Vol.:(0123456789) 1 3 Knee Surgery, Sports Traumatology, Arthroscopy https://doi.org/10.1007/s00167-018-5220-z KNEE Kinematic alignment more closely restores the groove location and the sulcus angle of the native trochlea than mechanical alignment: implications for prosthetic design Rocio Lozano 1  · Valentina Campanelli 2  · Stephen Howell 1  · Maury Hull 1,3,4 Received: 4 July 2018 / Accepted: 15 October 2018 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2018 Abstract Purpose Kinematic alignment (KA) and mechanical alignment (MA) position the prosthetic trochlea that guides patellar tracking differently. The present study determined whether KA or MA more closely restores the groove location and sulcus angle of the prosthetic trochlea to the native trochlea for three femoral component designs. Methods Ten 3D femur-cartilage models were created by combining computer tomographic (CT) and laser scans of native human cadaveric femurs. Three femoral component designs were positioned using KA and MA. Measurements of the pros- thetic and native trochlea were made along the arc length of the native trochlear groove. The alignment technique with the smaller absolute difference between prosthetic and native for the medial–lateral and radial locations of the groove and sulcus angle of the trochlea more closely restored the native trochlea. Results For three femoral component designs, KA more closely restored to native the mean medial–lateral location (p = 0.0033 to < 0.0001) and mean radial location (p = 0.0150 to < 0.0001) than MA. For two femoral component designs, KA more closely restored to native the mean sulcus angle (p = 0.0326 to 0.0006) than MA. However, the differences in the mean sulcus angles between KA and MA were less than 2° for all three designs. Conclusion KA more closely restored the native trochlea, which explains why the reported risk of patellofemoral complica- tions for KA is not higher than MA according to five randomized clinical trials. Small design modifications of the medial– lateral and radial locations and sulcus angle are strategies for restoring the native trochlea. Such modifications might further reduce the risk of patellofemoral complications. Level of evidence II. Keywords Bone model · Femur · Total knee replacement · TKR · Total knee arthroplasty · TKA · Trochlear groove · Patellar tracking · Simulation · Q-angle · Component alignment Introduction Kinematic (KA) and mechanical (MA) alignment tech- niques are based on two different paradigms of implant positioning that use the same total knee arthroplasty (TKA) implants [22]. KA is based on a patient-specific alignment paradigm that corrects the arthritic deformity to the pre- arthritic or constitutional alignment, which varies widely from 12° varus to − 16° valgus among the world populace [27]. KA sets the femoral and tibial components coincident with the native tibial–femoral articular surfaces, thereby restoring the native joint lines, limb alignment, knee laxi- ties, and tibial compartment forces without soft tissue release [9, 23, 24, 26]. MA is based on an average align- ment paradigm that changes the constitutional alignment * Maury Hull mlhull@ucdavis.edu 1 Department of Biomedical Engineering, University of California Davis, One Shields Ave, Davis, CA 95616, USA 2 THINK Surgical, 47201 Lakeview Blvd, Fremont, CA 94538, USA 3 Department of Mechanical Engineering, University of California Davis, One Shields Ave, Davis, CA 95616, USA 4 Department of Orthopaedic Surgery, University of California Davis Medical Center, 4860 Y Street, Suite 3800, Sacramento, CA 95817, USA