Comparison of 2 equine transfixation pin casts and the effects of pin removal.
Authors: Williams Jarred M, Elce Yvonne A, Litsky Alan S
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Transfixation Pin Cast Strain Comparison Transfixation pin casts (TPCs) are a cornerstone of equine fracture management, yet little evidence existed comparing different pin configurations or predicting how pin removal affects load distribution during healing. Williams and colleagues used a cadaver biomechanical model to test two common TPC designs—one with two threaded pins and one with four smooth Steinmann pins—whilst monitoring strain on the proximal phalanx under simulated weight-bearing loads ranging from 445 N to 5338 N. Both constructs significantly reduced strain on the dorsal cortex of P1 compared to uncasted limbs across nearly all loading ranges, with no meaningful difference between the two designs, suggesting that pin profile and thread characteristics are less critical than the overall constraint provided by the cast itself. Notably, proximal pin removal caused a 7–10% increase in strain depending on construct type, whilst distal pin removal increased strain by only 0.5–1%, indicating that proximal pins bear substantially greater load and their premature loss could compromise fracture stability. For practitioners, these findings suggest that both established TPC constructs offer comparable biomechanical protection and that careful monitoring or staged pin removal protocols should prioritise proximal pin integrity throughout the healing period.
Read the full abstract on PubMed
Practical Takeaways
- •Both 2-pin and 4-pin transfixation pin casts are mechanically equivalent for distal limb fracture support, allowing clinician choice based on patient factors and availability
- •Proximal pins are biomechanically critical to cast function; their removal should be delayed in fracture healing protocols, while distal pins may be removed earlier with minimal load redistribution
- •Progressive pin removal strategy should prioritize removing distal pins first to maintain structural integrity during early fracture healing
Key Findings
- •Both 2-pin and 4-pin transfixation pin cast constructs significantly reduced strain on the proximal phalanx compared to non-casted controls at all loads except 444.8 N
- •No significant difference in strain reduction was observed between the 2-pin positive profile construct and the 4-pin smooth pin construct
- •Proximal pin removal increased strain by 7% (2-pin) and 10% (4-pin), while distal pin removal increased strain by only 0.5% (2-pin) and 1% (4-pin)
- •Difference between proximal and distal pin removal effects was only statistically significant at high loads