After many patients, some of whom were unexpectedly young, had presented with medial migration of the hemi-prosthetic head and erosion of the glenoid, we decided 2 years ago to do preoperative DEXA on all shoulder replacement patients. The aim was first to determine normal bone mineral density (BMD) of the glenoid and secondly to predict which patients would be at risk.

We used the same DEXA method as for the hip. The glenoid was divided into three areas, numbered R1, R2 and R3, and we determined BMD in each of them.

Preliminary studies showed that patients fell into two groups. In one, BMD in the R2 and R3 areas was in the range 0.3 to 0.5. Most often the patients in this group were younger or had acute trauma and the contralateral shoulder was not pathological. BMD in the other group was in the range 0.9 to 1.3. Nearly all patients with OA of the shoulder fell into this group.

In this ongoing study, patients are followed up annually with clinical examination and standard radiographs. Follow-up to date has only been 2 years. So far no medial migration of the hemi-prosthetic head has been noted in patients in the group with BMD between 0.9 to 1.3.