Review Question - QID 212961

The patient is presenting with pelvic discontinuity due to severe acetabular bone loss and superomedial cup migration consistent with Paprosky 3B acetabular deficiency and pelvic discontinuity. Revision to a custom triflange cup would be a viable treatment approach.

Pelvic discontinuity in revision total hip arthroplasty is a rare treatment challenge due to extensive bone loss from osteolysis and prior surgery. Typically, the cup migrates superomedial towards the pelvic viscera and can place neurovascular structures at greater risk. This defect is classified as type 3B in the Paprosky classification. Treatment involves restoring pelvic stability through the healing of the anterior and posterior columns as well as reconstituting hip biomechanics with custom triflange cups, posterior column plating, distraction arthroplasty, or augments with highly porous cups.

Taunton et al. performed a multicenter retrospective review of 57 patients that underwent reconstruction of pelvic discontinuity with a custom triflange cup. The authors found that 81% of patients had a stable implant and healed discontinuity at final follow-up with implant cost being comparable to off-the-shelf options. The authors concluded that that custom triflange cup provides adequate fixation with good outcomes at a comparable cost to other fixation methods.

Jenkins et al. performed a retrospective review of 58 hips, of which 11 had pelvic discontinuity, that underwent revision with a tantalum porous cup and augments. The authors reported a high rate of radiolucency in Delee and Charnley zone III and implant failure in patients with pre-operative pelvic discontinuity that were revised with this technique. The authors recommend the use of alternative or adjunctive fixation in patients with pelvic discontinuity.

Regis et al. performed a retrospective review of 18 patients that underwent revision with antiprotrusio cage and bulk allograft for pelvic discontinuity. The authors found a 72.2% survival rate at 16.6 years with cases of failure demonstrating graft resorption and acetabular loosening. The authors suggested that bulk allografting with antiprotrusio cages provide an effective means to address pelvic discontinuity.

Figure A demonstrates an AP radiograph of the pelvis with pelvic discontinuity. Illustration A depicts the Paprosky classification system. Illustration B depicts the DeLee and Charley as well as the Gruen zones.

Incorrect Answers:
Answers 1, 2, 3: The patient has a Paprosky 3B acetabular defect with pelvic discontinuity.
Answer 5: Revision with a cemented acetabular cup would not stabilize the pelvic discontinuity in such a manner to allow for healing of the anterior and posterior columns. Furthermore, cemented cups are associated with high loosening rates.