Radiographic findings in patients suspected of subacromial impingement syndrome: prevalence and reliability

Abstract

Objective: Aims were to (i) report prevalence and (ii) evaluate reliability of the radiographic findings in examinations of patients suspected of subacromial impingement syndrome (SIS), performed before a patient's first consultation at orthopaedic department.

Materials and methods: This cross-sectional study examined radiographs from 850 patients, age 18 to 63 years, referred to orthopaedic clinic on suspicion of SIS. Prevalence (%) of radiographic findings were registered. Inter- and intrarater reliability was analysed using expected and observed agreement (%), kappa coefficients, Bland-Altman plots, or intraclass coefficients.

Results: A total of 850 patients with a mean age of 48.2 years (SD = 8.8) were included. Prevalence of the radiographic findings was as follows: calcification 24.4%, Bigliani type III (hooked) acromion 15.8%, lateral/medial acromial spurs 11.1%/6.6%, acromioclavicular osteoarthritis 12.0%, and Bankart/Hill-Sachs lesions 7.1%. Inter- and intrarater Kappa values for most radiographic findings ranged between 0.40 and 0.89; highest values for the presence of calcification (0.85 and 0.89) and acromion type (0.63 and 0.66). The inter- and intrarater intraclass coefficients ranged between 0.41 and 0.83; highest values for acromial tilt (0.79 and 0.83) and calcification area (0.69 and 0.81).

Conclusion: Calcification, Bigliani type III (hooked) acromion, and acromioclavicular osteoarthritis were prevalent findings among patients seen in orthopaedic departments on suspicion of SIS. Spurs and Bankart/Hill-Sachs lesions were less common. Optimal reliabilities were found for the presence of calcification, calcification area, and acromial tilt. Calcification qualities, acromion type, lateral spur, and acromioclavicular osteoarthritis showed suboptimal reliabilities. Newer architectural measures (acromion index and lateral acromial angle) performed well with respect to reliability.

Keywords: Impingement; Prevalence; Radiograph; Reliability; Shoulder.

Fig. 1

Standard projections. Anterior–posterior projections with humerus in external rotation (A) and internal rotation (B) and outlet view (C)

Fig. 2

Subacromial calcification

Fig. 3

Lateral spurs in three different patients—bird beak type (A + B) and heel type (C)

Fig. 4

AC-joint arthritis with narrowing of joint and spurring of medial acromion

Fig. 5

Acromion types. Type I—flat (A). Type II—curved (B). Type III—hooked (C)

Fig. 6

Medial acromion spurs

Fig. 7

Architectural measures. Acromial tilt (A). Lateral acromial angle (B). Acromion index (C)

Fig. 8

Flowchart of the study

Fig. 9

Architectural measures and calcification size: Bland–Altman plots with limits of agreement and intraclass correlation coefficients