Underwater versus Closed Drainage System for Surgical Treatment of Chronic Subdural Hematoma.

OBJECTIVES: Chronic subdural hematoma (CDH) is a prevalent condition in neurosurgery. Standard care includes surgical evacuation with drainage of residual subdural cavity. We hypothesized that effective and timely drainage of subdural space may improve clinical and radiological outcomes. This study was conducted to compare the effectiveness of standard closed drainage and underwater drainage. METHODS: Medical data of 300 surgically treated chronic subdural hematoma CDH patients were retrospectively collected and analyzed. The patients were divided into two 2 groups: Group I with underwater drainage, and Group II with closed drainage. Groups were compared in terms of gender, age, complication rates, recurrence rates, seizure rates, and length of hospital stay. RESULTS: Underwater drainage was found superior to closed system by all clinical and radiographic parameters. The recurrence rate was significantly lower in Group I (2%) compared to with Group II (10%). Subdural empyema was observed in 10 patients in Group II and none in Group I. The seizure rate was higher in Group II (18%) compared to with Group I (5%). Postoperative pneumocephalus rates was were 20% in Group I and 54% in Group II. The length of hospital stay was 6±2.6 days in Group I and 8.9±6.1 days in Group II. The length of intensive care unit (ICU) stay was 0.6±1.12 days in Group I and 2.7±5 days in Group II. A minority (5%) of the patients in Group II required reoperation due to recurrence. CONCLUSIONS: The use of underwater system significantly the reduces the rates of pneumocephalus, seizures, infection, and recurrence. Additional benefits are shorter intensive care unit ICU and total hospital stays.

Safety and Efficacy of Posterior Upper Rib Excision and Decompression Technique for Surgical Treatment of Neurogenic Thoracic Outlet Syndrome.

BACKGROUND: There are several approaches used for surgical treatment of neurogenic thoracic outlet syndrome (n-TOS). The posterior upper rib excision and decompression technique is a novel technique that was developed and used by the author for the past 8 years. The purpose of this paper is to report clinical outcomes of patients treated with this approach. METHODS: All patients with n-TOS operated by single surgeon from 2015 to 2023 were retrospectively analyzed. Demographic, clinical, radiologic, surgical, and postoperative data were collected and reported with emphasis on efficacy and complications. The surgical success was evaluated subjectively as excellent, good, fair, poor, and bad. Radiologic data were analyzed to assess the extent of accessory/first rib removal. RESULTS: Eighty procedures were performed in 61 patients with a mean follow-up of 1153 (87-3048) days. The majority (60.7%) of patients were women, with 39.3% being men. In 11 cases (18%) causative factor was bone abnormality. Two patients were previously operated at another centers (3.3%). Total mean subjective improvement rate was 91.5%. More than half (55) of the patients reported "excellent" (>75%) and 6 "good" improvements (50%-75%); no fair, poor, and worse outcomes were reported. Patients reporting "good" outcome had statistically significant shorter follow-ups than the "excellent" group (P < 0.001). Complications included pleural opening, Horner syndrome, and apical hematoma, none of which were permanent. CONCLUSIONS: The posterior upper rib excision and decompression approach provides excellent clinical outcomes in patients with n-TOS. It allows better intraoperative visualization and removal of the first rib and full decompression of the neurovascular bundle.

Inter-Specimen Analysis of Diverse Finite Element Models of the Lumbar Spine.

Over the past few decades, there has been a growing popularity in utilizing finite element analysis to study the spine. However, most current studies tend to use one specimen for their models. This research aimed to validate multiple finite element models by comparing them with data from in vivo experiments and other existing finite element studies. Additionally, this study sought to analyze the data based on the gender and age of the specimens. For this study, eight lumbar spine (L2-L5) finite element models were developed. These models were then subjected to finite element analysis to simulate the six fundamental motions. CT scans were obtained from a total of eight individuals, four males and four females, ranging in age from forty-four (44) to seventy-three (73) years old. The CT scans were preprocessed and used to construct finite element models that accurately emulated the motions of flexion, extension, lateral bending, and axial rotation. Preloads and moments were applied to the models to replicate physiological loading conditions. This study focused on analyzing various parameters such as vertebral rotation, facet forces, and intradiscal pressure in all loading directions. The obtained data were then compared with the results of other finite element analyses and in vivo experimental measurements found in the existing literature to ensure their validity. This study successfully validated the intervertebral rotation, intradiscal pressure, and facet force results by comparing them with previous research findings. Notably, this study concluded that gender did not have a significant impact on the results. However, the results did highlight the importance of age as a critical variable when modeling the lumbar spine.

Advances in CSF shunt devices and their assessment for the treatment of hydrocephalus.

INTRODUCTION: Hydrocephalus is a neurological disorder caused by excessive accumulation of the cerebrospinal fluid (CSF) in the ventricles of the brain. It can be treated by diverting the extra fluid to different parts of the body using a device called a shunt. This paper reviews different shunt devices that are used for this purpose. AREAS COVERED: Shunts have high failure rates either due to infection or mechanical failure, therefore there is still ongoing work to address these two main handicaps. They require additional devices for performance assessment. Here, the paper also reviews different approaches for assessing shunt limitations. Moreover, future prospects are also discussed. EXPERT OPINION: This study shows that shunt devices still remain an important treatment option for hydrocephalus. However, further efforts are required to design more advanced shunts, to eliminate high failure rates in clinical use. Sophisticated sensor systems that can accurately detect and regulate changes in CSF drainage to optimize drainage for individual needs. Moreover, shunt infection problem is still present despite recent improvements such as antibiotic impregnated catheters.

Endoscopic Endonasal Approach to Giant Pituitary Adenomas: Surgical Outcomes and Review of the Literature.

OBJECTIVE: To present the outcomes of endoscopic endonasal surgery for giant pituitary adenomas and discuss the extent of resection to minimize morbidity and mortality. METHODS: We retrospectively reviewed medical records of 44 patients with giant pituitary adenomas who underwent endoscopic endonasal surgery. Clinical presentation, laboratory results, imaging studies, clinical outcomes, extent of resection, and complications were collected and analyzed. Factors affecting long-term outcome according to surgical technique were identified and analyzed. RESULTS: Radical resection (RR) was defined as either gross total resection or near-total resection (90%-100% of the tumor). There were 28 patients (63.6%) who underwent RR, 10 patients (22.7%) who underwent subtotal resection, and 6 patients (13.6%) who underwent partial resection. Visual improvement was achieved in 27 patients (81.8%). Thirteen patients (72.2%) with pituitary dysfunction had improvement in at least 1 preoperative endocrinological dysfunction. RR rates for dumbbell and multilobular tumors were 44.4% and 28.6%, respectively. Surgical complications were observed in 14 (31.8%) patients. Major vascular injury occurred in 3 patients (6.8%). Mean follow-up period was 38.5 months (range, 1-70 months). No patients with RR had recurrence or residual tumor progression. Ten patients (22.7%) received adjuvant radiation therapy after resection. Two patients were reoperated on for tumor regrowth, and 3 patients (including the 2 patients with tumor regrowth) were lost to follow-up. CONCLUSIONS: Long-term follow-up results and low recurrence rate of tumors indicate that RR is effective to decrease morbidity and mortality.

Risk of intervertebral disc joint puncture during lumbar puncture.

OBJECTIVE: Penetration of intervertebral disc joint during lumbar puncture might be unnoticed during procedure. However, accelerated degeneration of the disc joint is a long-term consequence of inadvertent penetration. In this paper, we aimed to demonstrate and evaluate the risk of disc puncture during standard lumbar puncture. PATIENTS AND METHODS: 50 human cadavers were used in this study. Disc puncture risk was assessed by using worst case scenario model. Lumbar puncture was performed in a standard fashion using midline route at L3-4, L4-5 and L5-S1 levels. The needle was advanced until it hit resistance from the bone. Lateral X-ray was used to visualize the needle position. Needle ended up in two possible locations - posterior vertebral body wall and intervertebral disc space. RESULTS: The probability of puncturing the joint was 20 % for L3-4, 38 % for L4-5, 16 % for L5-S1. Total probability of disc penetration was 25 %. Statistical analysis revealed significantly increased risk for performing LP at L4-5 level in comparison with L5-S1 (p = 0.023). CONCLUSION: Lumbar puncture carries significant risk of intervertebral disc penetration. This complication is not realized during the procedure and lead to accelerated joint degeneration.

Surgical Anatomy of the Posterior Intermuscular Approach to the Brachial Plexus.

Background: First rib resection and scalenectomy is a well-established treatment option for thoracic outlet syndrome. The posterior approach is rarely used due to extensive muscle sacrifice resulting in significant procedural morbidity. In this paper, we report the surgical anatomy of modified and less-invasive muscle-sparing posterior approach. Methods: Eleven human cadavers were used in this study. With specific care to preserve muscles' integrity, the brachial plexus was exposed by dissecting through the posterior neck musculature. A muscular triangle was found under the trapezius muscle, which provided direct access to deeper structures. Four anatomical reference points were identified to denote a 3-dimensional space enclosing proximal brachial plexus. Results: A muscular triangle was found under the trapezius muscle in all cadavers. It was bordered infero-medially by rhomboid minor, supero-medially by splenius capitis, and laterally by levator scapula muscles. The inferomedial border (rhomboid) was 55 mm (48-80), superomedial border (splenius capitis) was 60.5 mm (42-89), and the lateral border (levator scapulae) was 99 mm (60-130). A consistent vein was present inside the triangle and could be used as an anatomical landmark. The 4 reference points were C5, T1 intervertebral foramina, transverse tubercle, and scalene tubercle of the first rib. Removal of the first rib could be performed without brachial plexus retraction. The latter was exposed from neural foramina to lateral border of the first rib. Conclusions: The posterior approach provides ample space to for exposure and manipulation with the first rib and proximal brachial plexus.

Surgically Treated Epilepsy due to Developmental Venous Anomaly of the Brain: Case Report and Review of the Literature.

BACKGROUND: A congenital malformation of the brain vessels, developmental venous anomaly (DVA) is considered a benign lesion, requiring no intervention unless symptomatic. Epilepsy is a well-known clinical manifestation of DVA. Successful surgery for DVA-associated epilepsy with has been sporadically reported in the literature; however, in all published cases, the anomaly was left intact along with the accompanying lesion. Here we present a surgical case of DVA located in the vicinity of the motor cortex causing drug-resistant simple partial epilepsy. CASE DESCRIPTION: A 34-year-old man was referred due to medically intractable simple partial seizures. He was found to have DVA anterior to the motor cortex that was surgically removed. Following the surgical resection, the patient's seizures stopped, and there were no long-term complications of the procedure. CONCLUSIONS: DVA removal can be performed in selected cases, but more studies are needed to assess the complication rate.

Initial Results of Using Blood Beta 2 Transferrin as a Marker of the Functional Status of a Shunt.

OBJECTIVE: Ventriculoperitoneal shunt is the most common cerebrospinal fluid diversion procedure to treat hydrocephalus. With the change of physiologic cerebrospinal fluid absorption site from arachnoid granulations to the peritoneum, beta 2 transferrin enters the systemic circulation. Therefore, the detection of beta 2 transferrin in the blood can possibly be used as a noninvasive method to assess the functional status of the shunt. The objective of this study was to study the presence of beta 2 transferrin in patients with functional shunts and in shunts suspected of being malfunctional. METHODS: Blood samples were obtained from a group of 20 patients with functional ventriculoperitoneal shunts, from a control group of 10 age-matched healthy volunteers, and from 8 patients with suspected shunt malfunction (6 ventriculoperitoneal, 2 lumboperitoneal). Blood serum beta 2 transferrin levels were measured by enzyme-linked immunosorbent assay with specific anti-beta 2 transferrin antibodies. RESULTS: The mean age in the ventriculoperitoneal shunt group was 36.5 years (range, 24-50 years). The mean age in the control group was 39.5 years (range, 32-48). There was no statistical difference in age between the groups. Beta 2 transferrin levels were 1.99 ± 1.02 ng/mL in the ventriculoperitoneal shunt group and 0.05 ± 0.02 ng/mL in the control group; the statistical difference was strongly significant (P < 0.001). Patients presenting with suspected shunt malfunction had preoperative low beta 2 transferrin levels (0.10 ± 0.12). Postoperatively, their beta 2 transferrin levels increased to 1.75 ± 0.46 ng/mL, and the difference was statistically significant (P = 0.012). CONCLUSION: Blood beta 2 transferrin can be used as a noninvasive test to assess the functional status of a shunt.

U-shaped Dural Flap: A Simple Method for Transcranial Skull Base Defect Repair-Technical Report.

Accidental anterior skull base defects associated with surgery are difficult to treat. There are several methods for the repair, yet postoperative rhinorrhea can occur despite the closure. A 56-year-old female patient was admitted for the treatment of a paraclinoid internal carotid artery aneurysm. The surgery included removal of the anterior clinoid process, unroofing the optic canal, decompressing the optic nerve, and clipping the aneurysm. During the surgery, the planum sphenoidale was accidentally drilled and the nasal cavity exposed. The dural defect was repaired using a U-flap technique. No postoperative cerebrospinal fluid (CSF) rhinorrhea occurred in the patient, and she was discharged on postoperative day 3. On follow-up examination the patient did not have evidence of CSF leakage.

Cranial and spinal injuries in motorcycle accidents: A hospital-based study.

BACKGROUND: Injuries caused by motorcycle accidents have been reported in several studies with an examination from a general trauma point of view. However, to our knowledge, there is no detailed study specific to central nervous system injuries. This research was focused on central nervous system injuries associated with motorcycle accidents. METHODS: The medical records of 540 patients who were admitted to the emergency department between 2008 and 2016 as the result of a motorcycle accident were retrospectively evaluated. Data were collected from electronic medical records, follow-up forms, and radiological images. Information on patient age, gender, type and site of injury, helmet use, alcohol level, Glasgow Coma Scale score on admission, length of stay in the intensive care unit and hospital, neurological status on discharge, and follow-up was collected and analyzed. RESULTS: A total of 486 of 540 patients (90%) were male, 54 (10%) were female, and the mean age was 31+-18 years (range: 2-85 years, median: 25 years). Cranial injuries were detected in 320 cases (59%). The distribution of cranial injuries was: epidural hemorrhage (12.6%), subdural hemorrhage (15.2%), depressed fracture (10.4%), linear fracture (23%), skull base fracture (5.5%), diffuse axonal injury (9.3%), subarachnoid hemorrhage (25.2%), intracerebral hemorrhage (13.5%), and contusion (26.3%). Spinal fractures were detected in 52 cases (9.6%). Twenty-two (4.07%) of the spinal fractures were observed in the cervical region, 10 (1.85%) in the thoracic region, and 20 (3.7%) in the lumbar region. The mean length of stay in the hospital was 8.2+-4 days and 7 days in the intensive care unit. Sixty-eight patients (12.6%) died. Traumatic cranial entities other than linear fracture were associated with an elevated level of mortality. A Glasgow Coma Scale score of 6 or less was associated with significant mortality (68%). CONCLUSION: A detailed report of motorcycle accident-associated central nervous system injuries is provided. The use of protective equipment, such as helmets, significantly reduced the rate of cerebral injury and death.

Shunt Tapping Versus Lumbar Puncture for Evaluating Cerebrospinal Fluid Infections in a Pediatric Population.

AIM: To compare the results of lumbar puncture (LP) and shunt tapping in pediatric patients with suspected ventriculoperitoneal shunt infection. MATERIAL AND METHODS: Medical records of pediatric patients with suspected shunt infections were retrospectively analyzed. All patients had cerebrospinal fluid samples obtained either via shunt tapping, LP or both. The diagnosis of infection was made when at least one cerebrospinal fluid had positive culture results. The patients with negative cerebrospinal fluid culture results were followed up for at least 6 months to monitor the occurrence of central nervous system infection. RESULTS: There were 20 patients in the study (12 males, 8 females). Cerebrospinal fluid was obtained by shunt tapping in 11, by lumbar puncture in 9 and by both methods in one patient. Thirteen patients [ Shunt tapping: 5/11 (45%), LP: 7/9 (78%), Both: 1) ] were diagnosed with shunt infection on the basis of cerebrospinal fluid culture. Seven patients with negative cerebrospinal fluid culture were found to have infections unrelated to shunts and did not show evidence of cerebrospinal fluid infection during the follow-up period. Although the percentage of detecting the infection was higher in LP group, both groups showed negative predictive value of 100%. CONCLUSION: Both shunt tapping and LP are effective in establishing the diagnosis of shunt infection in suspected patients.

Examination of metal mobilization from a gunshot by scanning acoustic microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma optical emission spectroscopy: a case report.

BACKGROUND: Projectile foreign bodies are known to cause chronic heavy metal toxicity due to the release of metal into the bloodstream. However, the local effect around the metallic object has not been investigated and the main goal of our study is to examine the influence of the object in close proximity of the object. CASE PRESENTATION: A 36-year-old Caucasian woman with one metallic pellet close to her sciatic nerve due to a previous shotgun injury at the gluteal area presented with a diagnosis of recurrent lumbar disk herniation at L4-5 level. A physical examination confirmed chronic neuropathy and she underwent a two-stage surgery. The surgery included removal of the foreign body, followed by discectomy and fusion at the involved level. During the removal of the metallic foreign body, a tissue sample around the pellet and another tissue sample from a remote area were obtained. The samples were analyzed by scanning acoustic microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Lead, chromium, copper, cadmium, iron, manganese, selenium, and zinc elements in tissue, blood, and serum specimens were detected by inductively coupled plasma optical emission spectroscopy. CONCLUSIONS: An acoustic impedance map of the tissue closer to the metallic body showed higher values indicating further accumulation of elements. Energy-dispersive X-ray spectroscopy results confirmed scanning acoustic microscopy results by measuring a higher concentration of elements closer to the metallic body. Scanning electron microscopy images showed that original structure was not disturbed far away; however, deformation of the structure existed in the tissue closer to the foreign body. Element analysis showed that element levels within blood and serum were more or less within acceptable ranges; on the other hand, element levels within the tissues showed pronounced differences indicating primarily lead intoxication in the proximity of the metallic body. We can state that residues of metallic foreign bodies of gunshot injuries cause chronic metal infiltration to the surrounding tissue and induce significant damage to nearby neural elements; this is supported by the results of scanning acoustic microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma optical emission spectroscopy.

Posterior Upper Rib Excision for Neurogenic Thoracic Outlet Syndrome---Feasibility and Early Outcomes.

BACKGROUND: There are several surgical treatment options for neurogenic thoracic outlet syndrome (n-TOS). However, the first rib has been shown to be the common denominator of all TOS forms and the degree of its resection has been shown to correlate with the long-term success. OBJECTIVE: To demonstrate the feasibility of posterior upper rib excision (PURE) and report early outcomes. METHODS: Nine patients presented with signs and symptoms of n-TOS. Preoperative evaluation involved physical and neurological examination, arm visual analog score (VAS), cervical X-ray, magnetic resonance imaging (MRI) of the cervical spine, and brachial plexus MRI. All patients were operated at a single institution by a single surgeon. Postoperatively, clinical and radiological data were collected. RESULTS: There were 2 men and 7 women in the study with 10 procedures performed. The age range was 18 to 45 with mean of 36.6 yr. Mean preoperative arm visual analog scale score was 7.8. The patients underwent posterior upper rib excision (PURE) by a single surgeon. One patient had bilateral surgery. The causes of TOS were fibrous bands, enlarged C7 transverse processes, narrow scalene triangle, and accessory ribs. All patients improved after surgery in terms of arm pain and quality of life. Postoperative mean visual analog scale score was 1.1 at 6 mo. In addition, neurological examination was normal at 6 mo postoperatively and all patients returned to their previous full-time jobs. CONCLUSION: Posterior upper rib excision is a feasible surgical option for n-TOS.

Cerebrospinal Fluid and Hydrocephalus: Physiology, Diagnosis, and Treatment.

BACKGROUND: Cerebrospinal fluid (CSF) is found around and inside the brain and vertebral column. CSF plays a crucial role in the protection and homeostasis of neural tissue. METHODS: Key points on the physiology of CSF as well as the diagnostic and treatment options for hydrocephalus are discussed. RESULTS: Understanding the fundamentals of the production, absorption, dynamics, and pathophysiology of CSF is crucial for addressing hydrocephalus. Shunts and endoscopic third ventriculostomy have changed the therapeutic landscape of hydrocephalus. CONCLUSIONS: The treatment of hydrocephalus in adults and children represents a large part of everyday practice for the neurologist, both in benign cases and cancer-related diagnoses.

Transdiscal mid- and upper thoracic vertebroplasty: first description of 2 exemplary cases.

Kyphoplasty and vertebroplasty are established treatment methods to reinforce fractured vertebral bodies. In cases of previous pedicle screw instrumentation, vertebral body cannulation may be challenging. The authors describe, for the first time, an approach through the adjacent inferior vertebra and disc space in the thoracic spine for cement augmentation. A 78-year-old woman underwent posterior fusion with pedicle screws after vertebrectomy and reconstruction with cement and Steinmann pins for a pathological T-7 fracture. Two months later she developed a compression fracture of the vertebral body at the lower part of the construct, and a vertebroplasty was performed. Because a standard transpedicular route was not available, an inferior transdiscal trajectory was used for the cement injection. A 73-year-old man with a history of rheumatoid arthritis underwent cervicothoracic fusion posteriorly for subluxation. He developed pain in the upper thoracic area, and the authors performed a transdiscal vertebroplasty at T-2. The standard transpedicular route was not possible. The vertebral body was satisfactorily filled up with cement. Clinically both patients benefited significantly in terms of back pain and showed an uneventful follow-up of 3 months. Transdiscal vertebroplasty can achieve good results in the mid- and upper thoracic spine when a standard transpedicular trajectory is not possible, and can therefore be a good alternative in select cases.

Robotics in Neurosurgery: Evolution, Current Challenges, and Compromises.

BACKGROUND: Advances in technology have pushed the boundaries of neurosurgery. Surgeons play a major role in the neurosurgical field, but robotic systems challenge the current status quo. Robotic-assisted surgery has revolutionized several surgical fields, yet robotic-assisted neurosurgery is limited by available technology. METHODS: The literature on the current robotic systems in neurosurgery and the challenges and compromises of robotic design are reviewed and discussed. RESULTS: Several robotic systems are currently in use, but the application of these systems is limited in the field of neurosurgery. Most robotic systems are suited to assist in stereotactic procedures. Current research and development teams focus on robotic-assisted microsurgery and minimally invasive surgery. The tasks of miniaturizing the current tools and maximizing control challenge manufacturers and hinder progress. Furthermore, loss of haptic feedback, proprioception, and visualization increase the time it takes for users to master robotic systems. CONCLUSIONS: Robotic-assisted surgery is a promising field in neurosurgery, but improvements and breakthroughs in minimally invasive and endoscopic robotic-assisted surgical systems must occur before robotic assistance becomes commonplace in the neurosurgical field.

The current testing protocols for biomechanical evaluation of lumbar spinal implants in laboratory setting: a review of the literature.

In vitro biomechanical investigations have become a routinely employed technique to explore new lumbar instrumentation. One of the most important advantages of such investigations is the low risk present when compared to clinical trials. However, the best use of any experimental data can be made when standard testing protocols are adopted by investigators, thus allowing comparisons among studies. Experimental variables, such as the length of the specimen, operative level, type of loading (e.g., dynamic versus quasistatic), magnitude, and rate of load applied, are among the most common variables controlled during spinal biomechanical testing. Although important efforts have been made to standardize these protocols, high variability can be found in the current literature. The aim of this investigation was to conduct a systematic review of the literature to identify the current trends in the protocols reported for the evaluation of new lumbar spinal implants under laboratory setting.

Balancing rigidity and safety of pedicle screw fixation via a novel expansion mechanism in a severely osteoporotic model.

Many successful attempts to increase pullout strength of pedicle screws in osteoporotic bone have been accompanied with an increased risk of catastrophic damage to the patient. To avoid this, a single-armed expansive pedicle screw was designed to increase fixation strength while controlling postfailure damage away from the nerves surrounding the pedicle. The screw was then subsequently tested in two severely osteoporotic models: one representing trabecular bone (with and without the presence of polymethylmethacrylate) and the other representing a combination of trabecular and cortical bone. Maximum pullout strength, stiffness, energy to failure, energy to removal, and size of the resulting block damage were statistically compared among conditions. While expandable pedicle screws produced maximum pullout forces less than or comparable to standard screws, they required a higher amount of energy to be fully removed from both models. Furthermore, damage to the cortical layer in the composite test blocks was smaller in all measured directions for tests involving expandable pedicle screws than those involving standard pedicle screws. This indicates that while initial fixation may not differ in the presence of cortical bone, the expandable pedicle screw offers an increased level of postfailure stability and safety to patients awaiting revision surgery.

Biomechanical comparison of an interspinous fusion device and bilateral pedicle screw system as additional fixation for lateral lumbar interbody fusion.

BACKGROUND: This investigation compares an interspinous fusion device with posterior pedicle screw system in a lateral lumbar interbody lumbar fusion. METHODS: We biomechanically tested six cadaveric lumbar segments (L1-L2) under an axial preload of 50N and torque of 5Nm in flexion-extension, lateral bending and axial rotation directions. We quantified range of motion, neutral zone/elastic zone stiffness in the following conditions: intact, lateral discectomy, lateral cage, cage with interspinous fusion, and cage with pedicle screws. FINDINGS: A complete lateral discectomy and annulectomy increased motion in all directions compared to all other conditions. The lateral cage reduced motion in lateral bending and flexion/extension with respect to the intact and discectomy conditions, but had minimal effect on extension stiffness. Posterior instrumentation reduced motion, excluding interspinous augmentation in axial rotation with respect to the cage condition. Interspinous fusion significantly increased flexion and extension stiffness, while pedicle screws increased flexion/extension and lateral bending stiffness, with respect to the cage condition. Both posterior augmentations performed equivalently throughout the tests except in lateral bending stiffness where pedicle screws were stiffer in the neutral zone. INTERPRETATION: A lateral discectomy and annulectomy generates immediate instability. Stand-alone lateral cages restore a limited amount of immediate stability, but posterior supplemental fixation increases stability. Both augmentations are similar in a single level lateral fusion in-vitro model, but pedicle screws are more equipped for coronal stability. An interspinous fusion is a less invasive alternative than pedicle screws and is potentially a conservative option for various interbody cage scenarios.