These authors point out that aseptic loosening of glenoid implants is the primary revision cause in anatomic total shoulder arthroplasty (aTSA). They hypothesized that lower preoperative glenoid bone mineral density (BMD) was associated with aseptic glenoid implant loosening in aTSA. They retrospectively reviewed 93 patients (69 females and 24 males; mean age, 69.2 years) having an aTSA with a keeled glenoid component (shown below)
Patients had preoperative computed tomography (CT) scans on which BMD was measured in 3D using a reliable semi-automated quantitative method, in the following six contiguous volumes of interest (VOI): cortical, subchondral cortical plate (SC), subchondral trabecular, and three successive adjacent layers of trabecular bone.
Aseptic loosening of glenoid implants was assessed using conventional shoulder radiographs performed at regular followup visits at 3, 6, 12, and 24 months, followed by once a year or every two years, depending on the patient’s clinical course. In the case of radiological uncertainty and/or onset of clinical symptoms (e.g. pain, feeling of instability or locking, decreased range of motion), shoulder CT arthrography was performed. Radiographic prosthetic loosening was defined as the presence and/or enlargement over time of complete (thickness >1.5 mm) radiolucent lines at the glenoid bone-cement interface, and/or migration (>5 mm), tilt (>5°), or shift of the glenoid component.
Glenoid implants showed radiographic loosening of 11% at 5 years and 43% at 10 years.
Only the SC VOI showed significantly lower BMD in the loosening group (622±104 HU) compared with the control group (658±88 HU) (p=0.048) with a relatively small effect size.
Comment: This was a radiographic study; the authors do not present data on the number of cases revised because of glenoid component loosening. The authors do not present data on the relationship of radiographic changes to the comfort and function of the arthroplasty.
The rates of radiographic loosening were not well correlated with glenoid type.
The surgeon cannot control the bone density of the patient. However, when performing shoulder arthroplasty on patients with osteopenia, it would seem important to minimize the amount of glenoid reaming with an attempt to preserve the subchondral bone.
