Soft Tissue Anatomy Research Articles

Course Review: The Hand and Wrist Sculpture Course.

The Hand and Wrist Sculpture Course, organized by the Surgical Sculpture Workshops and badged by the British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS), is a 2-day innovative course aimed at trainees in plastic and orthopedic surgery, as well as therapists, teaching about the bony and soft tissue anatomy through a hands-on sculpting workshop for application in clinical work. The course is delivered by an expert faculty of hand surgeons with a keen interest in art and sculpture, and costs £300. The following review details the course and provides a detailed evaluation of the course.

Retraction Note: Hummingbird-sized dinosaur from the Cretaceous period of Myanmar

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Fully guided implant surgery using Magnetic Resonance Imaging – An in vitro study on accuracy in human mandibles

The objective of this in vitro study was to assess the accuracy of fully guided implant placement following virtual implant planning based on MRI. 16 human cadaver hemimandibles with single missing teeth (n=3), partially edentulous (n=6) and edentulous situations (n=7) were imaged using MRI. MRI and optical scans obtained with an intraoral scanner, were imported into an implant planning software. Virtual prosthetic and implant planning were performed regarding hard- and soft tissue anatomy. Drill guides were manufactured, and fully guided implant placement was performed. Buccal and lingual bone and implant nerve distance were measured by three examiners in preoperative MRI and postoperative CBCT. The implant position was assessed using a software for deviation of implant positions displayed in CBCT and optical scans, respectively. MRI displayed relevant structures for implant planning such as cortical and cancellous bone, inferior alveolar nerve and neighboring teeth. Implant planning, CAD/CAM of drill guides and guided implant placement were performed. Deviations between planned and actual implant positions in postoperative CBCT and optical scans were 1.34 mm (SD 0.84 mm) and 1.03 mm (SD 0.46 mm) at implant shoulder; 1.41 mm (SD 0.88 mm) and 1.28 mm (SD 0.52 mm) at implant apex, and 4.84° (SD 3.18°) and 4.21° (SD 2.01°). Measurements in preoperative MRI and postoperative CBCT confirmed the compliance with minimum distances of implants to anatomical structures. Relevant anatomical structures for imaging diagnostics in implant dentistry are displayed with MRI. The accuracy of MRI-based fully guided implant placement in vitro is comparable to the workflow using CBCT.

3T Magnetic Resonance Imaging of the Thumb-normal Appearances and Common Injuries

Thumb is unique not only in its orientation and function compared to the other fingers but also in its bony and soft-tissue anatomy. It is important to understand methods to acquire appropriate image of the thumb along its axis, become familiar with the normal magnetic resonance imaging anatomy of the thumb and develop an understanding of the appearance of common injuries, all of which help in proper management. With proper scanning technique, it is possible to identify all the ligaments, tendons, and pulleys of the thumb. Checklist ensures that all the structures are systematically seen and injuries are consciously looked for in a case of thumb trauma.

Facial Analysis: Correlation Between Cephalometric Angles and Types of Facial Profile

Objective: to correlate the nasolabial angles (ANL) and mentholabial groove (ASML) with the straight, concave and convex facial profiles, determined through subjective analysis, for application in orthodontic facial analysis. Method: a cross-sectional, retrospective and analytical study was carried out, with a sample of 184 documents from patients aged between 21 and 36 years old, being 107 woman and 77 man; belonging to the collection of the Specialization Course in Orthodontics, UNIFIP / PB, Brazil. The profile photographs were analyzed, through the subjective method, by visual analysis, under inter-examiner calibration, for classification of the profiles in: straight, concave and convex. For this, the projections of the upper and lower lips were considered, as well as their relationship with the projection of the chin and nose. In lateral radiographs, ANL and ASML angles were drawn for cephalometric analysis. The angles were transcribed through the construction of the facial profile of soft tissues from teleradiographies, in a negatoscope, outlined with ultrafan paper, through the contour of the anatomical soft tissue profile. The data were tabulated on a specific form for this purpose. Results: the majority of the sample consisted of women (58.2%); by brown patients (63.6%); convex profiles (50.0%); and with woman ANL angles 103.53º (± 9.78) and man 103.27º (± 11.65); and ASML, within the normal range 132, 07º (± 9.54º) for both sexes, respectively. There was no significant correlation between facial profiles and ANL and ASML angles. Conclusion: the ANL and ASML angles did not influence the facial profiles for the studied sample.

CT guided cervical medial branch block and radiofrequency ablation

The purpose of this report is to describe the procedure for CT fluoroscopy– guided Cervical medial branch block and facet radiofrequency ablation. CT fluoroscopic guidance allows more-precise needle tip positioning with visualization of bony landmarks and at the same time be aware of the adjoining soft tissue anatomy with good localization of adjacent critical non-targeted areas such as the neural foramina and the dorsal root ganglia. This serves as an alternative method for performing medial branch blocks and facet radiofrequency ablation.

Establishing sample-preparation protocols for X-ray phase-contrast CT of rodent spinal cords: Aldehyde fixations and osmium impregnation

BackgroundDense and unbiased cellular-resolution representations of extended volumetric central nervous system soft-tissue anatomy are difficult to obtain, even in experimental post-mortem settings. Interestingly, X-ray phase-contrast computed tomography (X-PCI-CT), an emerging soft-tissue-sensitive volumetric imaging technique, can provide multiscale organ- to cellular-level morphological visualizations of neuroanatomical structure. New MethodHere, we tested different nervous-tissue fixation procedures, conventionally used for transmission electron microscopy, to better establish X-PCI-CT-specific sample-preparation protocols. Extracted rat spinal medullas were alternatively fixed with a standard paraformaldehyde-only aldehyde-based protocol, or in combination with glutaraldehyde. Some specimens were additionally post-fixed with osmium tetroxide. Multiscale X-PCI-CT datasets were collected at several synchrotron radiation facilities, using state-of-the-art setups with effective image voxel sizes of 3.03 to 0.33 μm3, and compared to high-field magnetic resonance imaging, histology and vascular fluorescence microscopy data. ResultsMultiscale X-PCI-CT of aldehyde-fixed spinal cord specimens resulted in dense histology-like volumetric representations and quantifications of extended deep spinal micro-vascular networks and of intra-medullary cell populations. Osmium post-fixation increased intra-medullary contrast between white and gray-matter tissues, and enhanced delineation of intra-medullary cellular structure, e.g. axon fibers and motor neuron perikarya. Comparison with Existing MethodsVolumetric X-PCI-CT provides complementary contrast and higher spatial resolution compared to 9.4 T MRI. X-PCI-CT’s advantage over planar histology is the volumetric nature of the cellular-level data obtained, using samples much larger than those fit for volumetric vascular fluorescence microscopy. ConclusionsDeliberately choosing (post-)fixation protocols tailored for optimal nervous-tissue structural preservation is of paramount importance in achieving effective and targeted neuroimaging via the X-PCI-CT technique.

The Development of Appendicular joint cartilages in Alligator mississippiensis: Evolutionary and Biomechanical Implications for Archosauria

Crocodylians and birds are the two surviving lineages within Archosauria, a clade of morphologically and ecologically diverse vertebrates that evolved highly disparate locomotor postures. The appendicular joints of crocodylians and birds differ substantially, thus complicating inferences of ancestral morphology and evolutionary transitions. Recent studies have indicated that the American alligator, an extant crocodylian, use a wide spectrum of cartilaginous and other connective tissues to construct the hip joint. However, little is known about the distribution and use of cartilage throughout other appendicular joints, as well the ontogenetic transition of the crocodilian chondro‐osseous interface during early development. In particular, the hyaline cartilage on the proximal femur of late embryonic alligators possesses a convex, cone‐like extension that inserts deep into the metaphysis. This morphology is not seen in juvenile and adults, but is superficially similar to the cartilage cone‐metaphyseal trough articulation inferred in early members of multiple archosaurian groups. The method by which alligators and other archosaurs reduced the cartilage cone during ontogeny and evolution, as well as the functional significance of the cartilage cone itself, are poorly understood.This study examined the ontogenetic transitions of proximal appendicular joints in the American alligator, spanning from in ovo stages to the first year of life. We used dissection, histology, and imaging techniques to assess the articular soft tissue anatomy at the chondro‐osseous junction of the proximal‐ and distal epiphyses of the femur and humerus. Additionally, osteological correlates for joint cartilage were identified on fully skeletonized limb bone elements and compared with bony morphology seen in fossil archosauromorphs.At the onset of hatching, the alligator did not reduce the cartilage cone via decreasing the “depth” of cartilaginous extension into the metaphysis, as inferred for early archosaurs. Instead, neonatal alligators regress the cartilage cone via multiple invasion fronts of trabecular bones, such that the subchondral growth plate of hatchlings presents a convex surface perforated by numerous cartilage canals, similar to those found in young birds. These results suggest that the ontogenetic loss of cartilage cone in the alligator is different from the evolutionary loss of cartilage cone hypothesized for early archosaurs. Instead, the role of cartilage thinning, fibrocartilage sleeve development and calcified epiphyseal cartilage may be highly associated within different sauropsid lineages in response to evolutionary changes in joint loading regimes.Support or Funding InformationThis research is supported by the Missouri State University Faculty Research Grant

Soft tissue augmentation around dental implants with connective tissue graft (CTG) and xenogenic collagen matrix (XCM). 1-year randomized control trail

BackgroundThe anatomy of soft tissues around dental implants is extremely important to prevent inflammatory periimplant diseases and ensure healthy, stable and long-term survival of a dental implant. Various methods and materials for increasing the physiological thickness of tissues have been described including connective tissue graft (CTG) and xenogenic collagen matrix (XCM). While assessing various materials it is necessary to establish objective measurement method to determine the minimum amount of tissue thickness to maintain a stable level of bone around the implant. The aim of the study was to determine the effect of soft tissues in the implant area on the marginal bone level in the implant area and to define of the critical gingival thickness to minimize marginal bone level (MBL) loss. Methods75 bone level implants (Conelog® Camlog, Switzerland) were inserted in the aesthetic area. Thickening of soft tissues was performed using CTG and XCM. 12 months after the loading with final restoration, the thickness of soft tissues in the implant area was examined with ultrasound USG device (Pirop®, Echoson, Poland), and each implant was subjected to RVG examination, where MBL loss was determined. ResultsA tendency to occur less MBL loss was found when thicker gingiva was present. The higher soft tissue thickness was, the lower MBL loss has occurred. A critical value for tissue thickness was determined as TKT ≤ 2.88. ConclusionsIn case of thin biotype soft tissue augmentation is required when value of tissue thickness in ultrasound measure is less than 2.88 mm.

Hummingbird-sized dinosaur from the Cretaceous period of Myanmar

Skeletal inclusions in approximately 99-million-year-old amber from northern Myanmar provide unprecedented insights into the soft tissue and skeletal anatomy of minute fauna, which are not typically preserved in other depositional environments1-3. Among a diversity of vertebrates, seven specimens that preserve the skeletal remains of enantiornithine birds have previously been described1,4-8, all of which (including at least one seemingly mature specimen) are smaller than specimens recovered from lithic materials. Here we describe an exceptionally well-preserved and diminutive bird-like skull that documents a new species, which we name Oculudentavis khaungraae gen. et sp. nov. The find appears to represent the smallest known dinosaur of the Mesozoic era, rivalling the bee hummingbird (Mellisuga helenae)-the smallest living bird-in size. The O.khaungraae specimen preserves features that hint at miniaturization constraints, including a unique pattern of cranial fusion and an autapomorphic ocular morphology9 that resembles the eyes of lizards. The conically arranged scleral ossicles define a small pupil, indicative of diurnal activity. Miniaturization most commonly arises in isolated environments, and the diminutive size of Oculudentavis is therefore consistent with previous suggestions that this amber formed on an island within the Trans-Tethyan arc10. The size and morphology of this species suggest a previously unknown bauplan, and a previously undetected ecology. This discovery highlights the potential of amber deposits to reveal the lowest limits of vertebrate body size.

Intact Periorbita Can Prevent Post-Traumatic Enophthalmos Following a Large Orbital Blow-Out Fracture.

Treatment of orbital floor fractures is predicated on the restoration of orbital volume to prevent enophthalmos or hypoglobus. Globe position is the result of a complex interplay between the bony orbital anatomy and the soft tissue envelope. Studies on orbital fractures have frequently suggested criteria for repair on the basis of bony defect size or volume change. In this report, we describe a case of a large orbital floor defect (4.8 cm2) with intact periorbita and no herniation of soft tissue contents in a young male following facial trauma. The patient was followed for 1-year clinically and did not develop enophthalmos. This case demonstrates that bony injury alone is not sufficient to produce enophthalmos, and that the interplay between the soft tissue and bony anatomy is a critical determinant of globe position following orbital trauma.

Deep learning robotic guidance for autonomous vascular access

Medical robots have demonstrated the ability to manipulate percutaneous instruments into soft tissue anatomy while working beyond the limits of human perception and dexterity. Robotic technologies further offer the promise of autonomy in carrying out critical tasks with minimal supervision when resources are limited. Here, we present a portable robotic device capable of introducing needles and catheters into deformable tissues such as blood vessels to draw blood or deliver fluids autonomously. Robotic cannulation is driven by predictions from a series of deep convolutional neural networks that encode spatiotemporal information from multimodal image sequences to guide real-time servoing. We demonstrate, through imaging and robotic tracking studies in volunteers, the ability of the device to segment, classify, localize and track peripheral vessels in the presence of anatomical variability and motion. We then evaluate robotic performance in phantom and animal models of difficult vascular access and show that the device can improve success rates and procedure times compared to manual cannulations by trained operators, particularly in challenging physiological conditions. These results suggest the potential for autonomous systems to outperform humans on complex visuomotor tasks, and demonstrate a step in the translation of such capabilities into clinical use. Getting safe and fast access to blood vessels is vital to many methods of treatment and diagnosis in medicine. Robot-assisted or even fully autonomous methods can potentially do the task more reliably than humans, especially when veins are hard to detect. In this work, a method is tested that uses deep learning to find blood vessels and track the movement of a patient’s arm.

Patellar-Trochlear Morphology in Pediatric Patients From 2 to 11 Years of Age: A Descriptive Analysis Based on Computed Tomography Scanning.

Despite the critical role the trochlea plays in patellofemoral (PF) pathology, the development of the trochlea is poorly understood. The purpose of this study was 2-fold: (1) Describe quantitative osseous and soft tissue anatomy of the patella and trochlea in skeletally immature cadaveric specimens utilizing known measurements used in PF instability, and (2) evaluate additional measurement techniques in the sagittal plane as they relate to PF morphologic development. Thirty-one skeletally immature fresh frozen cadaveric knees between the ages of 2 and 11 years old were evaluated using 0.625 mm computed tomography scans. In the axial plane, measurements included condylar height asymmetry, trochlear facet asymmetry, trochlear depth, osseous sulcus angle, cartilaginous sulcus angle, patella sulcus angle, and tibial tubercle-trochlear groove distance. In the sagittal plane, measurements included previously undescribed measurements of trochlear length and condylar height asymmetry which are based on the anterior femoral cortex. Analysis of trochlear morphology using condylar height asymmetry (both axial and sagittal), trochlear facet asymmetry, and trochlear depth and length demonstrated an increase in the size of the medial and lateral trochlea as age increased. There was more variability in the change of size of the medial trochlea (height, length, and facet length) than the lateral trochlea. The osseous sulcus angle, cartilaginous sulcus angle, and patella sulcus angle decreased (became deeper) with age until after 8 years and then plateaued. This cadaveric analysis demonstrated that there is an increase in the medial and lateral trochlear height as age increased by all measurements analyzed. The findings also demonstrate that the shape of the patella and trochlea change concurrently, which suggests that there may be interplay between the 2 during development. These new sagittal measurement techniques evaluating the medial, central, and lateral trochlear height and length with respect to age may help guide clinicians when investigating patellar instability in skeletally immature patients. Level IV.

Seated buttocks anatomy and its impact on biomechanical risk

AimThe objective of this study was to describe the amount, types, and shapes of tissue present in the buttocks during sitting (i.e., seated buttocks soft tissue anatomy), and the impact of seated buttocks soft tissue anatomy on biomechanical risk. Materials and methodsThe buttocks of 35 people, including 29 full-time wheelchair users with and without a history of pelvic pressure ulcers were scanned sitting upright on 3” of flat HR45 foam in a FONAR Upright MRI. Multi-planar scans were analyzed to calculate bulk tissue thickness, tissue composition, gluteus maximus coverage at the ischium, the contour of the skin, and pelvic tilt. ResultsBulk tissue thickness varied from 5.6 to 32.1 mm, was composed mostly of adipose tissue, and was greatest in the able-bodied cohort. Skin contours varied significantly across status group, with wheelchair users with a history of pressure ulcers having tissue with a peaked contour with a radius of curvature of 65.9 mm that wrapped more closely to the ischium (thickness at the apex = 8.2 mm) as compared to wheelchair users with no pressure ulcer history (radius of curvature = 91.5 mm and apex thickness = 14.5 mm). Finally, the majority of participants presented with little to no gluteus coverage over their ischial tuberosity, regardless of status group. ConclusionsThis study provides quantitative evidence that Biomechanical Risk, or the intrinsic characteristic of an individual's soft tissues to deform in response to extrinsic applied forces, is greater in individuals at greater risk for pressure ulcers.

Avulsion Injuries of the Hand and Wrist.

Injuries of the hand and wrist are frequently encountered in radiology. Avulsions of the hand and wrist are a heterogeneous group of injuries, but they often have a characteristic imaging appearance that relates to the intricate bone and soft-tissue anatomy and the mechanism of injury. The imaging appearance and this intricate form and function dictate treatment of hand and wrist avulsions. This article reviews frequently and infrequently encountered avulsion injuries and describes abnormalities that may mimic the imaging appearance of avulsions. Specifically discussed entities include the Bennett and reverse Bennett fracture, ulnar collateral ligament avulsion, radial and ulnar styloid process avulsion, triquetral avulsion, mallet and jersey finger, central slip avulsion, and acute and chronic volar plate avulsion injuries. Uncommon avulsion injuries are also described and include avulsions of the scapholunate ligament, extensor carpi radialis longus and brevis tendons, trapeziometacarpal ligament, radial collateral ligament, and flexor digitorum profundus tendon. Emphasis is placed on the relevant anatomy and typical imaging findings for each diagnosis, with pertinent clinical history, pathophysiologic evaluation, and treatment discussed briefly. Understanding the anatomy and expected imaging findings can aid the radiologist in recognizing and characterizing these injuries.©RSNA, 2020.

Histology and structural integration of the major morphologies of the Cypriniform Weberian apparatus.

The Weberian apparatus, a diagnostic feature of otophysan fishes, is a novel hearing adaptation integrating several developmental and morphological systems (ear-vertebral column-swim bladder). Otophysan fishes are one of the largest and most successful freshwater clades, with over 10,000 species across most continents. The largest otophysan order, Cypriniformes, dominates the freshwaters of Asia, Europe, North America, and Africa. Spanning such a wide variety of environments, the Weberian apparatus undergoes morphological modifications to maintain functionality. Within Cypriniformes, we propose three distinct morphological classes of the Weberian apparatus based on the level of skeletal expansion around the swim bladder: simple (typical of most Cyprinidae), anterior plate (found in families such as Gyrinocheilidae, Catostomidae, and Botiidae), and encapsulated (either single-capsule as found, e.g., in Gobionidae and Cobitidae, or double-capsule as found, e.g., in Nemacheilidae and Balitoridae). Little ontological or comparative data exists regarding the construction or integration of these different morphologies, and less is known about the tissue level integration and variation within these morphologies. We used paraffin histology to document the hard and soft tissue anatomy of the Weberian apparatus in six species representing all morphological classes. We found sites of similarity across the morphologies including size and structure of the saccule, aspects of ossicle ossification, and swim bladder tunica composition, indicating potential sites of developmental and functional constraint. In contrast, we found differences across both auditory and nonauditory features in otic chamber size, ossification within ossicles and other vertebral elements, and composition of ligaments, indicating likely sites of adaptability. Some of these changes are likely evolutionary (taxonomic), but may be influenced by the environmental niche occupied by the clade. These results show a clear need for increased ontological and comparative study of the complete cypriniform Weberian apparatus, particularly histologically, as well as increased auditory studies across morphological types.

Soft-tissue anatomy of an Orsten-type phosphatocopid crustacean from the Cambrian Furongian of China revealed by synchrotron radiation X-ray tomographic microscopy

Fossils of Orsten-type preservation represented by Skara and Phosphatocopida have been reported from the Cambrian Furongian of Western Hunan, China. Their taxonomy and external morphology are well known, but their internal soft-tissue anatomy has not been revealed yet. With the application of synchrotron radiation X-ray tomographic microscopy, here we describe the internal soft-tissue anatomy of an Orsten-type preserved phosphatocopid crustacean assigned to Hesslandona angustata. The internal organs and tissues of this specimen were collapsed after death to form a visceral mass situated within the labrum and underneath the sternal cuticle. The visceral mass contains the digestive system, including digestive tract and possible digestive glands. The digestive tract starts from the mouth, followed by oesophagus (foregut) and midgut, whereas the hind gut and anus are unknown due to incomplete preservation. Two bilaterally symmetric knob-like structures beside the midgut may be digestive glands (midgut diverticula). The visceral mass also contains other structures that may be related to nerve tissues and/or muscles, but identification as specific organs or tissues is uncertain.

Horizontal change of philtrum after orthognathic surgery in patients with facial asymmetry

BackgroundSoft tissue asymmetry such as lip canting or deviation of the philtrum is an important influencing factor for unbalanced facial appearance. Lip canting could be improved by the correction of the occlusal canting or positional change of the mentum. Although there are many studies about changes of lip canting, however, postoperative changes of philtrum deviation have not been yet reported. In this study, we investigate the positional change of the philtrum after orthognathic surgery and influencing factors.MethodsPositional change of the philtrum was evaluated in 41 patients with facial asymmetry who underwent bimaxillary surgery, in relation to other anatomical soft tissue landmarks using a frontal clinical photo. The surgical movement of the maxillary and mandibular dental midline and canting were measured in postero-anterior cephalogram before and 1 day after surgery. The same procedure was repeated in patients with more than 1.5 mm perioperative change of the mandibular dental midline after bimaxillary surgery.ResultsMaxillary dental midline shifting and canting correction did not have a significant correlation with lateral movement of the philtrum midline. However, the mandibular shift had a statistically significant correlation with a lateral movement of the philtrum (p < 0.05) as well as other linear parameters and angle values.ConclusionThe horizontal change of the philtrum is influenced by lateral mandibular movement in patients with facial asymmetry, rather than maxillary lateral movement.

MRI of the penis.

This article reviews the anatomy and magnetic resonance imaging (MRI) appearance of the penis. The recommended technique for MRI of the penis is outlined, with discussion of the benefits and drawbacks to imaging the penis after artificial erection. Common penile pathologies are reviewed, with a summary of their clinical features, MRI appearance, and treatment. The ability to demonstrate the erectile bodies and vasculature helps to evaluate vascular pathologies such as priapism, Mondor disease, and cavernosal thrombosis. MRI is also a useful tool to assess for traumatic abnormalities of the penis, with the depiction of soft tissue anatomy and fascial layers allowing for evaluation of penile fracture and penile contusion. Malignant disease of the penis is also reviewed, including squamous cell carcinoma, urethral carcinoma, metastases, and rare neoplasms. Staging of these neoplasms is addressed, with discussion of how MRI can be used to assess the extent of tumor involvement. MRI also clearly demonstrates the tunica albuginea, which allows for evaluation of Peyronie's disease.

Contrast-enhanced XROMM reveals in vivo soft tissue interactions in the hip of Alligator mississippiensis.

Extant archosaurs exhibit highly divergent articular soft tissue anatomies between avian and crocodilian lineages. However, the general lack of understanding of the dynamic interactions among archosaur joint soft tissues has hampered further inferences about the function and evolution of these joints. Here we use contrast-enhanced computed tomography to generate 3D surface models of the pelvis, femora, and hip joint soft tissues in an extant archosaur, the American alligator. The hip joints were then animated using marker-based X-Ray Reconstruction of Moving Morphology (XROMM) to visualize soft tissue articulation during forward terrestrial locomotion. We found that the anatomical femoral head of the alligator travels beyond the cranial extent of the bony acetabulum and does not act as a central pivot, as has been suggested for some extinct archosaurs. Additionally, the fibrocartilaginous surfaces of the alligator's antitrochanter and femoral neck remain engaged during hip flexion and extension, similar to the articulation between homologous structures in birds. Moreover, the femoral insertion of the ligamentum capitis moves dorsoventrally against the membrane-bound portion of the medial acetabular wall, suggesting that the inner acetabular foramen constrains the excursion of this ligament as it undergoes cyclical stretching during the step cycle. Finally, the articular surface of the femoral cartilage model interpenetrates with those of the acetabular labrum and antitrochanter menisci; we interpret such interpenetration as evidence of compressive deformation of the labrum and of sliding movement of the menisci. Our data illustrate the utility of XROMM for studying in vivo articular soft tissue interactions. These results also allow us to propose functional hypotheses for crocodilian hip joint soft tissues, expanding our knowledge of vertebrate connective tissue biology and the role of joint soft tissues in locomotor behavior.