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

There is continued concern over complication rates (20–30% of cases) in locked proximal humeral plating. The most common sequelae of this is screw penetration of the humeral head. This is associated with natural settling of the fracture, malreducition in varus, insufficent medial support of the fracture. The proximity of the screws to the articular surface can also be influential on outcome if collapse occurs. Our operative technique is to establish the rotation of the humeral head where the drill appears closest to the articular margin (by sequential xray screening) and subtract from this to avoid intra-articular penetration of the humeral head. 55 Consecutive patients of average age 56.4 years (14.7–86.1), 17 male and 38 females, who underwent PHILOS plating were identified using Bluespier database. Xrays were analysed for fracture pattern, restoration of neck-shaft angle, plate positioning, number and configuration of screws and presence of screw penetration both intra-operatively and at postoperative follow-up. There were 6.07 screws used per head (total 330). There was one intraoperative screw penetration and 3 patients had evidence of screw penetration at follow-up, which required implant removal (total screw penetration rate of 7%). There was one case of AVN. The mean neck shaft angle was 137 degrees (anatomical 135 degrees). Accurate reduction of fractures and placement of screws in the humeral head using image intensifier can act to minimise risk of screw penetration and make some of the complications of locked proximal humeral plating avoidable

We have investigated the role of the penetration of saline on the shear strength of the cement-stem interface for stems inserted at room temperature and those preheated to 37°C using a variety of commercial bone cements. Immersion in saline for two weeks at 37°C reduced interfacial strength by 56% to 88% after insertion at room temperature and by 28% to 49% after preheating of the stem. The reduction in porosity as a result of preheating ranged from 71% to 100%. Increased porosity correlated with a reduction in shear strength after immersion in saline (r = 0.839, p < 0.01) indicating that interfacial porosity may act as a fluid conduit

We studied various aspects of graft impaction and penetration of cement in an experimental model. Cancellous bone was removed proximally and local diaphyseal lytic defects were simulated in six human cadaver femora. After impaction grafting the specimens were sectioned and prepared for histomorphometric analysis. The porosity of the graft was lowest in Gruen zone 4 (52%) and highest in Gruen zone 1 (76%). At the levels of Gruen zones 6 and 2 the entire cross-section was almost filled with cement. Cement sometimes reached the endosteal surface in other Gruen zones. The mean peak impaction forces exerted with the impactors were negatively correlated with the porosity of the graft

Abstract. Objectives. Impingement of total hip replacements (THRs) can cause rim damage of polyethylene liners, and lead to dislocation and/or mechanical failure of liner locking mechanisms[1]. A geometric model of a THR in situ was previously developed to predict impingement for different component orientations and joint motions of activities[2]. However, the consequence of any predicted impingement is unknown. This study aimed to develop an in-vitromethod to investigate the effects of different impingement scenarios. Method. A ProSim electro-mechanical single-station hip simulator (Simulation Solutions) was used, and the 32mm diameter metal-on-polyethylene THRs (DePuy Synthes) were assessed. The THR was mounted in an inverted orientation, and the input (motion and loading) applied simulated a patient stooping over to pick an object from the floor[3]. The impingement severity was varied by continuing motion past the point of impingement by 2.5° or 5°, and compressive load applied in the medial-lateral direction was varied from 100N to 200N. Each test condition was applied for 40,000 cycles (n=3). Rim penetration was assessed using a CMM and component separation was measured during the tests. Results. Varying the impingement severity from 2.5° to 5° increased rim penetration two-fold (by >0.05mm) and increased medial-lateral component separation three-fold (by >0.3mm) (both p<0.001). Increasing the medial-lateral load had less effect on the rim penetration and component separation, with exception of rim penetration with the higher impingement severity condition. Conclusion. The impingement severity influenced the medial-lateral component separation, suggesting that increasing the impingement severity could increase the risk of dislocation. The impingement severity, which could be predicted from geometric modelling, was also found to significantly affect rim penetration, meaning this method could be used alongside geometric modelling to predict impingement severity in a range of scenarios. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Extensor mechanism and abductor reconstructions in total joint arthroplasty are problematic. Growing tendon into a metallic implant would have great reconstructive advantages. With the introduction of porous metal implants, it was hoped that tendons could be directly attached to implants. However, the effects of the porous metal structure on tissue growth and pore penetration is unknown. In this rat model, we investigated the effect of pore size on tendon repair fixation using printed titanium implants with differing pore sizes. There were four groups of six Sprague Dawley rats (n = 28) plus control (n=4). Implants had pore sizes of 400µm (n=8), 700µm (n=8), and 1000µm (n=8). An Achilles tendon defect was created, and the implant positioned and sutured between the cut ends. Harvest occurred at 12-weeks. Half the specimens underwent tensile load to failure testing, the other half fixed and processed for hard tissue analysis. Average load to failure was 72.6N for controls (SD 10.04), 29.95N for 400µm (SD 17.95), 55.08N for 700µm (SD 13.47), and 63.08N for 1000µm (SD 1.87). The load to failure was generally better in the larger pore sizes. Histological evaluation showed that there was fibrous tendon tissue within and around the implant material, with collagen fibers organized in bundles. This increases as the pore diameter increases. Printing titanium implants allows for precise determination of pore size and structure. Our results showed that tendon repair utilizing implants with 700µm and 1000µm pores exhibited similar load to failure as controls. Using a defined pore structure at the attachment points of tendons to implants may allow predictable tendon to implant reconstruction at the time of revision arthroplasty

Non-optimal clinical alignment of components in total hip replacements (THRs) may lead to edge loading of the acetabular cup liner. This has the potential to cause changes to the liner rim not accounted for in standard wear models. A greater understanding of the material behaviours could be beneficial to design and surgical guidance for THR devices. The aim of this research was to combine finite element (FE) modelling and experimental simulation with microstructural assessment to examine material behaviour changes during edge loading. A dynamic deformable FE model, matching the experimental conditions, was created to simulate the stress strain environment within liners. Five liners were tested for 4Mc (million cycles) of standard loading (ISO14242:1) followed by 3Mc of edge loading with dynamic separation (ISO14242:4) in a hip simulator. Microstructural measurements by Raman spectroscopy were taken at unloaded and highly loaded rim locations informed by FE results. Gravimetric and geometric measurements were taken every 1Mc cycles. Under edge loading, peak Mises stress and plastic deformation occur below the surface of the rim during heel strike. After 7Mc, microstructural analysis determined edge loaded regions had an increased crystalline mass fraction compared to unloaded regions (p<0.05). Gravimetric wear rates of 12.5mm. 3. /Mc and 22.3mm. 3. /Mc were measured for standard and edge loading respectively. A liner penetration of 0.37mm was measured after 7Mc. Edge loading led to an increase in gravimetric wear rate indicating a different wear mechanism is occurring. FE and Raman results suggest that changes to material behaviour at the rim could be possible. These methods will now be used to assess more liners and over a larger number of cycles. They have potential to explore the impact of edge loading on different surgical and patient variables

In the context of regenerative medicine for the treatment of musculoskeletal pathologies mesenchymal stromal cells (MSCs) have shown good results thanks to secretion of therapeutic factors, both free and conveyed within the extracellular vesicles (EV), which in their totality constitute the “secretome”. The portfolio and biological activity of these molecules can be modulated by both in vitro and in vivo conditions, thus making the analysis of these activities very complex. A deep knowledge of the targets regulated by the secretome has become a matter of fundamental importance and a homogeneous and complete molecular characterization is still lacking in the field of applications for the musculoskeletal system. Therefore, the aim of this work was to characterize the secretome obtained from adipose-derived MSCs (ASCs), and its modulation after pre-conditioning of the ASCs. Pre-conditioning was done by culturing cells in the presence of i) high levels of IFNγ, as proposed for the production of clinical grade secretome with enhanced regenerative potential, ii) low levels of inflammatory stimuli, mimicking conditions found in the osteoarthritis (OA) synovial fluid. Furthermore, EVs ability to migrate within cartilage, chondrocyte and synoviocytes obtained from OA patients was evaluated. The data showed that more than 50 cytokines / chemokines and more than 200 EV-microRNAs are detectable at various intensity levels in ASCs secretomes. The majority of the most abundantly present molecules are involved in the remodelling of the extracellular matrix and in the homeostasis and chemotaxis of inflammatory cells including macrophages, which in OA are often characterized by an M1 inflammatory polarization, promoting their transition to an M2 anti-inflammatory phenotype. Inflammatory priming with IFNγ and synovial fluid-like conditions were able to further increase the ability of the secretome to interact with inflammatory cells and modulate their migration. Finally, the penetration of the EVs in the cartilage explants resulted a rapid process, which begins a few minutes after administration of the EVs that are able to reach a depth of 30-40 μm in 5 hours. The same capacity for interaction was also verified in chondrocytes and synoviocytes isolated from the cartilage and synovial membrane of OA patients. Thanks to the soluble factors and EV-microRNAs, the ASCs secretome has shown a strong propensity to modulate the inflammatory and degenerative processes that characterize OA. The inflammatory pre-conditioning through high concentrations of inflammatory molecules or in conditions similar to the synovial fluid of OA patients was able to increase this capacity by increasing their chemotactic power. The microscopy data also support the hypothesis of the ability of MSC-EVs to influence the chondrocytes residing in the ECM of the cartilage and the synovial cells of the synovial membrane through active interaction and the release of their therapeutic content

Tourniquet is widely used in orthopedic surgery to reduce intraoperative bleeding and improve visualization. We evaluated the effect of tourniquet application on both peri- and postoperative cefuroxime concentrations in subcutaneous tissue, skeletal muscle, calcaneal cancellous bone, and plasma. The primary endpoint was the time for which the free drug concentration of cefuroxime was maintained above the clinical breakpoint minimal inhibitory concentration (T>MIC) forStaphylococcus aureus (4 µg/mL). Ten patients scheduled for hallux valgus or hallux rigidus surgery were included. Microdialysis catheters were placed for sampling of cefuroxime concentrations bilaterally in subcutaneous tissue, skeletal muscle, and calcaneal cancellous bone. A tourniquet was applied on the thigh of the leg scheduled for surgery. Cefuroxime (1.5 g) was administered intravenously as a bolus 15 minutes prior to tourniquet inflation, followed by a second dose 6 hours later. The mean tourniquet duration (range) was 65 (58; 77) minutes. Dialysates and venous blood samples were collected for 12 hours. For cefuroxime the T>MIC (4 μg/mL) ranged between 4.8–5.4 hours across compartments, with similar results for the tourniquet and non-tourniquet leg. Comparable T>MIC and penetration ratios were found for the first and second dosing intervals. We concluded that administration of cefuroxime (1.5 g) 15 minutes prior to tourniquet inflation is safe in order to achieve tissue concentrations above 4 µg/mL throughout surgery. A tourniquet application time of approximately 1 hour did not affect the cefuroxime tissue penetration in the following dosing interval

Introduction. Beneath infection, instability and malalignment, aseptic tibial component loosening remains a major cause of failure in total knee arthroplasty (TKA) [1]. This emphasizes the need for stable primary and long-term secondary fixation of tibial baseplates. To evaluate the primary stability of cemented tibial baseplates, different pre-clinical test methods have been undergone: finite element analysis [2], static push-out [3,4] or dynamic compression-shear loading [5] until interface failure. However, these test conditions do not reflect the long-term endurance under in vivo loading modes, where the tibial baseplate is predominantly subjected to compression and shear forces in a cyclic profile [5,6]. To distinguish between design parameters the aim of our study was to develop suitable pre-clinical test methods to evaluate the endurance of the implant-cement-bone interface fixation for tibial baseplates under severe anterior (method I) and internal-external torsional (method II) shear test conditions. Materials & Methods. To create a clinically relevant cement penetration pattern a 4. th. generation composite bone model was customised with a cancellous core (12.5 PCF cellular rigid PU foam) to enable for high cycle endurance testing. VEGA System. ®. PS & Columbus. ®. CRA/PSA ZrN-multilayer coated tibial baseplates (2×12) were implanted in the customised bone model using Palacos. ®. R HV bone cement (Figure 1). An anterior compression-shear test (method II) was conducted at 2500 N for 10 million cycles and continued at 3000 N & 3500 N for each 1 million cycles (total: 12 million cycles) simulating post-cam engagement at 45° flexion. An internal-external torsional shear test (method II) was executed in an exaggeration of clinically relevant rotations [7,8] with ±17.2° for 1 million cycles at 3000 N tibio-femoral load in extension. After endurance testing either under anterior shear or internal-external torsion each tibial baseplate was mounted into a testing frame and maximum push-out strength was determined [3]. Results. The cement penetration depth and characteristic pattern were comparable to 3D-CT scans of 24 cemented human tibiae from a previous study [5]. From the final push-out testing, no statistical significant differences could be found for anterior compression-shear testing (method I) with VEGA System. ®. PS (2674 ± 754 N) and Columbus. ®. CRA/PSA (2177 ± 429 N) (p = 0.191), as well as internal-external torsional shear testing (method II) between VEGA System. ®. PS (2561 ± 519 N) and Columbus. ®. CRA/PSA (2825 ± 515 N) tibial baseplates (p = 0.399). Discussion. The newly developed methods allow the evaluation of the endurance behaviour of the implant-cement-bone interface fixation for tibial baseplates in comparison to clinically long-term established knee systems, based on a combination of a suitable artificial bone model and severe anterior and internal-external torsional high cycle shear test conditions

Summary Statement. Fretting and corrosion has been identified as a clinical problem in modular metal-on-metal THA, but remains poorly understood in modern THA devices with polyethylene bearings. This study investigates taper damage and if this damage is associated with polyethylene wear. Introduction. Degradation of modular head-neck tapers was raised as a concern in the 1990s (Gilbert 1993). The incidence of fretting and corrosion among modern, metal-on-polyethylene and ceramic-on-polyethylene THA systems with 36+ mm femoral heads remains poorly understood. Additionally, it is unknown whether metal debris from modular tapers could increase wear rates of highly crosslinked PE (HXLPE) liners. The purpose of this study was to characterise the severity of fretting and corrosion at head-neck modular interfaces in retrieved conventional and HXLPE THA systems and its effect on penetration rates. Patients & Methods. 386 CoCr alloy heads from 5 manufacturers were analyzed along with 166 stems (38 with ceramic femoral heads). Metal and ceramic components were cleaned and examined at the head taper and stem taper by two investigators. Scores ranging from 1 (mild) to 4 (severe) were assigned in accordance with the semi-quantitative method adapted from a previously published technique. Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Devices implanted less than 1 year were excluded from this analysis because in the short-term, creep dominates penetration of the head into the liner. Results. The majority of the components were revised for instability, infection, and loosening. Mild to severe taper damage (score ≥2) was found in 77% of head tapers and 52% of stem tapers. The extent of damage was correlated to implantation time at the head taper (p=0.0004) and at the stem taper (p=0.0004). Damage scores were statistically elevated on CoCr heads than the matched stems (mean score difference=0.5; p<0.0001) and the two metrics were positively correlated with each other (ρ=0.41). No difference was observed between stem taper damage and head material (CoCr, ceramic) (p=0.56), nor was a correlation found between taper damage and head size (p=0.85). The penetration rate across different formulations of HXLPE was not found to be significantly different (p=0.07), and therefore grouped together for further analysis. Within this cohort, penetration rate was not found to be associated with head size (p=0.08) though a negative correlation with implantation time was noted (ρ=−0.35). When analyzed along with taper damage scores, a correlation was not observed between head taper damage scores and HXLPE penetration rates (p=0.51). Discussion. The results of this study do not support the hypothesis that 36+ mm ceramic or CoCr femoral heads articulating on HXLPE liners are associated with increased risk of corrosion among HXLPE liners when compared with smaller diameter heads. A limitation of this study is the semi-quantitative scoring technique, heterogeneity of the retrieval collection and short implantation time of the larger diameter heads. Because corrosion may increase over time in vivo, longer-term follow-up, coupled with quantitative taper wear measurement, will better assess the natural progression of taper degradation in modern THA bearings

Introduction and Objective. Found in bone-associated prosthesis, Cutibacterium acnes (C. acnes) is isolated in more than 50% of osteoarticular prosthesis infections, particularly those involving shoulder prostheses. Ongoing controversies exist concerning the origin of C. acnes infection. Few reports construct a reasonable hypothesis about probable contaminant displaced from the superficial skin into the surgical wound. Indeed, despite strict aseptic procedures, transecting the sebaceous glands after incision might result in C. acnes leakage into the surgical wound. More recently, the presence of commensal C. acnes in deep intra-articular tissues was reported. C. acnes was thus detected in the intracellular compartment of macrophages and stromal cells in 62.5% of the tested patients who did not undergo skin penetration. Among bone stromal cells, mesenchymal stem cells (MSCs) are predominantly found in bone marrow and periosteum. MSCs are the source of osteogenic lines of cells capable of forming bone matter. In this study, the pathogenicity of C. acnes in bone repair context was investigated. Materials and Methods. Human bone marrow derived MSCs were challenged with C. acnes clinical strains harvested from non-infected bone site (Cb). The behaviour of Cb strain was compared to C. acnes took from orthopaedic implant-associated infection (Ci). The infective capabilities of both strains was determined following gentamicin-based antibiotic protection assay. The morphology and ultrastructural analysis of infected MSCs was performed respectively through CLSM pictures of Phalloidin. ®. stained MSCs cytoskeleton and DAPI labelled Cb, and transmission and scanning electron microscopies. The virulence of intracellular Ci and Cb (Ci-MSCs and Cb-MSCs) was investigated by biofilm formation on non-living bone materials; and the immunomodulatory response of infected MSCs was investigated (PGE-2 and IDO secretion detected by ELISA). Bone cells (osteoblasts and PMA differentiated macrophages) were then challenged with Cb-MSCs and Ci-MSCs. Intracellular accumulation of ROS within infected macrophages was assessed by flow cytometry after 2 h of infection and the catalase production by Cb-MSC and Ci-MSC was evaluated. Statistical analyses were performed using Mann & Whitney test. Results. Following MSCs infection by C. acnes, the rate of viable bacteria inside MSCs was about 4% and 6% for Cb and Ci, respectively. Cb showed however a lower invasiveness in comparison to Ci (0.6-fold, p=0.01), confirming the higher pathogenicity of Ci. The ultrastructural and morphology analysis of infected MSCs confirmed the presence of bacteria free in MSCs cytoplasm, localized between F-actin fibers of MSCs, which preserved their elongated morphology. Considering the high level of secreted immunomodulatory mediators (PGE-2 and IDO), our results suggest that Cb-infected MSCs could promote a transition of macrophages from a primarily pro-inflammatory M1 to a more anti-inflammatory M2 phenotype. In comparison with Cb, Cb-MSCs increased significantly the formation of biofilm on TA6V and PEEK but reduced the biofilm formation on 316L SS. Ci-MSCs showed a significant increase in biofilm formation on PEEK vs Ci, while no difference in biofilm formation was noticed on TA6V and 316L SS. Regarding the ability of MSCs bacteria to infect osteoblasts, our results showed a higher infective capabilities of Cb-MSCs versus Cb (>2-fold, p=0.02), while no difference was noticed between Ci and Ci-MSCs. Along with an increase in catalase production by Cb-MSCs, we noticed its higher persistence to macrophage degradation. Conclusions. Taken together, our results demonstrate a shift in commensal Cb to pathogenic following infection. Indeed, Cb- MSCs acquires features that (i) increase biofilm formation on orthopedic based materials, (ii) increase the osteoblast infection and (iii) develop resistance to the macrophage degradation, through the increase of catalase production. Overall, these results showed a direct impact of C. acnes on bone marrow derived MSCs, providing new insights into the development of C. acnes during implant-associated infections

The direction of wear in the acetabular socket has implications for the amount of debris that is generated during movement, for the magnitude of eccentric loading and for the incidence of impingement of the neck. We observed the direction of penetration with respect to a global co-ordinate system in 84 acetabular components retrieved at reoperation. The mean direction of wear relative to the open face of the sockets was found to be 37° with a range from 0° to 87°. For those values determined using the inclination of the socket on the prerevision radiograph, the mean direction of penetration in the coronal plane had a lateral, rather than a medial, component. The mean angle was 84° (SD 17°) with respect to the horizontal. The angle of penetration was found to correlate significantly with the depth, in that the lateral component became larger as the wear progressed. There was also a significant correlation between the rate of penetration and the direction of wear. Despite the theoretical advantage of penetration in the superolateral direction, i.e., along the margin of the socket, in reducing the probability of impingement of the neck, no significant correlation was seen between the angle of penetration and the period of use in vivo. This may suggest that impingement of the femoral neck on the rim of the socket may not be the dominant factor in loosening of the socket but can still be important in a few cases

Introduction. Durable bone fixation of uncemented porous-coated acetabular cups can be observed at a long-term, however, polyethylene (PE) wear and osteolysis may affect survivorship. Accurate wear measurements correlated with clinical data may offer unique research information of clinical interest about this highly debated issue. Objetive. We assessed the clinical and radiological outcome of a single uncemented total hip replacement (THR) system after twenty years analysing polyethylene wear and the appearance of osteolysis. Materials and Methods. 82 hips implanted between 1992 and 1995 were prospectively evaluated. The mean follow-up was 20.6 years (range, 18 to 23). A hemispherical porous-coated acetabular cup matched to a proximally hydroxyapatite-coated anatomic stem and a 28 mm standard PE liner, sterilised by gamma irradiation in air, was used in all hips. Radiological position and the possible appearance of loosening and osteolysis were recorded over time. Penetration of the prosthetic head into the liner was measured by the Roentgen Monographic Analysis (ROMAN) Tool at 6 weeks, 6 months, one year and yearly thereafter. Results. Six cups were revised due to wear and four due to late dislocation. All cups were radiographically well-fixed and all stems showed radiographic ingrowth. Six un-revised hips showed osteolysis on the acetabular side and two on the proximal femoral side. Creep at one year was 0.30 (±0.23) mm. Mean total femoral head penetration was 1.23 mm at 10 years, 1.52 mm at 15 years and 1.92 mm at 23 years. Overall mean wear was 0.12 (± 0.1) mm/year and 0.09 (±0.06) mm/year after the creep period. Mean wear was 0.08 (± 0.06) mm/year in hips without osteolysis and 0.14 (±0.03) mm/year in revised hips or with osteolysis (p<0.001). Conclusions. Although continued durable fixation can be observed with a porous-coated cups and a proximally hydroxyapatite-coated anatomic stem, true wear continues to increase at a constant rate over time. PE wear remains as the main reason for revision surgery and osteolysis in uncemented THR and does not stop after twenty years

Objectives. Our objective was to perform a systematic review of the literature and conduct a meta- analysis to investigate the effect of initial varus or valgus displacement of proximal humerus on the outcomes of patients with proximal humerus fractures treated with open reduction and internal fixation. Methods. In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement standards, we performed a systematic review. Electronic databases MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched to identify randomised and non-randomised studies comparing postoperative outcomes associated with initial varus versus initial valgus displacement of proximal humerus fracture. The Newcastle–Ottawa scale was used to assess the methodological quality and risk of bias of the selected studies. Fixed-effect or random-effects models were applied to calculate pooled outcome data. Results. We identified two retrospective cohort studies and one retrospective analysis of a prospective database, enrolling a total of 243 patients with proximal humerus fractures. Our analysis showed that initial varus displacement was associated with a higher risk of overall complication (RR 2.28, 95% CI 1.12–4.64, P = 0.02), screw penetration (RR 2.30, 95% CI 1.06–5.02, P = 0.04), varus displacement (RR 4.38, 95% CI 2.22–8.65, P < 0.0001), and reoperation (RR 3.01, 95% CI 1.80–5.03, P < 0.0001) compared to valgus displacement. There was no significant difference in avascular necrosis (RR 1.43, 95% CI 0.62–3.27, P = 0.40), infection (RR 1.49, 95% CI 0.46–4.84, P = 0.51), and non-union or malunion (RR 1.37, 95% CI 0.37–5.04, P = 0.64). Conclusions. The best available evidence demonstrates that initial varus displacement of proximal humerus fractures is associated with higher risk of overall complication, screw penetration, varus displacement, and reoperation compared to initial valgus displacement. The best available evidence is not adequately robust to make definitive conclusions. Further high quality studies, that are adequately powered, are required to investigate the outcomes of initial varus and valgus displacement in specific fracture types

Summary Statement. This study assesses oxidation, mechanical behavior and revision reasons of 2. nd. generation HXLPE used in total hip and knee arthroplasty. While oxidation was low for both X3 and E1 HXLPEs, oxidative regional variations were detected in the sequentially annealed cohort. Introduction. First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1. st. generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2. nd. generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2. nd. generation HLXPEs. The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA. Methods. 251 2. nd. Generation HXLPE hip and knee components were consecutively retrieved during revision surgeries and continuously analyzed in a prospective, IRB approved, multicenter study. 123 acetabular liners (Implanted 1.2y; Range 0–5.0y) and 117 tibial inserts (Implanted 1.6y; Range 0–5.8y) were highly crosslinked and annealed in 3 sequential steps (X3). Five acetabular liners (Implanted 0.6y; Range 0–2.0y) and six tibial inserts (Implanted 1.3y; Range 0.5–1.8y) were diffused with Vitamin E (E1). Patient information was collected from medical records. Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Surface damage of tibial components was assessed using the Hood method. Thin sections were taken from the acetabular liners (along the superior/inferior axis) and the tibial components (along the medial condyle and central spine) for oxidation analysis and analyzed according to ASTM 2102. Mechanical behavior was assessed via the small punch test (ASTM 2183). Results. The liners and tibial components fabricated from both HXLPEs were revised predominantly for loosening, instability, and infection. The average penetration rate for the Sequentially Annealed group was low (PR=0.045mm/yr). Pitting, scratching and burnishing were the predominant damage mechanisms of the tibial inserts within both material groups, with no evidence of delamination. Oxidation indices were low (Mean OI≤0.3) and similar between liners and inserts of the Sequentially Annealed components at the bearing and backside surface (p≥0.15). Oxidation was positively correlated with implantation time at the bearing surface of the Sequentially Annealed groups (Rho>0.29, p<0.005). The Ultimate Load of the Sequentially Annealed acetabular liners was statistically higher than the tibial components (p<0.001), however the mean difference was minimal (∼6N). Discussion. This study evaluated the properties of 2. nd. generation HXLPEs used in THA and TKA. Sequentially Annealed liners had penetration rates comparable with 1. st. generation HXLPEs. While oxidation was low for both sequentially annealed and Vitamin E HXLPEs, we were able to detect regional variations in the oxidative in the sequentially annealed cohort. Longer-term retrievals are necessary to fully assess the oxidative stability of Vitamin E diffused HXLPE used in TKA and THA

Thermal osteonecrosis is a side effect when used Kirschner (K) wires and drills in orthopaedic surgeries. This osteonecrosis may endanger the fixation. Orthopaedic surgeons sometimes have to use unsharpened K-wires in emergent surgery. The thermal effect of used and unsharpened K wire is ambiguous to the bone. This experimental study aims to assess the thermal osteonecrosis while drilling bone with three different types of K-wires especially a previously used unsharpened wire and its thermographic measurements correlation. Two different speeds of rotation were chosen to investigate the effect of speed on thermal necrosis to the bone. A total of 16 New Zealand white rabbits weighing a mean of 2.90 kg (2.70 – 3.30 kg) were used. All rabbits were operated under general anaesthesia in a sterile operating room. Firstly, 4 cm longitudinal lateral approach was used to the right femur and then the femur was drilled with 1.0 mm trochar tip, spade tip and previously used unsharpened K-wires and 1.0 mm drill bit at 1450 rpm speed. Left femur was drilled with same three type K-wires and drill bit at 330 rpm speed. One cm distance was left among four penetrations on the femur. The thermal changes were recorded by Flir® E6 Thermal Camera from 50 cm distance and 30-degree angle. Thermographic measurements saved for every drilling process and recorded for the highest temperature (°C) during the drilling. All subjects were sacrificed post-operatively on the eighth day and specimens were prepared for the histological examination. The results of osteonecrosis assessment score and thermographic correlation were evaluated statistically. Histological specimens were evaluated by the scoring of osteonecrosis, osteoblastic activity, haemorrhage, microfracture and inflammation. Results were graded semi-quantitatively as none, moderate or severe for osteonecrosis, haemorrhage and inflammation. The microfracture and osteoblastic activity were evaluated as present or absent. There was no meaningful correlation between osteonecrosis and the drilling speed (p=0.108). There was less microfracture zone which was drilled with trochar tip K-wires at 1450 rpm speed (p=0.017). And the drilling temperature of trochar tip K-wires was higher than the others(p=0.001). Despite this evaluation, osteonecrosis zone of spade and unsharpened tip K-wires were more than trochar tip K-wires (p=0.039). The drill bit at 330 rpm caused the least osteonecrosis and haemorrhage and respectfully the lowest drilling temperature (p=0,001). The osteoblastic activity shows no difference between the groups. (p=0,122; 0,636;0.289). On the contrary to the literature, our experiment showed that there is no meaningful correlation between osteonecrosis score and temperature produced by drilling. The histological assessment showed the osteonecrosis during short drilling time but, not clarify the relation with drilling temperature. Eventually, the osteonecrosis showed a positive correlation with drilling time independently of drilling temperature at 330 rpm. (p=0,042) These results show that we need more studies to understand about osteonecrosis and its relationship with drilling heat temperature. Trochar tip K-wires creates higher drilling temperature but less osteonecrosis than a spade and unsharpened cut tip K-wires. Using unsharpened tip K-wire causes more osteonecrosis. Previously used and, unsharpened K-wires should be discarded

Introduction. Severe ‘discogenic’ back pain may be related to the ingrowth of nerves and blood vessels, although this is controversial. We hypothesise that ingrowth is greater in painful discs, and is facilitated in the region of annulus fissures. Methods. We compared tissue removed at surgery from 22 patients with discogenic back pain and/or sciatica, and from 16 young patients with scoliosis who served as controls. Wax-embedded specimens were sectioned at 7μm. Nerves and blood vessels were identified using histological stains, and antibodies to PGP 9.5 and CD31 respectively. Results. Blood vessels were identified in 77% of ‘painful’ discs compared to 44% of scoliotic discs (p=0.013), and they were more common in the anterior anulus compared to the posterior (p=0.026). Maximum penetration of blood vessels from the peripheral anulus was 4.7 mm (in ‘painful’ discs) and 2.0 mm (in control discs), and penetration increased with histological grade of disc degeneration in the ‘painful’ discs (p=0.002). In 16/17 ‘painful’ discs, blood vessels were within 1 mm of an anulus fissure, or the disc periphery. Nerves were found in 36% of ‘painful’ discs (all with blood vessels) and 25% of control discs. Nerve ingrowth was always less than or equal to blood vessel ingrowth, with a maximum observed penetration of 1.5 mm from the annulus periphery. Discussion. In degenerated and painful discs, the ingrowth of nerves appears to follow that of blood vessels, and is facilitated in the region of annulus fissures. No nerves were seen >2mm from the annulus periphery, suggesting that previous reports of nerves in the disc nucleus may refer to vertical growth from a vertebral endplate rather than radial growth through the annulus. Results support the view that discogenic back pain is associated with pain-sensitisation events in the disc periphery. Acknowledgements. Research funded by BackCare. M Stefanakis would like to thank the Greek Institute of Scholarships (I.K.Y) for financial support

Crosslinking has been already used for about 80 years to enhance the longevity of polyethylene cables. The polymer alteration has been achieved with peroxide, silane or irradiation. The medical devices industry discovered the benefit of this technology for its tribological applications like hip or knee bearings in the 2000s as crosslinking improves considerably the abrasion resistance of the material. The more current methods used are Gamma and Beta irradiation. On the basis of economical (rising prices of Cobalt), environmental (the radioactive source can not be turned off), technological (low dose rate) drawbacks for Gamma respectively low penetration for Beta irradiation we decided to investigate an alternative technology: the X-Ray irradiation, which provides a homogeneous crosslinking in a relatively short time. We analyzed the wear, mechanical, thermal, oxidative and network properties of two vitamin E doped UHMWPE: first crosslinked with E-Beam, second with X-Ray. There wasn't any significant difference between the X-Ray and the E-Beam crosslinked material

Modular hip prostheses were introduced to optimize the intra-surgical adaptation of the implant design to the native anatomy und biomechanics of the hip. The downside of a modular implant design with an additional modular interface is the potential susceptibility to fretting, crevice corrosion and wear. For testing hip implants with proximal femoral modularity according to ISO & ASTM, sodium chloride solutions are frequently used to determine the fatigue strength and durability of the stem-neck connection. The present study illustrate that the expansion of standard requirements of biomechanical testing is necessary to simulate metal ion release as well as fretting and crevice corrosion by using alternative test fluids. To assess the primary stability of tibial plateaus in vitro, different approaches had been undergone: cement penetration depth analysis, static tension or compression loading until interface failure. However, these test conditions do not reflect the in vivo physiologic loading modes, where the tibial plateau is predominantly subjected to combined compression and shear forces. The objectives were to evaluate the impact of the tibial keel & stem length on the primary stability of a posterior-stabilised tibial plateau under dynamic compression-shear loading conditions in human tibiae