Natural Joint Research Articles

Stability of the Natural Joint Side in Unilateral Alloplastic Total Temporomandibular Joint Replacement Using a Ready-Made System

An alloplastic total joint replacement (TJR) is an effective and reliable treatment option in non-salvageable end-stage temporomandibular joint (TMJ) disease. However, unilateral alloplastic TJR of the TMJ (TMJ TJR) could affect the other side natural joint because the physiologic action of both condyles is quite different during mandibular movement. In this study, we examined whether the unilaterally replaced alloplastic TMJ TJR affects the other side natural joint condition over long periods of time. Eight patients who received alloplastic TJR on one side were subjects in this study. All alloplastic TJR implants were stable in situ. The average maximum mouth opening was 37.5 mm (range 19–49 mm) pre-operatively and 44.1 mm (range 34–57 mm) post-operatively. This parameter gradually increased and reached the maximum at about twelve months after surgery. The post-operative change of pain level was significantly reduced from 3.5 to 0 on a pain scale of zero to ten. No significant complications in any joints were observed within the follow-up period. The shape of the natural joint sides showed slight changes but were functionally stable during the observation period. In this study, unilateral alloplastic TJR showed stable and reliable clinical results, either alloplastic TJR or healthy joint sides for quite long period of time.

A Moving Contact of Articulation Enhances the Biosynthetic and Functional Responses of Articular Cartilage

Biomechanical influences play a fundamental role in the structural, functional, and biosynthetic properties of articular cartilage. During physiologic joint loading, the contact area between two surfaces migrates due to the primary and secondary motions of the joint. It has been demonstrated that a migratory contact area plays a critical role in reducing the coefficient of friction at the cartilage surface. However, a detailed analysis of the influences that a migratory contact area plays on the structural, functional, and biosynthetic properties remain to be explored. In this study, bovine cartilage explants were placed in a biotribometer. Explants were subjected to compression and shear forces of migratory contact area, namely moving contact (MC) articulation, or stationary contact area, namely stationary contact (SC) articulation. Free swelling explants were used as control. In a separate study, bovine cartilage-bone grafts were used for frictional testing. On histologic analysis, the SC group had evidence of surface fibrillations, which was not evident in the MC group. Compared to the SC group, the MC group cartilage explants had increased chondrocyte viability, increased lubricin synthesis, and comparable proteoglycan synthesis and release. MC articulation had reduced coefficient of friction as compared to SC articulation. MC articulation led to reduced surface roughness as compared to SC articulation. In conclusion, a migratory contact area can play an important role in maintaining the structural, function, and biosynthetic properties of articular cartilage. This study provides further evidence of the importance of migratory contact area and in vitro assessment of natural joint movement, which can be further evaluated in the context of cartilage homeostasis and disease.

Carving cognition and language at their joints

Echoing Socrates’ remarks to Phaedrus — namely, that it is by “perceiving and bringing together in one idea the scattered particulars, that one may make clear by definition the particular thing which he wishes to explain”, and that we shall divide things “where the natural joints are, and not trying to break any part, after the manner of a bad carver” (Phaedrus, 265d-e) —, one could say that in some ways each of the papers in this special issue aims at carving an aspect of cognition, or language, or both, at its joints. This does not imply that this is a volume of Platonist variations. However, it calls our attention to the metaphysical framework of contemporary understandings of cognition and language.

Mid-term results of short versus conventional cementless femoral stems in patients with bilateral osteonecrosis of the femoral head.

This study aimed to compare the clinical and radiographic mid-term results between short and conventional stems. Patients with bilateral osteonecrosis of the femoral head (ONFH) who had undergone bilateral staged THAs using short stem in one hip and conventional stem in the contralateral hip were included. The Harris Hip Score (HHS), thigh pain, patient's joint perception (PJP) and patients' preferred hip were recorded. Using x-ray, osseointegration and stress shielding were analyzed and compared between stems. There were 35 cases (70 hips) with the mean age of 46.3years (25-63), and the mean follow-up was 75.1months (60-108). HHS was significantly improved in both short and conventional groups (p < 0.001). There was mild thigh pain in 2 cases (5.7%) of the short stem group and 6 cases (17.1%) of the conventional group. With regard to the PJP, we found slightly more natural joint feeling in the short stem group. Of the patients' preferred hip, 11 cases (31.4%) preferred short stem hip and 6 cases (17.1%) preferred conventional stem hip. The short stem group showed osseointegration mainly in the proximal part. The conventional stem group showed osseointegration mainly in the distal part. We found stress shielding grade 1 in 31 cases (88.6%) and grade 2 in 3 cases (8.6%) in the conventional stem group, whereas only grade 1 in 34 cases (97.1%) in the short stem group. The clinical results were promising in both short and conventional stems; however, short stem showed less thigh pain, slightly more natural joint feeling (PJP) and more patients' preferred hip. The short stem provided more favorable results for proximal load transfer and slightly less stress shielding.

Experimental Study on Influence of Chemical Corrosion on Mechanical Property of Fissured Granite

The effect of chemical corrosion and natural joints on the damage characteristics and strength of rock masses is highly important for the construction of rock engineering and energy extraction. Therefore, the intact granite is processed into prefabricated fissured granite specimens with a fissure angle of 0°, 30°, and 45°. Chemical corrosion tests are then performed on the prefabricated fissured granites. The pH of the solution gradually becomes neutral; the mass loss of the granite specimens and the mineral compositions of the fissure surface are measured and analyzed. The scanning electron microscopy (SEM) and uniaxial compression tests are performed on the granite specimens after chemical corrosion. After chemical corrosion, the surface of the fissure becomes loose. The various mineral components of the specimens have been changed to different degrees or converted into other mineral components. The peak strength and elastic modulus of the prefabricated fissured granites with the three fissure angles present a clear decrease, as the time of chemical corrosion increases. The stress intensity factors at the fissured tip are also analyzed. The stress intensity factors of the specimens with a fissure angle of 0°, 30°, and 45° decrease from 0.017, 0.35, and 0.84 to 0.013, 0.30, and 0.74 MPa·m1/2, respectively, as the time of the chemical corrosion increases. And the chemical corrosion has the largest effect on the intensity factors of the specimens with a fissure angle of 45° among the three angles. These experimental results could improve the understanding of the long-term stability of underground engineering in the multifield coupling environment.

Arthroscopically assisted transmalleolar internal fixation of a lateral osteochondral lesion of the talus

Osteochondral lesions (OCL) of the talus can be caused by isolated or recurrent traumatic events. The established surgical treatment techniques are predominantly based on defect coverage by stimulation of fibrous cartilage or transplantation of osteochondral tissue or chondrocytes. An alternative is the preservation of an intact autochthonous hyaline cartilage surface with reconstruction of the subchondral lamella and the natural joint congruence. This anatomical technique can be used for selected acute and chronic OCL and can frequently be carried out arthroscopically. This article presents the indications, contraindications, advantages and targets as well as the planning and execution of arthroscopically assisted transmalleolar internal fixation of a lateral OCL of the talus.

Mechanics of Bio-tribology in Bionic Joints- Analytical Approach

Bionic joints are extraordinary bearings and which are still unexplored. The bio-tribology deals with the study of lubrication methods, and mechanisms involved in natural joints. In the first part of the present work, the review of various lubrication methods is carried out. The anatomical description of knee joint lubrication is explored. The natural joints are found to be not governed by any of the single lubrication methods but all the lubrication methods are necessary to explain the lubrication in natural joints. In other words, one can say that the mixed lubrication method is the best suitable way to explore the bio-tribology of natural joints. The second part deals with the study of mechanics of the bio-tribology of the Knee joint. The Knee condyle’s spherical shape is used to develop the geometrical construction for analytical study. The soft cartilaginous tissue and menisci tissue are treated as an elastic material medium with elastic modulus E, whose surface is covered with synovial fluid film. The effect of applied force on film thickness is found to vary logarithmically. Anyway, the application of a higher magnitude of force will not affect the velocity of indentation. This study is useful to validate the numerical solutions of the bio-tribology study. This also helps in developing the surrogate models of bionic joints to analyse them with the least computational power and provides a platform to study the fluid-structure interactions.

A Lightweight Exoskeleton-Based Portable Gait Data Collection System.

For the controller of wearable lower-limb assistive devices, quantitative understanding of human locomotion serves as the basis for human motion intent recognition and joint-level motion control. Traditionally, the required gait data are obtained in gait research laboratories, utilizing marker-based optical motion capture systems. Despite the high accuracy of measurement, marker-based systems are largely limited to laboratory environments, making it nearly impossible to collect the desired gait data in real-world daily-living scenarios. To address this problem, the authors propose a novel exoskeleton-based gait data collection system, which provides the capability of conducting independent measurement of lower limb movement without the need for stationary instrumentation. The basis of the system is a lightweight exoskeleton with articulated knee and ankle joints. To minimize the interference to a wearer’s natural lower-limb movement, a unique two-degrees-of-freedom joint design is incorporated, integrating a primary degree of freedom for joint motion measurement with a passive degree of freedom to allow natural joint movement and improve the comfort of use. In addition to the joint-embedded goniometers, the exoskeleton also features multiple positions for the mounting of inertia measurement units (IMUs) as well as foot-plate-embedded force sensing resistors to measure the foot plantar pressure. All sensor signals are routed to a microcontroller for data logging and storage. To validate the exoskeleton-provided joint angle measurement, a comparison study on three healthy participants was conducted, which involves locomotion experiments in various modes, including overground walking, treadmill walking, and sit-to-stand and stand-to-sit transitions. Joint angle trajectories measured with an eight-camera motion capture system served as the benchmark for comparison. Experimental results indicate that the exoskeleton-measured joint angle trajectories closely match those obtained through the optical motion capture system in all modes of locomotion (correlation coefficients of 0.97 and 0.96 for knee and ankle measurements, respectively), clearly demonstrating the accuracy and reliability of the proposed gait measurement system.

Study on the Biotribological Properties of Ti6Al7Nb and Ultra High Density Molecular Weight Polyethylene at Different Lubricant Temperature

Higher frictional heat will be produced during the service process of artificial hip joint prosthesis in vivo than natural joint, which would cause the rise of the temperature of synovial fluid and the change of the wear resistance of prosthetic materials. In this work, the biotribological properties of ZrO2/Ti6Al7Nb and ZrO2/UHMWPE pairs at different lubricant temperatures were investigated. The results show that there is a strong correlation between the wettability and average friction coefficient of Ti6Al7Nb, while there is also a strong correlation between the wettability and mass loss of UHMWPE. The wear loss of Ti6Al7Nb and UHMWPE decreases gradually and the friction coefficient increases gradually as the lubricant temperature rises from 20 ℃ to 46 ℃, which is mainly affected by the precipitation process of protein. As a protective layer, it can reduce the wear rate, but as a third body, it can participate in the friction process and increase the friction coefficient. The characteristics of lubricant change greatly at 60 ℃, but the increase of temperature is not the only reason for the precipitation of synovial protein. The synergistic effect with the friction process results in a significant change on the wear mechanism of Ti6Al7Nb and UHMWPE under this condition. The wear mechanism of Ti6Al7Nb is mainly abrasive wear and adhesion wear at different lubricant temperature. With the increase of lubricant temperature, the proportion of adhesion wear mechanism becomes larger. Due to the low thermal deformation temperature and thermal conductivity, the wear mechanism of UHMWPE changed obviously at 60 ℃, and the wear morphology is mainly plastic deformation.

Shoulder kinematics plus contextual target information enable control of multiple distal joints of a simulated prosthetic arm and hand

BackgroundProsthetic restoration of reach and grasp function after a trans-humeral amputation requires control of multiple distal degrees of freedom in elbow, wrist and fingers. However, such a high level of amputation reduces the amount of available myoelectric and kinematic information from the residual limb.MethodsTo overcome these limits, we added contextual information about the target’s location and orientation such as can now be extracted from gaze tracking by computer vision tools. For the task of picking and placing a bottle in various positions and orientations in a 3D virtual scene, we trained artificial neural networks to predict postures of an intact subject’s elbow, forearm and wrist (4 degrees of freedom) either solely from shoulder kinematics or with additional knowledge of the movement goal. Subjects then performed the same tasks in the virtual scene with distal joints predicted from the context-aware network.ResultsAverage movement times of 1.22s were only slightly longer than the naturally controlled movements (0.82 s). When using a kinematic-only network, movement times were much longer (2.31s) and compensatory movements from trunk and shoulder were much larger. Integrating contextual information also gave rise to motor synergies closer to natural joint coordination.ConclusionsAlthough notable challenges remain before applying the proposed control scheme to a real-world prosthesis, our study shows that adding contextual information to command signals greatly improves prediction of distal joint angles for prosthetic control.

A long-term cross-sectional study with modified forgotten joint score to assess the perception of artificial joint after total knee arthroplasty.

Background and purpose: The ultimate goal for an arthroplasty surgeon is to provide the patient a joint that feels more like a natural joint. The Modified Forgotten Joint Score (MFJS) is a newly introduced functional scoring system that has a superior ability to assess this property among arthroplasty patients. The objective of this study is to evaluate the long-term temporal association of the MFJS and total knee arthroplasty (TKA). Methods: We assessed 360 patients post TKA with MFJS questionnaire. The patient groups were distributed at follow-up intervals of 3 weeks (n = 55), 6 months (n = 45), 1 year (n = 57), 2 years (n = 40), 3 years (n = 49), 5 years (n = 49), 7 years (n = 39), and 10 years (n = 26). Higher score suggests a forgotten artificial joint. Results: Post-operative mean MFJS scores were 64.4 ± 7.6 at 3 weeks, 87.7 ± 5.6 at 6 months, 89.2 ± 3.1 at 1 year, 89.9 ± 2.6 at 2 years, 89.4 ± 3.2 at 3 years, 89.1 ± 4 at 5 years, 84.5 ± 8.8 at 7 years, and 82.7 ± 11.9 at 10 years. The score at 3 weeks was significantly lesser than the average scores at other follow-up intervals. The score at 6 months was significantly higher compared to the score at 10 years. The average score at 1 year, 2 years, 3 years, and 5 years were significantly higher compared to the average score at 7 years and 10 years. Conclusion: The trend of the MFJS score was found to drastically improve from 3 weeks to 6 months and peak in 2 years after which the score tends to attain a plateau up to 5 years following which there is a decline in the score at 7- and 10-years post-surgery. Age did not have an influence on the variation in functional score in any of the follow-up groups. MFJS has a strong positive correlation with the well-recognised KOOS scoring system.Level of evidence: IV

A New Statistical Parameter for Determining Joint Roughness Coefficient (JRC) considering the Shear Direction and Contribution of Different Protrusions

The mechanical properties of joints are important factors affecting the safety and stability of rock mass. The joint roughness coefficient (JRC) is a parameter for describing the roughness morphology of the joint surface, and its accurate quantification is very important to predict the shear strength. In the current statistical parameter methods for the estimation of joint roughness, the size of different protrusions on the joint surface was completely ignored, which did not correspond to the real failure mechanism of rock joint during the shear process. In this study, a new statistical parameter WPA was proposed for the estimation of JRC considering the shear direction and the contributions of different protrusions. First, the 10 standard roughness joint profiles were digitized based on image processing technology, and the obtained coordinate data were proved to be reliable by the calculation results of existing parameters. Secondly, the WPA value of 10 standard roughness joint profiles was calculated at a 0.5 mm sampling interval in two directions. The functional relationship between WPA and JRC indicated that they should be established in the same shear direction to maintain a high correlation. The JRC values of 10 standard roughness joint profiles in direction 2 were obtained based on the functional relationship established between WPA and JRC in direction 1, and the roughness of these 10 joint profiles was confirmed to be influenced by direction. Next, the effect of sampling interval on WPA was investigated. As the sampling interval increases, the WPA values gradually decreased and the correlation between them and JRC gradually declined. In practical application, a smaller sampling interval was recommended for more accurate prediction. Finally, the geometric coordinate data of 21 joint profiles given in the literature and 4 natural joint surfaces were obtained by graphics processing technology and 3D scanning technology, respectively. The JRC values of them were separately estimated by WPA in different directions. The results showed that the new statistical parameter WPA proposed in this paper can well describe the joint roughness considering the shear direction and the contribution of different protrusions.

Suggested New Statistical Parameter for Estimating Joint Roughness Coefficient considering the Shear Direction

The 10 standard roughness joint profiles provided a visual comparison to get the joint roughness coefficient (JRC) of rock joint surface, but the accuracy of this method is influenced by human factors. Therefore, many researchers try to evaluate the roughness morphology of joint surface through the statistical parameter method. However, JRC obtained from most of the existing statistical parameters did not reflect the directional property of joint surface. Considering the 10 standard profiles as models of different roughness joints, we proposed a new idea for the accurate estimation of JRC. Based on the concept of area difference, the average of positive area difference (Sa) and sum of positive area difference (Ss) were first proposed to reflect the roughness of joint surfaces on the basis of directional property, and their fitting relationship with JRC was also investigated. The result showed that the Sa and Ss calculated by shearing from right to left (FRTL) and JRC backcalculated from right to left (FRTL) came to a satisfying power law. The correlation between JRC and Sa was better than that of Ss. The deviation between the predicted value calculated by Sa and the true value was smaller than that obtained from the existing statistical parameters. Therefore, Sa was recommended as a new statistical parameter to predict the JRC value of joint profile. As the sampling interval increased from 0.5 to 4 mm, the correlation between Sa and JRC gradually decreased, and the accuracy of the prediction results also declined. Compared with the single JRC values for joint profiles mentioned in the literature, the forward and reverse JRC were obtained. Based on the laboratory direct shear test of the natural joint surface, the JRC values of two joint surfaces in four shear directions were backcalculated by the JRC‐JCS model. Based on 3D scanning and point cloud data processing technology, JRC of joint surface in different directions were obtained by Sa method, and they are very close to those obtained by JRC‐JCS model. It is confirmed that Sa could accurately estimate the joint roughness coefficient and reflect its anisotropy.

Treatment effects of intra-articular triamcinolone acetonide in an equine model of recurrent joint inflammation.

Intra-articular triamcinolone acetonide is a widely used treatment for joint inflammation despite limited scientific evidence of its efficacy. To investigate if intra-articular triamcinolone acetonide has sustained anti-inflammatory effects using an equine model of repeated joint inflammation. Randomised controlled experimental study. For three consecutive cycles 2weeks apart, inflammation was induced in both middle carpal joints of eight horses by injecting 0.25ng lipopolysaccharide (LPS). After the first LPS injection only, treatment with 12mg triamcinolone acetonide (TA) followed in one randomly assigned joint, while the contralateral joint was treated with sterile saline (control). Clinical parameters (composite welfare scores, joint effusion, joint circumference) were recorded and synovial fluid samples were analysed for various biomarkers (total protein, WBCC; PGE2 ; CCL2; TNFα; MMP; GAGs; C2C; CPII) at fixed timepoints (post injection hours 0, 8, 24, 72 and 168). The effects of time and treatment on clinical and synovial fluid parameters and the presence of time-treatment interactions were tested using a linear mixed model for repeated measures with horse as a random effect, and time and treatment as fixed effects. The TA treated joints showed significantly higher peak synovial GAG concentrations (Difference in means 283.1875µg/mL, 95% CI 179.8, 386.6, P<0.000), and PGE2 levels (Difference in means 77.8025pg/mL, 95% CI 21.2, 134.4, P<0.007) after the first inflammation induction. Significantly lower TP levels were seen with TA treatment after the second induction (Difference in means -7.5g/L, 95% CI -14.8, -0.20, P<0.04) . Significantly lower WBCC levels were noted with TA treatment after the first (Difference in means -23.7125×109 cells/L, 95% CI -46.7, -0.7, P<0.04) and second (Difference in means -35.95×109 cells/L, 95% CI -59.0, -12.9, P<0.002) inflammation inductions. Significantly lower general MMP activity was also seen with TA treatment after the second inflammation inductions (Difference in means -51.65 RFU/s, 95% CI -92.4, -10.9, P<0.01). This experimental study cannot fully reflect natural joint disease. In this model, intra-articular TA seems to have some anti-inflammatory activity (demonstrated by reductions in TP, WBCC and general MMP activity) up to 2weeks post treatment but not at 4weeks. This anti-inflammatory effect appeared to outlast a shorter-lived, potentially detrimental effect illustrated by increased synovial GAG and PGE2 levels after the first induction.

Inflammation, Bone Healing and Osteonecrosis: From Bedside to Bench.

Osteonecrosis of the epiphyseal and metaphyseal regions of major weight-bearing bones of the extremities is a condition that is associated with local death of bone cells and marrow in the afflicted compartment. Chronic inflammation is a prominent feature of osteonecrosis. If the persistent inflammation is not resolved, this process will result in progressive collapse and subsequent degenerative arthritis. In the pre-collapse stage of osteonecrosis, attempt at joint preservation rather than joint replacement in this younger population with osteonecrosis is a major clinical objective. In this regard, core decompression, with/without local injection of bone marrow aspirate concentrate (BMAC), is an accepted and evidence-based method to help arrest the progression and improve the outcome of early-stage osteonecrosis. However, some patients do not respond favorably to this treatment. Thus, it is prudent to consider strategies to mitigate chronic inflammation concurrent with addressing the deficiencies in osteogenesis and vasculogenesis in order to save the affected joint. Interestingly, the processes of inflammation, osteonecrosis, and bone healing are highly inter-related. Therefore, modulating the biological processes and crosstalk among cells of the innate immune system, the mesenchymal stem cell-osteoblast lineage and others are important to providing the local microenvironment for resolution of inflammation and subsequent repair. This review summarizes the clinical and biologic principles associated with osteonecrosis and provides potential cutting-end strategies for modulating chronic inflammation and facilitating osteogenesis and vasculogenesis using local interventions. Although these studies are still in the preclinical stages, it is hoped that safe, efficacious, and cost-effective interventions will be developed to save the host’s natural joint.

Fluoroscopy-based subject-specific knee joint constraints for the estimation of prosthesis kinematics and contact velocities during gait

Estimation of the kinematics of the natural or prosthetic knee joint from skin markers is challenging due to soft tissue artefact (Camomilla et al. 2017). A solution can be to perform a multibody k...

Characterization of rock joint surface anisotropy considering the contribution ratios of undulations in different directions

Anisotropy in rock joint is strongly dependent on undulating surface morphology. Recent research of the morphology showed the parameter can express the different types of anisotropic characteristics of the joint surface separately. This report aims to analyze the common characteristic of the anisotropic distribution and exhibit the anisotropic variation trend. The joint morphology function consists of two morphology functions of regular plane in orthogonal directions, and the anisotropic variation determined by the contribution ratios of the two morphology. The roughness weight ratio in orthogonal direction of joint surface is used as an index to describe the anisotropic variation behavior, which proposes the anisotropic variation coefficient (AVC). On this basis, it is divided into 5 levels from strong anisotropic to isotropic. According to the assumption of anisotropic arc distribution, the anisotropic analytic function is derived and the agreement between the deduced curves and measured data therefore suggests the possibility of defining the morphology anisotropy through the index AVC. Finally, we verify the characteristic of three natural rock joints, and prove the proposed function can reflect the anisotropic distribution trend. The new index can be used to describe the anisotropic variation behaviour of rock joint surfaces.

Posterior stabilized total knee arthroplasty reproduces natural joint laxity compared to normal in kinematically aligned total knee arthroplasty: a matched pair cadaveric study.

As the goal of kinematic aligned (KA) total knee arthroplasty (TKA) is to preserve soft tissue tension to the native knee, many KA surgeons recommend cruciate-retaining (CR) prosthesis. However, how a posterior-stabilizing (PS) prosthesis affects the biomechanics of a KA TKA remains unclear. This cadaveric study tested the hypothesis that a PS prosthesis in KA TKA would produce biomechanics similar to CR prosthesis and KA TKA with a PS prosthesis would produce more native knee biomechanics than mechanical aligned (MA) TKA with PA prosthesis. Fourteen cadaver knees (7 pairs) were mounted on a knee-testing system to measure knee motion during flexion. For each pair, 1 knee was assigned to KA TKA and the other to MA TKA. In the KA TKA group, the native knee, CR TKA, and PS TKA were tested sequentially. MA TKA was performed using conventional measured resection techniques with a PS prosthesis. All kinematics were measured and compared with the native knee before and after surgery. A PS prosthesis restored femoral rollback similar to a CR prosthesis. CR TKA showed less lateral rollback at knee flexion ≤ 60° than the native knee. There were no differences in soft tissue tensions among the native knee, CR, and PS prosthesis, except in varus tension at 30° of flexion. Varus tension of CR TKA was larger than those of PS TKA and the native knee after KA TKA with < 1 degree difference. Meanwhile, KA TKA achieved knee motion that was closer to the native knee than did MA TKA at ≥ 60° of flexion when using a PS prosthesis. There were no differences in soft tissue tension between KA-PS and MA-PS TKA. After KA TKA, a PS prosthesis affords similar femoral rollback and soft tissue tension when compared with a CR prosthesis. A PS TKA may be a feasible strategy for patients requiring a PS prosthesis when performing KA TKA. Therapeutic Laboratory study, I.

Retrieval analysis of an explanted NuNec cervical disc: A case report

Retrieval analyses allow investigation of the efficacy of artificial implants to replace diseased or damaged natural joints. Implants are not always removed due to mechanical failure; a well-functioning implant may require removal due to causing pain. As an alternative treatment to fusion, total disc replacement is an evolving treatment. Recently, to eliminate the possible failure mechanisms observed in metal-on-polymer and metal-on-metal artificial discs, an all-polymer cervical artificial disc has been introduced. The NuNec cervical arthroplasty system is a self-mating, all-polymer design which utilizes a ball-in-socket configuration with each component made of polyether ether ketone. For the first time, a retrieval analysis of a NuNec cervical disc, which has been removed due to pain from a 54-year-old female patient, has been undertaken. The main reason associated with pain was the size of the implant which was found to be too big for the patient. The time in vivo of the implant was 2 years and at the time of removal, the implant was thought to be functioning well. The average surface roughness values of the socket and the ball of the explanted NuNec disc were measured as 0.067 ± 0.056 μm (Sa) and 0.037 ± 0.023 μm (Sa). Compared to an unused disc, the surface roughness significantly decreased (p = 0.00). The articulating surfaces of the explant had negative skewness and burnished appearances. Evidence for both abrasive and adhesive wear mechanisms was observed on the explant. The hydroxyapatite coatings at the backsides were completely lost.

Numerical model on predicting hydraulic fracture propagation in low-permeability sandstone

Hydraulic fracture propagation is hard to predict due to natural joints and crustal stress. This process may lead to uncontrollable changes in hydrogeological conditions. Therefore, prediction and control of fracture propagation are paramount to permeability increase in ore-bearing reservoir. The coupled fluid-solid model was utilized to predict the hydraulic fracture propagation in low-permeability sandstone of a uranium mine. For this study, the model was modified to allow fractures to propagate randomly by using the cohesive zone method. The simulation was developed on a three-step process. First, geological data required to run the model, including crustal stress, strength and permeability, were assembled. Next, fracture propagation under different conditions of stress and injection volume were simulated. In the final step, experimental data required to validate the model were obtained. The simulation results indicate that the principal stress, distribution and orientation of natural fracture have vital influence on fracture propagation and induced complex fracture network. This work provides a theoretical basis for the application of hydraulic fracture in low-permeability sandstone reservoir and ensures the possibility to predict the generation of complex fracture network.