Clinical assessment of tibial polyethylene thickness: Comparison of radiographic measurements with as-implanted and as-retrieved thicknesses☆
Section snippets
Methods
We studied 66 posterior cruciate-retaining Anatomic Modular Knee (DePuy, Johnson & Johnson, Warsaw, IN) primary total knee arthroplasties that required revision of the tibial component for wear or osteolysis (Fig. 1). Single-leg standing anteroposterior radiographs (35 × 43 cm) were taken at 6 weeks after arthroplasty and again at less than 7 months (mean, 3 months) before revision.
The minimum polyethylene thickness of each compartment was measured on each radiograph via 2 methods and adjusted
Measurement reproducibility
Radiographic polyethylene thickness measurements were made to the nearest 0.1 mm. Mean differences between the first and second measurement within the same compartment were 0.1 ± 0.1 mm for each method. Caliper measurements of explanted polyethylene thickness were made to the nearest 0.01 mm. The mean difference between each pair of caliper observations was 0.08 ± 0.08 mm.
Comparison of methods
The metal-to-middle method proved to be significantly more accurate than the metal-to-metal method on the 6-week radiographs
Discussion
In this investigation, the metal-to-middle method proved to be a more accurate approach for estimating tibial polyethylene thickness than the more commonly used metal-to-metal method. The metal-to-middle method is more accurate because its accuracy is less compromised by anteroposterior tilt of the baseplate shadow. However, medially eccentric wear with the studied design closed the gap between the accuracy of the 2 methods. As the magnitude of medial compartment wear increased, the point of
References (13)
- et al.
The porous-coated anatomic total knee experience
J Arthroplasty
(1996) - et al.
Radiographic wear assessment in a total knee prosthesis
J Arthroplasty
(1996) - et al.
The Insall-Burstein total knee replacement in osteoarthritis
J Arthroplasty
(1999) - et al.
Accurate in vivo measurement of polyethylene wear in total knee arthroplasty
J Arthroplasty
(2002) - et al.
Osteolysis around cementless porous-coated anatomic knee prosthesis
J Bone Joint Surg Br
(1994) - et al.
The posterior stabilized total knee prosthesis
J Bone Joint Surg Am
(1995)
Cited by (0)
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No benefits or funds were received in support of this study.