Bionate® nucleus disc replacement: bench testing comparing two different designs.

BACKGROUND: Intervertebral disc nucleus degeneration initiates a degenerative cascade and can induce chronic low back pain. Nucleus replacement aims to replace the nucleus while the annulus is still intact. Over time, several designs have been introduced, but the definitive solution continues to be elusive. Therefore, we aimed to create a new nucleus replacement that replicates intact intervertebral disc biomechanics, and thus has the potential for clinical applications. MATERIALS AND METHODS: Two implants with an outer ring and one (D2) with an additional midline strut were compared. Static and fatigue tests were performed with an INSTRON 8874 following the American Society for Testing and Materials F2267-04, F2346-05, 2077-03, D2990-01, and WK4863. Implant stiffness was analyzed at 0-300 N, 500-2000 N, and 2000-6000 N and implant compression at 300 N, 1000 N, 2000 N, and 6000 N. Wear tests were performed following ISO 18192-1:2008 and 18192-2:2010. GNU Octave software was used to calculate movement angles and parameters. The statistical analysis package R was used with the Deducer user interface. Statistically significant differences between the two designs were analyzed with ANOVA, followed by a post hoc analysis. RESULTS: D1 had better behavior in unconfined compression tests, while D2 showed a "jump." D2 deformed 1 mm more than D1. Sterilized implants were more rigid and deformed less. Both designs showed similar behavior under confined compression and when adding shear. A silicone annulus minimized differences between the designs. Wear under compression fatigue was negligible for D1 but permanent for D2. D1 suffered permanent height deformation but kept its width. D2 suffered less height loss than D1 but underwent a permanent width deformation. Both designs showed excellent responses to compression fatigue with no breaks, cracks, or delamination. At 10 million cycles, D2 showed 3-times higher wear than D1. D1 had better and more homogeneous behavior, and its wear was relatively low. It showed good mechanical endurance under dynamic loading conditions, with excellent response to axial compression fatigue loading without functional failure after long-term testing. CONCLUSION: D1 performed better than D2. Further studies in cadaveric specimens, and eventually in a clinical setting, are recommended. Level of evidence 2c.

Selective block of grey communicantes in upper thoracic sympathectomy. A feasibility study on human cadaveric specimens.

Background: Sympathetic chain interruption is the gold standard treatment for essential hyperhidrosis. Postoperative compensatory hyperhidrosis, the main reason for patients' dissatisfaction, is reduced by selectively lesioning white and grey rami communicantes (ramicotomy).Objective: To develop an endoscopic surgical technique that interrupts only T3 and T4 grey rami communicantes to minimize compensatory hyperhidrosis.Material and Methods: T3 and T4 grey rami communicantes ramicotomy in fifteen cold-preserved cadavers through a uniportal axillary endoscopic approach. The sympathetic chain, its ganglia, and white rami communicantes were left intact. On opening the chest, the sympathetic chain, rami communicantes and ganglia were dissected, photographed, measured and excised for histological examination.Results: Dissecting the grey rami communicantes is feasible as they consistently lie between the intercostal nerve and the homonymous sympathetic ganglion. At some levels, Kuntz nerves, as well as more than one grey ramus communicans, can be found. White rami communicantes are more medial, therefore damaging them can be avoided. Intercostal veins can be obstructive, but these can be controlled via coagulation or clipping if necessary.Conclusion: Uniportal endoscopic selective excision of the T3 and T4 grey rami communicantes is feasible without damaging the white rami communicantes, the sympathetic chain or its ganglia. Clipping the grey rami communicantes is technically possible but not reliable due to their thin diameter. This study confirms that T3 and T4 grey rami sympathetic block is technically feasible. Its application might reduce compensatory hyperhidrosis, but clinical studies are needed.

High frequency of lumbar fusion in patients denied surgical treatment of the sacroiliac joint.

PURPOSE: Effective treatment of medical conditions relies on proper diagnosis. Clinical trials show the safety and effectiveness of sacroiliac joint (SIJ) fusion in patients with chronic SI joint dysfunction. To what extent is the condition under recognised? OBJECTIVE: To determine whether under recognition of SIJ pain affects healthcare trajectories in Spanish patients with low back pain. METHODS: Retrospective study of characteristics and consequences of 189 patients with persistent SIJ pain seen in an outpatient neurosurgery clinic. RESULTS: Patients with SIJ pain who were denied surgical treatment had a longer pain duration, higher likelihood of prior lumbar fusion, and a high rate (63%) of lumbar fusion within 2 years prior to SIJ pain diagnosis, which, in most cases, provided little benefit. CONCLUSIONS: Lack of knowledge of the role of the SIJ in chronic low back pain probably results in diagnostic confusion and may lead to misdirected treatment.

Radial to axillary nerve transfer.

Axillary nerve injury is common after brachial plexus injuries, particularly with shoulder luxation. Nerve grafting is the traditional procedure for postganglionic injuries. Nerve transfer is emerging as a viable option particularly in late referrals. At the proximal arm the radial and axillary nerves lie close by. Sacrificing one of the triceps muscle nerve branches induces little negative consequences. Transferring the long head of the triceps nerve branch is a good option to recover axillary nerve function. The surgical technique is presented in a video, stressing the steps to achieve a successful result. The video can be found here: https://youtu.be/WbVbpMuPxIE .

Can we safely monitor posterior fossa intracranial pressure? A cadaveric study.

BACKGROUND: measuring intracranial pressure (ICP) is considered the gold standard of care for brain injury. While supratentorial ICP monitoring has been adopted everywhere, posterior fossa ICP monitoring is rarely performed. In this study, we aimed to evaluate the feasibility of inserting ICP sensors into the posterior fossa of cadavers, to measure ICP in the posterior fossa. METHODS: An ICP sensor was transcranially implanted into the posterior fossa of fifteen fresh adult cadavers. An extracranial point was defined in the retroauricular area 2 cm behind the tip of the mastoid process and 2 cm below the transverse sinus, in order to implant an ICP probe. The cranial cavity was opened and measures were taken of the distance that the ICP sensor had penetrated inside the posterior fossa, as well as the distance to nearby venous sinuses (lateral, transverse, sigmoid, inferior petrosal sinus, and jugular bulb). The cerebellar hemisphere was searched for any possible damage. RESULTS: the selected extracranial point (2 cm behind the tip of the mastoid process and 2 cm below the transverse sinus) was a safe location. Intracranial structures such as the brainstem and the cerebellar hemisphere were not damaged. The implanted ICP probe was at least 2 cm away from the venous sinuses, which were not damaged. CONCLUSION: ICP monitoring is safe and reliable at the described ICP probe placement site of the posterior fossa.

Biplanar x-ray fluoroscopy for sacroiliac joint fusion.

Chronic pain originating from the sacroiliac joint (SI) can cause severe dysfunction. Although many patients respond to conservative management with NSAIDs, some do need further treatment in the form of SI joint fusion (SIJF). To achieve safe and successful SIJF, intraoperative x-ray fluoroscopy is mandatory to avoid serious damages to nearby vascular and neural structures. Each step of the procedure has to be confirmed by anteroposterior (AP) and lateral projections. With a single-arm x-ray, the arch has to be moved back and forth for the AP and lateral projections, and this lengthens the procedure. To achieve the same results in less time, the authors introduced simultaneous biplanar fluoroscopy with 2 x-ray arches. After the patient is positioned prone with the legs spread apart in the so-called Da Vinci position, one x-ray arch for the lateral projection is placed at a right angle to the patient, and a second x-ray machine is placed with its arch between the legs of the patient. This allows simultaneous AP and lateral x-ray projections and, in the authors' hands, markedly speeds up the procedure. Biplanar fluoroscopy allows excellent AP and lateral projections to be made quickly at any time during the surgical procedure. This is particularly useful in cases of bilateral SI joint fusion if both sides are done at the same time. The video can be found here: https://youtu.be/TX5gz8c765M .

Transdiscal C6-C7 contralateral C7 nerve root transfer in the surgical repair of brachial plexus avulsion injuries.

BACKGROUND: Repair of complete brachial plexus avulsion injuries may require contralateral C7 nerve root transfer. The available techniques might allow direct neuroraphy in about 50 % of cases but the others require interposing nerve grafts or humeral shaft shortening. We aimed to see if transdiscal C6-C7 contralateral C7 nerve root transfer is technically feasible and if it allows direct coaptation with the contralateral nerve roots in 100 % of cases. METHODS: In ten fresh-frozen adult cadavers, the C7 nerve root was sectioned just before it connects with other brachial plexus branches and re-routed though the C6-C7 disc space to the contralateral side. A complete C6-C7 discectomy was performed and the disc space kept open with the aid of an autologous iliac crest bone graft. RESULTS: Transdiscal C6-C7 contralateral C7 nerve root transfer is technically feasible. In our cadavers, it provided 5.3 ± 1.2 SDcm of extra length that allowed direct coaptation with the contralateral nerve roots, mainly C8 and T1. CONCLUSIONS: Transdiscal C6-C7 contralateral C7 nerve root transfer is technically feasible. In our dissections it lengthens the available C7 nerve root stump by 5.3 ± 1.2SDcm. The increase was 4 cm versus the retropharyngeal route making direct coaptation with the contralateral C8 and T1 nerve roots possible.

Higher serum prealbumin levels are associated with higher graft take and wound healing in adult burn patients: A prospective observational trial.

INTRODUCTION: Nutritional support is essential in burn care. There are few studies investigating the effect of nutrition on burn healing. The purpose of this study was to determine the relationship between perioperative serum prealbumin levels and the probability of autologous skin graft take in burned patients. MATERIALS AND METHODS: A prospective observational study was carried out with burned adults recruited consecutively from April 2019 until September 2021. Serum prealbumin was determined perioperatively. The percentage of graft take was evaluated over the first 5 postoperative dressing changes. Time until full epithelialization (absence of wounds) was also registered. RESULTS: A total of 60 patients were recruited, mostly middle-aged people with moderate flame burns. Serum prealbumin levels and graft take had a weak-moderate, nonlinear, statistically significant correlation. They were also an independent predictor of full epithelialization on the fifth dressing change, together with burn depth. Higher perioperative serum prealbumin levels were significantly associated with a reduction in time until full epithelialization. CONCLUSIONS: Perioperative serum prealbumin levels are significantly correlated with the probability of split-thickness skin autograft take in burned patients and with a reduced time to achieve complete epithelialization. They were an independent predictor of full graft take.

Cadaveric biomechanical studies of ADDISC total lumbar disc prosthesis.

BACKGROUND: Most total disc replacements provide excessive mobility and not reproduce spinal kinematics, inducing zygapophyseal joint arthritic changes and chronic back pain. In cadaveric lumbosacral spines, we studied if a new lumbar disc prosthesis kinematics mimics the intact intervertebral disc. METHODS: In eight cold preserved cadaveric lumbosacral spines, we registered the movement ranges in flexion, extension, right and left lateral bending, and rotation in the intact status, post-discectomy, and after our prosthesis implantation, comparing them for each specimen. FINDINGS: Comparing the intact lumbosacral spine with the L4-L5 prosthesis implanted specimens, we saw statistically significant differences in lateral bending and right rotation but not in the full range of rotation. Analyzing segments, we also noticed statistically significant differences at L4-L5 in flexion-extension and rotation. On the other hand, the L4-L5 discectomy, compared to the baseline spine condition, showed a statistically significant mobility increase in flexion, extension, lateral bending, and axial rotation, with an abnormal instantaneous center of rotation, which destabilizes the segment partly due to anterior annulus surgical removal. Disc prosthesis implantation reversed these changes in instantaneous center of rotation, but the prosthesis failed to restore the initial range of motion due to the destabilization of the ligaments in the operated disc. INTERPRETATION: The ADDISC total disc replacement reproduces the intact disc kinematics and Instantaneous Center of Rotation, but the prosthesis fails to restore the initial range of motion due to ligament destabilization. More studies will be necessary to define a technique that restores the damaged ligaments when implanting the prosthesis.

Back Pain: Pathophysiology, Diagnosis, and Treatment.

Although back pain is one of the most common medical conditions [...].

Barbed Dental Ti6Al4V Alloy Screw: Design and Bench Testing.

BACKGROUND CONTEXT: Dental implants are designed to replace a missing tooth. Implant stability is vital to achieving osseointegration and successful implantation. Although there are many implants available on the market, there is room for improvement. PURPOSE: We describe a new dental implant with improved primary stability features. STUDY DESIGN: Lab bench test studies. METHODS: We evaluated the new implant using static and flexion-compression fatigue tests with compression loads, 35 Ncm tightening torque, displacement control, 0.01 mm/s actuator movement speed, and 9-10 Hz load application frequency, obtaining a cyclic load diagram. We applied variable cyclic loadings of predetermined amplitude and recorded the number of cycles until failure. The test ended with implant failure (breakage or permanent deformation) or reaching five million cycles for each load. RESULTS: Mean stiffness was 1151.13 ± 133.62 SD N/mm, mean elastic limit force 463.94 ± 75.03 SD N, and displacement 0.52 ± 0.04 SD mm, at failure force 663.21 ± 54.23 SD N and displacement 1.56 ± 0.18 SD mm, fatigue load limit 132.6 ± 10.4 N, and maximum bending moment 729.3 ± 69.43 mm/N. CONCLUSIONS: The implant fatigue limit is satisfactory for incisor and canine teeth and between the values for premolars and molars for healthy patients. The system exceeds five million cycles when subjected to a 132.60 N load, ensuring long-lasting life against loads below the fatigue limit.

ADDISC lumbar disc prosthesis: Analytical and FEA testing of novel implants.

The intact intervertebral disc is a six-freedom degree elastic deformation structure with shock absorption. "Ball-and-socket" TDR do not reproduce these properties inducing zygapophyseal joint overload. Elastomeric TDRs reproduce better normal disc kinematics, but repeated core deformation causes its degeneration. We aimed to create a new TDR (ADDISC) reproducing healthy disc features. We designed TDR, analyzed (Finite Element Analysis), and measured every 500,000 cycles for 10 million cycles of the flexion-extension, lateral bending, and axial rotation cyclic compression bench-testing. In the inlay case, we weighted it and measured its deformation. ADDISC has two semi-spherical articular surfaces, one rotation centre for flexion, another for extension, the third for lateral bending, and a polycarbonate urethane inlay providing shock absorption. The first contact is between PCU and metal surfaces. There is no metal-metal contact up to 2000 N, and CoCr28Mo6 absorbs the load. After 10 million cycles at 1.2-2.0 kN loads, wear 140.96 mg (35.50 mm3), but no implant failures. Our TDR has a physiological motion range due to its articular surfaces' shape and the PCU inlay bumpers, minimizing the facet joint overload. ADDISC mimics healthy disc biomechanics and Instantaneous Rotation Center, absorbs shock, reduces wear, and has excellent long-term endurance.

Finite Element Analysis of a Bionate Ring-Shaped Customized Lumbar Disc Nucleus Prosthesis.

Study design: Biomechanical study of a nucleus replacement with a finite element model. Objective: To validate a Bionate 80A ring-shaped nucleus replacement. Methods: The ANSYS lumbar spine model made from lumbar spine X-rays and magnetic resonance images obtained from cadaveric spine specimens were used. All materials were assumed homogeneous, isotropic, and linearly elastic. We studied three options: intact spine, nucleotomy, and nucleus implant. Two loading conditions were evaluated at L3-L4, L4-L5, and L5-S1 discs: a 1000 N axial compression load and this load after the addition of 8 Nm flexion moment in the sagittal plane plus 8 Nm axial rotation torque. Results: Maximum nucleus implant axial compression stresses in the range of 16-34 MPa and tensile stress in the range of 5-16 MPa, below Bionate 80A resistance were obtained. Therefore, there is little risk of permanent implant deformation or severe damage under normal loading conditions. Nucleotomy increased segment mobility, zygapophyseal joint and end plate pressures, and annulus stresses and strains. All these parameters were restored satisfactorily by nucleus replacement but never reached the intact status. In addition, annulus stresses and strains were lower with the nucleus implant than in the intact spine under axial compression and higher under complex loading conditions. Conclusions: Under normal loading conditions, there is a negligible risk of nucleus replacement, permanent deformation or severe damage. Nucleotomy increased segmental mobility, zygapophyseal joint pressures, and annulus stresses and strains. Nucleus replacement restored segmental mobility and zygapophyseal joint pressures close to the intact spine. End plate pressures were similar for the intact and nucleus implant conditions under both loading modes. Manufacturing customized nucleus implants is considered feasible, as satisfactory biomechanical performance is confirmed.

Bionate Biocompatibility: In Vivo Study in Rabbits.

Response to foreign materials includes local tissue reaction, osteolysis, implant loosening, and migration to lymph nodes and organs. Bionate 80A human explants show minor wear and slight local tissue reaction, but we do not know the response at the spinal cord, nerve roots, lymph nodes, or distant organs. This study aims to figure out reactions against Bionate 80A when implanted at the spinal epidural space of 24 20-week-old New Zealand white rabbits. In one group of 12 rabbits, we implanted Bionate 80A on the spinal epidural space, and another group of 12 rabbits was used as the control group. We studied tissues, organs, and tissue damage markers on blood biochemistry, urine tests, and necropsy. The animals' clinical parameters and weight showed no statistically significant differences. At 3 months, the basophils increased slightly in the implant group, platelets decreased in all, and at 6 months, implanted animals showed slight eosinophilia, but none of these changes was statistically significant. External, organ, and spinal tissue examination showed neither toxic reaction, inflammatory changes, or noticeable differences between groups or survival periods. Under microscopic examination, the Bionate 80A particles induced a chronic granulomatous response always outside the dura mater, with giant multinucleated cells holding phagocytized particles and no particle migration to lymph nodes or organs. Thus, it was concluded that Bionate particles, when implanted in the rabbit lumbar epidural space, do not generate a significant reaction limited to the surrounding soft tissues with giant multinucleated cells. In addition, the particles did not cross the dura mater or migrate to lymph nodes or organs.

Bionate Lumbar Disc Nucleus Prosthesis: Biomechanical Studies in Cadaveric Human Spines.

DESIGN: cadaveric spine nucleus replacement study. OBJECTIVE: determining Bionate 80A nucleus replacement biomechanics in cadaveric spines. METHODS: in cold preserved spines, with ligaments and discs intact, and no muscles, L3-L4, L4-L5, and L5-S1 nucleus implantation was done. Differences between customized and overdimensioned implants were compared. Flexion, extension, lateral bending, and torsion were measured in the intact spine, nucleotomy, and nucleus implantation specimens. Increasing load or bending moment was applied four times at 2, 4, 6, and 8 Nm, twice in increasing mode and twice in decreasing mode. Spine motion was recorded using stereophotogrammetry. Expulsion tests: cyclic compression of 50-550 N for 50,000 cycles, increasing the load until there was extreme flexion, implant extrusion, or anatomical structure collapse. Subsidence tests were done by increasing the compression to 6000 N load. RESULTS: nucleotomy increased the disc mobility, which remained unchanged for the adjacent upper level but increased for the lower adjacent one, particularly in lateral bending and torsion. Nucleus implantation, compared to nucleotomy, reduced disc mobility except in flexion-extension and torsion, but intact mobility was no longer recovered, with no effect on upper or lower adjacent segments. The overdimensioned implant, compared to the customized implant, provided equal or sometimes higher mobility. Lamina, facet joint, and annulus removal during nucleotomy caused more damaged than that restored by nucleus implantation. No implant extrusion was observed under compression loads of 925-1068 N as anatomical structures collapsed before. No subsidence or vertebral body fractures were observed under compression loads of 6697.8-6812.3 N. CONCLUSIONS: nucleotomized disc and L1-S1 mobility increased moderately after cadaveric spine nucleus implantation compared to the intact status, partly due to operative anatomical damage. Our implant had shallow expulsion and subsidence risks.

Reporting ChAracteristics of cadaver training and sUrgical studies: The CACTUS guidelines.

INTRODUCTION: Recent systematic reviews highlighted increasing use of cadaveric models in the surgical training, but reports on the characteristics of the models and their impact on training are lacking, as well as standardized recommendations on how to ensure the quality of surgical studies. The aim of our survey was to provide an easy guideline that would improve the quality of the studies involving cadavers for surgical training and research. METHODS: After accurate literature review regarding surgical training on cadaveric models, a draft of the CACTUS guidelines involving 10 different items was drawn. Afterwards, the items were improved by questionnaire uploaded and spread to the experts in the field via Google form. The guideline was then reviewed following participants feedback, ergo, items that scored between 7 and 9 on nine-score Likert scale by 70% of respondents, and between 1 and 3 by fewer than 15% of respondents, were included in the proposed guideline, while items that scored between 1 and 3 by 70% of respondents, and between 7 and 9 by 15% or more of respondents were not. The process proceeded with Delphi rounds until the agreement for all items was unanimous. RESULTS: In total, 42 participants agreed to participate and 30 (71.4%) of them completed the Delphi survey. Unanimous agreement was almost always immediate concerning approval and ethical use of cadaver and providing brief outcome statement in terms of satisfaction in the use of the cadaver model through a short questionnaire. Other items were subjected to the minor adjustments. CONCLUSION: 'CACTUS' is a consensus-based guideline in the area of surgical training, simulation and anatomical studies and we believe that it will provide a useful guide to those writing manuscripts involving human cadavers.

Selective T3-T4 sympathicotomy versus gray ramicotomy on outcome and quality of life in hyperhidrosis patients: a randomized clinical trial.

Compensatory hyperhidrosis is the leading cause of patients' dissatisfaction after thoracic sympathicotomy. The study aimed to reduce compensatory hyperhidrosis to increase patients' satisfaction. A prospective randomized study on palmar hyperhidrosis, May 2016-September 2019. Twenty-one patients T3-T4 sympathicotomy and 21 T3-T4 gray ramicotomy. Data prospectively collected. Analysis at study's end. Focus on the sweating, temperature, quality of life baseline and postoperatively, compensatory hyperhidrosis, hand dryness, patients' satisfaction, and if they would undergo the procedure again and recommend it. No baseline differences between groups. Hyperhidrosis was controlled postoperatively in all patients. No mortality, serious complications, or recurrences. Sympathicotomy worse postoperative quality of life (49.05 (SD: 15.66, IR: 35.50-63.00) versus ramicotomy 24.30 (SD: 6.02, IR: 19.75-27.25). After ramicotomy, some residual sweating on the face, hands, and axillae. Compensatory sweating worse with sympathicotomy. Satisfaction higher with ramicotomy. Better results with ramicotomy than sympathicotomy regarding hand dryness, how many times a day the patients had to shower or change clothes, intention to undergo the procedure again or recommend it to somebody else, and how bothersome compensatory hyperhidrosis was. T3-T4 gray ramicotomy had better results than T3-T4 sympathicotomy, with less compensatory sweating and higher patients' satisfaction.

ICR in human cadaveric specimens: An essential parameter to consider in a new lumbar disc prosthesis design.

STUDY DESIGN: Biomechanical study in cadaveric specimens. BACKGROUND: The commercially available lumbar disc prostheses do not reproduce the intact disc's Instantaneous centre of Rotation (ICR), thus inducing an overload on adjacent anatomical structures, promoting secondary degeneration. AIM: To examine biomechanical testing of cadaveric lumbar spine specimens in order to evaluate and define the ICR of intact lumbar discs. MATERIAL AND METHODS: Twelve cold preserved fresh human cadaveric lumbosacral spine specimens were subjected to computerized tomography (CT), magnetic resonance imaging (MRI) and biomechanical testing. Kinematic studies were performed to analyse range of movements in order to determine ICR. RESULTS: Flexoextension and lateral bending tests showed a positive linear correlation between the angle rotated and the displacement of the ICR in different axes. DISCUSSION: ICR has not been taken into account in any of the available literature regarding lumbar disc prosthesis. Considering our results, neither the actual ball-and-socket nor the withdrawn elastomeric nucleus models fit the biomechanics of the lumbar spine, which could at least in part explain the failure rates of the implants in terms of postoperative failed back syndrome (low back pain). It is reasonable to consider then that an implant should also adapt the equations of the movement of the intact ICR of the joint to the post-surgical ICR. CONCLUSIONS: This is the first cadaveric study on the ICR of the human lumbar spine. We have shown that it is feasible to calculate and consider this parameter in order to design future prosthesis with improved clinical and biomechanical characteristics.

Variability of Clinical and Angiographic Results Based on the Treatment Preference (Endovascular or Surgical) of Centers Participating in the Subarachnoid Hemorrhage Database of the Working Group of the Spanish Society of Neurosurgery.

OBJECTIVES: Since the introduction of endovascular treatment for cerebral aneurysms, hospitals in which subarachnoid hemorrhage is treated show different availability and/or preferences towards both treatment modalities. The main aim is to evaluate the clinical and angiographic results according to the hospital's treatment preferences applied. METHODS: This study was conducted based on use of the subarachnoid hemorrhage database of the Vascular Pathology Group of the Spanish Neurosurgery Society. Centers were classified into 3 subtypes according to an index in the relationship between endovascular and surgical treatment as: endovascular preference, high endovascular preference, and elevated surgical preference. The clinical results and angiographic results were evaluated among the 3 treatment strategies. RESULTS: From November 2004 to December 2017, 4282 subarachnoid hemorrhage patients were selected for the study: 630 (14.7%) patients from centers with surgical preference, 2766 (64.6%) from centers with endovascular preference, and 886 (20.7%) from centers with high endovascular preference. The surgical preference group obtained the best angiographic results associated with a greater complete exclusion (odds ratio: 1.359; 95% confidence interval: 1.025-1.801; P = 0.033). The surgical preference subgroup obtained the best outcome at discharge (65.45%), followed by the high endovascular preference group (61.5%) and the endovascular preference group (57.8%) (odds ratio: 1.359; 95% confidence interval: 1.025-1.801; P = 0.033). CONCLUSIONS: In Spain, there is significant variability in aneurysm exclusion treatment in aneurysmal subarachnoid hemorrhage. Surgical centers offer better results for both surgical and endovascular patients. A multidisciplinary approach and the maintenance of an elevated quality of surgical competence could be responsible for these results.

S1 Pedicle Subtraction Osteotomy in Sagittal Balance Correction. A Feasibility Study on Human Cadaveric Specimens.

BACKGROUND: A cadaveric feasibility study was carried out. Osteotomies to correct fixed sagittal imbalance are usually performed at L3/ L4. OBJECTIVE: To investigate the feasibility of S1 pedicle subtraction osteotomy to correct spinal deformity and spinopelvic parameters, achieving better results with more limited exposure. The data obtained will allow a fixation construct specific for this osteotomy to be designed. METHODS: S1 pedicle subtraction osteotomy was performed on 12 cadaveric specimens. Baseline and postprocedural computed tomography and biomechanical studies were performed. Data were analyzed with a fixation system SolidWorks model, and the redesigned fixation construct was described and analyzed with an ANSYS model. RESULTS: S1 pedicle subtraction osteotomy is technically feasible. The fixation can be achieved with L4, L5, and iliac screws connected with bars. The system can be reinforced with a polyetheretherketone cage placed anteriorly in the S1 body osteotomy site, a cross-connecting bar, a double iliac screw, or an anterior interbody cage placed at the L5-S1 disc. The fixation strength is improved by angulating the iliac rod channel 10°, adding a semi-sphere to the locking screw contact surface and 2 fins to its saddle. The redesigned construct showed suitable stress and deformation levels, achieving the expected biomechanical requirements. DISCUSSION: Compared with surgery on higher levels, S1 pedicle subtraction osteotomy allows greater correction with shorter fixation, because the osteotomy is performed at a more caudal level, modifying the spinopelvic parameters. CONCLUSIONS: S1 pedicle subtraction osteotomy is technically feasible. Finite element analysis results indicate that it has appropriate biomechanical properties.