The Effect of Drill Hole Size on the Fixation Strength of a Cemented Prosthetic Patellar Button

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This study used a cadaver model to analyze different patellar preparations compared to the standard technique described for the Duracon (Stryker, Mawah, New Jersey) all polyethylene patellar component. This was done to determine which method provides the best reduction in shear stress across the bone-prosthesis interface.

All patellae underwent the standard bony preparation recommended for implantation of a 33X9-mm all-polyethylene symmetric patellar button based on manufacturer guidelines. The patellae were then randomly assigned to 1 of 3 preparations: a standard chamfered preparation, 4.5- or 9.5-mm diameter drill and then cemented into place. The entire construct was then mounted to a servohydraulic testing machine, cycled between 0 N and 50 N, and then tested to failure. The mean forces obtained prior to failure were 258.5 N, 293 N, 353.1 N (chamfer, 4.5 mm, and 9.5 mm, respectively).

A statistical difference was noted in strength to failure between the 9.5 mm preparation and the chamfer preparation. A finite element model was also used to correlate results. The creation of larger diameter holes in the patella statistically reduces shear stress across the bone-prosthesis interface. This information may assist in the reduction of patellar implant failures.

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