[Early failure of restrained acetabuli in relapsing dislocation of total hip prostheses]

Dislocation is one of the major complications after a total hip replacement and several treatment alternatives have been described for it. One of them is the use of restrained acetabular implants, which led us to conducting an analysis of the failures of this type of components implanted in our center, focusing on the association between relapsing dislocation and the malpositioning of the locking ring.

A total of 41 restrained components were implanted in 39 patients to treat the relapsing dislocation of total hip replacements. Mean postoperative follow-up was 24 months. The patients' demographics, the history of the causes for the dislocations and the treatment provided prior to the use of the restrained implant were all considered. The complications were also reviewed, with major ones being the revision rates and the re-dislocation of the prostheses and the acetabular insert locking ring, as well as the probable causes of failure of the antidislocation device.

A total of 10 re-dislocations occurred during the follow-up; 70% of them in patients with malpositioning of the locking ring, with a statistically significant difference (p < 0.05). At the end of the follow-up period periacetabular radiolucent lines were seen in 9.09%.

There are no papers in the literature that analyze the relation between malpositioning of the locking ring and repeated dislocations. The failure rate reported in our series was high. Restrained implants represent an alternative for relapsing dislocation, but they have to be very carefully placed.