Health profession students' outlooks on the medical profession during the COVID-19 pandemic: a global perspective.

BACKGROUND: This article summarizes a global study of the effect of the COVID-19 pandemic on junior health professions students' outlook on medicine. The pandemic has significantly affected health professions education. There is limited understanding of how students' pandemic experiences will affect them, and what impact these events may have on their career paths or the future of the professions. This information is important as it impacts the future of medicine. METHODS: In the Fall 2020 semester, 219 health professions students at 14 medical universities worldwide responded to the question: 'Has this experience (with COVID-19) changed your outlook on medicine as a profession?'. Short essay responses were semantically coded and organized into themes and subthemes using an inductive approach to thematic analysis. RESULTS: 145 responses were submitted. Themes were identified: (1) students reflected on the interaction between politics and healthcare; (2) reported becoming more aware of the societal expectations placed on healthcare professionals, including undertaking high risks and the sacrifices that healthcare professionals must make; (3) found reassurance from the recognized importance of healthcare professionals and expressed pride to be entering the profession; and (4) reflected on the current state of healthcare, including its limitations and future. CONCLUSION: Most students, independent of the extent of the pandemic in their respective countries, noted a change in their outlook regarding medicine. An overall positive outlook was noted in most junior students. Educators need to work on nurturing these sentiments and attitudes to help young students maintain a healthy relationship towards their chosen profession.

A thematic analysis of students' discussions on death and body donation in international online focus groups.

Historically, Anatomy education is an in-person discipline involving exposure to human body donors that facilitates personal and professional growth through, in part, the initiation of reflection on the topic of death. However, during the COVID-19 pandemic the decreased exposure to cadaveric anatomy for many health professions students may have influenced the depth of their individual reflections on this topic. Accordingly, this study aimed to investigate the effect of an alternate approach-focus group discussions between peers with varying degrees of exposure to cadaveric material-that may offer one strategy to stimulate deep reflection on the topic of death. A programmatic intervention was introduced, wherein students (n = 221) from 13 international universities discussed differences in their anatomy courses during small focus group sessions as part of an online exchange program. An inductive semantic thematic analysis was conducted on responses to an open-ended text-response question on how the activity influenced students' reflections about death. Resulting themes were organized into categories that described the content and topics of the students' discussions as they grappled with this sensitive topic. The students reportedly engaged in deep reflection and expressed an increased sense of connectedness with their peers, despite their disparate exposure levels to cadaveric anatomy and being physically distanced. This demonstrates that focus groups with students experiencing different laboratory contexts can be used to help all students reflect on the topic of death and that interchanges between dissecting and non-dissecting students can initiate thoughts about death and body donation among non-dissecting students.

Effect of shape and size of supraspinatus tears on rotator cuff strain distribution: an in vitro study.

BACKGROUND: The impact of the size and shape of a supraspinatus tear on the strain of the intact rotator cuff and the kinematics of the shoulder is still unknown. This, however, can be relevant when deciding whether surgical reconstruction is required to prevent an increase in a tendon defect. In this study, the effect of tear width and shape on rotator cuff strain and glenohumeral kinematics was evaluated during active abduction. METHODS: Twelve fresh-frozen cadaveric shoulders with intact rotator cuffs were used in this study. We created 50% and 100% wide (full-thickness) crescent-shaped (CS) tears (n = 6) and reverse L-shaped (rLS) tears (n = 6) in the supraspinatus tendon and measured strain and kinematics during active humeral elevation until 30°. RESULTS: Both tear shapes and sizes led to an increase in internal rotation, supraspinatus loading force, and superior translation of the humerus. For the 100% wide tear size, anterior translation was observed in the CS tear group, whereas in the rLS tear group, this translation occurred mainly in the posterior direction. Strain was higher in the infraspinatus during the first 25° of abduction in comparison with the supraspinatus tendon in both tear shape groups. An analysis of the anterior and posterior tear borders showed a higher strain concentration on the same side of the tear in the CS tear group with 50% and 100% wide tears. CONCLUSIONS: The influence of different tear shapes on translation in the anterior-posterior direction was evident as both CS and rLS tears led to an oppositely directed translation of the humeral head. The strain analysis showed a stress-shielding effect of the infraspinatus at the beginning of abduction. Therefore, special attention must be paid to correctly identify the tear extension and adequately reconstruct the rotator cuff footprint. Moreover, the constant location of maximum strain in the CS tear group may lead to an earlier progression than in the rLS tear group.

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

BACKGROUND: During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA. The aim of the present study is to investigate the effects of different degrees of PTS on femorotibial kinematics in MS TKA. MATERIALS AND METHODS: An MS TKA was performed in seven fresh-frozen human specimens successively with 0°, 3°, and 6° of PTS. After each modification, weight-bearing deep knee flexion (30-130°) was performed, and femorotibial kinematics were analyzed. RESULTS: A lateral femoral rollback was observed for all three PTS modifications. With an increasing PTS, the tibia was shifted more anteriorly on the lateral side (0° PTS anterior tibial translation -9.09 (±9.19) mm, 3° PTS anterior tibial translation -11.03 (±6.72) mm, 6° PTS anterior tibial translation 11.86 (±9.35) mm). No difference in the tibial rotation was found for the different PTS variants. All PTS variants resulted in internal rotation of the tibia during flexion. With a 3° PTS, the design-specific medial rotation point was achieved more accurately. CONCLUSIONS: According to our findings, we recommend a PTS of 3° when implanting the MS prosthesis used in this study.

The Anatomy Course During COVID-19: The Impact of Cadaver-Based Learning on the Initiation of Reflection on Death.

Background: During the COVID-19 pandemic, in-person cadaveric dissection laboratories for teaching anatomy were omitted by many schools around the world. While knowledge domains can be easily evaluated via remote exams, non-traditional discipline-independent skills such as those encouraged through reflection on the topic of death are often overlooked. This study investigated how different anatomy course formats played a role in initiating students' reflections on death during the COVID-19 pandemic. Method: In fall 2020, 217 medical, dental, premedical, and health sciences students from 13 international universities discussed differences in their anatomy courses online. Formats of anatomy courses ranged from dissection-based, prosection-based, hybrid (combination of dissection and prosection) to no laboratory exposure at all. Students' responses to the question, "Did/does your anatomy course initiate your thinking about life's passing?" were collected, and they self-reported themes that were present in their reflections on death using a multiple-choice prompt. Statistical analyses to detect differences between students with and without exposure to cadavers were performed using the chi-squared test. Results: When comparing students who had exposure to human anatomical specimens to those who had no exposure, the majority of students with exposure thought that the course did initiate thoughts about life's passing, compared to students without exposure (P < 0.05). Reflection themes were consistent across groups. Discussion: These findings indicate that anatomy dissection courses are important for the initiation of students' feelings about the topic of death. Omission of cadaveric dissection- or prosection-based laboratories will decrease the likelihood that students initiate reflection on this topic and gain important transferable skills.

Anatomical and biomechanical evaluation of the lateral calcaneo-cuboid and bifurcate ligaments.

BACKGROUND: This study aims to analyze the ligaments of the dorso-lateral calcaneo-cuboid joint and to assess the biomechanical relevance of the bifurcate ligament. METHODS: 16 specimens were analyzed for their ligamentous anatomy of the dorso-lateral calcaneo-cuboid joint and side-alternating assigned to two groups with varying ligamentous dissection order. The Chopart joint was stressed in plantar, medial, and lateral direction measuring the displacement by an 3D motion tracker for every dissection step. RESULTS: 37.5% of specimens had all ligaments (lateral calcaneo-cuboid, dorsal calcaneo-cuboid, bifurcate calcaneo-cuboid, bifurcate calcaneo-navicular), 37.5% were lacking bifurcate´s calcaneo-cuboid-portion, and 25% presented without dorsal calcaneo-cuboid. Biomechanical testing revealed no significant displacement within the calcaneo-cuboid or talo-navicular joint for any stressed state except for axial compression with dissected dorsal talo-navicular joint capsule in Group 2. CONCLUSION: Broad morphological variability and missing significant displacement regardless of its integrity, make the bifurcate ligament appear of limited biomechanical relevance.

The effect of cement augmentation on pedicle screw fixation under various load cases : results from a combined experimental, micro-CT, and micro-finite element analysis.

AIMS: Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. METHODS: Micro-finite element (µFE) models were created from micro-CT (µCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S4). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. RESULTS: Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R2 > 0.87) and FV (R2 > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95). CONCLUSION: This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797-806.

Minimally Invasive Approaching in Hip Surgery-An Anatomical Investigation of 20 Specimens.

Background and objectives: Based on the preparation of 20 formalin-fixed anatomical cadavers, the feasibility of the anterior, minimally invasive approach to the hip joint was investigated in each side of the body. The hypothesis of the study was that the Lateral Femoral Cutaneous Nerve can be spared under the use of this approach. Materials and Methods: The anterior approach to the hip was performed via an incision of 8 cm. The position of the nerve was noticed in relation to the skin incision, and the distance was measured in millimeters. The nerves main, gluteal and femoral trunk were distinguished and investigated for injury. Results: No injury of the main trunk was noticed. The average distance of the main trunk to the skin incision was 14.9 and 15.05 mm in the medial direction, respectively (p < 0.001). Injury of the gluteal branch has to be considered at an overall rate of 40%. Conclusions: The anterior, minimally invasive approach to the hip joint can be performed without injury of the Lateral Femoral Cutaneous Nerve.

Experimental study of an implantable fiber-optic microphone on human cadavers.

In this paper, we present the results of an experimental study about a novel fiber optical vibrometer, aimed to be used as a totally implantable fiber-optic microphone for hearing aids. The sensor head, implanted inside the human cadaver middle ear, detects the amplitude of the incus vibrations, which are produced by an external acoustical source. The probe beam of coherent vertical cavity surface emitting laser (VCSEL) radiation is directed to the incus and the phase-modulated reflected beam is captured and demodulated. The problem of interferometric fading was solved using two quasi-quadrature signals, passively produced by the 3 × 3 single-mode fiber-optic coupler, processed by a special embedded algorithm. The implanted optoelectronic module works with very low-power consumption, performs real-time signal processing and outputs an analogue signal proportional to the incus vibration. The amplitude of the incus vibrations at different sound pressure levels (SPL) from 40 to 90 dB and at frequencies from 100 Hz to 10 kHz were measured by the implanted system. The system was evaluated on five cadaver skulls. The measured amplitudes were in the range of 1 pm to 5 nm, depending on the subjected skull and the applied sound pressure.

Alternatives to Student Outbound Mobility-Improving Students' Cultural Competency Skills Online to Improve Global Health Without Travel.

Introduction: Student outbound mobility is a major element in internationalization of medical education and global health education. However, this approach is often criticized, as it is inherently inequitable. Internationalization at home is a newer concept that aims to provide students with international skills and experiences without exchange travel. We report detailed outcomes of an international online program during the COVID-19 pandemic, which aimed to include acquisition of cultural awareness and competency-similar to what the students would have obtained if they had travelled abroad. Method: Sixty-eight students from 12 international universities participated in international small peer group collaborative work, and online networking. Perceived improvement of cultural competency using Likert scale and open-ended questions was used as a measure of success. Furthermore, students' definition of cultural competency in the different countries was obtained. Results: Students improved their cultural competency skills. Data analysis supported statistically significant improvement of the above skills after the program, in comparison to the start of the program. Discussion: Internationalization of medical education can be achieved at home-via structured online peer exchanges-and can provide students with intercultural skills and networking opportunities that are typically achieved via international in-person travel. The above represents a socially just and equitable way to reach all students and can result in improvement of their cultural competency, preparing them for their work in global health, and thereby resulting in improvement of global health. Supplementary Information: The online version contains supplementary material available at 10.1007/s40670-021-01332-9.

Initiating Students' Reflections on Life's Passing in the Anatomy Course - an International Observation at 14 Universities.

BACKGROUND: Medical and dental students' feelings and thoughts about the topic of death and life's passing are often associated with learning in the gross anatomy course, when students begin working with a deceased body donor in order to study human anatomy. Little is known of whether the format of anatomy teaching has an impact on these experiences. An observational study was performed to capture the initiation of students' sentiments on the topic of life's passing during the anatomy course at 14 international universities, identify common themes regarding these thoughts, and to study the connection to variations in anatomy course formats and included elements. METHOD: Preclinical anatomy students reflected on one question (i.e., "How did your experience in the anatomy laboratory bring about your reflections on the meaning of life and human existence as well as the sanctity of one's passing?"). Written assignments were collected and anonymously coded. Information on anatomy courses was obtained via faculty questionnaires. RESULT: A variety of themes were identified at the different schools, correlated with different anatomy formats and elements. Results indicate that the courses that offer hands-on cadaveric dissections may play an important role in triggering these sentiments. DISCUSSION: The initiation of students' sentiments about the topic of death varies and includes several themes. There can be a connection to the way anatomy is taught, particularly if hands-on comprehensive cadaveric dissection or prosections are included. CONCLUSION: In summary, anatomy courses can initiate students' thinking about life's passing - particularly in schools that offer hands-on cadaveric dissections or prosections.

An Observation of Healthcare Professions Students' Perceptions During the COVID-19 Pandemic.

This study conveys preclinical healthcare professions students' sentiments at 14 universities during the 2020 COVID-19 pandemic. Essays about students' thoughts and experiences were thematically sorted and revealed a variety of sentiments spanning from positive (e.g., pride, respect) to the more negative (e.g., anxiety, guilt, disappointment, anger). Themes revealed respect for the healthcare profession, but also the realization of its limitations, sacrifices, and risks. Healthcare profession educators need to be aware that the COVID-19 pandemic has affected students emotionally and may have long-term effects on the global healthcare profession. This study can serve as a historic documentation of how this generation of students felt and adds to the literature on how the pandemic affected the healthcare profession.

High-Resolution Ultrasonography of the Transverse Cervical Nerve.

The transverse cervical nerve (TCN) is a superficial cutaneous branch of the cervical plexus that innervates the skin of the anterolateral neck. Therefore, it is exposed to injury in anterolateral cervical surgery, which can cause neuropathic pain. To provide a method with which to relieve patients' pain, this study aimed to evaluate the possibility of visualization, diagnostic assessment and blockade of the TCN with high-resolution ultrasound (HRUS). HRUS with high-frequency probes (15-22 MHz), guided ink-marking and consecutive dissection on both sides in nine fresh cadaver necks (n = 18) was conducted. On both sides of 20 healthy volunteers (n = 40), the distances between the greater auricular nerve (GAN) and the TCN at the posterior border of the sternocleidomastoid muscle were measured. Finally, cases referred to HRUS examinations because suspected TCN lesions were assessed. The TCN was visible in all anatomic specimens and in healthy volunteers. Dissection confirmed HRUS findings in all anatomic specimens (100%). In healthy volunteers, the mean distance between the GAN and the TCN was 10.42 ± 3.20 mm. The median visibility, rated on a five-point Likert scale, was four, reflecting good diagnostic quality. There were six patients with visible abnormalities on HRUS. This study confirmed the reliable visualization of the TCN with HRUS in anatomic specimens, healthy volunteers and patients.

An International Partnership of 12 Anatomy Departments - Improving Global Health through Internationalization of Medical Education.

Background: At a time of global interconnectedness, the internationalization of medical education has become important. Anatomy as an academic discipline, with its close connections to the basic sciences and to medical education, can easily be connected with global health and internationalization of medical education. Here the authors present an international program based on a partnership between twelve anatomy departments in ten countries, on four continents. Details of a proposed plan for the future direction of the program are also discussed. Objective: The aim is to improve global healthcare by preparing future global healthcare leaders via early international networking, international collaboration and exchange, intercultural experience, and connecting two seemingly distant academic disciplines - anatomy and global health - via internationalization of medical education. Methods: Based in the anatomy course, the program involved early international collaboration between preclinical medical and dental students. The program provided a stepwise progression for learning about healthcare and intercultural topics beyond pure anatomy education - starting with virtual small groups of international students, who subsequently presented their work to a larger international audience during group videoconferences. The above progressed to in-person visits for research internships in the basic sciences within industrialized countries. Findings: Students appreciated the international and intercultural interaction, learned about areas outside the scope of anatomy (e.g., differences in healthcare education and delivery systems, Public and Global Health challenges, health ethics, and cultural enrichment), and valued the exchange travel for basic sciences research internships and cultural experience. Conclusions: This unique collaboration of international anatomy departments can represent a new role for the medical anatomy course beyond pure anatomy teaching - involving areas of global health and internationalization of medical education - and could mark a new era of international collaboration among anatomists.

The vascularized fascia lata free flap: an anatomical study and clinical considerations.

PURPOSE: Fascia lata (FL) is often used as fascial component of the anterolateral thigh (ALT) flap in head and neck reconstruction. No distinct data exist on whether the FL has its own reliable vascular supply and whether the fascia alone can be harvested as a fascia lata free flap. METHODS: We dissected 25 thighs of 15 cadavers. The lateral circumflex femoral artery (LCFA) was identified, and the size of stained fascia and skin were measured after injection of methylene blue into the descending branch (DB). Finally, topography of fascial vessels was determined. RESULTS: Staining of fascia and skin paddle was found in all 25 cases. Ascending skin perforators of the DB of the LCFA gave off branches for supply of the FL enabling harvest of a fascia lata free flap. Septo- or musculocutaneous perforators pierced FL and entered skin within the proximal 38.6-60% of the thigh. The mean length and width of stained FL was 15.8 ± 4.1 cm and 8.7 ± 2.0 cm, respectively, and size of stained FL ranged from 40.0 to 336.0 cm2. In 20 cases (80%), skin paddles were 2.4 times larger on average compared to corresponding FL. CONCLUSION: We could demonstrate that the FL receives its own vascular supply from perforators of the DB originating from the LCFA. Hence, harvest of a fascia lata free flap is possible, reliable, and the size of the fascia is suitable for reconstruction of small and large defects of the head and neck.

Pulmonary artery denervation using catheter-based ultrasonic energy.

AIMS: Pulmonary arterial hypertension is a devastating disease characterised by pulmonary vascular remodelling and right heart failure. Radio-frequency pulmonary artery denervation (PDN) has improved pulmonary haemodynamics in preclinical and early clinical studies; however, denervation depth is limited. High-frequency non-focused ultrasound can deliver energy to the vessel adventitia, sparing the intima and media. We therefore aimed to investigate the feasibility, safety and efficacy of ultrasound PDN. METHODS AND RESULTS: Histological examination demonstrated that innervation of human pulmonary arteries is predominantly sympathetic (71%), with >40% of nerves at a depth of >4 mm. Finite element analysis of ultrasound energy distribution and ex vivo studies demonstrated generation of temperatures >47ºC to a depth of 10 mm. In domestic swine, PDN reduced mean pulmonary artery pressure induced by thromboxane A2 in comparison to sham. No adverse events were observed up to 95 days. Histological examination identified structural and immunohistological changes of nerves in PDN-treated animals, with sparing of the intima and media and reduced tyrosine hydroxylase staining 95 days post procedure, indicating persistent alteration of the structure of sympathetic nerves. CONCLUSIONS: Ultrasound PDN is safe and effective in the preclinical setting, with energy delivery to a depth that would permit targeting sympathetic nerves in humans.

Anatomical Evidence of Acupuncture Meridians in the Human Extracellular Matrix: Results from a Macroscopic and Microscopic Interdisciplinary Multicentre Study on Human Corpses.

For more than 2500 years, acupuncture has been applied to support the healing of different diseases and physiologic malfunctions. Although various theories of the meridian system and mechanisms were formulated to explain the functional basis of acupuncture, the anatomical basis for the concept of meridians has not been resolved. The aim of the present study was to search for replicable anatomical structures that could relate to meridians. To this end, four human specimens and additionally two lower legs were dissected anatomically. Our study found evidence that acupuncture meridians were part of the human extracellular matrix and that fascia was an important part of the anatomic substrate of acupuncture meridians. At the same time, we found vessel-nerve-bundles, which were hypothesized to account for 80% of acupuncture points, only in a few acupuncture points. Therefore, our findings contradict the theory that acupuncture points are only located along the nervous channels.

Design of skin islands for a myocutaneous serratus anterior free flap-An anatomical study and clinical implication for pharyngeal reconstruction after laryngopharyngectomy.

OBJECTIVES: The main purpose of this study was to evaluate flap size and flap design of skin islands in myocutaneous serratus anterior free flaps (SAFFs) in fresh cadavers and to further investigate whether myocutaneous SAFFs are suitable flaps for pharyngeal reconstruction after laryngopharyngectomy. METHODS: Dissection and injection of methylene blue were performed in 20 hemithoraces of 13 fresh cadavers to evaluate flap size and location of skin islands. Based on these pre-clinical data, we performed pharyngeal reconstruction with myocutaneous SAFF in five patients after laryngopharyngectomy. RESULTS: Perfused skin paddles were found in all specimens with a mean size of perfused skin islands of 85.6 ± 49.8 cm2 . Lengths and widths of skin islands ranged from 10-21 cm and 6-20.5 cm respectively. Flap size did not significantly differ between males and females (P = 0.998), left compared to right hemithoraces (P = 0.468) and between paired specimens (P = 0.915). All skin islands were found within the upper 29.3%-51.7% of hemithorax (calculated from axilla to costal arch), and between latissimus dorsi muscle posteriorly and anterior axillary line anteriorly. Accordingly, myocutaneous SAFFs were used for pharyngeal reconstruction after laryngopharyngectomy in five patients with advanced hypopharyngeal carcinomas. Three patients had uneventful courses, while one patient developed immediate intraoperative flap loss and another patient developed partial necrosis of SAFF on postoperative day 7. CONCLUSION: Skin islands of SAFF have reliable blood supply, which allow harvest of large myocutaneous SAFFs that can be used also for pharyngeal reconstruction after laryngopharyngectomy.

Microvessels may Confound the "Swallow Tail Sign" in Normal Aged Midbrains: A Postmortem 7 T SW-MRI Study.

BACKGROUND AND PURPOSE: Susceptibility weighted imaging (SWI) plays a role in the differential diagnosis of Parkinson's disease, but lacks widespread acceptance in clinical routine. In a descriptive pilot study, we assessed hypointense microstructures of the normal substantia nigra pars compacta at ultrahigh-field strength for interpretation of the "swallow tail sign." METHODS: Magnetic resonance imaging at 7 Tesla was performed in five postmortem samples obtained from subjects not affected by Parkinson's disease. Susceptibility weighted images, including minimum intensity projections, were created followed by consensus assessment for microvascular confound. Histological workup in this case-control study included iron and myelin staining. Seven Tesla SWI images from the reference cohort of nine living subjects, all of which showed a positive "swallow tail sign" in their midbrains, were assessed visually. RESULTS: All specimens showed microvessels running through the dorsal pars compacta and along the caudolateral circumference of the red nucleus. Hypointense imaging patterns in the medial part of the "swallow tail" were due to susceptibility effects of iron deposits and microvessels. In eight out of nine control subjects, one or more microvessels were detected medial to the dorsolateral nigral hyperintensity or at least unilaterally in the medial part of the "swallow tail." One microvessel crossing nigrosome 1 was found in two in-vivo cases. CONCLUSION: Both iron deposits and microvessels contribute to the hyposignal surrounding nigrosome 1 in susceptibility weighted imaging of normal aged midbrains at ultrahigh-field strength. When assessing the substantia nigra for the presence or absence of the "swallow tail sign," intrinsic vessels may be a sporadic confounder.

Regional Collagen Fiber Network in the Articular Disc of the Human Temporomandibular Joint: Biochemical 3-Tesla Quantitative Magnetic Resonance Imaging Compared to Quantitative Histologic Analysis of Fiber Arrangement.

AIMS: To evaluate the regional collagen fiber network in the human temporomandibular joint (TMJ) disc by using biochemical magnetic resonance imaging (MRI) and quantitative histology. METHODS: MRI of 5 heads (10 TMJ discs) obtained from partially dentate or edentulous cadavers was performed at 3-Tesla MRI by using a flexible, 8-channel transmit-receive coil. After MRI, all 10 discs were processed histologically. Percentages of coronal, sagittal, and transverse collagen fibers were assessed stereologically for the anterior, central, and posterior parts of the disc. An anisotropy index was calculated for collagen fiber arrangement in all three regions of interest. RESULTS: In the central part of the TMJ disc, collagen fibers were arranged anisotropically with a preferentially sagittal direction. In the anterior and posterior parts, evidence for fibers being arranged isotropically (randomly) without preferred direction was found. Mean MRI T2 values appeared to be correlated with the anisotropy index of collagen fibers (r = -0.45; P < .05). When tested individually, T2 values of the isotropic anterior and posterior disc regions showed a partial but significant correlation with the anisotropy index of collagen fibers (r = -0.54; P < .05), whereas the anisotropic central part did not (P > .05). CONCLUSION: This study has provided the first systematic comparison of quantitative data on collagen fiber isotropy and anisotropy assessed in histologic sections with biochemical quantitative MRI for human TMJ fibrous cartilage.