Positional stability of polylactide pins with various surface textures in sheep tibia

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Polymer Chemistry

Background:

• Resorbable pins are used in orthopedic surgery for bone fixation.
• Pin loosening is a common complication, influenced by material properties and surface characteristics.
• Understanding factors affecting implant stability is crucial for improving patient outcomes.

Purpose of the Study:

• To evaluate the effect of surface geometry (smooth vs. textured) and polymer composition on the positional stability of resorbable pins in sheep tibiae.
• To determine if pin swelling and bone ingrowth contribute to implant anchoring and prevent loosening.
• To compare the performance of poly(L-lactide) (PLLA), poly(L/D-lactide) (PLDLA), and poly(L/DL-lactide) (PLDL) pins.

Main Methods:

• Resorbable pins were fabricated using injection molding from PLLA, PLDLA, and PLDL polymers.
• Pins featured either a smooth or textured surface.
• Pins were implanted into sheep tibiae, and their positional stability was assessed post-implantation.

Main Results:

• Smooth PLLA pins showed a loosening rate of 9.4% (3 out of 32).
• Smooth PLDLA and PLDL pins exhibited no loosening, suggesting swelling-induced expansion may enhance stability.
• Textured pins, regardless of polymer composition, demonstrated no loosening, with evidence of new bone ongrowth securing implant anchorage.

Conclusions:

• Both polymer composition (promoting swelling) and surface texture (enabling bone ingrowth) significantly enhance the positional stability of resorbable orthopedic pins.
• Textured surfaces appear to provide superior implant anchoring through direct bone apposition.
• The choice of resorbable polymer and surface design are critical factors in preventing implant loosening in orthopedic applications.