The Survivorship of the Uncemented Iso-Elastic Monoblock Acetabular Component at a Mean of 6-Year Follow-up

Abstract

Background: Aseptic loosening, caused by wear and osteolysis, is the most frequent reason for hip replacement revision in the UK. To prevent aseptic loosening, an acetabular component with vitamin E added to irradiated highly cross-linked polyethylene (HXLPE) was developed to reduce oxidative degradation.

Questions/purposes: A prior study of the vitamin E-blended HXLPE acetabular component after 2 years of follow-up reported no adverse reactions or abnormal mechanical behavior. To further examine this hypothesis of reducing wear and osteolysis, we sought to evaluate outcomes after 6-year follow-up.

Methods: A cohort of 95 of the 112 initial patients (84.2%) completed the 6 years of follow-up after receiving a vitamin E-blended HXLPE acetabular component. Evaluation was performed in terms of clinical (visual analog scale [VAS] score, VAS score with weight-bearing, VAS score for satisfaction, and Harris Hip Score) and radiological (inclination, polar gap, radiolucencies, migration, and 2-D linear femoral head penetration rate) assessment.

Results: The mean VAS score for patient satisfaction was 8.75 and the mean Harris Hip Score was 91.8. There were two revisions because of deep infections and one because of a peri-prosthetic femoral fracture. Two acetabular components migrated initially; however, delayed acetabular stabilization occurred. Both patients had good clinical scores at 72 months. The mean femoral head penetration rate was 0.036 mm/year.

Conclusions: This prospective cohort study has shown no adverse reactions concerning the vitamin E additive, promising wear rates, no signs of osteolysis, a 100% survival rate for aseptic loosening, and an all-cause survivorship percentage of 97.4% at 6 years of follow-up.

Keywords: femoral head penetration; iso-elastic; monoblock cup; polyethylene; total hip arthroplasty; vitamin E.

Fig. 1

The uncemented monoblock acetabular cup with vitamin E–blended highly cross-linked polyethylene.

Fig. 2

Summary of follow-up (FU).

Fig. 3

The mean visual analog scale (VAS) scores for pain while resting, pain during weight-bearing, and patient satisfaction and the Harris Hip Score at the first day post-operatively, and at months 3, 12, 24, and 72.

Fig. 4

Total and mean femoral head penetration (FHP) rate from the first day post-operatively to months 3, 12, 24, and 72. FHP in mm, mean FHP rate in mm/year.