Hybrid SPECT/CT for the assessment of a painful hip after uncemented total hip arthroplasty

Background The diagnosis of hip pain after total hip replacement (THR) represents a highly challenging question that is of increasing concern to orthopedic surgeons. This retrospective study assesses bone scintigraphy with Hybrid SPECT/CT for the diagnosis of painful THR in a selected cohort of patients. Methods Bone SPECT/CT datasets of 23 patients (mean age 68.9 years) with a painful hip after THR were evaluated. Selection of the patients required an inconclusive radiograph, normal serum levels of inflammatory parameters (CRP and ESR) or a negative aspiration of the hip joint prior to the examination. The standard of reference was established by an interdisciplinary adjudication-panel using all imaging data and clinical follow-up data (>12 month). Pathological and physiological uptake patterns were defined and applied. Results The cause of pain in this study group could be determined in 18 out of 23 cases. Reasons were aseptic loosening (n = 5), spine-related (n = 5), heterotopic ossification (n = 5), neuronal (n = 1), septic loosening (n = 1) and periprosthetic stress fracture (n = 1). In (n = 5) cases the cause of hip pain could not be identified. SPECT/CT imaging correctly identified the cause of pain in (n = 13) cases, in which the integrated CT-information led to the correct diagnosis in (n = 4) cases, mainly through superior anatomic correlation. Loosening was correctly assessed in all cases with a definite diagnosis. Conclusions SPECT/CT of THA reliably detects or rules out loosening and provides valuable information about heterotopic ossifications. Furthermore differential diagnoses may be detected with a whole-body scan and mechanical or osseous failure is covered by CT- imaging. SPECT/CT holds great potential for imaging-based assessment of painful prostheses

Biomechanical and Clinical Alterations of the Hip Joint Following Femoral Neck Fracture and Implantation of Bipolar Hip Endoprosthesis

A B S T R A C T The implantation of a bipolar partial hip endoprosthesis is a treatment of choice for displace

Biomechanical and Clinical Alterations of the Hip Joint Following Femoral Neck Fracture and Implantation of Bipolar Hip Endoprosthesis

The implantation of a bipolar partial hip endoprosthesis is a treatment of choice for displaced medial femoral neck fracture. We present an experimental study which asses and compare biomechanical and clinical status through period before and after hip fracture and implantation of bipolar partial hip endoprosthesis. This study encompassed 75 patients who suffered from an acute medial femoral neck fracture and were treated with the implantation of a bipolar partial hip endoprosthesis. Their biomechanical status (stress distribution on the hip joint weight bearing area) and clinical status (Harris Hip Score) were estimated for the time prior to the injury and assessed at the follow-up examination that was, on average, carried out 40 months after the operation. Despite ageing, the observed Harris Hip Score at the follow-up examination was higher than that estimated prior to the injury (77.9>69.6; p=0.006). Similarly, the hip stress distribution was reduced (2.7 MPa<2.3 MPa; p=0.001). While this reduction can be attributed to a loss of weight due to late ageing, the principal improvement came from the operative treatment and corresponding restoration of the biomechanical properties of the hip joint. The implantation of a bipolar partial hip endoprosthesis for patients with displaced medial femoral neck fractures improves the biomechanical and clinical features of the hip, what should have on mind during making decision about treatment

ITAP: Clinical outcomes and implant design optimisation using numerical modelling

Redistribution of the flow of forces through the body, such as that after amputation and/or implantation of a skeletally anchored amputation prostheses, leads to bone remodelling. Periprosthetic bone resorption can destabilise skeletally anchored amputation prostheses. Therefore, implants that minimise bone resorption will achieve a more successful long term bone fixation. Bone remodelling outcome measures rely on implant design using mechanoregulatory bone remodelling theory. Mechanoregulation is implemented by functions that link a local mechanical stimulus to a local change in the structure or properties of bone material. This thesis uses the strain adaptive remodelling theory at the time of implantation with periprosthetic strain energy density as the outcome parameter. Clinical trial data was collected from a patient with a skeletally anchored amputation prostheses; The Intraosseous Transcutaneous Amputation Prosthesis (ITAP). The clinical trial ran from 2008 – 2019, the data was investigated for patterns between implant design and fixation success. This thesis reports trends in fixation success and bone change using a developed fixation success score. There was an ideal implant length to bone length ratio range and a straight, tapered stem with a flared bone collar growth shape were beneficial to fixation success. Conversely, one or more parameters associated with pressfit fixation were detrimental to fixation success. Results between the clinical and numerical data compared favourably; clinically, regions of periprosthetic bone growth were also observed by regions of high strain energy density in the finite element analysis and vice versa at the implant tip and osteotomy face. This thesis provides skeletally anchored amputation prostheses design guidelines that will minimise bone resorption when measured with strain energy density. Moreover, that future skeletally anchored amputation prostheses parameterised design can and should be used as a tool to assess bone fixation outcome in pre-clinical assessments

Mechanical and biological aspects of impaction bone grafting in revision hip surgery and the use of a new synthetic bone graft

AIMS: This thesis aims to examine the biological and mechanical factors which influence the strength of impacted morsellised bone graft. The use of synthetic materials as bone graft enhancers was also analysed (Controlled Release Glass - Corglaes®, Giltech Ltd, Ayr, Scotland and Tricalcium Phosphate Hydroxyapatite - TCP/HA, Stryker Howmedica Osteonics, Berkshire, UK). METHODS: Phase I - the mechanical strength of different fresh frozen human bone graft preparations were analysed in the laboratory, looking specifically at the effect of particle size, washing the graft and using synthetic additives. Phase II - mixtures of bone graft and bone graft/Corglaes®, which had been identified as being mechanically stronger than standard bone graft, were analysed for their biological response in an in-vivo ovine defect model, compared to controls. Bone densitometry and histological analysis was performed. Phase III - a mixture of bone graft and Corglaes® was compared to the current 'gold standard' of allograft bone alone, in a simulated revision in-vivo ovine femoral hip replacement model. Outcome measures of subsidence, micromotion on cyclical loading and histomorphometry were performed. RESULTS: Phase 1 - Fresh frozen human bone-graft behaves in a similar fashion to theoretical predictions based on Engineering principles. These principles follow Soil Mechanics theory and are commonly used by engineers when designing stable foundations for roads or buildings. In general, when the spread of different particle sizes is uniform over a given range, the material is stronger (more resistant to shear) than if the particles are all the same size. This allowed determination of which bone mills produce the strongest graft. These results were dependent on the degree of fluid release on graft milling, with more fluid release when the average particle size is reduced. Shear strength was improved for all mills after washing the morsellised graft or by the addition of synthetic additives (Corglaes® and TCP/HA). Phase 2 - The defect model allowed analysis of remodelling of the impacted pellets, highlighting rapid dissolution of the Corglaes®, without a significant inflammatory response. The model may be closer to a fracture model when the histological results of phase III are considered. Phase 3 - No statistically significant difference in subsidence over the implantation period (12 weeks) or micromotion of the retrieved implant / femur composites could be elicited between the two groups. Histological analysis revealed the distal impacted graft to be in an isolated environment, both from biological ingress and solution exchange. Bone graft and Corglaes® that was remodelled or resorbed after time in the Phase II defect experiments, was little changed with time in the distal femur. The proximal femur histologically behaved in a similar fashion to the defect experiments. This suggests that a defect model alone is not ideal to analyse materials for impaction grafting. CONCLUSIONS: • Graft strength is variable depending on the bone mill that produces it - washing bone graft improves the strength from all bone mills tested. • Tight compaction with smaller particles does not inhibit neovascularisation. • Novel biomaterials by themselves were inferior mechanically and biologically. • 50/50 mixes of allograft and Corglaes® are stronger mechanically and do not appear to have an adverse effect on biological incorporation. • In this sheep hemiarthroplasty model, subsidence, micromotion and histomorphometry results better replicate the equivalent reported human results than previous models, especially unloaded defect models in lower vertebrates

Clinical, industrial, and research perspectives on powder bed fusion additively manufactured metal implants

For over ten years, metallic skeletal endoprostheses have been produced in select cases by additive manufacturing (AM) and increasing awareness is driving demand for wider access to the technology. This review brings together key stakeholder perspectives on the translation of AM research; clinical application, ongoing research in the field of powder bed fusion, and the current regulatory framework. The current clinical use of AM is assessed, both on a mass-manufactured scale and bespoke application for patient specific implants. To illuminate the benefits to clinicians, a case study on the provision of custom cranioplasty is provided based on prosthetist testimony. Current progress in research is discussed, with immediate gains to be made through increased design freedom described at both meso- and macro-scale, as well as long-term goals in alloy development including bioactive materials. In all cases, focus is given to specific clinical challenges such as stress shielding and osseointegration. Outstanding challenges in industrialisation of AM are openly raised, with possible solutions assessed. Finally, overarching context is given with a review of the regulatory framework involved in translating AM implants, with particular emphasis placed on customisation within an orthopaedic remit. A viable future for AM of metal implants is presented, and it is suggested that continuing collaboration between all stakeholders will enable acceleration of the translation process

Preclinical tests of endoprostheses of hip joint using finite element methods

W opracowaniu przedstawiono metodę wykonania testów przedklinicznych w aplikacjach endoprotezy stawu biodrowego w układzie anatomicznym. Metoda polegała na modelowaniu różnych konstrukcji endoprotez wykonanych z różnych biomateriałów i wirtualnym osadzaniu, w odwzorowanych na podstawie tomografii komputerowej (CT), strukturach kostnych. Wykorzystanie metody elementów skończonych pozwoliło na przeprowadzenie analiz numerycznych w zamodelowanych obiektach badań. W warunkach przenoszenia obciążeń lokomocyjnych dokonywana była wizualizacja rozkładów naprężeń, przemieszczeń i odkształceń w endoprotezie, kości miednicznej oraz w bliższym końcu kości udowej. Wyniki badań pozwoliły porównać rozwiązania konstrukcyjne endoprotez stawu biodrowego oraz ocenić charakter oddziaływania sztucznego stawu na otaczające tkanki kostne w warunkach indywidualnego pacjenta.The method of preclinical tests in application of endoprostheses of hip joint in the anatomical system is presented in this elaboration. The method is based on the modeling of different constructions of endoprostheses made from different biomaterials. The endoprostheses were virtually placed in natural bone structures and obtained from the computer tomography diagnostic (CT). The use of the finite element method allowed to carry on numerical analyses in modeled objects of tests. The visualization of distribution of stresses, displacements and deformations in endoprostheses, pelvis bone and femoral bone was conducted in the conditions of transfer of load. The results of tests let to compare the construction solutions of endoprostheses of hip joint and estimate the interaction of artificial hip joint on the surrounding bone tissues in individual patientconditions

Development of Optimal Total Hip Joint Replacement

Total hip replacement (THR) is a surgical process in which the hip joint is replaced by a hip prosthesis. It is one of the most popular and cost effective surgery. In particular in 2014, 83,125 primary procedures were recorded. Some of these operations need to be carried out again for different reasons after sometime. These are called revision (replacement of the prosthesis) procedures. Important studies and statistics suggest that the number of THR procedures is projected to increase by almost 175% by 2030. Aseptic loosening appears to be the most significant cause of failure in THR. Aseptic loosening might lead to revision surgery and in turn can be avoided by enhancing the stability and durability of the hip replacement. Primary stability attained after surgery is a determinant issue for the long-term stability of cementless hip arthroplasty. Primary stability is the level of relative micromotion between the femur and the prosthesis induced via the physiological joint forces following the surgery. The hip prosthesis is also exposed to dynamic loadings and activities of daily living, which can induce the stress distribution on the prosthesis of the hip joint model and affect the durability of the implant. The aim of this study is to develop an optimal total hip replacement (THR) implant with new and improved design features to achieve stability and durability. The micromotion between bone and implant interface and the stress distribution on the prosthesis and femur assembly has been reviewed and investigated. The laboratory testing were carried out on the femur including the compression, torsion and Brinell hardness testing. A compression testing using strain gauge technique done on the hip implant. Finite element analysis software used to simulate all compression and torsion testing assuming the same boundary and loading conditions and subsequently the computational results were compared with the earlier experimental data to verify the experiments and models used. 7 The comparative micromotion studies and findings of other researchers were used beside the clinical follow-up reports on success or failure rates of related hip designs, to justify the best solutions for design factors. In this computational approach researchers usually use finite element methodology to calculate micromotion of elements, sometimes known as migration. The elements exceeding the threshold limit would simulate the migration and subsequently eliminated from the assembly. This procedure recurs until reaching the convergence that derives a stable mechanical equilibrium. One of the restrictions of micromotion analysis was the inability to divide the final results into axial and rotational components. Therefore it would have been inappropriate to eventually conclude the best femoral stem, without considering the sustaining torsional loadings. Another limitation was that the micromotion analysis would not reflect the stress distribution on the hip prosthesis and consequently would ignore the potential high stress concentration that is associated with post operative pain as well as low durability and long-term stability. For these reasons stress analysis was carried out under dynamic loadings of nine different activities to examine the von Mises stress, shear stress and principal stress distribution of a cementless hip implant. In each activity realistic boundary and loading conditions of a complete assembly of femur and hip implant were investigated which includes defining of many variables including different geometry, material properties, boundary conditions, forces and moments of varying magnitude and orientation over specific time intervals. The critical points and areas that were developed in the entire 3D model were evaluated and explained. The finite element analysis which verified by experimental testing and hold the clinical relevance were used to decide the best optimal hip stem design amongst different presented design concepts. This was accompanied and improved with further stress analysis of different design factors to get the final optimal model. High offset stem option is a unique feature that helps tightening the abductor and boosts the hip implant stability with the ability to adjust neck and offset. It gives a surgeon more options to fix the most accurate offset and do the operation more effectively. The final optimal design and its advantages were presented in the last chapter