THE TENSILE PROPERTIES OF THE INTACT, REPAIRED AND RECONSTRUCTED MEDIAL PATELLO FEMORAL LIGAMENT

Abstract

We sought to identify the tensile properties of the medial patellofemoral ligament (MPFL), and determine whether its repair was sufficient as a means of restoring stability after acute lateral patella dislocation. We also sought to establish whether there was a correlation between the tensile properties of the anterior cruciate ligament (ACL) and the MPFL.

16 hind limbs of Merino Wethers were obtained and stored fresh frozen. The specimens were thawed overnight, dissected out and then placed in a water bath at 37 degrees centigrade for 30 minutes prior to testing. All testing was carried out in the water bath to approximate a more physiological environment. For each specimen the ACL was first tested to failure on an Instron 8511. The MPFL was then tested to failure, then repaired and retested to failure. Finally a reconstruction was carried out, using a flexor tendon, which was again tested to failure.

Results:

There was no correlation between ACL and MPFL strength (p=0.677). Statistical analysis showed that the intact MPFL was significantly stronger than the repaired MPFL (P=0.001) but no different to the reconstructed MPFL (P=0.224), with no difference between repaired and reconstructed (P=0.174). A Power analysis showed that there was not adequate power to detect a significant difference between the last two pairs, and that we would have needed over 35 specimens to show a difference.

This study does not support carrying out a repair of the MPFL following an acute lateral patella dislocation, as it does not restore its tensile properties. It further suggests that a reconstruction may better restore the tensile properties of this ligament.