Abstract
BackgroundTotal hip replacement has recently followed a progressive evolution towards principles of bone- and soft-tissue-sparing surgery. Regarding femoral implants, different stem designs have been developed as an alternative to conventional stems, and there is a renewed interest towards short versions of uncemented femoral implants. Based on both experimental testing and finite element modeling, the proposed study has been designed to compare the biomechanical properties and clinical performance of the newly introduced short-stem Minima S, for which clinical data are lacking with an older generation stem, the Trilock Bone Preservation Stem with an established performance record in short to midterm follow-up.Methods/designIn the experimental study, the transmission of forces as measured by cortical surface-strain distribution in the proximal femur will be evaluated using digital image correlation (DIC), first on the non-implanted femur and then on the implanted stems. Finite element parametric models of the bone, the stem and their interface will be also developed. Finite element predictions of surface strains in implanted composite femurs, after being validated against biomechanical testing measurements, will be used to assist the comparison of the stems by deriving important data on the developed stress and strain fields, which cannot be measured through biomechanical testing. Finally, a prospective randomized comparative clinical study between these two stems will be also conducted to determine (1) their clinical performance up to 2 years’ follow-up using clinical scores and gait analysis (2) stem fixation and remodeling using a detailed radiographic analysis and (3) incidence and types of complications.DiscussionOur study would be the first that compares not only the clinical and radiological outcome but also the biomechanical properties of two differently designed femoral implants that are theoretically classified in the same main category of cervico-metaphyseal-diaphyseal short stems. We can hypothesize that even these subtle variations in geometric design between these two stems may create different loading characteristics and thus dissimilar biomechanical behaviors, which in turn could have an influence to their clinical performance.Trial registrationInternational Standard Randomized Controlled Trial Number, ID: ISRCTN10096716. Retrospectively registered on May 8 2018.
Highlights
Total hip replacement has recently followed a progressive evolution towards principles of bone- and soft-tissue-sparing surgery
We can hypothesize that even these subtle variations in geometric design between these two stems may create different loading characteristics and dissimilar biomechanical behaviors, which in turn could have an influence to their clinical performance
As Total hip arthroplasty (THA) is increasingly being performed in patients who are younger and more active, the need for better implant design for bone and soft tissue preservation is mandatory; short, uncemented femoral implants are an alternative considering that they provide the following theoretical advantages [62,63,64,65,66,67,68]: (1) demonstrate more physiological load transfer distribution to the proximal femur, reducing proximal stress shielding, (2) facilitate minimally invasive surgical techniques, (3) preserve metaphyseal bone stock by a more proximal fixation, (4) provide more favorable conditions in the potential revision setting, (5) are viable alternatives in cases of metaphyseal-diaphyseal mismatch and (6) have decreased rates of thigh pain
Summary
Total hip replacement has recently followed a progressive evolution towards principles of bone- and soft-tissue-sparing surgery. Different stem designs have been developed as an alternative to conventional stems, and there is a renewed interest towards short versions of uncemented femoral implants. A rigid primary fixation and a larger area of metaphyseal contact are the essential requirements for a successful osteointegration of these shorter stems with an ultimate goal to produce a more physiological load transfer to the femur eliminating the stressshielding effect of the standard long stems. These hypothetical benefits still need to be verified [11]
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