Equal Primary Fixation of Resurfacing Stem, but Inferior Cup Fixation With Anterolateral vs Posterior Surgical Approach. A 2-Year Blinded Randomized Radiostereometric and Dual-energy X-Ray Absorptiometry Study of Metal-on-Metal Hip Resurfacing Arthroplasty.

BACKGROUND

The anterolateral (AntLat) surgical approach may spare the blood supply to the femoral head and improve the accuracy of cup positioning in metal-on-metal hip resurfacing arthroplasty. Thereby, potentially lessen complications such as avascular head necrosis, femoral neck narrowing and fracture, improve implant fixation, and lessen periprosthetic bone mineral density (BMD) loss.

METHODS

Between November 2008 and January 2012, a randomized clinical trial was performed at Aarhus University Hospital. A total of 49 patients (28 males) were allocated to metal-on-metal hip resurfacing arthroplasty by the AntLat (n = 25) or the posterior (Post; n = 24) surgical approach. Patients were followed with radiostereometric analysis, measurements of periprosthetic BMD, clinical outcome scores of Harris hip score and visual analogue scale, serum metal ions, and conventional radiographs.

RESULTS

At 3 months, cups in the AntLat group had higher total translations of mean 1.00 ± 0.70 mm vs mean 0.64 ± 0.45 mm in the post group (P = .04), and higher total rotations of mean 2.44° ± 1.36° vs mean 1.39° ± 1.17° in the Post group (P = .002). All migrations of cup and stem were similar at 1 and 2 years postoperative (P > .07). At 1 year, periprosthetic BMD since postoperative at the medial side of the stem was reduced to mean 98.45% ± 8.57% in the AntLat group, and increased to mean 105.57% ± 11.07% in the Post group (P = .02), but measurements were comparable at 2 years (P = .05).

CONCLUSION

Cups inserted by the AntLat approach migrated more until 3 months postoperative. This illustrates a less good primary cup fixation with the AntLat approach; however, all cups were well-fixed after 3 months' follow-up indicating a good secondary fixation.