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Flattening of the trochlear tali is clinically observed as structural and functional changes advance in patients with hemarthropathy of the ankle. However, the degree of this flattening has not yet been quantified, and distribution of the morphological changes across the talus not yet defined. Chronologically sequential MR images of both a hemophilic patient group (N = 5) and a single scan from a nondiseased, sex-matched, control group (N = 11) were used to take four measurements of the trochlear talus morphology at three locations (medial, central and lateral) along the sagittal plane. Three ratios of interest were defined from these to assess whether the talar dome flattens with disease. The control group MRI measurements were validated against literature data obtained from CT scans or planar X-Rays. The influence of disease on talar morphology was assessed by direct comparison of the hemophilic cases with the control group. The values for all three ratios, in all locations, differed between the control and the hemophilic group. Flattening was indicated in the hemophilic group in the medial and lateral talus, but differences in the central talus were not statistically significant. This work demonstrates that morphological assessment of the talus from MR images is similar to that from CT scans or planar X-Rays. Talar flattening does occur with hemarthropathy, especially at the medial and lateral edges of the joint surface. General flattening of the trochlear talus was confirmed in this small patient sample, however the degree and rate of change is unique to each ankle.

Page 363, affiliations section, “On behalf of the ICARA Study Group” should instead read “and the ICARA study group”.

Background Impingement resulting in soft tissue damage has been observed in hips with abnormal morphologies. Geometric parameterisation can be used to automatically generate a range of bone geometries for use in computational models, including femurs with cam deformity on the femoral neck. Methods This study verified patient-specific parametric finite element models of 20 patients with cam deformity (10 female, 10 male) through comparison to their patient-specific segmentation-based equivalents. The parameterisation system was then used to generate further models with parametrically defined geometry to investigate morphological changes in both the femur and acetabulum and their effects on impingement. Findings Similar findings were observed between segmentation-based and parametric models when assessing soft tissue strains under impingement conditions, resulting from high flexion and internal rotations. Parametric models with cam morphology demonstrated that clinically used alpha angles should not be relied on for estimating impingement severity since planar views do not capture the full three-dimensional geometry of the joint. Furthermore, the parametric approach allowed study of labral shape changes, indicating higher strains can result from bony overcoverage. Interpretation The position of cams, as well as their size, can affect the level of soft tissue strain occurring in the hip. This highlights the importance of reporting the full details of three-dimensional geometry used when developing computational models of the hip joint and suggests that it could be beneficial to stratify the patient population when considering treatment options, since certain morphologies may be at greater risk of elevated soft tissue strain.

Intervertebral disc degeneration is one of the leading causes of back pain, but treatment options remain limited. Recently, there have been advances in the development of biomaterials for nucleus augmentation; however, the testing of such materials preclinically has proved challenging. The aim of this study was to develop methods for fabricating and testing bone-disc-bone specimens in vitro for examining the performance of nucleus augmentation procedures. Control, nucleotomy and treated intervertebral disc specimens were fabricated and tested under static load. The nucleus was removed from nucleotomy specimens using a trans-endplate approach with a bone plug used to restore bony integrity. Specimen-specific finite element models were developed to elucidate the reasons for the variations observed between control specimens. Although the computational models predicted a statistically significant difference between the healthy and nucleotomy groups, the differences found experimentally were not significantly different. This is likely due to variations in the material properties, hydration and level of annular collapse. The deformation of the bone was also found to be non-negligible. The study provides a framework for the development of testing protocols for nucleus augmentation materials and highlights the need to control disc hydration and the length of bone retained to reduce inter-specimen variability.