We aimed to test the biomechanically predicted hypothesis that in massive rotator cuff tears irreparable by conventional methods the newly developed Nottingham Augmentation Device (NAD) would provide greater functional improvement than that gained from the gold standard of arthroscopic subacromial decompression. Thirty patients treated between 2001 and 2004 were assessed by pre- and six month post-operative Constant scoring. Fifteen underwent open acromioplasty and cuff reconstruction using the NAD (mean age 67.3), while 15 underwent a standard arthroscopic decompression (mean age 67.4). The two groups were matched retrospectively based on size of cuff tear, age and sex. Data was analysed using the student’s t-test at the 95% confidence interval. Both groups displayed a statistically significant increase in Constant score after surgery. The mean increase for NAD patients was 18.7 points compared with 17.6 points for those undergoing arthroscopic decompression. However there was no significant difference between the two groups’ improvement and this was even so in the power sub-category, where increased benefit was predicted with the NAD. The NAD requires greater surgical access, operating time and peri-operative analgesia, and no active mobilisation for six weeks. The arthroscopic technique is minimal access, rapid, involves no prosthesis or foreign body insertion and allows immediate mobilisation. However, with clear biomechanical benefits of the NAD seen in vitro, our results may simply reflect cuff tears in an older population group with irreversible tissue changes and less rehabilitative potential. A randomised prospective trial in a younger patient group with more acute tears and less tissue atrophy would appear the next step in determining the NAD’s place in the management of massive rotator cuff tears.