Introduction and Objective. Forced external rotation is hypothesized as the key mechanism of syndesmotic ankle injuries. This complex trauma pattern ruptures the syndesmotic ligaments and induces a three-dimensional deviation from the normal distal tibiofibular joint configuration. However, current diagnostic imaging modalities are impeded by a two-dimensional assessment, without taking into account ligamentous stabilizers. Therefore, our aim is two-fold: (1) to construct an articulated statistical shape model of the normal ankle with inclusion of ligamentous morphometry and (2) to apply this model in the assessment of a clinical cohort of patients with syndesmotic ankle injuries. Materials and Methods. Three-dimensional models of the distal tibiofibular joint were analyzed in asymptomatic controls (N= 76; Mean age 63 +/− 19 years), patients with syndesmotic ankle injury (N = 13; Mean age 35 +/− 15 years), and their healthy contralateral equivalent (N = 13). Subsequently, the statistical shape model was generated after aligning all ankles based on the distal tibia. The position of the syndesmotic ligaments was predicted based on previously validated iterative shortest path calculation methodology. Evaluation of the model was described by means of accuracy, compactness and generalization. Canonical Correlation Analysis was performed to assess the influence of syndesmotic lesions on the distal tibiofibular joint congruency. Results. Our presented model contained an accuracy of 0.23 +/− 0.028 mm. Mean prediction accuracy of ligament insertions was 0.53 +/− 12 mm. A statistically significant difference in anterior syndesmotic distance was found between ankles with syndesmotic lesions and healthy controls (95% CI [0.32, 3.29], p = 0.017). There was a significant correlation between presence of syndesmotic injury and the morphological distal tibiofibular configuration (r = 0.873, p <0,001). Conclusions. In this study, we constructed a bony and ligamentous statistical model representing the distal tibiofibular joint Furthermore, the presented model was able to detect an elongation injury of the anterior inferior tibiofibular ligament after traumatic syndesmotic lesions in a clinical patient cohort

Bone infections due to fractures or implants are a big medical problem. In experimental medicine, many experimental models have been created on different animal species to simulate the disease condition and to do experience treatments. The aim of this paper was to present an antibacterial efficacy of using a bone allograft developed according to the Marburg system of bone bank on a model of chronic osteomyelitis induced in rabbits. In research was used 54 rabbits. Osteomyelitis was induced in rabbits by a human strain of St. aureus ATCC 43300, in the rabbit femur. There have been created 3 groups of animals. In 1. st. group used antibiotic impregnated biodegradable material “PerOssal”. In 2. nd. group used antibiotic impregnated whole bone allograft. In 3. rd. group used antibiotic impregnated perforated bone allograft. Evaluation of installation and evolution of the disease was done by microbiological. A separate study of microbiological data is presented here. This study showed, in the 1. st. and 3. rd. groups there is a persistent decrease in CFU by 14 knocks to 120.4 in the 1. st. group and to 3.5 in the 3. rd. group, and in the 2. nd. group, on the contrary, there is an increase in CFU to 237.33. This shows the lack of effectiveness of using a whole bone allograft. The results showed, after 7 days there was no statistically significant difference between the groups. After 14 days the perforated bone allograft impregnated with antibiotic was better than the biodegradable material “PerOssal”

Glenoid and humeral head bone defects have long been recognized as major determinants in recurrent shoulder instability as well as main predictors of outcomes after surgical stabilization. However, a universally accepted method to quantify them is not available yet. The purpose of the present study is to describe a new CT method to quantify bipolar bone defects volume on a virtually generated 3D model and to evaluate its reproducibility.

A cross-sectional observational study has been conducted. Forty CT scans of both shoulders were randomly selected from a series of exams previously acquired on patients affected by anterior shoulder instability. Inclusion criterion was unilateral anterior shoulder instability with at least one episode of dislocation. Exclusion criteria were: bilateral shoulder instability; posterior or multidirectional instability, previous fractures and/or surgery to both shoulders; congenital or acquired inflammatory, neurological, or degenerative diseases. For all patients, CT exams of both shoulders were acquired at the same time following a standardized imaging protocol. The CT data sets were analysed on a standard desktop PC using the software 3D Slicer. Computer-based reconstruction of the Hill-Sachs and glenoid bone defect were performed through Boolean subtraction of the affected side from the contralateral one, resulting in a virtually generated bone fragment accurately fitting the defect. The volume of the bone fragments was then calculated. All measurements were conducted by two fellowship-trained orthopaedic shoulder surgeons. Each measurement was performed twice by one observer to assess intra-observer reliability. Inter and intra-observer reliability were calculated. Intraclass Correlation Coefficients (ICC) were calculated using a two-way random effect model and evaluation of absolute agreement. Confidence intervals (CI) were calculated at 95% confidence level for reliability coefficients. Reliability values range from 0 (no agreement) to 1 (maximum agreement).

The study included 34 males and 6 females. Mean age (+ SD) of patients was 36.7 + 10.10 years (range: 25 – 73 years). A bipolar bone defect was observed in all cases. Reliability of humeral head bone fragment measurements showed excellent intra-observer agreement (ICC: 0.92, CI 95%: 0.85 – 0.96) and very good interobserver agreement (ICC: 0.89, CI 95%: 0.80 – 0.94). Similarly, glenoid bone loss measurement resulted in excellent intra-observer reliability (ICC: 0.92, CI 95%: 0.85 – 0.96) and very good inter-observer agreement (ICC: 0.84, CI 95%:0.72 – 0.91).

In conclusion, matching affected and intact contralateral humeral head and glenoid by reconstruction on a computer-based virtual model allows identification of bipolar bone defects and enables quantitative determination of bone loss.

Objectives. Regenerative medicine is an emerging field aimed at the repair and regeneration of various tissues. To this end, cytokines (CKs), growth factors (GFs), and stem/progenitor cells have been applied in this field. However, obtaining and preparing these candidates requires invasive, costly, and time-consuming procedures. We hypothesised that skeletal muscle could be a favorable candidate tissue for the concept of a point-of-care approach. The purpose of this study was to characterize and confirm the biological potential of skeletal muscle supernatant for use in regenerative medicine. Methods. Semitendinosus muscle was used after harvesting tendon from patients who underwent anterior cruciate ligament reconstructions. A total of 500 milligrams of stripped muscle was minced and mixed with 1 mL of saline. The collected supernatant was analysed by enzyme-linked immunosorbent assay (ELISA) and flow cytometry. The biological effects of the supernatant on cell proliferation, osteogenesis, and angiogenesis in vitro were evaluated using human mesenchymal stem cells (hMSCs) and human umbilical cord vein endothelial cells (HUVECs). Results. The supernatant contained several GFs/CKs, with especially high levels of basic fibroblast growth factor, and CD34+ cells as the stem/progenitor cell fraction. With regard to biological potential, we confirmed that cell proliferation, osteoinduction, and angiogenesis in hMSCs and HUVECs were enhanced by the supernatant. Conclusions. The current study demonstrates the potential of a new point-of-care strategy for regenerative medicine using skeletal muscle supernatant. This attractive approach and readily-available material could be a promising option for tissue repair/regeneration in the clinical setting. Cite this article: M. Yoshikawa, T. Nakasa, M. Ishikawa, N. Adachi, M. Ochi. Evaluation of autologous skeletal muscle-derived factors for regenerative medicine applications. Bone Joint Res 2017;6:277–283. DOI: 10.1302/2046-3758.65.BJR-2016-0187.R1

Duchenne muscular dystrophy (DMD) is a prevalent childhood neuromuscular disease characterized by progressive skeletal and cardiac muscle degeneration due to dystrophin protein deficiency. Despite ongoing drug development efforts, no cure exists, with limited success in preclinical studies. To expedite DMD drug development, we introduce an innovative organ-on-a-chip (OOC) platform. This microfluidic device sustains up to six 3D patient-derived skeletal muscle tissues, enabling real-time evaluation of anti-DMD treatments. Our in vitro model recreates myotube integrity loss, a hallmark of DMD, by encapsulating myogenic precursors in a fibrin-composite matrix using a PDMS casting mold. Continuous contractile regimes mimic sarcolemmal instability, monitored through tissue contractibility and Creatine Kinase (CK) levels—an established marker of muscle damage. We further enhance our platform with a nanoplasmonic CK biosensor, enabling rapid, label-free, and real-time sarcolemmal damage assessment. Combining these elements, our work demonstrates the potential of OOCs in accelerating drug development for DMD and similar neuromuscular disorders.

Despite the growing success of OCA transplantation in treating large articular cartilage lesions in multiple joints, revisions and failures still occur. While preimplantation subchondral drilling is intended to directly decrease allograft bioburden and has been associated with significant improvements in outcomes after OCA transplantation, the effects of size, number, and spacing of subchondral bone drill sites have not been fully evaluated. This study aimed to investigate the effects of drill size with or without pulse-lavage of OCA subchondral bone by quantifying remnant marrow elements using histomorphometry.

With IRB and ACUC approvals, human and canine OCAs were acquired for research purposes. Portions of human tibial plateau OCAs acquired from AATB-certified tissue banks that would otherwise be discarded were recovered and sectioned into lateral and medial hemiplateaus (n=2 each) with a thickness of 7 mm. Canine femoral condyles and tibial plateaus were split into lateral and medial components with a thickness of 7 mm (n=8). Using our clinical preimplantation preparation protocol, holes were drilled into the subchondral bone of each condyle and hemiplateau OCA using either 1.6 mm OD or 3.2 mm OD drill bits from the cut surface to the cortical subchondral bone plate. One femoral condyle and one hemiplateau per drill bit size were pulse-lavaged while the corresponding OCAs were not. The mean total %-fill remaining marrow elements for each treatment group was calculated.

Little to no quantifiable bone marrow element retention was noted to remain within the subchondral bone of human or canine OCA specimens after subchondral drilling of allograft bone with either drill bit size evaluated and with or without pulse-lavage. The %-fill was consistent across zones, ranging from 1-5%.

This project was designed to provide a preliminary histologic evaluation of the effects of drill size on OCA preimplantation preparation efficacy based on amount of remaining bone marrow elements in human and canine femoral condyle and tibial plateau specimens. Based on these initial findings, choice of drill bit size for OCA subchondral drilling may need to be based on the associated biomechanical effects rather than effects on donor bone marrow element removal.

In severe cases of total knee arthroplasty which cannot be treated with off-the-shelf implants anymore custom-made knee implants may serve as one of the few remaining options to restore joint function or to prevent limb amputation. Custom-made implants are specifically designed and manufactured for one individual patient in a single-unit production, in which the surgeon is responsible for the implant design characteristics in consultation with the corresponding engineer.

The mechanical performance of these custom-made implants is challenging to evaluate due to the unique design characteristics and the limited time until which the implant is needed. Nevertheless, the custom-made implant must comply with clinical and regulatory requirements. The design of custom-made implants is often based on a underlying reference implant with available biomechanical test results and well-known clinical performance. To support surgeons and engineers in their decision whether a specific implant design is suitable, a method is proposed to evaluate its mechanical performance.

The method uses finite element analysis (FEA) and comprises six steps: (1) Identification of the main potential failure mechanism and its corresponding FEA quantity of interest. (2) Reproduction of the biomechanical test of the reference implant via FEA. (3) Identification of the maximum value of the corresponding FEA quantity of interest at the required load level. (4) Definition of this value as the acceptance criteria for the FEA of the custom-made implant. (5) Reproduction of the biomechanical test with the custom-made implant via FEA. (6) Conclusion whether the acceptance criteria is fulfilled or not.

The method was applied to two exemplary cases of custom-made knee implants. The FEA acceptance criteria derived from the reference implants were fulfilled in both custom-made implants. Subsequent biomechanical tests verified the FEA results.

This study suggests and applies a non-destructive and efficient method for pre-clinical testing of a single-unit custom-made knee implant to evaluate whether the design is mechanically suitable.

Mechanical failure of spine posterior fixation in the lumbar region Is suspected to occur more frequently when the sagittal balance is not properly restored. While failures at the proximal extremity have been studied in the literature, the lumbar distal junctional pathology has received less attention. The aim of this work was to investigate if the spinopelvic parameters, which characterize the sagittal balance, could predict the mechanical failure of the posterior fixation in the distal lumbar region.

All the spine surgeries performed in 2017-2019 at Rizzoli Institute were retrospectively analysed to extract all cases of lumbar distal junctional pathology. All the revision surgeries performed due to the pedicle screws pull-out, or the breakage of rods or screws, or the vertebral fracture, or the degenerative disc disease, in the distal extremity, were included in the junctional (JUNCT) group. A total of 83 cases were identified as JUNCT group. All the 241 fixation surgeries which to date have not failed were included in the control (CONTROL) group. Clinical data were extracted from both groups, and the main spinopelvic parameters were assessed from sagittal standing preoperative (pre-op) and postoperative (post-op) radiographs with the software Surgimap (Nemaris). In particular, pelvic incidence (PI), sagittal vertical axis (SVA), pelvic tilt (PT), T1 pelvic angle (TPA), sacral slope (SS) and lumbar lordosis (LL) have been measured.

In JUNCT, the main failure cause was the screws pull-out (45%). Spine fixation with 7 or more levels were the most common in JUNCT (52%) in contrast to CONTROL (14%). In CONTROL, PT, TPA, SS and PI-LL were inside the recommended ranges of good sagittal balance. For these parameters, statistically significant differences were observed between pre-op and post-op (p<0.0001, p=0.01, p<0.0001, p=0.004, respectively, Wilcoxon test). In JUNCT, the spinopelvic parameters were out of the ranges of the good sagittal balance and the worsening of the balance was confirmed by the increase in PT, TPA, SVA, PI-LL and by the decrease of LL (p=0.002, p=0.003, p<0.0001, p=0.001, p=0.001, respectively, paired t-test) before the revision surgery. TPA (p=0.003, Kolmogorov-Smirnov test) and SS (p=0.03, unpaired t-test) differed significantly in pre-op between JUNCT and CONTROL. In post-op, PI-LL was significantly different between JUNCT and CONTROL (p=0.04, unpaired t-test). The regression model of PT vs PI was significantly different between JUNCT and CONTROL in pre-op (p=0.01, Z-test).

These results showed that failure is most common in long fused segments, likely due to long lever arms leading to implant failure. If the sagittal balance is not properly restored, after the surgery the balance is expected to worsen, eventually leading to failure: this effect was confirmed by the worsening of all the spinopelvic parameters before the revision surgery in JUNCT. Conversely, a good sagittal balance seems to avoid a revision surgery, as it is visible is CONTROL. The mismatch PI-LL after the fixation seems to confirm a good sagittal balance and predict a good correction. The linear regression of PT vs PI suggests that the spine deformity and pelvic conformation could be a predictor for the failure after a fixation.

Screw fixation is an established method for anterior cruciate ligament (ACL) reconstruction, although with a high rate of implant-related complications. An allograft system for implant fixation in ACL reconstruction, the Shark Screw ACL (surgebright GmbH) could overcome some of the shortcomings of bioabsorbable screws, such as foreign body reaction, need for implant removal and imaging artefacts. However, it needs to provide sufficient mechanical stability. Therefore, the aim of this study was to investigate the biomechanical stability, especially graft slippage, of the novel allograft system versus a conventional bioabsorbable interference screw (BioComposite Interference Screw; Arthrex Inc.) for tibial implant fixation in ACL reconstruction.

Twenty-four paired human proximal tibiae (3 female, 9 male, 72.7 ± 5.6 years) underwent ACL reconstruction. The quadrupled semitendinosus and gracilis tendon graft were fixed in one specimen of each pair using the allograft fixation system Shak Screw ACL and the contralateral one using an interference screw. All specimens were cyclically loaded at 1 Hz with peak load levels monotonically increased from 50 N at a rate of 0.1 N/cycle until catastrophic failure. Relative movements of the graft versus the tibia were captured with a stereographic optical motion tracking system (Aramis SRX; GOM GmbH).

The two fixation methods did not demonstrate any statistical difference in ultimate load at graft slippage (p = 0.24) or estimated survival at slippage (p = 0.06). Both, the ultimate load and estimated survival until failure were higher in the interference screw (p = 0.04, and p = 0.018, respectively). Graft displacement at ultimate load reached values of up to 7.2 mm (interference screw) and 11.3 mm (Shark Screw ACL).

The allograft screw for implant fixation in ACL reconstruction showed similar behavior in terms of graft slippage compared to the conventional metal interference screw but underperformed in terms of ultimate load. However, the ultimate load may not be considered a direct indicator of clinical failure.

Objectives. Implant-related infection is one of the most devastating complications in orthopaedic surgery. Many surface and/or material modifications have been developed in order to minimise this problem; however, most of the in vitro studies did not evaluate bacterial adhesion in the presence of eukaryotic cells, as stated by the ‘race for the surface’ theory. Moreover, the adherence of numerous clinical strains with different initial concentrations has not been studied. Methods. We describe a method for the study of bacterial adherence in the presence of preosteoblastic cells. For this purpose we mixed different concentrations of bacterial cells from collection and clinical strains of staphylococci isolated from implant-related infections with preosteoblastic cells, and analysed the minimal concentration of bacteria able to colonise the surface of the material with image analysis. Results. Our results show that clinical strains adhere to the material surface at lower concentrations than collection strains. A destructive effect of bacteria on preosteoblastic cells was also detected, especially with higher concentrations of bacteria. Conclusions. The method described herein can be used to evaluate the effect of surface modifications on bacterial adherence more accurately than conventional monoculture studies. Clinical strains behave differently than collection strains with respect to bacterial adherence. Cite this article: M. Martinez-Perez, C. Perez-Jorge, D. Lozano, S. Portal-Nuñez, R. Perez-Tanoira, A. Conde, M. A. Arenas, J. M. Hernandez-Lopez, J. J. de Damborenea, E. Gomez-Barrena, P. Esbrit, J. Esteban. Evaluation of bacterial adherence of clinical isolates of Staphylococcus sp. using a competitive model: An in vitro approach to the “race for the surface” theory. Bone Joint Res 2017;6:315–322. DOI: 10.1302/2046-3758.65.BJR-2016-0226.R2

Currently implemented accuracy metrics in open-source libraries for segmentation by supervised machine learning are typically one-dimensional scores [1]. While extremely relevant to evaluate applicability in clinics, anatomical location of segmentation errors is often neglected.

This study aims to include the three-dimensional (3D) spatial information in the development of a novel framework for segmentation accuracy evaluation and comparison between different methods.

Predicted and ground truth (manually segmented) segmentation masks are meshed into 3D surfaces. A template mesh of the same anatomical structure is then registered to all ground truth 3D surfaces. This ensures all surface points on the ground truth meshes to be in the same anatomically homologous order. Next, point-wise surface deviations between the registered ground truth mesh and the meshed segmentation prediction are calculated and allow for color plotting of point-wise descriptive statistics. Statistical parametric mapping includes point-wise false discovery rate (FDR) adjusted p-values (also referred to as q-values).

The framework reads volumetric image data containing the segmentation masks of both ground truth and segmentation prediction. 3D color plots containing descriptive statistics (mean absolute value, maximal value,…) on point-wise segmentation errors are rendered. As an example, we compared segmentation results of nnUNet [2], UNet++ [3] and UNETR [4] by visualizing the mean absolute error (surface deviation from ground truth) as a color plot on the 3D model of bone and cartilage of the mean distal femur.

A novel framework to evaluate segmentation accuracy is presented. Output includes anatomical information on the segmentation errors, as well as point-wise comparative statistics on different segmentation algorithms. Clearly, this allows for a better informed decision-making process when selecting the best algorithm for a specific clinical application.

Introduction and Objective

Lower limb fractures are amongst the most common surgically managed orthopaedic injuries, with open reduction and internal fixation (ORIF) as the conventional method of treatment of the fibula. In recent years, dedicated intramedullary implants have emerged for fibula fixation in tandem with the move towards minimally invasive surgery in high-risk patients. This is the largest multicentre review to date with the aim of establishing the clinical outcomes following intramedullary nail (IMN) fixation of the fibula and to identify the absolute indication for fibula IMN fixation.

Summary Statement. In young, active patients cementless THR demonstrates excellent prosthetic stability by RSA and outstanding clinical outcomes at 5 years using a tapered titanium femoral stem, crosslinked polyethylene liners and either titanium or tantalum shells. Introduction. Early femoral implant stability is essential to long-term success in total hip replacement. Radiostereometric analysis (RSA) provides precise measurements of micromotion of the stem relative to the femur that are otherwise not detectable by routine radiographs. This study characterised micromotion of a tapered, cementless femoral stem and tantalum porous-coated vs. titanium acetabular shells in combination with highly cross-linked UHMWPE or conventional polyethylene liners using radiostereometric analysis (RSA) for 5 years following THR. Patients and Methods. This IRB-approved, prospective, double randomised, blinded study, involved 46 patients receiving a primary THR by a single surgeon. Each patient was randomised to receive a titanium (23) (Trilogy, Zimmer) or tantalum (23) (Modular Tantalum shell, Zimmer) uncemented hemispheric shell and either a highly-crosslinked or conventional polyethylene liner. Tantalum RSA markers were implanted in each patient. All patients had a Dorr A or B femoral canal and received a cementless, porous-coated titanium tapered stem (M/L Taper, Zimmer). All final femoral broaches were stable to rotational and longitudinal stress. RSA examinations, Harris Hip, UCLA, WOMAC, SF-12 scores were obtained at 10 days, 6 months, and annually through 5 years. Results. All patients demonstrated statistically significant improvement in Harris Hip, WOMAC, and SF-12 PCS scores post-operatively. Evaluation of polyethylene wear demonstrated that median penetration measurements were significantly greater in the conventional compared to the HXPLE liner cohorts at 1 year through 5 years follow-up (p<0.003). At 5 years, conventional liners showed 0.38 ± 0.05mm vertical wear whereas HXLPE liners showed 0.08 ± 0.02mm (p<0.003). Evaluation of the femoral stems demonstrated that the rate of subsidence was highest in the first 6 months (0.09mm/yr), with no other detectable motion through 5 years. Two outlying patients had significantly higher stem subsidence values at 6 months (0.7 mm and 1.0mm). One stem stabilised without further subsidence after 6 months (0.7mm), and the other stem stabilised at 1 year (1.5mm). Neither patient has clinical evidence of loosening. Evaluation of acetabular shells demonstrated less median vertical translation in tantalum than titanium shells at each time-point except at 3-years follow-up, however due to large standard errors, there was no significant difference between the two designs (p>0.05). These large standard errors were predominantly caused by two outliers, neither of which had clinical evidence of loosening. Discussion/Conclusion. In this RSA study of young THR patients, cementless tapered femoral stems, highly crosslinked polyethylene liners, and tantalum or titanium acetabular shells all demonstrated excellent performance through 5 years follow-up. Highly crosslinked polyethylene liners demonstrated significantly less wear than conventional liners. The femoral stem showed excellent stability through 5 years, with no clinical or radiologic episodes of failure. The small amount of micromotion seen is less than that previously reported for similar tapered, cementless stems and approaches the accuracy of RSA (0.05mm). Both acetabular shells demonstrated excellent stability with minimal micromotion at 5 years without significant differences in migration. All patients demonstrated significant clinical improvement in pain and function and additional RSA evaluation of these patients is planned

µCT images are commonly analysed to assess changes in bone density and architecture in preclinical murine models. Several platforms provide automated analysis of bone architecture parameters from volumetric regions of interest (ROI). However, segmentation of the regions of subchondral bone to create the volumetric ROIs remains a manual and time-consuming task. This study aimed to develop and evaluate automated pipelines for trabecular bone architecture analysis of mouse proximal tibia subchondral bone.

A segmented dataset involving 62 knees (healthy and arthritic) from 10-week male C57BL/6 mice were used to train a U-Net type architecture, with µCT scans (downsampled) input that output segmentation and bone volume density (BV/TV) of the subchondral trabecular bone. Segmentations were upsampled and used in tandem with the original scans (10µ) as input for architecture analysis along with the thresholded trabecular bone. The analysis considered the manually and U-Net segmented ROIs using two available pipelines: the ITKBoneMorphometry library and CTan (SKYSCAN). The analyses included: bone volume (BV), total volume (TV), BV/TV, trabecular number (TbN), trabecular thickness (TbTh), trabecular separation (TbSp), and bone surface density (BSBV).

There was good agreement for bone measures between the manual and U-Net pipelines utilizing ITK (R=0.88-0.98) and CTan (R=0.91-0.98). ITK and CTan showed good agreement for BV, TV, BV/TV, TbTh and BSBV (R=0.9-0.98). However, a limited agreement was seen between TbN (R=0.73) and TbSb (R=0.59) due to methodological differences in how spacing is evaluated.

This U-Net/ITK pipeline seamlessly automated both segmentation and quantification of the proximal tibia subchondral bone. This automated pipeline allows the analysis of large volumes of data, and its open-source nature may enable the standardization of stereologic analysis of trabecular bone across different research groups.

Little information exists when using cell viability assays to evaluate cells within whole tissue, particularly specific types such as the intervertebral disc (IVD). When comparing the reported methodologies and the protocols issued by manufacturers, the processing, working times, and dye concentrations vary significantly, making the assay's reproducibility a costly and time-consuming trial and error process. This study aims to develop a detailed step-by-step cell viability assay protocol for evaluating IVD tissue.

IVDs were harvested from bovine tails (n=8) and processed at day 0 and after 7 days of culture. Nucleus pulposus (NP) and the annulus fibrosus (AF) 3 mm cuts were incubated at room temperature (26˚C) with a Viability/Cytotoxicity Kit containing Calcein AM and Ethidium Ethidium homodimer-1 for 2 hr, followed by flash freezing in liquid nitrogen. Thirty µm sections were placed in glass slides and sealed with nail varnish or Antifade Mounting Medium. The IVD tissue was imaged within the next 4h after freezing using an inverted confocal laser-scanning microscope equipped with 488 and 543 nm laser lines.

Cell viability at day 0 (NP: 92±9.6 % and AF:80±14.0%) and day 7 (NP: 91±7.9% and AF:76±20%) was successfully maintained and evaluated. The incubation time required is dependent on the working temperatures and tissue thickness. The calcein-AM dye will not be retained in the cells for more than four hours.

The specimen preparation and culturing protocol have demonstrated good cell viability at day 0 and after seven days of culture. Processing times and sample preparation play an essential role as the cell viability components in most kits hydrolyse or photobleach quickly. A step-by-step replicable protocol for evaluating the cell viability in IVD will facilitate the evaluation of cell and toxicity-related outcomes of biomechanical testing protocols and IVD regenerative therapies.

Aim of this study was the development of a dynamic FE-framework to identify worst-case size combinations and kinematics in a virtual wear simulator setup covering five daily activities and high, dynamic loads.

Two cruciate sacrificing knee designs (D1 & D2) were tested physically on a wear-testing machine prior the model development using a high demanding, daily activity protocol (HDA) [1]. A simplified FE-setup was generated, reduced to the 3D geometries of the assembly whereas the representation of the mechanical wear simulator conditions and the load transmission was achieved by joint elements. Inertial and other time-related effects of the physical situation were compensated by a system of spring- and damper elements.

Using a time-series signal optimization approach on the anterior-posterior translation and the internal-external rotation results for each activity, 38 variable parameters were varied in between pre-defined limits in a semiautomatic workflow. For each design, two consecutive cycles of a single activity were analysed and the results of the second cycle were used for the optimization. Based on the determined values, a single set of averaged parameter settings was identified that covers all activity cycles sufficiently.

A total of 1010 dynamic analyses were carried out in order to find a sharable set of parameter values.

In this study, an efficient simulation workflow for design evaluation was developed. Therefore, a HDA wear-testing machine was simplified to boundary conditions and stabilizing elements, using a single set of parameters for all activities. The calculated kinematics were in a comparable range to the machine output. Further applications of the method were found in systematic analyses of entire implant systems to achieve consistent kinematics over the size compatibility range in the design process of new implant systems.

Objectives. This study aimed to evaluate the histological and mechanical features of tendon healing in a rabbit model with second-harmonic-generation (SHG) imaging and tensile testing. Materials and Methods. A total of eight male Japanese white rabbits were used for this study. The flexor digitorum tendons in their right leg were sharply transected, and then were repaired by intratendinous stitching. At four weeks post-operatively, the rabbits were killed and the flexor digitorum tendons in both right and left legs were excised and used as specimens for tendon healing (n = 8) and control (n = 8), respectively. Each specimen was examined by SHG imaging, followed by tensile testing, and the results of the two testing modalities were assessed for correlation. Results. While the SHG light intensity of the healing tendon samples was significantly lower than that of the uninjured tendon samples, 2D Fourier transform SHG images showed a clear difference in collagen fibre structure between the uninjured and the healing samples, and among the healing samples. The mean intensity of the SHG image showed a moderate correlation (R. 2. = 0.37) with Young’s modulus obtained from the tensile testing. Conclusion. Our results indicate that SHG microscopy may be a potential indicator of tendon healing. Cite this article: E. Hase, K. Sato, D. Yonekura, T. Minamikawa, M. Takahashi, T. Yasui. Evaluation of the histological and mechanical features of tendon healing in a rabbit model with the use of second-harmonic-generation imaging and tensile testing. Bone Joint Res 2016;5:577–585. DOI: 10.1302/2046-3758.511.BJR-2016-0162.R1

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.

To analyse bone stresses in humerus-megaprosthesis construct in response to axial loading under varying implant lengths in proximal humeral replacement following tumour excision.

CT scans of 10 cadaveric humeri were processed in 3D Slicer to obtain three-dimensional (3D) models of the cortical and cancellous bone. Megaprostheses of varying body lengths (L) were modelled in FreeCAD to obtain the 3D geometry. Four FE models: group A consisting of intact bone; groups B (L=40mm), C (L=100mm) and D (L=120mm) comprising of humerus-megaprosthesis constructs were created. Isotropic linear elastic behaviour was assigned for all materials. A tensile load of 200N was applied to the elbow joint surface with the glenohumeral joint fixed with fully bonded contact interfaces. Static analysis was performed in Abaqus. The bone was divided at every 5% bone length beginning distally. Statistical analysis was performed on maximum von Mises stresses in cortical and cancellous bone across each slice using one-way ANOVA (0-45% bone length) and paired t-tests (45-70% bone length). To quantify extent of stress shielding, average percentage change in stress from intact bone was also computed.

Maximum stress was seen to occur distally and anteriorly above the coronoid fossa. Results indicated statistically significant differences between intact state and shorter megaprostheses relative to longer megaprostheses and proximally between intact and implanted bones. Varying levels of stress shielding were recorded across multiple slices for all megaprosthesis lengths. The degree of stress shielding increased with implant lengthening being 2-4 times in C and D compared to B.

Axial loading of the humerus can occur with direct loading on outstretched upper limbs or indirectly through the elbow. Resultant stress shielding effect predicted in longer megaprosthesis models may become clinically relevant in repetitive axial loading during activities of daily living. It is recommended to use shorter megaprosthesis to prevent failure.

Biphasic calcium phosphate (BCP) with a characteristic needle-shaped submicron surface topography (MagnetOs) has attracted much attention due to its unique bone-forming ability which is essential for repairing critical-size bone defects such as those found in the posterolateral spine. Previous in vitro and ex-vivo data performed by van Dijk LA and Yuan H demonstrated that these specific surface characteristics drive a favorable response from the innate immune system.

This study aimed to evaluate and compare the in vivo performance of three commercially-available synthetic bone grafts, (1) i-FACTOR Putty^®, (2) OssDsign^® Catalyst Putty and (3) FIBERGRAFT^® BG Matrix, with that of a novel synthetic bone graft in a clinically-relevant instrumented sheep posterolateral lumbar spine fusion (PLF) model. The novel synthetic bone graft comprised of BCP granules with a needle-shaped submicron surface topography (MagnetOs) embedded in a highly porous and fibrillar collagen matrix (MagnetOs Flex Matrix).

Four synthetic bone grafts were implanted as standalone in an instrumented sheep PLF model for 12 weeks (n=3 bilateral levels per group; levels L2/3 & L4/5), after which spinal fusion was determined by manual palpation, radiograph and µCT imaging (based on the Lenke scale), range-of-motion mechanical testing, and histological and histomorphological evaluation.

Radiographic fusion assessment determined bilateral robust bone bridging (Lenke scale A) in 3/3 levels for MagnetOs Flex Matrix compared to 1/3 for all other groups. For µCT, bilateral fusion (Lenke scale A) was found in 2/3 levels for MagnetOs Flex Matrix, compared to 0/3 for i-FACTOR Putty^®, 1/3 for OssDsign^® Catalyst Putty and 0/3 for FIBERGRAFT^® BG Matrix. Fusion assessment for MagnetOs Flex Matrix was further substantiated by histology which revealed significant graft resorption complemented by abundant bone tissue and continuous bony bridging between vertebral transverse processes resulting in bilateral spinal fusion in 3/3 implants.

These results show that MagnetOs Flex Matrix achieved better fusion rates compared to three commercially-available synthetic bone grafts when used as a standalone in a clinically-relevant instrumented sheep PLF model.