1,873 research outputs found

    Non-invasive computer-assisted measurement of knee alignment

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    The quantification of knee alignment is a routine part of orthopaedic practice and is important for monitoring disease progression, planning interventional strategies, and follow-up of patients. Currently available technologies such as radiographic measurements have a number of drawbacks. The aim of this study was to validate a potentially improved technique for measuring knee alignment under different conditions. An image-free navigation system was adapted for non-invasive use through the development of external infrared tracker mountings. Stability was assessed by comparing the variance (F-test) of repeated mechanical femoro-tibial (MFT) angle measurements for a volunteer and a leg model. MFT angles were then measured supine, standing and with varus-valgus stress in asymptomatic volunteers who each underwent two separate registrations and repeated measurements for each condition. The mean difference and 95% limits of agreement were used to assess intra-registration and inter-registration repeatability. For multiple registrations the range of measurements for the external mountings was 1° larger than for the rigid model with statistically similar variance (p=0.34). Thirty volunteers were assessed (19 males, 11 females) with a mean age of 41 years (range: 20-65) and a mean BMI of 26 (range: 19-34). For intra-registration repeatability, consecutive coronal alignment readings agreed to almost ±1°, with up to ±0.5° loss of repeatability for coronal alignment measured before and after stress maneuvers, and a ±0.2° loss following stance trials. Sagittal alignment measurements were less repeatable overall by an approximate factor of two. Inter-registration agreement limits for coronal and sagittal supine MFT angles were ±1.6° and ±2.3°, respectively. Varus and valgus stress measurements agreed to within ±1.3° and ±1.1°, respectively. Agreement limits for standing MFT angles were ±2.9° (coronal) and ±5.0° (sagittal), which may have reflected a variation in stance between measurements. The system provided repeatable, real-time measurements of coronal and sagittal knee alignment under a number of dynamic, real-time conditions, offering a potential alternative to radiographs

    Standardising the clinical assessment of coronal knee laxity

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    Clinical laxity tests are used for assessing knee ligament injuries and for soft tissue balancing in total knee arthroplasty. This study reports the development and validation of a quantitative technique of assessing collateral knee laxity through accurate measurement of potential variables during routine clinical examination. The hypothesis was that standardisation of a clinical stress test would result in a repeatable range of laxity measurements.Non- invasive infrared tracking technology with kinematic registration of joint centres gave real-time measurement of both coronal and sagittal mechanical tibiofemoral alignment. Knee flexion, moment arm and magnitude of the applied force were all measured and standardised. Three clinicians then performed six knee laxity examinations on a single volunteer using a target moment of 18Nm. Standardised laxity measurements had small standard deviations (within 1.1°) for each clinician and similar mean values between clinicians, with the valgus laxity assessment (mean of 3°) being slightly more consistent than varus (means of 4° or 5°).The manual technique of coronal knee laxity assessment was successfully quantified and standardised, leading to a narrow range of measurements (within the accuracy of the measurement system). Minimising the subjective variables of clinical examination could improve current knowledge of soft tissue knee behaviour

    Factors influencing wider acceptance of Computer Assisted Orthopaedic Surgery (CAOS) technologies for Total Joint Arthroplasty

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    Computer-assisted orthopaedic surgery (CAOS) promises to improve outcomes of joint arthroplasty through better alignment and orientation of implants, but take up has so far been modest. Following an overview of CAOS technologies covering image-guided surgery, image-free and robotic systems, several factors for lack of penetration are identified. These include poor validation of accuracy, lack of standardisation, inappropriate clinical outcomes measures for assessing and comparing technologies, unresolved debate about the effectiveness of minimally invasive surgery, and issues of medical device regulations, cost, autonomy of surgeons to choose equipment, ergonomics and training. The paper concludes that dialogue between surgeons and manufacturers is needed to develop standardised measurements and outcomes scoring systems that are more appropriate for technology comparisons, and encourages an increased awareness of user requirements

    Hip Joint Center Localization with an Unscented Kalman Filter

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    The accurate estimation of the hip joint centre (HJC) in gait analysis and in computer assisted orthopaedic procedures is a basic requirement. Functional methods, based on rigid body localisation, assessing the kinematics of the femur during circumduction movements (pivoting) have been used for estimating the HJC. Localising the femoral segment only, as it is usually done in total knee replacement procedure, can give rise to estimation errors, since the pelvis, during the passive pivoting manoeuvre, might undergo spatial displacements. This paper presents the design and test of an unscented Kalman filter that allows the estimation of the HJC by observing the pose of the femur and the 3D coordinates of a single marker attached to the pelvis. This new approach was validated using a hip joint mechanical simulator, mimicking both hard and soft tissues. The algorithm performances were compared with the literature standards and proved to have better performances in case of pelvis translation greater than 8 mm, thus satisfying the clinical requirements of the application

    Development of an Active Elbow Motion Simulator and Coordinate Systems to Evaluate Kinematics in Multiple Positions

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    Elbow disorders are common as a consequence of both traumatic and degenerative conditions. Relative to disorders of the lower limb, there is comparatively little evidence to direct the treatment of many elbow disorders. Biomechanical studies are required to develop and validate the optimal treatment of elbow disorders prior to their application in patients. Clinically relevant simulation of elbow motion in the laboratory can be a powerful tool to advance our knowledge of elbow disorders. This work was undertaken with the rationale that simulation and quantification of elbow motion could be improved significantly. This treatise includes the development and evaluation of an in-vitro elbow motion simulator which, with the humerus horizontally positioned, is the first to achieve active flexion and extension in a vertical plane. Additionally, it is capable of operating in the vertical, varus and valgus positions, and while maintaining full forearm pronation or supination. The simulator controller employs a Cascade PID configuration with feedforward transfer functions, which achieves unified control of flexion angle and muscle tension for multiple muscles. Feedback of the elbow joint angle and muscle tension is utilized to achieve closed-loop control. A performance evaluation in a full series of specimens clearly demonstrated that the actual joint angle is not more than 5 degrees removed from the desired setpoint during flexion or extension in any position. Also, a new method for creating upper extremity bone segment coordinate systems which are derived from elbow flexion and forearm rotation was developed and tested. This produced joint kinematics with significantly less inter-subject variability than traditional anatomy-derived coordinate systems. This minimally-invasive method also provides increased statistical power for laboratory based studies and may prove useful for clinical applications. The new simulation techniques developed herein were applied to an in-vitro investigation of olecranon fracture repair with clinical significance. This study revealed valuable insights into a common repair procedure. This was made possible by the previously unattainable measurements that these new techniques now provide. These developments will assist surgeons and other investigators in the design and evaluation of treatments for elbow disorders, and contribute to the betterment of patient care

    Recent trends, technical concepts and components of computer-assisted orthopedic surgery systems: A comprehensive review

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    Computer-assisted orthopedic surgery (CAOS) systems have become one of the most important and challenging types of system in clinical orthopedics, as they enable precise treatment of musculoskeletal diseases, employing modern clinical navigation systems and surgical tools. This paper brings a comprehensive review of recent trends and possibilities of CAOS systems. There are three types of the surgical planning systems, including: systems based on the volumetric images (computer tomography (CT), magnetic resonance imaging (MRI) or ultrasound images), further systems utilize either 2D or 3D fluoroscopic images, and the last one utilizes the kinetic information about the joints and morphological information about the target bones. This complex review is focused on three fundamental aspects of CAOS systems: their essential components, types of CAOS systems, and mechanical tools used in CAOS systems. In this review, we also outline the possibilities for using ultrasound computer-assisted orthopedic surgery (UCAOS) systems as an alternative to conventionally used CAOS systems.Web of Science1923art. no. 519

    Characterization of a Contact-Stylus Surface Digitization Method Using Collaborative Robots: Accuracy Evaluation in the Context of Shoulder Replacement or Resurfacing

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    Total shoulder arthroplasty (TSA) is the third most common joint replacement. While robot-assisted hip and knee replacement technologies have enjoyed extensive development, this has been limited in the upper limb. This work focused on quantifying the localization accuracy of a robotic system, and evaluating its efficacy in the context of TSA. A collaborative robot was fitted with a stylus tip to perform manual surface digitizations using the robot’s encoder output. In the first experiment, two precision-machined master cubes, representing the working volume around a glenoid structure, were used for system validation. Next, cadaveric glenoids were digitized and compared to a ‘gold standard’ laser scanner. Digitization errors were 0.37±0.27 mm, showing that collaborative robotics can be used for osseous anatomy digitization. This thesis presents two novel concepts: 1) use of collaborative robotics for manually operated surface digitizing, and 2) optical fiducial technique, allowing registration between a laser scanner and stylus digitizer

    DYNAMIC MEASUREMENT OF THREE-DIMENSIONAL MOTION FROM SINGLE-PERSPECTIVE TWO-DIMENSIONAL RADIOGRAPHIC PROJECTIONS

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    The digital evolution of the x-ray imaging modality has spurred the development of numerous clinical and research tools. This work focuses on the design, development, and validation of dynamic radiographic imaging and registration techniques to address two distinct medical applications: tracking during image-guided interventions, and the measurement of musculoskeletal joint kinematics. Fluoroscopy is widely employed to provide intra-procedural image-guidance. However, its planar images provide limited information about the location of surgical tools and targets in three-dimensional space. To address this limitation, registration techniques, which extract three-dimensional tracking and image-guidance information from planar images, were developed and validated in vitro. The ability to accurately measure joint kinematics in vivo is an important tool in studying both normal joint function and pathologies associated with injury and disease, however it still remains a clinical challenge. A technique to measure joint kinematics from single-perspective x-ray projections was developed and validated in vitro, using clinically available radiography equipmen

    Application of 3D imaging technology to anterior cruciate ligament surgery

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    Includes bibliographical references (leaves 155-160)

    Non-invasive quantification of knee kinematics: a cadaver study

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    The ability to quantify kinematic parameters of the knee is crucial in understanding normal biomechanics, recognising the presence of pathology and its severity, planning treatment and evaluation of outcomes. Current methods of quantifying lower limb kinematics remain limited in allowing accurate dynamic assessment. Computer assisted surgery systems have been validated in quantifying kinematic parameters, but remain limited to the operative setting. Recently, image-free computer assisted surgery technology has been adapted for non-invasive use and validated in terms of repeatability in measuring coronal and sagittal femorotibial mechanical alignment in extension. The aim of this thesis was to develop and implement a set of validation protocols to quantify the reliability, precision and accuracy of this non-invasive technology in quantifying lower limb coronal and sagittal femorotibial mechanical alignment, anteroposterior and rotatory laxity of the knee by comparison with a validated, commercially available image-free computer assisted surgery system. Pilot study confirmed feasibility of further experimental work and revealed that the noninvasive method measured with satisfactory precision and accuracy: coronal mechanical femorotibial alignment (MFTA) from extension to 30° knee flexion, anteroposterior translation in extension and tibial rotatory laxity during flexion. Further experiments using 12 fresh cadaveric limbs revealed that the non-invasive method gave satisfactory precision and agreement with the invasive system measuring MFTA without stress from extension to 40° knee flexion, and with 15Nm coronal stress from extension to 30° knee flexion. Using 100N of anterior force on the tibia, the non-invasive system was acceptably precise and accurate in measuring sagittal tibial displacement from extension to 40° flexion. End of range apprehension, such as has been proven repeatable in measuring tibial rotatory laxity was used and the non-invasive method gave superior 3 precision and accuracy to most reported non-invasive devices in quantifying tibial rotatory range of motion. Non-invasive optical tracking systems provide a means to quantify important kinematic parameters in health and disease, and could allow standardisation of knee examination increasing communicability and translation of findings from the out-patient to operative setting. This technology therefore could allow restoration of individual specific kinematics in knee arthroplasty and soft-tissue reconstruction
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