Biomechanics and Outcomes of Modern Tibial Polyethylene Inserts.

PURPOSE OF REVIEW: There have been many attempts to use variations in tibial polyethylene design to better recreate normal knee kinematics in the total knee arthroplasty. The goal of this review is to provide an overview of the various types of tibial inserts that exist and review the theoretical mechanics versus what was demonstrated in vivo. RECENT FINDINGS: Many polyethylene inserts have been attempted to re-create normal knee kinematics, but none have been able to successfully do so. Previously the only two types of inserts were posterior stabilized (PS) and cruciate retaining (CR) polyethylene inserts. Both of these have shown excellent long-term survival but neither has demonstrated native kinematics. Initially, it was thought that retention of the posterior cruciate ligament (PCL) would allow for more native kinematics, but fluoroscopic evidence has shown that the PCL alone cannot accomplish this. Newer inserts try to restore femoral roll back and the screw home mechanism. The bicruciate retaining total knee inserts are having the most "normal" kinematics, suggesting the importance of both the ACL and PCL in knee biomechanics. Modern polyethylene inserts show favorable short-term data with bicruciate retaining inserts having the best kinematics; however, long-term studies are still needed to determine if survivorship and patient outcomes remain favorable.

Fibrin-Associated Diffuse Large B Cell Lymphoma Found on Revision Arthroplasty of the Knee.

Fibrin-associated diffuse large B cell lymphoma (FA-DLBCL) is a rare Epstein-Barr viruspositive B cell lymphoma that is nonmass-forming, does not directly produce symptoms, and is incidentally discovered on histological examination of tissues excised for other reasons. Despite overlap in morphologic and immunophenotypic features with aggressive B cell neoplasms, FA-DLBCL shows an excellent clinical outcome, even with surgical excision alone. We report an extremely rare occurrence of FA-DLBCL found in association with a metallic implant on revision arthroplasty of the knee. This report also illustrates the need for an integrated multidisciplinary approach for accurate diagnosis and avoidance of overtreatment.

Assessment of an Orthopedic Surgery Rotation on Musculoskeletal Competency in Emergency Medicine Residency Training.

OBJECTIVE: To determine baseline knowledge of emergency medicine (EM) residents at 2 different residency training programs and assess if a 4-week orthopedic surgery rotation would improve musculoskeletal (MSK) knowledge as assessed by the basic competency exam (BCE). This study also sought to compare variations of the BCE to determine how emergency physicians would perform on the full 25-question assessment vs a modified 18-question test. DESIGN: Residents from 2 different EM residency training programs were given the BCE to determine baseline MSK knowledge prior to their orthopedic surgery rotations. A postrotation BCE was given to the residents from both EM training programs upon completion of their orthopedic surgery rotation. Both prerotation and postrotation tests were reviewed and scored independently by a panel of experts and later assessed by 2 independent reviewers. SETTING: San Antonio Military Medical Center, SA Tx Level I Trauma, Tertiary Care Center University of Texas Health, SA, Tx, Level 1 Trauma, Tertiary Care Center. PARTICIPANTS: A total of 54 EM residents completed both the prerotation test and pos-rotation test. RESULTS: EM residents at both programs had significantly improved test scores after an orthopedic surgery rotation. Baselines scores of PGY-2 residents were higher than PGY-1 residents. CONCLUSIONS: EM residents can improve their competency in MSK education with a 4-week rotation in orthopedic surgery. Further studies are needed to determine knowledge retention and to identify components of an optimal orthopedic rotation.