When and How Is Patella Tracking Best Assessed in Total Knee Arthroplasty Surgery?

Much emphasis has been placed on the role of patella resurfacing in total knee arthroplasty (TKA), yet the impact of soft tissue balancing has frequently been understated. The authors used a novel system to precisely assess patellofemoral joint (PFJ) tracking intraoperatively, to determine the impact of both retinacular reconstruction and tourniquet use on PFJ kinematics. PFJ kinematics assessed intraoperatively for 20 consecutive TKA patients. Measurements were recorded using both the "no thumb technique" and following reconstruction of the retinaculum with two positional sutures. The tourniquet was deflated and both measurements were repeated. Tourniquet inflation was not found to have a significant impact on the patella tracking (mean translation 0.9 mm, p = 0.15). Patella retinacular reconstruction generated a significant medialization of the patella by a mean of 5.5 mm (p < 0.0001) when compared with the traditional retinacular open "no thumb technique." The use of a tourniquet has been shown to have no effect on patella tracking. Reconstruction of the patella retinaculum markedly improves patella tracking, generating a mean medialization of 15%. The authors advocate the routine use of two positional sutures to restore the patella retinaculum, before trialing the patella component, as a reproducible means of assessing the PFJ kinematics.

Can Tibial Cementation Be Enhanced in Knee Arthroplasty Surgery?

Aseptic loosening of the tibial component continues to be a significant mode of failure in total knee arthroplasty surgery. Surface cemented components preserve tibial bone stock, but are reliant on a strong bone-cement interface. This study compares standard surface cemented tibial component design to a tibial component with the addition of an undersurface cement containment skirt. The hypothesis was that the addition of a 2-mm underside skirt would allow cement containment and pressurization during implantation, which might improve the overall survival. Two identical tibial components were used, out of which one had the 2-mm underside skirt removed for the purposes of this study. Overall, 12 tibial Sawbones were prepared identically and transducers placed in the medial and lateral plateau. Each component was implanted six times, according to the manufacturer's operative technique. The series of implantation experiments showed no difference in cement pressurization (p = 0.86) regardless of the tibial component design used, with a wide variation in pressure measurements occurring in both groups. The tibial component skirt has not demonstrated any enhancement in cement pressurization. The cement containment skirt might still be advantageous by increasing the cement mantle thickness without causing excessive bone penetration; however, the biological effects cannot be predicted without further clinical evaluation.

Use of an anatomic long-stemmed component in femoral impaction grafting.

We describe a challenging femoral revision for aseptic loosening in a relatively young and active man. The femur had gross osteolysis, an absent calcar and a cortical diaphyseal defect at the level of the isthmus (Paprosky 3b defect). The cortical defects were repaired and the whole femur then restored with Femoral Impaction Grafting (FIG) using custom-made impaction instruments and an anatomic shaped collarless, polished, tapered femoral component.In the active adult, bone restoring revision techniques such as impaction grafting should be considered to give a realistic prospect of host bone augmentation rather than simply aiming for a distally fixed stem in a patulous femoral canal.