Real-space visualization of intrinsic magnetic fields of an antiferromagnet.

Characterizing magnetic structures down to atomic dimensions is central to the design and control of nanoscale magnetism in materials and devices. However, real-space visualization of magnetic fields at such dimensions has been extremely challenging. In recent years, atomic-resolution differential phase contrast scanning transmission electron microscopy (DPC STEM)1 has enabled direct imaging of electric field distribution even inside single atoms2. Here we show real-space visualization of magnetic field distribution inside antiferromagnetic haematite (α-Fe2O3) using atomic-resolution DPC STEM in a magnetic-field-free environment3. After removing the phase-shift component due to atomic electric fields and improving the signal-to-noise ratio by unit-cell averaging, real-space visualization of the intrinsic magnetic fields in α-Fe2O3 is realized. These results open a new possibility for real-space characterization of many magnetic structures.

Simultaneous bilateral total knee arthroplasty is safe and effective for patients in different ages.

BACKGROUND: Simultaneous bilateral total knee arthroplasty is considered beneficial for patients with bilateral end-stage knee osteoarthritis, even though there could be potential postoperative complications. Presently, there is a paucity of evidence of the efficacy and safety of SB-TKA for elderly patients. This study aimed to compare the clinical outcomes of simultaneous bilateral total knee arthroplasty by different age groups. METHODS: A total of 216 knees of 108 patients, who underwent simultaneous bilateral total knee arthroplasty for osteoarthritis at our hospital between April 2015 and September 2018, were divided into three groups based on age: 60s (44 knees), 70s (106 knees), and 80s (66 knees). Perioperative data and postoperative clinical outcomes 1 year after surgery were compared between the age groups. RESULTS: The patients in the Group 60s were characterized by a higher body mass index (BMI) (P < 0.01), a lower pre-operative knee function score (P < 0.01), longer operation time (P < 0.01), greater intra-operative (P < 0.01), and postoperative bleeding (P = 0.026). No significant difference was found in terms of occurrence of various postoperative complications, although deep vein thrombosis and delirium occurred slightly more frequently in the Group 70s and the Group 80s than in the Group 60s group. The Knee Society Knee Score, a function score, and patient satisfaction scores were significantly improved in all groups 1 year after surgery. Moreover, these indexes of clinical outcomes were similar among the three groups. CONCLUSION: Performing simultaneous bilateral total knee arthroplasty in 80s patients was found to be as safe and effective as in the 60s and 70s patients. LEVEL OF EVIDENCE: 3 (A retrospective cohort study).

Second-look arthroscopy after meniscus repair and synovial mesenchymal stem cell transplantation to treat degenerative flaps and radial tears of the medial meniscus: A case report.

BACKGROUND: The purpose of this study was to compare arthroscopic findings of a degenerative flap and radial tear of the medial meniscus (MM) before and one year after treatment by meniscus repair and synovial mesenchymal stem cell (MSC) transplantation. METHODS: Patients with a degenerative flap and radial MM tear that would generally be treated by meniscectomy were included. The patients ranged in age from 45 to 62 years and all underwent meniscus repair and synovium harvest at time 0. The digested synovium was cultured with autologous serum for 12 days, and an average of 4 × 107 MSCs were transplanted at two weeks. A second-look arthroscopy was performed at 52 weeks (n = 6). The average duration of symptoms was 24 months. For flap tears, arthroscopic findings were quantified in terms of the presence, stability, and smoothness of the meniscus at each zone and area. The Lysholm score was evaluated throughout the 52 week follow-up. RESULTS: Four patients with MM flap tears showed deficiencies in the central area at the posterior junctional zone before treatment, but this zone was completely restored to a stable and smooth condition in two patients and partially restored in the other two patients. The arthroscopy score for a flap tear at the central area of the posterior junctional zone was 0.3 ± 0.5 before treatment and 4.3 ± 2.1 after treatment. The score was significantly higher after treatment (p < 0.05, n = 4). The original radial MM tears in two patients were healed one year after treatment. Lysholm scores were significantly higher at 4 and 52 weeks after treatment than before treatment (n = 6). CONCLUSIONS: Arthroscopic findings for a degenerative flap and radial tear of the MM were improved at the central area of the posterior junctional zone one year after meniscus repair and MSC transplantation.

Knee laxity, lateral meniscus tear and distal femur morphology influence pivot shift test grade in ACL injury patients.

PURPOSE: Although several factors have been considered to be associated with pivot shift test grade in ACL injured patients, a conclusion regarding which factors contribute to the pivot shift test grade has not been reached. The purpose of this study was to identify factors associated with preoperative pivot shift test grade. METHODS: Three hundred and sixty-six consecutive patients who underwent ACL reconstruction in our hospital were enrolled in the study. Patients were divided into two groups on the basis of preoperative pivot shift test grade (Mild: grade 0-3, Severe: grade 4-6). First, 13 independent variables (age, gender, period from injury to surgery, hyperextension, KT measurement, contralateral side pivot shift test grade, medial and lateral tibial slope, lateral condyle length, lateral condyle height, distal femoral condyle offset, medial and lateral meniscus tear) were analyzed by one-way ANOVA and Chi-squared test. Binary Logistic regression was then performed based on the results of univariate analyses (independent variables of p < 0.2 were included). RESULTS: Hyperextension, lateral meniscus tear, contralateral side pivot shift test grade, distal femoral condyle offset and KT measurement were identified as risk factors for preoperative pivot shift grade via logistic regression analysis. CONCLUSION: The current study revealed that hyperextension, lateral meniscus tear, contralateral side pivot shift test grade, distal femoral condyle offset and anterior instability were associated with preoperative pivot shift grade. Patients with above factors that cannot be modified during surgery may need special consideration when ACL reconstruction is performed, as greater preoperative pivot shift has been proven to be a risk factor for residual pivot shift after ACL reconstruction. LEVEL OF EVIDENCE: III.

Trends in arthroplasty in Japan by a complete survey, 2014-2017.

BACKGROUND: Precise knowledge of the prevalence and trends of arthroplasty can facilitate the design of medical plans for efficient treatments. The National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) Open Data Japan provides statistics about the annual number of arthroplasties (knee, hip, shoulder, finger, elbow, and foot/ankle) through health insurance claim numbers for these surgeries. The purpose of this study was to document the annual arthroplasty numbers between 2014 and 2017 in Japan and to analyze their four-year trends, gender differences, age distributions, and regional differences as revealed by the complete survey. METHODS: Numbers of arthroplasty surgeries were extracted from the NDB Open Data Japan for 2014-2017. For "knee", "hip", "shoulder", "finger", "elbow", and "foot/ankle" arthroplasties, we showed the annual arthroplasty numbers, annual arthroplasty numbers by age group, annual arthroplasty numbers in individual prefectures, and annual arthroplasty numbers per 100,000 population in individual prefectures. RESULTS: The annual arthroplasty numbers in 2017 were 146,189 for all joints, 82,304 for knees, 59,029 for hips, 2454 for shoulders, 1551 for fingers, 536 for elbows, and 291 for feet/ankles. For the four years up to 2017, the rate of alteration in the number of arthroplasties was +14% for total arthroplasties, +9% for knees, +21% for hip joints, +97% for shoulders, + 8% for fingers, -10% for elbows, and +25% for feet/ankles. The proportion of females was 70-90% and the peak age was between the late 60s and late 70s for all joints. Variations in arthroplasty numbers per population by prefecture appeared to be small for knees and hips and large for other joints. CONCLUSIONS: We revealed the annual total number of arthroplasties for each joint in Japan using the NDB Open Data Japan for the first time.

Morphological changes in synovial mesenchymal stem cells during their adhesion to the meniscus.

Synovial mesenchymal stem cells (MSCs) are an attractive cell source for transplantation because of their high chondrogenic potential, especially in areas like the meniscus of the knee. A synovial MSC suspension placed onto the meniscus for 10 min promoted healing of repaired meniscal tears that generally do not heal. Here, we quantified the proportion of human synovial MSCs that adhered to a porcine abraded meniscus, clarified their morphological changes, and revealed the mechanism by which the synovial MSCs adhered to the meniscus. The numbers of adhering cells at immediately after 10, 60 min and 6, 24 h after suspension placement were calculated. The meniscus surface was examined by scanning electron microscopy, and 50 cells were randomly selected at each time period, classified, and quantified for each of the six donors. Approximately 28% of the synovial MSCs immediately adhered to the meniscus after placement and the proportion of adhered cells increased further with time. All cells maintained a round shape for 60 min, and then transformed to a mixture of round and semi-flattened cells. By 24 h, flattened cells covered the meniscus. Microspikes were observed in 36% of the floating synovial MSCs and in 76% of the cells on the meniscus shortly after placement on the meniscus, then the proportion of cells with pseudopodia increased. The bleb-dominant cell proportion significantly decreased, and the smooth-dominant cell proportion increased within 60 min. Microspikes or the bodies of synovial MSCs were trapped by meniscal fibers immediately after placement. The proportion of adhered cells increased with time, and the cell morphology changed dynamically for 24 h as the synovial MSCs adhered to the meniscus. The MSCs in the round morphological state had a heterogeneous morphology. The microspikes, and the subsequent development of pseudopodia, may play an important role in adhesion onto the meniscus.

The effect of a centralization procedure for extruded lateral meniscus on load distribution in porcine knee joints at different flexion angles.

BACKGROUND: Meniscal extrusion results in loss of the ability to resist hoop strain and biomechanical overload on the joint articular surface. A centralization technique has been developed to overcome these problems. In this study, we analyzed the biomechanics of the extruded and centralized lateral meniscus (LM) in porcine knee joints at different flexion angles. METHODS: Porcine knee joints (n = 8) were set in the universal tester and each knee was tested under the following states: 1) intact; 2) extrusion-meniscal extrusion was created by resecting the posterior root of the LM and posterior synovial capsule; and 3) centralization-centralization was performed by two anchors inserted in the lateral tibial plateau. Deviation distance of the meniscus, contact pressure, and contact area in the anterior LM, middle LM, posterior LM, and the contact pressure of the tibial cartilage were evaluated with an axial compressive force of 200 N at knee flexion angles of 30°, 45°, 60°, and 90°. RESULTS: The deviation distance of LM significantly increased in extrusion but was restored to the intact status after centralization at all angles. Both the contact pressure and area significantly decreased in extrusion and were restored after centralization close to the intact status in the anterior and middle LM; in the posterior LM, however, decreased contact pressure and area were not restored after centralization. The contact pressure of the tibial cartilage increased significantly in extrusion but decreased close to the intact status after centralization. CONCLUSIONS: This centralization procedure could reduce extrusion of the LM and restore the load-distributing function of the anterior-middle LM. However, the procedure itself could not restore hoop function in cases where the defect lies in the posterior LM.

Biomechanical analysis of the centralization procedure for extruded lateral menisci with posterior root deficiency in a porcine model.

PURPOSE: The purpose of this study was to investigate the biomechanical properties of load distribution following a centralization procedure for extruded lateral menisci with posterior root deficiency in a porcine model. METHODS: Six porcine knee joints were analyzed in a universal tester, as follows: 1) Intact; 2) Extrusion (meniscus extrusion was created by resecting the posterior root of the lateral meniscus, as well as the posterior synovial capsule); and 3) Centralization (two anchors were inserted at the lateral tibial plateau, and the meniscus was sutured to secure it close to the original position). Meniscus extrusion was evaluated using two markers put on the posterior cruciate ligament and the lateral meniscus, and the load distribution were assessed using a pressure mapping sensor system after applying a loading force of 200 N to the knee joint. RESULTS: Distance between two markers (mm, Average; 95% CI) was larger in the extrusion group (21.9; 17.8, 25.6) than in the intact (18.1; 15.1, 22.7) or the centralization (15.3; 12.9, 18.0) groups. The contact area (mm2) in the middle of the meniscus was significantly smaller in the extrusion group (45.8; 18.5, 73.2) than in the intact (85.7; 72.1, 99.2) or the centralization (98.3; 88.8, 107.8) groups. The maximum contact pressure (MPa) in the tibial plateau was significantly higher in the extrusion group (0.37; 0.35, 0.40) than in the intact (0.29; 0.21, 0.37) or the centralization (0.29; 0.22, 0.36) groups. CONCLUSIONS: The centralization procedure enabled a reduction of the meniscus extrusion in the lateral meniscus with posterior root deficiency and restored the maximum load and contact pressure to values close to those of the normal knee joint.

Stable Magnetic Skyrmion States at Room Temperature Confined to Corrals of Artificial Surface Pits Fabricated by a Focused Electron Beam.

Stable confinement of elemental magnetic nanostructures, such as a single magnetic domain, is fundamental in modern magnetic recording technology. It is well-known that various magnetic textures can be stabilized by geometrical confinement using artificial nanostructures. The magnetic skyrmion, with novel spin texture and promise for future memory devices because of its topological protection and dimension at the nanometer scale, is no exception. So far, skyrmion confinement techniques using large-scale boundaries with limited geometries such as isolated disks and stripes prepared by conventional microfabrication techniques have been used. Here, we demonstrate an alternative technique confining skyrmions to artificial nanostructures (corrals) built from surface pits fabricated by a focused electron beam. Using aberration-corrected differential phase contrast scanning transmission electron microscopy, we directly visualized stable skyrmion states confined at a room temperature to corrals made of artificial surface pits on a thin plate of Co8Zn8Mn4. We observed a stable single-skyrmion state confined to a triangular corral and a unique transition into a triple-skyrmions state depending on the perpendicular magnetic field. Furthermore, we made an array of stable single-skyrmion states by using concatenated triangular corrals. Artificial control of skyrmion states with the present technique should be a powerful way to realize future nonvolatile memory devices using skyrmions.

Direct Visualization of Local Electromagnetic Field Structures by Scanning Transmission Electron Microscopy.

The functional properties of materials and devices are critically determined by the electromagnetic field structures formed inside them, especially at nanointerface and surface regions, because such structures are strongly associated with the dynamics of electrons, holes and ions. To understand the fundamental origin of many exotic properties in modern materials and devices, it is essential to directly characterize local electromagnetic field structures at such defect regions, even down to atomic dimensions. In recent years, rapid progress in the development of high-speed area detectors for aberration-corrected scanning transmission electron microscopy (STEM) with sub-angstrom spatial resolution has opened new possibilities to directly image such electromagnetic field structures at very high-resolution. In this Account, we give an overview of our recent development of differential phase contrast (DPC) microscopy for aberration-corrected STEM and its application to many materials problems. In recent years, we have developed segmented-type STEM detectors which divide the detector plane into 16 segments and enable simultaneous imaging of 16 STEM images which are sensitive to the positions and angles of transmitted/scattered electrons on the detector plane. These detectors also have atomic-resolution imaging capability. Using these segmented-type STEM detectors, we show DPC STEM imaging to be a very powerful tool for directly imaging local electromagnetic field structures in materials and devices in real space. For example, DPC STEM can clearly visualize the local electric field variation due to the abrupt potential change across a p-n junction in a GaAs semiconductor, which cannot be observed by normal in-focus bright-field or annular type dark-field STEM imaging modes. DPC STEM is also very effective for imaging magnetic field structures in magnetic materials, such as magnetic domains and skyrmions. Moreover, real-time imaging of electromagnetic field structures can now be realized through very fast data acquisition, processing, and reconstruction algorithms. If we use DPC STEM for atomic-resolution imaging using a sub-angstrom size electron probe, it has been shown that we can directly observe the atomic electric field inside atoms within crystals and even inside single atoms, the field between the atomic nucleus and the surrounding electron cloud, which possesses information about the atomic species, local chemical bonding and charge redistribution between bonded atoms. This possibility may open an alternative way for directly visualizing atoms and nanostructures, that is, seeing atoms as an entity of electromagnetic fields that reflect the intra- and interatomic electronic structures. In this Account, the current status of aberration-corrected DPC STEM is highlighted, along with some applications in real material and device studies.

Comparison of mesenchymal stem cells obtained by suspended culture of synovium from patients with rheumatoid arthritis and osteoarthritis.

BACKGROUND: Mobilization of mesenchymal stem cells (MSCs) from the synovium was revealed using a "suspended synovium culture model" of osteoarthritis (OA). The pathology of rheumatoid arthritis (RA) differs from that of OA. We investigated whether mobilization of MSCs from the synovium also occurred in RA, and we compared the properties of synovial MSCs collected from suspended synovium culture models of RA and OA. METHODS: Human synovium was harvested during total knee arthroplasty from the knee joints of patients with RA (n = 8) and OA (n = 6). The synovium was suspended in a bottle containing culture medium and a culture dish at the bottom. Cells were harvested from the dish and analyzed. RESULTS: No significant difference was observed between RA and OA in the harvested cell numbers per g of synovium. However, the variation in the number of cells harvested from each donor was greater for RA than for OA. The harvested cells were multipotent and no difference was observed in the cartilage pellet weight between RA and OA. The surface epitopes of the cells in RA and OA were similar to those of MSCs. CONCLUSION: Mobilization of MSCs from the synovium was demonstrated using a suspended synovium culture model for RA. The harvested cell numbers, chondrogenic potentials, and surface epitope profiles were comparable between the RA and OA models.

Direct imaging of local atomic structures in zeolite using optimum bright-field scanning transmission electron microscopy.

Zeolites are used in industries as catalysts, ion exchangers, and molecular sieves because of their unique porous atomic structures. However, direct observation of zeolitic local atomic structures via electron microscopy is difficult owing to low electron irradiation resistance. Subsequently, their fundamental structure-property relationships remain unclear. A low-electron-dose imaging technique, optimum bright-field scanning transmission electron microscopy (OBF STEM), has recently been developed. It reconstructs images with a high signal-to-noise ratio and a dose efficiency approximately two orders of magnitude higher than that of conventional methods. Here, we performed low-dose atomic-resolution OBF STEM observations of two types of zeolite, effectively visualizing all atomic sites in their frameworks. In addition, we visualized the complex local atomic structure of the twin boundaries in a faujasite (FAU)-type zeolite and Na+ ions with low occupancy in eight-membered rings in a Na-Linde Type A (LTA) zeolite. The results of this study facilitate the characterization of local atomic structures in many electron beam-sensitive materials.

Magnetic Field Observation in a Magnetic Tunnel Junction by Scanning Transmission Electron Microscopy.

A magnetic tunnel junction (MTJ) consists of two ferromagnetic layers separated by a thin insulating layer. MTJs show tunnel magnetoresistance effect, where the resistance in the direction perpendicular to the insulator layer drastically changes depending on the magnetization directions (parallel or antiparallel) in the ferromagnetic layers. However, direct observation of local magnetizations inside MTJs have been challenging. In this study, we demonstrate direct observation of magnetic flux density distribution inside epitaxially grown Fe/MgO/Fe layers using differential phase contrast scanning transmission electron microscopy. By utilizing newly-developed tilt-scan averaging system for suppressing diffraction contrasts, we clearly visualize parallel and antiparallel states of ferromagnetic layers at nanometer resolution.

Comparison of Clinical Outcomes after Revision Anterior Cruciate Ligament Reconstruction using a Bone-patellar Tendon-bone Autograft and that Using a Double-Bundle Hamstring Tendon Autograft.

PURPOSE: The purpose of this study was to compare clinical outcomes between revision anterior cruciate ligament reconstruction (ACLR) using a bone-patellar tendon-bone (BPTB) autograft and that using a double-bundle hamstring tendon (HT) autograft. METHODS: Consecutive cases of revision ACLRs were reviewed. The Lysholm knee scale and Knee Osteoarthritis Outcome Score (KOOS) were recorded at the final follow-up. The pivot shift test, Lachman test, and anterior knee laxity measurement using an arthrometer were evaluated before revision ACLR and at final follow-up. Contralateral knee laxity was also evaluated, and side-to-side differences noted. The Lysholm knee scale, KOOS, the pivot shift test, Lachman test, and anterior knee laxity were compared between HT versus BPTB autograft recipient groups using the Mann-Whitney test or the t-test. RESULTS: Forty-one patients who underwent revision ACLR and followed up for at least 2 years were included. The graft source was a BPTB autograft in 23 patients (BPTB group) and a double-bundle HT autograft in 18 patients (HT group). The mean postoperative follow-up period was 44 ± 28 months in the BPTB group and 36 ± 18 in the HT group (p = 0.38). The HT group had significantly higher KOOS in the pain subscale (less pain) than the BPTB group at the final follow-up (BPTB group 84.2 vs. HT group 94.4; p = 0.02). The BPTB group showed significantly smaller side-to-side difference in anterior knee laxity (superior stability) than the HT group (0.3 vs. 2.6 mm; p < 0.01). The percentage of patients with residual anterior knee laxity in the BPTB group was significantly lower than that in the HT group (9.5% vs. 46.7%; odds ratio, 8.3; p = 0.02). STUDY DESIGN: This was a level 3 retrospective study. CONCLUSION: Revision ACLR with a BPTB autograft was associated with superior results regarding restoration of knee joint stability as compared with that with a double-bundle HT autograft, whereas double-bundle HT autograft was superior to BPTB autograft in terms of patient-reported outcomes of pain. The rest of the patient-reported outcomes were equal between the two groups.

Development of tilt-scan system for differential phase contrast scanning transmission electron microscopy.

Differential phase contrast (DPC) scanning transmission electron microscopy can directly visualize electromagnetic fields inside a specimen. However, their image contrast is not only sensitive to the electromagnetic fields in the sample, but also the changes in diffraction conditions such as sample bends or thickness changes. These additional contrasts are called diffraction contrasts, and sometimes make it difficult to extract pure electromagnetic field information from the experimental DPC images. In this study, we developed a beam scan system that can acquire many DPC images from the same sample region with arbitrarily varying incident beam tilt angles to the sample. Then, these images are precisely averaged to form tilt-scan averaged DPC images. It is shown that the diffraction contrast can be effectively reduced in the tilt-scan averaged DPC images.

MRI study of medial meniscus degeneration of osteoarthritic knees with or without posterior root tear.

PURPOSE: The purpose of this study was to compare the medial meniscus (MM) degeneration, meniscus extrusion, and tibial joint inclination by using MRI to consider the pathogenesis of posterior root tear (PRT) in medial-type knee osteoarthritis (KOA) both with and without medial meniscus posterior root tear (MMPRT). METHODS: This study used open MRI with flexion sagittal view and included 324 medial-type osteoarthritic knees with a Kellegren-Lawrence grade of 2 or less. Following the exclusion process, 151 knees were selected for MRI analysis. MM degeneration grading was performed according to Jerosch by 5 degrees of 0-4 in four different portions from anterior to posterior. MM medial extrusion (MMME), MM posterior extrusion (MMPE), medial tibial medial slope (MTMS), and medial tibial posterior slope (MTPS) were measured according to previous studies. RESULTS: MM degeneration in the anterior portion to MCL averaged 1.72 ± 0.67 in the PRT group (n = 48) and 1.40 ± 0.78 in the non-PRT group (n = 103). The degeneration grade was statistically higher in the PRT group than in the non-PRT group (p = 0.050). There was no difference in MM degeneration in the other three portions. MMME averaged 4.02 ± 1.12 mm in the PRT group and 3.11 ± 1.11 mm in the non-PRT group. MMPE averaged 4.22 ± 0.87 mm in the PRT group and 2.83 ± 1.12 mm in the non-PRT group. Both MMME and MMPE in the PRT group were statistically larger than those in the non-PRT group (p < 0.001). There was no difference in MTMS between the two groups. MTPS averaged 6.34 ± 2.25° in the PRT group and 5.28 ± 2.23° in the non-PRT group. The MTPS of the PRT group was statistically larger than that of the non-PRT group (p = 0.007). CONCLUSION: The severity of MM degeneration, extrusion of MM, and degree of tibial slope were compared between medial-type KOA with and without PRT using an open MRI. MM degeneration was more severe anteriorly in the PRT group. The PRT group showed larger MMME and MMPE with greater MTPS. LEVEL OF EVIDENCE: III. Retrospective cohort study.

Surgical Repair of Symptomatic Wrisberg Variant Discoid Lateral Mensicus with Pull-Out Repair and Capsulodesis.

Wrisberg variant discoid lateral meniscus (DLM) is a congenital anatomic variation of the meniscus in the knee joint, which is an uncommon type of the DLM. We present a surgical technique in a case of symptomatic Wrisberg variant DLM. To improve the instability due to the lack of the posterior attachment of meniscotibial ligament, the posterior portion of DLM was attached to the insertion site of normal LM posterior root using pull-out repair technique. In addition, a longitudinal tear from the anterior to the middle portion of DLM was repaired with outside-in and inside-out techniques. Finally, a capsulodesis using knotless anchors was performed from outside of the joint to prevent the meniscus extrusion after the surgery. Knee symptoms such as pain, catching, and ROM restriction disappeared at 3 months after the surgery. Postoperative magnetic resonance imaging showed a slightly sharpened shape of the DLM, and the attachment of the posterior portion of the DLM was observed. Longitudinal tear of the DLM was healed without cleavage. This procedure is useful to improve the symptoms of the knee joint with Wrisberg variant DLM and to preserve the function of the meniscus.

Biomechanical analysis of a centralization procedure for extruded lateral meniscus after meniscectomy in porcine knee joints.

The recently developed arthroscopic centralization for lateral meniscal extrusion has obtained satisfactory short-term clinical and radiological results and improves the meniscus biomechanical properties. However, the effectiveness of treatment for meniscus extrusion after partial meniscectomy still requires elucidation. This study investigated the effect of centralization with modifications from a mechanical viewpoint. Porcine knee joints (N = 6) were set in a universal tester under the following conditions: (1) Intact; (2) Meniscectomy: Inner half of the posterior half meniscus was removed; (3) Extrusion: Posterior meniscus was dislocated laterally by transecting the posterior root and the meniscotibial ligament; (4) Centralization-1: Centralization procedure using one anchor; (5) Centralization-2: Centralization procedure using two anchors; and (6) Centralization-ad: Centralization with capsular advancement using two anchors. Load distributions and contact pressure in the meniscus and tibial cartilage were evaluated with an axial compressive force of 200 N. After meniscectomy, the tibial cartilage load increased and that of the medial margin of the posterior part of the meniscus decreased. When the meniscus was extruded, the load was concentrated only on the tibial cartilage. Centralization-1 increased the load on the meniscus, while Centralization-2 further increased the meniscus load but decreased the tibial cartilage load. Centralization-ad further decreased the load on the tibial plateau. The average contact pressure of the tibial cartilage was significantly higher in the Extrusion group than in the Intact group or the Centralization-ad group. From a biomechanical viewpoint, centralization with capsular advancement was the most effective of the tested procedures for treatment for an extruded meniscus after partial meniscectomy.

Yields of mesenchymal stromal cells from synovial fluid reflect those from synovium in patients with rheumatoid arthritis.

The yield of primary synovial mesenchymal stromal cells (MSCs) from synovium of patients with rheumatoid arthritis (RA) is highly variable, but cell transplantation therapy with autologous synovial MSCs requires accurate prediction of the synovial MSC yield per synovium weight. Here, we determined whether the yield of synovial fluid MSCs might predict the ultimate yield of primary MSCs from the synovium of RA knees. Synovial fluid and synovium were harvested during total knee arthroplasty from the knee joints of 10 patients with RA. Synovial fluid (1.5 mL) was diluted fourfold and plated equally into six 60 cm2 dishes. Nucleated cells from digested synovium were similarly plated at 1 × 104 cells in 6 dishes. All dishes were cultured for 14 days and analyzed for MSC yields and properties, including in vitro chondrogenesis. The cultured synovial cell number was correlated with the cultured synovial fluid cell number (n = 10, R2 = 0.64, p < 0.01). Synovial fluid cells formed cell colonies and showed MSC-like surface epitopes and multi-differentiation potential. However, the cartilage pellet weight indicated a greater chondrogenic potential of the synovial MSCs (n = 8). The primary MSC yields from synovial fluid and synovium were correlated, indicating that the synovial fluid MSC yield can predict the ultimate synovial MSC yield.

Comparison of adhesion of thawed and cultured synovial mesenchymal stem cells to the porcine meniscus and the relevance of cell surface microspikes.

BACKGROUND: Placement of a cultured synovial mesenchymal stem cell (MSC) suspension on a repaired meniscus for 10 min accelerated meniscus repair. Upon placement of the MSC suspension on the meniscus, microspikes projecting from the MSC surface trap meniscus fibers and promote MSC adhesion. Thawed cryopreserved MSCs are preferred materials for meniscus repair, as they can be transplanted without additional culture. However, the adhesion ability of thawed cryopreserved MSCs is unknown. Here, we compared the proportion of cultured versus thawed MSCs adhering to a porcine meniscus immediately and 10 min after placement. We also investigated the relationship between adhesion and the number of microspikes on the synovial MSCs. METHODS: Synovial MSCs were prepared from the knees of four donors with osteoarthritis. The "cultured MSCs" were thawed MSCs that were re-cultured and suspended in PBS for transplantation. A similarly prepared suspension was cryopreserved, thawed again, suspended in PBS, and used without further culture as the "thawed MSCs." MSCs with at least three microspikes in SEM images were defined as microspike-positive MSCs. Porcine meniscus surfaces were abraded, cut into a cylindrical shape, and treated with MSC suspension. Non-adherent cells were counted immediately and again 10 min after placement to calculate the adhesion proportion. RESULTS: The proportion of microspike-positive MSCs was significantly higher in thawed (53 ± 3%) than in cultured (28 ± 5%) MSC suspensions. MSC adhesion to the meniscus was significantly better for the thawed than for the cultured MSC suspensions immediately after placement on the meniscus, but no differences were detected after 10 min. The proportion of MSCs with microspikes in the cell suspension was significantly correlated with the proportion of adhered MSCs immediately after the placement, but not 10 min later. Addition of FBS to the cryopreservation medium promoted a concentration-dependent increase in the proportion of microspike-positive cells. CONCLUSIONS: Thawed MSCs adhered better than cultured MSCs immediately after placement, but adhesion was similar for both MSC preparations after 10 min. Immediately after placement, the presence of microspikes was associated with better adhesion of synovial MSCs to the meniscus.