PMC7262377_01
X-rays fromprevious recent hospitalization.
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Six days before coming to our attention, the patient was hospitalized in a nearby institute for a first episode of hip dislocation (Fig. 1a) which was treated with closed reduction. Following clinical observation and post-reduction X-rays (Fig. 1b) the patient was discharged with the indication to continue his regular follow-up.
X-rays takenbefore (a) and after (b) closed reduction in our department (the arrows point to the "bubble sign"). Control radiograph after revision surgery (c).
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Upon admission, radiographic evaluation showed recurrence of left THA dislocation (Fig. 2a). Closed reduction under sedation was successfully performed, however subsequent X-rays showed the implant's head/neck was not centered in the acetabular cup and a circular radiolucent area next to the femur (also known as "bubble sign") (Fig. 2b). The surgeon therefore proceeded to replace the femoral head with a longer neck (V40 Femoral Head 28 + 8 mm, Stryker) to obtain stability together with a new PE liner (Fig. 2c).
X-rays takenbefore (a) and after (b) closed reduction (the arrows point to the "bubble sign").
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Radiographical evaluation revealed dislocation of the implant, happening between the cup and the PE liner as the latter is clearly visible around the metal head (Fig. 3a). Post-reduction X-rays confirmed the suspect: the PE liner lost engagement with the metal head and located just above the superior acetabular margin (Fig. 3b).
The PE liner was retrieved among soft tissues (a) with no noticeable sign of wear (b). Control radiograph after revision surgery (c).
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The PE was retrieved showing no noticeable sign of wear (Fig. 4a-b). The acetabular cup appeared mobilized and was therefore replaced (Avantage Acetabular Cup size 50, Zimmer Biomet) together with the femoral head (BioBall 28 mm XXL, Merete) and PE liner (Fig. 4c).