Assessment of Normal Knee Kinematics Using High-Speed Stereo-Radiography System

The measurement of dynamic joint kinematics in vivo is important in order to understand the effects of joint injuries and diseases as well as for evaluating the treatment effectiveness. Quantification of knee motion is essential for assessment of joint function for diagnosis of pathology, such as tracking and progression of osteoarthritis and evaluation of outcome following conservative or surgical treatment. Total knee arthroplasty (TKA) is an invasive treatment for arthritic pain and functional disability and it is used for deformed joint replacement with implants in order to restore joint alignment. It is important to describe knee kinematics in healthy individuals for comparison in diagnosis of pathology and understanding treatment to restore normal function. However measuring the in vivo dynamic biomechanics in 6 degrees of freedom with an accuracy that is acceptable has been shown to be technically challenging. Skin marker based methods, commonly used in human movement analysis, are still prone to large errors produced by soft tissue artifacts. Thus, great deal of research has been done to obtain more accurate data of the knee joint by using other measuring techniques like dual plane fluoroscopy. The goal of this thesis is to use high-speed stereo radiography (HSSR) system for measuring joint kinematics in healthy older adults performing common movements of daily living such as straight walking and during higher demand activities of pivoting and step descending in order to establish a useful baseline for the envelope of healthy knee motion for subsequent comparison with patients with TKA. Prior to data collection, validation and calibration techniques as well as dose estimations were mandatory for the successful accomplishment of this study

Objective clinical performance outcome of total knee prostheses. A study of mobile bearing knees using fluoroscopy, electromyography and roentgenstereophotogrammetry

The aim of the thesis was to to assess with accurate and objective methods the function and fixation of total knee prostheses with special emphasis on mobile bearing total knee designs. The mobile bearing of a rotating platform design showed limited motion or no motion during a step-up task thereby nullifying the theoretical advantages of a mobile bearing prosthesis. Apatite coated implants show excellent mid-term Roentgen Stereophotogrammetric Analysis (RSA) results and offer some clinical advantages above cemented total knee arthroplasty. A prospective RSA study also revealed that the studied mobile bearing design is more predictable and forgiving with respect to micromotion of the tibial component than a posterior stabilised prosthesis. However, mobile bearing prostheses showed to be more demanding for the soft tissue structures surrounding the knee joint. The techniques used in gait analysis and fluoroscopy are sensitive for measurement errors. This restricts the applicability and interpretation of the results acquired when using these methods. In general one needs to be aware of the limitations of measurement tools since one needs accurate and objective methods to assess evidence about the clinical performance of (new) total knee prostheses.Biomet Nederland B.V., DePuy Nederland B.V., Mathys Orthopaedics B.V., Medis medical imaging systems B.V., Medis specials B.V., Smith & Nephew B.V, Stryker Nederland B.V., Wright Medical Nederland B.V., Zimmer Nederland B.V.UBL - phd migration 201

Development of a Computational Model to Predict the In Vivo Contact Mechanics of Modern Total Knee Arthroplasty

This dissertation focuses on the development of a computationally efficient and fast method that incorporates the kinematics obtained from fluoroscopy and extends it to the prediction of the in-vivo contact mechanics at the femoro-tibial articulation in modern knee implants for the deep knee bend activity. In this endeavor, this dissertation deals with the use of an inverse dynamic rigid body model characterizing the slip and roll behavior observed in the femoro-polyethylene articulation and a coupled deformation model where the polyethylene in knee implants are modeled as hexahedral discrete element networks. The performance of this method is tested by comparing force predictions from a telemetric knee and finite element analysis. Finally, the method is applied to study the in vivo contact mechanics and mechanics of the quadriceps mechanism in six popular knee designs. During the deep knee bend activity, the contact force generally increased with flexion. However, the medial lateral forces were not equally distributed and the medial lateral force distribution generally varied from 60%- 40% at full extension to as high as 75%-25% at full flexion in some patients. Also, the magnitude of axial force in the superior-inferior direction was the highest and was found to contribute around 98%-99% of the total load acting at the femorotibial joint. The forces in the medio-lateral and antero-posterior directions were low and the maximum magnitude observed was around 0.5BW. The contact areas and contact pressures were much more sensitive to the geometries involved and the in vivo kinematics. Though no definite pattern was observed for the variation of the contact areas throughout flexion, the contact pressures increased in both condyles with increasing flexion. Also, the contact pressures on the medial condyle were higher than the contact pressures observed in the lateral condyle. The patellofemoral and the quadriceps force ratio increased with the increase in flexion while the patellar ligament and the quadriceps force ratio decreased with increasing flexion. In some patients at high flexion, the quadriceps force and as a result the patellofemoral, patellar ligament and the knee contact forces were found to decrease due to the wrapping of the quadriceps coupled with posterior movement of the femoral condyles leading to the increase in the quadriceps moment arm

Model-based shape matching of orthopaedic implants in RSA and fluoroscopy

Model-based shape matching is commonly used, for example to measure the migration of an implant with Roentgen stereophotogrammetric analysis (RSA) or to measure implant kinematics with fluoroscopy. The aim of this thesis was to investigate the general usability of shape matching and to improve the reliability of shape matching for RSA and fluoroscopy. Several improvements were made to the usability and reliability of model-based shape matching for RSA and fluoroscopy. An automatic contour detection approach was proposed, integrating directly into the estimation of position and orientation of the implant. The accuracy of such estimation was also improved by taking the relation between implant parts into account. The robustness of model-based shape matching was assessed when it is applied fully automatically, demonstrating that manual supervision remains necessary. The standardization of validating new fluoroscopic methods could be a welcome addition to the biomechanical field, making it a lot easier to compare results between methods and experiments. As the technology of fluoroscopy advances, the amount of high quality data is getting larger, and may soon grow beyond the capabilities of manual, supervised pose estimation methods. It is therefore imperative that fully automatic unsupervised methods are developed.UBL - phd migration 201

Contribution to the clinical validation of a generic method for the classification of osteoarthritic and non-pathological knee function

The Cardiff Dempster-Shafer (DS) classifier is a generic automated technique for analysing motion analysis (MA) data. It can accurately discriminate between level gait characteristics of non-pathological (NP) and osteoarthritic (OA) knee function. It can also quantify and visualise the functional outcome of a total knee replacement (TKR). A number of studies were undertaken to explore and enhance this method. The training set for the classifier was increased by 48% by collecting additional knee function data for level gait. Knee function for nine new patients was classified pre and post-TKR surgery. At 12 months post-TKR, two patients exhibited non-dominant NP knee function. The remaining patients did not recover NP gait. This finding is similar to previous classifications of level gait. To improve the distinction between varying degrees of knee function, stair gait was introduced into the trial. A staircase was designed and validated. Adduction and flexion moments acting about the knee joint and medial component of the ground reaction force were found to be important in the classification of OA and NP knee function from stair gait. Using a combination of these variables the DS classifier was able to characterise OA and NP function for 15 subjects correctly with 100% accuracy, determined using a leave-one-out method of cross validation. The variables were tested to assess the outcome of TKR surgery. The patient assessed recovered NP stair gait post surgery. An image based study was undertaken to investigate the quality of the MA data used in the DS classifier. A step up/down activity for 5 NP and 5 TKR subjects was recorded using non-simultaneous MA and dynamic fluoroscopy. Accurate knee kinematics were computed from the fluoroscopy images using KneeTrack image registration software. MA measured significantly larger knee joint translations and non-sagittal plane rotations. The largest errors in MA derived kinematics were 9.53 for adduction-abduction range of motion (ROM) measured from the NP cohort and 2.63cm compression-distraction ROM of the tibio-femoral joint, measured from the TKR cohort. The generic nature of the DS classifier was tested by its application to distinguish hip function following a lateral (LA) and posterior (PA) approach to total hip arthroplasty. The use of different variables was investigated with the classifier. The best classifier was able to distinguish between NP and LA function with 96.7% accuracy, LA and NP with 86.2% accuracy and between LA and PA with 81.5% accuracy. The PA approach was found to lead to more characteristic NP hip function than LA. These studies show that variables from stair gait should be included in addition to level gait in the classifier. Due to errors when measuring non-sagittal plane rotations using MA, these should be interpreted with caution. The generic nature of the classifier has been proven by its application to another joint, thus answering another orthopaedic question.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Multiscale Musculoskeletal Modeling of the Lower Limb to Perform Personalized Simulations of Movement

Computational modeling has been used for many decades to inform design and decision-making in several fields of engineering, such as aerospace, automotive, petroleum, and others. However, it still struggles to have a similar impact in fields of medicine, such as orthopaedics. Three of the challenges that have limited the use of computational modeling in the clinical practice and in product development are model validation, personalization, and realism. Validation is a challenge because several internal parameters of the human body, such as muscle forces, are not safely measurable in vivo and, consequently, a thorough comparison between model outputs and experimental measurements is not always possible. Personalization is an additional issue because the inherent variability across a population needs to be accounted for in a model. Finally, the computational burden of simulations performed with a musculoskeletal model limits its level of realism. The purpose of the work presented in this dissertation is to investigate the applicability of state-of-the-art tools, and propose novel approaches to foster an evolution of computational modeling in orthopaedics. Specifically, (1) the reliability of the knee contact force predictions of a musculoskeletal model commonly used in the literature was analyzed using a global probabilistic analysis for three subjects with instrumented implants; (2) subject-specific and activity-specific moment arms of the muscles spanning the knee were estimated replacing the generic passive cadaveric motion implemented in the knee joint of a musculoskeletal model with in vivo kinematics measured from stereo-radiography images; (3) subject-specific joint mechanics for 6 total knee arthroplasty patients performing daily activities was estimated with a sequential multiscale modeling approach that combined joint loads estimated with a whole body musculoskeletal model, personalized joint geometries, and subject-specific fluoroscopy-measured kinematics; finally, (4) a closed-loop muscle control strategy was designed to track experimental joint kinematics and concurrently estimate muscle forces and knee mechanics with a finite element musculoskeletal model of the lower limb including a deformable representation of the joint. The utility of the modeling techniques proposed in this dissertation is presented within a clinical perspective in order to encourage the utilization of musculoskeletal modeling for clinical applications and product development

Spatial Sensors for Quantitative Assessment of Retrieved Arthroplasty Bearings

Evaluation of retrieved joint arthroplasty bearings provides unique evidence related to the physiological environment in which bearing materials are expected to perform. This dissertation describes the development of novel spatial sensors and measurement strategies for standardized, quantitative assessments of arthroplasty bearings, including total knee replacements, unicompartmental knee replacements, and total hip replacements. The approach is to assess bearings that endured a finite duration of function in patients, with particular emphasis on expanding our understanding of the biomechanical conditions specific to bearing function and wear in the physiological environment. Several quantifiable parameters are identified that prove comparable to pre-clinical in vitro tibological evaluations, including knee wear simulation and analytical modeling. These comparisons provide clinical relevance to the existing methodologies, helping to verify that the biomechanical simulations accurately represent the in vivo conditions they are meant to simulate. The broad objective of this dissertation is to improve the longevity and function of arthroplasty bearing materials and designs. Assessments from the retrieved prostheses are discussed within the context of developing comprehensive approaches for the prospective evaluation of new materials and designs in joint replacements

Contribution to the clinical validation of a generic method for the classification of osteoarthritic and non-pathological knee function

The Cardiff Dempster-Shafer (DS) classifier is a generic automated technique for analysing motion analysis (MA) data. It can accurately discriminate between level gait characteristics of non-pathological (NP) and osteoarthritic (OA) knee function. It can also quantify and visualise the functional outcome of a total knee replacement (TKR). A number of studies were undertaken to explore and enhance this method. The training set for the classifier was increased by 48% by collecting additional knee function data for level gait. Knee function for nine new patients was classified pre and post-TKR surgery. At 12 months post-TKR, two patients exhibited non-dominant NP knee function. The remaining patients did not recover NP gait. This finding is similar to previous classifications of level gait. To improve the distinction between varying degrees of knee function, stair gait was introduced into the trial. A staircase was designed and validated. Adduction and flexion moments acting about the knee joint and medial component of the ground reaction force were found to be important in the classification of OA and NP knee function from stair gait. Using a combination of these variables the DS classifier was able to characterise OA and NP function for 15 subjects correctly with 100% accuracy, determined using a leave-one-out method of cross validation. The variables were tested to assess the outcome of TKR surgery. The patient assessed recovered NP stair gait post surgery. An image based study was undertaken to investigate the quality of the MA data used in the DS classifier. A step up/down activity for 5 NP and 5 TKR subjects was recorded using non-simultaneous MA and dynamic fluoroscopy. Accurate knee kinematics were computed from the fluoroscopy images using KneeTrack image registration software. MA measured significantly larger knee joint translations and non-sagittal plane rotations. The largest errors in MA derived kinematics were 9.53 for adduction-abduction range of motion (ROM) measured from the NP cohort and 2.63cm compression-distraction ROM of the tibio-femoral joint, measured from the TKR cohort. The generic nature of the DS classifier was tested by its application to distinguish hip function following a lateral (LA) and posterior (PA) approach to total hip arthroplasty. The use of different variables was investigated with the classifier. The best classifier was able to distinguish between NP and LA function with 96.7% accuracy, LA and NP with 86.2% accuracy and between LA and PA with 81.5% accuracy. The PA approach was found to lead to more characteristic NP hip function than LA. These studies show that variables from stair gait should be included in addition to level gait in the classifier. Due to errors when measuring non-sagittal plane rotations using MA, these should be interpreted with caution. The generic nature of the classifier has been proven by its application to another joint, thus answering another orthopaedic question

Foot and Ankle Motion Analysis Using Dynamic Radiographic Imaging

Lower extremity motion analysis has become a powerful tool used to assess the dynamics of both normal and pathologic gait in a variety of clinical and research settings. Early rigid representations of the foot have recently been replaced with multi-segmental models capable of estimating intra-foot motion. Current models using externally placed markers on the surface of the skin are easily implemented, but suffer from errors associated with soft tissue artifact, marker placement repeatability, and rigid segment assumptions. Models using intra-cortical bone pins circumvent these errors, but their invasive nature has limited their application to research only. Radiographic models reporting gait kinematics currently analyze progressive static foot positions and do not include dynamics. The goal of this study was to determine the feasibility of using fluoroscopy to measure in vivo intra-foot dynamics of the hindfoot during the stance phase of gait. The developed fluoroscopic system was synchronized to a standard motion analysis system which included a multi-axis force platform. Custom algorithms were created to translate points of interest from 2D fluoroscopic image space to global tri-axial space. From these translated points of interest, a hindfoot specific model was developed to quantify sagittal plane talocrural and subtalar dynamics. The new hindfoot model was evaluated and applied to a pilot population of thirteen healthy adults during barefoot and toe-only rocker walking conditions. The barefoot kinematic and kinetic results compared favorably with barefoot dynamics reported by other authors. As a result of the barefoot study, it was concluded that inter-subject variability in sagittal plane kinematics was higher for the talocrural joint than the subtalar joint. The toe-only rocker analysis was the first report of hindfoot kinematics within a rocker sole shoe modification. Hindfoot kinematic inter-subject variability was significantly lower in the toe-only rocker condition when compared to barefoot results. This study represents the first use of fluoroscopy to quantify in vivo intra-foot dynamics during the stance phase of gait. Talocrural and subtalar dynamics of healthy adult subjects are reported. The technology developed for this study is capable of examining soft tissue and bony abnormalities associated with the pathologic foot. Based on the overall results of this study, it is recommended that development continue for further analysis within the clinical environment, and examination of complex in vivo foot and ankle dynamics