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Comparative Study
. 2010 Oct;468(10):2734-8.
doi: 10.1007/s11999-010-1330-8. Epub 2010 Mar 30.

Rotational References for Total Knee Arthroplasty Tibial Components Change With Level of Resection

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Free PMC article
Comparative Study

Rotational References for Total Knee Arthroplasty Tibial Components Change With Level of Resection

Bradley P Graw et al. Clin Orthop Relat Res. .
Free PMC article

Abstract

Background: Various landmarks can guide tibial component rotational alignment in routine TKA, but with the deeper tibial resection levels common in complex primary and revision TKAs, it is unknown whether these landmarks remain reliable.

Questions/purposes: We asked whether three techniques for determining tibial component rotation based on local anatomic landmarks are reliable deeper tibial resection levels.

Patients and methods: The femoral transepicondylar axis was identified by three independent reviewers on MR images of knees from 24 men and 24 women and transposed at a traditional tibial resection level and at the level of the proximal, middle, and distal parts of the proximal tibiofibular joint. Three axes were drawn on axial slices at these levels: the geometric center of the tibial plateau to the medial 1/3 of the tubercle, the posterior condylar line of the tibia, and the largest mediolateral dimension of the tibia. These lines were compared with the transposed femoral epicondylar axis line.

Results: The posterior condylar line of the tibia is the least variable local landmark for tibial component positioning at deep resection levels.

Conclusions: Assuming the normal posterior condylar line of the tibia is visible at revision, setting the tibial component at 10° external rotation with respect to the posterior condylar axis of the tibia gets the tibial component within 10° of proper rotation in 86% to 98% of patients, even to the distal part of the proximal tibiofibular joint. The experienced surgeon then can adjust this position based on cues from an assortment of other axes.

Figures

Fig. 1
Fig. 1
A box and whiskers plot incorporating the measurements of all three observers is shown. The vertical axis represents the difference in degrees between the position of the measured axis and the reference femoral epicondylar axis. The line in the box denotes the median value, the upper and lower ends of the box span the central half of all the values, and the whiskers indicate the range of values. The TUB axis was the most accurate across all resection levels, but the ranges, as spanned by the error bars, were smallest with the PC axis. ML is the axis defined by the greatest mediolateral dimension of the tibial surface. PC is the posterior tibial condylar axis. TUB is the axis connecting the geometric center of the tibial plateau with the medial 1/3 of the tibial tubercle. Resection levels are 6–8 mm below the tibial surface, and the proximal (P), middle (M), and distal (D) levels of the proximal tibiofibular joint.
Fig. 2
Fig. 2
A graph shows the mean positions of the three axes in relation to the reference femoral epicondylar axis. The mean ML and PC axes moved toward internal rotation with deeper resection levels. In contrast, the mean TUB axis moved toward external rotation, and was the most accurate (closest to zero) across all resection levels.

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