Morphine after anterior cruciate ligament reconstruction: pain reduction did not exceed the MCID

A retrospective analysis of prospectively collected data at a sports surgery center compared two analgesic protocols after primary isolated anterior cruciate ligament reconstruction. Each matched group included 556 patients. The opioid group received oral morphine sulfate as needed in addition to multimodal analgesia; the non-opioid group received multimodal analgesia alone. Listed components of multimodal analgesia included paracetamol, nefopam, and ketoprofen.

Key findings

Adding morphine was associated with lower pain scores during the first 3 postoperative days. On day 0, visual analogue scale (VAS) scores were 5.6 ± 2.7 in the non-opioid group (n = 536/556) versus 5.3 ± 2.7 in the opioid group (n = 522/556; p = 0.0339). On day 1, the corresponding values were 5.2 ± 2.4 (n = 545/556) and 4.8 ± 2.4 (n = 543/556; p = 0.0014).

Dizziness on day 0 was more frequent without morphine: 100/536 patients (18.7%) versus 70/522 (13.4%; p = 0.0236). There was a trend toward more complications in the non-opioid group: 11/556 (2.0%) versus 3/556 (0.5%; p = 0.0558), mainly due to Cyclops syndrome and knee stiffness. Reoperation rates were similar (p > 0.05).

Clinical relevance

Despite statistical significance, the mean difference in VAS scores did not exceed the minimal clinically important difference (MCID). Lower pain scores therefore should not be equated with an established clinically important benefit from adding morphine.