Abstract

A hot swollen joint is a commonly encountered condition in clinical practice. With a broad range of differentials, septic arthritis (SA) is perhaps one of the most concerning. Treated by culture-specific antibiotics and arthroscopic lavage, some patients require multiple washouts. We aimed to determine:

(1) What are the risk factors for development of SA?

(2) What are the risk factors for repeat washout in SA patients?

(3) What are the important clinical differences between a periprosthetic joint infection (PJI) and SA cohort?

All patients presenting to the emergency department, orthopaedic, and rheumatology clinics between January 2020 to January 2021 with a hot, swollen joint were retrospectively evaluated. Patients with previous trauma on the ipsilateral joint, with data missing from their medical records in any of the variables required for analysis, <24 months follow-up were excluded.

Variables of interest in the three-month period preceding the diagnosis of SA were compared between SA and non-SA patients. Factors with a p-value of p<0.100 in univariate analysis were included in a stepwise multivariate logistic regression model. Similar analyses were performed to compare SA patients with multiple washouts with those needing one washout. Demographical and clinical data for PJI patients were collected to delineate important differences with SA cohort.

211 patients were included (SA:28;PJI:24;pseudogout:32;gout:26;others:101). Multivariate analysis showed rheumatoid arthritis (RA), skin infection, and liver disease were risk factors for SA. Amongst patients with septic arthritis, multivariate analysis showed that WBC levels above normal limits (3.6-10.5×109 cells/L) and RA were risk factors for multiple washouts.

Between the SA and PJI cohorts, BMI (p=0.002) was significantly lower in the former, whilst WBC level (p=0.023) and CRP (p<0.0001) was significantly higher in the former.

Early diagnosis of septic arthritis requires understanding the risk factors, namely RA, skin infection, and liver disease. Considering PJI and septic arthritis as the same entity can lead to wrong clinical judgement, and clinicians should be aware of important differences. We believe that the models in this study are of prognostic value to clinicians who are presented with the common presenting compliant of a hot swollen joint.

In this study, we aimed to investigate tibiofemoral and allograft loading parameters after OCA transplantation using tibial plateau shell grafts to characterize the clinically relevant biomechanics that may influence joint kinematics and OCA osseointegration after transplantation. The study was designed to test the hypothesis that there are significant changes in joint loading after tibial plateau OCA transplantation that may require unique post-operative rehabilitation regimens in patients to restore balance in the knee joint.

Fresh-frozen cadaveric knees (n=6) were thawed and mounted onto a 6 DOF KUKA robot. Specimens were size matched to +2 mm for the medial-to-lateral width of the medial tibial hemiplateaus. Three specimens served as allograft recipient knees and three served as donor knees. Recipient knees were first tested in their native state and then tested with size-matched medial tibial hemiplateau shell grafts (n=3) prepared from the donor knees using custom-cut tab-in-slot and subchondral drilling techniques. Tekscan sensors were placed in the joint spaces to evaluate the loading conditions under 90N biaxial loading at full extension of the knee before and after graft placement. The I-Scan system used in conjunction analyzed the total force, pressure distribution, peak pressure, and center of force within the joint space.

Data demonstrated significant difference (p<0.05) in joint space loading after graft implantation compared to controls in both lateral and medial tibial plateaus. The I-Scan pressure mapping system displayed changes in femoral condylar contact points as well.

The results demonstrated that joint space loading was significantly different (p<0.05) between all preoperative and postoperative cadaveric specimens. Despite the best efforts to size match grafts, slight differences in the host's joint geometry resulted in shifts of contact areas between the tibial plateau and femoral condyle therefore causing either an increase or decrease in pressure measured by the sensor. This concludes that accuracy in graft size matching is extremely important to restoring close to normal loading across the joint and this can be further ensured through postoperative care customized to the patient after OCA surgery.

To analyze the effect of tooth extraction site preservation on bone mineral density 6 months after surgery.

From 2020 to 2021, two adjacent teeth (37, 38) of the same patient were extracted at the same time, and then 37 were selected for site preservation, implanted with Bio-oss bone powder, covered with double Bio-gide membrane, reduce tension and sutured. After 6 months of self-healing, 38 was taken CBCT, and the gray value measurement tool in the software was used to measure the bone mineral density of 37 bone graft areas and 38 extraction sockets.

Bone density was high in the center of the bone graft area after the extraction site, and the density decreased in the adjacent alveolar socket, but the gray value was still higher than 38 for natural healing.

Extraction site surgery can improve bone mass and quality at the extraction site. It is good for implanting.

Australian Football (AF) is a popular sport in Australia, with females now representing one-third of participants. Despite this, the injury profiles of females versus males in largely unknown. The current study investigated fractures, dislocations and tendon ruptures in females versus males presenting to emergency departments (ED) with an AF injury.

All patients, regardless of age, presenting to one of 10 EDs in Victoria, Australia, with an AF injury were included. Data were prospectively collected over a 10-month period, coinciding with a complete AF season. Data were extracted from patient medical records regarding injury-type, body-part injured and treatments required. Female and male data were compared with chi-squared tests.

Of the 1635 patients presenting with an AF injury, 595 (36.0%) had a fracture, dislocation or tendon rupture, of whom 85 (14.3%) were female and the average age was 20.5 years (SD 8.0). Fractures accounted for most injuries (n=478, 80.3% of patients had a fracture), followed by dislocations (n=118, 19.8%) and tendon ruptures (n=14, 2.4%). Upper limb fractures were more common than lower limb fractures (71.1% v 11.5% of fractures). Females were more likely to fracture their hands or fingers than males (45.7% v 34.3%). Males were more likely to fracture ribs (5.4% v 0%). Most fractures (91.2%) were managed in the ED, with the remainder being admitted for surgery (GAMP/ORIF). Males were more likely to be admitted for surgery than females (11.2% v 5.9%). Regarding dislocations (n=118), females were more likely to dislocate the patella (36.8% v 8.1% of dislocations). Only males sustained a tendon rupture (n=14): finger extensor or flexor (57.1%), achilles tendon (28.6%) and patella tendon (14.3%).

Orthopaedic AF injuries are common presentations to EDs in Victoria, though few require specialist orthopaedic intervention. Injury profiles differed between genders suggesting that gender specific injury prevention and management might be required.

For clinical movement analysis, optical marker-based motion capture is the gold standard.

With the advancement of AI-driven computer vision, markerless motion capture (MMC) has emerged. Validity against the marker-based standard has only been examined for lightly-dressed subjects as required for marker placement. This pilot study investigates how different clothing affects the measurement of typical gait metrics.

Gait tests at self-selected speed (4 km/h) were performed on a treadmill (Motek Grail), captured by 9 cameras (Qualisys Miqus, 720p, f=100Hz) and analyzed by a leading MMC application (Theia, Canada). A healthy subject (female, h=164cm, m=54kg) donned clothes between trials starting from lightly dressed (LD: bicycle tight, short-sleeved shirt), adding a short skirt (SS: hip occlusion) or a midi-skirt (MS: partial knee occlusion) or street wear (SW: jeans covering ankle, long-sleeved blouse), the lattern combined with a short jacket (SWJ) or a long coat (SWC). Gait parameters (mean±SD, t=10s) calculated (left leg, mid-stance) were ankle pronation (AP-M), knee flexion (KF-M), pelvic obliquity (PO-M) and trunk lateral lean (TL-M) representing clinically common metrics, different joints and anatomic planes. Four repetitions of the base style (LD) were compared to states of increased garment coverage using the t-test (Bonferroni correction).

For most gait metrics, differences between the light dress (LD) and various clothing styles were absent (p>0.0175), small (< 2SD) or below the minimal clinically important differences (MCID). For instance, KF-M was for LD=10.5°±1.7 versus MD=12.0°±0.5 (p=0.07) despite partial knee cover. AP-M measured for LD=5.2°±0.6 versus SW=4.1°±0.7 (p<0.01) despite ankle cover-up. The difference for KF-M between LD=10.5°±1.7 versus SWL=6.0°±0.9, SW and SWJ (7.6°±1.5, p<0.01) indicates more intra-subject gait variability than clothing effect.

This study suggests that typical clothings styles only have a small clinically possibly negligible effect on common gait parameters measured with MMC. Thus, patients may not need to change clothes or be instructed to wear specific garments. In addition to avoiding marker placement, this further increases speed, ease and economy of clinical gait analysis with MMC facilitating high volume or routine application.

The prevalence of gluteal tendinopathy (GT) associated with osteoarthritis of the hip is difficult to determine as it is frequently undiagnosed or misdiagnosed as trochanteric bursitis. Its relationship to total hip arthroplasty (THA) outcomes is currently unknown. The aim of this study was to determine the incidence of GT at the time of hip arthroplasty and examine the relationship between GT and patient reported outcomes (PROMS) before and after THA.

Patients undergoing THA for primary osteoarthritis between August 2017 and August 2020 were recruited. Tendinopathy was assessed and graded at time of surgery. PROMS included the Oxford Hip Score (OHS), HOOS JR, EQ-5D, and were collected preoperatively and at one year after THA. Satisfaction with surgery was also assessed at 1 year.

797 patients met eligibility criteria and were graded as Grade 1: normal tendons (n =496, 62%), Grade 2: gluteal tendinopathy but no tear (n=222, 28%), Grade 3: partial/full thickness tears or bare trochanter (n=79, 10%). Patients with abnormal gluteal tendons were older (p=0.001), had a higher mean BMI (p=0.01), and were predominately female (p=0.001). Patients with higher grade tendinopathy had statistically significant inferior PROMS at one year, OHS score (44.1 v 42.9 v 41.3, p 0.001) HOOS JR (89.3 V 86.3 V 85.6 p 0.005). Increasing gluteal tendon grade was associated with a greater incidence of problems with mobility (p=0.001), usual activities (p=0.001) and pain (p=0.021) on EQ5D. There was a 3 times relative risk of overall dissatisfaction with THA in the presence of gluteal tears.

This study demonstrated that gluteal tendinopathy was commonly observed and associated with inferior 1-year PROMS in patients undergoing THA for OA. Increasing degree of tendinopathy was a negative prognostic factor for worse functional outcomes and patient satisfaction.

Common tendon injuries impair healing, leading to debilitation and an increased re-rupture risk. The impact of oxygen-sensing pathways on repair mechanisms, vital in regulating inflammation and fibrosis, remains unclear despite their relevance in tendon pathologies. Recent studies show that pulsed electromagnetic field (PEMF) reduce inflammation in human tendon cells (hTDCs) and in hypoxia-induced inflammation. We investigated the hypoxia's impact (1% and 2% oxygen tension) using magnetic cell sheet constructs (IL-1β-magCSs) primed with IL-1β. IL-1β-magCSs were exposed to low OT (1h, 4h,6h) in a hypoxic chamber. To confirm the role of PEMF (5Hz, 4mT, 50% duty cycle) on hypoxia modulation, IL-1β-magCSs, previously exposed to OT, were 1h-stimulated with PEMF. Our results show a significant increase in HIF- 1a and HIF-2a expression on IL-1β-magCSs after exposure to 2%-OT at all time points, compared to 1%- OT and normoxia. TNFa, IL-6, and IL-8 expression increased after 6 hours of 1%-OT exposure. PEMF stimulation of hypoxic IL-1β-magCSs led to decreased pro-inflammatory genes and increased anti-inflammatory (IL-4,IL-10) expression compared to unstimulated magCSs. IFN-g, TNF-α, and IL-6 release increased after 6 hours, regardless of %-OT, while IL-10 levels tended to rise after PEMF stimulation at 2%-OT. Also, NFkB expression was increased on IL-1β-magCSs exposed to 4 h and 6 h of 2%-OT, suggesting a link between NFkB and the production of pro-inflammatory factors. Moreover, PEMF stimulation showed a significantly decreased NFkB level in IL-1β-magCSs.

Overall, low OT enhances expression of hypoxia-associated genes and inflammatory markers in IL-1β-magCSs with the involvement of NFkB. PEMF modulates the response of magCSs, previously conditioned to hypoxia and to inflammatory triggers, favouring expression of anti-inflammatory genes and proteins, supporting PEMF impact in pro-regenerative tendon strategies.

Acknowledgements: ERC CoG MagTendon(No.772817), FCT under the Scientific Employment Stimulus-2020.01157.CEECIND. Thanks to Hospital da Prelada for providing tendon tissue samples (Portugal), and TERM

RES Hub (Norte-01-0145-FEDER-022190).

Early identification of patients at risk for impaired tendon healing and corresponding novel therapeutic approaches are urgent medical needs. This study aimed to clarify the role of CD3+ T-cells during acute Achilles tendon (AT) healing. Blood and hematoma aspirate were taken from 26 patients during AT reconstruction, and additional blood samples were obtained during clinical follow-up at 6, 26 and 52 weeks after surgery. T-cell subsets were analyzed by flow cytometry using CD3, CD4, CD8, CD11a, CD57 and CD28 antibodies. Clinical follow-up included functional tests, MRI assessments, and subjective questionnaires. In vitro, the functional behavior of patient-derived tenocytes was investigated in co-cultures with autologous unpolarized CD4+ or CD8+ T-cells, or IFNy-polarized CD8+ or IL17-polarized CD4+ Tcells (n=5-6). This included alterations in gene expression (qPCR), MMP secretion (ELISA), migration rate (scratch wound healing assay) or contractility (collagen gels). Analysis revealed that elevated CD4+ T-cell levels and reduced CD8+ T-cell levels (increased CD4/CD8 ratio) in hematoma aspirate and pre-operative blood were associated with inferior clinical outcomes regarding pain and function at 26 and 52 weeks. Increased levels of CD8+ -memory T-cell subpopulations in blood 6 weeks after surgery were associated with less tendon elongation. In vitro, tenocytes showed increased MMP1/2/3 levels and collagen III/I ratio in co-culture with unpolarized and/or IL17-polarized CD4+ T-cells compared to unpolarized CD8+ T-cells. This coincided with increased IL17 receptor expression in tenocytes co-cultured with CD4+ T-cells. Exposure of tenocytes to IL17-polarized CD4+ T-cells decreased their migration rate and increased their matrix contractility, especially compared to IFNy-polarized CD8+ T-cells. The CD4+ /CD8+ T-cell ratio could serve as prognostic marker for early identification of patients with impaired AT healing potential. Local reduction of CD4+ T-cell levels or their IL17 secretion represent a potential therapeutic approach to improve AT healing and to prevent weakening of the tendon ECM.

Energy storing tendons such as the human Achilles and equine superficial digital flexor tendon (SDFT) are prone to age-related injury. Tendons have poor healing capacity and a lack of effective treatments can lead to ongoing pain, reduced function and re-injury. It is therefore important to identify the mechanisms underpinning age-related tendinous changes in order to develop more effective treatments. Our recent single cell sequencing data has shown that tendon cell populations have extensive heterogeneity and cells housed in the tendon interfascicular matrix (IFM) are preferentially affected by ageing. There is, however, a lack of established surface markers for cell populations in tendon, limiting the capacity to isolate distinct cell populations and study their contribution to age-related tendon degeneration. Here, we investigate the presence of the cell surface proteins MET proto-oncogene (MET), integrin subunit alpha 10 (ITGA10), fibroblast activation protein alpha (FAP) and platelet derived growth factor receptor alpha (PDGFRA) in the equine SDFT cell populations and their co-localisation with known markers.

Using Western blot we validated the specificity of selected antibodies in equine tissue before performing immunohistochemistry to establish the location of the respective proteins in the SDFT. We subsequently used double labelling immunofluorescence with the established mural cell marker desmin (DES) to distinguish between tenocyte and mural cell populations.

In situ, MET, ITGA10, and FAP presence was found in cells throughout the tendon whereas PDGFRA was present in cells within the IFM. Double labelling immunofluorescence with the mural cell marker DES showed lack of co-localisation between PDGFRA and DES suggesting PDGFRA is labelling an IFM cell population distinct from those associated with blood vessels.

PDGFRA is a promising target for the specific cell sorting of IFM-localised tenocytes, enabling their isolation and subsequent characterisation.

Acknowledgments: The authors acknowledge the Biotechnology and Biological Sciences Research Council (BB/W007282/1) for funding this work.

Osteoarthritis, the most common degenerative joint disease, significantly impairs life quality and labor capability of patients. Synovial inflammation, initiated by HMGB1 (High mobility group box 1)-induced activation of macrophage, precedes other pathological changes. As an upstream regulator of NF-κB (nuclear factor-kappa B) and MAPK (mitogen-activated protein kinase) signaling pathway, TAK1 (TGF-β activated kinase 1) participates in macrophage activation, while its function in osteoarthritis remains unveiled. This study aims to investigate the role of TAK1 in the pathogenesis of osteoarthritis via both in vitro and in vivo approaches.

We performed immunohistochemical staining for TAK1 in synovial tissue, both in osteoarthritis patients and healthy control. Besides, immunofluorescence staining for F4/80 as macrophage marker and TAK1 were conducted as well. TAK1 expression was examined in RAW264.7 macrophages stimulated by HMGB1 via qPCR (Quantitative polymerase chain reaction) and Western blotting, and the effect of TAK1 inhibitor (5z-7 oxozeaenol) on TNF-α production was evaluated by immunofluorescence staining. Further, we explored the influence of intra-articular shRNA (short hairpin RNA) targeting TAK1 on collagenase-induced osteoarthritis in mice.

Immunohistochemical staining confirmed significant elevation of TAK1 in osteoarthritic synovium, and immunofluorescence staining suggested macrophages as predominant residence of TAK1. In HMGB1-stimulated RAW264.7 macrophages, TAK1 expression was up-regulated both in mRNA and protein level. Besides, TAK1 inhibitor significantly impairs the production of TNF-α by macrophages upon HMGB1 stimulation. Moreover, intra-articular injection of lentivirus loaded with shRNA targeting TAK1 (sh-TAK1) reduced peri-articular osteophyte formation in collagenase-induced osteoarthritis in mice.

TAK1 exerts a potent role in the pathogenesis of osteoarthritis by mediating the activation of macrophages.

Occlusal loading and muscle forces during mastication aids in assessment of dental restorations and implants and jaw implant design; however, three-dimensional bite forces cannot be measured with conventional transducers, which obstruct the native occlusion. The aim of this study was to combine accurate jaw kinematics measurements, together with subject-specific computational modelling, to estimate subject-specific occlusal loading and muscle forces during mastication.

Motion experiments were performed on one male participant (age: 39yrs, weight: 82kg) with healthy dentition. Two low-profile magnetic sensors were fixed to the participant's teeth and the two dental arches digitised using an intra-oral scanner. The participant performed ten continuous of chewing on a polyurethane rubber sample of known material properties, followed by maximal compression (clenching). This was repeated at the molars, premolars of both the left and right sides, and central incisors. Jaw motion was simultaneously recorded from the sensors, and finite element modelling used to estimate bite force. Specifically, simulations of chewing and biting were performed by driving the model using the measured kinematics, and bite force magnitude and direction quantified. Muscle forces were then evaluated using a rigid-body musculoskeletal model of the patient's jaw.

The first molars generated the largest bite forces during chewing (left: 309 N, right: 311 N) and maximum-force biting (left: 496 N, right: 495 N). The incisors generated the smallest bite forces during chewing (75 N) and maximum-force biting (114 N). The anterior temporalis and superficial masseter muscles had the largest contribution to maximum bite force, followed by the posterior temporalis and medial pterygoid muscles.

This study presents a new method for estimating dynamic occlusal loading and muscle forces during mastication. These techniques provide new knowledge of jaw biomechanics, including muscle and occlusal loading, which will be useful in surgical planning and jaw implant design.

Intramedullary nails (IMNs) are the current gold standard for treatment of long bone diaphyseal and selected metaphyseal fractures. Their design has undergone many revisions to improve fixation techniques, conform to the bone shape with appropriate anatomic fit, reduce operative time and radiation exposure, and extend the indication of the same implant for treatment of different fracture types with minimal soft tissue irritation.

The IMNs are made or either titanium alloy or stainless steel and work as load-sharing internal splints along the long bone, usually accommodating locking elements – screws and blades, often featuring angular stability and offering different configurations for multiplanar fixation – to secure secondary fracture healing with callus formation in a relative-stability environment. Bone cement augmentation of the locking elements can modulate the construct stiffness, increase the surface area at the bone-implant interface, and prevent cut-through of the locking elements.

The functional requirements of IMNs are related to maintaining fracture reduction in terms of length, alignment and rotation to enhance fracture healing. The load distribution during patient's activities is along the entire bone-nail interface, with nail length and anatomic fit being important factors to avoid stress risers.

Stratification is required to ensure that only those patients likely to benefit, receive Autologous Chondrocyte Implantation (ACI); ideally by assessing a biomarker in the blood. This study aimed to assess differences in the plasma proteome of individuals who respond well or poorly to ACI.

Isobaric tag for relative and absolute quantitation (ITRAQ) mass spectrometry and label-free proteomics analyses were performed in tandem as described previously by our group (Hulme et al., 2017; 2018; 2021) using plasma collected from ACI responders (n=10) compared with non-responders (n=10) at each stage of surgery (Stage I, cartilage harvest and Stage II, cell implantation).

iTRAQ using pooled plasma detected 16 proteins that were differentially abundant at baseline in ACI responders compared with non-responders (n=10) (≥±2.0 fold; p<0.05). Responders demonstrated a mean Lysholm (patient reported functional score from 0–100) improvement of 33±13 and non-responders a mean worsening of −13±13 points. The most pronounced plasma proteome shift was seen in response to Stage I surgery in ACI non-responders, with 48 proteins being differentially abundant between the two surgical procedures. We have previously noted this marked shift in response to initial surgery in the SF of ACI non-responders, several of these proteins were associated with the Acute Phase Response. One of these proteins, clusterin, could be confirmed in patients’ plasma using an independent immunoassay using individual samples. Label-free proteomic data from individual samples identified only cartilage acidic protein-1 (known to associate with osteoarthritis progression) to be significantly more abundant at Stage I in the plasma of non-responders.

This study indicates that proteins can be identified within the plasma that have potential use in ACI patient stratification. Further work is required to validate the findings of this discovery-phase work in larger ACI cohorts.

Periprosthetic joint infections (PJI) are one of the most common reasons for orthopedic revision surgeries. In previous studies, it has been shown that silver modification of titanium (Ti-6Al-4V) surfaces by PMEDM (powder mixed electrical discharge machining) has an antibacterial effect on Staphylococcus aureus adhesion. Whether this method also influences the proliferation of bacteria has not been investigated so far. Furthermore, the effect is only limitedly investigated on the ossification processes. Therefore, the aim of this work is to investigate the antibacterial effect as well as the in vitro ossification process of PMEDM machined surfaces modified by integration of silver.

In this study, we analyzed adhesion and proliferation of S. aureus in comparison to of surface roughness, silver content and layer thickness of the silver-integrated-PMEDM surfaces (N = 5). To test the in vitro ossification, human osteoblasts (SaOs-2) and osteoclasts (differentiated from murine-bone-marrow-macrophages) were cultured on the silver surfaces (N = 3).

We showed that the attachment of S. aureus on the surfaces was significantly lower than on the comparative control surfaces of pure Ti-6Al-4V without incorporated silver, independently of the measured surface properties. Bacterial proliferation, however, was not affected by the silver content. No influence on the in vitro ossification was observed, whereas osteoclast formation was drastically reduced on the silver-modified surfaces.

We showed that 1 to 3% of silver in the surface layer significantly reduced the adhesion of S. aureus, but not the proliferation of already attached bacteria. At the same time, no influence on the in vitro ossification was observed, while no osteoclasts were formed on the surface. Therefore, we state that PMEDM with simultaneous silver modification of the machined surfaces represents a promising technology for endoprostheses manufacturing to reduce infections while at the same time optimizing bone ingrowth.

Treatment of posterior malleolar (PM) ankle fractures remain controversial. Despite increasing recommendation for small PM fragment fixation, high quality evidence demonstrating improved clinical outcomes over the unfixated PM is limited. We describe the medium-to-long term clinical and radiographical outcomes in younger adult patients with PM ankle fractures managed without PM fragment fixation.

A retrospective cohort study of patients aged 18-55 years old admitted under our orthopaedic unit between 1st of April 2009 and 31st of October 2013 with PM ankle fractures was performed. Inclusion criteria were that all patients must mobilise independently pre-trauma, have no pre-existing ankle pathologies, and had satisfactory bimalleolar and syndesmotic stabilisation. Open fractures, talar fractures, calcaneal fractures, pilon fractures, subsequent re-injury and major complications were excluded. All PM fragments were unfixated. Clinical outcomes were evaluated using Foot and Ankle Ability Measure (FAAM) with activities of daily living (ADL) and sports subscale, visual analogue scale (VAS) and patient satisfaction ratings. Osteoarthrosis was assessed using modified Kellgren-Lawrence scale on updated weightbearing ankle radiographs.

61 participants were included. Mean follow-up was 10.26 years. Average PM size was 16.19±7.39%. All participants were evaluated for clinical outcomes, demonstrating good functional outcomes (FAAM-ADL 95.48±7.13; FAAM-Sports 86.39±15.52) and patient satisfaction (86.16±14.42%), with minimal pain (VAS 1.13±1.65). Radiographical outcomes were evaluated in 52 participants, showing no-to-minimal osteoarthrosis in 36/52 (69.23%), mild osteoarthrosis in 14/52 (26.92%) and moderate osteoarthrosis in 2/52 (3.85%). Clinical outcomes were not associated with PM fragment size, post-reduction step-off, dislocation, malleoli fractured or syndesmotic injury. PM step-off and dislocation were associated with worse radiographical osteoarthrosis. Other published medium-to-long term studies reported overall good outcomes, with no differences after small fragment fixation.

The unfixated smaller posterior malleolus fragment demonstrated overall satisfactory clinical and radiographical outcomes at 10-year follow-up and may be considered a valid treatment strategy.

Anterior approach total hip arthroplasty (AA-THA) has a steep learning curve, with higher complication rates in initial cases. Proper surgical case selection during the learning curve can reduce early risk. This study aims to identify patient and radiographic factors associated with AA-THA difficulty using Machine Learning (ML).

Consecutive primary AA-THA patients from two centres, operated by two expert surgeons, were enrolled (excluding patients with prior hip surgery and first 100 cases per surgeon). K- means prototype clustering – an unsupervised ML algorithm – was used with two variables - operative duration and surgical complications within 6 weeks - to cluster operations into difficult or standard groups.

Radiographic measurements (neck shaft angle, offset, LCEA, inter-teardrop distance, Tonnis grade) were measured by two independent observers. These factors, alongside patient factors (BMI, age, sex, laterality) were employed in a multivariate logistic regression analysis and used for k-means clustering. Significant continuous variables were investigated for predictive accuracy using Receiver Operator Characteristics (ROC).

Out of 328 THAs analyzed, 130 (40%) were classified as difficult and 198 (60%) as standard. Difficult group had a mean operative time of 106mins (range 99–116) with 2 complications, while standard group had a mean operative time of 77mins (range 69–86) with 0 complications. Decreasing inter-teardrop distance (odds ratio [OR] 0.97, 95% confidence interval [CI] 0.95–0.99, p = 0.03) and right-sided operations (OR 1.73, 95% CI 1.10–2.72, p = 0.02) were associated with operative difficulty. However, ROC analysis showed poor predictive accuracy for these factors alone, with area under the curve of 0.56. Inter-observer reliability was reported as excellent (ICC >0.7).

Right-sided hips (for right-hand dominant surgeons) and decreasing inter-teardrop distance were associated with case difficulty in AA-THA. These data could guide case selection during the learning phase. A larger dataset with more complications may reveal further factors.

Adult Spine Deformity (ASD) is a degenerative condition of the adult spine leading to altered spine curvatures and mechanical balance. Computational approaches, like Finite Element (FE) Models have been proposed to explore the etiology or the treatment of ASD, through biomechanical simulations. However, while the personalization of the models is a cornerstone, personalized FE models are cumbersome to generate. To cover this need, we share a virtual cohort of 16807 thoracolumbar spine FE models with different spine morphologies, presented in an online user-interface platform (SpineView). To generate these models, EOS images are used, and 3D surface spine models are reconstructed. Then, a Statistical Shape Model (SSM), is built, to further adapt a FE structured mesh template for both the bone and the soft tissues of the spine, through mesh morphing. Eventually, the SSM deformation fields allow the personalization of the mean structured FE model, leading to generate FE meshes of thoracolumbar spines with different morphologies. Models can be selectively viewed and downloaded through SpineView, according to personalized user requests of specific morphologies characterized by the geometrical parameters: Pelvic Incidence; Pelvic Tilt; Sacral Slope; Lumbar Lordosis; Global Tilt; Cobb Angle; and GAP score. Data quality is assessed using visual aids, correlation analyses, heatmaps, network graphs, Anova and t-tests, and kernel density plots to compare spinopelvic parameter distributions and identify similarities and differences. Mesh quality and ranges of motion have been assessed to evaluate the quality of the FE models. This functional repository is unique to generate virtual patient cohorts in ASD.

Acknowledgements: European Commission (MSCA-TN-ETN-2020-Disc4All-955735, ERC-2021-CoG-O-Health-101044828)

There is an evolving body of evidence that demonstrates the role of epigenetic mechanisms, such as DNA-methylation in the pathogenesis of OA. This systematic review aims to summarize the current evidence of DNA methylation and its influence on the pathogenesis of OA.

A pre-defined protocol in alignment with the PRISMA guidelines was employed to systematically review eight bibliographic databases, to identify associations between DNA-methylation of articular chondrocytes and osteoarthritis. A search of Medline (Ovid), Embase, Web-of-Science, Scopus, PubMed, Cinahl (EBSCOhost), Cochrane Central and Google Scholar was performed between 1st January 2015 to 31st January 2021. Data extraction was performed by two independent reviewers.

During the observation period, we identified 15 gene specific studies and 24 genome wide methylation analyses. The gene specific studies mostly focused on the expression of pro-inflammatory markers, such as IL8 and MMP13 which are overexpressed in OA chondrocytes. DNA hypomethylation in the promoter region resulted in overexpression, whereas hypermethylation was seen in non-OA chondrocytes. Others reported on the association between OA risk genes and the DNA methylation pattern close to RUNX2, which is an important OA signal. The genome wide methylation studies reported mostly on differentially methylated regions comparing OA chondrocytes and non-OA chondrocytes. Clustering of the regions identified genes that are involved in skeletal morphogenesis and development. Differentially methylated regions were seen in hip OA and knee OA chondrocytes, and even within different regions of an OA affected knee joint, differentially methylated regions were identified depending on the disease stage.

This systematic review demonstrates the growing evidence of epigenetic mechanisms, such as DNA methylation, in the pathogenesis of OA. In recent years, there has been a focus on the interplay between OA risk genes and DNA methylation changes which revealed a reactivation of genes responsible for endochondral ossification during development. These are important findings and may help to identify eventual future therapeutic targets. However, the current body of literature is mostly showing the differences in DNA methylation of OA chondrocytes and non-OA chondrocytes, but a true longitudinal analysis demonstrating the DNA methylation changes actually happening is still not available.

While high-performance ceramics like alumina and zirconia exhibit excellent wear resistance, they provide poor osseointegration capacity. As osseointegration is crucial for non-cemented joint prostheses, new techniques have been successfully developed for biofunctionalizing high-performance ceramic surfaces. Stable cell adhesion can be achieved by covalently bound specific peptides. In this study we investigate the effect of sterilization processes on organo-chemically functionalized surfaces.

To enhance the performance of alumina-toughened zirconia ceramics (ATZ), a 3-aminopropyldiisopropylethoxysilane (APDS) monolayer was applied and coupled with cyclo-RGD peptides (cRGD) by using bifunctional crosslinker bis(sulfosuccinimidyl)suberat (BS³). The samples were sterilized using e-beam or gamma-sterilization at 25 kGy, either before or after biofunctionalization with cRGD. Functionalization stability was investigated by contact angle measurements. The functionality of cRGD after sterilization was demonstrated using proliferation tests and cytotoxicity assays. Immunofluorescence staining (pFAK, Actin, DAPI) was conducted to evaluate the adhesion potential between the samples and human mesenchymal stem cells (hMSCs).

Functionalized samples before and after sterilization showed no significant difference regarding their contact angles. A proliferation test demonstrated that the cells on functionalized samples proliferate significantly more than on untreated samples before and after sterilization. hMSCs showed a significant higher proliferation on gamma sterilized samples compared to all other groups after 14 days. It was confirmed that the samples did not exhibit cytotoxic behavior before or after sterilization. Fluorescence microscopy demonstrated that both, cells on sterilized and on non-sterilized samples, expressed high levels of pFAK-Y397.

The investigated functionalization enables improved adhesion and proliferation of hMSCs and is stable against the investigated sterilization processes. This is of importance as the option of having a sterile product enables the start of the translation of this biofunctional coating towards preclinical and subsequently first-in-man applications.

Acknowledgments: We acknowledge the financial support of the Federal Ministry of Education and Research, BMBF (13GW0452A-C).