Tendon tears that have been left for a long period of time can result in atrophy or wasting of the muscle to which they attach and this can be extensive. The final phase of atrophy involves replacement of the muscle with fatty fibrous tissue and once this occurs the muscle has a very poor chance of functioning again. Long standing tears can also result in arthritic change in the shoulder and once arthritis has set in, the rotator cuff tear repair will often not be successful in relieving the symptoms of pain and dysfunction. Significant arthritic change will often be a contra-indication to performing a repair of the rotator cuff.
Patient compliance can also be a factor. The repair is a temporary reattachment of the tendon to the bone and long term success of the repair relies of the healing process to occur between the tendon and the bone. If the repair of the tendon is subjected to too much stress then it can fail as with any mechanical structure. The repair relies on sutures to reattach the tendon to the bone, these sutures can break if they are put under too much strain or they can dislodge from the bone or tear through the tendon itself. Close observation of the recommended precautions following surgery is important to prevent failure of the surgical repair.
Normally improvement in pain and function of the shoulder is experienced by 6 months following the surgical procedure, occasionally it takes longer.