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Abstract: The purpose of this study was to describe the intra- and inter-observer variability of the registration of bony landmarks and alignment axes on a Computed Axial Tomography (CT) scan. Six cadaver specimens were scanned. Three-dimensional surface models of the knee were created. Three observers marked anatomic surface landmarks and alignment landmarks. The intra- and inter-observer variability of the point and axis registration was performed. Mean intra-observer precision ranks around 1 mm for all landmarks. The intra-class correlation coefficient (ICC) for inter-observer variability ranked higher than 0.98 for all landmarks. The highest recorded intra- and inter-observer variability was 1.3 mm and 3.5 mm respectively and was observed for the lateral femoral epicondyle. The lowest variability in the determination of axes was found for the femoral mechanical axis (intra-observer 0.12° and inter-observer 0.19°) and for the tibial mechanical axis (respectively 0.15° and 0.28°). In the horizontal plane the lowest variability was observed for the posterior condylar line of the femur (intra-observer 0.17° and inter-observer 0.78°) and for the transverse axis (respectively 1.89° and 2.03) on the tibia. This study demonstrates low intra- and inter-observer variability in the CT registration of landmarks that define the coordinate system of the femur and the tibia. In the femur, the horizontal plane projections of the posterior condylar line and the surgical and anatomical transepicondylar axis can be determined precisely on a CT scan, using the described methodology. In the tibia, the best result is obtained for the tibial transverse axis. [Copyright &y& Elsevier]

The aim of this study was to measure and compare the ultimate failure strengths and cyclic fatigue strengths of currently available meniscal suturing devices. No statistically significant difference in failure load was found between a vertical loop suture (mean 46.3 N), a horizontal mattress suture (52.5 N), the T-fix Device® (47.5 N), and the 16-mm (39.2 N) and 13-mm (32.8 N) Bionix Arrow®. Statistically inferior results were seen with the 10-mm Bionix Arrow® (18.8 N), the S.D. Sorb Stapler® (4.3 N), and the 12-mm Arthrex Meniscal Dart® (10.5 N) (P<0.01). The Mitek Meniscal Repair System® (28.1 N) performed intermediate, with significantly better results than the S.D. Sorb Stapler® and the 12-mm Arthrex Dart®, but significantly worse than the vertical and horizontal sutures, the T-fix® and Bionix 16-mm Device® (P<0.01). Cyclic fatigue strength was significantly less for the 10-mm Bionix Arrow®, the S.D. Sorb Stapler®, and the 12-mm Arthrex Meniscal Dart® (P<0.01) compared to all other devices. We conclude that the 13- and 16-mm Bionix Arrow® and the T-fix Device® have comparable ultimate failure strengths and cyclic fatigue strengths to conventional meniscal suturing techniques. The 10-mm Bionix Arrow®, S.D. Sorb Stapler®, and the 12-mm Arthrex Meniscal Dart®, however, have far inferior failure and cyclic fatigue strengths and their clinical application should be questioned. [Copyright &y& Elsevier]

Purpose: Modular bicompartmental knee arthroplasty (BKA) for treatment of medio-patellofemoral osteoarthritis (OA) should allow for close to normal kinematics in comparison with unicondylar knee arthroplasty (UKA) and the native knee. There is so far no data to support this., Scope: Six fresh frozen full leg cadaver specimens were prepared and mounted in a kinematic rig with six degrees of freedom for the knee joint. Three motion patterns were applied with the native knee and after sequential implantation of medial UKA and patellofemoral joint replacement (PFJ): passive flexion-extension, open chain extension, and squatting. During the loaded motions, quadriceps and hamstrings muscle forces were applied. Infrared cameras continuously recorded the trajectories of marker frames rigidly attached to femur, tibia and patella. Prior computer tomography allowed identification of coordinate frames of the bones. Strains in the collateral ligaments were calculated from insertion site distances., Results: UKA led to a less adducted and internally rotated tibia and a more strained medial collateral ligament (MCL). Addition of a patellofemoral replacement led to a more posterior position of both femoral condyles, a more dorsally located tibiofemoral contact point and higher MCL strain with squatting., Conclusion: In comparison to UKA modular BKA leads to a more dorsal tibial contact point, a medial femoral condyle being located more posteriorly, and more MCL strain. Mainly the changes to the trochlear anatomy as introduced by PFJ may account for these differences., (© 2014 Elsevier B.V. All rights reserved.)

Although several techniques exist for cementing the femoral component in TKA, no data are available on which is the best one to use. We therefore compared four cementing techniques in an anatomical open pore sawbone model (n=20), in order to investigate the influence of cementation technique on overall cement penetration as well as length of the cement mantle over the different cuts. The technique which included cement application onto the anterior and distal bone surfaces, as well as the posterior flanges of the prosthesis, was statistically superior to the other techniques. We therefore advocate this technique as the standard for cementing the femoral component.