Abstract
Osteolysis is one of a major cause of failure that affect long term survival rate in THA. Hard-on-hard bearing surface were developed to reduce wear and osteolysis, such as ceramic-on-ceramic which is the lowest wear rate was introduced but it still has squeaking and ceramic fracture. Metal-on-metal bearing surface significantly reduce wear rate but it still release metal ion which affect local tissue reaction. Then ceramic-on-metal is another choice of bearing with combine the advantage of reduce wear rate, metal ion release, no stripe wear, no squeaking and no ceramic fracture. However after clinical use ALTRs may occur and disturb the longevity of THA.
During January 2009 to December 2009 we performed 98 THR with the same femoral stem and acetabular cup with difference bearing which were 87 cases of metal on cross-linked PE, 8 cases of ceramic on metal and 5 cases of metal on metal. Routinely postoperative care were done with clinical evaluation, plain x-rays and Harris hip score. After 5 years follow up there are clinical problems in ceramic on metal THA with decrease clinical score and progressive osteolysis in radiographic finding in 2 cases then we investigated to find the cause of this problem and revise the components. We preformed magnetic resonance imaging and collect blood sample for ESR, CRP and Cobalt and Chromium level. We revised 2 cases of ceramic on metal THA, during surgery we collected tissue for bacterial and AFB and histopathology. All retrieval components were studied for wear pattern. First patient have thigh pain and progressive osteolysis after year 4th of follow up. She had normal ESR and CRP with high level of cobalt and chromium level. We revised both components and tissue histopathology showed metallosis with chronic inflammation. Another patient had failure due to ALTRs with mixed solid-cystic mass at trochanteric bursa but component is stable then only bearing surface were change. Wear pattern at femoral head was in weight bearing area with corresponding to apical center wear of metal liner.
Our study showed that only in group of ceramic-on-metal THA that have 5 years follow up have early reoperation due to osteolysis and tissue reaction. We routinely stop to use this bearing since 2010. But we have small number of cases in our study to conclude that is bearing are not suitable for clinical usage.
