Comparison of Cannulated Screw With Tension Band Wiring Versus Compressive Cannulated Locking Bolt and Nut Device (CompresSURE) in Patella Fractures—A Cadaveric Biomechanical Study

Abstract

The purpose of this study was to determine if proximity of cannulated lag screws to the articular surface of the patella combined with the tension band technique affects resistance to fracture gap opening, and if an alternative locking nut and bolt device without a tension band behaves in a biomechanically similar fashion. Thirty-three cadaveric knees were allocated to 3 transverse patella fracture fixation groups: cannulated lag screw placement close to the articular (TBA) or non-articular (TBNA) surface with tension, and placement of a compressive locking nut and bolt device without tension band (CompresSURE) close to the articular surface. Knees were cycled through flexion-extension motion for 1000 cycles during which the fracture gap opening was quantified after the first flexion-extension cycle and after the 1,000 th cycle using an optoelectronic motion analysis system. After the first range of motion cycle, there was no significant difference in fracture gap opening between the 3 groups on the articular surface (P > 0.600). Total fracture gap displacement after the 1,000 th cycle was not significantly different between groups (P > 0.408). In general and irrespective of fixation technique, fractures opened in a wedge-like fashion with larger measured gap on the ventral surface relative to the articulating surface. When combined with the tension band, the proximity of cannulated lag screws to the articular surface did not affect resistance to fracture gap opening. Additionally, the stand-alone CompreSURE cannulated locking nut and bolt device without tension band was able to resist fracture gap opening in transverse fractures as effectively as the cannulated screw with tension band technique.