Accuracy and feasibility of dual fluoroscopy and model-based tracking to quantify in vivo hip kinematics during clinical exams

pre-printAccurate measurements of in-vivo hip kinematics may elucidate the mechanisms responsible for impaired function and chondrolabral damage in hips with femoroacetabular impingement (FAI). The objectives of this study were to quantify the accuracy and demonstrate the feasibility of using dual fluoroscopy to measure in-vivo hip kinematics during clinical exams used in the assessment of FAI. Steel beads were implanted into the pelvis and femur of two cadavers. Specimens were imaged under dual fluoroscopy during the impingement exam, FABER test, and rotational profile. Bead locations measured with model-based tracking were compared to those measured using dynamic radiostereometric analysis. Error was quantified by bias and precision, defined as the average and standard deviation of the differences between tracking methods, respectively. A normal male volunteer was also imaged during clinical exams. Bias and precision along a single axis did not exceed 0.17 and 0.21 mm, respectively. Comparing kinematics, positional error was less than 0.48 mm and rotational error was less than 0.58°. For the volunteer, kinematics were reported as joint angles and bone-bone distance. These results demonstrate that dual fluoroscopy and model-based tracking can accurately measure hip kinematics in living subjects during clinical exams of the hip

Correlations between the alpha angle and femoral head asphericity: Implications and recommendations for the diagnosis of cam femoroacetabular impingement

pre-printObjective: To determine the strength of common radiographic and radial CT views for measuring true femoral head asphericity. Patients and Methods: In 15 patients with cam femoroacetabular impingement (FAI) and 15 controls, alpha angles were measured by two observers using radial CT (0º, 30º, 60º, 90º) and digitally reconstructed radiographs (DRRs) for the: anterior-posterior (AP), standing frog-leg lateral, 45° Dunn with neutral rotation, 45° Dunn with 40°external rotation, and cross-table lateral views. A DRR validation study was performed. Alpha angles were compared between groups. Maximum deviation from a sphere of each subject was obtained from a previous study. Alpha angles from each view were correlated with maximum deviation. Results: There were no significant differences between alpha angles measured on radiographs and the corresponding DRRs (p = 0.72). Alpha angles were significantly greater in patients for all views (p ≤0.002). Alpha angles from the 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views had the strongest correlations with maximum deviation (r = 0.831; r 20 = 0.823; r=0.808, respectively). The AP view had the weakest correlation (r = 0.358). Conclusion: DRRs were a validated means to simulate hip radiographs. The 45° Dunn with 40° external rotation, cross-table lateral, and 60º radial views best visualized femoral asphericity. Although commonly used, the AP view did not visualize cam deformities well. Overall, the magnitude of the alpha angle may not be indicative of the size of the deformity. Thus, 3D reconstructions and measurements of asphericity could improve the diagnosis of cam FAI. Key Words: Cam Femoroacetabular Impingement Alpha Angle, Femur Asphericity, Digitally Introduction Cam-type femoroacetabular impingement (FAI) has been implicated as a cause of chondrolabral damage, hip osteoarthritis (OA), and musculoskeletal pain in young adults [1-3]. Cam FAI is characterized by an aspherical femoral head and/or insufficient femoral head-neck offset [4,5]. Identifying the degree of femoral head asphericity is important as the underlying goal of surgery to correct cam FAI is to restore a more normal, spherical morphology to the femoral head. The alpha angle is a two-dimensional (2D) radiographic measure of femoral head asphericity that is commonly used to diagnose cam FAI [6-8]. Although, first proposed by Notzli et al. for only an oblique axial view of the femur, use of the alpha angle has been extended to several radiographic projections and radial computed tomography (CT) or magnetic resonance (MR) views [7,9-14]. Unfortunately, alpha angle measurements can vary between views of the same femur [10,15,16]. Consequently, the ideal view to diagnose cam FAI remains unknown [15,17]. One approach to identify the optimal view in which to measure the alpha angle has been to quantify observer repeatability. However, reports of repeatability have not been consistent and repeatability is not necessarily a measure of effectiveness [18,19]. Another approach has been to correlate alpha angles from standard radiographic views to oblique axial or radial MRI/CT views [12,14,15,17]. Still, alpha angle measurements from radial views are not generated automatically, and thus do not provide a true reference standard. In addition, radial views do not consider the geometry of the entire femoral head. Alternatively, subject-specific 3D reconstructions of femur morphology, generated from volumetric CT or MR images, can be used to visualize the anatomy of the entire femoral head. By fitting the 3D reconstruction to a sphere, UU IR Author Manuscript UU IR Author Manuscript University of Utah Institutional Repository Author Manuscript one can quantify the size of a deformity as maximum deviation from the sphere, herein referred to as 'true femoral head asphericity' [20,21]

Germline genetic variants in men with prostate cancer and one or more additional cancers

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138930/1/cncr30817.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138930/2/cncr30817_am.pd

Total ankle replacement in patients with gouty arthritis

Gout is the most common cause of inflammatory arthritis in men and older women. The purpose of this review was to assess prosthetic component stability, postoperative pain relief, functional outcome, and quality of life of patients with gouty ankle arthritis who were treated with total ankle replacement

Acetabular Paralabral Cyst: An Unusual Cause of Femoral Vein Compression

Acetabular labral tears are a known cause of hip pain in the young, active patient. Labral tears can be due to trauma, femoroacetabular impingement, capsular laxity, dysplasia, and degenerative pathology. Paralabral cysts are relatively common in association with labral tears of the hip, with cysts seen on magnetic resonance imaging studies in as many as 50% to 70% of patients with labral tears. In some cases the cysts can become sizeable and cause neurovascular compression. Nonoperative interventions for the management of paralabral cysts in the shoulder and knee have shown high recurrence rates. In the shoulder and knee, arthroscopic debridement of paralabral cysts has shown good results with lower recurrence rates and resolution of neurovascular function. In the hip there is limited literature regarding surgical management of paralabral cysts. We present a surgical technique for arthroscopic decompression of acetabular paralabral cysts combined with labral repair