Controlling Pain After a Total Hip Replacement

Patients are surprised after a total hip replacement by how much it can hurt those first few days. They do okay while sitting or resting, but once they get up to move: ouch! Surgeons are working hard to find ways to control that pain without using opioids (narcotics) with their many side effects.

A new approach has been started by some surgeons. That’s the use of nerve blocks for the first 24 to 48 hours after surgery. In this study, three types of post-operative pain control methods were compared. The first was the standard patient-controlled analgesic (PCA) using a self-administered pain pump. With the push of a button patients can dispense an opioid-based medication. In this study, they used a morphine derivative called hydromorphone.

The second group had a femoral nerve block along with PCA. The third group had a lumbar plexus block (also with PCA). All drugs were given for 48 hours. The nerve block was set up in the operating room after the spinal anesthetic that was used during the hip replacement surgery had worn off.

The block is administered by placing a needle (catheter tip) between the psoas muscle and the quadratus lumborum muscle in the hip area. This places the catheter tip close to the nerve being blocked and is referred to as a perineural placement of the catheter.

Correct placement of the needle was verified by injecting a dye in the area and using an X-ray to confirm proper positioning. The surgeons also used a second method to check the catheter. They connected the catheter to a nerve stimulator. By stimulating the nerve, they could cause a contraction of the muscle controlled by that nerve.

In this way, they made sure the right area was blocked. After that test was completed and the nerve stimulator was removed, then a one-time large dose of drug was injected in the area. The perineural catheter was used to infuse a low dose of numbing agent (ropivacaine) for the next 48 hours.

With a successful nerve block, the patients experienced a numb sensation (to cold and to pinprick) in the skin supplied by the sensory portion of the nerve being blocked. Muscle strength for the muscles affected by blocking the motor portion of the nerve(s) was also assessed. Most often the muscles controlling the hip and knee were affected.

Everyone in all three groups also got an injection of ketorolac while still in the recovery room. This nonsteroidal antiinflammatory was delivered directly to the muscles for pain control.

The real test of these pain control measures was in physical therapy. Pain was measured before, during, and after therapy while moving the hip and walking. Amount of hydromorphone used was recorded. And any side effects such as nausea, vomiting, itching, difficulty breathing, or delirium were also noted.

The authors report the best results occurred when using the lumbar plexus block. As suspected, pain control while at rest wasn’t the issue. The real problem came when patients tried to move the hip. Patients who had the lumbar block had less pain. With less motor block they could walk farther. And they used less hydromorphone for successful pain control, so there were fewer side effects preventing movement. And in the lumbar plexus block group, twice as many patients as in the femoral nerve block group used no opioid at all for the entire 48-hour test period.

The use of PCA alone was linked with more serious cases of delirium or confusion. The PCA group also suffered more negative side effects compared to the groups receiving PCA with a nerve block. Opioid-related side effects were more common in the femoral nerve block compared with the lumbar plexus group. Patients in the lumbar plexus group also rated their satisfaction higher than patients in the other two groups.

The authors made note of the fact that these post-anesthesia blocks were performed in a special care unit in the hospital. This makes it possible to move patients along without holding up the operating room for the next patient. This may be important for private hospitals with concern for improving efficiency and cost-cutting measures (compared with university or teaching hospitals).

In either setting, the use of continuous nerve blocks after surgery for a total hip replacement was quite successful. Continuous lumbar plexus block combined with PCA seems to offer better pain control and faster return of function than PCA alone or with femoral nerve block with PCA.