Can standard implants reproduce the native kinematics of a TKA patient?

Abstract

Total knee arthroplasty (TKA) is a reliable surgical procedure, yet up to a fifth of primary implant patients remains unsatisfied. Musculoskeletal modeling (MSM) has the potential to explore the relationship between implant alignment and functional outcome [3]. Consequently, implant alignment can be quantitatively optimized to restore the pre- TKA joint behavior and, therefore, achieve the most favorable functional outcome for the specific patient. For this reason, we developed a method to optimize the implant alignment, with the aim of restoring the native kinematics and ligament elongations of the patient before undergoing TKA. Subject-specific optimization towards ligament elongations demonstrated to accurately emulate the pre-TKA ligament behavior, in contrast to the mechanically aligned approach. However, the values of the optimized implant positions resulting from the pre-TKA kinematic optimization were extreme in some cases. The presented modelling approach is a promising starting point for allowing surgeons to evaluate the patient-specific implant alignment and restore the patient- specific biomechanics.

Pre-Planning the Surgical Target for Optimal Implant Positioning in Robotic-Assisted Total Knee Arthroplasty

“…Optimizing solely for the ligament strains resulted in a 57.2% average reduction in the dMCL and sMCL, 59.7% and 55.4% in the LCL and ALL, respectively, and 75.2% on average in the PCL, OPL, and PC. These outcomes are consistent with those of Quilez et al [33], who accurately emulated the pre-operative ligament elongations using a modelbased response surface methodology. The authors reported optimal implant position within ±5 mm and ±3 • from MA.…”

“…Proximal shifting of the femoral component by 3.7 mm increased the joint gap, which eventually resulted in overall lower strains compared to the MA state. The slope of the tibial component also had a considerable impact, in accordance with an earlier study [33], which, however, suggested a tibial slope up to 15 • to restore the pre-operative kinematics, which may not be clinically realistic. The required changes in implant position were larger than the accuracy attained in robotic-assisted surgery, except for the external rotation of the femoral component, which still falls within the achievable range of accuracy [10,11].…”

“…where x indicates the positional parameter of the femoral and tibial component with lb and ub denoting its lower and upper boundaries, respectively (Table 1). The boundary conditions are relative to the initially estimated MA femoral and tibial component positions and are comparable to those used in similar studies [31][32][33]. The width of the FE boundaries of the femoral component was narrower to avoid anterior notching of the femoral cortex greater than 3 mm, which can be detrimental to the surgical outcomes [34,35].…”

Using a patella reduced technique while balancing a TKA results in restored physiological strain in the collateral ligaments: an ex vivo kinematic analysis

“…More in general, proper soft tissue balance is indeed commonly accepted to be vital for post -operative outcome as it leads to stability, and longer implant survival [9]. Nevertheless, there is still much debate on the exact definition of an optimally balanced TKA and consequently no gold standard currently exists [56,57]. However, Babazadeh et al defined a balanced knee joint as: a full range of flexion-extension motion, symmetrical medial/lateral balance at both full extension and 90 of flexion, correct varus/valgus alignment in flexion/extension, a well tracking patella during full motion, without excessive rollback of the femur on the tibia and correct rotational balance between the tibial and femoral components [58].…”