Computed tomography to identify preoperative guidelines for internal fixation of the distal sesamoid bone in horses: an in vitro study.
Authors: Perrin Roland, Launois Thomas, Brogniez Laurent, Desbrosse Francis G, Coomer Richard P, Clegg Peter D, Reda Ayalu A, Gehin Simon G, Vandeweerd Jean-Michel E
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Fractures of the distal sesamoid bone (navicular bone) in horses present a surgical challenge, particularly when internal fixation via lag screw is the chosen treatment; however, the optimal trajectory for screw insertion through this small, complex structure has not been clearly established. Using cadaveric equine forelimbs, researchers employed computed tomography imaging to map the three-dimensional anatomy of intact distal sesamoid bones and determine safe corridors for cortical screw placement along the longitudinal axis, with success defined as complete screw containment within bone without breaching articular or flexural surfaces. CT-guided placement of 3.5 mm implants achieved a satisfactory trajectory in 87% of attempts (7 of 8 limbs), compared to only 63% success with 4.5 mm screws (5 of 8 limbs), suggesting that smaller implants offer a wider margin for error within the bone's geometry. These findings provide evidence-based preoperative planning guidance for equine surgeons considering distal sesamoid fracture repair, though clinicians should note this was an in vitro study and would benefit from subsequent clinical validation. The superior performance of 3.5 mm implants warrants consideration when selecting hardware for this technically demanding procedure, potentially improving healing outcomes and reducing iatrogenic damage to crucial articular and tendon surfaces.
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Practical Takeaways
- •Use preoperative CT imaging to plan cortical screw insertion direction in distal sesamoid bone fractures—this significantly improves surgical outcomes
- •Prefer 3.5 mm cortical screws over 4.5 mm screws for distal sesamoid fixation based on higher success rates and better margin of safety within bone
- •CT-guided preoperative planning reduces risk of implant placement damaging critical articular surfaces and the flexor tendon
Key Findings
- •CT imaging successfully identified anatomic landmarks for 3.5 mm cortical screw insertion with 87% satisfactory placement (7/8 limbs)
- •4.5 mm implants showed lower success rate of 63% (5/8) for proper directional placement
- •Satisfactory placement required the entire screw length to remain within the distal sesamoid bone without damaging articular or flexural surfaces