Abstract. Objectives. Obesity is prevalent with nearly one third of the world's population being classified as obese. Total knee arthroplasty (TKA) is an effective treatment option for high BMI patients achieving similar outcomes to non-obese patients. However, increased rates of aseptic loosening in patients with a high BMI have been reported. In patients with high BMI/body mass there is an increase in strain placed on the implant fixation interfaces. As such component fixation is a potential concern when performing TKA in the obese patient. To address this concern the use of extended tibial stems in cemented implants or cementless fixation have been advocated. Extend tibial stems are thought to improve implant stability reducing the micromotion between interfaces and consequently the risk of aseptic loosening. Cementless implants, once biologic fixation is achieved, effectively integrate into bone eliminating an interface. This retrospective study compared the use of extended tibial stems and cementless implants to conventional cemented implants in high BMI patients. Methods. From a prospectively maintained database of 3239 primary Attune TKA (Depuy, Warsaw, Indiana), obese patients (body mass index (BMI) >30 kg/m²) were retrospectively reviewed. Two groups of patients 1) using a tibial stem extension [n=162] and 2) cementless fixation [n=163] were compared to 3) a control group (n=1426) with a standard tibial stem cemented implant. All operations were performed by or under the direct supervision of specialist arthroplasty surgeons. Analysis compared the groups with respect to class I, II, and III (BMI >30kg/m², >35 kg/m², >40 kg/m²) obesity. The primary outcome measures were all-cause revision, revision for aseptic loosening, and revision for tibial loosening. Kaplan-Meier survival analysis and Cox regression models were used to compare the primary outcomes between groups. Where radiographic images at greater than 3 months post-operatively were available, radiographs were examined to compare the presence of peri-implant radiolucent lines. Results. The mean follow-up of 4.8, 3.4, and 2.5 years for cemented, stemmed, and cementless groups respectively. In total there were 34 all-cause revisions across all the groups with revision rates of 4.55, 5.50, and 0.00 per 1000-implant-years for cemented, stemmed, and cementless groups respectively. Survival Analysis did not show any significant differences between the three groups for all-all cause revision. There were 6 revisions for aseptic loosening (5 tibial and 1 femoral); all of which were in the standard cemented implant group. In contrast there were no revisions in the stemmed or cementless implant groups, however, this was not significant on survival analysis. Analysis looking at class I, II, and III obesity also did not show any significant differences in survival for all cause revision or aseptic loosening. Conclusion. This retrospective analysis showed that there were no revisions required for aseptic loosening when either a cemented stemmed or cementless implant were used in obese patients. These findings are in line with other studies showing that cementless fixation or extended stem implants are a reasonable option in obese patients who represent an increasing cohort of patients requiring TKR. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Intraoperative fractures although rare are one of the complications known to occur while performing a total hip arthroplasty (THA). However, due to lower incidence rates there is currently a gap in this area of literature that systematically reviews this important issue of complications associated with THA. Method: We looked into Electronic databases including PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), the archives of meetings of orthopaedic associations and the bibliographies of included articles and asked experts to identify prospective studies, published in any language that evaluated intra-operative fractures occurring during total hip arthroplasty from the year 1950-2020. The screening, data extraction and quality assessment were carried out by two researchers and if there was any discrepancy, a third reviewer was involved. Fourteen studies were identified. The reported range of occurrence of fracture while performing hip replacement surgery was found to be 0.4-7.6%. Major risk factors identified were surgical approaches, Elderly age, less Metaphyseal-Diaphyseal Index score, change in resistance while insertion of the femur implants, inexperienced surgeons, uncemented femoral components, use of monoblock elliptical components, implantation of the acetabular components, patients with ankylosing spondylitis, female gender, uncemented stems in patients with abnormal proximal femoral anatomy and with cortices, different stem designs, heterogeneous fracture patterns and toothed design. Intraoperative fractures during THA were managed with cerclage wire, femoral revision, intramedullary nail and cerclage wires, use of internal fixation plates and screws for management of intra operative femur and acetabular fractures. The main reason for intraoperative fracture was found to be usage of cementless implants but planning and timely recognition of risk factors and evaluating them is important in management of intraoperative fractures. Adequate surgical site exposure is critical especially during dislocation of hip, reaming of acetabulum, impaction of implant and preparing the femoral canal for stem insertion. Eccentric and increased reaming of acetabulum to accommodate a larger cup is to be avoided, especially in females and elderly patients as the acetabulum is thinner. However, this area requires more research in order to obtain more evidence on effectiveness, safety and management of intraoperative fractures during THA

The success of cementless orthopaedic implants relies on bony ingrowth and active bone remodelling. Much research effort is invested to develop implants with controllable surface roughness and internal porous architectures that encourage these biological processes. Evaluation of these implants requires long-term and costly animal studies, which do not always yield the desired outcome requiring iteration. The aim of our study is to develop a cost-effective method to prescreen design parameters prior to animal trials to streamline implant development and reduce live animal testing burden. Ex vivo porcine cancellous bone cylinders (n=6, Ø20×12mm) were extracted from porcine knee joints with a computer-numerically-controlled milling machine under sterile conditions within 4 hours of animal sacrifice. The bone discs were implanted with Ø6×12mm additive manufactured porous titanium implants and were then cultured for 21days. Half underwent static culture in medium (DMEM, 10% FBS, 1% antibiotics) at 37°C and 5% CO. 2. The rest were cultured in novel high-throughput stacked configuration in a bioreactor that simulated physiological conditions after surgery: the fluid flow and cyclic compression force were set at 10ml/min and 10–150 N (1Hz,5000 cycles/day) respectively. Stains were administered at days 7 and 14. Samples were evaluated with widefield microscopy, scanning electron microscopy (SEM) and with histology. More bone remodelling was observed on the samples cultured within the bioreactor: widefield imaging showed more remodelling at the boundaries between the implant-bone interface, while SEM revealed immature bone tissue integration within the pores of the implant. Histological analysis confirmed these results, with many more trabecular struts with new osteoid formation on the samples cultured dynamically compared to static ones. Ex vivo bone can be used to analyse new implant technologies with lower cost and ethical impact than animal trial. Physiological conditions (load and fluid flow) promoted bone ingrowth and remodelling

Abstract. Introduction. The long-term biological success of cementless orthopaedic prostheses is highly dependent on osteointegration. Pre-clinical testing of new cementless implant technology however, requires live animal testing, which has anatomical, loading, ethical and cost challenges. This proof-of-concept study aimed to develop an in vitro model to examine implant osteointegration under known loading/micromotion conditions. Methods. Fresh cancellous bone cylinders (n=8) were harvested from porcine femur and implanted with additive manufactured porous titanium implants (Ø4 × 15 mm). To simulate physiological conditions, n=3 bone cylinders were tested in a bioreactor system with a cyclic 30 µm displacement at 1Hz for 300 cycles every day for 15 days in a total of 21 days culture. The chamber was also perfused with culture medium using a peristaltic pump. Control bone cylinders were cultured under static conditions (n=5). Samples were calcein stained at day 7. Post-testing, bone cylinders were formalin fixed and bony ingrowth was measured via microscopy. Results. Viability of the freshly harvested ex vivo bone cylinders was maintained for up to 28 days. Two samples remain unanalysed due to COVID lockdown, one in each group. Similar to osteointegration seen in live animal models, evidence of bony ingrowth was seen more markedly at the bone-implant interface under dynamic conditions. This was evident by a greater intensity of calcein staining, confirming the deposition of new bone, at the bone-implant interface. In comparison, under static conditions, calcein staining was observed randomly all over the cylinder. Conclusion. This proof-of-concept study demonstrates that implant bony adaptation and ingrowth can be measured in vitro under known cyclic micromotion/loading conditions. This comparatively low cost, low ethical impact, controlled loading laboratory method has potential to accelerate the rate of implant development whilst conforming with the principles of NC3Rs. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Infection remains among the first reasons for failure of joint prosthesis. Currently, the golden standard for treating prosthetic joint infections (PJIs) is two-stage revision. However, two-stage procedures have been reported to be associated with higher costs and possible higher morbidity and mortality, compared to one-stage. Furthermore, recent studies showed the ability of a fast-resorbable, antibacterial-loaded hydrogel coating to reduce surgical site infections after joint replacement, by preventing bacterial colonization of implants. Aim of this study was then to compare the infection recurrence rate after a one-stage, cemenless exchange, performed with an antibacterial coated implant versus a standardized two-stage revision procedure. In this two-center prospective study, 22 patients, candidate to revision surgery for PJI, were enrolled to undergo a one-stage revision surgery with cementless implants, coated intra-operatively with a fast-resorbable, antibiotic-loaded hyaluronan and poly-D,L-lactide based hydrogel coating (“Defensive Antibacterial Coating”, DAC, Novagenit, Italy). DAC was reconstructed according to manufacturer indications and loaded with Vancomycin or Vancomycin + Meropenem, according to cultural examinations, and directly spread onto the implant before insertion. This prospective cohort was compared with a retrospective series of 22 consecutive patients, matched for age, sex, host type, site of surgery, that underwent a two stage procedure, using a preformed, antibiotic-loaded spacer (Tecres, Italy) and a cementless implant. The second surgery, for definitive implant placing, was performed only after CRP normalization and no clinical sign of infection. Clinical, laboratory and radiographic evaluation were performed at 3, 6 and 12 months, and every 6 months thereafter. Infection recurrence was defined by the presence of a sinus tract communicating with the joint, or at least two among the following criteria: clinical signs of infections; elevated CRP and ESR; elevated synovial fluid WBC count; elevated synovial fluid leukocyte esterase; a positive cultural examination from synovial fluid; radiographic signs of stem loosening. The two groups did not differ significantly for age, sex, host type and site of surgery (18 knees and 4 hips, respectively). The DAC hydrogel was loaded intra-operatively, according to cultural examination, with vancomycin (14 patients) or vancomycin and meropenem (8 cases). At a mean follow-up of 20.2 ± 6.3 months, 2 patients (9.1%) in the DAC group showed an infection recurrence, compared to 3 patients (13.6%) in the two-stage group. No adverse events associated with the use of DAC or radiographic loosening of the stem were observed at the latest follow-up months. This is the first report on one-stage cementless revision surgery for PJI, performed with a fast-resorbable antibacterial hydrogel coating. Our data, although in a limited series of patients and at a relatively short follow-up, show similar infection recurrence rate after one-stage exchange with cementless, coated implants, compared to two-stage revision. These findings warrant further studies in the possible applications of antibacterial coating technologies to treat implant-related infections

Summary. The 80% porous structure of trabecular metal allows for bone ingrowth in more than 90% of the available surface. The Nexgen LPS Uncemented Knee using a trabecular metal tibial component has performed well at minimum of 5 years’ follow-up. Introduction. Total Knee Arthroplasty prostheses most frequently used in today's practice have cemented components. These have shown excellent clinical results. The fixation can however weaken with time, and cement debris within the articulation can lead to accelerated wear. Cementless implants are less commonly used, but some have also shown good long-term clinical results. The potential advantages of cementless implants are retention of bone stock, less chance of third-body wear due to the absence of cement, shorter operative time, and easier treatment of periprosthetic fractures. The posterior stabilised knee replacement has been said to increase tangential shear stresses on the tibial component and increases contact stresses on the cam and post mechanism hence the great debate of cruciate retaining or cruciate sacrificing implants. Objectives. We report the results of a prospective cohort of consecutive primary total knee arthroplasties using an uncemented posterior stabilised prosthesis using a trabecular metal (tantalum) tibial component at a minimum 5-year follow-up. Methods. Prospective 5 year follow-up of patients undergone an uncemented posterior stabilised total knee replacement using a trabecular metal tibial component (NexgenLPS). Clinical examination, Oxford knee score, Knee society score, SF12 and radiological evaluation undertaken at review. Results. 81 patients, 45 female, 36 male. Left 31, Right 50. Mean age 74.3 yrs range (51–90). SF12, mean: 31.8 range (25–37). Oxford Knee Score Pre-op Mean 20.1 range (9–36) Post op: Mean 32.1 range (9–48). Knee Society score. Pain Mean 91.8; range (60–100). Functional score mean 76.2; range (30–100). Mean Range of movement 110.5 degrees range (90–125). No evidence of loosening at 5 yrs. No deep infection. No Revisions. Conclusion. Although there are a variety of methods of achieving satisfactory initial fixation in cementless components, trabecular metal has an advantage owing to its cellular structure resembling bone. The 80% porous structure of trabecular metal allows for bone ingrowth in more than 90% of the available surface. The Nexgen LPS Uncemented Knee using a trabecular metal tibial component used in this series has shown no evidence of loosening at a minimum of 5 years’ follow-up and the prosthesis as a whole has performed very well clinically. Its early results are comparable to those prostheses most commonly used as reported by the arthroplasty registers. The longer term results from this prosthesis are awaited with interest

The reduced stability of hydroxyapatite (HA)-coated implants in osteopenic conditions is considered to be a major problem. We therefore developed a model of a boosted cementless implantation in osteopenic rats. Twelve-week-old rats were either ovariectomised (OVX) or sham-operated (SO), and after 24 weeks plain or HA-coated implants were inserted. They were treated with either a prostaglandin EP4 receptor agonist (ONO-4819) or saline for one month. The EP4 agonist considerably improved the osteoporosis in the OVX group. Ultrastructural analysis and mechanical testing showed an improvement in the implant-bone attachment in the HA-coated implants, which was further enhanced by the EP4 agonist. Although the stability of the HA-coated implants in the saline-treated OVX rats was less than in the SO normal rats, the administration of the EP4 agonist significantly compensated for this shortage. Our results showed that the osteogenic effect of the EP4 agonist augmented the osteoconductivity of HA and significantly improved the stability of the implant-bone attachment in the osteoporotic rat model

The tissues surrounding 65 cemented and 36 cementless total joint replacements undergoing revision were characterised for cell types by immunohistochemistry and for cytokine expression by in situ hybridisation. We identified three distinct groups of revised implants: loose implants with ballooning radiological osteolysis, loose implants without osteolysis, and well-fixed implants. In the cemented series, osteolysis was associated with increased numbers of macrophages (p = 0.0006), T-lymphocyte subgroups (p = 0.03) and IL-1 (p = 0.02) and IL-6 (p = 0.0001) expression, and in the cementless series with increased numbers of T-lymphocyte subgroups (p = 0.005) and increased TNFα expression (p = 0.04). For cemented implants, the histological, histochemical and cytokine profiles of the interface correlated with the clinical and radiological grade of loosening and osteolysis. Our findings suggest that there are different biological mechanisms of loosening and osteolysis for cemented and cementless implants. T-lymphocyte modulation of macrophage function may be an important interaction at prosthetic interfaces

Summary Statement. The current biomecahnical study demonstrated that the stemless peripheral leg humeral component prototype and central screw humeral component prototype achieved similar initial fixation as stemmed Global Advantage humeral component in terms of resultant micromotion in total shoulder arthroplasty. Introduction. A stemless humeral component may offer a variety of advantages over its stemmed counterpart, e.g. easier implantation, preservation of humeral bone stock, fewer humeral complications, etc. However, the initial fixation of a stemless humeral component typically depends on cementless metaphyseal press-fit, which could pose some challenges to the initial stability. Long-term success of cementless implants is highly related to osseous integration, which is affected by initial implant-bone interface motion. 1. The purpose of the study was to biomechanically compare micromotion at the implant-bone interface of three humeral components in total shoulder arthroplasty. Patients & Methods. Three humeral components were evaluated: Global Advantage, a central screw prototype, and a peripheral leg prototype. All components were the smallest sizes available. Global Advantage is a stemmed design. Both central screw prototype and peripheral leg prototype are stemless designs. Five specimens were tested for each design. Composite analogue humeral models were utilized to simulate the humeral bone. The cortical wall had a thickness of 3 mm and a density of 481 kg/m. 3. , while the cancellous density was 80 kg/m. 3. The model was custom fabricated to accommodate 40 mm humeral component and had a 45° resected surface and a square base to facilitate test setup. Each humeral component was implanted per its surgical technique. The construct was clamped in a vise with the humeral shaft angled at 27°. A MTS test system was employed to conduct the test. A sinusoidal compressive load from 157 N to 1566 N (2BW) was applied to the humeral component at 1 Hz for 100 cycles. The implant-bone interface micromotion was measured with a digital image correlation system which had a resolution of less than 1 micron. The micromotion measurement was transformed to 2 components: 1 was parallel and the other perpendicular to the humeral resection surface. Peak-valley micromotion from the last 10 cycles were averaged and utilised for data analyses. A one-way ANOVA and post-hoc Tukey tests were performed to compare the micromotion of different designs (α=0.05). Results. Micromotion of Global Advantage parallel to the resection (X-Axis) was significantly less than that of central screw prototype and peripheral leg prototype. Micromotion of peripheral leg prototype perpendicular to the resection (Y-Axis) was significantly less than Global Advantage and central screw prototype. There was no significant difference between different designs in resultant micromotion. Discussion/Conclusion. Clinical studies have shown that current stemless shoulder prosthesis yielded encouraging results in mid-term follow-ups. Particularly, the stemless Arthrex Eclipse humeral component, a central screw design, has been reported to have a secure bony fixation and ingrowth at an average of 23 months postoperatively. 4. The current study demonstrated that the stemless peripheral leg prototype and central screw prototype achieved similar initial fixation as stemmed Global Advantage in terms of resultant micromotion, and provided biomechanical evidence that stemless humeral components could have comparable initial stability to stemmed counterparts

The Trident acetabular system is the second most common cementless cup implanted in the UK. Recent studies have shown that malseating of the liner can be as high as 16.4%. We felt this was very high and were prompted to review our series and early clinical outcomes. We reviewed 118 hips in 110 patients, implanted between from 2005-2007. We reviewed initial post operative X-rays using the technique described by Howcroft to identify malseating. The posterior approach was used in all cases. All cups were Trident PSL and all 85 Patients had OA, 10 RA, 8 AVN, 5 DDH, 3 OA post trauma, 2 Perthes, 2 Psoriatic Arthritis, 3 other. We only identified 3 malseated cups in 118 hips. 2 were in patients with OA secondary to trauma and 1 in primary OA. The rate of malseating for trainees operating was 5 % and only 1% when consultants were operating. There were no adverse events in these patients. No-one required revision. Oxford Hip Score (OHS) improved from 47 pre-op to 20 post op. This was compared to 47 and 22 in the correctly seated group (115 cases). Surprisingly the subgroup with the poorest OHS at 1 year had surgery for DDH, with a mean OHS of 31. The reasons for this are unclear. Contrary to other studies our malseating rate is very low. We do not feel that malseating is a problem with Trident if adequate exposure is obtained. In those patients with sclerotic bone, we suggest over reaming the rim of the acetabulum by 1mm to avoid excess deformation of the shell which may lead to difficulty with seating the liner. We suggest trainees are supervised closely when using Trident

Introduction. Unicompartmental Knee Replacement (UKR) is an appealing alternative to Total Knee Replacement (TKR) when the patient has isolated compartment osteoarthritis (OA). A common observation post-operatively is radiolucency between the tibial tray wall and the bone. In addition, some patients complain of persistent pain following implantation with a UKR; this may be related to elevated bone strains in the tibia. The aim of this study was to investigate the mechanical environment of the tibia bone adjacent to the tray wall, following UKR, to determine whether this region of bone resorbs, and how altering the mechanical environment affects tibia strains. Materials and methods. A finite element (FE) model of a cadaver tibia implanted with an Oxford UKR was used in this study, based on a validated model. A single static load, measured in-vivo during a step-up activity was used. There was a 1 mm layer of cement surrounding the keel in the cemented UKR, and the cement filled the cement pocket. In accordance with the operating procedure, no cement was used between the tray wall and bone. For the cementless UKR a layer of titanium filled the cement pocket. An intact tibia was used to compare to the cemented and cementless UKR implanted tibiae. The tibia was sectioned by the tray wall, defining the radiolucency zone (parallel to the vertical tray wall, 2 mm wide with a volume of 782.5 mm. 3. ), corresponding to the region on screened x-rays where radiolucencies are observed. Contact mechanics algorithms were used between all contacting surfaces; bonded contact was also introduced between the tray wall and adjacent bone, simulating a mechanical tie between them. Strain energy density (SED), was compared between the intact and implanted tibia for the radiolucency zone. Equivalent strains were compared on the proximal tibia between the intact and implanted tibia models. Forty patients (20 cemented, 20 cementless) who had undergone UKR were randomly selected from a database, and assessed for radiolucency. Results. The SED in the radiolucency zone was 80% lower in the cemented and cementless tibia, compared to the intact tibia, without a mechanical tie between the tibial tray wall and adjacent bone. When a mechanical tie was introduced the SED in the radiolucency zone was 35% higher in the cemented and cementless tibia, compared to the intact tibia. The strain on the proximal tibia was reduced by 20% when a mechanical tie was used between the tray wall and adjacent bone. Radiolucency at the tray wall was observed in all forty radiographs examined. Discussion. This work has presented a static snapshot of the load being carried through the proximal tibia following implantation with an Oxford UKR. It has been shown that by introducing a mechanical tie between the tibial tray wall and the adjacent bone, the SED in the region observed to have radiolucency is increased; this has the potential of reducing the likelihood of a radiolucency occurring in that region. Moreover, the strain observed in the proximal tibia was reduced when a mechanical tie was introduced, which may reduce the incidence of pain following implantation with a UKR. It is recommended that integration between the bone and the tray wall is important for UKR

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting.

Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured.

Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum.

The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting.

In an attempt to increase the life of cementless prostheses, an hydroxyapatite-coated implant which releases a bisphosphonate has been suggested as a drug-delivery system. Our in vitro study was designed to determine the maximum dose to which osteoblasts could be safely exposed.

Our findings demonstrated that zoledronate did not impair the proliferation of human osteoblasts when used at concentrations below 1 μm. Murine cells can be exposed to concentrations as high as 10 μm.

A concentration of 0.01% of titanium particles did not impair the proliferation of either cell line. Zoledronate affected the alkaline phosphatase activity of murine osteoblasts through a chelation phenomenon. The presence of titanium particles strongly decreased the alkaline phosphatase activity of murine osteoblasts. We did not detect any synergic effect of zoledronate and titanium particles on the behaviour of both human and murine osteoblasts.