Fixation and Bone Remodeling Around a Low Stiffness Stem in Revision Surgery

Abstract

Femoral stems with reduced stiffness have the potential of decreasing stress shielding and could be an alternative in revision surgery when restoration of bone stock is required. We retrospectively reviewed 38 patients (40 stems) with a central core of cobalt-chromium surrounded by a polymer and an outer titanium mesh layer containing a proximal coating of hydroxyapatite/tricalcium phosphate; 30 of the 38 patients (32 hips) had a minimum 2-year followup. We impacted morselized allograft around the stem in 28 of 32 revisions. Repeated radiostereometric examinations showed medial, distal, and posterior migration (median, 0.21 mm, 0.17 mm, and 0.96 mm, respectively) of the femoral head center for up to 6 months followed by stabilization. Measurements of bone mineral density in the seven Gruen zones at 6 months revealed either a decrease (down to a median of 3%), no change, or a slight increase (up to 5%) followed by a further increase up to 2 years in three of the regions (2, 3, and 5). Conventional radiography at 2 years demonstrated graft remodeling and incomplete radiolucent lines in 19 hips, mainly in Regions 1 and 7. Two hips were reoperated on as a result of dislocation, but none of the stems had been revised.

Highly Crosslinked Polyethylene Does Not Reduce Aseptic Loosening in Cemented THA 10-year Findings of a Randomized Study

“…In four cases, some of the stem markers could not be visualized or had poor fixation, leaving insufficient number of markers or too high condition number in the stem segment. In these cases, the translation of the femoral head center was used [29]. Precision estimates of cup migration and proximal femoral head penetration in this study have been presented previously [11].…”

Strength and fracture mechanism of iron reinforced tricalcium phosphate cermet fabricated by spark plasma sintering

“…It has to be pointed out that the magnitude of the Young's modulus of the TCP/Fe cermet better fit the elastic properties of cortical bone (Young's modulus ~ 3-30 GPa [39,40]) than other HA/Ti [5,6] or HA/Ag [8] cermets with Young's modulus in the range of 50 to 80 GPa. Young's modulus closer to the stiffness bone is beneficial to avoid the stress shielding effect due to severe stress concentration on the implant-bone interface [43].…”

High strength, biodegradable and cytocompatible alpha tricalcium phosphate-iron composites for temporal reduction of bone fractures

“…The functional and safe reduction of bone fractures require load-bearing biocompatible materials with elastic modulus similar to that of cortical bone [1,2]. Traditionally, biocompatible metallic materials, such as stainless steel, cobalt-chromium alloys, titanium and its alloys, are used for internal fixation of fractures because of their high yield strength and toughness [3].…”