Use Of Pedicle Screw Fixation Research Articles

Evaluation of the Efficacy and Safety of FFX Facet Cages Compared With Pedicle Screw Fixation in Patients With Lumbar Spinal Stenosis: A Long-Term Study.

Hybrid retrospective/prospective study. The study evaluated the long-term safety and efficacy of the FFX facet cage versus pedicle screw (PS) fixation in patients with lumbar spinal stenosis (LSS). A previous single-arm study reported on the safety, fusion rate, and patient outcomes associated with the use of the FFX facet cage in patients with lumbar spinal stenosis. There are no long-term studies reporting outcomes with this device compared with the use of pedicle screw fixation. Following a medical records review, subjects meeting the inclusion and exclusion criteria were consented to and enrolled in the prospective arm of the study. CT scans and dynamic X-rays were performed to assess fusion rates, range of motion, and translation. Adverse events during the 2-year post-index procedure were also analyzed. Preoperative and 2+ year Visual Analogue Scale (VAS) back and leg scores and Oswestry Disability Index (ODI) were also obtained. A total of 112 subjects were enrolled with 56 patients included in the PS and FFX groups. Mean age was 63.1±11.2 and 67.1±10.9 years and the mean number of levels operated was 1.8±0.8 and 2.3±1.0, respectively, for the PS and FFX groups. There was no difference between the 2 groups for the primary composite fusion endpoint assessed with the FFX group achieving a 91% bony facet fusion rate. There was also no difference in postoperative complications or adverse events during the 2-year follow-up period. A higher percentage of patients in the PS group (10.7%) required reoperation compared with the FFX group (3.6%). Although both groups experienced significant improvements in VAS and ODI scores versus preoperative assessment, there was no difference between the 2 groups. The present study documents the long-term safety and efficacy of the FFX device in patients with LSS with a reduction in reoperation rate when compared with PS fixation. Level III.

Effect of Pedicle Screw Size on Surgical Outcomes Following Surgery for 412 Adolescent Idiopathic Scoliosis Patients.

Retrospective Review. The objective of this study was to determine differences in surgical and post-operative outcomes in AIS patients undergoing spinal deformity correction surgery using standard or large pedicle screw size. Use of pedicle screw fixation in spinal deformity correction surgery is considered safe and effective. Still, the small size of the pedicle and the complex 3D anatomy of the thoracic spine makes screw placement challenging, with improper pedicle screw fixation leading to catastrophic complications including injuries to nerve roots, spinal cord, and major vessels. Thus, insertion of larger diameter screw sizes has raised concerns amongst surgeons, especially in the pediatric population. AIS patients undergoing PSF between 2013 and 2019 were included. Demographic, radiographic, and operative outcomes collected. Patients in the large screw size group (GpI) received 6.5mm diameter screw sizes at all levels while standard screw size group (GpII) received 5.0 to 5.5mm diameter screw sizes at all levels. Kruskall-Wallis and Fisher's exact test performed for continuous and categorical variables respectively.Subanalyses included (1) screw accuracy in patients with available CT scans, (2) stratified analysis of large- and standard-screw patients with ≥60% flexibility rate, (3) stratified analysis of large- and standard-screw patients with <60% flexibility rate, and (4) matched analysis of large- and standard-screw patients by surgeon and year of surgery. GpI patients experienced significantly higher overall curve correction ( P <0.001), with 87.6% experiencing at least one grade reduction of apical vertebral rotation from preoperative to postoperative visit( P =0.008).Patients with larger screws displayed higher postoperative kyphosis. No patient experienced medial breaching. Large screw sizes have similar safety profiles to standard screws without negatively impacting surgical and perioperative outcomes in AIS patients undergoing PSF. Additionally, coronal, sagittal, and rotational correction is superior for larger-diameter screws in AIS patients.

Morphometric analysis of Lumbar Pedicle in our population based on computed tomography

Background: The use of pedicle screw fixation for management of various spinal disorders has become popular worldwide in recent years. Pedicle screw fixations has implications in spinal fusion by transpedicular screw insertion to achieve stability in various spinal disorders such as, fractures, scoliosis, spondylosis thesis, tumours and iatrogenic or degenerative spinal instability. It is essential for the spine surgeon to have a comprehensive knowledge of the spinal morphometric dimensions since misplacement of the pedicle screw carries significant risk for the patient. It is challenging to perform pedicle screw fixation technically due to complex anatomy. Objective: To assess the lumbar pedicle morphometry in south Indian population based on CT scans. Materials and Methods: The present prospective observational study was carried out by the department of Orthopedics at JSS Medical College, Mysore from November 2018 to September 2020. A total of 100 patients who underwent Computed tomography of lumbar spine and Computed tomography abdomen and pelvis in JSS Hospital, Mysuru during the study period were included in the study. Results: The mean transverse pedicle Isthmus width was the least at L1 level (6.64mm) and highest at L s level (15.66mm). There was significant difference between male and female Vertebral Diameters.

The Use of Crosslinks with Posterior Pedicular Screw Fixation in Lumbar Spondylolisthesis

Abstract Background Pedicle screw instrumentation has gained wide popularity for stabilization of spinal fusions. The use of pedicle screw fixation has increased fusion rates. The placement of segmental pedicle screws and cross-links in short segment posterior pedicle screw constructs has been shown to increase the construct stiffness in some planes. Aim of the Work to evaluate addition of crosslinks to posterior pedicular screw fixation as a modality for surgical management of lumbar spondylolisthesis. Patients and Methods This study included 50 patients with lumbar spondylolisthesis divided into two groups according to the surgical approach used in treatment. One group with Posterolateral fixation by transpedicular screws and rods and the other Group had cross-links added to the posterior construct. Results There was no significant difference in postoperative JOA score between both groups, while comparing mean of preoperative and postoperative JOA scores in each group showed a significant rise of the score in each group after surgery. There was no significant difference in the variables of postoperative sagittal alignment between both groups, while comparing mean of preoperative and postoperative sagittal alignment variables in each group revealed a significant reduction of the disc height percent in both groups, and in slip angle and lumbar lordosis angle in group B. Regarding postoperative rate and degree of improvement in the studied groups, there was no significant difference in the rate and degree of improvement between both groups. Conclusion no appreciable benefit from using cross-links was found in short-segment fixation of lumbar spondylolisthesis, where there’s no or little torsional instability encountered.

Real-time non-radiation-based navigation using 3D ultrasound for pedicle screw placement

BACKGROUND CONTEXT Spinal fusion surgeries increased by 137% between the years 1998–2008 and the requirement will continue to grow as the implications for fusion expand. Furthermore, total hospital charges, excluding charges for readmission, for 3.6 million spinal fusion surgeries, performed between 2001-2010 in United States, were more than $287 billion. Many such cases involved the use of pedicle screw fixation. Screw placement accuracy impacts fusion rate, adjacent level disease, and risk for neurovascular complications. Reported rates for screw misplacement, which required reoperation, were ranging up to 42%. Image guided surgical systems have provided means to improve screw placement accuracy, however, the clinical accuracy requirements for certain levels of spine still exceed the accuracy of current image guided surgical systems. Furthermore, most of these systems are based on the use of intra-operative two-dimensional (2D)/three-dimensional (3D) fluoroscopy imaging which operate with ionizing radiation. Finally, most of the available commercial systems are expensive resulting in a significant capital expense to the hospital, have a steep learning curve, and require new workflow to be established. PURPOSE The purpose of this work is to demonstrate that with improved modeling, segmentation and registration tools real-time 3D ultrasound can be used for spinal imaging and has potential to be used in spinal fusion surgeries. Our long-term goal is the successful integration of 3D ultrasound (US) as a standard of care intra-operative imaging modality for spinal fusion surgeries which has not been achieved so far. STUDY DESIGN/SETTING The computational methods developed during the project period were evaluated on in vivo ultrasound scans collected from healthy individuals. Data collection involved the use of a clinical grade ultrasound machine as well as a point of care wireless ultrasound device. Evaluations were performed against gold standard expert annotations. PATIENT SAMPLE A total of 27 healthy subjects were enrolled during the study. We have also collected retrospective spine CT scans in order to built a statistical spine shape model. OUTCOME MEASURES Evaluation studies were performed by measuring surface localization accuracy, classification accuracy and target registration accuracy. METHODS We have designed new artificial intelligence methods for segmentation, enhancement and classification of spine surfaces from ultrasound data. In order to provide a solution for manual operation of the ultrasound transducer during data collection, we have developed methods, based on deep learning, for automatic guidance of the ultrasound transducer to the correct scan plane. Finally, we have developed a novel machine learning-based point cloud registration method which does not require initialization to start the registration. RESULTS Our proposed methods outperform current state of the art in accuracy, robustness and processing time. For anatomical landmark localization we have obtained 0.1 mm (Standard deviation 0.2 mm) accuracy with a processing time of 54 milliseconds. We achieve submillimeter anatomical landmark localization accuracy. Sensitivity and specificity values for scan plane and vertebrae level classification were greater than 86%. CONCLUSIONS Our specific contribution in this work include: 1) a robust, accurate and fast spine bone enhancement and segmentation method from ultrasound data; 2) a multi-modal intra-operative image fusion strategy which can be applied to different orthopedic procedures as well. Future work will involve validation of our proposed methods on cadaver studies for pedicle screw guidance. The proposed ultrasound-based navigation system can also be used in conjunction with any existing 2D fluoroscopy/CT-nav-based navigation in order to provide additional augmentation and improve the overall accuracy of these systems while reducing the radiation exposure. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Current concepts in level selection for fusion in the adolescent idiopathic scoliosis patient

Over the past several decades, level selection for fusion in the patient with adolescent idiopathic scoliosis (AIS) has evolved alongside technique. Now, with the near ubiquitous use of pedicle screw fixation, selection criteria have changed to minimize the number of levels fused, especially distally in the lumbar spine. With each additional motion segment preserved, it has been suggested that postoperative function can be improved and the risk of degenerative disease down the line may be decreased. Currently, the Lenke classification for AIS is the most widely used system to describe AIS pathology. Understanding where the structural and nonstructural curves are may help determine the extent of fusion required distally. Proximally, shoulder balance is still considered a key consideration for upper instrumented vertebra (UIV) selection. In terms of the lowest instrumented vertebra (LIV), we focus on two key concepts to prevent serious complications such as distal junctional kyphosis (DJK) or adding-on phenomenon: the last touched vertebra (LTV) and the stable sagittal vertebra. In the AP radiograph, identifying the LTV as the LIV may allow the surgeon to save a fusion level without increasing risk of DJK or adding-on. However, one must also consider the sagittal plane; the authors identify the stable sagittal vertebra on the lateral radiograph to help determine the optimal LIV; of these two criteria, the more distal level will be selected to decrease the chance of adverse outcomes.

The use of sublaminar bands in treatment of spinal deformity: an operative technique

Background: Pedicle screws are commonly used in the surgical treatment and correction of spinal deformity. In recent years, polyester bands have been used as adjuncts to pedicle screws and hooks. Currently, the implementation of polyester sublaminar bands in the treatment of pediatric spinal deformity has led to improved results with similar complications as other techniques. This paper further highlights the innovative use of sublaminar bands utilized in a hybrid construct leading to improved results. Furthermore, we describe the surgical technique and indications for sublaminar bands in pediatric spinal deformity. Methods: Innovative sublaminar band hybrid construct description and comparison to current practices regarding surgical indications, complications, and comparative outcomes compared to the use of pedicle screw fixation. Results: The described hybrid sublaminar band implementation further validates the use of hybrid constructs as an innovative method and approach to pediatric spinal deformity. Hybrid constructs with sublaminar band utilization may become more favored in the future as they continue to have a safe track record within the literature and are able to optimize sagittal correction better than an all-pedicle screw construct, all while reducing operative time, blood loss, and radiation exposure. Conclusions: This novel surgical technique of sublaminar band utilization offers a user-friendly procedure with a short learning curve. This technique, if applied in the correct surgical candidates, has been proven to be a successful method of spinal deformity correction in pediatric spinal fusions. Level of Evidence: Level IV.

Therapeutic influence of using intermediate screws or not in short segment navigated percutaneous pedicular screws fixation for thoracolumbar compression fracture

Objective To investigate the therapeutic influence of short segment fixation with navigated percutaneous pedicle screws in the treatment of thoracolumbar compression fracture and whether use of pedicle screw fixation affects the treatment efficacy. Methods A retrospective case control study was conducted on the clinical data of 38 patients with thoracolumbar compression fracture admitted between January 2014 and October 2016. There were 27 males and 11 females, with an average age of 35.9 years (range, 21-59 years). There were 14 cases with injured segment at T12, 14 cases at L1, and 10 cases at L2, all of which were classified as Type A according to AO typing. The patients were divided into screw group (n=22) and non-screw group (n=16). The pedicle screws were placed into the upper and lower adjacent segments of the fracture vertebra or the fracture vertebra by percutaneous fluoroscopy-guided navigation. The operation time, intraoperative blood loss, Visual analogue scale (VAS) before and after operation, anterior vertebral body height, Cobb angle, and complications in two groups were recorded. Results All patients were followed up for 12-30 months, average 15.2 months. No significant differences were found between the screw group and the non-screw group with respect to operation time [(44.7±12.6)minutes vs. (39.3±11.9)minutes] and blood loss [(56.8±13)ml vs. (48.4±11.0)ml](P>0.05). In the screw group, preoperative VAS was (6.7±1.5) points, and VAS at postoperative 1 week, six months and 1 year were (2.3±0.9) points, (1.1±0.3) points and (0.9±0.5)points, respectively (P 0.05). In the screw group, anterior vertebral body height was (59. 5±13.6)% preoperatively, and anterior vertebral body height at postoperative 1 week, six months and 1 year was (90.6±7.7)%, (89.3±8.3)% and (88.4±7.9)% (P 0.05). In the screw group, preoperative Cobb angle was (15.6±4.1)° , and Cobb angle at postoperative 1 week, six months and 1 year was (3.0±1.8)°, (5.0±1.9)° and (5.9±1.8)°, respectively (P 0.05). No spinal cord injuries because of pedicle screws were observed after operation in both groups. Conclusions For thoracolumbar compression fracture, short segment fixation with navigated percutaneous pedicle screws has the advantages of shorter operation time, less bleeding, better postoperative pain relief, and fewer complications. In addition, the postoperative VAS, anterior vertebral body height and sagittal Cobb angle are improved significantly. However, use of pedicle screw fixation in fracture vertebra does not have significant influence on the treatment efficacy. Key words: Spinal fractures; Fracture fixation, internal; Pedicle screws

36 - Subaxial cervical pedicle screw fixation: safe zone for screw placement—a systematic review

BACKGROUND CONTEXT: The use of pedicle screw fixation in the cervical spine has been considered an unacceptable risk for intraoperative neurovascular (nerves and blood vessels) injuries due to the proximity of the cervical neurovascular structures to the pedicle.

Unstable thoracolumbar spinal injuries treated by pedicle screw fixation: A short-term evaluation

Context: The incidence of spinal cord injury, especially in thoraco-lumbar junction has increased substantially owing to increase in high energy blunt trauma. Since it tends to affect younger population, they become a huge emotional, social and financial problem to the patient and their families. This study evaluates the use of pedicle screw fixation for preservation of remaining spinal cord function, restoration of spinal alignment, and achievement of pain-free fracture site, early mobilization and maximization of neurological recovery. Aims: Assess functional and radiological outcome after pedicle screw fixation and analysing the complications. Settings and Design: Institution based prospective, longitudinal study. Materials and Methods: Pedicle screw fixation of 10 adult patients with unstable thoraco-lumbar spinal trauma and their follow-up. Statistical Analysis Used: Patients evaluated pre and post operatively, both clinically (ASIA scale) and radiologically at regular intervals. Results: Out of 10 patients, according to the ASIA impairment scale, during pre-operative period, 50% were graded as grade A, 20% as grade B, and 30% as C. During last follow up, grade A was 50%, grade B was 10%, C was 20%, D was 20%. 80% of the patients had shown no complications, only pressure sore (20%) and wound dehiscence (10%) were observed in the study group. Conclusions: Pedicle screw fixation is a better option for early ambulation and recovery. It achieves reduction and stability in both anterior and posterior column injuries. Earlier the intervention better the prognosis. Large scale trials are needed to assess the true magnitude of the problem and their management in the developing world.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 12: pedicle screw fixation as an adjunct to posterolateral fusion.

The utilization of pedicle screw fixation as an adjunct to posterolateral lumbar fusion (PLF) has become routine, but demonstration of a definitive benefit remains problematic. The medical evidence indicates that the addition of pedicle screw fixation to PLF increases fusion rates when assessed with dynamic radiographs. More recent evidence, since publication of the 2005 Lumbar Fusion Guidelines, suggests a stronger association between radiographic fusion and clinical outcome, although, even now, no clear correlation has been demonstrated. Although several reports suggest that clinical outcomes are improved with the addition of pedicle screw fixation, there are conflicting findings from similarly classified evidence. Furthermore, the largest contemporary, randomized, controlled study on this topic failed to demonstrate a significant clinical benefit with the use of pedicle screw fixation in patients undergoing PLF for chronic low-back pain. This absence of proof should not, however, be interpreted as proof of absence. Several limitations continue to compromise these investigations. For example, in the majority of studies the sample size is insufficient to detect small increments in clinical outcome that may be observed with pedicle screw fixation. Therefore, no definitive statement regarding the efficacy of pedicle screw fixation as a means to improve functional outcomes in patients undergoing PLF for chronic low-back pain can be made. There appears to be consistent evidence suggesting that pedicle screw fixation increases the costs and complication rate of PLF. High-risk patients, including (but not limited to) patients who smoke, patients who are undergoing revision surgery, or patients who suffer from medical conditions that may compromise fusion potential, may appreciate a greater benefit with supplemental pedicle screw fixation. It is recommended, therefore, that the use of pedicle screw fixation as a supplement to PLF be reserved for those patients in whom there is an increased risk of nonunion when treated with only PLF.

Do Multilevel Ponte Osteotomies in Thoracic Idiopathic Scoliosis Surgery Improve Curve Correction and Restore Thoracic Kyphosis?

To compare the routine use of posterior-based (Ponte) osteotomies to complete inferior facetectomies in thoracic idiopathic scoliosis. Hypokyphosis is common in thoracic adolescent idiopathic scoliosis. The use of pedicle screw fixation in deformity correction can exacerbate this hypokyphosis. We hypothesized that by utilizing posterior-based Ponte osteotomies rather than facetectomies, we could improve coronal plane correction and decrease the loss of kyphosis during curve correction. The radiographs and clinical charts of patients with idiopathic scoliosis (Lenke types I, II) who underwent isolated thoracic posterior spinal fusion utilizing primarily pedicle screw constructs from January 2008 to August 2010 were reviewed. Maximum preoperative Cobb angle, thoracic kyphosis (T5-T12), levels instrumented, number of posterior-based osteotomies, operative time, estimated blood loss, and postoperative residual coronal Cobb angle and kyphosis were recorded. Operative time per level, blood loss per level, percent main curve correction, and change in thoracic kyphosis was calculated. Patients having undergone complete inferior facetectomies and those with multilevel Ponte osteotomies were then compared. Eighteen patients underwent posterior spinal fusion with osteotomies and 19 patients had complete inferior facetectomies during this time period. The osteotomy cohort had a larger preoperative Cobb angle [59±10 vs. 52±8 (mean±SD); P=0.03]. No difference was observed in the preoperative kyphosis (22±15 vs. 25±12) or in levels fused (9±1 vs. 8±1). Patients with routine osteotomies had them performed at 76% of the levels instrumented. No significant difference was found in terms of percentage of coronal plane correction (84% in both groups), average postoperative kyphosis 28±8 versus 25±7, or the change in kyphosis 6±14 versus 0±2 degrees, in the osteotomy and the facetectomy groups, respectively. Estimated blood loss per level was significantly higher in the osteotomy group (97±42 mL vs. 66±25 mL; P=0.01) as was time per level 31±5 versus 23±3 minutes/level (P<0.001). This study shows a significantly higher blood loss and operative time associated with the use of routine posterior osteotomies in the thoracic spine without a significant improvement in coronal or sagittal correction.

Impact of Pedicle Screw Fixation on Loss of Deformity Correction in Patients With Adolescent Idiopathic Scoliosis

Loss of coronal correction has been reported in the presence of a solid posterior fusion mass in patients who are skeletally immature. Significant increases in postoperative coronal curvature are typically attributed to the presence of pseudarthrosis, loss of instrumentation fixation, or adding-on. We evaluated the clinical and radiographic factors associated with a loss of correction that was not attributed to these etiologies as well as the impact of pedicle screw fixation on loss of correction. A prospective, longitudinal study database was retrospectively queried for patients with at least 2 years of follow-up who underwent surgery for adolescent idiopathic scoliosis. Loss of correction was defined (1) clinically, as a >5 degree increase in the inclinometer reading at any time interval after surgery, excluding preoperative values; or (2) radiographically, as an increase of ≥ 10 degrees in the coronal Cobb angle of an instrumented curve. Patients with pseudarthrosis, adding-on, or loss of fixation were excluded. Ninety-three of 800 patients (11.6%) had loss of deformity correction. Twenty-one patients (2.5%) had >5 degrees of inclinometer change and 76 patients (9.5%) had ≥10 degrees of Cobb change, with a mean loss of 10.85±4.2 degrees. When comparing pedicle screw constructs only, 10% of patients developed loss of correction as opposed to 20% of the patients with hybrid constructs (P=0.036). Factors associated with loss of correction were: age, hybrid construct, magnitude of thoracic curve, thoracic apical translation, and T1 tilt angle. This study reports a high percentage of loss of coronal correction (12%) after 2 years of follow-up that was not associated with infection, adding-on, or apparent pseudarthrosis. Larger magnitude thoracic curves with apical deviation and hybrid constructs were associated with an increased likelihood of loss of curve correction where use of pedicle screw fixation seems to decrease its incidence. III.

Use of All-pedicle-screw Constructs in the Treatment of Adolescent Idiopathic Scoliosis

All-pedicle-screw constructs are safe and biomechanically advantageous in the management of adolescent idiopathic scoliosis. Safe and reproducible placement of thoracic pedicle screws is dependent on a thorough understanding of normal and abnormal anatomy, meticulous technique, and the use of neuromonitoring and fluoroscopy. Improvement in the biomechanical properties secondary to the use of pedicle screw fixation has led to shorter fusions with improved deformity correction. Coronal, sagittal, and rotational correction is superior to that obtained with hook instrumentation. Improved derotation may decrease the need for thoracoplasty, thus eliminating the risk of associated morbidity. Superior control of the deformity with all-pedicle-screw fixation, as well as the use of adjunctive posterior releases, often obviates the need for an anterior approach, even in severe curves measuring 70 degrees to 100 degrees . Improved correction, shorter fusion, and the lower morbidity associated with posterior-only approaches may compensate for higher implant costs.

Is instrumented pedicle fixation of the lumbar vertebrae used on too large a scale?--thoughts on indication

The use of pedicle screw fixation can be considered as a mile-stone in developments in spinal surgery in the past decade because of its benefits in the field of correction of spinal deformities due to scoliosis, following fractures, in the treatment of spinal tumours and in some cases of spondylolisthesis. Their widest use, however, has been in the treatment of degenerative disc disease for which its continued use--not only because of a higher morbidity--must be brought into question.

Imaging Assessment of Lumbar Pedicle Screw Placement

This is a diagnostic study in which cadavers were evaluated by imaging and dissection after pedicle screw placement. This study was designed to evaluate the accuracy of plain radiographs and/or CT in determining pedicle instrumentation. One biomechanical advantage provided by pedicle screws fixation is improved fusion rates. The accuracy of pedicle screw placement has relied on radiograph and CT. Our goal is to evaluate the accuracy of these methods. Cadaveric lumbar spines were exposed by a posterior approach. Titanium pedicle screws were inserted. Radiographs and CTs were obtained. The spines were then dissected to examine screw location. A blinded examiner reviewed the imaging. Screws were considered misaligned if they were extrapedicular or had evidence of cortical perforation. The sensitivity of radiographs, CT, and combined is 93.9%, 94%, and 98.7%, respectively. The specificity of radiograph, CT, and combined is 12.5%, 36.7%, and 40.7%, respectively. The positive predictive value for radiograph, CT, and combined is 83.2%, 88.1%, and 90.4%, respectively. The negative predictive value for radiograph, CT, and combined is 30.8%, 55.9%, and 84.6%, respectively. The accuracy of radiograph, CT, and combined is equal to 79.4%, 84.4%, and 90%, respectively. Patients who present with significant complaints of pain or neurologic deficits, optimal determination of pedicle screw positions is with the combination of radiographs and CT. Furthermore, routine evaluation of patients' status post pedicle screw fixation can be reliable obtained with radiographs. The biomechanical advantage of pedicle screw fixation has improved fusion rates and diminished the number of levels required for stability. Despite the widespread clinical use of pedicle screw fixation, there is relatively little literature concerning accuracy. This study was designed to evaluate the accuracy of plain radiographs and/or CT in determining the proper position of pedicle screws.

Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 12: pedicle screw fixation as an adjunct to posterolateral fusion for low-back pain

This review focused on an examination of the literature on the surgical treatment of low-back pain in patients with DDD or low-grade degenerative spondylolisthesis treated with PLF, with or without the use of pedicle screw fixation. All Class I and the majority of Class II and Class III medical evidence on this topic indicates that the addition of pedicle screw fixation to PLF increases fusion success rates when assessed based on plain x-ray films with dynamic imaging. Although there does appear to be a positive relationship between radiographic fusion and clinical outcome, no convincing correlation has been demonstrated. Although several reports suggest that clinical outcomes are improved with the addition of pedicle screw fixation, there are conflicting findings from similarly classified evidence sources (primarily Class II and III). Furthermore, the largest contemporary randomized controlled study on this topic failed to demonstrate a significant beneficial effect for the use of pedicle screw fixation in patients treated with PLF for chronic low-back pain. This absence of proof should not, however, be interpreted as a proof of absence. For example, in this same study, patient satisfaction scores improved from approximately 60% to approximately 70% with the addition of pedicle screw fixation. This difference in outcome may be clinically relevant. Similarly, the improvement in ODI scores was 40% greater in the group of patients treated with pedicle screw fixation compared with those treated with PLF alone. If an analysis to determine the sample size necessary to ensure a power of 0.8 (or an 80% chance of detecting a significant effect) in a study in which the good outcome rate is 60% in the control group and 70% in the treatment group is performed, approximately 355 patients would be needed in each treatment group (http://department.obg.cuhk.edu.hk). Alternatively, if a similar analysis is performed using the differential scores obtained in the ODI measurements reported in the paper by Fritzell, et al., approximately 225 patients would be needed per treatment group (http://calculators.stat.ucla.edu/powercalc). Although Fritzell, et al., did not detect a significant benefit associated with the use of pedicle screw fixation as an adjunct to PLF, their sample size severely limited the power of their study to detect such a benefit. All studies reviewed suffer from similar lack of power. Therefore, no definitive statement regarding the efficacy of pedicle screw fixation as a means to improve functional outcomes in patients undergoing PLF for chronic low-back pain can be made. There appears to be consistent evidence suggesting that pedicle screw fixation increases the costs and complication rate of PLF. It is recommended, therefore, that the use of pedicle screw fixation as a supplement to PLF be reserved for those patients in whom there is an increased risk of nonunion when treated with PLF. High-risk patients include, but are not limited to patients who smoke, who are undergoing revision surgery, or who suffer systemic diseases known to be associated with poor bone healing.

Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 9: fusion in patients with stenosis and spondylolisthesis

The best medical evidence available in the literature confirms the utility of fusion for improving patient outcomes following decompression for stenosis associated with spondylolisthesis. The majority of evidence from other studies comparing outcomes after decompression alone or decompression combined with PLF in patients with stenosis and spondylolisthesis also favors the performance of PLF. The medical evidence regarding the use of pedicle screw fixation in this patient population is rated as Class III and is inconsistent. A consistent benefit associated with the use of pedicle screw fixation has been reported in patients with preoperative instability or kyphosis. Iatrogenic instability following decompression is associated with poor outcomes and may also be treated with PLF involving supplemental instrumentation. The precise definition of instability or kyphosis has varied among researchers and requires further study.

Pedicle dimensions of the thoracic and lumbar vertebrae in the Greek population

The aim of this study is to understand the magnitude of the pedicle's diameters for the use of pedicle screw fixation in spinal instrumentation. Pedicle dimensions from T1 to L5 were measured in 16 whole human cadaver spines (eight women and eight men). The mean age at the time of death was 67.2 (range: 59-84 years). The external transverse, the external sagittal, and the internal transverse diameter pedicle widths were measured with electronic calipers both on the right and left pedicles. The widest external transverse diameter was at the L5 level with a mean of 13.61 mm (range: 10.29-16.20 mm). The narrowest external transverse pedicle diameter was at the T5 level with a mean of 5.09 mm (range: 4.10-6.88 mm). The widest external sagittal pedicle diameter was at the T11 level with a mean of 17.02 mm (range: 14.84-19.57 mm), while the narrowest one was at T1 level with a mean of 8.90 mm (range: 7.18-11.37 mm). The maximum internal transverse pedicle diameter was at the L5 level with a mean 8.95 mm (range: 7.10-11.21 mm), while the minimum was at the T5 level with a mean 3.90 mm (range: 3.10-4.82 mm). Statistical significant greater pedicle dimensions were found in males at multiple levels. Pedicle dimensions at the levels from T3 to T8 need preoperative evaluation with computed tomography before the insertion of pedicle screws with diameter more than 5 mm. Pedicles at T12 to L5 levels may accommodate screws of 7 mm diameter.

Saturday, November 2, 2001 2:14–2:57 pm Concurrent Session 6B: Lumbar Fusion Instrumentation/Monitoring: 2:14 Sensitivity and specificity of X-ray and computed tomography in assessing lumbar pedicle screw placement

Purpose of study: The biomechanical advantage of pedicle screw fixation has improved fusion rates and diminished the number of levels required for stability. Despite the widespread clinical use of pedicle screw fixation, there is relatively little literature concerning accuracy. This study was designed to evaluate the accuracy of plain radiographs and/or computed tomography (CT) in determining the proper position of pedicle screws.Methods used: Eighteen fresh human cadaveric specimens had the lumbar spine exposed by a standard posterior approach. Titanium pedicle screws (6.5 mm) were inserted in the standard fashion. The lumbar spines were then dissected out en bloc. Anteroposterior and lateral plain films and CT scans were obtained. The posterior spinal elements and dura were then removed to examine screw location. A different examiner then reviewed the radiographs and CT to determine pedicle screw position. Screws were considered out if there was evidence of cortical perforation or if the screw was extrapedicular.of findings: The sensitivity and specificity of plain radiographs was 84.3% and 28.6%, respectively, and 89.3% and 61.9%, respectively, for CT. The combination of CT and plain radiographs increased the sensitivity and specificity to 99.3% and 100%, respectively. A nonparametric chi squared analysis failed to demonstrate any statistical difference between plain radiographs and CT (p<.05). However, statistical comparison of either CT or plain radiographs to that of both modalities showed a significant difference (p<.05). In addition, the accuracy of either CT or plain radiographs were similar. However, when imaging modalities were combined, the accuracy increased to 99%.Relationship between findings and existing knowledge: There is relatively little literature concerning accuracy of pedicle screw placement. Our study is the first to define, by means of anatomical dissection, sensitivity and specificity of plain radiograph and CT scan.Overall significance of findings: The purpose of our study was to evaluate the ability of either plain radiographs or CT to determine accurately whether a pedicle screw was properly positioned. Our findings indicate that there was no statistical difference between CT and plain radiographs. However, there was a statistically significant difference when both modalities were used together.Disclosures: No disclosures.Conflict of interest: No conflicts.