OLECRANIZATION OF THE PATELLA

Olecranization of the patella is a technique employed by some to maint ain the normal anatomic relationship of the femorotibial articulation following posterior cruciate ligament (PCL) repairs and reconstruction s. It involves temporarily placing a large diameter pin longitudinally through the patella and into the tibia. The patella thus becomes a bo ny shelf and, in theory holds the tibia forward protecting the knee fr om a posterior drawer force. This technique appears desirable in that it allows postoperative knee motion while theoretically affording prot ection to the PCL. Unfortunately, it is based on an erroneous concept that the spatial relationship of the patella and tibia remains constan t 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 st udied 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 degrees arc through which the patella traverses relative t o the tibia during knee flexion. The patellar arc is a 22 degrees 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 measu rement, radiographic measurement, and fluoroscopy, we found that olecr anization of the patella not only fails to protect the PCL, but actual ly induces a detrimental posterior drawer force during knee flexion. B ased on clinical experience and laboratory findings, we strongly recom mend that olecranization of the patella be abandoned as a means of pos toperative ligamentous protection following PCL repair or reconstructi on.