Cervical Disc Space Research Articles

363 Anatomic Study of Cervical Neural Foraminal Dimensions, Interpedicular Distance, and Disc Space Height From C2-T1 Using Computed Tomography of 1,000 Patients

INTRODUCTION: The normative relationships among cervical neuroforaminal dimensions (NFD), interpedicular distance (IPD), and disc space height (DSH) remain unknown. METHODS: We reviewed CT imaging of 1,000 patients between 18 and 35 years of age without spinal pathology to measure cervical NFD, defined as follows: foraminal height, sagittal anterior-to-posterior width, and area. Anterior, middle, and posterior DSH, and IPD were also measured. Interobserver reliability was assessed via the intraclass correlation coefficient (ICC) two-way mixed model on absolute agreement. RESULTS: Bilateral NFD followed bimodal distribution patterns moving caudally from C2-T1, whereas DSH measurements exhibited multimodal distribution patterns and IPD demonstrated a unimodal distribution clustered at the lower cervical spine. Significant differences were observed in NFD, DSH, and IPD measurements with respect to patient sex and race taking into consideration patient demographic and anthropometric characteristics. The African American cohort demonstrated the smallest NFD, DSH, and IPD measurements, followed by the Hispanic cohort, followed by the Caucasian cohort. Weak-to-moderate correlations were observed among NFD, DSH, and IPD measurements across all levels. CONCLUSIONS: This study describes 70,800 DSH, NFD, and IPD measurements from C2-T1 using CT imaging of young patients without spinal pathology. Findings from this study may provide normative guidelines necessary to establish the foundation for diagnosis of cervical neuroforaminal stenosis. Surprisingly, this study found no strong, or even moderate, correlations between normative NFD, DSH, and IPD measurements across all levels from C2-T1. Patient sex, ethnicity, and height are associated with NFD, DSH, and IPD, though patient weight is not.

Morphometric analysis of cervical disc space height and interpedicular distance using computed tomography.

This study utilized computed tomography (CT) to establish normative radiographic morphometric measurements of cervical disc space height (DSH) and interpedicular distance (IPD) and document the influence of patient sex, race, ethnicity, and anthropometric characteristics. Cervical CTs of 1000 patients between 18 and 35 years of age without known spinal pathology were reviewed. Statistical analyses included the assessment of associations between patient height, weight, sex, race, and ethnicity regarding DSH and IPD. Irrespective of disc level, average DSH measurements were as follows: anterior height of 2.6 ± 1.0 mm, middle height of 4.1 ± 1.2 mm, and posterior height of 1.8 ± 1.0 mm. IPD was only measured between C3 and C7 vertebrae, and irrespective of disc level, the mean IPD measurement was 21.1 ± 1.5 mm. Significant differences for anterior, middle, posterior DSH, and IPD were observed in all disc levels. Significant differences in DSH and IPD were observed for all anthropometric factors of sex, race, and ethnicity relative to vertebral level. Males had significantly larger DSH and IPD measurements across all vertebral levels compared to females. Caucasians had larger DSH and IPD at select vertebral levels compared to African Americans and Hispanics. This study describes measurements of DSH and IPD between C2 and T1 levels in 1000 healthy 18-35-year-old subjects without known pathology. DSH and IPD measurements varied based on patient sex, race, ethnicity, and disc level.

162. Cervical total disc replacement: available implant size matters

<h3>BACKGROUND CONTEXT</h3> Multiple cervical total disc replacement (TDR) studies have found this procedure to produce outcomes noninferior or superior to anterior cervical discectomy and fusion (ACDF). While restoration of disc height of a collapsed, degenerated segment is a goal of TDR surgery, there are potential problems with over-distracting the segment with an implant. Several biomechanical studies have investigated the potential impact of prosthesis height, particularly with respect to implant sizes larger than the natural disc space height, found that increased implant height was associated with decreased range-of-motion and reduced facet overlap, possibly altering the loading of the adjacent facet joints. These changes have also been found to be possible contributing factors to the development of heterotopic ossification. With respect to implant height, one study found that in 36% of a study population, the height of the cervical disc space was less than the minimal height of available TDRs, which is generally 5 mm. <h3>PURPOSE</h3> The purposes of this study were to: 1) analyze the heights of cervical disc spaces to be replaced with a TDR; 2) measure the heights of the disc spaces adjacent to the treated level (providing insight to normal disc height), and 3) investigate the frequency of use of a smaller height TDR implant when available. <h3>STUDY DESIGN/SETTING</h3> The study was based on a post hoc analysis of data collected prospectively as part of a Food and Drug Administration (FDA) Investigational Device Exemption (IDE) trial. <h3>PATIENT SAMPLE</h3> Radiographic measurements were made from 148 patients enrolled in the trial and 16 patients who were training cases for the trial. <h3>OUTCOME MEASURES</h3> Radiographic measures used in the study included disc heights of level operated with a TDR and the heights of levels adjacent to these segments. Also, the size of the TDR implants used was recorded. <h3>Methods</h3> Radiographs were used to measure the disc heights of 164 level treated with TDR and 261 adjacent nonoperated levels from C3-4 to C6-7. All radiographic measures were performed by a central facility specializing in image assessment. For each level, the recorded disc height was the average of the anterior and posterior disc heights. To investigate the TDR implant size selected by the operating surgeon, data from the Simplify_® Cervical Artificial Disc FDA IDE trial were analyzed. The device is available in 4, 5, and 6 mm heights. The device height selected was recorded and used in the current study. Of note, the 4 mm height became available only after trial enrollment was 13% complete. <h3>Results</h3> Measurements made of the 261 levels adjacent to a degenerated level to be treated by TDR found that 55% of disc spaces had a height of 4 mm or less. Among the levels to be replaced with a TDR, 82% were less than 4 mm in height. In the FDA trial in which a 4 mm device was available, it was selected for use in 38% of patients, a 5 mm device was used in 53% and a 6 mm implant was used in 9% of patients. <h3>Conclusions</h3> This study found that many disc levels to receive a TDR had a height of <4mm. Even among the adjacent segments not being operated, 55% were of height <4 mm, suggesting that motion preserving implants of greater heights may have the potential to overdistract the disc space. In a recent FDA IDE trial, which offered a 4mm TDR implant height, this was selected in 39% of patients, suggesting surgeon preference for the smaller implant in an appreciable number of patients. Further investigation is warranted to determine if the lower height implants are related to more favorable clinical and/or radiographic results. <h3>FDA DEVICE/DRUG STATUS</h3> Simplify Cervical Disc Replacement (Approved for this indication)

Analysis of Cervical Spine Alignment Change after Modified Kurokawa Cervical Laminoplasty in the Patients with Cervical Myelopathy and Straight Cervical Spine.

Laminoplasty is widely used to decompress the spinal cord in patients with multilevel cervical lesions. Straight cervical alignment may not be a good candidate for laminoplasty because of postoperation progression of kyphosis and loss of cervical spine range of motion (ROM). However, clinical outcomes of laminoplasty did not show a strong and consistent effect based on cervical sagittal alignment. Moreover, the kyphosis progression and ROM change after operation for the patients with preoperative strange cervical alignment are still unclear. This study is to evaluate the change of cervical alignment and ROM in patients with straight cervical alignment after modified Kurokawa cervical laminoplasty. Thirty patients with multiple-level cervical spondylosis (CSM) and straight cervical alignment were included. All patients underwent laminoplasty with the reconstruction of the spinous process-ligament-muscular complex (SPLMC). The modified JOA score was analyzed for clinical assessment. The change of cervical alignment, ROM, T1 slope, and intervertebral disc space Cobb angle were analyzed for radiological assessment. The average JOA score at preoperative and 2 years follow-up were 7.8 ± 1.4 and 13.6 ± 2.1, respectively. The recovery ratio was 63%. At the 2 years follow-up, there were 18 patients who acquired lordotic cervical alignment. 10 patients remained as straight cervical curve, and 2 patients' cervical alignment developed mild kyphosis. 28 out of 30 patients showed improvement of cervical alignment. The cervical alignment was improved from 1.29 ± 10.04° preoperative to 9.58 ± 8.65° postoperative. However, the ROM decreased from 36.8 ± 18.92 preoperative to 25.08 ± 12.10° postoperative. A positive correlation was found between the C2/4 angle change and cervical alignment change, T1 slope and cervical alignment, cervical alignment, and neutral position flexion reserved ROM. A negative correlation was found between the C1/2 angle change and cervical alignment change. Laminoplasty with a reconstruction of SPLMC followed by appropriate postoperative muscle exercises may be an encouraging way to maintain or improve physiological alignment and prevent postoperation kyphosis deformity for the CSM patients with straight cervical alignment at 2 years follow-up.

Accuracy of various fluoroscopic landmarks for determination of midline implant placement within the cervical disc space.

The traditional teaching has been that proper function of a cervical disc replacement is dependent upon appropriate placement, which includes centering the device in the coronal plane. The purpose of this study was to identify the most reliable anatomical landmark for determining midline placement of an implant within the cervical disc space under fluoroscopy. Digital fluoroscopy images were taken for each cervical level at 0°, 2.5°, 5°, 7.5°, 10°, and 15° from the mid-axis by rotating the C-arm beam of six cadavers. Thin-slice CT scanning of the same levels was subsequently performed. Three independent reviewers measured the distance between anatomic structures: (a) tip of the right uncinate; (b) medial border of the right pedicle; and (c) center of the spinous processes for different x-ray angles across cervical levels C3-7. Both the uncinate and pedicle demonstrated superior overall accuracy to that of the spinous process (p ≤ 0.02) at all angles except at 0° for the pedicle where the difference was not statistically significant. Overall (pooled C3-7), the accuracy of the uncinate did not differ significantly from that of the pedicle at any fluoroscopic angle. The center of the spinous process measurement was particularly sensitive to deviations from the perfect anteroposterior fluoroscopy image. The results of this investigation suggest that the tip of the uncinate and the medial border of the pedicle are more accurate measures of midline in the cervical spine than the center of the spinous process and are less susceptible to inadvertent off-axis imaging.

Cervical disc width index is a reliable parameter and consistent in young growing Dutch Warmblood horses.

Intervertebral disc disease, as well as the associated alteration of the radiographic intervertebral disc space width, has been reported in horses. Disc height index (DHI) has proven to be an accurate and objective parameter in other species but data related to this parameter are lacking in horses. Therefore, the aims of this retrospective longitudinal diagnostic accuracy study were (a) to evaluate the reliability of measurements within and between observers of the equine Disc Width Index (EDWI) as a parameter for radiographic equine cervical intervertebral disc space width, and (b) to evaluate the sequential development of the EDWI over time. For this, EDWI from all intervertebral disc spaces between second cervical (C) to first thoracic (Th) vertebrae were obtained in a group of 39 Dutch Warmblood horses at 1, 5, and 18 months of age, by one European College of Veterinary Diagnostic Imaging (ECVDI) board‐certified veterinary radiologist (S.V.) and two veterinary students. Bland‐Altmann plots and intraclass Correlation Coefficient revealed a good intra‐ and interobserver agreement. A linear mixed‐effect model did reveal that mean EDWI increases significantly toward the caudal cervical spine, but did not differ significantly for a certain location over time or between sexes. Spearman's rank test did show a significant correlation between the vertebral alignment angle induced by different head‐neck positions and a normalized EDWI (ρ = 0.33, P < .0001). Student's t‐test revealed that the presence of C6‐C7 transposition of the transverse processes did not influence EDWI significantly. It was concluded that EDWI represents a reliable parameter for equine cervical radiographic intervertebral disc space width. Practical implementation of EDWI warrants monitoring in a group of adult horses while maintaining a standardized head‐neck position.

Association between anterior bone loss and anterior heterotopic ossification in hybrid surgery

BackgroundHybrid surgery (HS) has become an alternative procedure for the treatment of multilevel cervical degenerative disc disease with satisfactory outcomes. However, some adverse outcomes have recently emerged, such as heterotopic ossification (HO) and anterior bone loss (ABL). Furthermore, HO was found mostly located in the posterior and lateral of the cervical intervertebral disc space. The mechanism of anterior heterotopic ossification (AHO) formation may be different, and its relationship with ABL was uncertain.MethodsRadiographical and clinical outcomes of ninety-seven patients who had undergone contiguous two-level HS between December 2010 and December 2017 and with a minimum of 2-year follow-up were analyzed. Postoperative radiographs were evaluated and compared to the initial postoperative films to determine the incidence of ABL and AHO.ResultsThe overall incidence rate of ABL was 44.3% (43/97). It was identified in 70.6% of AHO cases (33.3% mild, 41.7% moderate, 25.0% severe) and 38.8% of non-AHO cases (38.7% mild, 45.2% moderate, 16.1% severe). A significant association between ABL and AHO occurrence was found (P = 0.016). There was no significant difference in prosthesis–endplate depth ratio or disc space angle change between the AHO group and the non-AHO group (P > 0.05). Compared with data preoperatively, clinical outcome scores significantly improved after surgery in both the AHO and non-AHO groups, with no significant differences between the two groups (P > 0.05).ConclusionABL was common in HS, and it related to AHO. The formation of AHO could be an integral part of postoperative bone remodeling, as well as ABL.

Morphometric analysis of cervical intervertebral disc space to reduce neural complications during anterior approaches to the cervical spine

BackgroundAlthough neurovascular complications rarely occur during surgical procedures, they have serious consequences. We reviewed the limits of safe surgery to decrease the possibility of neurovascular injuries. MethodsFour measurements were performed for each patient at the vertebral levels adjacent to the intervertebral discs at C3–C4, C4–C5, C5–C6, and C6–C7. These measurements were: 1)midline anteroposterior diameter of the intervertebral disc, 2)transverse diameter of the intervertebral disc, 3)right and left measurements of the line vertically drawn to the disc anterior from the most lateral point of the dura mater, and 4)measurement of the distance from measurement 3 to the right and left root. ResultsAverage anteroposterior and transverse vertebral diameters were determined to be 18.11 and 27.15 mm, respectively. Average of the results of the 3rd measurement was 5.51 mm on the right and 5.36 on the left. Average of the 4th measurement was 7.8 mm on the right 7.75 mm on the left. The shortest interval was at the C3-4 level and the longest interval was at the C6-7 level. ConclusionDetermining the safe surgery limits will help surgeons evaluating suitable implant sizes and decreasing the perioperative complications during decompression to cervical vertebrae and instrument procedures.

Anterior osteotomy for rigid cervical deformity correction.

Rigid deformities of the cervical spine can be associated with significant pain, disability, and impaired quality of life. Historical treatments generally utilized posterior approaches including the opening wedge osteotomy and pedicle subtraction osteotomy (PSO). Translation can occur during osteoclasis of the opening wedge osteotomy, making it inherently less stable than a PSO. The PSO is limited to lower cervical or upper thoracic levels due to the vertebral artery and sensitivity of cervical nerve roots to compression during osteotomy closure. The anterior osteotomy, defined as an osteotomy through the cervical disc space and uncovertebral joints back to the level of the transverse foramen bilaterally, is a powerful correction technique that can be applied throughout the cervical spine. It can also be used to correct deformities in the coronal plane. This review will summarize the technical nuances of the anterior osteotomy including patient selection, preoperative planning, and surgical technique.

P128. The association of preoperative disc height with radiographic and clinical outcomes following ACDF

BACKGROUND CONTEXT Disc space collapse often occurs later in the natural course of cervical degenerative disc disease, and during anterior cervical discectomy and fusion (ACDF), restoration of disc space height and lordosis can assist with decompression and restoration of alignment. It is unclear if the amount of preoperative cervical disc space collapse correlates with outcomes following ACDF. PURPOSE The aim of the present study was to characterize preoperative disc space height in a sample of ACDF patients and to determine the association with postoperative clinical and radiographic outcomes following ACDF. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE Analysis of consecutive patients who underwent a single-level ACDF between 2008-2015 for cervical radiculopathy and/or myelopathy, with more than 6 months of clinical and radiographic follow-up was conducted. Exclusion criteria were patients under 18 years of age at the time of surgery, previous cervical fusion or concomitant posterior cervical surgery, had postoperative follow up less than 6 months, or had an ACDF for cervical spine fracture, tumor, or infection. OUTCOME MEASURES Preoperative disc height was measured in terms of preoperative anterior vertebral distance (pAVD), mid-vertebral distance (pMVD), and posterior vertebral distance (pPVD). Sagittal parameters were also measured, and included change in C2-C7 lordosis, T1 angle, levels fused, sagittal vertical axis (SVA), fusion mass lordosis, proximal and distal adjacent segment lordosis. Visual Analog Scale (VAS) neck, VAS arm, and Neck Disability Index (NDI) scores were collected at each postoperative clinical visit. The rates of adjacent segment disease, reoperation, fusion, and subsidence (postoperative disc space collapse >2mm) were determined for the study period. METHODS Radiographs were reviewed preoperatively and immediately postoperatively, and at final follow up along with patient-reported outcomes. Bivariate and multivariate logistic regressions were subsequently used to compare clinical outcomes between disc height. Multivariate analyses controlled for differences in baseline patient characteristics. RESULTS A total of 120 patients were included. At final follow-up, pAVD was associated with increased lordosis, SVA and proximal lordosis. Additionally, pMVD was associated with increased postoperative SVA (p=0.025), and final SVA (p=0.011). Preoperative PVD was associated with decreased postoperative distal lordosis (p=0.037) and increased final SVA (p=0.032). Notably, greater pAVD was associated with greater final VAS arm scores (p=0.022), greater pMVD was associated with increased final VAS neck (p=0.037) and final VAS arm scores (p=0.040), and greater pPVD was associated with greater final VAS neck (p=0.031) and arm (p=0.023) scores. Greater AVD, MVD, and PVD were all associated with a decreased preoperative to postoperative difference in VAS neck (p-value range 0.034-0.04). CONCLUSIONS Increased anterior, middle and posterior preoperative disc height were all associated with increased final SVA, among other parameters. Patients with well-maintained preoperative disc heights had greater final VAS neck scores, VAS arm scores, and had less postoperative improvement in VAS neck scores compared to patients with preoperative collapsed discs. These results suggest that patients with preoperative cervical disc space collapse may have superior outcomes compared to patients with maintained cervical disc height, and future studies are needed to further explore these differences. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Role of Surgery in Management of Discitis

Background: discitis is an inflammation of the vertebral disc space which may spontaneous or post spinal surgery; that is often diagnosed late. With good response to conservative treatment and in some condition the plan of management is surgical. Aim of the Work: to assess the role of surgery in management of discitis and which approach is appropriate, with comparison between conservative and surgical management and the relationship between risk factors and outcome. Patients and Methods: this prospective and retrospective study was conducted on 25 patients of specific criteria confirmed to have discitis by clinical presentation, radiological findings and laboratory investigations. Results: discitis is more common in old age that occurred in lumbar more that dorsal or cervical disc space with risk factors such as failed spinal surgery (40%), DM (36%), HCV +ve (8%), TB (8%), Brucella (4%) and addiction (4%) of past history with affect the outcome. There was a statistically significant relation between location of discitis and pre modified ranking scale, while modified ranking scale pre and post management were statistically highly significant in each cervical, dorsal and lumbar. Conclusion: both conservative and surgical management have good outcome. But we observed that the risk factors like DM and addiction worsened the prognosis. We also observed that the shorter surgical maneuver the better is the outcome.

Plate Construct versus Stand-Alone Cage in ACDF. Does the Plate Maintain a Sagittal Plane Correction: Clinical Outcome and Radiological Findings Correlation

Introduction Anterior cervical discectomy and fusion (ACDF) is the treatment of choice of cervical degenerative disc disease which cause neurological symptoms include radiculopathy and myelopathy, and it can be done by different techniques which includes several options for implants like disc spacers made of autograft or allograft bone, porous metal, polyether ether ketone (PEEK) and anterior plates and screws. The purpose of this study is to compare the role of anterior plate constructs (ACDF-CPC) and stand-alone cage (ACDF-CA) in maintain of Sagittal plane correction, clinical and radiological findings. Material and Methods Retrospective study of 24 patients who underwent ACDF in Hamad General Hospital, 16 cases with ACDF-CA and 8 cases ACDF-CPC. Radiological findings (cervical lordosis, segmental lordosis, cage subsidence, disc height) and clinical outcome (Odom's criteria, dysphagia and swallowing problems) are compared (pre-op, 3–6 months post op, 12–18 months post op). Results Cervical Lordosis, segmental lordosis, and disc space height at the operated levels increased an average of 5.4°, 3.1°, and 1.5 mm in ACDF-CA and 3.2°, 3.4°, 3.5 mm in ACDF-CPC, with good to excellent result in ACDF-CA and fair to good result in ACDF-CPC according to Odom's criteria, with more dysphagia and dysphonia in ACDF-CPC. The maintaining of sagittal plane correction, disc space height, and cage subside are decrease during follow up in both groups, but clinical outcome was stable in most of the cases comparing to immediate post op finding. Conclusion Anterior cervical discectomy and fusion by stand-alone cage or anterior plate is achieved good clinical outcome and significant correction in sagittal plane and disc space height, but no significant difference between two groups in maintaining the sagittal plane correction and disc space.

INTERVERTEBRAL AND INTRAVERTEBRAL RATIOS IN DOBERMAN PINSCHER DOGS WITH CERVICAL SPONDYLOMYELOPATHY

No screening method is currently available to differentiate dogs with and without cervical spondylomyelopathy. Intravertebral and intervertebral ratios are used in horses and can predict cervical vertebral malformation. Intervertebral ratios could be a useful screening method for canine cervical spondylomyelopathy. Our purpose was to compare cervical intervertebral and intravertebral ratios in normal vs. affected Doberman pinschers. Forty dogs were studied, 27 affected and 13 normal. Cervical radiographs were obtained in all dogs. The minimum intra- and intervertebral sagittal diameter ratios were established for each cervical vertebrae and disc space from C(2) to C(7) . Comparisons were made between groups and specific vertebral body and disc levels. The effect of gender, age, and method of measurement (analog or digital radiographs) was also studied. There was no difference in either the intervertebral or intravertebral ratio between normal vs. affected dogs. The ratios decreased progressively along the cervical spine, being smallest at C(6) -C(7) and C(7) , respectively. Age, gender, and method of measurement had a significant influence on both inter- and intravertebral ratios, with smaller ratios seen as dogs aged and in male dogs. Based on our results, inter- or intravertebral ratios have no value to distinguish between clinically normal Doberman pinschers and Doberman pinschers with cervical spondylomyelopathy.

Head Injury Football Player

HISTORY: 17 year-old junior high school football defensive end sustained a concussion while tackling. During an early season football scrimmage, he tackled a player using the spearing technique. Immediately after the game was finished, he had an immediate, intense headache and vomited. There was no motor weakness, impaired sensation, or pain in his neck or upper limbs. Over the next few weeks, he had persistent bi-frontal headaches, radiating from the para-cervical area, usually aggravated by heavy lifting and straining. He had neck pain that was worse in the morning and exacerbated by flexion. Manual therapy helped relieve headaches and neck pain. He had multiple episodes of involuntary loss of stool that occurred in the act of passing gas. PHYSICAL EXAMINATION: Examination revealed moderate tenderness over the facet joints of C1-C2 and C2-C3 on the right side. Normal sensation, strength, and reflexes in the upper and lower limbs. There was full active, pain-free, range of motion with the neck. Spurling's maneuver was provocative of neck pain without radiation bilaterally. Cervical traction relieved his neck pain. Cranial nerves II-XII were normal. DIFFERENTIAL DIAGNOSIS: 1. Concussion with post-traumatic headache 2. Vertebro-basilar insufficiency 3. Cervical spinal cord neuropraxia TEST AND RESULTS: MRI cervical spine without contrast: Cervical vertebral body and disc space height, alignment, marrow signal, and spinal cord is normal. AP diameter of central canal measures 10 mm at C4-C5, while AP diameter of the central canal at C5 measures 16 mm. Torg ratio at C4-C5 measures 60% MRI/MRA Neck and Brain with and without contrast: Left-sided vertebral artery terminates as the left posterior inferior cerebellar artery. Right-sided vertebral artery is strongly dominant. Brain parenchyma is normal FINAL WORKING DIAGNOSIS: 1. Vertebro-basilar insufficiency 2. Cervical spinal stenosis and cord neuropraxia 3. Cervical facet arthropathy, C2-C3 TREATMENT AND OUTCOMES: 1. No clearance to return to football and contact sports. He is still experiencing cervicogenic headaches without a return to premorbid functional level. 2. Excluded neck manipulation and mobilization in treatment program, due to risk of occluding the one good vertebral artery. 3. Hyperbaric oxygen treatment transiently relieved headaches.

Caudal cervical arthrodesis using a distractable fusion cage in a dog

This case report describes a cervical fusion cage, surgical technique and the long-term outcome of caudal cervical arthrodesis used to stabilise dynamic spinal cord compression at the sixth and seventh cervical intervertebral disc space (C6, C7) in a dog. A seven-year-old, 41 kg, entire male Dobermann Pinscher was admitted for progressive ataxia of two weeks duration. Neurological examination revealed ambulatory tetraparesis. Computed tomographic myelogram scans in neutral and traction positions of the neck were performed and were used to determine presence of a dynamic component. A C6-C7 surgical distraction and stabilisation using a distractable intervertebral fusion cage was performed. There was not any deterioration of neurological status was observed on postoperative neurological evaluation. Within eight weeks after surgery, gait and postural abilities had returned to normal. Computed tomography evaluation indicated a complete bridging callus within and outside the cage at 15 weeks after surgery. There were not any complications or recurrences of initial neurological deficits observed during the 40 month follow-up period. Based on the follow-up period data, a C6-C7 dynamic spinal cord compression with disc protrusion was successfully treated by a distractable cervical fusion cage.

Anatomic mapping and evaluation of the esophagus in relation to the cervical vertebral body

The relationship of the esophagus to the cervical vertebral body (CVB), disc space and longus colli (LC) muscles, to our knowledge, has not been previously studied. The purpose of this study was to quantify the relationship of the esophagus to the CVB, disc space and LC. 30 patients were selected for a retrospective review of computed tomography (CT) scans. Measurements between the esophagus and the C5, C6, and C7 vertebral bodies as well as the C5/6 and C6/7 disc spaces were performed in the midline, 3 mm right and left of midline, and at the edge of the LC on both sides. The closest distance of the esophagus to the CVB and disc space occurs at the midline (range 1.02-1.31 mm at each level). The furthest distance occurred at the edge of the right LC (range 2.67-3.30 mm at each level). The mean distance from the edge of the right LC to the midline was significantly greater (P < 0.01) than mean distance from the edge of the left LC to the midline. No statistical significant differences were observed when comparing measurements at the individual vertebral bodies and disc spaces. The results of the study demonstrate that the esophagus lies in closest proximity to the CVB and disc space in the midline. A larger potential space exists between the esophagus and the CVB and disc space at the edge of the LC. These results may provide insight into a potential cause of post-operative dysphagia. Furthermore, it may help guide the future design of cervical plates to better utilize the potential space between the esophagus and the CVB and disc space at the edge of the LC.

P47. The Effect of Decreasing the Cervical Disc Space Height on the Facet Joint

BACKGROUND CONTEXT: Some change in disc space height is usually seen after inserting an artificial disc. It has already been reported by the current authors that there is an adverse effect on the facet joint as a result of increasing disc space height. To date, no study has addressed the effect that decreasing disc space height has on the facet joints in the cervical spine.

How the Increase of the Cervical Disc Space Height Affects the Facet Joint

In vitro study on the effect of increasing the height of the cervical disc space on the facet joint. To demonstrate how facet joint articulation is affected by increasing the cervical disc space height. A surgeon attempts to increase the disc space and inserts a larger artificial disc than normal in order to keep the intervertebral foramen open and the prosthesis stable. However, it is hypothesized by the current authors that this procedure could have an adverse effect on the facet joints. Computerized tomography images passing through the disc space and the center of the C4-C7 facet joints (sagittal plane) were obtained from 15 cadaveric cervical spine specimens. A 1-mm incremental increase to a total 5 mm in disc space height was performed to simulate the changes seen in disc replacement. The change in the facet joint articulation overlap and space in the sagittal plane at normal and each displacement was measured. Each 1-mm incremental increase in disc space at C4-C5 translated to a decrease in the facet joint articulation overlap in the sagittal plane by approximately 8%. The mean facet joint space increased approximately 0.8 mm. At the C5-C6 and the C6-C7 levels, the articulation overlap decreased by approximately 7% and the facet joint space increased approximately 0.8 mm. There is a significant decrease of the facet joint articulation overlap in the sagittal plane and an increase in the facet joint space following an increase in the cervical disc space. The inappropriate increase of the disc space height may result in facet joint subluxation and could lead to the accelerated failure of the artificial disc.

Disc height loss after anterior cervical microdiscectomy with titanium intervertebral cage fusion.

The use of a graft in cervical inter-vertebral disc repair is still a controversial procedure. The aim of the treatment is to restore the physiological disc height and to achieve fusion. This study was performed to determine the rate of narrowing of the cervical intervertebral disc after using a titanium cervical intervertebral cage (BAK-C; Sulzer Spine Tech, Minneapolis, MN). 43 patients were included in the study. Each had a cervical disc protrusion, resulting in radiculopathy. All underwent surgery involving an anterior one level cervical microdiscectomy and fusion with a cylindrical titanium cage. The mean follow-up time was 18+/-5 months. The extent of the mean narrowing rate of disc space was 35.6+/-9%. The fusion rate was 98% and the mean time to fusion was 6 months. The use of a cervical intervertebral cage in anterior cervical microdiscectomy does not prevent the loss of the height of the cervical disc space after the operation.

Clinical Significance of Cervicomedullary Deformity in Chiari II Malformation

Objective: The purpose of this study was to determine if there is a difference in the caudal extent of brain stem herniation and the degree of cervicomedullary deformity between symptomatic and asymptomatic Chiari II patients. Methods: Magnetic resonance imaging and the clinical presentation of 14 symptomatic and 59 asymptomatic patients were analyzed. The level of the cervicomedullary deformity below the foramen magnum was measured in both groups. The level of the deformity was identified by the cervical vertebral body or disc space level. Results and Conclusion: Review of our results shows no obvious relationship between the level of cervicomedullary deformity and the presenting symptoms or the outcome after surgical decompression. We conclude that the level of herniation and the cervicomedullary deformity is not a reliable marker to determine which patients may become symptomatic and require decompression or to determine prognosis.