Introduction The current understanding of morphological deformities of the hip such as femoroacetabular impingement (FAI), Legg-Calve-Perthes disease (LCPD), and slipped capital femoral epiphysis (SCFE) is based on 2-dimensional metrics, primarily involving the femoral head, that only partially describe the complex skeletal morphology. Objective This study aimed to improve the 3-dimensional understanding of shape variations during normal growth, and in LCPD and SCFE, through statistical shape modeling. Design Thirty-two patients with asymptomatic, LCPD, and SCFE hips, determined from physical and radiographic examination, were scanned using 3-D CT at a voxel size of (0.5–0.9mm)2 in-plane and 0.63mm slice thickness. Statistical shape modeling was performed on segmented proximal femoral surfaces to determine modes of variation and shape variables quantifying 3-D shape. In addition, conventional variables were determined for all femora. Results Proximal femur shape was described by 8 modes of variation and corresponding shape variables. Statistical shape variables were distinct with age and revealed coordinated, growth-associated differences in neck length-to-width ratio, femoral head medialization, and trochanter protrusion. After size and age-based shape adjustment, diseased proximal femora were characterized by shape variables distinct from those of asymptomatic hips. The shape variables defined morphology in health and disease, and were correlated with certain conventional variables of shape, including neck-shaft angle, head diameter, and neck diameter. Conclusion 3-D quantitative analyses of proximal femoral bone shape during growth and in disease are useful for furthering the understanding of normal and abnormal shape deviations which affect cartilage biomechanics and risk of developing osteoarthritis.
With continued development and improvement of tissue engineering therapies for small articular lesions, increased attention is being focused on the challenge of engineering partial or whole synovial joints. Joint-scale constructs could have applications in the treatment of large areas of articular damage or in biological arthroplasty of severely degenerate joints. This review considers the roles of shape, loading and motion in synovial joint mechanobiology and their incorporation into the design, fabrication, and testing of engineered partial or whole joints. Incidence of degeneration, degree of impairment, and efficacy of current treatments are critical factors in choosing a target for joint bioengineering. The form and function of native joints may guide the design of engineered jointscale constructs with respect to size, shape, and maturity. Fabrication challenges for joint-scale engineering include controlling chemo-mechano-biological microenvironments to promote the development and growth of multiple tissues with integrated interfaces or lubricated surfaces into anatomical shapes, and joint-scale bioreactors which nurture and stimulate the tissue with loading and motion. Finally, evaluation of load-bearing and tribological properties can range from tissue to joint scale and can focus on biological structure at present or after adaptation.
SYNOPSIS Introduction The size and shape of joints markedly affect their biomechanical properties, but the macroscopic 3-dimensional (3-D) mechanism and extent of cartilage and joint maturation during normal growth are largely unknown. Aims The purposes of this study were to qualitatively illustrate the development of the cartilage-bone interface in the knee during postnatal growth in humans and C57BL/6 wild-type mice, and to quantitatively define the 3-D shape using statistical shape modeling as well as to assess growth strain rates in the mouse distal femur. Methods Clinical computed tomography (CT) scans of asymptomatic knees (0.3–0.6mm in-plane resolution, 0.63mm slice thickness) were obtained from six patients between 4 to 12 years old. Micro-CT scans of mouse knees (9μm isotropic resolution) were from twenty-one mice between 12 to 120 days postnatal. Human and mouse images were compared qualitatively with 2-D images and 3-D reconstructions. Mouse femora shape parameters were determined with statistical shape modeling, and strain rates and directions during growth were mapped. Results The attainment of cartilage-bone interface shape of the distal femur and proximal tibia were qualitatively similar in humans and mice, with marked differences in growth plate morphology. Mouse distal femur shape was described by 11 independent parameters that accounted for >90% of total shape variation during growth. Each shape parameter described changes in specific anatomical regions of the distal femur and varied with age. Shape parameters and strains in the medial and lateral condyles, as well as intercondylar notch, varied greatly between postnatal days 16 to 30. Directions of growth strain across ages corresponded well with the appearance of anatomical landmarks within the distal femur. Conclusion Accurate quantification of the cartilage-bone interface geometry is imperative for furthering the understanding of the macroscopic mechanisms of cartilage maturation and overall joint development.
Objective To assess collagen network alterations occurring with flow and other abnormalities of articular cartilage at medial femoral condyle (MFC) sites repaired with osteochondral autograft (OATS) after 6 and 12 months, using quantitative polarized light microscopy (qPLM) and other histopathological methods Design The collagen network structure of articular cartilage of OATS-repaired defects and non-operated contralateral control sites were compared by qPLM analysis of parallelism index (PI), orientation angle (α) relative to the local tissue axes, and retardance (Γ) as a function of depth. qPLM parameter maps were also compared to ICRS and Modified O’Driscoll grades, and cell and matrix sub-scores, for sections stained with H&E and Safranin-O, and for Collagen-I and II Results Relative to non-operated normal cartilage, OATS-repaired regions exhibited structural deterioration, with low PI and more horizontal α, and unique structural alteration in adjacent host cartilage: more aligned superficial zone, and reoriented deep zone lateral to the graft, and matrix disorganization in cartilage overhanging the graft. Shifts in α and PI from normal site-specific values were correlated with histochemical abnormalities and co-localized with changes in cell organization/orientation, cloning, or loss, indicative of cartilage flow, remodeling, and deterioration, respectively Conclusions qPLM reveals a number of unique localized alterations of the collagen network in both adjacent host and implanted cartilage in OATS-repaired defects, associated with abnormal chondrocyte organization. These alterations are consistent with mechanobiological processes and the direction and magnitude of cartilage strain.
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