Promising work on bioactive glasses (BAGs) in bone defect regeneration has led to their clinical implementation. However, the effects of the ionic dissolution products of different types and the physical interaction modalities of BAGs on the behavior and function of mesenchymal stromal cells (MSCs) of human patients have not received sufficient attention. Recently, we showed that the in vitro response of hMSC to micron-sized, monodispersed BAGs is dependent on dosage, composition, and mode of interaction¹. Two commercially available and widely used types of BAGs, namely the silicate BAGs 45S5 and 1393, were used to study hMSC cell behavior. Interestingly, exposure to 1393 BAG resulted in superior metabolic activity, proliferation, and cell spreading compared to 45S5 BAG in similar dosage, suggesting that additional cellular functions could also be differentially modulated by both glasses¹. In the context of bone regeneration, the hMSCs’ potential to secrete angiogenic factors as well as deposit mineralized matrix upon exposure to BAG dissolution products was investigated in the present study. Aside from dose-dependent effects of both glasses, 45S5 BAG induced a significant pro-angiogenic response, demonstrated by robust tube formation in HUVECs in the presence of MSC conditioned media. 1393 BAG, on the other hand, stimulated osteogenesis by upregulating osteogenic gene expression and mineralized matrix deposition. Based on these results, combining the pro-angiogenic 45S5 BAG and the pro-osteogenic 1393 BAG might be an attractive strategy to target the multiple processes underlying bone regeneration. These results highlight how different BAGs can be utilized to promote MSC-mediated bone regeneration.

Introduction

The Hamann-Todd collection at the Cleveland Museum of Natural History (Cleveland, OH, USA) includes 63 paediatric skeletal specimens in varying condition and completeness. The initial data collection included representative skeletons of children aged 1–18 years. The aim of this study was to better understand the growth patterns of the paediatricspine and ribs.

The present study was conducted to analyze the specific morphological features of press-fitted quadriceps tendon-patellar bone grafts that determine primary graft stability in ACL-reconstruction.

Ten quadriceps tendon-patellar bone grafts were harvested from fresh frozen human cadaveric knees (age 52–82) and fixed to porcine femora in a press-fit technique. Four specimens were prepared for histological analysis of the bone-tendon junction, while a modified technique for tissue-plastination was applied to 6 specimens to investigate the microscopic and microradiographic features of the bone-to-bone interface.

Analysis of the bone-tendon junction revealed a serious damage of the fibrocartilage at the attachment zone according to the impaction of the patellar bone plug with implantation. Microradiographs and microscopy of the plastinated specimens showed that there is a trabecular interaction between the bony interfaces of the graft and the femoral tunnel, representing an early osseous integration with local increase of radiopacity. In consequence, both elevated compressive forces as well as increased frictional resistance seem to contribute to the primary stability of press-fit fixated grafts.

The stability of quadriceps tendon-patellar bone grafts in press-fit technique to a certain degree depends on bone quality, allowing compressive forces to arise at the bone-to-bone interface. Loss of graft stability, however, is caused by disturbance of the integrity of the bone-tendon junction while impacting the patellar bone plug into the femoral tunnel.

We developed an endoscopically controlled device for cement removal out of the femoral canal. This system (Swiss OrthoClast) uses simple ballistic principles to effect mechanical fracturing of the bone cement. A special extraction set facilitates removal of the distal cement layer and of the intramedullary plug. The cement removal procedure, even in the depth of the femur, is controlled with an endoscopical system via monitor. Handling of this device will be demonstrated. We report our clinical results of 45 procedures with this device.

Material and methods: 45 patients (14 male ,31 female, average age at revision 72.9 years) were revised after an average follow-up period of 91.2 months (range 0-252 months) after primary THR due to mechanical loosening (n=38) or infection (n=7). All procedures were analysed and evaluated with a standardized documentation.

Results: 90% of the revisions showed type 1 bone defects according to Paprosky’s classification. In all but three cases cement removal with this method was complete. We saw one case of femoral fissuration in a patient with osteoporosis and one cortical perforation while drilling in the K-wire of the extraction tool. The time for cement removal varied between 5 and 75 minutes with an average of 27.1 minutes in the aseptical and 36.9 minutes in the septical group. Only in the very first cases we had problems with the endoscopic view.

Conclusion: Swiss OrthoClast facilitate cement removal out of the femur and avoids cortical fenestration. The optical system is effective and helpful, even for extraction of the distal cement layer and the medullary plug. This mechanical system has no side effects like development of heat, dust or toxic products during cement removal. Disadvantages might be the learning curve for the surgeon and its costs.