The humerus, glenoid, scapula, acromion, clavicle and surrounding soft tissues make up the shoulder. There are three significant articulations: the sternoclavicular joint, the acromioclavicular joint and the glenohumeral joint. The glenohumeral joint is the most commonly dislocated major joint in the body.
Ligaments and surrounding musculature, including the rotator cuff muscles, contribute to shoulder joint stability. The rotator cuff is composed of the four muscles: supraspinatus, infraspinatus, teres minor and subscapularis that interlock to function as one unit. These muscles help with internal and external rotation of the shoulder and importantly depress the humeral head against the glenoid as the arm is elevated. The tendons join together to form one tendon, the rotator cuff tendon. This passes through the subacromial space. The subacromial bursa, which has a large number of pain sensors, fills the space between the acromion and the rotator cuff tendon. [ 1 ]
Webster and Walker (2006) examined the safety and effectiveness of prolonged low-dose, continuous intravenous (IV) or subcutaneous ketamine infusions in non-cancer outpatients. A total of 13 outpatients with neuropathic pain were administered low-dose IV or subcutaneous ketamine infusions for up to 8 weeks under close supervision by home health care personnel. Using the 10-point VAS, 11 of 13 patients (85 %) reported a decrease in pain from the start of infusion treatment to the end. Side effects were minimal and not severe enough to deter treatment. Prolonged analgesic doses of ketamine infusions were safe for the small sample studied. The authors concluded that these findings demonstrate that ketamine may provide a reasonable alternative treatment for non-responsive neuropathic pain in ambulatory outpatients. Moreover, the authors stated that additional studies should follow to ascertain optimal dose and duration for specific pain disorders and to minimize side effects. They also noted that questions regarding which patients would be most susceptible to this type of therapy and when treatment should be instituted remain unanswered.