Optimal analgesia after TKR is essential for reducing postoperative complications, and improving patient recovery and satisfaction (8). The inclusion of opioids in pain management protocols increases the risk of complications and adverse events, particularly pronounced in elderly osteoarthritic patients (9). This is the rationale for the introduction of multimodal, opioid-sparing pain protocols after TKR. The results of this prospective randomized study demonstrate that a multimodal opioid-sparing protocol after TKR can provide better postoperative pain control, greater range of motion of the operated knee, and reduce opioid consumption than a traditional opioid-containing protocol and a traditional opioid-containing protocol with LIA added.
In the present study, statistically significant lower postoperative pain score was observed in the opioid-sparing cohort compared with the traditional cohorts at each postoperative time point. Previous studies have reported equivalent pain control after TKR with both opioid-sparing and opioid-based pain management protocols (9,10). This discrepancy could be due to differences in surgical procedures or pain management protocols. Multimodal analgesia includes preoperative, intraoperative, and postoperative analgesic regimens that target numerous pain pathways, and aim to maximize analgesic efficacy while minimizing adverse side effects. Multimodal analgesia was first introduced by Wall in 1988 (11). Currently, there are various protocols with different combinations of different types of drugs, their dosages and routes of administration, which have different results in terms of efficacy compared to other analgesic protocols. The pain protocol in our study consists of pre-emptive analgesia combined with spinal anesthesia and local infiltration analgesia. Pre-emptive analgesia is an anti-nociceptive intervention that starts before the surgical procedure, and usually combines paracetamol, cyclooxygenase-2 inhibitors, and pregabalin because of their synergistic analgesic effects (2). In our study, the same drugs were used, but only in oral dosage form. Local infiltration analgesia has emerged as an alternative postoperative analgesic regimen for femoral nerve blockade without affecting quadriceps muscle strength (12), adductor canal blockade with significantly better postoperative pain control (13) and epidural anesthesia with less frequent adverse effects, such as urinary retention, hypotension and motor blockade (14). Nevertheless, there is still no consensus on the optimal composition and infiltration technique of LIA. Usually, LIA cocktails consist of levobupivacaine or ropivacaine, ketorolac, morphine and adrenaline diluted with saline to a total volume of 80 to 150 ml (2). In our study, only levopubivacaine diluted in saline was used. Liposomal levobupivacaine, ropivacaine and ketorolac are not approved as drugs in our country. In our institute, adrenaline is excluded from LIA cocktails because of the lack of benefits and possible adverse effects of adrenaline in LIA mixtures according to TKR (15,16).
The results of the study show that the opioid-sparing pain management protocol significantly reduces the consumption of opioids for breakthrough pain in the first 10 days after surgery. These results are consistent with those of Padila et al. and Post et al. (9,17). In the Peters et al. study, significantly lower narcotic consumption was found for the opioid-sparing cohort undergoing total hip arthroplasty, whereas consumption was similar in patients undergoing TKR (18).
We found that the multimodal opioid-sparing approach minimized overall opioid consumption, but the rate of adverse events after TKR did not differ between the two groups. No adverse event related to local anesthetic or cyclooxygenase-2 inhibitor toxicity was noted. While Peters et al. (18) found similar results, Post et al. (17) and Padila et al. (9) reported a reduction in adverse effects in opioid-sparing cohorts, including nausea, vomiting, pruritus, constipation and dizziness, which can negatively affect patient well-being and early postoperative rehabilitation.
The rehabilitation program is an important component of postoperative recovery. Early mobilization after TKR may result in better functional outcomes and reduced morbidity (19). It follows that assessment of range of the motion is important to ensure early mobilization after TKR (20). There are many factors, such as preoperative ROM, soft tissue status, alignment of the knee, muscle strength of the knee, psychological condition, and surgical procedure, that affect the postoperative ROM (21,22). These aspects were not investigated in this study. One of the most important factors influencing ROM is probably postoperative pain. This assumption can be confirmed by the results of this study. It was found that ROM of the subjects in the multimodal opioid-sparing cohort performed significantly better than the traditional cohorts due to better pain control at both measurement time points.
Limitation
This study has several limitations that may represent potential bias. The study was conducted at a single institution, but 5 different orthopedic surgeons were involved in the TKR. Although the surgeons underwent standardized training in the proper use of LIA, the method of LIA administration may vary, and the efficacy of the periarticular injections is highly dependent on technique. Another limitation is that patient-reported pain scores are subjective and individual characteristics affecting pain perception may vary among patients. Finally, this study was limited to inpatient pain management. No post-discharge pain analysis was performed.
The strength of this study is its prospective nature with randomization to equal comparison cohorts with similar demographic characteristics. In addition, to reduce bias in the analysis of total opioid use, we did not include patients with chronic preoperative opioid use.