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Purpose: In vivo kinematics of skeletal joints and prostheses is affected by gravity; therefore, absolute tilt must be taken into account. However, current fluoroscopic kinematic analysis cannot measure the tilt. This study introduces and validates a method for defining the horizontal plane in fluoroscopy systems to measure the tilt of an object. Methods: A rectangular metal plate (200 ​× ​200 ​× ​10 ​mm) with a flatness of 0.03/100 ​mm was horizontally adjusted using a leveler (sensitivity of 0.02° and accuracy of ±0.06°), and its three-dimensional coordinate was calculated from a two-dimensional fluoroscopic image. A coordinate calculation formula was developed, with precision and accuracy assessed via computer simulations. Actual fluoroscopic tests included four aspects: accuracy under the same condition; accuracy under different X-ray tube height; reproducibility when changing X-ray tube height; and reproducibility when the flat panel was tilted and returned. Results: The theoretical measurement error indicated by the computer simulations was 0.0 ​± ​0.2° on the xy-plane and 0.0 ​± ​0.0° on the yz-plane. The actual experimental results showed that the horizontal plane tilt was measured to be −0.2 ​± ​0.1° tilt on the xy-plane and 0.3 ​± ​0.0° tilt on the yz-plane for the device used in this study. The F-test showed no significant differences between the computer simulations and the actual experiments. There were no significant differences between the four actual tests. Conclusions: This method enables the horizontal plane to be defined and the tilt of an object to be measured in fluoroscopic kinematic analysis.

Background/objective: This study aimed to clarify the kinematics of bi-cruciate-retaining (BCR) total knee arthroplasty (TKA) by comparing the mechanical alignment (MA) and functional alignment (FA) methods and to evaluate differences between the two alignment methods. Methods: The in vivo kinematics of 20 MA TKA and 20 FA TKA knees were investigated under fluoroscopy during squatting using a two-to three-dimensional registration technique. Accordingly, knee flexion angle, axial rotational angle, varus–valgus angle, anteroposterior translation of the medial and lateral low contact points of the femoral component relative to the tibial component and kinematic pathway were evaluated. Results: No difference in the knee flexion angle was observed between the MA and FA TKA groups. Femoral external rotation was observed in both groups and no significant difference was observed. Significant varus alignment from extension to early flexion range was observed in the FA TKA group. The posterior translation of the medial side was smaller in the FA TKA group than in the MA TKA group. Conversely, no significant difference in the anteroposterior translation of the lateral side was observed. In the kinematic pathway, a medial pivot motion from 0° to 20° of flexion and a lateral pivot motion beyond 20° of flexion were observed in both groups. Conclusion: During squatting in BCR TKA, the FA TKA group significantly showed varus alignment and smaller posterior translation of the medial side than the MA TKA group from extension to early flexion range.

Background: Previous studies have aimed to determine the use of certain risk factors in predicting the occurrence of noncontact anterior cruciate ligament (ACL) injuries. Unfortunately, evidence regarding noncontact ACL injuries in male American football players is limited. This prospective cohort study aimed to identify intrinsic risk factors for noncontact ACL injury among male American football players. Methods: This study evaluated 152 male American football players in Japan for potential noncontact ACL injury risk factors during a preseason medical assessment, including anthropometric, joint laxity, and flexibility, muscle flexibility, muscle strength, and balance measurements. A total of 25 variables were examined. Participants were monitored during each season for noncontact ACL injury, as diagnosed by physicians. Results: Noncontact ACL injuries occurred in 11 knees of 11 players (prevalence; 7.1 %). Injured players were significantly more likely to have lightweight (P = 0.049). No statistically significant between-group differences were found for any other variables. Participants with a lower hamstring to quadriceps (H/Q) ratio (P = 0.04) were more likely to sustain noncontact ACL injuries. Conclusion: Lower H/Q ratio and lower body weight were significantly associated with new-onset noncontact ACL injury in male American football players. These findings will help develop strategies to prevent noncontact ACL injuries in male American football players.

Abstract Purpose The tibial anatomical anteroposterior (AP) axis “Akagi's line” was originally defined on computed tomography (CT) in total knee arthroplasty (TKA); however, its intraoperative reproducibility remains unknown. This study aimed to evaluate the intraoperative reproducibility of the Akagi's line and its effect on postoperative clinical outcomes. Methods This prospective study included 171 TKAs. The rotational angle of the intraoperative Akagi's line relative to the original Akagi's line (RAA) defined on CT was measured. The RAA was calculated based on the tibial component rotational angles relative to the intraoperative Akagi's line measured using the navigation system and CT. The effects of RAA on postoperative clinical outcomes and rotational alignments of components were also evaluated. Results The mean absolute RAA (standard deviation) value was 5.5° (3.9°). The range of RAA was 22° internal rotation to 16° external rotation. Intraoperative Akagi's line outliers (RAA > 10°) were observed in 14% of the knees (24 knees). In outlier analysis, the tibial component rotation angle was externally rotated 6.5° (5.6°) in the outlier group and externally rotated 3.7° (4.2°) in the nonoutlier group (≤10°), with a significant difference between the two groups. Additionally, the outlier group (RAA > 10°) showed lower postoperative clinical outcomes. Conclusion The original Akagi's line defined on CT showed insufficient reproducibility intraoperatively. The poor intraoperative detection of Akagi's line could be the reason for the tibial component rotational error and worse postoperative clinical outcomes. Level of Evidence Level IV, case series.

Purpose: Graft failure or recurrence of instability without obvious trauma remains one of the problems following anterior cruciate ligament (ACL) reconstruction. This retrospective study aimed to identify risk factors for abnormal knee laxity after anatomical ACL reconstruction. Methods: A total of 291 patients who underwent primary anatomical ACL reconstruction were included in this study. Sex, age, body mass index (BMI), time to surgery, medial meniscal status, lateral meniscal status, graft materials, initial graft tension protocol, preoperative and postoperative pivot shift test and side-to-side differences in anterior tibial translation using the arthrometer were reviewed. Abnormal knee laxity was defined as constituting one or both of the following criteria: (i) a side-to-side difference of ≥3 mm by arthrometer; and (ii) a positive pivot shift test, being “glide,” “clunk”, or “gross”. Results: Abnormal knee laxity occurred in 30 patients (10.3%) at a median follow-up of 25 months. Results of univariate analysis indicated that a higher likelihood of abnormal knee laxity was associated with female sex, greater BMI, longer time to surgery, higher initial graft tension protocol, and lateral meniscus resection. Multivariate logistic regression analysis showed that abnormal knee laxity was significantly associated with time to surgery [1-month increase; odds ratio (OR), 1.01], higher initial graft tension protocol (vs. lower tension; OR, 3.5), and lateral meniscus resection (vs. intact and repaired lateral meniscus; OR, 12.8). Conclusion: Higher initial graft tension protocol, chronicity of ACL deficiency, and lateral meniscus resection were risk factors for abnormal knee laxity after anatomical ACL reconstruction. Level of evidence: Level III retrospective prognostic study.

Purpose: This study aimed to review the causes of failure after total knee arthroplasty (TKA), focusing on the causes of revision and persistent pain. Methods: A literature search was conducted in the databases of PubMed, Cochrane Library, and Google Scholar for articles published before October 4, 2022. In addition, registry data from 11 countries were obtained from national registry archives. Results: National registry data and recent articles show that aseptic loosening, infection, instability, patellofemoral complication, and pain are major overall causes of TKA revisions. The most common etiologies of TKA revisions were aseptic loosening in six countries and infection in four countries. In contrast, polyethylene wear has become one of the minor reasons for revision, although it used to be one of the major causes of revision. Additionally, various causes of persistent pain include improper component placement, oversizing, patellofemoral overstuffing, ligament imbalance, elevated joint lines, kinematic abnormalities, and preoperative psychological factors such as catastrophizing state and central sensitization of pain. Conclusions: With the evolution of surgical techniques and prosthetic designs, a paradigm shift in the etiology of failure mechanisms after TKA might have occurred. However, the number of patients with TKA failure suffering from persistent pain and requiring revision is increasing. Thus, orthopedic surgeons must understand the current situations of TKA failures to improve clinical outcomes and reduce post-TKA dissatisfaction.

Purpose: Attempts have been made to enhance knee prostheses design to improve clinical outcomes including bi-cruciate stabilized (BCS) TKA design and single-radius (SR) femoral component design. The complication rate of first generation BCS (fBCS) TKA was higher than that of standard TKA. Regarding BCS TKA, modification of the fBCS TKA system to the second-generation BCS (sBCS) TKA system was performed to avoid complications. This study aimed to compare the midterm clinical results of sBCS TKA and SR TKA. Methods: We retrospectively reviewed data from TKA patients. A total of 142 patients who were followed up for at least 5 years were enrolled: 61 TKAs using sBCS and 81 TKAs using the posterior stabilized (PS) single-radius (SR) design. The clinical results at 6 months, 2 years, and 5 years postoperatively were compared between the sBCS and SR PS groups. Results: At 6 months postoperatively, the maximum flexion angle (MFA) of the sBCS group was larger than that of the SR PS group. At 2 years, MFA, KOOS subscales of pain and ADL in the sBCS group were better and at 5 years, the MFA, KOOS subscales of pain and QOL in the sBCS group were better than those in the SR group. There was no significant differences of the ratios of complications and revision surgeries between the two groups. Conclusion: The midterm clinical results of sBCS TKA were better than those of SR PS TKA in terms of the MFA and KOOS subscales of pain and QOL.

Purpose: “Rotational self-alignment mechanism'' was designed for mobile-bearing total knee arthroplasty (MB TKA) to maintain a natural femorotibial rotational alignment independent of component rotational alignment. However, it is clinically unknown if the influence of component rotational alignment on a postoperative anatomical femorotibial rotational angle (FTRA) in MB TKA is eliminated. This study aimed to determine the effect of component rotational alignments on postoperative anatomical FTRA in MB TKA as compared to fixed-bearing TKA (FB TKA). Methods: This research comprised a total of 161 knees: 54 ​MB TKAs and 107 FB TKAs. In computed tomography, the postoperative FTRA and rotational alignment of tibial and femoral components to anatomical axes were assessed, and the association between the postoperative FTRA and perioperative radiographic data, including component rotational alignments, was examined. Result: Rotational alignments of both tibial and femoral components did not correlate postoperative FTRA in MB TKA (tibial component: r ​= ​−0.15, p ​= ​0.26, femoral component: r ​= ​0.22, p ​= ​0.10), however, in FB TKA, rotational alignment of tibial component did correlate postoperative FTRA, while that of femoral component did not (tibial component: r ​= ​−0.65, p ​

Abstract Background Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA). Methods Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras). Results The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs. Conclusions The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs.

Abstract Background Given the frequency of hamstring strain injuries (HSI) among male college American football players, several studies have attempted to determine whether certain risk factors can predict their occurrence. However, no consensus on modifiable risk factors for HSIs in male college American football players has yet been reached to prevent these injuries. This study aimed to clarify risk factors for HSI prospectively in college male American football players. Methods A total of 78 male college American football players, whose positions were limited to skill positions, were medically assessed for potential risk factors of HSI. The preseason medical assessment included anthropometric measurements, joint laxity and flexibility, muscle flexibility, muscle strength, and balance ability. Results HSI occurred in a total of 25 thighs from 25 players (32.1%). Injured players had significantly lower hamstring flexibility (p = 0.02) and hamstring to quadriceps strength ratio (H/Q) (p = 0.047) compared to uninjured players. Additionally, injured players had significantly lower general joint laxity scores, especially for the total (p = 0.04), hip (p = 0.007), and elbow (p = 0.04) scores, compared to uninjured players. Conclusions Lower hamstring flexibility, lower hamstring to quadriceps strength ratio, and lower general joint laxity score were identified as risk factors for HSI in male college American football players placed in skill positions. The muscle flexibility and H/Q ratio could be useful in preventing HSI in such players.

Background: Tunnel widening (TW) after anterior cruciate ligament (ACL) reconstruction has been a research area of interest in ACL reconstruction. In recent years, it has been noted that posterior tibial slope (PTS) affects several types of outcomes after ACL reconstruction including TW. However, the relationships between femoral and tibial TW and between PTS and TW following anatomical ACL reconstruction using a bone–patellar tendon–bone (BTB) graft are often not understood. Therefore, the purpose of this study was to retrospectively clarify the magnitude of femoral and tibial TW and the effect of PTS on TW following anatomical ACL reconstruction using a BTB graft. Methods: A total of 111 patients who underwent isolated ACL reconstructions using BTB grafts were included in this study. Femoral and tibial tunnel aperture areas were measured using three-dimensional computed tomography (3D CT) at 1 week and 1 year postoperatively, and femoral and tibial TW (%) was calculated. Lateral and medial PTS was also measured using 3D CT. Results: As compared with 1 week postoperatively, the mean tibial tunnel aperture areas increased by 30.6% ± 28.5%, and the mean femoral tunnel aperture areas increased by 28.3% ± 27.9% when measured at 1 year postoperatively. Although no significant difference was observed between femoral and tibial TW, a significant positive correlation was noted between femoral and tibial TW (r = 0.240, p = 0.011). A significant correlation was observed only between lateral PTS and tibial TW (r = 0.354, p

Abstract Background In bicruciate-stabilized total knee arthroplasty (BCS-TKA), the relationship between the postoperative kinematics and sports subscales in patient-reported outcome measures (PROMs) remains unknown. The purpose of this study was to determine the relationship between kinematics and sports subscales using the PROMs after BCS-TKA. Methods Sixty-one patients with severe knee osteoarthritis were examined at 13.5 ± 7.8 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. Range of motion of the knee, axial rotation of the femur relative to the tibial component, and anteroposterior (AP) translation of the medial and lateral femorotibial contact points were measured using a 2D-to-3D registration technique. In addition, the relationship between the kinematics and improvement of the sports subscales in the Knee Injury and Osteoarthritis Outcome Score (KOOS) was evaluated. Results In rotation angle, the femoral external rotation was observed from 0 to 50° of flexion. The amount of femoral external rotation did not correlate with PROMs-SP. In medial AP translation, posterior translation was observed from 0 to 20° and 80–110° of flexion. Mild anterior translation was observed from 20 to 80° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with squatting. In lateral AP translation, posterior translation was observed from 0 to 20° and 80–110° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with running, jumping, twisting/pivoting, and kneeling. Conclusion Femoral rollback at high flexion during squatting may be important to improve sports performance after BCS-TKA.

Abstract Background The choice of mobile bearing (MB) thickness is essential for obtaining successful results after mobile-bearing Oxford unicompartmental knee arthroplasty (UKA). This study aimed to investigate the effects of a 1-mm difference in bearing thickness on intraoperative MB movement and intraoperative knee kinematics in Oxford UKAs. Methods We prospectively investigated the effects of a 1-mm difference in bearing thickness on intraoperative MB movement and knee kinematics in 25 patients who underwent Oxford UKAs when surgeons didn’t know which bearing thickness to choose with 1-mm difference. A trial tibial component that was scaled every 2 mm was used to measure the intraoperative MB movement, and the tibial internal rotation relative to the femur and the knee varus angle was simultaneously evaluated using the navigation system as the knee kinematics. We separately evaluated sets of two MB thicknesses with 1-mm differences, and we compared the intraoperative parameters at maximum extension; 30º, 45º, 60º, and 90º flexion; and maximum flexion between the thicker MB (thick group) and the thinner MB (thin group). Results The MB in the thin group was located significantly posteriorly at 90º flexion compared with that in the thick group; however, there were no differences at the other flexion angles. There was significantly less tibial internal rotation in the thin group at 90º flexion than that in the thick group; however, there were no differences at the other flexion angles. The knee varus angles in the thick group were significantly smaller than those in the thin group by approximately one degree at all angles other than at 30º and 45º flexion. Conclusion The thicker MB could bring the less posterior MB movement and the more tibial internal rotation at 90º flexion, additionally the valgus correction angle in the thicker MB should be paid attention. These results could help surgeons to decide the thickness of MBs when they wonder the thickness of MB.

Abstract Background Tibial internal rotation following total knee arthroplasty (TKA) is important in achieving favorable postoperative clinical outcomes. Studies have reported the effect of intraoperative soft tissue balance on tibial internal rotation in conventional TKA, no studies have evaluated the effects of soft tissue balance at medial or lateral compartments separately on tibial internal rotation in bi-cruciate stabilized (BCS) TKA. The purpose of this study was to clarify the relationship between medial or lateral component gaps and rotational knee kinematics in BCS TKA. Methods One hundred fifty-eight knees that underwent BCS TKA were included in this study. The intraoperative medial and lateral joint laxities which was defined as the value of component gap minus the thickness of the tibial component were firstly divided into two groups, respectively: Group M-stable (medial joint laxity, ≤ 2 mm) or Group M-loose (medial joint laxity, ≥ 3 mm) and Group L-stable (lateral joint laxity, ≤ 3 mm) or Group L-loose (lateral joint laxity, ≥ 4 mm). And finally, the knees enrolled in this study were divided into four groups based on the combination of Group M and Group L: Group A (M-stable and L-stable), Group B (M-stable and L-loose), Group C (M-loose and L-stable), and Group D (M-loose and L-loose). The intraoperative rotational knee kinematics were compared between the four Groups at 0°, 30°, 60°, and 90° flexion, respectively. Results The rotational angular difference between 0° flexion and maximum flexion in Group B at 30° flexion was significantly larger than that in Group A at 30° flexion (*p

Abstract We analyzed the implantation effects on cruciate ligament force in unicompartmental knee arthroplasty (UKA) and determined whether kinematics is associated with the cruciate ligament force. We examined 16 patients (17 knees) undergoing medial UKA. Under fluoroscopy, each participant performed a deep knee bend before and after UKA. A two-dimensional/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Forces in the anteromedial and posterolateral bundles of both the anterior cruciate ligament (aACL and pACL) and the anterolateral and posteromedial bundles of the posterior cruciate ligament (aPCL and pPCL) during knee flexion were analyzed pre- and post-UKA. Correlations between changes in kinematics and ligament forces post-UKA were also analyzed. Preoperatively, the aACL forces were highly correlated with anteroposterior (AP) translation of the lateral condyles (Correlation coefficient [r] = 0.59). The pPCL forces were highly correlated with the varus–valgus angulation (r = − 0.57). However, postoperatively, the PCL forces in both bundles were highly correlated with the AP translation of the medial femoral condyle (aPCL: r = 0.62, pPCL: r = 0.60). The ACL and PCL forces of the knees post-UKA were larger than those of the knees pre-UKA. Kinematic changes were significantly correlated with the cruciate ligament force changes.

Abstract Background This study aims to elucidate and compare the relationship between the knee flexion angle and patient-reported outcome measures (PROM) in both non-weight-bearing (NWB) and weight-bearing (WB) conditions. Methods This retrospective cohort study included 61 knees (47 patients) who underwent total knee arthroplasty. The knee flexion angle was measured by three conditions: NWB in manual goniometer, NWB in fluoroscopic three-dimensional (3D) analysis and WB in the fluoroscopic 3D analysis. The PROM was evaluated by postoperative 2011 Knee Society Score (2011 KSS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Correlations between the knee flexion angle and PROM was analyzed using Spearman’s correlation coefficient. Additionally, whether the angular difference between NWB and WB correlated with the PROM or not was evaluated. Results The NWB knee flexion angle in a goniometer, NWB in 3D analysis, and WB in 3D analysis were 124.6° ± 8.4°, 118.0° ± 10.5°, and 109.5° ± 13.3°, respectively. The angular difference was 8.5° ± 12.8°. No PROM correlation existed in NWB using a goniometer. Moreover, significant positive correlations in 2011 KSS symptoms (r = 0.35) and 2011 KSS functional activities (r = 0.27) were noted in NWB using 3D analysis. Significant positive correlations existed in 2011 KSS symptoms (r = 0.32), 2011 KSS functional activities (r = 0.57), KOOS pain (r = 0.37), KOOS activity of daily living (ADL; r = 0.45), KOOS sports (r = 0.42), and KOOS quality of life (r = 0.36) in WB using 3D analysis. Significant negative correlations were noted in 2011 KSS functional activities (r = − 0.45), KOOS ADL (r = − 0.30), and KOOS sports (r = − 0.38) in angular difference. Conclusions The WB knee flexion angle better correlated with PROM compared with NWB by evaluation of 3D analysis. The larger the angular difference existed between NWB and WB, the lower the PROM score.

Abstract Background Although Oxford unicompartmental knee arthroplasty (UKA) is used in patients of wide age ranges, there is no clear information regarding the age differences in terms of intraoperative femorotibial rotational kinematics and its influence on clinical outcomes. Therefore, this study was conducted to examine the age differences in terms of intraoperative rotational kinematics and postoperative clinical outcomes and to analyze their relationship with classification according to the age group. Methods We investigated 111 knees of patients who underwent Oxford UKA using a navigation system and divided them into two groups: elderly (aged ≥75 years; 48 knees) and nonelderly (aged

Abstract Background One of the causes of dissatisfaction following total knee arthroplasty (TKA) is abnormal knee kinematics. A newly designed bi-cruciate stabilized (BCS) TKA system has been developed to produce close-to-normal kinematics because of its anatomic tibiofemoral articular geometry and cam-post mechanism. Although BCS TKA is expected to improve patient satisfaction, no reports have described the appropriate technique or soft tissue handling required to achieve excellent satisfaction with BCS TKA. This study is to identify intraoperative surgical predictors of patient satisfaction after BCS TKA. Methods We studied 104 knees with primary varus knee osteoarthritis that underwent BCS TKA with a navigation system retrospectively. Surgical parameters including coronal, sagittal and axial alignment and joint laxity in each compartment that affected patient satisfaction was evaluated. Satisfaction score was evaluated with use of the 2011 Knee Society Scoring system. The multivariate regression analysis included age, gender, body mass index and intraoperative parameters that correlated with satisfaction scores in the univariate analysis (P

Introduction: Clinical studies of intra-articular injection of mesenchymal stem cells for osteoarthritis (OA) indicate its efficacy. Here, we retrospectively investigated the associations of pretherapeutic magnetic resonance imaging (MRI) findings with the clinical outcomes up to 6 months, after intra-articular administration of adipose-derived stem cells (ASCs) to knee OA patients. Methods: We first analyzed alterations of the visual analog scale (VAS) and knee injury and osteoarthritis outcome score (KOOS) in 57 knees of 34 patients from whom clinical scores were obtained before ASC therapy, and at 1, 3, and 6 months. Among the patients, we further examined MRI findings of 34 knees of 19 patients whose pretherapeutic MRI data were available. Results: The mean improvement of VAS and KOOS-total during 6 months was 2.6 ± 4.0 (from 6.1 ± 2.5 to 3.5 ± 2.9, P

Abstract Background There are no previous reports on the complications around the femoral component of cementless Oxford unicompartmental knee arthroplasty (UKA). However, we experienced two cases of femoral migration to the proximal side, which caused bearing dislocations after cementless Oxford UKA. Case presentation Case1. In an 82-year-old woman, bearing dislocation occurred 13 months postoperatively because of femoral migration that was resolved with an revision surgery to cemented component and thicker mobile insert. Case2. In a 52-year-old man, first bearing dislocation occurred 7 months postoperatively. Five months after revising the insert to a thicker one, another dislocation occurred mainly because of the femoral migration. Eventually, a revision to total knee arthroplasty was necessary. Conclusions The inferred main reasons of femoral migration of cementless Oxford were osteoporosis for the first case and early return to high performance sports activity for the second case. Although several merits of using cementless prosthesis, particularly better fixation and lesser radiolucency than cemented prosthesis, have been reported, surgeons should pay attention to the patient’s bone quality and advise a slow return to high-level physical activity.

Background: One of the causes of dissatisfaction following total knee arthroplasty (TKA) is abnormal knee kinematics. A newly designed bi-cruciate stabilized (BCS) TKA system has been developed to produce close-to-normal kinematics because of its anatomic tibiofemoral articular geometry and cam-post mechanism. Although BCS TKA is expected to improve patient satisfaction, no reports have described the appropriate technique or soft tissue handling required to achieve excellent satisfaction with BCS TKA. This study is to identify preoperative and intraoperative predictors of patient satisfaction after BCS TKA. Methods: Altogether, we studied 113 knees with primary varus knee osteoarthritis that underwent BCS TKA with a navigation system. Preoperative parameters including Knee Society Score and patient-reported scores [the Knee injury and Osteoarthritis Outcome Score (KOOS)] and intraoperative parameters including coronal, sagittal and axial alignment and joint laxity in each compartment that affected patient satisfaction was evaluated. Satisfaction score was evaluated with use of the 2011 Knee Society Scoring system. The multivariate regression analysis included age and preoperative and intraoperative parameters that correlated with satisfaction scores in the univariate analysis ( P < 0.05). Results: The mean satisfaction score was 28.2 ± 6.1. Multivariate regression analysis showed that the predictors of patient satisfaction were a preoperative high KOOS score for activities of daily living ( P < 0.001), male sex ( P = 0.005), older age ( P = 0.027), and minimal medial joint laxity during flexion ( P = 0.031). Conclusion: When performing BCS TKA, surgeons should pay attention to maintaining proper stability of the medial compartment, especially during flexion.

The degradation mechanism of an Sn4P3 electrode as Na-ion battery anode was investigated by using a transmission electron microscopic observation. At the first desodiation, we confirmed that Sn nanoparticles with 6 nm in size were dispersed in an amorphous-like P matrix. Compared to this, we observed aggregated Sn particles with sizes exceeding 50 nm after the drastic capacity fading. The capacity fading mechanism was for the first time confirmed to be Sn aggregation. To improve the capacity decay, we carried out the two kinds of charge−discharge cycling tests under the reduced volume changes of Sn particles and P matrix by limiting desodiation reactions of NaSn and Na3P, respectively. The Sn4P3 electrode exhibited an excellent cyclability with the discharge capacity of 500 mA h g−1 for 420 cycles under the limited desodiation, whereas the capacity decay was accelerated under the limited sodiation. The results suggest that the Sn aggregation can be improved by the reduced volume change of the P matrix, and that it is very effective for improving anode performance of Sn4P3 electrode. Keywords: Tin phosphide (Sn4P3), Ionic liquid electrolyte, Na-ion battery, Negative electrode material, Nanostructure

The Saccharomyces cerevisiae Trm11 and Trm112 complex (Trm11-Trm112) methylates the 2-amino group of guanosine at position 10 in tRNA and forms N2-methylguanosine. To determine the elements required in tRNA for methylation by Trm11-Trm112, we prepared 60 tRNA transcript variants and tested them for methylation by Trm11-Trm112. The results show that the precursor tRNA is not a substrate for Trm11-Trm112. Furthermore, the CCA terminus is essential for methylation by Trm11-Trm112, and Trm11-Trm112 also only methylates tRNAs with a regular-size variable region. In addition, the G10-C25 base pair is required for methylation by Trm11-Trm112. The data also demonstrated that Trm11-Trm112 recognizes the anticodon-loop and that U38 in tRNAAla acts negatively in terms of methylation. Likewise, the U32-A38 base pair in tRNACys negatively affects methylation. The only exception in our in vitro study was tRNAValAAC1. Our experiments showed that the tRNAValAAC1 transcript was slowly methylated by Trm11-Trm112. However, position 10 in this tRNA was reported to be unmodified G. We purified tRNAValAAC1 from wild-type and trm11 gene deletion strains and confirmed that a portion of tRNAValAAC1 is methylated by Trm11-Trm112 in S. cerevisiae. Thus, our study explains the m2G10 modification pattern of all S. cerevisiae class I tRNAs and elucidates the Trm11-Trm112 binding sites.

The concentration of divalent cations is well-known to influence molecular processes such as enzymatic activity and RNA folding. Here the authors attempt to reproduce physiological conditions for RNA folding in vitro and establish an important contribution of chelated magnesium ions in enhancing RNA function.

To date, numerous modified nucleosides in tRNA as well as tRNA modification enzymes have been identified not only in thermophiles but also in mesophiles. Because most modified nucleosides in tRNA from thermophiles are common to those in tRNA from mesophiles, they are considered to work essentially in steps of protein synthesis at high temperatures. At high temperatures, the structure of unmodified tRNA will be disrupted. Therefore, thermophiles must possess strategies to stabilize tRNA structures. To this end, several thermophile-specific modified nucleosides in tRNA have been identified. Other factors such as RNA-binding proteins and polyamines contribute to the stability of tRNA at high temperatures. Thermus thermophilus, which is an extreme-thermophilic eubacterium, can adapt its protein synthesis system in response to temperature changes via the network of modified nucleosides in tRNA and tRNA modification enzymes. Notably, tRNA modification enzymes from thermophiles are very stable. Therefore, they have been utilized for biochemical and structural studies. In the future, thermostable tRNA modification enzymes may be useful as biotechnology tools and may be utilized for medical science.

The article focuses on the role of modified nucleosides in Ribonucleic Acid (RNA) folding studies inside peptide-rich droplets, shedding light on potential contributions to metabolic processes. Topics include the importance of compartmentalization of RNA in membraneless organelles, the influence of covalent RNA modifications on its structure in these compartments, and the use of next-generation sequencing.