A pilot trial comparing the tear-out behavior in screw-sockets and cemented polyethylene acetabular components - a...

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Biomechanics

Background:

• Removal of well-fixed acetabular components after total hip arthroplasty (THA) is challenging and can lead to bone loss.
• Optimal fixation methods for acetabular components remain debated.

Purpose of the Study:

• To compare the tear-out resistance and failure behavior of osseointegrated versus non-integrated screw cups.
• To examine differences between screw cups and cemented polyethylene cups regarding stability.

Main Methods:

• Tear-out testing was performed on ten human coxal bones from cadavers.
• Tested acetabular components included osseointegrated screw cups (n=4), non-integrated screw cups (n=3), and cemented polyethylene cups (n=3).
• Axial failure load and mechanical work for tear-out were measured to assess stability.

Main Results:

• Osseointegrated screw cups showed slightly higher tear-out resistance (1.61±0.26kN) than non-integrated screw cups (1.23±0.39kN).
• Cemented polyethylene cups exhibited the lowest tear-out resistance (1.18±0.24kN).
• Failure patterns differed between screw sockets and cemented polyethylene cups.

Conclusions:

• Osseointegration did not significantly enhance the axial tear-out stability of cementless screw cups.
• The bone-implant interface strength of cementless screw cups appears comparable to cemented polyethylene cups.
• Acetabular component removal should utilize osteotomes or curved cutting devices, not tear-out, to preserve bone stock.