Joint Replacement Implants Research Articles

Can physical joint simulators be used to anticipate clinical wear problems of new joint replacement implants prior to market release?

One of the most important mandates of physical joint simulators is to provide test results that allow the implant manufacturer to anticipate and perhaps avoid clinical wear problems with their new products. This is best done before market release. This study gives four steps to follow in conducting such wear simulator testing. Two major examples involving hip wear simulators are discussed in which attempts had been made to predict clinical wear performance prior to market release. The second one, involving the DePuy ASR implant systems, is chosen for more extensive treatment by making it an illustrative example to explore whether wear simulator testing can anticipate clinical wear problems. It is concluded that hip wear simulator testing did provide data in the academic literature that indicated some risk of clinical wear problems prior to market release of the ASR implant systems. This supports the idea that physical joint simulators have an important role in the pre-market testing of new joint replacement implants.

Influence of particulate and dissociated metal-on-metal hip endoprosthesis wear on mesenchymal stromal cells in vivo and in vitro

In hip arthroplasty the implants' articulating surfaces can be made of a cobalt-chromium-molybdenum (CoCrMo) alloy. The use of these metal-on-metal (MoM) pairings can lead to the release of wear products such as metallic particles and dissociated metal species, raising concerns regarding their safety amongst orthopedic surgeons and the public. MoM-wear particles are reported to be heterogeneous in their physicochemical properties, are capable of inducing adverse effects on a cellular level and are thought to be involved in relevant clinical problems like aseptic osteolysis. Yet, it remains elusive how MoM-wear affects bone forming cells and their progenitors: bone marrow residing mesenchymal stromal cells (MSCs). This study introduces an assessment of the in vivo exposure to particulate and dissociated Co and Cr and evaluates the effects of MoM-wear on MSCs. The exposure to MoM-wear products in vivo and in vitro leads to a decrease in MSCs' osteogenic matrix mineralization and alkaline phosphatase activity on a cellular and systemic level. In conclusion, MoM-wear products are released in the periprosthetic region and elevate bone marrow Co and Cr concentrations towards levels that impair osteogenic differentiation of MSCs. Therefore, the ongoing use of CoCrMo alloys for articulating surfaces in joint replacement implants needs critical reconsideration.

The biological response to orthopedic implants for joint replacement. II: Polyethylene, ceramics, PMMA, and the foreign body reaction.

Novel evidence-based prosthetic designs and biomaterials facilitate the performance of highly successful joint replacement (JR) procedures. To achieve this goal, constructs must be durable, biomechanically sound, and avoid adverse local tissue reactions. Different biomaterials such as metals and their alloys, polymers, ceramics, and composites are currently used for JR implants. This review focuses on (1) the biological response to the different biomaterials used for TJR and (2) the chronic inflammatory and foreign-body response induced by byproducts of these biomaterials. A homeostatic state of bone and surrounding soft tissue with current biomaterials for JR can be achieved with mechanically stable, infection free and intact (as opposed to the release of particulate or ionic byproducts) implants. Adverse local tissue reactions (an acute/chronic inflammatory reaction, periprosthetic osteolysis, loosening and subsequent mechanical failure) may evolve when the latter conditions are not met. This article (Part 2 of 2) summarizes the biological response to the non-metallic materials commonly used for joint replacement including polyethylene, ceramics, and polymethylmethacrylate (PMMA), as well as the foreign body reaction to byproducts of these materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1685-1691, 2017.

Biologic Responses to Orthopedic Implants: Innate and Adaptive Immune Responses to Implant Debris.

Almost 20% of joint replacement implants fail at 15 to 20 years. Reports suggest that systemic effects of metal-on-metal implants and local effects of total joint arthroplasty implants contributing to implant failure are immune system based. Sometimes implant wear debris can cause implant failure resulting from bone fracture, infection, or implant fracture/failure; most often, aseptic osteolysis or loosening leads to wear debris. Debris is produced by wear (primary) or by corrosion. Corrosion-chemical oxidation comprising reduction reactions involving electron transport-produces electrochemical degradation. Metallic implant degradation occurs when electrochemical dissolution and mechanical/physical wear are combined (i.e., tribocorrosion). With metal-on-metal implants, even with relatively low levels of wear and particle release, pathology caused by metal debris such as pseudotumor/fibrous tissue growth can lead to early implant failure.

Variation in Costs of Spinal Implants in United States Academic Medical Centers.

Retrospective study of benchmarking database. To evaluate the variability in direct costs of spinal implants across various academic medical centers, determining variability between and within specific manufacturers, and to measure the relationship between purchasing volume and price. Spinal implants are a significant component of the cost of surgery. There is an absence of transparency of how much various medical centers in the United States pay for implants because of the use of nondisclosure agreements as part of price negotiations. Transparency of information on costs and awareness of costs by physicians will be useful in managing costs in a value-based health care economy. Purchasing records of 45 academic medical centers over a 12-month period were examined. Purchasing volume and unit pricing for pedicle screws (PS), anterior cervical plates (ACP), and transforaminal lumbar interbody fusion (TLIF) cages were collected for 6 manufacturers. Overall variation in implant costs across centers and for each manufacturer was determined as was the relationship between purchasing volume and unit price. We found variation in implant costs between medical centers, and between manufacturers for PS, ACP and TLIF similar to joint replacement implants. Regression analysis showed that for each 10-fold increase in purchasing volume, the unit price decreased by $126 for PS, $242 for ACP, and $789 for TLIF. There was variation in implant costs between medical centers and manufacturers of implants, with a small negative relationship between purchasing volume and cost. Transparency in cost negotiation, surgeon awareness of costs and alignment between surgeon and hospital goals may help decrease the cost of spinal implants, and the cost of care for patients undergoing instrumented fusions.

Experimental and Numerical Models of Complex Clinical Scenarios; Strategies to Improve Relevance and Reproducibility of Joint Replacement Research.

This research review aims to focus attention on the effect of specific surgical and host factors on implant fixation, and the importance of accounting for them in experimental and numerical models. These factors affect (a) eventual clinical applicability and (b) reproducibility of findings across research groups. Proper function and longevity for orthopedic joint replacement implants relies on secure fixation to the surrounding bone. Technology and surgical technique has improved over the last 50 years, and robust ingrowth and decades of implant survival is now routinely achieved for healthy patients and first-time (primary) implantation. Second-time (revision) implantation presents with bone loss with interfacial bone gaps in areas vital for secure mechanical fixation. Patients with medical comorbidities such as infection, smoking, congestive heart failure, kidney disease, and diabetes have a diminished healing response, poorer implant fixation, and greater revision risk. It is these more difficult clinical scenarios that require research to evaluate more advanced treatment approaches. Such treatments can include osteogenic or antimicrobial implant coatings, allo- or autogenous cellular or tissue-based approaches, local and systemic drug delivery, surgical approaches. Regarding implant-related approaches, most experimental and numerical models do not generally impose conditions that represent mechanical instability at the implant interface, or recalcitrant healing. Many treatments will work well in forgiving settings, but fail in complex human settings with disease, bone loss, or previous surgery. Ethical considerations mandate that we justify and limit the number of animals tested, which restricts experimental permutations of treatments. Numerical models provide flexibility to evaluate multiple parameters and combinations, but generally need to employ simplifying assumptions. The objectives of this paper are to (a) to highlight the importance of mechanical, material, and surgical features to influence implant-bone healing, using a selection of results from two decades of coordinated experimental and numerical work and (b) discuss limitations of such models and the implications for research reproducibility. Focusing model conditions toward the clinical scenario to be studied, and limiting conclusions to the conditions of a particular model can increase clinical relevance and research reproducibility.

What do patients know about their joint replacement implants?

Following a hip or knee replacement, patients may have little information about their prosthesis. This can lead to anxiety in the face of media reports about failing implants or misconceptions about how to live with a joint replacement. The aim of this study was to determine the level of understanding amongst patients who had undergone joint replacement in order to inform the development of an educational intervention. A cross-sectional, questionnaire-based survey. The survey was administered to patients attending an orthopaedic arthroplasty follow up clinic between June 2012 and October 2012. Patients were selected in a convenience sampling manner and had all undergone joint replacement at least three months prior to the survey. Responses were available from 52 patients; 49/52 (94%) of patients did not know what model of joint replacement they had and 44/52 (85%) did not know what materials the implant was made from. There was wide variation in recall of advice about activity restrictions. Whilst patients used the internet and other sources to look for advice, this survey suggests the most appropriate educational intervention for this population would involve written information including advice about type of implant, activity restrictions, dental treatment and airport security detectors.

Novel biological strategies for treatment of wear particle-induced periprosthetic osteolysis of orthopaedic implants for joint replacement

Wear particles and by-products from joint replacements and other orthopaedic implants may result in a local chronic inflammatory and foreign body reaction. This may lead to persistent synovitis resulting in joint pain and swelling, periprosthetic osteolysis, implant loosening and pathologic fracture. Strategies to modulate the adverse effects of wear debris may improve the function and longevity of joint replacements and other orthopaedic implants, potentially delaying or avoiding complex revision surgical procedures. Three novel biological strategies to mitigate the chronic inflammatory reaction to orthopaedic wear particles are reported. These include (i) interference with systemic macrophage trafficking to the local implant site, (ii) modulation of macrophages from an M1 (pro-inflammatory) to an M2 (anti-inflammatory, pro-tissue healing) phenotype in the periprosthetic tissues, and (iii) local inhibition of the transcription factor nuclear factor kappa B (NF-κB) by delivery of an NF-κB decoy oligodeoxynucleotide, thereby interfering with the production of pro-inflammatory mediators. These three approaches have been shown to be viable strategies for mitigating the undesirable effects of wear particles in preclinical studies. Targeted local delivery of specific biologics may potentially extend the lifetime of orthopaedic implants.

Ten year follow-up of pyrocarbon implants for proximal interphalangeal joint replacement

Results of anatomical resurfacing of the proximal interphalangeal joint using pyrocarbon implants showed reasonable clinical results with a high radiographic migration rate. The aim was to investigate the subjective, clinical, and radiographic results 10 years following surgery, and to compare them with our 2-year follow-up data. We re-evaluated 12 patients with 15 proximal interphalangeal implants on average 9.7 years after surgery. Pain significantly improved from 7.6 on a visual analogue scale pre-operatively to 1.4 at 2 years, and to 0.7 at the final follow-up. The mean total range of motion in all replaced joints was 36° pre-operatively and 39° at the 2-year follow-up, but had decreased significantly to 29° at 10 years. We saw one implant migration in addition to the eight migrated implants we already found 2 years after surgery. The moderate clinical results, combined with the high migration rate, mean that we no longer use this kind of implant.

Acoustic Emission Monitoring of Total Hip Arthroplasty Implants

Acoustic Emission (AE) monitoring of patients with Total Joint Replacement (TJR) implants uses an array of four passive ultrasonic receivers to undertake in-vivo monitoring of the acoustic events created by patients with TJR implants. This manuscript presents and compares the results of in-vivo and in-vitro measurements of the acoustic signature created by a range of Total Hip Replacement (THR) implants. A major focus of this investigation is in the characterization of squeaking of hard-on-hard bearing surface combinations. The presence of an audible squeak of the bearing surface can cause significant embarrassment and potential discomfort to patients. It has been identified that squeaking is primarily identified at the main bearing interface and the fundamental peak falls in the range of 2-5kHz, with multiple higher harmonics also observed. The frequency of the primary squeak is seen to vary based on bearing surface type of both the acetabular liner and femoral head (ceramic-on-ceramic, metal-on- metal bearing combinations)Comparison is also drawn between in-vivo and in-vitro testing through the use of implant components retrieved during revision surgery of patients previously subjected to in-vivo testing. In the trials presented within this manuscript, strong correlation was achieved between the two test methods. In-vivo signal magnitudes were substantially smaller than those recorded from bench tests directly on the implant. However, characteristic frequencies were very similar in both cases, indicating that tissue attenuation reduces signal magnitude, but the influence of any period shifting of signals through the soft tissue were minimal. These initial results provide an important base for future testing and provide useful insight into the underlying cause of audible squeaking of total hip replacement patients with hard-on-hard bearing surfaces.

Evaluation of taper joints with combined fatigue and crevice corrosion testing: Comparison to human explanted modular prostheses

The requirement for revision surgery of total joint replacements is increasing and modular joint replacement implants have been developed to provide adjustable prosthetic revision systems with improved intra-operative flexibility.An electrochemical study of the corrosion resistance of the interface between the distal and proximal modules of a modular prosthesis was performed in combination with a cyclic fatigue test. The complexity resides in the existence of interfaces between the distal part, the proximal part, and the dynamometric screw.A new technique for evaluating the resistance to cyclic dynamic corrosion with crevice stimulation was used and the method is presented.In addition, two components of the proximal module of explanted Ti6Al4V and Ti6Al7Nb prostheses were investigated by optical and electron microscopy.Our results reveal that: The electrolyte penetrates into the interface between the distal and proximal modules during cyclic dynamic fatigue tests, the distal module undergoes cracking and corrosion was generated at the interface between the two models; The comparison of the explanted proximal parts with the similar prostheses evaluated following cyclic dynamic crevice corrosion testing showed that there were significant similarities indicating that this method is suitable for evaluating materials used in the fabrication of modular prostheses.

What do patients know about their joint replacement implants?

What do patients know about their joint replacement implants?

Single-stage treatment of temporomandibular joint ankylosis using patient specific total joint replacement implants and virtual surgical planning

Background: Temporomandibular joint (TMJ) ankylosis is a debilitating condition that can result in pain, trismus and a poor quality of life. Causes include trauma, infection and the rheumatoid diseases.

Möglichkeiten und Grenzen der schaftfreien Oberarmkopfprothese

Currently there are five manufacturers offering stemless implants for shoulder joint replacement. A total number of almost 10,000 stemless implants have been used in shoulder arthroplasty since 2004. There are two different types of metaphyseal anchorage, one obtained by impaction of a fin system and in the other implant system cage screw fixation is used. Regarding revision surgery the different types of implants show varying advantages and disadvantages in terms of secondary approach to the glenoid and the metaphyseal component. Because of the small number of cases and short period of observation at the present time none of the implant systems show a decisive superiority. In sclerotic bone the cage screw system seems to be advantageous whereas impaction using the fin system seems to be preferable in osteoporotic bone and conditions with defects of the bone. A prerequisite for all types of stemless shoulder implants is good quality bone. There should not be bony defects under the surface of the area of head resection. Stemless implants are not indicated for acute fractures.

Manufacturing lot affects polyethylene tibial insert volume, thickness, and surface geometry

To perform wear measurements on retrieved joint replacement implants, a reference geometry of the implant's original state is required. Since implants are rarely individually scanned before implantation, a different, new implant of the same kind and size is frequently used. However, due to manufacturing variability, errors may be introduced into these measurements, as the dimensions between the retrieved and reference components may not be exactly the same. The hypothesis of this study was that new polyethylene tibial inserts from different manufacturing lots would demonstrate greater variability than those from the same lot. In total, 12 new tibial inserts of the same model and size were obtained, 5 from the same lot and the remainder from different lots. The geometry of each tibial insert was obtained using microcomputed tomography. Measurements of tibial insert volume, thickness, and three-dimensional surface deviations were obtained and compared between tibial inserts from the same and different manufacturing lots. Greater variability was found for the tibial inserts from different manufacturing lots for all types of measurements, including a fourfold difference in volume variability (p < 0.001) and a maximum of 0.21 mm difference in thickness (p < 0.001). Investigators should be aware of this potential confounding error and take steps to minimize it, such as by averaging together the geometries of multiple new components from different manufacturing lots for use as the reference geometry.

Promotion of osteogenic differentiation of stem cells and increase of bone-bonding ability in vivo using urease-treated titanium coated with calcium phosphate and gelatin

Because of its excellent biocompatibility and low allergenicity, titanium has been widely used for bone replacement and tissue engineering. To produce a desirable composite with enhanced bone response and mechanical strength, in this study bioactive calcium phosphate (CaP) and gelatin composites were coated onto titanium (Ti) via a novel urease technique. The cellular responses to the CaP/gelatin/Ti (CaP/gel/Ti) and bone bonding ability were evaluated with proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) on CaP/gel/Ti and CaP/Ti in vitro. The results showed that the optical density values, alkaline phosphatase expression and genes expression of MSCs on CaP/gel/Ti were similar to those on CaP/Ti, yet significantly higher than those on pure Ti (p < 0.05). CaP/gel/Ti and CaP/Ti rods (2 mm in diameter, 10 mm in length) were also implanted into femoral shaft of rabbits and pure Ti rods served as control (n = 10). Histological examination, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements were performed at 4 and 8 weeks after the operation. The histological and SEM observations demonstrated clearly that more new bone formed on the surface of CaP/gel/Ti than in the other two groups at each time point. The CaP/gel/Ti bonded to the surrounding bone directly with no intervening soft tissue layer. An interfacial layer, containing Ti, Ca and P, was found to form at the interface between bone and the implant on all three groups by EDS analysis. However, the content of Ca, P in the surface of CaP/gel/Ti implants was more than in the other two groups at each time point. The CaP/gel/Ti modified by the urease method was not only beneficial for MSCs proliferation and osteogenic differentiation, but also favorable for bone bonding ability on Ti implants in vivo, suggesting that Ti functionalized with CaP and gelatin might have a great potential in clinical joint replacement or dental implants.

Doped TiO2 anodic layers of enhanced antibacterial properties

Ti–6Al–4V joint replacement implants foster uncemented fixation in orthopaedic surgery. However, bacterial colonization competes with host cells and ultimately may produce implant-related difficult-to-treat infections, justifying the efforts to obtain infection-resistant materials. In a previous work, the authors demonstrated the antibacterial properties of anodic fluoride-TiO2 nanostructured layers on Ti–6Al–4V alloy. In this work, the anodizing bath has been modified in order to grow fluoride-TiO2 barrier layers (FBL). A bacterial adherence protocol, run with reference and six different clinical strains of Staphylococcus aureus and Staphylococcus epidermidis, showed a statistically significant decrease in the percentage of covered surface (p<0.0001, Kruskal–Wallis test) for FBL specimens when compared with non fluoride-containing specimens, i.e. chemically polished Ti–6Al–4V and F-free TiO2 barrier layers. The results obtained on the F-barrier layers allowed discrimination between the effects of the presence of fluoride in the layer and the layer nanostructure on bacterial adhesion.

Adverse reactions to metal-on-metal implants

New data demonstrate that cobalt ions promote immune system activation through Toll-like receptor 4 signalling. This finding adds to our understanding of the adverse innate and adaptive immune reactions evoked by debris released from metal-on-metal total or resurfacing joint replacement implants, which have provoked recommendations against their use.

Scapholunate Instability: Current Concepts in Diagnosis and Management

Injuries to the scapholunate joint are the most frequent cause of carpal instability and account for a considerable degree of wrist dysfunction, lost time from work, and interference with activities. Although it is insufficient to cause abnormal carpal posture or collapse on static radiographs, an isolated injury to the scapholunate interosseous ligament may be the harbinger of a relentless progression to abnormal joint mechanics, cartilage wear, and degenerative changes. Intervention for scapholunate instability is aimed at arresting the degenerative process by restoring ligament continuity and normalizing carpal kinematics. In this review, we discuss the anatomy, kinematics, and biomechanical properties of the scapholunate articulation and provide a foundation for understanding the spectrum of scapholunate ligament instability. We propose an algorithm for treatment based on the stage of injury and the degree of secondary ligamentous damage and arthritic change.

(iv) Enhancing the safety and reliability of joint replacement implants

A new Stratified Approach For Enhanced Reliability (SAFER) pre-clinical simulation testing of joint prostheses is presented in this article. The aim of this approach is preclinical systematic testing of wear performance in the much wider envelope of conditions found clinically rather than relying only on the standard testing conditions that are currently used. The approach includes variations in surgical delivery, variations in kinematics, variations in the patient population and degradation of the biomaterial properties. Clinical experience of existing prostheses has been used to validate the new in vitro methods.