Design concepts, indications, and surgical technique for use of the protrusio shell.

Major deficiencies of the medial wall of the acetabulum arising from severe protrusio acetabula, migrated endoprostheses, old central fracture dislocations, and intrapelvic socket protrusions are a serious threat to the success and longevity of total hip arthroplasty. However, excessive strain on the weakened medial wall can be substantially reduced by the use of the protrusio shell. Treatment of existing complications includes augmenting and bone grafting the defect. The surgical technique is demanding but not complex. The protrusio shell is designed to conform to the anatomy of the acetabulum and permits independent positioning of the acetabular component in its optimum attitude. Major bony defects in the medial wall should be occluded by the autografts or allografts in conjunction with the use of the protrusio shell.