Abstract
PurposeThe purpose of the present study was to correlate highly accurate CT measurements of pre-revision total knee arthroplasty (TKA) implant position with findings of retrieval analysis post-revision, to understand the clinical relevance of TKA orientation.MethodsThis study involved 53 retrieved TKA implants with pre-revision 3D-CT scans used to determine coronal (varus–valgus), sagittal (tibial slope) and rotational (internal rotation–external rotation) TKA orientation as well as tibiofemoral leg axis. Differences between femoral and tibial angles to describe the "relative rotational mismatch" were also calculated. All tibial inserts were forensically analyzed using the Hood score. Statistical analysis was performed to investigate correlations between TKA component orientation and surface damage (p < 0.05).ResultsFemoral components were found to have axial rotations mainly within ± 3° (68%), whilst 45% of the tibial components and 66% of the relative rotational mismatches were > 3° and < − 3°, respectively. The majority of femoral and tibial components (87% in both cases), as well as the femorotibial angle (70%), showed coronal orientations within ± 3°. The 64% of the tibial components showed posterior tibial slopes out of both the 0°–3° and 5°–7° ranges. There was a significant correlation between tibial slope and damage score on polyethylene tibial inserts (r = 0.2856; p = 0.0382) as well as a significant correlation between implants’ position in the axial plane and damage score on polyethylene tibial inserts (r = 0.6537, p = 0.0240).ConclusionsThis is the first study to use accurate measurements from pre-revision 3DCT to compare tibial and femoral orientation in all three planes with retrieval findings in total knee replacements. A significant correlation between implant position and polyethylene surface damage was found. These results showed the importance of optimizing component position to minimize polyethylene damage. Further analysis involving more accurate polyethylene wear measurements are fundamental to fully understand the role of components’ orientation in TKAs.
Highlights
Materials and methodsTotal knee arthroplasty (TKA) is a common intervention with an excellent survival rate; up to 20% of patients have reported poor outcomes, leading to revision [1]
The 3D-computed tomography (CT) imaging revealed that 68% of the femoral components had a rotation within ± 3°, whilst the rest showed rotations smaller than − 3°. 43% of the tibial components showed orientations ± 3°, whilst 45% and 12% had axial rotations greater than 3° and smaller than − 3°, respectively
The most important finding of the present study was a significant correlation between relative rotational mismatch and the severity and location of polyethylene damage in implants revised for malposition
Summary
Total knee arthroplasty (TKA) is a common intervention with an excellent survival rate; up to 20% of patients have reported poor outcomes, leading to revision [1]. This phenomenon has global dimensions: the demand for revision of TKAs is projected to grow by 601% between 2005 and 2030 in the United States [2] and the same trend is expected in Europe and Asia Pacific [3, 4]. The most commonly reported reasons for revision are aseptic loosening, pain, infection, instability, stiffness, polyethylene wear, malposition, patellofemoral problems and dislocation/subluxation [1, 5,6,7,8,9]. Suboptimal flexion was found in cruciate retaining TKA with reduced posterior tibial slope [16]
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