Effect of Corrective Surgery on Lower Limb Mechanics in Patients with Crouch Gait

Crouch gait a progressively degrading gait deviation associated with the neurological disorder cerebral palsy. If left untreated it can lead to anterior knee pain and a loss of ambulation. At present there exists no agreed upon metric for determining the surgical procedures used to treat crouch gait and there is insufficient means to analytically compare the results of different procedures. The aims of this thesis work were to create a pipeline to transform a patient’s gait analysis data into a finite element model, develop a model of sufficient complexity to evaluate a range of outcomes by which to judge the efficacy of a surgical procedure, analyze the change between pre- and post-operative models and the changes between models with different surgical procedures, and to quantify the impact of varying different surgical parameters. A generic lower limb rigid body musculoskeletal model was developed and used in conjunction with patient-specific static and dynamic motion capture to create scaling factors and joint kinematics, respectively. The musculoskeletal model was scaled and converted into a finite element model. This lower torso model was integrated with a detailed finite element model of the knee joint including patella, femur and tibia heads, associated articular cartilage, patellofemoral ligaments, patellar tendon, and quadriceps tendons. This type of combined finite element model was created for each patient, pre- and post-operatively, for a series of patient’s treated for crouch gait at Children’s Hospital Colorado. Each model was modified to replicate the surgical procedure(s) that each individual patient underwent. Comparison between pre- and post-operative models show significant improvement in tibiofemoral flexion-extension and patellar articular cartilage stress in post-operative models. In order to assess the effect of surgical parameters on muscle efficiency, the finite element model was modified such that tibiofemoral flexion-extension was controlled by adaptive muscle forces calculated using a proportional-integral feedback control system. The feedback system adjusted quadriceps and hamstrings forces to try and meet a target flexion profile. A feedback control model was created for three patients; subsequently, each model was modified to run multiple simulations with modified surgical procedures and parameters. The models were modified to include distal femoral extension osteotomy procedures of 0º, 15º, or 30º, or patella tendon advancement procedures with 0 cm, 1 cm, or 2 cm shortening. The muscle forces needed to reach the target kinematics were compared. Further simulations are required to identify clear links between surgical decisions and patient-specific parameters, but the developed model shows promise for future studies both for crouch gait and other musculoskeletal pathologies

Patient Specific Alignment, Anatomy, Recovery and Outcome in Total Knee Arthroplasty

Total knee arthroplasty (TKA), despite being an otherwise highly successful medical operation, has a recurrent problem of dissatisfaction and recurrent pain rates in the 15-20% range. A variety of factors contribute to this incidence of dissatisfaction which can broadly be considered to fall into one of three groups: factors driven by the surgical outcome, pre-existing factors relating to the patients psychology, appropriateness for surgery or expectation level, and factors driven by the patient’s recovery and their management during that recovery process. With consideration to the extensive variation between patients, it is reasonable to posit that addressing patient specific factors in selection for surgery, alignment of components during surgery and post-operative management may reduce the instance of post-operative dissatisfaction. The first goal of this thesis was to understand the variation of patient anatomy as it relates to standard practice in TKA. Following the finding of extensive variation, a bio-mechanical rigid body dynamics simulation of the knee joint was developed to determine the degree to which this variation was reflected in the kinematic behaviour of the implanted knees. Later studies showed extensive kinematic variation that was responsive to variation in the alignment of the components as well as well as significantly related to patient reported outcome. Later studies further investigated how outcome related to patient selection for surgery and recovery of the patient as measured with simple activity monitoring. From this work, a pre-operative simulation assessment tool has been developed, the Dynamic Knee Score (DKS), and paired with selection and recovery management tools forms the basis of 360 Knee Systems surgical planning and patient management, which has been used in over 3,000 primary TKA’s to date

Effects of Surgical Repair or Reconstruction on Radiocarpal Mechanics from Wrists with Scapholunate Ligament Injury

Osteoarthritis as a result of injury/trauma is a significant problem, and there is still a need to develop tools for evaluating joint injuries and the effectiveness of surgical treatments. For the wrist in particular, injury to the scapholunate ligament from impact loading, can lead to scapholunate joint instability. Without treatment, this can lead to progressive development of wrist osteoarthritis. Joint contact pressures are important mechanical factors in the etiology of osteoarthritis, and these can be determined non-invasively through computer modeling. Hence, the goal of this work was to investigate the effects of scapholunate ligament injury and surgical repair on radioscapholunate contact mechanics, through surface contact modeling (SCM) and finite element modeling (FEM). The modeling process required geometries, boundary conditions and a contact relationship. Magnetic resonance imaging (MRI) was used to acquire images of the normal, injured and post-operative wrists, while relaxed and during active grasp loading. Surface and volumetric models were generated from the relaxed images, while kinematic boundary conditions were determined from image registration between the relaxed and loaded images. To improve the automatic image registration process, the effects of initial manual registration on the outcome of final registration accuracy, were investigated. Results showed that kinematic accuracy and subsequent contact mechanics were improved by performing a manual registration to align the image volumes as close as possible, before auto-registration. Looking at the effects of scapholunate ligament injury, results showed that contact forces, contact areas, peak and mean contact pressures significantly increased in the radioscaphoid joint. The locations of contact also shifted with injury. This novel data showed that contact mechanics was altered for the worse after injury. Novel contact mechanics data on the effects of surgical repair were also obtained. Results showed that radiolunate peak and mean contact pressures decreased significantly compared to injured, which indicated the possibility of restoring normal mechanics post surgery. SCM results were compared to FEM results to demonstrate the feasibility of the surface contact modeling approach for clinical applications. Contact parameters compared well between the two techniques. This work demonstrated the potential of MRI-based SCM as a tool to evaluate joint injuries and subsequent treatments, for clinical applications

Application of Computational Lower Extremity Model to Investigate Different Muscle Activities and Joint Force Patterns in Knee Osteoarthritis Patients during Walking

Many experimental and computational studies have reported that osteoarthritis in the knee joint affects knee biomechanics, including joint kinematics, joint contact forces, and muscle activities, due to functional restriction and disability. In this study, differences in muscle activities and joint force patterns between knee osteoarthritis (OA) patients and normal subjects during walking were investigated using the inverse dynamic analysis with a lower extremity musculoskeletal model. Extensor/flexor muscle activations and torque ratios and the joint contact forces were compared between the OA and normal groups. The OA patients had higher extensor muscle forces and lateral component of the knee joint force than normal subjects as well as force and torque ratios of extensor and flexor muscles, while the other parameters had little differences. The results explained that OA patients increased the level of antagonistic cocontraction and the adduction moment on the knee joint. The presented findings and technologies provide insight into biomechanical changes in OA patients and can also be used to evaluate the postoperative functional outcomes of the OA treatments

Computational Modeling of Nonlinear Behavior in Orthopaedics

Total knee replacement (TKR) is one of the most common orthopaedic procedures performed in the USA and is projected to exceed 4.3 million by 2030. Although TKR surgery has a success rate of 95% at 10 years for most TKR designs, revision surgery still occurs approximately once for every ten primary TKR surgeries. Failure modes in TKR involve the interplay between implant mechanical performance and surrounding biological tissues. The orthopaedic community has turned to computational modeling as an effective tool to analyze these complex interactions and improve patient outcomes. The objective of these studies was to utilize a combined computational and experimental approach to investigate modes of TKR failure where material nonlinearity plays a significant role in the biomechanics under investigation. A finite element (FE) model of a modular TKR taper junction was developed in order to investigate the stress environment in relation to corrosive behavior under in vivo loading conditions. Linear elastic and elastoplastic material models were defined and angular mismatch parametrically varied in order to determine the sensitivity of model predicted stresses to material model selection and taper junction geometry. It was determined that positive angle mismatches cause plastic deformation and overestimated stresses in linear elastic analyses compared to elastoplastic analyses. Calculated stresses were also strongly correlated with angle mismatch when varied ±0.25o. Model stress distributions agreed with corrosion patterns evident on retrieved modular TKR components and magnitudes corresponding with corrosive behavior in vitro. Additionally, a series of passive FE TKR models were developed in order to investigate the intrinsic relationship between TKR component alignment, ligament tensions, and knee kinematics during intraoperative assessments. A kinematically-driven model was developed and validated with an open source dataset, and was able to discriminate clinical outcomes based on calculated ligament tensions when input in vivo kinematics. Patient-specific simulations found greater tension in lateral ligaments for poor outcome patients compared to good outcome patients, and statistically significant differences in tensions for the POL, PFL, DMCL, and ALS ligaments during mid-flexion. A force-driven model was also developed and validated with in vitro cadaver testing, and found that variation in tibial component alignment of ±15o influence intraoperative ligament tensions. However, definitive trends between TKR component alignment and ligament tension were not discerned. Nonetheless, both modeling approaches were found to be sensitive to subclinical abnormalities. These findings suggest mechanical stress is a key contributor to taper junction corrosion and that ligament tensions are the mechanism leading to abnormal function in the passive TKR knee. These studies contributed innovative computational models that provide a foundation to advance the understanding of these complex relationships, and modeling frameworks that exemplify sound verification and validation practices

A simulation-enhanced intraoperative planning tool for robotic-assisted total knee arthroplasty

The purpose of the present study was to investigate current methods of surgical planning used in conjunction with robotics-assisted total knee arthroplasty (raTKA) to determine if improvements could be made using advanced computational techniques. Thus, through the use of musculoskeletal multi-body dynamic simulations, an enhanced surgical planning tool was developed, which provides insight on active postoperative joint mechanics. Development of the tool relied on patient-specific simulations using single-leg and full-body models. These simulations were constructed using two publicly-available datasets (Orthoload and SimTK); in particular, joint loading data obtained from subjects during various activities. Simulation parameters were optimized using a design-of experiments (DOE) methodology and validation of each of the models was conducted by calculating the root mean square error (RMSE) between joint loading calculated using the model and the corresponding results given in the appropriate dataset. Optimized and validated variants of each of the models were used in conjunction with the results of DOE studies that characterized the influence of a number of surgical planning variables on various biomechanical responses and linear regression analysis to derive knee performance equations (KPEs). In literature studies, some of the aforementioned responses have been strongly correlated with two outcomes commonly reported by dissatisfied TKA patients, namely, anterior knee pain and poor proprioception. In a proof-of-concept study, KPEs were used to calculate optimal positions and orientations of the femoral and tibial components in the case of one subject featured in the SimTK dataset. These results differed from corresponding ones reportedly achieved for the implant components in the subject. This trend suggests there is potential to improve robotic surgical planning for current-generation raTKA systems through the use of musculoskeletal simulation. Use of the proposed surgical planning tool does not require computational resources beyond what are used with a specified current-generation raTKA system (Navio Surgical System). Furthermore, there are only minimal differences between the workflow involving the proposed planning tool and that when Navio Surgical System is used. A number of recommendations for future studies are made, such as larger scale simulation validation work and use of more complex regression techniques when deriving the KPEs

Bicruciate-retaining total knee arthroplasty: What's new?

Primary total knee arthroplasty (TKA) is a widespread procedure to address end stage osteoarthritis with good results, clinical outcomes, and long-term survivorship. Although it is frequently performed in elderly, an increased demand in young and active people is expected in the next years. However, a considerable dissatisfaction rate has been reported by highly demanding patients due to the intrinsic limitations provided by the TKA. Bicruciate-retaining (BCR) TKA was developed to mimic knee biomechanics, through anterior cruciate ligament preservation. First-generation BCR TKA has not gained popularity due to its being a challenging technique and having poor survival outcomes. Thanks to implant design improvement and surgeon-friendly instrumentation, second-generation BCR TKA has seen renewed interest. This review will focus on surgical indications, kinematical basis, clinical results and latest developments of second-generation BCR TKA

The impact of hip abductor muscle status on in vivo joint loads through kinematics and muscle activity 51 months following total hip arthroplasty

Background: Well-established clinical scores show that total hip arthroplasty (THA) in primary hip osteoarthritis alleviates pain and markedly improves the performance of activities of daily living (ADLs). However, objective measurements show that THA patients’ movement and electrophysiological patterns do not match those of healthy age- matched individuals. Surgical incision as well as intraoperative soft tissue traction and compression cause iatrogenic damage of the hip muscles, which is associated with their atrophy and fatty degeneration. An unfavorable muscle status may negatively affect joint loads. An improper in vivo hip joint resultant contact force (Fres) may shorten an implant’s lifespan and also determine functional outcome following THA. This retrospective analysis aimed to identify whether kinematics and electrophysiological activity mediate the impact of structural muscle impairment on kinetics. Materials and methods: In order to determine the Fres, instrumented femoral prostheses were implanted via a direct lateral approach. Nine patients (two females, seven males) participated in synchronous recordings of load patterns and surface electromyography along with three-dimensional mapping of motion sequences at a mean of 51 months (period: 35-64 months) postoperatively. The hip movement patterns of five ADLs (level walking, ascending stairs, descending stairs, standing up, sitting down) and the electrophysiological activity of the hip abductors gluteus maximus muscle, gluteus medius muscle, and tensor fasciae latae muscle (TFL) were assessed and correlated with both the hip abductor muscle status (total muscle volume [TMV], fat ratio [FR]) evaluated by postoperative computed tomography images and the in vivo Fres. Findings: Across all ADLs, the results yield high inter-individual variability. Compared to asymptomatic control groups in the literature, this study’s patients produced reduced extension and lower sagittal range of motion (ROM) in level walking, while stair negotiation resulted in higher flexion and greater ROM in the sagittal plane. Particularly TFL activity patterns are shaped by irregularities and hyperactivity. TMV and FR have an effect on both motion patterns in the sagittal and frontal planes and shape and timing of muscle activity. Furthermore, compensatory movement strategies and abnormal muscle activity may lead to not only higher but also lower hip joint loads. Interpretation: The data do not provide conclusive evidence of muscle damage affecting joint loads via atypical movement and electrophysiological patterns. Overall, however, the results support the hypothesis that structural impairment of hip abductors may lead to the development of pathomechanical movement patterns and irregular muscle activity, which in turn may adversely affect hip joint loads.Fragestellung: Gängige klinische Scores zeigen, dass die Implantation einer Hüfttotalendoprothese bei primärer Coxarthrose die Schmerzen der Patienten bedeutend lindern und die Ausführung von Aktivitäten des täglichen Lebens merklich verbessern kann. Ergebnisse objektivierbarer Messmethoden zeigen jedoch, dass weder die Bewegungsmuster noch die Muskelaktivität dieser Patienten denen gesunder Gleichaltriger entspricht. Die Implantation einer Hüfttotalendoprothese führt entweder über ein Schnitt- oder ein Quetschtrauma zu einer iatrogenen Schädigung der Hüftmuskulatur, was mit deren Atrophie und Verfettung einhergeht. Ein abträglicher Muskelstatus kann sich ungünstig auf die Hüftgelenksbelastung auswirken. Die resultierende Hüftkontaktkraft ist ein bedeutender Faktor für die Haltbarkeit einer Hüfttotalendoprothese, die das funktionelle Ergebnis eines endoprothetischen Ersatzes mitbestimmt. Das Ziel dieser retrospektiven Analyse war es, das Verständnis für die auf die in vivo resultierende Hüftgelenksbelastung wirkenden Zusammenhänge zwischen periartikulärer Muskelschädigung, pathologischen Bewegungsabläufen und irregulärer Muskelaktivität zu erweitern. Material und Methodik: Zwecks in-vivo-Bestimmung der Hüftkontaktkräfte erfolgte per transglutealem Zugang die Implantation von instrumentierten Hüfttotalendoprothesen. Neun Patientinnen und Patienten (zwei weiblich, sieben männlich) nahmen zum durchschnittlichen Zeitpunkt von 51 Monaten (Zeitraum: 35-64 Monate) postoperativ an synchronen Belastungsmessungen, dreidimensionalen Bewegungserfassungen und Oberflächen-Elektromyographie-Messungen teil. Die Bewegungsmuster der Hüfte von fünf Aktivitäten des alltäglichen Lebens (ebenes Gehen, treppauf Gehen, treppab Gehen, Aufstehen, Hinsetzen) sowie die Muskelaktivität der Hüftabduktoren (M. gluteus maximus, M. gluteus medius, M. tensor fasciae latae) wurden erfasst und jeweils mit dem anhand von postoperativen computertomographischen Aufnahmen evaluierten Muskelstatus (Gesamtvolumen, prozentuale Verfettung) und der Hüftkontaktkraft korreliert. Ergebnisse: Über alle Aktivitäten hinweg ergab sich aus den Messergebnissen eine hohe interindividuelle Streuung. Im Vergleich zu symptomlosen Kontrollgruppen aus der Literatur zeigte sich beim Gehen eine reduzierte Extension und ein geringerer Bewegungsumfang in der Sagittalebene. Beim Treppengang hingegen erfolgten eine höhere Flexion und ein größerer Bewegungsumfang in der Sagittalebene. Insbesondere die Aktivitätsmuster des M. tensor fasciae latae waren von Unregelmäßigkeiten und Überaktivität geprägt. Die Daten zeigen auf, dass Muskelvolumen und -verfettung sowohl die Hüftbewegung in der Sagittal- und Frontalebene als auch die elektrophysiologische Form und den Zeitablauf von Muskelaktivität beeinflussen. Die Ergebnisse weisen ferner darauf hin, dass beeinträchtigte Bewegungsabläufe und gestörte Muskelaktivität nicht nur eine Erhöhung, sondern auch eine Verminderung der Hüftkontaktkraft bewirken können. Schlussfolgerung: Die Daten liefern keine stichhaltigen Beweise für einen durchgehenden Effekt einer Muskelschädigung über atypische Bewegungsabläufe und elektrophysiologische Signale auf die Gelenkbelastungen. Jedoch bekräftigen die Ergebnisse insgesamt die Hypothese, dass eine strukturelle Beeinträchtigung der Hüftabduktoren zur Entstehung von pathomechanischen Bewegungsmustern und unregelmäßiger Muskelaktivität führen kann, was sich wiederum ungünstig auf die Hüftkontaktkräfte auswirken kann

Three-dimensional virtual bone bank system workflow for structural bone allograft selection: a technical report

Structural bone allograft has been used in bone defect reconstruction during the last fifty years with acceptable results. However, allograft selection methods were based on 2-dimensional templates using X-rays.Thanks to preoperative planning platforms, three dimensional (3D) CT-derived bone models were used to define size and shape comparison between host and donor. The purpose of this study was to describe the workflow of this virtual technique in order to explain how to choose the best allograft using a virtualbone bank system. We measured all bones in a 3D virtual environment determining the best match. The use of a virtual bone banksystem has allowed optimizing the allograft selection in a bone bank, providing more information to the surgeons before surgery.In conclusion, 3D preoperative planning in a virtual environment for allograft selection is an important and helpful tool in order to achieve a good match between host and donor.Fil: Ritacco, Lucas. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Farfalli, Germán Luis. Hospital Italiano; ArgentinaFil: Milano, Federico Edgardo. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ayerza, Miguel Ángel. Hospital Italiano; ArgentinaFil: Muscolo, Domingo L.. Hospital Italiano; Argentina. Hospital Italiano; ArgentinaFil: Aponte Tinao, Luis. Hospital Italiano; Argentin