Extent of Fatty Infiltration of Lumbar Paraspinal Muscles as a Proxy for Frailty and Its Relationship with Perioperative Outcomes in Patients Undergoing Elective Spinal Surgery. - Kulkarni R; Walton C; D'Amico C; Bertolino M; Silvestre J; Rivas G; Lewis S; Nielsen C; Glaser J; Reitman C; Lawrence J; Ravinsky R (Global spine journal, 2026)