Linear and Volumetric Wear of Tibial Inserts in Posterior Cruciate-Retaining Knee Arthroplasties

Section: Resultscontrasting

confidence: 52%

Durability of a Cruciate-retaining TKA With Modular Tibial Trays at 20 Years

Callaghan

Beckert

Hennessy

et al. 2013

“…The PFC implant studied here also uses a relatively flat, nonconforming surface, particularly the posterior-lipped insert. Despite the potentially deleterious effects of thin [2,10,22,34], flat [4,19] inserts on polyethylene wear, the revision rates in our patients were low and occurred late.…”

Section: Discussionmentioning

confidence: 61%

Routine Surveillance of Modular PFC TKA Shows Increasing Failures after 10 Years

Malin

Callaghan

Bozic

et al. 2010

Background/rationale A 10-year survivorship of 100% was reported for patients with PFC cruciate-retaining prostheses. Beyond 10 years, we observed additional polyethylene wear likely related to thin liners gammairradiated in air and were concerned this wear might predispose to implant construct failure. Questions/purposes We therefore determined (1) the functional scores at a minimum of 15 years followup, (2) rates of radiographic failure, (3) overall revision rates, and (4) mode of failure after 10 years and the fate of the revised implants. Methods We retrospectively reviewed 75 patients with 101 press-fit condylar posterior cruciate-retaining prostheses. At a minimum followup of 15 years, 35 patients (47 knees) were living and evaluated clinically. No patients were lost to followup. Results There were no revisions during the first 11 years and six reoperations subsequently were performed in five patients (6% overall rate of revision but 12.8% in patients who survived more than 15 years). Three of six revisions had concerning liner wear at 10 years and all six were revised for polyethylene wear. Polyethylene exchange was performed in four of the five patients who underwent revisions, all of whom were doing well at an average of 7.2 years (range, 4.7-9

“…There are two possible explanations for the lower wear seen in our retrievals. First is the absence of gamma-in-air polyethylene in our study compared with its presence in four of five retrieval studies [1,2,9,15]. The second reason is the relationship among penetration, deformation, and wear.…”

Section: Discussionmentioning

confidence: 72%

“…Lesser contributors to the variation are multiple surgeons and different surgical techniques for fixed-bearing and rotating-platform knees. We did our best to control for these variables (Table 1) but like other studies that evaluate revision retrievals, we could not control all variables [1,2,9,14,15]. Although this study only used one manufacturer, there were three designs evaluated.…”

Section: Discussionmentioning

confidence: 99%

“…Unfortunately, volumetric analysis of retrieved tibial polyethylene components is rarely performed. When threedimensional retrieval analysis is performed, it has been limited in the ability to separate wear from penetration because the volumetric calculation is typically based on shapes generated from multiple penetration measurements [1,2,9,14,15].…”

Section: Introductionmentioning

confidence: 99%

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Can Microcomputed Tomography Measure Retrieved Polyethylene Wear? Comparing Fixed-bearing and Rotating-platform Knees

Engh

Zimmerman

Hopper

et al. 2013

Background Wear of total knee polyethylene has been quantified gravimetrically with thickness measurements and evaluation of surface wear modes. However, these techniques do not localize volumetric wear. Questions/Purposes We used micro-CT scans of retrieved total knee liners and unworn, new liners to determine the volume and location of wear. Methods We retrieved 12 fixed and 12 rotating-platform bearings after a mean 52 months of use. Inserts were weighed and thickness was measured. Micro-CT scans of retrieved and matched new liners were superimposed to compare the location and magnitude of wear. Results The average total wear was 254 ± 248 mm 3 . The average wear rate was 58 ± 41 mm 3 /year. Wear was 69% of penetration, demonstrating the contribution of deformation to knee wear. Rotating-platform wear rate was 43 ± 25 mm 3 /year and the fixed-bearing rate was 74 ± 49 mm 3 /year. Five percent of the rotating-platform wear rate came from the backside compared with 14% of the fixed-bearing wear rate. Conclusions Micro-CT can determine the volume and location of wear of retrieved tibial liners. Because the magnitude of the manufacturing tolerances was approximately half the magnitude of the total wear on average, accounting for the potential influence of tolerances is important to accurately measure volumetric wear if the unworn (preimplantation) geometry of the insert is unknown. Without accounting for tolerances, this technique may not be applicable for retrievals with a short followup that have low wear. However, application of micro-CT could be of value in determining the exact location of wear in knee simulator studies in which the same insert is measured repeatedly and manufacturing tolerances are not a concern.