Screw Tip Research Articles

Shorter screw lengths in dynamic Dynesys fixation have less screw loosening: From clinical investigation to finite-element analysis.

The dynamic Dynesys Stabilization System preserves lumbar mobility at instrumented levels. This study investigated the effect of screw length on screw loosening (SL) after dynamic Dynesys fixation and screw displacement during lumbar motion, using clinical investigation and finite-element (FE) analysis. Clinical data of 50 patients with degenerative spondylolisthesis treated with decompression and Dynesys fixation in 2011 were analyzed retrospectively. Horizontal sliding displacement and vertical displacement of screw tips at L4 were analyzed postoperatively using displacement-controlled FE analysis at the L4-L5 level with screw lengths 45 (long screw), 36 (median screw), and 27 (short screw), and 6.4 mm in diameter, under flexion, extension, lateral bending, and rotation. In 13 patients (13/50, 26%), 40 screws (40/266, 15%) were loose at mean follow-up of 101.3 ± 4.4 months. Radiographic SL at 35, 40, 45, and 50 mm were 7.7%, 10.7%, 12.1%, and 37.5%, respectively, regardless of the fixation level ( p = 0.009). FE analysis revealed that the long screw model with corresponding longer lever arm had maximal horizontal sliding displacement under all directions and maximal vertical displacement, except for lateral bending. Shorter screws in Dynesys fixation may help avoid dynamic SL. Clinically, 50 mm screws showed the greatest SL and median screw screws demonstrated the least displacement biomechanically.

The ideal site of cement application in cement augmented sacroiliac screw fixation: the biomechanical perspective

PurposeTo compare construct stability of cement augmented sacroiliac screws using two different cementation sites in a biomechanical fragility fracture model of the pelvis.MethodsA fracture model with an incomplete fracture of the sacral ala and complete fracture of the anterior pelvic ring mimicking a FFP IIB fragility fracture of the pelvis was established in five fresh frozen human cadaveric pelvises. Sacral fracture stabilization was achieved with bilateral 7.3 mm fully threaded sacroiliac screws. Cement augmentation was performed at the tip of the screw (body of S1; Group A) on one side, and at the midshaft of the screw (sacral ala; Group B) on the contralateral side. Biomechanical testing was conducted separately on both sides comprising cyclic loading of axial forces transferred through the tested hemipelvis from L5 to the ipsilateral acetabulum. Combined angular displacement in flexion and internal rotation (“gap angle”), angular displacement of the ilium in relation to the screw (“screw tilt ilium”), and screw tip cutout were evaluated.ResultsRelative interfragmentary movements were associated with significantly higher values in group A versus group B for “gap angle” (2.4° vs. 1.4°; p < 0.001), and for “screw tilt ilium” (3.3° vs. 1.4°; p < 0.001), respectively. No significant difference was indicated for screw tip cutout between the two groups (0.6 mm [Group A] vs. 0.8 mm [Group B]; p = 0.376).ConclusionThe present study demonstrated less fragment and screw displacements in a FFP IIB fracture model under physiologic cyclic loading by cement augmentation of sacroiliac screws at the level of the lateral mass compared to the center of vertebral body of S1.

Risk Factors for Allograft Subsidence Following Anterior Cervical Discectomy and Fusion

The purpose this study was to precisely characterize patterns of allograft subsidence following anterior cervical discectomy and fusion (ACDF) utilizing computed tomography scans, determine risk factors for cervical allograft subsidence, and investigate the impact of subsidence on pseudarthrosis rates. We performed a retrospective review of patients undergoing 1-to 3-level ACDF utilizing allograft interbodies with anterior plating between 2011 and 2019. Subsidence measurements were performed by 2 independent reviewers on computed tomography scans obtained 6months postoperatively. Subsidence was then classified as mild if subsidence into the inferior and superior endplates were both ≤2mm, moderate if the worst subsidence into the inferior- or superior endplate was between 2 and 4mm, or severe if the worst subsidence into the inferior- or superior endplate was ≥4mm. Multivariate analysis was performed to identify risk factors for the development of subsidence. We identified 98 patients (152 levels) for inclusion. A total of 73 levels demonstrated mild subsidence (≤2mm), 61 demonstrated moderate subsidence (2-4mm), and 18 demonstrated severe subsidence (≥4mm). On multivariate analysis, risk factors for severe subsidence included excessive vertebral endplate resection and lower screw tip to vertebral body height ratio. Severe subsidence was associated with an increased rate of pseudarthrosis (94.1% vs. 13.6%) without an associated increase in reoperation rate. Following ACDF with allograft interbodies, 50% of interbodies will subside >2mm and 10% of interbodies will subside >4mm. Risk factors for severe subsidence should be mitigated to decrease the risk of pseudarthrosis.

Experimental investigation on screw reinforcement of timber members under compression perpendicular to the grain

This paper investigates the effect of screw reinforcement on the capacity of timber members under compression perpendicular to the grain. The predictions of existing capacity models are compared to the experimental results of 39 timber specimens, distinguished by different load, screw and geometric configurations. Current capacity models assume two failure mechanisms, mainly characterized by their location, i.e. the contact area of the applied load (first mode) or the screw tips (second mode). However, the experimental tests reveal that the second mode never occurs despite the model predicting the occurrence of the second mode in more than half of the tested specimens. Additionally, the experimental tests show the fallacy of existing models in accurately estimating the capacity associated with the second failure mode. Parallely, the model appears to be relatively conservative for the first failure mode.

Fixation stability scoring in inter-trochanteric femur fractures treated with osteosynthesis: A retrospective observational study

To find out the validity of a newly proposed fixation stability scoring system in IT fractures treated with osteosynthesis and its limitations if any.: Retrospective analysis of hospital records of patients with various types of intertrochanteric fractures treated surgically at Sri Siddhartha medical college, Tumkur from January 2021 till August 2022. The exclusion criteria were non-ambulatory patients prior to fall, non surgically treated patients, patients loosing follow up or patients who are not alive at the time of study. The scoring was done by three different observers for each patient’s immediate post operative x-ray, repeated at 1 month interval. Radiographs at the final follow up were assessed for fracture union or fixation failure. Parameters of the scoring system: 1) cortical buttress in AP view radiograph, 2) cortical buttress in lateral view radiograph, 3) Tip apex distance (TAD) of principle lag screw, 4) Entry point (in case of IM nail), 5) Location of tip of principle screw in the desired Cleveland zone. 6) Placement of Richard screw in the inferior half of neck (in case of DHS), 7) Use of additional derotation screw (DRS) (in case of DHS). Scores of all the observers showed statistically significant correlation with fixation failure rates. Results were good with the score of 7.5 and above, fair with 6.5 and above and poor when the score was below 6.5. The minimum acceptable score was 6.5 for extra-medullary devices and 7 for intra-medullary devices.: The newly proposed scoring system appears to be valid and promising intra operative guide for fixation of intertrochanteric fractures with a few limitations. Large scale multi centre prospective studies are needed in the future to support the current study or to further simplify this scoring system.

Cystic duct recanalization with a screw tip stent retriever aids plastic stent delivery in endoscopic transpapillary gallbladder drainage.

Cystic duct recanalization with a screw tip stent retriever aids plastic stent delivery in endoscopic transpapillary gallbladder drainage.

Association between lower Hounsfield units and proximal junctional kyphosis and failure at the upper thoracic spine.

The aim of this study was to analyze risk factors and avoidance techniques for proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in the upper thoracic spine with an emphasis on bone mineral density (BMD) as estimated by Hounsfield units (HU). A retrospective chart review identified patients at least 50 years of age who underwent instrumented fusion extending from the pelvis to an upper instrumented vertebra (UIV) between T1 and T6 and had a preoperative CT, pre- and postoperative radiographs, and a minimum follow-up of 12 months. HU were measured in the UIV, the vertebral body cephalad to the UIV (UIV+1), and the L3 and L4 vertebral bodies. Numerous perioperative variables were collected, including basic demographics, smoking and steroid use, preoperative osteoporosis treatment, multiple frailty indices, use of a proximal junctional tether, UIV soft landing, preoperative dual-energy x-ray absorptiometry, spinopelvic parameters, UIV screw tip distance to the superior endplate, UIV pedicle screw/pedicle diameter ratio, lumbar lordosis distribution, and postoperative spinopelvic parameters compared with age-adjusted normal values. Eighty-one patients were included in the study (21 men and 60 women) with a mean (SD) age of 66 years (6.9 years), BMI of 29 (5.5), and follow-up of 38 months (25 months). Spinal fusion constructs at the time of surgery extended from the pelvis to a UIV of T1 (5%), T2 (15%), T3 (25%), T4 (33%), T5 (21%), and T6 (1%). Twenty-seven patients (33%) developed PJK and/or PJF; 21 (26%) had PJK and 15 (19%) had PJF. Variables associated with PJK/PJF with p < 0.05 were included in the multivariable analysis, including HU at the UIV/UIV+1, HU at L3/L4, DXA femoral neck T-score, UIV screw tip distance to the superior endplate, UIV pedicle screw/pedicle diameter ratio, and postoperative lumbar lordosis distribution. Multivariable analysis (area under the curve = 0.77) demonstrated HU at the UIV/UIV+1 to be the only independent predictor of PJK and PJF with an OR of 0.96 (p = 0.005). Patients with < 147 HU (n = 27), 147-195 HU (n = 27), and > 195 HU (n = 27) at the UIV/UIV+1 had PJK/PJF rates of 59%, 33%, and 7%, respectively. In patients with upper thoracic-to-pelvis spinal reconstruction, lower HU at the UIV and UIV+1 were independently associated with PJK and PJF, with an optimal cutoff of 159 HU that maximizes sensitivity and specificity.

Biomechanical Comparison and Three-Dimensional Analysis of Cement Distribution Patterns for Different Pedicle Screw Designs.

The purpose of this study to explore strategies for reducing cement leakage during cement-augmented pedicle screw fixation, we compared the cement distribution patterns and biomechanical strengths of different types of cement-augmented fenestrated screws and traditional cement-augmented techniques. We compared five screw groups in this study: (1) Cannulated screws (Cann); (2) distal one-hole screws (D1); (3) distal two-hole screws (D2); (4) middle two-hole screws (M2); and (5) traditional screws with a traditional cement injection technique (Trad). The screws were inserted into cancellous bone blocks using a controlled, adequate cement injection pressure (1.6–2.0 kg), and an appropriate cement viscosity. Center to screw tip distance, three-dimensional distribution, and pull-out strength for cement were compared between groups. The average distance between the cement center and the screw tip was highest in the M2 group, suggesting a higher risk of cement leakage into the spinal canal. The Trad group had the highest migration distance in the z-axis, also reflecting a higher risk of leakage into the spinal canal. The D1 group had the highest pull-out strength (253 ± 48.82 N and 797 ± 58.31 N) in bone blocks representing different degrees of osteoporosis, and the D2 group had the second highest pull-out strength in the severe osteoporosis model. Overall, D1 screws appeared to be the best option for optimizing biomechanical function and minimizing the risk of cement leakage into the spinal canal in patients with osteoporotic bone undergoing spinal surgery.

CT-Navigated Spinal Instrumentations-Three-Dimensional Evaluation of Screw Placement Accuracy in Relation to a Screw Trajectory Plan.

Background and Objectives: In the literature, spinal navigation and robot-assisted surgery improved screw placement accuracy, but the majority of studies only qualitatively report on screw positioning within the vertebra. We sought to evaluate screw placement accuracy in relation to a preoperative trajectory plan by three-dimensional quantification to elucidate technical benefits of navigation for lumbar pedicle screws. Materials and Methods: In 27 CT-navigated instrumentations for degenerative disease, a dedicated intraoperative 3D-trajectory plan was created for all screws. Final screw positions were defined on postoperative CT. Trajectory plans and final screw positions were co-registered and quantitatively compared computing minimal absolute differences (MAD) of screw head and tip points (mm) and screw axis (degree) in 3D-space, respectively. Differences were evaluated with consideration of the navigation target registration error. Clinical acceptability of screws was evaluated using the Gertzbein–Robbins (GR) classification. Results: Data included 140 screws covering levels L1-S1. While screw placement was clinically acceptable in all cases (GR grade A and B in 112 (80%) and 28 (20%) cases, respectively), implanted screws showed considerable deviation compared to the trajectory plan: Mean axis deviation was 6.3° ± 3.6°, screw head and tip points showed mean MAD of 5.2 ± 2.4 mm and 5.5 ± 2.7 mm, respectively. Deviations significantly exceeded the mean navigation registration error of 0.87 ± 0.22 mm (p < 0.001). Conclusions: Screw placement was clinically acceptable in all screws after navigated placement but nevertheless, considerable deviation in implanted screws was noted compared to the initial trajectory plan. Our data provides a 3D-quantitative benchmark for screw accuracy achievable by CT-navigation in routine spine surgery and suggests a framework for objective comparison of screw outcome after navigated or robot-assisted procedures. Factors contributing to screw deviations should be considered to assure optimal surgical results when applying navigation for spinal instrumentation.

P45. Titanium cervical cage subsidence: postoperative CT analysis defining incidence and associated risk factors

<h3>BACKGROUND CONTEXT</h3> Substantial variability in both the measurement and classification of subsidence limits the strength of conclusions that can be drawn from previous studies. <h3>PURPOSE</h3> The purpose of this study was to precisely characterize patterns of cervical cage subsidence utilizing computed tomography scans, determine risk factors for cervical cage subsidence and investigate the impact of subsidence on pseudarthrosis rates. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>METHODS</h3> We performed a retrospective review of a patients who underwent one- to three-levels of ACDF utilizing titanium interbodies with anterior plating between the years 2018 to 2020. Subsidence measurements were performed by two independent reviewers on CT scans obtained 6 months postoperatively. Subsidence was then classified as mild if subsidence into the inferior and superior endplate were both ≤2mm, moderate if the worst subsidence into the inferior or superior endplate was between 2 to 4mm, or severe if the worst subsidence into the inferior or superior endplate was ≥4mm. <h3>RESULTS</h3> A total of 51 patients (100 levels) were included in this study. A total of 48 levels demonstrated mild subsidence (<2mm), 38 demonstrated moderate subsidence (2–4mm), and 14 demonstrated severe subsidence (>4mm). Risk factors for severe subsidence included male gender, multilevel constructs, greater mean vertebral height loss, increased cage height, lower Taillard Index, and lower screw tip to vertebral body height ratio. Severe subsidence was not associated with an increased rate of pseudarthrosis. <h3>CONCLUSIONS</h3> Following ACDF with titanium cervical cages, subsidence is an anticipated postoperative occurrence and is not associated with an increased risk of pseudarthrosis. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Deformable 3D-2D image registration and analysis of global spinal alignment in long-length intraoperative spine imaging.

Spinal deformation during surgical intervention (caused by patient positioning and/or the correction of malalignment) confounds conventional navigation due to the assumptions of rigid transformation. Moreover, the ability to accurately quantify spinal alignment in the operating room would provide an assessment of the surgical product via metrics that correlate with clinical outcomes. A method for deformable 3D-2D registration of preoperative CT to intraoperative long-length tomosynthesis images is reported for an accurate 3D evaluation of device placement in the presence of spinal deformation and automated evaluation of global spinal alignment (GSA). Long-length tomosynthesis ("Long Film," LF) images were acquired using an O-arm imaging system (Medtronic, Minneapolis USA). A deformable 3D-2D patient registration was developed using multi-scale masking (proceeding from the full-length image to local subvolumes about each vertebra) to transform vertebral labels and planning information from preoperative CT to the LF images. Automatic measurement of GSA (main thoracic kyphosis [MThK] and lumbar lordosis [LL]) was obtained using a spline fit to registered labels. The "Known-Component Registration" method for device registration was adapted to the multi-scale process for 3D device localization from orthogonal LF images. The multi-scale framework was evaluated using a deformable spine phantom in which pedicle screws were inserted, and deformations were induced over a range in LL ∼25°-80°. Further validation was carried out in a cadaver study with implanted pedicle screws and a similar range of spinal deformation. The accuracy of patient and device registration was evaluated in terms of 3D translational error and target registration error, respectively, and the accuracies of automatic GSA measurements were compared to manual annotation. Phantom studies demonstrated accurate registration via the multi-scale framework for all vertebral levels in both the neutral and deformed spine: median (interquartile range, IQR) patient registration error was 1.1mm (0.7-1.9mm IQR). Automatic measures of MThK and LL agreed with manual delineation within -1.1°±2.2° and 0.7°±2.0° (mean and standard deviation), respectively. Device registration error was 0.7mm (0.4-1.0mm IQR) at the screw tip and 0.9° (1.0°-1.5°) about the screw trajectory. Deformable 3D-2D registration significantly outperformed conventional rigid registration (p<0.05), which exhibited device registration errors of 2.1mm (0.8-4.1mm) and 4.1° (1.2°-9.5°). Cadaver studies verified performance under realistic conditions, demonstrating patient registration error of 1.6mm (0.9-2.1mm); MThK within -4.2°±6.8° and LL within 1.7°±3.5°; and device registration error of 0.8mm (0.5-1.9mm) and 0.7° (0.4°-1.2°) for the multi-scale deformable method, compared to 2.5mm (1.0-7.9mm) and 2.3° (1.6°-8.1°) for rigid registration (p<0.05). The deformable 3D-2D registration framework leverages long-length intraoperative imaging to achieve accurate patient and device registration over the extended lengths of the spine (up to 64cm) even with strong anatomical deformation. The method offers a new means for the quantitative validation of spinal correction (intraoperative GSA measurement) and the 3D verification of device placement in comparison to preoperative images and planning data.

The percutaneous learning curve of 3rd generation minimally-invasive Chevron and Akin osteotomy (MICA)

BackgroundMinimally-invasive Chevron and Akin osteotomy (MICA) represents the third-generation percutaneous hallux valgus surgery which is characterized by an extra-articular osteotomy, stable internal fixation and a high potential for correction. Compared to other percutaneous techniques of the foot, MICA is generally regarded as an advanced and demanding surgical procedure with a flat learning curve. The aim of this study is to analyze a single-surgeons experience with his first 50 consecutive MICA procedures. MethodsBetween May 2018 and February 2021, 50 consecutive MICA procedures performed by the author with the "K-wires-First technique" were prospectively analyzed focusing on surgery duration, number of fluoroscopies, correction results and surgery-associated complications. A modification of the original MICA technique as described by its inaugurators Redfern and Vernois allows the use of a standard-sized C-arm and aims to reduce revison rates and conversion to open surgery by placing the guidewires prior to performing the osteotomy. ResultsThe average surgery time for all MICA procedures was 46.8 min (SD 12.1, range 31–90 min). The average amount of fluoro shots required to perform MICA was n = 126.6 (SD 40.8, range 65–231). Comparing the preoperative and 6-week postoperative radiographs, the IMA decreased after MICA by a mean of 10.8° from 16.2° to 5.4° and the HVA by a mean of 22.1° from 30.6° to 8.5°. One case required intraoperative conversion to open hallux correction. There were 4 feet in three patients with secondary screw removal of the Chevron fixation due to prominent proximal screw tips. ConclusionsAlthough the learning curve of 3rd generation MICA is flat and requires specific training and intensive practice, the rate of complications is not elevated compared to other percutaneous hallux valgus techniques. Strict adherence to the principles of 3rd generation MICA with stable fixation and meticulous intraoperative control of each surgical step helps to reduce surgery-associated complications. The learning curve showed a continous improvement in regard to surgery time and use of fluoroscopy. After 40 procedures, the surgery time consistently dropped under 45 min and required less than 100 fluoro-shots. The modified surgical technique may help reduce Chevron screw mal-positioning when using large C-arm fluoroscopy for this procedure.

Dorsal Fixation of Coronal Hamate and Fifth Metacarpal Base Fractures: An Anatomic Evaluation of the Ulnar Nerve

Traumatic drill overshoot during dorsal fixation of coronal hamate and fifth metacarpal base fractures risks iatrogenic ulnar nerve injury. This study describes the anatomic relationships between exiting volar drill tips and ulnar nerve branches. Dorsal drilling of hamate bones and fifth metacarpal bases was performed on cadavers. Dorsal hamate bodies were subdivided into 4 quadrants: (1) distal-ulnar, (2) distal-radial, (3) proximal-ulnar, and (4) proximal-radial. Screws measuring 5 mm more than the dorsal-to-volar bone depths were placed in each quadrant to represent drill exit trajectories with consistent overshoot. A single screw was similarly placed 5 mm distal to the midline articular surface of the dorsal fifth metacarpal base. Distances between estimated drill tips and ulnar nerve branches were measured. Ten cadaver hands were examined. The fifth metacarpal base screw tips directly abutted the ulnar motor branch in 6 hands, and were within 1 mm in 4 hands (mean, 0.4 ± 0.5 mm). Distances from the tips to the ulnar motor and sensory branches were largest in the distal-radial quadrant (11.8 ± 0.8 mm and 9.2 ± 1.9 mm, respectively) and smallest in the proximal-ulnar quadrant (7.3 ± 1.5 mm and 4.3 ± 1.1 mm, respectively). Distances to the ulnar motor and sensory branches were similar between the proximal-ulnar and distal-ulnar quadrants, and between the proximal-radial and distal-radial quadrants. Dorsal drilling of coronal hamate fractures appears to be safe, as volar drill tips are well away from ulnar nerve motor and sensory branches. Distances to ulnar nerve branches are largest, and theoretically safest, with dorsal drilling in the distal-radial hamate. Dorsal drilling of fifth metacarpal base fractures appears to carry a high risk for potential ulnar motor nerve injury. These findings may help minimize potential risks for iatrogenic ulnar nerve injury with dorsal drilling of hamate and fifth metacarpal base fractures.

Experimental study on shear performance of steel-timber screw connectors with grout pockets

The steel-timber composite floor is an environmentally friendly structural form. The shear connectors between the timber and H-steel are the key to designing the steel-timber composite floors, and the strength and ductility of the connection are directly affected by the failure modes of the connectors. A new connection that anchors the screw tips in the grout pockets is presented in this paper. In this connection, the glulam around the screw tip is removed, and the grout is added after the screws have been tightened in the glulam to form a hybrid anchorage of the grout and glulam to the screw. Nine groups of double-shear tests were conducted to investigate the influences of with or without grout pockets, the size of grout pockets, and the row number of connectors on the performance of steel-timber composite connections. Firstly, compared with the common specimens connected by screws, the screw tips were restrained more firmly in specimens with grout pockets. The peak load Fmax, initial stiffness ks,0.4 and ductility D of the specimens with grout pockets were increased by a maximum of 25.2, 55.9 and 33.6%, respectively. Secondly, with the increase in the radius and depth of the grout pockets, the secondary stiffness ks,0.7 and the peak shear capacity Fmax of the specimens increased accordingly. Thirdly, after the screw tips were anchored in the grout pockets, the screws stably exhibited the failure mode of double plastic hinges (model III), achieving active control of the failure modes of the screws. There is a critical ratio of grout anchor length to the total length of the screw (L0/L) such that the tip plastic hinge is close to the grout pocket. In the end, the shear capacity equation for failure mode of double plastic hinges (model III) in Eurocode 5 can be used to calculate the peak capacity of this new connection, and the calculation results have a large safety margin.

Development and validation of an automated planning tool for navigated lumbosacral pedicle screws using a convolutional neural network

Background contextNavigation and robotic systems have been increasingly applied to spinal instrumentation but dedicated screw planning is a time-consuming prerequisite to tap the full potential of these techniques. PurposeTo develop and validate an automated planning tool for lumbosacral pedicle screw placement using a convolutional neural network (CNN) to facilitate the planning process. Study Design/SettingRetrospective analysis and processing of CT and screw planning data randomly selected from a consecutive registry of CT-navigated instrumentations from a single academic institution. Patient SampleData from 179 cases was processed for CNN training and validation (155 for training, 24 for validation) leveraging a total of 1182 screws (1052 for training, 130 for validation). Outcome MeasuresQuantitative and qualitative (Gertzbein-Robbins classification [GR]) validation via comparison of automatically and manually planned reference screws, inter-rater and intra-rater variability. MethodsAnnotated data from CT-navigated instrumentation was used to train a CNN operating in a vertebra instance-based approach employing a state-of-the-art U-Net framework. Internal five-fold cross-validation and external validation on an independent cohort not previously involved in training was performed. Quantitative validation of automatically planned screws was performed in comparison to corresponding manually planned screws by calculating the minimal absolute difference (MAD) of screw head and tip points, length and diameter, screw direction and Dice coefficient. Results were evaluated in relation to inter-rater and intra-rater variability of manual screw planning. ResultsAutomated screw planning was successful in all targeted 130 screws. Compared with manually planned screws as a reference, mean MAD of automatically planned screws was 4.61±2.27 mm for screw head, 3.96±2.19 mm for tip points and 5.51±3.64° for screw direction. These differences were either statistically comparable or significantly smaller when compared with interrater variability of manual screw planning (p>.99 for head point and direction, p=.004 for tip point, respectively). Mean Dice coefficient of 0.61±0.16 indicated significantly greater agreement of automatic screws with the manual reference compared with interrater agreement (Dice 0.56±0.18, p<.001). Automatically planned screws were marginally shorter (MAD 3.4±3.2 mm) and thinner (MAD mean 0.3±0.6 mm) compared with the manual reference, but with statistical significance (p<.0001, respectively). Automatically planned screws were GR grade A in 96.2% in qualitative validation. Planning time was significantly shorter with the automatic approach (0:41 min vs. 6:41 min, p<.0001). ConclusionsWe derived and validated a fully automated planning tool for lumbosacral pedicle screws using a CNN. Our validation showed noninferiority to manual screw planning and provided sufficient accuracy to facilitate and expedite the screw planning process. These results offer a high potential to improve workflows in spine surgery when integrated into navigation or robotic assistance systems.

Pelvic Osteotomy in Patients With Previous Sacral-Alar-Iliac (SAI) Fixation.

Patients with neuromuscular disease are at high risk for developing hip dysplasia and scoliosis. The purpose of this study was to investigate the technical challenges and outcomes of pelvic osteotomy in patients with prior sacral-alar-iliac (SAI) fixation. We reviewed clinical and radiographic records of patients aged 18 years and below who underwent pelvic osteotomy after SAI fixation. We recorded technical challenges during the osteotomy, time from SAI fixation to osteotomy, type of osteotomy, migration index, and distance from the SAI screw to the acetabulum. A 2-sample Wilcoxon rank-sum test was used to assess the data. Nineteen patients were included. Technical challenges were defined as having greater intraoperative fluoroscopy times and noted difficult osteotomy in the operative report. The mean time from SAI fixation to pelvic osteotomy was 2.2±1.5 years. For all 12 Chiari osteotomies, the ilium could not be laterally displaced; however, medial displacement of the distal segment of the osteotomy allowed adequate coverage. All 7 Dega osteotomies were performed by cutting the cortex at the tip of the SAI screw. The screw improved proximal leverage and provided a strong buttress for bone graft. The mean migration index before pelvic osteotomy was 59±19%, and at most recent follow-up was 13±4%. Twelve patients, who had a noted complicated osteotomy, had SAI screws that were ≤1.87 cm ( P <0.01) from the acetabulum and significantly increased intraoperative fluoroscopy time (1.76 vs. 1.18 min, P <0.01). The presence of SAI screws may cause iliac osteotomies to be technically challenging if the tip of the SAI screw is ≤1.87 cm to the acetabulum. When initially implanting SAI screws in neuromuscular patients, surgeons should attempt to place screw tips ∼2 cm from the acetabulum in the event these patients require subsequent pelvic osteotomy. Level IV.

Minimally Invasive (Percutaneous) Pedicle Srews as the Treatment of Choice in Thoracolumbar Spine Fractures

Introduction. Minimally invasive techniques of transpedicular fusion have become very common and seem to displace classical open techniques. Pedicle screws fusion is the procedure of choice in unstable traumatic lumbar and thoracic spine fractures of.Aim. The aim of the study was to answer whether open techniques are still used in injuries or whether they have been completely replaced by MISS.Material and Methods. The manuscript presents an analysis of patients treated in 2017–2021 in the Department of Neurosurgery, Neurotraumatology and Pediatric Neurosurgery of Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University.Results. Based on the analysis of medical documentation, it was found that every case of traumatic thoracolumbar spine fracture in 2017–2021 was treated using minimally invasive techniques. According to the documentation, the last case of using open surgical technique in the case of trauma was in 2016. It was noted that percutaneous techniques dominated the surgical treatment of thoracolumbar spine fractures and replaced the classic techniques in our department, which are used only, in some cases, in treatment of non-traumatic spondylolisthesis.Conclusions. Therefore, percutaneous techniques are currently the procedure of choice in spine injuries fusion in our hospital. The use of percutaneous techniques reduces the surgical traumatization of tissues (it is important to avoid additional traumatization and blood loss in traumatic patients). It has been pointed out that these procedures are performed by neurosurgeons who, in teaching process, used percutaneous techniques often and now prefer this method. The use of percutaneous techniques has important aspect in the field of neurosurgical nursing, because care of the operated area consists in observing few (4–16) smaller wounds, not one long wound (as in classic techniques), and these wounds are located directly above the titanium screw tips, which must under neurosurgical nurse care. (JNNN 2022;11(1):3–7)

Anterior vertebral body tethering for idiopathic scoliosis: how well does the tether hold up?

Durability of outcomes following vertebral body tethering (VBT) is a concern and may be impacted by tether breakage (TB), which has been unstudied in a large cohort. We characterized TB rates and their impact on clinical outcomes in the largest single-surgeon series to date. Inclusion criteria were VBT patients with AIS, major Cobb angle ≤ 75°, and minimum 2-year follow-up (FU). TBs were identified on 1- and 2-year FU X-rays. TB rates between single-cord and double-cord tethers were evaluated using two-proportion z test. Curve correction rates and SRS-22 scores between patients with and without TB at 2years were evaluated using Mann-Whitney U test. 69 patients were included. By 2-year FU, 18 (27%) had experienced TB. TB primarily occurred in major (70%) versus minor curves and thoracolumbar tethers (75%) versus thoracic. TB rates between thoracolumbar single (32%) and double-cord tethers (30%) were not significantly different (p = 0.88). Mean major curve correction at 2-year FU was lower (p = 0.02) in patients with major curve TB (48° to 24°, 50%) versus those without (53°-21°, 60%). 2 patients (3%) required reoperation, 1 due to foraminal encroachment from a screw tip and 1 for curve progression with TB. TB rate was 27% at 2years following VBT. Broken major curve tethers are associated with minor loss of correction that may not be clinically significant. TB rates are higher for thoracolumbar curvatures and double cords may not be protective against TB. Further study of long-term TB rates is imperative. IV.

Paravertebral foramen screw fixation for posterior cervical spine surgery: clinical case series.

The goal of this study was to clarify the clinical utility of paravertebral foramen screws (PVFSs) and to determine intraoperative indicators for appropriate screw placement during posterior cervical fusion surgery to improve its safety. The authors included data from 46 patients (29 men and 17 women, mean age 61.7 years) who underwent posterior cervical spine surgery with 94 PVFSs. Of the 94 PVFSs, 77 were used in C6, 9 in C3, 5 in C4, and 3 in C5. According to the cervical lateral radiographic view, the authors divided the 94 PVFSs into 3 groups as follows: a longer group, in which the tip of PVFS was located anteriorly from the line of the posterior wall of the vertebral body (> +0 mm); an intermediate group, in which the screw tip was located up to 2 mm posteriorly to the posterior wall of the vertebral body (-2 to 0 mm); and a shorter group, in which the screw tip was located more than 2 mm posteriorly (< -2 mm). The accuracy of screw placement was assessed using CT imaging in the axial plane, and the proportion of screws penetrating a vertebral foramen or a transverse foramen was compared between the 3 groups. Screw loosening was defined as a lucent zone around the screw evaluated on cervical radiography at 1 year after surgery. Complications related to PVFS insertion and revision surgery related to PVFS were evaluated. The authors classified 25 PVFSs into the longer group, 43 into the intermediate group, and 26 into the shorter group. The proportion of screws penetrating a vertebral foramen was largest in the shorter group, and the proportion penetrating a transverse foramen was largest in the longer group. Screw loosening was confirmed for 3 of 94 PVFSs. One PVFS inserted in C6 unilaterally within a long construct from C2 to C7 showed loosening, but it did not cause clinical symptoms. Revision surgery was required for 2 PVFSs inserted in C3 bilaterally as the lower instrumented vertebra in occiput-cervical fusion because they pulled out. There was no neurovascular complication related to PVFS insertion. PVFSs are useful for posterior cervical fusion surgery as alternative anchor screws, and the line of the posterior wall of the cervical body on lateral fluoroscopic images is a potential intraoperative reference to indicate an appropriate trajectory for PVFSs.

10 Tip-Apex Distance in DHS &amp; IM Nail Fixations for Hip Fractures

Abstract Aim Dynamic hip screws (DHS) and intramedullary nail (IMN) fixations have been successful in treating extracapsular hip fractures. Tip to apex distance (TAD) is defined as the total sum of distance from tip of the lag screw to the femoral head tip on both AP and lateral radiographs. Baumgartner et al. defined TAD&amp;lt;25 mm to be predictive of a successful result, with reduced rates of metalwork failure. Therefore, this study aims to assess if TAD principles are practiced during DHS and IMN fixations. Method 102 patients were identified between December 2019 and February 2020. The distance was measured on AP and lateral radiographs to calculate the TAD. Patients were followed up for 1 year where the fractures either united or failed. Results Patients recruited had age ranges between 19–103 years old, of which 36% are male and 64% are female. 68% had underwent DHS while 32% underwent IM nail. In the DHS group, 13 patients had TAD of &amp;gt;25 mm, 28 with TAD of 20–25 mm, 18 with TAD of 15–20mm and 6 with TAD of &amp;lt;15 mm. For the IM nail group, there are 7 with TAD of 20–25 mm, 13 with TAD of 15–20mm and 10 with TAD of &amp;lt;15 mm. Conclusions There were no IM nails that exceeded TAD of 25mm, but 13 DHS fixations were &amp;gt;25mm. 12/13 DHS fixations &amp;gt;25mm TAD were performed by trainees. We advocate emphasis on the TAD principle and re-enforcing to orthopaedic trainees to improve the outcome of DHS in patients with neck of femur fractures.