Joint Surface Research Articles

Three-dimensional damage and rupture patterns of different thicknesses of rock mass with open joints under blast loading

There are an immense number of discontinuous structural surfaces represented by tensile joints in natural rock mass, in which the thickness of tensile joints determines the form how stress wave interacts with joint surface, which has a significant influence on the fracture behavior of jointed rock mass under blast loading. Open joint specimens were prepared using 3D printing technology, an indoor 3D blasting experiment was carried out with respect to different open joint thicknesses. Through CT scanning and three-dimensional reconstruction, the rupture and the distribution patterns of three-dimensional cracks of the post-blasting specimens were compared, and the rupture characteristics of the rock masses with different open joint thicknesses under blast loading were analyzed. The blasting process of the rock masses with open joints was inverted by AUTODYN numerical simulation software, the effects of open joint thickness on the propagation of stress wave and the three-dimensional damage characteristics of rock mass were revealed. Results showed that under the blast load, the wing cracks derived from the end of the open joints are greatly affected by the thickness of the joints and as the joint thickness increases, the annular derived cracks formed on the right outer surface of the specimen gradually decrease. In case of a change in the open joint thickness, the intensity at which the stress wave diffracts and transmits through the end of the joint will be directly affected. This makes it hard for the wing cracks at the end to initiate, the distribution density of the radial tension cracks traversing through the open joint surface attenuates obviously, resulting in the decrease of the fractal dimension and the damage extent of the specimen. As the thickness of open joints increases, the blast stress wave running through the joint surface will endure a time delay and reduced intensity, the closure of the joint surface gradually reduces, and the degree of stress concentration at the end gets weak. In the course of stress wave propagation, the rock mass on the back-blast side of the joint endures the combined actions of compressive stress field, tensile and tangential stress field and compressive and tangential stress field. As the thickness of open joint increases, the time point for the back-blast side to reach the peak stress is delayed, the intensity of the composite stress field subjected to compressive and tangential stress field decreases, and the normal displacements on the near-blast side and the back-blast side of the joint follow the opposite trend.

Monitoring and Analysis of the Collapse at Xinjing Open-Pit Mine, Inner Mongolia, China, Using Multi-Source Remote Sensing

The collapse of open-pit coal mine slopes is a kind of severe geological hazard that may cause resource waste, economic loss, and casualties. On 22 February 2023, a large-scale collapse occurred at the Xinjing Open-Pit Mine in Inner Mongolia, China, leading to the loss of 53 lives. Thus, monitoring of the slope stability is important for preventing similar potential damage. It is difficult to fully obtain the temporal and spatial information of the whole mining area using conventional ground monitoring technologies. Therefore, in this study, multi-source remote sensing methods, combined with local geological conditions, are employed to monitor the open-pit mine and analyze the causes of the accident. Firstly, based on GF-2 data, remote sensing interpretation methods are used to locate and analyze the collapse area. The results indicate that high-resolution remote sensing can delineate the collapse boundary, supporting the post-disaster rescue. Subsequently, multi-temporal Radarsat-2 and Sentinel-1A satellite data, covering the period from mining to collapse, are integrated with D-InSAR and DS-InSAR technologies to monitor the deformation of both the collapse areas and the potential risk to dump slopes. The D-InSAR result suggests that high-intensity open-pit mining may be the dominant factor affecting deformation. Furthermore, the boundary between the collapse trailing edge and the non-collapse area could be found in the DS-InSAR result. Moreover, various data sources, including DEM and geological data, are combined to analyze the causes and trends of the deformation. The results suggest that the dump slopes are stable. Meanwhile, the deformation trends of the collapse slope indicate that there may be faults or joint surfaces of the collapse trailing edge boundary. The slope angle exceeding the designed value during the mining is the main cause of the collapse. In addition, the thawing of soil moisture caused by the increase in temperature and the reduction in the mechanical properties of the rock and soil due to underground voids and coal fires also contributed to the accident. This study demonstrates that multi-source remote sensing technologies can quickly and accurately identify potential high-risk areas, which is of great significance for pre-disaster warning and post-disaster rescue.

Improving mechanical behavior of adhesively bonded composite joints by incorporating reduced graphene oxide added polyamide 6,6 electrospun nanofibers

Adhesive joining of fiber-reinforced polymer (FRP) composites requires adequate interface tailoring and careful surface preparation to obtain a strong bond between components. This study aimed to improve the mechanical performance of adhesively bonded unidirectional carbon fiber-based (CFRP) composite parts by modifying joint surfaces with graphene-added electrospun Polyamide 6,6 (PA66) nanofibers. Reduced graphene oxide (rGO) was dispersed at 10 % wt/v PA66 solution at three different concentrations below rGO saturation limits. Bead-free nanofibers with homogenous graphene distribution were obtained on a prepreg by electrospinning. Addition of up to 2 % rGO yielded complete dispersion through the nanofiber network while the higher values created local agglomerations. Surface wetting experiments showed conversion of slightly hydrophobic surfaces to complete hydrophilic with electrospun nanofiber coating and the lowest contact angle was obtained at 2 % wt/v rGO addition (26.18°±2.03°). Composite plates were produced in a hot press keeping the modified prepregs on top. Plates with different surface treatments joined by secondary bonding using 3 plies of FM 300 K film adhesive. Mechanical properties of adhesively bonded composites were tested by Single lap joint and Charpy impact tests. We achieved an 18 % increase in shear strength and 31 % increase in impact strength by adding 2 % wt/v ratio rGO into PA66 electrospun nanofiber.

Study on Mechanical Model for Postpeak Shear Behavior of Rock Joints Based on Degradation Characteristics of the 3D Morphology

The 3D morphology of the joint surface significantly influences the shear behavior of the jointrock. Constant normal load (CNL) direct shear tests with different shear displacement were conducted to understand the shear stress changing with joint roughness and damage degree during shear. The rough joint specimens were prepared using 3D scanning and printing techniques, and shear tests with different normal stresses and shear displacements were performed. Four different parameters and the damaged area quantitatively described by the image binarization and box dimension were calculated and compared to study the roughness evolution of joint surfaces. The experimental results demonstrated that the roughness parameter and shear stress decrease and approach constant values with increasing shear displacement. A JRC degradation model was presented based on regression analyses to evaluate the JRC values of rock joints under various displacements to replace it in the JRC–JCS model. Additionally, a new postshear behavior modeling was proposed for rock joints based on surface degradation characteristics under various initial joint roughness coefficients (JRC0) and normal stress. The stress–displacement curves resulting from the proposed modified model work well in predicting the postpeak stress–displacement curve, which can prove the effectiveness of the postpeak shear behavior modeling.

A novel combined rivet and its effect on mechanical properties and failure behavior in double-sided self-pierce riveting

Double-sided self-pierce riveting (DSSPR) has great application potential in joining the same or dissimilar sheets due to its simplified die structure, high joining efficiency, and smooth joint surface. Previous studies have shown that changing rivet parameters, such as chamfered angle position, can improve joining strength, but the improvement effect is still relatively limited. In this paper, to significantly enhance the joining strength, a novel combined rivet structure was proposed and used in the DSSPR process of Al5052 sheets, and its effect on strength improvement and the underlying mechanism were investigated. Morphological change, strain, and stress distribution of the combined rivets during the joining process were investigated through experiments and numerical simulations. Tensile shear tests were conducted to compare the shear strength of the combined rivets and conventional rivets. Moreover, the failure behaviors of joints including macroscopic failure mode and microscopic surface morphology were analyzed, and the mechanism for combined rivets to enhance the joining strength was illustrated. Results showed that adopting the new combined rivets can significantly improve joint strength. Compared with a single conventional tubular rivet, the tensile shear strength and energy absorption of combined rivets can increase by up to 91% and 261%, respectively. Two types of failure modes were discovered according to the failure behaviors of sheets, which were characterized by the detachment of rivets and the tearing characteristics of the sheet. This paper provides a new approach for the rivet design and joining strength improvement strategy for the DSSPR process.

Acellular Aragonite-Based Scaffold for the Treatment of Joint Surface Lesions of the Knee: A Minimum 5-Year Follow-Up Study.

A novel aragonite-based scaffold has been developed. In this study, mid-term clinical and magnetic resonance imaging (MRI) results on 12 patients affected by isolated chondral or osteochondral lesions of the knee treated by the scaffold implantation have been evaluated at a mean follow-up of 6.5 (range: 5-8) years. The study population consisted of 3 females and 9 males, mean age 34.4 (20-51) years. The lesion was located on the medial femoral condyle, the trochlea, and the lateral femoral condyle in 5, 5, and 2 patients, respectively. In all cases, a single lesion over grade 3 of the International Cartilage Restoration and Joint Preservation Society (ICRS) classification was treated: in 9 cases by implantation of one plug, and in 2 cases with 2 plugs; the mean size of the lesion was 2.5 cm2 (1-7). One patient failed and was revised with a custom-made metal implant (Episealer). Overall, Knee Injury and Osteoarthritis Outcome Score (KOOS) significantly improved from 45 ± 13 preoperatively to 86 ± 13 at final follow-up. All KOOS subscales improved significantly: pain subscale increased from 48 ± 12 to 92 ± 11; symptoms from 66 ± 13 to 91 ± 13; activity of daily living (ADL) from 60 ± 19 to 90 ± 21; sport from 23 ± 20 to 75 ± 20; finally, quality of life (QoL) increased from 27 ± 14 to 77 ± 19. Long-term MRI MOCART score was 64. This study shows continued significant clinical improvement and good magnetic resonance imaging (MRI) findings with a minimum 5 years follow-up after implantation of a novel aragonite derived scaffold for the treatment of cartilage lesions of the knee. One patient failed and was revised with a custom-made metal implant (Episealer).

Digital mucous cyst marsupialization: Surgical technique

Digital mucous cysts are benign synovial fluid collections that typically involve the lateral or dorsal surfaces of the distal interphalangeal joints (DIPJs) or beneath the proximal nail fold. They are typically found in the setting of arthritic degeneration of the underlying joint and occur most frequently between the fifth and seventh decades. 1 Many treatment options for digital mucous cysts have been described, ranging from conservative/minimally invasive to complete surgical excision, with no consensus on best technique. Here, a surgical approach is presented which allows access to address the cyst pedicle as well as any underlying osteophyte while preserving the overlying skin with good outcomes even with compromised or involved dermis and epidermis. This is a reproducible, readily adaptable technique. The surgical technique is presented and reviewed in detail.

Arthroscopic Transtibial Pullout Repair and Tibial Condylar Valgus Osteotomy for Medial Meniscus Posterior Root Tear With Varus Knee

As an important structure for maintaining the hoop tension of the medial meniscus of the knee joint, the posterior root is receiving increasing attention. Medial meniscus posterior root tear is an important reason for the occurrence, development, and kinematics changes of knee osteoarthritis. It is necessary to repair the posterior root of meniscus for restoring joint kinematics and improving clinical efficacy. This Technical Note reports a medial meniscus posterior root tear repair technique using arthroscopic transtibial pullout repair (ATPR) combined with tibial condylar valgus osteotomy. The aim of this technique is to repair the posterior root of the medial meniscus while correcting the force line through osteotomy, opening the joint gap, improving the joint surface fit, providing a good mechanical environment for meniscus repair, thereby improving the healing rate of the posterior root of the meniscus and reducing the risk of retear. Although clinical evidence is currently limited, we believe that this technology may have more clinical advantages compared with ATPR alone or ATPR combined with high tibial osteotomy.

Effect of a compression staple on correction of varus deformity during arthroscopic ankle arthrodesis

BackgroundArthroscopic ankle arthrodesis (AAA) has become popular because of its higher rate of bone union, lower invasiveness, and shorter hospital stays compared to those of open arthrodesis. However, postoperative malalignment is often observed for severe varus deformity, which can cause nonunion, pain, and adjacent joint arthrosis. A compression staple can provide a persistent, strong compressive force on the bone surface. This study aimed to clarify the difference in alignment correction in AAA by comparing a compression staple and screws fixation with screws-only fixation pre- and postoperatively. MethodsSeventy ankles in 67 patients undergoing AAA were retrospectively reviewed. AAA with three screws through the distal tibia was performed in 53 ankles, and 17 ankles underwent AAA with a compression staple and two screws. After the preparation of the joint surface arthroscopically, patients in the S group had three canulated cancellous screws inserted through the medial tibia. Patients in the CS group had a compression staple placed at the lateral aspect of the tibiotalar joint and two screws inserted through the medial side. Clinical scores and pre-and postoperative alignment on plain radiographs were compared between the two procedures. ResultsThere were no significant differences in the pre-and postoperative Japanese Society for Surgery of the Foot scale. One ankle in the S group exhibited nonunion. There were no significant differences in talar tilt and tibiotalar angles between the groups. The tibial plafond angle in the CS group was significantly lower than that in the S group (p < 0.05). Postoperatively, talar tilt and tibiotalar angles on the coronal image, and the lateral tibiotalar angle in the CS group were significantly lower than those in the S group (p < 0.05). ConclusionAAA with a compression staple and two-screw fixations could obtain more optimal alignments than AAA with screw-only fixation, even in cases with severe varus deformity.

Non-contact measurement method of displacement of spherical joints in long-span space steel structures

For long-span space steel structures after a long period of operation, it is crucial to quickly and accurately measure the deformation for structural safety evaluation. To address the challenges in deformation measurement of space steel structures, this paper presents a non-contact, three-dimensional coordinate measurement method for key ball joints in their spatial positions. A high-precision Laser Total Station is utilized to measure the surface of the ball joints at multiple points. Three-dimensional coordinates of the center of the ball joints are then accurately determined by using three-dimensional analytical method and the least square error method. Subsequently, the deformation of key joints of the long-span space structures is obtained by comparing the determined coordinates with their initial coordinates. An engineering application by adopting the propose method to measure the deformation of a large-span steel structure gymnasium in Guangdong Province is presented. This method not only can be used to evaluate the safety of existing space steel structures, but also can be applied to rapid measurements and positioning of new long-span steel structures to improve the measurement efficiency and personnel safety.

4D printed multifunctional wearable strain sensors with programmable sensing characteristics

Combining 4D-printed bilayer actuators with the slit structure and sensing capabilities unique to the process further promotes the use of 4D printing in biomedical devices, human-computer interaction, intelligent self-protection devices, and humanoid robots. In this study, we propose an adaptive multifunctional strain sensor (AMSS) 4D printing strategy based on the shape memory properties of polylactic acid (PLA), a bioslit structural sensing unit, and a bi-directional deformation design of a bilayer structure. The obtained AMSS was shown to have excellence sensitivity to strain, mechanical, and temperature stimuli. In particular, thanks to the 3D printed slit structure and phase transition properties of the PLA printing layer, the AMSS macro-microstructure can be precisely tuned, and its sensing performance is shown to be intelligently programmable. The built-in structural design-induced macro-deformation enables AMSS to adaptively fit human joint surfaces for full-range human motion recognition. In addition, the close correlation of strain-sensing during AMSS shape transformation enables position self-sensing and strain self-sensing of AMSS. Further, through the integration and separation of resistive signals, we are able to recognize temperature and mechanical stimuli. Finally, we integrate the wireless sensing module into the AMSS to improve the portability and wearability of the sensor.

Study on the double-sided shear test and three-dimensional numerical simulation of anchor cable with C-shaped tube

Using an indoor pipe-cable-rod double-sided shear test system, tests for double-sided shear are carried out on three types of prestressed anchor cables and anchor cables with C-shaped tubes that eliminate the joint surface's resistance to movement. The shear failure characteristics and shear strength contribution of the anchor cable with C-shaped tube were compared and analyzed. For the anchor cable with C-shaped tube, the C-shaped tubes' geometrical specifications were altered and the effects of the C-shaped tubes' thickness and diameter on the anchor cables with C-shaped tubes' shear strength were investigated. The research results showed that the thickness of the C-shaped tube had a substantial impact on improving the ultimate shear capacity of the anchor cable with C-shaped tube. With the increase in the thickness of the C-shaped tube, the increment of the ultimate shear capacity showed an exponential growth trend. However, under the same thickness, the ultimate shear capacity had a negative correlation with the diameter of the C-shaped tube. In addition, the anchor cable with C-shaped tube was the subject of numerical simulation research using the three-dimensional numerical simulation program ABAQUS. The stress distribution and the development trend with increasing shear load were obtained. The simulation findings revealed that the numerical model and the outcomes of the laboratory tests were in good agreement, which might serve as a guide for future research.

Increased Risk for Non-Union in First Metatarsophalangeal Joint Arthrodesis following High-Velocity Reaming: A Retrospective Study

Objective: Arthrodesis of the first metatarsophalangeal joint (MTPJ) is a reliable procedure for treating various pathologies related to this joint. However, non-union is a common and debilitating complication of the procedure. The purpose of this study was to assess whether the use of a mechanical reamer to prepare the joint surface increases the risk of non-union compared to traditional manual osteotomy. Methods: A retrospective study of all patients who underwent their first MTPJ arthrodesis surgery in our medical center between 2010 and 2015. The articular surface preparation of the MTPJ was either manually performed (Group 1) or mechanically conducted with reamers (Group 2). Data regarding demographic characteristics, indications for surgery, osteosynthesis methods, and post-operative complications, including non-union, infection, and revision rates, were collected for all patients. Results: A total of 83 patients with 92 primary first MTPJ arthrodesis (44 cases in Group 1 and 48 cases in Group 2) were included with a mean follow-up time of 45.3 months (SD 16.8). The two groups were comparable in terms of age, gender, comorbidities, indication for surgery, and follow-up time. The non-union rate was 15.9% in Group 1 and 25% in Group 2 (p = 0.28). Group 2 showed a significantly higher rate of revision surgery compared to Group 1 (43.7% vs. 22.7%, p = 0.03). Conclusions: The mechanical reamer group had a higher non-union rate and a significantly higher rate of revision surgery compared to low-energy manual joint preparation. In light of these findings, the use of mechanical reamers for joint preparation in the first MTPJ arthrodesis was discontinued at our medical center.

Extracellular vesicles derived from mesenchymal stem cells mediate extracellular matrix remodeling in osteoarthritis through the transport of microRNA-29a.

Knee osteoarthritis (KOA) is a common orthopedic condition with an uncertain etiology, possibly involving genetics and biomechanics. Factors like changes in chondrocyte microenvironment, oxidative stress, inflammation, and immune responses affect KOA development. Early-stage treatment options primarily target symptom relief. Mesenchymal stem cells (MSCs) show promise for treatment, despite challenges. Recent research highlights microRNAs (miRNAs) within MSC-released extracellular vesicles that can potentially promote cartilage regeneration and hinder KOA progression. This suggests exosomes (Exos) as a promising avenue for future treatment. While these findings emphasize the need for effective KOA progression management, further safety and efficacy validation for Exos is essential. To explore miR-29a's role in KOA, we'll create miR-29a-loaded vesicles, testing for early treatment in rat models. Extraction of bone marrow MSC-derived extracellular vesicles, preparation of engineered vesicles loaded with miR-29a using ultrasonication, and identification using quantitative reverse transcription polymerase chain reaction; after establishing a rat model of KOA, rats were randomly divided into three groups: Blank control group injected with saline, normal extracellular vesicle group injected with normal extracellular vesicle suspension, and engineered extracellular vesicle group injected with engineered extracellular vesicle suspension. The three groups were subjected to general behavioral observation analysis, imaging evaluation, gross histological observation evaluation, histological detection, and immunohistochemical detection to compare and evaluate the progress of various forms of arthritis. General behavioral observation results showed that the extracellular vesicle group and engineered extracellular vesicle group had better performance in all four indicators of pain, gait, joint mobility, and swelling compared to the blank control group. Additionally, the engineered extracellular vesicle group had better pain relief at 4 wk and better knee joint mobility at 8 wk compared to the normal extracellular vesicle group. Imaging examination results showed that the blank control group had the fastest progression of arthritis, the normal extracellular vesicle group had a relatively slower progression, and the engineered extracellular vesicle group had the slowest progression. Gross histological observation results showed that the blank control group had the most obvious signs of arthritis, the normal extracellular vesicle group showed signs of arthritis, and the engineered extracellular vesicle group showed no significant signs of arthritis. Using the Pelletier gross score evaluation, the engineered extracellular vesicle group had the slowest progression of arthritis. Results from two types of staining showed that the articular cartilage of rats in the normal extracellular vesicle and engineered extracellular vesicle groups was significantly better than that of the blank control group, and the engineered extracellular vesicle group had the best cartilage cell and joint surface condition. Immunohistochemical detection of type II collagen and proteoglycan showed that the extracellular matrix of cartilage cells in the normal extracellular vesicle and engineered extracellular vesicle groups was better than that of the blank control group. Compared to the normal extracellular vesicle group, the engineered extracellular vesicle group had a better regulatory effect on the extracellular matrix of cartilage cells. Engineered Exos loaded with miR-29a can exert anti-inflammatory effects and maintain extracellular matrix stability, thereby protecting articular cartilage, and slowing the progression of KOA.

Avulsion Fracture of the Tibial Tuberosity in Adolescents: A Rare Case and Surgical Fixation Technique

Background: Only 3% of all proximal tibial fractures result in an avulsion fracture of the tibial tuberosity. It is often seen in youngsters between the ages of 3 and 6 and is less frequent after puberty.&#x0D; Case Report: A 15-year-old boy was presented with severe left knee pain following a high jump. X-ray and computed tomography (CT) scan showed a tibial tuberosity fracture with joint surface involvement. The damaged part was fixed with a 4.5mm cannulated screw and washer, reinforced with 2 SwiveLock anchors. In the sixth week, full weight bearing and full range of motion (ROM) were obtained.&#x0D; Conclusion: The primary objective in managing tibial tubercle fractures is the restoration of both the extensor mechanism and the integrity of the joint surface in cases where they have been compromised.&#x0D;

Frozen inactivated autograft replantation for bone and soft tissue sarcomas.

The frozen inactivation of autologous tumor bones using liquid nitrogen is an important surgical method for limb salvage in patients with sarcoma. At present, there are few research reports related to frozen inactivated autograft replantation. In this study, we retrospectively collected the clinical data of patients with bone and soft tissue sarcoma treated with liquid nitrogen-frozen inactivated tumor bone replantation, and analyzed the safety and efficacy of this surgical method. The healing status of the frozen inactivated autografts was evaluated using the International Society of Limb Salvage (ISOLS) scoring system. Functional status of patients was assessed using the Musculoskeletal Tumor Society (MSTS) scale. This study included 43 patients. The average length of the bone defect after tumor resection is 16.9cm (range 6.3-35.3 cm). Patients with autograft not including the knee joint surface had significantly better healing outcomes (ISOLS scores) (80.6% ± 15% vs 28.2% ± 4.9%, P<0.001) and limb function (MSTS score) (87% ± 11.6% vs 27.2% ± 4.4%, P<0.001) than patients with autografts including the knee joint surface. The healing time of the end of inactivated autografts near the metaphyseal was significantly shorter than that of the end far away from the metaphyseal (9.8 ± 6.3 months vs 14.9 ± 6.3 months, P=0.0149). One patient had local recurrence, one had an autograft infection, five (all of whom had an autograft including the knee joint surface) had joint deformities, and seven had bone non-union. Frozen inactivated autologous tumor bone replantation is safe and results in good bone healing. But this method is not suitable for patients with autograft involving the knee joint surface.

Degradation mechanisms of concrete cold joint surfaces under sulfate cycles and varying pouring intervals

In concrete structures, particularly in arid and saline environments, the cold joint surface often serves as a primary entry point for erosion damage, thus dictating the lower limit of structural durability. This study investigates the erosion and damage mechanisms of cold joint concrete under such conditions, focusing on specimens with varying pouring intervals (0.25 d, 0.5 d, 1 d, 7 d, and 28 d). These specimens underwent 0, 30, 90, and 150 sulfate dry‒wet cycles, with their degradation assessed through compression‒shear tests. The findings reveal a logarithmic relationship between the cold joint surface adhesion and the pouring interval, and similarly, there is a logarithmic relationship between the internal friction angle and the pouring interval. Shorter intervals correspond to a higher rate of decrease in both adhesion and internal friction angle, while longer intervals result in lower, eventually stabilizing, values of these properties. Scanning Electron Microscopy analysis indicates that inherent defects in the cold joint surface expedite sulfate penetration into the concrete. As the number of sulfate cycles increases, ettringite formation in the cracks leads to their expansion and interconnection, diminishing the shear resistance of the cold joint surface. The study shows that the pouring interval significantly influences corrosion resistance, with its effects becoming more pronounced after a threshold of sulfate cycles (approximately 90). Shear strength is found to be more susceptible to sulfate erosion compared to compressive strength, with a faster degradation rate. After 80 to 110 erosion cycles, the adhesion corrosion resistance drops to 75%, while the compressive strength remains above this threshold.

Surgical Outcomes of Full Endoscopic Posterior Cervical Foraminotomy for Proximal Cervical Spondylotic Amyotrophy.

Retrospective analysis of case series. This study aimed to clarify the effects of full endoscopic posterior cervical foraminotomy (FPCF) on cervical spondylotic amyotrophy (CSA). The method for decompressing the ventral nerve root and anterior horn (AH) in CSA is controversial. Patients without myelopathy who underwent FPCF for proximal CSA between 2017 and 2022 were analyzed. The outcome measure was the results of the manual muscle testing (MMT) of the deltoid and biceps. Preoperative nerve root and AH compression were evaluated by magnetic resonance imaging. The intervertebral foramen morphology and bony decompression extent were evaluated by computed tomography. FPCF was performed at the C4/5 level and at the C4/5 and C5/6 levels in 14 and 11 patients, respectively. The width of the narrowest intervertebral foramen was significantly narrower on the affected side than on the healthy side at the C4/5 (2.5 mm vs. 3.6 mm) and operated C5/6 (1.9 mm vs. 3.1 mm) levels. AH compression occurred at the C4/5 and C5/6 levels in 28% and 21% of the patients, respectively. Bony decompression was performed laterally beyond the narrowest foramen at the C4/5 and C5/6 levels in 96% and 91% of the patients, respectively. Compared with patients without AH compression, in those with AH compression, the lamina was resected medially by an average of >1.7 mm and >3.6 mm at the C4/5 and C5/6 levels, respectively. Furthermore, 76% and 81% of the facet joint surfaces were preserved at the C4/5 and C5/6 levels, respectively. Postoperative MMT grade improvement was excellent, good, and fair in 64%, 20%, and 16% of the patients, respectively. FPCF was effective for treating proximal CSA.

Unusual presentation of talonavicular joint pigmented villonodular synovitis: a case report

BackgroundPigmented villonodular synovitis is a rare yet locally invasive disorder impacting synovial tissues. This case report delineates the atypical manifestation of pigmented villonodular synovitis in the talonavicular joint, detailing its diagnostic complexity and successful management.Case presentationA 56-year-old Iranian patient with a 4-year history of chronic ankle pain, initially diagnosed with degenerative joint disease post-trauma based on imaging, underwent talonavicular fusion surgery. An unexpected pigmented villonodular synovitis mass was encountered during the procedure. Subsequent interventions encompassed tumor resection, talonavicular joint fusion, and allograft bone grafting. Despite the initial intervention, persistent pain and nonunion necessitated a secondary procedure, involving joint surface curettage and autograft bone grafting. At the 12-month follow-up, the patient remained pain-free without tumor recurrence.ConclusionThis case report highlights the significance of considering pigmented villonodular synovitis as a crucial differential diagnosis in chronic ankle pain, even when there is evidence of degenerative joint disease and a history of trauma. Magnetic resonance imaging serves a crucial role in accurate diagnosis. Treatment necessitates precise tumor removal, appropriate bone grafting techniques and secure fixation.Level of evidence: IV.

Analysis of the thermal lubrication characteristics of cycloid pinwheel transmission mechanisms in RV reducers

In this paper, the cycloidal pin wheel drive mechanism of the secondary drive component of the rotary vector (RV) reducer is studied. Under the condition of grease lubrication, considering tooth profile modifications and machining errors, we established a three-dimensional load-bearing contact analysis model of a cycloid pinwheel transmission mechanism. We studied the time-varying contact characteristics of the gear teeth and dynamic joint surfaces of the inner and outer races of a crankshaft bearing. Considering the thermal effects, we proposed an analysis model of the lubrication characteristics of cycloid pinwheel transmission mechanisms. We also studied the thermal lubrication properties, such as load de-formation, lubrication film thickness, contact pressure and temperature increase at the lubrication contact area. The accuracy of the model was verified by temperature experiments on the inner raceway of an RV reducer bearing and the evolution law of the dynamic thermal lubrication characteristics of the inner and outer races of the crankshaft bearing, the meshing gear tooth pair and the whole process of single pin tooth meshing were revealed. This study provides an effective method for analyzing the temperature increases of the key joints of RV reducers.