Smart implants in orthopedic surgery, improving patient outcomes: a review

Figures & data

Figure 1 Orthopedic implants, such as the total knee replacement components shown left, have sufficient size and volume for placement of sensors (S), electronics (E) and antenna (A) components within.

Notes: This facilitates their modification into smart implants. Once placed in the body (right), radiofrequency (RF) communications facilitate data collection from the implant.

Figure 2 Strain gages are mounted onto the surface of implants such as the cervical spinal interbody cage shown and require lead wires connecting them to signal conditioning electronics.

Note: The gages shown are 2.5 mm in width and are coated with parylene C to isolate them from the body.

Figure 3 The technology that enables smart orthopedic implants has evolved over several decades, as shown in the total hip prostheses, from tethered electronics (left) to wireless systems that require signal conditioning electronics (E) with antennas (A) to be housed inside the implant (center) to passive sensors (P) that require no electronics and little-to-no modification of the implant (right).

Figure 4 When a fracture is treated with open reduction and internal fixation, forces applied through the bone are transmitted through the plate.

Notes: As shown in the tibia, initially, the fracture is not capable of bearing forces. However, as the fracture heals, the newly formed bone can bear more load, while the plate shares less load. In this way, monitoring forces through the plate is used as an indicator of fracture healing.