AANS 2005: A Trip Report
BY JOHN MCCORMICK, APRIL 25, 2005
Last week we joined the droves of neurosurgeons at AANS in New Orleans to check out papers, presentations, posters and product. Always a quiet and less populated conference compared to the annual NASS spine meeting, AANS offers a hard science neuro-based lens on the subject of spine surgery.
With many discussions going on about aneurisms, Parkinson's disease, gamma knife techniques and the like, we rolled up our sleeves and focused mainly on the issues highlighted at the conference on spine. Below we summarize our notes on some of the courses we attended, abstracts of interest to the orthopedic industry and other tidbits we picked up along the way.
AANS to Issue Guidelines on Spinal Fusion
We kept hearing echoes through the convention halls and nuggets in casual conversations that AANS may possibly be releasing a meta-data analysis on spinal fusion outcomes and will potentially issue surgery guidelines based on this analysis. We understand that the guidelines may be released as early as May or possibly later in the summer.
Fred Geisler Presents Data on the Charité
See our interview from the conference with Dr. Geisler. Dr. Geisler presented final two year follow up results of the artificial disc IDE study. From his abstract, it was stated that "the Charité group experienced numerically superior improvement in ODI and VAS scores than the Fusion group at all time points, with statistical significance at all but the 2-year follow-up ([mean ODI decrease at 2 years: C=-24.3, F=-21.6] [mean VAS decrease at 2 years: C=-56.7%, F=-47.8%]). Subject satisfaction was significantly higher in the Charité group (C=74%, F=53%). Aside from graft site pain in 18.2% of the Fusion group, the complication rates were similar for both groups. Range of motion increased to 92% of baseline in the Charité group at 6 months and 114% of baseline at 2 years."
The issues we found that dominated surgeons minds at the conference surrounded patient selection and reimbursement.
A European Study on Medtronic's Bryan Cervical Disc
The Jan Goffin, etal. two-year follow up study was presented on Medtronic's Bryan cervical disc technology with Paul McCormick, MD as discussant. Outcomes met or exceeded expectations with strong evidence of motion preservation (85% to 90% of the cases). No significant cases of device subsidence or migration were found with n=102 (82 single-level, 20 multi-level). We attended a separate presentation course on Tuesday where Dr. Goffin himself presented a four-year Bryan follow up study with n=31 where 27 patients experienced preserved motion and 20 had excellent outcomes. No cases of adjacent level disease were reported.
A 2003 clinical paper presented by Goffin etal. states that "at least 5 years of follow-up will be needed to assess the long-term functionality of the prosthesis and protective influence on adjacent levels." He also noted in his Tuesday presentation that the artificial cervical discs may preserve motion, but not restore previously lost motion.
Dr. Goffin is viewed to be one of the world's leading experts on cervical disc arthroplasty.
Adverse Effects from INFUSE?
A study was presented on the use of INFUSE (RhBMP-2) in anterior cervical spinal fusions in an afternoon session. INFUSE is Medtronic's recently approved bone morphogenic protein used in spinal fusions and questions about optimal dosing is a much discussed topic among surgeons. This study by Lisa B. Shields, MD , etal. presented "151 patients who underwent either an anterior cervical discectomy and fusion (ACDF) (n=138) or anterior cervical vertebrectomy and fusion (n=13) augmented with INFUSE. The study viewed the rate of complications to be "high" as a result of inflammatory responses. According to the abstract, "a total of 35 patients (23.3%) experienced complications after the use of INFUSE in the cervical spine. Fifteen patients were diagnosed with a hematoma (11 on Days 4 or 5), of which eight were surgically evacuated. Thirteen individuals experienced either a prolonged hospital stay (greater than 48 hours) or hospital re-admission due to swallowing/breathing difficulties or dramatic swelling without hematoma."
Single- versus Multilevel Cervical Disc Replacements
The Cleveland Clinic's highly respected Edward C. Benzel was discussant on the Luiz Pimenta, etal. two-year study of Single- versus Multilevel Cervical Disc Replacements. 41 single level patients were compared to 34 bi-level patients and 8 multi-level patients with Porous Coated Motion (PCM) cervical discs.
An aspect of the study was to help shed light on data that patients with multi-level fusions have worse outcomes than those with single fusions. Do discs have the same issue? Surprisingly, the multi-level cervical disc arthroplasty results (neck disability index, Odom and VAS scores) were superior to single level - an exact contrast to fusion. The authors view possible causality to be associated with "better restoration of global motion of the cervical spine".
Cauda Equina Syndrome from Herniated Lumbar Discs
William C. Olivero, etal. "Cauda Equina Syndrome: A Reappraisal" was presented. Cauda equina syndrome (CES) is a rare condition that occurs when the lumbar nerve roots are compressed by herniated discs causing nerve damage. Other causes include ruptured disk, tumor, infection, fracture or other narrowing of the spinal canal. Nerve roots that control the function of the bladder and bowel are especially vulnerable and this is considered a surgical emergency. The study included 27 patients with complete CES and four with incomplete CES. The majority of the patients in the study were treated with unilateral hemilaminotomy with mesial facetectomy. 25 (93%) of 27 patients had minimal or no bladder difficulties on long-term follow-up and were continent. Eighty percent regained normal or near normal motor function. Fifty percent had no or minimal sensory complaints.
Although it is widely viewed that surgery no more than 48 hours from the onset of CES is viewed to be appropriate, 17 of the cases in the study occurred after 48 hours.
Anterior Cervical Discectomy vs. Fusion
The Foley/German study used in the recent Orthofix clinical trial for its cervical electrical stimulation device was leveraged to evaluate discectomy versus fusions. In that particular trial, 323 patients were segmented into four quadrants with stim/no stim and fusion or discectomy. In both the stim/no stim cases, fused patients experience greater pain relief than non-fused patients at 6 months post-op with 240 patients available for evaluation. VAS scores at rest and with activity were superior. Although this study has been out for some time, the high enrollment makes it interesting. It would be interesting to see these results with a longer follow-up period, however.
