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Speirs A.D.,CHEO Research Institute I | Benoit D.L.,University of Ottawa | Beaulieu M.L.,University of Ottawa | Lamontagne M.,University of Ottawa | Beaule P.E.,University of Ottawa
HSS Journal | Year: 2012

Background: The hip joint is generally considered a ball-and-socket joint, the center of which is used as an anatomic landmark in functional analyses and by surgical navigation systems. The location of the hip center has been estimated using functional techniques using various limb motions. However, it is not clear which specific motions best predicted the functional center. Purpose: This study aims to compare the predicted functional center of the hip evaluated from multiplanar circumduction and star motions, and to compare this functional center with the geometric center. Methods: Eight hips in four fresh-frozen cadavers were used and verified as morphologically normal in CT scans. Three-dimensional motion of each lower limb was recorded using arrays of reflective markers rigidly attached to the femur and pelvis. Each hip was manipulated to produce circumduction or star motion, i. e., abduction-adduction and flexion extension. The hip was then dissected and the bearing surface traced with a probe, from which a best-fit sphere was calculated. The functional center was calculated from the motion data and compared to the geometric technique. Results: There was no difference between the functional hip center predicted by circumduction or star motions, although this was offset from the geometric hip center by up to 14 mm. For all except two hips, the functional center was less than 6 mm from the geometric hip in each anatomic direction. Test-retest differences were smaller for circumduction than for star motions. Conclusions: Estimation of the hip center based on motion of the femur relative to the pelvis could localize the geometric center of the joint within 14 mm and circumduction motions were more repeatable. Clinical Relevance: Many surgical navigation systems make use of the functional hip center as a landmark for alignment or reconstruction. Errors associated with this would have a very minor influence in lower limb alignment, e. g., for knee reconstruction, but could affect proximal femoral geometry relevant to hip reconstruction. © 2012 Hospital for Special Surgery.


Almoussa S.,Ottawa Hospital | Barton C.,Ottawa Hospital | Speirs A.D.,CHEO Research Institute I | Gofton W.,Ottawa Hospital | Beaule P.E.,Ottawa Hospital
Journal of Bone and Joint Surgery - Series A | Year: 2011

Background: Assessing the adequacy of bone resection when correcting cam-type femoroacetabular impingement can be difficult when the surgeon is inexperienced or when less-invasive arthroscopic surgical techniques are used. The primary purpose of the present study was to compare, using a Sawbones model, the results of computer-assisted navigated osteochondroplasty of the femoral neck junction with correction with use of femoral head spherometer gauges. The second objective was to compare the results of computer-assisted osteochondroplasty performed by surgeons who had varied experience with the procedure. Methods: We calculated and compared the post-resection alpha angle in custom-molded Sawbones models with camtype impingement following both surgical techniques, performed by three surgeons with varied experience with the procedure. The alpha angle was measured at two positions (the three o'clock and one-thirty positions of the femoral headneck junction) before and after resection. Results: At the three o'clock position, there were no significant differences between the computer-navigation and spherometer groups (p = 0.83). There was undercorrection at the one-thirty position, with the median alpha angle being greater in the navigation group as compared with the spherometer group (71.0 compared with 58.6; p = 0.05). In the navigation group, there were no significant differences in the post-resection mean alpha angle among the three surgeons at either the one-thirty plane or the three o'clock plane. Conclusions: Navigation enabled the inexperienced surgeon to perform an equivalent amount of bone resection as the more experienced surgeons. However, all surgeons did not sufficiently resect the cam deformity as compared with the gold-standard open technique at the one-thirty position. Clinical Relevance: The limitations of computer-assisted surgery should be understood, and adequate training for surgical correction of cam-type femoroacetabular impingement remains essential. Copyright © 2011 by The Journal of Bone and Joint Surgery, Incorporated.


PubMed | CHEO Research Institute I
Type: Journal Article | Journal: HSS journal : the musculoskeletal journal of Hospital for Special Surgery | Year: 2013

The hip joint is generally considered a ball-and-socket joint, the center of which is used as an anatomic landmark in functional analyses and by surgical navigation systems. The location of the hip center has been estimated using functional techniques using various limb motions. However, it is not clear which specific motions best predicted the functional center.This study aims to compare the predicted functional center of the hip evaluated from multiplanar circumduction and star motions, and to compare this functional center with the geometric center.Eight hips in four fresh-frozen cadavers were used and verified as morphologically normal in CT scans. Three-dimensional motion of each lower limb was recorded using arrays of reflective markers rigidly attached to the femur and pelvis. Each hip was manipulated to produce circumduction or star motion, i.e., abduction-adduction and flexion extension. The hip was then dissected and the bearing surface traced with a probe, from which a best-fit sphere was calculated. The functional center was calculated from the motion data and compared to the geometric technique.There was no difference between the functional hip center predicted by circumduction or star motions, although this was offset from the geometric hip center by up to 14mm. For all except two hips, the functional center was less than 6mm from the geometric hip in each anatomic direction. Test-retest differences were smaller for circumduction than for star motions.Estimation of the hip center based on motion of the femur relative to the pelvis could localize the geometric center of the joint within 14mm and circumduction motions were more repeatable.Many surgical navigation systems make use of the functional hip center as a landmark for alignment or reconstruction. Errors associated with this would have a very minor influence in lower limb alignment, e.g., for knee reconstruction, but could affect proximal femoral geometry relevant to hip reconstruction.

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