Is L2 paravertebral block comparable to lumbar plexus block for postoperative analgesia after total hip arthroplasty?

Background: Continuous lumbar plexus block (LPB) is a well-accepted technique for regional analgesia after THA. However, many patients experience considerable quadriceps motor weakness with this technique, thus impairing their ability to achieve their physical therapy goals.
Questions/purposes: We asked whether L2 paravertebral block (PVB) provides better postoperative analgesia (defined as decreased postoperative opioid consumption and lower pain scores), better preservation of motor function, and decreased length of hospital stay (LOS) compared to LPB in patients undergoing THA.
Methods: Sixty patients undergoing minimally invasive THA under standardized spinal anesthesia were enrolled in this randomized controlled study. After exclusions, 53 patients were randomized into the L2 PVB (n = 27) and LPB (n = 26) groups. Patient-controlled analgesia was available for 24 hours. Motor and pain assessments were performed in the recovery room and at the end of 24 hours. LOS was also noted.
Results: Postoperative opioid consumption during the first 24 hours was less in the LPB group (mean ± SD: 24 ± 15 mg morphine) than in the L2 PVB group (32 ± 15 mg morphine; p = 0.005); however, postoperative pain scores were not different between groups. Postoperative motor and rehabilitation outcomes and LOS were also similar.
Conclusions: Our study demonstrates that use of a LPB results in slightly less morphine consumption but comparable pain scores when compared with continuous L2 PVB. No difference was noted in terms of motor preservation or LOS. Although the difference in morphine consumption was only slightly in favor of the LPB group, the advantage of L2 PVBs noted by previous authors as preservation of motor function, was not seen. At our institute where LPBs have been performed for years, there seems to be no real advantage in switching to L2 PVBs. However, L2 PVB could be a reasonable alternative for operators who are wary of LPBs due to their high potential for complications and/or requiring advanced skills for its placement. But, since L2 PVBs are relatively new, not much is known about their complication profile. We recommend a thorough understanding of both techniques before attempting to place them.
Level of Evidence: Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.