title: Femoral strain changes after total hip arthroplasty--patient-specific finite element analyses 12 years after operation.
abstract: Periprosthetic stress-shielding after total hip arthroplasty (THA) is a well-known phenomenon. Many authors have used the finite element (FE) method to show the effects of THA on animal or human femora. In most cases they have performed cadaver experiments. The current project is a FE analysis based on a retrospective computerized tomography (CT) in vivo data set of 11 patients 12 years after THA. In order to control the analysis, a computationally created stem was implanted at the femur model of the not operated contralateral side. In comparison to the not operated side, there was a significant reduction of the strain energy density (SED) values in all regions of interest (ROI) with the greatest effect near the distal tip of the stem. Only zone 1 showed no clear trend which may be due to load application at the greater trochanter causing local strain peaks. The median SED values changed by -31.65% (ROI 1), -25.64% (ROI 2), -30.82% (ROI 3), -12.35% (ROI 4), -40.10% (ROI 5), -30.37% (ROI 6) and -43.38% (ROI 7). As far as we are aware, the current combination of in vivo CT density data with FE strain analyses after THA is based on the largest number of patients and the longest follow-up period. This combination enables analysis and prediction of the influence of implantation upon bone and can be compared with of remodelling theories. The assessment of mechanical strain data during a follow-up trial could be a new approach for analyzing different hip stems in clinical biomechanics.
authors.affiliation: Clinic of Orthopaedic Surgery and Traumatology, Hessisch Lichtenau, Germany; Department of Orthopaedic Surgery, Philipps-University of Marburg, Germany. mlengsfeld@lichtenau-ev.de
authors.forename: Markus
authors.initials: M
authors.lastname: Lengsfeld
authors.forename: Rene
authors.initials: R
authors.lastname: Burchard
authors.forename: Daniel
authors.initials: D
authors.lastname: Günther
authors.forename: Thomas
authors.initials: T
authors.lastname: Pressel
authors.forename: Jan
authors.initials: J
authors.lastname: Schmitt
authors.forename: Ronald
authors.initials: R
authors.lastname: Leppek
authors.forename: Peter
authors.initials: P
authors.lastname: Griss
mesh_terms: D000328:Adult; D000497:Alloys / Q000737:chemistry; D019644:Arthroplasty, Replacement, Hip; D016477:Artifacts; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000473:pathology*; D020342:Finite Element Analysis; D006615:Hip / Q000473:pathology; D006622:Hip Prosthesis; D006801:Humans; D008875:Middle Aged; D013314:Stress, Mechanical; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D014057:Tomography, X-Ray Computed
chemical_list: D000497:Alloys; D014025:Titanium