A 68-year-old man with a 5-year history of lumbar spinal stenosis presents with progressive bilateral leg pain and claudication. Imaging shows severe stenosis at L4–L5 with facet hypertrophy and ligamentum flavum thickening. He has failed conservative management for 6 months. During preoperative assessment, he is found to have a serum creatinine of 1.8 mg/dL and eGFR of 35 mL/min/1.73 m². Which of the following is the MOST appropriate next step in his management?