Conrad Wang

The Biomechanical Effect of Posterior Cruciate Ligament Reconstruction on Knee Joint Function Kinematic Response to Simulated Muscle Loads

Background The effectiveness of posterior cruciate ligament reconstruction in restoring normal kinematics under physiologic loading is unknown. Hypothesis Posterior cruciate ligament reconstruction does not restore normal knee kinematics under muscle loading. Study Design In vitro biomechanical study. Methods Kinematics of knees with an intact, resected, and reconstructed posterior cruciate ligament were measured by a robotic testing system under simulated muscle loads. Anteroposterior tibial translation and internal-external tibial rotation were measured at 0°, 30°, 60°, 90°, and 120° of flexion under posterior drawer loading, quadriceps muscle loading, and combined quadriceps and hamstring muscle loading. Results Reconstruction reduced the additional posterior tibial translation caused by ligament deficiency at all flexion angles tested under posterior drawer loading. Ligament deficiency increased external rotation and posterior translation at angles higher than 60° of flexion when simulated muscle loading was applied. Posterior cruciate ligament reconstruction reduced the posterior translation and external rotation observed in posterior cruciate ligament-deficient knees at higher flexion angles, but differences were not significant. Conclusion Under physiologic loading conditions, posterior cruciate ligament reconstruction does not restore six degree of freedom knee kinematics. Clinical Relevance Abnormal knee kinematics may lead to development of long-term knee arthrosis.

The Effect of Posterior Cruciate Ligament Reconstruction on Patellofemoral Contact Pressures in the Knee Joint Under Simulated Muscle Loads

Background The mechanism of cartilage degeneration in the patellofemoral joint (PFJ) and medial compartment of the knee following posterior cruciate ligament (PCL) injury remains unclear. PCL reconstruction has been recommended to restore kinematics and prevent long-term degeneration. The effect of current reconstruction techniques on PFJ contact pressures is unknown. Purpose To measure PFJ contact pressures after PCL deficiency and reconstruction. Method Eight cadaveric knees were tested with the PCL intact, deficient, and reconstructed. Contact pressures were measured at 30 °, 60 °, 90 °, and 120 ° of flexion under simulated muscle loads. Knee kinematics were measured by a robotic testing system, and the PFJ contact pressures were measured using a thin film transducer. A single bundle achilles tendon allograft was used in the reconstruction. Results PCL deficiency significantly increased the peak contact pressures measured in the PFJ relative to the intact knee under both an isolated quadriceps load of 400 N and a combined quadriceps/hamstrings load of 400 N/200 N. Reconstruction did not significantly reduce the increased contact pressures observed in the PCL-deficient knee. Conclusion The elevated contact pressures observed in the PCL-deficient knee and reconstructed knee might contribute to the long-term degeneration observed in both the non-operatively treated and PCL-reconstructed knees.

The effect of graft stiffness on knee joint biomechanics after ACL reconstruction--a 3D computational simulation.

OBJECTIVE The objective was to determine the effect of varying graft stiffness and initial graft tension on knee kinematics and graft tension after anterior cruciate ligament reconstruction. DESIGN A 3D computational knee model was used. BACKGROUND Many factors influencing the biomechanical outcome of anterior cruciate ligament reconstruction have been investigated. However, there are no reports on the effect of variations in graft stiffness on knee behavior. METHODS A 3D computational knee model was used to simulate anterior cruciate ligament reconstruction using three different grafts with stiffnesses similar to the anterior cruciate ligament (graft 1), a 10mm bone-patellar tendon-bone graft (graft 2), and a 14 mm bone-patellar tendon-bone graft (graft 3). The initial graft tension was set to 0 or 40 N with the knee at 30 degrees of flexion. A 134 N anterior tibial drawer load and a 400 N quadriceps load were applied to the knee, and kinematics and graft tension were calculated. RESULTS When fixed with no initial tension, graft 1 was found to under-constrain the knee, while graft 2 slightly over-constrained the knee, and graft 3 over-constrained the knee when compared to the intact knee. When an initial graft tension of 40 N was used, all of the reconstructed knees were more constrained than when an initial tension of 0 N was used. CONCLUSIONS This study suggests that graft stiffness has a direct impact on knee biomechanics after anterior cruciate ligament reconstruction. An optimal anterior cruciate ligament reconstruction can be achieved if the anterior cruciate ligament is replaced by a graft with similar structural stiffness. RELEVANCE This study showed that if the graft material and fixation sites are selected such that the anterior cruciate ligament structural stiffness is retained, normal knee kinematics can be restored.

Extensor Carpi Ulnaris Tendon Rupture in an Ice Hockey Player A Case Report

Ulnar wrist pain has previously been described in athletes. Reported causes include triangular fibrocartilage complex tears, lunotriquetral ligament tears, stenosing tenosynovitis of the extensor carpi ulnaris tendon sheath, and recurrent subluxation of the extensor carpi ulnaris tendon. To our knowledge, there has been no report of athletes with ulnar wrist pain and dysfunction caused by rupture of the extensor carpi ulnaris tendon. We present a case report of a professional ice hockey player who had ulnar wrist pain caused by rupture of the extensor carpi ulnaris tendon. The tendon was successfully reconstructed by using a palmaris longus tendon graft.

Arthroscopic shoulder reconstruction: fast-track recovery and outpatient treatment.

Arthroscopic shoulder reconstructive surgery has been handled in many different ways. However, there currently is significant evidence and experience to show that doing this surgery on an outpatient basis is not only cost-effective and efficient, but safe and beneficial to patients. New arthroscopic surgical techniques and the use of regional interscalene anesthesia have been shown to provide effective and comfortable intraoperative conditions, while allowing for prolonged analgesia and quicker recovery with minimal side effects. The authors will discuss their approach to surgery, anesthesia, and recovery for outpatient shoulder reconstruction.