The early migration of a partially cemented fluted pegged glenoid component using radiostereometric analysis.

BACKGROUND: Radiostereometric analysis measures the position of rigid bodies in 3 dimensions with very high precision and can be used to measure early micromotion of glenoid implants.
MATERIALS AND METHODS: Radiostereometric analysis was used to measure migration of 11 partially cemented fluted pegged glenoid components in patients with osteoarthritis who underwent shoulder arthroplasty during a 2-year period. Patients were evaluated using the American Shoulder and Elbow Surgeons (ASES) and Constant scores and by a computed tomography (CT) scan at the 2-year follow-up.
RESULTS: Migration patterns could be classified into 2 groups: The first group showed little if any migration, the second group rotated by 4° or more as early as 3 months after operation. The maximum total point motion reached up to 2 mm by the 6-month follow-up. At 12 months, the 2 groups could be identified by the presence or absence of focal lucency around the central peg. At the end of 2 years, CT scans were able to classify the same 2 migration patterns by the presence or absence of osseointegration around the cementless central peg of the glenoid implant. The clinical effect of the absence of osseointegration in this novel glenoid component is unknown because both groups had similar clinical results at 2 years.
CONCLUSION: Rapid early migration associated with focal lucency and absence of osseointegration was observed in 6 of 11 components. We postulate that lack of initial fixation leads to early movement of the glenoid component and failure of osseointegration.