The use of intraoperative navigation and robotic surgery for minimally invasive lumbar fusion has been increasing over the past decade. The aim of this study is to evaluate postoperative clinical outcomes, intraoperative parameters, and accuracy of pedicle screw insertion guided by intraoperative navigation in patients undergoing lumbar interbody fusion for spondylolisthesis. Patients who underwent posterior lumbar fusion interbody using intraoperative 3D navigation since December 2021 were included. Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and Short Form Health Survey-36 (SF-36) were assessed preoperatively and postoperatively at 1, 3, and 6 months. Screw placement accuracy, measured by Gertzbein and Robbins classification, and facet joint infringement, measured by Yson classification, were assessed by intraoperative Cone Beam CT scans performed at the end of instrumentation. Finally, operation time, intraoperative blood loss, hospital stay, and screw insertion time were evaluated. This study involved 50 patients with a mean age of 63.7 years. VAS decreased from 65.8±23 to 20±22 (p<.01). ODI decreased from 35.4%±15 to 11.8%±14 (p<.01). An increase of SF-36 from 51.5±14 to 76±13 (p<.01) was demonstrated. The accuracy of “perfect” and “clinically acceptable” pedicle screw fixation was 89.5% and 98.4%, respectively. Regarding facet violation, 96.8% of the screws were at grade 0. Finally, the average screw insertion time was 4.3±2 min, hospital stay was 4.2±0.8 days, operation time was 205±53 min, and blood loss was 169±107 ml. Finally, a statistically significant correlation of operation time with hospital stay, blood loss and placement time per screw was found. We demonstrated excellent results for accuracy of pedicle screw fixation and violation of facet joints. VAS, ODI and SF-36 showed statistically significant improvements from the control at one month after surgery. Navigation with intraoperative 3D images represents an effective system to improve operative performance in the surgical treatment of spondylolisthesis

In this work, we propose a new quantitative way of evaluating acute compartment syndrome (ACS) by dynamic mechanical assessment of soft tissue changes. First, we have developed an animal model of ACS to replicate the physiological changes during the condition. Secondly, we have developed a mechanical assessment tool for quantitative pre-clinical assessment of ACS. Our hand-held indentation device provides an accurate method for investigations into the local dynamic mechanical properties of soft tissue and for in-situ non-invasive assessment and monitoring of ACS. Our compartment syndrome model was developed on the cranial tibial and the peroneus tertius muscles of a pig's leg (postmortem). The compartment syndrome pressure values were obtained by injecting blood from the bone through the muscle. To enable ACS assessment by a hand-held indentation device we combined three main components: a load cell, a linear actuator and a 3-axis accelerometer. Dynamic tests were performed at a frequency of 0.5 Hz and by applying an amplitude of 0.5 mm. Another method used to observe the differences in the mechanical properties inside the leg was a 3D Digital Image Correlation (3D-DIC). Videos were taken from two different positions of the pig's leg at different pressure values: 0 mmHg, 15 mmHg and 40 mmHg. Two strains along the x axis (Exx) and y axis (Eyy) were measured. Between the two pressure cases (15 mmHg and 40 mmHg) a clear deformation of the model is visible. In fact, the bigger the pressure, the more visible the increase in strain is. In our animal model, local muscle pressures reached values higher than 40 mmHg, which correlate with observed human physiology in ACS. In our presentation we will share our dynamic indentation results on this model to demonstrate the sensitivity of our measurement techniques. Compartment syndrome is recognised as needing improved clinical management tools. Our approach provides both a model that reflects physiological behaviour of ACS, and a method for in-situ non-invasive assessment and monitoring

Joint surface restoration of deep osteochondral defects represents a significant unmet clinical need. Moreover, untreated lesions lead to a high rate of osteoarthritis. The current strategies to repair deep osteochondral defects such as osteochondral grafting or sandwich strategies combining bone autografts with ACI/MACI fail to generate long-lasting osteochondral interfaces. Herein, we investigated the capacity of juvenile Osteochondral Grafts (OCGs) to repair osteochondral defects in skeletally mature animals. With this regenerative model in view, we set up a new biological, bilayered, and scaffold-free Tissue Engineered (TE) construct for the repair of the osteochondral unit of the knee. Skeletally immature (5 weeks old) and mature (11 weeks old) Lewis rats were used. Cylindrical OCGs were excised from the intercondylar groove of the knee of skeletally immature rats and transplanted into osteochondral defects created in skeletally mature rats. To create bilayered TE constructs, micromasses of human periosteum-derived progenitor cells (hPDCs) and human articular chondrocytes (hACs) were produced in vitro using chemically defined medium formulations. These constructs were subsequently implanted orthotopically in vivo in nude rats. At 4 and 16 weeks after surgery, the knees were collected and processed for subsequent 3D imaging analysis and histological evaluation. Micro-computed tomography (µCT), H&E and Safranin O staining were used to evaluate the degree of tissue repair. Our results showed that the osteochondral unit of the knee in 5 weeks old rats exhibit an immature phenotype, displaying active subchondral bone formation through endochondral ossification, the absence of a tidemark, and articular chondrocytes oriented parallel to the articular surface. When transplanted into skeletally mature animals, the immature OCGs resumed their maturation process, i.e., formed new subchondral bone, partially established the tidemark, and maintained their Safranin O-positive hyaline cartilage at 16 weeks after transplantation. The bilayered TE constructs (hPDCs + hACs) could partially recapitulate the cascade of events as seen with the immature OCGs, i.e., the regeneration of the subchondral bone and the formation of the typical joint surface architecture, ranging from non-mineralized hyaline cartilage in the superficial layers to a progressively mineralized matrix at the interface with a new subchondral bone plate. Cell-based TE constructs displaying a hierarchically organized structure comprising of different tissue forming units seem an attractive new strategy to treat osteochondral defects of the knee

DVC allowed measurements of displacement and strain distribution in bone through the comparison of two, or more, 3D images. Hence, it has a potential as a diagnostic tool in combination with clinical CT. Currently, traditional computed tomography (CT) allows for a detailed 3D analysis of hard tissues, but imaging in a weight-bearing condition is still limited. PedCAT-CT (Curvebeam, USA) emerged as a novel technology allowing, for the first time, 3D imaging under full-weight bearing (Richter, Zech et al. 2015). Specifically, a PedCAT-CT based DVC was employed to establish its reliability through the strain uncertainties produced on bone structure targets, preliminarily to any further clinical studies. In addition, a reverse engineering FE modeling was used to predict possible force associated to displacement errors from DVC. Three porcine thoracic vertebrae were used as bone benchmark for the DVC (Palanca, Tozzi et al. 2016, Tozzi, Dall'Ara et al. 2016). The choice of using porcine vertebrae (in a CT designed for foot/ankle) was driven by availability, as well as similar dimensions to the calcaneus. Each vertebra was immersed in saline solution and scanned twice without any repositioning (zero-strain-test) with a pedCAT-CT (Curvebeam, USA) obtaining an isotropic voxel size of 370 micrometers. Volumes of interest of 35 voxel were cropped inside the vertebrae. Displacement and strains were evaluated using DVC (DaVis-DC, LaVision, Germany), with different spatial resolution. The displacement maps were used to predict the force uncertainties via FE (Ansys Mechanical v.14, Ansys Inc, Canonsburg, PA). Each element was assigned a linear elastic isotropic constitutive law (Young modulus: 8 GPa, Poisson's ratio: 0.3, as in (Follet, Peyrin et al. 2007)). Overall, the precision error of strain measurement was evaluated as the average of the standard deviation of the absolute value of the different component of strain (Liu and Morgan 2007). The force uncertainties obtained with the FE analysis produced magnitudes ranging from 231 to 2376 N. No clear trend on the force was observed in relation to the spatial resolution. Precision errors were smaller than 1000 microstrain in all cases, with the lowest ranging from 83 microstrain for the largest spatial resolution. Full-field strain on the bone tissue did not seem to highlight a preferential distribution of error in the volume. The precision errors showed that the pedCAT-CT based DVC can be sufficient to investigate the bone tissue failure (7000–10000 microstrain) or, physiological deformation if well-optimized. FE analysis produced important force uncertainties up to 2376 N. However, this is a preliminary investigation. Further investigation will give a clearer indication on DVC based PedCAT-CT, as well as force uncertainties predicted. So far, the DVC showed its ability to measure displacement and strain with reasonable reliability with clinical-CT as well

The human musculoskeletal system is a biological composite of hard and soft material phases organized into a complex 3D structure. The replication of mechanical properties in 3-dimensional space, so called ‘4D’ techniques, therefore promises next-generation of prosthetics and engineering structures for the musculoskeletal system. Approaches using in situ indentation of tissue correlated with micro computed tomography (μCT) are used here to provide a 4D data set that is representative of the native tissue at high fidelity. Multi-material 3D printing is exploited to realize the collected 4D data set by using materials with a wide range of mechanical properties and printing structures representative of native tissue. We demonstrate this correlative approach to reproduce bone structures and highlight a workflow approach of indentation, μCT and 3D printing to potentially mimic any structure found in the musculoskeletal system. Structures in the human musculoskeletal system, such as bone [1] and tendon-bone connective tissue [2], can be considered as complex composites of hard and soft materials. Development of prosthetics capable of replacing body parts lost to trauma, disease or congenital conditions requires the accurate replication of the required body part. 3D printing promises considerable advantages over other manufacturing methods in mimicking native tissue, including the ability to produce complex structures [3]. However, accurate representation of whole body parts down to tissue microstructures requires correlative approaches where mechanical properties in 3-dimensional space are known. The objective of this study is to apply in situ indentation, correlate to 3D imaging of bone using μCT and finally 3D print mimicked structures. Samples of bovine compact bone were imaged at high resolution using μCT (Xradia Versa 510, Zeiss, USA). A custom build in situ micro indentation setup within the μCT was used to map the mechanical properties of the bone at multiple positions. Correlation between sample x-ray attenuation and corresponding elastic modulus found from indentation was established. Data was converted to a 4D data set of elastic modulus values in 3D space, segmented and exported to the 3D printer. An inkjet 3D printer (Projet 5500X, 3D Systems, USA) was used to print materials with a range of mechanical properties that approach those found in the native bone material. Macroscopic testing on both bone samples and 3D printed samples were carried out using standard compression (Instron, UK). Preliminary results indicated similarity between 3D printed structures and native bone tissue. Macroscopic testing of bone samples and 3D printed equivalents showed additional similarities in stress-strain behaviour. Our preliminary work presented here indicates that the workflow of 3D imaging correlated to point mechanical measurements using indentation is suitable to give a 4D dataset that is representative of the native bone tissue. 3D printing is able to produce structures that start to mimick bone but are critically dependent on the data segmentation, particularly averaging imaging data to a resolution that is appropriate for the 3D printer

High resolution imaging techniques such as atomic force microscopy, provide a platform to study the fibrillary architecture of biological tissues, but are not capable of imaging the internal microstructure of tissues in 3D. Conversely, multiphoton microscopes facilitate 3D imaging to study the spatial relationship of micro-components within tissues, but without the resolution of atomic force microscopy. The lamina splendens is the most superficial layer of articular cartilage. It is believed to play a crucial role in the health of the tissue. However, the precise form of this layer is uncertain as it has never been independently studied. Here, we use multiphoton microscopy and atomic force microscopy to demonstrate the anatomic form of the lamina splendens. The lamina splendens were peeled from the femoral condyles of healthy, adult sheep (n=20). Using atomic force microscopy, we show that the collagen and elastin form an interweaving fibrillary network at the surface of the lamina splendens and at the interface of the lamina splendens with the underlying cartilage. Moreover, using fluorescent stains; sulforhodamine B and acridine orange, multiphoton microscopy shows the heterogeneous distribution of collagen, elastin and chondrocytes throughout the depth of the lamina splendens. Our results demonstrate the fibrillary and component level architecture of the lamina splendens. We believe our findings provide the backbone of knowledge to advance tissue engineering techniques that will lead to more promising strategies to treat cartilage pathologies, including osteoarthritis. Furthermore, our results provide a starting point to determine the role of the lamina splendens in cartilage pathology

Additive Manufacturing techniques such as Selective laser melting (SLM) are increasingly used in the fabrication of hip, knee and other orthopaedic implants. This is due to the ability of these techniques to print geometrically complex parts with osteoconductive features, resulting in a decreased chance of aseptic loosening. To facilitate wider adoption of SLM, in-situ process monitoring is required. This paper examines the robustness of a novel monitoring systems ability to detect voids within the bulk of a component with varying part density. This work reports the results of a printing study carried out with Ti6Al4V parts using a production scale Renishaw system. This system is equipped with the recently developed in-situ monitoring system, called InfiniAM Spectral. InfiniAM measures the level of optical emissions emitted during the build process. The Spectral software creates a 3D representation of the part, in near real time, based on the level of emissions detected. In this work, Spectral 3D images are compared with those generated after printing using a micro CT scanner. The latter creates a virtual 3D representation of the part and has the ability to detect part defects and voids, as well as quantify part density, within the body of a component. In this work, parts were designed with voids of diameters in the range 200 to 600 μm. The sensitivity of the in-situ monitoring system was correlated with post process analysis of the void dimensions. Additionally, the detection of part density variation due to a variation of input energy, was also evaluated

Introduction. Better functional outcomes, lower pain and better stability have been reported with knee designs which restore physiological knee kinematics. Also the ability of the TKA design to properly restore the physiological femoral rollback during knee flexion, has shown to be correlated with better restoration of the flexor/extensor mechanism, which is fundamental to the function of the human knee. The purpose of the study is to compare the kinematics of three different TKA designs, by evaluating knee motion during Activities of Daily Living. The second goal is to see if there is a correlation between the TKA kinematics and the patient reported outcomes. Methods. Ten patients of each design, who are at least 6 months after their Total Knee Replacement, will be included in this study. Seven satisfied and 3 dissatisfied patients will be selected for each design. In this study 5 different movements will be analysed: flexion/extension; Sitting on and rising from a chair, Stair climbing, descending stairs, Flexion and extension open chain and squatting. These movements will be captured with a fluoroscope. The 2D images that are obtained, will be matched with the 3D implants. This 3D image will be processed with custom-made software to be able to analyse the movement. Tibio-femoral contact points of the medial and lateral condyles, tibio-femoral axial rotation, determination of the pivot-point will be analysed and described. After this analysis, a correlation between the kinematics and the KOOS and KSS will be investigated. Results. (The results of the first six patients are shown, more patients are currently being tested.) The average weight-bearing ROM of the implants is 108.48° +/− 19.68°

Introduction. The stability of the elbow joint following an acute elbow dislocation is dependent on associated injuries. The ability to identify these concomitant injuries correctly directs management and improves the chances of a successful outcome. Interpretation of plain radiographs in the presence of either a dislocation or post-reduction films with plaster in-situ is difficult. This study aimed to assess the ability of orthopaedic registrars to accurately identify associated bony injuries on initial plain radiographs using CT as the gold standard for comparison. Methods. Patients over the age of 16 years undergoing an elbow CT scan within one week of a documented elbow dislocation between 1st June 2010 and 1st June 2014 were included in the study. Three orthopaedic registrars independently reviewed both the initial dislocation and immediate post reduction plain radiographs to identify any associated bony injuries. This radiograph review was repeated by each registrar after two weeks. The incidence of associated injuries as well as the inter- and intra-observer variability was calculated. Results. 28 patients were included in the study. 54% of the patients were female and the mean age was 45 years (range 16 to 90 years). The incidence of a radial head fracture was 54%, coronoid fracture 43% and epicondyle avulsion 18% on CT. The inter-observer reliability was only shown to be fair amongst registrars and the intra-observer variability moderate. Conclusions. Computerised tomography is a useful adjunct in the assessment of associated osseous injuries following an elbow dislocation due to the presence of a high number of injuries. Plain radiographs alone have been shown to have only a fair and moderate inter and intra-observer variability respectively, therefore a low threshold to obtain further 3D imaging should be practised. Level of Evidence. IV

Summary Statement. In this study, we employed a novel imaging modalities, the synchrotron radiation microcomputed tomography (SRμCT) to visualise the 3D morphology of the spinal cord microvasculature and successfully obtained the 3D images. Introduction. Understanding the morphology of the spinal cord microvasculature in three-dimensions (3D) is limited by the lack of an effective high-resolution imaging technique. In this study, we used two novel imaging modalities, conventional x-ray microcomputed tomography (CμCT) and synchrotron radiation microcomputed tomography (SRμCT), to visualise the 3D morphology of the spinal cord microvasculature and to compare their utility in basic science research. Methods. (1) Sample Preparation: Ten adult Sprague-Dawley male rats (250–300 g) were randomly divided into A and B groups (n = 5). Both groups were subjected to angiography with contrast agent (Microfil MV-122, Flow Tech, CA, USA). The samples in group A were examined by CμCT, and the group B samples were analyzed through SRμCT scanning. After scanning, the samples was photographed with a stereomicroscope. (2) Images Analysis: The morphometric parameters in 2D were calculated using the Image-Pro Plus program (Ver. 6.0, Media Cybernetics. Bethesda, MD, USA), In the 3D dataset, the algorithms for the analysis of vessel structures in the VG Studio Max software package (Volume Graphics GmbH, Germany) were applied to calculate the morphological parameters of the spinal cord microvasculature. Results. The reconstructed tomographic slices of the rat spinal cord microvasculature obtained by these two techniques are illustrated. In the 2D tomographic view, the area with a high gray value, which indicates the location of the vessels, could be easily differentiated from the neural parenchymal background. The CμCT slices dataset only provided indistinctive images with weak apparent artefacts. In contrast, extensive distributions of the microvessels were found in the intrinsic neural parenchyma in the SRμCT slices. (2) The 3D reconstructed image obtained through SRμCT, provided a clear and precise configuration of the complex spatial structure and connectivity of the intensive microvasculature of the spinal cord when compared with CμCT. (3) The extracted 3D spatial distribution image of the spinal cord microvasculature was able to match the specimen's morphology photographed with a stereomicroscope. Discussion & Conclusion. In this study, we have combined two emerging techniques to capture the 3D morphological features of the rat spinal cord microvasculature in vitro for the first time. With the help of contrast agents and the advanced computed tomography algorithm, both CμCT and SRμCT were able to provide a valuable 3D volumetric dataset of the spinal cord vascular structure. These datasets could be extracted and analyzed from different angles and at multiple levels, which are analysis that were not previously possible with the conventional histological methods. However, when compared with CμCT, SRμCT was able to achieve higher-resolution vascular imaging and to obtain detailed 3D morphological features of the spinal cord microvasculature. These data imply that SRμCT may be regarded as a unique imaging technique that is more suitable than CμCT for 3D angioarchitectural investigation in preclinical neurovascular research

Summary Statement. We successfully delineated the 3D micro morphology of chondrocytes in patella-patellar tendon using IL-XPCT for the first time. Compared with conventional histology, IL-XPCT can not only provide a higher resolution imgaing but also keep the 3D integrity of the specimen. Introduction. The morphology of the bone-tendon junction was complex and quite different from other organs, which result the injured bone-tendon junction repair process too slowly. To study the micro morphology of the bone-tendon junction in 3D may have a great significant value to revealing the repair mechanisms of this pathological process and accelerating injured bone-tendon junction repair. However, it was hindered by the convention methods such as histologic section. In our study, a novel imaging tool, synchrotron radiation based in-line x-ray phase contrast imaging (IL-XPCT) was used to research the 3D micro morphology of the bone-tendon junction. Methods. 1) Sample Preparation: 3 patella-patellar tendons was harvested from the knee joint of New Zealand adult rabbits and was immediately fixed, rinsed in water for 2 hours. Dehydration was done using a series of graded ethanol. The sample was cut out for the CCD pixel resolution in sagittal section. 2) Image Acquisition: The IL-XPCT was performed at the BL13W1 of the Shanghai Synchrotron Radiation Facility (SSRF) in China. The CCD pixel resolution was 0.74 μm. Image Acquisition include three steps, such as the the acquisition of tomo projections, CT slices and and 3D reconstruction of patella-patellar tendon on full scale by using VG Studio Max version 2.1. 3) Histological characterization observation: After scanning, the specimen was cut to histologic sectioning and used for morphology staining by safranin O staining and H&E staining. The histological morphology then compared with the IL-XPCT imaging dateset. Results. (1) The tissue gradations of patella-patellar tendon are clearly detected by IL-XPCT. (2) The 3D reconstruction image of patella-patellar tendon sample were largely match with the histological morphology stained by safranin O and H&E in sagittal view. (3) After the image segmentation, the 3D micro morphology of the bone-tendon junction could be vividly visualised in multi-angles. Through manipulate threshold of the 3D image, we can successfully obtained the 3D morphology of the chondrocyte, and the smallest diameter is approximately 5μm. Discussion & Conclusion. In the present study, we successfully delineated the 3D micro morphological features of chondrocytes in normal patella-patellar tendon using SR-based IL-XPCT for the first time. Compared with conventional histology, IL-XPCT can not only provide a higher resolution ratio without distortion but also keep the three-dimensional integrity of the specimen. Above all, IL-XPCT opens access to a new dimension in the morphological investigation of bone-tendon junction tissues, giving important complementary information to the conventional morphological analyses in view of the three-dimensional composition of bone-tendon junction tissues, On the other hand, it could be helpful to understanding the repair processes of bone-tendon junction injury and promoting the injured bone-tendon junction repair fast and high quality

3D imaging is commonly employed in the surgical planning and management of bony deformity. The advent of desktop 3D printing now allows rapid in-house production of specific anatomical models to facilitate surgical planning. The aim of this pilot study was to evaluate the feasibility of creating 3D printed models in a university hospital setting. For requested cases of interest, CT DICOM images on the local NHS Picture Archive System were anonymised and transferred. Images were then segmented into 3D models of the bones, cleaned to remove artefacts, and orientated for printing with preservation of the regions of interest. The models were printed in polylactic acid (PLA), a biodegradable thermoplastic, on the CubeX Duo 3D printer. PLA models were produced for 4 clinical cases; a complex forearm deformity as a result of malunited childhood fracture, a pelvic discontinuity with severe acetabular deficiency following explantation of an infected total hip replacement, a chronically dislocated radial head causing complex elbow deformity as a result of a severe skeletal dysplasia, and a preoperative model of a deficient proximal tibia as a result of a severe tibia fracture. The models materially influenced clinical decision making, surgical intervention planning and required equipment. In the case of forearm an articulating model was constructed allowing the site of impingement between radius and ulnar to be identified, an osteotomy was practiced on multiple models allowing elimination of the block to supination. This has not previously been described in literature. The acetabulum model allowed pre-contouring of a posterior column plate which was then sterilised and eliminated a time consuming intraoperative step. While once specialist and expensive, in house 3D printing is now economically viable and a helpful tool in the management of complex patients

In-situ assessment of collateral ligaments strain could be key to improving total knee arthroplasty outcomes by improving the ability of surgeons to properly balance the knee intraoperatively. Ultrasound (US) speckle tracking methods have shown promise in their capability to measure in-situ soft tissue strain in large tendons but prior work has also highlighted the challenges that arise when attempting to translate these approaches to the in-situ assessment of collateral ligaments strain. Therefore, the aim of this project was to develop and validate an US speckle tracking method to specifically assess in-situ strains of both the MCL and LCL. We hypothesize that coefficients of determination (R. 2. ) would be above 0.90 with absolute differences below 0.50% strain for the comparison between US-based and the reference strain, with better results expected for the LCL compared with the MCL. Five cadaveric legs with total knee implants (NH019 2017-02-03) were submitted to a varus (LCL) and valgus (MCL) ramped loading (0 – 40N). Ultrasound radiofrequency (rf) data and reference surface strains data, obtained with 3D digital image correlation (DIC), were collected synchronously. Prior to processing, US data were qualitatively assessed and specimens displaying substantial imaging artefacts were discarded, leaving five LCL and three MCL specimens in the analysis. Ultrasound rf data were processed in Matlab (The MathWorks, Inc., Natick, MA) with a custom-built speckle tracking approach adapted from a method validated on larger tendons and based on normalized cross-correlation. Digital image correlation data were processed with commercial software VIC3D (Correlated Solutions, Inc., Columbia, SC). To optimize speckle tracking, several tracking parameters were tested: kernel and search window size, minimal correlation coefficient and simulated frame rate. Parameters were ranked according to three comparative measures between US- and DIC-based strains: R. 2. , mean absolute error and strains differences at 40N. Parameters with best average rank were considered as optimal. To quantify the agreement between US- and DIC-based strain of each specimen, the considered metrics were: R. 2. , mean absolute error and strain differences at 40N. The LCL showed a good agreement with a high average R. 2. (0.97), small average mean absolute difference (0.37%) and similar strains at 40N (DIC = 2.92 ± 0.10%; US = 2.99 ± 1.16%). The US-based speckle tracking method showed worse performance for the MCL with a lower average correlation (0.55). Such an effect has been observed previously and may relate to the difficulty in acquiring sufficient image quality for tracking the MCL compared to the LCL, which likely arises due to structural or mechanical differences; notably MCL is larger, thinner, more wrapped around the bone and stretches less. However, despite these challenges, the MCL tracking still showed small average mean absolute differences (0.44%) and similar strains at 40N (DIC = 1.48 ± 0.06%; US = 1.44 ± 1.89%). We conclude that the ultrasound speckle tracking method developed is ready to be used as a tool to assess in-situ strains of LCL. Concerning the MCL strain assessment, despite some promising results in terms of strain differences, further work on acquisition could be beneficial to reach similar performance

A tendon is a fibrous connective tissue that acts to transmit tensile forces between muscles and bones. It mainly consists of soluble substance, collagen and small volume of elastic fibres, which are produced by tenoblasts and tenocytes. The Achilles tendon is the thickest tendon in the human body that subjects to some of the highest tensile force, thus disorders and ruptures commonly happen. As the insoluble fibrous components in Achilles tendons, the collagen fibrils and elastic fibres have unique spatial structure that plays important functional roles. Despite this, the understanding of relationship between them is still limited due to the lack of imaging evidence. Using confocal and second harmonic generation microscopy, this study aims to comprehensively investigate the spatial relationship of collagen, elastic fibres and tenocytes in hydrated tendons. Longitudinal sections of 50 µm thick and transverse sections of 20 µm thick were cryo-sectioned respectively from the mid-portion of ten rabbit Achilles tendons. Sections were stained with 0.03g/L Acridine Orange (AO) and 1mg/ml Sulforhodamine B (SRB) solution respectively for labelling the nucleus and elastic fibres. The Leica TCS SP2 multiphoton microscopy containing second harmonic generation microscopy can image collagen without labelling. The sections were scanned by the multiphoton microscopy, and images were processed and reconstructed into 3D images to study the spatial structure of collagen, elastic fibres and cells in Achilles tendons. A rabbit Achilles tendon consists of three sub-tendons named flexor digitorum superficialis tendon, medial gastrocnemius tendon and lateral gastrocnemius tendon. Loose connective tissue connects the three sub-tendons and ensures efficient sliding between sub-tendons. The 3D network shows that the mid-portion of Achilles tendons is composed of longitudinal collagen and elastic fibres, while spindle tenocytes rest along the collagen and elastic fibres. Tenocytes appear to have a closer microstructural relationship with the elastic fibres. In comparison with the collagen, tenocytes and elastic fibres only occupy a very small volume in the 3D network. The elastic fibres exist in both tendon proper and endotenons. The tendon sheath and loose connective tissue have a higher cell density, and the cells are large and round while compared with tenocytes. As a component of the extracellular matrix (ECM) in Achilles tendons that closely mediates with the tenocytes, the elastin may participate in the force transition and interaction between tenocytes and the ECM. The elastic fibres may also endow Achilles tendons with unique mechanical properties to stand for tensile force

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.

Reconstruction of severe acetabular defects during revision hip arthroplasty presents a significant surgical challenge. Such defects are associated with significant loss of host bone stock, which must be addressed in order to achieve stable implant fixation. A number of imaging techniques including CT scanning with 3D image reconstruction are available to assist the surgeon in the pre-operative planning of such procedures. We describe the use of a novel technique to assist the pre-operative planning of severe acetabular defects during revision hip arthroplasty. Patient and Methods – We present the use of this technique in the case of a 78 year old patient who presented 20 years from index procedure with severe hip pain and inability to weight bear due aseptic loosening of a previously revised total hip arthroplasty. A Paprosky 3B defect was noted with intra-pelvic migration of the acetabular component. Pre-operative investigations included: inflammatory markers, pelvic CT scan with 3D reconstruction, pelvic angiography and hip aspiration. Using DICOM images obtained from the CT scan, we used free open source software to carry out a 3D surface render of the bony pelvis. This was processed and converted to a suitable format for 3D printing. Using selective laser sintering, a physical 3D model of the pelvis, acetabular component and proximal femur were produced. Using this model the surgeon was able to gain an accurate representation of both the position of the intra-pelvic cup and more accurately assess the loss of bone stock. This novel technique is particularly useful in the pre-operative planning of such complex acetabular defects in order to determine if/which reconstruction technique is most likely to be successful. 3D printing is a relatively recent technology, which has numerous potential clinical applications. This is the first reported case of this technology being used to assess acetabular defects during revision hip arthroplasty. The use of this technology gives the surgeon a 3D model of the pelvis, quickly (7 days from CT) and at a tenth of the cost (£280) of producing such a model through the traditional commercial routes. The model allowed the surgeon to size potential implant, quantify the amount of bone graft required (if applicable) and to more accurately classify the loss of acetabular bone stock

Total ankle replacement (TAR) is contraindicated in patients with significant talar collapse due to AVN and in these patients total talus body prosthesis has been proposed to restore ankle joint. To date, five studies have reported implantation of a custom-made talar body in patients with severely damaged talus, showing the limit of short-term damage of tibial and calcaneal thalamic joint surfaces. Four of this kind of implants have been performed. The first two realized with “traditional” technology CAD-CAM has been performed in active patients affected by “missing talus” and now presents a survival follow-up of 15 and 17 years. For the third patient affected by massive talus AVN we designed a 3D printed porous titanium custom talar body prosthesis fixed on the calcaneum and coupled with a TAR, first acquiring high-resolution 3D CT images of the contralateral healthy talus that was “mirroring” obtaining the volume of fractured talus in order to provide the optimal fit. Then the 3D printed implant was manufactured. The fourth concern a TAR septic mobilization with high bone loss of the talus. The “two-stage” reconstruction conducted with the implant of total tibio-talo-calcaneal prosthesis “custom made” built with the same technology 3D, entirely in titanium and using the “trabecular metal” technology for the calcaneous interface. Weightbearing has progressively allowed after 6 weeks. No complications were observed. All the implants are still in place with an overall joint mobility ranging from 40° to 60°. This treatment requires high demanding technical skills and experience with TAR and foot and ankle trauma. The 15 years survival of 2 total talar prosthesis coupled to a TAR manufactured by a CAD-CAM procedure encourages consider this 3D printed custom implant as a new alternative solution for massive AVN and traumatic missing talus in active patients

Summary Statement. Demineralised bone matrix augmented tendon-bone fixations in the animal model show less scar tissue and an enthesis morphology closer to the physiologic one which may lead to a more resistant repair construct. Introduction. Rotator cuff repair is one of the most common operative procedures in the shoulder. Yet despite its prevalence recurrent tear rates of up to 94% have been reported in the literature. High failure rates have been associated with tendon detachment from bone at the tendon – bone interface. Exogenous agents as biological strategies to augment tendon – bone healing in the shoulder represent a new area of focus to improve patient outcomes. Demineralised bone matrix (DBM) contains matrix bound proteins, exposed through acid demineralization step of DBM manufacture, and has long been recognised for its osteoinductive and osteoconductive properties. We hypothesised that DBM administered to the bone bed prior to the reattachment of the tendon, will upregulate healing and result in enhanced tissue morphology that more closely resembles that of a normal enthesis. An established ovine transosseous equivalent rotator cuff model was used. Methods. Following ethics approval, 10 adult wethers (18 months) were randomly allocated to control, n=4 (without DBM) or DBM, n=6 (DBM administered to bone bed) groups. The infraspinatus tendon was detached from its insertion and repaired in a transosseous equivalent fashion using PEEK suture anchors. In treatment animals 0.25cc of ovine DBM, previously prepared using a modified Urist protocol, was injected into two drill holes within the bony tendon footprint. Animals were culled at 4 weeks following surgery and processed for tissue histology and microcomputed tomography (μCT) endpoints. Results. No infection or tendon detachment following repair was noted in either group. 3D reconstructed images of μCT scans verified correct DBM and suture anchor placement. Histological images demonstrated distinct differences in tissue morphology between the two groups; however there was no evidence of the four – zoned structure characteristic of a healthy tendon bone insertion, in any specimens. In the control group specimens, the tendon midsubstance was highly disorganised with randomly arranged collagen fibres and diminutive areas of fibrocartilage. In the treatment group, large regions between tendon and bone were occupied by fibrocartilage. Within the fibrocartilage region, insertional collagen fibres appeared organised and chondrocytes were orientated in the direction of the insertional collagen fibres. Organised collagen fibre orientation within the tendon midsubstance was observed, though this was not consistent throughout all the specimens. DBM particles were resorbed and trabecular bone occupied the DBM holes. The PEEK anchors were all in direct contact with the ongrowing bone indicating good quality integration and fixation. Discussion. This study showed that DBM augmented tendon to bone repair leads to an upregulated cellular activity resulting in increased amounts of fibrocartilage between the repaired tendon and underlying bone. The upshot of this is an improved tissue organization which more closely resembles the morphology of the normal enthesis. Introduction of osteoinductive DBM at the tendon – bone interface during surgery may reduce failure rates associated with rotator cuff repair and improve clinical outcomes

Summary Statement. The current study introduced the effects of projection errors on ankle morphological measurements using CT-based simulated radiographs by correlation analysis between 2D/3D dimensions and reliability analysis with randomised perturbations while measuring planar parameters on radiographs. Introduction. Clinical success of total ankle arthroplasty (TAA) depends heavily on the available anatomy-based information of the morphology for using implants of precisely matched sizes. Among the clinically available medical imaging modalities, bi-planar projective radiographs are commonly used for this purpose owing to their convenience, low cost, and low radiation dose compared with other modalities such as MRI or CT. However, the intrinsic articular surface of the ankle joint is not symmetrical and oblique which implies that it is difficult to describe all the anatomical dimensions in detail with only one radiograph, thereby hindering the determination of accurate ankle morphometric parameters. The purposes of this study were to compare the measurements of ankle morphology using 3D CT images with those on planar 2D images; and to quantify the repeatability of the 2D measurements under simulated random perturbations. Patients & Methods. Fifty-eight fresh frozen cadaveric ankle specimens were used in the current study. Each specimen was fixed in the neutral position with a plastic frame. After fixation, the specimen-fixation construct was scanned using a 16-slice spiral CT scanner (GE BrightSpeed 16, C&G Technologies, USA) with a slice thickness of 0.625 mm. A global coordinate system was embedded in the ankle specimen with the origin at the geometric center of the talus, the anteroposterior (A/P) axis in parallel to the base-plate, the superoinferior (S/I) axis perpendicular to the base-plate, and the mediolateral (M/L) axis as the line perpendicular to both the A/P and S/I axes. Fourteen 3D morphological parameters were automatically determined using a house-developed program in MATLAB R2010a (The MathWorks, Inc., USA). A simulated standard digital radiography system, in which the X-ray focus was 1 meter away from the image plane, was also introduced to determine the planar 2D morphological parameters for comparing with those determined in 3D. Reliability with randomised perturbations during measurements was also assessed in terms of the intra-class correlation coefficients using a 2-way mixed-effects average model (ICC3, k) for intra-examiner assessments. All statistical analysis was performed using SPSS 13.0 (SPSS Inc., USA). Results. Most of the morphological parameters had high correlation and reliability, except for the maximal tibial thickness (MTiTh), distance between most vertex of tibial mortise to the level of MTiTh (MDV) and radius of trochlea tali (TaR) had moderate to low correlation which were 0.54, 0.37 and 0.09 respectively. The ICC coefficients indicated that the MDV, talus width (TaW) and inclination angle between two most vertex points of trochlea tali (MLATa) had moderate and poor reliability which were 0.59, 0.49 and 0.07 respectively. Discussion/Conclusion. The current study introduced the effects of projection errors on ankle morphological measurements using CT-based simulated radiographs by correlation analysis between 2D/3D dimensions and reliability analysis with randomised perturbations while measuring planar parameters on radiographs. MTiTh and MDV are the important parameters to help surgeon pre-surgical decision-making. TaW is one of the critical parameters for choosing accurate sise of TAA implant. It implies that the respectively accurate pose of ankle is critical during bi-planar radiography

Objectives

Preservation of both anterior and posterior cruciate ligaments in total knee arthroplasty (TKA) can lead to near-normal post-operative joint mechanics and improved knee function. We hypothesised that a patient-specific bicruciate-retaining prosthesis preserves near-normal kinematics better than standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining prostheses in TKA.