PARP-1 inhibition attenuates the inflammatory response in the cartilage of a rat model of osteoarthritis

Aims Poly (ADP-ribose) polymerase (PARP) inhibitor has been reported to attenuate inflammatory response in rat models of inflammation. This study was designed to investigate the effect of PARP signalling in osteoarthritis (OA) cartilage inflammatory response in an OA rat model. Methods The OA model was established by anterior cruciate ligament transection with medial meniscectomy in Wistar rats. The poly (ADP-ribose) polymerase 1 (PARP-1) shRNA (short hairpin (sh)-PARP-1) and negative control shRNA (sh-NC) were delivered using a lentiviral vector and were intra-articularly injected into rats after surgery. The weight-bearing distribution of the hind limbs and the knee joint width were measured every two weeks. The expression levels of PARP-1, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in cartilage were determined using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot. The serum concentrations of inflammatory cytokines were detected using enzyme-linked immunosorbent assay (ELISA). Results PARP-1 expression level significantly increased in the cartilage of the established OA rat model. sh-PARP-1 treatment suppressed PARP-1 levels, decreased the Δ Force (the difference between the weight on ipsilateral limb and contralateral limb) and the knee joint width, inhibited cartilage matrix catabolic enzymes, and ameliorated OA cartilage degradation and attenuated inflammatory response. Conclusion PARP-1 inhibition attenuates OA cartilage inflammatory response in the OA rat model. Cite this article: Bone Joint Res 2021;10(7):401–410.

During Arthroscopic Repair of Medial Meniscal Tears: Do Not Be Afraid to Perform “Pie Crust” Technique

In the absence of effective long-term repair of meniscal injuries, damage to the knee may lead to the development of osteoarthritis. Recent reports have recommended meniscal repair to be undertaken in all cases of meniscal tears. However, the most common complication encountered during repair of the medial meniscus is iatrogenic cartilage and meniscal injury due to its unclear visualization. The aim of this study is to evaluate the long-term clinical and radiological results of the pie-crust (PC) technique performed during the repair of medial meniscal tears. This retrospective study included 86 patients who underwent arthroscopic medial meniscus repair. PC technique was performed if the medial joint width was less than 5 mm. The patient population was divided into two groups as who underwent meniscus repair with PC technique (PC + repair group) or not (repair group). All patients were evaluated clinically (Kujala score, International Knee Documentation Committee (IKDC) subjective score, Lysholm score, and Tegner activity score) and radiologically (medial joint width and valgus laxity angle). When the medial joint width measurements before the PC technique and at the postoperative first and sixth months were compared, it was found to be statistically significant (p < 0.05). However, there was no significant difference between the preoperative and 12-month postoperative joint width measurements (p > 0.05). At the 12-month follow-up, no statistically significant difference was determined for the valgus laxity angle in the PC group compared with preoperative values (p > 0.05). The follow-up Kujala score, IKDC subjective score, Lysholm score, and Tegner activity score were similar between the groups. The clinical scores in both groups were determined to have statistically significant increase at 12-month postoperatively compared with the preoperative values (p < 0.05). The results of this study showed that performing the PC technique prior to medial meniscal tear repair increase the medial joint visualization safely and effectively without permanent valgus laxity.

Reliability and sensitivity of radiographic measures of hip dysplasia in childhood Charcot-Marie-Tooth disease

Background: Hip dysplasia is a lack of femoral head coverage and disruption of hip and acetabular alignment and congruency, with severity ranging from mild subluxation in nascent at-risk hips to complete dislocation. Presentation of hip dysplasia in neuromuscular conditions can be sub-clinical or associated with a limp with or without hip pain, abductor and flexor weakness and reduced hip range of motion. Untreated hip dysplasia leads to early onset osteoarthritis requiring hip arthroplasty in early adulthood. Hip dysplasia occurs in 6–20% of children with Charcot-Marie-Tooth disease, however little is known about the reliability and sensitivity of detection on plain film pelvic radiographs. Methods: 14 common measures of hip dysplasia on anteroposterior pelvis radiographs were independently assessed by 2 orthopaedic specialists in 30 ambulant children with Charcot-Marie-Tooth disease. Hip health was also categorised based on clinical impression to assess the sensitivity of radiographic measures to identify hip dysplasia status. Results: 8 measures (acetabular index, head width, lateral centre-edge angle, lateral uncoverage, medial joint width, migration percentage, neck shaft angle, triradiate status) exhibited ‘excellent’ reliability between clinical evaluators. 5 of the 30 patients (17%) were identified as having nascent hip dysplasia. Reliable radiographic measures that significantly distinguished between nascent hip dysplasia and healthy hips were acetabular index, lateral centre edge angle, medial joint width and migration percentage. Conclusions: We have identified a subset of reliable and sensitive radiographic hip measures in children with Charcot-Marie-Tooth disease to prioritise during hip screening to mitigate the deleterious effects of hip dysplasia, pain and disability in adulthood.

Effects of core splice joint width on the performance of composite sandwich structures with honeycomb core: An experimental study

Composite sandwich structures are commonly considered in large-scale aerospace applications due to their performance on a per mass basis. The nature of a large-scale sandwich structure generally necessitates the use of multiple sections of core to fill out the structural form. These core sections must be spliced together to ensure that shear loads are appropriately transmitted throughout the core. Because core installation in a large-scale component is a challenging operation, core splice joint width can be difficult to control in manufacturing. As such, the effects of core splice joint width on sandwich structure performance should be well understood. This study examines the effects of core splice joint width in honeycomb sandwich structures via mechanical testing and post-failure analysis. A threshold core splice joint width is shown to exist with respect to core shear, while the integrity of the facesheet-to-core interface is shown to degrade with increasing core splice joint width.

A Novel Seam Tracking Technique with a Four-Step Method and Experimental Investigation of Robotic Welding Oriented to Complex Welding Seam

The seam tracking operation is essential for extracting welding seam characteristics which can instruct the motion of a welding robot along the welding seam path. The chief tasks for seam tracking would be divided into three partitions. First, starting and ending points detection, then, weld edge detection, followed by joint width measurement, and, lastly, welding path position determination with respect to welding robot co-ordinate frame. A novel seam tracking technique with a four-step method is introduced. A laser sensor is used to scan grooves to obtain profile data, and the data are processed by a filtering algorithm to smooth the noise. The second derivative algorithm is proposed to initially position the feature points, and then linear fitting is performed to achieve precise positioning. The groove data are transformed into the robot’s welding path through sensor pose calibration, which could realize real-time seam tracking. Experimental demonstration was carried out to verify the tracking effect of both straight and curved welding seams. Results show that the average deviations in the X direction are about 0.628 mm and 0.736 mm during the initial positioning of feature points. After precise positioning, the average deviations are reduced to 0.387 mm and 0.429 mm. These promising results show that the tracking errors are decreased by up to 38.38% and 41.71%, respectively. Moreover, the average deviations in both X and Z direction of both straight and curved welding seams are no more than 0.5 mm, after precise positioning. Therefore, the proposed seam tracking method with four steps is feasible and effective, and provides a reference for future seam tracking research.

Simplified Plastic Hinge Model for Reinforced Concrete Beam–Column Joints with Eccentric Beams

In nonlinear analysis for performance-based design of reinforced concrete moment frames, a plastic hinge spring element is predominantly used in order to simply and accurately describe the inelastic behavior of beam–column joints, including strength degradation. Although current design codes and guidelines provide various beam–column joint models, the focus is on concentric beam–column joints. Therefore, more studies are required for eccentric beam–column joints, which are also common in practice. In the present study, to consider the effect of beam eccentricity on the behavior of beam–column joints, a simplified plastic hinge model was proposed using the effective joint width of current design codes. The proposed model was compared to the cyclic loading test results of beam–column joints with/without beam eccentricity. The comparison showed that the simplified plastic hinge model with the effective joint width of NZS 3101-2006 or Eurocode 8 is considered acceptable for design purpose.

DISTORTIONS IN A PERSON'S BODY PERCEPTION AFTER PERFORMING DYNAMIC TASKS IN VIRTUAL REALITY

The article presents a study in the peculiarities of a person’s perception of the size of his own bodydistortion after a short-term immersion in a virtual environment and performing mobile purposeful tasks in it on behalf of a virtual character. The characteristic distortions in the perception of the sizes of the body parts most involved in the virtual activity in the direction of their increase were revealed. Thus, the study participants demonstrated characteristic statistically significant distortions in the perception of such parameters as neck length, shoulder length, hand length, body length, elbow joint width and head width. Distortions in the perception of the size of the upper half of the body (above the waist) correspond to those parts of the subjects’ bodies, the movement of which in space during the performance of the intra-environment task had the greatest functional significance. Immersion in virtual reality, mediated by a VR headset, leads to the formation of a specialvirtual environment perception in the recipient’s psyche. In this case, the perception of oneself also turns out to be tied to the perception of the controlled virtual character. Due to the uncertainty of its size and the blurring of the visual outlines, the image of one’s own body temporarily merges with the operatively formed image of the character, as a result of which an instrumental interiorization of its dimensions occurs. Thus, it is clearly demonstrated that the perception of the person’s body during the immersion in a virtual environment is connected to the nature of the performed movements.

Effect of Lap Joint Width to the Shear and Peel Stress Distribution of Bi-Adhesive

A single lap joint is one of the most popular types of adhesive joints. This joint is very easy to apply and gives satisfactory results. However, there is an extensive shear stress distribution at both ends in a single lap joint and shallow in the middle. In this research, the performance test of the bi-adhesive with different joint widths was carried out. We modelled with 2D FEM consisting of adherent aluminum, two adhesives DP490 and ESP110 and then performed a static test to obtain shear and peel stress distribution. The results presented that using a bi-adhesive improved the shear stress distribution compared to a single adhesive individually. By adjusting the length ratio of each adhesive, the optimum conditions will be obtained. The peak stress will decrease, and the stress distribution will be better. In addition, the wider the lap joint, the stress distribution will be more evenly distributed. The peak stresses at the ends and in the middle of the joint are getting smaller in both the single adhesive individually and the bi-adhesive. This result is a recommendation for the user to increase the strength of the adhesive joint.

Deep neuromuscular paralysis during hip arthroscopic surgery: influence on perineal tissue pressures and hip joint width

Pudendal nerve injuries are not an uncommon side effect of patient positioning on a traction table, and muscle relaxation has been suggested to mitigate this risk by reducing pressure on the perineum. A total of 40 patients scheduled for hip arthroscopic surgery under general anaesthesia were recruited. After induction of anaesthesia, pressures on the perineum were measured in 20 subjects by means of an ultra-thin pressure sensor mat wrapped around the perineal post. Perineal pressures were assessed after the induction of anaesthesia, after leg traction and after deep muscle relaxation. In 22 subjects, the hip joint width was measured radiographically at the same time points. Pressures on the perineum were high after traction (median maximum pressure 2540 g cm−2). Neuromuscular paralysis reduced perineal pressures only minimally, but significantly (−5 g cm−2; P = 0.007). Traction increased hip joint width significantly [mean 66 (12)%; P = 0.001) and muscle relaxation further increased joint width by a mean of 3.2 (0–20)% (P = 0.001). Muscle relaxation was more beneficial for male patients (joint width increase 6.8% versus 2.8%; P = 0.04), as well as patients in whom traction alone did not achieve sufficient joint width. Muscle relaxation reduced the perineal pressure during hip arthroscopic surgery by only a negligible amount. With regard to joint space, relaxation may be of highest benefit in male patients and/or patients in whom traction alone produces only a relatively small increase in joint width (trial registration: ANZCTR 12617000191392).

The evaluation of von Mises stress field in bonded tiling ceramics as function of the elastic modulus of the tile-adhesive and joint grout mortars

The application of ceramic elements in exterior environments such as facades and floors is a common practice, even when more compliant supports are applied. Such conditions naturally conduct to significant stress increase at the level of the system bonding of ceramic elements. For example, thermal differential expansions in the different materials as result of the temperature gradient from the external surface up to internal layers can build-up stresses at the interfaces, in a magnitude level in excess of the bonding stresses binding them. A proposed finite element modeling was applied in previous works, in which the temperature field distribution from the origin of the thermal source induces a temperature variation carried out incrementally in the simulation. A temperature gradient is assumed from the exposed face, through the elements interfaces until the internal ceramic-adhesive mass. Using the same numerical model, this research led to the evaluation of the equivalent von Mises thermal stress criterion. Adopting different elastic modulus combinations for the tile adhesive and the joint grout, it is recognized how much this property can impact the final stresses and contribute to the best option about the field of application. In fact, independently from the adopted conditions, it is shown that best joint performance is particularly achieved when elastic modulus of the joint grout has lower values, such as 0.1 GPa. On another hand, other key parameters are also very relevant, as the case of the joint width and the support rigidity level.