A comparison of acute pull-out strength between two-way and one-way transfixation pin insertion for external skeletal fixation in canine bone.
This study tested the hypothesis that two-way insertion of an external skeletal fixator transfixation pin would weaken the pin-bone interface. Smooth and partially threaded (end) transfixation pins were placed in tibiae of 32 cadavers by slow speed drilling or hand placement through a predrilled pilot hole. In one bone of each tibial pair, pins were inserted 2 cm beyond the distal cortex and retracted to a predetermined position (two-way). In the contralateral limb, the pins were inserted in one forward motion to the predetermined position (one-way). The peak force (Newtons) required to extract the pins (pull-out strength) axially at a rate of 1 mm/sec was determined by using a universal testing machine. A significant (p < .05) decrease in pull-out strength was found in pins placed by two-way insertion (674 +/- 410) as opposed to one-way insertion (766 +/- 432). The results of this in vitro study suggest that one-way insertion should be used clinically to decrease weakening of the pin-bone interface and prevent possible failure of external fixators. A significantly greater pull-out strength was found for threaded pins placed in the proximal diaphysis (1459 +/- 330 Newtons) compared to the distal metaphysis (873 +/- 297 Newtons).
Department of Veterinary Clinical Medicine and Surgery, College of Veterinary Medicine, Washington State University, Pullman 99164-6610.
W S
WS
Dernell
J
J
Harari
D M
DM
Blackketter
D000818:Animals; D001858:Bone Nails / Q000662:veterinary*; D004285:Dogs / Q000293:injuries / Q000601:surgery*; D016267:External Fixators / Q000662:veterinary*; D005592:Fracture Fixation / Q000379:methods / Q000662:veterinary*; D013718:Tensile Strength; D013977:Tibia / Q000293:injuries / Q000601:surgery*