International Spine, Pain & Performance

BACKGROUND: The optimal dosing and delivery strategies for intrathecal ziconotide are debated. Previous research suggests that high volume, low concentration dosing techniques may decrease side effects and enhance analgesic effect. Previous studies that have investigated the effects of diluting ziconotide have examined continuous infusions of the medication through an intrathecal pump. OBJECTIVES: This study investigates the trial phase to determine if diluting the bolus dose leads to improved outcomes. The hypothesis of the authors is that the dilution of ziconotide will improve the trial outcomes. STUDY DESIGN: This single-center, retrospective, case-control study included 62 patients with chronic pain refractory to conservative therapy who received a one-time intrathecal bolus dose of ziconotide. METHODS: The study included 62 patients who received a single outpatient trial dose of ziconotide. The study was approved by an institutional review board. Data were collected from electronic medical records. Doses ranged from a total of 2.5 µg–5 µg in a volume of 0.5 mL–5 mL. The primary endpoints were the number of patients that achieved significant pain relief (>= 50%) and the presence or absence of side effects. Statistical analysis was performed using a c2 test to evaluate side effects and meaningful pain relief and an unpaired, 2-tailed t test to evaluate pain relief percentage. RESULTS: There were no differences in side effects experienced by the patients in the Undiluted Group compared to the patients in the Diluted Group (21% vs 25%; P = 0.679). There were no differences in pain relief in the Undiluted Group compared to the Diluted Group (59% vs 61%; P = 0.880). The mean (SD) pain relief in the Undiluted Group was 46% (± 40%) compared to 51% (± 41%) in the Diluted Group (P = 0.645). A power analysis revealed a 68% power to detect a difference between the groups. LIMITATIONS: These results are limited by the accuracy of the chart review and sample size; therefore, additional investigation may be warranted. CONCLUSION: This study demonstrates there is no substantial difference between diluted and undiluted bolus doses of intrathecal ziconotide in regard to analgesic effect or side effects. KEY WORDS: Ziconotide, analgesic, chronic pain, calcium channel, spinal cord

Chronic knee pain from osteoarthritis (OA) affects a significant proportion of adults over 40. Total knee arthroplasty (TKA) remains the standard for advanced OA, yet up to 20% of patients experience chronic postsurgical pain (CPSP). Genicular nerve radiofrequency ablation (GNRFA) can alleviate pain in those unresponsive to conservative treatments or TKA. However, anatomical variability of the genicular nerves may limit treatment durability. This retrospective, single-center observational study investigated whether using a novel V-shaped active tip needle-which creates larger lesions-could improve outcomes. Fifty patients with symptomatic knee OA or CPSP, who had a ≥50% reduction in pain after diagnostic genicular nerve blocks, underwent GNRFA with a V-shaped active tip needle between September 2020 and January 2022. Pain and function were assessed using the visual analogue scale (VAS) at rest and during movement, Western Ontario and McMaster Universities Arthritis Index (WOMAC), Douleur Neuropathique en 4 Questions (DN4), and EuroQol-5 Dimensions (EQ-5D) at baseline and 1, 3, 6, and 9 months post-procedure. By 6 months, 64% of patients showed ≥50% reduction in VAS pain scores, sustained at 9 months (p<0.0001). Median WOMAC scores improved from 62.0 at baseline to 40.0 at 6 months (p<0.0001). DN4 scores declined from a median of 4.0 at baseline to 2.0 at 6 months and 1.0 at 9 months (p<0.001). EQ-5D scores demonstrated significant enhancement in quality of life (p<0.01). Pain intensity differences at rest and during movement remained substantially improved at 9 months (p<0.0001). GNRFA using a V-shaped active tip needleis a promising intervention for chronic knee pain, offering significant and sustained pain relief and functional improvement. Larger lesions created by the novel needle may overcome anatomical challenges, though further randomized studies are warranted to validate efficacy and safety.