Introduction. Surgical spacesuits are in widespread use. Only one previous study (JBJS 1998) has assessed the quality of the environment within the space suit. They demonstrated that surgical spacesuits could allow re-breathing of carbon dioxide (CO. 2. ). However, they had no control group and performed a vigorous exercise protocol which may have been an unfair test. The design of helmet systems has also evolved in the last decade. We have conducted the first investigation into CO. 2. levels inside the modern space suit. There is a Workplace Exposure Limit for inspired CO. 2. as determined by the Health and Safety Executive (UK), which is 0.506kPa. We wondered whether re-breathing of CO. 2. in space suits would lead to inspired CO. 2. which breaches this level. Methods. We used an anaesthetic room gas analyzer via nasal cannulae to measure inspired (ICO. 2. ) levels in 12 healthy volunteers. Readings were taken while wearing a surgical space suit with the fan on high and low settings. These were compared with a normal surgical facemask. Readings were repeated on mild exertion to simulate the effort of performing arthroplasty surgery. Results. [Frequency of ICO2 >0.5kPa (12 subjects)]. Discussion. Despite the design modifications, modern space suits allow re-breathing of CO. 2. This is more marked with exertion and with low fan settings where ICO. 2. can exceed workplace limits. This may account for symptoms of headache and drowsiness reported after a prolonged period in the suit during arthroplasty surgery. We recommend the use of high fan settings at all times

We randomly allocated 50 total knee replacements to scrub teams wearing body-exhaust suits (BES) or Rotecno occlusive clothing. The effectiveness of the clothing was assessed using air and wound bacterial counts. Bacteria were recovered from 62% of wounds (64% BES, 60% Rotecno). The mean air count was 0.5 CFU/ m. 3. with BES and 1.0 CFU/m. 3. with Rotecno (p = 0.014). The mean wound counts were 14 bacteria/wound with BES and eight bacteria/wound with Rotecno (p = 0.171). There was no correlation between the air and wound counts (r = −0.011, Spearman’s). The higher air counts suggest that Rotecno occlusive clothing is less effective than BES, but wounds were equally contaminated with both types of clothing suggesting that at very low levels of air contamination the contribution of bacteria to the wound from the air is irrelevant. Even doubling the air counts from 0.5 to 1.0 CFU/m. 3. had no detectable effect on the wound. This allows a reassessment to be made of other sources of contamination the effect of which would previously have been overwhelmed by contamination from air

Knee arthroscopy is typically approached from the anterior, posteromedial and posterolateral portals. Access to the posterior compartments through these portals can cause iatrogenic cartilage damage and create difficulties in viewing the structures of the posterior compartments. The purpose of this study was to assess the feasibility of needle arthroscopy using direct posterior portals as both working and visualising portals. For workability, the needle scope was inserted advanced from anterior between the cruciate ligament bundle and the lateral wall of the medial femoral condyle until the posterior compartments were visualised. For visualisation, direct postero-lateral and -medial portals were established. The technique was performed in 9 knees by two experienced researchers. Workability and instrumentation of the posteromedial compartment and meniscus was achieved in 56%. The posterior horns could not be visualised in four specimens as the straight lens could not provide a more medial field of view. Visualisation from the direct medial posterior portal allowed a clear view of the medial meniscus, femoral condyle and posterior cruciate ligament in all specimens. Workability and instrumentation of the posterolateral compartment was not possible with the needle scope. Direct posterior approaches for the posteromedial compartment access are challenging with the current needle scope options and could only be achieved in over 50%. The postero-lateral compartment was not accessible. An angled lens or a flexible Needle scope would be better suited for developing this technique further

Introduction. Reducing infection in total joint replacement by using ultra clean air and protective enclosed suits (space suits) has become the standard in many operating theatres without good supporting evidence. This study examined the impact of laminar flow and space suits on the rate of revision for early infection following total hip (THR) and knee (TKR) replacement. Method. We used the 10-year results of the New Zealand Joint Registry to compare the rates of revision for early infection between laminar flow and conventional theatres both with and without the use of space suits. We separated hospitals and surgeons who had worked with and without space suits in both environments to exclude other confounding variables. Results. There were 51,485 THR and 36,826 TKR registered with laminar flow theatres used for 50% of the procedures and space suits used in 44% of cases. In THR there was a significant increase in revision for early infection in those procedures performed with the use of a space suit (p< 0.0001), for those performed in a laminar flow theatre (p< 0.003) and those procedures performed in a laminar flow theatre with a space suit (p< 0.001). The results were similar in TKR with the use of a space suit (p< 0.001), in laminar flow theatres (p< 0.019) and when laminar flow and space suits were used (p< 0.001). The results were unchanged when the surgeons and hospitals were analysed individually. Conclusion. The rate of revision for early infection has not been reduced by using laminar flow and space suits. The results of this study question the rationale for the increasing use and cost to the health system of these modalities in routine joint replacement

Aim. The coronavirus disease 2019 (COVID-19) pandemic presents significant challenges to healthcare systems globally. Orthopaedic surgeons are at risk of contracting COVID-19 due to their close contact with patients in both outpatient and theatre environments. The aim of this review was to perform a literature review, including articles of other coronaviruses, to formulate guidelines for orthopaedic healthcare staff. Methods. A search of Medline, EMBASE, the Cochrane Library, World Health Organization (WHO), and Centers for Disease Control and Prevention (CDC) databases was performed encompassing a variety of terms including ‘coronavirus’, ‘covid-19’, ‘orthopaedic’, ‘personal protective environment’ and ‘PPE’. Online database searches identified 354 articles. Articles were included if they studied any of the other coronaviruses or if the basic science could potentially applied to COVID-19 (i.e. use of an inactivated virus with a similar diameter to COVID-19). Two reviewers independently identified and screened articles based on the titles and abstracts. 274 were subsequently excluded, with 80 full-text articles retrieved and assessed for eligibility. Of these, 66 were excluded as they compared personal protection equipment to no personal protection equipment or referred to prevention measures in the context of bacterial infections. Results. There is a paucity of high quality evidence surrounding COVID-19. This review collates evidence from previous coronavirus outbreaks to put forward recommendations for orthopaedic surgeons during the COVID-19 pandemic. The key findings have been summarized and interpreted for application to the orthopaedic operative setting. Conclusion. For COVID-19 positive patients, minimum suggested PPE includes N95 respirator, goggles, face shield, gown, double gloves, and surgical balaclava. Space suits not advised. Be trained in the correct technique of donning and doffing PPE. Use negative pressure theatres if available. Minimize aerosolization and its effects (smoke evacuation and no pulse lavage). Minimize further unnecessary patient-staff contact (dissolvable sutures, clear dressings, split casts)

Using an institutional database we have identified over 1000 femoral revisions using extensively porous-coated stems. Using femoral re-revision for any reason as an endpoint, the survivorship is 99 ± 0.8% (95% confidence interval) at 2 years, 97 ± 1.3% at 5 years, 95.6 ± 1.8% at 10 years, and 94.5 ± 2.2% at 15 years. Similar to Moreland and Paprosky, we have identified pre-revision bone stock as a factor affecting femoral fixation. When the cortical damage involved bone more than 10cm below the lesser trochanter, the survivorship, using femoral re-revision for any reason or definite radiographic loosening as an endpoint, was reduced significantly, as compared with femoral revisions with less cortical damage. In addition to patients with Paprosky Type 3B and 4 femoral defects, there are rare patients with femoral canals smaller than 13.5mm or larger than 26mm that are not well suited to this technique. Eight and 10 inch stems 13.5 or smaller should be used with caution if there is no proximal bone support for fear of breaking. Patients with canals larger than 18mm may be better suited for a titanium tapered stem with flutes. While a monolithic stem is slightly more difficult for a surgeon to insert than a modular femoral stem there is little worry about taper junction failure

We maintain a database on 1000 femoral revisions using extensively porous-coated stems. Using femoral rerevision for any reason as an endpoint, the survivorship is 99 ± 0.8% (95% confidence interval) at 2 years, 97 ± 1.3% at 5 years, 95.6 ± 1.8% at 10 years, and 94.5 ± 2.2% at 15 years. Similar to Moreland and Paprosky, we have identified prerevision bone stock as a factor affecting femoral fixation. When the cortical damage involved bone more than 10 cm below the lesser trochanter, the survivorship, using femoral rerevision for any reason or definite radiographic loosening as an endpoint, was reduced significantly, as compared with femoral revisions with less cortical damage. In addition to patients with Paprosky type 3B and 4 femoral defects there are rare patients with femoral canals smaller than 13.5 mm or larger than 26 mm that are not well suited to this technique. Eight and 10 inch stems 13.5 mm or smaller should be used with caution if there is no proximal bone support for fear of breaking. Patients with canals larger than 18 mm may be better suited for a titanium tapered stem with flutes. While a monolithic stem is slightly more difficult for a surgeon to insert than a modular femoral stem there is little worry about taper junction failure

Using an institutional database we have identified over 1000 femoral revisions using extensively porous-coated stems. Using femoral re-revision for any reason as an endpoint, the survivorship is 99 ± 0.8% (95% confidence interval) at 2 years, 97 ± 1.3% at 5 years, 95.6 ± 1.8% at 10 years, and 94.5 ± 2.2% at 15 years. Similar to Moreland and Paprosky, we have identified pre-revision bone stock as a factor affecting femoral fixation. When the cortical damage involved bone more than 10 cm below the lesser trochanter, the survivorship, using femoral re-revision for any reason or definite radiographic loosening as an endpoint, was reduced significantly, as compared with femoral revisions with less cortical damage. In addition to patients with Paprosky type 3B and 4 femoral defects, there are rare patients with femoral canals smaller than 13.5 mm or larger than 26 mm that are not well suited to this technique. Eight and 10 inch stems 13.5 or smaller should be used with caution if there is no proximal bone support for fear of breaking. Patients with canals larger than 18 mm may be better suited for a titanium tapered stem with flutes. While a monolithic stem is slightly more difficult for a surgeon to insert than a modular femoral stem there is little worry about taper junction failure

I use monolithic, cylindrical, fully porous coated femoral components for many femoral revisions. Our institutional database holds information on 1000 femoral revisions using extensively porous-coated stems. To date, 27 stems have been re-revised (14 for loosening, 4 for infection, 7 for stem fracture, 2 at time of periprosthetic femoral fracture). Using femoral re-revision for any reason as an end point, the survivorship is 99 ± 0.8% (95% confidence interval) at 2 years, 97 ± 1.3% at 5 years, 95.6 ± 1.8% at 10 years, and 94.5 ± 2.2% at 15 years. Similar to Moreland and Paprosky, we have identified pre-revision bone stock as a factor affecting femoral fixation. Among the 777 femoral revisions graded for femoral bone loss, 59% of the femurs were graded as having no cortical damage before the revision, 29% had cortical damage extending no more than 10 cm below the lesser trochanter, and 12% had cortical damage that extended more than 10 cm below the lesser trochanter. When the cortical damage involved bone more than 10 cm below the lesser trochanter, the survivorship, using femoral re-revision for any reason or definite radiographic loosening as an end point, was reduced significantly, as compared with femoral revisions with less cortical damage. In addition to patients with Paprosky type 3B and 4 femoral defects there are rare patients with femoral canals smaller than 13.5 mm or larger than 26 mm that are not well suited to this technique. Eight and 10” stems 13.5 or smaller should be used with caution if there is no proximal bone support for fear of breaking. Patients with canals larger than 18 mm may be better suited for a titanium tapered stem with flutes. While a monolithic stem is slightly more difficult for a surgeon to insert than a modular femoral stem there is little worry about taper junction failure

I prefer monolithic, cylindrical, fully porous coated femoral components for most femoral revisions. Our institutional database holds information on 1000 femoral revisions using extensively porous-coated stems. To date, 27 stems have been rerevised (14 for loosening, 4 for infection, 7 for stem fracture, 2 at time of periprosthetic femoral fracture). Using femoral rerevision for any reason as an end point, the survivorship is 99 ± 0.8% (95% confidence interval) at 2 years, 97 ± 1.3% at 5 years, 95.6 ± 1.8% at 10 years, and 94.5 ± 2.2% at 15 years. Similar to Moreland and Paprosky, we have identified prerevision bone stock as a factor affecting femoral fixation. Among the 777 femoral revisions graded for femoral bone loss, 59% of the femurs were graded as having no cortical damage before the revision, 29% had cortical damage extending no more than 10cm below the lesser trochanter, and 12% had cortical damage that extended more than 10cm below the lesser trochanter. When the cortical damage involved bone more than 10cm below the lesser trochanter, the survivorship, using femoral rerevision for any reason or definite radiographic loosening as an end point, was reduced significantly, as compared with femoral revisions with less cortical damage. In addition to patients with Paprosky type 3B and 4 femoral defects there are rare patients with femoral canals smaller than 13.5mm or larger than 26mm that are not well suited to this technique. Eight and 10-inch stems 13.5 or smaller should be used with caution if there is no proximal bone support for fear of breaking. Patients with canals larger than 18mm may be better suited for a titanium tapered stem with flutes. While a monolithic stem is slightly more difficult for a surgeon to insert than a modular femoral stem there is little worry about taper junction failure

Introduction. A total knee arthroplasty (TKA) is the standard of care treatment for end-stage osteoarthritis (OA) of the knee. Over the last decade, we have observed a change in TKA patient population to include younger patients. This cohort tends to be more active and thus places more stress on the implanted prothesis. Bone cement has historically been used to establish fixation between the implant and host bone, resulting in two interfaces where loosening may occur. Uncemented fixation methods provide a promising alternative to cemented fixation. While vulnerable during the early post-operative period, cementless implants may be better suited to long-term stability in younger patient cohorts. It is currently unknown whether the surgical technique used to implant the cementless prostheses impacts the longevity of the implant. Two different surgical techniques are commonly used by surgeons and may result in different load distribution across the joint, which will affect bone ingrowth. The overall objective of the study is to assess implant migration and in vivo kinematics following cementless TKA. Methods. Thirty-nine patients undergoing a primary unilateral TKA as a result of OA were recruited prior to surgery and randomized to a surgical technique based on surgeon referral. In the gap balancing surgical technique (GB) soft tissues releases are made to restore neutral limb alignment followed by bone cuts (resection) to balance the joint space in flexion and extension. In the measured resection surgical technique (MR) bone cuts are first made based on anatomical landmarks and soft tissue releases are subsequently conducted with implant components in-situ. Patients returned 2 weeks, 6 weeks, 12 weeks, 24 weeks, and 52 weeks following surgery for radiographic evaluation. Kinematics were assessed 52 weeks post-operatively. Results. No significant difference was observed between groups in maximum total point motion (MTPM) at any time point during the first post-operative year. MTPM of both the tibial and femoral component did not significantly change between the six month and one year follow up visits for both the GB (6 mths=0.67 ±0.34mm, 1 yr=0.65 ±0.52, p=0.71) and MR (6 mths= 0.79 ±0.53mm, 1 yr= 0.82 ±0.43mm, p=0.56) cohorts. MTPM for both components over the follow up period is displayed in Figure 1. No significant difference was observed in contact location or pattern on the medial condyle during deep flexion (Figure 2A). A significant difference (p=0.01) was observed, however, between surgical techniques in the lateral contact location at full extension (Figure 2B). No significant difference was observed in the magnitude of AP excursion for both the medial and lateral condyles within and between groups. Conclusion. Surgical technique did not impact the MTPM of an uncemented TKA design during the first post-operative year. By the six month post-operative period tibial and femoral MTPM plateaus indicating that osseointegration between the host bone and implanted components has occurred. Kinematic evaluation indicates contact locations anterior to the midline of the sagittal plane, paradoxical anterior translation, and a lateral pivot point, regardless of surgical technique

There is limited evidence in the literature suggesting that ceramic-on-ceramic (CoC) THA is associated with lower risk of revision for prosthetic joint infection (PJI) than other bearing combinations especially metal-on-polyethylene (MoP) and metal-on-metal (MoM). Pitto and Sedel reported hazard ratios of 1.3 – 2.1 for other bearing surfaces vs. CoC. Of interest, the PJI rate was not significantly lower in the first 6 months, when most infections occur, but only became significant in the long term. While factors such as patient age, fixation, mode, O.R. type, use of body exhaust suits, and surgeon volume were considered in the multivariate analysis, BMI, medical comorbidities, and ASA class were not. This is a major weakness that casts doubt on the conclusion, since those three factors are MAJOR risk factors for PJI AND all three factors are more likely to be unevenly distributed, much more likely present in groups other than CoC. The data was also limited by the fact that it was drawn from a retrospective review of National Registry data, The New Zealand Joint Registry. While similar findings have recently been reported from the Australian Joint Registry, the danger in attributing differences in outcomes to implants alone is possibly the single greatest danger in interpreting registry results. While device design can impact implant survival, other factors such as surgical technique, surgeon, hospital, and especially patient factors have a far greater likelihood of explaining differences in observed results. A recent report from the same New Zealand joint registry reported that obesity, ASA class, surgical approach, and trainee operations all were associated with higher PJI and all would be more likely in non-CoC THAs. Accuracy of diagnosis is also a major concern. Revision for trunnionosis is more common in non-CoC THA and is frequently misdiagnosed as PJI. Numerous non-registry studies and reviews have compared PJI in CoC vs. other bearing and none have concluded than the incidence of PJI differed significantly

I prefer monolithic, cylindrical, fully porous coated femoral components for most femoral revisions. Our institutional database holds information on 1000 femoral revisions using extensively porous-coated stems. To date, 27 stems have been rerevised (14 for loosening, 4 for infection, 7 for stem fracture, 2 at time of periprosthetic femoral fracture). Using femoral rerevision for any reason as an end point, the survivorship is 99 ± 0.8% (95% confidence interval) at 2 years, 97 ± 1.3% at 5 years, 95.6 ± 1.8% at 10 years, and 94.5 ± 2.2% at 15 years. Similar to Moreland and Paprosky, we have identified prerevision bone stock as a factor affecting femoral fixation. Among the 777 femoral revisions graded for femoral bone loss, 59% of the femurs were graded as having no cortical damage before the revision, 29% had cortical damage extending no more than 10 cm below the lesser trochanter, and 12% had cortical damage that extended more than 10 cm below the lesser trochanter. When the cortical damage involved bone more than 10 cm below the lesser trochanter, the survivorship, using femoral rerevision for any reason or definite radiographic loosening as an end point, was reduced significantly, as compared with femoral revisions with less cortical damage. In addition to patients with Paprosky type 3B and 4 femoral defects there are rare patients with femoral canals smaller than 13.5 mm or larger than 26 mm that are not well suited to this technique. Eight and 10” stems 13.5 or smaller should be used with caution if there is no proximal bone support for fear of breaking. Patients with canals larger than 18 mm may be better suited for a titanium tapered stem with flutes. While a monolithic stem is slightly more difficult for a surgeon to insert than a modular femoral stem there is little worry about taper junction failure

Introduction. Problematic bone defects are encountered regularly in orthopaedic practice particularly in fracture non-union, revision hip and knee arthroplasty, following bone tumour excision and in spinal fusion surgery. At present the optimal source of graft to ‘fill’ these defects is autologous bone but this has significant drawbacks including harvest site morbidity and limited quantities. Bone marrow has been proposed as the main source of osteogenic stem cells for the tissue-engineered cell therapy approach to bone defect management. Such cells constitute a minute proportion of the total marrow cell population and their isolation and expansion is a time consuming and expensive strategy. In this study we investigated human bone marrow stem cells as a potential treatment of bone defect by looking at variability in patient osteogenic cell populations as a function of patient differences. We produced a model to predict which patients would be more suited to cell based therapies and propose possible methods for improving the quality of grafts. Methods. Bone marrow was harvested from 30 patients undergoing elective total hip replacement surgery in Musgrave Park Hospital, Belfast (12 males, 18 females, age range 52-82 years). The osteogenic stem cell fraction was cultured and subsequently analysed using colony forming efficiency assays, flow cytometry, fluorescence activated cell sorting and proteomics. Results. The number and proliferative capacity of osteogenic stem cells varied markedly between patients. Statistical analysis revealed significantly better osteogenic capacity in:. male patients. samples in which the growth hormone Fibroblastic Growth Factor-2 was added to culture medium. patients who used the cholesterol lowering agent simvastatin. Patient use of inhaled steroids and NSAIDs were found to have detrimental effects. A statistical model to predict marrow profiles based on these variables was produced. Conclusions. Stem cell based tissue engineering represents the future of the treatment of bone defect. This study provides evidence that inter-patient variability in marrow cell colony forming and proliferation ability can in some way be explained by patient associated factors. Using this knowledge, we can identify which patients would be best suited to this method of treatment and propose techniques for enhancement of their graft profiles

Tibial plateau fractures classically present in a bimodal distribution associated with high energy mechanisms in the younger population and fragility fractures in the elderly populations as a result they are well suited for looking at the effect major trauma centre status. Military trauma surgeons in training should be exposed to as much young high-energy trauma as possible to equip them for operations. Retrospective review of all tibial plateaus presenting to RVI 20 months before MTC status and 20 months following this. 61 patients pre, 66 post. Schatzker grade 1–4 were similar pre and post change. Post change there was an increase in Schatzker 5 (62%) and 6 (27%). High energy injuries were most common in younger males, cause was falls followed by RTAs. MTC status has meant an increase in high energy tibial plateaus (Schatzker 5–6) These were predominantly seen in younger males with high-energy mechanisms. As this is likely to be replicated across all injuries, we would recommend military trauma surgeons have a significant period of time training in major trauma centres to ensure adequate exposure to young high energy trauma

Aseptic loosening is the most common cause of failure in load bearing orthopaedic implants. This is most often attributed to stress shielding, which is caused by a mismatch in mechanical properties between the implant and bone, predominantly stiffness. The implant causes a redistribution of the forces through the bone leading to localised tissue resorption in low stress areas and over time loosening of the implant. To address this, the implant design may be modified to introduce porous structures that reduced overall stiffness. Conventional methods of creating porous structures include the space holder method and gas foaming, although these allow control of the pore size and volume fraction, the position of the voids is random and potentially non-uniform, creating unpredictable mechanical properties. Using additive manufacture predictable porous lattice structures can be built. Two methods for creating lattice structure are explored here: controlled stochastic lattices, and layers of repeating unit cells. Due to the predictable nature of these design methods the mechanical properties can be tailored to suit the needs of the implants. In addition to mechanical optimisation the porous lattice structures can be optimised for osseointegration properties. The ability of the tissue to grow into the implant are affected by; the size of the pores, how interconnected the pores are, the overall void fraction (porosity), the shape and roughness of the pores, and whether the structure is coated. Although additive manufacture allows great design freedoms, there are also some manufacturing constraints to consider including resolution which is determined by powder and laser spot size, and strut angle since these cannot be too close to horizontal or they will collapse during the build unless supported. This preliminary work uses Finite Element Analysis to model the compressive properties of lattice structures with different design parameters, with the intention to optimise for mechanical, osseointegration and manufacturability properties. Cylinders of the lattice structures were generated in Simpleware ScanIP (Synopsys, Exeter, UK) and their compression was modelled in Ansys Workbench 18.2 (Canonsburg, PA, USA) in accordance with ISO 13314. Stress distributions for each lattice structure were produced which showed the stochastic lattice did not undergo banded deformation unlike the repeating unit cell based lattices. Future work will physically test the lattices and feed that data back into the model for further optimisation. Other relevant mechanical testing will be modelled and performed in order to choose the optimal lattice design for future implants

Total hip arthroplasty (THA) is effective, reproducible, and durable in the treatment of hip joint arthritis. While improvements in polyethylene materials have significantly reduced wear rates and osteolysis, aseptic loosening of implants remains one of the leading causes of revision THA. Additionally, fears of dislocation and instability have driven the increase in the utilization of larger diameter femoral heads in primary THA which can lead to increased wear when coupled with a polyethylene articulation. Finally, the increasing number of younger and active patients undergoing THA raises questions with regards to the ability of modern conventional bearings to provide durability and longevity beyond second and third decades following joint implantation. Ceramic-on-ceramic articulations are ideally suited for today's young and high demand patients undergoing primary THA. It has the lowest in-vitro wear properties of any bearing couple and the wear characteristics are further improved by its wettability and lubrication particularly when larger heads are utilised. Additionally, improvements in material properties and prosthesis design have significantly decreased fracture rates and increased the reliability of these implants. Furthermore, reported outcomes and longevity of modern ceramic-on-ceramic THAs in younger patients have all shown excellent survivorship despite patients achieving and maintaining a very high level of activity and function. In short, it is the bearing couple most in tune with current market demands and utilization trends. While registry data and meta-analyses of published literature have failed to show the superiority of ceramic-on-ceramic articulations compared to conventional bearings at 10 years, there is evidence that even highly crosslinked polyethylene (HXPE) is not immune to wear. Selvarajah et al. reported steady, in-vivo wear rates of HXPE exceeding 0.1mm/year threshold in young THA patients with 36mm ceramic ball heads. Additionally, small osteolytic lesions have been observed in hips with HXPE bearings at 12–14 years follow up. Finally, analysis of all controlled randomised studies have shown less osteolysis of ceramic-on-ceramic hips compared to polyethylene articulations. The significance of these lesions are unclear but the question remains: Can HXPE as a bearing be able to provide over 30 years of service needed to outlast patients younger than 60 years?. Concerns with cost, squeaking, and fractures do not make ceramic-on-ceramic bearings suitable for all patients undergoing primary THA. However, in young, healthy and active patients, a modern ceramic- on-ceramic articulation is most likely to provide the lowest wear rates, lowest risk of osteolysis, and greatest chance for life-long durability

INTRODUCTION. There is great potential for the use of computational tools within the design and test cycle for joint replacement devices. The increasing need for stratified treatments that are more relevant to specific patients, and implant testing under more realistic, less idealised, conditions, will progressively increase the pre-clinical experimental testing work load. If the outcomes of experimental tests can be predicted using low cost computational tools, then these tools can be embedded early in the design cycle, e.g. benchmarking various design concepts, optimising component geometrical features and virtually predicting factors affecting the implant performance. Rapid, predictive tools could also allow population-stratified scenario testing at an early design stage, resulting in devices which are better suited to a patient-specific approach to treatment. The aim of the current study was to demonstrate the ability of a rapid computational analysis tool to predict the behaviour of a total hip replacement (THR) device, specifically the risk of edge loading due to separation under experimental conditions. METHODS. A series of models of a 36mm BIOLOX. ®. Delta THR bearing (DePuy Synthes, Leeds, UK) were generated to match an experimental simulator study which included a mediolateral spring to cause lateral head separation due to a simulated mediolateral component misalignment of 4mm. A static, rigid, frictionless model was implemented in Python (PyEL, runtime: ∼1m), and results were compared against 1) a critically damped dynamic, rigid, FE model (runtime: ∼10h), 2) a critically damped dynamic, rigid, FE model with friction (µ = 0.05) (runtime: ∼10h), and 3) kinematic experimental test data from a hip simulator (ProSim EM13) under matching settings (runtime: ∼6h). Outputs recorded were the variation of mediolateral separation and force with time. RESULTS/DISCUSSION. The low cost PyEL model successfully replicated experimental trends in maximum separation with changing swing phase load. PyEL provided a good estimate of the high separation values which resulted from lower swing phase loads, but overestimated the separation resulting from higher swing phase loads. The separation verses time curve of the dynamic rigid FE (with and without friction) closely matched that of the PyEL model. Inertia caused a small delay when moving into and out of the cup (peak delay ∼0.025s). Therefore there was no substantial advantage to the more costly dynamic finite element models as a predictive design tool for hard-on-hard bearings

There is limited evidence in the literature suggesting that ceramic-on-ceramic (CoC) THA is associated with lower risk of revision for prosthetic joint infection (PJI) than other bearing combinations especially metal-on-poly (MoP) and metal-on-metal (MoM). Pitto and Sedel reported hazard ratios of 1.3 – 2.1 for other bearing surfaces versus CoC. Of interest, the PJI rate was not significantly lower in the first 6 months, when most infections occur, but only became significant in the long term. While factors such as patient age, fixation, mode, OR type, use of body exhaust suits, and surgeon volume were considered in the multivariate analysis, BMI, medical comorbidities, and ASA class were not. This is a major weakness that casts doubt on the conclusion, since those three factors are MAJOR risk factors for PJI AND all three factors are more likely to be unevenly distributed, and much more likely present in groups other than CoC. The data was also limited by the fact that it was drawn from a retrospective review of National Registry data, The New Zealand Joint Registry. While similar findings have recently been reported from the Australian Joint Registry, the danger in attributing differences in outcomes to implants alone is possibly the single greatest danger in interpreting registry results. While device design can impact implant survival, other factors such as surgical technique, surgeon, hospital, and especially patient factors have a far greater likelihood of explaining differences in observed results. A recent report from the same New Zealand joint registry reported that obesity, ASA class, surgical approach, and trainee operations all were associated with higher PJI and all would be more likely in non-CoC THAs. Accuracy of diagnosis is also a major concern. Revision for trunnionosis is more common in non-CoC THA and is frequently misdiagnosed as PJI. Numerous non-registry studies and reviews have compared PJI in CoC vs. other bearings and none have concluded than the incidence of PJI differed significantly

Aims

The use of fluoroscopy in orthopaedic surgery creates risk of radiation exposure to surgeons. Appropriate personal protective equipment (PPE) can help mitigate this. The primary aim of this study was to assess if current radiation protection in orthopaedic trauma is safe. The secondary aims were to describe normative data of radiation exposure during common orthopaedic procedures, evaluate ways to improve any deficits in protection, and validate the use of electronic personal dosimeters (EPDs) in assessing radiation dose in orthopaedic surgery.