We've known for some time that cFNB produces pain relief comparable to continuous lumbar epidural analgesia. [4-5] But subjects who receive cFNB are less likely to suffer side effects such as nausea, vomiting, itching, and hypotension. [4-5] The selectivity of cFNB preserves function in the non-operative limb, which may aid in early ambulation. Patients also benefit from early removal of their urinary catheters, since these are not indicated for cFNB. Using cFNB instead of eipdurals also avoids the potentially disastrous complication of epidural hematoma.  Most importantly, patients receiving adequate pain relief from cFNBs can be discharged to home.
That said, cFNBs are not perfect. Some patients with cFNBs alone still experience posterior knee pain and require IV opioids or even sciatic nerve blocks during the early post-op period, [3, 7-9] and will not qualify for early discharge. Using ambulatory perineural infusion requires a concerted effort from the surgical, paing management, pharmacy, nursing, and physical therapy teams. It also requires social preparedness; we never discharge a patient with a continuous nerve block catheter unless there's a caregiver who can assist with ambulation, transportation, and catheter management.
Cutting the post-op stay by two days leads to significant hospitalization cost savings.  Though we lose two days' revenue, we free up beds and can do more surgery as a result.
If your facility performs a high volume of TKA and the average post-op stay is 4 days or more, an integrated patient care program including continuous peripheral nerve blocks may help speed patient discharge while improving the quality of recovery and potentially reducing costs.
Dr. Mariano is Associate Clinical Professor of Anesthesiology and Chief, Division of Regional Anesthesia and Acute Pain Medicine, University of California, San Diego Medical Center.