Abstract. Objectives. This abstract provides an update on the Open Ankle Models being developed at the University of Bath. The goal of this project is to create three fully open-source finite element (FE) ankle models, including bones, ligaments, and cartilages, appropriate musculoskeletal loading and boundary conditions, and heterogeneous material property distribution for a standardised representation of ankle biomechanics and pre-clinical ankle joint analysis. Methods. A computed tomography (CT) scan data (pixel size of 0.815 mm, and slice thickness of 1 mm) was used to develop the 3D geometry of the bones (tibia, talus, calcaneus, fibula, and navicular). Each bone was given the properties of a heterogeneous elastic material based on the CT greyscale. The density values for each bone element were calculated using a linear empirical relation, ρ= 0.0405 + (0.000918) HU and then power law equations were utilised to get the Young's Modulus value for each bone element [1]. At the bone junction, a thickness of cartilage ranging from 0.5–1 mm, and was modelled as a linear material (E=10 MPa, ν=0.4 [2]). All ligament insertions and positions were represented by four parallel spring elements, and the ligament stiffness and material attributes were applied in accordance with the published literature [2]. The ankle model was subjected to static loading (balance standing position). Four noded tetrahedral elements were used for the discretization of bones and cartilages. All degrees of freedom were restricted at the proximal ends of the tibia and fibula. The ground reaction forces were applied at the underneath of the calcaneus bone. The interaction between the cartilages and bones was modelled using an augmented contact algorithm with a sliding elastic contact between each cartilage. A tied elastic contact was used between the cartilages and the bone. FEbio 2.1.0 (University of Utah, USA) was used to construct the open-source ankle model. Results. When the double-legged stance phase loading condition was taken into consideration, stress at the antero-medial tibial wall (ranged from 1 to 7 MPa) was found to be similar to the prior work [2], indicating bulk of the load transfer was through this region. The maximum principal strain was predicted at the different regions on bones around the ankle joint. The proximal surface of the talus, and tibial distal surface were shown to have the highest maximum principal strains followed by antero-medial walls of the tibia bone, at the proximal location. Conclusions. The present open 3D FE model of the ankle will assist researchers in better understanding ankle biomechanics, precisely predicting load transfer, and examining the ankle to address unmet clinical needs for this joint. The results of the current investigation are realistic in terms of load transfer and stress-strain distribution across the ankle joint and well comparable to those reported in the literature [2]. However, sensitivity and ankle instability simulations will be performed in future work to investigate the model's reliability and robustness. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15° and 30° dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load. The peak pressure increased significantly from neutral alignment to the 30° cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15° (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30° (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure. These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability

The posterolateral approach to ankle joint is well suited for ORIF of posterior malleolar fractures. There are no major neurovascular structures endangering this approach other than the sural nerve. The sural nerve is often used as an autologous peripheral nerve graft and provides sensation to the lateral aspect of the foot. Hence every attempt must be made to protect the sural nerve. The aim of this paper is to measure the precise distance of the sural nerve from surrounding soft tissue structures. This is a retrospective image review study including patients with MRI of their ankle from January 09 - Nov 2010. We indentified 78 MRI scans out of which 64 were deemed eligible for assessment. All measurements were made from Axial T1 slices. Measurements were made from the lateral aspect of the TA to the central of the sural nerve, central of sural nerve to the posterior aspect of the peronei muscles and central of the sural nerve to the posterior aspect of fibula. Data were collected on a Microsoft Excel spreadsheet and the descriptive statistics calculated. The key findings of the paper is the safety window for the sural nerve from the lateral border of TA is 7mm, 1.3cm and 2cm at 3 cm above ankle joint, at the ankle joint and at the distal tip of fibula respectively. Similarly the safety window for the nerve from the posterior aspect of fibula is 2cm, 1.6cm, 1.6cm at 3cm above ankle, at the ankle joint and the distal tip of fibula respectively. Our study demonstrates the close relationship of the nerve in relation to tendoachilles, peronei and fibula in terms of exact measurements. The safety margins established in this study should enable the surgeon in preventing endangerment of the sural nerve encountered in this approach

To study the effect of ligament injuries and surgical repair we investigated the three-dimensional kinematics of the ankle joint complex and the talocrural and the subtalar joints in seven fresh-frozen lower legs before and after sectioning and reconstruction of the ligaments. A foot movement simulator produced controlled torque in one plane of movement while allowing unconstrained movement in the remainder. After testing the intact joint the measurements were repeated after simulation of ligament injuries by cutting the anterior talofibular and calcaneofibular ligaments. The tests were repeated after the Evans, Watson-Jones and Chrisman-Snook tenodeses. The range of movement (ROM) was measured using two goniometer systems which determined the relative movement between the tibia and talus (talocrural ROM) and between the talus and calcaneus (subtalar ROM). Ligament lesions led to increased inversion and internal rotation, predominantly in the talocrural joint. The reconstruction procedures reduced the movement in the ankle joint complex by reducing subtalar movement to a non-physiological level but did not correct the instability of the talocrural joint

Several emerging reports suggest an important involvement of the hindfoot alignment in the outcome of knee osteotomy. At present, studies lack a comprehensive overview. Therefore, we aimed to systematically review all biomechanical and clinical studies investigating the role of the hindfoot alignment in the setting of osteotomies around the knee.

A systematic literature search was conducted on multiple databases combining “knee osteotomy” and “hindfoot/ankle alignment” search terms. Articles were screened and included according to the PRISMA guidelines. A quality assessment was conducted using the Quality Appraisal for Cadaveric Studies (QUACS) - and modified methodologic index for non-randomized studies (MINORS) scales.

Three cadaveric, fourteen retrospective cohort and two case-control studies were eligible for review. Biomechanical hindfoot characteristics were positively affected (n=4), except in rigid subtalar joint (n=1) or talar tilt (n=1) deformity. Patient symptoms and/or radiographic alignment at the level of the hindfoot did also improve after knee osteotomy (n=13), except in case of a small pre-operative lateral distal tibia- and hip knee ankle (HKA) angulation or in case of a large HKA correction (>14.5°). Additionally, a pre-existent hindfoot deformity (>15.9°) was associated with undercorrection of lower limb alignment following knee osteotomy. The mean QUACS score was 61.3% (range: 46–69%) and mean MINORS score was 9.2 out of 16 (range 6–12) for non-comparative and 16.5 out of 24 (range 15–18) for comparative studies.

Osteotomies performed to correct knee deformity have also an impact on biomechanical and clinical outcomes of the hindfoot. In general, these are reported to be beneficial, but several parameters were identified that are associated with newly onset – or deterioration of hindfoot symptoms following knee osteotomy. Further prospective studies are warranted to assess how diagnostic and therapeutic algorithms based on the identified criteria could be implemented to optimize the overall outcome of knee osteotomy.

Remark: Aline Van Oevelen and Arne Burssens contributed equally to this work

Syndesmotic ankle lesions involve disruption of the osseous tibiofibular mortise configuration as well as ligamentous structures stabilizing the ankle joint. Incomplete diagnosis and maltreatment of these injuries is frequent, resulting in chronic pain and progressive instability thus promoting development of ankle osteoarthritis in the long term. Although the pathogenesis is not fully understood, abnormal mechanics has been implicated as a principal determinant of ankle joint degeneration after syndesmotic ankle lesions. Therefore, the focus of this presentation will be on our recent development of a computationally efficient algorithm to calculate the contact pressure distribution in patients with a syndesmotic ankle lesion, enabling us to stratify the risk of OA development in the long term and thereby guiding patient treatment

The incisura fibularis (IF) provides intrinsic stability to the ankle joint complex by interlocking the distal tibia and fibula. Despite a high frequency of ligamentous ankle injuries, scant attention has been given to the morphology of the IF morphology incisura fibularis in the onset and development of these lesions. Therefore, we systematically reviewed the relation between ligamentous ankle disorders and the morphometrics of the IF. A systematic literature search was conducted on following databases: PubMed, Embase and Web of Science. Search terms consisted of ‘ankle trauma’, ‘ankle injury’, ‘ankle sprain’, ‘ankle fracture’, ‘tibiofibular’, ‘fibular notch’, ‘fibular incisura’, ‘incisura fibularis’, ‘morphometric analysis’, ‘ankle syndesmosis’, ‘syndesmotic stability’. The evaluation instrument developed by Hawker et al. was used to assess the quality of the selected studies. This protocol was performed according to the PRISMA guidelines and is registered on PROSPERO (CRD42021282862). Nineteen studies were included and consisted of prospective cohort (n=1), retrospective comparative (n=10), and observational (n=8) study design. Comparative studies have found certain morphological characteristics in patients with ankle instability. Several studies (n=5) have correlated a shallow IF depth with a higher incidence of ankle injury. A significant difference has also been found concerning the incisura height and angle (n=3): a shorter incisura and more obtuse angle have been noted in patients with ankle sprains. The mean Hawker score was 28 out of 36 (range=24-31). A shallower IF is associated with ligamentous ankle lesions and might be due to a lower osseous resistance against tibiofibular displacement. However, these results should be interpreted in light of moderate methodological quality and should always be correlated with clinical findings. Further prospective studies are needed to further assess the relation between the incisura morphometrics and ligamentous disorders of the ankle joint. Keywords: ankle instability, ankle injury, incisura fibularis, fibular notch, tibiofibular morphometrics, ankle syndesmosis

Abstract. Background. Proximal fibular osteotomy (PFO) was defined to provide a treatment option for knee pain caused by gonarthrosis(1). Minor surgical procedure, low complication rate and dramatic pain relief were the main reasons for popularization of this procedure(2, 3). However, changes at the knee and ankle joint after PFO were not clarified objectively in the literature. Questions/purposes. We asked: 1) Does PFO change the maximum and average pressures at the medial and lateral chondral surface of the tibia plateau? 2) Are chondral surface stresses redistributed at the knee and ankle joint after PFO? 3)Does PFO change the distribution of total load on the knee joint? 4) Can PFO lead to change in alignment of lower limb?. Methods. This study was conducted at Maltepe University Faculty of Medicine Hospital, Orthopedics and Traumatology Department and Yildiz Technical University Mechanical Engineering Department in Istanbul, Turkey, between September 2019 and February 2020. Finite element analysis (FEA) was used to evaluate effects of PFO(4). One 62 years old, female volunteer's X-ray, computer tomography and magnetic resonance imaging images were used for creating right lower limb model. Two different lower limb models were created. One of them was osteotomized model (OM) which was created according to definition of PFO and the other was non-osteotomized model (NOM). To obtain a stress distribution comparison between the two models, 350 N of axial force was applied to the femoral heads of the models. Results. After PFO, the maximum contact pressures at the medial and lateral tibial cartilages decreased 83.2% and 66.9%, respectively at the knee joint. The average contact pressure decreased 26.1% at the medial tibial cartilage and increased 42.4% at the lateral tibial cartilage. The Von Mises stresses decreased 57.1% at the femoral cartilage and decreased 79.1% at tibial cartilage. The stress on the tibial cartilage increased 44.6%, and stress on the talar cartilage increased 7.1% at the ankle joint. Under a 350 N axial force, distribution of the total load at the knee joint was changed and become more homogenous in OM compared to NOM. Change in lower extremity alignment after PFO could not be evaluated with FEA. Conclusion. FEA revealed that PFO causes some changes in knee and ankle joint kinematics. Main loading at the knee joint shifted from medial tibial cartilage to the lateral tibial cartilage after PFO. Additionally, the stresses on each cartilage were redistributed across a wider and more peripheral area. These changes could be the main reason for pain relief at the knee joint. FEA also demonstrated that the Von Mises stresses of the tibial and talar cartilages of the ankle joint increased after PFO. This stress increase may cause long-term arthritic changes in the ankle joint. Level IV; in silico study

Recently, several smartphone applications (apps) have been developed and validated for ankle ROM measurement tools like the universal goniometer. This is the first innovative study introduces a new smartphone application to measure ankle joint ROM as a remote solution. This study aimed to assess the correlation between smartphone ROM and universal goniometer measurements, and also report the evaluation of the DijiA app by users. The study included 22 healthy university students (14F/8M; 20.68±1.72 years) admitted to Yeditepe University. Fourty four feet was measured by both the universal goniometer (UG) and DijiA app. The datas were analyzed through using the intraclass correlation coefficient (ICC). The DijiA app was evaluated by usability testing with representative users. Pearson correlation coefficient test showed moderate correlation between the DijiA and UG for dorsiflexion (DF) and plantar flexion (PF) measurements (Pearson correlation coefficient: r=0.323, for DF; r=0.435 for PF 95% confidence interval). The application usability was found as high with 76.5 average score and users liked it. The DijiA app may be a more convenient and easy way to measure ankle DF and PF-ROM than UG. It can be used to evaluate ROM in clinical practice or home using as a personal smartphone

Management of ankle arthritis in young patients is challenging. Although ankle arthrodesis gives consistent pain relief, it leads to loss of function and adjacent joint arthritis. Ankle joint distraction (AJD) has been shown to give good outcomes in adults with osteoarthritis or post-traumatic arthritis. The efficacy in children or young adults and those with juvenile idiopathic arthritis is less well evidenced. Clinical notes and radiographs of all patients (n=6) managed with AJD in one tertiary referral centre were retrospectively reviewed. Radiographs were taken pre-surgery, intra-operatively, 1 month following frame removal and at the last follow up, tibiotalar joint space was assessed using ImageJ software. Measurements were taken at the medial, middle and lateral talar dome using frame components as reference. Radiographic data for patients with a good clinical outcome was compared with those who did not. At time of surgery mean age was 16.1 years (12 – 25 years). Mean follow up was 3.4 years (1.5 – 5.9 years). Indications were juvenile idiopathic arthritis (4) post-traumatic (1) and post-infective arthritis (1). Three patients at last follow up had a good clinical outcome. Two patients required revision to arthrodesis (1.3 and 2.4 years following distraction). One patient had spontaneous fusion. One patient required oral antibiotics for pin site infection. Inter-observer reliability was 95%. Mean joint space was 1.17mm (SD = 0.87mm) pre-operatively which increased to 6.72mm (SD = 2.23mm) at the time of distraction and 2.09mm (SD = 1.14mm) at the time of removal. At one-year follow up, mean joint space was 1.96mm (SD = 1.97mm). Outcomes following AJD in this population are variable although significant benefits were demonstrated for 50% of the patients in this series. Radiographic joint space preoperatively did not appear to be associated with need for arthrodesis. Further research in larger groups of young patients is required

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

Falls in adults are a major problem and can lead to injuries and death. In order to better understand falls and successful recoveries, identifying kinematics, kinetics, and muscle forces during recovery from loss of balance is crucial. To obtain reactive gait patterns, participants must be subjected to unexpected perturbations such as trips and slips. Previous researchers have reported kinetics recovery data following stumbling; however, the muscle force recovery patterns remain unknown. To better target exercises to reduce the risk of falls, we must first understand which muscles, their magnitude, and their coordination patterns, play a role in a successful recovery from a trip and a slip. Additionally, knowing the successful patterns of lower limb function can help with the diagnosis of faulty movements. A total of 20 healthy adults in their twenties with similar athletic backgrounds were perturbed on a split-belt treadmill using Computer-Assisted Rehabilitation Environment (Motkforce Link) at a preset speed of 1.1m/s. Two kinds of perturbations were administered: slip and trip. Slips were simulated by accelerating one belt, whereas trips were simulated by decelerating one belt. Both perturbations had similar intensity and only differed in the direction. Computational modeling was used to obtain lower-limb function during the compensatory step. SPM paired t-test was used to compare differences in recovery strategies between slip and trip through magnitude and patterns of joints. There were no significant differences in joint angles post tripping vs post-slipping. Results of net joint moments showed that compensating for the loss of balance due to tripping required a higher ankle plantarflexion moment than slipping (at 22-52%; 1.2± 0.3vs0.4±0.2, p<0.001). Additionally, larger gluteus maximus (at 40-50%;8.7±3.8vs2.7±1.1N/kg, p=0.001), gluteus medius (at23~33%; 22.6±5.7vs6.8±3.6N/kg, p<0.001) were generated than post-slipping, respectively. These findings suggested that greater GMAX and GMED forces are required post-trip recovery than slip. Future analysis of trip recovery showed the importance of ankle joint in recovering from forward and backward fall. These results can be used as references in remote diagnosis of joint and muscle weakness and assessment of the risk of falls with the use of accelerometers

Abstract. Objectives. The fidelity of a 3D model created using image segmentation must be precisely quantified and evaluated for the model to be trusted for use in subsequent biomechanical studies such as finite element analysis. The bones within the ankle joint vary significantly in size and shape. The purpose of this study was to test the hypothesis that the accuracy and reliability of a segmented bone geometry is independent of the particular bone being measured. Methods. Computed tomography (CT) scan data (slice thickness 1 mm, pixel size 808±7 µm) from three anonymous patients was used for the development of the ankle geometries (consisting of the tibia, fibula, talus, calcaneus, and navicular bones) using Simpleware Scan IP software (Synopsys, Exeter, UK). Each CT scan was segmented 4 times by an inexperienced undergraduate, resulting in a total of 12 geometry assemblies. An experienced researcher segmented each scan once, and this was used as the ‘gold standard’ to quantify the accuracy. The solid bone geometries were imported into CAD software (Inventor 2023, Autodesk, CA, USA) for measurement of the surface area and volume of each bone, and the distances between bones (tibia to talus, talus to navicular, talus to calcaneus, and tibia to fibula) were carried out. The intra-class coefficient (ICC) was used to assess intra-observer reliability. Bland Altman plots were employed as a statistical measure for criteria validity (accuracy) [1]. Results. The average ICC score was 0.93, which is regarded as a high reliability score for an inexperienced user. The talus to navicular and talus to tibia separations, which had the smallest distances, showed a slight decrease in reliability and this was observed for all separations shorter than 2 mm. According to the Bland-Altman plots, more than 95% of the data points were inside the borders of agreement, which is an excellent indication of accuracy. The bias percentage (average error percentage) varied between 1% and 4% and was constant across all parameters, with the proportion rising for short distance separations. Conclusions. The current study demonstrates that an inexperienced undergraduate, with access to software manuals, can segment an ankle CT scan with excellent reliability. The present study also concluded that all five bones were segmented with high levels of accuracy, and this was not influenced by bone volume or type. The only factor found to influence the reliability was the magnitude of distance between bones, where if this was smaller than 2 mm it reduced the reliability, indicating the influence of CT scan resolution on the segmentation reliability. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Skeletal kinematics are traditionally measured by motion analysis methods such as optical motion capture (OMC). While easy to carry out and clinically relevant for certain applications, it is not suitable for analysing the ankle joint due to its anatomical complexity. A greater understanding of the function of healthy ankle joints could lead to an improvement in the success of ankle-replacement surgeries. Biplane video X-ray (BVX) is a technique that allows direct measurement of individual bones using highspeed, dynamic X-Rays. Objective. To develop a protocol to quantify in-vivo foot and ankle kinematics using a bespoke High-speed Dynamic Biplane X-ray system combined with OMC. Methods. Two healthy volunteers performed five level walks and step-down trials while simultaneous capturing BVX and synchronised OMC. participants undertook MR imaging (Magnetom 3T Prisma, Siemens) which was manually segmented into 3D bone models (Simpleware Scan IP, Synopsis). Bone position and orientation for the Talus, Tibia and Calcaneus were calculated by manual matching of 3D Bone models to X-Rays (DSX Suite, C-Motion, Inc.). OMC markers were tracked (QTM, Qualisys) and processed using Visual 3D (C-motion, Inc.). Results. Initial results for level walking showed that OMC overestimated the rotational range of motion (ROM) in all three planes for the tibiotalar joint compared with BVX (Sagittal: OMC 30°/BVX 20°, Frontal: OMC 16°/BVX 15° and Transverse: OMC 20°/BVX 17°). For the subtalar joint, OMC (22°) over-estimated sagittal ROM compared with BVX (14°) and underestimated the ROM in the other planes (Frontal: OMC 8°/BVX 15° and Transverse: OMC 18°/BVX 20°). Conclusions. The results highlight the discrepancy between OMC and BVX methods. However, the BVX results are consistent with previous literature. The protocol developed here will form the foundation of future patient-based studies to investigate in-vivo ankle kinematics. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Osteoarthritis of the first metatarsophalangeal (MTP1) joint is a common disorder in elderly, resulting in pain and disability. Arthrodesis of this joint shows satisfactory results, with relieve of pain in approximately 85% of the patients. However, the compensation mechanism for loss of motion in the MTP1 joint after MTP1 arthrodesis is unknown. A reduced compensation mechanism of the foot may explain the disappointing result of MTP1 arthrodesis in the remaining 15% of the patients. This study was conducted to elucidate this compensation mechanism. We hypothesize that the ankle and forefoot are responsible for compensation after MTP1 arthrodesis. Gait was evaluated in eight patients with arthrodesis of the MTP1 joint (10 feet) and twelve healthy controls (21 feet) by using a sixteen-camera Vicon-system. The four-segmental, validated Oxford-Foot-Model was used to investigate differences in range of motion of the hindfoot-tibia, forefoot-hindfoot and hallux-forefoot segment during stance. For statistical analysis, the unpaired t-test with Bonferroni correction (p<0.0125) was performed. No differences in spatiotemporal parameters were observed between both groups. In the frontal plane, MTP1 arthrodesis decreased the range of motion in midstance, while an increased range of motion was observed in terminal stance for the hindfoot relative to the tibia in the transversal plane. Subsequently range of motion in the forefoot in preswing was increased. This resulted in less eversion in the hindfoot during midstance, increased internal rotation of the hindfoot during terminal stance and more supination in the forefoot during preswing in the MTP1 arthrodesis group. Motion of the hallux was restricted in the loading response (i.e. plantar flexion) and terminal stance (i.e. dorsiflexion). As hypothesized, both the ankle and the forefoot are responsible for compensation after MTP1 arthrodesis, because arthrodesis causes less eversion and increased internal rotation of the hindfoot and increased supination of the forefoot. As expected, both dorsiflexion and plantar flexion of the hallux was restricted due to arthrodesis. These findings suggest a gait pattern in which the lateral arch of the foot is more loaded and the stiff hallux is avoided during the stance phase of gait. Our results indicate that proper motion of the forefoot and ankle joint is important when considering arthrodesis of the MTP1 joint. Therefore, we emphasize careful assessment the range of motion in the forefoot and ankle joint in the pre-operative situation, since patients with a decreased range of motion in the forefoot and ankle joint have a less functioning compensation mechanism. We currently perform a study to evaluate the strength of the positive correlation between the pre-operative range of motion in the forefoot and ankle joint and the clinical outcome

The ankle radiograph is a commonly requested investigation as the ankle joint is commonly injured. Each radiograph exposes 0.01 mSv of radiation to the patient that is equivalent to 1.5 days of natural background radiation [1]. The aim of the clinical audit was to use the Ottawa Ankle Rule to attempt to reduce the number of ankle radiographs taken in patients with acute ankle injuries and hence reduce the dose of ionising radiation the patient receives. A retrospective audit was undertaken. 123 ankle radiograph requests and radiographs taken between May and July 2018 were evaluated. Each ankle radiograph request including patient history and clinical examination was graded against the Ottawa Ankle Rule. The rule states that 1 point(s) indicates radiograph series; (1) malleolar and/or midfoot pain; (1) tenderness over the posterior 6cm or tip of the lateral or medial malleolus (ankle); (1) tenderness over the navicular or the base of the fifth metatarsal (foot); (1) unable to take four steps both immediately and in the emergency department [2]. Patients who score 0 do not need radiograph series. Each radiograph was reviewed if a fracture was present or not. The clinical audit identified 14 true positives where the Ottawa Ankle Rule scored 1 and the patient had an ankle fracture, and 2 false negatives (sensitivity 88%). There were 81 false positives, and 23 true negatives (specificity 22%). Therefore, a total of 23/123 ankle radiographs were unnecessary which is equivalent to 34.5 days of background radiation. The negative predictive value of the Ottawa Ankle Rule in this audit was 92%. The low rate of Ottawa rule utilisation may unnecessarily cause patient harm that should be addressed. An educational intervention with physicians combined with integration of the Ottawa rule scoring in ankle radiograph requests is planned with re-audit in 6 months

Abstract. Objectives. Over 1% of the global population suffers with ankle osteoarthritis (OA), yet there is limited knowledge on the changes to subchondral bone with OA. In other joints, it has been shown that bone becomes osteosclerotic, with fewer, thicker trabeculae that become hypomineralised, causing an increased apparent bone volume fraction (BV/TV). Microstructural alterations reduce overall joint strength, which may impact the success of late-stage surgical interventions, such as total ankle arthroplasty (TAA). Previous ankle studies have evaluated changes to cartilage, bone plate and bone morphology with OA, hence this study aimed to characterise changes to trabecular architecture. Methods. Three ankle joints were isolated from non-diseased cadaveric feet (three males: 43, 50 and 57 years, MEEC 18-027). Cylindrical subchondral bone specimens (N=6, 6.5 mm Ø) were extracted from the tibial plafond. Osteoarthritic bone samples (N=6, distal tibia) were sourced from local patients (three males: 65, 58 and 68 years, NREC 07/Q1205/27) undergoing TAA surgery. Specimens were imaged using µCT at a 16 µm isotropic resolution (µCT-100 ScanCo Medical). Virtual cores of bone (6.5 mm Ø) were extracted from the image data of the osteoarthritic specimens and trimmed to a height of 4 mm. BoneJ was used to evaluate key morphological indices: BV/TV; anisotropy (DA); trabecular thickness (Tb.Th); trabecular density (Conn.D) and ellipsoid factor (EF) which characterises rod/plate geometry. Differences between the two groups of specimens were evaluated using a t-test with Bonferroni correction. Results. Significant increases in BV/TV and Tb.Th (p<0.01) were observed with OA compared to non-diseased. Differences in EF showed a shift to more rod-dominated structure with OA, but this was not significant. No significant differences to DA and Conn.D were observed. Conclusions. The results of this study agree with trends observed in other OA joints, but would benefit from a larger sample size. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. The ankle cartilage has an important function in walking movements, mainly in sports; for active young people, between 20 and 30 years old, the incidence of osteochondral lesions is more frequent. They are also more frequent in men, affecting around 21,000 patients per year in USA with 6.5% of ankle injuries generating osteochondral lesions. The lesion is a result of ankle sprain and is most frequently found in the medial location, in 53% of cases. The main objective of this work was to develop an experimental and finite element models to study the effect of the ankle osteochondral lesion on the cartilage behavior. Materials and Methods. The right ankle joint was reconstructed from an axial CT scan presenting an osteochondral lesion in the medial position with 8mm diameter in size. An experimental model was developed, to analyze the strains and influence of lesion size and location similar to the patient. The experimental model includes two cartilages constructed by Polyjet™ 3D printing from rubber material (young modulus similar to cartilage) and bone structures from a rigid polymer. The cartilage was instrumented with two rosettes in the medial and lateral regions, near the osteochondral region. The fluid considered was water at room temperature and the experimental test was run at 1mm/s. The Finite element model (FE) includes all the components considered in the experimental apparatus and was assigned the material properties of bone as isotropic and linear elastic materials; and the cartilage the same properties of rubber material. The fluid was simulated as hyper-elastic one with a Mooney-Rivlin behavior, with constants c1=0.07506 and c2=0.00834MPa. The load applied was 680N in three positions, 15º extension, neutral and 10º flexion. Results. The experimental strain measured in the cartilage in the rosettes presents similar behavior in all experiments and repetitions. The maximum value observed near the osteochondral lesion was 3014(±5.6)µε in comparison with the intact condition it was 468 (±1.95)µε. The osteochondral lesion increases the strains around 6.5 times and the synovial liquid reduces the intensity of strain distribution. The numerical model presents a good correlation with the experiments (R2 0.944), but the FE model underestimates the values. Discussion and conclusion. As a first conclusion, the size of the osteochondral lesion is important for the strains developed in cartilage. The size of lesion greater than 10mm is critical for the strains concentration. The synovial fluid present an important aspect in the strains measured, it reduces the strains in the external surface of cartilage and induces an increase in the lower part. This phenomenon should be addressed in more studies to evaluate this effect

Total ankle replacement (TAR) is the main surgical option in case of severe joint osteoarthritis. The high failure rate of current TAR is often associated to inappropriate prosthetic articulating surfaces designed according to old biomechanical concepts such the fixed axis of rotation, thus resulting in non-physiological joint motion. A recent image-based 3D morphological study of the normal ankle (Siegler et al. 2014) has demonstrated that the ankle joint surfaces can be approximated by a saddle-shaped cone with its apex located laterally (SSCL). We aimed at comparing the kinematic effects of this original solution both with the intact joint and with the traditional prosthetic articulating surfaces via in-silico models and in-vitro measurements. Native 3D morphology of ten normal cadaver ankle specimens was reconstructed via MRI and CT images. Three custom-fit ankle joint models were then developed, according to the most common TAR designs: cylindrical, symmetrically-truncated medial apex cone (as in Inman's pioneering measures), and the novel lateral apex cone, i.e. SSCL. Bone-to-bone motion, surface-to-surface distance maps, and ligament forces and deformations were evaluated via computer simulation. Prototypes of corresponding prosthesis components were designed and manufactured via 3D-printing, both in polymer-like-carbon and in cobalt-chromium-molybdenum powders, for in-vitro tests on the cadaver specimens. A custom testing rig was used for application of external moments to the ankle joint in the three anatomical planes; a motion tracking system with trackers pinned into the bone was used to measure tibial, talar and calcaneal motion (Franci et al. 2009), represented then as tibiotalar, subtalar and ankle complex 3D joint rotations. Each ankle specimen was tested in the intact joint configuration and after replacement of the articulating surfaces according with the three joint models: cylindrical, medial apex cone and SSCL. Results. Small intra-specimen data variability in cycle-to-cycle joint kinematics was found in all cadaver ankles, the maximum standard deviation of all rotation patterns being smaller than 2.0 deg. In-silico ligament strain/stress analysis and in-vitro joint kinematic and load transfer measurements revealed that the novel SSCL surfaces reproduce more natural joint patterns than those with the most common surfaces used in current TAR. TAR based on a saddle-shaped skewed truncated cone with lateral apex is expected to restore more normal joint function. Additional tests are undergoing for further biomechanical validation. The present study has also demonstrated the feasibility and the quality of the full process of custom TAR design and production for any specific subject. This implies a thorough procedure, from medical imaging to the production of artificial surfaces via 3D printing, which is allowing for personalised implants to become the future standard in total joint replacement

Treatment of comminuted intraarticular calcaneal fractures remains controversial and challenging. Anatomic reduction with stable fixation has demonstrated better outcomes than nonoperative treatment of displaced intraarticular fractures involving the posterior facet and anterior calcaneocuboid joint (CCJ) articulating surface of the calcaneus. The aim of this study was to investigate the biomechanical performance of three different methods for fixation of comminuted intraarticular calcaneal fractures. Comminuted calcaneal fractures, including Sanders III-AB fracture of the posterior facet and Kinner II-B fracture of the CCJ articulating calcaneal surface, were simulated in 18 fresh-frozen human cadaveric lower legs by means of osteotomies. The ankle joint, medial soft tissues and midtarsal bones along with the ligaments were preserved. The specimens were randomized according to their bone mineral density to 3 groups for fixation with either (1) 2.7 mm variable-angle locking anterolateral calcaneal plate in combination with one 4.5 mm and one 6.5 mm cannulated screw (Group 1), (2) 2.7 mm variable-angle locking lateral calcaneal plate (Group 2), or (3) interlocking calcaneal nail with 3.5 mm screws in combination with 3 separate 4.0 mm cannulated screws (Group 3). All specimens were biomechanically tested until failure under axial loading with the foot in simulated midstance position. Each test commenced with an initial quasi-static compression ramp from 50 N to 200 N, followed by progressively increasing cyclic loading at 2Hz. Starting from 200 N, the peak load of each cycle increased at a rate of 0.2 N/cycle. Interfragmentary movements were captured by means of optical motion tracking. In addition, mediolateral X-rays were taken every 250 cycles with a triggered C-arm. Varus deformation between the tuber calcanei and lateral calcaneal fragments, plantar gapping between the anterior process and tuber fragments, displacement at the plantar aspect of the CCJ articular calcaneal surface, and Böhler angle were evaluated. Varus deformation of 10° was reached at significantly lower number of cycles in Group 2 compared to Group 1 and Group 3 (P ≤ 0.017). Both cycles to 10° plantar gapping and 2 mm displacement at the CCJ articular calcaneal surface revealed no significant differences between the groups (P ≥ 0.773). Böhler angle after 5000 cycles (1200 N peak load) had significantly bigger decrease in Group 2 compared to both other groups (P ≤ 0.020). From biomechanical perspective, treatment of comminuted intraarticular calcaneal fractures using variable-angle locked plate with additional longitudinal screws or interlocked nail in combination with separate transversal screws seems to provide superior stability as opposed to variable-angle locked plating only