Retrograde drain-based analgesic cocktail injection for pain control and early mobilization after total knee arthroplasty: a prospective observational study.

BACKGROUND: Effective postoperative pain management is essential for enhanced recovery following total knee arthroplasty (TKA). Although the routine use of drains in TKA is declining, they can provide a sterile conduit for local analgesic administration. Multimodal analgesia is widely used, but optimal delivery methods remain under evaluation. This study investigates the efficacy and safety of retrograde drain-based injection of an analgesic cocktail for early pain relief and mobilization after TKA. METHODS: A prospective observational study was conducted in 30 patients undergoing primary unilateral TKA at a single center between January and June 2024. All surgeries were performed under spinal anesthesia without peripheral nerve blocks or periarticular infiltration. Following wound closure and drain placement, a multimodal cocktail (bupivacaine, ketorolac, dexamethasone, normal saline; total 30 mL) was injected retrogradely via the drain, which was then clamped for two hours. Visual Analog Scale (VAS) pain scores were recorded at 6, 12, 24, and 48 h postoperatively. Functional outcomes included time to first mobilization, active knee range of motion (ROM) on day 3, and quadriceps activation by straight leg raise (SLR). Safety outcomes were drain-related complications assessed up to two weeks postoperatively. RESULTS: Mean VAS scores were 2.6 ± 0.9 at 6 h, 3.1 ± 1.1 at 12 h, 3.8 ± 1.0 at 24 h, and 3.5 ± 0.8 at 48 h. The mean time to first mobilization was 15.2 ± 3.1 h. By day 3, the mean active ROM was 78.6° ± 6.4, and quadriceps activation improved from 60.0% on day 1 to 93.3% on day 3. No drain-related infections or hematomas were observed. CONCLUSION: Retrograde injection of a multimodal analgesic cocktail via the drain appears to be a safe and feasible adjunct for postoperative analgesia in TKA, providing encouraging early results in terms of pain control and mobilization. Further controlled studies are warranted to validate its comparative efficacy.