Olecranization of the patella

Olecranization of the patella is a technique employed by some to maintain the normal anatomic relationship of the femorotibial articulation following posterior cruciate ligament (PCL) repairs and reconstructions. It involves temporarily placing a large diameter pin longitudinally through the patella and into the tibia. The patella thus becomes a bony shelf and, in theory, holds the tibia forward, protecting the knee from a posterior drawer force. This technique appears desirable in that it allows postoperative knee motion while theoretically affording protection to the PCL. Unfortunately, it is based on an erroneous concept that the spatial relationship of the patella and tibia remains constant throughout knee flexion. Negative experience at our institution with this technique prompted our investigation. Using lateral radiographs of 20 normal knees taken at four different positions of flexion, we studied the relative motion that occurs between the patella and tibia in the sagittal plane during knee flexion from 0 degrees to 90 degrees, and defined two separate arcs of patellar motion. The patellar tendon arc is a 30 degree arc through which the patella traverses relative to the tibia during knee flexion. The patellar arc is a 22 degree arc on which the patella flexes relative to itself during knee flexion. We also studied the effect that olecranization of the patella has on the PCL in six cadaver knees. Using a combination of direct tension measurement, radiographic measurement, and fluoroscopy, we found that olecranization of the patella not only fails to protect the PCL, but actually induces a detrimental posterior drawer force during knee flexion.(ABSTRACT TRUNCATED AT 250 WORDS)