Abstract
PurposeTo assess a novel method of three-dimensional (3D) joint line (JL) restoration based on the contralateral tibia and fibula.Methods3D triangular surface models were generated from computed tomographic data of 96 paired lower legs (48 cadavers) without signs of pathology. Three segments of the tibia and fibula, excluding the tibia plateau, were defined (tibia, fibula, tibial tuberosity (TT) and fibular tip). A surface registration algorithm was used to superimpose the mirrored contralateral model onto the original model. JL approximation and absolute mean errors for each segment registration were measured and its relationship to gender, height, weight and tibia and fibula length side-to-side differences analyzed. Fibular tip to JL distance was measured and analyzed.ResultsMean JL approximation did not yield significant differences among the three segments. Mean absolute JL error was highest for the tibia 1.4 ± 1.4 mm (range: 0 to 6.0 mm) and decreased for the fibula 0.8 ± 1.0 mm (range: 0 to 3.7 mm) and for TT and fibular tip segment 0.7 ± 0.6 (range: 0 to 2.4 mm) (p = 0.03). Mean absolute JL error of the TT and fibular tip segment was independent of gender, height, weight and tibia and fibula length side-to-side differences. Mean fibular tip to JL distance was 11.9 ± 3.4 mm (range: 3.4 to 22.1 mm) with a mean absolute side-to-side difference of 1.6 ± 1.1 mm (range: 0 to 5.3 mm).Conclusion3D registration of the contralateral tibia and fibula reliably approximated the original JL. The registration of, TT and fibular tip, as robust anatomical landmarks, improved the accuracy of JL restoration independent of tibia and fibula length side-to-side differences.Level of evidenceIV
Highlights
Restoration of the original joint line (JL) in total knee arthroplasty (TKA) remains crucial for optimal functional and clinical outcome [6] but challenging, especiallyThe aim is to restore the original anatomical JL as accurately as possible
We hypothesized that the JL can be restored accurately from the contralateral 3D registration including the tibial tuberosity and fibular tip as anatomical landmarks
A 3D coordinate system was defined according to [5]; z-axis equal directional vector as the anatomical tibia axis defined by an oriented bounding box (OBB) [26], x-axis: lateral, y-axis: anterior
Summary
Restoration of the original joint line (JL) in total knee arthroplasty (TKA) remains crucial for optimal functional and clinical outcome [6] but challenging, especiallyThe aim is to restore the original anatomical JL as accurately as possible. Landmarks as the epicondyles are prone to bony destruction and are not always identifiable in a revision setting To overcome these limitations, Maderbacher et al proposed to restore the JL based from the contralateral fibular tip using weight-bearing x-rays [14]. A growing interest has evolved regarding three-dimensional (3D) registration and planning based on the contralateral unaffected anatomy [4, 17] This method could potentially improve accuracy in JL restoration and be of high interest for planning revision TKA [22]. No JL restoration method based on the contralateral 3D registration exists to date, to the best of our knowledge It remains unclear which anatomical landmarks most reliably approximate the JL. We investigated the effect of anatomical side-to side differences and patient demographics on the accuracy of the JL restoration
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