The 2012 Mark Coventry Award: A Retrieval Analysis of High Flexion versus Posterior-stabilized Tibial Inserts

Abstract

Background High flexion (HF) implants were introduced to increase ROM and patient satisfaction, but design changes to the implant potentially have deleterious effects on polyethylene wear. It is unclear whether the HF implants affect wear. Questions/purposes We therefore examined whether the design changes between HF and posterior-stabilized (PS) tibial inserts would affect overall damage or damage on their articular surface, backside, and tibial post and whether flexion angle achieved related to damage. Methods We matched 20 retrieved HF inserts to 20 retrieved PS inserts from the same implant system on the basis of duration of implantation, body mass index, and age. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. Five inserts were scanned using micro-CT to further quantify instances of severe post notching. We determined overall damage with a scoring system.

Peripheral snap-fit locking mechanisms and smooth surface finish of tibial trays reduce backside wear in fixed-bearing total knee arthroplasty

“…2011, Paterson et al. 2013). The main drawback of the Hood score is that it does not provide any information regarding polyethylene wear, which is expressed as either gravimetric or volumetric loss of material (Billi et al.…”

“…2013, Paterson et al. 2013). Additionally, in a retrieval study, artifacts caused by inlay deformation during extraction must be corrected manually, which is time-consuming and reduces the overall measurement accuracy.…”

Radiostereometric Analysis Permits In Vivo Measurement of Very Small Levels of Wear in TKA

“…Femoral rollback is encouraged through a dished design. In prior retrieval studies of the Genesis II, linear wear rates of 0.03 to 0.09 mm/year have been reported for the articular surface [12,35] along with a backside wear rate of 0.008 mm/year [32] and damage to the anterior and posterior aspects of the post in posteriorstabilized designs [25]. Retrieval studies of the Genesis II have also identified that increased surface damage and greater thinning of the medial condyle are associated with increasingly varus leg alignment [20,24,50].…”

“…RSA offers the potential to examine measure wear of implants that are still in the patient's body and contrast this to previous retrieval findings. The Genesis II™ (Smith & Nephew, Memphis, TN, USA) is one example of an implant system that has a long and successful clinical track record [21] and has been widely examined in implant retrieval studies [2,12,15,20,24,25,32,35,50]. The Genesis II was designed with strong mediolateral conformity to enable greater contact area, decreasing contact stresses.…”

Highly Crosslinked Polyethylene Improves Wear But Not Surface Damage in Retrieved Acetabular Liners

“…However, it is possible that the semiquantitative grading of damage resulting from wear may not correlate with the actual wear or the wear rate of the retrieved polyethylene liners. Micro-CT has been reported as a useful tool for quantifying wear in retrieval studies, including those of acetabular liners [28,32].…”