3-dimensional metrics of proximal femoral shape deformities in Legg-Calvé-Perthes disease and slipped capital femoral epiphysis.

Legg-Calvé-Perthes disease (LCPD) and slipped capital femoral epiphysis (SCFE) are two common pediatric hip disorders that affect the 3-dimensional shape and function of the proximal femur. This study applied the principles of continuum mechanics to statistical shape modeling (SSM) and determined 3-D metrics for the evaluation of shape deformations in normal growth, LCPD, and SCFE. CT scans were obtained from 32 patients with asymptomatic, LCPD, and SCFE hips ((0.5-0.9 mm)2 in-plane resolution, 0.63 mm slice thickness). SSM was performed on segmented proximal femoral surfaces, and shape deformations were described by surface displacement, strain, and growth plate angle metrics. Asymptomatic normal femurs underwent coordinated, growth-associated surface displacements and anisotropic strains that were site-specific and highest at the greater trochanter. After size- and age-based shape adjustment, LCPD femurs exhibited large displacements and surface strains in the femoral head and neck, with associated changes in femoral head growth plate angles. Mild SCFE femurs had contracted femoral neck surfaces, and surface displacements in all regions tended to increase with severity of slip. The results of this paper provide new 3-D metrics for characterizing the shape and biomechanics of the proximal femur. Statement of Clinical Significance: Quantitative 3-D metrics of shape may be useful for understanding and monitoring disease progression, identifying target regions for shape modulation therapies, and objectively evaluating the success of such therapies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1526-1535, 2018.

Threshold Limit Graphical Approach to Understanding Outcome Predictive Metrics: Data from the Osteoarthritis Initiative.

Scatter plots, bar charts, linear regressions, analysis of variance, and other graphics and tests are frequently used to document associations between an independent variable and an outcome. However, these methods are also frequently limited when understanding how to use an independent variable in subsequent research or patient management. A novel graphical approach to visualizing data-the threshold limit graph-was therefore developed. Publically available data from the Osteoarthritis Initiative was used to illustrate the graphical approach to understanding the association between the change in joint space width (ΔJSW, independent variable) over four years, and knee symptoms at four years (using the Knee Injury and Osteoarthritis Outcome Score [KOOS], dependent variable). Using data for 4,202 knees, the traditional scatter plot and linear regression approach showed a significant but weak linear relationship between the symptom subscore of the KOOS and ΔJSW. However, the threshold level of ΔJSW that affects symptoms was not clear from the data. The same dataset was then plotted using the threshold limit graphical approach, which revealed a non-linear relationship between the variables. In contrast to the scatter plot, plotting the average KOOS symptom subscore for subgroups of the data, with each subgroup defined using sequentially increasing or decreasing ΔJSW thresholds revealed that symptoms got worse with joint space loss, but only when there was a significant amount of ΔJSW. A threshold limit analysis was repeated using small, randomly selected subsets of the data (N = ~100) to demonstrate the utility of the technique for identifying trends in smaller datasets. The threshold limit graph is a simple, graphical approach that may prove helpful in understanding how an independent variable might be used to predict outcomes. This approach provides an additional option for visualizing and quantifying associations between variables.

Development of a computer-assisted forensic radiographic identification method using the lateral cervical and lumbar spine.

Medical examiners and coroners (ME/C) in the United States hold statutory responsibility to identify deceased individuals who fall under their jurisdiction. The computer-assisted decedent identification (CADI) project was designed to modify software used in diagnosis and treatment of spinal injuries into a mathematically validated tool for ME/C identification of fleshed decedents. CADI software analyzes the shapes of targeted vertebral bodies imaged in an array of standard radiographs and quantifies the likelihood that any two of the radiographs contain matching vertebral bodies. Six validation tests measured the repeatability, reliability, and sensitivity of the method, and the effects of age, sex, and number of radiographs in array composition. CADI returned a 92-100% success rate in identifying the true matching pair of vertebrae within arrays of five to 30 radiographs. Further development of CADI is expected to produce a novel identification method for use in ME/C offices that is reliable, timely, and cost-effective.

Structural and functional maturation of distal femoral cartilage and bone during postnatal development and growth in humans and mice.

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. This study qualitatively illustrates the development of the bone-cartilage interface in the knee during postnatal growth in humans and C57BL/6 wild-type mice, quantitatively defines the 3-D shape using statistical shape modeling, and assesses growth strain rates in the mouse distal femur. 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.

Association of 3-Dimensional Cartilage and Bone Structure with Articular Cartilage Properties in and Adjacent to Autologous Osteochondral Grafts after 6 and 12 months in a Goat Model.

OBJECTIVE: The articular cartilage of autologous osteochondral grafts is typically different in structure and function from local host cartilage and thereby presents a remodeling challenge. The hypothesis of this study was that properties of the articular cartilage of trochlear autografts and adjacent femoral condyle are associated with the 3-D geometrical match between grafted and contralateral joints at 6 and 12 months after surgery. DESIGN: Autografts were transferred unilaterally from the lateral trochlea (LT) to the medial femoral condyle (MFC) in adult Spanish goats. Operated and contralateral Non-Operated joints were harvested at 6 and 12 months, and analyzed by indentation testing, micro-computed tomography, and histology to compare (1) histological indices of repair, (2) 3-D structure (articular surface deviation, bone-cartilage interface deviation, cartilage thickness), (3) indentation stiffness, and (4) correlations between stiffness and 3-D structure. RESULTS: Cartilage deterioration was present in grafts at 6 months and more severe at 12 months. Cartilage thickness and normalized stiffness of Operated MFC were lower than Non-Operated MFC within the graft and proximal adjacent host regions. Operated MFC articular surfaces were recessed relative to Non-Operated MFC and exhibited lower cartilage stiffness with increasing recession. Sites with large bone-cartilage interface deviations, both proud and recessed, were associated with recessed articular surfaces and low cartilage stiffness. CONCLUSION: The effectiveness of cartilage repair by osteochondral grafting is associated with the match of 3-D cartilage and bone geometry to the native osteochondral structure.

Shape, loading, and motion in the bioengineering design, fabrication, and testing of personalized synovial joints.

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 joint-scale 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 developing 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.