Wear, bone density, functional outcome and survival of vitamin E incorporated polyethylene cups in reversed hybrid total hip arthroplasty: a randomized controlled trial

Uncemented total hip replacement is a widely used treatment in young patients
with osteoarthritis of the hip (age < 70). One of the most important factors
determining late implant failure in total hip replacement is aseptic loosening
of the cup. There is evidence that hemispheric uncemented cups show a higher
tendency in periacetabular osteolysis due to increased polyethylene (PE) wear
in contrast to cemented cups. In addition, in vitro testing of PE cups
incorporated with vitamin E shows good wear and increased mechanical
properties. This is due to the anti-oxidant effect of vitamin E preventing
weakening of the polyethylene after crosslinking. Therefore, cementation of a
vitamin E stabilized PE cup, combined with an uncemented stem (a reversed
hybrid total hip prosthesis) might lead to less PE wear in contrast to the use
of a PE cup without vitamin E.

Furthermore, the influence of vitamin E stabilized PE cups on acetabular bone
mineral density (BMD) is unknown. Hypothetically, it might lead to changes in
acetabular bone mineral density due to different mechanical properties.

Finally, it is hypothesized that less osteolysis will develop in reversed
hybrid total hip arhroplasty combined with vitamin E-stabilized PE cups.

The primary objective is to compare polyethylene wear at 10 years between a
reversed hybrid total hip arthroplasty with vitamin E stabilized polyethylene
versus a reversed total hip arthroplasty without the adjunction of vitamin E to
polyethylene.

Secondary objectives are to determine whether there are differences between the
2 groups:
1. in polyethylene wear at 1 and 3 years postoperatively
2. in acetabular bone mineral density at 1 and 2 years postoperatively.
3. in acetabular and proximal femoral osteolytic changes at 1, 3 and 10 years
postoperatively.
4. in patient-reported and physician-reported functional outcome at 6 weeks and
1, 3, 5, 7 and 10 years postoperatively.
5. in quality of life and physical activity behaviour at 1, 3, 5, 7 and 10
years postoperatively.
6. in survival determined at 5 and 10 years postoperatively.

Double-blinded randomized controlled trial

150 patients

75 patients reversed hybrid + vitamin E
75 patients reversed hybrid - vitamin E

Both investigated groups will receive a total hip arthroplasty (reversed
hybrid: cemented cup and uncemented stem) as is performed in usual daily
practice. The only difference is the adjunction of vitamin E in group 1 to the
polyethylene.

Both groups:
- cemented cup, using Gentamycine cement (Palacos®R+G, Heraeus), applying
modern cementing techniques including lavage and pressurization.
- cementless 28 mm femoral component: a proximally plasma sprayed porous coated
titanium alloy (Ti6Al4V) stem (Mallory-Head, Biomet).

Group 1:
- cemented vitamin E stabilized polyethylene acetabular component (Exceed ABT
Cemented Cup System, E1 Antioxidant Infused Technology, Biomet)

Group 2 (control group):
- cemented polyethylene acetabular component without the adjunction of vitamin
E (Exceed ABT Cemented Cup System, ArCom, Biomet).

X-rays and/or DEXA-scans will be performed postoperatively as follows: 6 weeks
(X-ray and DEXA-scan), 1 (X-ray and DEXA-scan), 2 (only DEXA-scan), 3 and 10
years (only X-rays). Patients will be asked to fill out questionnaires at 6
weeks, 1, 3, 5, 7 and 10 year postoperatively.
No extra visits have to be made, except for the DEXA-scans. These will be
performed separately (3 times). The remaining data will be gathered during
standard visits to the outpatient clinic which will take only a few minutes
extra.

Except for the usual risks of a total hip arthroplasty procedure, an extra
(minimal) risk is added due to the DEXA-scans. However, this radiation exposure
is neglectable (one DEXA-scan resembles 2 days of natural background radiation)