Background and Objectives. This investigation was designed to evaluate combined spinalepidural anesthesia with a needle-through-needle technique using two different needle sets. One kit has a standard 16-gauge Tuohy needle and a 26-gauge spinal needle that extends 13 mm beyond the tip of the Tuohy needle (set A). The other kit consists of a 16-gauge Tuohy needle with an aperture in its curve (back hole) for the insertion of a 26-gauge spinal needle that protrudes 10 mm beyond the tip of the epidural needle (set B).

Methods. Combined spinal-epidural anesthesia was used in 40 consecutive consenting patients scheduled for elective total knee arthroplasty who were randomized into two groups. Needle set A was used in group A, and needle set B was used in group B. Special attention was paid to difficulties in performing the blocks and to any complications of the technique.

Results. The length of the spinal needle was inadequate in 15% of patients from group B, whereas the length in group A was adequate in all. The aperture on the back of the Tuohy needle from group B provides a better “feel” of dural puncture. There was no difficulty in the insertion of the epidural catheter. There was no evidence of subarachnoid placement of the epidural catheter in either group. None of the patients had unexpectedly extensive spinal block. No patient developed postdural puncture headache. All patients had adequate surgical anesthesia. Infusion of bupivacaine (0.1%) with fentanyl (2 μg/mL) provided adequate postoperative analgesia. No respiratory depression was noted.

Conclusions. Combined spinal-epidural provides satisfactory surgical and postoperative analgesia for total knee arthroplasty. An improved needle set for the needle-through-needle technique would be one with a modified Tuohy needle having an aperture at the back and a spinal needle protruding more than 13 mm beyond the Tuohy needle.