Bony Attachment Research Articles

Psoriatic arthritis: Ultrasound peculiarities with particular emphasis on enthesitis.

The prevalence of psoriatic arthritis among patients with psoriasis has a marked variability with ethnic and geographic variations. Inflammatory changes associated with psoriatic arthritis include bone erosion, tenosynovitis, and synovial hypertrophy, but enthesitis is considered the hallmark. Both X-ray and magnetic resonance imaging (MRI) are usefull in the diagnosis of psoriatic arthritis, but ultrasonography is the best imaging modality to assess entheses. Ultrasound findings of enthesitis include a loss of the regular fibrillar architecture, hypoechoic thickening, hypervascularization of tendons, ligaments, and joint capsules at their bony attachment, bony changes (including irregularities and erosions). Ultrasound has also proved the ability to detect inflammatory subclinical findings and to be useful in the follow-up of therapies.

A Rare Case of Soft Tissue Osteoma of Hand.

Osteomas are benign, slow-growing, differentiated tumours, which are primarily located in the region of maxillofacial skeleton. Osteoma involving the soft tissues with no bony attachments is a very rare event. A 68-year-old woman with comorbidities (diabetes mellitus type II, primary hypertension, pacemaker in situ) presented with a painless solid mass in the thenar region of her right palm, which appeared almost 1 and half years ago and showed a progressive enlargement in the last few months. Under regional anaesthesia, an excisional biopsy was performed and the histopathological evaluation of the lesion confirmed the diagnosis of soft tissue osteoma. The postoperative follow-up period was uneventful without any complication.

Surgical anatomy of the femoral nerve in formalin prefixed cadavers in an adult Kenya population

Background: Ethnic variations involving femoral nerve have been described in literature. This nerve is the largest branch of the lumbar plexus. It innervates the hip flexors, knee extensors, and sensory function to medial and anterior aspects of the thigh. Risks of insults to nerve can be non-iatrogenic (trauma), and iatrogenic (approaches to the acetabulum, pelvis and proximal femur). The study aimed at providing precise description of variant anatomy of nerve, hence will help surgeons avoid iatrogenic insults.Methods: An anatomic descriptive cross-sectional study design involving fifty six (56), formalin prefixed adult cadaveric specimens. The length of the femoral nerve in relation to the inguinal ligament and its bony attachments, and the patterns of distribution of main branches in the regions were defined. Results: Males- 35 (Left=17, Right=18); Females- 21(Left=7, Right=14). Femoral nerve location: 53.02 mm (SD 14.59) from the ipsilateral anterior superior iliac spine (ASIS). Nerve trunk in relation to inguinal ligament measured: 47.85mm (SD 13.719) from the psoas muscle proximally and branched 29.32 mm (SD 14.239) distally. Innervations and branches: quadriceps in all specimens (Posterior); Sartorius muscles (Anterior), with noted variability in individual muscles. Branching pattern variations: 6 limbs (10.71%) at ligament level, 2(3.57%) limbs more proximal, while one nerve was split by a slip from the psoas muscle and then united 25.88mm proximal to ligament. The variations in sex were not statistically significant (p> 0.05).Conclusion: The anatomical course, length and branches of the femoral nerve in relation to inguinal ligament concur to great extent with described anatomic studies with some noted variability. Surgeons should be aware of the anatomic variations of femoral nerve and be cautious when operating in the zones traversed by the nerve.

Enthesis strength, toughness and stiffness: an image-based model comparing tendon insertions with varying bony attachment geometries.

Tendons of the body differ dramatically in their function, mechanics and range of motion, but all connect to bone via an enthesis. Effective force transfer at the enthesis enables joint stability and mobility, with strength and stiffness arising from a fibrous architecture. However, how enthesis toughness arises across tendons with diverse loading orientations remains unclear. To study this, we performed simultaneous imaging of the bone and tendon in entheses that represent the range of tendon-to-bone insertions and extended a mathematical model to account for variations in insertion and bone geometry. We tested the hypothesis that toughness, across a range of tendon entheses, could be explained by differences observed in interactions between fibre architecture and bone architecture. In the model, toughness arose from fibre reorientation, recruitment and rupture, mediated by interactions between fibres at the enthesis and the bony ridge abutting it. When applied to tendons sometimes characterized as either energy-storing or positional, the model predicted that entheses of the former prioritize toughness over strength, while those of the latter prioritize consistent stiffness across loading directions. Results provide insight into techniques for surgical repair of tendon-to-bone attachments, and more broadly into mechanisms for the attachment of highly dissimilar materials.

Evaluation of bone formation on orthopedic implant surfaces using an ex-vivo bone bioreactor system

Recent advances in materials and manufacturing processes have allowed the fabrication of intricate implant surfaces to facilitate bony attachment. However, refinement and evaluation of these new design strategies are hindered by the cost and complications of animal studies, particularly during early iterations in the development process. To address this problem, we have previously constructed and validated an ex-vivo bone bioreactor culture system that can maintain the viability of bone samples for an extended period ex-vivo. In this study, we investigated the mineralization of a titanium wire mesh scaffold under both static and dynamic culturing using our ex vivo bioreactor system. Thirty-six cancellous bone cores were harvested from bovine metatarsals at the time of slaughter and divided into five groups under the following conditions: Group 1) Isolated bone cores placed in static culture, Group 2) Unloaded bone cores placed in static culture in contact with a fiber-mesh metallic scaffold, Group 3) Bone cores placed in contact with a fiber-mesh metallic scaffold under the constant pressure of 150 kPa, Group 4) Bone core placed in contact with a fiber-mesh metallic scaffold and exposed to cyclic loading with continuous perfusion flow of media within the ex-vivo culture system and Group 5) Bone core evaluated on Day 0 to serve as a positive control for comparison with all other groups at weeks 4 and 7. Bone samples within Groups 1–4 were incubated for 4 and 7 weeks and then evaluated using histological examination (H&E) and the Live-Dead assay (Life Technologies). Matrix deposits on the metallic scaffolds were examined with scanning electron microscopy (SEM), while the chemical composition of the matrix was measured using energy-dispersive x-ray spectroscopy (EDX). We found that the viability of bone cores was maintained after seven weeks of loading in our ex vivo system. In addition, SEM images revealed crystallite-like structures on the dynamically loaded metal coupons (Group 4), corresponding to the initial stages of mineralization. EDX results further confirmed the presence of carbon at the interface and calcium phosphates in the matrix. We conclude that a bone bioreactor can be used as an alternate tool for in-vivo bone ingrowth studies of new implant surfaces or coatings.

Morphometric relationships between dimensions the anterior talofibular ligament and calcaneofibular ligament in routine magnetic resonance imaging

PurposeThis study aimed to test the hypothesis that routine MRI ankle can be used to evaluate dimensions and correlations between dimensions of single and double fascicular variants of the ATFL and the CFL.MethodsWe reviewed ankle MRIs for 251 patients. Differences between the length, thickness, width, and length of the bony attachments were evaluated twice. P < .05 was considered as significant.ResultsFor the ATFL, we observed a negative correlation between thickness and width, with a positive correlation between thickness and length (p < 0.001). The average values for the ATFL were thickness, 2.2 ± 0.05 mm; length, 21.5 ± 0.5 mm; and width, 7.6 ± 0.6 mm. The average values for the CFL were thickness, 2.1 ± 0.04 mm; length, 27.5 ± 0.5 mm; and width, 5.6 ± 0.3 mm. A negative correlation was found between length and width for the CFL (p < 0.001).ConclusionsRoutine MRI showed that most dimensions of the ATFL and CFL correlate with each other, which should be considered when planning new reconstruction techniques and developing a virtual biomechanical model of the human foot.Level of evidenceIII

Anomalous insertion of anterior and posterior horns of medial meniscus. Case report

BackgroundAnatomical variations of the attachment of medial meniscus are a common finding. However, anomalies of the posterior horn are extremely rare. Only two cases of posterior root anomaly have been described prior to the routine use of arthroscopy for evaluation and treatment of meniscal pathology. In this report, we present an anomaly of both the anterior and posterior roots of the medial meniscus that posed both a diagnostic and therapeutic dilemma.Case presentationThe patient is young male soccer player who is currently 16 years of age and began having the atraumatic onset of pain and symptoms that limited performance starting at age 14 and was referred for failure of response to nonoperative treatment. Diagnostic arthroscopy revealed the presence of an anteromedial meniscofemoral ligament whereas the posterior root showed no bony attachment. The radiographic and arthroscopic findings are described. The clinical decision was made after to proceed with observation, reassurance, and gradual return to full activity with physiotherapy guidance.Discussion and conclusionThe absence of injury, the mild complaints reported by the patient, his age, skeletal immaturity, and remaining growth led us to adopt a conservative approach to treating this anatomic variant and currently the patient is able to participate fully in sports without symptoms or restrictions.

Effects of selective breeding for voluntary exercise, chronic exercise, and their interaction on muscle attachment site morphology in house mice.

Skeletal muscles attach to bone at their origins and insertions, and the interface where tendon meets bone is termed the attachment site or enthesis. Mechanical stresses at the muscle/tendon-bone interface are proportional to the surface area of the bony attachment sites, such that a larger attachment site will distribute loads over a wider area. Muscles that are frequently active and/or are of larger size should cause attachment sites to hypertrophy (training effect); however, experimental studies of animals subjected to exercise have provided mixed results. To enhance our ability to detect training effects (a type of phenotypic plasticity), we studied a mouse model in which 4 replicate lines of High Runner (HR) mice have been selectively bred for 57generations. Selection is based on the average number of wheel revolutions on days 5 & 6 of a 6-day period of wheel access as young adults (6-8weeks old). Four additional lines are bred without regard to running and serve as non-selected controls (C). On average, mice from HR lines voluntarily run ~3 times more than C mice on a daily basis. For this study, we housed 50 females (half HR, half C) with wheels (Active group) and 50 (half HR, half C) without wheels (Sedentary group) for 12weeks starting at weaning (~3weeks old). We tested for evolved differences in muscle attachment site surface area between HR and C mice, plastic changes resulting from chronic exercise, and their interaction. We used a precise, highly repeatable method for quantifying the three-dimensional (3D) surface area of four muscle attachment sites: the humerus deltoid tuberosity (the insertion point for the spinodeltoideus, superficial pectoralis, and acromiodeltoideus), the femoral third trochanter (the insertion point for the quadratus femoris), the femoral lesser trochanter (the insertion point for the iliacus muscle), and the femoral greater trochanter (insertion point for the middle gluteal muscles). In univariate analyses, with body mass as a covariate, mice in the Active group had significantly larger humerus deltoid tuberosities than Sedentary mice, with no significant difference between HR and C mice and no interaction between exercise treatment and linetype. These differences between Active and Sedentary mice were also apparent in the multivariate analyses. Surface areas of the femoral third trochanter, femoral lesser trochanter, and femoral greater trochanter were unaffected by either chronic wheel access or selective breeding. Our results, which used robust measurement protocols and relatively large sample sizes, demonstrate that muscle attachment site morphology can be (but is not always) affected by chronic exercise experienced during ontogeny. However, contrary to previous results for other aspects of long bone morphology, we did not find evidence for evolutionary coadaptation of muscle attachments with voluntary exercise behavior in the HR mice.

Anatomic Considerations of Perinasal Musculature for Improved Dental Show During Smile in Facial Synkinesis.

Introduction:There is an anatomic explanation for upper lip and midfacial tethering resulting in lack of motion in facial synkinesis.Objective:To measure the effect of perinasal chemodenervation on dental show in the synkinetic population and clarify the anatomic relationship of perinasal musculature.Methods:Literature search was performed on anatomy of the perinasal modiolus, and anatomic evaluation was performed through human anatomic specimen dissection. Photographic outcomes were observed in synkinetic patients receiving chemodenervation to smile antagonists with and without perinasal muscle injections and assessed through naive observer survey. Retrospective outcomes for all patients receiving perinasal chemodenervation was collected utilizing Facial Clinimetric Evaluation Scale, Sunnybrook Facial Grading System (FGS), Facial Disability Index (FDI), and the Synkinesis Assessment Questionnaire.Results:Anatomic dissections demonstrated muscular confluence spanning the nasal sidewall and upper lip tethering the soft tissue to bone. Thirty-four of 53 chemodenervation patients received perinasal Botox experiencing improvement in synkinetic symptoms of the upper lip, nose, and improved dental show as noted on paired t-test for FGS (p = 0.00096), and FDI social p = 0.015) also supported by naive observer surveys (p = 0.03).Conclusions:Human anatomic specimen dissections support a perinasal confluence of musculature with bony attachments that can be successfully treated with chemodenervation in facial synkinesis patients.

Human orbital muscle in adult cadavers and near-term fetuses: its bony attachments and individual variation identified by immunohistochemistry.

To compare fetal and adult morphologies of the orbital muscle (OM) and to describe the detailed topographical anatomy in adults. Using unilateral orbits from 15 near-term fetuses and 21 elderly cadavers, semiserial horizontal or sagittal paraffin sections were prepared at intervals of 20-100µm. In addition to routine histology, we performed immunohistochemistry for smooth muscle actin. At near term, the OM consistently extended widely from the zygomatic bone or the greater wing of the sphenoid to the maxilla or ethmoid. Thus, it was a large sheet covering the future inferior orbital fissure. In contrast, the adult OM was a thin and small muscle bundle connecting (1) the greater wing of the sphenoid to the maxilla (11/19 cadavers), (2) the lesser wing of the sphenoid to the maxilla (5/19) or the greater wing (3/19). The small OM was likely to be restricted within the greater wing (5/19 cadavers) or the maxilla (3/19). Two of these five types of OM coexisted in eight orbits. OM attachment to the lesser wing was not seen in fetuses, whereas ethmoid attachment was absent in adults. The lesser wing attachment of the OM seemed to establish after birth. A growing common origin of the three recti was likely involved in "stealing" the near-term OM attachment from the ethmoid. The strong immunoreactivity of remnant-like OM in the elderly suggests that OM contraction is still likely to occur against the increased flow through a thin vein. However, the contraction might have no clinical significance.

Mesenchymal stem cell-derived exosomes: therapeutic implications for rotator cuff injury.

Rotator cuff injuries are a common clinical condition of the shoulder joint. Surgery that involves reattaching the torn tendon to its humeral head bony attachment has a somewhat lower success rate. The scar tissue formed during healing of the rotator cuff leads to poor tendon-related mechanical properties. To promote healing, a range of genetic interventions, as well as cell transplantation, and many other techniques have been explored. In recent years, the therapeutic promise of mesenchymal stem cells (MSCs) has been well documented in animal and clinical studies. Some data have suggested that MSCs can promote angiogenesis, reduce inflammation and cell proliferationand increase collagen deposition. These functions are likely paracrine effects of MSCs, particularly mediated through exosomes. Here, we review the use of MSCs-related exosomes in tissues and organs. We also discuss their potential utility for treating rotator cuff injuries, and explore the underlying mechanisms of their effects.

Osseointegration of retrieved 3D-printed, off-the-shelf acetabular implants.

AimsThe main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants.MethodsWe compared two groups, one made via 3D-printing (n = 7) and the other using conventional techniques (n = 7). We collected implant details, type of surgery and removal technique, patient demographics, and clinical history. Bone integration was assessed by macroscopic visual analysis, followed by sectioning to allow undecalcified histology on eight sections (~200 µm) for each implant. The outcome measures considered were area of bone attachment (%), extent of bone ingrowth (%), bone-implant contact (%), and depth of ingrowth (%), and these were quantified using a line-intercept method.ResultsThe two groups were matched for patient sex, age (61 and 63 years), time to revision (30 and 41 months), implant size (54 mm and 52 mm), and porosity (72% and 60%) (p > 0.152). There was no difference in visual bony attachment (p = 0.209). Histological analysis showed greater bone ingrowth in 3D-printed implants (p < 0.001), with mean bone attachment of 63% (SD 28%) and 37% (SD 20%), respectively. This was observed for all the outcome measures.ConclusionThis was the first study to investigate osseointegration in retrieved 3D-printed acetabular implants. Greater bone ingrowth was found in 3D-printed implants, suggesting that better osseointegration can be achieved. However, the influence of specific surgeon, implant, and patient factors needs to be considered.Cite this article: Bone Joint Res 2021;10(7):388–400.

Three-dimensional visualization of the human membranous labyrinth: The membrana limitans and its role in vestibular form.

The inner ear contains the end organs for balance (vestibular labyrinth) and hearing (cochlea). The vestibular labyrinth is comprised of the semicircular canals (detecting angular acceleration) and otolith organs (utricle and saccule, which detect linear acceleration and head tilt relative to gravity). Lying just inferior to the utricle is the membranous membrana limitans (ML). Acting as a keystone to vestibular geometry, the ML provides support for the utricular macula and acts as a structural boundary between the superior (pars superior) and inferior (pars inferior) portions of the vestibular labyrinth. Given its importance in vestibular form, understanding ML morphology is valuable in establishing the spatial organization of other vestibular structures, particularly the utricular macula. Knowledge of the 3D structure and variation of the ML, however, remain elusive. Our study addresses this knowledge gap by visualizing, in 3D, the ML and surrounding structures using micro-CT data. By doing so, we attempt to clarify: (a) the variation of ML shape; (b) the reliability of ML attachment sites; and (c) the spatial relationship of the ML to the stapes footplate using landmark-based Generalized Procrustes, Principal Component and covariance analyses. Results indicate a consistent configuration of three distinct bony ML attachments including an anterolateral, medial, and posterior attachment which all covary with bony structure. Our results set the stage for further understanding into vestibular and more specifically, utricular macula spatial configuration within the human head, offering the potential to aid in clinical and evolutionary studies which rely on a 3D understanding of vestibular spatial configuration.

Membrana limitans shape variation and its role in vestibular form

The membrana limitans (ML) is a membranous vestibular structure found within the bony labyrinth, housed in the petrous temporal bone. It is located inferior to the semicircular canals (which detect changes in angular acceleration of the head) and adjacent to both otolith organs, the utricle and saccule (responsible for detecting linear acceleration of the head and gravity). The ML forms the keystone to vestibular geometry, acting as a support for the majority of the utricular macula and respective neural substrate, and provides a structural boundary between the superior (pars superior) and inferior (pars inferior) portions of the vestibular labyrinth. Despite its importance, knowledge of ML 3D structure and morphological variation is limited. Here we test the hypothesis that there is consistency among ML bony attachment sites in humans. We use a sample comprised of micro-CT scans of nine human temporal bones soaked in 2 per cent osmium tetroxide after fixation in Karnovsky's fixative in order to better visualize the membranous labyrinth. Each ML was 3D reconstructed and the extent of bony attachment site variation was assessed using landmark-based Generalized Procrustes and Principal Component Analyses. Results indicate a consistent, yet locally variable configuration with distinct anterolateral, medial and posterior attachments of the ML to the bony wall of the labyrinth. The anterolateral attachment originates just superior to the posteriormost edge of the stapes footplate and stretches anteriorly. This is often a discontinuous attachment (observed in seven of nine ears) which occasionally attaches onto the posterior one-third of the footplate itself (observed in two of nine ears). The length of the medial attachment is the most variable, yet in all ears it attaches along the superior border of the spherical recess which houses the saccule. The posterior attachment is the least variable and its medial boundary forms a consistent attachment to the bony lip of the vestibular aqueduct (observed in all ears). These results also support previous findings suggesting the ML forms a discontinuous support system within the vestibule among humans. This exploratory analysis sets the stage for further understanding into utricular biomechanics and vestibular geometry, especially related to details of otolith organ structure and their relationships to bony anatomy.

The Effect of Tooth Loss on Craniofacial Morphology

The morphology of the craniofacial skeleton is known to be responsive to changing biomechanical loads produced by feeding. Edentulism, or tooth loss, has previously been shown to have an impact on the structure of the craniofacial bones, particularly the alveolar bone and palate, as well as on the material properties of the cortical bone. However, it is less clear what effect tooth loss has on the masticatory muscles and their bony attachment sites. In this study, we use geometric morphometrics on human skulls to compare the shape of the mandible and facial skeleton in edentulous and dentate individuals. Following from previous work, we expect that edentulous individuals will exhibit decreased alveolar bone height in both the mandible and maxilla. We further hypothesize that edentulous individuals will display a recession of bone at the insertion sites of the masticatory muscles, namely the zygomatic arch and the mandibular ramus. CT scans of individuals greater than 50 years of age (n=40) were obtained from the New Mexico Decedent Imaging Database (NMDID). Individuals with no teeth were sorted into the edentulous group, while individuals with more than 22 of 36 teeth were sorted into the functionally dentate. 3D Slicer software was used to generate 3D models, and 3D fixed and sliding landmarks were placed along the mandible, maxilla, zygomatic arch, palate, and orbit. Principal component analysis (PCA) and Procrustes ANOVAs were performed separately on the Procrustes-aligned coordinate data for the crania and mandibles. We identified significant differences in facial and mandibular shape between groups. In both cases, differences were largely driven by resorption along the alveolus. Variation in the morphology of edentulous individuals suggests that the time since tooth loss and behavioral factors, such as denture wearing, may impact the degree of alveolar resorption. Interestingly, edentulous individuals tended to have relatively smaller coronoid processes and posteriorly extended mandibular angles. This suggests that tooth loss may result in greater relative atrophy of the temporalis muscle, a jaw elevator/retractor, compared to the masseter muscle, another jaw elevator which is involved in resisting gravity and positional jaw closure. Further studies are needed to investigate the impact of tooth loss on muscle morphology to confirm this. These additive effects between bone resorption and muscle atrophy likely explain the altered facial morphology demonstrated by edentulous populations.

Functional Myology of the Neck in Primates

The neck is often used to study postural and locomotor behaviors across primates. Partially due to the complexity of this 3D system, there has not yet been a quantitative study of comparative nuchal muscle function. In this study, we applied innovative methods to visualize, quantify, and compare the epaxial muscles among primate taxa to characterize the relationship between trunk posture, extreme head turning behaviors, and forelimb-dominated below branch suspensory locomotion and muscle function. DiceCT imaging, 3D muscle fascicle-tracking, and 3D muscle visualization were all used to compare the attachment sites, orientations, and estimates of force for 19 muscles across five species that displayed contrasting postural and locomotor behaviors. To explore estimates of muscle force and 3D orientation of muscle bellies, ternary diagrams were used. Results show that most muscle forces scale with isometry, but musculature varies according to positional behavior and function. Semisuspensory species have a more dorsoventrally oriented cranial bellies of the trapezius muscle than closely related, but non-suspensory taxa. Pronograde primates have more powerful longissimus capitis muscles compared to orthograde primates. Carlito, noted for its pronounced head turning behaviors, has a more transversely oriented and more powerful sternocleidomastoid in addition to more powerful obliquus capitis superior muscle. The latter is also seen in Propithecus. These findings support the hypothesis that estimates of muscle force for certain key neck muscles are related to positional behaviors in primates. Therefore, the bony attachment sites of the muscles that were observed to vary among taxa could aid in understanding locomotor behaviors in extinct primates.

Novel 3D MRI technique to measure perineal membrane structural changes with pregnancy and childbirth: Technique development and measurement feasibility.

We aimed to develop and validate a new MRI-based perineal membrane reconstruction and morphological measurement technique, and test its feasibility on nulliparous and parous women to determine the effects of pregnancy and childbirth on the perineal membrane. The perineal membrane was traced on high-resolution MRI using 3D Slicer® and analyses performed using Rhinoceros 6.0 SR23®. Validation was done by comparing MRI-based perineal membrane reconstruction to dissection measurements in a cadaver. Feasibility of reconstruction was assessed in the following three groups: nulliparous (NP), primiparous women who underwent cesarean delivery (CD), and primiparous women with vaginal delivery (VD). The following parameters were measured: (1) swinging door angle, (2) bony and (3) soft tissue attachment lengths, (4) separation at perineal body level, (5) surface area, and (6) hiatal area. ANOVA and post-hoc comparisons were performed, and the effect sizes (d) were reported. Model reconstruction was similar to cadaver dissection findings. Morphological measurements were feasible in all women (NP, n= 10; CS, n= 6; VD, n= 19). Swinging door angle was 13o greater in CD (p = 0.03; d = 1.15) and 16o greater in VD (p < 0.001; d = 1.41) compared to NP. VD showed 13% larger separation at the perineal body than NP (p = 0.097, d = 0.84) and 23% larger hiatal area than CD (p = 0.14, d = 0.94). This novel and anatomically validated MRI-based perineal membrane reconstruction technique is feasible. Preliminary findings show that pregnancy and childbirth both influence perineal membrane morphology with VD being associated with the largest swinging door angle and perineal body separation.

The equine navicular apparatus as a premier enthesis organ: Functional implications.

Navicular syndrome has been traditionally characterized by progressive lameness with chronic degeneration of the navicular bone. Advances in imaging techniques have revealed that its associated soft tissue structures are also affected. This distribution of lesions is explained by conceptualizing the equine navicular apparatus as an enthesis organ that facilitates the dissemination of mechanical stress throughout the tissues of the foot. The navicular apparatus has the same structural adaptations to mechanical stress as the human Achilles tendon complex. These adaptations efficiently dissipate mechanical force away from the tendon's bony attachment site, thereby protecting it from failure. The comparison of these two anatomically distinct structural systems demonstrates their similar adaptations to mechanical forces, and illustrates that important functional insights can be gained from studying anatomic convergences and cross‐species comparisons of function. Such a functional conceptualization of the equine navicular apparatus resolves confusion about the diagnosis of navicular syndrome and offers insights for the development of mechanically based therapies. Through comparison with the human Achilles complex, this review (1) re‐conceptualizes the equine navicular apparatus as an enthesis organ in which mechanical forces are distributed throughout the structures of the organ; (2) describes the relationship between failure of the navicular enthesis organ and lesions of navicular syndrome; (3) considers the therapeutic implications of navicular enthesis organ degeneration as a form of chronic osteoarthritis; and based upon these implications (4) proposes a focus on whole body posture/motion for the development of prehabilitative and rehabilitative therapies similar to those that have already proven effective in humans.

Lateral pterygoid muscle enthesis reconstruction in total temporomandibular joint replacement: An animal experiment with radiological correlation

A novel total temporomandibular joint replacement (TMJR) was developed with CADskills BV (Ghent, Belgium), aiming to achieve reinsertion of the (LPM) onto a scaffold in the implant. In order to investigate the possibility of reinsertion of the LPM, an animal experiment was conducted.An in vivo sheep experiment was conducted, which involved implanting sheep with a TMJR. Clinical parameters were recorded regularly and computed tomography (CT) scan images of two randomly selected sheep per scan were made at 1, 3, and 6 months. After 9.5 months, the sheep were euthanized, and CT scans of all animals were performed in order to evaluate the LPM's enthesis.A total of 13 sheep were implanted with a TMJR. One sheep was used as a sham. Radiographs revealed four outcome types of enthesis reconstruction. In four sheep, there was no reconstruction between the implant and the LPM. In three sheep, there was a purely soft tissue connection of 0.5–0.9 mm (average 0.7 mm) between the ostectomized bony LPM insertion and the implant's lattice structure. A combination of partial bony and partial soft tissue enthesis attachment (0.3–0.5 mm, average 0.4 mm) was found in three sheep. A bony ingrowth of the enthesis into the scaffold occurred in two sheep. A secondary bony connection between the mandible and the insertion of the LPM was found in 10 of 13 sheep. Four fossa components were found to be displaced, yet TMJ function remained in these ewes. The heterotopic ossification that was seen may be a confounding factor in these results.This in vivo experiment showed promising results for improving the current approach to TMJR with the possibility of restoring the laterotrusive function. The fossa displacement was considered to be due to insufficient fixation and predominant laterotrusive force not allowing for proper osseointegration. Further optimization of the reattachment technique, scaffold position and surface area should be done, as well as trials in humans to evaluate the effect of proper revalidation.

A monotreme-like auditory apparatus in a Middle Jurassic haramiyidan.

Among extant vertebrates, mammals are distinguished by having a chain of three auditory ossicles (the malleus, incus and stapes) that transduce sound waves and promote an increased range of audible-especially high-frequencies1. By contrast, the homologous bones in early fossil mammals and relatives also functioned in chewing through their bony attachments to the lower jaw2. Recent discoveries of well-preserved Mesozoic mammals have provided glimpses into the transition from the dual (masticatory and auditory) to the single auditory function for the ossicles, which is now widely accepted to have occurred at least three times in mammal evolution3-6. Here we report a skull and postcranium that we refer to the haramiyidan Vilevolodon diplomylos (dating to the Middle Jurassic epoch (160million years ago)) and that shows excellent preservation of the malleus, incus and ectotympanic (which supports the tympanic membrane). After comparing this fossil with other Mesozoic and extant mammals, we propose that the overlapping incudomallear articulation found in this and other Mesozoic fossils, in extant monotremes and in early ontogeny in extant marsupials and placentals is a morphology that evolved in several groups of mammals in the transition from the dual to the single function for the ossicles.