Shoulder impingement: relationship of clinical symptoms and imaging criteria

To establish, in patients with subacromial impingement syndrome, (1) the relationship between pain and shoulder function, as determined by the Constant score, and morphological findings, as determined by radiographs and magnetic resonance imaging (MRI) and (2) the relationship between acromial shape and minimum acromiohumeral distance (AHD).

Cross-sectional study.

Tertiary care center.

Forty-seven patients (33 males and 14 females; mean age, 51.7 years) with unilateral subacromial impingement syndrome who had failed to respond to conservative therapy for at least 6 months.

The Constant score was determined preoperatively; acromial shape (type I, flat; type II, curved; and type III, hooked) was evaluated on preoperative outlet view radiographs and oblique sagittal T1-weighted MRIs; AHD was evaluated on preoperative anteroposterior radiographs and oblique coronal T1-weighted MRIs.

Correlation coefficients and the simple kappa statistic were calculated. Student t test and mean differences with 95% confidence limits were reported for group comparisons.

The Constant score was fairly correlated with AHD (r = 0.39, P < 0.01) but not with acromial shape. Patients with an AHD < or =7 mm on MRI scored significantly lower than those with an AHD >7 (mean difference, 18.5; P < 0.01). Acromial shape and AHD were not correlated, neither on radiographs nor on MRI.

AHD seems to better reflect the clinical status of patients with subacromial impingement, but without rotator cuff tears, than acromial shape. Acromial shape is not a good descriptor of subacromial space narrowing.