-sectional area of the C4/5 foramen was significantly smaller compared with the C5/6 (P < .001). C5/6 was significantly narrower than C6/7 (P < .001) foramen with and without disc augmentation. C3/4 was not significantly different from more caudal levels. There was no difference between male and female specimens, while African Americans had smaller foraminal sizes than Caucasians.

CONCLUSIONS

This study provides the largest anatomical reference of the cervical intervertebral foramen. In a mature spine without facet joint hypertrophy or osteophytic changes, the C4/5 foramen was narrower than C5/6, which was narrower than C6/7. Understanding the relative foraminal areas in the nonpathological cervical spine is crucial to understanding degenerative changes as well as the anatomical changes in pathologies that affect the intervertebral foramen.

Relationship Between Foraminal Area and Degenerative Changes in the Lower Cervical Spine With Implications for C5 Nerve Root Palsy

Preoperative foraminal stenosis at C4/5 is a predisposing risk factor for C5 nerve root palsy in elderly patients. However, the area of the C4/5 intervertebral foramen and its relationship to the extent of arthrosis and lower foraminal areas (C5/6 and C6/7) are unknown. The authors sought to compare the areas of the cervical intervertebral foramen at the C4/5, C5/6, and C6/7 levels, noting any differences across race or sex and the relationship between foraminal area and arthrosis grade. A total of 600 cervical foramina from an osseous collection were examined. One hundred specimens between the ages of 60 and 80 years were selected, 50 from each sex and race (white and African American). Foramina were photographed bilaterally at C4/5, C5/6, and C6/7. Vertical height and mid-sagittal width were digitally measured. The degree of arthrosis within each intervertebral foramen was graded by 2 of the authors independently using the Kellgren-Lawrence grading system. Average age of death for specimens was 69.3±5.9 years. The mean foraminal areas at C4/5 (P=.001) and C5/6 (P<.001) were significantly smaller than at C6/7. Whites had larger foraminal areas than African Americans at C4/5 (P=.05) and C6/7 (P=.01). Arthrosis grade was found to make a significant contribution to foraminal area at C4/5 (standardized beta=-0.267; P<.001), but not at C5/6 or C6/7. A higher grade of arthrosis was associated with a narrower intervertebral foramen at the C4/5 level in osseous specimens from elderly individuals. [Orthopedics. 2018; 41(4):e506-e510.].

Dynamic foraminal dimensions during neck extension and rotation in fusion and artificial disc replacement: an observational study

BACKGROUND

Changes in the dimensions of the cervical neural foramina (CNF) are considered to be a key factor in nerve root compression and development of cervical radiculopathy. However, to what extent foraminal geometry differs between patients who underwent anterior cervical discectomy and fusion (ACDF) and those who underwent total disc arthroplasty with an artificial disc (AD) during physiological motion is largely unknown.

PURPOSE

The objective of this study is to compare CNF dimensions during physiological neck motion between ACDF and AD.

STUDY DESIGN/SETTING

This is a retrospective comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution.

PATIENT SAMPLE

A total of 16 single-level C5-C6 ACDF (4 males, 12 females; 28-71 years) and 7 single-level C5-C6 cervical arthroplasty patients (3 males, 4 females; 38-57 years), at least 12 months after surgery (23.6±6.8 months) were included.

OUTCOME MEASURES

Patient demographics, preoperative magnetic resonance imaging (MRI)-based measurements of cervical spine degeneration, and 2-year postoperative measurements of dynamic foraminal geometry were the outcome measures.

METHODS

Biplane X-ray images were acquired during axial neck rotation and neck extension. A computed tomography scan was also acquired from C3 to the first thoracic vertebrae. The subaxial cervical vertebrae (C3-C7) were reconstructed into three-dimensional (3D) bone models for use with model-based tracking. Foraminal height (FH) was calculated as the 3D distance between the superior point of the inferior pedicle and the inferior point of the superior pedicle using custom software. Foraminal width (FW) was similarly calculated as the 3D distance between the anterolateral aspect of the superior vertebral body inferior notch and the posterolateral aspect of the inferior vertebral body superior notch. Dynamic foraminal dimensions were quantified as the minimum (FH.Min, FW.Min), the range (FH.Range, FW.Range), and the median (FH.Med, FW.Med) of each trial and then averaged over trials. Mixed model analysis of variance framework was used to examine the differences between ACDF and AD groups. The initial severity of disc degeneration as determined from preoperative MRI images was introduced as covariates in the models.

RESULTS

At the operated level (C5-C6), FH.Med and FH.Range were smaller in ACDF than in AD during axial rotation and neck extension (p<.003 to p<.05). At the superior adjacent level (C4-C5), no significant difference was found. At the inferior adjacent level (C6-C7), FW.Range was greater in ACDF than in AD during axial rotation and extension (p<.05). At the non-adjacent level (C3-C4), FW.Range was greater in ACDF than in AD during extension (p<.008).

CONCLUSIONS

This study demonstrated decreases in foraminal dimensions and their range for ACDF compared with AD at the operated level. In contrast, it demonstrated increases in the range of foraminal dimensions during motion for ACDF compared with AD at the non-operated segments. Together, these data support the notion that increased mobility at the non-operated segments after ACDF may contribute to a greater risk for adjacent segment degeneration. Because of the significant presence of range variables in the findings, the current data also indicate that a dynamic evaluation is likely more appropriate for evaluation of the differences in foramina between ACDF and AD than a static evaluation.

Morphometric changes of the cervical intervertebral foramen: A comparative analysis of pre-manipulative positioning and physiological axial rotation

BACKGROUND

Cervical foraminal impingement has been described as a source of radicular pain. Clinical tests and head motions have been reported for affecting the intervertebral foramen (IVF) dimensions. Although manual approaches are proposed in the management of cervical radiculopathy, their influence on the foraminal dimensions remains unclear.

OBJECTIVES

To investigate the influence of pre-manipulative positioning versus cervical axial rotation on the foraminal dimensions of the lower cervical spine.

METHODS

Thirty asymptomatic volunteers underwent CT scan imaging in neutral position and axial rotation or pre-manipulative positioning. The manipulation task was performed at C4-C5 following a multiple components procedure. 3D kinematics and IVF (height, width and area) were computed for each cervical segment.

RESULTS

The results showed that foraminal changes are dependent on motion types and cervical levels. With reference to head rotation, IVF opening occurred on the ipsilateral side during pre-manipulative positioning while axial rotation involved the contralateral side. Regardless of the side considered, magnitudes of opening were similar between both attitudes while narrowing was lower at the target and adjacent levels during the pre-manipulative positioning. Some associations between segmental motion and IVF changes were observed for the target level and the overlying level.

CONCLUSIONS

The present study demonstrated that pre-manipulative positioning targeting C4-C5 modified IVF dimensions differently than the passive axial rotation. The findings suggest that techniques which incorporate combined movement positioning influence segmental motion and IVF dimensions differently at the target segment, compared to unconstrained rotation. Further investigations are needed to determine the clinical outcomes of such an approach.

Influences of different lower cervical bone graft heights on the size of the intervertebral foramen: multiple planar dynamic measurements with laser scanning

The aim of this study is to evaluate the influences of different bone graft heights on the size of the intervertebral foramen, which will help determine the optimal graft height in clinical practice. Six fresh adult cadavers were used, with the C5-C6 vertebral column segment defined as the functional spinal unit (FSU). After discectomy, the C5/6 intervertebral height was set as the baseline height (normal disc height). We initially used spiral computed tomography (CT) to scan and measure the middle area of the intervertebral foramen when at the baseline height. Data regarding the spatial relationship of C5-C6 were subsequently collected with a laser scanner. Grafting with four different sized grafts, namely, grafts of 100, 130, 160, and 190% of the baseline height, was implanted. Moreover, we scanned to display the FSU in the four different states using Geomagic8.0 studio software. Multiple planar dynamic measurements (MPDM) were adopted to measure the intervertebral foramen volume, middle area, and areas of internal and external opening. MPDM with a laser scanner precisely measured the middle area of the intervertebral foramen as spiral CT, and it is easy to simulate the different grafts implanted. With the increase of the bone graft height, the size of the intervertebral foramen began to decrease after it increased to a certain point, when grafts of 160% of the baseline height implanted. MPDM of the intervertebral foramens with laser scanning three-dimensional (3D) reconstitution are relatively objective and accurate. The recommended optimal graft height of cervical spondylosis is 160% of the mean height of adjacent normal intervertebral spaces.

Quantitative Gross and CT measurements of Cadaveric Cervical Vertebrae (C3 - C6) as Guidelines for the Lateral mass screw fixation

BACKGROUND

Lateral mass screw fixation is the treatment of choice for posterior cervical stabilization. Long or misdirected screws carry a risk of injury to spinal nerve roots or vertebral artery. This study was aimed to assess the gross anatomic and CT measurements of typical cervical vertebrae for the selection of lateral mass screws.

METHODS

Dimensions of the articular pillars were measured on 1) Dry cervical vertebrae with Vernier calipers and 2) Multiplanar reformations of CT scans of the same vertebrae with Viewer software package. The data was statistically evaluated.

RESULTS

The transverse diameter of the articular pillars with Vernier calipers varied from 6.0 to 15.4 mm (mean=10.5 mm ± 1.5) and on CT scans ranged from 8.2 - 16.1 mm (mean=11.6 mm ± 1.4). The antero-posterior diameter, an estimate of the screw length by Roy-Camille technique varied from 3.9 to 12.7 mm (mean=8.6 mm ± 1.6) by Vernier calipers and from 6.4 to 13.3 mm (mean=9.1 ± 1.2) on CT scans. The oblique AP diameter, an estimate of screw length by Magerl method varied from 10.8 to 20.3 mm (mean=14.9 mm ± 1.8) by Vernier calipers and from 11.4 to 19.3 mm (mean=14.5 mm ± 1.7) on CT. The CT measurements for height, transverse and AP diameter of the articular pillars were 0.5 - 1.0 mm larger than dimensions by Vernier calipers. No statistically significant difference was observed between the caliper and CT measurements for the oblique AP diameter.

CONCLUSION

CT measurements of the articular pillars may slightly overestimate the desired screw length selected by spine surgeons when compared to actual anatomy. Although means of the articular pillars correspond to the screw lengths used, substantial number of observations below 10 mm for Roy-Camille trajectory and below 14 mm for Magerl trajectory requires careful preoperative planning and intra-operative confirmation to avoid long/misdirected lateral mass screws.

Dimensional changes of the neuroforamina in subaxial cervical spine during in vivo dynamic flexion-extension

BACKGROUND CONTEXT

Neuroforaminal stenosis is one of the key factors causing clinical symptoms in patients with cervical radiculopathy. Previous quantitative studies on the neuroforaminal dimensions have focused on measurements in a static position. Little is known about dimensional changes of the neuroforamina in the cervical spine during functional dynamic neck motion under physiological loading conditions.

PURPOSE

This study aimed to investigate the in vivo dimensional changes of the neuroforamina in human cervical spine (C3-C7) during dynamic flexion-extension neck motion.

STUDY DESIGN

A case-control study was carried out.

METHODS

Ten asymptomatic subjects were recruited for this study. The cervical spine of each subject underwent magnetic resonance image scanning for construction of three-dimensional (3-D) vertebrae models from C3 to C7. The cervical spine was then imaged using a dual fluoroscopic system while the subject performed a dynamic flexion-extension neck motion in a sitting position. The 3-D vertebral models and the fluoroscopic images were used to reproduce the in vivo vertebral motion. The dimensions (area, height, and width) were measured for each cervical neuroforamen (C3/C4, C4/C5, C5/C6, and C6/C7) in the following functional positions: neutral position, maximal flexion, and maximal extension. Repeated measures analysis of variance and post hoc analysis were used to examine the differences between levels and positions.

RESULTS

Compared with the neutral position, almost all dimensional parameters (area, height, and width) of the subaxial cervical neuroforamina decreased in extension and increased in flexion, except the neuroforaminal area at C5/C6 (p=.07), and the neuroforaminal height at C6/C7 (p=.05) remained relatively constant from neutral to extension. When comparisons of the overall change fromextension to flexion were made between segments, the overall changes of the neuroforaminal area and height revealed no significant differences between segments, and the width overall change of the upper levels (C3/C4 and C4/C5) was significantly greater than the lower levels (C5/C6 and C6/C7) (p<.01).

CONCLUSIONS

The dimensional changes of the cervical neuroforamina showed segment-dependent characteristics during the dynamic flexion-extension. These data may have implications for diagnosis and treatment of patients with cervical radiculopathy.

Virtual pathology of cervical radiculopathy based on 3D MR/CT fusion images: impingement, flattening or twisted condition of the compressed nerve root in three cases

Background

There have been several imaging studies of cervical radiculopathy, but no three-dimensional (3D) images have shown the path, position, and pathological changes of the cervical nerve roots and spinal root ganglion relative to the cervical bony structure. The objective of this study was to introduce a technique that enables the virtual pathology of the nerve root to be assessed using 3D magnetic resonance (MR)/computed tomography (CT) fusion images that show the compression of the proximal portion of the cervical nerve root by both the herniated disc and the preforaminal or foraminal bony spur in patients with cervical radiculopathy.

Findings

MR and CT images were obtained from three patients with cervical radiculopathy. 3D MR images were placed onto 3D CT images using a computer workstation.

The entire nerve root could be visualized in 3D with or without the vertebrae. The most important characteristic evident on the images was flattening of the nerve root by a bony spur. The affected root was constricted at a pre-ganglion site. In cases of severe deformity, the flattened portion of the root seemed to change the angle of its path, resulting in twisted condition.

Conclusions

The 3D MR/CT fusion imaging technique enhances visualization of pathoanatomy in cervical hidden area that is composed of the root and intervertebral foramen. This technique provides two distinct advantages for diagnosis of cervical radiculopathy. First, the isolation of individual vertebra clarifies the deformities of the whole root groove, including both the uncinate process and superior articular process in the cervical spine. Second, the tortuous or twisted condition of a compressed root can be visualized.

The surgeon can identify the narrowest face of the root if they view the MR/CT fusion image from the posterolateral-inferior direction. Surgeons use MR/CT fusion images as a pre-operative map and for intraoperative navigation. The MR/CT fusion images can also be used as educational materials for all hospital staff and for patients and patients’ families who provide informed consent for treatments.

Cervical neural space narrowing during simulated rear crashes with anti-whiplash systems

PURPOSE

Chronic radicular symptoms have been documented in whiplash patients, potentially caused by cervical neural tissue compression during an automobile rear crash. Our goals were to determine neural space narrowing of the lower cervical spine during simulated rear crashes with whiplash protection system (WHIPS) and active head restraint (AHR) and to compare these data to those obtained with no head restraint (NHR). We extrapolated our results to determine the potential for cord, ganglion, and nerve root compression.

METHODS

Our model, consisting of a human neck specimen within a BioRID II crash dummy, was subjected to simulated rear crashes in a WHIPS seat (n = 6, peak 12.0 g and ΔV 11.4 kph) or AHR seat and subsequently with NHR (n = 6, peak 11.0 g and ΔV 10.2 kph with AHR; peak 11.5 g and ΔV 10.7 kph with NHR). Cervical canal and foraminal narrowing were computed and average peak values statistically compared (P < 0.05) between WHIPS, AHR, and NHR.

RESULTS

Average peak canal and foramen narrowing could not be statistically differentiated between WHIPS, AHR, or NHR. Peak narrowing with WHIPS or AHR was 2.7 mm for canal diameter and 1.6 mm, 2.7 mm, and 5.9 mm(2) for foraminal width, height and area, respectively.

CONCLUSIONS

While lower cervical spine cord compression during a rear crash is unlikely in those with normal canal diameters, our results demonstrated foraminal kinematics sufficient to compress spinal ganglia and nerve roots. Future anti-whiplash systems designed to reduce cervical neural space narrowing may lead to reduced radicular symptoms in whiplash patients.

Automated measurement of neural foramen cross-sectional area during in vivo functional movement

An automated technique to measure neural foramen cross-sectional area during in vivo, multi-planar movements is presented. This method combines three-dimensional (3D) models of each vertebra obtained from CT scans with in vivo movement data collected using high-speed biplane radiography. A novel computer algorithm that automatically traces a path around the bony boundary that defines the neural foramen at every frame of X-ray data is described. After identifying the neural foramen boundary, the cross-sectional area is calculated. The technique is demonstrated using data collected from a patient with cervical radiculopathy who is tested before and after conservative treatment. The technique presented here can be applied when 3D, dynamic, functional movements are performed. Neural foramen cross-sectional area can be quantified at specific angles of intervertebral rotation, allowing for matched comparisons between two trials or two test sessions. The present technique is ideal for longitudinal studies involving subjects who receive conservative or surgical treatments that may affect spine motion.

Anatomical considerations for the placement of cervical transarticular screws

Object

The object of this study was to determine the safe screw placement technique for cervical transarticular screw fixation.

Methods

Twenty cadaveric adult cervical spines were studied. All soft tissues surrounding the cervical spinal nerves from C-2 to T-1 were dissected carefully to expose the lateral mass, facet joint, transverse process, vertebral artery (VA), and spinal nerves (ventral and dorsal rami). After the proper entrance and exit points for the transarticular screws were determined, posterior transarticular screw implantation was performed under direct visualization from C2–3 to C5–6. A CT scan was performed to check the screw placement. The angle and length of the transarticular screw trajectory, the distance between the tip of the screw and the VA, and the sagittal safety angle were measured on the CT scan. Statistical analysis was performed using ANOVA (p < 0.05). Sagittal and axial orientations of transarticular screws were carefully analyzed.

Results

There was no nerve or artery impingement or penetration. The average caudal angle of the screws in the sagittal plane was 37.3° ± 5.0° and the lateral angle in the axial plane was 16.6° ± 4.6°. The average distance between the tip of the screw and the VA (the posterior border of the VA foramen) was 5.8 ± 1.5 mm. The average sagittal safety angle was 41.9° ± 5.6°. No difference was observed according to the vertebral level. The average bone purchase was 18.7 ± 1.4 mm. Bone purchase was significantly greater at C2–3 (23.2 ± 1.6 mm) than at C3–4 through C5–6 (17.2 ± 1.3 mm, p < 0.05).

Conclusions

This study establishes anatomical guidelines to allow for safe cervical transarticular screw insertion. The starting point of transarticular screws should be 1 mm medial to the midpoint of the lateral mass. The “ideal” drilling angle is approximately 37° in the inferior direction and 16° in the lateral direction for the C2–3 through the C5–6 levels. The screw should be directed as laterally as possible in the axial plane without causing the lateral mass to fracture and as caudally as the occipital bone permits in the sagittal plane. The ideal screw size would be 3.5 mm in diameter and 18 mm in length.

Longitud de las raíces cervicales en resonancia magnética: relación con la parálisis postoperatoria de la quinta raíz cervical

OBJETIVO: determinar la longitud de la raíz C5. MÉTODOS: se estudiaron con resonancia magnética (Signa 1,5 T, cortes axiales de 5 mm de espesura, TR=850, TE=26, FOV=200) las columnas cervicales de 50 pacientes (29 hombres - 21 mujeres) entre 26 y 68 años. Se incluyeron solo casos con cervicalgia y/o cervicobraquialgia. Se midió (en mm) la longitud de las raíces cervicales tercera a séptima, derechas e izquierdas. La comparación de los promedios se realizó a través del análisis de varianza, para un nivel de significación α=0,05 con IC de 95%. Las comparaciones post-hoc se hicieron empleando el test de Bonferroni. RESULTADOS: se observó que el lado (derecho o izquierdo) y el sexo (varón o mujer) no tuvieron incidencia estadísticamente significativa en el valor de la longitud de las raíces (p>0,05). La raíz C5 tuvo un tamaño significativamente diferente (p<0,05) a cada una de las raíces, pero se comprobó que la raíz más corta era C3. CONCLUSIÓN: la raíz C5 no es la más corta.

Quantitative changes in the cervical neural foramen resulting from axial traction: in vivo imaging study

BACKGROUND CONTEXT

Cervical traction has a long history as a method of conservative treatment for cervical spine diseases. However, information on quantitative changes in the cervical neural foramen resulting from axial traction in vivo is lacking.

PURPOSE

To quantitatively evaluate the changes in the neural foramen of the cervical spine during axial traction in vivo.

STUDY DESIGN

A prospective radiographic analysis of the cervical neural foramen of adult volunteers.

PATIENT SAMPLE

Fifteen healthy volunteers (10 men, 5 women) without any history of cervical spine disease.

OUTCOME MEASURES

The changes in cervical cross-sectional foraminal areas and heights were measured.

METHODS

Cervical magnetic resonance (MR) images of the volunteers were taken at the neutral position and were reconstructed in the oblique plane perpendicular to the long axis of each neural foramen from the C2-3 to the C6-7 level. The changes in the neural foraminal dimensions at incremental axial traction forces (0, 5, 10, and 15 kg) were analyzed.

RESULTS

After each 5-kg incremental increase in traction weight, there was a significant (p value less than .05) increase in area and height of the intervertebral foramen compared with the position in which no weight was applied. There was an average increase of 5.81%, 16.56%, and 18.9% in the foraminal area and an average increase of 3.75%, 8.67%, and 10.43% in foraminal height compared with the position with no weight at traction of 5, 10, and 15 kg, respectively. There was no statistically significant difference for the increase in foraminal area and height from 10 to 15 kg of traction (p value greater than .05).

CONCLUSIONS

There was a significant increase in intervertebral foraminal area and height after each 5-kg increment in traction weight compared with the position in which no weight was applied. From 10 to 15 kg of traction, there was no significant change in the foraminal area and height.

Quantitative anatomy of subaxial cervical lateral mass: an analysis of safe screw lengths for Roy-Camille and magerl techniques

STUDY DESIGN

Determination of lateral mass screw lengths with Roy-Camille and Magerl techniques of screw insertion using computerized tomography in 98 young, asymptomatic North American volunteers.

OBJECTIVE

To provide reliable and normative data on safe screw lengths using the Roy-Camille and Magerl techniques of lateral mass fixation in the subaxial cervical spine.

SUMMARY OF BACKGROUND DATA

Lateral mass screw lengths have been studied in the past using differing subject and measurement characteristics and small sample sizes. Results demonstrated considerable variation in screw length and influencing factors. Inappropriate screw lengths can result in neurovascular injury during screw insertion, facet joint damage, or inadequate fixation.

METHODS

Bicortical screw lengths were bilaterally measured at each spinal level from C3-C7 in 98 young volunteers using computed tomography reconstructions through the lateral masses obtained in the plane of the screw in Roy-Camille and Magerl techniques.

RESULTS

With both techniques, trajectories were longest at C4-C6, shorter at C3, and shortest at C7. Screw lengths were greater in males when compared with females at all levels. Average Magerl screw lengths were approximately 2.6 mm longer at C3-C6 levels, and approximately 1.3 mm longer at the C7 level when compared with Roy-Camille technique. There was minimal correlation between screw lengths and anthropometric measurements including stature, body weight, and neck length.

CONCLUSION

Significant variations exist at each subaxial level with either technique. We recommend the surgeon determine screw lengths for fixation at each level using preoperative sagittal oblique computed tomography scans, which provide the most accurate technique of preoperative templating for screw length.

Morphologic and morphometric magnetic resonance imaging features of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy

OBJECTIVE

To compare morphologic and morphometric features of the cervical vertebral column and spinal cord of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy (CSM; wobbler syndrome) detected via magnetic resonance imaging (MRI).

ANIMALS

16 clinically normal and 16 CSM-affected Doberman Pinschers.

PROCEDURES

For each dog, MRI of the cervical vertebral column (in neutral and traction positions) was performed. Morphologically, MRI abnormalities were classified according to a spinal cord compression scale. Foraminal stenosis and intervertebral disk degeneration and protrusion were also recorded. Morphometric measurements of the vertebral canal and spinal cord were obtained in sagittal and transverse MRI planes.

RESULTS

4 of 16 clinically normal and 15 of 16 CSM-affected dogs had spinal cord compression. Twelve clinically normal and all CSM-affected dogs had disk degeneration. Foraminal stenosis was detected in 11 clinically normal and 14 CSM-affected dogs. Vertebral canal and spinal cord areas were consistently smaller in CSM-affected dogs, compared with clinically normal dogs. In neutral and traction positions, the intervertebral disks of CSM-affected dogs were wider than those of clinically normal dogs but the amount of disk distraction was similar between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

The incidence of intervertebral disk degeneration and foraminal stenosis in clinically normal Doberman Pinschers was high; cervical spinal cord compression may be present without concurrent clinical signs. A combination of static factors (ie, a relatively stenotic vertebral canal and wider intervertebral disks) distinguished CSM-affected dogs from clinically normal dogs and appears to be a key feature in the pathogenesis of CSM.

Human osseous intervertebral foramen width

Alterations of the width of the human intervertebral foramen can play a pathophysiological role in low back pain. Osseous dimensions of the human intervertebral foramen are rarely recorded. Therefore, we present reference data obtained from skeletal samples of known lifestyle, population affinity, sex, and age at death. Cervical, thoracic, and lumbar vertebrae of functional transition zones of 71 macroscopically normal spines from early 19th century AD Swiss burial sites were selected. The intervertebral foramen widths (IFW) were analyzed with respect to possible lateralization and the impact of sex, individual age, and stature. Neither a significant side difference nor a correlation of IFW with individual age or stature could be found. Females show somewhat larger IFW than males, especially in the lumbar region. Data comparisons with earlier studies are limited due to methodological differences and possible interpopulational variations. Furthermore, the osseous intervertebral foramen only reveals a glimpse of the clinically relevant in vivo structure. Nevertheless, more focus on the osseous dimensions of the intervertebral foramen will provide baseline data of this important anatomical landmark. These data could also explore the peculiarities of the intervertebral foramen, such as its reverse sex dimorphism.

Head-turned rear impact causing dynamic cervical intervertebral foramen narrowing: implications for ganglion and nerve root injury

OBJECT

A rotated head posture at the time of vehicular rear impact has been correlated with a higher incidence and greater severity of chronic radicular symptoms than accidents occurring with the occupant facing forward. No studies have been conducted to quantify the dynamic changes in foramen dimensions during head-turned rear-impact collisions. The objectives of this study were to quantify the changes in foraminal width, height, and area during head-turned rear-impact collisions and to determine if dynamic narrowing causes potential cervical nerve root or ganglion impingement.

METHODS

The authors subjected a whole cervical spine model with muscle force replication and a surrogate head to simulated head-turned rear impacts of 3.5, 5, 6.5, and 8 G following a noninjurious 2-G baseline acceleration. Continuous dynamic foraminal width, height, and area narrowing were recorded, and peaks were determined during each impact; these data were then statistically compared with those obtained at baseline. The authors observed significant increases (p < 0.05) in mean peak foraminal width narrowing values greater than baseline values, of up to 1.8 mm in the left C5-6 foramen at 8 G. At the right C2-3 foramen, the mean peak dynamic foraminal height was significantly narrower than baseline when subjected to rear-impacts of 5 and 6.5 G, but no significant increases in foraminal area were observed. Analysis of the results indicated that the greatest potential for cervical ganglion compression injury existed at C5-6 and C6-7. Greater potential for ganglion compression injury existed at C3-4 and C4-5 during head-turned rear impact than during head-forward rear impact.

CONCLUSIONS

Extrapolation of present results indicated potential ganglion compression in patients with a non-stenotic foramen at C5-6 and C6-7; in patients with a stenotic foramen the injury risk greatly increases and spreads to include the C3-4 through C6-7 as well as C4-5 through C6-7 nerve roots.

Calculation of dynamic spinal ligament deformation

OBJECTIVE

Previous methods to determine spinal ligament deformation have included either custom-designed transducers or computational methods using rigid body transformation of kinematic data. Goals of the present study were to describe a computational methodology to determine dynamic deformations of an arbitrarily oriented ligament in a spine specimen and its associated errors.

METHODS

Calculation of ligament deformation in a spinal segment with vertebral motion tracking flags utilized digital stereophotography, lateral neutral posture radiograph, and detailed quantitative anatomy to develop geometrical relationships between flag markers and ligament attachment points. A custom jig, consisting of two flags each with four markers, was constructed to quantify errors associated with computed ligament deformation, flag marker translation, and flag rotation.

RESULTS

Average error in ligament deformation was dependent upon motion direction and ranged between 0.03 mm (SD 0.45 mm) and 0.28 mm (SD 0.18 mm). Average error for flag marker translation ranged between 0.02 mm (SD 0.14 mm) and 0.11 mm (SD 0.39 mm), and for flag rotation ranged between -0.06 degrees (SD 0.17 degrees ) and 0.07 degrees (SD 0.12 degrees ).

CONCLUSIONS

Accuracy of the present technique was equivalent to or greater than that of previous methods. The present technique utilized relatively cost-effective digital stereophotography, and may be used to calculate strain in ligaments not readily accessible for transducer application. The methodology has wide-spread applicability for analyses of dynamic or static spinal or other ligament strains, and may be used to determine spinal canal and intervertebral foramen narrowing and area reduction.

Dynamic intervertebral foramen narrowing during simulated rear impact

STUDY DESIGN

A biomechanical study of intervertebral foraminal narrowing during simulated automotive rear impacts.

OBJECTIVES

To quantify foraminal width, height, and area narrowing during simulated rear impact, and evaluate the potential for nerve root and ganglion impingement in individuals with and without foraminal spondylosis.

SUMMARY OF BACKGROUND DATA

Muscle weakness and paresthesias, documented in whiplash patients, have been associated with neural compression within the cervical intervertebral foramen. To our knowledge, no studies have comprehensively examined dynamic changes in foramen dimensions.

METHODS

There were 6 whole cervical spine specimens (average age 70.8 years) with muscle force replication and surrogate head that underwent simulated rear impact at 3.5, 5, 6.5, and 8 g, following noninjurious baseline 2 g acceleration. Peak dynamic narrowing of foraminal width, height, and area were determined during each impact and statistically compared to baseline narrowing.

RESULTS

Significant increases (P < 0.05) in average peak foraminal width narrowing above baseline were observed at C5-C6 beginning with 3.5 g impact. No significant increases in average peak foraminal height narrowing were observed, while average peak foraminal areas were significantly narrower than baseline at C4-C5 at 3.5, 5, and 6.5 g.

CONCLUSIONS

Extrapolation of the present results indicated that the highest potential for ganglia compression injury was at the lower cervical spine, C5-C6 and C6-C7. Acute ganglia compression may produce a sensitized neural response to repeat compression, leading to chronic radiculopathy following rear impact.

Quantitative analysis of changes in cervical intervertebral foramen size with vertebral translation

STUDY DESIGN

Simulated translation of the C5 vertebra was performed in 20 embalmed cadaveric cervical spines, and cross-sectional areas of the C4-C5 and C5-C6 intervertebral foramina were measured and compared before and after translation of the C5 vertebra.

OBJECTIVE

To determine the relationship of cross-sectional intervertebral foraminal areas to the degrees of vertebral translation.

SUMMARY OF BACKGROUND DATA

The common feature of clinical instability and adjacent diseases of the cervical spine is malalignment of the cervical spine (i.e., there is ventral and dorsal translation of vertebral body with respect to the adjacent upper and lower vertebral body, respectively). To our knowledge, no previous study has analyzed the quantitative effect of vertebral translation on the size of the intervertebral foramina.

METHODS

The cross-sectional areas of the intervertebral foramina at C4-C5 and C5-C6 were measured on computerized tomography. The images were then transferred to the personal computer, where consecutive dorsal translations of C5 vertebrae with a 1-mm increment from 1 to 5-mm displacements were performed using Microsoft paint software (Microsoft, Corp., Redmond, WA). National Institutes of Health (Bethesda, MD) Image J software (V1.33m) was then used to measure the areas of both sides of C4-C5 and C4-C6 foramina at normal and each displacement level in the computer.

RESULTS

Following dorsal translation of C5 vertebra, anterolisthesis of C4 relative to C5 and retrolisthesis of C5 relative to C6 was noted. No significant difference was found between the measured values using Aquarius Image software (Microsoft, Corp.) on computerized tomography and National Institutes of Health image J software on the desktop computer (P > 0.05). When compared with normal values, there was an increase in the C4-C5 intervertebral foraminal area (i.e., 6%, 14%, 18%, 21%, and 26% with anterolisthesis of C4 relative to C5 following 1, 2, 3, 4, and 5-mm dorsal translation of the C5 vertebra, respectively). There was a 12% decrease in the C5-C6 intervertebral foraminal area, with each 1-mm incremental retrolisthesis of C5 relative to C6 vertebra. Statistically significant differences were found among residual cross-sectional foraminal areas following different degrees of dorsal translation (P < 0.05).

CONCLUSION

There is a significant increase in size with anterolisthesis and decrease in size with retrolisthesis of upper and lower adjacent vertebral intervertebral foramina, respectively.

Clinical characterizations and radiologic findings of pure foraminal-type cervical disc herniation: CT discography as a useful adjuvant in its precise diagnosis

STUDY DESIGN

A retrospective study of 15 cases of pure foraminal type cervical disc herniation (CDH) was performed.

OBJECTIVES

The objectives were to describe the clinical characteristics and to assess the radiologic findings.

SUMMARY OF BACKGROUND DATA

Although foraminal lumbar disc herniation has been reported, pure foraminal-type CDH has not been fully elucidated. It is not only a rare condition but also a difficult one to diagnose.

METHODS

All patients underwent MRI, CT myelography (CTM), and CT discography (CTD). Herniated discs were removed by the posterior approach. Clinical symptoms were evaluated at preoperative and postoperative period.

RESULTS

On MRI, 2 cases were positive, 6 cases were suspected, and 7 cases were negative. On CTM, 7 cases were positive and 8 cases were negative; and on CTD, all cases were positive. As to the association between the herniated disc and posterior longitudinal ligament, 12 cases were intraligamentous. The association between the herniated disc and nerve root revealed that 10 discs were at the axillary portion of the nerve root.

CONCLUSIONS

Pure foraminal-type CDH may be overlooked with conventional MRI or CTM, so CTD should be performed. It provides valuable and additional information in difficult or ambiguous cases such as pure foraminal type.

Quantitative anatomic evaluation of cervical lateral mass fixation with a comparison of the Roy-Camille and the Magerl screw techniques

STUDY DESIGN

An anatomic and computed tomography (CT) study of the Roy-Camille and the Magerl techniques with quantitative comparison of the safety zones of the two surgical techniques.

OBJECT

The purpose of this study was to compare quantitatively the safety zones of the Roy-Camille and the Magerl techniques as a function of the vertebral level from C3-C6.

SUMMARY OF BACKGROUND DATA

The two most popular techniques for lateral mass screws are the Roy-Camille and the Magerl technique. Nerve roots, vertebral artery, facet joints, and the spinal cord are at risk during the placement of lateral mass screws. Several anatomic studies are reported, but there is no comparative and quantitative evaluation. The influence of the vertebral level was never reported.

METHODS

Lateral mass screws were first implanted on four cervical spines according to the two surgical techniques. Screws were then extracted and their cavities filled with a blue casting medium. To determine the precise limits of each safety zone in the sagittal plane, the specimens were sectioned according to the sagittal angulation of the two screwing techniques. The correlations between the anatomic landmarks on the specimen and the anatomic landmarks on the CT scan were established. One hundred and sixty lateral mass screws were then implanted in 20 cervical spines from C3-C6. A CT was done before and after placing lateral mass screws. On the morphologic CT scan, we measured the sagittal safety angle (SSA) for each surgical technique and also performed a morphometry of lateral masses. On the control CT scan, we analyzed screws placement in relation to the sagittal safety zone.

RESULTS

The mean SSA was 15.8 +/- 6.3 degrees for the Roy-Camille technique and 18.7 +/- 3.8 degrees for the Magerl technique, P < 0.005. With respect to the vertebral level, the Roy-Camille safety zone decreased from C3-C6 with a greater angulation at C3-C4 (20.4 +/- 4.7 degrees ) than at C5-C6 (11.6 +/- 4.3 degrees ), P < 0.001. Such variations were not observed for the Magerl technique, the SSA of which was 19.4 +/- 3.6 degrees at C5-C6 and 17.9 +/- 4 degrees at C3-C4, P < 0.01. Lateral masses became more elongated and thinner at the lower segment of the cervical spine with a C3-C4 height/thickness ratio = 1.1 +/- 0.3 and a C5-C6 height/thickness ratio = 1.3 +/- 0.2, P < 0.005. Roy-Camille screws (19%) were found out of the safety zone at C3-C4 whereas 37.5% were found outside at C5-C6, P < 0.05. We observed opposite results for Magerl screws with 38% screws out of the safety zone at C3-C4 and only 17.5% outside at C5-C6, P < 0.05.

CONCLUSION

The Roy-Camille technique demonstrated a progressive decrease of its safety zone from C3-C6. At C5 and C6 there is a great probability to have a transarticular screw with a Roy-Camille screw. A similar variation was not observed for the Magerl technique. These anatomic results seem to be in relation with the morphologic variability of lateral masses from C3-C6 as demonstrated by an increase of the height/thickness ratio at the lower part of the cervical spine. According to these anatomic considerations and previously published biomechanical data, Roy-Camille technique appears to be the best option at C3 and C4. On the opposite at C5 and C6, the choice is more difficult considering that there is no biomechanical difference between the two techniques and that the Magerl technique is safer but a more demanding procedure.

Age-dependent changes of the normal human spine during adulthood

The impact of aging on the morphology of the osseous spine is still debated. Clinical studies usually record combined aging effects, as well as age-related degenerative changes. The aim of this study was to determine the impact of (degeneration-independent) aging on the morphology of the osseous human spine during adulthood. Various osseous dimensions of human spinal landmarks at all major vertebral levels have been assessed in macroscopically normal Swiss skeletons (N = 71), with historically known sex and age at death, as well as in larger Central European skeletal samples (N = 277) with anthropologically determined individual age and sex. All measurements were correlated with individual age (or age group) by linear regression and analyzed separately for each sex. Only few osseous spinal dimensions, and only in men, correlate significantly with individual age. Generally, the significant dimensions show an increase in size during adulthood. Similar tendencies, but with significant alterations of spinal measurements in women as well, can be found in the larger samples with anthropologically determined sex and age group. Increase of certain spinal dimensions found in this study may be a reflection of an increase in the robustness of individuals with age. Because of the absence of a significant secular alteration of stature within the well-recorded sample, we exclude secular change in body dimensions as a major bias.

The effect of posterior cervical distraction on foraminal dimensions utilizing a screw-rod system

STUDY DESIGN

Cadaveric human cervical spine anatomic study using posterior lateral mass screw-rod instrumentation to assess foraminal enlargement via distraction techniques.

OBJECTIVES

To determine the role of posterior cervical distraction on foraminal dimensions and to ascertain the impact of this technique on segmental kyphosis.

SUMMARY OF BACKGROUND DATA

Management of cervical spondylotic radiculopathy includes removal of offending compressive structures and enlarging the neuroforamen via anterior discectomy with interbody fusion or posterior laminoforaminotomy.

METHODS

Six human cervical spines were prepared and posterior exposure performed. Lateral mass screws were inserted from C5 to C7 and a longitudinal rod attached. Distraction was applied between the screw heads at 2 mm intervals and accuracy confirmed with digitized calipers. Pre- and postdistraction computed tomography was performed including axial and reformatted images. Foraminal area, height, and width and sagittal alignment and disc heights were evaluated.

RESULTS

The results suggest that minimal posterior distraction of 4 to 6 mm at C5-C6 and C6-C7 may enlarge the neuroforamen by 10 to 18 mm. Foraminal height and width increased minimally from baseline to maximum distraction; however, these measurements did not reach statistical significance at either level. A decrease of segmental lordosis at C5-C6 was noted from baseline to 8 mm of distraction. Statistically significant kyphosis from baseline was present at 6 mm of distraction leading to overall 5.2 +/- 1.4degrees change in alignment. At C6-C7, statistically significant kyphosis was not present until 8 mm of distraction (4.62 +/- 2.23degrees).

CONCLUSIONS

This study suggests that posterior cervical instrumented distraction in the setting of foraminal stenosis is a reasonable supplement to direct laminoforaminotomy and nerve root decompression. Distraction leads to minimal segmental kyphosis, allowing this technique to serve as an adjunct for additional foraminal enlargement.

Clinical perspectives on secular trends of intervertebral foramen diameters in an industrialized European society

Low back pain origins have been a matter of great controversy. While spinal stenosis is now radiologically traceable, the alteration of intervertebral foramen is less clear. The aim of this study was to assess "secular trends"-alterations occurring from one generation to the next-in osseous intervertebral foramina of the major vertebral segments in an industrialized society, and to discuss their possible clinical implication. The macerated "maximum intervertebral foramen width" and "intervertebral foramen height" of all major vertebral levels in 71 non-pathologic Swiss adult skeletons from the nineteenth and early twentieth century, with known individual age and sex and similar geographic and socio-economic background, were measured by sliding caliper at validated landmarks. A secular trend of the increase in "maximum intervertebral foramen width" is found for most levels, with females showing a more prominent alteration. Additionally, the non-pathologic "maximum intervertebral foramen width" does not change with respect to individual age, nor is a significant side difference detectable. "Intervertebral foramen height," hereby defined as the difference of the dorsal vertebral body height minus pedicle height, demonstrates for most levels, and either sex, an insignificant negative secular trend. Neither stature nor skeletal robustness vary significantly through time within this particular sample. The results of this study, despite obvious inadequacies of methods used, exclude secular narrowing of the "maximum intervertebral foramen width" as the only cause of radiculopathy or spinal stenosis. Furthermore, we found a mild insignificant decrease of the clinically more relevant "intervertebral foramen height." Nevertheless, the detected short-time variability of the bony intervertebral foramen, independent of individual stature, skeletal robustness or age, argues for an enhanced focus on the understanding of clinically relevant changes of spinal morphology from generation to generation.

The relationship between disc degeneration and morphologic changes in the intervertebral foramen of the cervical spine: a cadaveric MRI and CT study

A cadaveric study was performed to investigate the relationship between disc degeneration and morphological changes in the intervertebral foramen of cervical spine, including the effect on the nerve root. Seven fresh frozen human cadavers were dissected from C1 to T1, preserving the ligaments, capsules, intervertebral disc and the neural structures. The specimens were scanned with MRI and then scanned through CT scan in the upright position. Direct mid-sagittal and 45 degree oblique images were obtained to measure the dimension of the intervertebral disc height, foraminal height, width, area and segmental angles. Disc degeneration was inversely correlated with disc height. There was a significant correlation between disc degeneration and foraminal width (p<0.005) and foraminal area (p< 0.05), but not with foraminal height. Disc height was correlated with foraminal width but not with height. The segmental angles were decreased more in advanced degenerated discs. There was a correlation between nerve root compression and decreased foraminal width and area (p<0.005). This information and critical dimensions of the intervertebral foramen for nerve root compression should help in the diagnosis of foraminal stenosis of the cervical spine in patients presenting with cervical spondylosis and radiculopathy.

Clinical importance of ligamentous and osseous structures in the cervical uncovertebral foraminal region

The vertebral artery, cervical spinal nerves, spinal nerve roots, and the bony and ligamentous tissue related to the cervical vertebrae are structures whose anatomy determines the path of a surgical approach. Defining the anatomy and, in particular, determining the precise location of vulnerable structures at the intervertebral foramen and the uncovertebral foraminal region (UVFR), a region defined by the uncinate process anteriorly, the facet joint posteriorly and the foramen transversarium laterally, has critical significance when selecting the safest surgical approach. We studied the anatomy of the vertebral artery, cervical spinal nerves, and spinal nerve roots within the UVFR in six cadaver specimens. We also obtained measurements of bony structures in 35 dry cervical vertebral columns, from C3-C7. The uncinate process (UP) projects superiorly from the posterolateral aspect of each cervical vertebral body, except for the first and second vertebrae. Because the posterior part of the UP lies adjacent to the vertebral artery, spinal nerve, and spinal nerve roots, its resection creates sufficient space to decompress these structures directly. The posterolateral surface of the UP is covered by ligamentous tissue that originates from the posterior longitudinal ligament and protects the neural and vascular structures during their decompression in the UVFR.

Dimensions of the lumbar intervertebral foramina as determined from the sagittal plane magnetic resonance imaging scans of 95 normal subjects

OBJECTIVES

This was a 2-part study. Part 1 evaluated the reliability of measurements of the intervertebral foramina (IVF) from magnetic resonance imaging (MRI) scans, and part 2 developed a morphometric database of IVF dimensions from normal living subjects.

DESIGN

Part 1 was a blinded reliability study using 7 observers, and part 2 developed a morphometric database using 2 teams of 3 observers, all blinded to the results of each other.

SUBJECTS

Ninety-five normal subjects (46 women, 49 men) were stratified by age (range 14-84 years, average 38.8 years).

OUTCOME MEASURES

Part 1: Interclass correlation coefficients (ICCs) were calculated for intraobserver and interobserver reliability for 3 dimensions of the lumbar IVFs. Part 2: A database was developed using the same measures. In addition, the relationships between IVF dimensions and age, height, weight, sex, and left versus right sides of subjects were evaluated.

RESULTS

Part 1: All ICCs were very high (> 0.94). Part 2: 8550 measurements were made, and a morphometric database of 95 subjects, stratified by age and sex, was completed. Differences in IVF size associated with age, height, weight, sex, and side were described.

CONCLUSIONS

Measurements taken from MRI scans of IVFs were performed reliably. The morphometric database and IVF relationships should aid clinicians and researchers in evaluating patients with suspected foraminal stenosis and help further investigate IVF pathology and treatment of such pathology.

Differential Diagnosis and Management of Spinal Nerve Root-related Pain

Pain originating from spinal nerve roots demonstrates multiple pathogeneses. Distinctions in the patho-anatomy, biomechanics, and pathophysiology of spinal nerve roots contribute to pathology, diagnosis, and management of root-related pain. Root-related pain can emerge from the tension events in the dura mater and nerve tissue associated with primary disc related disorders. Conversely, secondary disc-related degeneration can produce compression on the nerve roots. This compression can result in chemical and mechanical consequences imposed on the nervous tissue within the spinal canal, lateral recess, intervertebral foramina, and extraforminal regions. Differences in root-related pathology can be observed between lumbar, thoracic, and cervical spinal levels, meriting the implementation of different diagnostic tools and management strategies.

Conduction block in neuralgic amyotrophy

We describe two cases of neuralgic amyotrophy with electrophysiological evidence of conduction block across the lower trunk of the brachial plexus. Low-output impedance stimulation of the cervical spinal roots in combination with collision was used to accurately demonstrate the conduction block. Complete electrophysiological recovery of the conduction block occurred within 3 months. Early clinical and electrophysiological recovery in both patients suggests that, in some cases, demyelination may predominate early in the course of neuralgic amyotrophy.

The anatomic relation among the nerve roots, intervertebral foramina, and intervertebral discs of the cervical spine

STUDY DESIGN

An anatomic study of the cervical intervertebral foramina, nerve roots, and intradural rootlets performed using a surgical microscope.

OBJECTIVES

To investigate the anatomy of cervical root compression, and to obtain the anatomic findings related to cervical foraminotomy for the treatment of cervical radiculopathy.

SUMMARY OF BACKGROUND DATA

Cervical foraminotomy is a procedure performed frequently for the management of cervical radiculopathy. However, anatomic studies of cervical foraminotomy have not been fully elucidated.

METHODS

In this study, 18 cadavers were obtained for the study of the cervical spine. All the soft tissues were dissected from the cervical spine. Thereafter, laminectomy and facetectomy were performed on C4 through T1 using a surgical microscope. The nerve roots and surrounding anatomic structures, including intervertebral discs and foramina, were exposed. In addition, the intradural rootlets and their intersegmental connections were observed.

RESULTS

The shape of the intervertebral foramina approximated a funnel, the entrance zone being the most narrow part and the root sleeves conical, with their takeoff points from the central dural sac being the largest part. Therefore, compression of the nerve roots occurred at the entrance zone of the intervertebral foramina. Anteriorly, compression of the nerve roots was caused by protruding discs and osteophytes of the uncovertebral region, whereas the superior articular process, the ligamentum flavum, and the periradicular fibrous tissues affected the nerve posteriorly. The C5 nerve roots were found to exit over the middle aspect of the intervertebral disc, whereas the C6 and C7 nerve roots were found to traverse the proximal part of the disc. The C8 nerve roots had little overlap with the C7-T1 disc in the intervertebral foramen. The C6 and C7 rootlets passed two disc levels in the dural sac. Also, a high incidence of the intradural connections between the dorsal rootlets of C5, C6, and C7 segments was found.

CONCLUSIONS

This study demonstrated the anatomy of the nerve roots, rootlets, and intervertebral foramina, and may aid in understanding the pathology of cervical radiculopathy. The presence of intradural connections between dorsal nerve roots and the relation between the course of the nerve root and the intervertebral disc may explain the clinical variation of symptoms resulting from-nerve root compression in the cervical spine. To perform cervical foraminotomy for cervical radiculopathy, it is necessary to understand the detailed anatomy of the intervertebral foramina thoroughly.

The natural history of the cervical foramen in symptomatic and asymptomatic individuals aged 20-60 years as measured by magnetic resonance imaging. A descriptive approach

STUDY DESIGN

This study was intended to identify normal degenerative morphologic evolution in the bony foramen in asymptomatic subjects by decade in comparison with symptomatic subjects of like decades.

OBJECTIVES

To determine normal degenerative changes in the cervical spine caused by the aging process that predispose a person to foraminal stenosis and radiculopathy.

SUMMARY OF BACKGROUND DATA

Cervical radiculopathy is a common problem caused by degenerative changes as people age. The characteristics of the foramen that result in stenosis are not known.

METHODS

Five to six symptomatic and asymptomatic people in each decade volunteered for magnetic resonance imaging. Lordosis, disc heights, and ratio of spinal cord diameter to spinal canal diameter were measured at C4-C5, C5-C6, and C6-C7 from sagittal magnetic resonance images. Foraminal heights, widths, and areas were measured at the isthmus of the same foramen from oblique images.

RESULTS

Foraminal heights, widths, and areas were larger in asymptomatic patients than in symptomatic patients. Morphologic analysis showed that inferior facet hypertrophy tended to decrease the width of the foramen in aging people. Disc heights, lordosis, and ratio of spinal cord diameter to spinal canal diameter showed no significant differences.

CONCLUSIONS

Foraminal height affects overall foraminal area but tends to change little with age. Width also affects overall area and not only decreases in older people but also significantly affects the available area for the exiting nerve root.