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). Methods: 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. Results: 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 79.2 points (range, 47.6 to 97.6) (P<0.01). The mean d'Aubigne 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 min were seen in 30% of the patients. The mean migration of the acetabular component was not significant (P>0.05). Conclusion: The authors support the use of the cementless oblong revison 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.