Impingement pressure and tension forces of the anterior cruciate ligament.

This study examined the impingement behavior of the uninjured ACL and the impingement pressure and tension forces of the ACL to draw conclusions for ACL reconstructions. A miniature pressure sensor was inserted between the ACL and the intercondylar roof of 15 knees of human cadavers before and after a 3-mm notch roof resection (thickness of the sensor); tension of the ACL was measured after attaching the tibial insertion to a load cell. A long-arm goniometer was used to determine corresponding extension angles. The beginning of contact of the ACL with the notch roof was between -1 and -2 degrees of knee extension. Pressure for full passive extension was 855.6+/-279.1 and 346.4+/-287.7 kPa, and ACL tension averaged 101.9+/-38.4 N. Tension forces in passive hyperextension were higher than those detected when a 200-N Lachman test was performed (83.5+/-25.1 N). There was a significant correlation between extension capability and impingement pressure. Impingement of the ACL was detected in all knees. Full passive extension exerts biomechanical pressure and tension on the ACL. Tension forces of the ACL are higher in passive hyperextension than during a Lachman test with 200 N. The impingement behavior found for the uninjured ACL is simulated in an ACL reconstruction when the center tibial tunnel position is used.