No abstract

This study revealed that preoperative physiologic passive knee HE ≥5° is present in one-third of patients who undergo revision ACLR. HE ≥5° was an independent significant predictor of graft failure after revision ACLR with a >2-fold OR of subsequent graft rupture in revision ACL surgery. Registration: NCT00625885 ( ClinicalTrials.gov identifier).

Recently, a knee prosthesis containing an electron beam irradiated (58 – 72 kGy, nominal dose of 65 kGy), melt-annealed, highly crosslinked UHMWPE (HXPE) tibial insert has been developed. In the present study, the wear and delamination resistance of the HXPE tibial insert and its fatigue performance under a posterior loading condition have been evaluated against its conventional gamma-sterilized UHMWPE counterpart (37kGy, in nitrogen). The test methodologies used were newly developed with the aim to evaluate this new material under severe testing conditions. In comparison to the gamma controls, the HXPE inserts: (a) wore significantly less (achieving wear reductions of 81% and 73% over 5 and 20 million cycles, respectively); (b) exhibited significantly improved delamination resistance; and (c) exhibited significantly improved posterior loading fatigue resistance.

The in-vitro wear behavior in the presence of abrasive particles was determined for two highly crosslinked ultrahigh molecular weight polyethylenes (HXPE), one in clinical application for hips and the other for knees. The wear studies were performed in joint simulators and were largely comparative, with conventional ultrahigh molecular weight polyethylene (UHMWPE) gamma irradiated 37 kGy in nitrogen used as the control. The test methodology used for these three-body wear tests was developed in-house. It was found that the wear advantage of the HXPEs relative to the conventional UHMWPE observed under clean conditions is largely preserved in the presence of the abrasive particles used (alumina and bone cement for hips, bone cement for knees) under the test conditions. These results suggest that the surface molecular chain orientation-inhibition mechanism proposed to account for the increased wear resistance of highly crosslinked polyethylenes undergoing micro adhesive/abrasive wear is still operational even when a thicker surface layer is disturbed in the presence of abrasive particles. Therefore, the wear of the UHMWPE is not simply dependent on the bulk mechanical properties of the UHMWPE. The higher than expected wear of the 22 mm hip liners compared to the 32 mm liners in the presence of abrasive particles suggests that the wear rate of the UHMWPE becomes stress dependent rather than load dependent for sufficiently high stresses.

Technical advances have enabled the identification of high-resolution cell types within tissues based on single-cell transcriptomics. However, such analyses are restricted in human brain tissue due to the limited number of brain donors. In this study, we integrate mouse and human data to predict cell-type proportions in human brain tissue, and spatially map the resulting cellular composition. By applying feature selection and linear modeling, combinations of human and mouse brain single-cell transcriptomics profiles can be integrated to "fill in" missing information. These combined "in silico chimeric" datasets are used to model the composition of nine cell types in 3,702 human brain samples in six Allen Human Brain Atlas (AHBA) donors. Cell types were spatially consistent regardless of the scRNA-Seq dataset (91% significantly correlated) or AHBA donor (p-value = 4.43E-20 by t-test) used in the model. Importantly, neuron nuclei location and neuron mRNA location were correlated only after accounting for neural connectivity (p-value = 1.26E-10), which supports the notion that gene expression is a better indicator than nuclei location of cellular localization for cells with large and irregularly shaped cell bodies, such as neurons. These results advocate for the integration of mouse and human data in models of brain tissue heterogeneity.