Augmentation of bone growth onto the acetabular cup surface using bone marrow stromal cells in total hip replacement surgery

Aseptic loosening of acetabular components in total hip arthroplasty is the major cause of implant failure. Our hypothesis was that spraying autologous bone marrow-derived stromal cells (BMSCs) in fibrin glue onto the surface of hydroxyapatite-coated uncemented acetabular components would increase bone formation and contact in a caprine model. Ten million BMSCs were sprayed onto the acetabular cup at the time of surgery. Animals in the control group received fibrin glue only. Ground reaction force measurements were taken preoperatively and at 6 and 12 weeks postsurgery. After retrieval at 12 weeks new bone formation, bone-implant contact and fibrous tissue thickness adjacent to the cup were quantified. Viability and proliferation assays showed that the majority of the BMSCs survived spraying in fibrin glue at pressures of up to 1.5 atm. New bone growth adjacent to the bone implant interface in the BMSC-treated group (71.42 +/- 8.97%) was 30% greater than in control (54.22 +/- 16.56%) although this difference was not statistically significant. However, significantly increased new bone formation was measured at the periphery of the cup (zone 5) in the BMSC-treated group (71.97 +/- 10.91%) when compared with control (23.85 +/- 15.13%, p = 0.028). Bone-implant contact was significantly greater in the BMSC-treated group (20.03 +/- 4.64%) (control: 13.71 +/- 8.32%, p = 0.027); correspondingly, the average thickness of the fibrous tissue membrane where present was significantly reduced at the periphery of the cups in the BMSC-treated group (327.49 +/- 20.38 mum) when compared with control (887.21 +/- 158.89 mum) (p = 0.02). This study has clinical applications as greater bone contact at the cup surface will improve fixation and may decrease longer-term aseptic loosening by preventing wear debris-induced bone loss at the implant interface.