Text

Objectives and questions: Highly cross-linked polyethylene (HXLPE) has been increasingly adopted in total knee arthroplasty (TKA) to reduce wear-related failure. While excellent long-term data exist for total hip arthroplasty, evidence regarding wear mechanisms and delamination of HXLPE inserts in TKA remains limited. The aim of this study was to evaluate wear patterns, delamination, and potential risk factors in retrieved HXLPE tibial inserts.

Material and methods: An institutional review board–approved implant retrieval database was screened for revised TKAs with HXLPE tibial inserts. Inclusion criteria were revision for any reason after a minimum in situ time of two years. A total of 74 HXLPE inserts from four manufacturers were analyzed (36 AOX, 27 X3, 8 XLPE, 3 Vivacit-E). Inserts included 48 posterior-stabilized (PS), 17 varus–valgus constrained (VVC), 4 cruciate-retaining (CR), and 5 deep-dished/medial congruent designs. Two blinded observers performed a qualitative five-grade delamination assessment and quantitative wear analysis using the Hood and Wright scoring system. Pre-revision radiographs were reviewed to assess lower limb alignment (e.g. hip-knee-ankle (HKA) angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and posterior tibial slope) and component positioning. Inter-rater reliability was calculated using intraclass correlation coefficients (ICC).

Results: Inter-rater reliability was excellent for the qualitative delamination grading (ICC = 0.90; 95% CI 0.83–0.93) and good for the Hood and Wright wear score (ICC = 0.86; 95% CI 0.37–0.95). Signs of polyethylene surface damage or delamination (grade ≥2) were identified in 24 of 74 inserts (32.4%), while any degree of surface damage or delamination (grade ≥1) was observed in 55 inserts (74.3%). Higher-grade delamination (grade ≥3) was present in 6.6% (6 of 74) of cases. Inserts with increased constraint (PS/VVC) accounted for 65 of 74 implants (87.8%) and demonstrated more pronounced wear and damage patterns compared with low-constraint designs. Radiographic analysis revealed coronal or sagittal malalignment outside accepted target ranges in a substantial proportion of cases, suggesting a potential association between biomechanical factors and polyethylene degradation.

Discussion and conclusions: Despite improved material properties, HXLPE tibial inserts in TKA demonstrate a high prevalence of wear-related surface damage (Grade 1 and 2) and clinically relevant delamination (Grade 3 and 4). Increased implant constraint and suboptimal limb alignment or component positioning may contribute to polyethylene failure. These findings emphasize the importance of accurate surgical technique and appropriate implant selection to optimize polyethylene longevity in TKA.