Morphometric assessment of tibial nerve and its branches around the ankle.

It is essential to understand the considerable variations in bifurcation patterns of the tibial nerve (TN) and its peripheral nerves at the level of the tarsal tunnel to prevent iatrogenic nerve injury during surgical nerve release or nerve block. A total of 16 ankles of 8 human cadavers were dissected to investigate the branching patterns of the TN, using 2 imaginary lines passing through the tip of the medial malleolus (MM) as reference lines. Bifurcation patterns and detailed information on the relative locations of the medial plantar, lateral plantar, medial calcaneal, and inferior calcaneal nerves to the reference lines were recorded. The most common bifurcation pattern was Type 1 in 12 ankles (75%), followed by Type 2 in 2 ankles (13%). One medial calcaneal nerve (MCN) was seen in 11 (69%) specimens and 2 MCN branches were seen in 5 (31%) specimen. 88% of the MCN branches bifurcated from the TN, whereas 6% originated from both TN and lateral plantar nerve (LPN). At the level of the tip of the MM, 2 of 7 parameters showed statistically significant difference between both sexes (P < .05). There was a statistically significant difference between left and right ankles in 2 of 7 measurements (P < .05). Further morphometric analysis of the width, distance, and angle between the TN branches and the tip of MM showed a highly variable nature of the location of the peripheral nerve branches.

Heterogenous effect of early adulthood stress on cognitive aging and synaptic function in the dentate gyrus.

Cognitive aging widely varies among individuals due to different stress experiences throughout the lifespan and vulnerability of neurocognitive mechanisms. To understand the heterogeneity of cognitive aging, we investigated the effect of early adulthood stress (EAS) on three different hippocampus-dependent memory tasks: the novel object recognition test (assessing recognition memory: RM), the paired association test (assessing episodic-like memory: EM), and trace fear conditioning (assessing trace memory: TM). Two-month-old rats were exposed to chronic mild stress for 6 weeks and underwent behavioral testing either 2 weeks or 20 months later. The results show that stress and aging impaired different types of memory tasks to varying degrees. RM is affected by combined effect of stress and aging. EM became less precise in EAS animals. TM, especially the contextual memory, showed impairment in aging although EAS attenuated the aging effect, perhaps due to its engagement in emotional memory systems. To further explore the neural underpinnings of these multi-faceted effects, we measured long-term potentiation (LTP), neural density, and synaptic density in the dentate gyrus (DG). Both stress and aging reduced LTP. Additionally, the synaptic density per neuron showed a further reduction in the stress aged group. In summary, EAS modulates different forms of memory functions perhaps due to their substantial or partial dependence on the functional integrity of the hippocampus. The current results suggest that lasting alterations in hippocampal circuits following EAS could potentially generate remote effects on individual variability in cognitive aging, as demonstrated by performance in multiple types of memory.

Evaluation and Classification of Supraorbital Nerve Emerging Patterns.

BACKGROUND: Numerous significant variations in the supraorbital nerve (SON) pass through the notches and foramina. During endoscopic forehead lifting, the passage and the location of the nerve against the frontal bone render it susceptible to injury, resulting in diminished or absent sensation in the corresponding location. We attempted to obtain accurate knowledge of the SON emergence routes. METHODS: Data of patients who underwent an endoscopic forehead lift in a plastic surgery clinic between November 2015 and August 2021 were retrospectively analyzed. Deep and superficial branch pathways of SONs were identified and compared according to side and gender. We also classified the nerve patterns into six types. RESULTS: Altogether, 942 patients (1884 SON cases) were evaluated. Out of the patients, 86 patients were male, and 856 were female. The overall mean age was 48.6 (± 13.1) years. In the deep branches, 49% came from the notch, and 51% came from the foramen. In the superficial branches, 67% came from the notch, and 33% of superficial branches came from the foramen. Unlike the deep branch, superficial branches from the notch were significant. Deep and superficial branches of male patients were much more notched than those of female patients. Branches emerged together in 56% and separately in 44% of the cases. CONCLUSION: The absolute number of SON notches was higher than that of SON foramina. This study with the largest number of SON cases will help surgeons understand the variation and course of SON. LEVEL OF EVIDENCE IV: This journal requires that authors 38 assign a level of evidence to each article. For a full 39 description of these Evidence-Based Medicine ratings, 40 please refer to the Table of Contents or the online 41 Instructions to Authors www.springer.com/00266 .

Anatomical Structures to Be Concerned With During Peripherally Inserted Central Catheter Procedures.

BACKGROUND: The central line has been frequently used for drug and nutrition supply and regular blood sampling of patients with chronic diseases. However, this procedure is performed in a highly sensitive area and has several potential complications. Therefore, peripherally inserted central catheters (PICC), which have various advantages, are being extensively used. Although the number of PICC procedures is increasing, the anatomy for safe procedures has not yet been properly established. Therefore, we studied basic anatomical information for safe procedures. METHODS: We used 20 fixed cadavers (40 arms) donated to the Korea University College of Medicine. The mean age was 76.75 years (range, 48-94 years). After dissection of each arm, the distribution pattern of the basilic vein and close structures was recorded, and some important parameters based on bony landmarks were measured. In addition, the number of vein branches (axillary region) and basilic vein diameter were also checked. RESULTS: The mean length from the insertion site to the right atrium was 38.39 ± 2.63 cm (left) and 34.66 ± 3.60 cm (right), and the basilic vein diameter was 4.93 ± 1.18 mm (left) and 4.08 ± 1.49 mm (right). The data showed significant differences between the left and right arms (P < 0.05). The mean distance from the basilic vein to brachial artery was 8.29 ± 2.78 mm in men and 7.81 ± 2.78 mm in women, while the distance to the ulnar nerve was 5.41 ± 1.67 mm in men and 5.52 ± 2.06 mm in women. CONCLUSION: According to these results, the right arm has a shorter distance from the insertion site to the right atrium, and the left arm has a wider vein diameter, which is advantageous for the procedure. In addition, the ulnar nerve and brachial artery were located close to or behind the insertion site. Therefore, special attention is required during the procedure to avoid damaging these important structures.

The Activation of the LIMK/Cofilin Signaling Pathway via Extracellular Matrix-Integrin Interactions Is Critical for the Generation of Mature and Vascularized Cardiac Organoids.

The generation of mature and vascularized human pluripotent stem cell-derived cardiac organoids (hPSC-COs) is necessary to ensure the validity of drug screening and disease modeling. This study investigates the effects of cellular aggregate (CA) stemness and self-organization on the generation of mature and vascularized hPSC-COs and elucidates the mechanisms underlying cardiac organoid (CO) maturation and vascularization. COs derived from 2-day-old CAs with high stemness (H-COs) and COs derived from 5-day-old CAs with low stemness (L-COs) were generated in a self-organized microenvironment via Wnt signaling induction. This study finds that H-COs exhibit ventricular, structural, metabolic, and functional cardiomyocyte maturation and vessel networks consisting of endothelial cells, smooth muscle cells, pericytes, and basement membranes compared to L-COs. Transcriptional profiling shows the upregulation of genes associated with cardiac maturation and vessel formation in H-COs compared with the genes in L-COs. Through experiments with LIMK inhibitors, the activation of ROCK-LIMK-pCofilin via ECM-integrin interactions leads to cardiomyocyte maturation and vessel formation in H-COs. Furthermore, the LIMK/Cofilin signaling pathway induces TGFß/NODAL and PDGF pathway activation for the maturation and vascularization of H-COs. The study demonstrates for the first time that LIMK/Cofilin axis activation plays an important role in the generation of mature and vascularized COs.

Topographical Analysis of Pacinian Corpuscle in the Pulp of Human Cadaver Finger Tip Pulp: A Pilot Cadaver Study.

Background: The human hand is a specialised organ for fine motion and sensation and has a relatively large representation in the homunculus. The pathway of sensation starts from information sent by mechanoreceptors in the hand. This study reports the topography of the Pacinian corpuscle in the fingertips of a human cadaver. Methods: All 10 digits from both hands of a fresh-frozen cadaver were examined. Glabrous skin distal to the distal interphalangeal joint was harvested superficial to the periosteum including fat and subcutaneous tissue. The glabrous skin were divided into 10 sections that included five distal and five proximal sections. Modified gold chloride staining was performed. Sectioned specimens were observed under a light microscope and the density of Pacinian corpuscles was determined in each segment. The density of the corpuscles was compared between the radial/ulnar and proximal/distal segments and also between digits from the right hand versus those from the left hand. Results: Pacinian corpuscles were observed only in the subcutaneous tissue. There was no significant difference in density of the corpuscles between the distal and proximal segments or between the right and left hands. There was a statistically significant greater density of Pacinian corpuscles on the radial segments of all digits except the thumb. Conclusions: There is a greater density of Pacinian corpuscles on the radial side of the human fingertip in all digits except the thumb.

Ultrasonographic features of ulnar nerve instability around the elbow in fresh cadavers.

Ultrasound (US) is commonly used to evaluate ulnar nerve instability (UNI) and snapping of the medial head of the triceps brachii muscle (ST). We aimed to determine the diagnostic accuracy of US in evaluating UNI, through cadaveric dissection, and to evaluate the US features and relationships of UNI and ST according to elbow flexion. Dynamic US was performed with elbow extension, 90° flexion, and full flexion positions on 18 elbows from 9 fresh cadavers. UNI was classified into N (normal), S (subluxation), and D (dislocation) types. On US exams, the following findings and parameters were evaluated: the presence of UNI and ST; the horizontal distance from the apex of the medial epicondyle (ME) to the margins of the UN and medial head of the triceps brachii muscle (ME_UN and ME_TB, respectively); cross-sectional area and flattening ratio (FR) of UN. After US, all cadavers were dissected to expose the UN and TB, and elbow flexion and extension were simulated to confirm UNI and ST. The gross anatomic findings of UNI and ST were consistent with the US findings. In extension and 90° flexion positions, all cases were type N. In full flexion position, types N and S occurred in 10 (56%) and 8 (44%) elbows, respectively. FR and ME_UN in 90° flexion position, FR, ME_UN, and ME_TB in full flexion position differed significantly between types S and N. Positive correlations were found between ME_UN and ME_TB in 90° flexion and full flexion positions. Dynamic US accurately assessed UNI and ST. UNI was positively correlated to medial TB movement.

A Cadaveric Study of a Safe and Accurate Electromyographic Needle Approach to the Rhomboid Major.

OBJECTIVE: This study aimed to investigate a safe and accurate electromyographic needle insertion site of the rhomboid major (RM) muscle using cadaver dissection. DESIGN: Dissection of the trapezius and rhomboid major muscles around the scapula was performed in 18 scapulae from nine fresh cadavers. The point (point A) at which the lateral margin of the lower trapezius muscle crossed the medial border of the scapula and the distal insertion point (point DI) of the rhomboid major muscle to the medial scapula were determined. The midpoint (point M) between points A and DI was also determined. The distance from the inferior angle of the scapula to each point was measured. RESULTS: The length of the medial scapula was 12.9 ± 1.2 cm from the root of the scapular spine to the inferior angle of the scapula. Points A, DI, and M were located at a mean distance of 8.4 ± 0.7, 1.8 ± 0.4, and 5.1 ± 0.5 cm proximal to the inferior angle of the scapula, respectively. CONCLUSIONS: Needle electromyographic examination of the rhomboid major muscle can be performed safely and accurately using the lower part of the rhomboid major muscle, as investigated in this anatomical study.

MAX: a simple, affordable, and rapid tissue clearing reagent for 3D imaging of wide variety of biological specimens.

Transparency of biological specimens is crucial to obtaining detailed 3-dimensional images and understanding the structure and function of biological specimens. This transparency or tissue clearing can be achieved by adjusting the refractive index (RI) with embedding media and removing light barriers such as lipids, inorganic deposits, and pigments. Many currently available protocols consist of multiple steps to achieve sufficient transparency, making the process complex and time-consuming. Thus, in this study, we tailored the recipe for RI adjustment media named MAX based on the recently reported MACS protocol to achieve a single-step procedure, especially for ECM-rich tissues. This was achieved by the improvement of the tissue penetrability of the RI-matching reagent by combining MXDA with sucrose or iodixanol. While this was sufficient for the 3D imaging in many applications, MAX can also be combined with modular processes for de-lipidation, de-coloration, and de-calcification to further maximize the transparency depending on the special features of the tissues. Our approach provides an easy alternative for tissue clearing and 3D imaging.

Whole structural reconstruction and quantification of epidermal innervation through the suction blister method and skin-clearing technique.

Three-dimensional (3-D) analysis of intraepidermal nerve fibers (IENFs) is conducted to advance assessment methods for peripheral neuropathies and pruritic skin disorders. The skin-clearing technique was proven to be a reliable method for 3-D imaging of IENFs. Nonetheless, it still requires further improvement in the imaging process. The aim of this study was to standardize the 3-D evaluation method of IENFs and to suggest promising 3-D biomarkers for clinical application. A total of nine healthy individuals were prospectively enrolled. The newly adopted suction blister method was combined with the tissue-clearing technique. The detailed structure of the IENFs was reconstructed and quantified using the neuron tracing software. The suction blister method showed improved linear integrity of IENFs compared with those obtained from the previously used salt-split skin test. The 3-D parameters most significantly related to natural aging were the convex hull two-dimensional perimeter and the total length (both p = 0.020). The meaningful correlations were followed by total volume (p = 0.025), ends (p = 0.026), convex hull 3-D surface, and complexity (both p = 0.030). Thus, the 3-D parameters could be utilized as possible biomarkers to identify ambiguous pathologies of peripheral neuropathies and pruritic skin disorders.

Three-dimensional imaging for the analysis of human epidermal melanocytes.

Three-dimensional (3-D) analysis of human epidermal melanocytes is required for deeper understanding of melanocytic disorders. The purpose of this study was to standardize 3-D imaging and quantification for the evaluation of epidermal melanocytes. The epidermal specimen was obtained using the suction blister method from a patient with melanocytic nevus on the forearm skin. Cutaneous ACT-PRESTO, the tissue-clearing and labeling technique, was subsequently performed. With the 3-D image analysis program, morphological reconstruction and quantification of selected perilesional and melanocytic nevus areas were possible. The region of melanocytic nevus showed higher numbers of total melanocytic dendrites and similar numbers of cell bodies compared with perilesional area. In addition, the mean area and volume of cell bodies increased in the melanocytic nevus area compared with the results in the perilesional area. The 3-D evaluation method of human epidermal melanocytes can be applied to investigate novel pathologies related to hyper- or hypo-pigmentary disorders.

Optimal placement for needle electromyography of the supinator muscle: Cadaveric studies.

INTRODUCTION/AIMS: The existing methods for needle electromyography are confusing as to which is the safest and most effective. Our aim was to identify the optimal and safest needle electromyographic insertion site in the supinator muscle. METHODS: We performed a two-step cadaveric dissection of the supinator muscle and related neurovascular structures. The study was performed using 18 upper limbs of 9 fresh adult cadavers (step 1) and 14 upper limbs of 7 fresh adult cadavers (step 2). In step 1, an imaginary line connecting the radial head (RH) and midpoint of the dorsal wrist (RW line) was drawn, and the distance from the RH to the point where the RW line and posterior interosseous nerve (PIN) intersect (L_CROSS) was measured on the RW line. In step 2, the needle was inserted 30 mm distal to the RH according to the results of step 1. After injection with India ink, dissection was performed to measure the distance between the needle insertion site and PIN (L_CROSS_Inj) on the RW line. RESULTS: The median L_CROSS was 51.4 (35.5-65.6) mm. Needle insertion spared the PIN in all cases during step 2, and the needle was inserted into the supinator muscle in all cases. The median L_CROSS_Inj was 27.4 (13.2-39.8) mm. DISCUSSION: A safe and accurate needle insertion site for the supinator muscle is approximately 30 to 40 mm distal to the RH along the RW line.

Production of human spinal-cord organoids recapitulating neural-tube morphogenesis.

Human spinal-cord-like tissues induced from human pluripotent stem cells are typically insufficiently mature and do not mimic the morphological features of neurulation. Here, we report a three-dimensional culture system and protocol for the production of human spinal-cord-like organoids (hSCOs) recapitulating the neurulation-like tube-forming morphogenesis of the early spinal cord. The hSCOs exhibited neurulation-like tube-forming morphogenesis, cellular differentiation into the major types of spinal-cord neurons as well as glial cells, and mature synaptic functional activities, among other features of the development of the spinal cord. We used the hSCOs to screen for antiepileptic drugs that can cause neural-tube defects. hSCOs may also facilitate the study of the development of the human spinal cord and the modelling of diseases associated with neural-tube defects.

Cerebral Cortex Changes in Basketball Players.

BACKGROUND: Plastic changes to brain structure and function have been reported in elite athletes of various sports. Interestingly, different regions of the brain were engaged according to the type of sports analyzed. Our laboratory reported no difference in total cerebellar volume of basketball players compared to that in the control group using the manual segmentation method. Further detailed analyses showed that elite basketball players had increased volume of the striatum and vermian lobules VI-VII of the cerebellum. We analyzed the brain magnetic resonance imaging (MRI) of basketball players to understand their cerebral cortical plasticity through automatic analysis tools for MRI. METHODS: Brain MRI data were collected from 19 male university basketball players and 20 age-, sex-, and height-matched control groups. In order to understand the changes in the cerebral cortices of basketball players, we employed automated MRI brain analysis techniques, including voxel-based morphometry (VBM) and surface-based morphometry (SBM). RESULTS: VBM showed increased gray and white matter volume in both precentral gyri, paracentral lobules and increased gray matter volume in the right anterior superior temporal gyrus. SBM revealed a left dominant increase in both pericentral gyri. Fractal dimensional analysis showed an increase in the area of both precentral gyri, the left subcallosal gyrus, and the right posterior cingulate gyrus. These results suggest a significant role not only for the primary motor cortex, but also for the cingulate gyrus during basketball. CONCLUSION: Plastic changes of both precentral gyri, the pericentral area, paracentral lobules, and the right superior temporal gyrus were observed in elite basketball players. There was a strong increase of fractal complexity in both precentral gyri and a weak increase in the right posterior cingulate gyrus and left collateral gyrus. In this study, plastic regions linked to functional neuroanatomy were related to the competence required to play basketball.

Complications of Nasopharyngeal Swabs and Safe Procedures for COVID-19 Testing Based on Anatomical Knowledge.

Nasopharyngeal swabs have been widely to prevent the spread of coronavirus disease 2019 (COVID-19). Nasopharyngeal COVID-19 testing is a generally safe and well-tolerated procedure, but numerous complications have been reported in the media. Therefore, the present study aimed to review and document adverse events and suggest procedural references to minimize preventable but often underestimated risks. A total of 27 articles were selected for the review of 842 related documents in PubMed, Embase, and KoreaMed. The complications related to nasopharyngeal COVID-19 testing were reported to be rarely happened, ranging from 0.0012 to 0.026%. Frequently documented adverse events were retained swabs, epistaxis, and cerebrospinal fluid leakage, often associated with high-risk factors, including severe septal deviations, pre-existing skull base defects, and previous sinus or transsphenoidal pituitary surgery. Appropriate techniques based on sufficient anatomical knowledge are mandatory for clinicians to perform nasopharyngeal COVID-19 testing. The nasal floor can be predicted by the line between the nostril and external ear canal. For safe testing, the angle of swab insertion in the nasal passage should remain within 30° of the nasal floor. The swab was gently inserted along the nasal septum just above the nasal floor to the nasopharynx and remained on the nasopharynx for several seconds before removal. Forceful insertion should be attempted, and alternative examinations should be considered, especially in vulnerable patients. In conclusion, patients and clinicians should be aware of rare but possible complications and associated high-risk factors. The suggested procedural pearls enable more comfortable and safe nasopharyngeal COVID-19 testing for both clinicians and patients.

LEFTY-PITX2 signaling pathway is critical for generation of mature and ventricular cardiac organoids in human pluripotent stem cell-derived cardiac mesoderm cells.

The generation of mature ventricular cardiomyocytes (CMs) resembling adult CMs from human pluripotent stem cells (hPSCs) is necessary for disease modeling and drug discovery. To investigate the effect of self-organizing capacity on the generation of mature cardiac organoids (COs), we generated cardiac mesoderm cell-derived COs (CMC-COs) and CM-derived COs (CM-COs) and evaluated COs. CMC-COs exhibited more organized sarcomere structures and mitochondria, well-arranged t-tubule structures, and evenly distributed intercalated discs. Increased expressions of ventricular CM, cardiac metabolic, t-tubule formation, K+ ion channel, and junctional markers were confirmed in CMC-COs. Mature ventricular-like function such as faster motion vector speed, decreased beats per min, increased peak-to-peak duration, and prolonged APD50 and APD90 were observed in CMC-COs. Transcriptional profiling revealed that extracellular matrix-integrin, focal adhesion, and LEFTY-PITX2 signaling pathways are upregulated in CMC-COs. LEFTY knockdown affected ECM-integrin-FA signaling pathways in CMC-COs. Here, we found that high self-organizing capacity of CMCs is critical for the generation of mature and ventricular COs. We also demonstrated that LEFTY-PITX2 signaling plays key roles for CM maturation and specification into ventricular-like CM subtype in CMC-COs. CMC-COs are an attractive resource for disease modeling and drug discovery.

Transplantation of 3D bio-printed cardiac mesh improves cardiac function and vessel formation via ANGPT1/Tie2 pathway in rats with acute myocardial infarction.

A novel tissue engineering strategy using 3D bio-print technology has become a promising therapeutic method for acute myocardial infarction (AMI) in an animal model. However, the application of 3D bio-printed tissue remains limited due to poor graft survival. Therefore, it is a scientific priority to enhance graft survival by precisely adjusting the 3D environment of encapsulated cells. In this study, novel transplantable 3D cardiac mesh (cMesh) tissue with a porous mesh structure was presented using human cardiomyocytes, human cardiac fibroblasts, and gelatin-methacryloyl-collagen hydrogel. Cardiomyocytes and cardiac fibroblasts were well spreaded. The cardiomyocytes were connected with a gap junction channel in bio-printed cMesh and a 3D cardiac patch with an aggregated structure. Porous cMesh demonstrated structural advantages by increased phosphorylation of mTOR, AKT, and ERK signals associated with cell survival. Transplanted cMesh in rats with AMI improved long-term graft survival, vessel formation, and stabilization, reduced fibrosis, increased left ventricle thickness, and enhanced cardiac function. Our results suggest that porous cMesh provides structural advantages and a positive therapeutic effect in an AMI animal model.

Lessons from Cadaver Dissection during the COVID-19 Pandemic.

The rapid increase of the coronavirus disease 2019 pandemic from mid-February 2020 has led the anatomy department of the Korea University College of Medicine to cease the dissection laboratory. However, the hands-on anatomy laboratory experience is paramount to maximizing learning outcomes. In this paper, we share the experiences and lessons learned through the face-to-face cadaveric dissection experience during this disruptive situation. To minimize infection risks, the following strategies were applied: first, students' on-campus attendance was reduced; second, body temperatures and symptoms were checked before entering the laboratory, and personal protective equipment was provided to all participants; and third, a negative pressure air circulation system was used in the dissection room. We suggest that conducting face-to-face cadaveric anatomy dissection is feasible when the daily count of newly infected cases stabilizes, and there is ample provision of safety measures to facilitate hands-on education.

Oral Commissure Lift: A Retrospective Analysis of Complication Rates and Overall Outcomes.

BACKGROUND: Downward-turning oral commissures and sagging mouth corners can present an unfavorable impression. We introduced a new oral commissure lift procedure and investigated its effectiveness and complication rates. METHODS: Patients who underwent oral commissure lift in the plastic surgery clinic between January 2010 and December 2017 were enrolled retrospectively. Pre-and postoperative photographs were evaluated to measure oral commissure angles and analyze surgical complications, including visible scarring, unnatural appearance, and asymmetry. Many patients underwent a oral commissure lift with a simultaneous facelift. To exclude potential bias, we compared angular changes between patients receiving both oral commissure lift and facelift, with those receiving only oral commissure lift. Moreover, oral commissure angles of patients only receiving facelift were also measured. Statistical significance was set at p < 0.05. RESULTS: Oral commissure lift was performed in 51 patients. The mean ages and follow-up periods were 46.7 ± 11.9 years, and 25.2 ± 22.9 months, respectively. The preoperative mean angles of the right and left oral commissures measured - 3.1 ± 4.0° and - 3.4 ± 3.7°, respectively, and postoperative mean angles measured 3.6 ± 3.2° and 3.3 ± 3.5°, respectively. Postoperative changes in oral commissure angles were statistically significant (p < 0.05). The low complication rate included undercorrection in one patient, asymmetry in one patient, and visible scarring in three patients. We found no statistically significant differences in the studies excluding bias. CONCLUSIONS: The new oral commissure lift procedure for correcting sagging oral commissures was simple, safe, and effective with a low complication rate. LEVEL OF EVIDENCE IV: 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 .