Osseointegration of the lower limb: Reduction of mechanical strain on the abutment
Mr Eric MOLLARET INGÉNIEURa, Dr Marion BERTRAND MARCHANDb
a Clinique St Roch / Dr Marion Bertrand Marchand, b Clinique St Roch
The osseointegration improves the quality of life for amputees and brings indolence.
Unlike a socket, the abutment concentrates stresses. The tall and heavy patients have to face break of abutment. Abutment’s change have to be done in operating room under general anesthesia.
In the case of a patient varus / valgus, how to reduce the mechanical stresses on the abutment in order to reduce the frequency of changing this critical part ?
Materials and methods
This study has focused on a patient valgum osseointegrated since January 2012 and in very good health.
We have evaluated in static position (bipodal support, without speed or acceleration, frontal plane) mechanical stress at the junction abutment - implant in three different cases :
+ Prosthesis aligned with the abutment
+ Prosthesis aligned with the abutment with varus due to slight plastic deformation of the abutment
+ Prosthesis vertically and translated in the frontal plane with a load line passing through the bottom of the abutment and the femoral head.
We have used a telemetry, goniometer, ruler, CAD software, and scientific calculator.
The third case was possible by a long length of the residual femur’s bone.
For a patient whose weight is 80 kg and the size 1.88m, the valuesof the torque at the junction abutment - implant are:
Case 1: 20.8 Nm
Case 2: 31, 68 Nm
Case 3: 2.24 Nm.
We find between the case 1 and case 3:
+A sharp reduction of flows all around the abutment
+A better ambulation
The mechanical stress applied to the abutment is divided by 10 for a load line - in the frontal plane - from the bottom of the abutment to the femoral head.
We can say that a such setting is more physiological :
+ reduces strain and increases the life of the abutment for all patients.
+ decreases patient’s anxiety.
R.BRANEMARK , J. BAHUAUD , M.BERTRAND (2006)
KAPHINGST et FITZLAFF (1990)
Mécanique points matériels, solides, fluides, JP PEREZ (1995)
Keywords : osseointegration, reduction of mechanical strain, titanium OPRA