Effect of acetabular component orientation on recurrent dislocation, pelvic osteolysis, polyethylene wear, and component migration

500

406

Background Few studies have examined factors that affect acetabular cup positioning. Since cup positioning has been linked to dislocation and increased bearing surface wear, these factors affecting cup position are important considerations. Question/purposes We determined the percent of optimally positioned acetabular cups and whether patient and surgical factors affected acetabular component position. Methods We obtained postoperative AP pelvis and crosstable lateral radiographs on 2061 consecutive patients who received a THA or hip resurfacing from 2004 to 2008. One thousand nine hundred and fifty-two hips had AP pelvic radiographs with correct position of the hip center, and 1823 had both version and abduction angles measured. The AP radiograph was measured using Hip Analysis Suite TM to calculate the cup inclination and version angles, using the lateral film to determine version direction. Acceptable ranges were defined for abduction (30°-45°) and version (5°-25°).Results From the 1823 hips, 1144 (63%) acetabular cups were within the abduction range, 1441 (79%) were within the version range, and 917 (50%) were within the range for both. Surgical approach, surgeon volume, and obesity (body mass index [ 30) independently predicted malpositioned cups.

Section: Introductionmentioning

confidence: 99%

The John Charnley Award: Risk Factors for Cup Malpositioning: Quality Improvement Through a Joint Registry at a Tertiary Hospital

Callanan

Jarrett

Bragdon

et al. 2011

500

406

“…Although authors disagree about recommendations for where the acetabular component should be positioned (for example, some would describe ideal acetabular inclination as 45°± 10°, while others would say 40°± 10°), it is agreed suboptimal acetabular positioning can lead to construct instability and detrimental wear characteristics [4,11,19,23]. Although more horizontal component positioning reportedly reduces the rate of dislocation, there appear to be higher contact stresses when the acetabulum is positioned this way [21,22], which may lead to increased PE wear [10,21,22,30]. A potential alternative to conventional metalon-PE bearing surfaces is alumina-ceramic-on-ceramic.…”

Section: Introductionmentioning

confidence: 99%

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%).

“…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.