ABSTRACT
Proximal tibial aspect ratio (PTAR) is closely related to age, disease status and cutting parameters with considerable inter-individual variation independent of gender and race, nevertheless the aspect ratio of tibial components from different manufacturers remains relatively constant from smallest to largest size. As a result, component mismatching is an unavoidable dilemma during tibia preparation in total knee arthroplasty (TKA). Various prosthesis systems all can achieve more than 80% coverage on proximal tibia, whereas their optimal fit rates are generally not more than 50%. It is difficult for symmetrical components to avoid anteroposterior mismatch, internal malrotation tends to occur when maximum coverage is pursued on the resected surface with a medial dominant plateau or lower PTAR. Although it is easier to achieve a balance of rotation and coverage with anatomical components, significant anteromedial overhang tends to appear on the resected surface with a symmetrical or lateral dominant plateau. Further researches should focus on the law of inter-individual variability of proximal tibial morphology, the quantitative definition of "ideal matching" safety zone of key morphological parameters on different areas of proximal tibia and the methodology of realizing"ideal matching"in the majority patients with the least amount of component sizes. In addition, with the rapid development of additive manufacturing and digital orthopedic technology, individual customized implant is expected to become a breakthrough point in the field of TKA component fitting.
ABSTRACT
Component malrotation is one of the major causes of failure in total knee arthroplasty.Based on previous researches,Insall line has excessive external rotation tendency.Although Akagi line is the most recognized anatomical axis at present,it still has a certain tendency of internal rotation.The tibial posterior condylar axis is not suitable for symmetrical component and yet the Curve-on-Curve technique is not suitable for anatomic component.In addition,reference to any fixed anatomical markers cannot ensure the rotation consistency of tibiofemoral component in extension position.Although range of motion technique is beneficial to tibiofemoral rotation synchronization,its clinical effect seems to be unstable.Nevertheless,Patients can obtain good postoperative results with all major techniques.Before the recognized "gold standard" is defined,orthopedic surgeons can determine the rotation alignment of tibial component according to their most accustomed surgical method.With a deeper understanding of knee anatomy,biomechanics and kinematics,digital assistive technology may be expected to become a breakthrough in the tibial rotational alignment.
