The Effect of Sono-guided Suprascapular Nerve Block Combined With Axillary Nerve Block in Arthroscopic Rotator Cuff Repair: a Randomized Controlled Trial

All procedures described in the present study were approved by the Institutional Review Board of our hospital, and all patients gave written informed consent to participate in the present study. Between November 2012 and July 2013, forty-two patients with rotator cuff tear who had undergone arthroscopic rotator cuff repairs were enrolled in this study. Rotator cuff tears were diagnosed by use of preoperative magnetic resonance imaging (MRI), and the size of a rotator cuff was confirmed at the time of arthroscopic operation. Indication for surgery was symptomatic full thickness rotator cuff tear or partial thickness rotator cuff more than 50% thickness in case of failed conservative therapy. Among them, 21 patients were randomly allocated into group I, and received suprascapular nerve block (SSNB) and axillary nerve block (ANB) with each 10mL ropivacaine. The other 21 patients were allocated into group II, and received SSNB with 10mL ropivacaine and ANB with 10mL normal saline.

For the cases in this study, the inclusion criteria were (1) an definite rotator cuff tear on preoperative MRI which needed repair, (2) accept an arthroscopic surgery including rotator cuff repair, (3) more than 20 years old,(4) accept preemptive regional block and patient controlled analgesia (PCA). Some patients were excluded for the following reasons (1)did not underwent arthroscopic rotator cuff repair (2) stopped PCA before postoperative 48 hours due to associated side effect (3) history of previous shoulder operation or fracture, (4) a concomitant neurologic disorder around the shoulder

Visual analogue scale (VAS) pain score, American Shoulder and Elbow Surgeons (ASES) shoulder score, Constant score, height, and weight, etc were checked preoperatively. All the regional blocks were preemptively performed under sono-guidance. PCA was set at the fixed dose (0.05 ug/kg of loading dose and 0.03ug/min.kg of continuous dose, fentanyl) to remove the effect of variable amount of PCA. VAS pain score, patient's satisfaction (SAT), the percentage of lateral pain of affected shoulder, and Lateral Pain Index (LPI: VAS × the percentage of lateral pain of shoulder ÷ 100) was checked postoperative 1, 3, 6, 12, 18, 24, 36, and 48 hours. VAS pain score was selected from 0 to 10. 0 was no pain and 10 was severe pain that the patient had ever experienced.1 SAT was also selected from 0 to 10. 0 was unsatisfactory and 10 was very satisfactory. The percentage of lateral pain was determined as a value between 0 and 100. LPI was determined as VAS pain score × the percentage of lateral pain of shoulder ÷ 100. Rebound of postoperative pain was confirmed if there had been an increase of VAS pain score after postoperative 1 hour.

Power analysis indicated that a total sample size of 34 patients (17 patients in each cohort) would provide a statistical power of 99% with a 2-sided α level of .05 to detect significant differences in VAS at postoperative 6 hours, assuming an effect size of 1.56 (mean difference: 2.5, standard deviation: 1.6). This was based on the mean and standard deviation of VAS at postoperative 6 hours observed in a pilot study of 20 patients. Double blinded randomization was performed as follows. The 48 patients who had met the inclusion criteria were randomly assigned to 1 of 2 groups depending on the combined ANB. Randomization was performed with a computer random sequence generator by an independent nurse, who prepared a syringe for combined ANB according to the assignment. The patient and all the medical staff who participated in the operation were blinded of the assignment. After this study, according to the exclusion criteria, two patient with no rotator cuff tear and three patient with only rotator cuff fraying who underwent only arthroscopic debridement were excluded from this study. One patient who stopped PCA at postoperative 1 hour was done, too. In the end, the 42 patients were included in this study. Among them, 21 patients belonged to group I, and the other 21 patients belonged to group II.

All the regional blocks were preemptively performed. When the patient was positioned in beach chair position, SSNB and ANB were performed by one anesthesiologist under sono-guidance. 23 gauge spinal needle was used. Just after skin preparation using povidone Iodine solution, a thin layer of sterile ultrasound transmission gel was placed between the ultrasound transducer and the skin. SSNB was done at first and the entry site was the mid point between an anterolateral angle of acromion and medial end of scapular spine. With the linear probe parallel to the scapular spine, the suprascapular notch was identified and the block was performed penetrating the transverse scapular ligament because the scapular nerve and artery were located at the suprascapular notch. Just after the SSNB, ANB was performed and the entry site was the point 1.5 cm medial and 2cm inferior to posterolateral angle of acromion. With the linear probe parallel to the longitudinal axis of the humerus, posterior circumflex artery was identified and the block was done at just above the artery. The color Doppler sonography may be helpful for identifying the arterial structures, but they were sometimes undetectable, and therefore they could be identified by detecting a pulsatile motion.