What is the trouble with trunnions?

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Tribology

Background:

• Adverse local tissue reactions (ALTRs) in total hip arthroplasty (THA) are increasingly linked to tribocorrosion debris from modular femoral stems.
• The diverse presentations and causes of ALTRs, along with biological responses, are critical factors in THA failure.

Purpose of the Study:

• To review clinical problems associated with modular stems since 1988.
• To identify THA design features linked to taper junction tribocorrosion.
• To characterize the debris and biological responses to taper tribocorrosion.

Main Methods:

• Systematic review of MEDLINE and EMBASE for studies on modular femoral stem failure modes.
• Second review focused on design features, debris characteristics, and biological responses to tribocorrosion.
• Included laboratory studies, case reports, and clinical evidence levels.

Main Results:

• Tribocorrosion-associated ALTR, taper junction dissociation, and stem fracture were reported failure modes.
• THA component features like trunnion geometry and large femoral heads are associated with tribocorrosion.
• Tribocorrosion debris (chromium-orthophosphate) may be more biologically reactive than standard wear debris.

Conclusions:

• An increase in ALTR publications related to modular hip prostheses is noted.
• Implant design changes (larger heads, smaller trunnions) and increased recognition contribute to reported issues.
• Future research should focus on analyzing retrieved implants, developing in vitro corrosion tests, and identifying ALTR biomarkers.