Intraoperative neurophysiologic monitoring in spine surgery. Developments and state of the art in France in 2011.

Intraoperative spinal cord monitoring consists in a subcontinuous evaluation of spinal cord sensory-motor functions and allows the reduction the incidence of neurological complications resulting from spinal surgery. A combination of techniques is used: somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), neurogenic motor evoked potentials (NMEP), D waves, and pedicular screw testing. In absence of intraoperative neurophysiological testing, the intraoperative wake-up test is a true form of monitoring even if its latency long and its precision variable. A 2011 survey of 117 French spinal surgeons showed that only 36% had neurophysiological monitoring available (public healthcare facilities, 42%; private facilities, 27%). Monitoring can be performed by a neurophysiologist in the operating room, remotely using a network, or directly by the surgeon. Intraoperative alerts allow real-time diagnosis of impending neurological injury. Use of spinal electrodes, moved along the medullary canal, can determine the lesion level (NMEP, D waves). The response to a monitoring alert should take into account the phase of the surgical intervention and does not systematically lead to interruption of the intervention. Multimodal intraoperative monitoring, in presence of a neurophysiologist, in collaboration with the anesthesiologist, is the most reliable technique available. However, no monitoring technique can predict a delayed-onset paraplegia that appears after the end of surgery. In cases of preexisting neurological deficit, monitoring contributes little. Monitoring of the L1-L4 spinal roots also shows low reliability. Therefore, monitoring has no indication in discal and degenerative surgery of the spinal surgery. However, testing pedicular screws can be useful. All in all, thoracic and thoracolumbar vertebral deviations, with normal preoperative neurological examination are currently the essential indication for spinal cord monitoring. Its absence in this indication is a lost opportunity for the patient. If neurophysiological means are not available, intraoperative wake-up test is a minimal obligation.

Influence of screw type on initial coronal and sagittal radiological correction with hybrid constructs in adolescent idiopathic scoliosis. Correction priorities.

BACKGROUND: Pedicle screw constructs for spinal instrumentation in patients with adolescent idiopathic scoliosis (AIS) are effective in providing coronal plane correction but can result in loss of kyphosis, which in turn can lead to loss of lordosis. Hybrid constructs have been found superior over pedicle screw constructs in terms of thoracic kyphosis restoration. In this study, our objective was to compare outcomes with monoaxial versus polyaxial screws in an AIS population treated with hybrid constructs. HYPOTHESIS: Monoaxial screws provide better correction in the coronal plane but result in loss of thoracic kyphosis, whereas thoracic kyphosis is preserved when polyaxial screws are used. MATERIAL AND METHODS: We retrospectively analysed data from 60 patients (mean age, 15years) with Lenke 1, 2, or 3 AIS treated using a hybrid construct with self-retaining bilaminar hook claws cranially, pedicle screws between the last instrumented vertebra and T11 caudally, and sublaminar universal clamps between the two extremities of the construct. Monoaxial screws were used in the first 30 patients (MS group) and polyaxial screws in the next 30 patients (PS group). Student's t test was performed to compare the two groups in terms of thoracic Cobb angle correction and T4-T12 kyphosis 3 months after surgery. RESULTS: No significant preoperative differences were found between the two groups. At last follow-up, the residual Cobb angle was significantly greater in the PS group than in the MS group (20.3° versus 15°) with a percentage of correction of 72.1% in the MS group versus 64.8% in the PS group. In the sagittal plane, the thoracic kyphosis was significantly greater in the PS group than in the MS group (26.6° versus 23°). DISCUSSION: This preliminary study shows that, even within a population managed using hybrid constructs, which are associated with less iatrogenic hypokyphosis, differences exist according to the technique used. The importance of sagittal spinal balance has been abundantly documented in the literature, and sagittal malalignment, particularly due to iatrogenic factors, is associated with poorer clinical outcomes in adults with spinal deformities. Therefore, there is a critical need to determine whether the treatment priority is optimal correction in the coronal plane or in the sagittal plane. We believe that the main focus should be sagittal plane correction, even at the expense of a slight decrease in coronal plane correction. Long-term studies are needed to confirm our preliminary findings.

Reciprocal sagittal alignment changes after posterior fusion in the setting of adolescent idiopathic scoliosis.

PURPOSE: Surgical adolescent idiopathic scoliosis (AIS) management can be associated with loss of thoracic kyphosis and a secondary loss of lumbar lordosis leading to iatrogenic flatback. Such conditions are associated with poorer clinical outcomes during adulthood. The aim of this study was to evaluate sagittal plane reciprocal changes after posterior spinal fusion in the setting of AIS. METHODS: Thirty consecutive adolescents (mean age 14.6 years) with AIS Lenke 1, 2 or 3 were included in this retrospective study with 2 year follow-up. Full-spine standing coronal and lateral radiographs were obtained preoperatively, at 3 and 24 months postoperatively. Coronal Cobb angle, thoracic kyphosis (TK) and lumbar lordosis (LL) were measured. Surgical procedure was similar in all the cases, with use of pedicular screws between T11 and the lowest instrumented vertebra (≥L2), sublaminar hooks applied in compression at the upper thoracic level and sub-laminar bands and clamps in the concavity of the deformity. Statistical analysis was done using t test and Pearson correlation coefficient. RESULTS: Between preoperative and last follow-up evaluations a significant reduction of Cobb angle was observed (53.6° vs. 17.2°, p < 0.001). A significant improvement of the instrumented thoracic kyphosis, TK (19.7° vs. 26.2°, p < 0.005) was noted, without difference between 3 and 24 months postoperatively. An improvement in lumbar lordosis, LL (43.9° vs. 47.3°, p = 0.009) was also noted but occurred after the third postoperative month. A significant correlation was found between TK correction and improvement of LL (R = 0.382, p = 0.037), without correlation between these reciprocal changes and the amount of coronal correction. CONCLUSION: Results from this study reveal that sagittal reciprocal changes occur after posterior fusion when TK is restored. These changes are visible after 3 months postoperatively, corresponding to a progressive adaptation of patient posture to the surgically induced alignment. These changes are not correlated with coronal plane correction of the deformity. In the setting of AIS, TK restoration is a critical goal and permits favorable postural adaptation. Further studies will include pelvic parameters and clinical scores in order to evaluate the impact of the noted reciprocal changes.

Adult scoliosis: prevalence, SF-36, and nutritional parameters in an elderly volunteer population.

STUDY DESIGN: A prospective self-assessment analysis and evaluation of nutritional and radiographic parameters in a consecutive series of healthy adult volunteers older than 60 years. OBJECTIVES: To ascertain the prevalence of adult scoliosis, assess radiographic parameters, and determine if there is a correlation with functional self-assessment in an aged volunteer population. SUMMARY OF BACKGROUND DATA: There exists little data studying the prevalence of scoliosis in a volunteer aged population, and correlation between deformity and self-assessment parameters. METHODS: There were 75 subjects in the study. Inclusion criteria were: age > or =60 years, no known history of scoliosis, and no prior spine surgery. Each subject answered a RAND 36-Item Health Survey questionnaire, a full-length anteroposterior standing radiographic assessment of the spine was obtained, and nutritional parameters were analyzed from blood samples. For each subject, radiographic, laboratory, and clinical data were evaluated. The study population was divided into 3 groups based on frontal plane Cobb angulation of the spine. Comparison of the RAND 36-Item Health Surveys data among groups of the volunteer population and with United States population benchmark data (age 65-74 years) was undertaken using an unpaired t test. Any correlation between radiographic, laboratory, and self-assessment data were also investigated. RESULTS: The mean age of the patients in this study was 70.5 years (range 60-90). Mean Cobb angle was 17 degrees in the frontal plane. In the study group, 68% of subjects met the definition of scoliosis (Cobb angle >10 degrees). No significant correlation was noted among radiographic parameters and visual analog scale scores, albumin, lymphocytes, or transferrin levels in the study group as a whole. Prevalence of scoliosis was not significantly different between males and females (P > 0.03). The scoliosis prevalence rate of 68% found in this study reveals a rate significantly higher than reported in other studies. These findings most likely reflect the targeted selection of an elderly group. Although many patients with adult scoliosis have pain and dysfunction, there appears to be a large group (such as the volunteers in this study) that has no marked physical or social impairment. CONCLUSIONS: Previous reports note a prevalence of adult scoliosis up to 32%. In this study, results indicate a scoliosis rate of 68% in a healthy adult population, with an average age of 70.5 years. This study found no significant correlations between adult scoliosis and visual analog scale scores or nutritional status in healthy, elderly volunteers.

Endoscopic thoracoplasty and anterior spinal release in scoliotic deformity.

Severe rigid and complex deformities of the spine often require a first stage procedure to adequately mobilize the spine to provide adequate flexibility during the actual application of instrumentation for surgical correction. This first stage involves soft tissue releases and removal of intervertebral disks from the anterior spine. Exposure to the anterior spine has traditionally been accomplished through thoracotomy or a thoracolumbar incision. The open thoracotomy, however, has several disadvantages, such as post-thoracotomy pain, a large scar, and breathing difficulties. Since the first thoracoscopy at the beginning of this century, the procedure, at first limited by the available technology, has gradually gained more uses and favor among physicians. The last 10 years have seen significant improvement in optical technology and instrumentation. These advances have allowed the spine surgeon to begin performing anterior spinal releases using endoscopic techniques. These endoscopic techniques can carry the same efficacy as the open thoracotomy but less morbidity. Thoracoplasty, the resection of rib segments, is an excellent way to not only correct the convex rib deformities seen in scoliosis but it is also an excellent source of bone which can be used as a graft for fusion. Although traditionally, thoracoplasty has also been done through an open procedure, it can be performed endoscopically. This prospective study presents nine patients who underwent combined endoscopic anterior spinal release and thoracoplasty followed by same day posterior instrumentation and fusion for correction of their spinal deformities. All nine procedures were completed successfully endoscopically. It is our conclusion that in the hands of an experienced surgeon, the endoscopic technique is an excellent procedure providing the same efficacy as the open thoracotomy. There is however a learning curve associated with the procedure. In addition, a team approach in which the surgeon and an experienced anesthesiologist with experience with double lumen intubation and selective single lung ventilation and thoracoscopic surgery is crucial. Although there were no surgical complications related to the thoracoscopic technique one patient did require prolonged intubation postoperatively, which leads us to believe that single lung ventilation in and of itself is very demanding and each patient must be considered carefully prior to its undertaking.

[Review of surgical cases which have deteriorated over time]. / Reprise des malades déjà opérés qui se sont détériorés avec le temps.

Revision for unacceptable outcomes of surgical spine treatment is not uncommon. As a result of extended life expectancy a new group of patients have expectations for full range of activities in spite of an ongoing degenerative spine process. The higher standards of this population coupled with less tolerance toward pain and deformities, no longer well tolerated in the Accident resulted in increased demand for surgical treatment. Instruments and techniques having been refined in the last 30 years have greatly improved the treatment and surgical outcome of spine deformity and spine degeneration however in spite of a better understanding of spine biomechanics progress often came via trial and error. The study presented here is based upon 154 patients, adolescents and adults who underwent revision surgery for a host of problems related to malalignment, instability or a combination of both. 102 presented decompensations after scoliosis surgery and 52 older adults presented a "failed back". Surgical revision is intrusive, requiring osteotomies often via anterior and posterior approaches with implantation of new instrumentation aiming for a solid arthrodesis. All complications of this revision surgery totaled 23%. Results at 5 year 8 months follow up show a 78% patient's improvement. The learning points from this experience are to give priority to spine balance and junctional zones in planning primary or revision surgery. It is important to recognize the place of preventive realignment to prevent further fusion extension to the cervical spine or at the opposite side of the spectrum further extension to the sacrum.

Simultaneous anterior and posterior approaches to the spine for revision surgery: current indications and techniques.

Revision spinal surgery often requires attention to both the anterior and the posterior portions of the spine. Staged, sequential, and more recently simultaneous anterior and posterior approaches have been proposed. A simultaneous approach has the distinct advantage of allowing complete and constant control of the anterior and posterior portions of the spine during surgery. The simultaneous approach has been shown to offer decreased operating time, blood loss, complication rate, and hospital length of stay as compared with staged procedures. The evolution in spinal instrumentation and ancillary equipment has greatly advanced the simultaneous technique. The development of a special operating table has facilitated patient positioning and intraoperative patient adjustments, optimizing operative exposure for the anterior and posterior surgical teams. The two-rod and four-rod techniques offer the surgeon the possibility to safely address complex deformities, particularly in kyphosis.

An algorithm for selection of instrumentation levels in scoliosis.

Appropriate levels for instrumentation and fusion in scoliosis have been a matter of debate among surgeons since the introduction of operative management of this deformity. We set out to examine the hypothesis that the amount of correction achieved in all planes during surgical instrumentation of a curve should be less than, or comparable to, the degree of correction attainable at any non-instrumented adjacent curve. An algorithm was designed to facilitate preoperative planning and intraoperative performance of spinal fusion procedures in the management of scoliosis. To test the validity of the hypothesis and the proposed algorithm, measurements were taken from the preoperative radiographs of 200 patients. The dimensions of the curves were obtained from an initial set of four X-ray films: (1) standing anteroposterior film of the whole spine, (2) standing lateral film of the whole spine, (3) two properly performed side-bending films including each curve of the spine. With this data, a plan was designed using the algorithm. The results of this plan were compared with the actual results of the surgery, which were revealed only at this stage. All patients in whom actual instrumentation levels fell within those predicted by the proposed algorithm had no imbalance at follow-up. All patients whose actual instrumentation levels were short of those recommended by the algorithm showed obvious imbalance on final postoperative standing radiograph.

A multi-center prospective study of the CD Spinal System in patients with degenerative disc disease.

This paper reports on 41 patients available for 24 months' follow-up who were entered into a prospective, multi-center study of the safety and efficacy of using the CD Spinal System (Sofamor Danek) containing pedicle screws and rods to treat adult patients with degenerative disc disease. All of these patients were implanted with only the CD Spinal System in an attempt at fusing four levels or less with autogenous bone graft only. At 24 months the results were compared to literature controls in regard to fusion, pain, function, neurological status, and complications. For function and neurological status, the CD Spinal System results were found to be statistically equal to and for fusion, pain, and complications, found to be statistically better than the noninstrumented literature controls with the same disease condition and demographics.

Management of flatback and related kyphotic decompensation syndromes.

STUDY DESIGN: The authors, in this retrospective study, examined a group of patients with flatback syndrome and a related kyphotic decompensation syndrome. Results of nonrealignment treatment as well as revision surgery with sagittal realignment were reviewed. OBJECTIVES: To determine effectiveness of physical therapy and limited surgical (instrumentation removal) as well as major realignment surgical treatment in the sagittally malaligned spine. SUMMARY OF BACKGROUND DATA: Flatback is a sagittal plane deformity associated with distraction instrumentation for scoliosis correction. Kyphotic decompensation syndrome involves malaligned fusions from the sacrum for disease other than scoliosis. Several studies describe surgical realignment for flatback involving instrumentation systems no longer commonly applied. Guidelines for a systematic approach to flatback and kyphotic decompensation syndromes are lacking. METHODS: Forty-eight patients with flatback and kyphotic decompensation syndromes were reviewed. Treatment groups were defined by treatment approach and level of previous fusion. Effectiveness of treatment was reviewed in terms of radiographic sagittal alignment and self-reported pain. RESULTS: Twenty patients were treated without realignment revision surgery. Twenty-eight patients were treated with anterior and posterior osteotomies and realignment with instrumentation. For patients originally fused to the sacrum, realignment averaged 12 cm. Pain was reduced from 7 to 3 (10-point scale). In patients fused to L4 or L5, realignment averaged 7 cm. Pain was reduced from 6 to 2. Magnetic resonance imaging revealed viable caudal discs in four patients who were consequently spared extension of fusion to the sacrum. CONCLUSIONS: Treatment without realignment surgery demonstrated long-term success in 27% of cases. The latter all had two intact discs below the previous fusion and sagittal malalignment less than 4 cm. Realignment surgery effectively reduced pain in patients failing a conservative approach.

The sagittal pelvic tilt index as a criterion in the evaluation of spondylolisthesis. Preliminary observations.

STUDY DESIGN: Radiographic analysis of a pediatric population with spondylolisthesis was performed to examine sagittal plane pelvic rotation and degree of slip over time. OBJECTIVES: To determine whether the degree of standing sagittal offset of L5 with respect to the acetabulum correlated with slip progression and symptoms. SUMMARY OF BACKGROUND DATA: The natural history of isthmic spondylolisthesis remains unclear. Attempts to predict slip progression in the clinical setting, and thus the possible need for eventual surgical intervention, remain imprecise. Predicting slip progression based on sagittal alignment of the L5 vertebra with respect to the acetabulum has been proposed by some investigators. METHODS: Fifty-two children and adolescents were followed clinically and radiographically for an average of 5.6 years. Serial lateral standing radiographs that included the hips and lumbar spine were measured to compute a sagittal pelvic tilt index. The latter value is a ratio of relative distances from the center of S2 to the projection of L5 and the center of the femoral heads on the horizontal. RESULTS: Of the 52 patients studied, 38 have remained asymptomatic without significant slip progression or change in sagittal pelvic tilt index ratio. Of the original group, 13 patients had significant symptoms and revealed a decrease in the sagittal pelvic tilt index over time. Eight of the 13 stabilized at the end of adolescence, whereas 5 had continued decrease in the sagittal pelvic tilt index ratio. These five required operative treatment for pain and progressive slip. CONCLUSIONS: The sagittal pelvic tilt index gives the examiner an objective measure of the stability of the lumbosacral junction by quantifying the relationship between S2, the center of the hip, and L5. A decreasing sagittal pelvic tilt index ratio in this preliminary series correlated with slip progression and risk of conservative treatment failure, whereas those patients with a stable sagittal pelvic tilt index did not progress and remained clinically asymptomatic.

Intraoperative monitoring of motor evoked potentials: a review of 116 cases.

We reviewed the results of motor evoked potential (MEP) and somatosensory evoked potential (SEP) monitoring during 116 operations on the spine or spinal cord. We monitored MEPs by electrically stimulating the spinal cord and recording compound muscle action potentials from lower extremity muscles and monitored SEPs by stimulating posterior tibial or peroneal nerves and recording both cortical and subcortical evoked potentials. We maintained anesthesia with an N2O/O2/opioid technique supplemented with a halogenated inhalational agent and maintained partial neuromuscular blockade using a vecuronium infusion. Both MEPs and SEPs could be recorded in 99 cases (85%). Neither MEPs nor SEPs were recorded in eight patients, all of whom had preexisting severe myelopathies. Only SEPs could be recorded in two patients, and only MEPs were obtained in seven cases. Deterioration of evoked potentials occurred during nine operations (8%). In eight cases, both SEPs and MEPs deteriorated; in one case, only MEPs deteriorated. In four cases, the changes in the monitored signals led to major alterations in the surgery. We believe that optimal monitoring during spinal surgery requires recording both SEPs and MEPs. This provides independent verification of spinal cord integrity using two parallel but independent systems, and also allows detection of the occasional insults that selectively affect either motor or sensory systems.

Epithelioid sarcoma of the spine: a case report.

STUDY DESIGN: This case report illustrates a patient presenting with sciatica and diagnosed with epithelioid sarcoma involving the spine. OBJECTIVES: The treatment of this patient involved multiple mass resections and decompressions of the spinal canal. Radio- and chemotherapy were applied once a clear diagnosis was obtained. SUMMARY OF BACKGROUND DATA: Epithelioid sarcoma is a rare tumor mainly arising in the extremities. Confusion with a benign inflammatory process are possible. Treatment after histologic diagnosis involves wide resection. To our knowledge, this report represents the first case of epithelioid sarcoma involving the spine. METHODS: After initial discectomy, recurrent scarring and mass formation required multiple decompression procedures and fusion. The initial pathology revealed inflammatory reaction on fibrosis. In a later procedure, the histologic diagnosis of epithelioid sarcoma was made. Radiotherapy and chemotherapy were begun immediately. RESULTS: Despite aggressive resections, radiotherapy, and chemotherapy, the patient died 3 months after the last surgical procedure. CONCLUSION: Spinal epithelioid sarcoma can be mistaken for a benign inflammatory process. After a histologic diagnosis, aggressive wide resection is necessary. Multiple recurrences are documented with this tumor in other sites. Prognosis in trunk involvement is less favorable than involvement of the extremities. The role of adjuvant radio- and chemotherapy is unclear for spinal involvement.

Simultaneous anterior and posterior approaches for correction of late deformity due to thoracolumbar fractures.

Thirty-one patients with an average age of 27 years were included in this study to analyze the short-term results of simultaneous anterior and posterior approaches in the treatment of late complications of thoracolumbar fractures. The complications treated were pseudoarthrosis and malunion resulting in neurologic compromise and pain. There were 20 burst fractures, 2 fracture/dislocations, and 9 compression fractures in this group. Average preoperative Sagittal Index was 35 degrees, which improved to an average of 4 degrees after surgical treatment. The average Motor Index Score improved from 90 to 98 after surgery. Average follow-up was 16 months. Average estimated blood loss was 2000 ml and average operation time was 5 h. It was concluded that the late problems associated with thoracolumbar fractures can be addressed quite adequately with simultaneous anterior and posterior approaches. The simultaneous anterior and posterior approach is associated with decreases in operating time, blood loss, and hospital stay. Technical advantages of the simultaneous technique include elimination of acute instability between the stages, protection against dislodgment of the graft, and application of the posterior instrumentation under complete visualization of the anterior graft.

Monitoring of intraoperative motor-evoked potentials under conditions of controlled neuromuscular blockade.

Motor-evoked potentials were recorded after electrical spinal cord stimulation in 19 patients undergoing neurosurgical or orthopedic procedures. Anesthesia was maintained with nitrous oxide, opioids, and inhaled anesthetics. Vecuronium was infused sufficient to eliminate 90% of twitch tension. The spinal cord was stimulated using either epidural or subarachnoid electrodes. Compound muscle action potentials were recorded from quadriceps and tibialis anterior muscles. Well-formed, stable motor-evoked potentials were recorded in all but one patient, in whom a preexisting myelopathy was felt to preclude recording. Intraoperative deterioration of motor-evoked potentials occurred in one patient who had a postoperative neurologic deficit. This study demonstrates the feasibility and utility of intraoperative motor tract monitoring using direct spinal cord stimulation. Controlled neuromuscular blockade permits recording of compound muscle action potentials while eliminating patient motor activity that could interfere with surgery.

Results of spinal instrumentation of adolescent idiopathic scoliosis by King type.

The purpose of this study is to determine the usefulness of the King classification in predicting decompensation in adolescent idiopathic scoliosis. Fifty-one patients were reviewed with a mean follow-up of 25 months. Five patients had Type 1 adolescent idiopathic scoliosis: four were treated with Zielke/Cotrel-Dubousset instrumentation or Zielke instrumentation alone. Correction was greater than 51% in these cases and there was no decompensation. Twenty-three patients had Type II scoliosis. Nineteen of whom were treated with Cotrel-Dubousset instrumentation; 3 with Zielke and Cotrel-Dubousset instrumentation, and 1 with Zielke. The best correction occurred with anterior/posterior instrumentation. Decompensation occurred in 9 patients, all of whom were treated with Cotrel-Dubousset instrumentation alone. Fourteen patients had Type III scoliosis. All were treated with Cotrel-Dubousset instrumentation with correction of 65%. Decompensation occurred in 4 patients, all of whom were fused to or beyond the stable vertebra. Four patients had Type IV scoliosis; all were fused short of the stable vertebra with Cotrel-Dubousset instrumentation, resulting in correction of 52% and no decompensation. Five patients had Type V instrumentation; four were treated with Cotrel-Dubousset instrumentation and 1 with Zielke. There was no relationship between level of fusion and decompensation. Based on this study, the authors contend that the King classification is a valuable tool in the selection of type of instrumentation and fusion level.

Technique and results of fixation to the sacrum with iliosacral screws.

This article describes the technique of iliosacral screw fixation, as well as a retrospective review of 28 consecutive patients who had spine fusion to the sacrum with iliosacral screws, with a minimum follow-up of 2 years. The study included 6 male and 22 female patients. Average age at the time of surgery was 43 years, and mean follow-up time was 3.5 years. There were no neurologic complications at final follow-up evaluation. Ninety-five percent of the patients had radiographic evidence of fusion. Three patients required iliosacral screw removal because of suboptimal intraoperative Kirschner-wire placement. Optimal intraoperative radiographic evaluation for accurate iliosacral screw placement is recommended. The use of iliosacral screws is also a useful addition to the armamentarium of the spine surgeon when fixation to the sacrum is required.