Risk of vertebral artery injury: comparison between C1-C2 transarticular and C2 pedicle screws

BACKGROUND CONTEXT

To our knowledge, no large series comparing the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw have been published. In addition, no comparative studies have been performed on those with a high-riding vertebral artery and/or a narrow pedicle who are thought to be at higher risk than those with normal anatomy.

PURPOSE

To compare the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw in an overall patient population and subsets of patients with a high-riding vertebral artery and a narrow pedicle using computed tomography (CT) scan images and three-dimensional (3D) screw trajectory software.

STUDY DESIGN

Radiographic analysis using CT scans.

PATIENT SAMPLE

Computed tomography scans of 269 consecutive patients, for a total of 538 potential screw insertion sites for each type of screw.

OUTCOME MEASURES

Cortical perforation into the vertebral artery groove of C2 by a screw.

METHODS

We simulated the placement of 4.0 mm transarticular and pedicle screws using 1-mm-sliced CT scans and 3D screw trajectory software. We then compared the frequency of C2 vertebral artery groove violation by the two different fixation methods. This was done in the overall patient population, in the subset of those with a high-riding vertebral artery (defined as an isthmus height ≤ 5 mm or internal height ≤ 2 mm on sagittal images) and with a narrow pedicle (defined as a pedicle width ≤ 4 mm on axial images).

RESULTS

There were 78 high-riding vertebral arteries (14.5%) and 51 narrow pedicles (9.5%). Most (82%) of the narrow pedicles had a concurrent high-riding vertebral artery, whereas only 54% of the high-riding vertebral arteries had a concurrent narrow pedicle. Overall, 9.5% of transarticular and 8.0% of pedicle screws violated the C2 vertebral artery groove without a significant difference between the two types of screws (p=.17). Among those with a high-riding vertebral artery, vertebral artery groove violation was significantly lower (p=.02) with pedicle (49%) than with transarticular (63%) screws. Among those with a narrow pedicle, vertebral artery groove violation was high in both groups (71% with transarticular and 76% with pedicle screws) but without a significant difference between the two groups (p=.55).

CONCLUSIONS

Overall, neither technique has more inherent anatomic risk of vertebral artery injury. However, in the presence of a high-riding vertebral artery, placement of a pedicle screw is significantly safer than the placement of a transarticular screw. Narrow pedicles, which might be anticipated to lead to higher risk for a pedicle screw than a transarticular screw, did not result in a significant difference because most patients (82%) with narrow pedicles had a concurrent high-riding vertebral artery that also increased the risk with a transarticular screw. Except in case of a high-riding vertebral artery, our results suggest that the surgeon can opt for either technique and expect similar anatomic risks of vertebral artery injury.

A new technique for reduction of atlantoaxial subluxation using a simple tool during posterior segmental screw fixation: clinical article

OBJECT

The authors introduce a simple technique and tool to facilitate reduction of atlantoaxial subluxation during posterior segmental screw fixation.

METHODS

Two types of reduction tool have been designed: T-type and L-type. A T-shaped levering tool was used when a pedicle or pars screw was used for C-2, and an L-shaped tool was used when a laminar screw was used for C-2. Twenty-two patients who underwent atlantoaxial segmental screw fixation and fusion for the treatment of anteroposterior instability or subluxation, using either of these new types of reduction tool, were enrolled. Demographic, clinical, and surgical data, which had been prospectively collected in a database, were analyzed. The atlantodens interval was measured on lateral radiographs, and the space available for the spinal cord was measured on CT scans.

RESULTS

The authors could attain reduction of the atlantoaxial subluxation without difficulty using either type of tool. The preoperative atlantodens interval ranged from -16.9 to 10.9 mm in a neutral position, and the postoperative interval ranged from -2.8 to 3.0 mm, with negative values due to extension-type or mixed-type instability. The mean space available for the spinal cord significantly increased, from 9.5 mm preoperatively to 15.4 mm postoperatively (p < 0.001).

CONCLUSIONS

This technique allowed for controlled manipulation and reduction of the atlantoaxial subluxation without difficulty.

Range of motion loss after cervical laminoplasty: a prospective study with minimum 5-year follow-up data

BACKGROUND CONTEXT

Although numerous studies have reported on the loss of flexion-extension range of motion (ROM) associated with laminoplasty, few have reported on the time course of this loss of motion for a long-term follow-up period.

PURPOSE

We previously reported our early data on postlaminoplasty cervical ROM. In this article, we describe our minimum 5-year follow-up data to identify the time-dependent change in ROM after cervical laminoplasty.

STUDY DESIGN

A prospective cohort study.

PATIENT SAMPLE

The procedure was performed in 23 patients. Eighteen patients with a minimum 5-year follow-up were included in the study.

OUTCOME MEASURES

The time-dependent neck ROM changes observed in the neutral, flexion, and extension radiographs were used to measure the radiological outcome. The Japanese Orthopaedic Association classification and a numerical rating scale of axial neck pain and arm pain were used to evaluate clinical outcome.

METHODS

Twenty-three patients who received unilateral open-door laminoplasties, including miniplate fixation over three levels, were serially evaluated at regular set intervals postoperatively. Eighteen patients with a minimum 5-year follow-up were included in the study. The mean follow-up period was 68.1 months (range, 60-78 months). Nine patients had ossification of posterior longitudinal ligament (OPLL) and nine patients had cervical spondylotic myelopathy (CSM). Enrolled patients were divided into subgroups (OPLL vs. CSM; autofusion vs. nonautofusion) to compare the ROM between the groups. We evaluated the time-dependent neck ROM changes by taking neutral, flexion, and extension radiographs preoperatively and at 1, 3, 6, 9, 12, 18, and 24 months postoperatively. Follow-up radiographs were taken annually after a 2-year follow-up.

RESULTS

The preoperative and 1-, 3-, 6-, 12-, 24-, 36-, 48-, and 60-month postoperative ROM figures were 39.9 ± 11.2°, 35.0 ± 9.2°, 33.0 ± 11.0°, 30.1 ± 10.4°, 25.8 ± 13.1°, 24.7 ± 10.0°, 23.8 ± 6.5°, 24.6 ± 8.3°, and 23.6 ± 9.4°, respectively, and at the most recent follow-up, ROM was 24.5 ± 10.1°. Thus, the mean ROM decreased by 15.4 ± 8.4° (38.5%) by the last follow-up (p<.0001). In the OPLL group, we observed a more limited cervical ROM than in the CSM group (47.2% vs. 72.7%). As expected, in the laminar autofusion group, the ROM decreased significantly (55.6% decrease), whereas in the nonautofusion group, the ROM decreased less significantly (13.4% decrease) at the last follow-up. Postoperative axial pain did not correlate with the cervical ROM.

CONCLUSIONS

These results suggest that the loss of cervical ROM after laminoplasty is time-dependent, and patients with OPLL and laminar autofusion had less ROM. Postlaminoplasty ROM reduction can recover after several years, unless laminar autofusion occurs.

Neck Pain Following Cervical Laminoplasty: Does Preservation of the C2 Muscle Attachments and/or C7 Matter?

Study Design Systematic review. Objective In patients aged 18 years or older, with cervical spondylotic myelopathy or ossification of the posterior longitudinal ligament (OPLL), does sparing the C2 muscle attachments and/or C7-preserving cervical laminoplasty lead to reduced postoperative axial pain compared with conventional C3 to C7 laminoplasty? Do these results vary based on early active postoperative cervical motion? Methods A systematic review of the English-language literature was undertaken for articles published between 1970 and August 17, 2012. Electronic databases and reference lists of key articles were searched to identify studies evaluating C2/C3- or C7-preserving cervical laminoplasty for the treatment of cervical spondylotic myelopathy (CSM) or OPLL in adults. Studies involving traumatic onset, cervical fracture, infection, deformity, or neoplasms were excluded, as were noncomparative studies. Two independent reviewers assessed the level of evidence quality using the grading of recommendations assessment, development and evaluation (GRADE) system, and disagreements were resolved by consensus. Results We identified 11 articles meeting our inclusion criteria. Only the randomized controlled trial (RCT) showed no significant difference in late axial pain (at 12 months) when C7 spinous muscle preservation was compared with no preservation. However, seven other retrospective cohort studies showed significant pain relief in the preserved group compared with the nonpreserved group. The preservation group included those with preservation of the C7 spinous process and/or attached muscles, the deep extensor muscles, or C2 muscle attachment and/or C3 laminectomy (as opposed to laminoplasty). One study that included preservation of either the C2 or C7 posterior paraspinal muscles found that only preservation of the muscles attached to C2 resulted in reduced postoperative pain. Another study that included preservation of either the C7 spinous process or the deep extensor muscles found that only preservation of C7 resulted in reduced postoperative pain. Conclusion Although there is conflicting data regarding the importance of preserving C7 and/or the semispinalis cervicis muscle attachments to C2, there is enough evidence to suggest that surgeons should make every attempt to preserve these structures whenever possible since there appears to be little downside to doing so, unless it compromises the neurologic decompression.

Methods to decrease postoperative infections following posterior cervical spine surgery

BACKGROUND

To decrease surgical site infections, we initiated a protocol of preliminary preparation of the skin and surrounding plastic drapes with alcohol foam, and the placement of a suprafascial drain in addition to a subfascial drain in obese patients in 2004. In 2008, we additionally placed 500 mg of vancomycin powder into the wound prior to closure. The purpose of this study was to analyze the infection rates for three groups: Group C (control that received standard perioperative intravenous antibiotics alone), Group AD (alcohol foam and drain), and Group VAD (vancomycin with alcohol foam and drain).

METHODS

A consecutive series of 1001 all-posterior cervical spine surgical procedures performed at one institution by the senior author from 1995 to 2010 was retrospectively reviewed. These surgical procedures included foraminotomy, laminectomy, laminoplasty, arthrodesis, instrumentation, and/or osteotomies. There were 483 patients in Group C, 323 in Group AD, and 195 in Group VAD.

RESULTS

In Group C, nine (1.86%) of the 483 patients had an acute postoperative deep infection, in which methicillin-resistant Staphylococcus aureus was the most common pathogen. A significantly higher rate of infection was found in patients with an active smoking history (p = 0.008; odds ratio = 2.6 [95% confidence interval, 1.0 to 7.1]), rheumatoid arthritis (p = 0.005; odds ratio = 4.0 [95% confidence interval, 1.4 to 7.9]), and a body mass index of ≥30 kg/m2 (p = 0.005; odds ratio = 4.1 [95% confidence interval, 1.5 to 7.7]). Group AD (n = 323) had one infection, a significant decrease compared with Group C (p = 0.047). In Group VAD, none of the 195 patients had infections, which was also a significant decrease compared with Group C (p = 0.048).

CONCLUSIONS

In this study, preliminary preparation with alcohol foam and the placement of suprafascial drains for deep wounds resulted in one postoperative deep infection in 323 surgical procedures. The addition of intrawound vancomycin powder in 195 consecutive posterior cervical spine surgical procedures resulted in no infections and no adverse effects. To our knowledge, this is the first description of a technique for significantly decreasing postoperative cervical spine infections.

Why Are Spine Surgery Patients Lost to Follow-up?

Long-term outcome studies are frequently hindered by a decreasing frequency of patient follow-up with the treating surgeon over time. Whether this attrition represents a "loss of faith" in their index surgeon or the realities of a geographically mobile society has never been assessed in a population of patients undergoing spinal surgery. The purpose of this article is to determine the frequency with which patients who have undergone prior surgery and develop new problems attempt to follow-up with their index spine surgeon. The study design was a population survey. All patients seen at two university-based spine centers over a 3-month period were surveyed regarding prior spine surgery. The questionnaire asked details of the previous operation, whether the patient had sought follow-up with their index surgeon, why the patient did not continue treatment with that surgeon, and whether the patient was satisfied with their prior treatment. Sixty-nine patients completed the survey. Prior operations were lumbar (53 patients) and cervical (16). When asked the reason for not seeing their prior surgeon, 10 patients (15%) stated that they (the patient) had moved and 16 (23%) responded that their surgeon no longer practiced in the area. Thirteen (19%) were unhappy with their previous care, 22 (32%) were seeking a second opinion, and 7 (10%) were told they needed more complex surgery. Thirty-seven (54%) discussed their symptoms with their original surgeon before seeking another surgeon. Although 32 patients (46%) had not discussed their new complaints with their index surgeon, only 3 patients (4%) chose not to return to their prior surgeon despite having the opportunity to do so. Forty-nine patients (71%) were satisfied with their prior surgical care, and 42 patients (61%) would undergo the index operation again. Most of the patients seen at the authors' practices after undergoing prior spine surgery elsewhere failed to follow up with their prior spine surgeon for geographical reasons. It appears that the majority of patients who develop new spinal complaints will seek out their treating surgeon when possible. This suggests that patient attrition over long-term follow-up may reflect a geographically mobile population rather than patient dissatisfaction with prior treatment.

Adjacent segment disease and C-ADR: promises fulfilled?

Study design: Systematic review.

Clinical question: Do the rates and timing of adjacent segment disease (ASD) differ between cervical total disc arthroplasty (C-ADR) and anterior cervical discectomy and fusion (ACDF) in patients treated for cervical degenerative disc disease?

Methods: A systematic search of MEDLINE/PubMed and bibliographies of key articles was done to identify studies with long-term follow-up for symptomatic and/or radiographic ASD comparing C-ADR with fusion for degenerative disc disease of the cervical spine. The focus was on studies with longer follow-up (48–60 months) of primary US Food and Drug Administration trials of Prestige ST, Prodisc-C, and Bryan devices as available. Trials of other discs with a minimum of 24 months follow-up were considered for inclusion. Studies evaluating lordosis/angle changes at adjacent segments and case series were excluded.

Results: From 14 citations identified, four reports from three randomized controlled trials and four nonrandomized studies are summarized. Risk differences between C-ADR and ACF for symptomatic ASD were 1.5%–2.3% and were not significant across RCT reports. Time to development of ASD did not significantly differ between treatments. Rates of radiographic ASD were variable. No meaningful comparison of ASD rates based on disc design was possible. No statistical differences in adjacent segment range of motion were noted between treatment groups.

Conclusion: Our analysis reveals that, to date, there is no evidence that arthroplasty decreases ASD compared with ACDF; the promise of arthroplasty decreasing ASD has not been fulfilled.

Hemostatic techniques reduce hospital stay following multilevel posterior cervical spine surgery

BACKGROUND

Despite meticulous hemostasis, persistent postoperative drain output following posterior cervical spine procedures often necessitates a prolonged length of hospital stay. We sought to determine if thrombin-soaked absorbable gelatin compressed sponge can decrease postoperative drain output and the length of hospital stay after multilevel posterior cervical spine surgery.

METHODS

We performed a retrospective analysis of forty-three pairs of patients who had undergone either posterior cervical decompression and/or fusion of three or more levels by the same surgeon. The patients were matched according to intraoperative blood loss, age, sex, and number of involved levels. Control patients were managed between 2004 and 2007, whereas study patients were managed between 2008 and 2011. The only variable between the study and control groups was that, in the study group, absorbable gelatin compressed sponge was soaked in thrombin and applied over the exposed spine before wound closure. A subfascial drain was used in all patients. Total drain output, time for the drainage to decrease to <30 mL per eight-hour shift (at which point the drain was discontinued), the length of stay, the number of readmissions, and postoperative complications were analyzed.

RESULTS

Total drain output averaged 93 mL in the study group and 204 mL in the control group (p < 0.0001). The average time for the drainage to decrease to <30 mL per eight-hour shift was 2.5 shifts in the study group and 4.4 shifts in the control group (p < 0.0001). Length of stay averaged 1.3 days (cumulative total, fifty-seven days) in the study group and 2.2 days (cumulative total, ninety-five days) in the control group (p < 0.0001). Persistent drain output was the primary reason preventing discharge on the first postoperative day. There were no infections, epidural hematomas, or readmissions within thirty days of discharge in either group. No patient developed adverse reactions attributable to the thrombin-soaked absorbable gelatin compressed sponge.

CONCLUSIONS

Application of thrombin-soaked absorbable gelatin compressed sponge at the end of multilevel posterior cervical spinal surgery significantly decreased postoperative drain output and consequent hospital stay.

LEVEL OF EVIDENCE

Therapeutic Level III.

The risk of adjacent-level ossification development after surgery in the cervical spine: are there factors that affect the risk? A systematic review

STUDY DESIGN

Systematic review.

OBJECTIVE

To answer the following clinical questions: (1) What is the risk of adjacent-level ossification development (ALOD) in patients receiving noninstrumented cervical fusion, instrumented cervical fusion with a plate, or cervical total disc arthroplasty?; (2) What are the risk factors for ALOD?; (3) What is the time course for the development of ALOD?; and (4) Does ALOD affect outcomes and rates of reoperation?

SUMMARY OF BACKGROUND DATA

Anterior cervical plating, total disc arthroplasty, and noninstrumented fusion have all been used in the treatment of cervical disc disease. There are numerous reports that identify ALOD, a form of heterotopic ossification, as a major risk factor after performing these procedures. Few studies have compared these 3 procedures to evaluate the risk, timing, and outcomes related to postoperation ALOD.

METHODS

A systematic search was conducted in PubMed and the Cochrane Library for articles published between January 1, 1990, and December 31, 2011. We included all articles that described the risk of or risk factors for ALOD after surgical treatment of the cervical spine. Studies with patients older than 18 years or those treated for tumor or trauma were excluded from the study. In addition, those with posterior fusions, case reports, and case series with less than 10 patients were excluded.

RESULTS

A total of 5 studies met the inclusion criteria for our systematic review. The risk of ALOD with anterior cervical discectomy and fusion ranged from 41% to 64%, whereas the risk of ALOD after total disc replacement ranged from 6% to 24%. When ALOD did occur, there was a 2-fold higher risk of development at the cranial adjacent segment. The most important risk factor for the development of ALOD was the use of instrumentation and the plate-to-disc distance, although the surgical procedure type (corpectomy vs. discectomy and fusion) neared but did not reach statistical significance. Insufficient evidence was available to delineate the time course for its development and how ALOD affected outcomes.

CONCLUSION

The current body of literature suggests that ALOD will develop with the use of instrumentation and especially so if anterior instrumentation is placed within 5 mm of the adjacent cranial disc segment. In addition, total disc replacement showed lower rates for the development of ALOD compared with anterior cervical discectomy and fusion at both short- and long-term follow-up.

CONSENSUS STATEMENT

We recommend that the surgeon make every effort to keep the plate as far away from the adjacent disc as possible. Strength of Statement: Strong.

Less exposure surgery for multilevel anterior cervical fusion using 2 transverse incisions

Multilevel anterior cervical fusion often necessitates a large extensile incision for exposure and substantial retraction of the esophagus for placing long plates, potentially predisposing patients to complications such as dysphagia, dysphonia, and neurovascular injury. To the authors' knowledge, the use of 2 incisions as an option has not been published, and so it is not intuitive to young surgeons or widely practiced. In this report, the authors discuss the advantages and raise awareness of using 2 incisions for multilevel anterior cervical fusion, and they document a safe skin bridge length. They also describe the advantages of using 2 incisions for performing multilevel anterior cervical fusion either at contiguous or noncontiguous levels as in adjacent-segment disease. By using the 2-incision technique, the authors made the surgery technically easier and diminished the amount of esophageal retraction otherwise needed through 1 long transverse or longitudinal incision. A skin bridge of 3 cm was safe.

The feasibility of laminar screw placement in the subaxial spine: analysis using 215 three-dimensional computed tomography scans and simulation software

BACKGROUND CONTEXT

There have been several reports describing the usage of subaxial cervical laminar screws. However, the anatomic feasibility of placing such screws has not been thoroughly evaluated yet.

PURPOSE

To determine the feasibility of the laminar screw placement in the subaxial cervical spine using a large number of computed tomography (CT) scans and three-dimensional screw trajectory software.

STUDY DESIGN

Three-dimensional simulation study of screw placement.

PATIENT SAMPLE

Computed tomography scans of 215 consecutive patients were examined, for a total of 430 screws at each level of the subaxial cervical spine.

OUTCOME MEASURES

Successful screw placement without laminar cortical breach, facet joint violation, and collision between two screws in the same level.

METHODS

We simulated the placement of 4.0-mm subaxial (C3-C7) cervical laminar screws. Unilateral and bilateral screw placement was simulated, and their success rates were evaluated at each level of the subaxial cervical spine. This study was not supported by any financial sources. One of the authors received royalties for a posterior cervical fixation system, which is not the topic of this article and is not used or mentioned in this article.

RESULTS

The success rate of unilateral screw placement was the highest at C7 (91.4%), followed by C6 (31.9%), C3 (30.2%), C4 (6.3%), and C5 (4.0%). It was significantly higher (p<.001) in men than in women at C6 and C7 but not at the other levels. The success rate of bilateral screw placement was the highest at C7 (68.8%), followed by C3 (13.5%), C6 (8.8%), C4 (1.9%), and C5 (0.9%). It was significantly higher in men (83.5%) than in women (52.0%) at C7 (p<.001) but not at the other levels.

CONCLUSIONS

The relatively high success rate at C7, particularly of unilateral placement, suggests that laminar screw placement can be a sound alternative method for fixation at this level. However, careful preoperative CT scan evaluation and patient selection are required, particularly for bilateral fixation in women. At C3 and C6, unilateral screw placement can be considered in approximately 30% of patients after careful selection using preoperative CT scans. At C4 and C5, neither unilateral nor bilateral screw fixation is recommended for most patients.

Laminar closure after classic Hirabayashi open-door laminoplasty

STUDY DESIGN

Prospective analysis of preoperative and postoperative radiological data.

OBJECTIVE

To assess the incidence and extent of laminar closure after Hirabayashi open-door laminoplasty, as determined by multi-detector computed tomography (CT), and to investigate the influence of this phenomenon on spinal cord compression, as shown by magnetic resonance imaging (MRI).

SUMMARY OF BACKGROUND DATA

Although laminar closure occurs after laminoplasty, little is known about its progression or its effect on restenosis of the spinal canal.

METHODS

Thirty-five patients (132 laminae) underwent classic Hirabayashi laminoplasty and were followed for at least 12 months. Multi-detector CT was performed preoperatively, at 1 week, or less, and 6 months after surgery. At each level, the anteroposterior (AP) diameter of the spinal canal and the angle of the opened lamina were measured. MRI was performed preoperatively and 1 year after surgery to evaluate the severity of cord compression based on a six-grade classification system.

RESULTS

The mean AP diameter and the mean opening angle increased immediately after surgery (P <0.05 each) and decreased 6 months after surgery (P < 0.0001 each), with the AP diameter and opening angle decreasing by 9.4% and 10.2%, respectively. CT at 6 months showed fusion of the hinge in 91% of opened laminae. Segments with high-grade cord compression (grade ≥3) at 1 year showed greater decreases in AP diameter and opening angle (P < 0.05).

CONCLUSION

After classic Hirabayashi open-door laminoplasty, opened laminae showed reclosure at 6 months, with approximately 10% decrease in AP diameter and opening angle. Postoperative lamina closure was associated with recurrent spinal cord compression, suggesting the need for other augmenting techniques that keep the laminae opened.

Accuracy of the freehand technique for 3 fixation methods in the C-2 vertebrae

Object

Intraoperative imaging often does not provide adequate visualization to ensure safe placement of screws. Therefore, the authors investigated the accuracy of a freehand technique for placement of pars, pedicle, and intralaminar screws in C-2.

Methods

Sixteen cadaveric specimens were instrumented freehand by 2 experienced cervical spine surgeons with either a pars or pedicle screw, and bilateral intralaminar screws. The technique was based on anatomical starting points and published screw trajectories. A pedicle finder was used to establish the trajectory, followed by tapping, palpation, and screw placement. After placement of all screws (16 pars screws, 16 pedicle screws, and 32 intralaminar screws), the C-2 segments were disarticulated, radiographed in anteroposterior, lateral, and axial planes, and meticulously inspected by another spine surgeon to determine the nature and presence of any defects.

Results

A total of 64 screws were evaluated in this study. Pars screws exhibited 2 critical defects (1 in the foramen transversarium and 1 in the C2–3 facet) and an insignificant dorsal cortex breech, for an overall accuracy rate of 81.3%. Pedicle screws demonstrated only 1 insignificant violation (inferior facet/medial cortex intrusion of 1 mm) with an accuracy rate of 93.8%, and intralaminar screws demonstrated 3 insignificant violations (2 in the ventral canal, 1 in the caudad lamina breech) for an accuracy rate of 90.6%. Pars screws had significantly more critical violations than intralaminar screws (p = 0.041).

Conclusions

Instrumentation of the C-2 vertebrae using the freehand technique for insertion of pedicle and intralaminar screws showed a high success rate with no critical violations. Pars screw insertion was not as reliable, with 2 critical violations from a total of 16 placements. The freehand technique appears to be a safe and reliable method for insertion of C-2 pedicle and intralaminar screws.

Results of cervical arthroplasty compared with anterior discectomy and fusion: four-year clinical outcomes in a prospective, randomized controlled trial

BACKGROUND

The published two-year results of the pivotal U.S. Food and Drug Administration investigational device exemption trial with the use of the Bryan cervical disc arthroplasty compared with anterior cervical discectomy with fusion for treating single-level degenerative cervical disc disease revealed a significantly superior overall success rate in the arthroplasty group. The purpose of this study was to evaluate the midterm safety and effectiveness of the Bryan disc as an alternative to arthrodesis following anterior cervical discectomy.

METHODS

A prospective, multicenter randomized clinical trial was undertaken for the treatment of persistent radiculopathy or myelopathy due to single-level cervical disc herniations or spondylosis. Patients were randomized to treatment with either the Bryan disc (the arthroplasty group; 242 patients) or anterior cervical discectomy and fusion (the fusion group; 221 patients). Patients completed preoperative and postoperative self-assessment forms at specified intervals and had radiographs made preoperatively, at six weeks, and at three, six, twelve, twenty-four, and forty-eight months after surgery. The primary outcome measure was overall success, a composite variable of safety and efficacy measures. Numerous secondary measures were assessed. The follow-up data for up to twenty-four months have been previously published. We report in the present study the forty-eight-month data collected on 181 patients who received the Bryan disc and 138 patients who underwent anterior cervical discectomy and fusion.

RESULTS

The study groups were demographically similar. Substantial reduction in Neck Disability Index scores occurred in both groups compared with preoperative values. The greater improvement in the Neck Disability Index score in the Bryan disc cohort persisted through the four-year follow-up period (p < 0.001). The four-year overall success rates were 85.1% and 72.5% for the arthroplasty and fusion groups, respectively (p = 0.004). The improvement in the arm pain score was substantial for both groups and significantly greater in the Bryan disc cohort (p = 0.028), and the neck pain scores showed persistently greater improvement in the Bryan disc group at forty-eight months of follow-up (p = 0.001). Short Form-36 physical component score improvement remained greater among the Bryan disc cohort (p = 0.007). The mean range of motion for the Bryan disc was 8.08° and 8.48° at twenty-four and forty-eight months, respectively. Total and serious adverse event rates were similar between the groups.

CONCLUSIONS

The forty-eight-month follow-up data in the present report showed consistent, sustained significantly superior outcomes for cervical spine arthroplasty compared with cervical spine fusion. The arthroplasty cohort continued to show significantly greater improvements in Neck Disability Index, neck pain score, arm pain score, and Short Form-36 physical component score, as well as the primary outcome measure, overall success, at forty-eight months following surgery.

Adjacent-level cervical ossification after Bryan cervical disc arthroplasty compared with anterior cervical discectomy and fusion

BACKGROUND

Ossification of the anterior longitudinal ligament and the anulus adjacent to an anterior cervical arthrodesis has been termed adjacent-level ossification development. Initial studies suggested an association with the placement of plates <5 mm from an adjacent disc space. A follow-up study demonstrated that this ossification rarely occurs in association with arthrodeses without plate fixation. In the present study, our goal was to determine the incidence of adjacent-level ossification in patients who underwent cervical arthrodesis with plate fixation as compared with that in patients who underwent cervical arthroplasty.

METHODS

We performed a post hoc analysis of prospectively collected data. Radiographic data for all patients from a single site were used. All postoperative, two-year, and four-year follow-up lateral cervical spine radiographs were collected and formatted to occlude the surgical level, blinding the readers as to the procedure performed. Three independent blinded surgeons graded the cephalad adjacent level for the degree of ossification at each time point. The data were statistically analyzed for significant ossification grade differences between arthrodesis and arthroplasty.

RESULTS

A total of forty-six patients (twenty-one with a Bryan total disc arthroplasty and twenty-five with an arthrodesis) were included. Both cohorts were derived from previous participation in a Level-I multicenter prospective randomized controlled trial stratified by site. Ossification scores based on independent assessment by three readers at multiple follow-up times were used. The arthrodesis group had significantly higher ossification scores than the arthroplasty group at both the two-year (p = 0.003) and the four-year follow-up interval (p = 0.004). Both cohorts showed significant increases in ossification from the two-year follow-up to the latest follow-up (p = 0.001 for the anterior cervical arthrodesis group and p = 0.008 for the arthroplasty group).

CONCLUSIONS

Our data conclusively demonstrate that cervical intervertebral arthroplasty is associated with a significantly lower incidence of adjacent-level ossification than arthrodesis with plate fixation at both the two-year and the four-year follow-up. Arthroplasty has the advantage of not being associated with adjacent-level ossification, which may decrease cervical spine motion above and below the surgical level.

Optimal entry points and trajectories for cervical pedicle screw placement into subaxial cervical vertebrae

The present study was performed to determine the optimal entry points and trajectories for cervical pedicle screw insertion into C3-7. The study involved 40 patients (M:F = 20:20) with various cervical diseases. A surgical simulation program was used to construct three-dimensional spine models from cervical spine axial CT images. Axial, sagittal, and coronal plane data were simultaneously processed to determine the ideal pedicle trajectory (a line passing through the center of the pedicle on coronal, sagittal, and transverse CT images). The optimal entry points on the lateral masses were then identified. Horizontal offsets and vertical offsets of the optimal entry points were measured from three different anatomical landmarks: the lateral notch, the center of the superior edge and the center of lateral mass. The transverse angle and sagittal angles of the ideal pedicle trajectory were measured. Using those entry points and trajectory results, virtual screws were placed into the pedicles using the simulation program, and the outcomes were evaluated. We found that at C3-6, the optimal entry point was located 2.0-2.4 mm medial and 0-0.8 mm inferior to the lateral notch. Since the difference of 1 mm is difficult to discern intra-operatively, for ease of remembrance, we recommend rounding off our findings to arrive at a starting point for the C3-6 pedicle screws to be 2 mm directly medial to the lateral notch. At C7, by contrast, the optimal entry point was 1.6 mm lateral and 2.5 mm superior to the center of lateral mass. Again, for ease of remembrance, we recommend rounding off these numbers to use a starting point for the C7 pedicle screws to be 2 mm lateral and 2 mm superior to the center of lateral mass. The average transverse angles were 45° at C3-5, 38° at C6, and 28° at C7. The entry points for each vertebra should be adjusted according to the transverse angles of pedicles. The mean sagittal angles were 7° upward at C3, and parallel to the upper end plate at C4-7. The simulation study showed that the entry point and ideal pedicle trajectory led to screw placements that were safer than those used in other studies.

Risk of internal carotid artery injury during C1 screw placement: analysis of 160 computed tomography angiograms

BACKGROUND CONTEXT

Injury to the internal carotid artery (ICA) is a potentially catastrophic complication of C1-lateral mass (C1-LM) or C1-C2 transarticular screw insertion.

PURPOSE

This study was designed to determine the risk of injury to the ICA during placement of these screws using computed tomography angiography (CTA).

STUDY DESIGN

Radiographic analysis using CTA.

PATIENT SAMPLE

One hundred sixty CTAs were examined, for a total of 320 ICAs.

OUTCOME MEASURES

Not applicable.

METHODS

Fine-cut intravenous CTAs with multiplanar and three-dimensional reconstruction were reviewed. The position of the ICA in relation to the anterior cortex (AC) of C1, anterior end of the anterior tubercle (AT), and medial margin of the transverse foramen (TF) was measured bilaterally in three ascending and equidistant levels of the C1-AT.

RESULTS

The position of the ICA in relation to C1 was variable. The average distance between the ICA and the AC of C1 was only 3.7 mm. Furthermore, 96% of the time the posterior margin of the ICA was located posterior to the anteriormost aspect of the anterior C1 tubercle (average distance, 5.4 mm), making the ICA vulnerable to damage if a drill, tap, or screw was inserted to the depth of the anteriormost portion of the AT as seen on a lateral fluoroscopic or radiographic view. The medial margin of the ICA was located medial to the TF (a location potentially vulnerable to injury with bicortical screw placement) less often at the caudal aspect of the C1-AT (54%) than at its middle or cranial aspect (74% and 75%, respectively). No ICAs were located anterior to the medial 30% of the C1-LM or more medially.

CONCLUSIONS

Bicortical C1-LM or C1-C2 transarticular screw placement carries a potential risk of ICA injury. Given the wide variation in ICA location relative to C1, if bicortical C1 fixation is required, preoperative CTA should be considered to determine the optimal screw trajectory. In general, inferomedially angulated C1-LM screws appear to be safer with respect to the ICA injury than other potential trajectories.

Anterior cervical discectomy and fusion for the management of axial neck pain in the absence of radiculopathy or myelopathy

STUDY DESIGN

 Systematic reviewStudy rationale: Anterior cervical discectomy and fusion (ACDF) is a proven, effective treatment for relieving neck pain due to degenerative conditions of the cervical spine. Since most patients also present with radiculopathy or myelopathy, little is known as to the effectiveness of ACDF to relieve pain and improve function in patients without radicular or myelopathic symptoms.

OBJECTIVE

 To examine the clinical outcome in patients undergoing (ACDF) for axial neck pain without radicular or myelopathic symptoms.

METHODS

 A systematic review was undertaken for articles published up to March 2010. Electronic databases and reference lists of key articles were searched to identify studies evaluating ACDF for the treatment of axial neck pain only. Radiculopathy and myelopathy, patients who suffered severe trauma, or with tumor/metastatic disease or infection were excluded. Two independent reviewers assessed the strength of evidence using the grading of recommendations assessment, development and evaluation (GRADE) system, and disagreements were resolved by consensus.

RESULTS

 No comparative studies were identified. Three case series met our inclusion criteria and were evaluated. All studies showed a mean improvement of pain of at least 50% approximately 4-years following surgery. Functional outcomes improved between 32% and 52% from baseline. Most patients reported satisfaction with surgery, 56% in one study and 79% in another. Complications varied among studies ranging from 1% to 10% and included pseudoarthrosis (9%), nonunion and revision (3%) and screw removal (1%).

CONCLUSION

 There is low evidence suggesting that patients with axial neck pain without radicular or myelopathic symptoms may receive some improvement in pain and function following ACDF. However, whether this benefit is greater than nontreatment or other treatments cannot be determined with the present literature.

The long-term results of anterior surgical reconstruction in patients with postlaminectomy cervical kyphosis

BACKGROUND CONTEXT

Postlaminectomy kyphosis of the cervical spine is a challenging condition to treat because it has a combination of an exposed cord, progressive kyphosis, segmental instability, and anterior neural compression. The ideal mode of surgical correction remains controversial. In terms of surgical strategy, there are few large series that have reported the long-term results of anterior surgical treatment of this condition.

PURPOSE

This study was designed to determine the long-term results and outcomes of anterior surgical treatment alone for the patients of postlaminectomy cervical kyphosis.

STUDY DESIGN/SETTING

This is a retrospective review of prospectively collected data in an academic institution.

PATIENT SAMPLE

The sample comprises 23 patients who underwent anterior reconstruction surgery for the treatment of postlaminectomy kyphosis.

OUTCOME MEASURES

The outcome measures were neck disability index (NDI), visual analog scale (VAS) for neck and arm pain, Nurick grades, kyphosis angles, fusion status, and complications.

METHODS

Two independent spine surgeons reviewed the completed medical records and radiographs of 23 patients who had undergone multilevel anterior cervical hybrid decompression (corpectomy and discectomy) with instrumented fusions for postlaminectomy kyphosis by one surgeon at an academic institution. The clinical and radiographic outcomes were measured by NDI, VAS for neck and arm pain, Nurick grades, kyphosis angles, and fusion status at the time of preoperative, postoperative, and the last follow-up.

RESULTS

The mean follow-up was 44.5+/-31.0 months (range 24-120 months). The average preoperative kyphosis of 20.9 degrees was significantly improved to a lordosis of 14.0 degrees after surgery (p<.0001) and was maintained to a lordosis of 9.6 degrees at the final follow-up (p<.0001). The average correction angle of kyphosis was 30.5+/-11.7 degrees . The average preoperative, NDI, VAS, and Nurick grades were significantly improved at the last follow-up (all, p<.0001). The average levels of 0.9+/-0.7 corpectomy, 2.0+/-0.9 discectomy, and 3.8+/-1.4 anterior fusions were performed in each patient. Solid fusion was confirmed by computed tomography in all patients at a mean time of 3.8+/-1.2 months. There were six (26%) patients and seven (30.4%) complications: four (14.3%) graft-related complications (one implant displacement, one graft dislodgment, and one pseudarthrosis), one swallowing difficulty, one wound infection, one dura tear, and one pneumonia.

CONCLUSIONS

Our data suggest that multilevel anterior surgical treatment using hybrid decompression (corpectomy and discectomy) combined with instrumented fusion yields acceptable clinical and neurological improvement and effective correction of cervical kyphosis. The techniques used also appeared to decrease the incidence of graft-related complications compared with a previous report by the same author.

Comparison of anterior cervical fusion after two-level discectomy or single-level corpectomy: sagittal alignment, cervical lordosis, graft collapse, and adjacent-level ossification

BACKGROUND CONTEXT

Single-level corpectomy and two-level discectomy with anterior cervical plating have been reported to have comparable fusion and complication rates. However, there are few large series that have compared the two for sagittal alignment, cervical lordosis, graft subsidence, and adjacent-level ossification.

PURPOSE

To determine the differences between these two procedures for patients with two-level spondylosis by comparing the pre- and postoperative radiographic data.

STUDY DESIGN

Retrospective review of prospectively collected data in an academic institution.

PATIENT SAMPLE

Fifty-two with a single-level corpectomy and 45 with a two-level anterior cervical discectomy and fusion (ACDF).

OUTCOME MEASURES

Pre- and postoperative radiographic data for sagittal alignment, cervical lordosis, subsidence, and adjacent-level ossification.

METHODS

We retrospectively reviewed the lateral cervical radiographs of patients who had a solid fusion after a single-level cervical corpectomy or a two-level ACDF for the treatment of a degenerative cervical spondylosis by a surgeon at an academic institution. The choice of the operation was dependent on the presence or absence of retrovertebral compression. All patients underwent anterior cervical fusion using fibula strut allograft and variable-angle screw-plate fixation. None had had prior cervical spine surgery. Twenty-five were excluded because of inadequate radiographs and follow-up. There were 52 with a single-level corpectomy and 45 with a two-level ACDF. The following were analyzed: 1) sagittal alignment (modified method of Toyama); 2) cervical lordosis measured by Cobb angles of fusion constructs (fusion Cobb) and C2-C7 (C2-C7 Cobb); 3) graft collapse determined by the subsidence of anterior/posterior body height of fused segments (anterior/posterior subsidence) and the cranial/caudal plate-to-disc distances (cranial/caudal subsidence), and the difference between anterior and posterior body height for the fused levels (anteroposterior [AP] difference); and 4) the severity of ossification at two adjacent levels.

RESULTS

The mean durations of follow-up were 23.3+/-6.6 (corpectomy) and 25.7+/-6.2 (ACDF) months, range 12 to 45 months. There were no significant differences between the two groups in sagittal alignment, cervical lordosis, graft collapse, and adjacent-level ossification. Graft subsidence and loss of cervical lordosis occurred significantly more during the first 6 weeks after surgery (all measurements, p<.0001) than after 6 weeks, with no significant difference between the two groups. Posterior and caudal end plate subsidence significantly progressed after 6 weeks in Group 1 (p=.04, p=.02). The final follow-up Cobb angle positively correlated with preoperative and immediate postoperative Cobb angles (r=0.437, p<.0001; r=0.727, p<.0001), caudal subsidence (r=0.270, p=.008), and the final AP difference (r=0.915, p<.0001) but did not correlate with surgery level, preoperative and final sagittal alignments, anterior/posterior subsidence, and cranial subsidence. Anterior/posterior subsidence was significantly more strongly related with caudal subsidence (r=0.607, p<.0001; r=0.424, p<.0001) than cranial (r=0.277, p=.007; r=0.211, p=.040) but did not correlate with pre- and postoperative fusion Cobb, and preoperative and the last sagittal alignments.

CONCLUSIONS

Our data suggest that the two procedures yield comparable results in terms of sagittal alignment, cervical lordosis, graft subsidence, and adjacent-level ossification. Graft subsidence and loss of cervical lordosis appeared to occur mainly during the first 6 weeks after surgery. Single-level corpectomy and fusion continued to subside at the posterior portion of caudal end plate even after 6 weeks. On the other hand, graft subsidence did not correlate with preoperative and final postoperative sagittal alignments.

Effect of hyperglycemia on apoptosis of notochordal cells and intervertebral disc degeneration in diabetic rats

Object

Diabetes mellitus is thought to be an important etiologic factor in intervertebral disc degeneration. It is known that notochordal cells gradually disappear from the nucleus pulposus (NP) of the intervertebral disc with age by undergoing apoptosis. What is not known is whether diabetes has an effect on apoptotic rates of notochordal cells. The purpose of this study was to investigate the effect of hyperglycemia on apoptosis of notochordal cells and intervertebral disc degeneration in age-matched OLETF (diabetic) and LETO (control) rats.

Methods

Lumbar disc tissue (L1–2 through L5–6), including cranial and caudal cartilaginous endplates, was obtained from 6- and 12-month-old OLETF and LETO rats (40 rats, 10 in each of the 4 groups). The authors examined the NP using TUNEL, histological analysis, and Western blot for expression of matrix metalloproteinase (MMP)–1, -2, -3, and -13, tissue inhibitor of metalloproteinase (TIMP)–1 and -2, and Fas (apoptosis-related protein). The apoptosis index of notochordal cells was calculated. The degree of transition of notochordal NP to fibrocartilaginous NP was classified on a scale ranging from Grade 0 (no transition) to Grade 4 (transition > 75%). The degree of expression of MMP-1, -2, -3, and -13, TIMP-1 and -2, and Fas was evaluated by densitometry.

Results

At 6 and 12 months of age, OLETF rats showed increased body weight and abnormal 2-hour glucose tolerance tests compared with LETO rats. The apoptosis index of notochordal cells was significantly higher in the OLETF rats than in the LETO rats at both 6 and 12 months of age. The degree of transition of notochordal NP to fibrocartilaginous NP was significantly higher in the OLETF rats than in the LETO rats at 6 and 12 months of age. The expression of MMP-1, -2, -3, and -13, TIMP-1, and Fas was higher in the OLETF rats at 6 and 12 months of age. The expression of TIMP-2 was significantly higher in the OLETF rats than in the LETO rats at 6 months of age, but not at 12.

Conclusions

The findings suggest that diabetes is associated with premature, excessive apoptosis of NP notochordal cells. This results in an accelerated transition of a notochordal NP to a fibrocartilaginous NP, which leads to early intervertebral disc degeneration. It remains to be determined if these premature changes are due to hyperglycemia or some other factors associated with diabetes. Understanding the mechanism by which diabetes affects disc degeneration is the first step in designing therapeutic modalities to delay or prevent disc degeneration caused by diabetes mellitus.

Cervical disc arthroplasty compared with arthrodesis for the treatment of myelopathy. Surgical technique

BACKGROUND

Although there have been case reports describing the use of cervical disc arthroplasty for the treatment of myelopathy, there is a concern that motion preservation may maintain microtrauma to the spinal cord, negatively affecting the clinical results. As we are not aware of any studies on the use of arthroplasty in this scenario, we performed a cross-sectional analysis of two large, prospective, randomized multicenter trials to evaluate the efficacy of cervical disc arthroplasty for the treatment of myelopathy.

METHODS

The patients in the current study were a cohort of patients who were enrolled in the United States Food and Drug Administration Investigational Device Exemption studies of the Prestige ST and Bryan disc replacements (Medtronic, Memphis, Tennessee). The inclusion criteria were myelopathy and spondylosis or disc herniation at a single level from C3 to C7. Clinical outcome measures were collected preoperatively and at six weeks, three months, six months, twelve months, and twenty-four months postoperatively.

RESULTS

A total of 199 patients were included in the present study; 106 patients (53%) underwent arthroplasty, whereas ninety-three (47%) underwent arthrodesis. The Neck Disability Index, Short Form-36 scores, and specific arm and neck pain scores improved significantly from baseline at all time points. Patients in all four groups had improvement in the postoperative neurological status and gait function; at twenty-four months after surgery, 90% (95% confidence interval, 77.8% to 96.6%) of the patients in the arthroplasty group and 81% (95% confidence interval, 64.9% to 92.0%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Prestige ST trial and 90% (95% confidence interval, 75.8% to 97.1%) of the patients in the arthroplasty group and 77% (95% confidence interval, 57.7% to 90.1%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Bryan trial.

CONCLUSIONS

We found that patients in both the arthroplasty and arthrodesis groups had improvement following surgery; furthermore, improvement was similar between the groups, with no worsening of myelopathy in the arthroplasty group. While the findings at two years postoperatively suggest that arthroplasty is equivalent to arthrodesis for the treatment of cervical myelopathy for a single-level abnormality localized to the disc space, the present study did not evaluate the treatment of retrovertebral compression as occurs in association with ossification of the posterior longitudinal ligament, and we cannot comment on the treatment of this condition.

The prevalence cervical facet arthrosis: an osseous study in a cadveric population

BACKGROUND CONTEXT

Cervical facet arthrosis has been implicated as a cause for neck pain, radiculopathy, occipital headache, and ear pain.

PURPOSE

The objective of this study was to examine the occurrence of facet arthrosis in the cervical spine.

STUDY DESIGN/SETTING

This study examined cadaveric specimens from the Hamann Todd Collection.

PATIENT SAMPLE

None.

OUTCOMES MEASURES

None.

MATERIALS AND METHODS

Four hundred sixty-five skeletally mature human cervical spines from the Hamann Todd Collection in the Cleveland Museum of Natural History were obtained for analysis. We analyzed the facets for arthrosis. We graded no arthrosis as Grade 0. Facets with peripheral osteophytic reaction, but with no lateral mass distortion were graded as Grade 1. Facets with peripheral osteophytic reaction and lateral mass distortion were graded as Grade 2. Facets that were ankylosed were graded as Grade 3. Each specimen was examined bilaterally at levels from C2-C3 through C6-C7, yielding 4,650 specimen assessments. The data were analyzed to compare cervical levels, gender, facet side, age groups, and race. Proportion analysis, using the Fisher exact test, was used to assess for statistical difference between various groupings.

RESULTS

In the entire population of 465 specimens, the upper cervical specimens appeared to be affected by facet arthrosis more frequently than the lower levels; 12.37% of the specimens had bony evidence of arthrosis at the C2-C3 level; 13.33% of the specimens had arthrosis occur at the C3-C4 level; 14.62% at the C4-C5 level; 7.85% at the C5-C6 level, and 4.84% at the C6-C7 level. The large majority of all cervical facet arthrosis was found to be Grade 1 at all levels. In the older population, the prevalence of facet arthrosis is as high as 29.87% for the C4-C5 level. C4-C5 level appears to be affected the most frequently, followed by the C3-C4 level, then C2-C3, C5-C6, and C6-C7.

CONCLUSION

The prevalence of cervical facet arthrosis increases with age, and occurs more commonly in the upper cervical spine.

The effect of an anterior cervical operation for cervical radiculopathy or myelopathy on associated headaches

BACKGROUND

Headaches related to the cervical spine have been reported by various authors, and modalities of treatment are as varied as their speculated causes. The purpose of this study was to determine if anterior cervical reconstructive surgery (cervical arthrodesis and disc arthroplasty) for the treatment of radiculopathy or myelopathy also helps to alleviate associated headaches.

METHODS

We conducted a post hoc analysis of study cohorts combined from prospective studies comparing the results of Prestige and Bryan cervical arthroplasty devices and those of anterior cervical arthrodesis with allograft and anterior instrumentation. A total of 1004 patients (51.6% were male) were evaluated with use of the Neck Disability Index questionnaire preoperatively and at five points postoperatively, with the latest evaluation at twenty-four months, resulting in a follow-up of 803 patients.

RESULTS

At the twenty-four-month follow-up, the improvement from baseline with regard to headache was significant in both groups (p < 0.0001), with patients who underwent arthroplasty reporting numerically better pain scores. Most arthroplasty and arthrodesis patients (64% and 58.5%, respectively) had improvement in the pain score of at least one grade. Conversely, the pain scores for 8.4% of those who had an arthroplasty and 13.7% of those who had arthrodesis worsened by at least one grade. For the remainder, the score was unchanged. Overall, the patients who had an arthroplasty had significant improvement more frequently than did the patients who had arthrodesis (p = 0.011).

CONCLUSIONS

At two years postoperatively, patients undergoing anterior cervical operations, both those who have an arthroplasty and those who have an arthrodesis, for cervical radiculopathy and myelopathy can be expected to have significant improvement from baseline with regard to headache symptoms.

The increased expression of matrix metalloproteinases associated with elastin degradation and fibrosis of the ligamentum flavum in patients with lumbar spinal stenosis

Background

One of the characteristics of spinal stenosis is elastin degradation and fibrosis of the extracellular matrix of the ligamentum flavum. However, there have been no investigations to determine which biochemical factors cause these histologic changes. So we performed the current study to investigate the hypothesis that matrix metalloproteinases (MMPs), which possess the ability to cause extracellular matrix remodeling, may play a role as a mediator for this malady in the ligamentum flavum.

Methods

The ligamentum flavum specimens were surgically obtained from thirty patients with spinal stenosis, as well as from 30 control patients with a disc herniation. The extents of ligamentum flavum elastin degradation and fibrosis were graded (grade 0-4) with performing hematoxylin-eosin staining and Masson's trichrome staining, respectively. The localization of MMP-2 (gelatinase), MMP-3 (stromelysin) and MMP-13 (collagenase) within the ligamentum flavum tissue was determined by immunohistochemistry. The expressions of the active forms of MMP-2, MMP-3 and MMP-13 were determined by western blot analysis, and the blots were quantified using an imaging densitometer. The histologic and biochemical results were compared between the two conditions.

Results

Elastin degradation and fibrosis of the ligamentum flavum were significantly more severe in the spinal stenosis samples than that in the disc herniation samples (3.14 ± 0.50 vs. 0.55 ± 0.60, p < 0.001; 3.10 ± 0.57 vs. 0.76 ± 0.52, p < 0.001, respectively). The expressions of the active form of MMPs were identified in all the ligamentum flavums of the spinal stenosis and disc herniation patients. The expressions of active MMP-2 and MMP-13 were significantly higher in the spinal stenosis samples than that in the disc herniation samples (both p < 0.05). The expression of active MMP-3 was slightly higher in the spinal stenosis samples than that in the disc herniation samples, but the difference was not statistically significant (p = 0.131). MMP-2, -3, and -13 were positively stained on the ligamentum flavum fibroblasts.

Conclusions

The current results suggest that the increased expression of active MMPs by the ligamentum flavum fibroblasts might be related to the elastin degradation and fibrosis of the ligamentum flavum in the patients who suffer with lumbar spinal stenosis.

Cervical disc arthroplasty compared with arthrodesis for the treatment of myelopathy

BACKGROUND

Although there have been case reports describing the use of cervical disc arthroplasty for the treatment of myelopathy, there is a concern that motion preservation may maintain microtrauma to the spinal cord, negatively affecting the clinical results. As we are not aware of any studies on the use of arthroplasty in this scenario, we performed a cross-sectional analysis of two large, prospective, randomized multicenter trials to evaluate the efficacy of cervical disc arthroplasty for the treatment of myelopathy.

METHODS

The patients in the current study were a cohort of patients who were enrolled in the United States Food and Drug Administration Investigational Device Exemption studies of the Prestige ST and Bryan disc replacements (Medtronic, Memphis, Tennessee). The inclusion criteria were myelopathy and spondylosis or disc herniation at a single level from C3 to C7. Clinical outcome measures were collected preoperatively and at six weeks, three months, six months, twelve months, and twenty-four months postoperatively.

RESULTS

A total of 199 patients were included in the present study; 106 patients (53%) underwent arthroplasty, whereas ninety-three (47%) underwent arthrodesis. The Neck Disability Index, Short Form-36 scores, and specific arm and neck pain scores improved significantly from baseline at all time points. Patients in all four groups had improvement in the postoperative neurological status and gait function; at twenty-four months after surgery, 90% (95% confidence interval, 77.8% to 96.6%) of the patients in the arthroplasty group and 81% (95% confidence interval, 64.9% to 92.0%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Prestige ST trial and 90% (95% confidence interval, 75.8% to 97.1%) of the patients in the arthroplasty group and 77% (95% confidence interval, 57.7% to 90.1%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Bryan trial.

CONCLUSIONS

We found that patients in both the arthroplasty and arthrodesis groups had improvement following surgery; furthermore, improvement was similar between the groups, with no worsening of myelopathy in the arthroplasty group. While the findings at two years postoperatively suggest that arthroplasty is equivalent to arthrodesis for the treatment of cervical myelopathy for a single-level abnormality localized to the disc space, the present study did not evaluate the treatment of retrovertebral compression as occurs in association with ossification of the posterior longitudinal ligament, and we cannot comment upon the treatment of this condition.

Tandem stenosis: a cadaveric study in osseous morphology

BACKGROUND

Tandem stenosis is the occurrence of concurrent cervical and lumbar stenosis. The prevalence has been estimated to be from 5% to 25%. Symptomatic tandem stenosis can present with a confusing scenario of both neurogenic claudication and myelopathy symptoms.

PURPOSE

The purpose of this study was to determine 1) the prevalence of anatomic tandem stenosis in a cadaveric population, 2) if there was an associative relationship between lumbar and cervical stenosis, and 3) the positive predictive values of stenosis in one area for stenosis in the other.

STUDY DESIGN

We obtained 440 skeletally mature skeletons and examined the cervical and lumbar spines from the Hamann Todd Collection in the Cleveland Museum of Natural History.

METHODS

For the cervical spine, we measured the mid-sagittal canal diameter using digital calipers for every level from C3 through C7. The minimum full central sagittal diameter was recorded for each level. For the lumbar spine, we measured the minimum full mid-sagittal canal diameter for every level from L1 through L5, using digital calipers. Stenosis was defined as a mid-sagittal canal diameter of less than 12 mm at at least one level. After analysis of this data, a second analysis was performed after correcting the data for contemporary body size and radiographic manifestation.

RESULTS

The prevalence of tandem stenosis ranged from 0.9% to 5.4% in this population. The association of cervical and lumbar stenosis was found to be statistically significant (p < .05). Stenosis in one part of the spine positively predicts for stenosis in the other area of the spine 15.3% to 32.4% of the time.

CONCLUSION

Tandem stenosis should be considered when evaluating a patient with mixed claudication and myeloradiculopathy symptoms.

Perils of intravascular methylprednisolone injection into the vertebral artery. An animal study

BACKGROUND

Intravascular injection of particulate steroids during cervical nerve root blocks has been postulated to be a source of catastrophic neurologic complications that might be avoided with the use of non-particulate steroids. The objective of this study was to compare the effects of direct intravascular injection of particulate and non-particulate steroids on the spinal cord and central nervous system.

METHODS

Eleven adult pigs underwent direct injection, under fluoroscopic guidance, into the vertebral artery while under general anesthesia. A particulate steroid (methylprednisolone) was injected into four animals (Group 1), whereas seven animals received a non-particulate steroid (dexamethasone in four animals [Group 2] and prednisolone in three [Group 3]). Following injection, the animals were assessed by direct observation of physical activity and with magnetic resonance imaging. After the animals were killed, brain and spinal cord material was retrieved, fixed in paraformaldehyde for one week, and then subjected to histopathologic analysis.

RESULTS

All four animals in Group 1 failed to regain consciousness after the injection and required ventilatory support. The animals in Groups 2 and 3 recovered fully and demonstrated no evidence of neurologic injury. Magnetic resonance imaging revealed upper cervical cord and brain stem edema in Group 1, but not in Groups 2 and 3. Histologic analysis showed early evidence of hypoxic and ischemic damage-specifically, early eosinophilic neuronal necrosis, nuclear condensation, white-matter pallor, and extracellular edema-in Group 1 but not in Groups 2 and 3.

CONCLUSIONS

These data suggest that one etiology of neurologic complications following cervical nerve blocks may be inadvertent intravascular injection of particulate steroids, as all animals injected with methylprednisolone had neurologic deficits while none of the controls injected with non-particulate steroids were affected. To our knowledge, this study is the first to demonstrate that particulate steroids cause neurologic deficits and to suggest that use of non-particulate steroids might prevent such complications.

Preoperative Laryngeal Nerve Screening for Revision Anterior Cervical Spine Procedures

Objectives:

Anterior cervical spine procedures carry an inherent risk of recurrent laryngeal nerve (RLN) injury. Patients with persistent RLN paresis may be asymptomatic because of compensation from the opposite side. If such patients undergo an opposite-side anterior approach for revision surgery, they are at risk for a second RLN injury, creating the potential for bilateral vocal fold paresis and possible need for tracheotomy. A program of routine screening for laryngeal paresis was implemented for these patients. This retrospective study reviews the results of this screening process.

Methods:

Patients referred for preoperative laryngeal nerve screening were identified. Their charts were reviewed for the results of the videolaryngoscopic examination, and for any recommendations made based on the findings. Relevant history and other physical findings were recorded.

Results:

Fifty screening laryngeal examinations were performed in 47 patients, of whom 31 (66%) had previously undergone a single anterior cervical approach procedure, and 16 (34%) had undergone more than one. Thirteen of the examinations (26%) revealed abnormal laryngeal findings, including paresis or paralysis in 11 cases (22%), of which 5 were asymptomatic. The findings resulted in a recommendation of a cervical approach from the already-involved side. None of the revision procedures resulted in bilateral vocal fold paralysis. The risk of laryngeal nerve injury appears to increase as higher cervical levels are approached.

Conclusions:

Minimally symptomatic injuries of the laryngeal nerves from prior neck surgery create a potential serious risk of bilateral vocal fold paralysis with subsequent procedures. Preoperative laryngeal screening is a simple and effective method for reducing this risk.

Randomized, prospective, and controlled clinical trial of pulsed electromagnetic field stimulation for cervical fusion

BACKGROUND CONTEXT

Multilevel fusions, the use of allograft bone, and smoking have been associated with an increased risk of nonunion after anterior cervical discectomy and fusion (ACDF) procedures. Pulsed electromagnetic field (PEMF) stimulation has been shown to increase arthrodesis rates after lumbar spine fusion surgery, but there are minimal data concerning the effect of PEMF stimulation on cervical spine fusion.

PURPOSE

To determine the efficacy and safety of PEMF stimulation as an adjunct to arthrodesis after ACDF in patients with potential risk factors for nonunion.

STUDY DESIGN

A randomized, controlled, prospective multicenter clinical trial.

PATIENT SAMPLE

Three hundred and twenty-three patients with radiographic evidence (computed tomography-myelogram [CT-myelo] or magnetic resonance imaging [MRI]) of a compressed cervical nerve root and symptomatic radiculopathy appropriate to the compressed root that had failed to respond to nonoperative management were enrolled in the study. The patients were either smokers (more than one pack per day) and/or were undergoing multilevel fusions. All patients underwent ACDF using the Smith-Robinson technique. Allograft bone and an anterior cervical plate were used in all cases.

OUTCOME MEASURES

Measurements were obtained preoperatively and at each postoperative interval and included neurologic assessment, visual analog scale (VAS) scores for shoulder/arm pain at rest and with activity, SF-12 scores, the neck disability index (NDI), and radiographs (anteroposterior, lateral, and flexion-extension views). Two orthopedic surgeons not otherwise affiliated with the study and blinded to treatment group evaluated the radiographs, as did a blinded radiologist. Adverse events were reported by all patients throughout the study to determine device safety.

METHODS

Patients were randomly assigned to one of two groups: those receiving PEMF stimulation after surgery (PEMF group, 163 patients) and those not receiving PEMF stimulation (control group, 160 patients). Postoperative care was otherwise identical. Follow-up was carried out at 1, 2, 3, 6, and 12 months postoperatively.

RESULTS

The PEMF and control groups were comparable with regard to age, gender, race, past medical history, smoking status, and litigation status. Both groups were also comparable in terms of baseline diagnosis (herniated disc, spondylosis, or both) and number of levels operated (one, two, three, or four). At 6 months postoperatively, the PEMF group had a significantly higher fusion rate than the control group (83.6% vs. 68.6%, p=.0065). At 12 months after surgery, the stimulated group had a fusion rate of 92.8% compared with 86.7% for the control group (p=.1129). There were no significant differences between the PEMF and control groups with regard to VAS pain scores, NDI, or SF-12 scores at 6 or 12 months. No significant differences were found in the incidence of adverse events in the groups.

CONCLUSIONS

This is the first randomized, controlled trial that analyzes the effects of PEMF stimulation on cervical spine fusion. PEMF stimulation significantly improved the fusion rate at 6 months postoperatively in patients undergoing ACDF with an allograft and an anterior cervical plate, the eligibility criteria being patients who were smokers or had undergone multilevel cervical fusion. At 12 months postoperatively, however, the fusion rate for PEMF patients was not significantly different from that of the control group. There were no differences in the incidence of adverse events in the two groups, indicating that the use of PEMF stimulation is safe in this clinical setting.

Value of diagnostic lumbar selective nerve root block: a prospective controlled study

BACKGROUND AND PURPOSE

Although diagnostic lumbar selective nerve root blocks are often used to confirm the pain-generating nerve root level, the reported accuracy of these blocks has been variable and their usefulness is controversial. The purpose of this study was to evaluate the accuracy of diagnostic lumbar selective nerve root blocks to analyze potential causes of false results in a prospective, controlled, single-blinded manner.

MATERIALS AND METHODS

A total of 105 block anesthetics were performed under fluoroscopic guidance in 47 consecutive patients with pure radiculopathy from a single confirmed level: 47 blocks were performed at the symptomatic level, and 58 were performed at the adjacent asymptomatic "control" level. Contrast and local anesthetics were injected, and spot radiographs were taken in all cases. We calculated the diagnostic value of the block anesthetics using concordance with the injected level. We analyzed the potential causes of false results using spot radiographs.

RESULTS

On the basis of a definition of a positive block as 70% pain relief, determined by receiver-operator characteristic (ROC) analysis, diagnostic lumbar selective nerve root block anesthetics had a sensitivity of 57%, a specificity of 86%, an accuracy of 73%, a positive predictive value of 77%, and a negative predictive value of 71%. False-negatives were due to the following causes identifiable on spot radiographs: insufficient infiltration, insufficient passage of the injectate, and intraepineural injections. On the other hand, false-positives resulted from overflow of the injectate from the injected asymptomatic level into either the epidural space or symptomatic level.

CONCLUSION

The accuracy of diagnostic lumbar selective nerve root blocks is only moderate. To improve the accuracy, great care should be taken to avoid inadequate blocks and overflow, and to precisely interpret spot radiographs.

Risk factors for surgical site infection following orthopaedic spinal operations

BACKGROUND

Surgical site infections are not uncommon following spinal operations, and they can be associated with serious morbidity, mortality, and increased resource utilization. The accurate identification of risk factors is essential to develop strategies to prevent these potentially devastating infections. We conducted a case-control study to determine independent risk factors for surgical site infection following orthopaedic spinal operations.

METHODS

We performed a retrospective case-control study of patients who had had an orthopaedic spinal operation performed at a university-affiliated tertiary-care hospital from 1998 to 2002. Forty-six patients with a superficial, deep, or organ-space surgical site infection were identified and compared with 227 uninfected control patients. Risk factors for surgical site infection were determined with univariate analyses and multivariate logistic regression.

RESULTS

The overall rate of spinal surgical site infection during the five years of the study was 2.0% (forty-six of 2316). Univariate analyses showed serum glucose levels, preoperatively and within five days after the operation, to be significantly higher in patients in whom surgical site infection developed than in uninfected control patients. Independent risk factors for surgical site infection that were identified by multivariate analysis were diabetes (odds ratio = 3.5, 95% confidence interval = 1.2, 10.0), suboptimal timing of prophylactic antibiotic therapy (odds ratio = 3.4, 95% confidence interval = 1.5, 7.9), a preoperative serum glucose level of >125 mg/dL (>6.9 mmol/L) or a postoperative serum glucose level of >200 mg/dL (>11.1 mmol/L) (odds ratio = 3.3, 95% confidence interval = 1.4, 7.5), obesity (odds ratio = 2.2, 95% confidence interval = 1.1, 4.7), and two or more surgical residents participating in the operative procedure (odds ratio = 2.2, 95% confidence interval = 1.0, 4.7). A decreased risk of surgical site infection was associated with operations involving the cervical spine (odds ratio = 0.3, 95% confidence interval = 0.1, 0.6).

CONCLUSIONS

Diabetes was associated with the highest independent risk of spinal surgical site infection, and an elevated preoperative or postoperative serum glucose level was also independently associated with an increased risk of surgical site infection. The role of hyperglycemia as a risk factor for surgical site infection in patients not previously diagnosed with diabetes should be investigated further. Administration of prophylactic antibiotics within one hour before the operation and increasing the antibiotic dosage to adjust for obesity are also important strategies to decrease the risk of surgical site infection after spinal operations.

Timing of development of adjacent-level ossification after anterior cervical arthrodesis with plates

BACKGROUND CONTEXT

Although the prevalence and severity of adjacent-level ossification development after anterior cervical plating has previously been described, there are no investigations regarding the timing of ossification development.

PURPOSE

To determine the timing of adjacent-level ossification development and maturation and discern any differences in ossification development for patients who have a plate-to-disc distance (PDD) that is <5 mm versus =5 mm.

STUDY DESIGN/SETTING

Retrospective study.

PATIENT SAMPLE

One-hundred twelve visible cranial or caudal adjacent discs in 62 patients, with a minimum of 24 months follow-up, were assessed. Among them, 40 had a minimum of 36 months follow-up after surgery (range, 36-91 months).

OUTCOME MEASURES

Grading system of adjacent-level ossification.

METHODS

The PDD was measured on the postoperative lateral X-ray film and was used to divide the adjacent disc spaces into two groups. The first group had a PDD <5 mm, and the second group had a PDD >5 mm. The presence and severity of ossification were assessed at 3, 6, 12, and 24 months postoperatively and then annually and recorded into 4 grades: grade 0 (none) to grade 3 (complete bridging). We determined whether discs with no or mild (grade 1) ossification at a given follow-up period progressed to advanced (grade 2 or 3) by 24 months and the last follow-up (mean, 48.5 months).

RESULTS

Adjacent levels with even mild ossification by 3, 6, or 12 months had a high likelihood (87.5%, 62.5%, and 37.5%, respectively) of progression to advanced ossification by 24 months. The absence of ossification in the early postoperative period was no guarantee of avoiding ossification; 23.5% and 14.9% of those with no ossification at 3 and 6 months, respectively, progressed to advanced ossification by 24 months. On the other hand, only 1.8% of those with no ossification at 12 months progressed to advanced ossification. None of the 80 levels with no or grade 1 ossification at 24 months went on to advanced ossification by the last follow-up (mean, 48.5 months). The occurrence of ossification was significantly increased for levels with a PDD <5 mm (72.1%, 49/68) compared with levels with a PDD >5 mm (45.5%, 20/44). Of 28 cases with advanced ossification, 24 (78%) developed in levels with a PDD <5 mm.

CONCLUSIONS

We conclude that any adjacent-level ossification within the first 12 months postoperatively has a substantial likelihood of progression to advanced ossification by 24 months. However, those with no ossification at 12 or 24 months or mild ossification at 24 months are very unlikely to progress to advanced ossification.

The association of the activation-inducible tumor necrosis factor receptor and ligand with lumbar disc herniation

PURPOSE

Herniated nucleus pulposus fragments are recognized by the immune system as a foreign-body, which results in an autoimmune reaction. Human activation-inducible tumor necrosis factor receptor (AITR) and its ligand, AITRL, are important costimulatory molecules in the pathogenesis of autoimmune diseases. Despite the importance of these costimulatory molecules in autoimmune disease, their role in the autoimmune reaction to herniated disc fragments has yet to be explored. The purpose of the present study is to investigate whether the overexpression of AITR and AITRL might be associated with lumbar disc herniation.

MATERIALS AND METHODS

The study population consisted of 20 symptomatic lumbar disc herniation patients. Ten macroscopically normal control discs were obtained from patients with spinal fractures managed with anterior procedures that involved a discectomy. Peripheral blood samples from both the study patients and controls were collected. The expression levels of AITR and AITRL were investigated by flow cytometric analysis, confocal laser scanning microscopy, immunohistochemistry and by reverse transcriptase-polymerase chain reaction (RT-PCR). The soluble AITR and AITRL serum levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Flow cytometric analysis revealed significantly higher levels of both AITR and AITRL in the lumbar disc herniation patients than in the controls. The AITRL expression levels were also increased in patients with lumbar disc herniation, shown by using confocal laser scanning microscopy, immunohisto-chemistry, and RT-PCR. Finally, soluble AITR and AITRL were elevated in the patients with lumbar disc herniations.

CONCLUSION

The AITR and AITRL are increased in both the herniated disc tissue and the peripheral blood of patients with lumbar disc herniation.

Overexpressions of nerve growth factor and its tropomyosin-related kinase A receptor on chordoma cells

STUDY DESIGN

Immunohistochemistry and in situ apoptosis detection assay were performed on chordoma and notochordal cells.

OBJECTIVES

To investigate the expression levels of nerve growth factor (NGF) and its 2 receptors, tropomyosin-related kinase A (TrkA) and p75, as well as proliferation potential and apoptosis indexes in chordoma and notochordal cells.

SUMMARY OF BACKGROUND DATA

Chordomas arise from primitive notochordal remnants. Why these notochordal remnants undergo malignant transformation to chordoma remains unknown. The binding of NGF to the TrkA receptor promotes cell survival, while its binding to the p75 receptor triggers apoptosis. If there is simultaneous expression of both receptors, the effect of TrkA supersedes and the cells survive.

METHODS

We examined 10 surgically obtained sacral chordoma tissue samples to determine the expressions of NGF and TrkA and p75 receptors as well as markers of cellular proliferation and apoptosis. As controls, we used notochordal cells of L4-L5 discs obtained from ten 1-month old rats. We quantified the expressions of NGF and TrkA and p75 receptors as well as markers of cellular proliferation and apoptosis for both groups, respectively.

RESULTS

Chordoma and notochordal cells both expressed NGF as well as TrkA and p75 receptors. While the mean percentage of p75 receptor expression was very similar between chordoma and notochordal cells (P = 0.394), the mean percentages of TrkA and NGF expressions were significantly higher in chordoma cells than in notochordal cells (both P = 0.002). The mean proliferation potential index of chordoma cells was significantly higher than in notochordal cells (P < 0.01). Conversely, the mean apoptosis index of chordoma cells was significantly lower compared with that of notochordal cells (P = 0.03).

CONCLUSION

The current results suggest that increased expressions of NGF and TrkA receptor in chordoma cells might be a possible mechanism of malignant transformation of notochordal remnants to chordoma by negating apoptotic signal of p75 receptor.

A biochemical mechanism for resistance of intervertebral discs to metastatic cancer: Fas ligand produced by disc cells induces apoptotic cell death of cancer cells

Metastatic spinal cancer is characterized by the maintenance of normal disc structure until the vertebral body is severely destroyed by cancer cells. Anatomic features of the discs have been thought to be the main factor which confer the discs their resistance to metastatic cancer. However, little is known about the biochemical mechanism to prevent or attenuate the local infiltration of cancer cells into the discs. The purpose of this study was to investigate whether Fas ligand (FasL) produced by disc cells can kill Fas-bearing breast cancer cells by Fas and FasL interaction. Two human breast cancer cells (MCF-7 and MDA-MB-231) were obtained and cultured (1 x 10(6) cells/well), and the expression of Fas was investigated by western blot analysis. Annulus fibrosus cells were isolated and cultured, and the presence of FasL was quantified in the supernatants of three different numbers of annulus fibrosus cells (1x, 2x, and 4 x 10(6) cells/well) by ELISA assay. The MCF-7 and MDA-MB-231 cancer cells were cultured with supernatants of annulus fibrosus cells for 48 h. As controls, MCF-7 and MDA-MB-231 cancer cells were also cultured by themselves for 48 h. Finally, we determined and quantified the apoptosis rates of MCF-7 and MDA-MB-231 cancer cells by Annexin V-FITC and PI and TUNEL at 48 h, respectively. The expression of Fas was identified in MCF-7 and MDA-MB-231 cancer cells. The mean concentrations of FasL in supernatants of annulus fibrosus cells (1x, 2x, and 4 x 10(6) cells/well) were 10.8, 29.6, and 56.4 pg/mL, respectively. After treatment with the supernatant of three different numbers of annulus fibrosus cells, the mean apoptosis rate of MCF-7 cancer cells was increased (2.8%, P < 0.01; 6.7%, P < 0.001; 31.0%, P < 0.001) in a dose-dependent manner of FasL compared to that of control (1.1%). The mean apoptosis rate of MDA-MB-231 cancer cells was also increased (5.7%, P < 0.01; 11.1%, P < 0.001; 25.3%, P < 0.001) in a dose-dependent manner of FasL compared to that of control (2.1%). TUNEL also demonstrated direct evidence of apoptosis of MCF-7 and MDA-MB-231 cancer cells. Our results demonstrate that Fas-bearing cancer cells undergo apoptosis by FasL produced by disc cells, which may be considered as a potential biochemical explanation for the disc's resistance to metastatic cancer.

Cervical radiculopathy

Cervical radiculopathy is a disorder involving dysfunction of cervical nerve roots that commonly manifests as pain radiating from the neck into the distribution of the affected root. Acute cervical radiculopathy generally has a self-limited clinical course, with up to a 75% rate of spontaneous improvement. Thus, nonsurgical treatment is the appropriate initial approach for most patients. When nonsurgical treatment fails to relieve symptoms or if a significant neurologic deficit exists, surgical decompression may be necessary. Surgical outcomes for relief of arm pain range from 80% to 90% with either anterior or posterior approaches.

Fas/FasL interaction of nucleus pulposus and cancer cells with the activation of caspases

Spinal metastatic disease is characterised by the preservation of the intervertebral disc structure, even after severe destruction of the vertebral body by neoplastic tissues. Anatomical features of the discs are thought to be the reason for the disc's resistance to metastatic cancer. However, little is known about the biochemical mechanism to prevent or attenuate the local invasion of cancer cells into the discs. The purpose of this study was to investigate the hypothesis that Fas ligand (FasL) produced by nucleus pulposus cells can kill Fas-expressing cancer cells infiltrating into the discs by the activation of caspases. Fas-expressing MCF-7 breast cancer cells were cultured with (experimental group) and without (control group) supernatant of nucleus pulposus cells containing FasL (50 pg/ml) for 48 h. The apoptosis of MCF-7 breast cancer cells was determined by the TUNEL technique. In addition, the activation of caspase-8, -9 and -3 was investigated by Western blot analysis. After treatment with supernatant of the nucleus pulposus cells containing FasL, the apoptosis of MCF-7 breast cancer cells was significantly increased, along with the activation of caspase-8, -9 and -3 compared with those of the control group. Our results suggest that the Fas/FasL interaction of nucleus pulposus and cancer cells might be a potential mechanism of the disc's resistance to metastatic cancer.

Magnetic resonance imaging clarity of the Bryan, Prodisc-C, Prestige LP, and PCM cervical arthroplasty devices

STUDY DESIGN

Prospective, randomized, controlled and double-blinded study on imaging of artificial discs.

OBJECTIVE

The purpose of this study is to compare postoperative imaging characteristics of the 4 currently available cervical arthroplasty devices at the level of implantation and at adjacent levels.

SUMMARY OF BACKGROUND DATA

Cervical arthroplasty is being performed increasingly frequently for degenerative disc disease and, in most cases, with frank neural compression. Unlike lumbar arthroplasty, performed mainly for axial back pain, decompression of neural elements may need to be confirmed with postoperative imaging after cervical arthroplasty.

METHODS

Preoperative and postoperative magnetic resonance imaging scans of 20 patients who had undergone cervical arthroplasty were assessed for imaging quality. Five cases each of the Bryan (Medtronic Sofamor Danek, Memphis, TN), Prodisc-C (Synthes Spine, Paoli, PA), Prestige LP (Medtronic Sofamor Danek), and PCM devices (Cervitech, Rockaway, NJ) were analyzed. Six blinded spinal surgeons scored twice sagittal and axial T2-weighted images using the Jarvik 4-point scale. Statistical analysis was performed comparing quality before surgery and after disc implantation at the operated and adjacent levels and between implant types. RESULTS.: Moderate intraobserver and interobserver reliability was noted. Preoperative images of patients in all implant groups had high-quality images at operative and adjacent levels. The Bryan and Prestige LP devices allowed satisfactory visualization of the canal, exit foramina, cord, and adjacent levels after arthroplasty. Visualization was significantly impaired in all PCM and Prodisc-C cases at the operated level in both the spinal canal and neural foramina. At the adjacent levels, image quality was statistically poorer in the PCM and Prodisc-C than those of Prestige LP or Bryan. CONCLUSIONS.: Postoperative visualization of neural structures and adjacent levels after cervical arthroplasty is variable among current available devices. Devices containing nontitanium metals (cobalt-chrome-molybdenum alloys in the PCM and Prodisc-C) prevent accurate postoperative assessment with magnetic resonance imaging at the surgical and adjacent levels. Titanium devices, with or without polyethylene (Bryan disc or Prestige LP), allow for satisfactory monitoring of the adjacent and operated levels. This information is crucial for any surgeon who wishes to assess adequacy of neural decompression and where monitoring of adjacent levels is desired.

Prevalence of cervical spine stenosis. Anatomic study in cadavers

BACKGROUND

The sagittal diameter of the cervical spinal canal is of clinical importance in traumatic, degenerative, and inflammatory conditions. A small canal diameter has been associated with an increased risk of injury; however, there is a lack of reliable normative data on spinal canal diameters in different age groups in the United States population. The purpose of this study was to use direct measurement of skeletal specimens to determine the spectrum of the sagittal diameters of the cervical spinal canal, the frequency of cervical stenosis in the general population, and the prevalence of cervical stenosis for different age groups, races, and sexes.

METHODS

Four hundred and sixty-nine adult skeletal specimens of the cervical spine were obtained from the Hamann-Todd Collection in the Cleveland Museum of Natural History. With use of digital calipers, the distance from the posteriormost aspect of the vertebral body to the anteriormost aspect of the spinolaminar structure was measured and recorded for each specimen at every level from C3 to C7. Cervical stenosis was defined as a canal diameter of <12 mm. We analyzed the direct measurements and then assessed those data after correcting for size increases in the current population compared with the Hamann-Todd Collection. Finally, we analyzed the data after both that size correction and adjustment for radiographic magnification.

RESULTS

The average anterior-posterior canal diameter (and standard deviation) in all specimens at all levels was 14.1 +/- 1.6 mm. The canal diameters ranged from 9.0 to 20.9 mm, with a median diameter of 14.4 mm. Men had significantly larger cervical spinal canals than women at all of the levels that were evaluated. Specimens from donors who were sixty years of age or more at the time of death had significantly narrower canals than specimens from younger donors. There were no significant differences, with the numbers available, between black and white groups. After correcting for increased body size and adjusting for radiographic magnification, we estimated that cervical stenosis was present in 4.9% of the adult population, 6.8% of the population fifty years of age or older, and 9% of the population seventy years of age or older.

CONCLUSIONS

Cervical spine stenosis appears to be very common. The radiographic finding of cervical stenosis should therefore be correlated with the clinical presentation prior to decision-making regarding treatment.

POSTERIOR CERVICAL SPINE SURGERY FOR RADICULOPATHY

IT IS NOW common knowledge that cervical radiculopathy, frequently caused by disc herniation and/or degeneration, will often improve without surgical intervention. Only a small percentage of patients with the severity of symptoms necessitate surgical treatment. Surgery for radiculopathy is indicated for motor weakness, progressive neurological deficits, and progressive symptoms that do not improve with nonoperative treatment. Advantages and disadvantages exist for both ventral and dorsal approaches in the surgical treatment of cervical radiculopathy. Indications and results for dorsal nerve root decompression are discussed, and a review of our preferred techniques, including use of minimally invasive technology, is presented.

Update on cervical artificial disk replacement

Cervical disk arthroplasty, one of the emerging motion-sparing technologies, is currently undergoing evaluation in the United States as an alternative to arthrodesis for the treatment of cervical radiculopathy and myelopathy. With both arthrodesis and arthroplasty, the primary surgical goal is thorough decompression of neurocompressive pathology--directly by removal of osteophyte and disk and indirectly by disk distraction. There is, however, one principal difference between arthrodesis and arthroplasty. With a solid fusion, resorption of osteophytes (in accordance with Wolff's law) further enhances decompression. In contrast, osteophyte resorption will not occur with motion-preserving arthroplasty. There are many challenges when deciding between arthrodesis and arthroplasty. Prosthetic performance demands exacting implantation techniques to ensure correct placement, thus placing increasing demands on special instrumentation and surgical skills. It is also important to understand the tribology (the study of prosthetic lubrication, wear, and biologic effects) of disk arthroplasty and to be familiar with currently available information regarding kinematics, basic science, testing, and early clinical results.

Thorough decompression of the posterior cervical foramen

Regardless of the approach to the cervical spine, it is clear that surgical outcome is directly related to surgical technique. Posterior decompressions must be thorough and complete because laminoforaminotomies provide an excellent means of decompressing foraminal pathology. One of the distinct advantages of posterior laminoforaminotomy is that it offers direct visualization, exposure, and decompression of the nerve root without performing a fusion. A posterior laminoforaminotomy is the preferred approach for patients with a soft lateral disk herniation, for those at increased risk for nonunion, or those for whom an anterior procedure would not be optimal. To perform a thorough decompression and prevent iatrogenic instability and neurologic deficits, however, surgeons must be familiar with the anatomy of the foramen as well as the compressive pathology. Several issues must be addressed before performing a posterior laminoforaminotomy, namely, the absence of instability and junctional kyphosis, and the proper identification of the offending pathology.