Spinal extradural arachnoid cysts: a rare entity and review of the literature.

OBJECTIVE: Spinal extradural arachnoid cysts (SEDC) are rare primary spinal lesions, accounting for less than 1% of all spinal epidural lesions. The literature contains only case reports of this pathology, and treatment remains controversial due to its rarity. Major reported SEDC cases are caused by leaking out of cerebrospinal fluid through a dural defect in the thecal sac forming an extradural cyst. Other reports describe non-communicating SEDC cases where the dural defect was not identified. We report a literature review on SEDC and the case of a 53 year­old female who presented with type IA extradural cyst with subarachnoid space communication. METHODS: Literature review, preoperative imaging and surgical technique. RESULTS: The extradural cyst was excised completely and the dural defect was repaired. After surgical decompression, neurological symptoms gradually recovered. CONCLUSIONS: The extradural arachnoid cyst is an uncommon entity. Preoperative imaging is one of the determining elements in orienting the therapeutic management of the SEDCs. The choice of the surgical technique must be the least invasive in order to avoid postoperative complications. Subtotal or complete excision of the cyst, followed by obliteration of the communication stalk and repair of the dural defect is the gold standard treatment.

Lateral-PLIF for spinal arthrodesis: concept, technique, results, complications, and outcomes.

BACKGROUND: Posterior lumbar interbody fusion (PLIF) surgery represents an effective option to treat degenerative conditions in the lumbar spine. To reduce the drawbacks of the classical technique, we developed a variant, so-called Lateral-PLIF, which we then evaluated through a prospective consecutive series of patients. METHODS: All adult patients treated at our institute with single or double level Lateral-PLIF for lumbar degenerative disease from January to December 2017 were prospectively collected. Exclusion criteria were patients < 18 years of age, traumatic patients, active infection, or malignancy, as well as unavailability of clinical and/or radiological follow-up data. The technique consists of insert the cages bilaterally through the transition zone between the central canal and the intervertebral foramen, just above the lateral recess. Pre- and postoperative (2 years) questionnaires and phone interviews (4 years) assessed pain and functional outcomes. Data related to the surgical procedure, postoperative complications, and radiological findings (1 year) were collected. RESULTS: One hundred four patients were selected for the final analysis. The median age was 58 years and primary symptoms were mechanical back pain (100, 96.1%) and/or radicular pain (73, 70.2%). We found a high fusion rate (95%). A statistically significant improvement in functional outcome was also noted (ODI p < 0.001, Roland-Morris score p < 0.001). Walking distance increased from 812 m ± 543 m to 3443 m ± 712 m (p < 0.001). Complications included dural tear (6.7%), infection/wound dehiscence (4.8%), and instrument failure (1.9%) but no neurological deterioration. CONCLUSIONS: Lateral-PLIF is a safe and effective technique for lumbar interbody fusion and may be considered for further comparative study validation with other techniques before extensive use to treat lumbar degenerative disease.

Isolated atlas-duplication as a manifestation of persistent proatlas: a case report.

PURPOSE: Atlas-duplication is an exceedingly rare dysplasia of the craniocervical junction. To the best of our knowledge, only two cases of atlas-duplication have been reported and these were associated with complete anterior rachischisis and os odontoideum. We aimed to report a case of isolated atlas-duplication of incidental finding and without attributable symptoms which makes it unique. METHODS: Following a normal coronarography for a suspected myocardial infarction, a 60-year-old-man with no significant medical history developed a transient ischemic attack that justified brain computed-tomography angiography. RESULTS: There was no evidence for cerebral ischemic lesion, intracranial occlusion or significant artery disease. Bone analysis revealed eight cervical vertebral segments with an additional vertebral level located between the occiput and the atlas. This vertebra presented all the morphological characteristics of an atlas vertebra except for hypoplasia of the left transverse process. An incomplete anterior rachischisis was associated, and there was no other abnormality of craniocervical junction. The clinical examination revealed no neck pain, no limitation of joint amplitude and no neurological deficit. Apart from preventive treatment of ischemic stroke, no orthopedic or surgical treatment was undertaken. After 1.5 years of radiological monitoring, the patient remains symptom-free. CONCLUSIONS: Atlas-duplication is an exceedingly rare dysplasia of the craniocervical junction that may be found isolated and incidentally. If this variation does not necessarily warrant specific treatment, brain CT angiography is recommended to detect anatomical variations of the vertebral arteries.

Cysts associated with intramedullary ependymomas of the spinal cord: clinical, MRI and oncological features.

PURPOSE: Few published articles have explicitly focused on cysts associated with intramedullary (IM) ependymomas. The objective was to assess the clinical, MRI, and oncological results of patients operated for an IM ependymoma associated with a cystic portion. METHODS: During the study period, 23 IM tumors resected were cystic ependymomas. The modified McCormick scale was used to assess the neurological function of patients. The diagnosis of cystic spinal cord tumor was made on preoperative MRI. RESULTS: Two types of cysts were identified according to their location: either intra-tumoral cysts (ITC) or satellite cysts (SC). ITC (52.2%) were more frequent than SC (21.7%), but 26.1% of patients presented both. ITC were enhanced by gadolinium while SC were not. The solid portion of ependymomas with ITC was significantly larger than the one of ependymomas with SC (p = 0.002). The mean time to the first occurrence of symptoms was significantly shorter in patients with neurological deficit than those without a deficit (p = 0.04). GTR was achieved in 78.2% of cases. Complete excision of the cysts was easier when they were larger (p = 0.006). Sixty percent of cysts disappear postoperatively. Persistence of satellite cysts despite GTR of the tumor, and with no recurrence of a tumor on the post-operative MRI, was observed for 3 patients. CONCLUSION: ITC and SC are different in location, volume, gadolinium enhancement. Their surgical management is different since ITC are resected while SC are drained. Cystic recurrence and/or persistence are not synonymous with tumor recurrence.

Spinopelvic sagittal alignment of patients with transfemoral amputation.

PURPOSE: This study aims to describe the spinopelvic sagittal alignment in transfemoral amputees (TFAs) from a radiologic study of the spine with a postural approach to better understand the high prevalence of low back pain (LBP) in this population. METHODS: TFAs underwent X-rays with 3-D reconstructions of the full spine and pelvis. Sagittal parameters were analyzed and compared to the literature. Differences between TFAs with and without LBP were also observed. RESULTS: Twelve subjects have been prospectively included (TFA-LBP group (n = 5) and TFA-NoP group (n = 7)). Four of the five subjects of the TFA-LBP group and two of the seven in TFAs-NoP group had an imbalanced sagittal posture, especially regarding the T9-tilt, significantly higher in the TFA-LBP group than in the TFA-NoP (p = 0.046). Eight subjects (6 TFA-NoP and 2 TFA-LBP) had abnormal low value of thoracic kyphosis (TK). Moreover, the mean angle of TK in the TFA-NoP group was lower than in the TFA-LBP group (p = 0.0511). CONCLUSION: In the considered sample, TFAs often present a sagittal imbalance. A low TK angle seems to be associated with the absence of LBP. It can be hypothesized that this compensatory mechanism of the sagittal imbalance is the most accessible in this population. This study emphasizes the importance of considering the sagittal balance of the pelvis and the spine in patients with a TFA to better understand the high prevalence of LBP in this population. It should be completed by the analysis of the spinopelvic balance and the lower limbs in 3D. These slides can be retrieved under Electronic Supplementary Material.

Mortality, complication, and fusion rates of patients with odontoid fracture: the impact of age and comorbidities in 204 cases.

PURPOSE: The French Society of Spine Surgery (SFCR) conducted a prospective epidemiologic multicenter study. The purpose was to investigate mortality, complication, and fusion rates in patients with odontoid fracture, depending on age, comorbidities, fracture type, and treatment. METHODS: Out of 204 patients, 60 were ≤ 70 years and 144 were > 70 years. Demographic data, comorbidities, treatment types and complications (general medical, infectious, neurologic, and mechanical), and death were registered within the first year. Fractures were classified according to Anderson-D'Alonzo and Roy-Camille on the initial CT. A 1-year follow-up CT was available in 144 patients to evaluate fracture consolidation. RESULTS: Type II and oblique-posterior fractures were the most frequent patterns. The treatment was conservative in 52.5% and surgical in 47.5%. The mortality rate in patients ≤ 70 was 3.3% and 16.7% in patients > 70 years (p = 0.0002). Fracture pattern and treatment type did not influence mortality. General medical complications were significantly more frequent > 70 years (p = 0.021) and after surgical treatment (p = 0.028). Neurologic complications occurred in 0.5%, postoperative infections in 2.0%, and implant-related mechanical complications in 10.3% (associated with pseudarthrosis). Fracture fusion was observed in 93.5% of patients ≤ 70 years and in 62.5% >70 years (p < 0.0001). Pseudarthrosis was present in 31.5% of oblique-posterior fractures and in 24.3% after conservative treatment. CONCLUSIONS: Age and comorbidities influenced mortality and medical complication rates most regardless of fracture type and treatment choice. Pseudarthrosis represented the main complication, which increased with age. Pseudarthrosis was most frequent in type II and oblique-posterior fractures after conservative treatment.

Clinical and radiographic evaluation of bioactive glass in posterior cervical and lumbar spinal fusion.

INTRODUCTION: Spinal surgery of degenerative painful segments is a valuable treatment option in the management of chronic cervical and low back pain. The surgery consists in stabilizing and fusing painful vertebral segment(s). The objective of the study was to report our experience with 45S5 bioactive glass (BAG) to obtain inter-vertebral fusion in the context of posterior spine surgery. MATERIAL AND METHOD: In this retrospective study, 30 patients with a wide range of degenerative and traumatic conditions of the cervical or lumbar spine underwent spinal fusion utilizing a synthetic bone graft substitute of BAG (GlassBone™, Noraker, Lyon-Villeurbanne, France). The pain was evaluated by VAS score, and graft consolidation was assessed on according radiographic images at 1-year post-op. RESULTS: All patients underwent posterior spinal fusion either in the cervical or the thoraco-lumbar spine. Multi-level fusions represented the majority of the cohort (43% of patients with more than seven levels treated). Radiographic imaging demonstrated excellent fusion rates (93%) at final follow-up, equivalent to the outcomes reported in the literature for autogenous bone, with excellent bone bridging and no spinal implant loosening. Only two cases of non-union were encountered. Additionally, 90% of the patients demonstrated recovery at 1 year after surgery with a pain reduction of 60%. CONCLUSION: The results of this retrospective study suggest that the 45S5 BAG may be an interesting alternative option to autologous graft, in terms of safety and bone fusion efficiency. LEVEL OF EVIDENCE: IV Retrospective study.

A new quasi-invariant parameter characterizing the postural alignment of young asymptomatic adults.

PURPOSE: Our study aims to describe the postural alignment of young asymptomatic subjects from head to feet from bi-planar standing full-body X-rays, providing database to compare to aging adults. Novelty resides in the inclusion of the head and lower limbs in the erected posture's analysis. METHODS: For 69 young asymptomatic subjects (18-40 years old) 3D reconstructions of the head, spine, pelvis and lower limbs segments were performed from bi-planar full-body X-rays. Usual studied spinal, pelvic and lower limbs' parameters were computed in 3D, sagittal and frontal planes of the patient. Relationships between these parameters were investigated. Inclinations of different lines were studied to characterize the erected posture. RESULTS: Values found for spinal curvatures, pelvic parameters and lower limbs geometrical parameters agreed with the literature: thoracic kyphosis, lumbar lordosis, pelvic incidence, pelvic tilt and sagittal vertical axis were respectively in average of 26.9° (SD 7.2°), 30.5° (SD 7.5°), 51.0° (SD 9.4°), 11.1° (SD 5.6°) and -8.9 mm (SD 21.6 mm). The angle between the vertical and the line joining the most superior point of dentiform apophyse of C2 (OD) and the center of the bi-coxofemoral axis (HA) was the less variable one (SD 1.6°). CONCLUSIONS: This study on 3D postural alignment reports the geometry of the spine, pelvis and lower limbs, of the young asymptomatic adult. The less variable angle is the one of the line OD-HA with the vertical, highlighting the vertical alignment of the head above the pelvis. This study provides a basis for future comparisons when investigating aging populations.

Short isthmic versus long trans-isthmic C2 screw: anatomical and biomechanical evaluation.

INTRODUCTION: The Harms technique is now considered as the gold standard to stabilize C1-C2 cervical spine. It has been reported to decrease the risk of vertebral artery injury. However, the risk of vascular injury does not totally disappear, particularly due to the proximity of the trans-isthmic C2 screw with the foramen transversarium of C2. In order to decrease this risk of vertebral artery injury, it has been proposed to use a shorter screw which stops before the foramen transversarium. OBJECT: The main objective was to compare the pull-out strength of long trans-isthmic screw (LS) versus short isthmic screw (SS) C2 screw. An additional morphological study was also performed. METHOD: Thirteen fresh-frozen human cadaveric cervical spines were included in the study. Orientation, width and height of the isthmus of C2 were measured on CT scan. Then, 3.5-mm titanium screws were inserted in C2 isthmus according to the Harms technique. Each specimen received a LS and a SS. The side and the order of placement were determined with a randomization table. Pull-out strengths and stiffness were evaluated with a testing machine, and paired samples were compared using Wilcoxon signed-rank test and also the Kaplan-Meier method. RESULTS: The mean isthmus transversal orientation was 20° ± 6°. The mean width of C2 isthmus was less than 3.5 mm in 35 % of the cases. The mean pull-out strength for LS was 340 ± 85 versus 213 ± 104 N for SS (p = 0.004). The mean stiffness for the LS was 144 ± 40 and 97 ± 54 N/mm for the SS (p = 0.02). DISCUSSION: The pull-out strength of trans-isthmic C2 screws was significantly higher (60 % additional pull-out resistance) than SSs. Although associated with an inferior resistance, SSs may be used in case of narrow isthmus which contraindicates 3.5-mm screw insertion but does not represent the first option for C2 instrumentation. LEVEL OF EVIDENCE: Level V.

Relevance of using a compressive preload in the cervical spine: an experimental and numerical simulating investigation.

UNLABELLED: Simulating compressive action of muscles, a follower load attends to reproduce a more physiological biomechanical behaviour of the cervical spine. Only few experimental studies reported its influence on kinematics and intradiscal pressure in the cervical spine. STUDY DESIGN: In vitro human cadaveric and numerical simulating evaluation of a compressive preload in the cervical spine. OBJECTIVES: To analyse the influence of a compressive follower preload on the biomechanical behaviour of the cervical spine. METHODS: The present study was divided into two parts: part 1: in vitro investigation; part 2: numerical simulating analysis. Part 1: Twelve human cadaveric spines from C2 to T2 were evaluated intact and after application of a 50-N follower load. All tests were performed under load control by applying pure moments loading of 2 Nm in flexion/extension (FE), axial rotation (AR) and lateral bending (LB). Three-dimensional displacements were measured using an optoelectronic system, and intradiscal pressures were measured at two levels. Part 2: Using a 3D finite element model, we evaluated the influence of a 50- and 100-N compressive preload on intradiscal loads, facets forces and ranges of motion. Different positions of the follower load along the anteroposterior axis (±5 mm) were also simulated. RESULTS: Part 1: Mean variation of cervical lordosis was 5° ± 3°. The ROM slightly increased in FE, whereas it consistently decreased in AR and LB. Coupled lateral bending during AR was also reduced. Increase in hysteresis was observed on load-displacement curves only for AR and LB. Intradiscal pressures increased, but the aspect of load-pressure curves was altered in AR and LB. Part 2: Using the FE model, only minimal changes in ROM were noted following the simulation of a 50-N compressive load for the three loading conditions. Compared to intact condition, <10% variation was observed with regard to the different magnitude and positioning simulated. Intradiscal loads and facets forces were systematically increased by applying compressive preload. CONCLUSIONS: Although the follower load represents an attractive option to apply compressive preload during experimental tests, we found that this method could affect the native biomechanical behaviour of spine specimen depending on which movement was considered. Only minimal effects were observed in FE, whereas significant changes in kinematics and intradiscal pressures were observed for AR and LB.

Pedicle subtraction osteotomy in the lumbar spine: indications, technical aspects, results and complications.

Pedicle subtraction osteotomy (PSO) consists of creating posteriorly trapezoidal shape of a vertebra, usually L3 or L4, in order to recreate lordosis in the lumbar spine. It is usually indicated to treat rigid kyphotic lumbar spine associated with sagittal imbalance and due to degenerative changes or to iatrogenic flat back. PSO is technically demanding with high rates of complications and should be performed by experienced teams. We presently report our experience about PSO performed in the lumbar spine (below L1) through a series of 25 cases with a special focus on technical aspects and complications associated with the surgical procedure. Mean age was 64 ± 11 years old. PSO was performed at L4 in the majority of cases. Mean blood loss was 1,070 ± 470 ml, and mean duration of the surgery was 241 ± 44 min. VAS decreased from 7.5 ± 2 preoperatively to 3.2 ± 2.5 at 1 year, and ODI decreased from 64 ± 12 preoperatively to 32 ± 18 at 1 year, p < 0.05. Mean gain of lordosis after PSO varies from 20° to 40° and was measured to 27° ± 10° on average. Lumbar lordosis (T12-S1) was measured to 21° ± 10° preoperatively to 50° ± 11° postoperatively at 1 year, p < 0.05. A total of five major complications (20 %) were observed (two mechanical, one neurological and two infections) necessitating five reoperations. In conclusion, PSO was highly efficient to restore lumbar lordosis and correct sagittal imbalance. It was associated with a non-negligible, but acceptable rate of complications. To limit the risk of mechanical complications, we recommend fusing the adjacent disks whatever the approach (PLIF/TLIF/XLIF). Most complications can be reduced with adequate environment, informed anesthesiologists and experienced surgical team.

Complex osteotomies vertebral column resection and decancellation.

Pedicle subtraction osteotomy (PSO) is nowadays widely used to treat sagittal imbalance. Some complex malalignment cases cannot be treated by a PSO, whereas the imbalance is coronal or mixed or the sagittal imbalance is major and cannot be treated by a single PSO. The aim of this article was to review these complex situations--coronal imbalance, mixed imbalance, two-level PSO, vertebral column resection, and vertebral column decancellation, and to focus on their specificities. It wills also to evoke the utility of navigation in these complex cases.

Compensatory mechanisms contributing to keep the sagittal balance of the spine.

INTRODUCTION: Aging spine is characterized by facet joints arthritis, degenerative disc disease, bone remodeling and atrophy of extensor muscles resulting in a progressive kyphosis of the lumbar spine. OBJECTIVE: The aim of this paper is to describe the different compensatory mechanisms for patients with severe degenerative lumbar spine. MATERIAL AND METHODS: According to the severity of the imbalance, three stages are observed: balanced, balanced with compensatory mechanisms and imbalanced. For the two last stages, the compensatory mechanisms permit to limit the consequences of loss of lumbar lordosis on global sagittal alignment and therefore contribute to keep the sagittal balance of the spine. RESULTS: The basic concept is to extend adjacent segments of the kyphotic spine allowing for compensation of the sagittal unbalance but potentially inducing adverse effects. CONCLUSION: Finally, we propose a three-step algorithm to analyze the global balance status and take into consideration the presence of the compensatory mechanisms in the spinal, pelvic and lower limb areas.

Three-Dimensional Volumetric Magnetic Resonance Imaging Analysis of Syringomyelia Evolution After Posterior Fossa Decompression for Chiari Malformation Type1.

OBJECTIVE: This study aims to introduce a method of three-dimensional (3D) volume magnetic resonance imaging (MRI) measurements to evaluate the evolution of syringomyelia (SM) in adults with Chiari malformation type 1 (CM-1) after posterior fossa decompression (PFD), to provide reproducible and accurate measurements. METHODS: Radiologic and clinical data were obtained for 28 patients. MRI 3D syrinx volumes were evaluated by 2 observers using Philips Healthcare Tumor Tracking tool. RESULTS: The mean SM preoperative volume was 9.1 ± 15.3 cm3 versus 4.6 ± 8.7 cm3 postoperatively, corresponding to a volume variation reduced by -50% ± 33.4%. A total of 21 patients (75%) showed >25% reduction in SM volume postoperatively and 25 patients (89.2%) showed good to excellent postoperative clinical outcomes. Very high interobserver and intraobserver agreement was noted for 3D volumetric analysis with Cohen weighted κ coefficients (0.899-0.991). A negative correlation was found between the number of involved metameres and the postoperative SM volume reduction (Pearson correlation coefficient = 0.378; P = 0.047). Patients with better clinical outcomes had fewer syrinx septae (F = 8.830; P = 0.001). Similarly, better syrinx volume reduction was associated with fewer septae (F = 1.554; P = 0.233). A positive relationship was observed between clinical outcomes and postoperative syrinx volume reduction (F = 1.554; P= 0.233), with data similar to the reported literature. CONCLUSIONS: This study shows that 3D volume measurement of the syrinx cavity on MRI is a reproducible and accurate method to assess the postoperative evolution of SM in CM-1 after PFD. Most patients (75%) showed a reduction of SM volume, with a mean volume decrease of 50%. The reliability is yet to be validated in further larger studies.

Biomechanical Comparison of Facet Versus Laminar C2 Screws.

BACKGROUND: Transpedicular or transisthmic screws for C2 instrumentation represent the gold standard; however, the anatomy is not always compatible (hypoplastic pedicles, procidentia of the vertebral artery). Laminar screws (LS) have been proposed as a rescue technique and recently, bicortical facet screws (FS). To date, the biomechanical property of FS remains unknown. OBJECTIVE: To compare the pull-out resistance of bicortical facet (FS) vs laminar (LS) C2 screws. METHODS: Thirty-two human cadaveric C2 vertebrae were screened by CT scan imaging and dual x-ray absorptiometry before receiving both techniques and were randomized according to side and sequence (FS or LS first). Screw positioning was validated using 2-dimensional x-rays. Sixty-four mechanical tests were performed using pure tensile loading along the axis of the screws until pull-out. Mean pull-out strengths were compared using paired tests, multivariate and survival analysis (Kaplan-Meier curves). RESULTS: The morphometric data were consistent with previous studies. Over 64 tests, the mean pull-out strength of LS (707 ± 467 N) was significantly higher than that of FS (390 ± 230 N) ( P = .0004). Bone mineral density was weakly correlated with pull-out strength (r = 0.42 for FS and r = 0.3 for LS). Both techniques were mechanically equivalent for vertebrae in which intralaminar cortical grip was not achievable for LS. The mean pull-out strength for LS with laminar cortical grip (1071 ± 395 N) was significantly higher than that of LS without (423 ± 291 N) ( P < .0001). CONCLUSION: Our results suggest that bicortical FS of C2 offer less mechanical resistance than LS.

Sacrifice of Involved Nerve Root during Surgical Resection of Foraminal and/or Dumbbell Spinal Neurinomas.

Even if usually needed to achieve the gross total resection (GTR) of spinal benign nerve sheath tumors (NSTs), nerve root sacrifice remains controversial regarding the risk of neurological deficit. For foraminal NSTs, we hypothesize that the involved root is poorly functional and thus can be safely sacrificed. All spinal benign NSTs with foraminal extension that underwent surgery from 2013 to 2021 were reviewed. The impacts of preoperative clinical status and patient and tumor characteristics on long-term outcomes were analyzed. Twenty-six patients were included, with a mean follow-up (FU) of 22.4 months. Functional motor roots (C5-T1, L3-S1) were involved in 14 cases. The involved nerve root was routinely sacrificed during surgery and GTR was obtained in 84.6% of cases. In the functional root subgroup, for patients with a pre-existing deficit (n = 5/14), neurological aggravation persisted in one case at last FU (n = 1/5), whereas for those with no preop deficit (n = 9/14), a postoperative deficit persisted in one patient only (n = 1/9). Preoperative radicular pain was the only characteristic significantly associated with an immediate postoperative motor deficit (p = 0.03). The sacrifice of an involved nerve root in foraminal NSTs seems to represent a reasonable and relevant option to resect these tumors, permitting one to achieve tumor resection in an oncologic fashion with a high rate of GTR.

How was spinal surgery activity maintained during the COVID-19 pandemic? Results of a French multicenter observational study.

INTRODUCTION: The French Society of Spinal Surgery (SFCR) offered guidelines during the COVID pandemic. The objective of this work was to report the organization and activity in spinal surgery during the first month of confinement across 6 centers in France. The secondary objective was to monitor the adequacy of our practices within the SFCR guidelines. MATERIAL AND METHODS: This prospective multicenter observational study reported spinal surgery activity in each institution from March 16 to April 16, 2020, as well as the organizational changes applied. Surgical activity was compared to that of the same period in 2019 in each center and evaluated according to the SFCR guidelines, in order to control the adequacy of our practices during a pandemic period. RESULTS: During the peak of the epidemic, 246 patients including 6 COVID-positive patients were treated surgically. The most significant drops in activity were found in Strasbourg (-81.5%) and Paris (-65%), regions in which the health situation was the most critical, but also in Bordeaux (-75%) despite less viral circulation. Operating rooms functioned at 20 to 50% of their normal capacity. There was a significant reduction in procedures for degenerative spine conditions or deformities, in line with the SFCR guidelines. CONCLUSION: Maintaining spinal surgery is possible and desirable, even in times of health crisis. The indications must be considered according to the emergency criteria developed by learned societies and adapted to health developments and to the technical possibilities of treatment, by center. LEVEL OF PROOF: IV.

Cervical disc prosthesis versus arthrodesis using one-level, hybrid and two-level constructs: an in vitro investigation.

INTRODUCTION: The purpose of this experimental study was to analyse cervical spine kinematics after 1-level and 2-level total disc replacement (TDR) and compare them with those after anterior cervical arthrodesis (ACA) and hybrid construct. Kinematics and intradiscal pressures were also investigated at adjacent levels. METHODS: Twelve human cadaveric spines were evaluated in different testing conditions: intact, 1 and 2-level TDR (Discocerv™, Scient'x/Alphatec), 1 and 2-level ACA, and hybrid construct. All tests were performed under load control protocol by applying pure moments loading of 2 N m in flexion/extension (FE), axial rotation (AR) and lateral bending (LB). RESULTS: Reduction of ROM after 1-level TDR was only significant in LB. Implantation of additional TDR resulted in significant decrease of ROM in AR at index level. A second TDR did not affect kinematics of the previously implanted TDR in FE, AR and LB. One and 2-level arthrodesis caused significant decrease of ROM in FE, AR and LB at the index levels. No significant changes in ROM were observed at adjacent levels except for 1-level arthrodesis in FE and hybrid construct in AR. When analysis was done under the displacement-control concept, we found that 1 and 2-constructs increased adjacent levels contribution to global ROMC3-C7 during FE and that IDP at superior adjacent level increased by a factor of 6.7 and 2.3 for 2-level arthrodesis and hybrid constructs, respectively. CONCLUSION: Although 1- and 2-level TDR restored only partially native kinematics of the cervical spine, these constructs generated better biomechanical conditions than arthrodesis at adjacent levels limiting contribution of these segments to global ROM and reducing the amount of their internal stresses.

Sagittal alignment and kinematics at instrumented and adjacent levels after total disc replacement in the cervical spine.

BACKGROUND: The purpose of the study was to report radiological outcomes after total disc replacement (TDR) in the cervical spine through a 24 months follow-up (FU) prospective study with a special focus on sagittal alignment and kinematics at instrumented and adjacent levels. MATERIALS AND METHODS: Thirty-two patients, who sustained one-level TDR with a ball-and-socket arthroplasty (Discocerv(™) implant, Scient'x/Alphatec Spine, USA) were consecutively included in the study. Clinical (visual analogical scale and neck disability index) and radiological parameters were measured preoperatively and postoperatively at 3/6 months, 1-year and 2-year FU. Sagittal alignment, ranges of motion (ROM) and center of rotations (CORs) were analyzed using specific motion analysis software (Spineview(™), Paris, France). Patients CORs were compared with those of a control group of 39 normal and asymptomatic subjects. RESULTS: Both local and C3-C7 lordosis significantly increased postoperatively (+8° and +13° at 2 years, respectively). At instrumented level ROM in flexion-extension (FE) was measured to 10.2° preoperatively versus 7.5° at 1 year and 6.1° at 2 years. There were no differences in ROM at adjacent levels between pre and postoperative assessments. When compared with control group and preoperative measurements, we noted postoperative cranial shift of the COR at instrumented level for patients group. In contrast, there was no difference in CORs location at adjacent levels. CONCLUSION: Through this prospective study, we observed that cervical lordosis consistently increased after TDR. In addition, although ball-and-socket arthroplasty did not fully restore native segmental kinematics with significant reduction of motion in FE and consistent cranial shift of the COR, no significant changes in terms of ROM and CORs were observed at adjacent levels.

Clipping Test of a Radiculomedullary Artery During Resection of a Dorsal Spinal Meningioma.

Arterial supply of the spinal cord is derived from the anterior spinal artery (ASA) and 2 posterior spinal arteries. In the thoracic spine, a few segmental arteries give origins to radiculomedullary arteries (RMAs) that supply the ASA and posterior spinal arteries.1 In the lower thoracic spine, the supply is provided by the Adamkiewicz artery. Spinal meningiomas may be embedded and/or supplied by the RMA, which may be sacrificed to obtain complete resection. Safety of the thoracic RMA occlusion is controversial,2 especially if the Adamkiewicz artery is involved.3 Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEP) are proposed to detect spinal cord ischemia.4 The RMA supplies the anterior spinal cord, and MEPs seem to be more sensitive than SSEPs to test RMA occlusion.2 SSEP and MEP monitoring during temporary occlusion has been described and significantly changes at 2 and 7 minutes of occlusion.5-8 Safe occlusion with unchanged MEPs after 10-minute temporary occlusion of 32 segmental arteries was reported by Salame et al.9 We intraoperatively discovered an anterior T10 RMA supplying the adjacent meningioma (Video 1). We temporary clipped the artery for 8 minutes. MEPs were recorded before clipping and every 2 minutes. No changes were observed, and the artery was sacrificed. RMA or segmental artery ligature may be required and is frequently performed in deformity, oncologic, and vascular spine surgery. The clipping test with MEP monitoring is a useful and simple intraoperative tool to identify the critical afferents of the ASA. It doesn't require planification or supplementary materials. Further study might be performed to validate the technique.