Factors Influencing the Stability of Stems Fixed with Impaction Graft in Vitro

Abstract

Mechanical stability of the stem is believed to be an important factor in successful impaction grafting in revision THA. We asked whether particle size, femoral bone deficiencies, stem design, graft composition, and impaction technique influenced the initial stability of the stem in vitro using model femora and human bone particles. Bone particles made with a reciprocating blade-type bone mill contained larger particles with a broader size distribution than those made by a rotating drum-type bone mill and had higher stiffness on compression testing. The stiffness on torsional testing decreased as the degree of proximal-medial segmental deficiencies increased. The stiffness and maximum torque in a stem with a rectangular cross section and wide anteroposterior surface were higher in torsional tests. Adding hydroxyapatite granules to the bone particles increased the torsional stability. To facilitate compact bone particles, we developed a spacer between the guidewire and modified femoral packers. This spacer facilitated compacting bone particles from the middle up to the proximal and the technique increased the amount of impacted bone particles at the middle of the stem and also improved the initial stability of the stem. Stem design and degree of deficiencies influenced stiffness in the torsional test and the addition of hydroxyapatite granules enhanced torsional stiffness.

Effect of synthetic bone replacement material of different size on shear stress resistance within impacted native and thermodisinfected cancellous bone: an in vitro femoral impaction bone grafting model

“…The degree of impaction correlated with mechanic stability (Albert et al 2008 ; Fosse et al 2004 , 2006b , 2006c ) and inversely with porosity of bone (Frei et al 2004 ). Relevant differences of mechanic properties of impacted bone were reported depending on different impaction procedures (Bavadekar et al 2001 ; Fosse et al 2004 ; Phillips et al 2006a , 2006b ) since cortical bone grafts reduced subsidence of femoral stems (Kligman et al 2003 ; Ohashi et al 2009 ; Omoto et al 2008 ; Putzer et al 2014b ). According to processing bone grafts with thermodisinfection an impairment of mechanic stability and alteration of the impaction behavior could be expected (Cornu et al 2003 ; Fölsch et al 2016b ; Fosse et al 2006b , 2006c ) and less numbers of impaction impulses indicate a different impaction behavior of native and thermodisinfected cancellous bone (Fölsch et al 2018 ).…”

“…Porosity of impacted native and processed cancellous bone decreased towards the tip of the stem since the performance of impaction was not found correlated with the degree of impaction (Fölsch et al 2018 ; Fosse et al 2004 , 2006b , c ; Frei et al 2005a ; Ohashi et al 2009 ; Phillips et al 2006b ) (Table 2 ). Reduced micromovement distal might be related to the increased density of impacted native and processed cancellous bone (Cornu et al 2009 ; Fölsch et al 2018 ).…”

“…8 ) (Frei et al 2005b ) since increased air in the proximal region of thermodisinfected cancellous bone was shown (Fölsch et al 2018 ). This could be related to differences of micromovement at the proximal and distal point of measurement in the thermodisinfected bone specimens compared with native bone (Ohashi et al 2009 ) (Table 2 ). Less micromovement at the distal point of measurement was a consistent behavior of impacted native and thermodisinfected cancellous bone also being supplemented with small and large granules (Table 2 ).…”

“…Quality and shape of bone grafts were shown to influence deformation behavior during impaction bone grafting (Fosse et al 2006b , 2006c ; Giesen et al 1999 ) and in the proximal region cement distribution appears mainly related to the shape of particles (Fölsch et al 2018 ; Frei et al 2004 , 2006 ; Ohashi et al 2009 ). The impaction of processed irradiated bone grafts achieved more stiffness than native bone and structurally altered bone revealed a reduced elastic modulus (Cornu et al 2003 , 2009 ) since different motion of implants was found related to the dose of applied irradiation (Costi et al 2013 ).…”

“…Increased stiffness and compactness was found for processed compared with native cancellous bone (Cornu et al 2003 , 2004 , 2009 ; Fosse et al 2006a ; Nguyen et al 2013 ; Oakley and Kuiper 2006 ). The reduction of height of processed cancellous bone correlated with improvement of mechanic properties (Fosse et al 2006a ; Giesen et al 1999 ) including an increase of rotational stiffness (Ohashi et al 2009 ; Oakley and Kuiper 2006 ). Different impaction behavior and biomechanical properties of irradiated compared with native cancellous bone regarding the size of the particles were reported (Cornu et al 2009 ) since good clinical results were shown for femoral impaction bone grafting using irradiated allogeneic bone (Howie et al 2010 ).…”