Review Question - QID 220013

The patient appears to have had a total hip arthroplasty with a cemented acetabular component that has eroded through the medial wall, resulting in a Paprosky type 2C acetabular defect without pelvic discontinuity, making a revision to a jumbo cup with screws and morsellized allograft the most biomechanically stable and cost effective approach.

Acetabular bone loss in revision THA can be a complex issue to treat and is guided by the principles of the Paprosky classification reproduced in Illustration B. On a simplified level, when considering cost-effective and biomechanically stable methods to reconstruct acetabular defects, two basic requirements must be satisfied to avoid using more complex reconstruction methods: adequate column support and absence of pelvic discontinuity. This is because adequate column support and a competent hemipelvis allow the surgeon to "hang" a revision cup (either porous-hemispheric or jumbo cup) without the need for the time-intensive design and cost of custom components. In cases in which the hip center must be restored to mitigate any leg length discrepancy, as in severe Type III defects with migration, revision cup reconstruction can be paired with the use of tantalum metal augments, which does add cost, but provides enhanced biomechanical stability at a more economical price-point than cup-cage or triflange components.

Sheth et al. reviewed the evaluation and management of acetabular bone loss in revision total hip arthroplasty. The authors note that as the number of primary total hip arthroplasty (THA) procedures performed continues to rise, the burden of revision THA procedures is also expected to increase. They conclude that appropriate radiographs are critical in assessing acetabular bone loss, and specific classification schemes can identify bone loss patterns and guide available treatment options, which include impaction grafting and cementation of the acetabulum, non-cemented hemispheric acetabular reconstruction, structural allograft reconstruction, non-cemented reconstruction with modular porous metal augments, ring and cage reconstruction, oblong cup reconstruction, cup-cage reconstruction, and triflange reconstruction.

Ling et al. reviewed the use of porous tantalum augments for the reconstruction of acetabular defects in primary total hip arthroplasty. The authors retrospectively reviewed 19 patients (19 hips) with acetabular defects who underwent primary THA using tantalum augments, with a minimum follow-up of 2 years. They found that mean operation time and blood loss were 124.7 minutes and 530 mL, respectively, and there was no aseptic loosening, cup and augment migration, screw breakage, or presence of hip infection at last follow-up, with all hips being graded as radiographically stable at last follow-up. They concluded that porous tantalum augments combined with titanium shells led to satisfactory clinical and radiographic outcomes for the reconstruction of acetabular defects in primary THA at a mean 5.1 years of follow-up, offering a method of anatomical cup placement, in a simple operation, with a high rate of stable fixation.

Figure A is an AP radiograph of a revision total hip arthroplasty showing evidence of cemented acetabular and femoral components, with an obviously loose acetabular shell that has eroded through the medial wall allowing extrusion of cement into the pelvis. Illustration A is a post-op radiograph showing the press-fit jumbo cup reconstruction with restoration of the hip center, as well as a femoral-sided revision that required an extended trochanteric osteotomy (ETO) with cable fixation. Illustration B is a reproduction of the Paprosky classification of acetabular bone loss.

Incorrect Answers:
Answers 1 and 3: Given that there is adequate column support and no discontinuity, a cage and a triflange would be both very expensive and unnecessary.
Answer 2: There is no clinical evidence of infection necessitating a staged procedure with an antibiotic spacer.
Answer 5: A Paprosky type IIIA or B defect with loss of superolateral rim support would likely necessitate unitization of a porous shell to a superolateral augment to recreate the hip center and allow for primary acetabular stability; however, there is no indication that this is needed based on the description in the vignette.