The state of the art of osseointegration for limb prosthesis

Osseointegration (OI) is the direct attachment of bone onto a titanium implant. Recently, the term is used to describe "transdermal" implants that allow an external prosthesis to be connected directly to the skeleton. This technology eliminates the challenges of conventional socket-based prostheses, such as skin breakdown and poor fit, which are common in patients with major extremity amputations. Osseointegration patients demonstrate encouraging improvements in quality of life and function. Patients report improvement in prosthetic use, prosthetic mobility, global health, and pain reduction on a variety of clinical assessment tools. Various implants have been developed for osseointegration for amputees. These implants use a variety of fixation strategies and surface augments to allow for successful integration into the host bone. Regardless of design, all OI implants face similar challenges, particularly infections. Other challenges include the inability to determine when integration has occurred and the inability to detect loss of integration. These challenges may be met by incorporating sensing systems into the implants. The percutaneous nature of the metal devices can be leveraged so that internal sensors need not be wireless, and can be interrogated by external monitoring systems, thus providing crucial, real-time information about the state of the implant. The purpose of this review is to (1) review the basic science behind osseointegration, (2) provide an overview of current implants, practice patterns, and clinical outcomes, and (3) preview sensor technologies which may prove useful in future generations of transdermal orthopaedic implants.