In vitro mechanical evaluation of a novel pin-sleeve system for external fixation of distal limb fractures in horses: a proof of concept study.
Authors: Brianza Stefano, Brighenti Vittoria, Boure Ludovic, Sprenger Victor, Pearce Simon, Schwieger Karsten
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Pin-Sleeve Cast System for Equine Distal Limb Fractures Researchers evaluated a novel pin-sleeve cast (PSC) system as an alternative to the established transfixation pin cast (TPC) for external fixation of distal limb fractures in horses, recognising that pin loosening remains a significant clinical complication. Using bone substitutes under axial compression loading, they tested four PSC configurations with varying pin preloads against a standard TPC, measuring axial displacement and peri-implant strain with strain gauges, supplemented by failure and fatigue testing. The PSC system—particularly at highest pin preload—demonstrated significantly reduced peri-implant strain compared with TPC whilst maintaining equivalent axial displacement, and pin preload correlated inversely with displacement but not with strain; notably, the PSC system endured over 200,000 fatigue cycles, though it showed earlier plastic deformation during failure testing. These mechanical findings suggest that the PSC configuration could reduce pin loosening risk, a persistent problem affecting healing outcomes and requiring premature cast removal in equine practice. Whilst this in vitro work provides promising proof of concept, clinical validation in actual fracture cases is essential before widespread adoption, particularly regarding the interaction between the preload characteristics and long-term biological response at the pin-bone interface.
Read the full abstract on PubMed
Practical Takeaways
- •The pin-sleeve cast system may offer advantages over traditional transfixation pin casts by reducing strain around implants, potentially decreasing pin loosening complications
- •Proper pin preload adjustment appears critical—higher preload improves displacement control but clinicians should monitor for plastic deformation risk
- •This is preliminary in vitro work; clinical trials in live horses are needed before adoption into practice
Key Findings
- •PSC system with highest pin preload showed significantly lower axial displacement compared to TPC system
- •All PSC configurations demonstrated significantly reduced peri-implant strain compared to TPC system
- •Pin axial preload inversely correlated with axial displacement but had no effect on axial strain
- •PSC system withstood >200,000 fatigue cycles and has potential to reduce pin loosening risk