Intraprosthetic Dislocation: A Specific Complication of the Dual-mobility System

Abstract

Background The dual-mobility concept was proposed as an alternative to prevent postoperative dislocation events. However, intraprosthetic dislocation (IPD) is a troublesome and specific complication induced by the loss of the polyethylene retentive rim and escape of the femoral head from the polyethylene liner. The factors associated with IPD are unknown as only isolated cases have been reported and do not provide a clear understanding of the mechanisms of failure.Questions/purposes We therefore (1) identified features related to different types of IPD and (2) determined factors related to the timing of IPD. Methods We identified 81 cases (80 patients) with IPD from among 1960 primary THAs performed between January 1985 and December 1998. To classify the types of IPD we considered perioperative (presence of arthrofibrosis, cup loosening, and type of liner wear) and radiographic (radiographic cup loosening or migration, and ossification) features. Results We identified three types of IPD with the following causal mechanisms: Type 1 was pure IPD without arthrofibrosis and without cup loosening (n = 26), Type 2 was IPD secondary to blocking of the liner (n = 41), and Type 3 was IPD associated with a cup loosening (n = 14). The mean times of onset were, 11, 8, and 9 years after THA, respectively. We found no difference according to the stem design regarding timing of the IPD. Conclusions This new IPD classification allows clinicians to anticipate the possible conditions they will encounter with revision surgery and plan surgery (cup removal, liner exchange, synovectomy). The implant characteristics and this new classification accounted for the differences in the timing of occurrence.

Low Frequency of Early Complications With Dual-mobility Acetabular Cups in Cementless Primary THA

“…Mohammed et al [19] have reported severe metallosis after IPD in their case of a primary THA performed with a dual-mobility cup. Several other case reports have also demonstrated the potential complications of these designs [1,2,14,16,18,19,21,23]. Further studies detail this important complication of dualmobility articulations.…”

“…In the present study, we similarly evaluated a dualmobility articulation; however, it is different in design from most of the aforementioned studies. Although there are advantages to dual-mobility implants, they are not without disadvantages such as polyethylene wear, loosening, and the unique complication of IPD [1,2,14,16,18,19,21,23]. We therefore asked: (1) What is the cup survivorship when the dual-mobility articulation is used in the setting of primary THA?…”

“…Because serious complications have occasionally been reported with the use of these bearings [1,2,14,16,18,19,21,23], larger, longer term, comparative-and ideally, randomized-trials will be needed to establish the superiority of one approach over the other. National registries may also help to inform this choice, and we look forward with interest to reports of the world's registries on this topic.…”

“…Although there are advantages to this design, it is not without its disadvantages such as polyethylene wear and intraprosthetic dislocation (IPD) (unique to these articulations). Intraprosthetic dislocation may lead to others such as femoral head wear, metallosis, and impingement, which may cause implant failure and necessitate revision surgery [1,2,14,16,18,19,21,23].…”

Early Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty Implant Following Attempted Closed Reduction: A Case Report

“…Philippot et al recently postulated three mechanisms of intraprosthetic dislocation after analysis of 81 such cases from a series of 1960 primary dual-mobility THAs implanted between 1985 and 1998 [13]. Type I "pure" dislocation results from wear of the polyethylene retentive rim in an otherwise functional prosthesis; this accounted for 32% of cases.…”