Short Fixation Research Articles

How I do it: spine jack expansion kyphoplasty for AO spine A4 complete burst fracture with neurological deficit.

Some patients suffering from thoracolumbar complete burst fracture causing neurological deficit may be eligible for single-stage posterior-only three column reconstruction with spine jack expansion kyphoplasty. Short segment monoaxial pedicle screws are placed. Spine jack working channels are positioned in the comminuted vertebral body. Then, the surgeon can perform jack expansion kyphoplasty and short-segment fixation and distraction in the order best suited, considering whether the collapsed vertebral body has been expanded thanks to hyperlordosis positioning. This strategy allows to regain both native vertebral body height and proper regional sagittal balance. Wide decompression with laminectomy and arthrectomy is necessary at the level of posterior wall recession. Combination of short segment pedicle screw fixation with distraction and open spine jack kyphoplasty is technically feasible and avoids the need for corpectomy in complete burst fractures with neurological deficit.

Resection of Calcified and Giant Thoracic Disc Herniation Through Bilateral Postero-Lateral Approach and 360° Cord Release: A Technical Note

Background/Objectives: Surgical treatment of thoracic disc herniation (TDH) is risky and technically demanding due to its proximity to the spinal cord and the high possibility of the TDH being calcified (up to 40%), making the resection even more complex. Calcified TDH may be resected from an anterior via thoracotomy/thoracoscopy, lateral extra-cavitary, or a postero-lateral approach. Here, we present our experience in managing such pathology with an original technique Methods: This original technique, used successfully in more than 40 patients, is introduced, with a precise description of the surgical anatomy and the surgical steps to take. Indications for surgical management and neurological outcomes are also analyzed. This surgical approach consisted of transverso-pediculectomy, most often bilaterally, partial vertebral body drilling, 360° release of the cord, and short fixation. Results: A total of 44 patients were collected, with a mean age of 52.4 ± 11.7 years. Seven patients (15.9%) had complete calcifications, and thirty-one had partial calcifications (70.5%), while the remaining six did not have signs of calcifications. There were only 4 intraoperative complications (2 dural tears and 2 loss of evoked potentials). The TDH could be resected in total for 39 patients (88.6%) and partially, according to the “floating” technique, in 5 patients (11.4%). In the postoperative follow-up, all of the patients except two (presenting with sensory aggravation) reported an improvement in neurological conditions leading to an overall risk of neurological aggravation of 4.5%. Conclusions: The bilateral postero-lateral approach provides a large decompression of the cord (360°) and gives safe access to the TDH, even calcified, permitting high rates of total resection. It also prevents any prejudicial pressure on the spinal cord, reducing the risk of severe postoperative deficits and permitting optimal instrumentation (pedicle screw-based) of the spinal segment. The surgical sequence to resect the bony structures around the spinal cord is of great importance.

Oculomotor contributions to foveal crowding.

Crowding, the phenomenon of impaired visual discrimination due to nearby objects, has been extensively studied and linked to cortical mechanisms. Traditionally, crowding has been studied extrafoveally; its underlying mechanisms in the central fovea, where acuity is highest, remain de-bated. While low-level oculomotor factors are not thought to play a role in crowding, this study shows that they are key factors in defining foveal crowding. Here we investigate the influence of fixational behavior on foveal crowding and provide a comprehensive assessment of the magnitude and extent of this phenomenon (N=13 human participants, 4 males). Leveraging on a unique blend of tools for high-precision eyetracking and retinal stabilization, we show that removing the retinal motion introduced by oculomotor behavior with retinal stabilization, diminishes the negative effects of crowding. Ultimately, these results indicate that ocular drift contributes to foveal crowding re-sulting in the same pooling region being stimulated both by the target and nearby objects over the course of time, not just in space. The temporal aspect of this phenomenon is peculiar to crowding at this scale and indicates that the mechanisms contributing to foveal and extrafoveal crowding differ.Significance Statement: Foveated stimuli are often crowded. The effects of crowding have been extensively studied in the visual periphery and are thought to have a cortical origin. Nonetheless, foveal crowding mechanisms remain elusive. Here we show that acuity drops by two lines on a Snellen Chart when flankers surround a stimulus presented at the very center of gaze. Further, at this scale, crowding cannot be regarded as a purely cortical phenomenon. Because foveal neurons' receptive fields are the smallest, eye jitter during fixation introduces spatial uncertainty by sweeping target and surrounding distractors over the same cortical pooling region even during short fixation periods, exacerbating crowding effects.

Outcome of posterior short segment fixation with implanting pedicle screw at the fractured level for treatment of thoracolumbar fracture

IntroductionThoracolumbar fractures make up majority of the spinal fractures. Various techniques including long, short, mono and short segment screw fixation have been used to achieve stability. There are still few studies describing the results of short segment fixation with intermediate screw fixation in fractured vertebrae, despite the fact that all have adequate efficacy and stability. Materials and methods41 patients were studied and evaluated preoperatively, at discharge and at 2, 6, 12, 24 weeks and 1 year follow-up clinically using Greenough and Fraser Low Back Pain Score, the American Spinal Injury Association (ASIA) grading, four-point scale questionnaire for patient's satisfaction, sagittal index (SI) of injured vertebra and Cobb's angle. ResultsThe patient's mean age was 36.9 ± 11.7 years, majority (90.2 %) with lumbar (L1-L3) segment involvement. All the patients significantly improved neurologically immediately after surgery (p < 0.001) however the improvement was not significant at final follow up (p = 0.3) as compared to the preoperative ASIA grade (Kendall's tau-b test). Low back pain decreased significantly on subsequent follow-up as measured by Visual Analogue Scale (VAS) score (p < 0.001). The Low Back Pain Scale of Greenough and Fraser calculated at immediate post-operation and at 1 year follow up in comparison to pre-operation status showed a statistically significant improvement (p < 0.001). Sagittal index (SI) estimated at 6, 12, 24 weeks and 1 year follow-up in comparison to preoperative SI was higher and statistically significant (p < 0.001). Mean Cobb's angle significantly decreased during follow-up at 6, 12, 24 weeks and 1 year compared to preoperative angle (p < 0.001). Four Point Scale Questionnaire assessed at 1 year follow-up showed majority (82.9 %) were very satisfied with the outcome. ConclusionPosterior short segment with intermediate screw fixation in fractured vertebra is a feasible and stable treatment method for traumatic single thoracolumbar fracture with respect to the functional outcome, patient satisfaction and preservation of motion segment.

Efficacy and safety of short segment pedicle screw fixation in patients with neurologically intact burst fractures of the lower thoracic and lumbar spine: a meta-analysis of studies published over the last 20 years

Objective. To conduct a systematic review and meta-analysis of studies on the surgical treatment of patients with uncomplicated burst fractures of the lower thoracic and lumbar spine and to determine the effectiveness and safety of short transpedicular fixation (TPF) in this patient group.Material and Methods. The study included articles with the following criteria: publication date from January 1, 2004, to December 31, 2023; patient sample descriptions involving uncomplicated burst fractures from T10 to L5; TPF involving one segment adjacent to the fractured vertebra in both cranial and caudal directions without spinal fusion; descriptions of treatment outcomes or complications; and an average follow-up period of at least 12 months. Meta-analysis was conducted using the Comprehensive Meta-Analysis software, version 2.2.064. Depending on the level of heterogeneity (I² test), either a fixed-effects or random-effects model was applied. Begg’s or Egger’s test was used to assess publication bias, and any bias present was corrected using the trim-and-fill method.Results. The application of TPF resulted in a significant reduction in the overall Cobb angle by 5.9 degrees in the percutaneous group and by 7.6 degrees when using a midline approach. Regarding AVBCR (anterior vertebral body compression ratio), a reduction of 24.0 % and 24.8 % was observed in both groups, respectively. The overall complication rates were as follows: superficial infection, 2.2 %; deep infection, 2.0 %; and implant-associated complications, 5.6 %. No patient developed a neurological deficit. The levels of work adaptation W1 and W2 on the Denis scale were achieved in 70.9 % of patients. The overall quality of life, as measured by the Oswestry Disability Index, averaged 13.4 %.Conclusions. Short transpedicular fixation without additional spinal fusion or laminectomy appears to be an effective and safe method for treating burst fractures of the lower thoracic and lumbar spine without neurological deficits. This method allows for regression of kyphotic deformity in the long-term post-injury period by at least 5.9 degrees and restoration of anterior vertebral height by 24 %. The approach demonstrated relatively low overall postoperative complication rates. More than 90 % of patients were able to return to full-time work, either in their previous position or with reduced physical demands.

Safety and efficacy of short percutaneous fixation in AO3 and AO4 lumbar fractures: a single-centre experience of 35 cases.

Spinal fractures with subsequent bone fragment dislocation are among the injuries most feared by patients and physicians. The surgical strategy is tailored to the individual patient's characteristics and often consists of pedicle instrumentation with rod-screw systems. Short instrumentation has been associated with worse spinal correction and increased complications. However, recent studies have suggested similar results in terms of kyphosis correction and the maintenance of sagittal alignment compared to longer instrumentation. This single-center retrospective study was conducted between January 2018 and April 2021. We included 35 single lumbar burst fractures AO Spine grade A3 or A4 with evidence of intra-canal fragments. Patients underwent minimally invasive percutaneous posterior lumbar instrumentation with pedicle screws. Patients received short segmental fixation involving only one level above and below the fractured vertebra. An immediate postoperative computed tomography (CT) scan demonstrated a significant reduction in vertebral kyphotic deformation (11.7° ± 1.6 vs 16.7° ± 5, p<0.001) and sagittal Cobb angle (9.8° ± 1.3 vs 11.7° ± 1.5, p < 0.001). The correction was slightly reduced but remained significant at 12 months for both kyphotic (12.3° ± 1.4, p = 0.03) and sagittal Cobb (10.3° ± 0.9, p = 0.04). Upper lumbar vertebrae showed even larger correction indices compared to lower lumbar segments. No implant failure or screws pullout was seen at the last follow-up. Short spinal fixation is a safe and effective treatment of complete and incomplete burst fractures with posterior bone fragment dislocation. All included patients fared well and achieved good kyphotic correction with no perioperative or long-term complications.

A behavioral and eye movement study on inhibitory processing of action memory

Recent evidence highlights the critical role of effective interference inhibition for optimal memory performance, yet its function in action memory remains relatively underexplored. The current study investigated inhibitory processes in action memory during encoding and storage stages. In Experiment 1, 100 participants were divided into high and low cognitive inhibition groups using the Stroop color naming task. They performed either a subject-performed task (SPT) or a verbal task (VT) under varying semantic interference levels to assess the interaction between individual inhibitory abilities and the inhibition processing of action memory during encoding. Results indicated no significant difference in inhibition effects (IF) between high and low inhibition groups in SPT under high semantic interference, while in VT, those with high cognitive inhibition demonstrated significantly greater IF than those with low. Experiment 2, involving 57 participants, employed a point detection task and eye-tracking to explore attentional inhibition mechanisms during action memory storage. Behavioral results showed greater IF for SPT than VT under semantic interference. Eye-tracking revealed higher initial fixation rates and shorter durations for SPT subjects during the early processing stage, and significantly fewer and shorter fixations in the later stage compared to VT subjects. These findings imply stronger inhibitory processing in SPT during both encoding and storage stages under semantic interference, with attentional inhibition of action memories occurring predominantly in the later stage.

Biomechanical analysis of stabilization for thoracolumbar anterior spinal failure caused by osteolytic lesions, a finite element comparison of direct lateral corpectomy and posterior long segment instrumentation

BACKGROUND CONTEXTOsteolytic lesions caused by infection or metastatic disease of the spine can induce instability. Different surgical strategies are available to restore stability in this scenario, however little is known how various reconstruction techniques affect spinal biomechanics. PURPOSETo analyze and quantify the biomechanical effects of three different surgical reconstruction techniques in the treatment of a T12 osteolytic model. STUDY DESIGN/SETTINGFinite element analysis of the thoracic spine with a T12 osteolytic lesion. METHODSUsing CT scans from a 20-year-old man without structural deformity, simulation of an osteolytic lesion with a 50% defect at the posterior aspect of T12 vertebral body was created by a 490 N vertical force to T9. Next, three common instrumentation techniques treating the osteolytic lesion were modeled and biomechanically tested. These included: Model A, corpectomy with short segment fixation (T11-L1) and two long-segment instrumentations; Model B long segment fixation with triple rod construct; Model C long segment fixation with dual rod construct. A load of 480N was then applied on the spine models in vertically downward direction on T9. Von Mises stresses were measured (MPa) in the discs, vertebrae, and implants. RESULTSModel A demonstrated the lowest stress on construct material, adjacent vertebral bodies, and discs but increased stress on the instrumented vertebrae. Model B was more rigid and demonstrated lower construct stress compared to Model C. However, Model C had the lowest vertebral body stress in flexion, extension, and lateral bending in the most upper instrumented vertebral body, but the highest screw pull-out stress when compared to Model A and Model B. CONCLUSIONSThis osteolytic T12 model provides unique biomechanical data that can help to tailor surgical strategies in select scenarios. While optimal outcomes are best achieved with a construct tailored to a specific patient's need for stabilization, our findings can be generalized for instances of cancerous lesions, low bone density, and infectious causes. CLINICAL RELEVANCEThe results of this study can help with the choice of appropriate surgical reconstruction technique based on patient-specific characteristics.

Computational study of a dorsolumbar complete burst fracture and its fixation methods

PurposeDuring a fall, a significant part of the major forces is absorbed by the dorsolumbar column area. When the applied stresses exceed the yield strength of the bone tissue, fractures can occur in the vertebrae. Vertebral fractures constitute one of the leading causes of trauma-related hospitalizations, accounting for 15% of all admissions. Posterior pedicle screw fixation has become a common method for treating burst fractures. However, physicians remain divided on the number of fixed segments that are needed to improve clinical outcomes. The present work aims to understand the biomechanical impact of different fixation methods, improving surgical treatments.Design/methodology/approachA finite element model of the dorsolumbar spine (T11–L3) section, including cartilages, discs and ligaments, was created. The dorsolumbar stability was tested by comparing two different surgical orthopedic treatments for a fractured first lumbar vertebra on the L1 vertebra: the posterior short segment fixation with intermediate screws (PSS) and the posterior long segment fixation (PL). Distinct loads were applied to represent daily activities.FindingsResults show that both procedures provide acceptable segment fixation, with the PL offering less freedom of movement, making it more stable than the PSS. The PL approach can be the best choice for an unstable fracture as it leads to a stiffer spine segment.Originality/valueThis study introduces a novel computational model designed for the biomechanical analysis of dorsolumbar injuries, aiming to identify the optimal treatment approaches within both clinical and surgical contexts.

Factors associated with loss of vertebral height and kyphosis correction after intermediate screws in short segment pedicular fixation for type-A fractures of the thoracolumbar spine: A retrospective study.

In this article, we attempted to identify risk factors affecting the loss of vertebral height and kyphosis correction on type A thoracolumbar fractures. Patients with type A thoracolumbar fractures who underwent short segments with intermediate screws at the fracture level management between 2017 and 2022 were included in this study. Clinical factors including patients' demographic characteristics (age, sex), history (smoking, hypertension and/or diabetes), value of height/kyphosis correction, the thoracolumbar injury classification and severity score (TLICS), the load sharing classification (LSC) scores and bone mineral density were collected. Correlation coefficient, simple linear regression analysis and multivariate regression analysis were performed to identify the clinical factors associated with the loss of vertebral height/kyphosis correction. Finally, 166 patients were included in this study. The mean height and kyphosis correction were 21.8% ± 7.5% and 9.9° ± 3.8°, respectively, the values of the loss were 6.5% ± 4.0% and 3.9° ± 1.9°, respectively. Simple linear regression analysis and multivariate regression analysis showed that age, value of height correction, LSC scores and bone mineral density were significantly associated with the loss of vertebral height and kyphosis correction (P < .01) We could draw the conclusion that patients with older age, lower bone mineral density, higher LSC scores and diabetes are at higher risk of vertebral height and kyphosis correction loss increase. For these patients, appropriate clinical measures such as long segment fixation, control of blood glucose, and increase of bone density must be taken to reduce the loss of correction.

Complications and survival rates of subtrochanteric fractures are similar between short and long intramedullary nail fixation and independent of weight-bearing

PurposeIntertrochanteric fractures are treated surgically, allowing rapid weight-bearing to improve ambulation and lower complications and mortality. Subtrochanteric fractures are mechanically less stable and are traditionally treated with a non-weight approach and longer intramedullary nails. This study compared immediate weight-bearing versus limited weight-bearing and different intramedullary nail lengths regarding patient outcomes.MethodsWe analyzed all consecutive cases of low-energy subtrochanteric fractures treated surgically at our institution between January 2016 and November 2020. One hundred and nine patients were found. We compared nail length and immediate versus delayed weight-bearing concerning the length of stay, time to painless ambulation, time to radiographic fracture union, and revision rates. Fracture severity was also examined using the Seinsheimer classification.ResultsLength of stay and time to painless ambulation were shorter in the immediate weight-bearing group. Time to radiographic union and rate of complications were lower; however, they were not statistically significant. Conversely, no significant difference in revision rates was found. Regarding nail length, the length of stay was shorter, and the time to painless ambulation was faster in the short-length group. The rate of complications and time to union were similar. No difference in revision rate was found. Seinsheimer classification of the fracture did not influence the decision to allow weight-bearing or nail selection (p = 0.65).ConclusionsThis study demonstrates that immediate weight-bearing as tolerated and short intramedullary nails allow a quicker time for painless ambulation and hospitalization, with possibly fewer perioperative complications and faster radiographic union, without increasing complications.

Study on the Results of Laminectomy with Short Segment Pedicle Screw Fixation in Dorsolumbar Fractures with Respect to Anatomical Reduction, Functional Recovery, and Pain

Abstract Background: This study aimed to report the results of laminectomy with short-segment pedicle screw fixation in thoracolumbar fracture. Materials and Methods: Forty-two patients were analyzed prospectively, and followed up in the outpatient department for 24 months. Results: The results revealed that most of the patients in the study had reasonable to good neurological recovery in the postoperative period assessed in the form of an American spinal injury association impairment scale (ASIA) score. There was also an excellent improvement in the components of anatomical reduction like vertebral height, Cobb’s angle, and anterior wedge angle, which was directly related to the functional recovery of the patient. Postoperatively, the patients also got relief in pain in the dorsolumbar region assessed based on the Denis pain scale. Conclusion: This study concludes that laminectomy with pedicle screw fixation is an excellent option for patients with thoracolumbar fracture, it not only decompresses the spine but also provides stability with minimal manageable complications.

Radiological and Clinical Outcome of Thoracolumbar Burst Fracture Following Short Segment and Long Segment Pedicle Screw Fixation

INTRODUCTION: The indications for operative treatment and type of stabilization procedures for the treatment of thoracolumbar fracture remains controversial. Long-segment pedicle screw fixation permits correction of kyphotic deformity while short-segment pedicle screw fixation preserves motion segments, reduces costs and time of surgery. Our aim is to study the correlation and comparison between clinical and radiological outcome of both fixations and identify factors that might contribute to the outcome. MATERIALS AND METHODS: 60 patients with thoracolumbar spine fracture from 2017 to 2022 were identified. Age, gender, mechanism of injury, classification of fracture, duration of hospital stays and one-year post-operative outcome of Visual Analogue (VAS) pain score, and Oswestry Disability Index (ODI) score were documented. Pre- and post-operative AP/Lateral radiographs measurements of local kyphotic angle, Cobb angle were measured. Signs of fixation failure were examined at follow-up. RESULTS: Subjects mean age is 42.4, male predominance (85%) and work-related. The highest incidence was at level of L1 (56.7 %) in the long-segment and 46.7 % in short-segment. Most common injury was burst fracture (AO classification A3 A4 group) due to fall from height. There is shorter hospital stay documented in the short-segment fixation. Radiological outcome measured in both groups were comparable with no signs of fixation failure. Short-segment fixation group also resulted in better clinical and functional outcome at one-year follow-up. CONCLUSION: There is no significant difference in radiologic outcome of Cobb and kyphotic angle in both fixation groups. Short-segment fixation has significantly better clinical and functional outcome post-operative and at 1-year follow up.

Ambient and focal attention during complex problem-solving: preliminary evidence from real-world eye movement data.

Time course analysis of eye movements during free exploration of real-world scenes often reveals an increase in fixation durations together with a decrease in saccade amplitudes, which has been explained within the two visual systems approach, i.e., a transition from ambient to focal. Short fixations and long saccades during early viewing periods are classified as ambient mode of vision, which is concerned with spatial orientation and is related to simple visual properties such as motion, contrast, and location. Longer fixations and shorter saccades during later viewing periods are classified as focal mode of vision, which is concentrated in the foveal projection and is capable of object identification and its semantic categorization. While these findings are mainly obtained in the context of image exploration, the present study endeavors to investigate whether the same pattern of interplay between ambient and focal visual attention is deployed when people work on complex real-world tasks-and if so, when? Based on a re-analysis of existing data that integrates concurrent think aloud and eye tracking protocols, the present study correlated participants' internal thinking models to the parameters of their eye movements when they planned solutions to an open-ended design problem in a real-world setting. We hypothesize that switching between ambient and focal attentional processing is useful when solvers encounter difficulty compelling them to shift their conceptual direction to adjust the solution path. Individuals may prefer different attentional strategies for information-seeking behavior, such as ambient-to-focal or focal-to-ambient. The observed increase in fixation durations and decrease in saccade amplitudes during the periods around shifts in conceptual direction lends support to the postulation of the ambient-to-focal processing; however, focal-to-ambient processing is not evident. Furthermore, our data demonstrate that the beginning of a shift in conceptual direction is observable in eye movement behavior with a significant prolongation of fixation. Our findings add to the conclusions drawn from laboratory settings by providing preliminary evidence for ambient and focal processing characteristics in real-world problem-solving.

Towards the First Generation of Biomimetic Fixation for Resurfacing Arthroplasty Endoprostheses.

This paper presents advances in designs of resurfacing arthroplasty endoprostheses that occurred through their historical generations. The critical characteristics of contemporary generation hip resurfacing arthroplasty endoprostheses are given and the failures resulting from the specific generation cemented and short stem fixation of the femoral component are reviewed. On the background of these failures, the critical need arises for an alternative approach to the fixation of components of resurfacing arthroplasty leading towards the first generation of biomimetic fixation for resurfacing arthroplasty endoprostheses. The state of the art of the completed bioengineering research on the first biomimetic fixation for resurfacing arthroplasty endoprostheses is presented. This new design type of completely cementless and stemless resurfacing arthroplasty endoprostheses of the hip joint (and other joints), where endoprosthesis components are embedded in the surrounding bone via the prototype biomimetic multi-spiked connecting scaffold (MSC-Scaffold), initiates the first at all generations of biomimetic endoprostheses of diarthrodial joints.

Percutaneous short segmental fixation combined with bone cement augmentation for stage III Kümmell's disease without nerve deformity.

The objective of this study was to evaluate the safety and efficacy of percutaneous pedicle screw fixation combined with bone cement augmentation in the management of stage III Kümmell disease without nerve deformity. A retrospective analysis was conducted on 17 patients diagnosed with stage III Kümmell disease without nerve deformity, who underwent treatment with percutaneous pedicle screw fixation combined with bone cement augmentation between April 2019 and 2022. Preoperative, postoperative, and final follow-up clinical outcome measures were collected, including Visual Analog Scale scores and Oswestry Disability Index scores. Additionally, lateral radiography was used to measure the Cobb angle and height of the anterior border of the affected vertebral body. Operative time, volume of injected bone cement, intraoperative cement leakage, and other complications were recorded. All patients underwent successful surgery, resulting in significant reductions in Visual Analog Scale scores, Oswestry Disability Index scores, and Cobb angle postoperatively; meanwhile there was a significant increase in height of the anterior border of the affected vertebral body. No major complications occurred during the follow-up period. In conclusion, percutaneous pedicle screw short-segment fixation combined with bone cement augmentation appears to be an effective surgical option for treating stage III Kümmell disease without nerve deformities.

Esports experts have a wide gaze distribution and short gaze fixation duration: A focus on League of Legends players.

This study investigated the specific gaze control ability of expert players and low-skill players of League of Legends (LoL). Eleven expert and nine low-skill players were divided according to their official ranking. Then, the gaze movement of each participant when performing each task (e.g., easy task and moderate task) while competing against a computer artificial intelligence system was recorded. Experts were found to have a significantly wide horizontal gaze distribution. Additionally, experts had a consistently short gaze fixation duration during the moderate task. These results suggest that a wide horizontal gaze distribution allows experts to obtain information from a wider area. Additionally, the consistently short fixation duration of the experts indicated that they need only a short period to assess information, which is advantageous because large amounts of information need to be processed within a limited time while playing. This specific gaze control ability could be an important factor that contributes to the superior performance of expert LoL players.

Evidence for five types of fixation during a random saccade eye tracking task and changes in fixation duration as a function of time-on-task.

Our interest was to evaluate changes in fixation duration as a function of time-on-task (TOT) during a random saccade task. We employed a large, publicly available dataset. The frequency histogram of fixation durations was multimodal and modelled as a Gaussian mixture. For this specific task, we found five fixation types. The "ideal" response would be a single accurate saccade after each target movement, with a typical saccade latency of 200-250 msec, followed by a long fixation (> 800 msec) until the next target jump. We found fixations like this, but they comprised only 10% of all fixations and were the first fixation after target movement only 23.4% of the time. More frequently (57.4% of the time), the first fixation after target movement was short (117.7 msec mean) and was commonly followed by a corrective saccade. Across the entire 100 sec of the task, median total fixation duration decreased. This decrease was approximated with a power law fit with R2 = 0.94. A detailed examination of the frequency of each of our five fixation types over time on task (TOT) revealed that the three shortest duration fixation types became more and more frequent with TOT whereas the two longest fixations became less and less frequent. In all cases, the changes over TOT followed power law relationships, with R2 values between 0.73 and 0.93. We concluded that, over the 100 second duration of our task, long fixations are common in the first 15 to 22 seconds but become less common after that. Short fixations are relatively uncommon in the first 15 to 22 seconds but become more and more common as the task progressed. Apparently. the ability to produce an ideal response, although somewhat likely in the first 22 seconds, rapidly declines. This might be related to a noted decline in saccade accuracy over time.

Degree of kyphotic deformity correction with short segment percutaneous transpedicular fixation in thoracolumbar fractures

Degree of kyphotic deformity correction with short segment percutaneous transpedicular fixation in thoracolumbar fractures

CLINICO-RADIOLOGICAL OUTCOMES IN SHORT SEGMENT FIXATION INCLUDING FRACTURE LEVEL FOR UNSTABLE THORACOLUMBAR JUNCTION FRACTURES (T10-L2)

Background: Thoracolumbar region being a transition zone is frequently injured during trauma. Treatment aims to achieve stable fixation while preserving mobility, prevent deformity, and improve neurology. Short-segment fixation, with fracture level pedicle screw fixation, is popular for preserving motion. This study assesses the clinico-radiological outcomes for short segment fixation including fracture level for unstable thoracolumbar fractures. Methods: This was an observational study conducted at a tertiary care center from December 2020 to November 2022 after receiving ethical approval among single level burst fractures (AO type A3 &amp; A4) at the thoracolumbar junction. Patients with AO type B and C fractures, osteoporotic burst fractures, lack of surgical consent, and multi-level vertebral fractures were excluded from the study. The study utilized ASIA impairment scale, Visual Analogue Score(VAS), and radiological parameters (Kyphotic angle and Loss of vertebral body height) to assess patients immediately, postoperatively and at 6 weeks, 3 months, and 6 months follow-up. Results: Out of 20 patients,70% of the fractures were AO type A3, while the remaining 30% were type A4. The injury resulted in a 56.25 ± 13.75% loss of vertebral height. The mean kyphotic angle improved significantly from 24.38 ± 3.77 degrees preoperatively to 5.92 ± 1.91 degrees at 6 months post-operatively. The VAS scores showed significant improvement from 7.85 ± 0.67 preoperatively to 0.65 ± 0.81 at 6 months postoperatively. Conclusions: Use of pedicle screw in the fractured vertebra can result in significant improvement in post-operative pain and kyphosis correction utilizing fewer motion segment with satisfactory clinic-radiological outcome.