Evaluation of a Novel Screw Position in a Type III Distal Phalanx Fracture Model: An Ex Vivo Study.

The research aims to assess a new screw position used in repairing type III distal phalanx fractures and to look at the possible risks of solar canal penetration. The study found that the more distal screw positioning allows for a more rigid fracture fixation, but carries a higher risk of solar canal penetration.

Methods

• The experimental study was conducted using 24 disarticulated equine hooves and 24 isolated distal phalanges. These were cut in a sagittal plane and repaired with one of two different cortical screw placements in a lag fashion.
• The two groups differed in the placement of the screw. In group 1, the screw was inserted halfway between the proximal border of the solar canal and the subchondral bone surface on a line parallel to the dorsal cortex. For group 2, the screw was inserted more palmar/plantar.
• The strength of the construct was evaluated by three-point bending to failure. Solar canal penetration was assessed both by CT imaging and macroscopically.

Results

• The screws were longer in group 2 and in forelimbs. As such, the distal phalanges in group 2 had a more rigid fixation as compared to the conventional screw position with maximum point at failure 31% and bending stiffness 41% higher.
• A reduction in the lumen of the solar canal was observed in 13 out of 52 specimens, all of which belonged to group 2, out of which nine were forelimbs.

Conclusions

• The research concludes that more distal screw positioning, when compared to the conventional screw position, allows for the placement of a longer screw and renders a more rigid fracture fixation. This new strategy can be beneficial in the treatment of type III distal phalangeal fractures.
• However, the study also raises concerns about the higher risk of solar canal penetration associated with the novel screw position. This potential risk needs to be taken into account when considering this strategy for patient care.