Aims

Modular dual mobility (MDM) acetabular components are often used with the aim of reducing the risk of dislocation in revision total hip arthroplasty (THA). There is, however, little information in the literature about its use in this context. The aim of this study, therefore, was to evaluate the outcomes in a cohort of patients in whom MDM components were used at revision THA, with a mean follow-up of more than five years.

Aims

Tibial cones are often utilized in revision total knee arthroplasty (TKA) with metaphyseal defects. Because there are few studies evaluating mid-term outcomes with a sufficient cohort, the purpose of this study was to evaluate tibial cone survival and complications in revision TKAs with tibial cones at minimum follow-up of five years.

Introduction

Tibial cones are often utilized in revision total knee arthroplasty (TKA) with metaphyseal defects. However, there are few studies evaluating outcomes out to five years with a sufficient cohort. The purpose of this study was to evaluate implant survivorship and complications in revision TKAs with tibial cones.

Background

Modular dual mobility (MDM) acetabular components are often used to prevent dislocation in revision total hip arthroplasty (THA). As there is insufficient data on these components, the outcomes were evaluated in a cohort with a mean follow-up time of greater than five years.

Osteoinductive bone substitutes are in their developmental infancy and a paucity of effective grafts options persists despite clinical demand. Bone mineral substitutes such as hydroxyapatite cause minimal biological activity when compared to osteoinductive systems present biological growth factors in order to drive bone regeneration. We have previously demonstrated the in-vitro efficacy of a bioengineered system at presenting growth factors at ultra low-doses. This study aimed to translate this growth factor delivery system towards a clinically applicable implant.

Osteoinductive surfaces were engineered using plasma polymerisation of poly(ethyl acrylate) onto base materials followed by adsorption of fibronectin protein and subsequently growth factor (BMP-2). Biological activity following ethylene oxide (EO) sterilisation was evaluated using ELISAs targeted against BMP-2, cell differentiation studies and atomic force microscopy. Scaffolds were 3D printed using polycaprolactone/hydroxyapatite composites and mechanically tested using a linear compression models to calculate stress/strain. In-vivo analysis was performed using a critical defect model in 23 mice over an 8 week period. Bone formation was assessed using microCT and histological analysis. Finally, a computer modelling process was developed to convert patient CT images into surface models, then formatted into 3D-printable scaffolds to fill critical defects.

Following EO sterilisation, there was no change in scaffold surface and persistent availability of growth factors. Scaffolds showed adequate porosity for cell migration with mechanical stiffness similar to cancellous bone. Finally, the in vivo murine model demonstrated rapid bone formation with evidence of trabecular remodelling in samples presenting growth factors compared to controls.

Background

Trochanteric fractures account for up to 20% of all periprosthetic fractures occurring during or after total hip arthroplasties (THAs). They are frequently managed conservatively except in cases with significant displacement. There is a paucity of literature describing the indications and results of operative or non-operative management of these fractures.

Aims

A variety of surgical approaches are used for total hip arthroplasty (THA), all with reported advantages and disadvantages. A number of common complications can occur following THA regardless of the approach used. The purpose of this study was to compare five commonly used surgical approaches with respect to the incidence of surgery-related complications.

Aims

Tranexamic acid (TXA) has been shown to significantly reduce transfusion rates in primary total hip arthroplasties (THAs), but high-quality evidence is limited in the revision setting. The purpose of the current study was to compare the rate of blood transfusions and symptomatic venous thromboembolic events (VTEs) in a large cohort of revision THAs treated with or without intravenous (IV) TXA.

Several specimen specific vertebral (VB) models have been proposed in the literature; these replicate the typical set-up of a vertebral body mounted in bone cement and subject to a compressive ramp. VB and cement geometries are obtained from micro-CT images, the cement is typically assigned properties obtained from the literature while VB properties are inferred from the Hounsfield units- where the conversion factor between grayscale data and Young's modulus is optimised using experimental load-displacement data. Typically this calibration is performed on VBs dissected from the same spines as the study group. This, alongside the use of non-specific cement properties, casts some doubts on the predictivity of the models thus obtained. The predictivity of specimen specific FE models was evaluated in this study.

VBs obtained from three porcine cervical segments (C2-C6) were stripped of all soft tissues, potted in bone cement and subject to a compressive loading ramp. A speckle pattern was applied to the anterior part of the specimen for DIC imaging. Specimen specific FE models were constructed from these specimens and a conversion factor between grayscale and material properties was optimised. Cement properties were assigned based on literature data. VBs from a further cervical spine (C2-C7) were subject to the same experimental protocol. In this case, the models generated from microCT images the material properties of bone were assigned based on the average conversion factor obtained previously. The predicted load-displacement behaviour thus obtained was compared to experimental data. Generally, poor agreement was found between overall load-displacement. The use of generic cement properties in the models was found to be partly responsible for this. When the load displacement behaviour of the VB was studied in isolation, good agreement within one standard deviation was found with 4 out of 6 models showing good correlation between simulation and DIC data.

Objectives

The purpose of this study was to examine the bactericidal efficacy of hydrogen peroxide (H₂O₂) on Cutibacterium acnes (C. acnes). We hypothesize that H₂O₂ reduces the bacterial burden of C. acnes.

Digital image correlation (DIC) is rapidly increasing in popularity in biomechanical studies of the musculoskeletal system. DIC allows the re-construction of full field displacement and/or strain maps of the surface of an object. DIC systems typically consist of two cameras focussing on the same region of interest. This constrains the angle between the cameras to be relatively narrow when studying specimens characterised by complex geometrical features, giving rise to concerns on the accuracy of the out of plane estimates of movement.

The aim of this research was to compare the movement profiles of bony segments measured by DIC and by an optoelectronic motion capture system.

Five porcine cervical spine segments (C2-C6) were obtained from the local butcher. These were stripped of all anterior soft tissues while the posterior structures were left intact. A speckle pattern was applied to the anterior aspect of the specimens, while custom made infrared clusters were rigidly attached to the 3 middle vertebral bodies (C3-C5). The specimens were mounted in a custom made impact rig which fully constrained C6 but allowed C2 to translate in the axial direction of the segment. Images were acquired at 4kHz, both for the DIC (Photron Europe Ltd, UK) and motion capture cameras (Qualisys Oqus 400, Sweden). The in-plane and out of plane displacements of each of the VBs were plotted as a function of time and the similarity between the curves thus obtained was analysed using the SPM1D technique which allowed a comparison to be made in terms of t-statistics. No statistical differences were found between the two techniques in all axis of movement, however the out of plane movements were characterised by higher variance which is attributed to the uncertainty arising from the near parallel positioning of the cameras in the experimental set-up.

Head collisions in sport can result in catastrophic cervical spine injuries. Musculo-skeletal (MSK) modelling can help analyse the relationship between players' motion, external loading and internal stresses that lead to injury. However, the literature lacks sport specific MSK models. In automotive research the intervertebral disc behaviour has been represented as viscoelastic elements (“bushing”), whose stiffness and damping parameters are often estimated under quasi-static conditions and may lack validity in dynamic impacts. The aim of this study was to develop a validated cervical spine model for axial impacts for future use in the analysis of head-first rugby collisions.

A drop test rig was used to replicate a sub-catastrophic axial head impact. A load of 80 N from 0.5 m was applied to the cranial aspect of a C2-C6 porcine spinal specimen mounted in the neutral position. The 3D motion of C3-C5 vertebras (4 kHz) and the cranial axial load (1 MHz) were measured via motion capture (Qualysis, Sweden) and a uniaxial load cell (RDP Electronics Ltd, UK). Specimen specific models were created in NMSBuilder and OpenSim after the vertebrae geometries were obtained from the segmentation of micro-CT images of the specimens. The compressive viscoelastic properties of four vertebral joints (C2-C3 through to C5-C6) were optimised via a Genetic Algorithm (MATLAB v2016b, The Mathworks Inc) to minimise tracking errors.

The optimisation converged to a solution of 140–49000 kN/m and 2000–8000 Ns/m for stiffness and damping respectively (RMSE=5.1 mm). Simulated joint displacements ranged between 0.09 – 1.75 mm compared to experimental 0.1 – 0.8 mm.

Optimal bushing parameters were higher than previously reported values measured through quasi-static testing. Higher stiffness and damping values could be explained by the higher-dynamics nature of the event analysed related to a different part of the non-linear intervertebral disc load-displacement curve.

Cervical spine fractures are frequent in impact sports, such as rugby union. The consequences of these fractures can be devastating as they can lead to paraplegia, tetraplegia and death. Many studies have been conducted to understand the injury mechanisms but the relationship between player cervical spine posture and fracture pattern is still unclear. The aim of this study was to evaluate the influence of player cervical spine posture on fracture pattern due to an impact load. Nineteen porcine cervical spines (C2 to C6) were dissected, potted in PMMA bone cement and mounted in a custom made rig. They were impacted with a mean load of 6 kN. Eight specimens were tested in an axial position, five in flexion and six in lateral bending. All specimens were micro-CT imaged (Nikon XT225 ST Scanner, Nikon Metrology, UK) before and after the tests, and the images were used to assess the fracture patterns. The injuries were classified according to Allen-Ferguson classification system by three independent observers. The preliminary results showed that the main fracture modalities were consistent with those seen clinically. The main fractures for the axial orientation were observed in C5-C6 level with fractures on the articular process and endplates. These findings support the concept that the fracture patterns are related to the spine position and give an insight for improvements on sports rules in order to reduce the risk of injury.

Aims

Patients with flexion instability after total knee arthroplasty (TKA) often present with a recurrent effusion, which may be a haemarthrosis. While the radiographic factors contributing to flexion instability have been elucidated, the clinical diagnosis remains challenging. Our aim, in this study, was to determine the mean white cell count and differential profile in pre-operative aspirations of synovial fluid in a consecutive series of patients undergoing revision TKA for flexion instability.

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.

Background

The improvement of the rib cage deformity (RCD) after surgery correction has not been correlated in detail with the correction of vertebral axial rotation (AR). The loss of at the rib cage after correction has been never monitored. The hypothesis of this work was that the aesthetic improvement of RCD in adolescent idiopathic scoliosis (AIS) does not follow completely the reduction of thoracic AR after correction surgery. Moreover, lesser correction of thorax deformity could be expected in mature patients with more rigid curves.

Material-based strategies seek to engineer synthetic microenvironments that mimic the characteristics of physiological extracellular matrices for applications in regenerative therapies, including bone repair and regeneration. In our group, we identified a specific chemistry, poly(ethyl acrylate) (PEA), able to induce the organization of fibronectin (FN), upon adsorption of the protein, into fibrillar networks similar to the physiological ones, leading to enhanced cellular response, in terms of cell adhesion and differentiation. In this work, we exploit these FN networks to capture and present growth factors (GF) in combination with the integrin binding domain of FN during bone tissue healing.

Fibrillar conformation of FN adsorbed on PEA favors the simultaneous availability of the GF binding domain (FNIII12–14) next to the integrin binding region (FNIII9–10), compared to poly(methyl acrylate) (PMA), a material with similar chemistry, where FN adopts a globular conformation. The combined exposure of specific adhesive sequences recognized by integrins and GF binding domains was found to improve the osteogenic differentiation of mesenchymal stem cells. A higher expression of bone proteins was found when BMP2 is bound or sequestered on the material surface versus its administration in the culture media in vitro. The potential of this system as recruiter of GFs was also investigated in a critical-size bone segmental defect in mouse. The synergistic integrin-GF signalling, induced by fibrillar FN, promoted bone formation in vivo with lower BMP2 doses than current technologies. Furthermore, we optimized the system for its potential use in translational research, seeking to address the clinical need of using biocompatible and biodegradable material implants. Polycaprolactone scaffolds were synthesized and coated with a thin layer of plasma- polymerized PEA that recruits and efficiently presents GF during healing of critical size defects.

The material-driven FN fibrillogenesis provides a new strategy to efficiently reduce the GF doses administrated in bone regenerative therapies.

Polyether ether ketone (PEEK) has been increasingly employed as biomaterials for trauma, orthopeadic, and spinal implants. However, concern has been raised about the inertness of PEEK which limits bone integration. In this study, we have coated PEEK with a functional material seeking to promote osteogenic differentiation of human mesenchymal stem cells (hMSC).

We have used spray drying to coat poly(ethyl acrylate) (PEA) as a coating on PEEK. This technique is simple, allows a range of controlled coating thicknesses (from hundred nm to a few um), cost effective and easily translatable to scaffolds or implant surfaces for existing or new orthopaedic applications. PEA induces the organisation of fibronectin (FN) into nanonetworks upon simple adsorption from protein solutions. These FN nanonetworks on PEA represent a microenvironment for efficient growth factor binding and presentation in very low but effective doses. In this study we show cell adhesion and stem cell differentiation towards an osteogenic lineages when bone morphogenetic protein 2 (BMP2) was adsorbed on these engineered PEEK/PEA/FN microenvironments in very low doses.

Overall, the developed functional coatings on PEEK has the potential to allow the translation of this material into orthopaedic applications.

Aims

The aim of this study was to report a single surgeon series of consecutive patients with moderate hallux valgus managed with a percutaneous extra-articular reverse-L chevron (PERC) osteotomy.

Introduction

Bi-compartmental knee arthroplasty (BKA) is an alternative to total knee arthroplasty (TKA) for degenerative joint disease when present in only two compartments. BKA spares the cruciate ligaments and preserves bone in the healthy compartment, possibly leading to better knee kinematics and clinical outcomes when compared to TKA. While BKA is a technically demanding procedure when performed with manual instrumentation, robotic assistance allows for accurate implant placement and soft tissue balancing of the joint. Robotic unicompartmental knee arthroplasty (UKA) has shown favourable clinical outcomes and survivorship at short term (2 year) follow up compared to manual UKA. The purpose of this study is to evaluate the short term functional outcomes and survivorship of patients undergoing robotically assisted BKA.