Pilot Study on Pain and Sensation After Regional Anesthesia for Total Hip Arthroplasty

The Quadratus Lumborum block (QLB) is a newer regional analgesic technique that may be as effective as Lumbar Plexus blocks (LPB) at providing pain control following direct anterior approach (DAA) hip arthroplasty. The purpose of this study is to collect pilot data to help the design of a future randomized study, comparing a QLB to a LPB for DAA procedures. The investigators will assess for spinal resolution below the level of L5/S1 by assessing the presence of pin prick sensation at these levels. This will help determine if pain scores collected at 6hrs reflect analgesia provided by the preoperative LPB alone or if the data is confounded by the presence of spinal anesthesia. This data will help us determine if 6hrs is a feasible primary endpoint to assess pain scores. Additionally, assuming that spinal regression is complete by 6hrs, the VAS pain scores obtained will then be used to perform a power analysis to determine the necessary study size when comparing QLB to LPB for DAA hip arthroplasty.