Ph Escaré (Béziers), P Desbonnet (Castelnau Le Lez), J.L Tricoire (Toulouse), J. Trouillas (Gange)
Increasing frequency of indications for total hip arthroplasty, even for young patients and dysplasic acetabulums contributes to a huge escalation of revision procedures and leads sometimes to very severe bone defects. Acetabular loosenings occur more frequently than femoral ones, and are often painless for extended periods. They lead to osteolysis beginning on the anterior column and the medial side with preservation of the postero-superior part of the roof that seems to be preserved for a long time.
Many techniques have been developed to reconstruct bone deficiencies of the acetabulum, resulting from congenital dysplasia, erosive arthritis, or migrating replacement prosthesis.
In advanced bone loss (Paprosky III), the procedure must resolve two issues:
-The primary stability of the component
-The restoration of bone stock.
The authors have found a reliable but unrecognized anatomical structure of the pelvis: the “ilio ischiatic bar” (pelvic isthmus), a bar of bone between the ilium and the ischium that extends from the postero-superior part of the acetabulum to the low part of the sacro iliac joint. It drives the loads from the lower limb to the lumbar spine. It is the strongest part of the pelvic bone. After anatomic studies, the isthmus was found to have a true diaphysis structure with a medullary central cavity; it looks like a tube and is very resistant.
The cup is supported both by the pelvic isthmus and the acetabular remnants.
We have performed TDM exploration for all of our hip replacements, and we have not found any destruction of the isthmus, even in advanced cases of loosening.
The Integra revision acetabular cup (Lépine / France), implanted since September, 2003 is a safe and useful pedestal implant:
– A 50 mm long stem, inserted into the isthmus, just like a nail provides a very strong primary fixation, that can also be enhanced by screws
– A double layer of titanium and hydroxyapatite promotes the secondary fixation
– A bipolar arthroplasty on a metal insert prevents dislocations.
Our preliminary experience confirms the safety of the surgical technique and stability of the implant. The Integra revision acetabular cup is recommended for massive bone loss, particularly roof and both columns large cavitary defects (Paprosky III). Long term clinical success is expected with restoration of bone stock.