Using Statistical Shape Models to Optimize TKA Implant Design

Ingrid Dupraz,Julien Deckx,Arthur Bollinger,Michael Utz,Ronja Alissa Schierjott,Marnic Jacobs

doi:10.3390/app12031020

Abstract

(1) TKA implants should well fit on each patient’s anatomy. Statistical Shape Models (SSM) statistically represent the anatomy of a given population. The aims of this study were to assess how to generate a valid SSM for implant design and provide guidelines and examples on how to use the SSMs to evaluate the anatomic fit of TKA components. (2) Methods: A Caucasian SSM was built from 120 anatomies (65 female, 55 male) and an Asian SSM was based on 112 patients (75 female, 37 male). These SSMs were used to generate a database of 20 bone models. The AP/ML dimensions of the bone models were compared to those of the input population. Design input parameters, such as the tibial contour, trochlea, and femur curvature were extracted from the SSMs. Femur and patella components were virtually implanted on the bone models. (3) Results: the dimensions of the generated bone models well represented the population. The overhang of the femoral component as well as the coverage and peak restoration of the patella component were visualized. (4) Conclusions: SSMs can be used to efficiently gain input into TKA design and evaluate the implant fit on the studied population.

Highlights

To restore good function of the knee joint, total knee arthroplasty (TKA) implants should fit well to each patient’s anatomy
The t-test performed on the combined Statistical Shape Models (SSM) showed significant differences (p < 0.05) for 3 modes for the femur, 5 modes for the tibia and 3 modes for the patella
Comparing the global SSM with the subgroup SSMs allowed to draw conclusions about the main differences between the anatomies of each subgroups: the Caucasian SSMs were broad in ML, the male Asian SSM were large in AP, and the intercondylar notch of the female Asian SSM proved to be narrow

Summary

Introduction

To restore good function of the knee joint, total knee arthroplasty (TKA) implants should fit well to each patient’s anatomy. A good fit of the component is crucial to obtain good kinematics and a stable knee joint. Overhang of the component can cause soft-tissue irritation [1,2], while overstuffing of the patella can lead to anterior knee pain [3]. A good fit between the anterior shield and the trochlea is vital to restore satisfying patellofemoral kinematics [4]. Sufficient bone coverage is important [5] while overhang should be avoided to prevent soft-tissue irritations [1,6]. Finding a design that fits each patient well is very challenging, as bone morphology greatly varies among patients. Other factors, such as gender and pathology, influence the bone morphology

Objectives

Methods

Results

Conclusion