Correlation of Wear and Mechanics for Subjects having a Metal-on-Polyethylene Total Hip Arthroplasty Measured in vivo

Femoral head separation from the acetabular shell has been recorded, but clinical significance of this phenomenon has not yet been established. The objective of the study was to determine if there is a correlation between femoral head separation (sliding of the femoral head away from the acetabular cup), hip joint forces, and acetabular liner wear. Twenty subjects were strategically selected to participate in this study. All subjects were asked to perform gait on a treadmill while under fluoroscopic surveillance. The number of incidences involving femoral head separation was tallied and acetabular bearing surface forces were determined for each subject. A statistical correlation was done todetermine if femoral head sliding is related to the kinetics of the hip joint. Forty percent of the subjects were determined to have greater than 0.25 mm of wear. Twelve subjects demonstrated femoral head sliding leading to separation. Ten percent of the subjects tested demonstrated both wear and separation. The forces determined at the hip joint ranged from 1.75 to 1.85 times body weight. Although it was expected that subjects having more wear would have greater magnitudes of femoral head separation, the opposite was true. Kinematic data resulted in increased force magnitudes for a subject with separation then a subject with separation

AN AUTOMATED, DEEP LEARNING APPROACH TO SYSTEMATICALLY & SEQUENTIALLY DERIVE THREE-DIMENSIONAL KNEE KINEMATICS DIRECTLY FROM TWO-DIMENSIONAL FLUOROSCOPIC VIDEO

Total knee arthroplasty (TKA), also known as total knee replacement, is a surgical procedure to replace damaged parts of the knee joint with artificial components. It aims to relieve pain and improve knee function. TKA can improve knee kinematics and reduce pain, but it may also cause altered joint mechanics and complications. Proper patient selection, implant design, and surgical technique are important for successful outcomes. Kinematics analysis plays a vital role in TKA by evaluating knee joint movement and mechanics. It helps assess surgery success, guides implant and technique selection, informs implant design improvements, detects problems early, and improves patient outcomes. However, evaluating the kinematics of patients using conventional approaches presents significant challenges. The reliance on 3D CAD models limits applicability, as not all patients have access to such models. Moreover, the manual and time-consuming nature of the process makes it impractical for timely evaluations. Furthermore, the evaluation is confined to laboratory settings, limiting its feasibility in various locations. This study aims to address these limitations by introducing a new methodology for analyzing in vivo 3D kinematics using an automated deep learning approach. The proposed methodology involves several steps, starting with image segmentation of the femur and tibia using a robust deep learning approach. Subsequently, 3D reconstruction of the implants is performed, followed by automated registration. Finally, efficient knee kinematics modeling is conducted. The final kinematics results showed potential for reducing workload and increasing efficiency. The algorithms demonstrated high speed and accuracy, which could enable real-time TKA kinematics analysis in the operating room or clinical settings. Unlike previous studies that relied on sponsorships and limited patient samples, this algorithm allows the analysis of any patient, anywhere, and at any time, accommodating larger subject populations and complete fluoroscopic sequences. Although further improvements can be made, the study showcases the potential of machine learning to expand access to TKA analysis tools and advance biomedical engineering applications

Reconstruction of Patient-Specific Bone Models from X-Ray Radiography

The availability of a patient‐specific bone model has become an increasingly invaluable addition to orthopedic case evaluation and planning [1]. Utilized within a wide range of specialized visualization and analysis tools, such models provide unprecedented wealth of bone shape information previously unattainable using traditional radiographic imaging [2]. In this work, a novel bone reconstruction method from two or more x‐ray images is described. This method is superior to previous attempts in terms of accuracy and repeatability. The new technique accurately models the radiological scene in a way that eliminates the need for expensive multi‐planar radiographic imaging systems. It is also flexible enough to allow for both short and long film imaging using standard radiological protocols, which makes the technology easily utilized in standard clinical setups

Determination and Comparison of In Vivo Forces and Torques in Normal and Degenerative Lumbar Spines

In vivo motions of normal and degenerative lumbar spine patients performing extension/flexion were obtained using video fluoroscopy. 3-D models of each patient’s vertebrae were registered to the 2-D fluoroscopy images using a process developed at Rocky Mountain Musculoskeletal Research Laboratory. Temporal equations representing the motions were input into a math model and the forces at the contact point between vertebral levels and the body torques between the vertebrae were the output. The vertical forces in the normal and degenerative patients were similar and ranged from 0.35-0.42 times the body weight of the patient. The maximum torques were higher in the degenerative patient than in the normal patient. The maximum torques between L4 and L5 were 11.1 N*m in the degenerative patient and 9.72 N*m in the normal patient. At L3/L4, the maximum torque was 10.3 N*m in the degenerative and 9.03 N*m in the normal patient. The maximum torques in the degenerative patient were also higher than in the normal patient at the L2/L3 and L1/L2 levels. Left untreated these higher torques could cause deterioration of other levels as the spine tries to compensate for existing degenerative levels. This model will lead to a better understanding of the lumbar spine and could aid in treating lower back pain and in the design of spinal prostheses

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

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

Design of the High-Speed Stereo Radiography System

Orthopaedic pathologies often involve disruption of the mechanical environment of a joint at/below the mm scale. The ability to measure biomechanical kinematics at the sub-mm scale is essential for obtaining valuable insight into pathologies, but small motions of the joints are difficult to quantify. Estimates of skeletal kinematics are commonly made from optical motion capture systems and markers placed on the skin. The error caused by external marker movement is largely avoided with x-ray motion capture. Dynamic radiography uses a series of x-ray images recorded at high-speed and captures in-vivo joint motion. Uncovering the mechanical foundation of orthopaedic pathologies requires accurate and high-speed kinematic measurement of in-vivo 3D, six DOF joint motion. To meet these aims, requirements were established to guide the design, construction, and validation of a high-speed stereo radiography (HSSR) system. The completed system is capable of imaging major joints from the ankle to the cervical spine

Die Häufigkeit und klinische Relevanz einer Asymmetrischen Extensionslücke im Routineröntgen als neues Zeichen nach Knieendoprothetik

Trotz der sehr guten Ergebnisse in der Endoprothetik sind viele Patienten unzufrieden mit dem postoperativen Ergebnis. Obwohl diesbezüglich diverse Faktoren diskutiert wurden, ist die Ursache hierfür nicht immer klar. Grundlage der Studie war die Idee, routinemäßig erstellte postoperative Röntgenbilder auf die Häufigkeit und das Ausmaß der dort leicht zu beobachtenden asymmetrischen Extensionslücke zu untersuchen und deren Assoziation mit den berichteten Schmerzen nach Knieendoprothetik zu analysieren. Es wurden prospektiv erhobene Daten aus drei Multicenterstudien zu unterschiedlichen Behandlungsstrategien nach TKR herangezogen. Postoperative Röntgenbilder von 277 konsekutiven Patienten wurden digitalisiert und an Hand bekannter Abmessungen der Implantate kalibriert. Der Abstand zwischen tibialer und femoraler Komponente wurde sowohl medial als auch lateral bestimmt und die Differenz als Asymmetrische Extensionslücke definiert. Zur Identifizierung eines klinisch relevanten Grenzwertes für die AEL wurde der WOMAC-Schmerzscore 3 Monate postoperativ herangezogen. Die so definierten Gruppen wurden genutzt, um die Assoziation zur WOMAC-Schmerzskala bis zu 24 Monate postop. zu bestimmen. Es konnte eine hohe Anzahl an AEL nach Gelenkersatz identifiziert (AEL ≥ 1,0 mm bei 29,6 % der Patienten) und ein signifikanter Schwellenwert von ≥1,5 mm hinsichtlich der Assoziation mit postoperativ berichteten Schmerzen ermittelt werden. Mit zunehmender AEL fielen höhere Werte im WOMAC-Schmerzscore auf. Eine mediale AEL ≥1,5 mm ging mit größeren Schmerzen, eine laterale AEL ≥1,5 mm mit weniger Schmerzen im Vergleich zu Patienten ohne AEL nach 3 Monaten (p=0,036) und sechs Monaten (p=0,044) einher. Nach 12 und 24 Monaten war der Effekt nicht mehr signifikant. Somit scheint eine laterale AEL tolerabel, während eine mediale AEL vermieden werden sollte. Die ausschlaggebende Ursache für eine AEL ist bislang nicht abschließend geklärt. Hierzu, wie auch zur Beobachtung über einen noch längeren Zeitraum, bedarf es weiterer Untersuchungen