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This study aimed to investigate the accuracy of cup placement and determine the predictive risk factors for inaccurate cup positioning in robot-assisted total hip arthroplasty (THA). We retrospectively analyzed 115 patients who underwent robot-assisted THA between August 2018 and November 2019. Acetabular cup alignment and three-dimensional (3D) position were measured using pre- or postoperative computed tomography (CT) data. Absolute differences in cup inclination, anteversion, and 3D position were assessed, and their relation to preoperative factors was evaluated. The average measurement of the absolute differences was 1.8° ± 2.0° (inclination) and 1.9° ± 2.3° (anteversion). The average absolute difference in the 3D cup position was 1.1 ± 1.2 mm (coronal plane) and 0.9 ± 1.0 mm (axial plane). Multivariate analysis revealed that a posterior pelvic tilt [odds ratio (OR, 1.1; 95% confidence interval (CI), 1.00–1.23] and anterior surgical approach (OR, 5.1; 95% CI, 1.69–15.38) were predictive factors for inaccurate cup positioning with robot-assisted THA. This is the first study to demonstrate the predictive risk factors (posterior pelvic tilt and anterior surgical approach) for inaccurate cup position in robot-assisted THA.

Surgical site infection is one of the most severe complications of surgical treatments. However, the optimal procedure to prevent such infections remains uninvestigated. Ultraviolet radiation C (UVC) with a short wavelength has a high bactericidal effect; however, it is cytotoxic. Nonetheless, given that UVC with a wavelength of 222 nm reaches only the stratum corneum, it does not affect the skin cells. This study aimed to investigate the safety of 222-nm UVC irradiation and to examine its skin sterilization effect in healthy volunteers. This trial was conducted on 20 healthy volunteers. The back of the subject was irradiated with 222-nm UVC at 50-500 mJ/cm.sup.2, and the induced erythema (redness of skin) was evaluated. Subsequently, the back was irradiated with a maximum amount of UVC not causing erythema, and the skin swabs before and after the irradiation were cultured. The number of colonies formed after 24 hours was measured. In addition, cyclobutene pyrimidine dimer (CPD) as an indicator of DNA damage was measured using skin tissues of the nonirradiated and irradiated regions. All subjects experienced no erythema at all doses. The back of the subject was irradiated at 500 mJ/cm.sup.2, and the number of bacterial colonies in the skin swab culture was significantly decreased by 222-nm UVC irradiation. The CPD amount produced in the irradiated region was slightly but significantly higher than that of the non-irradiated region. A 222-nm UVC at 500 mJ/cm.sup.2 was a safe irradiation dose and possessed bactericidal effects. In the future, 222-nm UVC irradiation is expected to contribute to the prevention of perioperative infection.

The structure and function of the anterolateral complex (ALC) of the knee has created much controversy since the ‘re-discovery’ of the anterolateral ligament (ALL) and its proposed role in aiding control of anterolateral rotatory laxity in the anterior cruciate ligament (ACL) injured knee. A group of surgeons and researchers prominent in the field gathered to produce consensus as to the anatomy and biomechanical properties of the ALC. The evidence for and against utilisation of ALC reconstruction was also discussed, generating a number of consensus statements by following a modified Delphi process. Key points include that the ALC consists of the superficial and deep aspects of the iliotibial tract with its Kaplan fibre attachments on the distal femur, along with the ALL, a capsular structure within the anterolateral capsule. A number of structures attach to the area of the Segond fracture including the capsule-osseous layer of the iliotibial band, the ALL and the anterior arm of the short head of biceps, and hence it is not clear which is responsible for this lesion. The ALC functions to provide anterolateral rotatory stability as a secondary stabiliser to the ACL. Whilst biomechanical studies have shown that these structures play an important role in controlling stability at the time of ACL reconstruction, the optimal surgical procedure has not yet been defined clinically. Concern remains that these procedures may cause constraint of motion, yet no clinical studies have demonstrated an increased risk of osteoarthritis development. Furthermore, clinical evidence is currently lacking to support clear indications for lateral extra-articular procedures as an augmentation to ACL reconstruction. The resulting statements and scientific rationale aim to inform readers on the most current thinking and identify areas of needed basic science and clinical research to help improve patient outcomes following ACL injury and subsequent reconstruction. Level of evidence V.

Tendon rupture and nerve injury cause fatty infiltration of the skeletal muscle, and the adipokines secreted from the infiltrated adipocytes are known to contribute to chronic inflammation. Therefore, in this study, we evaluated the effects of the adipokines on chronic inflammation using a rat sciatic nerve-crushed injury model. In vitro and in vivo experiments showed that the expression of adiponectin was decreased (0.3-fold) and the expression of Il6 (~ 3.8-fold) and Tnf (~ 6.2-fold) was increased in the nerve-crushed group compared to that in the control group. It was also observed that the administration of an adiponectin receptor agonist decreased the levels of Il6 (0.38-fold) and Tnf (0.28-fold) and improved cellular viability (~ 1.9-fold) in vitro. Additionally, in the fatty infiltrated skeletal muscle, low adiponectin levels were found to be associated with chronic inflammation. Therefore, the local administration of adiponectin receptor agonists would prevent chronic inflammation.

Although immobility is a common cause of muscle atrophy, the mechanism underlying this causality is unclear. We here show that Krüppel-like factor 15 (KLF15) and IL-6 are upregulated in skeletal muscle of limb-immobilized mice and that mice with KLF15 deficiency in skeletal muscle or with systemic IL-6 deficiency are protected from immobility-induced muscle atrophy. A newly developed Ca2+ bioimaging revealed that the cytosolic Ca2+ concentration ([Ca2+]i) of skeletal muscle is reduced to below the basal level by immobilization, which is associated with the downregulation of Piezo1. Acute disruption of Piezo1 in skeletal muscle induced Klf15 and Il6 expression as well as muscle atrophy, which was prevented by antibodies against IL-6. A role for the Piezo1/KLF15/IL-6 axis in immobility-induced muscle atrophy was validated in human samples. Our results thus uncover a paradigm for Ca2+ signaling in that a decrease in [Ca2+]i from the basal level triggers a defined biological event.

Current treatment options for osteoporosis primarily involve pharmacotherapies, but they are often accompanied by undesirable side effects. Utilization of mechanical stress which can noninvasively induce bone formation has been suggested as an alternative to conventional treatments. Here, we examined the efficacy of mechanical stress induced by electrical stimulation, radial extracorporeal shock waves, and ultrasound for estrogen-deficient osteoporosis. Female Wistar rats were divided into following five groups: sham-operated group, untreated after ovariectomy, and treated with electrical stimulation, radial extracorporeal shock wave, or ultrasound starting at 8 weeks after ovariectomy for 4 weeks. Trabecular bone architecture of the femur was assessed by micro-CT and its biomechanical properties were obtained by mechanical testing. The femurs were further evaluated by histochemical, immunohistochemical, and real-time PCR analyses. Radial extracorporeal shock wave and ultrasound treatment improved trabecular bone microarchitecture and bone strength in osteoporotic rats, but not electrical stimulation. The shock wave decreased osteoclast activity and RANKL expression. The exposure of ultrasound increased osteoblast activity and β-catenin-positive cells, and they decreased sclerostin-positive osteocytes. These findings suggest that mechanical stress induced by radial extracorporeal shock wave and ultrasound can improve estrogen-deficient bone loss and bone fragility through promoted bone formation or attenuated bone resorption.

A short keel-cortex distance (KCD), especially to the posterior cortex, is a potential risk factor for tibial plateau fracture after Oxford mobile-bearing unicompartmental knee arthroplasty (OUKA). This study aimed to evaluate the effect of tibial component alignment in the coronal plane and tibial proximal morphology on the KCD. Included in this study were 51 patients scheduled for primary Oxford medial unicompartmental knee arthroplasty (UKA). The anterior and posterior KCD were preoperatively assessed using 3D simulation software with the component set perpendicular to the tibial mechanical axis (neutral), 3° valgus, 3° varus, and 6° varus, relative to neutral alignment. We evaluated the existence of overhanging medial tibial condyle where the medial eminence line, the line including the medial tibial eminence parallel to the tibial axis, passes outside of the tibial shaft. In all component alignments, patients with a medial overhanging condyle had significantly shorter posterior KCD than those without. In patients with a medial overhanging condyle, the posterior KCD significantly increased when the tibial component was placed in 3° varus (4.6 ± 1.5 mm, P  = 0.003 vs neutral, P  < 0.001 vs 3° valgus) and 6° varus (5.0 ± 1.4 mm , P  < 0.001 vs neutral, P  < 0.001 vs 3° valgus) compared with in neutral (3.5 ± 1.9 mm) or 3° valgus (2.8 ± 1.8 mm). In OUKA, varus implantation increased the KCD. This could potentially decrease the risk of fracture, even in knees with the overhanging medial condyle. Conversely, valgus implantation of the tibial component shortened the KCD, and should therefore be avoided.

Lower extremity alignment is very important after total knee arthroplasty (TKA). This study aimed to compare the plantar pressure distribution while walking and the overall limb alignment, including the hindfoot, between kinematically (KA) and mechanically aligned (MA) TKA. The plantar pressure distribution was investigated using a pressure plate during walking and one-leg standing among four groups: patients one year after KA-TKA (KA group; n = 25), patients one year after MA-TKA (MA group, n = 25), patients with osteoarthritis (OA) undergoing non-surgical care (OA group, n = 25), and healthy controls (Healthy group; n = 25). Conventional and true mechanical axes (the line from the femoral head to the lowest point of the calcaneus) were evaluated on unipedal standing long-leg radiographs in the KA, MA, and OA groups. Results were compared using analysis of variance. The OA group showed a lateral loading pattern in the mid- and rearfoot, while the MA group showed a medial rearfoot loading pattern during walking. On the contrary, the KA and Healthy groups showed an almost equal pressure distribution between the medial and lateral rearfoot. Moreover, although both mechanical axes in the KA group passed through the knee more medially, a more neutral alignment was achieved in the true mechanical axis compared to that in the MA group. KA-TKA results in more neutral weight-bearing through the true mechanical axis and allows patients to walk while maintaining medial and lateral rearfoot pressure more evenly than MA-TKA.

Purpose The aim of this study was to systematically review the existing literature comparing the postoperative outcomes after following hip arthroscopy in obese and non-obese patients. Methods Studies comparing the outcomes following hip arthroscopy of obese and non-obese patients were systematically identified via a computer-assisted literature search of Pubmed (Medline), EMBASE, and Cochrane Library using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Studies comparing the outcome of hip arthroscopy in different body mass index (BMI) groups were included. Data including patient-reported outcome measures (PROMs), revision arthroscopy rate, conversion rate to total hip arthroplasty (THA), and complications were collected. The methodological index for non-randomized studies (MINORS) and Newcastle–Ottawa Scale (NOS) were used to assess the quality of each study quality. The effect of heterogeneity was quantified by calculating the I 2 value. Results A total of eight studies were finally included in the qualitative analysis, and three studies of high quality involving 373 hips were included in the quantitative assessment. All the studies defined obesity as a BMI of  ≥ 30 kg/m 2 . The modified Harris Hip Score and the Non-Arthritic Hip Score were 5.1 (95% CI 1.1–9.1) and 9.0 (95% CI 5.0–13.1) points lower, respectively, in the obese group than in the non-obese group. The pooled odds ratios were 1.2 (95% CI 0.5–2.7) for revision arthroscopy, 2.4 (95% CI 1.3–4.6) for conversion to THA, and 3.2 (95% CI 1.2–8.6 for complications in favor of the non-obese group. The heterogeneity was low in all outcome assessments ( I 2 0–18%). Conclusion Obese patients had significantly lower PROMs than non-obese patients following hip arthroscopic surgery, and the THA conversion and complication rates were 2.4 times and 3.2 times higher, respectively. Understanding the effect of obesity on hip arthroscopy will allow appropriate surgical indications for surgery to be further refined and help obese patients to understand their individual risk profile. Level of evidence Systematic review of Level III–IV studies, Level IV.

We recently reported that cyclin-dependent kinase inhibitor 1 (p21) deficiency induces osteoarthritis susceptibility. Here, we determined the mechanism underlying the effect of p21 in synovial and cartilage tissues in RA. The knee joints of p21-knockout (p21 −/− ) ( n  = 16) and wild type C57BL/6 (p21 +/+ ) mice ( n  = 16) served as in vivo models of collagen antibody-induced arthritis (CAIA). Arthritis severity was evaluated by immunological and histological analyses. The response of p21 small-interfering RNA (siRNA)-treated human RA FLSs ( n  = 5 per group) to interleukin (IL)-1β stimulation was determined in vitro. Arthritis scores were higher in p21 −/− mice than in p21 +/+ mice. More severe synovitis, earlier loss of Safranin-O staining, and cartilage destruction were observed in p21 −/− mice compared to p21 +/+ mice. p21 −/− mice expressed higher levels of IL-1β, TNF-α, F4/80, CD86, p-IKKα/β, and matrix metalloproteinases (MMPs) in cartilage and synovial tissues via IL-1β-induced NF-kB signaling. IL-1β stimulation significantly increased IL-6, IL-8, and MMP expression, and enhanced IKKα/β and IκBα phosphorylation in human FLSs. p21-deficient CAIA mice are susceptible to RA phenotype alterations, including joint cartilage destruction and severe synovitis. Therefore, p21 may have a regulatory role in inflammatory cytokine production including IL-1β, IL-6, and TNF-α.