Fabian von Knoch

Particle-Induced Osteolysis in Three-Dimensional Micro-Computed Tomography

Small-animal models are useful for the in vivo study of particle-induced osteolysis, the most frequent cause of aseptic loosening after total joint replacement. Microstructural changes associated with particle-induced osteolysis have been extensively explored using two-dimensional (2D) techniques. However, relatively little is known regarding the 3D dynamic microstructure of particle-induced osteolysis. Therefore, we tested micro-computed tomography (micro-CT) as a novel tool for 3D analysis of wear debris-mediated osteolysis in a small-animal model of particle-induced osteolysis. The murine calvarial model based on polyethylene particles was utilized in 14 C57BL/J6 mice randomly divided into two groups. Group 1 received sham surgery, and group 2 was treated with polyethylene particles. We performed 3D micro-CT analysis and histological assessment. Various bone morphometric parameters were assessed. Regression was used to examine the relation between the results achieved by the two methods. Micro-CT analysis provides a fully automated means to quantify bone destruction in a mouse model of particle-induced osteolysis. This method revealed that the osteolytic lesions in calvaria in the experimental group were affected irregularly compared to the rather even distribution of osteolysis in the control group. This is an observation which would have been missed if histomorphometric analysis only had been performed, leading to false assessment of the actual situation. These irregularities seen by micro-CT analysis provide new insight into individual bone changes which might otherwise be overlooked by histological analysis and can be used as baseline information on which future studies can be designed.

Polyethylene Particle–Induced Bone Resorption in α-Calcitonin Gene–Related Peptide–Deficient Mice†

This study investigates the impact of α‐CGRP on bone metabolism after implantation of polyethylene particles. α‐CGRP knockout mice showed less osteolysis compared with wildtype mice. The local neurogenic microenvironment might be a crucial factor in particle‐induced osteolysis.

Retention treatment after periprosthetic total hip arthroplasty infection

PurposeThe purpose of this study was to compare infection control rates between implant retention and two-stage revision and assess the effectiveness of retention treatment in THA.MethodsTwenty-eight debridements with implant retention (retention group) and 65 staged revisions (removal group) were retrospectively analysed and risk factors that can contribute to failure of infection control were explored.ResultsFor the retention and removal groups, infection control rates were 50% and 78% after initial treatment, and 68% and 82% at latest follow-up, respectively. There were no significant differences in the number of additional operative procedures, total length of hospital stay, and duration of treatment between groups. Infection of revision THA, polybacterial and S. aureus infection were identified as risk factors for infection control.ConclusionsRetention treatment can be considered an initial treatment option in selected cases of primary THA, with a single organism, non-S. aureus infection with 50% chance of infection control and no disadvantages in terms of additional procedure, hospital stay, and treatment duration.

Total joint registries: a foundation for evidence-based arthroplasty.

An argument that national joint registries have improved outcomes for arthroplasty patients because they track device performance, reduce revision surgeries, and promote evidence-based surgery. Virtual Mentor is a monthly bioethics journal published by the American Medical Association.

Der acetabuläre Pressfit bei äquatorialer Beschichtung der zementfreien Hüftpfanne – eine finite-Elemente-Analyse Pressfit of equatorially roughened cementless acetabular components – a finite elements analysis

Zusammenfassung Fragestellung: Ist die Pressfit-Verankerung von zementfreien Hüftpfannen abhängig von der Rauigkeit des Poles? Um diese Frage zu beantworten, wurde der primäre Pressfit zweier zementfreier Hüftpfannen, die sich nur hinsichtlich der Rauigkeit des Poles unterscheiden, mittels einer finiten-Elemente-Analyse (FEA) verglichen. Material und Methode: Die Werkstoffeigenschaften des Knochens wurden als homogen, isotrop und linear-elastisch angenommen. Es wurden die Materialkennwerte von spongiösem Knochen bei drei unterschiedlichen Knochendichtewerten verwendet. Die getroffene Annahme der Isotropie stellt eine Näherung dar. Ergebnisse: Der Vergleich der beiden Prothesenformen zeigte, dass beide Modelle ähnliche Verformungen und Spannungen im Knochen verursachen. Schlussfolgerungen: Daher kann festgestellt werden, dass die Prothese mit abgefräster Oberfläche der mit ungefräster Oberfläche hinsichtlich der Pressfit-Verankerung in der finiten-Elemente-Analyse mechanisch gleichwertig ist.

Antiresorptive Effects of Simvastatin and OPG on Polyethylene Particle-Induced Osteolysis

The development of new pharmacological treatments for aseptic loosening is mainly based on its improved comprehension and molecular decryption. In this study we evaluated the effect of two substances, simvastatin and osteoprotegerin (OPG), in Ultra-High-Molecular-Weight-Polyethylene (UHMWPE)-particle-induced osteolysis. Data of two previous studies by our group based on the murine calvarial model of particle-induced osteolysis were pooled to form the study groups. The animals were divided into four groups: The animals in Group I received SHAM surgery only, UHMWPE-particles were implanted on the skulls of the animals in the other groups. Apart from the animals in Group II, all the other animals additionally received the substances mentioned above: The animals in Group III postoperatively received a daily dose of simvastatin and the animals in Group IV received a daily dose of OPG. Particle implantation resulted in a grossly pronounced osteolytic activity with significantly increased bone resorption values (p<0.001) and osteoclast numbers (p<0.001). Inhibition of particle-induced osteolysis was observed in the animals treated with simvastatin and OPG. In the group treated with simvastatin more bone resorption was observed (p=0.05) while an increased number of osteoclasts (p=0.002) was observed in the group treated with OPG. OPG seemed to have a more decelerating effect on particleinduced osteolysis than simvastatin. However, the study obtained evidence of the inhibitory effect on particle-induced osteolysis of both substances and they both seem to have a direct influence on osteoclast activity. This may play an important role in the prevention of osteolysis and therapy after total hip replacement in the future.