Biomechanical comparison of pin and tension-band wire fixation with a prototype locking plate fixation in a transverse canine patellar fracture model.
OBJECTIVE
To compare a locking plate (LP) with pin and tension-band wire (pin/TBW) for fixation of mid-patellar transverse fractures.


METHODS
Cadaveric canine stifle joints from 10 adult mixed breed dogs (23-36 kg) were used. Mid-patellar transverse osteotomies were randomly stabilized (in pairs) with either pin/TBW or a prototype LP. Cyclic loads (1 Hz, 500 cycles) at 100% body weight (90°-135° stifle joint extension), were applied. Survival or failure of constructs was defined as <2 mm fracture gap distraction at 500 cycles, or ≥2 mm fracture gap distraction at the number of cycles sustained, respectively. Number of cycles at failure and distraction gap were compared with a paired Student's t-test, and a survival analysis performed with a Mantel-Cox test. All constructs that survived cyclic testing were tested in single cycle load to failure (1.0 mm/sec; 110° stifle joint extension); yield strength was compared with a Wilcoxon rank sum test. Significance was set at p <0.05.


RESULTS
All 10/10 LP and three out of 10 pin/TBW fixations survived cyclic testing. Survival analysis, number of cycles at failure, and distraction gap all were significantly different between the two groups (p = 0.0011, p = 0.0013, and p <0.0001, respectively). Construct yield strength was not significantly different (p = 0.1273).


CONCLUSIONS
The failure mode with pin/TBW was consistently similar to failures observed clinically. The LP demonstrated consistent, reliable and stable fixation.
Sophie
S
Gibert
Michael P
MP
Kowaleski
Romano
R
Matthys
Reto
R
Nützi
Boris
B
Serck
Randy J. Boudrieau, DVM, Diplomate ACVS and ECVS, Department of Clinical Sciences, Tufts University School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA 01536, United States, Phone: +1 508 839 7960, E-mail: randy.boudrieau@tufts.edu.
Randy J
RJ
Boudrieau
D000818:Animals; D001696:Biomechanical Phenomena; D001858:Bone Nails / Q000662:veterinary*; D001860:Bone Plates / Q000662:veterinary*; D001864:Bone Wires / Q000662:veterinary*; D004285:Dogs / Q000293:injuries*; D005593:Fracture Fixation, Internal / Q000662:veterinary*; D050723:Fractures, Bone / Q000601:surgery / Q000662:veterinary*; D010329:Patella / Q000601:surgery
Biomechanical testing; canine; fracture gap; orthopaedic implant; patella