Landmark-based Measurements Research Articles

Deep learning algorithm for fully automated measurement of sagittal balance in adult spinal deformity.

Deep learning (DL) algorithms can be used for automated analysis of medical imaging. The aim of this study was to assess the accuracy of an innovative, fully automated DL algorithm for analysis of sagittal balance in adult spinal deformity (ASD). Sagittal balance (sacral slope, pelvic tilt, pelvic incidence, lumbar lordosis and sagittal vertical axis) was evaluated in 141 preoperative and postoperative radiographs of patients with ASD. The DL, landmark-based measurements, were compared with the ground truth values from validated manual measurements. The DL algorithm showed an excellent consistency with the ground truth measurements. The intra-class correlation coefficient between the DL and ground truth measurements was 0.71-0.99 for preoperative and 0.72-0.96 for postoperative measurements. The DL detection rate was 91.5% and 84% for preoperative and postoperative images, respectively. This is the first study evaluating a complete automated DL algorithm for analysis of sagittal balance with high accuracy for all evaluated parameters. The excellent accuracy in the challenging pathology of ASD with long construct instrumentation demonstrates the eligibility and possibility for implementation in clinical routine.

Single-Splint, 2-Jaw Orthognathic Surgery for Correction of Facial Asymmetry: 3-Dimensional Planning and Surgical Execution.

Three-dimensional (3D) planning of orthognathic surgery (OGS) improves the treatment of facial asymmetry and malocclusion, but no consensus exists among clinicians regarding technical details. This study verified the consistency of authors' workflow and strategies between 3D planning and surgical execution for facial asymmetry. This retrospective study recruited consecutive patients (n=54) with nonsyndromic facial asymmetry associated with malocclusion. The stepwise workflow included orthodontic treatment, 3D imaging-based evaluation, planning, and transferring the virtual of single-splint 2-jaw OGS to actual surgery in all patients. Seven landmark-based measurements were selected for postoperative assessment of facial symmetry. Fifty patients had no anesthetic/surgical-related episode and procedure-related complications. Others experienced wound infection (n=1), transient TMJ discomfort (n=1), and facial numbness (n=3). Two cases had minor residual asymmetry (cheek and chin, respectively), but did not request revisionary bone or soft tissue surgery. Comparisons between the planned and postoperative 3D images with quantitative measurement revealed acceptable outcome data. The results showed a significant increase in facial symmetry at 7 landmark-based postoperative measurements for both male and female. This 3D-assisted pathway of OGS permitted achievement of consistent satisfactory results in managing facial asymmetry, with low rate of complications and secondary management.

Evolutionary transition from surface to subterranean living in Australian water beetles (Coleoptera: Dytiscidae) through adaptive and relaxed selection

Abstract Over the last 5 million years, numerous species of Australian stygobiotic (subterranean and aquatic) beetles have evolved underground following independent colonization of aquifers by surface ancestors, providing a set of repeated evolutionary transitions from surface to subterranean life. We used this system as an ‘evolutionary experiment’ to investigate whether relaxed selection has provided a source of variability for adaptive radiations into ecosystems containing open niches and whether this variability underpins phenotypic evolution in cave animals. Linear and landmark-based measurements were used to quantify the morphology of subterranean species from different aquifers, compared to interstitial and closely related aquatic surface species. Subterranean dytiscids were observed to be morphologically distinct, suggesting they have a different lifestyle compared to their surface relatives. However, variation in the measured traits was much greater in the subterranean species, and unstructured, showing no evidence of clustering that would indicate adaptation to specific niches. Furthermore, a previously identified pattern of repeated nonoverlapping size variation in beetles across aquifers was not correlated with repeated body shape evolution. The observed variability across body shape and limb traits provides support for the hypothesis that relaxed selection and neutral evolution underlie the phenotypic evolution in these species.

Defining Fragmentation Patterns of Archaeological Bone Remains without Typologies: A Landmark-Based Approach on Rodent Mandibula

Fragmentation is a recurring feature of archaeological faunal material, and impacts many aspects of zooarchaeological studies from taxonomical identification to biometric studies. It can result from anthropic and natural actions that occurred respectively before and/or after bone deposit. While several bone fragmentation typologies have been described, they are currently based on both macroscopic observations and researcher subjectivity and lack the universality necessary for inter-study comparisons. To fulfill this need we present a standardized landmark-based protocol for the description and quantification of mandibular fragmentation patterns, using two insular rodents of different sizes as models. The rice rats (Oryzomyini tribe) and the agouti (Dasyprocta) from the Lesser Antilles were abundant during the pre-Columbian Ceramic Age (500 BCE-1500 CE). Their mandibles’ shapes were quantified using the coordinates of 13 2D-landmarks. We show that landmark-based measurements can be used to:—assess the preservation differences between taxa of the same taxonomic group (e.g., rodents),—estimate the level of preservation of a skeletal part (e.g., mandible),—describe fragmentation patterns without pre-existing typologies and—facilitate the application of geometric morphometric methods to fragmented archaeological material. Our novel approach, leveraging fragmentation analyses and establishing specific fragmentation patterns, frees itself from existing typologies and could be systematically applied to future research.

Reproducibility of Novel Soft-Tissue Landmarks on Three-Dimensional Human Facial Scan Images in Caucasian and Asian

BackgroundThree-dimensional surface imaging is established in many disciplines for objective facial acquisition regarding anthropometry. Former studies addressed the validation of landmark-based measurements for single race. In order to distinguish racial difference, the reproducibility of the landmark measurements must first be validated.ObjectivesOur purpose is to validate the reproducibility of 46 facial soft-tissue landmarks on x, y, z axes to prove their reliability as 3D reference points.MethodsThe study included 80 European Caucasian and 80 Chinese volunteers. Standardized 3D surface imaging was performed using Vectra 3D system. Two raters identified and defined 46 landmarks (138 coordinates), then repeatedly 3D-imaged volunteers' facial region in separate sessions. Coordinates' reproducibility of landmarks is divided into three categories (< 0.5 mm, < 1 mm, and >1 mm) for intra- and inter-rater reproducibility assessments.ResultsCoordinates' reproducibility of 160 samples was distributed as follows: Intra-rater: < 0.5 mm (45%), < 1 mm (42%), >1 mm (13%); inter-rater: < 0.5 mm (31.2%), < 1 mm (42%), > 1 mm (26.8%). The reproducibility of landmarks in nasal tip region differs slightly between Caucasians and Asians. Compared to females, males typically have higher landmark reproducibility in lip and chin region. However, there were no differences in the reproducibility ranking of landmarks by gender.ConclusionThe majority of the 46 landmarks in the 3D plane are reproducible to 1 mm, which is clinically acceptable. All selected landmarks showed strong consistency across race and gender, suggesting their potential use as reference points in prospective clinical practice.Level of Evidence IVThis journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

A GWAS in Latin Americans identifies novel face shape loci, implicating VPS13B and a Denisovan introgressed region in facial variation.

To characterize the genetic basis of facial features in Latin Americans, we performed a genome-wide association study (GWAS) of more than 6000 individuals using 59 landmark-based measurements from two-dimensional profile photographs and ~9,000,000 genotyped or imputed single-nucleotide polymorphisms. We detected significant association of 32 traits with at least 1 (and up to 6) of 32 different genomic regions, more than doubling the number of robustly associated face morphology loci reported until now (from 11 to 23). These GWAS hits are strongly enriched in regulatory sequences active specifically during craniofacial development. The associated region in 1p12 includes a tract of archaic adaptive introgression, with a Denisovan haplotype common in Native Americans affecting particularly lip thickness. Among the nine previously unidentified face morphology loci we identified is the VPS13B gene region, and we show that variants in this region also affect midfacial morphology in mice.

Development of an Anatomic Landmark-Based Measurement of the Achilles Tendon

Category:Ankle; SportsIntroduction/Purpose:Achilles tendon ruptures (ATRs) occurred with an incidence of 2.5 per 100,000 person-years in 2016. This rate has been increasing over the last decade and it has been postulated that this is due to the increasing activity level of older people. With a high and increasing incidence of such a significant injury, further investigation must be done to optimize the treatment of ATRs. The degree of tendon lengthening has been correlated with clinical outcomes, with greater elongation being associated with worse outcomes. MRI and ultrasound techniques have been validated in measurement of Achilles tendon. We sought to develop a reliable, reproducible, and accurate measurement technique utilizing the manual palpation of anatomic landmarks that will be cost effective as well as convenient to perform, particularly intraoperatively.Methods:Both lower legs of 10 healthy subjects without history of Achilles tendon injury were examined using ultrasound and anatomic landmark-based measurement techniques. Subjects sat upright on the exam table and legs were held in flexion at the knee with slight external rotation with the ankle held at 90o, allowing the lower leg to rest flat on the exam table. The length from the medial head of the gastrocnemius to the bottom of the non-compressed heal pad was measured by three raters using the ultrasound and anatomic landmark-based techniques for inter-rater reliability. The measurements were repeated one week later for intra-rater reliability. Ultrasound measurements had excellent inter-rater (0.93) and intra-rater (0.82) correlation coefficients, while good inter-rater (0.76) and intra-rater (0.86) correlation coefficients were observed among anatomic landmark-based measurements. Achilles tendon length measured with ultrasound and anatomic landmark-based techniques were compared using a paired t-test.Results:The anatomic landmark-based technique produces longer measurements of the Achilles tendon (23.2 cm (sd 2.6 cm)) compared to measurements made using ultrasound (22.4 cm (sd 2.6)) (p<0.001). On average, the anatomic landmark-based technique measures 0.8 cm (95% Confidence Interval: 0.4, 1.2) longer than the ultrasound technique. The intraclass correlation coefficient between the anatomic landmark-based and ultrasound measurements is 0.90.Conclusion:While the anatomic landmark-based technique produces a longer measurement of the Achilles tendon, it may still be a reproducible measurement tool. If the change in tendon length is of interest, this technique may be a valid and simple way to monitor that variable. Comparison with MRI may be warranted to better determine the accuracy of the anatomic landmark-based Achilles tendon measure. These results compared with MRI may set the stage for further evaluation of this measurement technique in the operating room in subjects undergoing ATR repair.

Quantitative Assessment of Facial Asymmetry Using Three-Dimensional Surface Imaging in Adults: Validating the Precision and Repeatability of a Global Approach.

Comparison of global versus landmark analyses of facial asymmetry using three-dimensional photogrammetry to establish a precise method for evaluating facial asymmetry. The landmark-based approach utilized anthropometric data points. Our global approach involved registration of mirror images, independent of a midplane, to calculate a root mean square (RMS) value. We analyzed precision and technical and operator error of both methods. Three hundred fifty adults participated in this study. We found that the global method has better precision and repeatability with a significantly lower error rate than the landmark-based method. In adults, the average RMS was 0.6253 mm with a standard deviation of 0.16. Our facial asymmetry measurement is more accurate than landmark-based measurements. This method is quick, reliable, and results in generation of a RMS score and a corresponding color-coded facial map that highlights regions of higher and lower asymmetry. This method may be used as a screening tool for asymmetry in both the clinical and research settings.

Tooth Shape Differences Analyzed by Biometric and Morphometric Approaches: A Case Study on Two Morphologically Very Similar Lacustrine Cichlid Species

Tooth shape is generally considered to be under strong genetic control, and highly species specific. It is therefore widely used for taxonomic studies. The tooth shape-based morphological classification of the Eretmodini (a tribe of closely related cichlids endemic to Lake Tanganyika), has, however, been shown to be in conflict with recent molecular data, which suggests the occurrence of parallel evolution. A detailed biometric and morphometric analysis of tooth shape has been undertaken for two genetic lineages of the taxon Eretmodus cyanostictus . The use of both landmark-based measurements and elliptic Fourier analysis reveals differences between both lineages and supports the molecular phylogeny. These differences further endorse the interpretation of parallel evolution. In addition, we here present a powerful tool for the analysis of tooth shape.