Asymmetrical total knee arthroplasty does not improve patella tracking: a study without patella resurfacing

Abstract

It is often suggested that patella tracking after total knee arthroplasty (TKA) with an asymmetrical patella groove is more physiological than with a symmetrical patella groove. Therefore, this study tried to address two questions: what is the effect of TKA on patella tracking, and is patella tracking after asymmetrical TKA more physiological than patella tracking after symmetrical TKA? The patellar and tibial kinematics of five cadaveric knee specimens were measured in the intact situation, after the incision and suturing of a zipper, and after placement of a symmetrical TKA and an asymmetrical TKA, respectively. The patellae were not resurfaced. The flexion-extension kinematics were measured with an internal and external tibial moment to determine the envelope of motion (laxity bandwidth) of the tibio-femoral and patello-femoral articulation. The kinematics after TKA showed statistically significant changes in comparison to the intact situation: patellar medio-lateral translation, patellar tilt and tibial rotation were significantly affected. No statistically significant differences in knee kinematics were found between the symmetrical and the asymmetrical TKAs. We conclude that conventional TKA significantly changes physiological patello-femoral kinematics, and TKA with an asymmetrical patella groove does not improve the non-physiological tracking of the patella.

The Geometry of the Trochlear Groove

“…However, although the design of the components is a crucial factor affecting the postoperative patellar tracking pattern after knee arthroplasty, it also is determined by alignment, soft tissue releases, scar tissue, and the surgery in general. The question regarding whether an asymmetric or laterally positioned trochlear groove would result in more physiologic patellofemoral biomechanics remains unresolved [4,12]. The knowledge of the shapes of the surfaces of this joint and their relations to the alignment of the femur may help to identify and quantify trochlea dysplasia and other disorders relating to patellar maltracking.…”

Evaluation of patellofemoral joint in ADVANCE® Medial-pivot total knee arthroplasty

“…Generally, TKA causes the patella to tilt laterally between 20 and 30°of flexion [34]. In addition, isolated changes in trochlear groove alignment produced patellar shear forces [9], and Barink et al reported that even asymmetrical patella groove TKA could not improve patella tracking [34].…”

Influence of total knee arthroplasty on patellar kinematics and contact characteristics

“…Comparing the RP and APG inlays, no significant differences were found. In so far as the trochlea is the main determinant for the patellar position at flexion angles >30° [22], the choice of inlay has no significant influence on patellar kinematics. Instead, the design of the femoral component plays an essential role.…”

“…Instead, the design of the femoral component plays an essential role. In particular, an anatomical patellar groove orientation seems to be important [22]. The patellar groove of the LCS complete knee system extends perpendicularly from the intercondylar notch and rises into an anatomically shaped anterior flange.…”