Carl Lauryssen

Periodical shifts in the surgical correction of sagittal craniosynostosis.

OBJECTnCervical total disc replacement (CTDR) represents a relatively novel procedure intended to address some of the shortcomings associated with anterior cervical discectomy and fusion (ACDF) by preserving motion at the treated level. This prospective, randomized, multicenter study evaluates the safety and efficacy of a new metal-on-metal CTDR implant (Kineflex|C) by comparing it with ACDF in the treatment of single-level spondylosis with radiculopathy.nnnMETHODSnThe study was a prospective, randomized US FDA Investigational Device Exemption (IDE) pivotal trial conducted at 21 centers across the US. The primary clinical outcome measures included the Neck Disability Index (NDI), visual analog scale (VAS) scores, and a composite measure of clinical success. Patients were randomized to CTDR using the Kineflex|C (SpinalMotion, Inc.) cervical artificial disc or ACDF using structural allograft and an anterior plate.nnnRESULTSnA total of 269 patients were enrolled and randomly assigned to either CTDR (136 patients) or to ACDF (133 patients). There were no significant differences between the CTDR and ACDF groups when comparing operative time, blood loss, length of hospital stay, or the reoperation rate at the index level. The overall success rate was significantly greater in the CTDR group (85%) compared with the ACDF group (71%) (p = 0.05). In both groups, the mean NDI scores improved significantly by 6 weeks after surgery and remained significantly improved throughout the 24-month follow-up (p < 0.0001). Similarly, the VAS pain scores improved significantly by 6 weeks and remained significantly improved through the 24-month follow-up (p < 0.0001). The range of motion (ROM) in the CTDR group decreased at 3 months but was significantly greater than the preoperative mean at 12- and 24-month follow-up. The ROM in the ACDF group was significantly reduced by 3 months and remained so throughout the follow-up. Adjacent-level degeneration was also evaluated in both groups from preoperatively to 2-year follow-up and was classified as none, mild, moderate, or severe. Preoperatively, there were no significant differences between groups when evaluating the different levels of adjacent-level degeneration. At the 2-year follow-up, there were significantly more patients in the ACDF group with severe adjacent-level radiographic changes (p < 0.0001). However, there were no significant differences between groups in adjacent-level reoperation rate (7.6% for the Kineflex|C group and 6.1% for the ACDF group).nnnCONCLUSIONSnCervical total disc replacement allows for neural decompression and clinical results comparable to ACDF. Kineflex|C was associated with a significantly greater overall success rate than fusion while maintaining motion at the index level. Furthermore, there were significantly fewer Kineflex|C patients showing severe adjacent-level radiographic changes at the 2-year follow-up. These results from a prospective, randomized study support that Kineflex|C CTDR is a viable alternative to ACDF in select patients with cervical radiculopathy.

The Effect of Prone Positioning on Intraocular Pressure in Anesthetized Patients

Background Ocular perfusion pressure is commonly defined as mean arterial pressure minus intraocular pressure (IOP). Changes in mean arterial pressure or IOP can affect ocular perfusion pressure. IOP has not been studied in this context in the prone anesthetized patient. Methods After institutional human studies committee approval and informed consent, 20 patients (American Society of Anesthesiologists physical status I–III) without eye disease who were scheduled for spine surgery in the prone position were enrolled. IOP was measured with a Tono-pen® XL handheld tonometer at five time points: awake supine (baseline), anesthetized (supine 1), anesthetized prone (prone 1), anesthetized prone at conclusion of case (prone 2), and anesthetized supine before wake-up (supine 2). Anesthetic protocol was standardized. The head was positioned with a pinned head-holder. Data were analyzed with repeated-measures analysis of variance and paired t test. Results Supine 1 IOP (13 ± 1 mmHg) decreased from baseline (19 ± 1 mmHg) (P < 0.05). Prone 1 IOP (27 ± 2 mmHg) increased in comparison with baseline (P < 0.05) and supine 1 (P < 0.05). Prone 2 IOP (40 ± 2 mmHg) was measured after 320 ± 107 min in the prone position and was significantly increased in comparison with all previous measurements (P < 0.05). Supine 2 IOP (31 ± 2 mmHg) decreased in comparison with prone 2 IOP (P < 0.05) but was relatively elevated in comparison with supine 1 and baseline (P < 0.05). Hemodynamic and ventilatory parameters remained unchanged during the prone period. Conclusions Prone positioning increases IOP during anesthesia. Ocular perfusion pressure could therefore decrease, despite maintenance of normotension.

The safety of OP-1 for lumbar fusion with decompression-- a canine study.

OBJECTIVE: Bone morphogenetic proteins can serve as adjuncts to autologous bone to achieve bony fusion, and recombinant BMPs such as osteogenic protein-1 (OP-1) have the potential to replace autologous bone altogether as fusion substrate. However, relatively little is known about the safety of OP-1 for spinal fusion procedures. This study examined the effects of OP-1 intentionally placed in the subarachnoid space following thecal sac decompression, and used as graft substrate in a canine dorsolateral lumbar spine fusion model. METHODS: Lumbar decompression with dorsolateral fusion was performed on 30 canines. The dura was opened to simulate an intraoperative rent and OP-1 was placed in the subarachnoid space and in the fusion bed. Animals were sacrificed after 16 weeks and the spines were examined manually, radiographically and pathologically. RESULTS: All animals treated with OP-1 developed new bone in the subarachnoid space. This bone compressed the spinal cord, but no clinical or pathological features of neurotoxicity were noted. Mild spinal stenosis was noted at the site of dural decompression in the OP-1 treated animals. Over 80% of animals treated with OP-1 developed fusion as assessed by palpation (52% by CT criteria), while only 25% of control animals fused. CONCLUSIONS: Recombinant human OP-1 is effective at promoting fusion in a canine dorsolateral lumbar spine fusion model. However, bone growth can occur over exposed, decompressed dura, and it can form in the subdural and subarachnoid spaces. The use of OP-1 as an adjunct to spinal fusion appears to have merit, but its use must be carefully controlled to avoid unwanted bone formation and subsequent neural compression.OBJECTIVEnBone morphogenetic proteins can serve as adjuncts to autologous bone to achieve bony fusion, and recombinant BMPs such as osteogenic protein-1 (OP-1) have the potential to replace autologous bone altogether as fusion substrate. However, relatively little is known about the safety of OP-1 for spinal fusion procedures. This study examined the effects of OP-1 intentionally placed in the subarachnoid space following thecal sac decompression, and used as graft substrate in a canine dorsolateral lumbar spine fusion model.nnnMETHODSnLumbar decompression with dorsolateral fusion was performed on 30 canines. The dura was opened to simulate an intraoperative rent and OP-1 was placed in the subarachnoid space and in the fusion bed. Animals were sacrificed after 16 weeks and the spines were examined manually, radiographically and pathologically.nnnRESULTSnAll animals treated with OP-1 developed new bone in the subarachnoid space. This bone compressed the spinal cord, but no clinical or pathological features of neurotoxicity were noted. Mild spinal stenosis was noted at the site of dural decompression in the OP-1 treated animals. Over 80% of animals treated with OP-1 developed fusion as assessed by palpation (52% by CT criteria), while only 25% of control animals fused.nnnCONCLUSIONSnRecombinant human OP-1 is effective at promoting fusion in a canine dorsolateral lumbar spine fusion model. However, bone growth can occur over exposed, decompressed dura, and it can form in the subdural and subarachnoid spaces. The use of OP-1 as an adjunct to spinal fusion appears to have merit, but its use must be carefully controlled to avoid unwanted bone formation and subsequent neural compression.

Accurate Identification of adverse outcomes after cervical spine surgery

BACKGROUNDnRetrospective clinical studies frequently utilize surgeon records as a source of outcomes data. The accuracy of data derived from surgeon records, however, is unknown. The purpose of the present study was to evaluate the accuracy of surgeon records in documenting the prevalence of subjective adverse outcomes.nnnMETHODSnConsecutive patients who had undergone anterior cervical arthrodesis by four spine surgeons during a ten-month period were included. Surgeon records from the routine six-week, three-month, and six-month postoperative visits were examined for documentation of persistent dysphagia and dysphonia. Patients completed surveys inquiring about the presence and magnitude of symptoms at these three time-points. Agreement between the surgeon records and the patient surveys was analyzed with use of the kappa coefficient.nnnRESULTSnOne hundred and sixty-six patients had 342 postoperative visits. Dysphagia was documented twenty-six times in the surgeon records, compared with 107 times on the patient surveys. Dysphagia was thus underreported in 80% of cases. Similarly, dysphonia was documented ten times in the surgeon records, compared with seventy-two times on the patient surveys. Poor correlation between the surgeon records and the patient surveys was observed regardless of symptom severity, previous anterior cervical surgery, anterior arthrodesis of three motion segments or more, arthrodesis cephalad to the fifth cervical level, and anterior cervical plate use. Poor correlation between the surgeon records and the patient surveys also was observed for each surgeon, regardless of subspecialty or institution.nnnCONCLUSIONSnCorrelation between the surgeon records and the patient surveys was consistently poor, regardless of the specific patient and surgeon factor analyzed. While we chose to study dysphonia and dysphagia, it is conceivable that the results may be generalizable to many situations in which office notes are utilized to ascertain the prevalence of subjective adverse outcomes. These results suggest that the prevalence of such outcomes may be seriously underreported in studies that rely on the retrospective analysis of surgeon records.

Visual Loss after Spine Surgery: A Survey

OBJECTIVEnTo survey a large number of neurosurgical spine surgeons for data regarding the presence of risk factors in patients experiencing visual loss after spine surgery.nnnMETHODSnA survey was sent to current members (as of 1997) of the American Association of Neurological Surgeons/Congress of Neurological Surgeons, Section on Disorders of the Spine and Peripheral Nerves, with questions focusing on intraoperative factors that may predispose patients to perioperative visual loss.nnnRESULTSnTwo hundred ninety surveys were returned, and 24 patients with visual loss after spine surgery were reported by 22 surgeons. Although many of these patients had probable causative factors for visual loss after surgery (e.g., hypotension, low hematocrit level, coexisting disease), some did not (n = 8).nnnCONCLUSIONnThese results suggest the necessity of a high index of suspicion for evolving perioperative visual loss even in the absence of risk factors.

Adjacent fracture-dislocations of the lumbosacral spine: case report.

OBJECTIVE AND IMPORTANCEnTraumatic fracture-dislocations of the lumbosacral junction are rare, with all previously reported cases involving fracture-dislocations at a single level. No cases of multiple fracture-dislocations of contiguous spinal segments in the lumbosacral spine have been reported. A case of traumatic adjacent fracture-dislocations of the fifth lumbar segment is presented.nnnCLINICAL PRESENTATIONnAn 18-year-old male patient sustained open lumbar spinal trauma after a motor vehicle accident. A neurological examination revealed an L4 level. Radiographic evaluation of the spine revealed a three-column injury at L5 with spondyloptosis of the L5 vertebral body. Aorto-ilio-femoral angiography revealed no evidence of vascular injury.nnnINTERVENTIONnThe patient was treated with a combined anterior and posterior approach in a two-stage operation. Six months postoperatively, he was neurologically unchanged; however, he was able to walk with the aid of a cane. Plain films revealed normal alignment of the lumbosacral spine.nnnCONCLUSIONnThe management of traumatic lumbosacral fracture-dislocations requires careful consideration of retroperitoneal structures and possible exploration of the iliac vessels in addition to spinal reconstruction.

Anatomical relationship of the internal carotid artery to C-1: clinical implications for screw fixation of the atlas

OBJECTnVarious C1-2 instrumentation techniques have been developed to treat atlantoaxial instability. Screw fixation of C1-2 poses a risk of injury to the vertebral artery and internal carotid artery (ICA). Injury to the ICA caused by C-1 screws is extremely rare, but has been described. To characterize this risk, the authors studied the anatomical relationship of the ICA to the lateral mass of C-1.nnnMETHODSnThe authors studied 100 patients who had undergone computed tomography scanning and magnetic resonance imaging of the neck to assess the position of the ICA in association with the C-1 lateral mass. Each ICA was classified into 1 of the following 4 zones: Zone 1 (medial to lateral mass), Zone 2 (medial half of lateral mass), Zone 3 (lateral half of lateral mass), and Zone 4 (lateral to lateral mass). For patients with an ICA ventral to the lateral mass, the shortest distance between the ICA and lateral mass was measured to determine the margin of error with an overpenetrated bicortical screw.nnnRESULTSnOf the 100 patients, 58% had a left ICA in Zones 2 and 3 with a mean distance from the anterior cortex of 3.5+/-1.5 mm (+/- standard deviation), and 74% had a right ICA in Zones 2 and 3 with a mean distance from the anterior cortex of 3.9+/-1.6 mm. Both ICAs anterior to the lateral mass were noted in 47% of patients, and 84% had >or= 1 ICA anterior to the lateral mass. When the ICA was anterior to the lateral mass, it was more commonly in the lateral half (left ICA in 91% and right ICA in 92%). The left ICA was in Zone 1 in 1% and Zone 4 in 41%. The right ICA was in Zone 1 in 1% and Zone 4 in 25%.nnnCONCLUSIONSnA high percentage of patients demonstrate an ICA directly ventral to the C-1 lateral mass, which poses a risk of ICA injury caused by an overpenetrated bicortical screw.

Evaluation of Decompression and Interlaminar Stabilization Compared with Decompression and Fusion for the Treatment of Lumbar Spinal Stenosis: 5-year Follow-up of a Prospective, Randomized, Controlled Trial

Introduction If nonoperative treatment for lumbar stenosis fails, surgery may be considered. This traditionally includes decompression often combined with fusion. Desire for less extensive surgery led to developing new techniques and implants, including an interlaminar device designed with the goal of providing segmental stability without fusion, following decompression. The purpose of this study was to investigate 5-year outcomes associated with an interlaminar device. Methods This prospective, randomized, controlled trial was conducted at 21 centers. Patients with moderate to severe lumbar stenosis at one or two contiguous levels and up to Grade I spondylolisthesis were randomized (2:1 ratio) to decompression and interlaminar stabilization (D+ILS; n=215) using the coflex® Interlaminar Stabilization® device (Paradigm Spine, LLC) or decompression and fusion with pedicle screws (D+PS; n=107). Clinical evaluations were made preoperatively and at 6 weeks and 3, 6, 12, 18, 24, 36, 48, and 60 months postoperatively. Overall Food and Drug Administration success criteria required that a patient meet 4 criteria: 1) >15 point improvement in Oswestry Disability Index (ODI) score; 2) no reoperation, revision, removal, or supplemental fixation; 3) no major device-related complication; and 4) no epidural steroid injection after surgery. Results At 5 years, 50.3% of D+ILS vs. 44% of D+PS patients (p>0.35) met the composite success criteria. Reoperation/revision rates were similar in the two groups (16.3% vs. 17.8%; p >0.90). Both groups had statistically significant improvement through 60 months in ODI scores with 80.6% of D+ILS patients and 73.2% of D+PS patients demonstrating >15 point improvement (p>0.30). VAS, SF-12, and ZCQ scores followed a similar pattern of maintained significant improvement throughout follow-up. On the SF-12 and ZCQ, D+ILS group scores were statistically significantly better during early follow-up compared to D+PS. In the D+ILS group, foraminal height, disc space height, and range of motion at the index level were maintained through 5 years. Conclusion Both treatment groups achieved and maintained statistically significant improvements on multiple outcome assessments throughout 5-year follow-up. On some clinical measures, there were statistically significant differences during early follow-up favoring D+ILS. At no point were there significant differences favoring D+PS. Results of this 5-year follow-up study demonstrate that decompression and interlaminar stabilization with coflex is a viable alternative to traditional decompression and fusion in the treatment of patients with moderate to severe stenosis at one or two lumbar levels. Level of Evidence and Ethical Statements This is a Level I study. Institutional approval was received at each of the sites participating in the trial. Each patient gave informed consent to participate in the trial.

Three-Year Follow-up of the Prospective, Randomized, Controlled Trial of Coflex Interlaminar Stabilization vs Instrumented Fusion in Patients With Lumbar Stenosis.

BACKGROUNDnTraditional surgical options for the treatment of symptomatic lumbar spinal stenosis include decompression alone vs decompression and fusion; both options have potential limitations.nnnOBJECTIVEnTo report the 36-month follow-up analysis of the coflex Interlaminar Stabilization (Paradigm Spine, LLC, New York, New York) after decompression, examined under a Food and Drug Administration investigational device exemption clinical trial, which is intended to provide stabilization after decompression while preserving normal segmental motion at the treated level.nnnMETHODSnThe coflex trial was a prospective, randomized investigational device exemption study conducted at 21 clinical sites in the United States. Baseline and follow-up visits collected demographics, clinical, and radiographic status. The primary endpoint was a measure of composite clinical success 24 months postoperatively. For this current 36-month analysis, composite clinical success was calculated using analogous methods.nnnRESULTSnComposite clinical success at 36 months was achieved by 62.2% among 196 coflex Interlaminar Stabilization patients and 48.9% among 94 fusion patients (difference = 13.3%, 95% confidence interval, 1.1%-25.5%, P = .03). Bayesian posterior probabilities for noninferiority (margin = -10%) and superiority of cofle Interlaminar Stabilization vs fusion were >0.999 and 0.984, respectively. Substantial and comparable improvements were observed in both groups for patient-reported outcomes, although the percentage with a clinically significant improvement (≥15) in the Oswestry Disability Index seemed larger for the coflex Interlaminar Stabilization group relative to the fusion group (P = .008). Radiographic measurements maintained index level and adjacent level range of motion in coflex Interlaminar Stabilization patients, although range of motion at the level superior to fusion was significantly increased (P = .005).nnnCONCLUSIONnCoflex Interlaminar Stabilization for stenosis is proven to be effective and durable at improving overall composite clinical success without altering normal spinal kinematic motion at the index level of decompression or adjacent levels.nnnABBREVIATIONSnCCS, composite clinical successCEC, clinical events committeeFDA, Food and Drug AdministrationIDE, investigational device exemptionILS, Coflex Interlaminar StabilizationODI, Oswestry Disability IndexSF-12, Short-Form 12VAS, visual analogue scalesZCQ, Zurich Claudication Questionnaire.

Cervical total disc replacement using a novel compressible prosthesis: Results from a prospective Food and Drug Administration–regulated feasibility study with 24-month follow-up

Background Anterior cervical fusion, an established procedure to treat cervical radiculopathy, sacrifices the natural function of the disc, while placing increased stresses on adjacent spinal levels. In contrast, the cervical total disc replacement (cTDR) maintains motion and decreases adjacent-level stresses. The purpose of this study was to investigate the safety and effectiveness of a next-generation cTDR device in patients with symptomatic cervical radiculopathy. Methods This is a multicenter Food and Drug Administration–regulated feasibility study to evaluate safety and effectiveness of the M6-C Artificial Cervical Disc for the treatment of patients with symptomatic cervical radiculopathy at 1 or 2 levels from C3 to C7. Neck Disability Index (NDI), visual analog scales (VAS) assessing neck and arm pain, Short Form 36 Health Survey (SF-36), safety, and radiographic outcomes were assessed preoperatively, at 6 weeks and 3, 6, 12, and 24 months postoperatively. Results Thirty patients were enrolled at 3 clinical sites. Patients were implanted at either 1 or 2 levels. Mean NDI improved from 67.8 to 20.8 (P < .0001) at 24 months. Significant improvement was also observed through 24-month follow-up in neck and arm pain VAS (P < .0001) and in physical (P < .005) and mental component scores of the SF-36 at 3, 6, and 12 months (P < .008). There were no serious adverse events related to the device or procedure as adjudicated by an independent clinical events committee. Radiographically, disc space height increased more than 50% with a correlative increase in the postoperative disc angle. Range of motion decreased slightly from baseline during early follow-up but increased slightly and were maintained throughout the follow-up period. Conclusions The M6-C cervical artificial disc represents a new generation of cTDR design. Results of this study found the M6-C device to produce positive clinical and radiographic outcomes similar to other cTDRs, warranting further investigation.