Dr.-Ing. Anne Gebert de Uhlenbrock (Lauf), Markus Flohr (Plochingen), Dr. Kim Lars Häußler (Plochingen)
Abstract-Text (inkl. Referenzen und Bildunterschriften)
Introduction
Knowledge of loads acting in TKR is essential for designing and testing. Data of Bergmann et al.1 builds a foundation for load determination. However, the data is bound to the patients investigated, which received a medium implant size.
Objective
1) Matching the patient cohort studied by 1 with the one treated in clinics. 2) Development of a loading approach which considers implant size.
Materials and Methods
A literature review about distribution of patients regarding body mass index (BMI) was conducted and compared with the BMI of the patient cohort used by 1. For implant size load adaptation, a correlation between patients" height, weight and implant size was developed based on literature. This correlation was transferred to the medium femoral component size and extrapolated to smaller and larger sizes.
Results
Obese patients are categorized in different BMI groups. The patient cohort of 1 had a BMI of ~30, which is scaled to BMI ~34 using High100 data1. 9% to 27% of TKR patients showed a BMI≥35 and 1% to 10% showed a BMI≥40 depending on the patient cohort2,3. To cover highly obese patients (BMI~40) using a linear approach as 1, an increase in load magnitude of 18% is derived.Correlating body height with weight, implant size and its anterior/posterior dimension (APD) a generalized equation was derived based on 4: Weight=BMI*((APD*2.83-10.83)/100)2
Assigning this equation to an exemplary femoral portfolio scaling factors depicted in Table1 were calculated.
Summary
With this loading approach, a wider patient spectrum is covered, which especially refers to more obese patient collectives3. Scaling the load over the portfolio allows for more adequate loading of larger and smaller sizes leading to a more adequate design development and foundation for testing.
References
1Bergmann et al.,PLoS ONE 2014 9(1):e86035
2Swedish Arthroplasty Registry 2022
3AOANJRR 2023
4Hu et al.,J Clin Res & Rep 2020 3(1):e31579