Bone Preservation in a Novel Patient Specific Total Knee Replacement.

Background: The volume of total knee arthroplasty procedures is growing rapidly and, correspondingly, it is expected that the volume of revision procedures will grow rapidly as well.  Revision surgery is most successful when adequate bone remains on both the tibia and femur to allow for the least invasive revision.  We hypothesized that total knee arthroplasty with a patient-specific implant would result in significant bone preservation as compared to standard total knee arthroplasty with “off-the-shelf” implants. Methods: We evaluated 100 total knee arthroplasties which utilized patient-specific implants, versus 37 standard posterior stabilized and 32 standard posterior cruciate retaining total knee arthroplasties.  Bone resection was quantified utilizing intra-operative measurements of actual resected bone. Additionally we performed a virtual, CAD-based analysis of resections via CT imaging on 15 knees.  Findings: We found that patients had significantly less bone resected in all zones measured, on both the femur and tibia, when patient-specific implants with patient-specific jigs were used.  When assessed volumetrically with CAD imaging, standard implants resected 12-49% more bone than did patient-specific implants, depending on the size of the implant utilized. Interpretations: Utilizing patient-specific implants in total knee arthroplasty results in significant bone sparing as compared to standard total knee arthroplasty. This has the potential for less invasive revision surgery in the future, possibly obviating the need for dedicated revision implants or augments and other bone substituting devices