Changes in knee kinematics from applied external Tibial torque: Implications for stabilizing an anterior cruciate ligament deficient knee.

Background: Changes in knee kinematics from internal tibial torque under tibiofemoral compression force have been studied, but the potentially stabilizing effects of external tibial torque have not been reported. We hypothesized that for a given knee flexion angle, 1) external torque would significantly reduce anterior tibial translation, internal tibial rotation, and valgus tibial rotation before and after sectioning the anterior cruciate ligament and 2) changes in kinematics from applied external torque would be significantly greater with the cruciate cut.

Methods: A robotic test system was used to flex intact human knees continuously from 0° to 50° under 200 N compression, without and with 5 Nm external torque.

Cyclic testing of tibialis tendon allografts for anterior cruciate ligament reconstruction using suture-post versus spiked washer tibial fixation.

Background: The purpose of this study was to directly compare spiked washer and suture-post tibial-sided fixation techniques used for anterior cruciate ligament reconstruction by measuring anterior tibial translation during cyclic tests.

Methods: Fresh-frozen human knees were tested using a robotic system that applied 250 cycles of anterior-posterior tibial force (134 N) at 30° flexion, while recording tibial translation. Ten intact knees were tested to collect baseline data for native specimens.

In vitro determination of the passive knee flexion axis: Effects of axis alignment on coupled tibiofemoral motions.

The natural passive flexion axis of human cadaveric knees was determined using a technique that minimized coupled tibiofemoral motions (translations and rotations), and the kinematic effects of mal-positioned flexion axes were determined. The femur was clamped in an apparatus that allowed unconstrained tibial motions as the knee was flexed from 0° to 90°. To establish the natural flexion axis, the femur's position was adjusted such that coupled tibiofemoral motions were minimized.

Effects of tibiofemoral compression on ACL forces and knee kinematics under combined knee loads.

Injuries to the anterior cruciate ligament (ACL) can occur during landing from a jump or changing direction during a cutting maneuver. In these instances, the knee is subjected to combined forces and moments as it flexes under tibiofemoral compression force (TCF). We hypothesized that TCF would increase ACL forces and tibiofemoral motions under isolated and combined modes of loading relevant to knee injury.

Femoral Contact Forces in the Anterior Cruciate Ligament Deficient Knee: A Robotic Study.

Purpose: To measure contact forces (CFs) at standardized locations representative of clinical articular cartilage defects on the medial and lateral femoral condyles during robotic tests with simulated weightbearing knee flexion.

Methods: Eleven human knees had 20-mm-diameter cylinders of native bone/cartilage cored from both femoral condyles at standardized locations, with each cylinder attached to a custom-built load cell that maintained the plug in its precise anatomic position. A robotic test system was used to flex the knee from 0° to 50° under 200-N tibiofemoral compression without and with a 2 Nm internal tibial torque, 5 Nm external tibial torque, and 45 N anterior tibial force (AF).