Through modern surgical advancements, total hip replacements (THR) have become one of the most successful implant procedures to date. Even though long-term success rates are high, the staggering number of THR procedures performed (~365,000 per year in the United States alone) results in thousands of failed implants each year. Most implants fail through aseptic loosening and implant instability. Earlier implant designs utilized various types of synthetic bone cement, all of which elicited localized inflammatory responses and stimulated bone resorption. In response, physicians shifted towards cementless, porous-coated implants and this implant design is now used in a majority of THR procedures. However, effective and rapid fixation is critical to both the short- and long-term success of hip implants, especially given the increasingly young and active patient populations opting for THR. Thus, the need exists for improved hip implant design to facilitate rapid implant fixation in active and mobile patients. Unlike cemented implants, cementless implants achieve fixation by press-fitting surface-modified titanium into bone that eventually allows ingrowth. Due to the nature of these implants, adequate bone ingrowth is critical for patient recovery. Materials such as hydroxyapatite hasten bone ingrowth, but these coatings may promote osteolysis due to wear particles from degradation. As an alternative, bone marrow-derived mesenchymal stem cells (BMSCs) may be used as a treatment to promote bone formation. Current methods utilize ex vivo BMSC culture. This creates several practical and regulatory challenges. As an alternative, we have developed peptides that bind BMSCs with high specificity and affinity. Our goal is to attach these peptides onto the surface of the femoral components of hip implants to capture BMSCs from the implant?s marrow-rich surroundings onto the implant surface. In preliminary studies, we have demonstrated that mineralization in stem cell cultures is dependent upon cell concentration. Thus, we hypothesize that concentrating BMSCs on titanium implants will speed the patient recovery process and improve short-term clinical outcomes for cementless implants.
Even though long-term success rates are high, the staggering number of THR procedures performed (~365,000 per year in the United States alone) results in thousands of failed implants each year. Cementless implants now account for the majority of procedures, but rapid, adequate bone ingrowth is critical for patient recovery. We will develop coatings that promote bone formation by capturing stem cells from the native host bone marrow.
