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Abstract Purpose One of the most common types of coronal plane alignment of the knee (CPAK) is type I, which is characterised by varus alignment and apex distal joint line obliquity. The purpose of this study was to evaluate the association of changes in arithmetic hip–knee–ankle angle (aHKA) with both postoperative joint laxity and patient‐reported outcome measures (PROMs) in patients with CPAK type I following mechanical alignment (MA) total knee arthroplasty (TKA). Methods Of 111 consecutive knees in 92 patients with osteoarthritis who underwent primary TKA, 80 knees (72.0%) with CPAK type I phenotype preoperatively were evaluated. All TKAs were performed to achieve neutral MA by a medial stabilising gap balancing technique. Pre‐ to postoperative change in aHKA was defined as ΔaHKA. The 80 CPAK type I knees were divided into a larger ΔaHKA group (>7°) and a smaller ΔaHKA group (≤7°). PROMs, including the Knee Society Score and Forgotten Joint Score‐12, were assessed before and 2 years after surgery. Pre‐ and postoperative joint laxity was assessed using a Telos arthrometer. Results Twenty‐two knees showed a larger ΔaHKA, and postoperative lateral joint laxity in varus stress was significantly greater in these patients than in those with a smaller ΔaHKA (6.8° vs. 4.5°, p = 0.006). There were no significant differences between the groups in PROMs (p = n.s.). Conclusions Postoperative lateral laxity was associated with larger aHKA changes than smaller aHKA changes in CPAK type I knees after TKA. However, no statistically significant differences in PROMs were found according to the amount of change in aHKA. Level of Evidence Level III.

Purpose: Outcomes after combination of anterior cruciate ligament (ACL) reconstruction (ACLR) with unicompartmental knee arthroplasty (UKA) or high tibial osteotomy (HTO) have been widely reported, but previous systematic reviews have included articles published before 2000 and do not necessarily reflect recent trends. We conducted a thorough investigation to address (1): What are the recent surgical trends in simultaneous ACLR and UKA or HTO? and (2) What are the issues in these surgeries? based on a comprehensive systematic analysis. Methods: A systematic surveillance was performed in accordance with the PRISMA guideline. The inclusion criteria were as follows: simultaneous ACLR and UKA or HTO for medial osteoarthritis (OA) with ACL deficiency; clinical outcomes and complications recorded; publication date after 2000.A total of 1466 potentially relevant articles were identified; after exclusions, 31 articles that included 744 knees were analyzed. Fourteen articles included 330 knees underwent simultaneous ACLR and UKA (UKA group) and 17 articles included 414 knees underwent simultaneous ACLR and HTO (HTO group). Results: Overall, complications were found in 14 knees (4.2%) in the UKA group and 47 knees (11.3%) in the HTO group. Re-rupture of the ACL was observed in only the HTO group (6 knees: 1.4%). Revision to TKA occurred in 8 knees (2.4%) in the UKA group and 1 knee (0.2%) in the HTO group. No standardized outcome measures for clinical assessment were used for all studies. Conclusion: The systematic surveillance of studies published since 2000 on the outcomes and complications of simultaneous ACLR and UKA or HTO for medial OA with ACL deficiency indicates an increasing number of reports on simultaneous ACLR and HTO or UKA in recent years. Favorable clinical results were achieved in both treatment groups.

Abstract Autologous protein solution (APS) is made from platelet-rich plasma that extracts high-concentration growth factors and cytokines. Intra-articular APS injection was reported to improve knee osteoarthritis (KOA) pain and function. However, efficacy differences regarding osteoarthritis severity remained unknown. This retrospective study clinically assessed 220 knees with KOA in the Kellgren–Lawrence (KL) grades 2–4 that underwent APS injection using the Knee Injury and Osteoarthritis Outcome Score (KOOS). A telephone survey was performed for patients who dropped out to check symptom changes. The recalculated estimated responder rate included the telephone survey results. The 12-month follow-up was completed with 148 knees (67%), whereas 72 knees dropped out. The follow-up rate was significantly lower in KL4 than KL2 and 3. The KOOS significantly improved in 148 knees, whereas the KOOS was lower in KL4 than in KL2. The responder rate was 55% total, 58% in KL2, 57% in KL3, and 47% in KL4; however, the estimated responder rate, including the telephone survey, was 49% total, 55% in KL2, 54% in KL3, and 36% in KL4. This study showed improved clinical symptoms 1-year after APS injections for KOA, with a lower responder rate in KL4 than in KL2 or KL3.

Abstract Background Although the importance of kinematic evaluation of the sit-to-stand (STS) test of total knee arthroplasty (TKA) patients is clear, there have been no reports analyzing STS during the 30-s chair sit-up test (30 s-CST) with a focus on kinematic characteristics. This study aimed to demonstrate the clinical utility of kinematic analysis of STS during the 30 s-CST by classifying STS into subgroups based on kinematic parameters, and to determine whether differences in movement strategies are expressed as differences in clinical outcomes. Methods The subjects were all patients who underwent unilateral TKA due to osteoarthritis of the knee and were followed up for one year postoperatively. Forty-eight kinematic parameters were calculated using markerless motion capture by cutting STS in the 30 s-CST. The principal components of the kinematic parameters were extracted and grouped by kinematic characteristics based on the principal component scores. Clinical significance was examined by testing whether differences in patient-reported outcome measures (PROMs) were observed. Results Five principal components were extracted from the 48 kinematic parameters of STS and classified into three subgroups (SGs) according to their kinematic characteristics. It was suggested that SG2, using a kinematic strategy similar to the momentum transfer strategy shown in previous studies, performed better in PROMs and, in particular, may be associated with achieving a “forgotten joint”, which is considered the ultimate goal after TKA. Conclusions Clinical outcomes differed according to kinematic strategies used STS, suggesting that kinematic analysis of STS in 30 s-CST may be useful in clinical practice. Trial registration This study was approved by the Medical Ethical Committee of the Tokyo Women’s Medical University (approval number: 5628 on May 21, 2021).

Aims: Orthopaedic surgery requires grafts with sufficient mechanical strength. For this purpose, decellularized tissue is an available option that lacks the complications of autologous tissue. However, it is not widely used in orthopaedic surgeries. This study investigated clinical trials of the use of decellularized tissue grafts in orthopaedic surgery. Methods: Using the ClinicalTrials.gov (CTG) and the International Clinical Trials Registry Platform (ICTRP) databases, we comprehensively surveyed clinical trials of decellularized tissue use in orthopaedic surgeries registered before 1 September 2022. We evaluated the clinical results, tissue processing methods, and commercial availability of the identified products using academic literature databases and manufacturers’ websites. Results: We initially identified 4,402 clinical trials, 27 of which were eligible for inclusion and analysis, including nine shoulder surgery trials, eight knee surgery trials, two ankle surgery trials, two hand surgery trials, and six peripheral nerve graft trials. Nine of the trials were completed. We identified only one product that will be commercially available for use in knee surgery with significant mechanical load resistance. Peracetic acid and gamma irradiation were frequently used for sterilization. Conclusion: Despite the demand for decellularized tissue, few decellularized tissue products are currently commercially available, particularly for the knee joint. To be viable in orthopaedic surgery, decellularized tissue must exhibit biocompatibility and mechanical strength, and these requirements are challenging for the clinical application of decellularized tissue. However, the variety of available decellularized products has recently increased. Therefore, decellularized grafts may become a promising option in orthopaedic surgery. Cite this article: Bone Joint Res 2023;12(3):179–188.

Abstract Introduction This study evaluated the validity of the AP3 × ML3 reduction quality classification, which applies the concept of positive medial cortical support. Methods A total of 120 trochanteric fractures classified as AO Foundation/Orthopedic Trauma Association 31A1 and A2 were retrospectively analyzed. The validity of the AP3 × ML3 classification was evaluated by comparison with the Baumgaertner reduction quality criteria. When using the AP3 × ML3 classification, reduction quality was divided into three classes based on the degree of anterior cortical contact between the proximal and distal fragments. Reduction quality was also divided into three classes when using the Baumgaertner criteria. The frequency of mechanical complications, including cut­out, delayed union, and excessive migration of the lag screw, was retrospectively assessed. Intra-observer and inter-observer reliability was assessed using the intraclass correlation coefficient (ICC). Results Mechanical complications included 4 cases of cutout (3.3%) and 1 of delayed union (0.8%). Mechanical complications occurred for all levels of reduction quality in both classifications, except for the acceptable of the Baumgaertner criteria. When reduction quality was rated as good, acceptable, and poor the incidence of mechanical complications was 2.5%, 5.7%, and 16%, respectively, under the AP3 × ML3 classification and 3.3%, 0%, and 15.0%, respectively, under the Baumgaertner criteria. The ICC was 0.80 for intra-observer reliability and 0.57 for inter-observer reliability when using the AP3 × ML3 classification and 0.85 and 0.34, respectively, when using the Baumgaertner criteria. Conclusion The AP3 × ML3 classification was reliable and easy to use compared with the widely used Baumgaertner reduction quality criteria. Level of evidence 4

Objectives: This study aims to examine the 2-year outcomes of zoledronic acid (ZOL) with or without eldecalcitol (ELD) on bone mineral density (BMD) and fracture in Japanese patients with osteoporosis. Methods: The subjects were 98 patients who were randomly (1:1) assigned to treatment with ZOL combined with ELD (ZOL + ELD group; n = 51) and ZOL alone (ZOL group; n = 47). Treatment efficacy was examined based on a comparison of changes in BMD from baseline (ΔBMD) in the lumbar spine, total hip, and femoral neck in the 2 groups. Results: The percent change from baseline in BMD values for the lumbar spine, total hip, and femoral neck at 24 months were 10.8% ± 6.1%, 6.0% ± 6.6%, and 5.1% ± 5.1%, respectively, in the ZOL + ELD group, and 7.7% ± 6.2%, 5.1% ± 5.6%, and 2.9% ± 8.3%, respectively, in the ZOL group. The percent change from baseline BMD for the lumbar spine at 24 months differed significantly between the 2 groups. Conclusions: The effect of a combination of ZOL + ELD on BMD for 24 months was more favorable than that of ZOL alone. This drug combination is promising for the treatment of drug-naïve Japanese patients with primary osteoporosis.

Abstract Background Change in the joint line convergence angle (JLCA) of the knee after high tibial osteotomy (HTO) is difficult to predict accurately. Given that any change in JLCA is intra-articular, the shape of the articular surface, including the bone morphology of the proximal tibia, may affect the alignment of the knee joint postoperatively. The purpose of this study was to investigate the relationship between the shape of the tibial plateau and postoperative alignment of the knee joint by focusing on changes in JLCA. Methods One hundred and nine knees that underwent HTO were retrospectively reviewed. The shape of the tibial plateau was classified based on the slope of the medial and lateral articular surfaces as depressed, flat (within 3 degrees), or convex (pagoda-like). The relationship between the shape of the tibial plateau and radiological parameters was investigated. Results The shape of the tibial plateau was depressed in 38 knees, flat in 52 knees, and pagoda-like in 19 knees. There was a moderate correlation between the postoperative change in JLCA and the preoperative hip-knee-ankle angle for knees with a pagoda-shaped tibial plateau (r = 0.56) but not for the other two shapes. Conclusions These findings suggest that knees with marked varus deformity before HTO are likely to show more change in JLCA postoperatively if the tibial plateau is pagoda-shaped than if it has a depressed or flat shape. The advantage of focusing on the bone morphology of the proximal tibia is that surgeons can easily perform visual assessment using preoperative radiograph.

Introduction: Spine surgery is challenging in hemodialysis (HD)-dependent patients owing to their poor general condition. However, postoperative complications and the mortality and survival rates have not been specifically evaluated in a wide series. This study aimed to elucidate postoperative complications and the survival rate in cervical spine surgery in HD patients. Methods: This study included 109 HD patients (70 men, 39 women) who had undergone cervical spine surgery between July 1996 and May 2018. Based on radiological diagnosis, we divided them into the destructive spondyloarthropathy (DSA) and non-DSA groups. We investigated the causes of hemodialysis, postoperative complications, postoperative inpatient mortality rate, and survival rate. Results: The DSA and non-DSA groups included 100 surgeries in 89 patients and 21 surgeries in 20 patients, respectively. The mean age at surgery was 62.9 years for the DSA and 55.9 years for the non-DSA group (P=0.97). The DSA group had a shorter hemodialysis period at surgery compared with the non-DSA group (21.7 vs. 26.5 years, P0.05). However, significantly low survival rates were observed in HD caused by diabetes compared with that by chronic glomerulonephritis (P

Background During a conventional measured resection using the posterior reference method for total knee arthroplasty (TKA) in varus knees, proximal tibia is resected from the lateral joint surface for the same thickness as the implant. Distal femur is resected from the worn medial surface for the same thickness as the implant. Posterior femur is resected using the posterior reference method with an external rotation for appropriate degrees. In this situation, although the joint line of the tibia is leveled to the height of lateral joint surface, the posterior joint line of the femur is leveled to the center of medial and lateral posterior condyle, which is a few millimeters lower than the lateral posterior condyle. This discrepancy between the proximal tibia‐posterior femoral joint line causes a tight flexion gap in cruciate‐retaining TKA. Therefore, downsizing of the femur is necessary to adjust the posterior joint line to the level of the lateral condyle. Perspectives To avoid this circumstance, the postoperative joint line should be leveled to the center of the original medial and lateral joint surface. Proximal tibia is resected from the lateral joint surface 1 mm to 2 mm thicker than the implant. Distal femur is resected from the worn medial surface 1 mm to 2 mm thinner than the implant. Posterior femur is resected using the posterior reference method with an external rotation for appropriate degrees. In this situation, all the joint lines are leveled to the center of the medial and lateral joint surface. Otherwise, use of an anatomically shaped implant with a physiologic joint line is another option to avoid joint line discrepancy. Conclusions Adopting joint line theory for bone resection can prevent the flexion gap tightness that likely occurs in cruciate‐retaining TKA.

Abstract There is an essential demand for developing biocompatible grafts for knee anterior cruciate ligament reconstruction (ACLR). This study investigated cell infiltration into decellularized bovine tendon xenografts using a rat knee ACLR model. Twelve-week-old Sprague–Dawley rats were used. At weeks 1, 2, 4, 8, 16, 26, and 52 (each period, n = 6) after ACLR, rats receiving decellularized bovine tendon (group D, n = 42) or autologous tendon (group A, n = 42) as grafts underwent peritibial bone tunnel bone mineral density (BMD), histological, and immunohistological assessments. BMD increased over time in both the groups until week 16 and then remained unchanged without exhibiting significant differences between the groups. Initially, cellularity in group D was lower than that in group A; however, by weeks 4–8, both the groups were comparable to the native anterior cruciate ligament group and cellularity remained unchanged until week 52. Initially, group A had more M1 macrophages, indicating inflammation, whereas group D had more M2 macrophages, indicating tissue regeneration. Nonetheless, the M1 and M2 macrophage counts of both the groups were comparable at most times. This study revealed the excellent recellularization and tendon–bone integration abilities of decellularized tendons using a cross-species model.

Abstract Background Although favorable long-term survival of Oxford unicompartmental knee arthroplasty (UKA) has been reported regardless of postoperative varus alignment, the effect of degree of varus alignment on patient-reported outcome measures (PROMs) remains unclear. Furthermore, the Forgotten Joint Score-12 (FJS-12), which has a low ceiling effect, may be useful for such assessment. The objective of this study was to evaluate short-term clinical outcomes after Oxford UKA in knees with a greater degree of preoperative varus alignment focusing on use of the FJS-12. Methods This retrospective study involved 66 knees that had undergone primary Oxford UKA. Based on the hip-knee-ankle angle, the knees were divided into two alignment groups: severe varus group (≥ 185° varus alignment) and a mild varus group (

Abstract Background Knee replacement is a very effective and indispensable treatment option for end-stage knee arthritis, and the number of cases has been increasing worldwide. A replaced knee joint without patient joint awareness is thought to be the ultimate goal of artificial knees. Joint awareness reportedly correlates with patient satisfaction. Although numbness around a replaced knee is a minor but common problem, its effect on postoperative outcome is controversial. Joint awareness also is sensitive to subtle abnormalities of the joint, so it must be negatively affected by numbness. Although numbness is minor, it cannot be ignored to further improve knee replacement outcomes. This study investigated the relationship between patient-reported numbness and other patient-reported outcome measures (PROMs), including joint awareness, and kneeling. We developed a numbness score based on a 5-point Likert scale on frequency of numbness, with an intraclass correlation coefficient of 0.76 and higher scores indicating less numbness. Methods The numbness score, New Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score-12 (FJS-12), and other clinical and radiological data from 311 patients (394 primary knee replacements) were analyzed. Kneeling ability was evaluated by using kneeling-specific items in the KSS (KSS-Kneeling). Results No numbness was found in 170 knees (43.1%), and some degree of numbness was found in the remaining 224 knees (56.9%). The numbness score showed weak-to-moderate correlations with KSS-Symptoms (r = 0.44), KSS-Satisfaction (r = 0.41), KSS-Activities (r = 0.29), and all KOOS subscales (r = 0.23–0.44), and FJS-12 (r = 0.42). Multiple regression analyses suggested that midline incision positively affected the numbness score over the anteromedial incision (p = 0.04) and that a better numbness score (p = 0.001), male sex (p

Abstract Purpose The effect of open‐wedge high tibial osteotomy (OWHTO) on the preoperative neutral alignment of the knee is unknown. The purpose of this study was to clarify the clinical outcome of OWHTO with neutral alignment, defined as within 4 degrees of varus. Methods This retrospective study included 72 knees with varus that underwent medial OWHTO. The knees were divided according to the preoperative hip‐knee‐ankle angle into a neutral alignment group (≤ 4° of varus alignment) and a varus alignment group (> 4° of varus alignment). The Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Forgotten Joint Score‐12 (FJS‐12) were evaluated preoperatively and during at least 2 years of follow‐up postoperatively. Results There were no significant differences between the preoperative FJS‐12 (17.9 versus 23.7; p = 0.16) and postoperative FJS‐12 (57.3 versus 60.6; p = 0.52) or KOOS subscale scores (p > 0.05) in the neutral alignment group or the varus alignment group. Each group had a mean change in the KOOS subscale scores that exceeded the minimum clinically important difference. Conclusion The short‐term clinical results of OWHTO for neutral alignment were as favourable as those for varus malalignment. Level of evidence IV.

Abstract Purpose Prolongation of operation time due to registration and pin insertion has been reported with robotic‐assisted total knee arthroplasty (RATKA), and there has been concern about an increase in the postoperative incidence of deep vein thrombosis (DVT). In this study, we compared the incidence of DVT after RATKA with that after conventional manual TKA (mTKA). Methods This consecutive retrospective series included 141 knees that underwent primary TKA using the Journey II system. The CORI robot was used. There were 60 RATKAs and 81 mTKAs. Doppler ultrasound was performed in all patients on postoperative day 7 to determine whether DVT was present. Results The operation time was longer in the RATKA cohort (99.5 min vs 78.0 min, p

Abstract Introduction Chronic alcohol consumption (CAC) can induce several deleterious effects on the body, including the promotion of osteoporosis; however, the immunological mechanism underlying alcohol‐induced osteoporosis is still unclear. Methods We administered alcohol to mice for 4 weeks as the experimental CAC model and analyzed the bone and immune cells that are located in the vicinity of a bone. Results IL‐4 is known to be a suppressive factor for osteoclastogenesis, and we found that natural killer T (NKT)‐like cells, which showed NK1.1‐positive, CD3‐positive, and α‐galactosylceramide‐loaded CD1d tetramer‐negative, produced IL‐4 more effectively than CD4+ T and natural killer (NK) cells. The alcohol consumption facilitated a significant decrease of bone mineral density with the upregulation of nuclear factor of activated T cells 1 and receptor activator of NF‐κB ligand expression. Meanwhile, we confirmed that alcohol consumption suppressed the activity of antigen‐presenting cells (APCs) and NKT‐like cells, leading to decreased IL‐4 secretion. Moreover, these harmful effects of alcohol consumption were reduced by simultaneous treatment with a glycolipid antigen OCH. Conclusions Our results indicate that the inactivation of innate immune cells, APCs, and NKT‐like cells are likely to be crucial for alcohol‐induced osteoporosis and provide a new therapeutic approach for preventing osteoporosis.

Abstract Background No studies have directly evaluated kinematic changes during squatting before and after bicruciate-stabilized total knee arthroplasty (BCS-TKA) with the dual cam-post mechanism and asymmetric surfaces. This study investigated the effect of BCS-TKA on changes to pre- and postoperative skeletal knee kinematics, to identify factors associated with postoperative skeletal kinematic parameters. Methods Seventeen knees in 17 patients were prospectively recruited before primary TKA for advanced medial knee osteoarthritis. Subjects underwent BCS-TKA and were evaluated more than 1 year postoperatively. In vivo dynamic skeletal knee kinematics were evaluated using periodic radiographic images collected during squatting to quantify the tibiofemoral functional extension/flexion angle, anteroposterior (AP) translation, and axial rotation angle using image-matching techniques. Rotational alignments of femoral and tibial components were measured postoperatively using computed tomography images. Results The pre- and postoperative tibiofemoral functional extension/flexion angles during squatting were 12.2° ± 6.7°/100.1° ± 16.8° and 9.6° ± 8.6°/109.4° ± 16.8°, respectively, with a significant difference in flexion angle (p

Abstract Background Patellofemoral overstuffing after total knee arthroplasty (TKA) can cause limited range of motion and anterior knee pain. This study compared anterior prominence of femoral components among different prothesis designs in surgical simulation models utilizing the anterior reference (AR) and posterior reference (PR) techniques. Methods Surgical simulations were performed using on a three-dimensional planning system preoperative computed tomography data of consecutive 30 patients with knee osteoarthritis scheduled to undergo TKA. Four implant models were used: Attune, Persona, Journey II, and Legion. Rotational alignment was set parallel to the transepicondylar axis and size was selected based on the absence of notch formation in the femoral anterior cortex and the best fit with the shape of the medial posterior femoral condyle. For each combination of surgical technique (AR or PR method) and implant model, measurements were taken of the maximum medial, central, and lateral prominence of the implant from the anterior femoral cortex. Results Using either the AR or PR method, the medial and central prominences were significantly lower with Journey II than with the other models. The lateral prominence was the lowest with Attune in the AR method. The AR method was associated with significantly less prominence compared with the PR method, regardless of implant model. Conclusions The degree of anterior prominence of the femoral implant is affected by the implant design when the AR method is used. The PR method is associated with greater anterior prominence compared with the AR method, and the pitch size is an additional factor in the PR method. Surgeons should be familiar with implant designs, including the thickness of the anterior flange and the available size selections.

Abstract Background The incidence and characteristics of deep vein thrombosis (DVT) following total knee arthroplasty (TKA) without pharmacologic prophylaxis have not been fully investigated. This study aimed to determine whether there are any differences in the incidence, location, and characteristics of DVT following TKA with pharmacologic prophylaxis and without pharmacologic prophylaxis. Methods A total of 156 knees were retrospectively evaluated for DVT following TKA by duplex ultrasound on postoperative day 7, after excluding 60 knees from 216 consecutive knees because of antiplatelet or anticoagulant use before surgery, history of venous thromboembolism, or bleeding risk. The 156 knees included in the analysis were divided into two groups: with pharmacologic prophylaxis (n = 79) and without pharmacologic prophylaxis (n = 77). Results The overall incidence of DVT was 34% (54/156 knees). DVT was detected in 31.6% of knees with pharmacologic prophylaxis and in 37.6% of knees without pharmacologic prophylaxis; the difference was not statistically significant. Soleal vein thrombus was observed in 74.6% of the knees with DVT and non-floating thrombus was observed in 98.7%. There were no obvious between-group differences in thrombus characteristics such as compressibility, echogenicity, mean vein diameter, and whether the thrombus was attached to the vein wall or free-floating. Conclusions No differences were found in the incidence, location, or characteristics of DVT following TKA with or without pharmacological prophylaxis.

Objectives: To investigate effects of romosozumab treatment on disease activity and bone mineral density (BMD) in patients with rheumatoid arthritis (RA) and severe osteoporosis in comparison with effects of denosumab treatment. Methods: A total of 50 women were enrolled in this study. The subjects were randomized equally into 2 groups: the romosozumab group or the denosumab group. Disease activity score in 28 joints (DAS28)-erythrocyte sedimentation rate (ESR) and BMD at lumbar spine were evaluated. Results: The percent changes (Δ) in the BMD values at 3 and 6 months for the lumbar spine were as follows: romosozumab; 4.9% and 5.2%, denosumab: 2.3% and 3.2%. The ΔBMD for the lumbar spine at 3 months was significantly higher in the romosozumab group than in the denosumab group (P = 0.044). The DAS28-ESR at baseline, 3 and 6 months in the romosozumab group were 2.88, 2.60 (P = 0.427) and 2.58 (P = 0.588), respectively. The change from baseline in DAS28-ESR did not differ significantly between these 2 groups at any time point. Conclusions: The present study revealed that romosozumab treatment is more effective than denosumab treatment in increasing BMD of the lumbar spine at 3 months. Furthermore, the present study suggested that romosozumab treatment has no effects on the disease activity of RA in patients with RA and severe osteoporosis for 6 months.

Septic wrist arthritis in the pediatric population is very rare. Early diagnosis and therapeutic intervention are important in preventing sequelae of septic arthritis in children. We describe a case of a septic wrist arthritis in infant who was diagnosed by ultrasound-guided puncture, and treated with surgery.

Introduction: Revision surgery for recurrent lumbar disc herniation after surgical treatment is at times challenging due to epidural adhesions and scar. This study aimed to review the clinical results and safety of full-endoscopic lumbar discectomy via interlaminar (FELD-IL) and transforaminal (FELD-TF) approaches for revision surgery. Methods: We conducted a retrospective study including 52 lumbar disc herniation revision patients (mean age, 51.8 years; male/female, 13/39), with 17 FELD-IL and 35 FELD-TF cases. Complication incidences were assessed by reviewing surgical videos and postoperative magnetic resonance images of nerve decompression outcomes. Patients' responses to Japan Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and numerical rating scales (NRS) for lumbar pain, leg pain, and leg numbness were recorded before and during follow-up. The Wilcoxon-signed rank tests were utilized to compare pre- and postoperative group variables. Results: The average operation time was 33.0 min in FELD-IL and 31.7 min in FELD-TF. Seven FELD-IL cases required lamina excavation with high-speed drill bars for scar tissue dissection from the lamina. Dura injury occurred during the excavation in one case. No complication was noted in the FELD-TF group. Successful decompression of the nerve was achieved in all cases. Complete sets of JOABPEQ and NRS were obtained in 64.5% of FELD-IL and in 82.9% of FELD-TF. The mean follow-up period was 18.6 months. All the subdomain of JOABPEQ and NRS improved significantly postoperative in both groups. There was no difference regarding the improvement of scores between the procedures except NRS for lumbar pain, which was more favorable in FELD-IL. Recurrence of herniation occurred in one patient (6%) after FELD-IL and two patients (6%) after FELD-TF. Conclusions: Both FELD-IL and FELD-TF are safe and effective revision procedures for recurrent lumbar disc herniation. FELD-TF could be performed employing the same procedure as primary surgery in revisions, regardless of the previous surgical approach.

Abstract Background The traditional curriculum for medical students in Japan does not include sufficient opportunities for students to develop their skills for musculoskeletal (MSK) examination and clinical reasoning and diagnosis. Therefore, an effective programme is required to help medical students and residents improve their clinical skills in MSK. This paper aims to assess the clinical skills of medical students who have participated in a peer role-playing simulation programme using a mini clinical evaluation exercise (mini-CEX). Methods Participants were 90 female medical students who were completing their first orthopaedic clinical clerkship. They were divided into two groups. The simulation group participated in a role-play focussed on MSK cases as low-fidelity simulation, a structured debriefing with the course supervisor, and a self-reflection on Day 1 (n = 64). The control group did not participate in the role-play due to randomised clerkship schedules (n = 26). On Day 2 of the intervention, we observed and assessed all participants’ performances during MSK outpatient encounters using the mini-CEX. We compared the mini-CEX score between the simulation group and the control group; the Wilcoxon rank-sum test was used for statistical analysis. Results The mini-CEX scores for physical examination, clinical reasoning and diagnosis, and overall clinical competency were significantly higher in the simulation group than in the control group (p

Abstract Background Radiographic changes that appear relatively quickly after fixation of cementless stem in total hip arthroplasty (THA) vary depending on the stem design and fixation style. The present study compared radiographic changes between two types of rectangular curved short stems of similar shape. Methods This retrospective study included 118 hips that underwent primary cementless THA with an anterolateral supine approach using a rectangular, curved, short stem performed by the same surgeon between June 2015 and June 2019. Among the examined hips, 39 had a thicker porous coating stem (thicker group) and 66 had a thinner porous coating and reduced tip stem (thinner group) and at least 12-month follow-up. Radiographs taken during the final course observation were assessed. Propensity score matching was performed based on demographic data and comparisons were made using pairs of 25 hips each. Statistical analysis was performed using chi-square test and p values ≤ 0.05 indicated statistical significance. Results The pattern of the radiolucent lines showed a significant difference after matching (p = 0.0044). A “proximal and distal” pattern was most common in the thicker group and a “distal only” pattern was most common in the thinner group. There was notable and significant difference in cortical hypertrophy in the thicker group after matching (p = 0.024). Conclusions Although the two short stems were similar shapes, the short-term radiographic changes were different. The thinner group showed fewer radiographic changes than the thicker group, making it a more “silent” stem.

Abstract Background The neurovascular bundle containing the deep peroneal nerve has a potential risk of injury during open-wedge high tibial osteotomy (OWHTO), particularly due to drilling for bicortical fixation at distal screw holes. Therefore, monocortical fixation is recommended for distal fixation of a long locking plate as long as good stability is ensured. The purpose of this study was to analyse the biomechanical properties of monocortical fixation of distal locking screws for OWHTO. Methods Three-dimensional models of bone and fixation materials simulating OWHTO were created using computed tomographic data of patients and material data of a T-shaped long locking plate and screws. Three of the four distal screws of the locking plate were chosen for a bicortical fixation or monocortical fixation procedure. In addition, loss of correction was assessed by measuring the medial proximal tibial angle (MPTA) in patients who underwent OWHTO with two bicortical and two monocortical distal fixation screws at 1 month and 1 year after surgery. Results No significant differences in stress were observed in either the normal or osteoporotic bone model between the monocortical and bicortical fixation models, including in the area of the lateral hinge at the osteotomy site. Furthermore, there were no significant differences in MPTA between the early post-operative period and 1-year follow-up. Conclusions The monocortical fixation method for three distal screws of the locking plate did not worsen the mechanical properties of fixation for OWHTO using a long locking plate with four proximal and four distal screws. In actual surgery, the number of distal bicortical screws should be reduced based on the patient’s condition, taking into account the risk of lateral hinge fracture and unexpected surgical complications. Using at least two bicortical screws would be practical considering the various factors related to reduced fixing ability.

Abstract We report a case of tibial shaft fracture after open‐wedge distal tibial tuberosity osteotomy (OWDTO). The use of a lag screw for a lateral hinge fracture in OWDTO requires careful postoperative rehabilitation and follow‐up. We discuss concerns related to the mechanical strength at the osteotomy site after OWDTO to prevent fracture.

Objectives: The objective of this study was to compare the clinical outcomes of treatment with low- or intermediate-molecular-weight hyaluronic acid (HA) in patients with knee osteoarthritis (OA). Methods: In total, 59 patients with OA who fulfilled the criteria of the American College of Rheumatology for OA were enrolled. Patients were randomly assigned in a 1:1 ratio to the low- or intermediate-molecular-weight HA group. An intraarticular injection of HA into the knee joint was performed five times per week. The visual analog scale for pain (pain VAS) and Japanese Knee Osteoarthritis Measure (JKOM) score were analyzed at baseline and week 6 to assess the outcomes. Results: Pain VAS and JKOM score were significantly improved in both groups. At follow-up, there were no significant between-group differences in pain VAS or total JKOM score. Moreover, reduction in pain VAS and JKOM score was not significantly different between the two groups. Conclusions: Both low- and intermediate-molecular-weight HA have significant efficacy in the first-line treatment of patients with knee OA as indicated by patient-reported outcomes. However, there does not appear to be any difference between the efficacy of low- and intermediate-molecular-weight HA as indicated by the JKOM score. We believe that the results of this study provide important insights into the clinical management of Japanese patients with knee OA.

Abstract Purpose To describe the indications for, and surgical technique of, tibial condylar valgus osteotomy (TCVO). Indications TCVO is commonly performed in patients with middle-to-end-stage medial unicompartmental osteoarthritis. Among the most important TCVO indication criteria are the types of tibial plateau shape. The convex-type (also called “pagoda-type”), with over a 5° joint line convergence angle on the standing X-ray, meets the indication criteria for TCVO. Surgical technique An L-shaped osteotomy is performed from the medial side of the proximal tibia to the lateral beak of the intercondylar eminence. The apex of the L-shaped osteotomy line is on the medial border of the patellar tendon insertion. Surgeons should note the direction of the chisel (during the osteotomy) to the intercondylar eminence following fluoroscopic guidance. The posterior cortical bone is cut under a lateral view observation, and the crossed-leg position is adopted to prevent injury to the popliteal blood vessels. The spreader should be positioned at the posterior cortical bone to avoid increasing the tibial slope. The locking plate reliably stabilizes the osteotomy and helps shorten the period of postoperative rehabilitation. Conclusions TCVO adjusts varus deformity alongside joint congruity. Accurate identification of indications and a detailed surgical plan would ensure effective correction and proper alignment. Additional osteotomies are recommended in case of under-correction of the varus limb deformity. TCVO is an effective intervention in patients with advanced knee osteoarthritis and lateral joint laxity with the pagoda-type tibial plateau shape.

Abstract Background Some patients complain of noise after total knee arthroplasty (TKA). Controversy still exists on how the noise affects the clinical outcomes, including joint awareness, after TKA. The Forgotten Joint Score—12 (FJS-12) measures the clinical outcomes focusing on joint awareness after surgery. The Knee Society Scoring System—2011 (KSS-2011) includes questionnaires for satisfaction, expectation, and functional activities. The aim of this study is to clarify the relationship among FJS-12, KSS-2011, and the noise. Furthermore, the relationship between FJS-12 and KSS-2011 was validated. Methods Using FJS-12 and KSS-2011, 295 knees from 225 patients who underwent TKA were retrospectively evaluated. Noise perception was evaluated by a questionnaire with five grades, a method that follows the questionnaire form of FJS-12 (“Are you aware of the noise of your artificial joint?”; never, almost never, seldom, sometimes, mostly). Correlations among FJS-12, KSS-2011, and noise were analyzed. The patients were divided into four groups based on the mechanism of their implant [cruciate retaining, posterior stabilized, cruciate sacrificed, and bicruciate stabilized (BCS)]. FJS-12, KSS-2011, and noise were compared among the groups. Results A strong correlation was found between FJS-12 and total score of KSS-2011 (0.70; P

Abstract Background The Flexible Nichidai Knee Posterior Stabilized (FNK-PS) system was designed to provide relatively high varus-valgus stabilities without the stem extensions to patients with severe knee joint disorders. This is a combination of a large tibial post and high femoral cam adapted to a PS system. The aim of our study was to analyze the in vivo two-dimensional/three-dimensional registration kinematics of the FNK PS-total knee arthroplasty (TKA) system during deep knee bending. Methods Nineteen knees from 15 total knee arthroplasty (TKA) patients who were able to squat with enough knee flexion were selected. During deep knee bending under weight bearing (WB) and non-weight bearing (NWB) conditions, we quantified range of motion, axial rotation, femoral anteroposterior translation, and post-cam engagement angle. Results The maximum-flexion was significantly different between the two conditions. The mean axial femoral external rotation was 4.8° and 6.2° under WB and NWB conditions, respectively, at 120° flexion. Anteroposterior translation based on bicondylar posterior roll-back patterns was noted with increasing knee flexion. Both the medial and lateral femoral aspects were significantly more posterior during early to mid-flexion. Initial post-cam engagement occurred significantly earlier during flexion under NWB than under WB conditions. Under WB, the timing of the post-cam engagement correlated with the maximum flexion . Conclusions The kinematics of the semi-constrained PS system reproducibly exhibited a mild external rotation with smooth posterior roll-back. This was assisted by the engagement of the large tibial post and high femoral cam during the early phase of flexion.

Objectives: We aimed to investigate the change in the center of pressure (COP) path and distribution with or without orthosis for hallux valgus (HV) in patients with rheumatoid arthritis (RA). Methods: In total, 17 patients and 21 feet were enrolled. We measured the COP path using the COP path measurement device (F-Scan II system). The HV angle (HVA); the anteroposterior COP path length, which was measured as a percentage of the foot length (%Long); transverse width of the COP path which was measured from the most medial to the most lateral point and expressed as a percentage of maximum foot width (%Trans); and the final site of the walking locus were analyzed by comparing patients with RA with and without orthosis. Results: Testing without and with the orthosis showed that the HVAs were 31.8° ± 9.3° and 25.2° ± 6.8° (p < 0.001), the %Long values were 61.1% ± 5.5% and 69.2% ± 5.9% (p < 0.001), and the %Trans values were 28.0% ± 9.1% and 30.1% ± 8.3% (p = 0.108). The final site of the walking locus for the 1st interphalangeal joint without and with orthosis were 8 feet (38.1%) and 15 feet (71.4%) (p = 0.020), respectively. Conclusions: The results indicated that the orthosis for HV improved the walking path and should be considered as a therapeutic option in nonpharmacological treatment of RA.

Abstract Purpose Favorable clinical results have been reported following high tibial osteotomy (HTO) for medial meniscus posterior root tear (MMPRT) in knees with varus alignment. However, the effect on the preoperative neutral alignment of the knee is not known. This study sought to evaluate the clinical outcomes of medial open‐wedge HTO for MMPRT with neutral alignment. Methods We retrospectively reviewed 119 medial open‐wedge HTOs and analyzed 22 knees with MMPRT. The knees were divided according to the preoperative hip‐knee‐ankle angle into a moderate varus alignment group (≤4° of varus alignment) and a varus alignment group (> 4° of varus alignment). The Knee Injury and Osteoarthritis Outcome Score (KOOS) and Forgotten Joint Score‐12 (FJS‐12) values were evaluated preoperatively and at the latest follow‐up. The healing status of MMPRT at the time of second‐look arthroscopy, performed at a mean of 15.4 ± 4.2 months, was compared with that after the primary HTO. Results There were 11 knees in the moderate varus alignment group and 11 in the varus alignment group. In terms of perioperative patient‐reported outcome measures, there was no significant difference in the preoperative or postoperative KOOS subscale score or FJS‐12 score between the moderate varus and varus alignment groups. The healing rate was significantly higher in the moderate varus alignment group. Conclusion Favorable clinical results were obtained by medial open‐wedge HTO in knees with MMPRT and moderate varus alignment in the short term. Surgeons should consider the indications for medial open‐wedge HTO, even with moderate varus alignment, when planning treatment for MMPRT with persistent knee pain. Level of evidence IV

Optimal relative first metatarsal length is one of the keys to achieving sufficient results after osteotomy of the first metatarsal. An excessive shortening of the first metatarsal was associated with postoperative metatarsalgia, whereas a long first metatarsal has been implicated as a cause of hallux valgus. To adjust the relative first metatarsal length to the optimal range during surgery, a predictive tool would be beneficial for preoperative planning. However, there is no established tool for predicting relative first metatarsal length. Here, we report a simple method to predict postoperative relative first metatarsal length after proximal rotational closing-wedge osteotomy for rheumatoid forefoot deformities. Two board-certified orthopedic surgeons performed relative first metatarsal length prediction retrospectively on a computed radiography system in nine consecutive cases. Most of them underwent simultaneous modified shortening oblique osteotomy of the second metatarsal (7/9 cases). The interclass correlation coefficients of intraobserver and interobserver reliability for relative first metatarsal length prediction were 0.96 and 0.94, respectively. The mean absolute error on relative first metatarsal length prediction was 1.5 mm at 3-month postoperatively in the same case series. The average time required to perform the relative first metatarsal length prediction was 44.1 s (standard deviation 9.0). Predicting relative first metatarsal length preoperatively in a simple manner, which takes less than a minute to complete, has the potential to improve the surgical outcome of rheumatoid forefoot surgery.

Abstract This report presents a case of deep peroneal nerve palsy caused by an injury during drilling for distal locking screws of a T‐shaped locking plate used for osteosynthesis of medial open‐wedge high tibial osteotomy. A cadaveric simulation study reproduced the risk of injury during the surgery.

Introduction: The incidence of remote cerebellar hemorrhage (RCH) in patients with a dural tear during spinal surgery is unclear. The purpose of this study was to determine the incidence of RCH and the causative factors in these patients. Methods: Two hundred and thirty-nine patients underwent spinal surgery at our institution between March 2015 and September 2016. Eleven of these patients needed dural suturing intraoperatively. All patients underwent CT of the head on the first postoperative day and were categorized according to whether they had RCH or not. The mean values for the amount of intraoperative bleeding, maximum perioperative blood pressure, postoperative drainage volume, and complaints of headache during the first 24 h postoperatively were compared between the two groups using the Welch's two-sample t-test and Fisher's exact test. The follow-up duration was 12 months. Results: There were four patients in the RCH group and seven in the non-RCH group. The incidence of RCH was 36.4%. There were three cerebellar hemorrhages and one interhemispheric fissure hemorrhage in the RCH group. The mean intraoperative bleeding volume was 284 mL in the RCH group and 569 mL in the non-RCH group. The mean respective values for maximum perioperative blood pressure and postoperative drainage volume were 132 mmHg and 547 mL in the RCH group and 144 mmHg and 567 mL in the non-RCH group; none of the differences was statistically significant. However, complaints of headache in the first 24 h postoperatively were significantly more common in the RCH group than in the non-RCH group (100% vs. 14.3%; p = 0.01). All patients with intracranial bleeding had recovered 3 months after surgery. Conclusions: The incidence of RCH following a dural tear during spinal surgery was 36.4%. There was a significant association between RCH and increased reporting of headache during the first 24 h postoperatively.

Closed-wedge high tibial osteotomy (CWHTO) is more advantageous over open-wedge high tibial osteotomy in the following viewpoints: (1) compression force from the patellar tendon to the osteotomy site contribute to its stability, (2) patellar baja less likely occurs, and (3) hardware implant is placed under the thick muscle, which could prevent risk of irritation and infection. Although conventional CWHTO resects the wedge bone, including the anterior and posterior cortices, interlocking CWHTO preserves them while performing osteotomy for the anterior or posterior cortex with only the proximal or distal osteotomy line, respectively. When the wedge is being closed, the distal fragment is internally rotated overlying the anterior and posterior cortices on the proximal and distal cortices, respectively. As a result, good rotational stability and anterior advancement of the tibial tubercle are obtained. Interlocking CWHTO can be applied for patients with moderate patellofemoral osteoarthritis. Adopting an oblique osteotomy line enables secure multiple screw fixations for a long locking plate with a good fitting, allowing early postoperative weightbearing.

Purpose: This study investigated the clinical effects of different patellar components without being affected by the femoral component design in total knee arthritis (TKA) for patients with knee osteoarthritis (OA). Methods: In total, 48 patients with OA who met the criteria of the American College of Rheumatology for OA were enrolled and randomly assigned in a 1:1 ratio to two groups according to the usage of patellar component design for TKA (medialized dome type [dome group] or medialized anatomic type [anatomic group]). To evaluate the clinical outcomes for TKA, knee range of motion (ROM), pain intensity of 0–100 mm visual analog scale (pain VAS), and the Japanese Knee Osteoarthritis Measure (JKOM) score were obtained at baseline and year 1. Results: The difference in knee ROM, pain VAS, or total JKOM score at year 1 was not significant between the dome and anatomic groups ( p = 0.398, 0.733 and 0.536, respectively). Moreover, similar results were obtained for changes in knee ROM, pain VAS, or total JKOM scores from baseline. In both groups, the pain VAS and total JKOM scores were significantly improved at year 1. Conclusion: Both dome and anatomic groups in TKA are significantly effective for pain and function using the JKOM score. However, their efficacy did not differ, according to the JKOM score. Results of this study are rare information focusing on the patellar component design and provide one of the insights into the TKA clinical management.

This study retrospectively compared the perioperative bleeding, hemodynamics, and clinical outcomes of total knee arthroplasty (TKA) performed with and without a tourniquet between two age groups. We grouped 103 patients with knee osteoarthritis who underwent primary TKA based on age at surgery:

Background: An anterior cruciate ligament (ACL) reconstruction has become more common and the surgical morbidity has decreased, it has been performed not only in younger people to play sports but also middle-aged people, with satisfactory results. Therefore, some patients might have comorbidities for which they take medicines. Especially the medicines, such as systemic steroids, might influence the reconstructed ligament strength and durability. Case report: A 49-year-old woman who was taking oral steroids for autoimmune hepatitis suffered a spontaneous ACL injury. She complained of unstable symptoms in the knee despite initial conservative treatment. Then, she was treated operatively with autologous hamstring tendon grafts. Three years postoperatively, her knee remained stable with 1.8 mm side-to-side difference on a Kneelax arthrometer and with 1.6 mm on anterior stress radiographs. There was no rerupture or instability. Conclusion: The patient who had received systemic steroids for a long time recovered satisfactorily after the operation, with achievement of knee stability and possibility to prevent degenerative change in the knee joint. ACL reconstruction should be considered even in patients with such medication.

Open-wedge high tibial osteotomy is considered to be an effective surgical intervention for medial compartmental knee osteoarthritis. However, patella infra, which has been reported to be a result of tuberosity distalization after open-wedge high tibial osteotomy, changes the native patellofemoral biomechanics. This could raise abnormal patellofemoral contact stresses, which might be the trigger of patellofemoral arthrosis. To minimize the reduction in patellar height, we have developed a technique called open-wedge distal tuberosity tibial osteotomy. The benefits of this technique include increased bone-to-bone contact of the distal tuberosity cut surface after correction by cutting an arc osteotomy around the hinge position, which is the center of rotation. This technique also provides cortical support at the anterior osteotomy site without additional bone defect and, therefore, may be advantageous against weight-bearing stress on the osteotomy site. In all, open-wedge distal tuberosity tibial osteotomy could potentially be a unique open-wedge osteotomy that eliminates the risk for postoperative patellofemoral osteoarthritis and also could theoretically encourage rapid healing of the osteotomy, which could lead to early return to full physical activity.

BACKGROUND:Foot and ankle joint disorders are serious issues for patients with rheumatoid arthritis (RA). We compared the differences between patients with RA whose first symptom involved a foot or ankle joint (FOOT group) versus other joints (non-FOOT group) within the Institute of Rheumatology, Rheumatoid Arthritis (IORRA) cohort in our institute. PATIENTS AND METHODS:In the IORRA survey conducted in April 2016, patients were invited to complete six questionnaires about their first symptom at RA onset, current foot or ankle symptoms, daily living activities, and mental health. Disease activity, clinical laboratory variables, functional disability, quality of life, use and ratio of anti-inflammatory and antirheumatic drugs, daily living activities and mental health were compared between the two groups. RESULTS:Among 5,637 Japanese patients with RA who participated in the IORRA survey on April 2016, 5,479 (97.2%) responded to the questionnaire regarding their debut joint. Of these patients, 2,402 (43.8%) reported that their first symptom of RA involved a foot or ankle joint. The FOOT group (n = 2,164) had higher disease activity, higher disabilities, lower quality of life, lower activities of daily living, and poorer mental health and used anti-inflammatory drugs at a higher rate and at higher doses compared with the non-FOOT group (n = 2,164). On the other hand, the use of medications to suppress the disease activity of RA was similar between the groups. CONCLUSION:Clinicians should pay more attention to foot and ankle joints in daily practice so as not to underestimate the disease activity of RA.

Psoriatic arthritis (PsA) is a type of inflammatory arthritis characterized by cutaneous psoriasis, peripheral joint damage, axial joint damage, and enthesitis and is usually diagnosed after the appearance of psoriatic skin disease. PsA mutilans is relatively rare in Japan. In the present case, the patient was diagnosed with PsA with foot mutilans deformity only. Hand and spinal radiograph findings were unremarkable. As in the present case arthritis is occurred prior to the onset of skin lesion, we should make early diagnosis to prevent mutilans deformity.

Physicochemical properties of ash particles and their effects on the collection characteristics of electrostatic precipitator in the pulverized coal combustion system were investigated, focusing on enrichment processes of sulfur on the particle surface. An experimental system composed of one-dimensional laminar flow furnace, cyclone, bag-filter and electrostatic precipitator was used to derive the mutual relations among coal properties, combustion conditions and characteristics of ash particles collected in each device. The following conclusions were obtained. 1) Chemical properties on the particle surface are affected not only by the shape and surface structure of particles but also by particle size, temperature history and coal properties. 2) Soot particulates attached to the small ash particles enhances the enrichment of sulfur on them, and this effect depends on coal properties and combustion conditions. 3) Collection characteristics of ash particles in the electrostatic precipitator largely depend on the enrichment behavior of sulfur in it for the case of high sulfur coal.† This report was originally printed in KAGAKU KOGAKU RONBUNSHU, 10(6), 751-757 (1984) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Chemical Engineers, Japan.

Experimental and kinetic studies of the chemical role of CO2 in hydrocarbon reactions were conducted in a fuel-rich CH4 flat flame with air ratios varying from 0.60 to 0.74. Unburned hydrocarbons (CH4, C2H2, C2H4, and C2H6) in O2/CO2 combustion were found to be lower than those in air combustion. The differences in the CH4 oxidation characteristics between the air and O2/CO2 combustion were caused by the chemical role of CO2 in the reaction R1 (CO2 + H → CO + OH), R2 (CH2(S) + CO2 → CH2O + CO), and higher third body efficiencies of CO2 at an air ratio (λ) = 0.62 where the concentrations of reactants were high. The role of CO2 in R1, R2, and the higher third body efficiencies of CO2 decreased the rate of CH4 oxidation during the early stage of combustion, where O2 was present. Even though R2 did not directly compete with the main chain branching reaction R3 (H + O2 → H + OH) for H radicals, like R1 did, R2 changed the hydrocarbon reaction pathway, thereby decreasing the rate of R4 (CH3 + HO2 → CH3O + OH) which had negative sensitivity in CH4 oxidation. However, we found that R1 and R2 advance CH4 oxidation in the last stage of combustion where O2 was mostly consumed. This is attributed to the fact that the reactions R1 and R2 were able to advance without the presence of O2, and that R1 produced OH radicals that were active in hydrocarbon oxidation in the specific temperature range and R2 enhanced hydrocarbon oxidation when the rate of R4 was insignificant. Although R1 was the dominant reaction to reduce unburned hydrocarbons in the O2/CO2 combustion, the role of R2 was significant at λ = 0.62. Meanwhile, when the air ratio was 0.74 where concentrations of reactants were relatively low, the chemical role of CO2 is to only decrease the rate of CH4 oxidation due to the presence of an excessive amount of O2.

Osteophytes are physiological bony outgrowths that develop at the margins of the articular surfaces during the progression of osteoarthritis; they are associated with active endochondral bone formation processes and expressions of various growth factors. We believe they could be a source of bone grafts as a result of a potentially strong osteoinductive effect. Moreover, osteophytes can be easily harvested by arthroscopy in patients undergoing open-wedge high tibial osteotomy (OW-HTO) for medial unicompartmental knee osteoarthritis. Therefore, we have been using osteophyte autografts for osteotomy gaps in OW-HTO with positive preliminary results indicating rapid bone healing of osteotomy sites. In this technical note, we introduce a technique for harvesting autologous osteophytes by arthroscopy and implanting them into the gap formed after OW-HTO. We expect that autologous osteophyte grafting can be a useful method for accelerating bone union and therefore enabling weight bearing from an early stage after surgery, which will lead to an early return to social activities.

In this study, tar formation and steam-reforming mechanisms are discussed by separating the tars into heavy, middle, and light tars. Cellulose was heated in a drop-tube furnace under an Ar or Ar/steam atmosphere. After the tars were passed through the furnace for thermal cracking and polymerization, they were trapped by filters set at different temperatures (573, 393, and 273 K), and were respectively defined as heavy, middle, and light tars. Incondensable volatiles and gaseous products were measured using gas chromatography with thermal conductivity (GC-TCD), and flame ionization (GC-FID) detectors. The middle and light tars obtained under an Ar atmosphere were first characterized using time-of-flight mass spectrometry (TOF-MS). The analysis showed that the middle tar did not contain any low-boiling-point light tar components, while the light tar did contain them. It was also found that complex species in the tars were separated to a certain degree by changing the trap temperature. Moreover, the formation of heavy tar was quite different from that of the light tar. With increasing temperature, the formation of heavy tar was inhibited, while that of the light tar was enhanced during pyrolysis. The steam-reforming characteristics of these tars were also different. The heavy tar was barely reformed at a low temperature of 873 K, even with a long residence time, while the middle tar was well reformed by steam. While it was difficult to describe the tar formation and steam-reforming characteristics when the tar was considered as a single condensable matter, the tar formation and steam-reforming characteristics were clarified by separating the tars. This study shows that, to prevent tar emissions, the formation of heavy tar, which barely reacts with steam, should be inhibited during pyrolysis by controlling the heating.

The purpose of this study is to clarify the fundamental and general features of N2O formation during the combustion of pulverized biomass under low temperature. First, the effect of various important factors, i.e., combustion temperature, volatilization process (i.e., either slow or rapid dispersion), and nitrogen content in biomass on N2O formation were investigated by theoretical analysis. The analysis of the effect of combustion temperature on the formation of nitrous oxide showed that N2O emission level increases with the decrease in combustion temperature, and both N2O and NO levels are strongly dependent on the combustion temperature. In other words, there is a trade-off relationship between the formation of NO and that of N2O. The analysis of the effect of the slow/rapid volatilization process on the formation of nitrous oxide showed that the conversion ratio of biomass-N to N2O increases with the decrease in the dispersion of volatile matter per unit time; it means that biomass-N is effectively converted to N2O during slow volatilization. Further, the gasification reactions between CO2, O2, and C occur simultaneously on the surface of biomass particles during combustion. With respect to the effect of nitrogen content in biomass, the N2O emission level increases with the increase in N-content of the biomass, while the NO emission level remains constant during low-temperature combustion.

The effect of biomass size and aspect ratio on intra-particle tar decomposition has been investigated both numerically and experimentally to achieve a high rate of intra-particle tar decomposition. In one experiment, wood cylinders with a diameter of 8 mm and lengths of 2, 5, and 9 mm were pyrolyzed in an infrared reactor in an argon environment. The final reactor temperature was 973 K and the heating rate was 30 K/s. To make a calculation, a two-dimensional, unsteady state, single particle model was used, and the same convective and radiative heat fluxes were given to the top and side surface of all wood cylinders. Both calculation and experiment showed that tar yield when the length of the biomass was increased and the diameter was kept constant. The calculation showed that, first, tar was formed in the wood cylinder, and then it moved outwards during decomposition. To find an effective aspect ratio of the wood cylinder for further tar decomposition, calculations were also performed in which the aspect ratio (D/L) varied from 0.4 to 6.9 and the wood volume was fixed. As a result, a low aspect ratio was suited for intra-particle tar decomposition because of the difference in the thermal conductivity along the grain and radial directions, although there is an optimum aspect ratio because of the change of residence time. It is well known that the thermal conductivity of unpyrolyzed wood in the radial direction is much lower than that along the grain. By decreasing the aspect ratio, the ratio of the side surface area to total surface area increases. This means that more heat entered from side surface, and low thermal conductivity in the radial direction caused a temperature gradient in the cylinder. When the intra-particle temperature gradient was large, primary tar, which has been formed in the biomass with a relatively low temperature, passed through the side surface layer at high temperatures, enough to advance intra-particle tar decomposition before the tar was released. This resulted in the enhancement of intra-particle tar decomposition.