Bioactive glass scaffolds for bone loss in revision total knee arthroplasty (rTKA)

Bone loss that compromises implant fixation is a challenge in both total knee arthroplasty (TKA) and revision total knee arthroplasty (rTKA). One method to address this is the use of bioactive glass scaffolds designed with adequate load bearing strength, a degradation rate that matches that of bone formation and a microstructure similar to that of human trabecular bone. 

Titania-containing borate bioactive glass scaffolds based on the glass system (52-X) B2O3-12 CaO-6P2O5-14Na2O-16ZnO-XTiO2 with X varying from 0, 5 and 15 mol% of TiO2 incorporated, identified as BRT0, BRT1 and BRT3 scaffolds, respectively, were fabricated using a polymer foam replication technique. Increasing TiO2 decreased the pore sizes and the porosity of the scaffolds, but they were nevertheless within the range for human trabecular bone. BRT3 scaffolds with greater TiO2 content exhibited superior mechanical properties (compressive strength, flexural rigidity and flexural strength) compared to BRT0 and BRT1 scaffolds. After 30 days in de-ionized water increases in TiO2 content from 0 to 15 mol % increased the compressive strength from 3 to 6 MPa. The flexural rigidity and flexural strength of the scaffolds were found to depend strongly on porosity. Moreover, the results showed that the compressive strengths of the scaffolds were within the range for human trabecular bone, however their flexural strengths were lower than that of human trabecular bone. Ion release profile studies determined that by increasing TiO2 the cumulative ion release from the scaffolds decreased remarkably. Also, it was observed that immersing the scaffolds in de-ionized water resulted in an increase in pH of all the scaffold extracts from 7.0 to 8.5 after 30 days. 

An In-vitro study of the borate bioactive glass scaffolds using an MTT assay revealed that ions released from BRT1and BRT3 had no significant effect on proliferation and activity of pre-osteoblastic MC3T3-E1 cells at day 14. At day 30, all the scaffold extracts decreased proliferation and activity of MC3T3-E1 cells due to the closed nature of the test. However, live/dead cell assay results showed that the degradation products from all the scaffolds had no inhibitory effect on viability of MC3T3-E1 cells. BRT1 and BRT3 extracts also exhibited significant bactericidal efficacies against Escherishia coli, Staphylococcus aureus, Staphylococcus epidermidis. Moreover, evaluation of cell / bioactive glass surface interactions showed well-spread cells on BRT3 scaffolds. 

In conclusion, the superior physico-chemical, mechanical and biological properties of BRT3 scaffolds compared to BRT0 and BRT1 scaffolds, make them more desirable for addressing bone loss in rTKA.