Effect of cavity preparation and bone mineral density on bone‐interface densification and bone‐implant contact during press‐fit implantation of hip stems

Abstract

Implant loosening and periprosthetic fracture are two major revision causes for uncemented hip stems. The chosen method of cavity preparation could play a key role for both failure mechanisms. The aim of this study was to determine the dependence of the broach type as well as patient bone mineral density (BMD) on densification and contact conditions at the bone-implant interface. Hip stems were implanted into cadaveric femora using compaction, blunt extraction or sharp extraction broaches with computed tomography scans performed prior to broaching, after broaching and after stem implantation. Proximal periprosthetic bone densification as well as press-fit, contact area and stem seating relative to the last broach were determined. Median bone densification was higher with the compaction and blunt extraction broaches compared to sharp extraction broaches (181% and 177%, respectively, p ¼ 0.002). The bone densification of femora prepared with compaction broaching increased with higher BMD (R 2 ¼ 0.183, p ¼ 0.037), while stem seating decreased with higher BMD for all broach types (R 2 ¼ 0.259, p ¼ 0.001). Incomplete seated prostheses were associated with smaller press-fit and bone-implant contact area (R 2 ¼ 0.249, p ¼ 0.001; R 2 ¼ 0.287, p < 0.001). Clinical Significance: The results suggest that compaction broaching maximizes bone densification in patients with higher bone density.However, there appears to be an increased risk of insufficient stem seating in high-density bone that could limit the benefits for primary stability. For lower quality bone, the broach type appears to play a lesser role, but care must be taken to limit extensive stem seating which might increase periprosthetic fracture risk. ß

Topology Optimisation for Compliant Hip Implant Design and Reduced Strain Shielding

“…Aside from its increased compliance and the need for a powder drainage hole, this novel selectively hollowed stem is indistinguishable from the solid counterpart ( Figure 5 ), which may aid clinical translation, where each design change requires extensive testing and validation prior to clinical trial. For example, there is a complex interplay between broach design, technique and the stem to ensure suitable initial implant fixation [ 52 , 53 ]. Changing the outside shape of the stem would require the design of a new broach and re-validation to ensure that the desired fixation is achieved.…”

Subsidence and perioperative periprosthetic fractures using collarless hydroxyapatite-coated stem for displaced femoral neck fractures according to Dorr type

“…19,20 Several articles reveal the importance of BMD for treatment with uncemented collarless stem. 21,22 When inserting an uncemented femoral stem slightly larger than the prepared femoral canal, operation procedure can produce compression hoop stress. Lower bone density and different morphology can lead to different results.…”

Variability in Femoral Preparation and Implantation Between Surgeons Using Manual and Powered Impaction in Total Hip Arthroplasty

“…Unintentional shear forces as they may occur with manual techniques can lead to an inhomogeneous cavity and thus incongruent contact between the bone and the implant and reduced contact area. Besides the impaction approach variations in the contact area, the press-fit also depends on the bone quality [ 36 ]. However, this relation could not be confirmed in this study.…”

“…The large differences in the final implant seating observed for the powered impactions could be due to the lack of experience with the powered impaction device or the different haptic feedback compared to the mallet. This study was carried out using exclusively compaction broaches, and the results may be different using cutting extraction broaches especially for specimens with low BMD [ 36 ].…”