[Limits in cementless hip revision total hip arthroplasty. Midterm experience with an oblong revision cup]

Revision of an acetabular component in a patient who has severe periacetabular bone loss is a complex problem, particularly when there is not enough bone stock to allow placement of an acetabular component near the normal anatomical hip center. To fill the defect, a valuable option for revision arthroplasty is the cementless oblong revision cup (LOR).

50 consecutive revisions of the acetabular component were performed in 48 patients. The mean age at the time of revision was sixty-one years (range, thirty-three to seventy-eight years). Forty-eight hips were available for follow-up, at a mean of thirty-two months (range, eighteen to sixty-one months). The acetabular defect classified according to Paprosky, the migration and the radiolucencies were followed radiologically.

8 hips (16 %) were revised again: two because of infection (4 %) and six because of instability (12 %). The revised hips are not associated to the preoperative degree of acetabular defect (34 % defect type III) (P > 0.05). The mean Harris Hip score was corrected from 36.5 (range, 7.5 to 92.5) to 78.2 points (range, 47.6 to 97.6) (P < 0.01). The mean d'Aubigné Score was corrected from 8.3 (range, 4 to 6) to 15 points (range, 10 to 18) (P < 0.01). Neither pre- nor postoperative results were associated to the degree of acetabular defect (P > 0.05). However, patients with multiple revisions had a significantly reduced clinical outcome than patients with the first revision (P < 0.05). The hip center of rotation, cranially placed to the contralateral side (0.92 cm) was corrected by the revision to a more normal anatomic rotation center (0.27 cm). Partial zonal radiolucencies, always smaller than 1.5 mm were seen in 30 % of the patients. The mean migration of the acetabular component was not significant (P > 0.05).

The authors support the use of the cementless oblong revision cup if contact can be made with host bone to more than 50 %. If this is not possible, acetabular bone reconstruction combined with a roof ring and a cemented cup is the component of choice.