Background: The Duraloc cup is a frequently used metal backed hemispheric porous-coated cementless acetabular cup. Published radiological data on loosening rates remain contradictory. Despite to this contradictory radiological data is the good clinical performance of this cup reported by many authors. The aim of our study was to evaluate radiological outcome (cup migration, acetabular abduction angle, cup anteversion) and possible correlation to clinical data after 12 years.

Methods: Migration analysis of 40 cementless Duraloc 100 cups (38 patients, average age 57 years, range 52 to 68years, 25 male, 13 female) could be retrospectively performed after a 12 year follow up using Einzelbild-Roentgen-Analyse (EBRA) software. An average of 5 standardised anteriorposterior radiographs (range 4 – 8) could be evaluated. Clinical outcome was assessed using HHS score. Cup migration, acetabular abduction angle, cup anteversion, heterotocpic ossification and wear were determined. Statistical evaluation was performed using Mann- Whitney - U test and correlation analysis.

Results: At 12 years follow up the average horizontal migration was 1.51 mm (range 0 to 8.5 mm) and the average vertical migration was 1.44 mm (range 0 to 4.5 mm). The average cup abduction angle was 48° (range 30° to 58°, average cup anteversion was 16° (range 12 to 25°) Average wear of the polyethylene liner at latest follow up was 1.5 mm (range 1.1 to 2.1). Harris hip score improved from average 41 (range 30 – 55) to 90 (range 77 to 95) at latest follow up. We could not find any significance difference between cup migration and gender (p > 0.05). There was no positive correlation between clinical scores and migration data found (r² = 0.01). The cup diameter however showed positive correlation with cup migration (r² = 0.8).

Conclusion: Our study shows good radiological and clinical results of the Duraloc cup after 12 years. Radiological migration data did not show any correlation with clinical results. A greater cup diameter however is a risk factor for higher migration.

Background: Patients with femoral head osteonecrosis usually tend to be younger and more active when compared with osteoarthritis patients. Second generation metal-on-metal THA was reintroduced to reduce poly-ethylene-induced wear debris, and therefore increase longevity of implants.

The aim of this retrospective study was to compare full blood cobalt-chrome levels, patient activity, clinical/radiological outcome and implant survival in patients with osteonecrosis and osteoarthritis after a minimum follow up of 12 years.

Methods: Full blood cobalt-chrome levels of a consecutive series of 125 patients, consisting of 40 patients (38 male, 2 female, average age 35 years, range 28 to 46 years) with osteonecrosis (ON group) and 85 patients (60 male, 25 female, average age 58 years, range 52 to 68 years) with osteoarthritis (OA group) as primary diagnosis were retrospectively compared. Patient activity level was assessed using UCLA Score and clinical outcome was evaluated using HHS. Radiological outcome and implant survival (Kaplan Meyer analysis) was determined in both groups.

Results: Patients with osteonecrosis of the femoral head showed significant higher UCLA scores when compared to OA group (4 versus 7) (p < 0.05). Despite this higher patient activity no significant difference was found between cobalt-chrome full blood levels (2.1/1.6 μg/l, ON group, 1.9/1.8 μg/l OA group, respectively) (p > 0.05). No positive correlation between patient activity, acetabular cup abduction angle and cobalt-chrome levels was found (r² < 0.01). Clinical and radiological outcome were equal in both groups. Harris hip score was 91 points in the OA and 92 in the ON group (p > 0.05). Average cup inclination angle was 47° (range 32° to 55°) and 44° (range 30° to 56°) respectively (p > 0.05). Implant survival at 12 years follow up was 96% in the OA and 97% in the ON group.

Conclusion: After a minimum follow up of 12 years, we could not find increased metal levels in osteonecrosis patients when compared to the osteoartrithis group. Regarding our clinical and radiological outcome we cannot confirm previously published reports showing suboptimal results of THA in patients with osteonecrosis. Implant survival data did not differ among both group.

Metal on metal THA seems to be an effective and safe treatment option for these patients.