This Clinical Trial is being conducted to study an adjunctive treatment for rotator cuff repair; bone trephination."Trephination" is a procedure that involves making small perforations in the bone that the tendon is repaired to.The rotator cuff is repaired by sewing the tendon down to the bone in the shoulder. Trephination is a new technique that is used in addition to the standard method of repairing the rotator cuff tendon. The control group will undergo the standard repair for rotator cuff tears.

It is the investigators' hypothesis that healing rates in patients who undergo bone trephination will be higher compared with surgery without trephination in arthroscopic rotator cuff repair at 24 months post-operatively.

Rotator cuff repair carried out with current techniques has shown favourable results in terms of pain relief. However the re-tear rates remain high and are associated with significant morbidity in terms of functional outcome and shoulder strength. As rotator cuff disease becomes ever more prevalent with our aging population, it is imperative to determine if healing rates can be improved with autologous stem cell enhancement with pre-surgical preparation of the tendon insertion site through trephination. This trial is necessary both to provide optimal care of our patients, and to do so in a fiscally responsible fashion.

The primary outcome measure the re-tear rate as measured by ultrasound at 24 months post-operatively.

The secondary outcome measures are Western Ontario Rotator Cuff Index (WORC), Constant Score, and the American Shoulder and Elbow surgeons standardized assessment of shoulder function (ASES).

Inclusion Criteria:

1. Patients who have failed standard non-surgical management of their rotator cuff tear, and who would benefit from a surgical repair of the cuff.

   Failed medical management will be defined as persistent pain and disability despite adequate standard non-operative management for 6 months. Medical management will be defined as:

   1. The use of drugs including analgesics and non-steroidal anti-inflammatory drugs
   2. Physiotherapy consisting of stretching, strengthening and local modalities (ultrasound, cryotherapy, etc)
   3. Activity modification

2. Imaging, and intra-operative findings confirming a full thickness tear of the rotator cuff.

Exclusion Criteria:

1. Characteristics of the cuff tear that render the cuff irrepairable:

   fatty infiltration in the muscles grade III (50%) or greater; superior subluxation of the humeral head; retraction of the cuff to the level of the glenoid rim.

2. Partial thickness cuff tears.

3. Significant shoulder comorbidities e.g. Bankart lesion, osteoarthritis

4. Previous surgery on affected shoulder e.g. Previous rotator cuff repair.

5. Isolated subscapularis tendon tears

6. Active joint or systemic infection

7. Significant muscle paralysis

8. Rotator cuff tear arthropathy

9. Charcot's arthropathy

10. Significant medical comorbidity that could alter the effectiveness of the surgical intervention (eg. Cervical radiculopathy, polymyalgia rheumatica)

11. Major medical illness (life expectancy less then 1 year or unacceptably high operative risk)

12. Unable to speak or read English/French

13. Psychiatric illness that precludes informed consent

14. Unwilling to be followed for 24 months

15. Advanced physiologic age