Background. The R3 cementless acetabular system (Smith & Nephew, Memphis, Tennessee, United States) is a modular titanium shell with an asymmetric porous titanium powder coating. It supports cross-linked polyethylene, metal and ceramic liners with several options for the femoral head component. The R3 cup was first marketed in Australia and Europe in 2007. Two recent papers have shown high failure rates of the MoM R3 system with up to 24% (Dramis et al 2014, Hothi et al 2015). There are currently no medium term clinical papers on the R3 acetabular cup. Objectives. The aim of the study is to review our results of the R3 acetabular cup with a minimum of 5 year follow up. Study Design & Methods. Patients who were implanted with the R3 acetabular cup were identified from our centre”s arthroplasty database. Our centre started implanting the R3 acetabular cup in August 2009. For this study, we only included patients with a minimum of 5 year follow up (until June 2011). Over this time period, 293 consecutive THAs were performed in 286 patients, of which 7 were bilateral staged total hip arthroplasties. The primary outcome was revision. The secondary outcomes were the Oxford hip scores and radiographic evaluation. Results. The mean age of the patients was 69.4 years (range 20–100 years). There were 117 males and 169 females in our series. The majority of the total hip arthroplasties in our series were cementless (n=283, 97%) and the rest were hybrid (n=10, 3%). The articulation bearings were as follows: ceramic on ceramic (n=167; 57%), Ceramic on Poly XLPE (n=97; 33%), Oxinium-Poly XLPE (n=19; 6.5%), stainless steel- Poly XLXE (n=10; 3.5%). The mean pre-operative Oxford Hip Score was 23 (range 10–34) and the mean Oxford Hip Score was 40 (range 33–48) at the final follow-up. Radiological evaluation showed an excellent ARA-score in all patients at five years. None of the R3 cups showed osteolysis at final follow up. There were 3 revisions in our series, of which two R3 cup were revised. The risk of revision was 0.28% at 5 years. Using Weibull analysis, it gives a 10-year estimate of 98.8% survival for the R3 cup (95%CI 95.0 to 99.6). Conclusions. Our experience at a district general hospital using the R3 acetabular system with conventional bearings showed high survivorship and is consistent with the allocated Orthopaedic Data Evaluation Panel (ODEP) rating of 5A* as rated in 2015 in the United Kingdom

Results in patients undergoing total hip arthroplasty (THA) for femoral head osteonecrosis (ON) when compared with primary osteoarthritis (OA) are controversial. Different factors like age, THA type or surgical technique may affect outcome. We hypothesized that patients with ON had an increased revision rate compared with OA. We analysed clinical outcome, estimated the survival rate for revision surgery, and their possible risk factors, in two groups of patients.

In this retrospective cohort analysis of our prospective database, we assessed 2464 primary THAs implanted between 1989 and 2017. Patients with OA were included in group 1, 2090 hips; and patients with ON in group 2, 374 hips. In group 2 there were more men (p<0.001), patients younger than 60 years old (p<0.001) and with greater physical activity (p<0.001). Patients with lumbar OA (p<0.001) and a radiological acetabular shape type B according to Dorr (p<0.001) were more frequent in group 1. Clinical outcome was assessed according to the Harris Hip Score and radiological analysis included postoperative acetabular and femoral component position and hip reconstruction. Kaplan-Meier survivorship analysis was used to estimate the cumulative probability of not having revision surgery for different reasons. Univariate and multivariate Cox regression models were used to assess risk factors for revision surgery.

Clinical improvement was better in the ON at all intervals. There were 90 hips revised, 68 due to loosening or wear, 52 (2.5%) in group 1, and 16 (4.3%) in group 2. Overall, the survival rate for revision surgery for any cause at 22 years was 88.0 % (95% CI, 82-94) in group 1 and 84.1% (95% CI, 69 – 99) in group 2 (p=0.019). Multivariate regression analysis showed that hips with conventional polyethylene (PE), compared with highly-cross linked PEs or ceramic-on-ceramic bearings, (p=0.01, Hazard Ratio (HR): 2.12, 95% CI 1.15-3.92), and cups outside the Lewinnek´s safe zone had a higher risk for revision surgery (p<0.001, HR: 2.57, 95% CI 1.69-3.91).

Modern highly-cross linked PEs and ceramic-on-ceramic bearings use, and a proper surgical technique improved revision rate in patients undergoing THA due to ON compared with OA.

Cannulated hip screws are frequently used in the management of hip fractures. There have been concerns over the failure rate of the technique and the outcomes of those that subsequently require conversion to total hip replacement (THR). This study utilised a database of over 600 cannulated hip screw (CHS) fixations performed over a 14-year period and followed up for a minimum of one year (1-14). We identified 57 cases where a conversion to THR took place (40 females, 17 males, mean age: 71.2 years). Patient demographics, original mechanism of injury, fracture classification, reason for fixation failure, time until arthroplasty, implant type and post-arthroplasty complications were recorded. Clinical outcomes were measured using the Oxford Hip Score. The failure rate of cannulated screw treatment was 9.4% and the mean time from initial fixation to arthroplasty was 15.4 (16.5) months. Thirty six fractures were initially undisplaced and 21 were displaced. As one might expect the displaced cases tended to be younger but this didn't reach statistical significance [66.5(14.3) vs 72.7(13.1), p=0.1]. The commonest causes of failure were non-union (25 cases, 44%) and avascular necrosis (17 cases, 30%). Complications after THR consisted of one leg length discrepancy and one peri-prosthetic fracture. The mean Oxford score pre-arthroplasty was 12.2 (8.4), improving to 38.4 (11.1) at one-year. Although the pre op Oxford scores tended to be lower in patients with undisplaced fractures and higher ASA scores, the improvement was the same whatever the pre-op situation. The one-year Oxford score and the improvement in score are comparable to those seen in the literature for THR in general. In conclusion, CHS has a high success rate and where salvage arthroplasty is required it can provide good clinical outcomes with low complication rates

Malalignment is often postulated as the main reason for the high failure rate of total ankle replacements (TARs). Only a few studies have been performed to correlate radiographic TAR malalignment to the clinical outcome, but no consistent trends between TAR alignment parameters and the clinical outcome were found. No standard TAR alignment measurement method is present, so reliable comparison between studies is difficult. Standardizing TAR alignment measurements and increasing measurable parameters on radiographs in the clinic might lead to a better insight into the correlation between malalignment and the clinical outcome. This study aims to develop and validate a tool to semi-automatic measure TAR alignment, and to improve alignment measurement on radiographs in the clinic. A tool to semi-automatically measure TAR alignment on anteroposterior and lateral radiographs was developed and used by two observers to measure TAR alignment parameters of ten patients. The Intraclass Coefficient (ICC) was calculated and accuracy was compared to the manual measurement method commonly used in the clinic. The tool showed an accuracy of 76% compared to 71% for the method used during follow-up in the clinic. ICC values were 0.94 (p<0.01) and higher for both inter-and intra-observer reliability. The tool presents an accurate, consistent, and reliable method to measure TAR alignment parameters. Three-dimensional alignment parameters are obtained from two-dimensional radiographs, and as the tool can be applied to any TAR design, it offers a valuable addition in the clinic and for research purposes

Miniscrew implants (MSIs) are widely used to provide absolute anchorage for the orthodontic treatment. However, the application of MSIs is limited by the relatively high failure rate (22.86%). In this study, we wished to investigate the effects of amorphous and crystalline biomimetic calcium phosphate coating on the surfaces of MSIs with or without the incorporated BSA for the osteointegration process with an aim to facilitate the early loading of MSIs. Amorphous and crystalline coatings were prepared on titanium mini-pin implants. Characterizations of coatings were examined by Scanning electron microscopy (SEM), Confocal laser-scanning dual-channel-fluorescence microscopy (CLSM) and Fourier-transform infrared spectroscopy (FTIR). The loading and release kinetics of bovine serum albumin (BSA) were evaluated by Enzyme linked immunosorbent assay (ELISA). Activity of alkaline phosphate (ALP) was measured by using the primary osteoblasts. In vivo, a model of metaphyseal tibial implantation in rats was used (n=6 rats per group). We had 6 different groups: no coating no BSA, no coating but with surface adsorption of BSA and incorporation of BSA in the biomimetic coating in the amorphous and crystalline coatings. Time points were 3 days, 1, 2 and 4 weeks. Histological and histomorphometric analysis were performed and the bone to implant contact (BIC) of each group was compared. In vitro, the incorporation of BSA changed the crystalline coating from sharp plates into curly plates, and the crystalline coating showed slow-release profile. The incorporation of BSA in crystalline coating significantly decreased the activity of ALP in vitro. In vivo study, the earliest significant increase of BIC appeared in crystalline coating group at one week. The crystalline coating can serve as a carrier and slow release system for the bioactive agent and accelerate osteoconductivity at early stage in vivo. The presence of BSA is not favorable for the early establishment of osteointegration

Fracture related infection remains a major challenge in musculoskeletal trauma surgery. Despite best practice, treatment strategies suffer from high failure rates due to antibiotic resistance and tolerance. Bacteriophages represent a promising alternative as they retain activity against such bacteria. However, optimal phage administration protocols remain unknown, although injectable hydrogels, loaded with phage and conventional antibiotics, may support conventional therapy. In this study we tested the activity of meropenem, and two newly isolated bacteriophages (ϕ9 and ϕ3) embedded within alginate-chitosan microbeads and a hydrogel. Antibiotic and phage stability and activity were monitored in vitro, over a period of 10 days. In vivo, the same material was tested in treatment of a 5-day old Pseudomonas aeruginosa infection of a tibial plate osteotomy in mice. Treatment involved debridement and 5 days of systemic antibiotic therapy plus: i- saline, ii-phages in saline, iii-phages and antibiotics loaded into a hydrogel (n=7 mice/group). To assess the efficacy of the treatments, the infection load was monitored during revision surgery with debridement of the infected tissue after 5,10 and 13 days (euthanasia) by CFU and PFU quantification. In vitro testing confirmed that the stability of meropenem and activity of ϕ9 and ϕ3, was not affected within the alginate beads or hydrogel over 10 days. The in vivo study showed that all mice receiving phages and antibiotics loaded into a hydrogel survived the infection with a reduction of the bacterial load in the soft tissue. Active phages could be recovered from the infected site at euthanasia (10. 4. PFU/g). The hydrogel loaded with bacteriophages and meropenem showed a positive result in locally reducing the infection load indicating a synergistic effect of the selected antimicrobials. Overall, our new strategy shows encouraging results for improving the treatment of antibiotic-resistant biofilm infections that are related to medical implants

Rotator cuff tears are common, with failure rates of up to 94% for large and massive tears. 1. For such tears, reattachment of the musculotendinous unit back to bone is problematic, and any possible tendon-bone repair heals through scar tissue rather than the specially adapted native enthesis. We aim to develop and characterise a novel soft-hard tissue connector device, specific to repairing/bridging the tendon-bone injury in significant rotator cuff tears, employing decellularised animal bone partially demineralised at one end for soft tissue continuation. Optimisation samples of 15×10×5mm. 3. , trialled as separate cancellous and cortical bone samples, were cut from porcine femoral condyles and shafts, respectively. Samples underwent 1-week progressive stepwise decellularisation and a partial demineralisation process of half wax embedding and acid bathing. Characterisations were performed histologically for the presence/absence of cellular staining in both peripheral and central tissue areas (n=3 for each cortical/cancellous, test/PBS control and peripheral/central group), and with BioDent reference point indentation (RPI) for pre- and post-processing mechanical properties. Histology revealed absent cellular staining in peripheral and central cancellous samples, whilst reduced in cortical samples compared to controls. Cancellous samples decreased in wet mass after decellularisation by 45.3% (p<0.001). RPI measurements associated with toughness (total indentation depth, indentation depth increase) and elasticity (1st cycle unloading slope) showed no consistent changes after decellularisation. X-rays confirmed half wax embedding provided predictable control of the mineralised-demineralised interface position. Initial optimisation trials show proof-of-concept of a soft-hard hybrid scaffold as an immune compatible xenograft for irreparable rotator cuff tears. Decellularisation did not appreciably affect mechanical properties, and further biological, structural and chemical characterisations are underway to assess validity before in vivo animal trials and potential clinical translation

An increasingly used treatment for end-stage ankle osteoarthritis is total ankle replacement (TAR). However, implant loosening and subsidence are commonly reported complications, leading to relatively high TAR failure rates. Malalignment of the TAR has often been postulated as the main reason for the high incidence of these complications. It remains unclear to what extent malalignment of the TAR affects the stresses at the bone-implant interface. Therefore, this study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure. FE models of the neutrally aligned as well as malaligned CCI Evolution TAR implant (Van Straten Medical) were developed. Separate models were developed for the tibial and talar segment, with the TAR components in neutral alignment and 5° and 10° varus, valgus, anterior and posterior malalignment, resulting in a total of 9 differently aligned TAR models. Loading conditions of the terminal stance phase of the gait cycle, when the force on the ankle joint is highest (5.2x body weight), were applied. Peak and mean contact pressure and shear stress at the bone-implant interface were analyzed. Also, stress distributions on the bone-implant interface were visualized. In the neutrally aligned tibial and talar TAR models, peak contact pressures of respectively 98.4 MPa and 68.2 MPa, and shear stresses of respectively 49.3 MPa and 39.0 MPa were found. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. A maximum peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component and the highest shear stress found was 98.5 MPa for the 10° posterior malaligned talar model. Upon TAR malalignment contact stresses increase substantially, suggesting that proper orientation of the TAR is needed to minimize peak stresses on the bone-implant interface. This is in line with previous studies, which state that malalignment considerably increases bone strains, micromotion, and internal TAR contact pressures, which might increase the risk of TAR failure. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure

Orthopedic device-related bone infection is one of the most distressing complications of the surgical fixation of fractures. Despite best practice in medical and surgical interventions, the rate of infection remains stubbornly persistent, and current estimates indicate that treatment failure rates are also significant. As we approach the limit of the effectiveness of current anti-infective preventative and therapeutic strategies, novel approaches to infection management assume great importance. This presentation will describe our efforts to develop and test various hydrogels to serve as customized antibiotic delivery vehicles for infection prevention and treatment. Hydrogels offer solutions for many of the challenges faced by complex trauma wounds as they are not restricted spatially within a poorly defined surgical field, they often degrade rapidly with no compatibility issues, and releases 100% of the loaded antibiotic. The preliminary data set proving efficacy in preventing and treating infection in both rabbit and sheep studies will be described, including local antibiotic concentrations in the intramedullary canal over time, compared to that of the more conventional antibiotic loaded bone cement. These two technologies show potential for the prevention and treatment of infection in trauma patients, with a clear focus on optimized antibiotic delivery tailored for complex wounds

Abstract. Objectives. Tendon and ligament injury poses an increasingly large burden to society. With surgical repair and grafting susceptible to high failure rates, tissue engineering provides novel avenues for treatment. This systematic review explores in vivo evidence whether mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) can facilitate tendon and ligament repair in animal models. Methods. On May 26th 2021, a systematic search was performed on PubMed, Web of Science, Cochrane Library, Embase, using search terms ‘mesenchymal stem cell’ or ‘multipotent stem cell’ AND ‘extracellular vesicles’ or ‘exosomes’ AND ‘tendon’ or ‘ligament’ or ‘connective tissue’. Risk of bias was assessed using SYstematic Review Center for Laboratory animal Experimentation (SYRCLE) tool. Studies administering EVs isolated from human or animal-derived MSCs into in vivo models of tendon/ligament injury were included. In vitro, ex vivo, in silico studies were excluded, and studies without a control group were excluded. Data on isolation and characterisation of MSCs and EVs, and in vivo findings in animal models were extracted. Results. Out of 383 relevant studies, 11 case-control studies were included for data extraction, including a total of 448 animal subjects (range 10–90). Six studies utilised bone marrow-derived MSCs. All studies characterised their MSCs via flow cytometry, which expressed CD44 and CD90, and isolated EVs via ultracentrifugation (average diameter 125nm). Five studies utilised histological scoring systems, all of which reported a lower score with EV treatment, suggesting improved healing ability. Four studies reported increased anti-inflammatory cytokine expression (IL-10, TGF-β1); three studies reported decreased endogenous M1/M2 macrophage ratio with EV treatment. Eight studies reported increased maximum stiffness, breaking load, tensile strength in EV-treated tendons. Conclusion. MSC-EVs are effective therapeutic agents for tendon/ligament pathologies, attenuating the initial inflammatory response, and accelerating tendon matrix regeneration. Future randomised controlled trials are needed to definitely demonstrate MSC-EVs superiority in management of tendon/ligament injury

Proximal humerus fractures (PHF) are the third most common fractures in the elderly. Treatment of complex PHF has remained challenging with mechanical failure rates ranging up to 35% even when state-of-the-art locked plates are used. Secondary (post-operative) screw perforation through the articular surface of the humeral head is the most frequent mechanical failure mode, with rates up to 23%. Besides other known risk factors, such as non-anatomical reduction and lack of medial cortical support, in-adverse intraoperative perforation of the articular surfaces during pilot hole drilling (overdrilling) may increase the risk of secondary screw perforation. Overdrilling often occurs during surgical treatment of osteoporotic PHF due to minimal tactile feedback; however, the awareness in the surgical community is low and the consequences on the fixation stability have remained unproved. Therefore, the aim of this study was to evaluate biomechanically whether overdrilling would increase the risk of cyclic screw perforation failure in unstable PHF. A highly unstable malreduced 3-part fracture was simulated by osteotomizing 9 pairs of fresh-frozen human cadaveric proximal humeri from elderly donors (73.7 ± 13.0 ys, f/m: 3/6). The fragments were fixed with a locking plate (PHILOS, DePuy Synthes, Switzerland) using six proximal screws, with their lengths selected to ensure 6 mm tip-to-joint distance. The pairs were randomized into two treatment groups, one with all pilot holes accurately predrilled (APD) and another one with the boreholes of the two calcar screws overdrilled (COD). The constructs were tested under progressively increasing cyclic loading to failure at 4 Hz using a previously developed setup and protocol. Starting from 50 N, the peak load was increased by 0.05 N/cycle. The event of initial screw loosening was defined by the abrupt increase of the displacement at valley load, following its initial linear behavior. Perforation failure was defined by the first screw penetrating the joint surface, touching the artificial glenoid component and stopping the test via electrical contact. Bone mineral density (range: 63.8 – 196.2 mgHA/cm3) was not significantly different between the groups. Initial screw loosening occurred at a significantly lower number of cycles in the COD group (10,310 ± 3,575) compared to the APD group (12,409 ± 4,569), p = 0.006. Number of cycles to screw perforation was significantly lower for the COD versus APD specimens (20,173 ± 5,851 and 24,311 ± 6,318, respectively), p = 0.019. Failure mode was varus collapse combined with lateral-inferior translation of the humeral head. The first screw perforating the articular surface was one of the calcar screws in all but one specimen. Besides risk factors such as fracture complexity and osteoporosis, inadequate surgical technique is a crucial contributor to high failure rates in locked plating of complex PHF. This study shows for the first time that overdrilling of pilot holes can significantly increase the risk of secondary screw perforation. Study limitations include the fracture model and loading method. While the findings require clinical corroboration, raising the awareness of the surgical community towards this largely neglected risk source, together with development of devices to avoid overdrilling, are expected to help improve the treatment outcomes

Introduction and Objective. Hip fractures represent one of the most challenging injuries in orthopaedic practice due to the associated morbidity, mortality and the financial burden they impose on the health care systems. By many still considered as the gold standard in the management of intertrochanteric fractures, the Dynamic Hip Screw utilizes controlled collapse during weight bearing to stabilize the fracture. Despite being a highly successful device, mechanical failure rate is not uncommon. The most accepted intraoperative indicator for lag screw failure is the tip apex distance (TAD), yet lateral femoral wall thickness (LWT) is another evolving parameter for detecting the potential for lateral wall fracture with subsequent medialization and implant failure. The aim of this study is to determine the mean and cut off levels for LWT that warrant lateral wall fracture and the implications of that on implant failure, revision rates and implant choice. Materials and Methods. This prospective cohort study included 42 patients with a mean age of 70.43y with intertrochanteric hip fractures treated with DHS fixation by the same consultant surgeon from April 2019 to December 2019. The study sample was calculated based on a confidence level of 90% and margin of error of 5%. Fracture types included in the study are 31A1 and 31A2 based on the AO/OTA classification system. LWT was assessed in all patients preoperatively using Surgimap (Nemaris, NY, USA) software. Patients were divided into two groups according to the post-operative integrity of the lateral femoral wall, where group (A) sustained a lateral femoral wall fracture intraoperatively or within 12 months after the index procedure, while in group (B) the lateral femoral wall remained intact. All patients were regularly followed up radiologically and clinically per the Harris Hip Score (HHS) for a period of 12 months. Results. At 12 months five patients (12%) suffered a postoperative lateral wall fracture, while in 37 patients (88%) the lateral femoral wall remained intact. The mean preoperative LWT of patients with a postoperative lateral wall fracture was 18.04 mm (SD ± 1.58) compared to 26.22mm (SD ± 5.93) in the group without a lateral wall fracture. All patients with post-operative lateral femoral wall fracture belong to 31A2 group, while 78.4% of the patients that did not develop post-operative lateral femoral wall fracture belong to 31A1 group. Eighty percent of patients in group (A) experienced shortening, collapse, shaft medialization and varus deformity. The mean Harris hip score of group (A) was 39.60 at 3 months and 65.67 at 6 months postoperatively, while that of group (B) was 80.75 and 90.65 at 3 and 6 months respectively, denoting a statistically significant difference (P<0.001). Treatment failure meriting a revision surgery was 40 % in group (A) and 8% in group (B) denoting a statistically significant difference (p<0.001). The cut-off point of LWT below which there is a high chance of post-operative lateral wall fracture when fixed with DHS is 19.6mm. This was shown on the receiver operating curve (ROC) by plotting the sensitivity against the 100 % specificity with a set 95% confidence interval 0.721 – 0.954. When lateral wall thickness was at 19.6 mm, the sensitivity was 100% and specificity was 81.8%. The area under the curve (AUC) was 0.838, which was statistically significant (P = 0.015). Conclusions. Preoperative measurement of LWT in elderly patients with intertrochanteric hip fractures is decisive. The cut off point for postoperative lateral wall fracture according to our study is 19.6 mm; hence, intramedullary fixation has to be considered in this situation

Introduction. Pediatric femoral fracture including supracondylar and subtrochantric fracture constitutes 1.6% of all pediatrics fractures. 1. Elastic nails remain the standard treatment of choice in mid shaft transverse femoral fracture in children weighting less than 45kg. 2. But in subtrochantric and spiral femoral fracture, failure rate of TENS nails are quite high. 3. . Material and methods. We retrospectively reviewed 30 subtrochantric fracture in children (average age 9 years) treated with bridge plate by mini invasive approach. Result. All fracture united well in average 14 weeks. Single complication was 5mm limb lengthening due to fixation in traction on fracture table in one case. We strongly recommend bridge plate in complex femoral fracture in children

To date, the fixation of proximal humeral fractures with angular stable locking plates is still insufficient with mechanical failure rates of 18% to 35%. The PHILOS plate (DePuy Synthes, Switzerland) is one of the most used implants. However, this plate has not been demonstrated to be optimal; the closely symmetric plate design and the largely heterogeneous bone mineral density (BMD) distribution of the humeral head suggest that the primary implant stability may be improved by optimizing the screw orientations. Finite element (FE) analysis allows testing of various implant configurations repeatedly to find the optimal design. The aim of this study was to evaluate whether computational optimization of the orientation of the PHILOS plate locking screws using a validated FE methodology can improve the predicted primary implant stability. The FE models of nineteen low-density (humeral head BMD range: 73.5 – 139.5 mg/cm3) left proximal humeri of 10 male and 9 female elderly donors (mean ± SD age: 83 ± 8.8 years) were created from high-resolution peripheral computer tomography images (XtremeCT, Scanco Medical, Switzerland), using a previously developed and validated computational osteosynthesis framework. To simulate an unstable mal-reduced 3-part fracture (AO/OTA 11-B3.2), the samples were virtually osteotomized and fixed with the PHILOS plate, using six proximal screws (rows A, B and E) according to the surgical guide. Three physiological loading modes with forces taken from musculoskeletal models (AnyBody, AnyBody Technology A/S, Denmark) were applied. The FE analyses were performed with Abaqus/Standard (Simulia, USA). The average principal compressive strain was evaluated in cylindrical bone regions around the screw tips; since this parameter was shown to be correlated with the experimental number of cycles to screw cut-out failure (R2 = 0.90). In a parametric analysis, the orientation of each of the six proximal screws was varied by steps of 5 in a 5×5 grid, while keeping the screw head positions constant. Unfeasible configurations were discarded. 5280 simulations were performed by repeating the procedure for each sample and loading case. The best screw configuration was defined as the one achieving the largest overall reduction in peri-screw bone strain in comparison with the PHILOS plate. With the final optimized configuration, the angle of each screw could be improved, exhibiting significantly smaller average bone strain around the screw tips (range of reduction: 0.4% – 38.3%, mean ± SD: 18.49% ± 9.56%). The used simulation approach may help to improve the fixation of complex proximal humerus fractures, especially for the target populations of patients at high risk of failure

Surgical treatment of fragility sacrum fractures with percutaneous sacroiliac (SI) screw fixation is associated with high failure rates in terms of screw loosening, cut-through and turn-out. The latter is a common cause for complications, being detected in up to 20% of the patients. The aim of this study was to develop a new screw-in-screw concept and prototype implant for fragility sacrum fracture fixation and test it biomechanically versus transsacral and SI screw fixations. Twenty-seven artificial pelves with discontinued symphysis and a vertical osteotomy in zone 1 after Denis were assigned to three groups (n = 9) for implantation of their right sites with either an SI screw, the new screw-in-screw implant, or a transsacral screw. All specimens were biomechanically tested to failure in upright position with the right ilium constrained. Validated setup and test protocol were used for complex axial and torsional loading, applied through the S1 vertebral body. Interfragmentary movements were captured via optical motion tracking. Screw motions in the bone were evaluated by means of triggered anteroposterior X-rays. Interfragmentary movements and implant motions in terms of pull-out, cut-through, tilt, and turn-out were significantly higher for SI screw fixation compared to both transsacral screw and screw-in-screw fixations. In addition, transsacral screw and screw-in-screw fixations revealed similar construct stability. Moreover, screw-in-screw fixation successfully prevented turn-out of the implant, that remained at 0° rotation around the nominal screw axis unexceptionally during testing. From biomechanical perspective, fragility sacrum fracture fixation with the new screw-in-screw implant prototype provides higher stability than with the use of one SI screw, being able to successfully prevent turn-out. Moreover, it combines the higher stability of transsacral screw fixation with the less risky operational procedure of SI screw fixation and can be considered as their alternative treatment option

Osteoarthritis (OA) is a progressive and degenerative joint disease resulting in changes to articular cartilage. In focal early OA defects, autologous chondrocyte implantation (ACI) has a 2-fold failure rate due to poor graft integration and presence of inflammatory factors (e.g. Interleukin-1β). Bone marrow derived mesenchymal stem cells (MSCs) are an alternative cell source for cell-based treatments due to their chondrogenic capacity, though in vivo implantation leads to bone formation. In vivo, chondrocytes reside under an oxygen tension between 2–7% oxygen or physioxia. Physioxia enhances MSC chondrogenesis with reduced hypertrophic marker (collagen X and MMP13) expression compared to hyperoxic conditions (20% oxygen). This study sought to understand whether implantation of physioxic preconditioned MSCs improves cartilage regeneration in an early OA defect model compared to hyperoxic MSCs. Bone marrow extracted from New Zealand white rabbits (male: 5–6 months old; n = 6) was split equally for expansion under 2% (physioxia) or 20% (hyperoxia) oxygen. Chondrogenic pellets (2 × 105 cells/pellet) formed at passage 1 were cultured in the presence of TGF-β1 under their expansion conditions and measured for their wet weight and GAG content after 21 days. During bone marrow extraction, a dental drill (2.5mm diameter) was applied to medial femoral condyle on both the right and left knee and left untreated for 6 weeks. Following this period, physioxia and hyperoxia preconditioned MSCs were seeded into a hyaluronic acid (TETEC) hydrogel. Fibrous tissue was scraped and then MSC-hydrogel was injected into the right (hyperoxic MSCs) and left (physioxia MSCs) knee. Additional control rabbits with drilled defects had fibrous tissue scrapped and then left untreated without MSC-hydrogel treatment for the duration of the experiment. Rabbits were sacrificed at 6 (n = 3) and 12 (n = 3) weeks post-treatment, condyles harvested, decalcified in 10% EDTA and sectioned using a cryostat. Region of interest was identified; sections stained with Safranin-O/Fast green and evaluated for cartilage regeneration using the Sellers scoring system by three blinded observers. Physioxic culture of rabbit MSCs showed significantly shorter doubling time and greater cell numbers compared to hyperoxic culture (∗p < 0.05). Furthermore, physioxia enhanced MSC chondrogenesis via significant increases in pellet wet weight and GAG content (∗p < 0.05). Implantation of physioxic preconditioned MSCs showed significantly improved cartilage regeneration (Mean Sellers score = 7 ± 3; ∗p < 0.05) compared to hyperoxic MSCs (Sellers score = 12 ± 2) and empty defects (Sellers score = 17 ± 3). Physioxia enhances in vitro rabbit MSC chondrogenesis. Subsequent in vivo implantation of physioxia preconditioned MSCs improved cartilage regeneration in an early OA defect model compared to hyperoxic MSCs. Future studies will investigate the mechanisms for enhanced in vivo regeneration using physioxia preconditioned MSCs

Background. Intracapsular neck of femur fractures are one of the most common injuries seen in Orthopaedics. When the fracture is amenable to internal fixation there are 2 main treatment options, namely multiple cannulated hip screws (MCS) and 2-hole sliding hip screws (SHS). In this retrospective study we examine the outcomes associated with these two methods of internal fixation. At present there is little consensus regarding which treatment should be used. Methods. 161 patients were found to have suffered intracapsular neck of femur fracture treated with either SHS or MCS fixation over a 5 year period from April 2009 to April 2014, allowing at least 1 year follow up following injury. The patients imaging and clinical notes were then reviewed to ascertain the outcome of their treatment and any complications. Results. 93 patients were treated with a sliding hip screw compared to 68 that had been treated with cannulated screws. To ensure the fractures in each group were comparable in terms of fracture severity they were classified using gardens and pauwels score. The mean age of the group treated with SHS was 75.15 years, 7.69 years higher than those treated with MCS. The mean length of inpatient stay was 4.7 days longer for patients treated with sliding hip screws than those treated with cannulated screws, which is significantly more than would be predicted by age difference alone. Further patients were excluded for analysis of failure rate if they had not been sufficiently followed up, leaving 122 patients, 58 treated with MCS and 64 with SHS. A significantly higher (p=0.0136) proportion of patients treated with SHS (32%) suffered failure of their fixation compared to those treated with MCS (10%). The SHS group was further classified by whether or not a permanent derotation screw was employed. The use of a derotation screw provided protection against failure with a number needed to treat of 3.82, decreasing the failure rate to 14% which was not significantly more than the failure rate for MCS. Conclusions. We recommend that the first choice treatment for intracapsular neck of femur fractures amenable to internal fixation should be cannulated screws due to a lower rate of failure and shorter length of inpatient stay. If a surgeon has a strong preference for sliding hip screw we strongly recommend inserting a permanent derotation screw

Proximal humerus fractures are the third most common fragility fractures with treatment remaining challenging. Mechanical fixation failure rates of locked plating range up to 35%, with 80% of them being related to the screws perforating the glenohumeral joint. Secondary screw perforation is a complex and not yet fully understood process. Biomechanical testing and finite element (FE) analysis are expected to help understand the importance of various risk factors. Validated FE simulations could be used to predict perforation risk. This study aimed to (1) develop an experimental model for single screw perforation in the humeral head and (2) evaluate and compare the ability of bone density measures and FE simulations to predict the experimental findings. Screw perforation was investigated experimentally via quasi-static ramped compression testing of 20 cuboidal bone specimens at 1 mm/min. They were harvested from four fresh-frozen human cadaveric proximal humeri of elderly donors (aged 85 ± 5 years, f/m: 2/2), surrounded with cylindrical embedding and implanted with a single 3.5 mm locking screw (DePuy Synthes, Switzerland) centrally. Specimen-specific linear µFE (ParOSol, ETH Zurich) and nonlinear explicit µFE (Abaqus, SIMULIA, USA) models were generated at 38 µm and 76 µm voxel sizes, respectively, from pre- and post-implantation micro-Computed Tomography (µCT) images (vivaCT40, Scanco Medical, Switzerland). Bone volume (BV) around the screw and in front of the screw tip, and tip-to-joint distance (TJD) were evaluated on the µCT images. The µFE models and BV were used to predict the experimental force at the initial screw loosening and the maximum force until perforation. Initial screw loosening, indicated by the first peak of the load-displacement curve, occurred at a load of 64.7 ± 69.8 N (range: 10.2 – 298.8 N) and was best predicted by the linear µFE (R. 2. = 0.90), followed by BV around the screw (R. 2. = 0.87). Maximum load was 207.6 ± 107.7 N (range: 90.1 – 507.6 N) and the nonlinear µFE provided the best prediction (R. 2. = 0.93), followed by BV in front of the screw tip (R. 2. = 0.89). Further, the nonlinear µFE could better predict screw displacement at maximum force (R. 2. = 0.77) than TJD (R. 2. = 0.70). The predictions of non-linear µFE were quantitatively correct. Our results indicate that while density-based measures strongly correlate with screw perforation force, the predictions by the nonlinear explicit µFE models were even better and, most importantly, quantitatively correct. These models have high potential to be utilized for simulation of more realistic fixations involving multiple screws under various loading cases. Towards clinical applications, future studies should investigate if explicit FE models based on clinically available CT images could provide similar prediction accuracies

Aims

This study intended to investigate the effect of vericiguat (VIT) on titanium rod osseointegration in aged rats with iron overload, and also explore the role of VIT in osteoblast and osteoclast differentiation.