Secondary Patellar Resurfacing in TKA: A Combined Analysis of Registry Data and Biomechanical Testing

Abstract

The German Arthroplasty registry (EPRD) has shown that different prosthesis systems have different rates of secondary patellar resurfacing: four years after implantation, the posterior-stabilized (PS) Vega prosthesis has a 3.2% risk of secondary patellar resurfacing compared to the cruciate-retaining (CR) Columbus prosthesis at 1.0% (both Aesculap AG, Tuttlingen, Germany). We hypothesized that PS implants have increased retropatellar pressure and a decreased retropatellar contact area compared to a CR design, which may lead to an increased likelihood of secondary patellar resurfacing. Eight fresh frozen specimens (cohort 1) were tested with an established knee rig. In addition, a possible influence of the registry-based patient collective (cohort 2) was investigated. No significant differences were found in patient data–cohort 2-(sex, age). A generally lower number of PS system cases is noteworthy. No significant increased patella pressure could be detected with the PS design, but a lower contact area was observed (cohort 1). Lower quadriceps force (100°–130° flexion), increased anterior movement of the tibia (rollback), greater external tilt of the patella, and increasing facet pressure in the Vega PS design indicate a multifactorial cause for a higher rate of secondary resurfacing which was found in the EPRD patient cohort and might be related to the PS’ principle function.

Tibial sagittal and rotational alignment reduce patellofemoral stresses in posterior stabilized total knee arthroplasty

“…However, these cadaver studies did not control for the effect of component malalignment on PF contact. On the other hand, Bauer et al reported no differences in retropatellar contact pressure between PS and CR knees, but the patellae were not resurfaced, and external loads were low (50 N) 20 .…”

“…Most of the previous studies evaluating PF contact status were conducted in cadaveric knees 6 , 7 , 9 , 11 , 12 , 16 . However, it is technically challenging to apply large loads equivalent to multiples of body weights in cadaver experiments which tends to underestimate PF pressures 20 . In addition, surgical variations in bone cuts and inter-individual differences in bony anatomy and soft tissues tend to confound the analysis of PF contact.…”

Peripheral patellar denervation has a better effect in reducing postoperative anterior knee pain than patellar resurfacing in TKA

“…A large number of clinical practices have shown that, due to the changes in the existing mechanical properties and mucosa of the joint interface after TKA, the patella has lost its original motion performance. [ 17 ] If the patella is not replaced, it may cause wear of the patella and femoral implants, leading to adverse consequences. [ 17 ] Serious cartilage erosion is often found in the second operation.…”

Influence of kinematic alignment on femorotibial kinematics in medial stabilized TKA design compared to mechanical alignment

“…The established Munich knee rig, which has six degrees of freedom, performed an active movement of 30-130° of flexion in the knee joint at a speed of 3°/s [13][14][15][16][17][18]. The experimental setup does not allow movement at 0° flexion due to the uncontrolled hamstring muscles which normally induce the flexion movement.…”

“…The fibula head was fixed to the tibia with a cortical screw to ensure stability during the test-setup. The ends of the tibia and femur were embedded into metal cups using epoxy resin to clamp the knee joint into the knee rig [13][14][15][16][17][18]. To secure a malalignment of the femoral bone within the metal cups, the internal/ external rotation of the posterior condyles of the femur were aligned parallel to the hip flexion axis of the experimental setup in the transversal plane.…”