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.

Prediction of ACL Force Produced by Tibiofemoral Compression During Controlled Knee Flexion: A New Robotic Testing Methodology.

Tibiofemoral compression force (TCF) is an important component of anterior cruciate ligament (ACL) injuries. A new robotic testing methodology was utilized to predict ACL forces generated by TCF without loading the ligament. We hypothesized that ACL force, directly recorded by a miniature load cell during an unconstrained test, could be predicted by measurements of anterior tibial restraining force (ARF) recorded during a constrained test.

Effect of Different Preconditioning Protocols on Anterior Knee Laxity After ACL Reconstruction with Four Commonly Used Grafts.

Background: It is currently unknown if preconditioning an anterior cruciate ligament (ACL) graft prior to fixation is helpful in eliminating possible increases in anterior knee laxity. The purpose of this study was to measure cyclic increases in anterior tibial translation of four commonly used graft tissues subjected to four preconditioning protocols.

Methods: A robotic system was used to apply 250 cycles of anteroposterior force (134 N of anterior force followed by 134 N of posterior force) to ten intact knees (ACL controls) and then to a single knee reconstructed, for separate tests, with bone-patellar tendon-bone, bone-Achilles tendon, hamstring tendon, and tibialis tendon grafts following (1) no preconditioning, (2) preconditioning on a tension board (89 N of initial force held for twenty minutes), (3) preconditioning in situ (89 N of force applied to the tibial end of the graft during twenty-five flexion-extension cycles), and (4) a combination of protocols 2 and 3.

A comparison of 11 o'clock versus oblique femoral tunnels in the anterior cruciate ligament-reconstructed knee: knee kinematics during a simulated pivot test.

Background: Traditionally, a standard femoral tunnel for a single-bundle anterior cruciate ligament (ACL) reconstruction is positioned 6 to 7 mm anterior to the posterior wall at an 11 o'clock orientation in the femoral notch (right knee). However, some surgeons have advocated placing the femoral tunnel at a more oblique orientation at or near the femoral footprint of the ACL's posterolateral bundle (at approximately 9:30 to 10 o'clock in the notch) to provide the graft with a better mechanical advantage for controlling tibial rotation and eliminating the pivot shift.

Hypothesis: Moving the femoral tunnel from the standard location to an oblique position in the femoral notch will significantly reduce the magnitude of a simulated pivot shift.

Functional improvement after patients with rheumatoid arthritis start a new disease modifying antirheumatic drug (DMARD) associated with frequent changes in DMARD: the CORRONA database.

Objective: We examined the relationships of rheumatoid arthritis (RA), disease duration (DD), number of previous disease modifying antirheumatic drugs (DMARD), and frequency of DMARD changes, with regard to changes in function in patients with RA evaluated by modified Health Assessment Questionnaire (mHAQ) after the start of a new DMARD.

Methods: In total, 889 patients with active RA from the CORRONA database [patients had mHAQ>or=0.5 and/or Disease Activity Score 28-joint count (DAS28)>or=1.

How well do anatomical reconstructions of the posterolateral corner restore varus stability to the posterior cruciate ligament-reconstructed knee?

Background: With grade 3 posterolateral injuries of the knee, reconstructions of the lateral collateral ligament, popliteus tendon, and popliteofibular ligament are commonly performed in conjunction with a posterior cruciate ligament reconstruction to restore knee stability.

Hypothesis: A lateral collateral ligament reconstruction, alone or with a popliteus tendon or popliteofibular ligament reconstruction, will produce normal varus rotation patterns and restore posterior cruciate ligament graft forces to normal levels in response to an applied varus moment.

Study Design: Controlled laboratory study.

Biomechanical effects of medial-lateral tibial tunnel placement in posterior cruciate ligament reconstruction.

With most posterior cruciate (PCL) reconstruction techniques, the distal end of the graft is fixed within a tibial bone tunnel. Although a surgical goal is to locate this tunnel at the center of the PCL's tibial footprint, errors in medial-lateral tunnel placement of the tibial drill guide are possible because the position of the tip of the guide relative to the PCL's tibial footprint can be difficult to visualize from the standard arthroscopy portals. This study was designed to measure changes in knee laxity and graft forces resulting from mal-position of the tibial tunnel medial and lateral to the center of the PCL's tibial insertion.