Retropatellar forces after rupture of the PCL and patello-tibial transfixation: an in vitro study

Compared to injuries of the other knee ligaments, a rupture of the posterior cruciate ligament (PCL) is relatively rare. Treatment may be conservative or operative. A rupture that has been operated on temporarily can be stabilised using a Grammont patello-tibial transfixation (olecranisation). Flexion and extension between 30 degrees and 60 degrees are allowed. The advantage of this method is that it avoids complete immobilisation of the joint and also the reduction of pull on the PCL. However, patients treated with this method show long-term osteoarthritis of the retropatellar joint area. Our study aimed to show the distribution of forces at the dorsal patellar surface in the following: (1) knee with intact ligaments; (2) knee with PCL rupture; (3) knee with PCL rupture plus olecranisation. Fourteen fresh knee specimens were investigated in a Plitz/Wirth knee kinemator. The femur was fixed while the tibia was flexed between 5 degrees and 120 degrees. Pull was placed on the patella and on the dorsal side of the tibia with weights over the tendons of the quadriceps and the roots of the ischio-crural muscles. With the aid of a special measurement device in the patella, the medially laterally, proximally and distally acting forces in a movement cycle could be measured as well as the total retropatellar force in the above experimental setups.(ABSTRACT TRUNCATED AT 250 WORDS)