The influence of patient position on withdrawal force of lumbar epidural catheters after total knee arthroplasty: A randomized trial

Study objective Elderly patients with degenerative knee disease may have accompanying degenerative spine conditions. There are no studies on lumbar epidural catheter withdrawal forces in these patients. The aim of this study was to investigate withdrawal forces and possible associated risk factors in patients undergoing total knee arthroplasty (TKA). Design Prospective randomized trial. Setting Operating room and ward in a university hospital. Patients Seventy-eight patients aged 65 to 80 years who were undergoing TKA and combined spinal epidural anesthesia were enrolled. Interventions Lumbar epidural catheterization was performed in a lateral position before surgery and the patients were randomly allocated to one of 3 positions for removal: flexed lateral (L), prone (P), and sitting (S). On the third postoperative day, the lumbar epidural catheters were removed by a single investigator with the patient in the assigned position. Measurements We measured the peak tension during catheter withdrawal and evaluated the factors affecting peak tension. Main results The forces required to remove the catheters were considerably greater in the sitting and prone than in the flexed lateral position: group P (3.9 N [0.28-10.36]), group S (4.1 N [0.04-11.57]), and group L (1.3 N [0.07-3.65]) (P <.001). There was a positive correlation between the length of catheter in the epidural space and peak tension (P =.0026, β coefficient =.223). Conclusions For ease of removal of catheters from the lumbar epidural space, the flexed lateral position is recommended for elderly patients undergoing TKA. When placing the epidural catheter, the physician should be careful not to insert a catheter that is excessively long.