The subacromial space was measured, in the true AP view, from the dense cortical bone marking the inferior aspect of the acromion at a point directly above the humeral head and recorded as the smallest distance between this point and the articular cortex of the humeral head, as suggested by Petersson and Redlund-Johnell [13]. Magnification was estimated as 11%. All patients with hyperkyphosis and 16 volunteers were submitted to right shoulder CT evaluation too, in order to verify X-ray measurement reliability.

Subacromial space of our patients with hyperkyphosis was narrower than that of controls (Table 1). Gender and age did not influence this result. It is plausible that narrowness of the subacromial space may be attributed to the less posterior tilting of the scapula. This hypothesis is supported by Kebaetse and coworkers’ study [14]. Authors observed that patients with a slouched posture have less posterior tilt and less upward rotation of the scapula with respect to trunk-erect subjects, and that this anomalous orientation of the acromion may create a bony block that causes, or contributes to, impingement pathology with repetitive overhead activity. Our data confirmed Petersson’s method. Mean CT measure was slightly less than that calculated on X-ray radiographs. This could be due to the fact that the CT exam was performed with the patient in the supine position; therefore, the superior limb did not suffer from gravity effect. Another possible explanation might be that hyperkyphosis may slightly decrease in the supine position, thus decreasing antetilting. Imaging also confirmed that subacromial space is wider in males than in females and decreases with increasing age. Our patients with thoracic hyperkyphosis greater than 50° had a subacromial space lesser than that measured in patients with a less severe kyphosis (Fig. 2a–d). This suggests that subacromial width is directly related to severity of thoracic kyphosis. Since hyperkyphosis of patients with osteoporotic vertebral fractures may make it worse over time, due to possible occurrence of new vertebral fractures, subacromial decompression could give only temporary shoulder pain relief.