Journal of Orthopaedic Research - 2026-04-01 - Journal Article
Metal Fatigue Fracture After Revision Total Knee Arthroplasty: A Retrieval Analysis.
Kurtz MA, Gilbert JL, Shenoy AA, Klein GR, Malkani AL, Kurtz SM
Topics
Key Takeaway
Insufficient metaphyseal fixation at or near the modular junction—not patient weight or implant duration—is the primary driver of metal fatigue fracture in revision TKA, identified in 8 fractured components versus 489 stemmed controls.
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Summary
This retrieval study asked whether implant fixation quality, modular junction damage modes, and alloy microstructure contribute to metal fatigue fracture in revision TKA. Eight fractured components were analyzed with SEM and XPS alongside radiographic review and compared to 489 stemmed revision patients. Radiographs uniformly showed insufficient metaphyseal fixation at the modular junction; XPS confirmed an oxidized Ti-6Al-4V interface with intergranular corrosion, TiO increase (p<0.0001) and TiO2 decrease (p<0.0001) after sputter depth profiling, and fatigue crack propagation through both equiaxed Ti-6Al-4V and wrought CoCrMo grains.
Key Limitation
The fracture cohort of n=8 precludes multivariate analysis, making it impossible to isolate fixation quality from stem design geometry, alloy batch variability, or patient activity level as independent fracture predictors.
Original Abstract
Most revision total knee arthroplasty patients experience excellent clinical outcomes. However, case studies document rare occurrences of metal component fractures promoted by the high cycles and low stresses that occur during daily use. In vivo, the mechanism that initiates metal fatigue fracture remains unclear. To address this gap, we collected implants from two retrieval programs. We asked: (1) what is the role of implant fixation in promoting fatigue fracture? (2) within modular junctions, what damage modes are associated with crack initiation? (3) how do equiaxed Ti-6Al-4V and wrought CoCrMo microstructures influence crack propagation? First, we compared clinical data for n = 8 fracture and n = 489 stemmed revision patients. Then, we performed retrieval analysis, combining radiographs with scanning electron microscopy and X-ray photoelectron spectroscopy. We found no differences in weight (p = 0.07) or implantation time (p = 0.10) when comparing revision and fracture cohorts. Radiographs of fractured components showed insufficient metaphyseal fixation at or near the stem's modular junction. At the taper interface, we identified Ti-6Al-4V thread wear and CoCrMo pitting. Sectioning near a Ti-6Al-4V crack initiation site revealed an oxidized interface and an intergranular corrosion attack. On the free surface, TiO increased (p < 0.0001) and TiO 2 decreased (p < 0.0001) after 20 min of sputter time. Fatigue cracks propagated through equiaxed Ti-6Al-4V and wrought CoCrMo grains. These data support a hypothesized mechanism where insufficient implant fixation with bone or cement promotes localized damage accumulation within the modular junction, fatigue crack initiation and subsequent fracture.