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Mass spectrometry imaging (MSI) is a powerful technique enabling the visualization of the spatial distribution of different molecules in tissue biopsies with different pathologies. Sample handling and preparing adipose tissue for MSI is challenging and prone to molecular delocalization due to tissue melting. In this work, we developed a method for matrix-assisted laser desorption/ionization (MALDI)-MSI to study lipids in human infrapatellar fat pad (IPFP), a biomarker source in musculoskeletal pathologies, while preserving molecular spatial distribution. Cryosectioning at 15 μm with a temperature below -30 °C, thaw-mounting, and sublimation, was demonstrated to preserve IPFP's heterogeneous appearance and spatial distribution of lipids., Competing Interests: Declaration of competing interest MH, KE, GT, RH, PE, and BCP are supported by the Dutch Research Council (NWO) domain Applied and Engineering Sciences (P15-23). MH, BC, RH, and BCP are supported by the Dutch Province of Limburg through the LINK (Limburg Investeert in haar Kenniseconomie) program. PE and BCP are supported by the Dutch Arthritis Society. PE has got a speaker consultancy fee paid to institute by Episurf and Arthrex (support for attending meeting). PE is involved with participation on a Data Safety Monitoring Board or Advisory Board (paid to institute) by Expert panel for Atro-Medical and Advisory board of TETEC AG. PE is vice chair of the international registree committee for joint-preserving surgery of the ICRS (no payments). PE is shareholder in Chondropeptix and Avalanche Medical., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: Reconstruction plates, used to bridge segmental defects of the mandible after tumor resection or traumatic bone tissue loss, are subjected to repeated stresses of mastication. High stress concentrations in these plates can result in hardware failure. Topology optimization (TO) could reduce the peak stress by computing the most optimal material distribution in a patient-specific implant (PSI) used for mandibular reconstruction. The objective of this study was biomechanical validation of a TO-PSI., Methods: A computer-aided design (CAD) model with a segmental defect was created based on the geometry of a polyurethane mandible model. A standard-PSI was designed to bridge the defect. A TO-PSI was then designed with a maximum stress equal to the ultimate tensile stress of Ti6Al4V (930 MPa) during a loading condition of 378 N. Finite element analysis (FEA) was used to analyze stresses in both PSI designs during loading. The standard-PSI and TO-PSI designs were produced in triplicate by selective laser melting of Ti6Al4V, fixated to polyurethane mandible models with segmental defects identical to the CAD model, and subsequently subjected to continuous compression with a speed of 1 mm/min on a universal testing machine, while recording the load. Peak loads before failure in the TO-PSI group within a 30% range of the predicted peak load (378 N) were considered a successful biomechanical validation., Results: Fracture of the TO-PSI occurred at a median peak load of 334 N (range 304-336 N). These values are within the 30% range of the predicted peak load. Fracture of the mandible model in the standard-PSI group occurred at a median peak load of 1100 N (range 1010-1460 N). Failure locations during biomechanical testing of TO-PSI and standard-PSI samples corresponded to regions in the FEA where stresses exceeded the ultimate tensile strength of titanium and polyurethane, respectively., Conclusion: This study demonstrates a successful preliminary biomechanical validation of TO in the design process for mandibular reconstruction plates. Further work is needed to refine the finite element model, which is necessary to ultimately design TO-PSIs for clinical use., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Using water jets for orthopedic procedures that require bone drilling can be beneficial due to the absence of thermal damage and the always sharp cut. Previously, the influence of the water jet diameter and bone architectural properties on the drilling depth have been determined. To develop water jet instruments that can safely drill in orthopedic surgery, the impact of the two remaining primary factors were determined: the jet time (tjet [s]) and pressure (P [MPa]). To this end, 84 holes were drilled in porcine tali and femora with water jets using Ø 0.4mm nozzle. tjet was varied between 1, 3 and 5s and P between 50 and 70MPa. Drilling depths Lhole (mm), diameters Dhole (mm) and the volume of mineralized bone per unit volume (BV/TV) were determined with microCT scans. A non-linear regression analysis resulted in the predictive equation: Lhole= 0.22 * tjet(0.18) * (1.2-BV/TV) * (P-29) (R(2)=0.904). The established relation between the machine settings and drilling depth allows surgeons to adjust jet time and pressure for the patient׳s BV/TV to drill holes at a predetermined depth. For developers, the relation allows design decisions to be made that influence the dimensions, flexibility and accuracy of water jet instruments. For a pressure of 50MPa, the potential hole depth spread indicated by the 95% confidence interval is <1.6mm for all tested jet times. This maximum variance is smaller than the accuracy required for bone debridement treatments (2-4mm deep), which confirms that water jet drilling can be applied in orthopedic surgery to drill holes in bone with controlled depth., (Copyright © 2016 Elsevier Ltd. All rights reserved.)