High incidence of migration with poor initial fixation of the Accolade stem.

BACKGROUND

Numerous cementless femoral stem design variations are in clinical use. Because initial implant instability and micromotion are associated with aseptic loosening of the femoral component, migration analysis provides an early assessment of implant survivorship.

QUESTIONS/PURPOSES: We determined the (1) migration pattern of the Accolade cementless femoral stem; (2) clinical factors predisposing to stem migration; (3) self-reported patient outcomes; and (4) our current rate of aseptic stem loosening.

METHODS

We retrospectively analyzed 81 femoral stems for aseptic migration using Ein-Bild-Roentgen-Analyse-femoral component analysis. Postoperatively, patients completed the WOMAC and SF-12 questionnaires. We assessed radiographic factors potentially associated with subsidence: indices of bone shape and quality, canal fill of the implant, and radiographic signs of loosening. Minimum followup was 24 months (mean, 29 months; range, 24-48 months).

RESULTS

The average subsidence at 24 months was 1.3 mm (range, 0-1.5 mm). In the first 2 years, 36% of stems subsided more than 1.5 mm. Large stem size was associated with subsidence. Radiolucent lines (> 1.5 mm in three zones) were present in 10% of stems and associated with lower questionnaire scores. The 5-year survivorship for aseptic loosening of the 367 stems was 97% with revision as end point and 95% for radiographic failure.

CONCLUSIONS

The high incidence of migration and stems with radiographic failure raises concerns about patient clinical function and long-term survivorship of this stem design. This migration pattern may be due to poor initial stability with a subsequent lack of osseointegration. Our results differ from radiographic findings and clinical durability of other similar cementless stem designs.

LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.