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Femoral component malrotation in total knee arthroplasty (TKA) is clinically proven to cause dissatisfaction and impaired function. This study is an attempt to characterize the tibiofemoral kinematics following femoral malrotation in posterior stabilized (PS) TKA. It was hypothesized that internal malrotation would introduce the most pronounced changes. Six fresh-frozen cadaver specimens were mounted in a kinematic rig. Three motion patterns were applied with the native knee and following PS TKA (passive motion, open chain extension, and squatting) while infrared cameras recorded the trajectories of markers attached to femur and tibia. Three different femoral implants were tested: a conventional posterior stabilized component, and adapted components of the same implant with 5° of intrinsic external and internal rotation, respectively. The implantation of the PS TKA resulted in less tibial internal rotation (squat 33–70°, p

The recently reintroduced bicruciate-retaining Total Knee Arthroplasty (BCR TKA) is an interesting approach in the quest for close replication of knee joint biomechanics and kinematics closer to the native knee. Therefore, this study aimed at providing a detailed biomechanical view on the functional resemblance of BCR TKA to the native knee joint. Seven fresh-frozen full leg cadaver specimens (76 ± 10 year) were mounted in a 6 degrees-of-freedom kinematic rig that applied a dynamic squatting motion knee flexion. Two motion patterns were performed pre- and post-implantation of a fixed bearing BCR TKA: passive flexion–extension and squatting while an infrared camera system tracked the location of reflective markers attached to the tibia and femur. Additionally, specimen laxity was assessed using Lachman tests and varus/valgus stress tests in triplicate. Overall, differences in tibiofemoral kinematics between native knee and BCR TKA were small. Some minor differences appeared under the load of a squat: less internal tibial rotation and some minor paradoxical anterior translation of the medial femoral condyle during mid-flexion. BCR TKA may slightly elevate the joint line. Knee laxity as measured by the Lachman and varus/valgus tests was not significantly influenced by BCR TKA implantation. As both cruciate ligaments are preserved with BCR TKA the unloaded knee closely resembles native knee kinematics including preserving the rollback mechanism. The loss of the conforming anatomy of menisci and tibial cartilage and replacement via a relatively flat polyethylene inlay may account for the loss of tibial internal rotation and the slight paradoxical AP motion of the medial femoral condyle with BCR TKA. This phenomenon reproduces findings made earlier with fixed bearing unicondylar knee arthroplasty.

Balancing mobile-bearing (MB) unicondylar knee arthroplasty (UKA) is challenging. If performed improperly, potential complications include pain, implant loosening, or progression of osteoarthritis in the preserved compartment. The purpose of this study was to document effects of improper balancing on knee kinematics and joint contact stress. It was hypothesized that over-stuffing would lead to more valgus and higher lateral contact force. Seven fresh-frozen cadaver legs were mounted in a kinematic rig that applied three motion patterns to the specimens: passive flexion–extension, open chain extension, and squatting. During testing, an infrared camera system recorded the trajectories of markers rigidly attached to femur and tibia, while a pressure sensor measured contact pressure in the lateral compartment. Prior computer tomography scans allowed identification of coordinate frames of the bones and calculations of anatomical rotations and translations. Collateral ligament strains were calculated, and quadriceps forces recorded. Following testing on the native knee, a medial MB UKA was implanted in each specimen and all motion trials were repeated. Three inlay thicknesses were tested to simulate optimal balancing as well as under- (1 mm thinner) and over-stuffing (1 mm thicker) of the medial compartment relative to the optimal thickness. Under-stuffing of the medial compartment leads to kinematics closest to the native knee. Subjectively balanced and over-stuffed MB UKA knees were in more valgus. Lateral peak contact stress was higher from mid- to deep flexion following UKA in all three tested states; however, these results were not significant. Peak strain in the superficial medial collateral ligament (sMCL) was significantly higher in MB UKA, regardless of the inlay thickness mainly in mid-flexion. Inlay thickness had no significant impact on measured quadriceps force during squatting. The results underline the importance of optimal balancing. Over-stuffing should be avoided as it results in the largest kinematic changes relative to the native condition and induces higher strains in the sMCL. Based on the kinematic findings, it is advisable to use thinner inlays, as long as this is not compromising stability or risking inlay luxation.

It is assumed that unicondylar knee arthroplasty (UKA) features kinematics close to the natural knee. Clinical studies have also shown functional benefits for UKA. There is to date only little biomechanical data to support or explain these findings. The purpose of this study was to investigate whether UKA is able to preserve natural knee kinematics or not. Six fresh frozen full leg cadaver specimens were prepared to be mounted in a kinematic rig with six degrees of freedom for the knee joint. Three motion patterns were applied before and after medial UKA: 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 and calculations of anatomical rotations and translations. Native kinematics was reproduced after UKA in all the specimens. In the unloaded knee and during open chain extension, femoral rollback patterns after UKA were very close to those in the native knee. During squatting, the medial femoral condyle after UKA tended to be more posterior and superior with flexion and there was less tibial internal rotation. The tibia was found to be more in valgus after UKA during all motion patterns. As ligaments, lateral compartment and patellofemoral anatomy are preserved with UKA; the unloaded knee closely resembles native kinematics. The slight kinematic changes that were found under load are probably due to loss of the conforming medial meniscus and to the mismatch in geometry and stiffness introduced by UKA. These patterns resemble those found in knees with significant loss of function of the medial meniscus.

Purpose Several well-described techniques are available for the treatment of chondral and osteochondral defects. The aim of the study was to assess the efficacy of a singlestage procedure incorporating a new cell-free collagen type I gel for the treatment of small chondral and osteochondral defects in the knee evaluated at 2-year follow-up. Methods Fifteen patients were treated with a cell-free collagen type I gel matrix of 11 mm diameter. The grafts were implanted in the debrided cartilage defect and fixed by press-fit only. The clinical outcome was assessed preoperatively and at 6 weeks, and 6, 12 and 24 months after surgery using the International Knee Documentation Committee (IKDC) score, Tegner activity scale and visual analogue scale (VAS). Graft attachment rate was assessed 6 weeks postoperatively using magnetic resonance imaging (MRI). Cartilage regeneration was evaluated using the Magnetic Observation of Cartilage Repair Tissue (MOCART) score at 6, 12 and 24 months after implantation. Clinical results were correlated with MRI findings. Results Six male and nine female patients were included in this study, with a mean age of 26 (range: 19‐40). No complications were reported. The mean VAS values after 6 weeks and the mean IKDC patient values after 6 months were significantly improved from the preoperative values (P = 0.005 and P = 0.009, respectively). This improvement remained up to the latest follow-up. There were no significant differences between the median preoperative and postoperative Tegner values (n.s.). Significant improvement of the mean MOCART score was observed after 12 months and remained by 24 months (P \ 0.001). MR images showed that in 14 of the 15 patients, the graft was completely attached by 6 weeks postoperatively. At 24 months after implantation, MRI demonstrated complete filling in all cases with a mainly smooth surface, complete integration of the border zone, homogenous structure of the repaired tissue and nearly normal signal intensity. No correlation between any variables of the MOCART score and the clinical scores was observed. Conclusions The present study reveals that the new method produces both good clinical and magnetic resonance imaging results. Use of press-fit only implanted grafts of a smaller diameter leads to a high attachment rate at 24-month follow-up. Level of evidence IV.

Meniscal loss is associated with an increased risk of developing osteoarthritis. Tissue engineering solutions, which include the development of novel material scaffolds, are being utilised to aid the regeneration of meniscal tissue. The purpose of this study was to monitor the safety profile and the short-term efficacy of a novel polyurethane meniscal scaffold in the treatment of patients with painful knees following partial medial meniscectomy. Ten consecutive patients with segmental tissue loss from the medial meniscus were treated with the arthroscopic implantation of an Actifit® (Orteq Sports Medicine) polyurethane meniscal scaffold. Patients were followed up at 2 and 6 weeks, then again at 6 and 12 months. Primary outcome measures included reporting of complications and patient-reported outcome scores (KOOS, KSS, UCLA Activity scale, VAS pain). Secondary outcome was MRI assessment at 6 and 12 months looking at scaffold morphology, integration and associated joint injury/inflammation. Eight male and 2 female patients were included in the study with a mean age of 29 (range 18–45). No complications were reported. All patients were happy with their surgery. At 6 months, a statistically significant improvement (P

The theoretical superiority of mobile-bearing total knee arthroplasties (TKAs) has not yet been proven in clinical studies. The aim of the current study was to compare and to analyse in a patient population that had received either a fixed or a mobile TKA differences in gait analysis electromyography and clinical scores.In a prospective, randomized, patient- and observer-blinded clinical study, 33 patients with primary osteoarthritis of the knee were included. All patients received a Genesis II total knee replacement. Sixteen patients received a mobile and 17 a fixed-bearing cruciate retaining Genesis II TKA. Clinical and quality-of-life scores, electromyography and gait analysis were applied preoperatively and postoperatively with a follow-up of 24 months.In both groups, improvements from pre- to postoperative were detected. whereas the results of gait analysis and electromyography did not show any differences. The results from the clinical and the quality-of-life scores improved from pre- to postoperative, while the Knee Society Score showed a superiority of the mobile-bearing group (mean 159 ± 28) over the fixed-bearing group (mean 134 ± 41).No functional advantage of mobile over fixed-bearing TKA was detected, although the mobile-bearing group had better clinical results for which a reason could not be found. These results only apply to cruciate retaining mobile-bearing TKA with a bearing which allows both rotation and anteroposterior translation.