Smart instrumentation targets optimal joint hardware installation. Intelligent implants target the chronic assessment of joint health and hardware condition. Intelligent implants would facilitate the collection of data, closing the loop to drive best surgical practice, joint system design, and the improvement of outcomes. Intelligent devices could assist post-op in managing pain and promoting recovery. Intelligent implants could offer opportunity for early detection and less invasive intervention should problems arise acutely, or even long after implant. While the development of smart instrumentation is tactically important, the development of intelligent implants is vital to the improvement of outcomes, and should be central to the strategic vision for orthopedic technology development. KEY DISCUSSION POINTS. –. Define “smart” instruments in orthopedics and why there is a need for developing these devices to achieve optimal joint hardware installation. –. Define “intelligent” implants in orthopedics and why there is a need for developing these devices to facilitate the collection of data, and thereby “closing the loop” with smart instrumentation to drive best surgical practice and joint system design. –. Review clinical benefits of intelligent implants in post-operation pain management and recovery, as well as early problem detection facilitating less invasive intervention both acutely and chronically. –. Understand the latest advances in sensors and related technologies for orthopedic implants and implementing best practices for their use in medical design. –. Describe the reduction to practice of an intelligent implant tray capable of measuring and monitoring load, position, and the early onset of infection, and capable of delivering neuro-stimulation for pain management

Soft tissue balancing in total knee replacement may well be the determining factor in raising the fair patient satisfaction. The development of intelligent implants allows quantification of reactive loads to applied pressures. This can be tested in dynamic mode such as heel push test at surgery, or in static mode such as when testing for varus/valgus (VV) laxity of the collateral ligaments of the knee. We postulate that a well-balanced knee will have comparable if not equal load distribution across compartments in dynamic loading. When tested for laxity, we anticipate an equal or comparable response to VV applied loads under physiologic load range of 10–50N. This study sought to analyze the relationship between the kinematic (joint motion) and kinetic (force) effects to VV testing in the 0–15 degrees range of flexion. One goal was to demonstrate that testing the knee in locked extension (Screw Home effect) is unreliable and should be abandoned in favor of the more reliable VV testing at 10–15 degrees of flexion. This is a preliminary cadaveric study utilizing data from two hemibodies. The pelvis was fixed in a custom test rig with open or closed chain lower leg testing capability along a sliding rail with foot VV translational. Forces were applied at the malleoli with a wireless hand held dynamometer. Kinematic analysis of the hip-knee-ankle (HKA) tibiofemoral angle was derived from a commercial navigation system with mounted infrared trackers. Kinetic analysis was derived from a commercially available sensor imbedded in a tibial trial liner. Balance was optimized by conventional methods with the use of the sensor feedback until loads were roughly symmetrical and VV testing yielded symmetrical rise in opposite compartments. The VV testing was then performed with the knees locked at the femoral side in axial rotation and translational motion in any plane. Sagittal flexion was pre-set at 0, 10, and 15 degrees and progressive load was applied. Results. From the graphs one can observe significant differences between VV testing at 0 degrees (locked Screw Home), 10 degrees, and 15 degrees of flexion. The shaded area corresponds to the common range of VV stress testing loading pressure, typically less than 35N. The HKA deviates from neutrality no sooner than by the middle of the physiologic test zone. By 35N, the magnitude of the effect is also much less than that observed at 10 and 15 degrees (unlocked from Screw Home). From the kinetic analysis one can also note the significant difference in the High-Low spread throughout the testing range of applied pressure. If the surgeon tests in the low range of applied loads, he/she may not observe the kinematic joint opening effect. The kinetic effect seems more reliable as sensed loads are detectable earlier on. It is clear however that testing at 10–15 degrees offers a much better sensitivity to the VV laxity or stiffness as exemplified in the bottom portions of the figure. Therefore testing in locked Screw Home full extension may lead to underestimation of the true coronal laxity of the joint