Reproducibility of Frankfort horizontal plane on 3D multi-planar reconstructed MR images

Accuracy of Instrumented Mouthguards During Direct Jaw Impacts Seen in Boxing

PURPOSE

Measuring head kinematics data is important to understand and develop methods and standards to mitigate head injuries in contact sports. Instrumented mouthguards (iMGs) have been developed to address coupling issues with previous sensors. Although validated with anthropomorphic test devices (ATDs), there is limited post-mortem human subjects (PMHS) data which provides more accurate soft tissue responses. This study evaluated two iMGs (Prevent Biometrics (PRE) and Diversified Technical Systems (DTS) in response to direct jaw impacts.

METHODS

Three unembalmed male cadaver heads were properly fitted with two different boil-and-bite iMGs and impacted with hook (4 m/s) and uppercut (3 m/s) punches. A reference sensor (REF) was rigidly attached to the base of the skull, impact kinematics were transformed to the head center of gravity and linear and angular kinematic data were compared to the iMGs including Peak Linear Acceleration, Peak Angular Acceleration, Peak Angular Velocity, Head Injury Criterion (HIC), HIC duration, and Brain Injury Criterion.

RESULTS

Compared to the REF sensor, the PRE iMG underpredicted most of the kinematic data with slopes of the validation regression line between 0.72 and 1.04 and the DTS overpredicted all the kinematic data with slopes of the regression line between 1.4 and 8.7.

CONCLUSION

While the PRE iMG was closer to the REF sensor compared to the DTS iMG, the results did not support the previous findings reported with use of ATDs. Hence, our study highlights the benefits of using PMHS for validating the accuracy of iMGs since they closely mimic the human body compared to any ATD's mandible.

Biofidelity and Limitations of Instrumented Mouthguard Systems for Assessment of Rigid Body Head Kinematics

Instrumented mouthguard systems (iMGs) are commonly used to study rigid body head kinematics across a variety of athletic environments. Previous work has found good fidelity for iMGs rigidly fixed to anthropomorphic test device (ATD) headforms when compared to reference systems, but few validation studies have focused on iMG performance in human cadaver heads. Here, we examine the performance of two boil-and-bite style iMGs in helmeted cadaver heads. Three unembalmed human cadaver heads were fitted with two instrumented boil-and-bite mouthguards [Prevent Biometrics and Diversified Technical Systems (DTS)] per manufacturer instructions. Reference sensors were rigidly fixed to each specimen. Specimens were fitted with a Riddell SpeedFlex American football helmet and impacted with a rigid impactor at three velocities and locations. All impact kinematics were compared at the head center of gravity. The Prevent iMG performed comparably to the reference system up to ~ 60 g in linear acceleration, but overall had poor correlation (CCC = 0.39). Prevent iMG angular velocity and BrIC generally well correlated with the reference, while underestimating HIC and overestimating HIC duration. The DTS iMG consistently overestimated the reference across all measures, with linear acceleration error ranging from 10 to 66%, and angular acceleration errors greater than 300%. Neither iMG demonstrated consistent agreement with the reference system. While iMG validation efforts have utilized ATD testing, this study highlights the need for cadaver testing and validation of devices intended for use in-vivo, particularly when considering realistic (non-idealized) sensor-skull coupling, when accounting for interactions with the mandible and when subject-specific anatomy may affect device performance.

Determination of Novel, Cranium-Based Relationships for Construct Placement in Microtia Reconstruction for Hemifacial Microsomia Patients

OBJECTIVE

Determine if the ideal location of the construct in microtia reconstruction for hemifacial microsomia (HFM) can be more accurately derived from measurements on the cranium.

DESIGN

High-resolution computerized tomography (CT) images were analyzed through craniometric linear relationships.

SETTING

Our tertiary care institution from 2000 to 2021.

PATIENTS/PARTICIPANTS

Patients diagnosed with HFM and microtia, who had high-resolution craniofacial CT scans, yielding 36 patients accounting for 44 CT scans.

MAIN OUTCOME MEASURE(S)

First, the integrity of the posterior cranial vault among HFM patients was determined. If proven to be unaffected, it could be used as a reference in the placement of the construct. Second, the position of the ear in relation to the cranium was assessed in healthy age-matched controls. Third, if proven to be useful, the concordance of these cranium-based relationships could be validated among our HFM cohort.

RESULTS

The posterior cranial vault is unaffected in HFM (P > .001). Further, craniometric relationships between the tragus and the Foramen Magnum, as well as between the tragus and the posterior cranium, have been shown to be highly similar and equally precise in predicting tragus position in healthy controls (P > .001). These relationships held true across all age groups (P > .001), and importantly among HFM patients, where the mean absolute difference in predicted tragus position never surpassed 1.5 mm.

CONCLUSIONS

Relationships between the tragus and the cranium may be used as an alternative to distorted facial anatomy or surgeon's experience to assist in pre-operative planning of construct placement in microtia reconstruction for HFM patients.

Three-dimensional SPACE MR with CAIPIRINHA fourfold acceleration for assessing long head of biceps tendon

BACKGROUND

Data regarding controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) T2-weighted sampling perfection with application optimized contrast evolution (SPACE) with fourfold acceleration factor for assessing long head of biceps tendon (LHBT) disorder is lacking.

PURPOSE

To investigate the feasibility of 3D CAIPIRINHA SPACE with fourfold acceleration in assessing LHBT disorder.

MATERIAL AND METHODS

A total of 42 consecutive patients underwent shoulder magnetic resonance (MR) examinations including CAIPIRINHA SPACE with fourfold acceleration, and non-CAIPIRINHA SPACE with twofold acceleration, and 2D fast spin echo (FSE). A subjective score of depiction of LHBT was given to 3D sequence according to a 4-point scale (0-3, "poor" to "excellent"). The Wilcoxon signed rank test was used to compare depiction scores between 3D sequences. Three statuses of LHBT were defined in the study: normal, tendonitis, and tear. McNemar's test was used compare diagnostic accuracy.

RESULTS

LHBT was better depicted with CAIPIRINHA SPACE versus non-CAIPIRINHA SPACE (2.1 ± 0.4 vs. 1.5 ± 0.4; P < 0.001). Inter-modality agreement between CAIPIRINHA SPACE and 2D FSE was almost perfect (kappa = 0.884 ± 0.064). The sensitivity and specificity in detecting LHBT disorder were 95% (20/21) and 95% (20/21), respectively, for CAIPIRINHA SPACE, and 71% (15/21) and 76% (16/21), respectively, for non-CAIPIRINHA SPACE (P = 0.039).

CONCLUSION

Fourfold acceleration CAIPIRINHA is feasible in reducing the acquisition time of SPACE MR in the shoulder. 3D CAIPIRINHA SPACE with fourfold acceleration is highly accurate in detecting LHBT disorder.

MRI-based quantification of ophthalmic changes in healthy volunteers during acute 15° head-down tilt as an analogue to microgravity

Spaceflight is known to cause ophthalmic changes in a condition known as spaceflight-associated neuro-ocular syndrome (SANS). It is hypothesized that SANS is caused by cephalad fluid shifts and potentially mild elevation of intracranial pressure (ICP) in microgravity. Head-down tilt (HDT) studies are a ground-based spaceflight analogue to create cephalad fluid shifts. Here, we developed non-invasive magnetic resonance imaging (MRI)-based techniques to quantify ophthalmic structural changes under acute 15° HDT. We specifically quantified: (i) change in optic nerve sheath (ONS) and optic nerve (ON) cross-sectional area, (ii) change in ON deviation, an indicator of ON tortuosity, (iii) change in vitreous chamber depth, and (iv) an estimated ONS Young's modulus. Under acute HDT, ONS cross-sectional area increased by 4.04 mm² (95% CI 2.88-5.21 mm², p < 0. 000), while ON cross-sectional area remained nearly unchanged (95% CI -0.12 to 0.43 mm², p = 0.271). ON deviation increased under HDT by 0.20 mm (95% CI 0.08-0.33 mm, p = 0.002). Vitreous chamber depth decreased under HDT by -0.11 mm (95% CI -0.21 to -0.03 mm, p = 0.009). ONS Young's modulus was estimated to be 85.0 kPa. We observed a significant effect of sex and BMI on ONS parameters, of interest since they are known risk factors for idiopathic intracranial hypertension. The tools developed herein will be useful for future analyses of ON changes in various conditions.

Surface-based 3-dimensional cephalometry: An objective analysis of cranio-mandibular morphology

INTRODUCTION

The purpose of this study was to apply a previously reported homologous model for quantifying and visualizing the three-dimensional (3D) cranio-mandibular morphology.

METHODS

Twenty-eight 3D cone-beam computed tomography (CBCT) images of Japanese patients (7 to 13 years of age) showing skeletal Class 1 malocclusions were used in this study. Wire mesh fitting was conducted for each patient based on the assignment of landmarks to each 3D surface (homologous modeling). Cranial and mandibular images were generated using surface rendering of the CBCT images. The mean and standard deviation of each point on the wire mesh were calculated as the normative mean. Two operators conducted the process twice for seven patients, with a one-week interval between fittings. The intra- and inter-examiner reliability were determined using the 95% confidence interval minimal detectable change (MDC₉₅) for random error and intra-class correlation coefficients (ICCs).

RESULTS

The intra- and inter-examiner reliability of the mesh fitting method were almost perfect. Normative ranges of the cranial and mandibular surfaces of Japanese were determined.

CONCLUSIONS

A clinical method that enables practitioners to quantify and visualize the hard tissues of a patient's face in three dimensions with almost perfect reliability is presented. This method allows practitioners to evaluate how patients' skeletal characteristics differ from normative means in three dimensions.

Endoscopic treatment of combined metopic-sagittal craniosynostosis

OBJECTIVE

Combined metopic-sagittal craniosynostosis is traditionally treated with open cranial vault remodeling and fronto-orbital advancement, sometimes in multiple operations. Endoscopic treatment of this multisuture synostosis presents a complex challenge for the surgeon and orthotist.

METHODS

The authors retrospectively analyzed the preoperative and 1-year postoperative CT scans of 3 patients with combined metopic-sagittal synostosis, all of whom were treated with simultaneous endoscope-assisted craniectomy of the metopic and sagittal sutures followed by helmet therapy. Established anthropometric measurements were applied to assess pre- and postoperative morphology, including cranial index and interfrontal divergence angle (IFDA). Patients' measurements were compared to those obtained in 18 normal controls.

RESULTS

Two boys and one girl underwent endoscope-assisted craniectomy at a mean age of 81 days. The mean preoperative cranial index was 0.70 (vs control mean of 0.82, p = 0.009), corrected postoperatively to a mean of 0.82 (vs control mean of 0.80, p = 0.606). The mean preoperative IFDA was 110.4° (vs control mean of 152.6°, p = 0.017), corrected postoperatively to a mean of 139.1° (vs control mean of 140.3°, p = 0.348). The mean blood loss was 100 mL and the mean length of stay was 1.7 days. No patient underwent reoperation. The mean clinical follow-up was 3.4 years.

CONCLUSIONS

Endoscope-assisted craniectomy with helmet therapy is a viable single-stage treatment option for combined metopic-sagittal synostosis, providing correction of the stigmata of trigonoscaphocephaly, with normalization of the cranial index and IFDA.

In vivo estimation of optic nerve sheath stiffness using noninvasive MRI measurements and finite element modeling

The optic nerve sheath (ONS) is biomechanically important. It is acted on by tension due to ocular movements, and by fluid shifts and/or alterations in intracranial pressure (ICP) in human disease, specifically in pathologies leading to intracranial hypertension. It has also been hypothesized that the ONS is acted on by altered ICP in astronauts exposed chronically to microgravity. However, a non-invasive method to quantify ONS biomechanical properties is not presently available; knowledge of such properties is desirable to allow characterization of the biomechanical forces exerted on the optic nerve head and other ocular structures due to the ONS. Thus, the primary objective of this study was to characterize the biomechanical properties (stiffness) of the human ONS in vivo as a necessary step towards investigating the role of ICP in various conditions, including Spaceflight Associated Neuro-ocular Syndrome (SANS). We acquired non-invasive magnetic resonance imaging (MRI) scans of ostensibly healthy subjects (n = 18, age = 30.4 ± 11.6 [mean ± SD] years) during supine and 15-degree head-down-tilt (HDT) postures, and extracted ONS contours from these scans. We then used finite element modeling to quantify ONS expansion due to postural changes and an inverse approach to estimate ONS stiffness. Using this non-invasive procedure, we estimated an in vivo ONS stiffness of 39.2 ± 21.9 kPa (mean ± SD), although a small subset of individuals had very stiff ONS that precluded accurate estimates of their stiffness values. ONS stiffness was not correlated with age and was higher in males than females.

Does craniofacial morphology affect third molars impaction? Results from a population-based study in northeastern Germany

Objectives

It is still not clear why impaction of third molars occurs. Craniofacial morphology and facial parameters have been discussed to be strong predictors for third molar impaction. Thus, this study aimed to investigate the effect of craniofacial morphology on erupted or impacted third molars in a German population sample.

Materials and methods

Erupted and impacted third molars in 2,484 participants from the Study of Health in Pomerania were assessed by whole-body magnetic resonance imaging. Markers of facial morphology were determined in 619 individuals of those participants in whose 421 participants (16.7%) had at least one impacted third molar. Craniofacial morphology was estimated as linear measurements and was associated in a cross-sectional study design with impacted and erupted third molars by multinomial logistic regression models. Erupted third molars were used as reference outcome category and regression models were adjusted for age and sex.

Results

Maximum Cranial Width (Eurion-Eurion distance) was significantly associated with impacted third molars (RR: 1.079; 95% confidence interval 1.028–1.132). This association was even more pronounced in the mandible. Individuals with a lower total anterior facial height (Nasion-Menton distance) and a lower facial index also have an increased risk for impacted third molars in the mandible (RR 0.953; 95% confidence interval 0.913–0.996 and RR: 0.943; 95% confidence interval 0.894–0.995). No significant associations of third molar status with facial width (Zygion-Zygion distance), and sagittal cranial dimension (Nasion-Sella distance; Sella-Basion distance) were observed.

Conclusion

Individuals with an increased maximal cranial width have a higher risk for impaction of third molars in the mandible and in the maxilla. Individuals with a lower anterior total anterior facial height and lower facial index also have an increased risk for third molars impaction in the mandible. These findings could help orthodontic dentists, oral surgeons and oral and maxillofacial surgeons in decision-making for third molars removal in their treatment. These findings highlight the necessity of an additional analysis of the maximal cranial width by the Eurion- Eurion distance.

Skeletal, Dentoalveolar, and Periodontal Changes of Skeletally Matured Patients with Maxillary Deficiency Treated with Microimplant-assisted Rapid Palatal Expansion Appliances: A Pilot Study

Introduction

Microimplant-assisted rapid palatal expansion (MARPE) has recently been offered to adult patients for correcting maxillary transverse deficiency. However, there is limited information in the literature on the success of this appliance and its skeletal and dental effects on skeletally matured patients. The purpose of this study was to investigate the immediate skeletal, dentoalveolar, and periodontal response to MARPE appliance using cone-beam computed tomography in a skeletally matured patient as assessed by the cervical vertebral maturation method.

Materials and Methods

Eight consecutively treated patients (2 females, 6 males; mean age of 21.9 ± 1.5 years) treated with a maxillary skeletal expander were included in the study. Measurements were taken before and after expansion to determine the amount of midpalatal suture opening, upper facial bony expansion, alveolar bone bending, dental tipping, and buccal bone thickness (BBT). Data were analyzed using a one-way ANOVA and matched-pair t-test (α = 0.05).

Results

Midpalatal suture separation was found in 100% of the patients with no dislodged microimplants. Total maxillary expansion was attributed to 41% skeletal, 12% alveolar bone bending, and 48% dental tipping. Pattern of midpalatal suture opening was found to be parallel in both the coronal and axial planes. On average, the absolute dental tipping ranged from 4.17° to 4.96° and the BBT was reduced by an average of 39% measured at the premolars and molars.

Conclusions

The MARPE appliance can be a clinically acceptable, nonsurgical treatment option for correcting mild to moderate maxillary transverse discrepancies for skeletally matured adult patients with a healthy periodontium.

Procrustes-based geometric morphometrics on MRI images: An example of inter-operator bias in 3D landmarks and its impact on big datasets

Using 3D anatomical landmarks from adult human head MRIs, we assessed the magnitude of inter-operator differences in Procrustes-based geometric morphometric analyses. An in depth analysis of both absolute and relative error was performed in a subsample of individuals with replicated digitization by three different operators. The effect of inter-operator differences was also explored in a large sample of more than 900 individuals. Although absolute error was not unusual for MRI measurements, including bone landmarks, shape was particularly affected by differences among operators, with up to more than 30% of sample variation accounted for by this type of error. The magnitude of the bias was such that it dominated the main pattern of bone and total (all landmarks included) shape variation, largely surpassing the effect of sex differences between hundreds of men and women. In contrast, however, we found higher reproducibility in soft-tissue nasal landmarks, despite relatively larger errors in estimates of nasal size. Our study exemplifies the assessment of measurement error using geometric morphometrics on landmarks from MRIs and stresses the importance of relating it to total sample variance within the specific methodological framework being used. In summary, precise landmarks may not necessarily imply negligible errors, especially in shape data; indeed, size and shape may be differentially impacted by measurement error and different types of landmarks may have relatively larger or smaller errors. Importantly, and consistently with other recent studies using geometric morphometrics on digital images (which, however, were not specific to MRI data), this study showed that inter-operator biases can be a major source of error in the analysis of large samples, as those that are becoming increasingly common in the 'era of big data'.

A Simple Method for International Standardization of Photographic Documentation for Aesthetic Plastic Surgery

Due to the lack of internationally standardized, objective, and scientific photographic standardization methods, differences in photographic documents have gravely affected the truth of surgical outcomes by visual misperception or illusion, thus hindering the development of plastic surgery clinically and scholastically. Here I suggest a simple method for standardization of facial photographs. The method consists of an imaginary transverse line (tentatively the "PSA line") rather than the Frankfort horizontal plane and uses a white background with black grids and standard RGB with CMYK circles. This simplified method of photographic standardization would help our professional society to make international standards on facial photographic documentation to maintain scholastic ethics, conscience, and morals.

NO LEVEL ASSIGNED

This 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 .

Practical Application of Anatomy of the Oral Cavity in Forensic Facial Reconstruction

The oral cavity's importance in defining the facial region makes it a primary feature for forensic facial reconstruction (FFR). The aim of this study is to construct a pattern of reference for dimensions and proportions of the lips and establish parameters that may help estimate the vermilion borders' height dimensions and the mouth's width. By means of cone beam computed tomography, divided into two samples: sample 1 (n = 322; 137 male, 185 female) verified the linear distances delimited by anatomical landmarks in soft tissue. The sample 2 (n = 108; 40 male, 68 female), verified the proportions among the height of the vermilion borders, width of the mouth, and linear distances between craniometric landmarks in hard tissues, both from a Brazilian database. The measurements were completed using OsiriX, and the results were analyzed by means of descriptive statistics at a level of significance of 5%. The height of the vermilion borders corresponded to approximately 26% of the width of the mouth. The width of the mouth increased over the course of time in men and remained stable in women. In men, a mean intercanine distance of 75% of the total mouth's width was found; for women, it was 80%. The parameters of the relations between soft and hard tissues in the oral cavity region presented that the distance between landmarks ID-SM (Infradentale-Supramentale) corresponded to 55% of the height of the vermilion borders of the mouth for both sexes, while the distance between landmarks PM-SD (Philtrum medium-Supradentale) corresponded to 85% in men and 88% in women. Mean values of 97% of the width of the mouth in women and 93% in men were attributed to the distance between the mentonian foramina. It was not possible to estimate the height of the labial vermilion borders by the bone measurements, FIs-Fli (Foramen incisivus superius-inferius) and NS-GN (Nasospinale-Gnathion). Profound knowledge of the anatomy and morphology of the oral cavity may contribute to increasing the precision of FFRs and help with human identification.

Cranial Base and Posterior Cranial Vault Asymmetry After Open and Endoscopic Repair of Isolated Lambdoid Craniosynostosis

BACKGROUND

Previous studies have shown that open cranial vault remodeling does not fully address the endocranial deformity. This study aims to compare endoscopic-assisted suturectomy with postoperative molding helmet therapy to traditional open reconstruction by quantifying changes in cranial base morphology and posterior cranial vault asymmetry.

METHODS

Anthropometric measurements were made on pre- and 1-year postoperative three-dimensionally reconstructed computed tomography scans of 12 patients with unilateral lambdoid synostosis (8 open and 4 endoscopic-assisted). Cranial base asymmetry was analyzed using: posterior fossa deflection angle (PFA), petrous ridge angle (PRA), mastoid cant angle (MCA), and vertical and anterior-posterior (A-P) displacement of external acoustic meatus (EAM). Posterior cranial vault asymmetry was quantified by volumetric analysis.

RESULTS

Preoperatively, patients in the open and endoscopic groups were statistically equivalent in PFA, PRA, MCA, and A-P EAM displacement. At 1 year postoperatively, open and endoscopic patients were statistically equivalent in all measures. Mean postoperative PFA for the open and endoscopic groups was 6.6 and 6.4 degrees, PRA asymmetry was 6.4 and 7.6%, MCA was 4.0 and 3.2 degrees, vertical EAM displacement was -2.3 and -2.3 millimeters, and A-P EAM displacement was 6.8 and 7.8 millimeters, respectively. Mean volume asymmetry was significantly improved in both open and endoscopic groups, with no difference in postoperative asymmetry between the 2 groups (P = 0.934).

CONCLUSIONS

Patients treated with both open and endoscopic repair of lambdoid synostosis show persistent cranial base and posterior cranial vault asymmetry. The results of endoscopic-assisted suturectomy with postoperative molding helmet therapy are similar to those of open calvarial vault reconstruction.

Influence of maxillary advancement surgery on skeletal and soft-tissue changes in the nose - a retrospective cone-beam computed tomography study

Objectives

Surgical correction of skeletal maxillary retroposition is often associated with changes in the morphology of the nose. Unwanted alar flaring of the nose is observed in many cases. The aim of the present study was therefore to investigate the influence of surgical advancement of the maxilla on changes in the soft-tissue morphology of the nose. Having a coefficient that allows prediction of change in the nasal width in Caucasian patients after surgery would be helpful for treatment planning.

Materials and methods

All 33 patients included in this retrospective study were of Caucasian descent and had skeletal Class III with maxillary retrognathia. They were all treated with maxillary advancement using a combination of orthodontic and maxillofacial surgery methods. Two cone-beam computed tomography (CBCT) datasets were available for all of the study's participants (16 female, 17 male; age 24.3 ± 10.4 years): the first CBCT imaging was obtained before the planned procedure (T0) and the second 14.1 ± 6.4 months postoperatively (T1). Morphological changes were recorded three-dimensionally using computer-aided methods (Mimics (Materialise NV, Leuven/Belgium), Geomagic (Geomagics, Morrisville/USA)). Statistical analysis was carried out using SPSS 21 for Mac.

Results

The mean sagittal advancement of the maxilla was 5.58 mm. The width of the nose at the alar base (Alb) changed by a mean of + 2.59 mm (±1.26 mm) and at the ala (Al) by a mean of + 3.17 mm (±1.32 mm). Both of these changes were statistically highly significant (P = 0.000). The increase in the width of the nose corresponded to approximately half of the maxillary advancement distance in over 80 % of the patients. The nasolabial angle declined by an average of −6.65° (±7.71°).

Conclusions

Maxillary advancement correlates with a distinct morphological change in nasal width. This should be taken into account in the treatment approach and in the information provided to patients.