Biomechanical Comparison of Pin and Tension-band Wire vs Novel Locking Plate Fixation in a Transverse Patellar Fracture Model in the Dog

Introduction
Surgical repair of patella fractures is recommended based on results of many human experimental and clinical studies; various methods of pin and tension-band wiring fixation have been described using the mid-shaft transverse fracture as a model. Similar methods of fixation have been recommended in the dog. There currently is no published evidence in the dog that documents overall success with this method of fixation. Additionally, there is a general consensus (unpublished) that this technique is not usually successful in the dog. Our objective was to evaluate a prototype locking plate and pin and figure-of-8 tension-band wire for fixation of mid-transverse patellar fractures in an ex vivo experimental dog model.

Materials and Methods
Cadaveric canine stifle joints were obtained from 10 adult mixed breed dogs (23-36 kg). Mid-transverse patella ostoetomies were randomly stabilized (in pairs) with either pin and figure-of-8 tension-band wire or prototype locking plate system. Cyclic loads were applied at 100% body weight (90° to 135° extension) at 1 Hz for 500 cycles. Success/failure was defined as ≤2 mm/>2 mm distraction at the fracture gap, respectively. Number of cycles at failure and distraction gap after cyclic testing were compared between each stabilization group using a paired Student’s t-tests; all constructs that survived cyclic testing were then tested in acute load to failure (stiffness and yield strength), and were similarly evaluated. Significance was set at P<0.05.  [...]