The Effects of Topical Vancomycin on Mesenchymal Stem Cells: More May Not Be Better

The use of topical vancomycin is increasingly popular in spine surgery. Large retrospective reviews suggest that topical vancomycin provides a cost-effective decrease in post-operative infection. Currently, there is little that is known about the maximum dose that can be applied locally. When 1 gram of vancomycin is mixed into the bone graft and another 1 gram applied freely in a spine wound, the local concentration of antibiotic ranges from 260-2900 μg/mL in the immediate post-op period and 50-730 μg/mL by the second post-operative day. We hypothesized that exuberant doses of vancomycin would be toxic to mesenchymal stem cells (MSCs). Bone marrow was obtained from the femoral canal of patients undergoing routine elective total hip arthroplasty. Mesenchymal stem cells were isolated using plastic adhesion. Cells were exposed to a wide range of doses of vancomycin for 24 hours and then assessed for viability. Osteogenic potential was assessed with alizarin red staining. There was dose-dependent cell death with vancomycin use. MSC death was 9.43% at 400 μg/mL (p=0.047), 13.79% at 1600 μg/mL (p=0.0047), 19.35% at 3200 μg/mL (p