Ice cream cone (pedestal) prosthesis for chronic pelvic discontinuity

Background

Chronic pelvic discontinuity (CPD) is among the most challenging situations in revision total hip arthroplasty (THA) and is estimated to cause 1% to 5% of all acetabular revisions. ^, It is a distinct form of bone loss and is defined as a separation of the superior pelvis from the inferior pelvis by a fracture, osteolysis, or non-union. Risk factors for CPD are female sex, severe pelvic bone loss, prior pelvic radiation, and rheumatoid arthritis. Treatment options include traditional cage reconstructions, cup-cage constructs, custom triflange acetabular components, jumbo acetabular cups with porous metal augments, and acetabular distraction technique using highly porous revision acetabular shells, with or without modular porous metal augments. ^, The most influential factors for a successful outcome in the treatment of CPD are the remaining bone stock, the biologic in-growth potential, and the healing potential of the discontinuity.

In general, all reconstruction techniques for the treatment of severe acetabular bone loss with an associated CPD are based on achieving rigid fixation of the acetabular implant to the pelvis while stabilizing the hemipelvis either by the healing of the discontinuity or by using the acetabular component to bridge the inferior and superior pelvis.

In patients with massive bone loss of the anterosuperior and posteroinferior columns and a missing inferior border, where bridging the defect may be technically impossible, or a complex reconstruction is too invasive for the medical condition of the patient, the use of a pedestal cup or a so-called ice cream cup is a feasible and safe alternative. These types of implants, where a stem is anchored in the intramedullary space of the ilium, have traditionally been used for reconstruction following acetabular tumor (type II) resection , but in selected patients, it can also serve as a salvage procedure in revision THA.

Premise: 1. Anchorage of a pedestal cup is in the cranial posterior aspect of the ilium. The remaining bone stock must be of sufficient quality to ensure stable fixation and prevent early loosening, especially in cementless fixation. Thus, devitalized, irradiated bone or severe osteoporosis represent a contraindication for cementless fixation of a pedestal cup.

2. In the fixation area of the pedestal, sufficient sclerosis is necessary, as the support at the junction from the cylindrical to the tapered portion of the implant is essential for the primary stability of the socket. Insufficient cranial support is a risk factor for implant migration and loosening .

Surgical planning