Brian J. Rasquinha

Articular surface remodeling of the hip after periacetabular osteotomy.

AbstractPurposePeriacetabular osteotomies are a family of surgical procedures used to treat hip dysplasia. In a periacetabular osteotomy, the operating surgeon aims to increase acetabular coverage of the femoral head. The surgical correction has mechanical goals of increasing the stability of the joint and to improving the pressure distribution across the acetabulum. Although it is known that bone will remodel under changing load at the microstructural level, it is unclear whether there is any gross remodeling of the acetabulum or the femoral head in response to the change in loading following a periacetabular osteotomy. This observational study aims to quantify the shape of operative and contralateral hip joint surfaces pre and postoperatively to determine whether there are gross morphological changes in the shape of any of the bony articular surfaces of the joint.MethodsPreoperative and postoperative computed tomography (CT) scans were segmented as triangulated meshes. The bony articular surfaces of these meshes were then isolated. The vertices of these surfaces were fit to spheres and to general ellipsoids and, in the case of the acetabulum, examined in anatomical coordinate frames to look for changes between pre and postoperative segmentations.ResultsSpherical fit results were consistent preoperatively and postoperatively, with small changes in the radii of the spheres of best fit for both operative and nonoperative hips. Ellipsoid fitting showed variations between preoperative and postoperative scans in both eccentricity and orientation.ConclusionsBecause there is no clear evidence of gross articular surface remodeling, periacetabular osteotomy for an adult should be planned with the expectation that the patient’s existing articular structure will be preserved.

Crossing-Lines Registration for Direct Electromagnetic Navigation

Direct surgical navigation requires registration of an intraoperative imaging modality to a tracking technology, from which a patient image registration can be found. Although electromagnetic tracking is ergonomically attractive, it is used less often than optical tracking because its lower position accuracy offsets its higher orientation accuracy.

Principal components of wrist circumduction from electromagnetic surgical tracking

PurposeAn electromagnetic (EM) surgical tracking system was used for a functionally calibrated kinematic analysis of wrist motion. Circumduction motions were tested for differences in subject gender and for differences in the sense of the circumduction as clockwise or counter-clockwise motion.MethodsTwenty subjects were instrumented for EM tracking. Flexion–extension motion was used to identify the functional axis. Subjects performed unconstrained wrist circumduction in a clockwise and counter-clockwise sense. Data were decomposed into orthogonal flexion–extension motions and radial–ulnar deviation motions. PCA was used to concisely represent motions. Nonparametric Wilcoxon tests were used to distinguish the groups.ResultsFlexion–extension motions were projected onto a direction axis with a root-mean-square error of

On the use of laser scans to validate reverse engineering of bony anatomy.

5^\circ

Rectus Capitis Posterior Minor: Histological and Biomechanical Links to the Spinal Dura Mater

5∘. Using the first three principal components, there was no statistically significant difference in gender (all

A Toroidal Probe for Measuring Surgically Exposed Joint Centers.

p>0.20