Early Diagnosis of Ceramic Liner Fracture

Abstract

Osteolytic lesions due to wear debris are the major long-term problem associated with total hip replacement1. To avoid wear debris, hard-bearing-surface total hip prostheses with improved tribological properties have been introduced into surgical practice. Ceramic surfaces have had some promising long-term results2, and modern metal-backed alumina cups have been associated with very good clinical results3-5. Alumina has excellent tribological properties and a very high Young's modulus that leads to very good compression strength, but it has poor bending strength: it has no way to deform6. This means that ceramic can break without warning. Under normal physiologic conditions, modern ceramics never reach their fatigue limit, so ceramic head fractures are rare (a rate of 0.004%7 in one study). In contrast, ceramic liner fractures are not well recognized, and their frequency could be underestimated (Fig. 1). In addition, it is difficult to identify patients who are at risk because liner fractures can be due to multiple causes: dislocation, impingement, malpositioning, and microseparation8,9. Fig. 1 A ceramic liner fracture. The diagnosis is often difficult to make on the basis of standard radiographs. A fragment of ceramic is visible near the calcar (arrow). The liner was found to be fractured (arrow) at revision surgery. While many efforts have been made to improve the ceramic manufacturing process and the surgical technique for inserting ceramic components10, little has been reported regarding the early diagnosis of ceramic fracture. When a ceramic fracture involves the liner and is the consequence of repeated microtrauma, the diagnosis is rarely made early, except when ceramic fragments are visible on radiographs. Moreover, decision-making regarding revision surgery after a ceramic-on-ceramic prosthesis has failed is difficult: the ceramic fragments that have spread into the periarticular space are abrasive and …