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A clinically significant event of early mammalian embryogenesis is the generation and early development of the anterior-posterior (A-P) axis, the imaginary line along which the structures from head to tail will form. This axis not only appears before gastrulation but is also oriented in a specific way in relation to the long and short diameters of the bilaterally symmetric epiblast. In mice, the most widely used mammalian in vivo model of early embryogenesis, the A-P axis is normally aligned with the long epiblast diameter by the early streak (ES) stage, a time during early gastrulation around embryonic day 6.5 (E6.5). Incorrect orientation of the A-P axis by the ES stage, that is, being aligned with the short epiblast diameter, leads to failure in completing gastrulation and results in embryo death soon after. Knowing the orientation of this axis from when it forms before gastrulation (around E5.5) until just before the ES stage is crucial for: (a) understanding the ill-defined factors involved in its formation and early development since they must be spatially related to it, and (b) providing explanations for the underlying mechanism when it is incorrectly orientated. However, the orientation of the A-P axis in pre-ES embryos of the E5.5-E6.5 period remains unclear. Specifically, although it is thought that this axis initially aligns with the short epiblast diameter and subsequently changes its orientation to become aligned with the long diameter by an unidentified pre-gastrulation stage before the ES stage, this proposition remains unresolved. This is largely due to the lack of clearly defined morphological criteria for staging certain periods of pre-ES mouse embryos (especially when the A-P axis initiates and when gastrulation begins prior to the ES stage), which are a prerequisite for identifying A-P axis orientation at specific pre-ES stages. Furthermore, although the orientation of an extraembryonic trophoblast asymmetry, specifically the tilt of the ectoplacental cone (EPC), coincides with that of the A-P axis by the ES stage, it is unknown whether such an association also exists at pre-gastrulation stages during A-P axis formation. Knowing this would exclude or implicate this trophoblast asymmetry as an upstream factor in orientating the A-P axis when it forms. To address these issues, we established a more refined embryo staging for the E5.5-E6.5 period using a novel combination of live morphological criteria and used it to examine the orientation of the A-P axis and that of the EPC tilt at specific stages. First, contrary to current thinking, we show that when the A-P axis first appears at our newly described anterior visceral endoderm-1 (AVE-1) and AVE-2 stages, it aligns with the long epiblast diameter in all embryos. This orientation is maintained in most embryos at all subsequent pre-gastrulation stages, specifically at our AVE-3 and pre-streak stages (the remaining embryos of these stages had this axis aligned with the short epiblast diameter). Second, we identified for the first time the pre-ES stage when gastrulation initiates, which we named the nascent streak (NS) stage, and further subdivided it into NS-1 and NS-2. At variance with current belief, we provide evidence that the earliest stage just before the ES stage when all embryos align their A-P axis with the long epiblast diameter is not a pre-gastrulation stage, but the NS-2 stage (at NS-1, most but not all embryos had this A-P axis orientation). Third, we implicate the EPC tilt as a possible extraembryonic factor in promoting correct A-P axis orientation, as this tilt exists before the AVE-1 stage and its orientation coincided with that of the A-P axis in all embryos at AVE-1, AVE-2 and ES stages and almost all embryos at AVE-3, pre-streak and NS stages. Overall, our work: (a) identified the previously unresolved orientation of the mouse A-P axis within the epiblast before the ES stage during the E5.5-E6.5 period; (b) provides an alternative explanation for when this axis is incorrectly oriented by the ES stage, namely, its defective alignment with the short epiblast diameter by this stage could be due to its failure to align with the long epiblast diameter from the time of its formation; and (c) implicates the pre-existing orientation of the EPC tilt as a possible factor in orientating the newly formed A-P axis.

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The elastic properties of the folds govern the characteristics of vocal fold vibrations. This study addresses existing gaps by investigating the Young's modulus along the anterior-posterior direction in excised canine and cadaveric human vocal folds. Micro-indentation testing was conducted on six excised canines and three cadaveric human larynges. Multiple points along the medial glottal wall were indented to determine force-displacement, stress-strain relationships, and Young's modulus as a function of Green's strain. A vertical stiffness gradient was consistently observed in both canine and human samples, with higher stiffness in the inferior aspect compared with the superior aspect. The stiffness increased toward both the anterior and posterior directions from the mid-coronal plane, with a more pronounced increase at the posterior edge. Human vocal folds generally exhibited lower stiffness at low strains but were comparable to canine vocal folds at higher strains. These findings suggest that the canine larynx model is a reasonable representation of the human laryngeal tissues' elastic property trends. This analysis of the vertical stiffness gradient in canine and human vocal folds provides valuable data for improving experimental and numerical models of phonation.

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Wnt signal is crucial to correctly regenerate tissues along the original axis in many animals. Lizards are able to regenerate their tails spontaneously, while the anterior-posterior axis information required for the successful regeneration is still elusive. In this study, we investigated the expression pattern of Wnt ligands and HOX genes during regeneration. The results of in situ hybridization revealed that Wnt6 and Wnt10A mRNA levels are higher in wound epithelium (WE) than that in blastema during regeneration. In addition, we showed that Wnt agonist positively regulated the expression of HOXA13 in cultured blastema cells, while did not show similar effect on that of HOXB13, HOXC13 and HOXD13. Finally, we found that HOXA13 showed a gradient level along the anterior-posterior axis of regenerated blastema, with higher level at the caudal end. These data proposed that Wnt6, Wnt10A and HOXA13 might play an important role in establishing distal position for regeneration.

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Anterior-posterior (AP) stability is an important measure of knee performance after total knee arthroplasty (TKA). To improve the stabilizing effect of implants designed to compensate for the loss of the cruciate ligaments, it is important to understand the tibiofemoral contact situation within the native ligamentous situation of the knee and how it changes after cruciate ligament resection. This in vitro study introduces a new approach to accurately measure the tibiofemoral kinematics in a six-degrees-of-freedom joint motion simulator by tracking landmark-based coordinate systems and their corresponding bone geometries. The tibiofemoral contact situation was investigated by projecting the medial and lateral flexion facet centers onto the tibial plateau under AP shear forces across various flexion angles in thirteen knees. Tests were conducted pre- and post-cruciate ligament resection. Post-cruciate ligament resection, the femoral condyles shifted closer to or even exceeded the posterior border of the tibial plateau, but only slightly closer to the anterior border. This study presents a new methodology for measuring the tibiofemoral kinematics that can be applied to multiple loading profiles. It provides a basis for further investigations, including passive or active muscle forces, to enhance the design of total knee protheses and improve surgical outcomes.

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BACKGROUND: Anterior shoulder labral tearing has historically been considered the most common location of shoulder labral pathology. Recently, smaller studies have reported that posterior labral involvement may be more common than previously recognized. PURPOSE: To examine the location of surgically repaired labral tears by a single surgeon over a consecutive 23-year period. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A total of 1763 consecutive patients who underwent arthroscopic or open shoulder labral repair by a single seniorsports medicine fellowship-trained orthopaedic surgeon between April 2000 and April 2023 were retrospectively reviewed. Current Procedural Terminology codes were used to identify patients, which included 29806, 29807, 29822, and 29823. Exclusion criteria included isolated shoulder manipulation or glenohumeral joint or labral debridement that did not include repair. Intraoperative glenoid labral tears observed were categorized into 7 broad categories: (1) anterior labral tears, (2) posterior labral tears, (3) superior labral anterior posterior (SLAP) type II tears (A, B, or C), (4) SLAP type V tears, (5) SLAP type VIII tears, or (6) circumferential labral tears (combined SLAP, anterior, and posterior labral tear). Shoulders diagnosed with multiple tear patterns (ie, anterior and posterior) were also noted. RESULTS: During the 23-year period, 1763 patients underwent arthroscopic or open labral repair; they included 1295 male and 468 female patients, ranging in age from 12 to 70 years, with a mean age of 23.2 years and median age of 19 years. Overall, 28.4% of tears involved the anterior labrum, 64.9% involved the posterior labrum, and 59.6% involved the superior labrum. Regarding isolated tears, 9.3% were isolated anterior labral tears, 19.7% were isolated posterior labral tears, 11.5% involved the anterior and posterior labrum, 22.2% were isolated superior (SLAP type II-IV) tears, 3.63% were isolated SLAP type V tears, 29.8% were isolated SLAP type VIII tears, and 4.1% were circumferential tears. CONCLUSION: Posterior shoulder labral tearing was more common than anterior tearing in a large consecutive series of 1763 patients who underwent surgical repair. This highlights the importance of posterior labral pathology, which sometimes may be overlooked because of more vague complaints, with pain and loss of function being the most common.

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Recent studies have reported chronic rhinosinusitis (CRS) as an independent risk factor for stroke. However, the association with stroke depending on the affected sinuses has not been explored. This study aimed to elucidate the side- and sinus-specific relationship between CRS and ischemic stroke through imaging analyses. We retrospectively reviewed the medical records of patients who were diagnosed with ischemic stroke at a tertiary center. CRS was defined as having a total score of greater than or equal to 4, according to the Lund-Mackay scoring system, through brain magnetic resonance imaging or computed tomography. We investigated the side- and sinus-specific correlation between CRS and ischemic stroke. Subgroup analyses were performed for different age groups. CRS prevalence in patients with ischemic stroke was 18.4%, which was higher than the previously reported prevalence in the general population. Overall, there was no correlation between the directions of the CRS and ischemic stroke (p > 0.05). When each sinus was analyzed, the frontal (Cramer's V = 0.479, p < 0.001), anterior (Cramer's V = 0.396, p < 0.001)/posterior (Cramer's V = 0.300, p = 0.008) ethmoid, and sphenoid (Cramer's V = 0.383, p = 0.005) sinuses showed a statistically significant correlation with the side of stroke, but the maxillary sinus (Cramer's V = 0.138, p = 0.208) did not. In subgroup analyses, a significant right-side correlation between the two diseases was observed in the older-age subgroup (≥65 years old, Cramer's V = 0.142, p = 0.040). Diabetes mellitus (odds ratio = 1.596, 95% confidence interval = 1.204-2.116) was identified as an independent risk factor for having CRS in patients with ischemic stroke. CRS of the frontal, anterior/posterior ethmoid, and sphenoid sinuses has a directional relationship with ischemic stroke. Our results on which sinuses correlate with stroke advocate for the active surveillance of CRS in patients at high risk of ischemic stroke.

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The rotator cuff tear effects on glenohumeral joint tissues, such as superior labrum anterior-posterior (SLAP) lesions, have been studied experimentally or numerically in various cases. In relation to these studies, and as a novel feature of our study, infraspinatus (INF) muscle tear effects on other muscle force variations and stress and strain increases on glenoid labrum (GL), glenoid cartilage (GC) tissues, and a SLAP pathology were investigated. The ITK-SNAP Software (ISS) was used to segment the humerus and glenoid bone. The surface entities were segmented and exported to SolidWorks 2019, where the finite element model (FEM) was completed. Static optimizations of the muscle forces were calculated using a generic model in OpenSim 4.1 for the 0-3.88 s time interval to perform our finite element analyses (FEAs) in ANSYS 19.3 for the intact, partial torn, and fully torn INF muscle. The FEAs were also conducted for the specified time interval. The stress and strain increases on the GL, and GC tissues were determined to be critical when compared with yield strengths. In the case of fully torn INF, the GL and cartilage interfacial principal stress was calculated to be 3.3856 MPa. In the case of the fully torn INF, the principal stress that occurred on the GC tissue was calculated to be 42.465 MPa. In the case of the intact INF, the principal stress that occurred on the labrum was obtained as 4.257 MPa. These results showed that there was no detachment or disorder on the designated tissues caused by the INF muscle tear when the shoulder functioned at 60° of external rotation at 11° of abduction. Nonetheless, a minor amount of external force could cause severe pathological effects on the specified tissues.

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BACKGROUND: Anterior-posterior electrode placement is preferred in electrical cardioversion of atrial fibrillation. However, the optimal anterior-posterior electrode position in relation to the heart is not studied. METHODS AND RESULTS: We performed a prospective observational study on patients presenting for cardioversion of atrial fibrillation. Electrodes were placed in the anterior-posterior position and shock was delivered in a step-up approach (100 J→200 J→360 J). Fluoroscopic images were obtained, and distances were measured from points A, midanterior electrode; and B, midposterior electrode, to midpoint of the cardiac silhouette. Patients requiring one 100 J shock for cardioversion success (group I) were compared with those requiring >1 shock/100 J (group II). Logistic regression was used to determine the impact of electrode distance on low energy (100 J) cardioversion success. Computed tomography scans from this cohort were analyzed for anatomic landmark correlation to the cardiac silhouette. Of the 87 patients included, 54 (62%) comprised group I and 33 (38%) group II. Group I had significantly lower distances from the mid-cardiac silhouette to points A (5.0±2.4 versus 7.4±3.3 cm; P<0.001) and B (7.3±3.0 versus 10.0±3.8 cm; P=0.002) compared with group II. On multivariate analysis, higher distances from the mid-cardiac silhouette to point A (odds ratio, 1.33 [95% CI, 1.07-1.70]; P=0.01) and B (odds rsatio, 1.24 [95% CI, 1.05-1.50]; P=0.01) were independent predictors of low energy (100 J) cardioversion failure. Based on review of computed tomography scans, we suggest that the xiphoid process may be an easy landmark to guide proximity to the myocardium. CONCLUSIONS: In anterior-posterior electrode placement, closer proximity to the cardiac silhouette predicts successful 100 J cardioversion irrespective of clinical factors.

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A 20-year-old male national-level gymnast presented with left shoulder pain attributed to a superior labral anterior-posterior (SLAP) lesion. Physical examination revealed pain in the anterosuperior area at maximum shoulder elevation, with a positive combined abduction test and horizontal flexion test indicating a restriction in glenohumeral joint motion. Rather than directly addressing the SLAP lesion, ultrasound-guided hydrodissections of the thoracodorsal and axillary nerves were performed, leading to immediate alleviation of pain and mobility constraints. This innovative approach, emphasizing shoulder function, offers a novel therapeutic strategy for SLAP-associated shoulder pain in athletes.

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Structural and functional differences in the hippocampus have been related to the episodic memory and social impairments observed in autism spectrum disorder (ASD). In neurotypical individuals, hippocampal-cortical functional connectivity systematically varies between anterior and posterior hippocampus, with changes observed during typical development. It remains unknown whether this specialization of anterior-posterior hippocampal connectivity is disrupted in ASD, and whether age-related differences in this specialization exist in ASD. We examined connectivity of the anterior and posterior hippocampus in an ASD (N = 139) and non-autistic comparison group (N = 133) aged 5-21 using resting-state functional magnetic resonance imaging (MRI) data from the Healthy Brain Network (HBN). Consistent with previous results, we observed lower connectivity between the whole hippocampus and medial prefrontal cortex in ASD. Moreover, preferential connectivity of the posterior relative to the anterior hippocampus for memory-sensitive regions in posterior parietal cortex was reduced in ASD, demonstrating a weaker anterior-posterior specialization of hippocampal-cortical connectivity. Finally, connectivity between the posterior hippocampus and precuneus negatively correlated with age in the ASD group but remained stable in the comparison group, suggesting an altered developmental specialization. Together, these differences in hippocampal-cortical connectivity may help us understand the neurobiological basis of the memory and social impairments found in ASD.

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How animal body plans evolved and diversified is a major question in evolutionary developmental biology. To address this question, it is important to characterize the exact molecular mechanisms that establish the major embryonic axes which give rise to the adult animal body plan. The anterior-posterior (AP) axis is the first axis to be established in most animal embryos, and in echinoderm sea urchin embryos its formation is governed by an integrated network of three different Wnt signaling pathways: Wnt/ß-catenin, Wnt/JNK, and Wnt/PKC pathway. The extent to which this embryonic patterning mechanism is conserved among deuterostomes, or more broadly in metazoans, is an important open question whose answers could lead to a deeper appreciation of the evolution of the AP axis. Because Ambulacrarians (echinoderms and hemichordates) reside in a key phylogenetic position as the sister group to chordates, studies in these animals can help inform on how chordate body plans may have evolved. Here, we assayed the spatiotemporal gene expression of a subset of sea urchin AP Wnt patterning gene orthologs in the hemichordate, Schizocardium californicum. Our results show that positioning of the anterior neuroectoderm (ANE) to a territory around the anterior pole during early AP formation is spatially and temporally similar between indirect developing hemichordates and sea urchins. Furthermore, we show that the expression of wnt8 and frizzled5/8, two known drivers of ANE patterning in sea urchins, is similar in hemichordate embryos. Lastly, our results highlight divergence in embryonic expression of several early expressed Wnt genes (wnt1, wnt2 and wnt4). These results suggest that expression of the sea urchin AP Wnt signaling network is largely conserved in indirect developing hemichordates setting the foundation for future functional studies in S. californicum.

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PURPOSE: In this study, ultrasonography was used to measure medial meniscus (MM) extrusion under weight-bearing and nonweight-bearing conditions in both anterior cruciate ligament (ACL)-deficient and ACL-intact knee groups. This study aimed to determine the possible differences between these groups with an eventual impact on meniscal tears in ACL-deficient knees. METHODS: A total of 107 patients who underwent ACL reconstructive surgery between June 2022 and April 2023 were enroled. After applying exclusion criteria, 37 patients met the conditions for inclusion in the study and formed the ACL deficiency group (Group D). Of the 141 patients presenting to an outpatient clinic who agreed to have ultrasonography conducted on their nondiscomforting contralateral knee, 37 patients matched for age, sex, hip-knee-ankle angle and body mass index with Group D patients were selected for the ACL intact group (Group I). Ultrasonography was used to measure MM extrusion in weight-bearing and nonweight-bearing conditions for all participants. RESULTS: Seventy-four patients were included in the study (n = 37 per group). The supine position showed an MM extrusion of 1.2 ± 0.7 mm in Group I and 1.2 ± 0.7 mm in Group D (not significant). In the standing position, MM extrusion measured 2.0 ± 0.6 mm in Group I and 1.3 ± 0.8 mm in Group D. The difference in extrusion (Δextrusion) between the two positions was 0.8 ± 0.6 in Group I and 0.1 ± 0.2 in Group D, with statistical significance (p < 0.01). A consistent reduction in MM extrusion during weight-bearing was observed in patients with ACL deficiency, irrespective of the duration of ACL deficiency, age, sex and BMI. CONCLUSION: ACL deficiency did not significantly impact MM extrusion during nonweight-bearing conditions; however, less MM extrusion was observed in response to axial loading conditions. These findings indicate altered MM biomechanics due to increased anterior-posterior meniscal motion and rotational instability after ACL injury. LEVEL OF EVIDENCE: Level III.

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Most edentulous patients prefer fixed restoration or detachable prostheses over conventional complete dentures. The case report aims to address and discuss the clinical and laboratory steps of implant-supported, bar-retained maxillary overdenture and mandibular implant-supported, metal-acrylic resin, screw-retained, fixed complete denture. Impression techniques and laboratory steps are discussed and demonstrated to minimize the postfabrication or insertion complication. It lets you achieve the passive fit of the prosthesis that maintains the osseointegration by reducing stress on implants and the surrounding bone.

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When the ciliate Spirostomum ambiguum is transected into two pieces, both fragments regenerate and proliferate. In the anterior fragments, which have lost their contractile vacuoles due to transection, new contractile vacuoles were formed at their posterior ends in a few minutes. When the cells were cut into three pieces, new contractile vacuoles were formed in the anterior and middle fragments, both at their posterior ends. Thus, the anterior-posterior axis of S. ambiguum was maintained after transection. Morphological repair, including the formation of the contractile vacuole, was also observed when only the anteriormost portion was transected to cut out a small fragment that did not contain part of the macronucleus. Scanning electron microscopy was performed to observe changes in the shape of the cleavage surface of S. ambiguum during the wound healing process. Within minutes after cutting, the cut surface was covered with a cilia-free membrane, preventing leakage of cytoplasmic contents. The surface of the cut area then rounded with time and was covered with cilia, completing the repair of the cut area in about one day.

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Introduction: Whether a combined anterior-posterior (AP) approach offers additional benefits over the posterior-only (P) approach in adult spinal deformity (ASD) surgery remains unknown. In a cohort of patients undergoing ASD surgery, we compared the combined AP vs. the P-only approach in: (1) preoperative/perioperative variables, (2) radiographic measurements, and (3) postoperative outcomes. Methods: A single-institution, retrospective cohort study was performed for patients undergoing ASD surgery from 2009 to 2021. Inclusion criteria were ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up. The primary exposure was the operative approach: a combined AP approach or P alone. Postoperative outcomes included mechanical complications, reoperation, and minimal clinically important difference (MCID), defined as 30% of patient-reported outcome measures (PROMs). Multivariable linear regression was controlled for age, BMI, and previous fusion. Results: Among 238 patients undergoing ASD surgery, 34 (14.3%) patients underwent the AP approach and 204 (85.7%) underwent the P-only approach. The AP group consisted mostly of anterior lumbar interbody fusion (ALIF) at L5/S1 (73.5%) and/or L4/L5 (38.0%). Preoperatively, the AP group had more previous fusions (64.7% vs. 28.9%, p < 0.001), higher pelvic tilt (PT) (29.6 ± 11.6° vs. 24.6 ± 11.4°, p = 0.037), higher T1 pelvic angle (T1PA) (31.8 ± 12.7° vs. 24.0 ± 13.9°, p = 0.003), less L1-S1 lordosis (-14.7 ± 28.4° vs. -24.3 ± 33.4°, p < 0.039), less L4-S1 lordosis (-25.4 ± 14.7° vs. 31.6 ± 15.5°, p = 0.042), and higher sagittal vertical axis (SVA) (102.6 ± 51.9 vs. 66.4 ± 71.2 mm, p = 0.005). Perioperatively, the AP approach had longer operative time (553.9 ± 177.4 vs. 397.4 ± 129.0 min, p < 0.001), more interbodies placed (100% vs. 17.6%, p < 0.001), and longer length of stay (8.4 ± 10.7 vs. 7.0 ± 9.6 days, p = 0.026). Radiographically, the AP group had more improvement in T1PA (13.4 ± 8.7° vs. 9.5 ± 8.6°, p = 0.005), L1-S1 lordosis (-14.3 ± 25.6° vs. -3.2 ± 20.2°, p < 0.001), L4-S1 lordosis (-4.7 ± 16.4° vs. 3.2 ± 13.7°, p = 0.008), and SVA (65.3 ± 44.8 vs. 44.8 ± 47.7 mm, p = 0.007). These outcomes remained statistically significant in the multivariable analysis controlling for age, BMI, and previous fusion. Postoperatively, no significant differences were found in mechanical complications, reoperations, or MCID of PROMs. Conclusions: Preoperatively, patients undergoing the combined anterior-posterior approach had higher PT, T1PA, and SVA and lower L1-S1 and L4-S1 lordosis than the posterior-only approach. Despite increased operative time and length of stay, the anterior-posterior approach provided greater sagittal correction without any difference in mechanical complications or PROMs.

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BACKGROUND: In breast diffusion-weighted imaging (DWI), distortion and physiologic artifacts affect clinical interpretation. Image quality can be optimized by addressing the effect of phase encoding (PE) direction on these artifacts. PURPOSE: To compare distortion artifacts in breast DWI acquired with different PE directions and polarities, and to discuss their clinical implications. STUDY TYPE: Prospective. POPULATION: Eleven healthy volunteers (median age: 47 years old; range: 22-74 years old) and a breast phantom. FIELD STRENGTH/SEQUENCE: Single-shot echo planar DWI and three-dimensional fast gradient echo sequences at 3 T. ASSESSMENT: All DWI data were acquired with left-right, right-left, posterior-anterior, and anterior-posterior PE directions. In phantom data, displacement magnitude was evaluated by comparing the location of landmarks in anatomical and DWI images. Three breast radiologists (5, 17, and 23 years of experience) assessed the presence or absence of physiologic artifacts in volunteers' DWI datasets and indicated their PE-direction preference. STATISTICAL TESTS: Analysis of variance with post-hoc tests were used to assess differences in displacement magnitude across DWI datasets and observers. A binomial test and a chi-squared test were used to evaluate if each in vivo DWI dataset had an equal probability (25%) of being preferred by radiologists. Inter-reader agreement was evaluated using Gwet's AC1 agreement coefficient. A P-value <0.05 was considered statistically significant. RESULTS: In the phantom study, median displacement was the significantly largest in posterior-anterior data. While the displacement in the anterior-posterior and left-right data were equivalent (P = 0.545). In the in vivo data, there were no physiological artifacts observed in any dataset, regardless of PE direction. In the reader study, there was a significant preference for the posterior-anterior datasets which were selected 94% of the time. There was good agreement between readers (0.936). DATA CONCLUSION: This study showed the impact of PE direction on distortion artifacts in breast DWI. In healthy volunteers, the posterior-to-anterior PE direction was preferred by readers. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 1.

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One common method to determine tibiofemoral kinematics following total knee replacement (TKR) is to capture single-plane fluoroscopic images of a patient activity and determine anterior-posterior (AP) positions of the femoral condyles and internal-external (IE) tibial rotation. Although JointTrack is widely used to analyze such images, precision (i.e. repeatability) in determining AP positions and IE tibial rotations using the two publicly available programs has never been quantified. The objectives were to determine the precision and reproducibility of results using both programs. Fluoroscopic images of 16 patients who performed a weight-bearing deep knee bend following TKR were analyzed. JointTrack Manual (JTM) and JointTrack Machine Learning (JTML) were used to perform 3D model-to-2D image registration after which AP positions of the femoral condyles and IE tibial rotations were determined. Precision in AP positions and IE rotations was quantified. Intraclass correlation coefficients (ICCs) for both repeatability (i.e. intraobserver) and reproducibility (i.e. interobserver) also were determined. Precision using JTM was worse than JTML for AP positions of the medial and lateral femoral condyles (1.0 mm and 0.9 mm vs 0.3 mm and 0.4 mm, respectively; p < 0.001 for both). For IE tibial rotation, precision also was worse using JTM versus JTML (1.1º vs 0.9°, p = 0.010). ICC values for JTML indicated good to excellent agreement (range: 0.82-0.98) whereas ICC values for JTM indicated only moderate to good agreement (range: 0.58-0.88). JTML has better precision and reproducibility than JTM and also is more efficient to use. Therefore, use of JTML over JTM is strongly recommended.

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STUDY DESIGN: Systematic review. OBJECTIVE: To compare the efficacy of the posterior approach and combined anterior-posterior approach in the treatment of ankylosing spondylitis (AS) with cervical spine fracture by meta-analysis. METHODS: The databases PubMed, Web of Science, Embase, and Cochrane Library were searched for studies on the comparison of the posterior approach group and the combined anterior-posterior approach group in the treatment of ankylosing spondylitis combined with cervical spine fracture from database establishment to August 2023. The procedure time, intraoperative blood loss, the rates of neurological improvement, mean change in the postoperative neurological function, complication rates, rates of revised surgery, and mortality were extracted. Meta-analysis was performed using RevMan 5.4 software provided by Cochrane Library. RESULTS: A total of 11 retrospective cohort studies with a total of 215 patients were included in this study. The posterior approach group had lower intraoperative blood loss than the combined anterior-posterior approach group [Mean difference (MD) = -146.05, 95%CI(-187.40,-104.69), P < .00001]; the operation time was significantly less in the posterior approach group than in the combined anterior-posterior approach group [MD = -95.34, 95%CI(-113.13,-77.55), P < .00001]. There were no statistically significant differences in the neurological improvement rates, mean changes in postoperative neurological function, complication rates, modified surgery rates, and mortality rates. CONCLUSION: Both the posterior approach and combined anterior and posterior approach can achieve good results. Clinicians should develop an individualized approach based on the patient's fracture type, degree of spinal cord injury, fracture stability, fracture dislocation, general condition, and underlying disease.

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OBJECTIVE: An assessment of the effective diameter of a patient's body using electron densities of tissues inside the scan area (Deffρe) was proposed to overcome challenges associated with the estimation of water-equivalent diameter (Dw), which is used for size-specific dose estimate (SSDE). The aims of this study were to (1) investigate the Deffρe method in two different forms using a wide range of patient sizes and scanning protocols, and (2) compare between four methods used to estimate the patient size for SSDE. MATERIALS AND METHODS: Under IRB approval, a total of 350 patients of varying sizes have been collected retrospectively from the Hospital. The Dw values were assessed over six different CT body protocols: (1) chest with contrast media, (2) chest High-Resolution Computed Tomography (HRCT) without contrast media, (3) abdomen-pelvis with contrast media, (4) abdomen-pelvis without contrast media, (5) chest-abdomen-pelvis with contrast media, and (6) pelvis without contrast media. A MATLAB-based code was developed in-house to assess the size of each patient using the conventional effective diameter method (Deff), Deffρe by correcting either both the lateral (LAT) and anterior-posterior (AP) dimensions (Deff,LAT+APρe) or LAT only (Deff,LATρe), and Dw at the mid-CT slice of the patient images. RESULTS: The results of Deff,LAT+APρe and Deff,LATρe provided a better estimation for the chest protocols with the averages of absolute percentage difference (PD) values in the range of 3 - 7 % for all patient sizes as compared to the Dw method, whereas the averages of PD values for the Deff method were 9 - 15 %. However, Deff gave a better estimation for Dw values for the other body protocols, with differences of 2 - 4 %, which were lower than those obtained with the Deff,LAT+APρe and Deff,LATρe methods. For the chest protocols, statistically significant differences were found between Deff and the other methods, but there were no significant differences between all the methods for the other scanning protocols. The results show that the correction of both dimensions, LAT and AP, did not improve the accuracy of the Deffρe method, and, for most protocols, Deff,LAT+APρe gave larger range differences compared to those based on correction of the LAT dimension only. CONCLUSION: If the Dw cannot be assessed, the Deff,LATρe method may only be considered for the chest protocols as an alternative approach. The Deff method may also be used for all regions taking into account the application of a correction factor for the chest protocols to avoid a significant under or overestimation of the patient dose.

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PURPOSE: To compare the clinical and radiological results of the anterior approach versus the posterior approach versus the anterior-posterior approach for the treatment of thoracolumbar burst fractures. METHODS: The network meta-analysis was performed in accordance with the PRISMA Statement. Electronic searches of PubMed and Embase were conducted up to June 22, 2023, for relevant randomized controlled trials. STATA13.0 was used to perform network meta-analysis. p < .05 was considered significant. RESULTS: Nine RCTs with a total of 550 patients receiving surgical treatment in at least two of the three approaches, including anterior, posterior and anterior-posterior approaches, were included. The surgical duration and intraoperative bleeding volume in the posterior approach were significantly lower than those in the anterior (SMD, -1.72; 95% CI, -2.82, -0.62) and anterior-posterior approaches (SMD, 3.33; 95% CI, 1.65, 5.00). The surgical duration in the anterior approach was significantly lower than that in the anterior-posterior approach (SMD, 1.61; 95% CI, 0.12, 3.10). The Cobb angle in the anterior-posterior approach was significantly lower than that in the anterior approach (MD, -4.83; 95% CI, -9.60, -0.05). The VAS score in the posterior approach was significantly higher than that in the anterior approach (MD, 0.85; 95% CI, 0.55, 1.16) and anterior-posterior approach (MD, -0.84; 95% CI, -1.12, -0.55). No significant difference was identified among the three surgical approaches in implant failure rate and infection rate. CONCLUSION: All three approaches were safe approaches with advantages and disadvantages. The selection of surgical approaches for the treatment of thoracolumbar burst fractures may be individualized.

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