The pattern of BMD behind the press fit isoelastic acetabular component during the two years after implantation.
ID
Source
Brief title
Condition
- Bone and joint therapeutic procedures
Synonym
Research involving
Sponsors and support
Intervention
Outcome measures
Primary outcome
The main study parameter is bone mineral density (BMD). BMD is determined as
the mean mineral content (g/cm3) on a CT, measured in a zone of interest.
Measurements are performed 1 week post operative , 6 months and 2 year
(primairy endpoint) post operative.
Secondary outcome
Osteolyses, pain, functional outcome and adverse effects.
Background summary
The two types for fixating a THA are: cemented and non-cemented. During the
last decades both types of fixation have undergone many modifications to
optimize the primary en secondary (long term) fixation. Because of the
developments in medicine the patients who require a THA are getting younger,
live longer therefore necessitating THA revisions.
The main cause for THA revision is aseptic loosening. The acetabular part of
the THA has been largely overlooked because of the femoral problems during the
last 30 years. Now the acetabular part is being extensively studied to optimise
the life expectancy of the acetabular component. Attention has been diverted,
after solving the fixation problem, to the insert material and the retro
acetabular stress shielding principle.
Wolff's law states that bone in a healthy person or animal will adapt to the
loads it is placed under. If loading on a particular bone increases, the bone
will remodel itself over time to become stronger to resist that sort of
loading. The converse is true as well: if the loading on a bone decreases, the
bone will be adapted and become weaker.
The definition of stress shielding reads: Osteopenia occurring in bone as the
result of removal of normal stress from the bone by an implant. Metal backed
cups have an elastic modulus which is much lower in comparison with acetabular
bone. This difference leads to a non physiologic distribution of compressive
forces behind the acetabular cup. Peripheral rim overloading due to the
rigidity of the cup results in bone mineral density (BMD) elevation in the
peripheral zones and BMD decline in the retroacetabular zone behind the cup
(Wright et al 2001). The elastic modulus of PE lies closer to that of the
acetabular bone. This proximity results in a more physiologic load transfer
trough the acetabular cup resulting in none / less stress shielding in the
entire retroacetabular region.
Finite element models (FEM) have provided data concerning the retroacetabular
BMD decline (Weinans 1993, Huiskes 1987). At this time further FEM studies are
undertaken to investigate the rate and ROI of stress shielding in press fit
isoelastic acetabular components (this PhD thesis). The precise development of
aseptic loosening from stress shielding is only theoretical; the numbers of
published articles are increasing pointing towards the possible clinical
relevance. (Cambridge group Field et al 2006, Pitto et al 2006). Sabo et al
1998 points to the sequence of lowering of BMD and implant failure for CLS
femoral implants.
Study objective
The pattern of BMD behind the press fit isoelastic acetabular component during
the two years after implantation.
Study design
Prospective cohort clinical trial with 25 patients, included within 1 year at a
rough estimate.
Intervention
Placement of the press fit RM acetabular cup in cojoint with the CLS Spotorno
uncemented femoral stem.
Study burden and risks
BMD measurements can be performed using duel energy X-ray absorptiometry
(DEXA), computer tomography (CT) has been adopted to provide higher resolution
and 3D femoral and acetabular BMD measurements. Differentiation between
cortical and cancellous bone provide a better insight into the BMD. The
disadvantage of a higher radiation dose has been mentioned, however modern
techniques and selecting ROI*s lower the dose to approximately 0,5 -1,0 mSv.
Our own estimation ( measured during a simulation) of radiation dosage during
this study is 1-2 mSv per CT scan. The mean background radiation dosage which a
normal functioning persoon will endure each year is 2.5 mSv ( Health Council of
the Netherlands 2007). We believe that there are no adjuvant risks concerning
the radiation dosage during this study. A relative risk analysis shows that
decreasing risk for adverse effects due to radiation dossage with the aging of
the patient. Because our patient selection is made up of patients with primairy
OA of the hip we believe that there are no adjuvant risks.
The RM press fit cup is a proven prosthesis which is beeing used in many
countries throughout Europe.
Postbus 9011
6500 GM Nijmegen
NL
Postbus 9011
6500 GM Nijmegen
NL
Listed location countries
Age
Inclusion criteria
Patient selection:
- Unilateral THA
- Diagnosis: primary osteoarthritis (OA)
- No heterolateral complaints / symptoms fitting OA
- Patients should be - Informed consent should be given
Exclusion criteria
Exclusion criteria*s:
- No bone metabolism diseases
- No anti osteoporotic supplements and oestrogen medications
- Previous acetabular operative reconstructions (Bilateral)
- Post operative complications such as infections, recurrent luxations, acetabular fractures, non compliance with normal post operative care / rehabilitation program.
Design
Recruitment
Followed up by the following (possibly more current) registration
No registrations found.
Other (possibly less up-to-date) registrations in this register
No registrations found.
In other registers
| Register | ID |
|---|---|
| CCMO | NL19766.091.07 |