Verifying a C-arm-based roentgen stereophotogrammetric analysis protocol for assessing tibial implant movement in total knee arthroplasty.

Roentgen stereophotogrammetric analysis (RSA) is the "gold standard" technique for measuring sub-millimetric relative motion between implant and bone to quantify post-operative implant migration over time. The vast majority of RSA studies addressing implant motion in knee replacements, however, have been conducted using expensive biplanar radiography systems and commercial software that are not readily available at many institutions. In this study, we evaluated the feasibility of performing RSA using ordinary, readily available C-arm fluoroscopes and open-source software to assess tibial component migration.

The effect of artificial X-rays on C-arm positioning performance in a simulated orthopaedic surgical setting.

Purpose: We designed an Artificial X-ray Imaging System (AXIS) that generates simulated fluoroscopic X-ray images on the fly and assessed its utility in improving C-arm positioning performance by C-arm users with little or no C-arm experience.

Methods: The AXIS system was comprised of an optical tracking system to monitor C-arm movement, a manikin, a reference CT volume registered to the manikin, and a Digitally Reconstructed Radiograph algorithm to generate live simulated fluoroscopic images. A user study was conducted with 30 participants who had little or no C-arm experience.

The neutral posture of the cervical spine is not unique in human subjects.

Cervical spine injuries often happen in dynamic environments (e.g., sports and motor vehicle crashes) where individuals may be moving their head and neck immediately prior to impact.

A deep learning framework for segmentation and pose estimation of pedicle screw implants based on C-arm fluoroscopy.

Purpose: Pedicle screw fixation is a challenging procedure with a concerning rates of reoperation. After insertion of the screws is completed, the most common intraoperative verification approach is to acquire anterior-posterior and lateral radiographic images, based on which the surgeons try to visually assess the correctness of insertion. Given the limited accuracy of the existing verification techniques, we identified the need for an accurate and automated pedicle screw assessment system that can verify the screw insertion intraoperatively.

An intraoperative fluoroscopic method to accurately measure the post-implantation position of pedicle screws.

Purpose: Pedicle screw malplacement, leading to neurological symptoms, vascular injury, and premature implant loosening, is not uncommon and difficult to reliably detect intraoperatively with current techniques. We propose a new intraoperative post-placement pedicle screw position assessment system that can therefore allow surgeons to correct breaches during the procedure. Our objectives were to assess the accuracy and robustness of this proposed screw location system and to compare its performance to that of 2D planar radiography.

Cervical vertebral realignment when voluntarily adopting a protective neck posture.

Study Design: In vivo human volunteer study of the intervertebral postural changes and muscle activity levels while tensing the neck muscles.

Objective: To determine if actively tensing the neck muscles changes the posture of the cervical spine and, because axial impact neck injury often occurs while inverted, whether these changes exist both upright and upside down.

Summary Of Background Data: Rollover accidents are dynamic and complex events in which head contacts with the vehicle interior can cause catastrophic neck injuries.

Neck posture and muscle activity are different when upside down: a human volunteer study.

Rollover crashes are dynamic and complex events in which head impacts with the roof can cause catastrophic neck injuries. Ex vivo and computational models are valuable in understanding, and ultimately preventing, these injuries. Although neck posture and muscle activity influence the resulting injury, there is currently no in vivo data describing these parameters immediately prior to a head-first impact.

The pressure distribution of cerebrospinal fluid responds to residual compression and decompression in an animal model of acute spinal cord injury.

Study Design: In vivo large animal (pig) model study of cerebrospinal fluid (CSF) pressures after acute experimental spinal cord injury (SCI).

Objective: To determine how the CSF pressure (CSFP) and CSF pulse pressure amplitude (CSFPPA) cranial and caudal to the injury site change after an acute SCI with subsequent thecal occlusion and decompression.

Summary Of Background Data: Lowering intrathecal pressure via CSF drainage is currently instituted to prevent ischemia-induced SCI during thoracoabdominal aortic aneurysm surgery and was recently investigated as a potential intervention for acute traumatic SCI.

The interpretation of abdominal wall muscle recruitment strategies change when the electrocardiogram (ECG) is removed from the electromyogram (EMG).

The purpose of this study was to determine the effect of the ECG artifact on low-level trunk muscle activation amplitudes and assess the effectiveness of two methods used to remove the ECG. Simulations were performed and percent error in root mean square (RMS) amplitudes were calculated from uncontaminated and contaminated EMG signals at various ECG to EMG ratios. Two methods were used to remove the ECG: (1) filtering by adaptive sampling (FAS) and (2) Butterworth high pass filter at 30 Hz (BW-30 Hz HPF).

Detecting differences between asymptomatic and osteoarthritic gait is influenced by changing the knee adduction moment model.

Introduction: The adduction moment measured at the knee during gait is important to the study of osteoarthritis. The purpose of this study was to explore the effect of describing the knee adduction moment using three different biomechanical models, and furthermore, how the choice of model affects differences that are identified between asymptomatic and osteoarthritic gait.

Methods: Gait was measured for 44 asymptomatic subjects and 44 subjects with moderate osteoarthritis.