Human Cadaveric Specimens Research Articles

Feasibility and accuracy of a real-time depth-based markerless navigation method for hologram-guided surgery

BackgroundTwo-dimensional (2D) medical visualization techniques are often insufficient for displaying complex, three-dimensional (3D) anatomical structures. Moreover, the visualization of medical data on a 2D screen during surgery is undesirable, because it requires a surgeon to continuously switch focus. This switching focus problem also results in extensive use of intraoperative radiation to gain additional insights for a 3D configuration. The use of augmented reality (AR) has the potential to overcome these problems, for instance by using markers on target points that are aligned with the AR solution. However, placing markers for a precise virtual overlay are time-costly, always have to be visible within the field of view and disrupt the surgical workflow. In this study, we developed ARCUS, a depth-based, markerless AR navigation system, which overlays 3D virtual elements onto target body parts to overcome the limitations of 2D medical visualization techniques.Methods and resultsIn a phantom study, our markerless ARCUS system was evaluated for accuracy and precision by comparing it to a Quick Response (QR) code-based AR registration method. The evaluation involved measuring the Euclidean distance between target points on a 3D-printed face and their corresponding points on the virtual overlay using a robotic arm for precise measurements. Correlations between the measuring points provided by our markerless system and the actual measuring points on the 3D-print were high, with promising consistent Euclidean distances between the 3D points and the virtual points generated by both our markerless system and the Vuforia QR Code system. We also show two clinical examples of ex vivo case studies on cadaveric human specimens where our markerless ARCUS system could be applicable to.ConclusionThe markerless AR navigation system holds strong potential as a 3D visualization method in clinical settings. While both ARCUS and the Vuforia QR code-based method fell short of meeting the surgical threshold of a 2 mm offset, our markerless system demonstrated promising features such as instant registration, markerless operation, and potential compatibility with non-rigid structures. Its automated virtual overlay onto target body parts offers significant advantages, paving the way for investigations into future clinical use.

Comparison of T-POD and SAM Pelvic Sling II and the influence of attachment level in the initial management of unstable pelvic type C injuries – a cadaveric study

BackgroundType C pelvic fractures (AO/OTA) are severe injuries that frequently lead to bleeding and hemodynamic instability. Pelvic binders play a crucial role in their initial management. Placement at the correct level in the prehospital setting is challenging. The aim of this study was to compare two pelvic binders regarding their effectiveness in reducing intrapelvic volume and increasing intrapelvic pressure in patients with type C pelvic fractures (AO/OTA) when applied at three different levels.MethodsRotationally and vertically unstable pelvic injuries (AO/OTA classification 61-C1.1) were produced in five fresh-frozen human cadaveric specimens. Intrapelvic volume, vesical pressure and compression pressure within the pubic symphysis and the sacroiliac joint were measured when applying a SAM Pelvic Sling II and a T-POD at the level of the greater trochanter as well as levels higher and lower than recommended.ResultsComparison of the two pelvic binders positioned at the recommended level (greater trochanter) showed no significant difference in volume reduction (13.85 ± 31.37 cm3, p = 0.442), however, increase in vesical pressure was significantly higher when using the T-POD (5.80 ± 3.27 cmH2O, p = 0.017). When positioned at the level of the iliac crest, vesical pressure increase and intrapelvic volume reduction were significantly greater with the T-POD (14.00 ± 8.57 cmH2O, p = 0.022 and 10.45 ± 5.45 cm3, p = 0.031 respectively). Application of the SAM Pelvic Sling II below the greater trochanter led to a significantly greater decrease in volume (-32.26 ± 7.52 cm3, p = 0.003) than the T-POD. Comparison of the recommended attachment level with incorrect positioning led to no significant differences for the T-POD, while the SAM Pelvic Sling II achieved a significantly lower volume reduction when placed at the iliac crest (40.15 ± 14.57 cm3, p = 0.012) and a significantly lower increase in vesical pressure when applied below the greater trochanter (3.40 ± 1.52 cmH2O, p = 0.007).ConclusionDirect comparison of the two pelvic binders showed that the T-POD achieved significantly greater results when applied at the recommended level and was less susceptible to incorrect positioning. These outcomes support the preferred use of the T-POD for prehospital emergency pelvic stabilisation.

Capsule elongation occurs after first time shoulder dislocation A biomechanical in-vitro investigation on human cadaveric specimen

PurposeAs capsule elongation is assumed to weaken the static stability of the shoulder joint, the purpose of this biomechanical study was to demonstrate that capsule elongation occurs immediately after a first-time shoulder dislocation and not just after recurrent dislocation events. We hypothesize an increment in joint clearance due to joint capsule elongation after a first-time dislocation. MethodsAn experimental in-vitro study was conducted on 6 paired fresh frozen human shoulders (4 females; 2 males; 12 specimen) with a mean age of 80 (Range 67–89) years. The shoulder joint with the articular capsule was exposed and an inferior static tension force of 2.5 N was applied to the humerus prior to dislocation. Next, the humeral head was dislocated and was then immediately reduced back into the start position. The joint gap as well as joint capsule deformation was assessed using optical techniques. ResultsThe radiographic joint gap increased from 13.7 ± 6.9 mm (prior to dislocation) to 18.1 ± 6.5 mm (post dislocation) (p < .001). The increase in joint clearance was 4.4 mm. The joint capsule elongated from 5.9 ± 0.005 % (prior to dislocation) to 9.4 ± 0.007 % (post dislocation) (p < .001). The mean increase in joint capsule elongation was 3.5 %. ConclusionsCapsule elongation was observed immediately after a simulated first-time shoulder dislocation in an in-vitro model of elderly human cadavers. It might therefore not only be a phenomenon of recurrent dislocation events.

The mechanical properties of the spinal cord: a protocol for a systematic review of previous testing procedures and results

BackgroundSpinal cord compression is a pathology seen in routine clinical practice. However, there remain a number of unanswered questions around both the understanding of the pathogenesis and the best method of treatment of the condition. This is partly due to the issues of the real-life testing of the physical properties of the spinal cord, either through the use of cadaveric human specimens or through animal testing, both of which have methodological, as well as ethical, issues.Design and methodsThis paper details a protocol for a systematic review of the literature on the mechanical properties of the spinal cord. We will conduct a literature search of a number of electronic databases, along with the grey literature, as a single-stage search. All literature will be screened for appropriate studies which will then be reviewed fully to extract relevant information on the methodology and mechanics of the reported testing along with the results. Two reviewers will separately screen and extract the data, with a comparison of results to ensure concordance. Conflicts will be resolved through discussion and independent arbitration as required. The methodological quality of the studies will be assessed within the ARRIVE guidelines using the CAMARADES framework and SYRCLE risk of bias tool. A narrative synthesis will be created with the appropriate tables to describe the demographics and findings of the included studies.DiscussionThe systematic review described here will form the basis of an understanding of the current literature around the physical properties of the spinal cord. This will allow future work to develop a physical model of the spinal cord, which is translatable to patients for analysis and testing in a controlled and repeatable fashion. Such a model would be the basis for further clinical research to improve outcomes from this condition.Trial registrationProspero registration number: CRD42022361933.

The Effect of Concavity Restoration on Glenohumeral Stability in a Glenoid Bone Loss Model: Comparing the Distal Tibial Allograft Reconstruction and the Latarjet Procedure

Objectives: Glenoid bone loss occurs in more than 80% of patients with recurrent glenohumeral instability. The Latarjet procedure has become the gold standard for restoration of bone loss despite a high (15-30%) complication rate.1–3 Distal tibial allograft (DTA) reconstruction has recently gained interest due to its ability to restore width and concavity to the glenoid while providing a cartilage surface.4 The purpose of this study is to evaluate the restoration of glenohumeral anterior stability and glenoid concavity after DTA reconstruction when compared to the Latarjet procedure in a glenoid bone loss model. Methods: Five human cadaveric specimens (mean age: 62.2, range 57-69; 80% male) underwent preoperative computed tomography (CT) scans to assess native glenoid concavity as determined by the glenoid depth and bony shoulder stability ratio (BSSR). Stability testing was performed using a cadaveric shoulder simulator that allows 6 DoF at the glenohumeral joint. The specimens were placed with the scapula at 30° upward rotation and humerus at 60° glenohumeral abduction with a constant compressive force created by loading the supraspinatus, infraspinatus, teres minor, and subscapularis muscles (2lbs, 3lbs, 1lb and 4lbs respectively). A Kuka robot applied a 40N anterior force through the pectoralis tendon with the humerus in neutral as well as 60 degrees of external rotation. A motion capture system recorded humeral head translations for each condition. To create the Latarjet and DTA conditions, the coracoid was first harvested and the thickness was measured. A distal tibial allograft was then contoured to an identical size. A glenoid defect was created to match the thickness of the graft since both Latarjet and DTA aimed for a 100% glenoid restoration.. The following conditions were tested: 1. intact, 2. Bankart lesion, 3. bone loss model with DTA reconstruction, 4. Latarjet procedure without the conjoint tendon loaded, and 5. Latarjet with conjoint tendon loading (‘sling effect’). All specimens underwent post-testing CT scan to measure the BSSR of the DTA and Latarjet reconstructions. A repeated measures ANOVA was performed to determine if there was a significant difference in maximum anterior translation or BSSR between the distal tibial allograft reconstruction and Latarjet procedure (with or without the sling effect). Results: The mean preoperative glenoid depth measured 2.61±1.03mm with a BSSR of 0.40±0.16. However, postoperative measurements showed that BSSR for the DTA was greater than the Latarjet (0.46±0.11 vs 0.35±0.5). The maximum anterior translation was significantly lower after the DTA reconstruction than the Latarjet procedure without the sling effect (5.5mm vs 9.6mm, p = 0.044). However, there was no difference in anterior translation between the DTA reconstruction and Latarjet procedure with the sling effect applied (5.5mm vs 4.7mm, p = 0.36). The DTA reconstructed the glenoid with a significantly greater concavity than the Latarjet procedure (BSSR: 0.46 vs 0.35, p = 0.036). Conclusions: When addressing bone loss in glenohumeral instability, additional factors besides the restoration of glenoid width contribute to stability. The concave reconstruction produced by the distal tibial allograft decreases anterior translation compared to the flat reconstruction produced by the Latarjet, but there is no difference in translation between the DTA and Latarjet procedure when the sling effect is applied. The DTA reconstruction provides an alternative to the Latarjet procedure with equivalent biomechanical properties and less morbidity or change to the native shoulder structure.

Morphometric Comparison of Endoscopic Endonasal Transpterygoid and Precaruncular Contralateral Medial Transorbital Approaches to Sphenoid Sinus Lateral Recess.

The endoscopic endonasal transpterygoid approach (TPA), minimally invasive compared with the sublabial transmaxillary and transcranial approaches, still accounts for morbidity in benign lateral recess of sphenoid sinus (LRSS) pathologies. Others have suggested an alternative route to the LRSS, the endoscopic contralateral medial transorbital approach (cMTO). However, no quantitative evidence exists to support the clinical application of this approach. This cadaveric study, in a controlled laboratory setting, provides a morphometric comparison of the TPA and cMTO for accessing the LRSS. The study also details the anatomy and technical nuances for optimizing the cMTO corridor. Ten fresh preinjected human cadaveric specimens (20 sides) were dissected with neuronavigation, completing endoscopic cMTO and TPA on each side. Four parameters-working distance to lateral recess, surgical exposure area, angle of attack (AoA), and surgical freedom-were measured for each approach. Relevant osteological measurements in 10 dried human skulls were recorded. The mean distance from the superior margin of the lacrimal sac impression to the inferior margin of the trochlear fossa was 10.29 ± 1.13 mm, and that from the anterior ethmoidal artery foramina to the posterior lacrimal crest was 9.63 ± 1.23 mm. The mean exposure area around the LRSS was significantly higher in TPA (614.09 ± 40.38 mm2) than in cMTO (391.19 ± 59.01 mm2, P = .001). The mean AoA was 9.83° and 10.24° in the cMTO and TPA, respectively, in the craniocaudal direction (P = .529). In the horizontal plane, it was 9.29° and 10.76° (P = .012). There was no significant difference in surgical freedom between the cMTO and TPA (804.61 and 806.05 mm3, respectively; P = .993). Although comparatively limited exposure area, the cMTO approach has a similar AoA and surgical freedom as TPA and offers better visualization and ergonomic advantages. cMTO provides a feasible, less morbid, multiport technique for benign sphenoid sinus lateral recess pathologies.

Comparison of Strengths of Mandibular Angle Fractures Following Different Plate Designs: A Human Cadaver Study

Study Design This institutional cross-sectional study using cadaveric mandibles aimed to measure and compare the strengths of three plating designs utilized in osteosynthesis of mandibular angle fractures. Objective There have been prior studies on angle fracture fixation though few biomechanical studies on human cadaveric specimen. This study aims to directly compare the biomechanical strength of different plating designs to the mandibular angle fracture using a human cadaveric specimen substrate. Methods After receiving an angle osteotomy and either single plate, two plate, or 3D plate fixation, the specimens underwent biomechanical testing using the Instron 5565 mechanical testing unit. The primary outcomes measured were peak load at which permanent deformation started, displacement value at peak load, and load necessary for a specific amount of displacement at 1, 3, 5, and 7 mm. Results There were 15 hemi-mandibles in each group. Based on data analysis of all the specimens, there were no significant differences in the mandibular height, ramus width, mandibular thickness, angle height, and gonial angle between the hemimandibles.. This study demonstrated a statistically significant increased strength performance of the 3D plate over the single plate fixation and the 2-plate over the single plate fixation. The results between 2-plate and 3D plate were in similar values. Conclusions In terms of biomechanical strength, the 3D plate and two plate designs outperform the single plate design to mandibular angle fractures. There are various anatomical and patient specific situations that can aid in selection between them. In the absence of the favorable angle fracture and patient, biomechanical strength to the method of fixation selection needs to be considered.

Biomechanical evaluation of modified and traditional cortical bone trajectory technique on adjacent segment degeneration in transforaminal lumbar interbody fusion—finite element analysis

ObjectivesModified cortical bone trajectory (MCBT) technique was proposed by our team in previous studies, but its biomechanical properties at adjacent segments have not been discussed yet. Therefore, the purpose of this study is to investigate the biomechanical properties of modified cortical bone trajectory (MCBT) technique on adjacent segment degeneration (ASD) in transforaminal intradiscal lumbar disc fusion (TLIF) compare to traditional bone trajectory (TT) technique and cortical bone trajectory (CBT) technique.MethodsThe four human cadaveric lumbar specimens were provided by the anatomy teaching and research department of Xinjiang Medical University and four intact finite element models of the L1-S1 segment were generated. For each of these, three transforaminal lumbar interbody fusion procedures with three different fixation techniques were reconstructed at the L4-L5 segment, as follows: TT-TT (TT at both L4 and L5 segments), CBT-CBT (CBT at both L4 and L5 segments), MCBT-MCBT (MCBT at both L4 and L5 segments). The range of motion and von Mises stress of the intervertebral disc of the L3-L4 and L5-S1 segments were recorded with a 400N compressive load and 7.5 Nm moments in flexion, extension, left–right bending, and left–right rotation.ResultsThe peak ROM of the L3-L4 segment in the MCBT-MCBT group was reduced by 10.5%, 6.1%, 12.2%, 4.1%, and 1.5% in flexion, extension, left–right bending, and left rotation compared to the TT-TT group and reduced by 1.8%, 5.5%, 10.0%, 12.8%, and 8.8% in flexion, left–right bending, and left–right rotation compared to the CBT-CBT group, respectively. The MCBT-MCBT group has the lowest peak ROM of the L3-L4 segment in flexion, left bending, and right rotation, the lowest peak ROM of the L5-S1 segment in extension and right rotation, and the lowest peak von Mises stress of the intervertebral disc at the L5-S1 segment in right rotation compared to the TT-TT and CBT-CBT group. In addition, the peak von Mises stress at the L3-L4 segment was lowest and more dispersed in all motions, the MCBT-MCBT group exhibited lower peak ROM of the L5-S1 segment in flexion, extension, and right rotation, and showed lower peak von Mises stress of the disc at the L5-S1 segment in flexion, extension, and right rotation compared with the TT-TT group.ConclusionThe modified cortical bone trajectory technique may have a beneficial effect on reducing the incidence of ASD in the L4-L5 TLIF model compared to the traditional bone trajectory technique and cortical bone trajectory technique.

An Integrated System Using Ultrasound-Based Registration for Surgical Navigation of Iliosacral Screw Insertions.

Pelvic fractures often require fixation through iliosacral joint, typically guided by fluoroscopy using an untracked C-arm device. However, this involves ionizing radiation exposure and potentially inaccurate screw placement. We introduce the Navigated Orthopaedic Fixations using Ultrasound System (NOFUSS), a radiation-free ultrasound (US)-based end-to-end system for providing real-time navigation for iliosacral screw (ISS) insertions. We performed surgeries on 8 human cadaver specimens, inserting four ISSs per specimen to directly compare NOFUSS against conventional fluoroscopy. Six specimens yielded usable (marginal or adequate quality) US images. The median screw entry error, midpoint error, and angulations errors for NOFUSS were 8.4 mm, 7.0 mm, and 1.4◦, compared to 7.5 mm (p = 0.52), 5.7 mm (p = 0.30), and 4.4◦ (p = 0.001) for fluoroscopy respectively. NOFUSS resulted in 6 (50%) breaches, compared to 2 (16.7%) in fluoroscopy (p = 0.19). The median insertion time was 7m 37s and 12m 36s per screw for NOFUSS and fluoroscopy respectively (p = 0.002). The median radiation exposure during the fluoroscopic procedure was 2m 44s, (range: 1m 44s - 3m 18s), with no radiation required for NOFUSS. When considering the three cadavers that yielded only adequate-quality US images (12 screws), the measured entry errors were 3.6 mm and 8.1 mm respectively for NOFUSS and fluoroscopy (p = 0.06). NOFUSS achieved insertion accuracies on par with the conventionalfluoroscopicmethod,andreducedinsertiontimesandradiation exposure significantly. This study demonstrated the feasibility of an automated, radiation-free, US-based surgical navigation system for ISS insertions.

Beaver Tail Liver: A Morphological Study of Variation in the Left Lobe of the Liver.

The liver, the largest gland in a wedge-shape, is situated in the right hypochondrium, and exhibits variation in its lobes. Knowledge of variations in the lobes of the liver is crucial for accurate radiological diagnosis and successful abdominal surgeries. The elongation of the left lobe of the liver has gained significant attention in segmentectomy and liver transplant surgeries. During October and November 2023, cross-sectional observational research was done on 53 human cadaveric liver specimens obtained from different medical colleges in Gujarat, India. The livers were meticulously examined to determine the prevalence of Beaver tail liver and measurements such as length, breadth, and thickness were recorded and statistically analyzed. The study revealed that out of the 53 livers examined, 29 (54.72%) were classified as normal, while 19 (35.85%) fell into Netter's type 2 to 7 based on Netter's classification. Interestingly, 5 (09.43%) livers exhibited an elongated left lobe, referred to as a "sliver liver," which did not fit into any of the Netter's types. The beaver tail liver was found to be longer and broader compared to normal liver of the same size and weight (p<0.001). This study highlights the wide range of variations that can be observed in the lobes of the liver. The findings of this study will serve as a valuable resource for radiologists, anatomists, and surgeons, aiding them in accurate diagnoses and surgical procedures, thus minimizing the risk of misdiagnosis.

Mixed reality for spine surgery: a step into the future with a human cadaveric accuracy study.

Current application of mixed reality as a navigation aid in the field of spinal navigation points to the potential of this technology in spine surgery. Crucial factors for acceptance include intuitive workflow, system stability, reliability, and accuracy of the method. The authors therefore aimed to investigate the accuracy of the system in visualization of anatomical structures using mixed reality in the example of pedicles of the thoracic spine in a human cadaveric study. Potential difficulties and limitations are discussed. CT scans of a human cadaveric spinal column specimen were performed. After segmentation and import into the advanced HoloLens 2 software, the vertebrae were exposed. The vertebral arches were preserved on one side for a landmark-based surface registration, whereas pedicles were exposed on the other side in order to measure and evaluate deviation of the overlay holographs with regard to the exact anatomical structure. Accuracy was measured and statistically evaluated. In this work it was demonstrated that the overlay of the virtual 3D model pedicles with the real anatomical structures with anatomical landmark registration was within an acceptable surgical accuracy with the mean value of 2.1 mm (maximum 3.8 mm, minimum 1.2 mm). The highest accuracy was registered at the medial and lateral pedicle wall, and the measurement results were best in the region of the middle thoracic spine. The accuracy analysis for mixed reality (i.e., between the virtual and real anatomical situation of the thoracic spine) showed a very good agreement when focus was on the pedicles. This work is thus a rare proof of the precision of segmentation to the potential surgical area. The results encourage researchers to open up mixed reality technology in its development and application for spinal navigation.

Indentation mechanics and native collagen content in the cartilaginous endplate: A comparison between porcine cervical and human lumbar spines

This study characterized the regional indentation mechanics and native collagen content in cartilaginous endplates (CEPs) from the porcine cervical spine, young human lumbar spine, and aged human lumbar spine. Seventeen endplates were included in this study: six porcine cervical, nine young human lumbar, and two aged human lumbar. Width and depth measurements were obtained using a digital caliper and used to size-normalize and identify the central, anterior, posterior, and lateral regions. Regional microindentation tests were performed using a serial robot, where surface locations were loaded/unloaded at 0.1 mm/s and held at a constant 10 N force for 30 s. Loading stiffness and creep displacement were obtained from force-displacement data. Immunofluorescence staining for type I and type II collagen was subsequently performed on sagittal sections of all endplate regions. 255 images were obtained from which fluorescence intensity, sub-surface void area, and cartilage thickness were measured. CEPs from the young human lumbar spine were, on average, 27% more compliant, 0.891 mm thicker, had a lower fluorescence intensity for native collagen proteins within the cartilage (−58%) and subchondral bone (−24%), and had a sub-surface void area that was 19.7 times greater than porcine cervical CEPs. Compared to aged human lumbar CEPs, young human lumbar CEPs were 57% stiffer, 0.568 mm thicker, had a higher fluorescence intensity for native collagen proteins within the cartilage (+30%) and subchondral bone (+46%), and had a sub-surface void area that was 10.6 times smaller. Although not a perfect mechanical and structural surrogate, porcine cervical CEPs provided initial conditions that may be more representative of the young and healthy human lumbar spine compared to aged human cadaveric specimens. The indentation properties presented may have further applications to finite element models of the human lumbar spine.

Intraoperative visualization of the posterolateral ulnohumeral joint space is reliable to indicate overlengthening in radial head arthroplasty.

Avoiding overlengthening in radial head arthroplasty (RHA) is essential for the prognosis of the elbow joint. An overlengthening from 2mm is visible due to widening of the anterolateral ulnohumeral joint space but intraoperatively, this particular joint space is difficult to visualize. The commonly used Kocher approach allows visualization of the posterolateral joint space without additional instruments or further surgical release of the already unstable elbow. The aim of our study was to investigate whether the visualization of the posterolateral joint space is also a reliable method to indicate overlengthening in RHA. RHA was performed in five human cadaveric specimens with the forearm, wrist, and hand intact. The lateral ligament complex was detached and an anatomic transosseous refixation was performed. Six stages of implantation heights were documented: native joint (1), RHA at the anatomic height (2), + 2mm (3), + 4mm (4), + 6mm (5) and -2mm (6). Macroscopic measurement and digital image analysis of the posterolateral and anterolateral ulnohumeral joint spaces were performed. All stages of overlengthening showed a significant increase in posterolateral and anterolateral joint space widening (p < 0.05). The posterior and anterior joint space showed excellent intraclass correlation. Visualization of the posterolateral aspect of the ulnohumeral joint space is a reliable indicator for overlengthening in RHA without further compromising an already unstable elbow. Correlation to the findings of the anterolateral ulnohumeral joint space in different implants leads to the assumption that visualization of either the anterior or posterior ulnohumeral joint space is universally applicable to determine overlengthening in RHA, regardless of the type of the radial head implant.

Jawbone measurements of edentulous sites related to implant planning using magnetic resonance imaging compared to cone beam computed tomography: An exvivo study.

To compare measurements on images obtained by magnetic resonance imaging (MRI) and cone beam CT (CBCT) for height, width, and area in alveolar bone sites in human jaw specimens. Forty edentulous alveolar posterior sites in human cadaver specimens were imaged using CBCT scanners, and with zero-echo-time MRI (ZTE-MRI). Semi-automatic volume registration was performed to generate representative coronal sections of the sites related to implant planning. ZTE-MRI sections were also presented after grayscale inversion (INV MRI). Three observers measured bone height, bone width 5 mm from the alveolar crest, and bone area stretching from the width measurement to the top of the alveolar crest in the images. Interobserver agreement was assessed by intra-class correlation coefficients (ICC). The measurements were analyzed using two-way repeated measures ANOVA factoring observer and image type. ICC was >0.95 for bone height, width, and bone area. No significant differences among observers (p = 0.14) or image type (p = 0.60) were found for bone height. For bone width, observer (p = 0.14) was not a significant factor, while ZTE-MRI produced width estimates that were significantly different and systematically smaller than CBCT-based estimates (p ≤ 0.001). Observer (p = 0.06) was not a significant factor regarding the bone area measurements, contrary to the imaging type where ZTE-MRI led to significantly smaller area estimates than CBCT (p ≤ 0.001). Bone height measurements were essentially equivalent using CBCT and MRI. This was found regardless of grayscale choice for the MRI. However, ZTE-MRI resulted in smaller estimates of bone width and area.

High contrast cartilaginous endplate imaging in spine using three dimensional dual-inversion recovery prepared ultrashort echo time (3D DIR-UTE) sequence

PurposeTo investigate the feasibility and application of a novel imaging technique, a three-dimensional dual adiabatic inversion recovery prepared ultrashort echo time (3D DIR-UTE) sequence, for high contrast assessment of cartilaginous endplate (CEP) imaging with head-to-head comparisons between other UTE imaging techniques.MethodThe DIR-UTE sequence employs two narrow-band adiabatic full passage (AFP) pulses to suppress signals from long T2 water (e.g., nucleus pulposus (NP)) and bone marrow fat (BMF) independently, followed by multispoke UTE acquisition to detect signals from the CEP with short T2 relaxation times. The DIR-UTE sequence, in addition to three other UTE sequences namely, an IR-prepared and fat-saturated UTE (IR-FS-UTE), a T1-weighted and fat-saturated UTE sequence (T1w-FS-UTE), and a fat-saturated UTE (FS-UTE) was used for MR imaging on a 3 T scanner to image six asymptomatic volunteers, six patients with low back pain, as well as a human cadaveric specimen. The contrast-to-noise ratio of the CEP relative to the adjacent structures—specifically the NP and BMF—was then compared from the acquired images across the different UTE sequences.ResultsFor asymptomatic volunteers, the DIR-UTE sequence showed significantly higher contrast-to-noise ratio values between the CEP and BMF (CNRCEP-BMF) (19.9 ± 3.0) and between the CEP and NP (CNRCEP-NP) (23.1 ± 1.7) compared to IR-FS-UTE (CNRCEP-BMF: 17.3 ± 1.2 and CNRCEP-NP: 19.1 ± 1.8), T1w-FS-UTE (CNRCEP-BMF: 9.0 ± 2.7 and CNRCEP-NP: 10.4 ± 3.5), and FS-UTE (CNRCEP-BMF: 7.7 ± 2.2 and CNRCEP-NP: 5.8 ± 2.4) for asymptomatic volunteers (all P-values < 0.001). For the spine sample and patients with low back pain, the DIR-UTE technique detected abnormalities such as irregularities and focal defects in the CEP regions.ConclusionThe 3D DIR-UTE sequence is able to provide high-contrast volumetric CEP imaging for human spines on a clinical 3 T scanner.

Machine learning-directed electrical impedance tomography to predict metabolically vulnerable plaques.

The characterization of atherosclerotic plaques to predict their vulnerability to rupture remains a diagnostic challenge. Despite existing imaging modalities, none have proven their abilities to identify metabolically active oxidized low-density lipoprotein (oxLDL), a marker of plaque vulnerability. To this end, we developed a machine learning-directed electrochemical impedance spectroscopy (EIS) platform to analyze oxLDL-rich plaques, with immunohistology serving as the ground truth. We fabricated the EIS sensor by affixing a six-point microelectrode configuration onto a silicone balloon catheter and electroplating the surface with platinum black (PtB) to improve the charge transfer efficiency at the electrochemical interface. To demonstrate clinical translation, we deployed the EIS sensor to the coronary arteries of an explanted human heart from a patient undergoing heart transplant and interrogated the atherosclerotic lesions to reconstruct the 3D EIS profiles of oxLDL-rich atherosclerotic plaques in both right coronary and left descending coronary arteries. To establish effective generalization of our methods, we repeated the reconstruction and training process on the common carotid arteries of an unembalmed human cadaver specimen. Our findings indicated that our DenseNet model achieves the most reliable predictions for metabolically vulnerable plaque, yielding an accuracy of 92.59% after 100 epochs of training.

Quantifying internal intervertebral disc strains to assess nucleus replacement device designs: a digital volume correlation and ultra-high-resolution MRI study.

Introduction: Nucleus replacement has been proposed as a treatment to restore biomechanics and relieve pain in degenerate intervertebral discs (IVDs). Multiple nucleus replacement devices (NRDs) have been developed, however, none are currently used routinely in clinic. A better understanding of the interactions between NRDs and surrounding tissues may provide insight into the causes of implant failure and provide target properties for future NRD designs. The aim of this study was to non-invasively quantify 3D strains within the IVD through three stages of nucleus replacement surgery: intact, post-nuclectomy, and post-treatment. Methods: Digital volume correlation (DVC) combined with 9.4T MRI was used to measure strains in seven human cadaveric specimens (42 ± 18years) when axially compressed to 1kN. Nucleus material was removed from each specimen creating a cavity that was filled with a hydrogel-based NRD. Results: Nucleus removal led to loss of disc height (12.6 ± 4.4%, p = 0.004) which was restored post-treatment (within 5.3 ± 3.1% of the intact state, p > 0.05). Nuclectomy led to increased circumferential strains in the lateral annulus region compared to the intact state (-4.0 ± 3.4% vs. 1.7 ± 6.0%, p = 0.013), and increased maximum shear strains in the posterior annulus region (14.6 ± 1.7% vs. 19.4 ± 2.6%, p = 0.021). In both cases, the NRD was able to restore these strain values to their intact levels (p ≥ 0.192). Discussion: The ability of the NRD to restore IVD biomechanics and some strain types to intact state levels supports nucleus replacement surgery as a viable treatment option. The DVC-MRI method used in the present study could serve as a useful tool to assess future NRD designs to help improve performance in future clinical trials.

Upper cervical spine bone mineral content variations in elderly females

The purpose of the study was to determine the bone mineral densities (BMDs) of the C1 and C2 vertebrae and discuss their implications for autonomous vehicle environments and vulnerable road users. Using quantitated computed tomography (QCT), the BMDs were obtained at eight regions for the C1 vertebra and seven regions for the C2 vertebra. The spine surgeon author outlined the boundaries of each region, and nine elderly female human cadaver specimens were used. The regions were based on potential stabilization locations for fracture fixation. In the C1 vertebra, the BMD was greatest at the anterior tubercle, followed by the posterior tubercle, the posterior arch, and the lateral and anterior lateral masses. In the C2 vertebra, the distal odontoid had the greatest BMD, followed by the spinous process, the C2-lateral mass, the odontoid-body interface, and the anterior inferior aspect of the body. Use of these data in female-specific finite element models may lead to a better understanding of load paths, injuries, mechanisms, and tolerance.

Anterior Transarticular Crossing Screw Fixation for Atlantoaxial Joint Instability: A Biomechanical Study.

To evaluate the biomechanical stability of anterior transarticular crossing screw (ATCS) and compare it with anterior transarticular screw (ATS) which may provide basic evidence for clinical application. Eight human fresh cadaveric specimens (occiput-C4) were tested with 5 conditions including the intact status, the injury status (type II odontoid fracture), the injury+ATS fixation status (traditional bilateral ATS fixation); the injury+unilateral ATCS fixation status; and the injury+bilateral ATCS fixation status. Specimens were applied to a pure moment of 1.5 Nm in flexion-extension, lateral bending, and axial rotation, respectively. The range of motions (ROMs) and the neutral zones (NZs) of C1 to C2 segment were calculated and compared between 5 status. ATS and ATCS fixations significantly reduced the motions in all directions when compared with the intact and injury statues (p < 0.05). In flexion-extension, the ROMs of ATS, unilateral ATCS, and bilateral ATCS were 4.7° ± 2.5°, 4.1° ± 1.9°, and 3.2° ± 1.2°, respectively. Bilateral ATCS resulted in a significant decrease in ROM in flexion-extension when compared with ATS and unilateral ATCS (p = 0.035 and p = 0.023). In lateral bending and axial rotation, there was no significant difference in ROM between the 3 fixations (p > 0.05). Three fixations resulted in similar NZs in all directions (p > 0.05). ATCS is a biomechanically effective alternative or supplemental method for atlantoaxial instability.

Patient specific instrumentation in ACL reconstruction: a proof-of-concept cadaver experiment assessing drilling accuracy when using 3D printed guides

IntroductionAccurate positioning of the femoral tunnel in ACL reconstruction is of the utmost importance to reduce the risk of graft failure. Limited visibility during arthroscopy and a wide anatomical variance attribute to femoral tunnel malposition using conventional surgical techniques. The purpose of this study was to determine whether a patient specific 3D printed surgical guide allows for in vitro femoral tunnel positioning within 2 mm of the planned tunnel position.Materials and MethodsA patient specific guide for femoral tunnel positioning in ACL reconstruction was created for four human cadaveric knee specimens based on routine clinical MRI data. Fitting properties were judged by two orthopedic surgeons. MRI scanning was performed both pre- and post-procedure. The planned tunnel endpoint was compared to the actual drilled femoral tunnel.ResultsThis patient specific 3D printed guide showed a mean deviation of 5.0 mm from the center of the planned femoral ACL origin.ConclusionIn search to improve accuracy and consistency of femoral tunnel positioning in ACL reconstruction, the use of a patient specific 3D printed surgical guide is a viable option to explore further. The results are comparable to those of conventional techniques; however, further design improvements are necessary to improve accuracy and enhance reproducibility.