The purpose of this study was to investigate the value of 3DCT for arthroscopic subacromial decompression and the relationship between subacromial spur and rotator cuff tears. 96 shoulders with rotator cuff tears, 59 men 37 women, were evaluated by computed tomography pre and post arthroscopic rotator cuff repairs. The average age at operation was 64.8 years old (range 41-83). Subacromial spur was classified into 5 grades according to their size. Preoperative CTs showed that all of subacromial spur was located along coracoacromial ligament, and bottom aspect of acromion was like double floor. There were 0 grade 0, 48 grade 1, 24 grade 2, 24 grade 3, 0 grade 4 in preoperative CTs. 3 dimension computed tomography enabled us to evaluate more accurately than X-rays. There were 28 partial tears, 12 small tears, 21 medium, 14 large, 21 massive in size of tears. Higher grade of CT classification was larger tear and elder patient significantly, and in grade 3, 58% was large or massive tears. Otherwise, there was no relationship between subacromial spur and sex, duration of symptom, trauma. Preoperative 3DCT was useful for understanding range of decompression. Subacromial spur correlated with tear size and age significantly.
