Some solutions for massive loss of acetabular bone in hip reconstruction

Revision total hip arthroplasty (THA) is frequently complicated by loss of acetabular bone. The ideal reconstructive method for the severely deficient acetabulum in revision THA remains unsolved. Paprosky et al. (1) created a classification of acetabular bone loss based on the remaining pelvic bony anatomy and its ability to provide support for an acetabular component. Defects are classified by type, indicating whether the remaining acetabular structures are completely supportive (type 1), partially supportive (type 2), or non-supportive (type 3). Type 2A defects are a generalized oval enlargement of the acetabulum. Superior bone lysis is present but the superior rim remains intact. Type 2B defects are similar to type 2A, but the dome is more distorted and the superior rim is absent. Type 2C defects involve more localized destruction of the medial wall. Type 3 acetabular defects demonstrate severe bone loss resulting in major destruction of the acetabular rim and supporting structures. Type 3A bone loss pattern usually extends from the 10 o’clock to the 2 o’clock position around the acetabular rim. In type 3B defects the acetabular rim is absent from the 9 o’clock to the 5 o’clock position. In both type 3A and 3B defects the component usually migrates greater than 2 cm superiorly. Type 3A defects demonstrate moderate, but not complete, destruction of the teardrop (medial wall of the teardrop is still present) and moderate lysis of the ischium. Because the medial wall is present, the component usually migrates superolaterally. Type 3B defects show complete obliteration of the teardrop and severe lysis of the ischium, usually resulting in superomedial component migration.