Comparison of two concentrations of local anaesthetic for pain relief after shoulder rotator cuff repair

INTERVENTION: 0.4% ropivacaine for continuous interscalene block after rotator cuff repair for 48 hours postoperatively as required by the patient. CONDITION: Pain relief after shoulder rotator cuff repair PRIMARY OUTCOME: Reduced pain after rotator cuff repair, assessed by patient interrogation regarding analgesic consumption and pain scores using numerical rating pain score (NRPS). SECONDARY OUTCOME: Arm numbness/weakness INCLUSION CRITERIA: Patients requiring continuous interscalene analgesia following rotator cuff repair under the care of the two investigators.