Mechanical evaluation of pin and tension-band wire factors in an olecranon osteotomy model.
OBJECTIVE
To evaluate the effect of altering pin and wire diameter, wire position and configuration, and osteotomy angle on applied load and absorbed strain energy in a pin and tension-band wire (PTBW) fixation model.


METHODS
In vitro mechanical study.


METHODS
Delrin models (n=96).


METHODS
PTBW was applied to Delrin olecranon osteotomy models. A control configuration was defined and then altered, 1 variable (wire diameter, pin diameter, wire-hole position, wire configuration, osteotomy angle) at a time, to create 11 test configurations. Tensile force was applied and displacement at the caudal aspect of the osteotomy was measured. Fixation strength, in terms of tensile load and strain energy, was compared between control and each test configuration at 4 osteotomy displacements.


RESULTS
Models with larger wire, pins, or combined figure-of-eight/lateral wires were stronger than control, whereas those with smaller wire, pins, or a solitary lateral wire were weaker. The superior strength of the larger wire was apparent for all assessed osteotomy displacement.


CONCLUSIONS
PTBW fixation strength increases as implant diameter is increased, with wire diameter having greatest effect. Lateral wire configuration is weaker than figure-of-eight, but can be added to figure-of-eight configuration to increase strength. Wire-hole position and osteotomy angle have little effect on PTBW strength.


CONCLUSIONS
Wire diameter is the key determinant of PTBW strength, whereas pin diameter is somewhat less critical. Wire passage through an additional hole proximally provides equivalent strength and may avoid soft-tissue entrapment and subsequent loosening.
Neat
Benjamin C
BC
Department of Veterinary Clinical Sciences, Davis Medical Research Center, The Ohio State University, Columbus, OH 43210, USA. neatben@yahoo.com
Kowaleski
Michael P
MP
Litsky
Alan S
AS
Boudrieau
Randy J
RJ
D000818:Animals; D001696:Biomechanical Phenomena; D001864:Bone Wires / Q000662:veterinary*; D004285:Dogs / Q000293:injuries* / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000662:veterinary*; D006810:Humeral Fractures / Q000601:surgery / Q000662:veterinary*; D008953:Models, Anatomic; D010027:Osteotomy / Q000295:instrumentation / Q000662:veterinary*; D013718:Tensile Strength