Clinical Results of Ceramic on Cerannic Systems 113
Australian Experience with Ceramic Systems
W. K. Walter
Introduction
Polyethylene wear and associated osteolysis has been the main reason for failure of hip replacements in recent years. This unacceptably high polyethylene induced failure rate convinced us that modern ceramic on ceramic bearings would be more likely to give superior longterm results. We commenced using Biolox® Forte ceramic on ceramic articulations routinely in hip replacements in July 1997, and continue to use ceramic on ceramic bearings routinely in both primary and revision hip surgery.
From July 1997 to September 2004, we have carried out hip replacements using ceramic on ceramic bearings in 2503 hip replacements. The first 300 ot these hips have been reviewed at 5 year follow up.
Our Indications for Ceramic on Ceramic Bearings
We routinely use ceramic on ceramic as a bearing surface in primary hip replacements in a great majority of patients. In recent years we have been performing a moderate number of metal on metal resurfacing procedures especially in younger male patients.
There is a special place for ceramic on ceramic bearings in developmental dysplasia of the hip, as it allows the use of a small acetabular component, with a ceramic insert, as this overcomes the problems associated with thin polyethylene if polyethylene was used as an alternative.
Wherever possible in revision hip arthroplasty, ceramic on ceramic bearings are used. Most of these revisions have been carried out for osteolysis, secondary to polyethylene wear debris, and it seems unwise to insert further polyethylene where it can be avoided by converting the hip to a ceramic on ceramic bearing.
This can often be achieved by revision and replacement of the polyethylene acetabular component with a metal backed cup with a ceramic insert. On the femoral side, in many systems a well fixed stem can be left in place and the used chrome-cobalt ceramic head con be replaced with a modern ceramic head protected by a titanium alloy sleeve inside the ceramic head, designed and manufactured to fit the original toper on the femoral stem.
We routinely use a posterior surgical approach to the hip in both primary and revision surgery.
Results
Our experience using ceramic on ceramic bearings over 8 years is encouraging, and we continue to routinely use these bearings.
Patients ore followed up at regular intervals and information stored on a database.
I 1 4 SESSION 3.5
Ceramic Breakage
One male patient sustained breakage of a ceramic acetabular insert without significant trauma and required revision. There have been no other incidences of catastrophic ceramic failure to our knowledge.
Osteolysis
None of the patients have required revision for osteolysis, and none of the patient to date has shown evidence of significant acetabular or femoral osteolysis.
Edge Loading Wear
We have analyzed 16 alumina ceramic on ceramic bearings (Biolox® Forte).
These bearings were retrieved at the time of reoperation for a number of causes, including psoas tendonitis, infection, periprosthetic femoral fracture, and recurrent dislocation. Of these 16 patients, 11 had evidence of edge loading stripe wear due to micro-subluxation, the position of the wear stripes on the femoral heads and acetabular liners, indicating that the great majority of these were edge loading due to microsubluxation of the hip in the flexed position.
In none of these patients was the wear extensive, the deepest head wear in the series was 30 microns, giving a volumetric wear of the head of 2 cubic millimetres.
In those patients requiring re-operation after a long period, the region of edge loading stripe wear on the femoral head showed signs of repolishing, suggesting that the wear process may be self limiting, or at least may progress more slowly as the area of contact between the microsubluxed head and the rim of the ceramic liner gradually increased with the wear process, decreasing the load per unit area at the area of contact. Initially, with edge loading, the stress generated is very high due to the point contact but with time and wearing, the areas of contact increase with subsequent fall in the load per unit area of the contact area.
Squealcing Hips
Of the 2503 ceramic on ceramic bearings in this series, 10 have reported intermittent squeaking. We are currently analyzing these patients to try to determine the cause of the squeak. At least some are due to impingement of the neck of the implant against the rim of the cup but others appear to be arising directly from the ceramic bearing surfaces. None of these squeaking hips have to date required revision. It is planned to examine two of these squeaking hips arthroscopically in the near future.
Clinical Results of Ceramic on Ceramic Systems 115
Discussion
We have been using cerannic on ceramic bearings (Biolox Forte) now for over 7 years and have a large series of 2503 hips. None of these hips has required revision for osteolysis and this contrasts dramatically v^^ith our prior experience using polyethylene as a bearing surface. Ceramic breakage has not been a major problem with only one of these patients requiring revision for ceramic failure, with breakage of a ceramic cup insert.
Our major concern with these bearings is the high incidence of edge loading stripe wear, which occurs mainly with hip flexion. We take great core during surgery to make sure that the hip joint is reasonably "tight" and is not sloppy, which would encourage edge loading wear. We also take particular care at the time of surgery that the hip does not hove a tendency to partial subluxation when the hip is flexed and internally rotated. Often it is necessary to surgically excise a portion of the anterosuperior capsule which tends to become enfolded between the anterosuperior aspect of the trochanter and the anterosuperior part of the acetabulum, causing a tendency for the femoral head to lever away from the acetabular component when the hip is flexed and internally rotated.
Overall we have been satisfied with the results, particularly with the virtual absence of any osteolysis in these hips over an 8 year period.
Time will tell whether these ceramic on ceramic bearings ore superior to other alternatives over a 15-20 year period, but we remain optimistic that at this point in time and development, ceramic on ceramic bearings offer the best alternative in modern day hip replacement surgery.
References
1. Homodouche M., Boutin P. Daussange J., Bolonder M. E., Sedel L. Alumino-on-alumina total hip arthroplasty: a minimum 18.5-year follow-up study. J Bone Joint Surg Am 84-1:69- 11, 2002
2. D'Antonio J., Capello W., Manley M., Bierbaum B. New experience with alumina-on- alumina ceramic bearings for total hip arthroplasty. J Arthroplasty 17-4:390, 2002 3. Nevlos J., Ingham E., Doyle C , et al: Microseparation of the centers of alumina-alumina
artificial hip joints during simulator testing procedures clinically relevant wear rates and patterns. J Arthroplasty 15:793, 2000
4. V^alter W. L., Insley G. M., Walter W. K., Tuke M. A: Edge Loading in Third Generation Alumina Ceramic-on-Ceramic Bearings. - Stripe Wear. J Arthroplasty 19:402, 2004
