Towards planning of osteotomy around the knee with quantitative inclusion of the adduction moment: a biomechanical approach

Abstract

Purpose Despite practised for decades, the planning of osteotomy around the knee, commonly using the Mikulicz-Line, is only empirically based, clinical outcome inconsistent and the target angle still controversial. A better target than the angle of frontal-plane static leg alignment might be the external frontal-plane lever arm (EFL) of the knee adduction moment. Hypothetically assessable from frontal-plane-radiograph skeleton dimensions, it might depend on the leg-alignment angle, the hip-centre-to-hip-centre distance, the femur- and tibia-length. Methods The target EFL to achieve a medial compartment force ratio of 50% during level-walking was identified by relating in-vivo-measurement data of knee-internal loads from nine subjects with instrumented prostheses to the same subjects’ EFLs computed from frontal-plane skeleton dimensions. Adduction moments derived from these calculated EFLs were compared to the subjects’ adduction moments measured during gait analysis. Results Highly significant relationships (0.88 ≤ R2 ≤ 0.90) were found for both the peak adduction moment measured during gait analysis and the medial compartment force ratio measured in vivo to EFL calculated from frontal-plane skeleton dimensions. Both correlations exceed the respective correlations with the leg alignment angle, EFL even predicts the adduction moment’s first peak. The guideline EFL for planning osteotomy was identified to 0.349 times the epicondyle distance, hence deducing formulas for individualized target angles and Mikulicz-Line positions based on full-leg radiograph skeleton dimensions. Applied to realistic skeleton geometries, widespread results explain the inconsistency regarding correction recommendations, whereas results for average geometries exactly meet the most-consented “Fujisawa-Point”. Conclusion Osteotomy outcome might be improved by planning re-alignment based on the provided formulas exploiting full-leg-radiograph skeleton dimensions.

Higher Association of Pelvis-Knee-Ankle Angle Compared With Hip-Knee-Ankle Angle With Knee Adduction Moment and Patient-Reported Outcomes After High Tibial Osteotomy

“…A previous study on patients with a force-measuring knee implant reported significant correlations between the mediolateral load distribution and the external frontal plane lever arm (EFL), defined as the perpendicular line from the center of the knee joint to the line connecting the center of the ankle joint and the symphysis pubis. 6 These results supported the notion that the correlation between PKA and KAM peaks was higher than that between PKA and HKA before and after HTO because the concept of EFL when reflecting pelvic width is similar to PKA.…”

Correction to: Towards planning of osteotomy around the knee with quantitative inclusion of the adduction moment: a biomechanical approach

“…Author details 1 Fraunhofer Institute for Biomedical Engineering IBMT, Joseph-von-Fraunhofer-Weg 1, 66280 Sulzbach, Germany. 2…”

“…Author details 1 Fraunhofer Institute for Biomedical Engineering IBMT, Joseph-von-Fraunhofer-Weg 1, 66280 Sulzbach, Germany. 2 Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Zu Berlin and Berlin Institute of Health, Berlin, Germany.…”

“…1186/ s40634-021-00324-3. *Correspondence: margit.biehl@ibmt.fraunhofer.de 1 Fraunhofer Institute for Biomedical Engineering IBMT, Joseph-von-Fraunhofer-Weg 1, 66280 Sulzbach, Germany Full list of author information is available at the end of the article…”

“…In the original publication of this article [1], Additional files 1, 2 and 3 were incorrect. The formula in Additional file 1 must include the number “0.349” instead of “0.342”.…”