 The purpose of this study is to compare two medications currently injected intra-operatively to help decrease pain after surgery in patients undergoing a primary total hip replacement THR. The two medications are Exparel bupivacaine liposome injectable suspension plus bupivacaine with epinephrine versus bupivacaine with epinephrine. This study is looking to see if one medication works better than the other in managing post-operative pain after THR. The study hypothesis is that Exparel plus bupivacaine with epinephrine will demonstrate better pain management in THR patients post-operatively. Both medications are FDA-approved for post-operative analgesia. 