Volume 7, Issue 8 (September 2010)
Relative Motion of ACL Insertion Points In Vivo: A Case Study, Including Skiing Maneuvers
FASTRAK receivers were mounted on Kirschner-wires inserted in the distal femur and proximal tibia, respectively. Relative motions of the anterior cruciate ligament (ACL) insertion points were calculated for a hypothesised ACL while diagnostic and skiing load cases were applied to the knee. The highest strains, in descending order were: (i) Lachman test (13.5 %), (ii) 20 N•m internal rotation load (10.6 %) and (iii) latero-medial knee movement (6.4 %). The Lachman-procedure not only produces anterior tibial translation (5.5 mm) but as well internal rotation (10.0°). The medial knee movement produces valgus (2.3°) and external rotation (15.6°), but induces flexion (9.7°) as well, which therefore increases ACL load due to a non physiological instantaneous centre of rotation.