Compliant positioning of total hip components for optimal range of motion

Background Factors affecting risk for impingement and dislocation can be related to the patient, implant design, or surgeon. While these have been studied independently, the impact of each factor relative to the others is not known. Questions/purposes We determined the effect of three implant design factors, prosthetic placement, and patient anatomy on subject-specific ROM. Methods We virtually implanted hip geometry obtained from 16 CT scans using computer models of hip components with differences in head size, neck diameter, and neck-shaft angle. A contact detection model computed ROM before prosthetic or bony impingement. We correlated anatomic measurements from pelvic radiographs with ROM.

Section: Discussionsupporting

confidence: 78%

“…We previously identified ''safe zones'' for orienting acetabular and femoral components to minimize prosthetic impingement [11]. Computer models from other investigators also predicted similar combinations of orientations as being optimal [45]. However, these computer models did not account for bony impingement.…”

Section: Discussionmentioning

confidence: 99%

Bony Impingement Limits Design-related Increases in Hip Range of Motion

Bunn

Colwell

D’Lima

2012

“…The effects of the three different groups of acetabular cup inclination angles on the survivorship and clinical outcomes scores were investigated according to a modified recommendation made by Barrack [4], with acetabular positioning at 45°± 10°being optimal. Numerous publications have presented evidence for safe acetabular orientation [4,5,13,19,23,25,33,34,39]. Recent reports confirmed the recommended safe zone (45°± 10°) [4,5,39].…”

Section: Methodsmentioning

confidence: 89%

Does Acetabular Inclination Angle Affect Survivorship of Alumina-ceramic Articulations?

Johansson

Johnson

Zywiel

et al. 2011

Background Reports in the literature have linked high acetabular inclination angles to increased wear of ceramicon-ceramic bearings. However, many of these studies were only conducted in vitro and did not address the clinical relevance of such findings. Questions/purposes We therefore determined: (1) whether the cup inclination angle influences survival or function in patients with ceramic-on-ceramic implants; (2) the incidence of radiolucencies, osteolysis, and subsidence of ceramic-on-ceramic implants; and (3) whether the survival rate higher for ceramic-on-ceramic THAs than for conventional metal-on-polyethylene THAs.Methods We retrospectively reviewed 537 THAs performed in 512 prospectively followed patients having THA between October 1996 and October 2000. Eleven patients (12 hips) were lost to followup before 2 years, leaving 501 patients (525 THAs); of these, 421 were alumina ceramic-on-ceramic articulations and 104 cobaltchromium-on-polyethylene. The mean age was 54 years. We determined acetabular cup inclination angles, Harris hip scores, Health-Status-Questionnaire-12 scores, and presence and location of any radiolucencies, osteolysis, or radiographic subsidence. We compared survival using the Kaplan-Meier method. The minimum followup was 24 months (mean, 59 months; range, 24-120 months). Results Twenty-two of the 424 THAs (4.2%) were revised. We observed no difference in clinical or radiographic outcomes with respect to cup inclination angles. Radiographically, two loose acetabular components and two femoral components had subsided. The 5-year survival rate was slightly higher for ceramic-on-ceramic bearings (98%) than for metal-on-polyethylene (92%).

“…The conventional true value is the mean value determined after a limited or finite number of trials by a method considered accurate and precise enough for benchmarking [42]. Using a Philips Brilliance 16 series CT machine (Royal Philips Electronics NV, Eindhoven, The Netherlands), 1-mm-thick slices were obtained at 0.5-mm increments.…”

Section: Methodsmentioning

confidence: 99%

“…Extremes of component malpositioning are associated with an increased risk of dislocation and loosening [8,11,16,18,20,42,46]. 3D modeling and late implant retrievals have suggested even more subtle malpositioning is associated with edge impingement [3, 4, 22, 31-34, 45, 47].…”

Section: Introductionmentioning

confidence: 99%

Six Sigma Analysis of Minimally Invasive Acetabular Arthroplasty: A Preliminary Investigation

Heck¹,

Stiehl

2009

Minimally invasive techniques in THA may increase the difficulty of acetabular component insertion relative to the optimized position. We sought to determine the ability of eight surgeons to position an acetabular component placed using an anterior-lateral minimally invasive surgical (MIS) approach with conventional instruments or computer navigation using an optical imageless protocol compared with conventional true values determined by computed tomography (CT). We introduce a new approach, the Six Sigma process capability index, to assess outliers. Using the Six Sigma process capability index (Cp [ 1.3) and the criteria of Lewinnek et al. of ± 10°for adequate precision, three-dimensional (3D) CT was capable for inclination and anteversion. Computer navigation and visual cues with conventional instrumentation were precise for anteversion but not for inclination. We conclude image-free computer navigation was not better than conventional instrumentation with the surgeons' visual cues for acetabular cup placement. Six Sigma analysis allows comparison of various methods of referencing with literature controls, and our data suggest CT referencing is the most precise method.