Background. Previously, the Coonrad-Morrey elbow system has typically been performed using linked-type total elbow arthroplasty (TEA) implants. However, this implant have been reported to be associated with some problems, such as wearing down, loosening, the complexity of the necessary surgical techniques and inappropriate implant size for Asian people. The Discovery elbow system (Biomet Inc., Warsaw, US) has recently been developed and it has many advantages when compared to Coonrad-Morrey implant, but the treatment outcome for this system is unclear in patients with rheumatoid arthritis (RA). Objectives. The aim of this study was to clarify the outcome of TEA using the Discovery elbow system. Methods. Eleven RA patients (13 elbows) who underwent TEA using the Discovery elbow system were investigated in this study. Two patients (3 elbows) were males, and 9 patients (10 elbows) were females. Ten were right elbows, and 3 were left elbows. Two elbows has Larsen grade “disease, 7 had grade” disease and 4 elbows underwent revision surgery. The surgical approach used for all cases was Campbell's posterior approach. The Discovery elbow system was installed using cemented fixation. Two weeks after the operation, ROM exercise was started. The elbow ROM, Mayo elbow performance score (MEPS), and any complications observed at baseline, 6 months and 24 months after surgery were assessed. Results. The preoperative elbow ROM (mean±SD) was −33.4±4.4° in extension, 133.5±3.4° in flexion, 48.5±8.4° pronation and 67.7±5.7° in supination. The postoperative elbow ROM (mean±SD) was −18.5±6.2° in extension, 112.7±6.1° in flexion, 70.0±3.4° in pronation and 73.7±1.6° in supination. As a result, a significant improvement was observed in extension, flexion and pronation. The MEPS improved significantly at 6 months and 24 months after surgery. In addition, no implant loosening was found or revision surgery was required at 24 months after surgery. Conclusions. In this study, the elbow function was observed to significantly improve by TEA using the Discovery elbow system based on the short-time outcome. However, further study is still needed to clarify the long-term outcome of this implant in RA patients

Background. The quest for the perfectly designed elbow prosthesis continues as instability and loosening remain the foremost reasons for the failure of total elbow replacement (TER). The Discovery® Elbow System (Biomet, UK) (Figure 1), which has been used in UK since 2003, is one of the latest generations of linked prosthesis. This system was designed to decrease polyethylene-bushing wear, improve anatomic stem design, restore elbow joint biomechanics, and produce a hinge that could be easily revised. This report describes the short term outcome of TER using the Discovery® Elbow System. Patients and Methods. A total of 60 TERs including 48 primary and 12 revisions were performed between 2003 and 2008. Patients included 21 males (37%) and 36 females (63%) with a mean age of 63 years. The indications for primary TER were advanced rheumatoid arthritis (n=19), osteoarthritis (n=16), post traumatic osteoarthritis (n=9), acute fractures (n=3), and haemophilic arthropathy (n=1). The outcome was assessed using pain score, Liverpool Elbow Score (LES), and range of movement during a mean follow-up of 26 months. Associated complications were documented. Radiological assessment included evaluation for loosening, instability and periprosthetic fractures. Results. The mean LES was significantly (p<0.001) improved from 3.8 (±1) pre-operatively to 6.9 (±2) at the final follow- up. Significant improvements were noted in elbow flexion from 100° (±22) to 120° (±15), supination from 41° (±28) to 65° (±20) and pronation from 52° (±22) to 72° (±18). There was no significant change in elbow extension. Mean improvement in flexion-extension and pronation-supination arc was 22° and 44°, respectively. 46 cases (77%) were completely pain-free at the final follow-up. The main complications included deep infection (4 cases – treated with staged revision TER), postoperative ulnar neuropathy (3 cases–treated with decompression), intra-operative fractures of medial condyle (3 cases – treated non-operatively with brace), and elbow haemarthrosis (1 case). Discussion. TER with Discovery® Elbow System resulted in either no pain or mild pain in 87% of cases. Patients undergoing Acclaim, Souter-Strathclyde, GSB III, and Coonrad-Morrey TER have been reported to have no/mild pain in 64%, 67%, 50–92% and 60–100% of cases, respectively. A 22° improvement in flexion-extension arc is comparable to that of Acclaim (23°), Souter-Strathclyde (15°), GSB III (19–33°), and Coonrad-Morrey (17–26°) TER. An improvement of 44° in pronation-supination arc in our series is also comparable to that of 31–67° reported for GSB III and higher than the Coonrad-Morrey prosthesis (21–28°). In terms of complications, an infection rate of 6.7% is consistent with those reported for GSB III TER (7–11%) and Coonrad-Morrey (6–8%). The incidence of persistent ulnar neuropathy was lower compared to GSB III TER (11–14%), Coonrad-Morrey (12–26%), and Acclaim (8%). While the survival of Discovery TER was 93%, the survival of GSB III (5–6 years) and Coonrad-Morrey (5 years) has been reported as 71–85% and 72–90%. The results indicate that Discovery® Elbow System is an effective device for total elbow arthroplasty in terms of functional improvement, pain relief and range of motion at short-term follow-up

Osteosarcoma (OSA) is a rare, but disproportionately lethal cancer that predominantly affects children. Sadly, discovery of new therapies for OSA has largely been unsuccessful in the past 30 years; there is an urgent need to identify new treatments for OSA. Pet dogs with naturally-occurring OSA represent a unique comparative “model” to discover new treatments for OSA. Unlike humans, in which fewer than 1,000 cases of OSA occur each year, there are nearly 50,000 new cases each year of OSA in dogs. In addition, dogs have an intact immune system, a shared environment with humans, and more rapid progression of disease. Together these factors make dogs an important comparative model for new therapies for OSA. The purpose of this study was: 1) to validate this mouse-dog-human pipeline for drug discovery and 2) to validate CRM1 as a novel target for ostesoarcoma treatment. We developed patient-derived cell lines and xenografts of OSA from both dogs and humans and applied these models to identify new therapies for OSA using high-throughput drug screens in vitro followed by in vivo validation. Whole exome sequencing was performed on the patient-derived models and original tumors to identify potential driver mutations. A high-throughput screen in both dog and human OSA identified CRM1 inhibitors as effective at killing dog and human OSA patient-derived cell lines in vitro. In vivo, CRM1 inhibition led to significant tumor growth inhibition in patient-derived xenografts from dogs and humans. Western blotting demonstrated increased levels of CRM1 protein expression across nine different dog and human OSA cell lines compared to non-transformed human osteoblasts. CRM1 upregulation in OSA cells was further verified by immunofluorescence staining. Increased CRM1 expression was prognostic for poorer metastasis-free survival and poorer overall survival. Our cross-species personalized medicine pipeline identified CRM1 as a potential therapeutic target to treat OSA in both dogs and humans. Future studies are focused on testing CRM1 inhibitors in canine clinical trials

INTRODUCTION. Aseptic loosening is the most common failure mode for Total Elbow Arthroplasty (TEA) and is considered to be associated with accelerated polyethylene bearing wear [1, 2]. This study aimed to evaluate three commercially available implant designs under loads associated with daily living. The hypothesis was that more recent designs (Discovery and Nexel) provide greater articular contact areas resulting in lower polyethylene stresses compared to the Coonrad/Morrey (CM). METHODS. Motion tracking was performed on a healthy volunteer during elbow flexion at 0, 45, and 90° shoulder abduction because most daily activities occur with some shoulder abduction [3] resulting in varus stress about the elbow. This kinematic data was used in an OpenSim upper extremity musculoskeletal model [4] to estimate muscle and joint reaction loads with 5lb in hand, consistent with the common clinical restrictions following TEA. Computer aided assemblies of the smallest size implants for each system were imported to ANSYS for finite element analysis. Metallic components were treated as rigid and polyethylene components were modeled using a nonlinear elastoplastic constitutive model calibrated to material data. Articular contacts were frictional. Physiologic joint reaction forces and moments quantified in OpenSim were applied and the resulting peak articular contact area and peak bearing von Mises stresses were assessed. RESULTS. Simulated deformation patterns of CM bearings corresponded well to those reported in retrievals studies [1, 2] supporting the clinical relevance of the modeling approach. Peak stresses for CM and Nexel were consistently found in the central and side bearings respectively. The central bearing stresses remained 2–2.6 times lower in Nexel compared to CM. Peak stress for all three TEA systems increased with shoulder abduction (Fig.1, 2). Highest peak stresses (Fig.2) were obtained in CM and consistently exceeded the polyethylene yield limit; CM showed the lowest contact area (Fig.3). Nexel and Discovery experienced peak polyethylene stresses 26–34% and 17–39% lower than CM respectively (Fig.2). DISCUSSION. Our results support the hypothesis that newer TEA systems provide increased articular contact area and reduced bearing stresses during physiological loading. The cylindrical CM central bearing carries both the joint reaction force and moment leading to edge loading and high stresses (Fig.1). The design of the Nexel central bearing provides limited resistance to varus-valgus moment, thus transferring the moment to the side bearings and reducing central bearing stresses. The hemispherical Discovery bearing design was confirmed to offer a large articular contact area. However, non-concentricity of the contact spheres can lead to edge loading and high polyethylene stresses under off-axis forces. CM and Discovery utilize conventional polyethylene, whereas Nexel utilizes highly cross-linked Vitamin-E polyethylene. This study does not account for the increased wear resistance of Vitamin-E as compared to conventional polyethylene [5]. Long term clinical data are needed to demonstrate how these wear properties, as well as the geometric design which has been shown to impact stresses and contact patterns, translate to in vivo performance. For figures, please contact authors directly

In conventional DXA (Dual-energy X-ray Absorptiometry) analysis, pixel bone mineral density (BMD) is often averaged at the femoral neck. Neck BMD constitutes the basis for osteoporosis diagnosis and fracture risk assessment. This data averaging, however, limits our understanding of localised spatial BMD patterns that could potentially enhance fracture prediction. DXA region free analysis (RFA) is a validated toolkit for pixel-level BMD analysis. We have previously deployed this toolkit to develop a spatio-temporal atlas of BMD ageing in the femur. This study aims first to introduce bone age to reflect the overall bone structural evolution with ageing, and second to quantify fracture-specific patterns in the femur. The study dataset comprised 4933 femoral DXA scans from White British women aged 75 years or older. The total number of fractures was 684, of which 178 were reported at the hip within a follow-up period of five years. BMD maps were computed using the RFA toolkit. For each BMD map, bone age was defined as the age for which the L2-norm between the map and the median atlas at that age is minimised. Next, bone maps were normalised for the estimated bone age. A t-test followed by false discovery rate (FDR) analysis was applied to compare between fracture and non-fracture groups. Excluding the ageing effect revealed subtle localised patterns of loss in BMD oriented in the same direction as principal tensile curves. A new score called f-score was defined by averaging the normalised pixel BMD values over the region with FDR q-value less than 1e–6. The area under the curve (AUC) was 0.731 (95% confidence interval (CI)=0.689–0.761) and 0.736 (95% CI=0.694–0.769) for neck BMD and f-score. Combining bone age and f-score improved the AUC significantly by 3% (AUC=0.761, 95% CI=0.756–0.768) over the neck BMD alone (AUC=0.731, 95% CI=0.726–0.737). This technique shows promise in characterizing spatially-complex BMD changes, for which the conventional region-based technique is insensitive. DXA RFA shows promise to further improve fracture prediction using spatial BMD distribution

Periprosthetic joint infection (PJI) is a potentially devastating complication of joint replacement surgery. Osteocytes comprise 90–95% of all cells in hard bone tissue, are long-lived and are becoming increasingly recognised as a critical cell type in the regulation of bone and systemic physiology. The purpose of this study was to examine role of these cells in PJI pathophysiology and aetiology, with the rationale that their involvement could contribute to the difficulty in detecting and clearing PJI. This study examined the ability of human osteocytes to become infected by Staphylococcus aureus and the responses of both the host cell and pathogen in this scenario. Several S. aureus (MRSA) strains were tested for their ability to infect human primary osteocyte-like cells in vitro and human bone samples ex vivo. Bone biopsies were retrieved from patients undergoing revision total hip arthroplasty for either aseptic loosening associated with osteolysis, or for PJI. Retrieved bacterial colony number from cell lysates and colony morphology were determined. Gene expression was measured by microarray/bioinformatics analysis and/or real-time RT-PCR. Exposure to planktonic S. aureus (approx. 100 CFU/cell) resulted in intracellular infection of human osteocyte-like cells. We found no evidence of increased rates of osteocyte cell death in bacteria exposed cultures. Microarray analysis of osteocyte gene expression 24h following exposure revealed more than 1,500 differentially expressed genes (fold-change more than 2, false discovery rate p < 0.01). The gene expression patterns were consistent with a strong innate immune response and altered functionality of the osteocytes. Consistent patterns of host gene expression were observed between experimentally infected osteocyte-like cultures and human bone, and in PJI patient bone samples. Internalised bacteria switched to the quasi-dormant small colony variant (SCV) form over a period of 5d, and the ensuing infection appeared to reach a stable state. S. aureus infection of viable osteocytes was also identified in bone taken from PJI patients. We have demonstrated [1] that human osteocytes can become infected by S. aureus and respond robustly by producing immune mediators. The bony location of the infected osteocyte may render them refractory to clearance by immune cells, and osteocytes may therefore be an immune-privileged cell type. The phenotypic switch of S. aureus to SCV, a form less sensitive to most antibiotics and one associated with intracellular survival, suggests that infection of osteocytes may contribute to a chronic disease state. The osteocyte may therefore serve as a reservoir of bacteria for reinfection, perhaps explaining the high prevalence of infections that only become apparent after long periods of time or recur following surgical/medical treatment. Our findings also provide a biological rationale for the recognised need for aggressive bone debridement in the surgical management of PJI

Proximal humeral fractures occur frequently, with fixed angle locking plates often being used for their treatment. However, the failure rate of this fixation is high, ranging between 10 and 35%. Numerous variables are thought to affect the performance of the fixation used, including the length and configuration of screws used and the plate position. However, there is currently limited quantitative evidence to support concepts for optimal fixation. The variations in surgical techniques and human anatomy make biomechanical testing prohibitive for such investigations. Therefore, a finite element osteosynthesis test kit has been developed and validated - SystemFix. The aim of this study was to quantify the effect of variations in screw length, configuration and plate position on predicted failure risk of PHILOS plate fixation for unstable proximal humerus fractures using the test kit. Twenty-six low-density humerus models were selected and osteotomized to create a malreduced unstable three-part fracture AO/OTA 11-B3.2 with medial comminution which was virtually fixed with the PHILOS plate. In turn, four different screw lengths, twelve different screw configurations and five plate positions were simulated. Each time, three physiological loading cases were modelled, with an established finite element analysis methodology utilized to evaluate average peri-screw bone strain, this measure has been previously demonstrated to predict experimental fatigue fixation failure. All three core variables lead to significant differences in peri-screw strain magnitudes, i.e. predicted failure risk. With screw length, shortening of 4 mm in all screw lengths (the distance of the screw tips to the joint surface increasing from 4 mm to 8 mm) significantly (p < 0 .001) increased the risk of failure. In the lowest density bone, every additional screw reduced failure risk compared to the four-screw construct, whereas in more dense bone, once the sixth screw was inserted, no further significant benefit was seen (p=0.40). Screw configurations not including calcar screws, also demonstrated significant (p < 0 .001) increased risk of failure. Finally, more proximal plate positioning, compared to the suggested operative technique, was associated with reduced the predicted failure risk, especially in constructs using calcar screws, and distal positioning increased failure risk. Optimal fixation constructs were found when placing screws 4 mm from the joint surface, in configurations including calcar screws, in plates located more proximally, as these factors were associated with the greatest reduction in predicted fixation failure in 3-part unstable proximal humeral fractures. These results may help to provide practical recommendations on the implant usage for improved primary implant stability and may lead to better healing outcomes for osteoporotic proximal fracture patients. Whilst prospective clinical confirmation is required, using this validated computational tool kit enables the discovery of findings otherwise hidden by the variation and prohibitive costs of appropriately powered biomechanical studies using human samples

Peri-prosthetic joint infection (PJI) is one the most devastating complications of joint arthroplasty. Although PJI is an infrequent complication (the reported incidence is 1%-2% in the United States), it is the most common indication for revision total knee arthroplasty in the Medicare population and the third most frequent indication for revision total hip arthroplasty. Moreover, the prevalence of PJI appears to be on the rise, with a projected number exceeding 60,000 to 70,000 cases in the United States by 2020. It is estimated that more than 25% of revision procedures annually are attributed to PJI and this number is expected to increase in the upcoming years. The increase in the prevalence of obesity, diabetes, and other comorbidities among the patient population and the emergence of resistant infecting organisms are some of the reasons for the expected rise in the number of infections that medical community will witness. The challenges that PJI present to the orthopaedic community are on many fronts. Prevention of PJI has proven to be a difficult task indeed. Effective strategies for prevention of PJI are being refined. The Center for Disease Control will be publishing its updated Surgical Site Prevention Guidelines in the next few months that consists of specific recommendations for prevention of PJI. In recent years, strides are made in introducing novel molecular techniques for diagnosis of PJI, which may stand to change our practices. The current surgical technique for management of PJI, besides the immense cost, fall short of delivering high success to the patients. The major problem in eradication of infection relates to formation of biofilm on the implant surface and internalization of the organisms by affected cells. Biofilm is a sophisticated structure comprising of organisms embedded in multiple layers of glycoccalyx that allows the organisms to evade host immunity and is impenetrable to antibiotics. These organisms are capable of communicating through molecular mechanisms such as quorum sensing that affords them advantage for survival in the host environment. In recent years strategies to prevent colonization of the implant surface, an essential first step in formation of biofilm, or biofilm disruption techniques have been introduced. A recent International Consensus meeting on PJI that assembled more than 350 experts identified some of the best practices in this field and identified areas in need of future research. Moving into the future, the field of orthopaedics in general and PJI in particular stand to benefit from the discoveries in the field of molecular diagnostics, metabolomics and epigenetics

Much is made of the role of good judgment in the reduction of error, although it is undeniable that error has a role in the development of such judgment. Hence retrospectives from those with experience have merit if we can assume they have introspection and insight as well. In this panel discussion we will explore the experience of a group of renowned surgeons in the field of hip and knee reconstruction, and we will seek their wisdom on new techniques and technology, honed over a few decades of exciting discovery and oft-times unexpected disappointment. In addition, as the session title suggests, these revered colleagues will be invited to reflect on those they encountered, in person or otherwise, by happenstance or design, who profoundly influenced their careers and how that influence shaped their lives and the lives of those entrusted to their care. “If I have seen further than others, it is by standing upon the shoulders of giants” Sir Isaac Newton

Testing potential therapeutics in the regeneration of the disc requires the use of model systems. Although several animal models have been developed to test intervertebral disc (IVD) regeneration, application becomes costly when used as a screening method. The bovine IVD organ culture system offers an inexpensive alternative, however, in the current paradigm, the bony vertebrae is removed to allow for nutrient diffusion to disc cells. This provides limitations on the conditions and strategies one can employ in investigating IVD regeneration and mechanisms in degenerative disc disease (i.e. complex loading). Although one method has been attempted to extend the survival of bovine vertebrae containing IVDs (vIVD) cell viability declined after two weeks in culture. Our goal was to develop and validate a long-term organ culture model with vertebral bone, which could be used subsequently for studying biological repair of disc degeneration and biomechanics. Preparation of vIVDs: Bovine IVDs from the tails of 22–28-month-old steers were prepared for organ culture by parallel cuts through the adjacent vertebral bodies at 1cm from the endplates using an IsoMet®1000 Buehler precision sectioning saw. vIVDs were split into two groups: IVDs treated with PrimeGrowth Media kit (developed by Intervertech and licensed to Wisent Bioproducts) and IVDs with DMEM. The PrimeGrowth group was incubated for 1h in PrimeGrowth Isolation Medium (Cat# 319–511-EL) and the DMEM group for 1h in DMEM. After isolation, IVDs were washed in PrimeGrowth Neutralisation Medium (Cat# 319–512-CL) while the other IVDs were washed in DMEM. The discs isolated with PrimeGrowth and DMEM were cultured for up to 5 months in sterile vented 60 ml Leakbuster™ Specimen Containers in PrimeGrowth Culture Medium (Cat# 319–510-CL) and DMEM with no mechanical load applied. Live/Dead Assay: vIVDs cultured for 1 or 5 months were dissected and cell viability was assessed in different regions by confocal microscopy using Live/Dead® (Invitrogen) fluorescence assay. Glucose Diffusion: After one month of culture, vIVDs were incubated for 72h in diffusion medium containing PBS (1x), CaCl2 (1mM), MgCl2 (0.5mM), KCl2 (5mM), 0.1% BSA and 150µM 2-NDBG, a D-glucose fluorescent analogue. Discs were dissected and IVD tissues were incubated in guanidinium chloride extraction buffer. Extracts were measured for fluorescence. After 5 months in culture, vIVDs prepared with PrimeGrowth kit demonstrated approximately 95% cell viability in all regions of the disc. However, dramatic reductions (∼90%) in vIVD viability were measured in DMEM group after 1 month. vIVD viability was related to the amount of 2-NDBG incorporated into the disc tissue. We have developed a novel method for isolating IVDs with vertebral bone capable of long-term viability. This method may not only help in the discovery of novel therapeutics in disc regeneration, but could also advance our understanding on complex loading paradigms in disc degeneration

Background. Total elbow arthroplasty (TEA) has become an established procedure in the treatment of patients with rheumatoid arthritis (RA). However, there is little information on whether limited extension of the elbow affects clinical outcome scores after TEA and what causes the limited extension. Methods. We retrospectively analyzed fifty-four cases of primary TEA in patients with RA. There were seven men and thirty-nine women with a mean age of 63.6 years (range, thirty to eighty years). Thirty-seven of Coonrad-Morrey and seventeen of Discovery prostheses were used. The mean length of follow-up was 7.1 ± 4.0 years (range 2.0–14.6 years). Mayo Elbow Performing Score (MEPS) and radiological measurements were recorded. Anteroposterior and lateral radiographs were assessed before and after the operation and at the latest follow-up. Widening of the joint space was calculated by subtracting the length measured on the postoperative radiograph from that on the preoperative radiograph. Results. MEPS was significantly improved after surgery (51.2 to 91.1), especially in the domains of pain (18.6 to 43.1), stability (5.9 to 10) and daily function (10.7 to 21.0). Range of motion was significantly improved, in flexion (111.3° to 140.6°), pronation (62.1° to 72.3°), and supination (60.2° to 72.3°), but not in extension (30.0° to 28.8°). Simple and multivariate analyses showed that longer disease duration (p = 0.004), higher Larsen grade (p = 0.013), worse pronation/supination arc (p = 0.004) and worse postoperative extension (p = 0.033), but not postoperative flexion (p = 0.532), were significantly correlated with lower MEPS daily function. Conversely, simple and multivariate analyses showed that worse postoperative extension was correlated with lower MEPS daily function (p = 0.005) and worse preoperative extension (p < 0.001). Radiological analyses showed that, in the limited extension group (≧40°), the degree of extension was correlated with radiological widening of the joint. Conclusions. In linked TEA, perioperative widening of the elbow joint caused limited extension and worse daily function in patients with RA

The ability of mesenchymal stem cells (MSCs) to differentiate in vitro into chondrocytes, osteocytes and myocytes holds great promise for tissue engineering. Skeletal defects are emerging as key targets for treatment using MSCs due to the high responsiveness of bone to interventions in animal models. Interest in MSCs has further expanded in recognition of their ability to release growth factors and to adjust immune responses. Despite their increasing application in clinical trials, the origin and role of MSCs in the development, repair and regeneration of organs have remained unclear. Until recently, MSCs could only be isolated in a process that requires culture in a laboratory; these cells were being used for tissue engineering without understanding their native location and function. MSCs isolated in this indirect way have been used in clinical trials and remain the reference standard cellular substrate for musculoskeletal engineering. The therapeutic use of autologous MSCs is currently limited by the need for ex vivo expansion and by heterogeneity within MSC preparations. The recent discovery that the walls of blood vessels harbour native precursors of MSCs has led to their prospective identification and isolation. MSCs may therefore now be purified from dispensable tissues such as lipo-aspirate and returned for clinical use in sufficient quantity, negating the requirement for ex vivo expansion and a second surgical procedure. In this annotation we provide an update on the recent developments in the understanding of the identity of MSCs within tissues and outline how this may affect their use in orthopaedic surgery in the future. Cite this article: Bone Joint J 2014;96-B:291–8

Periprosthetic joint infection (PJI) is one the most devastating complications of joint arthroplasty. Although PJI is an infrequent complication (the reported incidence is 1%-2% in the United States), it is the most common indication for revision total knee arthroplasty in the Medicare population and the third most frequent indication for revision total hip arthroplasty. Moreover, the prevalence of PJI appears to be on the rise, with a projected number exceeding 60,000 to 70,000 cases in the United States by 2023. It is estimated that more than 25% of revision procedures annually are attributed to PJI and this number is expected to increase in the upcoming years. The increase in the prevalence of obesity, diabetes, and other comorbidities among the patient population and the emergence of resistant infecting organisms are some of the reasons for the expected rise in the number of infections that medical community will witness. The challenges that PJI presents to the orthopaedic community are on many fronts. Prevention of PJI has proven to be a difficult task indeed. Effective strategies for prevention of PJI are being refined. The Center for Disease Control will be publishing its updated Surgical Site Prevention Guidelines in the next few months that consists of specific recommendations for prevention of PJI. In recent years, strides are made in introducing novel molecular techniques for diagnosis of PJI, which may stand to change our practices. The current surgical technique for management of PJI, besides the immense cost, fall short of delivering high success to the patients. The major problem in eradication of infection relates to formation of biofilm, on the implant surface and internalization of the organisms by affected cells. Biofilm is a sophisticated structure comprising of organisms embedded in multiple layers of glycoccalyx that allows the organisms to evade host immunity and is impenetrable to antibiotics. These organisms are capable or communicating through molecular mechanisms such as quorum sensing that affords them advantage for survival in the host environment. In recent years strategies to prevent colonization of the implant surface, an essential first step in formation of biofilm, or biofilm disruption techniques have been introduced. A recent International Consensus meeting on PJI that assembled more than 350 experts identified some of the best practices in this field and identified areas in need of future research. Moving into the future, the field of orthopaedics in general and PJI in particular stand to benefit from the discoveries in the field of molecular diagnostics, metabolomics and epigenetics

In vivo oxidative degradation in ultra-high molecular weight polyethylene (UHMWPE) has gained significant attention in recent years, especially with the discovery of unanticipated oxidation in retrieved highly cross-linked bearings. While significant attention has been paid to mechanical property changes caused by oxidation, there has been little focus on understanding how wear rates are affected by these in vivo changes. Recent work has demonstrated the possibility of machining wear pins from retrieved UHMWPE bearings, but leveling of the pins removed the in vivo articular surface.[1] The goal of this study is to determine whether wear pins can be produced utilizing the native articular surface. Three materials were used for this study: a short-duration retrieved mobile-bearing conforming tibial insert with minimal oxidation (non-oxidized); a shelf-aged, oxidized, non-conforming fixed bearing tibial insert (oxidized); and standard NIST 1050 bar stock (NIST). Utilizing both conforming and non-conforming devices tests the technique over a range of articular curvatures, while testing a highly oxidized material tests the feasibility of maintaining the native surface when machining wear pins with compromised mechanical properties. FTIR analysis was performed at the articular surface of the devices near where the pins were taken, using ketone peak height as an indicator of oxidation. Wear rates were determined using a six station AMTI OrthoPod with an applied load of 100 N in multidirectional motion for a total of 2 million cycles. The oxidized material had a surface ketone level of 0.26, the non-oxidized device had a ketone level of 0.05, and the NIST sample had a ketone level less than 0.01. Two pins of each material were machined to ¼″ diameter with a length of the through thickness of the tibial inserts; soak controls were also produced. Figure 1 shows mass loss data for all six pins tested. Wear rates between the two pins of each group were fairly repeatable, and the wear rates of the different groups could be easily differentiated. The pins machined from NIST bar stock showed the best match-up, but pins machined from retrieved devices also showed good repeatability, with the non-conforming device showing better results than the conforming device. The ability to produce repeatable wear results with pins machined from in vivo devices is an important step in understanding how the wear rate changes over time in vivo. By maintaining the native articular surface, this test will give a more true representation of the in-vivo wear rate. This method will enable future investigations into how wear rates are affected by oxidation, absorbed chemical species, or other changes that occur in vivo

Reverse total shoulder arthroplasty was developed to address the treatment of patients with Cuff Tear Arthropathy. Despite of the clinical improvements seen with initial reverse shoulder replacements, several mechanical problems remain. Scapular notching has been reported between 24.5% and 96% of cases. Patients have also exhibited limited external rotation, either from impingement or slackening of remaining cuff musculature. Additionally, by medializing and moving the humerus distally, patients note a loss of the normal deltoid contour leading not only to cosmetic concerns, but possibly decreasing deltoid efficiency and creating a prosthesis with less inherent stability. Finally, although mechanical failure on the glenoid side initially was thought to be uncommon, various glenoid sided problems have been reported. Recognition of these problems led to clinical and basic science studies aimed at improving surgical technique and the design of reverse shoulder implants. During the last 10 years, our institution has been conducting biomechanical research examining the forces across the glenohumeral joint. Several different models have been created to replicate mechanical failures by integrating biomechanical information with our clinical investigations, including altering the position of the implant (tilt), the type of fixation of the implant (screw or peg), and glenoid-sided bone loss. We were able to address glenoid component failure (with initial rates of 10% in our clinical studies) by recommending locking screws to neutralize forces at the fixation site. These discoveries have reduced glenoid-sided fixation failures to less than 0.1%. In vitro kinematic function and factors that affect impingement free glenohumeral motion of reversed implants is another area of interest. The clinical relevance of impingement includes scapular-notching, pain from impingement, instability and excessive prosthetic wear. Several models that include motion in three different planes (flexion-extension, abduction-adduction and internal-external rotation) have been developed to study multiple prosthetic, technique and anatomic factors which can result from varying degrees of impingement. By integrating the results from these models into our clinical practice (e.g., selecting a more lateralized glenosphere, selecting a varus humeral component and inferiorly translating the glenoid component on the glenoid surface), we have been able to maintain low rates of notching (∼10% at 8 year follow-up). Finally, our current work involves development of a model that attempts to understand which factors might be influential in causing instability and stiffness. Thus, biomechanics research offers an excellent opportunity for interdisciplinary collaboration to solve complex clinical problems

The relevance of fluid-film lubrication, elasto-hydrodynamic lubrication and ‘tribolayers’ for hip bearings has been the subject of much debate (Fisher 2012). However, knowledge of the thickness and distribution of proteins in and around the wear zone of metal-on-polyethylene (MPE) bearings is scant. The efficacy of protein lubrication with metal-on-metal bearings (MOM) is in discovery. This simulator study was designed to analyze film formation on MOM bearings using varied protein concentrations. The hypotheses were that increasing protein concentrations in the serum lubricant would result in 1) greater thickness of protein films, and 2) reduced MOM wear. The hip simulator was run for 5 million cycles (5 Mc) duration using 28 mm MOM bearings (DJO Inc) run with the cups anatomical. Lubricant protein concentrations were 16.5, 33, and 66 mg/ml. At each test interval of 1 Mc, the proteins films on CoCr surfaces were analyzed by both interferometry and SEM imaging in main-wear, transition-wear and non-wear zones. Thickness of protein films was measured using non-contacting interferometry. Areas of wear zones were mapped and measured and the areas compared. MOM wear rates were assessed gravimetrically. It was found that the proteins formed two types of film (Figure 1). Type-1 was visually hazy in appearance, grainy in structure, and most commonly found in the main-wear zone. This type of protein film was always present in the main-wear zone but its thickness (approximately 0.05 μm) did not increase with increase in the lubricant protein concentrations. Type-2 was visually rainbow-like in appearance, more gel-like with thick clumps appearing as islands on the CoCr surfaces, and more common in the transition zone. This type of film was always present (approximately 1 μm thick) and its thickness notably increased in cups with increased lubricant protein concentrations. This film remained relatively consistent on femoral heads and did not change with increased protein concentrations (Figure 2). The type-1 protein films were always detectable in the actual wear zones but only the type-2 film showed a build-up with protein concentration and only inside the cups. This may be partially a response to the orbital simulator set up. In the Anatomical test mode, the cup is fixed with respect to the load axis and the head oscillates. Thus the main-wear zone on the head had a distributed type of wear patch and the main-wear zone in the cup was fixed. This configuration would allow the type-2 proteins to accumulate around the edge of the cup wear zone. In contrast, they would be scraped off the wear zone of the orbiting femoral head. This study showed that protein films endure even inside the main-wear zone of MOM bearings. In addition, collaborative studies have shown that the protein films are highly mobile and stream across the main-wear zones. Thus there is both an interaction with the CoCr surfaces and a degradation phenomenon that likely results in the protein-rich layers in the transition regions. Figure 1: SEM images of type 1 and type 2 protein films. Figure 2: Protein films on MOM bearings under three different protein concentrations

Anterior cervical discectomy and fusion for radiculopathy and myelopathy has the complication of the development of adjacent segment degeneration. Furthermore, reoperations may be required to treat complications of fusion, such as non-union, graft collapse, or expulsion. Cervical disc arthroplasty lays claim to preserving cervical motion and reducing the risks of adjacent segment disease in the treatment of cervical radiculopathy. We performed a prospective study in order to evaluate the radiological and clinical outcomes of cervical disc arthroplasty for single or two level disc disease with associated radiculopathy. Our study included a total of 26 patients. Each patient had cervical radiculopathy from nerve root compression due to degenerative disc disease at one or two levels. Diagnosis was made preoperatively on clinical examination and by means of MRI scanning. Each patient also had preoperative flexion and extension cervical spine x-rays in order to assess pre-operative range of neck movement. The outcomes of surgery were assessed prospectively. Range of motion at final follow-up was measured by flexion and extension view x-rays of the cervical spine. Clinical outcome was assessed by means of VAS scores for pain, SF12 for mental and physical health and the neck disability index (NDI). All complications were recorded. 14 of the patients had a follow-up for two years and the remaining 12 patients had a follow-up for one year. A Discovery disc arthoplasty by Scient'X was the implant used in all patients. A standard anterior cervical approach was used to achieve decompression and for the implantation of the prosthesis. On follow-up all patients had either maintenance or an improvement in the range of movement. There was no evidence of progression of degeneration in the segments adjacent to the arthroplasty prosthesis. Improvements in SF12, VAS, and NDI scores were seen from preoperative levels in 25 of the 26 patients. Complications included one patient with a horse voice post-operatively and one patient with minimal improvement of radicular symptoms. Post-operative MRI scanning demonstrated adequate decompression with this procedure and showed no evidence of progression of adjacent segment disease. There were no cases of implant subsidence or dislocations. We have found cervical disc arthroplasty to produce good clinical outcomes when used for single or two level cervical radiculopathy whilst maintaining neck motion with an acceptable complication rate. A longer follow-up is needed to further assess the risk of development of adjacent segment disease but we did not discover the development of adjacent segment disease in our study with a follow-up of upto 2 years

Aims

Elective orthopaedic services have had to adapt to significant system-wide pressures since the emergence of COVID-19 in December 2019. Length of stay is often recognized as a key marker of quality of care in patients undergoing arthroplasty. Expeditious discharge is key in establishing early rehabilitation and in reducing infection risk, both procedure-related and from COVID-19. The primary aim was to determine the effects of the COVID-19 pandemic length of stay following hip and knee arthroplasty at a high-volume, elective orthopaedic centre.

Aims

The new COVID-19 variant was reported by the authorities of the UK to the World Health Organization (WHO) on 14 December 2020. We aim to describe the clinical characteristics and nosocomial infection rates in major trauma and orthopaedic patients comparing the first and second wave of COVID-19 infection.

Aims

The purpose of our study was to determine which groups of orthopaedic providers favour virtual care, and analyze overall orthopaedic provider perceptions of virtual care. We hypothesize that providers with less clinical experience will favour virtual care, and that orthopaedic providers overall will show increased preference for virtual care during the COVID-19 pandemic and decreased preference during non-pandemic circumstances.