Anterior cruciate ligament reconstruction : Anatomic and biomechanical considerations of graft placement and fixation

Sammanfattning: This study, comprising 7 separate papers, is concerned with the mechanical causes of graft failure after intraarticular reconstruction of the anterior cruciate ligament (ACL). The study is predominantly experimental in design, but a clinical follow-up is also included to test a causal hypothesis of secondary graft elongation.Fixations of synthetic ACL substitutes with ligament staples had low security and the maximum tolerance loads were in parity with forces generated during daily activities, while screw fixations of looped ligaments had higher load to failure than a normal ACL.A stenosis, caused by osteophyte formation, was found at the intercondylar notch less than 2 years after an ACL tear, strongly suggesting impingement and wear as a possible mechanism of ACL substitute failure. The intercondylar notch was also found to be narrowed in patients with an acute tear of the ACL compared to a normal control group, thus implying causality.A standardized technique of graft placement, using a guide to aid bone drilling, was found more accurate and reproducible in achieving desired graft insertions compared to freehand drilling. This was evaluated by a new method for detennining the graft insertion locations on the femur and tibia, using a ratio related to the sagittal depth of the condyles.The ability to restore knee kinematics from an ACL deficient state, was evaluated for a drill guided graft route and an over-the-top route. The only effect of both methods, using a dacron graft tensioned in full extension, was restoring or partially restoring the increased anterior -posterior translation.A good in vitro and in vivo correlation was found between the patterns of change in dynamic fixation distance, as measured intraoperatively with an isometer, and tension in the fixed ACL substitute. The isometry measurement could not predict the magnitude of the frnal tension due to the biological variability in soft tissue compliance.Sagittal knee stability was measured at regular intervals for 2 years on patients who had an intraarticular ACL reconstruction with a patellar tendon substitute. Increasing anterior-posterior displacement was found for all patients as a group, and more for patients with an anterior femoralligament insertion location.A standardized treatment including aided bone drilling, notch plasty, isometry measurement, and restricted postoperative rehabilitation is recommended.