Femoral Triangle Block With Popliteal Plexus Block Versus Femoral Triangle Block Versus Adductor Canal Block for TKA

In this study we wish to investigate the analgesic effect 3 different nerve block regimes in patients following primary total knee arthroplasty (TKA). All nerve blocks were performed as single shot blocks with the administration of Marcain 5 mg/ml.

Regime A: proximal Femoral Triangle Block (FTB) with 10 ml including Intermediate Femoral Cutaneous Nerve Block (IFCNB) with 5 ml + Popliteal Plexus Block (PPB) with 10 ml.

Regime B: proximal FTB with 10 ml including IFCNB with 5 ml.

Regime C: Adductor Canal Block (ACB) with 25 ml.

The Adductor Canal Block (ACB) is frequently used after TKA, but it is limited to provide anesthesia from the anteromedial part of the knee region. The proximal Femoral Triangle Block (FTB) is also used for TKA, and also limited to provide anesthesia from the anterior medial part of the knee joint. The FTB anesthetize the saphenus nerve, the nerve to vastus medialis, and may anesthetize the medial femoral cutaneous nerve which innervates the distal medial thigh as well as the anteromedial knee region. We included the Intermediate Femoral Cutaneous Nerve block (IFCNB) in the FTB, as the nerves can be targeted in the subcutis on the anterior thigh and easily be anesthetized during the same procedure as FTB. IFCNB anesthetize the distal anterior thigh, which may include the proximal part of the surgical incision for TKA. In the following text the proximal FTB including IFCNB will be refered as "FTB" and the dose of 15 ml will refer to 10 ml for the proximal FTB and 5 ml used for the IFCNB.

A new nerve block technique, called Popliteal Plexus Block (PPB), is specifically designed to anaesthetize nerves involved in innervation of the back of the knee joint. The analgesic effect of PPB has not yet been evaluated in randomized, controlled, blinded trials. In order to optimize pain treatment for primary TKA by improving the pain-relieving effect of peripheral nerve blocks, we aim to evaluate the analgesic effects of three different nerve block regimens (FTB + PPB versus FTB versus ACB) after primary unilateral TKA. Our outcomes include postoperative pain scores, opioid consumption, muscle strength and mobilization.

Our hypothesis is that the combination of FTB + PPB provides superior postoperative pain treatment after TKA in comparison to both FTB or ACB. The combination of FTB + PPB will reduce opioid consumption (primary outcome) and postoperative pain scores without reducing muscle strength or impairing mobilization.

Eligibility Criteria:
Inclusion Criteria:

* Scheduled to undergo primary total knee arthroplasty in spinal anesthesia
* Able to perform a Timed Up and Go (TUG) test
* Age \> 50 years old
* Ability to give their written informed consent to participating in the study after having fully understood the contents of the study
* American Society of Anesthesiologists (ASA) physical status 1, 2, or 3

Exclusion Criteria:

* Patients who cannot cooperate
* Patients who cannot understand or speak Danish.
* Patients with allergy or intolerance to the medicines used in the study
* Patients with a daily intake of strong opioids (morphine, oxycodone, ketobemidone, methadone, fentanyl)
* Patients suffering from alcohol and/or drug abuse - based on the investigator's assessment
* BMI \> 40
* Diagnosed with chronic central or peripheral neurodegenerative disorders