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Nowadays, there is a growing need for using functionally graded materials (FGM) for using in bio-medical application. This need is prominent especially for the effect of gradient structures and in implant applications. To optimize both mechanical and biocompatibilities properties or change bio reactivity in each region, powder metallurgy technique is used in this study to fabricate titanium/hydroxyapatite (Ti/HAP) and other FGM implants with the concentration changed gradually in the longitudinal direction of cylindrical shapes. Concentration gradient was formed by packing dry powders into mold or sedimentation in solvent liquid processes. For the sintering process, three spark plasma sintering (SPS), high-frequency induction heating and electric furnace heating techniques were used to sinter the materials. During the fabrication of Ti/HAP FGMs and due to the stress relaxation in the implanted regions of bones, Brinell hardness decreased gradually from Ti part to HAP part. The results showed that the tissue reaction occurred gradiently in response to the graded structure of the FGM, which implies the possibility of controlling the tissue response through the gradient function of the FGM.

The material composition and surface structure of dental and orthopaedic implants have important effects on integration of the implants with the surrounding bone, and at the same time, the release of the constituent elements of the implants into the surrounding tissues. It is the aim of this paper to study the degree of release of Ti in relation to the surface roughness of the implants. For this purpose, screw shaped implants were prepared with two different surface topographies; one group was left as-machined, i.e. as machine-turned surface, and the second group was blasted with 25 µm Al₂O₃ particles. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using height and spatial descriptive parameters. The as-machined surfaces had an average surface roughness (S_a) of 0.96 µm and the blasted surfaces had an S_a value of 1.16 µm. The implants were inserted into rabbit bone for 1 year. Six samples (three of each type) were prepared for PIXE analysis. The PIXE analysis was done using proton beams from a tandem type accelerator. with an energy of 2 MeV. The results show that at distances of about 2 mm from implant surface, titanium release into hard tissues was found at similar amounts for the as-machined and the blasted implants inserted in the tibia.

A thin passive titanium dioxide, in its stoichiometric form, has a very high corrosion resistance, but the same conclusion can not be made on corrosion resistance of a surface which is not stoichiometrically titanium dioxide, or even a surface which is a composition of various elements and oxides. In practice, the implants available on the market have an oxide surface contaminated with other elements. The aim of this paper is to correlate clinical observations that show the deterioration of Ti made implants after certain period of insertion in the patients, and in vitro corrosion resistance of Ti implants with surface passive oxide layer. For this purpose, surface analysis of the retrieved failed implants were performed and in vivo animal experiments with relation to ion release from implants were done. Finally, on the basis of the clinical observation, in vivo animal test, and in vitro electrochemical corrosion test, a model is proposed to explain the corrosion and ion release from the Ti implant.

Fatigue properties of Ti-6Al-4V (TC4) subjected to 0.9% physiological saline solutions were presented in this paper. The ultrasonic fatigue test method has been used to investigate the very high cycle fatigue properties of commercial titanium alloy TC4 with the microstructure of tramsformed lamellar dipped into 0.9% physiological saline solution prior to testing. Three estimated times have been decided for subjecting at 37 °C, such as 24 hours, 2 weeks and 4 weeks. The results show that physiological saline solution treatment makes a little influence on the ultrasonic fatigue life of TC4. The slope of S-N curve decreases as the dipping time increases. Dipping tests for three estimated times also have been performed. When TC4 has been dipped into physiological saline solution for 4 weeks, homogeneous white points have been observed on specular facet specimen. And in the fracture surface of which has been dipped for 4 weeks, new inclusion sized 5-10 µm in the crack initiation has been observed. The fractography pictures show the fracture to be transcrystalline plastic. Cracks are initiated because of the subsurface inclusion and the facet slip of α-phase.

The possibilities of movement and electrochemical reduction of fibroin macroions in the presence of tricalcium phosphate ions in the form of a nanocoating during electrolysis have been studied. The manifestation of a non-Newtonian flow of a mixture of macroions and ions in a shear flow, the conditions for their electrochemical reduction in the form of a nanocoating with uniform morphology, and thickness on the electrode surface are revealed. It was found that the excess ions in the mixture and the uneven relief of the electrode surface contribute to the formation of a nanocoating with an inhomogeneous and uneven thickness.

Since the discovery of Bioglass^® by Hench, bioactive glasses have been used in many medical applications, such as drug delivery systems, nonload-bearing implants, and bone cements because of their excellent bioactivity and biocompatibility. However, due to their poor mechanical properties, these glasses cannot be used in load-bearing applications, where the metallic alloys are still main materials. One useful approach to solving the mechanical limitations of bioactive glasses is to apply the glasses as the coating on mechanically tough substrates; it was also recognized early that bioactive glasses could be used as coatings for prosthetic metallic implants. In this paper, the mechanism, characterization, and current status of some methods of preparation for bioactive glass coating on implants are introduced. In the end, to get the homogeneous and compact coating with perfect bonding strength, some ideas of improving the performance of coatings are also presented.

The present work deals with the fabrication of forsterite–hydroxyapatite (FS–HA) hybrid coatings on stainless-steel 316L using the pulsed laser deposition (PLD) technique. The stainless steel (SS 316L) as a metallic implant is widely used in hard tissue applications. The XRD studies have confirmed the crystalline behavior of synthesized FS powder with an average crystallite size of 54nm. The synthesized FS powder was mixed in different compositions (10, 20, 30wt.%) into HA for preparing PLD targets (pellets). The XRD of the prepared pellets by UTM has confirmed both phases of FS and HA. The Scanning Electron Microscopy (SEM) of the coated samples depicted the successful deposition of composite powders on the substrates (SS 316L). The Ellipsometer was used to investigate the thickness of different substrates and it was found as 243, 251, 255, and 257nm for CP1, CP2, CP3, and CP4, respectively. The bioactivity of the coated substrates with different compositions (pure HA, 10%, 20%, 30%, and pure FS) was investigated by immersing the samples in simulated body fluid (SBF) for 14days. The same samples were then characterized by SEM which confirms the apatite layer formation that reflects the bioactivity. The addition of FS powder into HA will stimulate the apatite formation which enhances the bioactivity. The Raman Spectroscopy of coated samples reveals the successful deposition of different compositions of FS–HA nanocomposite. The peaks of Raman spectroscopy were corresponding to the XRD results of the pellets (different compositions of FS–HA). The antimicrobial activity of different compositions of FS–HA against Escherichia coli (E. coli) bacteria also showed a significant zone of inhibition. The bioactivity and antimicrobial behavior of FS–HA along with successful deposition by PLD have shown better potential applications for biomedical implant coating.

Additive manufacturing (AM) of titanium (Ti) alloys has always fascinated researchers owing to its high strength to weight ratio, biocompatibility, and anticorrosive properties, making Ti alloy an ideal candidate for medical applications. The aim of this paper is to optimize the AM parameters, such as Laser Power (LP), Laser Scan Speed (LSS), and Hatch Space (HS), using Analysis of Variance (ANOVA) and Grey Relational analysis (GRA) for mechanical and surface characteristics like hardness, surface roughness, and contact angle, of Ti6Al4V ELI considering medical implant applications. The input parameters are optimized to have optimum hardness, surface roughness and hydrophilicity required for medical implants.

The purpose of this study was to compare the outcomes of volar plating using two different implants for distal radius fractures. Fifty-two patients with AO type C fractures were placed in either of two groups: the AO LDRS group (26 patients) or the Acu-Loc group (26 patients). Radiological parameters including radial length, radial inclination, volar tilt, and intra-articular step-off were significantly improved after surgery. The mean Mayo Wrist Performance Score was 84.6 in the AO LDRS group and 81.1 in the Acu-Loc group. The mean Subjective Wrist Value was 86.7% in the AO LDRS group and 86.3% in the Acu-Loc group. There were no significant differences between the two groups with respect to both radiological and clinical outcomes at the final follow-up evaluation. Volar fixed-angle plating for unstable distal radius fractures had satisfactory radiological and clinical outcomes. The difference of implant design did not influence overall final outcomes.

This in vitro biomechanical study reports on a new implant, called an intravertebral expandable pillar (IVEP). The implant is aimed at restoring the height and strength of collapsed vertebra after fracture in an osteoporotic patient. The hypothesis is that the IVEP can effectively restore the body height of the compressed vertebra and provide proper stiffness for the collapsed vertebra. Although the reported complication rate of percutaneous vertebroplasty by injection of polymethylmethacrylate (PMMA) is low, the sequelae are severe; other potential adverse effects of PMMA injection into the vertebral body include thermal necrosis of the surrounding tissue caused by a high polymerization temperature, and lack of long-term biocompatibility. We test the mechanical properties before and after fracture of 14 human cadaver lumbar vertebrae by a material testing system. The fractured vertebra was implanted with the IVEP, and its mechanical properties tested. The vertebral body height at each stage was evaluated by a digital caliper and radiographic films. After IVEP implantation, the vertebral body height restoration rate was 97.8%. The vertebral body height lost 12.7% after the same loading to create fracture. The vertebra lost half of its strength after compressed fracture, while IVEP implantation restored 86.4% of intact vertebra strength. The stiffness of intact vertebrae was significantly greater than that of untreated vertebrae after fracture and fractured vertebrae with IVEP treatment, while the stiffness of fractured vertebrae after IVEP treatment was significantly greater than that of untreated vertebrae after fracture. The bipedicularly implanted IVEP restores the initial height and strength of the vertebral body following an induced compression fracture, and could be used by a minimally invasive procedure to treat lumbar vertebra compression factures and avoid the disadvantage of using bone cement in vertebroplasty or kyphoplasty.

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Rough surface height distribution can be nonsymmetric, depending on the process of surface preparation. The prevalent processes for implant surface involve turning and milling, both resulting in surface height distributions of nonsymmetric nature. Asymmetry in a surface height distribution is manifested through a parameter known as skewness. Unlike Gaussian distribution, Weibull distribution permits characteristics such as skewness and kurtosis in data to be included in the mathematical description of a height distribution. This paper develops hip implant contact model based on Weibull distribution of surface heights. The elastic–plastic interaction of implant surfaces are considered as macroscopically spherical surfaces containing micron-scale roughness. Symmetric and asymmetric roughness height distribution are compared. The total contact force is related to the minimum mean surface separation of the contacting rough surfaces. The force is obtained using statistical integral function of the asperity heights over the possible region of interaction of the roughness of surfaces. Approximate equations are obtained that relate the contact force to the minimum mean surface separation explicitly. The approximate equations are used to derive hysteretic energy loss per load–unload sequence, contact frequency, and damping. It is shown that energy loss per cycle, contact frequency, and damping are lower for asymmetric surface roughness distribution.

Background: This study evaluated the feasibility of using a low-profile titanium (Ti) plate implant, also known as the Ti-button, for Zone II flexor tendon repair. We hypothesize that the use of the Ti-button can distribute the tensile force on the digital flexor tendons to achieve better biomechanical performance.

Methods: Twenty lacerated porcine flexor tendons were randomly divided into two groups and repaired using Ti-button or 6-strand modified Lim-Tsai technique. Ultimate tensile strength, load to 2 mm gap force, and mode of failure were recorded during a single cycle loading test. We also harvested twelve fingers with lacerated flexor digitorum profundus tendons from six fresh-frozen cadaver hands and repaired the tendons using either Ti-button method or modified Lim-Tsai technique. A custom-made bio-friction measurement jig was used to measure the gliding resistance and coefficient of friction of the tendon sheath interface at the A2 pulley.

Results: The ultimate tensile strength, load to 2 mm gap force, stiffness, and gliding resistance of the Ti-button repairs were 101.5 N, 25.7 N, 7.8 N/mm, and 2.2 N respectively. Ti-button repairs had significantly higher ultimate tensile strength and stiffness than the modified Lim-Tsai repair. However, Ti-button also increased the gliding resistance and coefficient of friction but there was no significant difference between the two repair techniques.

Conclusions: Ti-button repair displayed comparable mechanical properties to the traditional repair in terms of 2-mm gap formation and gliding resistance, but with a stronger repair construct. Thus, this deepened our interest to further investigate the potential of using Ti-button implant in Zone II flexor tendon repair by studying both the mechanical and biochemical (tendon healing) properties in more in-depth.

Background: Proximal interphalangeal joint (PIPJ) arthroplasty using a Swanson implant is commonly used for the treatment of PIPJ arthritis despite newer implants being available. Many patients develop arthritis in more than one digit and some tend to have multiple digits operated on in their lifetime. There is paucity of literature on the outcomes of multiple PIPJ arthroplasty in one sitting. The aim of this study is to determine the outcomes of PIPJ arthroplasty using a Swanson implant done for multiple digits at one sitting.

Methods: We retrospectively reviewed the outcomes of multiple Swanson PIPJ arthroplasty during a single operation from 2008 to 2018 in 13 patients (43 arthroplasties). We compared pre- and post-operative results of flexion/extension arcs, grip and pinch strength and questionnaires subsequently compared QuickDASH (Disabilities of Arm, Shoulder and Hand), Patient Evaluation Measure (PEM) and Visual Analogue Score (VAS) scores. Data were analysed with a Mann–Whitney U test.

Results: Patients on average attended 5.6 hand therapy sessions over 5.1 months post-operatively. Average flexion/extension arc improved from 31.9° pre-operatively to 37.2° post-operatively. Average grip strength increased from 7.2 kg to 10.2 kg. The QuickDASH, PEM and VAS scores improved in keeping with the reported literature. There were no implant failures.

Conclusion: We demonstrate similar outcomes for multi-digit Swanson PIPJ arthroplasty compared to the literature for single digit Swanson PIPJ arthroplasty. We conclude that multi-digit arthroplasty in a single operation is safe and effective.

Level of Evidence: Level IV (Therapeutic)

Background: Wrist arthroplasties have not achieved clinical outcomes comparable to those of shoulders and knees, being offered low-demand patients due to a high failure rate. In the 90s, there were no wrist arthroplasties available for high-demand patients. An experimental setup for the development of a new wrist arthroplasty intended for all wrist patients were done. A long-term final follow-up to evaluate the performance of the experimental arthroplasty was performed.

Methods: A novel uncemented modular wrist prosthesis with conical threaded fixation, metal-on-metal coupling and ball-and-socket articulation was developed. In an experimental study, eight patients (7 men, 53 years of age) were operated between 2001 and 2003, to treat non-inflammatory primary or secondary osteoarthritis. Published mid-term results (7–9 years) demonstrated satisfactory function, but two arthroplasties were converted to arthrodesis due to infection.

Results: At final follow-up 15–20 years after primary surgery, the remaining six patients still had a wrist arthroplasty (in three the original) in situ. The clinical results were good. Low pain (median = 0), Quick Disability of Arm, Shoulder and Hand (QDASH median 11) and Patient Rated Wrist and Hand Evaluation (PRWHE median = 14) scores were reported. Wrist active range of motion (AROM) was 64% and grip strength 86% compared to the opposite side. None regretted choosing arthroplasty knowing the outcome.

Conclusions: Despite technical errors and the implementation of an incomplete prototype, this new concept for arthroplasty has demonstrated promising long-term fixation, a stable articulation with good range of motion, satisfactory function and pain reduction in high-demand patients.

Level of Evidence: Level IV (Therapeutic)

Wrist arthroplasty is becoming more commonplace, with various implant choices available. The Motec (Swemac Orthopaedics AB, Linköping, Sweden) cementless ball-and-socket system is being increasingly utilised and is designed for the distal component to be implanted into the third metacarpal. However, distal component failure is a recognised complication. We outline our experience with the revision of this component into the second metacarpal. This technical note is presented through our experience of two patients who underwent revision arthroplasty for the management of peri-prosthetic fracture of the third metacarpal. This technique has demonstrated a safe and viable solution to this complication, achieving good anatomical centre of rotation, function, range of movement and patient satisfaction.

Level of Evidence: Level V (Therapeutic)

Background: Wrist arthroplasty is increasingly offered to patients with symptomatic wrist arthritis as an alternative to wrist arthrodesis. The purpose of this study was to present our outcomes with the ReMotion™ wrist arthroplasty in a consecutive series of patients with wrist arthritis from non-inflammatory conditions.

Methods: Thirteen (eight women, nine dominant wrists) patients, 68 (44–85) years of age with advanced radiocarpal arthritis due to SLAC/SNAC (11) and Kienbock disease (2) had a ReMotion™ (Stryker, Michigan, USA) wrist arthroplasty implanted, and were prospectively followed for 7 (4–9) years. The outcome measures included patient-rated wrist and hand evaluation (PRWHE) score, disabilities of the arm, shoulder and hand questionnaire (QuickDASH) score, visual analogue pain score (0–10) on the radial and ulnar aspect of the wrist at rest (VASrR/VASuR) and activity (VASrA/VASuA), active wrist range of motion (AROM) including flexion, extension, ulnar and radial deviation, pronation and supination and grip and key-pinch strength measured preoperatively and at yearly follow-ups by independent hand therapists.

Results: Six patients had ten re-operations during the follow-up including four revisions to a new arthroplasty. Four were considered loose at follow-up. A significant reduction in PRWHE (63 to 12), radial pain at activity (6 to 1) and increased pronation (85° v 90°) was observed.

Conclusions: We found a high complication and reoperation rate, two out of 13 had no complications or reoperations. The ReMotion™ arthroplasty should be used with caution in non-inflammatory wrist patients and the patients followed closely. A high reoperation and revision rate can be expected, and surgeons familiar with revision arthroplasty procedures should perform the surgery.

Level of Evidence: Level II (Therapeutic)

Arthroplasty of the small joints of the hand and fingers is a complex problem facing the hand surgeon. Pyrocarbon implants have been available for several decades. They were originally thought to provide better functional outcomes than silicone implants in patients, mostly due to recreation of the joint anatomy. In a recent publication, pyrocarbon proximal interphalangeal joint (PIPJ) arthroplasty was found to have a higher complication and revision rate. We present a patient with pyrocarbon metallosis of the PIPJ in a revision arthroplasty procedure.

Level of Evidence: Level V (Therapeutic)