Five-year migration of uncemented femoral components in total knee arthroplasty with either highly cross-linked or conventional polyethylene inserts: a blinded randomized controlled trial using radiostereometric analysis.

Aims: The aim of this study was to compare the migration of the femoral component, five years postoperatively, between patients with a highly cross-linked polyethylene (HXLPE) insert and those with a conventional polyethylene (PE) insert in an uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary aims included clinical outcomes and patient-reported outcome measures (PROMs). We have previously reported the migration and outcome of the tibial components in these patients. Methods: A double-blinded randomized controlled trial was conducted including 96 TKAs. The migration of the femoral component was measured with radiostereometry (RSA) at three and six months and one, two, and five years postoperatively. PROMs were collected preoperatively and at all periods of follow-up. Results: There was no clinically relevant difference in terms of migration of the femoral component or PROMs between the HXLPE and PE groups. The mean difference in migration (maximum total point motion), five years postopeatively, was 0.04 mm (95% CI -0.06 to 0.16) in favour of the PE group. Conclusion: There was no clinically relevant difference in migration of the femoral component, for up to five years between the two groups. These findings will help to establish a benchmark for future studies on migration of femoral components in TKA.

Five-year migration and insert wear of uncemented tibial components with either conventional polyethylene or sequentially annealed highly crosslinked polyethylene inserts: a blinded randomized controlled trial using radiostereometric analysis.

The primary objective of this study was to compare the five-year tibial component migration and wear between highly crosslinked polyethylene (HXLPE) inserts and conventional polyethylene (PE) inserts of the uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary objectives included clinical outcomes and patient-reported outcome measures (PROMs). A double-blinded, randomized study was conducted including 96 TKAs. Tibial component migration and insert wear were measured with radiostereometric analysis (RSA) at three, six, 12, 24, and 60 months postoperatively. PROMS were collected preoperatively and at all follow-up timepoints. There was no clinically relevant difference in terms of tibial component migration, insert wear, and PROMs between the HXLPE and PE groups. The mean difference in tibial component migration (maximal total point migration (MTPM)) was 0.02 mm (95% confidence interval (CI) -0.07 to 0.11), which is below the value of 0.2 mm considered to be clinically relevant. Wear after five years for HXLPE was 0.16 mm (95% CI 0.05 to 0.27), and for PE was 0.23 mm (95% CI 0.12 to 0.35). The mean difference in wear rate was 0.01 mm/year (95% CI -0.02 to 0.05) in favour of the HXLPE group. Wear is mainly present on the medial side of the insert. There is no clinically relevant difference in tibial component migration and insert wear for up to five years between the HXLPE conventional PE inserts. For the implant studied, the potential advantages of a HXLPE insert remain to be proven under clinical conditions at longer-term follow-up.

Comparable mid-term revision rates of primary cemented and cementless total knee arthroplasties in 201,211 cases in the Dutch Arthroplasty Register (2007-2017).

PURPOSE: Long-term failure of total knee arthroplasty (TKA) is mostly due to loosening of the prosthesis. In this study, the short- and mid-term revision rates of cemented vs cementless TKAs were investigated. Comparable short- and mid-term survival rates of both fixation methods were expected. METHODS: Data on all cemented and cementless TKAs performed between 2007 and 2017 were retrieved from the Dutch Arthroplasty Register. The cumulative crude incidence of revision of cemented and cementless TKA was calculated. Death was considered a competing risk. Revision rates were compared using multivariable Cox proportional hazard regression analysis. The associations between fixation method and type of revision or reason for revision were tested using logistic regression analyses. RESULTS: In total, 190,651 (94.8%) cemented and 10,560 (5.3%) cementless TKAs were evaluated. Both groups had comparable case characteristics. Cemented TKAs were inserted more often in cases with previous knee surgery compared to cementless TKAs (32% vs 27%). The cumulative incidence of revision after 9 years was 5.5% (CI 5.3-5.6%) for cemented and 5.8% (CI 5.2-6.4%) for cementless TKAs (p = 0.2). Cementless TKAs were more often revised due to loosening of the tibial (27% vs 18%; p < 0.001) or the femoral component (7% vs 5%; p = 0.005) than cemented TKAs. Cemented TKAs were more often revised due to infection (17% vs 9%; p = 0.004) than cementless TKAs. CONCLUSION: In conclusion, cemented and cementless TKAs have comparable short- and mid-term revision rates based on a nationwide register study. LEVEL OF EVIDENCE: III.

Measuring polyethylene wear in total knee arthroplasty by RSA: differences between weight-bearing and non-weight-bearing positioning.

Measuring the minimum-joint-space-width (mJSW) in total knee arthroplasty (TKA) in Roentgen stereophotogrammetric analysis (RSA) provides valuable information on polyethylene wear, a leading cause for TKA failure. Most existing studies use non-weight-bearing (NWB) patient positioning. The latter may compromise mJSW measurements due to knee laxity with subsequent non-contact between the TKA components. We investigated the difference in mJSW between weight-bearing (WB) and NWB images and the association with mediolateral (ML) knee stability. At one-year follow-up, 23 TKAs were included from an ongoing RSA study, and ML stability was evaluated. For each examination, the mJSW and femoral-tibial contact locations were measured. A linear regression model was used to analyze the association between the mJSW difference (NWB-WB) with the ML stability and contact locations. The mean mJSW difference was 0.28 mm medially and 0.20 mm laterally. Four TKAs had medium (5-9°) and 19 TKAs had high (<5°) ML stability. A higher mJSW difference was found for TKAs with medium stability (0.36 mm, P = 0.01). In conclusion, mJSW measurements in existing (NWB) RSA studies are influenced by knee laxity, but may still provide information on wear progression based on TKA with high ML stability. A direct comparison of mJSW measurements from WB and NWB data is not possible.