Influence of Different Damage Patterns of the Stem Taper on Fixation and Fracture Strength of Ceramic Ball Heads for Total Hip Replacement

Abstract

Background. Modularity finds frequent application in total hip replacement, allowing a preferable individual configuration and a simplified revision by retaining the femoral stem and replacing the prosthetic head. However, micromotions within the interface between the head and the stem taper can arise, resulting in the release of wear debris and corrosion products. The aim of our experimental study was to evaluate the influence of different taper damages on the fixation and fracture stability of ceramic femoral heads, after static and dynamic implant loading. Methods. Ceramic ball heads (36 mm diameter) and 12/14 stem tapers made of titanium with various mild damage patterns (intact, scratched, and truncated) were tested. The heads were assembled on the taper with a quasistatic load of 2 kN and separated into a static and a dynamic group afterwards. The dynamic group (n=18) was loaded over 1.5 million gait cycles in a hip wear simulator (ISO 14242-1). In contrast, the static group (n=18) was not mechanically loaded after assembly. To determine the taper stability, all heads of the dynamic and static groups were either pulled off (ASTM 2009) or turned off (ISO 7206-16). A head fracture test (ISO 7206-10) was also performed. Subsequent to the fixation stability tests, the taper surface was visually evaluated in terms of any signs of wear or corrosion after the dynamic loading. Results. In 10 of the 18 cases, discoloration of the taper was determined after the dynamic loading and subsequent cleaning, indicating the first signs of corrosion. Pull-off forces as well as turn-off moments were increased between 23% and 54% after the dynamic loading compared to the unloaded tapers. No significant influence of taper damage was determined in terms of taper fixation strength. However, the taper damage led to a decrease in fracture strength by approximately 20% (scratched) and 40% (truncated), respectively. Conclusion. The results suggest that careful handling and accurate manufacturing of the stem taper are crucial for the ceramic head fracture strength, even though a mild damage showed no significant influence on taper stability. Moreover, our data indicate that a further seating of the prosthetic head may occur during daily activities, when the resulting hip force increases the assembly load.

Efficacy of hydrated phospholipid polymer interfaces between all‐polymer bearings for total hip arthroplasty

“…3,4 Ceramic femoral heads could be an alternative to metal femoral heads in THAs, but they present limitations for revision surgery. 34 The concern is that the trunnion is likely to be damaged during the removal of the femoral head, and these damaged areas may lead to increased stress, responsible for initiating fractures in newly implanted ceramic femoral heads. If the head is not securely fixed onto the damaged taper, there may be a risk of increased wear due to abnormal movements at the head-stem neck junction.…”

“…Although the true clinical incidence of ALTR caused by metal taper corrosion is not well known, ALTR has been considered a serious complication 3,4 . Ceramic femoral heads could be an alternative to metal femoral heads in THAs, but they present limitations for revision surgery 34 . The concern is that the trunnion is likely to be damaged during the removal of the femoral head, and these damaged areas may lead to increased stress, responsible for initiating fractures in newly implanted ceramic femoral heads.…”

“Off-label” Usage of an Oxidized Zirconium Femoral Head in Revision of a Total Hip Arthroplasty with Mechanically Assisted Crevice Corrosion and a Legacy Taper

“…In addition, for large tapers such as the 14/16 used in this case, prefabricated ceramic heads may not be available. Likewise, the use of a ceramic head without at Ti (Ti) sleeve is thought to be at high risk for fracture [35] and is "off-label," although it has been performed successfully with minor existing trunnion damage and followed up to mid-term [36,37]. "Off-label" usage of a femoral head from another manufacturer is also a possibility but may be difficult because even tapers of the same nominal size may be different [38] and reliable seating is not guaranteed [39].…”

Comparative study by the finite element method of three activities of a wearer of total hip prosthesis during the postoperative period

“…The results show that careful handling and precise fabrication of the stem taper are critical for the fracture resistance of the ceramic head, although minor damage has no significant effect on taper stability. Furthermore, the obtained data suggest that further seating of the prosthetic head may occur during daily activities if synthetic hip forces increase the assembly load (Vogel et al 2020).…”