Prospective exploratory study: Bone Mineral Density changes of the acetabulum after revision hip arthroplasty using bone impaction grafting.

In revision total hip arthroplasty, bone loss of the acetabulum can be managed
by impacting porous bone chips. This technique to compensate a poor bone stock
in the acetabulum has been widely adapted. An adequate Bone Impaction Graft
(BIG) provides initial stability for the prosthesis to prevent subsidence and
to facilitate bone remodelling. When the BIG is stable, revascularisation and
incorporation of the graft into the host skeleton should occur; a process known
as *creeping substitution*. The bone stock quality and long term results of BIG
used in hip acetabular revision arthroplasty, to compensate for bone stock
defects have not been investigated so far. With the state of the art dual
energy X-ray absorptiometry (iDEXA; General Electronics, USA) the bone mineral
density (BMD) can be measured in specific regions of interest in the
acetabulum, an examination that has proven its value so far on BMD changes in
the femur and acetabulum with several types of hip prostheses. BMD changes
within the BIG*s regions of interest (ROI) can be seen as derivate of the bone
stock quality and subsequently the degree of creeping substitution.
In earlier studies we developed a reliable technique to demonstrate BMD changes
in specific ROI in the femoral neck following resurfacing hip arthroplasty.
Based on this experience we now would like to extrapolate this technique to
evaluated BMD changes after BIG. Prospective BMD data from the Acetabulum after
BIG may appear to be of value in a further understanding of stress shielding
and bone graft remodelling of this region.

We believe that it is important to gain further insight in the process of bone
graft remodeling and the preservation of bone stock after bone impaction
grafting.

Radiographs are far from conclusive and CT scan can not be repeated on regular
intervals for obvious reasons. Prospective follow-up of the BMD of the bone
impaction area will contribute to our further understanding. There is no
literature available on BMD changes in the acetabulum after bone impaction
grafting.

From our recent experiences with earlier research on BMD in specific ROI in the
femoral neck we are motivated to further explore the potential of our DEXA
technology and software in the field revision hip arthroplasty.

We hypothesize that BMD changes in the bone impaction grafted acetabulum can be
adequately monitored with modern DEXA techniques.

Research Questions are:

1. Can changes in BMD be interpreted as representative for the process of bone
remodelling in the bone impacted area?
2. Will bone impaction grafting of the acetabulum result in a well
preserverd/remodelled bone stock within 2 years after revision hip
arthroplasty?

This trial is a prospective exploratory follow-up study recording the clinical,
radiographic data, and bone mineral density data at specific time intervals
(preoperative, 1-14days postoperative at 3months, 6months, 1 year and 2 years
postoperative).

The DEXA scan will be used at 5 time intervals: within 1-14days postoperative,
at 3months, 6months, 1 year and 2 years postoperative

Since we have experience with earlier similar studies we do not expect
potential risks or research problems; the project is straight forward. Patient
inclusion is always an uncertain factor, however, from our experience and
history in this field only a slight delay can be expected.

-a DEXA scan has a very low radiation level and will not lead to an increased
healt risk, examination takes 15 minutes

-The questionairres to be filled in takes 10-15 minutes

-Total time will be around 30minutes at each study-interval (5 in total)