Review Question - QID 4427

Figure A shows pelvic discontinuity, which is consistent with a AAOS Type IV defect. Acetabular antiprotrusio cage with screw fixation and a posterior column plate is a reasonable treatment option for this condition.

Acetabular bone loss following total hip arthroplasty is a challenging problem with a wide variety of treatment options available. The two most widely accepted classification systems are the AAOS and Paprosky classifications. AAOS type I defects are segmental, type II are cavitary, type III are combined cavitary and segmental, type IV is discontinuity, and type V is arthrodesis. All of the treatment options listed above are described for pelvic discontinuity, with none being described as superior.

DeBoer et al. describe the results of 28 patients with pelvic discontinuity treated with a custom-made porous-coated triflange acetabular prosthesis. 20 of these patients were followed for 10 years. There were no re-operations, 5 hip dislocations, 1 sciatic nerve palsy, and an average improvement in the Harris hip score from 41 to 80.

Paprosky et al. retrospectively reviewed patients who had an acetabular revision using a trabecular metal acetabular component for a pelvic discontinuity and compared these patients with a cohort of patients who had a previous reconstruction for a pelvic discontinuity using an acetabular cage. They found a decreased incidence of pain and need for walking aids in those patients who had revision with a trabecular metal acetabular component.

Figure A shows pelvic discontinuity, likely acute given the lack of associated bony defects and recent fall. Illustration A details the AAOS hip acetabular defect classification and Illustration B is the often cited Paprosky classification.

Incorrect Answers:
Answer 1: Type III defects are combined cavitary and segmental.
Answer 3: Type II defects are cavitary.
Answer 4: Type I defects are segmental.
Answer 5: Type II defects are cavitary.