On the quantification and objective classification of instability in the healthy, osteoarthritic and prosthetic knee

Knee instability is a common complaint in osteoarthritis (OA), and a common reason for revision following total knee arthroplasty (TKA). Despite this, assessment of instability is hampered by the lack of a validated method of objective classification or quantification, with most research relying upon patient reports of frequency of symptoms. The aim of this thesis is to define a theoretical framework for instability in the knee, and to develop a protocol for the classification and quantification of instability in the native and prosthetic knee. Instability of the knee in this thesis is understood as the failure of the joint to return to a zero-state following perturbation using all the available active and passive mechanisms available to it, resulting in system collapse. Symptomatic instability is the awareness of reaching the boundary between the stable and unstable state. The prevalence of subjective instability in the end stage OA knee was measured from a publicly available database of pre-operative knee scores from TKA patients, while the prevalence of instability as a cause of revision was assessed from case note review of TKA revision patients from a tertiary referral orthopaedic unit. A single channel, tibia mounted accelerometer was selected for assessment of frontal plane knee movement during normal walking and a protocol developed its use. This was assessed for its repeatability and compared with standard gait analysis in healthy volunteers, and subjectively stable and unstable post-operative TKA patients. Found to be repeatable with differentiation of output between subjectively stable and unstable TKA, the protocol was adapted and used to compare subjectively stable and unstable OA knees prior to TKA. Using patient subjective assessment as classifier, wavelet transforms, Principal Component Analysis and linear regression was used to produce a classification model from the accelerometer data. The single accelerometer was found to produce classification with an accuracy of 84.6%, sensitivity of 93.3% and specificity of 72.7%, with area under the curve (AUC) of 0.797. This classification model for instability produces the basis from which the protocol can be adapted and developed to improve performance and ultimate quantify instability in the knee for use in clinical and research settings.Knee instability is a common complaint in osteoarthritis (OA), and a common reason for revision following total knee arthroplasty (TKA). Despite this, assessment of instability is hampered by the lack of a validated method of objective classification or quantification, with most research relying upon patient reports of frequency of symptoms. The aim of this thesis is to define a theoretical framework for instability in the knee, and to develop a protocol for the classification and quantification of instability in the native and prosthetic knee. Instability of the knee in this thesis is understood as the failure of the joint to return to a zero-state following perturbation using all the available active and passive mechanisms available to it, resulting in system collapse. Symptomatic instability is the awareness of reaching the boundary between the stable and unstable state. The prevalence of subjective instability in the end stage OA knee was measured from a publicly available database of pre-operative knee scores from TKA patients, while the prevalence of instability as a cause of revision was assessed from case note review of TKA revision patients from a tertiary referral orthopaedic unit. A single channel, tibia mounted accelerometer was selected for assessment of frontal plane knee movement during normal walking and a protocol developed its use. This was assessed for its repeatability and compared with standard gait analysis in healthy volunteers, and subjectively stable and unstable post-operative TKA patients. Found to be repeatable with differentiation of output between subjectively stable and unstable TKA, the protocol was adapted and used to compare subjectively stable and unstable OA knees prior to TKA. Using patient subjective assessment as classifier, wavelet transforms, Principal Component Analysis and linear regression was used to produce a classification model from the accelerometer data. The single accelerometer was found to produce classification with an accuracy of 84.6%, sensitivity of 93.3% and specificity of 72.7%, with area under the curve (AUC) of 0.797. This classification model for instability produces the basis from which the protocol can be adapted and developed to improve performance and ultimate quantify instability in the knee for use in clinical and research settings

Knee joint stiffness and function following total knee arthroplasty

Introduction: Studies show that Total Knee Arthroplasty (TKA) is successful for the majority of patients however some continue to experience some functional limitations and anecdotal evidence indicates that stiffness is a common complaint. Some studies have suggested an association between stiffness and functional limitations however there has been no previous work which has attempted to objectively quantify knee joint stiffness following TKA. The purpose of this study was to pilot and evaluate a method for the quantitative evaluation in joint stiffness in replaced knees, OA knees and healthy controls and to explore whether there is an association between stiffness and functional limitations post-TKA surgery. Methods: The first part of the study created a biomechanical model of knee stiffness and built a system from which stiffness could be calculated. A torque transducer was used to measure the resistance as the knee was flexed and extended passively and an electrogoniometer concurrently measured the angular displacement. Stiffness was calculated from the slope of the line relating the passive resistive torque and displacement. The torque and joint angle at which stiffness was seen to increase greatly was also noted. The system was bench tested and found to be reliable and valid. Further tests on 6 volunteers found stiffness calculations to have acceptable intra-day reliability. The second part was conducted on three groups: those with end-stage knee OA (n = 8); those who were 1 year post-TKA (n = 15) and age matched healthy controls (n = 12). Knee range of motion was recorded and participants then completed the WOMAC, the SF-12 and a Visual Analogue Score for stiffness as well as indicating words to describe their stiffness. Four performance based tests – the Timed Up and Go (TUG), the stair ascent/descent, the 13m walk and a quadriceps strength test were also undertaken. Finally, passive stiffness at the affected knee was measured. Results: 100% of OA, 80% of TKA and 58% of controls reported some stiffness at the knee. The OA group reported significantly higher stiffness than the OA or TKA groups. There was no difference in self-reported stiffness between the TKA and control groups. Of the total number of words used to describe stiffness, 52% related to difficulty with movement, 35% were pain related and 13% related to sensations. No significantly differences were found between groups in the objective stiffness measures. Significant differences were found however in threshold flexion stiffness angles between groups. When this angle was normalised, differences between groups were not significant. No significant differences were found between groups in the threshold stiffness torque. Greater self-reported stiffness was found to be associated with worse self-reported function. A higher flexion stiffness threshold angle was associated with slower timed tests of function but also with better quadriceps muscle strength. Conclusions: The results support anecdotal reports that perceived stiffness is a common complaint following TKA but there was no evidence to show that patients with TKA have greater stiffness than a control group. There was however evidence to show that patients’ were unable to distinguish between sensations of stiffness and other factors such as pain. Self-perceived increased stiffness was associated with worse functional performance. Greater stiffness however was not necessarily negative. Stiffness increases earlier in flexion range were associated with better functional performance. These results suggest that an ideal threshold range for stiffness may exist; above which negative perceptions of the knee result in worse function but below which, knee laxity and instability may also result in worse function

Clinical investigation of the functional outcome of fixed bearing versus mobile bearing knees

Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types.Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types

1st EFORT European Consensus: Medical & Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices

Innovations in Orthopaedics and Traumatology have contributed to the achievement of a high-quality level of care in musculoskeletal disorders and injuries over the past decades. The applications of new implants as well as diagnostic and therapeutic techniques in addition to implementation of clinical research, have significantly improved patient outcomes, reduced complication rates and length of hospital stay in many areas. However, the regulatory framework is extensive, and there is a lack of understanding and clarity in daily practice what the meaning of clinical & pre‐clinical evidence as required by the MDR is. Thus, understanding and clarity are of utmost importance for introduction of new implants and implant-related instrumentation in combination with surgical technique to ensure a safe use of implants and treatment of patients. Therefore EFORT launched IPSI, The Implant and Patient Safety Initiative, which starting from an inaugural workshop in 2021 issued a set of recommendations, notably through a subsequent Delphi Process involving the National Member Societies of EFORT, European Specialty Societies as well as International Experts. These recommendations provide surgeons, researchers, implant manufacturers as well as patients and health authorities with a consensus of the development, implementation, and dissemination of innovation in the field of arthroplasty. The intended key outcomes of this 1st EFORT European Consensus on “Medical & Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices”are consented, practical pathways to maintain innovation and optimisation of orthopaedic products and workflows within the boundaries of MDR 2017/745. Open Access practical guidelines based on adequate, state of the art pre-clinical and clinical evaluation methodologies for the introduction of joint replacements and implant-related instrumentation shall provide hands-on orientation for orthopaedic surgeons, research institutes and laboratories, orthopaedic device manufacturers, Notified Bodies but also for National Institutes and authorities, patient representatives and further stakeholders. We would like to acknowledge and thank the Scientific Committee members, all International Expert Delegates, the Delegates from European National & Specialty Societies and the Editorial Team for their outstanding contributions and support during this EFORT European Consensus

Patient-Specific Implants in Musculoskeletal (Orthopedic) Surgery

Most of the treatments in medicine are patient specific, aren’t they? So why should we bother with individualizing implants if we adapt our therapy to patients anyway? Looking at the neighboring field of oncologic treatment, you would not question the fact that individualization of tumor therapy with personalized antibodies has led to the thriving of this field in terms of success in patient survival and positive responses to alternatives for conventional treatments. Regarding the latest cutting-edge developments in orthopedic surgery and biotechnology, including new imaging techniques and 3D-printing of bone substitutes as well as implants, we do have an armamentarium available to stimulate the race for innovation in medicine. This Special Issue of Journal of Personalized Medicine will gather all relevant new and developed techniques already in clinical practice. Examples include the developments in revision arthroplasty and tumor (pelvic replacement) surgery to recreate individual defects, individualized implants for primary arthroplasty to establish physiological joint kinematics, and personalized implants in fracture treatment, to name but a few

The use of arthroplasty surgery in the treatment of severe isolated patellofemoral arthritis

Severe isolated patellofemoral arthritis is a highly debilitating disease. Total knee arthroplasty is considered the gold standard treatment, however, patellofemoral arthroplasty has certain advantages. This ‘less invasive’ procedure preserves the tibiofemoral joint and cruciate ligaments, facilitating a more rapid recovery and allows for a relatively straightforward revision if required in the future. As the use of patellofemoral arthroplasty steadily gains popularity in the orthopaedic community, it is important to establish a consensus on which treatment should be the primary intervention of choice. Through background reading and expert opinion, three areas of research were chosen for further investigation: 1. Extensor mechanism efficiency 2. Survival and complication proportions following patellofemoral arthroplasty and total knee arthroplasty 3. Assessment of differences in function and quality of life outcomes following patellofemoral arthroplasty and total knee arthroplasty The purpose of this thesis was to further inform the debate between the choice of total knee arthroplasty and patellofemoral arthroplasty for the treatment of severe isolated patellofemoral arthritis. Study I: The cadaveric biomechanics study compared the extensor mechanism efficiency of the native knee, patellofemoral arthroplasty, cruciate-retaining total knee arthroplasty and posterior-stabilising total knee arthroplasty. Patellofemoral resultant force, peak pressure and contact area were also analysed. The data produced a bimodal distribution during the flexion-extension cycle for all four conditions. The results showed patellofemoral arthroplasty produced the greatest extensor mechanism efficiency in the range of mid flexion to extension (50° to 0°). Further research is required to determine whether this efficiency translates to the clinical setting. Study II: The systematic review compared the survival and complication proportions of patellofemoral arthroplasty and total knee arthroplasty. The patellofemoral arthroplasty studies were divided into seven groups depending on femoral component design. Thirty-six out of the forty studies identified were uncontrolled retrospective case series’ and therefore subject to reporting and selection biases and overall provided low quality evidence. A meta-analysis could not be performed due to high clinical heterogeneity. Other limitations included variations in study design and length of follow-up. Despite, these weaknesses the review established inlay designs produced the poorest survival and complication outcomes. Malpositioning/misalignment and disease progression were the most common complications. Study III: The double-blind randomised clinical trial assessed for differences in function and quality of life outcomes between patellofemoral arthroplasty and total knee arthroplasty. The trial failed to show evidence of a difference between the two interventions. Complication rates were overall low but greater in the total knee arthroplasty group. Tests for significance were not performed due to the small numbers involved. Although, the study was underpowered, the data did not support superiority of patellofemoral arthroplasty over total knee arthroplasty. Therefore, future studies should test for non-inferiority and involve multiple centres to increase generalizability to the wider orthopaedic community

Novel Research about Biomechanics and Biomaterials Used in Hip, Knee and Related Joints

Joint replacement is a very successful medical treatment. However, the survivorship of hip, knee, shoulder, and other implants is limited. The degradation of materials and the immune response against degradation products or an altered tissue loading condition as well as infections remain key factors of their failure. Current research in biomechanics and biomaterials is trying to overcome these existing limitations. This includes new implant designs and materials, bearings concepts and tribology, kinematical concepts, surgical techniques, and anti-inflammatory and infection prevention strategies. A careful evaluation of new materials and concepts is required in order to fully assess the strengths and weaknesses and to improve the quality and outcomes of joint replacements. Therefore, extensive research and clinical trials are essential. The main aspects that are addressed in this Special Issue are related to new material, design and manufacturing considerations of implants, implant wear and its potential clinical consequence, implant fixation, infection-related material aspects, and taper-related research topics. This Special Issue gives an overview of the ongoing research in those fields. The contributions were solicited from researchers working in the fields of biomechanics, biomaterials, and bio- and tissue-engineering

Arthroscopy

This book covers a physical examination, imaging, differential diagnoses, and treatment of articular pathologies. For each diagnosis, the book sets out the typical presentation, options for non-operative and operative management, and expected outcomes. Practical and user-friendly, Arthroscopy is a useful resource for medical students and practitioners seeking fast facts on diagnosis and management. Its format makes it a perfect quick reference and its content breadth covers commonly encountered orthopedic problems in practice

Biotribology of Osteochondral Grafts in the Knee

Osteochondral grafts as a regenerative early intervention therapy provide a solution for the repair of osteochondral defects and in the long-term may prevent the requirement for total knee replacement. The successful application of osteochondral grafts and novel regenerative solutions is heavily reliant on the biomechanical, tribological and biological properties of the constructs. In order to successfully deliver novel early intervention solutions, there is a requirement to develop robust and stratified preclinical test methods. The aims of the project were twofold; firstly, using simple geometry biomechanical and biotribological models, investigate the stability, friction and wear of osteochondral grafts post implantation in the knee. Secondly, develop a method for the preclinical, functional assessment of friction and wear following osteochondral implantation in a natural knee simulation model. Initial biomechanical evaluation of osteochondral grafts indicated that the most significant factor determining graft stability post implantation was the ratio between graft and defect length and tissue species used. Porcine grafts and grafts implanted into defects longer than the graft length, were less inherently stable and subject to subsidence below congruency at lower loads. A simple geometry pin-on-plate reciprocating friction model was used to investigate the effects of osteochondral grafts on the tribology of the opposing articulating cartilage surface. Osteochondral grafts were compared with the native state (negative control), cartilage defects and stainless steel pins inserted both flush and proud of the cartilage surface (positive controls). The ability of osteochondral grafts to restore a congruent, low friction and wear articulation was evaluated. The simple geometry study demonstrated that osteochondral grafts have the potential to restore the articular surface without significantly disrupting the local tribology. A whole joint natural knee simulator capable of reproducing the physiological conditions in the knee was used to develop a novel preclinical test method to evaluate the friction and wear properties of osteochondral grafts in a porcine knee model. In summary, increased wear levels did not correlate with significant increases in shear force; osteochondral grafts demonstrated the potential to restore a low friction and wear articulation with no significant differences to the native state. The development of the simulation model represents a significant step in the preclinical testing of osteochondral grafts and may be applied to test regenerative osteochondral interventions, disease models and aid in the development of stratified interventions

Biotribology of Osteochondral Grafts in the Knee

Osteochondral grafts as a regenerative early intervention therapy provide a solution for the repair of osteochondral defects and in the long-term may prevent the requirement for total knee replacement. The successful application of osteochondral grafts and novel regenerative solutions is heavily reliant on the biomechanical, tribological and biological properties of the constructs. In order to successfully deliver novel early intervention solutions, there is a requirement to develop robust and stratified preclinical test methods. The aims of the project were twofold; firstly, using simple geometry biomechanical and biotribological models, investigate the stability, friction and wear of osteochondral grafts post implantation in the knee. Secondly, develop a method for the preclinical, functional assessment of friction and wear following osteochondral implantation in a natural knee simulation model. Initial biomechanical evaluation of osteochondral grafts indicated that the most significant factor determining graft stability post implantation was the ratio between graft and defect length and tissue species used. Porcine grafts and grafts implanted into defects longer than the graft length, were less inherently stable and subject to subsidence below congruency at lower loads. A simple geometry pin-on-plate reciprocating friction model was used to investigate the effects of osteochondral grafts on the tribology of the opposing articulating cartilage surface. Osteochondral grafts were compared with the native state (negative control), cartilage defects and stainless steel pins inserted both flush and proud of the cartilage surface (positive controls). The ability of osteochondral grafts to restore a congruent, low friction and wear articulation was evaluated. The simple geometry study demonstrated that osteochondral grafts have the potential to restore the articular surface without significantly disrupting the local tribology. A whole joint natural knee simulator capable of reproducing the physiological conditions in the knee was used to develop a novel preclinical test method to evaluate the friction and wear properties of osteochondral grafts in a porcine knee model. In summary, increased wear levels did not correlate with significant increases in shear force; osteochondral grafts demonstrated the potential to restore a low friction and wear articulation with no significant differences to the native state. The development of the simulation model represents a significant step in the preclinical testing of osteochondral grafts and may be applied to test regenerative osteochondral interventions, disease models and aid in the development of stratified interventions