Free Joint Research Articles

Stiffness parameter of brush-like polymers with rod-like side chains.

The stiffness parameter λ(-1) of brush-like polymers having rod-like side chains with the hard core potential was calculated. Side chains are, first, assumed to be connected with a free joint to the main chain. The free energy per molecule F was calculated invoking the single contact approximation in which only the interaction between two side chains is considered and the higher interactions are ignored. In the calculation, the contact is assumed to occur when the two side chains are in a plain and the condition for the angles between the side chain and the main chain to make a triangle by two side chains and the main chain was exactly taken into account. The change of F after bending the main chain with a certain curvature from the straight state was calculated to obtain λ(-1). The resulting λ(-1) came close to the experimental value for brush-like polymers with a poly(methacrylate) main chain and poly(hexylisocyanate) (PHIC) side chains if we add a constant as the intrinsic stiffness of the main chain, λ0 (-1), to it. By considering the potential function having a minimum when the angle between the side and main chains equals π/2, the data for brush-like polymers with a poly(styrene) main chain and PHIC side chains were also closely fitted by the theoretical values with an appropriate value of λ0 (-1) and the force constant of the angle.

Spontaneous Healing of the Ruptured Anterior Cruciate Ligament

Objectives:It is widely believed that ACL tears are incapable of healing. However, there are anecdotal experiences of the healed ACL and sporadic case reports and series documenting either clinical or radiographic evidence of healed ACL tears. A truly healed ACL would demonstrate a clinically stable knee on Lachman and pivot shift testing, normal return to function and MRI and/or arthroscopic documentation of a continuous ligament. This is in contrast to “copers” who have an ACL deficient knee but lack instability either because of good neuromuscular control or non-participation in activities which are heavily ACL dependent. In this prospective series we report on the presentation and 5 year follow-up of patients with both clinical and radiographically healed ACLs.Methods:19 patients who presented between July 2007 and April 2010 within 6 weeks of injury with clinical laxity and MRI confirmed ACL rupture. Patients subsequently demonstrated clinical knee stability at 8-12 weeks after pre-habilitation to obtain a pain free mobile joint. Prospective data was collected on these patients with MRI at 12 months, IKDC clinical and subjective scores, KT1000 instrumental laxity testing and Lysholm knee score at 12, 24 and 60 months.Results:At one year follow-up MRI 18/19 patients demonstrated a healed ACL with normal signal, normal trajectory and continuity of fibres. Remainder 1 patient demonstrated bridging of ACL tear with scar tissue and abnormal trajectory of fibers. 5 of 19 patients re-ruptured within 5 years of follow-up. At 5 years follow-up, intact healed ACL patients had a mean IKDC score of 88, mean Lysholm score of 92 and mean KT1000 score of 1.7 mm. 100% reported regular participation in strenuous sport.Conclusion:Although rare, spontaneous healing of the ACL is possible. The mechanism by which this occurs in unknown. It is recommended that reassessment of knee stability should be performed in the non-acute phase after an appropriate prehabilitation program prior to ACL reconstruction to ensure spontaneous healing of the ACL has not occurred.

Decentralized adaptive sliding mode control of a space robot actuated by control moment gyroscopes

An adaptive sliding mode control (ASMC) law is proposed in decentralized scheme for trajectory tracking control of a new concept space robot. Each joint of the system is a free ball joint capable of rotating with three degrees of freedom (DOF). A cluster of control moment gyroscopes (CMGs) is mounted on each link and the base to actuate the system. The modified Rodrigues parameters (MRPs) are employed to describe the angular displacements, and the equations of motion are derived using Kane’s equations. The controller for each link or the base is designed separately in decentralized scheme. The unknown disturbances, inertia parameter uncertainties and nonlinear uncertainties are classified as a “lumped” matched uncertainty with unknown upper bound, and a continuous sliding mode control (SMC) law is proposed, in which the control gain is tuned by the improved adaptation laws for the upper bound on norm of the uncertainty. A general amplification function is designed and incorporated in the adaptation laws to reduce the control error without conspicuously increasing the magnitude of the control input. Uniformly ultimate boundedness of the closed loop system is proved by Lyapunov’s method. Simulation results based on a three-link system verify the effectiveness of the proposed controller.

Microstructure and Mechanical Properties of the Weld Joint of Small Diameter Glass-Lined Metal Pipe with Inner Surface Layer

The width of 36mm of inner surface layer was formed by Ni625 welding wires in the ends of glass-lined 20# metal pipe, and the metal tubes were welded. The microstructure and the distribution of the main alloying elements of the weld joints were analyzed by optical microscope (OM) and electron probe microscope analysis (EPMA). The mechanical property and nondestructive inspection tests of the welded joints were carried out. The results show that the welded joints were divided into three layers including root layer, transition layer and cap layer. The microstructure in root layer was characterized by the cellular-dendrite structure. The transition layer contained martensite and retained austenite. The capping layer included acicular ferrite and pearlite. The defect free joint was produced and performed well. The concentration of nickel and chromium element in weld root were higher than inner surface layer which proves that welding wire of transition layer protects the major alloying elements in welding root.

Surgical and Clinical Outcome of Bipolar Hemiarthroplasty Over Unipolar Hemiarthroplasty in Case of Fracture Neck of Femur in Elderly- Done in CBMCH,B and Private Clinics

Back ground: Whether bipolar hemiarthroplasty[BH] for displaced femoral neck fractures has benefit over unipolar hemiarthroplasty[UH] remains controversial. Intracapsular fracture neck femur mainly occur in elderly person. The prime goal of treatment is to return the patient to their pre-fracture functional status. The surgical treatment is the treatment of choice, hip replacement arthroplasty (hemi or total) is a viable choice in treatment option. In this clinical study 96 elderly patients (age 55-78 years) with a displaced intracapsular femoral neck fracture were treatment over a six year period (December 2009 to December 2015). All of them underwent hemiarthroplasty either bipolar or unipolar, after appropriate medical and anesthetic fitness. The patients were reevaluated at two weeks, six weeks, at six months postoperative and assessed using mainly Harris hip score (HHS) and visual analogue scale (vas) for evaluation of clinical and surgical outcome Also x-ray done to seen erosion of acetabulam. The mean age of patients was 64.5 years and male female ratio 45.83% -54.17%. The mean HHS score was 83.5 for BH and 82.5 for UH at the end of the 6 months. The mean score on VAS scale was 4mm (mu) at 6 months for both BH and UH follow up visit. At the one year 03 cases of unipolar complications mild hip pain. No patients need revision surgery. Bipolar and unipolar hemiarthroplasty is the treatment of choice in elderly patient with displaced femoral neck fracture provides early ambulation, good functional outcome, pain free joint with minimal complications without the need for revision surgery. There is no significant differences between Bipolar and Unipolar arthroplasty surgically and clinically.
 CBMJ 2016 January: Vol. 05 No. 01 P: 27-32

The free moment in running and its relation to joint loading and injury risk

The purpose of this study was to explore the relationship between free moment (FM) characteristics, joint mechanics and injury risk, in order to evaluate the potential of the FM as a variable for runner classification into functional groups with similar footwear demands. Lower extremity joint mechanics, ground reaction forces and the FM of 222 male and female injury free runners were analysed using an optoelectric motion capture system and a force plate while running at 3.5 m/s. During a follow-up period of 6 months, runners were reporting any running-related injuries to an experienced orthopaedist. Different FM patterns could be extracted using functional principal component analysis (FPCA). The first two eigenfunctions derived from FPCA were able to predict about 87% of the variance in the data-set and could be related to the two main functions of FM application in straight running -- transversal plane whole body oscillation control and compensation of insufficient transversal moment cancellation. FM patterns differed with respect to lower extremity joint moments and joint kinematics, mostly in the transversal and frontal plane of motion. Runners suffering from patellofemoral pain syndrome showed FM patterns with distinct external rotation components and differed from their matching controls, even though the number of runners, who suffered from injuries were too low to allow valid inferences. In conclusion, it seems that the FM could be useful in the classification of runners into functional groups as it possesses a considerable inter-subject variability, a relationship to the mechanical demands put on lower extremity joints and potentially to injury risk, while being comparably easy to measure.

Effect of Preheating on Microstructure and Tensile Properties of Friction Stir Welded AA7075 Aluminium Alloy Joints

The high strength AA7075 aluminum alloy is commonly used in the aerospace components due to its exclusive mechanical properties like lightweight and high strength. This alloy cannot be welded by fusion welding techniques due to solidification cracking which severely degrade the mechanical properties of the joint. In contrast, through friction stir welding (FSW) process solidification relate defects can be eliminated. Anyhow, the strength of friction stir welded joint is influenced by process parameters and tool parameters. These parameters govern the heat input, metal flow, microstructure evolution and mechanical properties of the weld. In normal welding condition, (without preheating) heat is generated by friction force which is produced between tool and workpiece. In this paper an added heat input through preheating the metal before weld. This preheating temperature effects on microstructure, microhardness and tensile properties of the joints were investigated. From this study the following conclusions are derived. Sufficient heat input should be given to obtain defect free and quality joint. The results showed that, preheating the base metal to 100 °C prior to welding improved the tensile strength and joint efficiency compared to the joints made without preheating.

Effects of Tool Pin Design on Formation of Defects in Dissimilar Friction Stir Welding

Friction stir welding is an automatic process, falls under the category of solid state welding processes. In this study, friction stir welding was carried out on dissimilar copper to aluminum materials by nine different tool designs. Present investigation provides an insight on formation of defects under the effect of different tool pin designs. The tool pin profiles such as cylindrical, triangular, square and hexagonal were used in the present experimental investigation by keeping other parameters constant. These tool pin profiles were designed based on its static and dynamic constant areas from best suitable cylindrical profile. Besides, the defects were analyzed through visual observation, macrostructure, microstructural investigation and scanning electron microscope. The results revealed that, the copper particles detached from base material were large and irregular in case of polygonal pin designs. Maximum irregular and large copper particles were reported in welds made by triangular pin profiles. Additionally, polygonal pin profiles were generating defects such as voids, tunnel, cracks and fragmental defects irrespective of its static and dynamic constant areas. Furthermore, defects were decreased as the polygonal edges increases. Defect free macro joint was reported for cylindrical tool pin profile.

Transient Liquid Phase Bonding of AA-6063 to UNS S32304 Using Cu Interlayer

Transient liquid phase bonding of AA-6063 and UNS S32304 was performed in an inert atmosphere using a Gleeble (model 3800) thermo-mechanical simulator. Base metals were machined to rectangular dimensions of 30mm x 15mm. Aluminum samples were fabricated from a U-shaped extruded Al-6063 profile with 2mm thick, while duplex stainless steel samples were in form of coupons with 1mm thick. A copper foil with 99.9% purity and 10μm thickness was used as an interlayer between the base metal sheets. A compression load of 0.2KN was applied horizontally to the specimens. The effect of bonding temperature (550°C, 555°C, 560°C and 570°C) was studied on the microstructure of the joints using light and scanning electron microscopy. Compositional changes across the joint region were studied using energy dispersive X-ray spectroscopy. Although copper diffusion into aluminum results in an Al-Cu eutectic structure, the oxide layer on the aluminum surface controls the dissolution behavior of Cu and extent of wettability with the base metals. Although a defect free joint was produced at 570°C, X-ray diffraction results detected the formation of intermetallic compounds (FeAl3).

Unstable elbow dislocations: a case report of a new surgical technique.

This case report describes our first clinical experience of a previously described new surgical technique for the treatment of unstable simple elbow dislocations. The technique utilises a central strip of the distal triceps tendon which is harvested proximally at the musculotendonous junction and left attached at its insertion on the olecranon. The strip is the passed through the olecranon fossa and attached to the coronoid process to stabilise the joint. We encountered an early postoperative complication that led to a modification of our technique and ultimately an excellent recovery of a stable pain free joint with a full range of movement.

Disillusioning midterm results after UNI 2 total wrist arthroplasty in RA Patients

Total wrist arthroplasty attempts to produce a stable, pain free joint. Avoidance of arthrodesis is a strong impetus. Early results of the Universal total wrist arthroplasty KMIy in wrist arthritis were at least as encouraging as were reports with other implants. The five to ten year outcomes showed a 45% revision rate with arthrodesis rate below 10%. Our question was wether results withstand over time. Material and method Between 2002 and 2012, 12 rheumatoid patients all but one female had cementless UNI 2 total wrist arthroplasty - the only implant used by a single surgeon - on 14 wrists, average age of 68, 55 years (range 37–84 y.). Indication was panarthritis of the carpus with Simmen Grade I and II without major bone loss intact tendons without active synovitis or infection. No patient was dependent on walking aids. At follow-up average 6.9 years the only question was on the status of the implant whether radiological and mechanical stable or not. Two patients were lost to follow-up due to death for other medical reasons. Results During the follow-up 9 wrists or 75% of the surviving got clinically symptomatic with increasing pain, local swelling and radiovolar drift of the carpus. There was in any instance polyethylene wear accentuated on the radius, synovitis and secondary carpal tunnel syndrome. After an average of 5 years revision rate rose markedly. Radiologic and mechanical loosening of the carpal component was seen 7 times. Surgery - twice there was only the change of the polyethylene component necessary. Three times the carpal component had to be changed in combination with cancellous bone adjunct. Finally, 4 revisions ended in arthrodesis, two of those in first revision. At present, two more patients with three implants are due to reoperation. Thus, arthroplasty showed complication in 75% and mobility was lost in 33% of the surviving. Discussion Early results of the universal total wrist arthroplasty KMIy in rheumatoid arthritis were encouraging. Midterm results show an array of problems focussing on the carpal component. These studies generally sum up degenerative, posttraumatic and rheumatoid arthritis cases. To our knowledge ours is the only focusing on RA patients only. The majority of publications delude oneself to believe in total wrist arthroplasty in this category of patients. The authors own experience is much more deceiving. In our department total wrist arthroplasty in rheumatoid patients is no longer the treatment of choice.

Solid solution strengthening of transient liquid phase bonded nickel based superalloy

This paper aims at probing and quantifying the effect of filler alloy chemistry on solid solution strengthening mechanism of transient liquid phase bonded of a cast Ni–Fe–Nb based superalloy. Bonding was performed using three different nickel based filler alloys including Ni–4·5Si–3·2B, Ni–7Cr–4·5Si–3·2B–3Fe and Ni–15·2Cr–4B. The hardness of isothermal solidification zone was proved to be the controlling factor for the shear strength of the joints. It is concluded that the initial chromium content of the filler alloy and the extent of base metal dissolution, which in turn is controlled by the initial boron content of the filler alloy, play important roles in strengthening of the isothermal solidification zone. Bonding using Ni–15·2Cr–4B resulted in eutectic free joint with the highest shear strength.

Effect of Varying Process Parameters on the Microstructure and Mechanical Properties of Cu-Cr-Zr-Ti Alloy Brazed Using Cu-Mn-Ni-Sn-Fe Foil

Cu-Cr-Zr-Ti alloy is being used widely in aerospace engines, due to its synergetic combination of high strength and thermal conductivity. Brazing is the preferred process being adopted to realize intricate shapes and complex dimensions. In the present work, Cu-Cr-Zr-Ti alloy was brazed using Cu-Mn-Ni-Sn-Fe base brazing foil. This braze foil exhibits liquidus temperature of ~980°C. Brazing experiments were carried out at 1030°C under high vacuum condition. The effect of varying load (0.5-2 kg) has been studied in the current experiment. Microstructural study of the parent materials and joints were carried out using optical microscope (OM). Lap shear testing (1T configuration) of the brazed joints was evaluated to obtain shear strength values. Also, micro-hardness traverse has been carried out across the brazed joint. Applied load plays a significant role in obtaining defect free braze joint.

Influence of Process Parameters on Aluminium Alloy 6061-O Joints by Friction Stir Welding Process

The present work reports the influence of process parameters (tool speed, traverse speed and axial load) on the metallurgical and mechanical properties of joints fabricated by friction stir welding process. The samples were friction stir welded under tool rotational speed of 1120, 1250 & 1500 rpm and traversing speed of 0.5, 0.6 & 0.8 mm/sec with an axial load of 9000 Kg constant for all the trials. Single pass friction stir welding process was followed in this investigation. Metallographic analysis was carried out across various zones of weldments (Unaffected Base Metal, Heat Affected Zone, Thermo Mechanically Affected Zone and Nugget Zone). Mechanical tests (microhardness survey & tensile test) were evaluated and all the results were correlated with the parent base metal. For better understanding scanning electron microscope (SEM) analysis was carried out in the nugget zone to predict the flow of materials due to severe stirring process. It is observed from the results that joint fabricated with a tool speed of 1250 rpm, traverse speed of 0.8 mm/sec and axial load of 9000 Kg showed a defect free joint, with better refined grain structures and high tensile strength when compared to all other trials done.

Medial humeral epicondylitis in clinically affected cats.

To describe the clinical signs and histologic changes in cats clinically affected with medial humeral epicondylitis (MHE) and evaluate long-term outcome after either conservative or surgical treatment. Prospective cohort study. Client-owned cats (n = 17) with MHE. Cats diagnosed with MHE, based on clinical signs, radiographs and computed tomography (CT), were prospectively recruited. Cats were treated conservatively for an initial 4 weeks, followed by either surgery or continued conservative treatment. Followup examinations were performed at 6 and 12 weeks and at 6-49 months. Cats had a mean age of 10.3 years and presented for chronic lameness. Examination revealed pain on palpation caudodistal to the medial epicondyle and by exerting antebrachial supination/pronation with elbow and carpal flexion. Lameness was restricted to 1 limb although CT revealed bilateral disease in 11/17 cats. Free mineralized joint bodies were identified in 9/17 cats. Nine cats were treated surgically and 8 cats were treated conservatively. Intraoperative findings included new bone formation at the origin of the humeral head of the flexor carpi ulnaris muscle with displacement and adhesions of the ulnar nerve. Microscopic examination revealed neurogenic myopathy in 4/9 cats treated surgically. Seven of 9 cats treated surgically were free from lameness by 12 weeks. Seven of 8 cats treated conservatively were chronically lame throughout the study. Cats with forelimb lameness should be evaluated for MHE. This condition is associated with free joint bodies and neurogenic myopathy. Surgical treatment is associated with excellent outcome in the majority of cats.

Results of Hemi Arthroplasty in Fracture Neck of Femur in Elderly Person, CBMCHB Experience

Intracapsular femoral neck fracture is a common injury in elderly person. The primary goal of treatment is to return the patient to him or her pre-fracture functional status. The surgical treatment is the treatment of choice, lip replacement arthroplasty (hemi or total) is a viable treatment option. Thirty elderly patients (age 50-80 years) with a displaced intracapsular femoral neck fracture were under treatment over a five year period (January 2010 to December 2015). All of them underwent hemiarthroplasty either unipolar or bipolar, after appropriate medical and anesthetic fitness. The patients were reevaluated at six weeks, at six months postoperative interval and assessed using Harris hip score (HHS) and visual analogue scale (vas) for evaluation of outcome. The mean age of patients was 64.5 years and male female ratio was 43.3% - 56.7%. The mean HHS score was 85.3 by the end of the 6 months. The mean score on VAS scale was 60mm (moderate) at 2 weeks, 40mm (mild) at six weeks and 4mm (mu) at 6 months follow up visit. No significant complications were observed except hip pain. No patients needed revision surgery. Herniarthroplasty is the treatment of choice in elderly population with displaced femoral neck fracture (Garden type III or IV); provides early ambulation, good functional outcome, pain free joint with minimal complications without the need for revision surgery.
 CBMJ 2015 July: Vol. 04 No. 02 P: 8-12

Fate of Costochondral Graft in Temporomandibular Joint Reconstruction: A Histological Study.

To asses the fate of the costochondral graft (CCG) used to stimulate mandibular growth in the management of Temporomandibular joint (TMJ) reconsrtuction in ankylosis-histologically. Ten patients who had undergone CCG grafting for TMJ ankylosis between 1994-2009 in the department of Oral & Maxillofacial Surgery, Tamil Nadu Govt Dental College and Hospital, Chennai and had come back with reankylosis, were surgically explored and the graft along with the ankylotic mass was excised and evaluated histologically. There is no documented human study and clinically it is not possible. Histological evaluation revealed the presence of osseous tissue, fibrous tissue and osteocytes but no evidence of any chondroid tissue. Our study showing the absence of chondroid tissue raises the question on the rationale of CCG in TMJ reconstruction when other interpositional gap arthroplasty can achieve a disease free joint.

Brazing development and interfacial metallurgy study of tungsten and copper joints with eutectic gold copper brazing alloy

Current proposals for the divertor component of a thermonuclear fusion reactor include tungsten and copper as potentially suitable materials. This paper presents the procedures developed for the successful brazing of tungsten to oxygen free high conductivity (OFHC) copper using a fusion appropriate gold based brazing alloy, Orobraze 890 (Au80Cu20). The objectives were to develop preparation techniques and brazing procedures in order to produce a repeatable, defect free butt joint for tungsten to copper. Multiple brazing methods were utilised and brazing parameters altered to achieve the best joint possible. Successful and unsuccessful brazed specimens were sectioned and analysed using optical and scanning electron microscopy, EDX analysis and ultrasonic evaluation. It has been determined that brazing with Au80Cu20 has the potential to be a suitable joining method for a tungsten to copper joint.

Medium term outcomes of primary and revision Coonrad-Morrey total elbow replacement.

Background:Total elbow replacement (TER) is indicated in inflammatory arthritis, osteoarthritis and fractures that are not amenable to reconstruction. There is no series in literature, to the best of our knowledge, regarding the results of revision of the Souter-Strathclyde prosthesis (SSP) to the Coonrad-Morrey prosthesis (CMP). The aim of this study is to present the medium term results of primary CMP total elbow replacement and revision of the SSP to CMP.Materials and Methods:50 primary CMPs (Group I) and 11 revision CMPs (Group II) were included in the study. Demographic, operative, followup and radiological data were analysed. The indication for revision of the primary implant was peri-prosthetic fracture in six cases, aseptic loosening in four cases and instability in one case.Results:The mean age in Group I was 67.28 ± 12.45 years and in Group II was 57.09 ± 11.25 years. The mean period of followup was 8.08 ± 2.95 years and 7.46 ± 2.39. There was a significant improvement in range of motion and pain in both groups. The complications seen were nerve palsy, infection, fractures and heterotopic ossification. The 5-year survival rate in Group I was 94%. The results were good in 36 elbows, fair in 8 elbows and poor in 5 elbows. In Group II, the results were good in 8 elbows, fair in 2 elbows and poor in 1 elbow. The complications seen were nerve palsy, fractures and heterotopic ossification.Discussion:Primary CMP TER provides a functionally useful range of movement of 100° which is enough to perform most activities of daily living. It also produces a pain free and stable joint. Similar results are achieved after revision of the SSP to CMP. The unique toggle-hinge mechanism of articulation provides inherent stability and good survivorship.Conclusion:Semiconstrained prostheses like CMP provide good functional results and survivorship and are the implant of choice in both primary and revision total elbow replacements.

Adaptive postural control for joint immobilization during multitask performance.

Motor abundance is an essential feature of adaptive control. The range of joint combinations enabled by motor abundance provides the body with the necessary freedom to adopt different positions, configurations, and movements that allow for exploratory postural behavior. This study investigated the adaptation of postural control to joint immobilization during multi-task performance. Twelve healthy volunteers (6 males and 6 females; 21–29 yr) without any known neurological deficits, musculoskeletal conditions, or balance disorders participated in this study. The participants executed a targeting task, alone or combined with a ball-balancing task, while standing with free or restricted joint motions. The effects of joint configuration variability on center of mass (COM) stability were examined using uncontrolled manifold (UCM) analysis. The UCM method separates joint variability into two components: the first is consistent with the use of motor abundance, which does not affect COM position (VUCM); the second leads to COM position variability (VORT). The analysis showed that joints were coordinated such that their variability had a minimal effect on COM position. However, the component of joint variability that reflects the use of motor abundance to stabilize COM (VUCM) was significant decreased when the participants performed the combined task with immobilized joints. The component of joint variability that leads to COM variability (VORT) tended to increase with a reduction in joint degrees of freedom. The results suggested that joint immobilization increases the difficulty of stabilizing COM when multiple tasks are performed simultaneously. These findings are important for developing rehabilitation approaches for patients with limited joint movements.