Finite element analysis of shear stresses at the implant-bone interface of an acetabular press-fit cup during impingement / Finite-Elemente-Berechnung der Schubspannungen im Implantat-Knochen-Interface einer acetabulären Press-Fit-Pfanne bei Impingement

Abstract After total hip replacement (THR) impingement of the implant components causes shear stresses at the acetabular implant-bone interface. In the current study the finite element method (FEM) was applied to analyse the shear stresses at a fully bonded implant-bone interface assuming total ingrowth of the cup. The FE model of a press-fit acetabular component and the proximal part of the femoral component incorporates non-linear material and large sliding contact. The model was loaded with a superior-medial joint load of 435 N simulating a two-legged stance. Starting at initial impingement, the femoral component was medially rotated by 20°. The peak tilting shear stress of -2.6 MPa at the impingement site takes effect towards the pole of the cup. The torsional shear stress at the impingement site is zero. On each side of the impingement site, there are extrema of torsional shear stress reaching -1.8 and 1.8 MPa, respectively. The global peak shear stress during impingement may indicate a possible starting point for cup loosening. The pattern of the torsional shear stresses suggests that besides the symmetric lever-out, an additional asymmetrical tilting of the cup occurs that can be explained by the orientation of the applied joint load. Zusammenfassung Nach Hüftgelenkersatz kann Impingement (Anschlagen) der Implantatkomponenten Schubspannungen im acetabulären Implantat-Knochen-Interface verursachen. In der vorliegenden Studie wurde die Finite-Elemente-Methode (FEM) angewendet, um die Schubspannungen in einem durchgängig verbundenen Implantat-Knochen-Interface nach dem vollständigen knöchernen Einwachsen der Pfanne zu berechnen. Es wurde ein Finite-Elemente-Modell von einer acetabulären Press-Fit-Komponente und von dem proximalen Abschnitt einer femoralen Komponente erstellt. Das Modell berücksichtigt nichtlineares Materialverhalten und große Verschiebungen im Kontaktbereich. Während der Simulation des Zwei-Bein-Standes wurde das Modell mit einer superior-medial ausgerichteten Gelenkkraft von 435 N belastet. Die femorale Komponente wurde ausgehend von initialem Impingement um 20° nach medial rotiert. Der höchste Betrag der Kipp-Schubspannungen befindet sich mit -2,6 MPa an der Impingement-Stelle und ist in Richtung Pfannenpol orientiert. Die Torsions-Schubspannung ist an der Impingement-Stelle null. Auf beiden Seiten von der Impingement-Stelle liegt je ein Extremwert der Torsions-Schubspannung mit -1,8 und 1,8 MPa. Das globale Maximum der Schubspannung weist prinzipiell darauf hin, dass eine Impingement-Stelle ein möglicher Ausgangspunkt für die Pfannenlockerung sein könnte. Die Verteilung der Torsions-Schubspannungen deutet darauf hin, dass neben dem symmetrischen Hebelmechanismus eine zusätzliche asymmetrische Kippbewegung der Pfanne auftritt, die durch die Ausrichtung der aufgebrachten Gelenkkraft erklärt werden kann.

[1]  R Huiskes,et al.  Total hip reconstruction in acetabular dysplasia. A finite element study. , 1993, The Journal of bone and joint surgery. British volume.

[2]  D. D’Lima,et al.  Optimizing Acetabular Component Position to Minimize Impingement and Reduce Contact Stress , 2001, The Journal of bone and joint surgery. American volume.

[3]  T. Brown,et al.  Development and Physical Validation of a Finite Element Model of Total Hip Dislocation. , 1999, Computer methods in biomechanics and biomedical engineering.

[4]  H. Skinner,et al.  Constrained acetabular components. , 1994, The Journal of arthroplasty.

[5]  G. Bergmann,et al.  Hip contact forces and gait patterns from routine activities. , 2001, Journal of biomechanics.

[6]  D. Fisher,et al.  Constrained acetabular cup disassembly. , 1994, The Journal of arthroplasty.

[7]  R. Barrack,et al.  Virtual reality computer animation of the effect of component position and design on stability after total hip arthroplasty. , 2001, The Orthopedic clinics of North America.

[8]  R. Huiskes,et al.  Load transfer across the pelvic bone. , 1995, Journal of biomechanics.

[9]  R. Bader,et al.  [Ceramic cups for hip endoprostheses. 6: Cup design, inclination and antetorsion angle modify range of motion and impingement]. , 1999, Biomedizinische Technik. Biomedical engineering.

[10]  T. Brown,et al.  Salvage of a Recurrently Dislocating Total Hip Prosthesis with Use of a Constrained Acetabular Component. A Retrospective Analysis of Fifty-six Cases* , 1998, The Journal of bone and joint surgery. American volume.

[11]  J. Callaghan,et al.  Use of constrained acetabular components for hip instability: an average 10-year follow-up study. , 2003, The Journal of arthroplasty.

[12]  R Huiskes,et al.  Prestresses around the acetabulum generated by screwed cups. , 1994, Clinical materials.

[13]  John J Callaghan,et al.  Kinematics, kinetics, and finite element analysis of commonplace maneuvers at risk for total hip dislocation. , 2003, Journal of biomechanics.

[14]  B. K. Vaughn,et al.  Preliminary report on the S-ROM constraining acetabular insert: a retrospective clinical experience. , 1991, Orthopedics.

[15]  M. Ries,et al.  Effect of cementless acetabular cup geometry on strain distribution and press-fit stability. , 1997, The Journal of arthroplasty.

[16]  B. Kaper,et al.  Failure of a Constrained Acetabular Prosthesis of a Total Hip Arthroplasty. A Report of Four Cases* , 1998, The Journal of bone and joint surgery. American volume.

[17]  E. Schneider,et al.  The effect of interfacial parameters on cup-bone relative micromotions. A finite element investigation. , 2001, Journal of biomechanics.

[18]  E Steinhauser,et al.  Methode zur Evaluierung von Einflußfaktoren auf die Luxationsstabilität von künstlichen Hüftgelenken / Method for the Evaluation of Factors Influencing the Dislocation Stability of Total Hip Endoprotheses , 2004, Biomedizinische Technik. Biomedical engineering.

[19]  T D Brown,et al.  A Finite Element Analysis of Factors Influencing Total Hip Dislocation , 1998, Clinical orthopaedics and related research.

[20]  R. Brumback,et al.  Functional evaluation of the shoulder after transfer of the vascularized latissimus dorsi muscle. , 1992, The Journal of bone and joint surgery. American volume.

[21]  C. Jewett,et al.  The yielding, plastic flow, and fracture behavior of ultra-high molecular weight polyethylene used in total joint replacements. , 1998, Biomaterials.

[22]  T. Brown,et al.  Experimental and computational simulation of total hip arthroplasty dislocation. , 2001, The Orthopedic clinics of North America.

[23]  T. Brown,et al.  Salvage of Total Hip Instability With a Constrained Acetabular Component , 1998, Clinical orthopaedics and related research.