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Explant Acetabular Cup Removal System associated with less bone loss in revision THA
Use of the Explant Acetabular Cup Removal System to remove well-fixed cementless acetabular components was associated with less bone loss compared with removal using Aufranc gouges, according to results of this study.
Of 623 patients who underwent revision total hip arthroplasty (THA) between 2002 and 2013, researchers identified 47 patients (51 hips) who underwent revision of well-fixed cementless acetabular components for any reason except infection. Researchers divided patients into two groups based on the method of acetabular component removal, with 27 acetabular components removed with the Explant Acetabular Cup Removal System (Zimmer) and 24 acetabular components removed with Aufranc gouges.
Muyibat A. Adelani
Researchers measured bone loss by the difference between the initial acetabular component outer diameter and the final reamer outer diameter; the difference between the initial acetabular component outer diameter and the new acetabular component outer diameter; and the use of impaction bone grafting.
Results showed a median difference of 5 mm between the initial acetabular component outer diameter and the diameter of the final reamer in the Aufranc group vs. 3 mm in the Explant group. Researchers found a median change of 6 mm in the acetabular component outer diameter in the Aufranc group vs. 4 mm in the Explant group.
According to results, all hips were reconstructed with standard hemispherical or elliptical acetabular components, with 63% of hips in the Aufranc group and 56% of hips in the Explant group undergoing reconstruction with elliptical acetabular components. At the time of acetabular reconstruction, researchers noted hips in the Aufranc group were more likely to have bone grafting compared with the Explant group. – by Casey Tingle
Disclosures: Adelani reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.
Perspective
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This study quantifies what many revision surgeons have perceived for years: that the Zimmer Explant Osteotomes help to remove acetabular components and preserve acetabular bone for the subsequent reconstruction. While there are methodological weaknesses of the study that the authors concede, the conclusion is consistent with my suspicion that, on average, the Explant osteotomes preserve 2 mm more bone than using curved acetabular gouges. In my revision practice, the Explant osteotomes are a critical tool I have present for every revision I do, as the tool makes acetabular component removal faster, easier and safer for preservation of bone stock. It is comforting to have this data to support our current practice patterns.
There are a few tips I have learned to optimize use of the Explant system:
- Obtain the previous operative report to confirm the outer diameter of the cup being removed. Digital or acetate templates can be used to estimate the cup diameter, but this is not as accurate as knowing the precise size;
- Order trial liners and the screwdrivers for the cup being removed. The screws heads can have different shaped screwdriver tips (ie, star shaped) and having these available can simplify removal. Having the trial liners to replace once the screws have been removed are vital for use of the Explant system;
- Consider ordering custom ball sizes to use with liners of different inner diameters (for example, 36 mm, 38 mm and 40 mm) as the system typically comes with only 28-mm and 32-mm balls;
- Have bipolar head trials to place on the 28-mm explant ball when removing large diameter monoblock metal shells; and
- Keep the set filled with sharp blades.