The functional significance of aberrant cervical counts in sloths: insights from automated exhaustive analysis of cervical range of motion.

Besides manatees, the suspensory extant 'tree sloths' are the only mammals that deviate from a cervical count (CC) of seven vertebrae. They do so in opposite directions in the two living genera (increased versus decreased CC). Aberrant CCs seemingly reflect neck mobility in both genera, suggesting adaptive significance for their head position during suspensory locomotion and especially increased ability for neck torsion in three-toed sloths. We test two hypotheses in a comparative evolutionary framework by assessing three-dimensional intervertebral range of motion (ROM) based on exhaustive automated detection of bone collisions and joint disarticulation while accounting for interacting rotations of roll, yaw and pitch. First, we hypothesize that the increase of CC also increases overall neck mobility compared with mammals with a regular CC, and vice versa. Second, we hypothesize that the anatomy of the intervertebral articulations determines mobility of the neck. The assessment revealed that CC plays only a secondary role in defining ROM since summed torsion (roll) capacity was primarily determined by vertebral anatomy. Our results thus suggest limited neck rotational adaptive significance of the CC aberration in sloths. Further, the study demonstrates the suitability of our automated approach for the comparative assessment of osteological ROM in vertebral series.

Interspecific scaling patterns of talar articular surfaces within primates and their closest living relatives.

The articular facets of interosseous joints must transmit forces while maintaining relatively low stresses. To prevent overloading, joints that transmit higher forces should therefore have larger facet areas. The relative contributions of body mass and muscle-induced forces to joint stress are unclear, but generate opposing hypotheses. If mass-induced forces dominate, facet area should scale with positive allometry to body mass. Alternatively, muscle-induced forces should cause facets to scale isometrically with body mass. Within primates, both scaling patterns have been reported for articular surfaces of the femoral and humeral heads, but more distal elements are less well studied. Additionally, examination of complex articular surfaces has largely been limited to linear measurements, so that 'true area' remains poorly assessed. To re-assess these scaling relationships, we examine the relationship between body size and articular surface areas of the talus. Area measurements were taken from microCT scan-generated surfaces of all talar facets from a comprehensive sample of extant euarchontan taxa (primates, treeshrews, and colugos). Log-transformed data were regressed on literature-derived log-body mass using reduced major axis and phylogenetic least squares regressions. We examine the scaling patterns of muscle mass and physiological cross-sectional area (PCSA) to body mass, as these relationships may complicate each model. Finally, we examine the scaling pattern of hindlimb muscle PCSA to talar articular surface area, a direct test of the effect of mass-induced forces on joint surfaces. Among most groups, there is an overall trend toward positive allometry for articular surfaces. The ectal (= posterior calcaneal) facet scales with positive allometry among all groups except 'sundatherians', strepsirrhines, galagids, and lorisids. The medial tibial facet scales isometrically among all groups except lemuroids. Scaling coefficients are not correlated with sample size, clade inclusivity or behavioral diversity of the sample. Muscle mass scales with slight positive allometry to body mass, and PCSA scales at isometry to body mass. PCSA generally scales with negative allometry to articular surface area, which indicates joint surfaces increase faster than muscles' ability to generate force. We suggest a synthetic model to explain the complex patterns observed for talar articular surface area scaling: whether 'muscles or mass' drive articular facet scaling is probably dependent on the body size range of the sample and the biological role of the facet. The relationship between 'muscle vs. mass' dominance is likely bone- and facet-specific, meaning that some facets should respond primarily to stresses induced by larger body mass, whereas others primarily reflect muscle forces.

Multisite Percutaneous Bone Augmentation for the Treatment of Acetabular Osteolytic Metastases Involving the Articular Surfaces: A Randomised Trial.

INTRODUCTION: For patients with acetabular osteolytic metastases involving the articular surfaces, current treatments cannot efficiently rebuild the acetabular bone frame structure and strengthen bone defect area mechanics for weight-bearing. The purpose of this study is to show the operational procedure and clinical outcomes of multisite percutaneous bone augmentation (PBA) for the treatment of incidental acetabular osteolytic metastases involving the articular surfaces. METHODS: According to the inclusion and exclusion criteria, 8 patients (4 males and 4 females) were included in this study. Multisite (3 or 4 sites) PBA was successfully performed in all patients. The pain and function evaluation and imaging observation were examined by VAS and Harris hip joint function scores at the different time points (pre-procedure, 7 days, one month, last follow-up in 5-20 months). RESULTS: There were significant differences (p<0.05) in VAS and Harris scores before and after the surgical procedure. Moreover, these two scores had no obvious changes during the follow-up process (7 days after the procedure, one month after the procedure, and the last follow-up) after the procedure. CONCLUSION: The proposed multisite PBA is an effective and safe procedure for the treatment of acetabular osteolytic metastases involving the articular surfaces.

Estimating motion between avian vertebrae by contact modeling of joint surfaces.

Estimating the motion between two bones is crucial for understanding their biomechanical function. The vertebral column is particularly challenging because the vertebrae articulate at more than one surface. This paper proposes a method to estimate 3D motion between two avian vertebrae, by bones surface reconstruction and contact modeling. The neck of birds was selected as a case study because it is a functionally highly versatile structure combining dexterity and strength. As such, it has great potential to serve as a source for bioinspired design, for robotic manipulators for instance. First, 3D models of the vertebrae are obtained by computed tomography (CT). Next, joint surfaces of contact are approximated with polynomial surfaces, and a system of equations derived from contact modeling between surfaces is established. A constrained optimization problem is defined in order to find the best position of the vertebrae for a set of given orientations in space. As a result, the possible intervertebral range of motion is estimated.

Experimental evaluation of current and novel approximations of articular surfaces of the ankle joint.

Kinematics and flexibility properties of both natural and replaced ankle joints are affected by the geometry of the articulating surfaces. Recent studies proposed an original saddle-shaped, skewed, truncated cone with laterally oriented apex, as tibiotalar contact surfaces for ankle prosthesis. The goal of this study was to compare in vitro this novel design with traditional cylindrical or medially centered conic geometries in terms of their ability to replicate the natural ankle joint mechanics. Ten lower limb cadaver specimens underwent a validated process of custom design for the replacement of the natural ankle joint. The process included medical imaging, 3D modeling and printing of implantable sets of artificial articular surfaces based on these three geometries. Kinematics and flexibility of the overall ankle complex, along with the separate ankle and subtalar joints, were measured under cyclic loading. In the neutral and in maximum plantarflexion positions, the range of motion under torques in the three anatomical planes of the three custom artificial surfaces was not significantly different from that of the natural surfaces. In maximum dorsiflexion the difference was significant for all three artificial surfaces at the ankle complex, and only for the cylindrical and medially centered conic geometries at the tibiotalar joint. Natural joint flexibility was restored by the artificial surfaces nearly in all positions. The present study provides experimental support for designing articular surfaces matching the specific morphology of the ankle to be replace, and lays the foundations of the overall process for designing and manufacturing patient-specific total ankle replacements.

Topographic analysis of the glenoid and proximal medial tibial articular surfaces: a search for the ideal match for glenoid resurfacing.

BACKGROUND: Current knowledge is lacking concerning the appropriate site of osteochondral allograft harvest to match glenoid shape for the purposes of glenoid resurfacing. This has led to difficulty with adequate restoration of the geometry of the glenoid with currently available techniques. HYPOTHESIS: The medial tibial plateau will provide a suitable osteochondral harvest site because of its concavity and anatomic similarity to the glenoid. STUDY DESIGN: Descriptive laboratory study. METHODS: Computed tomography (CT) was performed on 4 cadaveric proximal tibias and 4 scapulae, allowing for 16 glenoid-tibial comparative combinations. Three-dimensional CT models were created and exported into point-cloud models. A local coordinate map of the glenoid and medial tibial plateau articular surfaces was created. Two zones of the medial tibial articular surface (anterior and posterior) were quantified. The glenoid articular surface was defined as a best-fit circle of the glenoid articular surface maintaining a 2-mm bony rim. This surface was virtually placed on a point on the tibial articular surface in 3D space. The tibial surface was segmented, and its 3D surface orientation was determined with respect to its surface. The 3D orientation of the glenoid surface was reoriented so that the direction of the glenoid surface matched that of the tibial surface. The least distances between the point-clouds on the glenoid and tibial surfaces were calculated. The glenoid surface was rotated 360° in 1° increments, and the mean least distance was determined at each rotating angle. RESULTS: When the centroid of the glenoid surface was placed on the medial tibial articular surface, it covered approximately two-thirds of the anterior or posterior tibial surfaces. Overall, the mean least distance difference in articular congruity of all 16 glenoid-medial tibial surface combinations was 0.74 mm (standard deviation, ±0.13 mm). The mean least distance difference of the anterior and posterior two-thirds of the medial tibial articular surface was 0.72 mm (±0.13 mm) and 0.76 mm (±0.16 mm), respectively. There was no significant difference between the anterior and posterior two-thirds of the tibia with regard to topographic match of the glenoid (P = .187). CONCLUSION: The findings suggest that the medial tibial articular surface provides an appropriate anatomic match to the glenoid articular surface. Both the anterior and posterior two-thirds of the medial tibial articular surface are potential sites for osteochondral graft harvest. CLINICAL RELEVANCE: This method can be applied to future studies evaluating the ideal sites of graft harvest to treat zonal glenoid bone wear and/or loss.

Morphological characteristics of the temporomandibular joint articular surfaces in patients with temporomandibular deisorders / Características morfológicas de las superficies articulares de la articulación temporomandibular de pacientes con trastornos temporomandibulares

The knowledge of the anatomical characteristics of the temporomandibular joint (TMJ) articular surfaces is essentital to enable physicians and dentists to recognize the morphological changes that occur in this articulation in patients with temporomandibular disorders (TMD). Several researchers associate the TMD with changes of TMJ articular surfaces. The careful identification of bone changes related to TMJ is critical, since these abnormalities are associated with signs and symptoms of TMD and the knowledge of TMD signs and symptoms is fundamental for correctly diagnosing and for adequate treatment planning. The aim of this study was to evaluate the morphological characteristics of the TMJ articular surfaces in patients with TMD diagnosed according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). In addition, therelationship between increasing age-osteoarthrosis was evaluated. For the sample we selected 19 patients, 17 female and 2 male, referred to the "Unidad de Trastornos Cráneo Cérvico Mandibulares (UCRACEM) - Universidad de Talca, Chile". The imaging assessment was carried out by Cone-Beam Computed Tomography (CBCT). In the imaging analysis of the articular surfaces 11 joints (28.94 percent) showed normal morphology. The bone changes found were: sclerosis, flattening, erosion, osteoarthrosis, osteophytes, subcondral cysts. We found statistically significant difference between increasing age-osteoarthrosis (p=0.00). Considering our results we concluded that bone changes of the TMJ articular surfaces in patients with TMD are very common, with sclerosis as the most frequent finding. It was also possible to conclude that there was a significant association between increasing age-osteoarthrosis.

El conocimiento de las características anatómicas de las superficies articulares de la articulación temporomandibular (ATM) es fundamental para que clínicos y odontólogos reconozcan las alteraciones morfológicas que ocurren en la articulación de pacientes con trastornos temporomandibulares (TTM). Diversos investigadores asocian los TTMs con alteraciones en las superficies articulares de la ATM. La identificación de los cambios óseos relacionados con la ATM es crítica, ya que estos se asocian a signos y síntomas de TTM, y el conocimiento de estos es fundamental para el correcto diagnóstico y adecuada planificación de tratamiento. El objetivo fue analizar las características morfológicas de las superficies articulares de la ATM en pacientes con diagnóstico de TTM, diagnosticado de acuerdo a los Criterios Diagnósticos para Investigación de los Trastornos Temporomandibulares (CDI/TTM), junto con analizar la relación existente entre incremento de edad-osteoartrosis. Fueron seleccionados 19 pacientes, 17 mujeres y 2 hombres, de la Unidad de Trastornos Cráneo Cérvico Mandibulares (UCRACEM) - Universidad de Talca, Chile. La evaluación imagenológica se realizó mediante el examen de Tomografía Computarizada Cone-Beam (TCCB). En el análisis de las superficies articulares, 11 (28,94 por ciento) presentaron morfología normal. Los cambios óseos encontrados fueron: esclerosis, aplanamiento de la cabeza de la mandíbula, erosión, osteoartrosis, osteofitos y quiste subcondral. Hubo relación estadística significativa entre incremento de edad-osteoartrosis (p=0,00). Nuestros hallazgos nos permiten concluir que los cambios óseos en las caras articulares de la ATM en pacientes con TTM son frecuentes, y la esclerosis el hallazgo más común. También se encontró asociación entre incremento de edad y osteoartrosis.