Hip, knee, and shoulder joints get worn over time, or damaged by disease or injury. They often require replacement because they cause pain and inhibit movement. Orthopedic surgeons perform more than 1 million joint replacements each year. The worn bone is replaced with plastic or metal implants and cemented in place. The surgery can provide immense relief and restore mobility. But sometimes these implants don’t integrate well with the bone, and ultimately they break free. Replacement surgeries are costly, increase the risk of infection, and are a major challenge for the patient to endure. But recently an NIH-funded team of chemical engineers at MIT developed a special coating for implants that promotes a stronger connection to new bone.
The coating contains layers of materials, just 100 nanometers thick, containing a natural ceramic like material called hydroxyapatite. This is actually a component of normal bone, and attracts stem cells to the implant interface, encouraging a tight bond to the implant. The coating also contains a natural bone promoting growth factor called bone morphogenetic protein-2 (BMP-2). BMP-2 stimulates stem cells to become bone-producing cells that can colonize the surface of the implant and regenerate bone tissue. Use of this coating on implants worked well in rats; the bone grew well and the connection between the native bone and implant was stronger than implants that had partial or no coating.
Next: trials in larger animals and then perhaps human trials with dental and hip or knee implants!
 Surface-mediated bone tissue morphogenesis from tunable nanolayered implant coatings. Shah NJ, Hyder MN, Moskowitz JS, Quadir MA, Morton SW, Seeherman HJ, Padera RF, Spector M, Hammond PT. Sci Transl Med. 2013 Jun 26.
NIH support: National Institute on Aging, National Cancer Institute