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High variability of proximal tibial asymmetry and slope: a CT data analysis of 15,807 osteoarthritic knees before TKA

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Knee Surgery, Sports Traumatology, Arthroscopy Aims and scope



As the correct rotational and sagittal alignment of the tibial tray are of key importance for optimal total knee arthroplasty (TKA) function, the objective of this study was to determine these individual variations in the proximal tibial geometry in terms of posterior tibial slope (PTS) and tibial surface asymmetry by analysing a large dataset of computer tomography (CT) information.


A retrospective two-part review was performed on 15,807 datasets that were generated during the design phase for a customized TKA implant. First, 15807 CAD (computer-aided-design) models derived from CT data were used to conduct the analysis on the variation of the PTS. Second, the axial cut of each proximal tibia in a consecutively selected subset of 2202 datasets was used to measure the tibial asymmetry.


The majority (65.5%) of tibiae had a posterior slope between 5° and 10°, while 26.5% of knees had a slope > 10°. The asymmetry measured as offset between the lateral and medial posterior boundaries was highly variable, with overall an increasing proportion of patients with high asymmetry with increasing tibial ML width. Only 14% of tibiae exhibited symmetric (< 2 mm offset) lateral and medial plateaus, and 22% had an offset > 5 mm.


This study from an extraordinary large data base reveals that tibial posterior slope and asymmetry of the tibial profile vary largely between patients receiving TKA with increasing tibial asymmetry with ML width. CT scans might help to preoperatively better select the best fitting TKA, otherwise surgeons intraoperatively will often have to deal with compromises regarding fitting, sizing and rotational issues.

Level of evidence

Retrospective case series, Level IV.

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This study received no funding.

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Correspondence to Andre Friedrich Steinert.

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Conflict of interest

One of the authors (SZ) is an employee of Conformis Inc (Billerica, MA, USA) and received compensations between 100,000 and 1,000,000. He also received stock values between 10,000 and 100,000. One of the authors (LS) received an intern research scholarship from Conformis Inc. One of the authors certifies that he (AS) has received personal fees for consultant teaching, during the study period, in an amount of less than USD 10,000 from Conformis Inc (Billerica, MA, USA), outside the submitted manuscript. One of the authors certifies that he (JB) has received personal fees for consultant teaching, during the study period, in an amount of less than USD 10,000, from Smith & Nephew (Smith & Nephew GmbH, Hamburg, Germany), Conformis Inc (Billerica, MA, USA) and DePuy Synthes (Umkirch, Germany), all outside the submitted manuscript.

Ethical approval

Since the present study is based on analysing anonymised CT data, IRB approval was not required. Any information that could identify patients was not used in the analysis. Investigators and Statistician dealt with anonymised data only. All procedures performed were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964. Declaration of Helsinki and its later amendments or comparable ethical standards.

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Every patient involved agreed by giving informed consent.

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Johannes Beckmann and Andre Friedrich Steinert share senior authorship.

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Meier, M., Zingde, S., Best, R. et al. High variability of proximal tibial asymmetry and slope: a CT data analysis of 15,807 osteoarthritic knees before TKA. Knee Surg Sports Traumatol Arthrosc 28, 1105–1112 (2020).

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