Abstract
Introduction
Peri-articular local anesthetic injections reduce post-operative pain in total knee arthroplasty and assist recovery. It is inconclusive whether intra-operative injection of peri-articular morphine is locally effective. The aim of this study is whether the addition of morphine to peri-articular injections in only unilateral knee improves post-operative pain, range of motion, swelling in patients with simultaneous bilateral total knee arthroplasty.
Materials and Methods
A prospective single-center double-blinded randomized controlled trial was undertaken to assess the local efficacy of adding morphine to intra-operative, peri-articular anesthesia in simultaneous bilateral total knee arthroplasty. Twenty eight patients with 56 TKAs were randomly divided into 2 groups, unilateral TKA with intraoperative peri-articular injection with adding morphine and the other side TKA without adding morphine. The morphine group received an intraoperative, peri-articular injection of local anesthetic (Ropivacaine 150mg), epinephrine (50μg), ketoprofen (25mg) and methylpredonisolone sodium (20mg) plus 0.1mg/kg of morphine. The no-morphine group received the same amount of local anesthetic, epinephrine, ketoprofen and methylpredonisolone sodium without morphine. The operating surgeon, operating staff, patients, physiotherapists, ward nursing staff and data collectors remained blinded for the duration of study. All surgeries were performed by the same operating team. A standard medial parapatellar approach was used in all operations. Post-operative analgesia was standardized to all participants with celecoxib daily for 3 weeks. Primary outcomes included visual analog pain scores (VAS), ROM and swelling of the thigh. Secondary outcomes included WOMAC and adverse outcomes.
Result
There were no significant differences between two groups for pre-operative ROM, pre-operative pain VAS or the circumference of the thigh. There were no statistically significant differences in primary and secondary outcomes between two groups (Figure 1, 2, 3).
Discussion
Multiple studies have demonstrated the clinical efficacy of multimodal peri-articular injection of analgesics in TKA for pain relief. However, the opioids often lead to nausea as an adverse effect, which is reported from 25% to 56%. The mechanism of pain relief by morphine is mainly the efficacy through the opioid receptor in central nerve system, and the other mechanism through local opioid receptor (μ-receptor) is rarely revealed for pain relief. Our study used morphine in unilateral TKA and no-morphine in the other side TKA and showed no significant difference in primary and secondary outcomes. These results revealed that the efficacy for pain relief in peri-articular injection without morphine is the same as that in no-morphine group. In conclusion, adding morphine in peri-articular injection could not be locally effective for pain relief.
