Abstract. OBJECTIVES. Dual mobility (DM) total hip replacements (THRs) were introduced to reduce the risk of hip dislocation in at-risk patients. DM THRs have shown good overall survivorship and low rates of dislocation, however, the mechanisms which describe how these bearings function in-vivo are not fully understood. This is partly due to a lack of suitable characterisation methodologies which are appropriate for the novel geometry and function of DM polyethylene liners, whereby both surfaces are subject to articulation. This study aimed to develop a novel semi-quantitative geometric characterisation methodology to assess the wear/deformation of DM liners. METHODS. Three-dimensional coordinate data of the internal and external surfaces of 14 in-vitro tested DM liners was collected using a Legex 322 coordinate measuring machine. Data was input into a custom Matlab script, whereby the unworn reference geometry was determined using a sphere fitting algorithm. The analysis method determined the geometric variance of each point from the reference surface and produced surface deviation heatmaps to visualise areas of wear/deformation. Repeatability of the method was also assessed. RESULTS. Semi-quantitative analysis of the surface deviation heatmaps revealed circumferential damage patterns similar to those reported in the literature. Additionally, the location of the damaged regions corresponded between the internal and external surfaces. Comparing five repeat measurements of the same liner, the maximum geometric variance of each surface varied by 1 µm (standard deviation) suggesting a high repeatability of the method. CONCLUSIONS. This study presents an effective and highly repeatable characterisation methodology to semi-quantitatively assess the wear/deformation of in-vitro tested DM liners. This method is suitable for the analysis of retrieved DM liners whereby no pre-service information is available, which may provide information about the complex in-vivo kinematics and mechanical failure mechanisms of these bearings

The periclavicular space is a conduit for the brachial plexus and subclavian-axillary vascular system. Changes in its shape/form generated by alteration in the anatomy of its bounding structures, e.g. clavicle malunion, cause distortion of the containing structures, particularly during arm motion, leading to syndromes of thoracic outlet stenosis etc., or alterations of scapular posture with potential reduction in shoulder function. Aim of this study was developing an in vitro methodology for systematic and repeatable measurements of the clinically poorly characterized periclavicular space during arm motion using CT-imaging and computer-aided 3D-methodologies. A radiolucent frame, mountable to the CT-table, was constructed to fix an upper torso in an upright position with the shoulder joint lying in the isocentre. The centrally osteotomized humerus is fixed to a semi-circular bracket mounted centrally at the end of the frame. All arm movements (ante-/retroversion, abduction/elevation, in-/external rotation) can be set and scanned in a defined and reproducible manner. Clavicle fractures healed in malposition can be simulated by osteotomy and fixation using a titanium/carbon external fixator. During image processing the first rib served as fixed reference in space. Clavicle, scapula and humerus were registered, segmented, and triangulated. The different positions were displayed as superimposed surface meshes and measurements performed automatically. Initial results of an intact shoulder girdle demonstrated that different arm positions including ante-/retroversion and abduction/elevation resulted solely in a transverse movement of the clavicle along/parallel to the first rib maintaining the periclavicular space. A radiolucent frame enabling systematic and reproducible CT scanning of upper torsos in various arm movements was developed and utilized to characterize the effect on the 3D volume of the periclavicular space. Initial results demonstrated exclusively transverse movement of the clavicle along/parallel to the first rib maintaining the periclavicular space during arm positions within a physiological range of motion

Abstract. Objectives. Develop a methodology to assess the long term mechanical behavior of intervertebral discs by utilizing novel sequential state testing. Methods. Bovine functional spinal units were sequentially mechanically tested in (1) native (n=8), (2) degenerated (n=4), and (3) treated states (n=4). At stage (2), artificial degeneration was created using rapid enzymatic degeneration, followed by a 24 hour hold period under static load at 42°C. At stage (3), nucleus augmentation treatments were injected with a hydrogel or a ‘sham’ (water, chondroitin sulfate) injection. The mechanical protocol employed applied a static load hold period followed by cyclic compressive loading between ∼350 and 750 N at 1 Hz. 1000 cycles were applied at each stage, and the final test on each specimen was extended up to 20000 cycles. To verify if test time can be reduced, functions were fitted using stiffness data up to 100, 1000, 2500, 5000, 10000 and 20000 cycles. Linear regression for the native specimens comparing the stiffness at various cycles to the stiffness at 20000 cycles was completed. Results. Independent of the disc state, as the number of cycles increased, the hysteresis decreased and the stiffness increased. The degenerated specimen stiffness was greater than the healthy and treated stiffness and the degenerate hysteresis loops were smaller. A mathematical model was found to successfully predict the high cycle behaviour of the disc reaching a root mean squared (RMS) error below 10% when using 5000 or more cycles. The linear regression gave a RMS error below 7.5% at 1000 cycles. Conclusions. A method was developed to consistently determine intervertebral disc mechanics through sequential testing. A shortened cyclic testing period was shown to be viable as a method to reduce preliminary test time for novel hydrogels, compared to currently literature. The methodology permits rapid preliminary assessment of intervertebral disc mechanics and treatments. 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

Summary Statement. There are no standardised methods for assessing the cement flow behaviour in vertebroplasty. We propose a novel methodology to help understand the interaction of cement properties on the underlying displacement of bone marrow by bone cement in porous media. Introduction. Concerns related to cement extravasation in vertebroplasty provide the motivation for the development of methodologies for assessing cements (novel and commercially available) and delivery systems. Reproducible and pathologically representative three-dimensional bone surrogates are used to understand the complex rheology underlying the two-phase flow in porous media. Patients & Methods. The bone surrogates were achieved by first developing CAD models then manufacturing the physical models through a suitable rapid prototyping technique. MicroCT 100 (Scanco Medical, Switzerland) was used to assess the variability in the model morphology (n=8). Contact angle measurements were performed on the material to compare the surface wettability to that of bone. The surrogates were filled with bone marrow substitute (Carboxymethyl cellulose 2.5 % in water, 0.4 Pa.s) then 5 ml of silicone oil (Dow Corning Corp. 200® Fluid, 60 Pa.s) was injected at a constant flow rate (3mL/min) using a syringe pump. The injection was radiographically monitored and the video sequences were captured. Experiments were repeated three times. The displacement of the syringe plunger and the force applied on the plunger were recorded. Image processing was performed on the video sequences to quantitatively describe the resulting flow patterns and calculate parameters including the time of leakage and the mean spreading distance. Results. The variability in the model morphology was very low with a strut thickness of 0.253 ± 0.010 mm and a pore spacing of 0.83 + 0.01 mm. The surface wettability was very similar between all materials with a contact angle around 65°. The measured displacement of the syringe plunger confirmed the flow rate to be constant at 3 ml/min. The peak injection pressure was 0.443 ± 0.013 MPa which is well below the reported clinical measurement of injection pressure during vertebroplasty. 1. Anterior oil leakage occurred at 34.6 ± 4.71 seconds. The oil never reached the posterior wall and the mean spreading distance at the end of the injection was 23.39 ± 1.11 mm. Discussion/Conclusion. These complex three-dimensional bone surrogates provide a clinically relevant representation of the in vivo situation in terms of geometry, porosity and permeability. They overcome limitations of previous models by being constant in terms of both porosity and geometry which is crucial to reduce the variability, render the experiments reproducible and shift the focus onto understanding the cement flow behaviour. The proposed methodology will help study cement-fluid interaction to get better representation of in vivo cement flow patterns and provide a tool for validating computational simulations. Funding was provided by the EU under the FP7 Marie Curie Action (PITN-GA-2009-238690-SPINEFX)

Introduction: Osteoarthritis of the thumb basal joint is a very common and disabling condition that frequently affects middle-aged women, sometimes bilaterally. The purpose of this work is to present the methodology of the preoperative and postoperative assessment carried out in 52 patients who underwent a trapeziometacarpal joint replacement procedure (Roseland prosthesis). Material and Methods: Total joint arthoplasty of the trapeziometacarpal joint was performed on 52 thumbs in 44 patients (15 dominants hands) to treat osteoarthritis (Eaton-Littler stages II and III) between 1995 and 2007. 18 patients were missed for follow-up purposes. Average age of 59,4 years. The Roseland trapeziometacarpal joint prosthesis was used in this study. We analyzed the ROM for abduction-adduction, flexo-extension of the trapeziometacarpal joint and the opposition of the thumb by the modified Kapandji test. We also measured radiographic distance of the TMC space in preoperative radiographies and compared it with the postoperative ones. Finally, strength was quantified for the lateral, tip-to-tip, and tridigital pinch in the treated hands. Pain was measured with VAS and the DASH questionnaire was completed by all the patients. The average follow-up period was of 5,3 years (range, 1,1–12,1 years). Results: At the final follow-up visit we obtained the following Results: for thumb abduction average 66°, thumb opposition to the base of the smaller finger was present in 58%, and thumb flexo-extension average 59°. The average tip-to-tip pinch strength was 2,7, for the lateral pinch 3,6 and for the tridigital pinch was 3,7. We observed that in 36% of the radiographies the TMC space was the same pre and postoperative. Average VAS and DASH scores were of 1,6 and 26,3 respectively. Five patients (10%) needed a revision surgery (2 for infection and 3 for aseptic loosening of the prosthesis). Conclusions: Most of the protocols evaluating surgical outcomes on the trapeziometarcarpal joint don’t allow a functional analysis of ROM and strength of this joint. That’s why we developed the idea of designing a new methodology, that we currently use in our centre, to analyze the functional outcome of the surgery on the trapeziometacarpal joint. We specially recommend the measurement of the tridigital pinch strength, as is the most representative feature of the hand function

Introduction and Objective. Medial Knee Osteoarthritis (MKO) is associated with abnormal knee varism, this resulting in altered locomotion and abnormal loading at tibio-femoral condylar contacts. To prevent end-stage MKO, medial compartment decompression is selectively considered and, when required, executed via High Tibial Osteotomy (HTO). This is expected to restore normal knee alignment, load distribution and locomotion. In biomechanics, HTO efficacy may be investigated by a thorough analysis of the ground reaction forces (GRF), whose orientation with respect to patient-specific knee morphology should reflect knee misalignment. Although multi-instrumental assessments are feasible, a customized combination of medical imaging and gait analysis (GA), including GRF data, rarely is considered. The aim of this study was to report an original methodology merging Computed-Tomography (CT) with GA and GFR data in order to depict a realistic patient-specific representation of the knee loading status during motion before and after HTO. Materials and Methods. 25 MKO-affected patients were selected for HTO. All patients received pre-operative clinical scoring, and radiological/instrumental assessments; so far, these were also executed post-operatively at 6-month follow-up on 7 of these patients. State-of-the-art GA was performed during walking and more demanding motor tasks, like squatting, stair-climbing/descending, and chair-rising/sitting. An 8-camera motion capture system, combined with wireless electromyography, and force platforms for GRF tracking, was used together with an own established protocol. This marker-set was enlarged with 4 additional skin-based non-collinear markers, attached around the tibial-plateau rim. While still wearing these markers, all analyzed patients received full lower-limb X-ray in standing posture a CT scan of the knee in weight-bearing Subsequently, relevant DICOMs were segmented to reconstruct the morphological models of the proximal tibia and the additional reference markers, for a robust anatomical reference frame to be defined on the tibia. These marker trajectories during motion were then registered to the corresponding from CT-based 3D reconstruction. Relevant registration matrices then were used to report GRF data on the reconstructed tibial model. Intersection paths of GRF vectors with respect to the tibial-plateau plane were calculated, together with their centroids. Results. Pre-operative clinical and radiological scoring confirmed MKO and associated abnormal varism. The morphological characterization of GRF was successfully achieved pre- and post- HTO on patient-specific tibial plateau. Pre-operative GFR patterns and peaks, including those related to knee joint moments, were observed medially on the knee, as expected. In post-HTO, these resulted lateralized and much closer to the tibial plateau spine, as desired. In detail, when post- is compared to pre-op, the difference of the centroids were, on average, 54.6±18.1 mm (min÷max: 36.7÷72.8 mm) more lateral during walking and 52.5±28.5 mm (24.7÷87.6 mm) during stair climbing. When reported in % of the tibial plateau width, these values became 69.2±20.1 (46.1÷81.4) and 78.1±30.1 (43.4÷98.0), respectively. Post-op also clinical scores and GA revealed a considerable overall improvement, especially in functional performances. Conclusions. The reported novel approach allows a combination of motion data, including GFR, and tibial-plateau morphology. Relevant pre- and post-operative routine application offer a quantification of the effect of the original deformity and executed joint realignment, and an assistance for surgical planning in case of HTO as well as ideally in other orthopedic treatments

Total knee arthroplasty can largely impact the functioning of a knee. To minimize the impact of surgery and increase patient satisfaction, it is believed that restoring knee stability and control of the laxity has the potential to improve surgical outcome. In that respect, it is hypothesized that a well-balanced knee restores the native knee's laxity and stability, whereas unbalanced conditions result in an increased laxity and instability. This study intends to precisely evaluate knee laxity and stability in a cadaveric model in order to improve the clinical evaluation of the knee laxity under surgical conditions. This paper provides insight in the design considerations and methodology of a novel knee simulator and the preliminary results. In a first phase, a new knee simulator has therefore been developed. This simulator allows quantifying the knee kinematics and surgical feel at the time of surgery in a laboratory environment. More specifically, full lower limb specimens can be mounted in the simulator. This overcomes the need for disarticulation at the hip and ankle, often reported in cadaveric testing. The latter is believed to potentially release the tension in the knee and should therefore be avoided. Note that in respect to surgical conditions no muscle activation is considered for this simulator. To facilitate a repeatable and unbiased evaluation of the knee kinematics, it is important that the knee simulator provides full kinematic freedom to the tested knee specimen. To obtain six degrees of freedom, a dedicated hip and ankle setup has been created (figure 1). The hip setup constrains the hip joint to a single axis hinge joint around the femoral head center. The remaining five degrees of freedom are built into the ankle setup. More specifically, the ankle setup has two translational degrees of freedom and full rotational freedom. The translational freedom is provided along the specimen's proximal-distal axis and medio-lateral axis. The rotational freedom is provided at a single point, using a ball in socket joint located along the mechanical axis of the tibia. The translation along the proximal-distal axis is thereby actively controlled by the operator, simulating heel push conditions. In addition to studying the neutral path kinematics, the presented simulator allows evaluating the laxity boundaries throughout the range of motion. Therefore, a constant internal/external torque can be applied to the tibia. Alternatively, a constant varus/valgus moment can be simulated. Second, following the design and construction of this simulator, a set of ten cadaveric knees has been tested on this simulator, both before and after TKA surgery. For the native knees, the results of these tests confirm the kinematic freedom provided to the tested knee. In addition, the laxity envelope around the neutral path can be realistically evaluated and quantified. Conclusion. Design and evaluation of new knee simulator that allows synchronous studying of the knee kinematics, contact loads and tensile forces, under neutral conditions and extreme varus/valgus moment or internal/external tibial torque

Dislocation post THA confers a higher risk of re-dislocation (Kotwal et al, 2009). The dual mobility (DM) cup design (1974) was aimed at improving the stability by increasing the femoral head to neck ratio (Cuthbert et al., 2019) combining the ideas of low friction arthroplasty with increased jump distance associated with a big head arthroplasty.

Understand the dislocation rates, rates of aseptic loosening, infection rate and revision rates between the 2 types of constructs to provide current and up-to date evidence.

Medline, pubmed, embase and Cochrane databases were used based on PRISMA guidelines. RevMan software was used for the meta-analysis. Studies (English literature) which used DM construct with atleast 6 months follow-up used as intervention and non DM construct as control were included. 2 independent reviewers conducted the review with a third reviewer in case of difference in opinion regarding eligibility. Primary outcome was dislocation rate and secondary outcome was rate of revision.

564 articles identified out of which 44 articles were screened for full texts and eventually 4 systematic review articles found eligible for the study. Thus, study became a review of systematic reviews. From the 4 systematic reviews, another 35 studies were identified for data extraction and 13 papers were used for meta-analysis. Systematic reviews evaluated, projected an average follow up of 6-8 years with significantly lower dislocation rates for DM cups. The total number of patients undergoing DM cup primary THA were 30,559 with an average age 71 years while the control group consisted of 218,834 patients with an average age of 69 years. DM group had lower rate of dislocation (p < 0.00001), total lower rate of cup revision (p < 0.00001, higher incidence of fracture (p>0.05).

DM THA is a viable alternative for conventional THA. The long-term results of DM cups in primary THA need to be further evaluated using high quality prospective studies and RCTs.

Abstract

Background

Magnetic resonance imaging (MRI) algorithm identifies end stage severely degenerated disc as ‘black’, and a moderately degenerate to non-degenerated disc as ‘white’. MRI is based on signal intensity changes that identifies loss of proteoglycans, water, and general radial bulging but lacks association with microscopic features such as fissure, endplate damage, persistent inflammatory catabolism that facilitates proteoglycan loss leading to ultimate collapse of annulus with neo-innervation and vascularization, as an indicator of pain. Thus, we propose a novel machine learning based imaging tool that combines quantifiable microscopic histopathological features with macroscopic signal intensities changes for hybrid assessment of disc degeneration.

The success of cementless orthopaedic implants relies on bony ingrowth and active bone remodelling. Much research effort is invested to develop implants with controllable surface roughness and internal porous architectures that encourage these biological processes. Evaluation of these implants requires long-term and costly animal studies, which do not always yield the desired outcome requiring iteration. The aim of our study is to develop a cost-effective method to prescreen design parameters prior to animal trials to streamline implant development and reduce live animal testing burden.

Ex vivo porcine cancellous bone cylinders (n=6, Ø20×12mm) were extracted from porcine knee joints with a computer-numerically-controlled milling machine under sterile conditions within 4 hours of animal sacrifice. The bone discs were implanted with Ø6×12mm additive manufactured porous titanium implants and were then cultured for 21days. Half underwent static culture in medium (DMEM, 10% FBS, 1% antibiotics) at 37°C and 5% CO₂. The rest were cultured in novel high-throughput stacked configuration in a bioreactor that simulated physiological conditions after surgery: the fluid flow and cyclic compression force were set at 10ml/min and 10–150 N (1Hz,5000 cycles/day) respectively. Stains were administered at days 7 and 14. Samples were evaluated with widefield microscopy, scanning electron microscopy (SEM) and with histology.

More bone remodelling was observed on the samples cultured within the bioreactor: widefield imaging showed more remodelling at the boundaries between the implant-bone interface, while SEM revealed immature bone tissue integration within the pores of the implant. Histological analysis confirmed these results, with many more trabecular struts with new osteoid formation on the samples cultured dynamically compared to static ones.

Ex vivo bone can be used to analyse new implant technologies with lower cost and ethical impact than animal trial. Physiological conditions (load and fluid flow) promoted bone ingrowth and remodelling.

Background: During the past decades many treatments and devices were developed in attempt to unload the diseased articular surface in knee Osteoarthritis (OA). A novel biomechanical device and treatment methodology (The APOS System) was introduced in order to unload the diseased articular surface during activity (dynamic wedging), strengthen dynamic stabilizers and train neuromuscular control by means of controlled biomechanical perturbations. The purpose of this study is to examine the effectiveness of APOS System in reducing pain and improving function in knee OA patients. Method: A double blind, randomized, prospective study was performed with 61 knee OA patients, aged 49–83 (66 ±8.1) years and graded 1–4 (3 ±1) according to Kellgren & Lawrence. Patients were randomized into research (active) and control (placebo) groups. All patients under-went 8 weeks of treatment. Patients were examined at baseline and supervised 4 times during the study. Patients in the research group used the biomechanical device that consists of 2 biomechanical elements located under the strategic weight bearing spots of each of the patient’s feet and a mounting and positioning mechanism embedded in designated shoes. The treatment methodology that was applied to the research group included dynamic wedging of the diseased articular surface. Patients in the control group used a placebo device without the biomechanical elements. Patients were assessed at baseline, after 4 weeks and after 8 weeks at the end of the study using Knee Society Score, WOMAC, SF-36, ALF and VAS. The assessment was performed without the examiner knowing the group affiliation of the patient. Results: The two groups were statistically similar (p> 0.05) at baseline with respect to age, Kellgren& Lawrence classification and all assessed parameters including subscales. Significant difference between groups over time was observed for Knee Score (p< 0.001), Knee Society Function Score (p< 0.001), WOMAC (p< 0.001), SF-36 (p< 0.001), ALF (p< 0.001) and VAS (p< 0.001). Significant improvement was observed in the research group throughout all assessed parameters (measured improvement for Knee Score, Knee Society Function Score, WOMAC, SF-36, ALF and VAS were a multiplication of 1.8, 1.4, 3, 1.4, 1.35 and 2 in the applicable scale respectively). A slight deterioration was observed in the control group throughout all assessed parameters at final assessment. Conclusion: The findings demonstrate that APOS System is effective and significantly improves function and reduces pain among knee OA patients

The purpose of this study was to measure the effect of the implementation of a LEAN continuous process improvement initiative on the waitlist in an ambulatory pediatric orthopaedic clinic.

LEAN is a set of principles that guide organizational thinking and form a comprehensive approach to continuous process improvement. In 2016, our health centre began its journey towards becoming a LEAN organization. The health centre's Strategy and Performance portfolio collaborated with the Orthopaedic Clinic Team to facilitate a Value Stream Analysis, which mapped the clinic process from referral to discharge from care. This informed the plan for targeted improvement events designed to identify and reduce non-value added activity, while partnering with patients and families to share their experiences with care in the clinic. Improvement events included: In-Clinic Patient Flow; Scheduling Process Review; Standardized Triage Process; Clinician Schedule; 5-S Large Cast and Sample Exam Rooms; Booking Orthopedics Clinic; and Travelling and Remote Care. During each event, solutions were identified to improve the patient experience, access, and clinic flow. These solutions have been standardized, documented, and continuously monitored to identify additional improvement opportunities. Comparison of wait-list and percentage of new patients seen within target window was performed from August 2017 to December 2018.

The LEAN initiative resulted in a 48% decrease in wait-list for new patients, which translated to an improvement from 39% to 70% of new patients seen within their target window. There was a 19% decrease in the 3400+ patient wait-list for follow-up appointments, an 85% reduction in follow-up patients waiting past their target date for an appointment, and the number of patients waiting over a year beyond their target appointment improved from over 300 patients to 0 patients. There was a 15% improvement in average length of clinic visit.

Without the addition of new resources, the implementation of a LEAN continuous process improvement initiative improved the waitlist for new patients in an ambulatory pediatric orthopaedic clinic by almost 50%. Solutions identified and implemented through the LEAN process have contributed to unprecedented improvements in access to care. In fulfilling one of the LEAN theory principles to “pursue perfection”, the paediatric orthopaedic clinic team has embraced a culture of continuous improvement and continues to use LEAN tools such as daily huddles and visual management to monitor solutions and identify gaps.

In different contemporary posterior-stabilized (PS) total knees, there are considerable variations in condylar surface radii and cam-post geometry. This is expected to result in differences in kinematics and functional outcomes in patients. The hypotheses of our study were: 1. Current PS design will show symmetric motion which is different from anatomic motion, and 2. An asymmetric PS design will produce motion closer to normal anatomic motion than symmetric designs. A special machine was constructed which could implement the ASTM standard test on constraint, by measuring the laxities. The rational for the test is to predict functional laxity ranges which will affect the kinematics in vivo. The machine set the knee at the required flexion angles and applied combinations of compressive, shear, and torque forces, to represent a range of everyday activities. The femorotibial contact points, the neutral path of motion, and the AP and internal-external laxities were used as the motion indicators. The benchmark was the motion data from anatomic knee specimens tested under the same conditions. Four contemporary PS designs with a range of geometries was selected for the tests, together with a design where the medial side was more constrained, the lateral side was less constrained, and the post was rounded. The output motions were compared between themselves, while all designs were compared with the anatomic data. The PS designs showed major differences in motion characteristics among themselves including the neutral path of motion and the AP and rotational laxities. These differences were related to the constraints of the condyles, and the cam-post designs. The four PS designs showed motion different from anatomic, including symmetric mediolateral motion, susceptibility to excessive AP medial laxity, and reduced laxity in high flexion. The asymmetric Guided Motion design alleviated some but not all of the abnormalities; in particular, while the lateral rollback with flexion and the near-constant position of the medial femoral condyle resembled anatomic behaviour, the rotational laxity was still limited in high flexion. The latter ws observed to be due to the ‘entrapment’ of the femoral condyles between the upwards posterior lip of the tibial plastic, and the posterior of the cam-post, a phenomenon seen on all designs. The conclusion of the study is that an asymmetric PS design may provide a path to achieving a closer match to anatomic kinematics. This may improve functional outcomes, and even provide a better ‘feel’ to the patient. However, there are still inherent challenges in PS design to closely achieve this goal. Other design configurations have also been formulated which could even more closely reproduce anatomic motion. However a pre-clinical testing method such as presented here, is one method for evaluation and can be used hand-in-hand with computational methods to produce an optimal design. The importance of the benchmark of the anatomic knee and the identification of the important parameters of the ASTM standard, notably the neutral path of motion and the laxity about the neutral path, are important aspects of the design methodology

INTRODUCTION:

Previous modalities such as static x-rays, MRI scans, CT scans and fluoroscopy have been used to diagnosis both soft-tissue clinical conditions and bone abnormalities. Each of these diagnostic tools has definite strengths, but each has significant weaknesses. The objective of this study is to introduce two new diagnostic, ultrasound and sound/vibration sensing, techniques that could be utilized by orthopaedic surgeons to diagnose injuries, defects and other clinical conditions that may not be detected using the previous mentioned modalities.

Purpose: To develop an experimental testing method to measure bone strains as a function of multiple implant stem designs in a single specimen, and to show the efficacy of this method with an application in the distal ulna.

Methods: Twenty-four strain gauges were applied to the surface of an isolated cadaveric ulna to measure anterior-posterior (AP) and medial-lateral (ML) bending loads at six locations along its length. The bone was potted in a custom-designed jig and positioned in a materials testing machine. Loads (5-25N) were applied to the ulnar head while strains were recorded. The ulnar head was removed and an 8cm threaded rod (diameter=5.8mm) was cemented into the canal, and subsequently removed after cement curing. This established a threaded cement mantle that would accept various threaded stem designs. To show the efficacy of this technique, testing was repeated with 5 and 7cm stems. The entire canal was then filled with cement and testing repeated to determine the effect of the residual cement void.

Results: All 24 strain gauges provided quality signals throughout the testing period. Strain varied linearly with load (R-squared=0.94–0.99). The initial threaded rod was easily removed, and there was no difficulty in placing subsequent stems within the mantle. Comparing the 5 and 7cm stems, little difference in strains was observed for the most proximal gauges (2%), with higher variations in the stem exit regions (17%). The cement-filled canal exhibited distal strains similar to the intact baselines (average 2% difference at 25N).

Conclusions: A reliable method has been developed that allows multiple stems to be tested in a single bone. Observed strain differences are therefore a function of implant parameters only (such as stem length), and are not influenced by differences in bone properties as occurs when testing multiple specimens. The layer of threaded bone cement did not impact the native bone strains. This experimental method will be useful to compare stem designs in a variety of bones, avoiding the need for large numbers of specimens due to the repeated measure experimental protocol.

Background

Body Mass Index (BMI) is used to quantify generalised obesity, but does not account for variations in soft tissue distribution.

Aims. Multiligament knee injuries (MLKI) are devastating injuries that can result in significant morbidity and time away from sport. There remains considerable variation in strategies employed for investigation, indications for operative intervention, outcome reporting, and rehabilitation following these injuries. At present no study has yet provided a comprehensive overview evaluating the extent, range, and overall summary of the published literature pertaining to MLKI. Our aim is to perform a methodologically rigorous scoping review, mapping the literature evaluating the diagnosis and management of MLKI. Methods. This scoping review will address three aims: firstly, to map the current extent and nature of evidence for diagnosis and management of MLKI; secondly, to summarize and disseminate existing research findings to practitioners; and thirdly, to highlight gaps in current literature. A three-step search strategy as described by accepted methodology will be employed to identify peer-reviewed literature including reviews, technical notes, opinion pieces, and original research. An initial limited search will be performed to determine suitable search terms, followed by an expanded search of four electronic databases (MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, and Web of Science). Two reviewers will independently screen identified studies for final inclusion. Dissemination. We will map key concepts and evidence, and disseminate existing research findings to the wider orthopaedic and sports medicine community, through both peer-reviewed and non-peer-reviewed literature, and conference and in-person communications. We will highlight gaps in the current literature and determine future priorities for further research. Cite this article: Bone Jt Open 2022;3(11):894–897