This study will compare two regional anesthesia strategies for pain management after total knee arthroplasty in adults. Both strategies use an adductor canal block (ACB) to provide analgesia while preserving quadriceps muscle strength. The ACB is then combined with either a sacral erector spinae plane block (S-ESPB) or an iPACK (infiltration between the popliteal artery and the posterior capsule of the knee) block to improve posterior knee analgesia.

All patients will receive an ultrasound-guided adductor canal block with 20 mL of 0.2% ropivacaine. They will then be randomly assigned to one of two groups:

Group 1: ACB combined with a sacral erector spinae plane block (S-ESPB) using 20 mL of 0.2% ropivacaine.

Group 2: ACB combined with an iPACK block using 20 mL of 0.2% ropivacaine. Both techniques aim to provide effective postoperative analgesia while minimizing motor blockade and allowing for early mobilization. It is not known whether combining ACB with S-ESPB or with iPACK provides superior pain control, reduces opioid requirements, or results in better functional recovery after total knee arthroplasty.

The main purpose of this study is to compare the time to first rescue analgesia and overall postoperative pain control between the two regional anesthesia strategies. The study will also evaluate opioid consumption, motor function, functional mobility, side effects, and block-related complications.

We hypothesize that both combinations will provide effective analgesia, but their impact on pain intensity, duration of analgesia, and functional recovery may differ.

Total knee arthroplasty (TKA) is associated with significant postoperative pain, which can limit early mobilization, delay rehabilitation, and increase opioid use. Inadequate pain control may lead to complications such as decreased range of motion, prolonged hospitalization, and reduced patient satisfaction. Regional anesthesia techniques are a cornerstone of multimodal analgesia protocols for TKA.

The adductor canal block (ACB) is a motor-sparing technique that targets the saphenous nerve and nerve to vastus medialis while largely preserving quadriceps strength. However, ACB alone may not provide sufficient analgesia for posterior knee structures. To address this limitation, it is often combined with other blocks that target posterior knee innervation.

The iPACK (infiltration between the popliteal artery and the posterior capsule of the knee) block is designed to anesthetize the articular branches supplying the posterior capsule of the knee without causing significant motor block. The sacral erector spinae plane block (S-ESPB) is a more proximal truncal block, which may provide analgesia to the posterior knee and surrounding structures through spread of local anesthetic in the fascial planes.

This randomized controlled trial will compare two regional anesthesia strategies in patients undergoing total knee arthroplasty:

Adductor canal block (ACB) combined with sacral erector spinae plane block (S-ESPB).

Adductor canal block (ACB) combined with iPACK block. In both groups, 20 mL of 0.2% ropivacaine will be used for each block (ACB + S-ESPB or ACB + iPACK). All patients will receive standard perioperative care and multimodal analgesia according to institutional protocols.

The primary outcome of the study is the time to first rescue analgesia within 48 hours after surgery. Secondary outcomes include pain intensity at rest and during movement, total opioid consumption, motor function (quadriceps strength), postoperative nausea and vomiting, hemodynamic events, block-related complications, time to first mobilization, and patient satisfaction with pain management.

The study aims to determine whether combining ACB with S-ESPB or with iPACK results in better analgesia and functional outcomes after TKA. The results may help optimize regional anesthesia protocols for total knee arthroplasty and improve postoperative recovery.

Inclusion Criteria:

• Age 65 years or older
• Scheduled for elective unilateral total knee arthroplasty under spinal or general anesthesia
• ASA physical status I-III
• Planned use of regional anesthesia with an adductor canal block as part of multimodal analgesia
• Ability to communicate pain intensity using the NRS scale
• Written informed consent obtained from the patient

Exclusion Criteria:

• Refusal or inability to provide informed consent
• Allergy, intolerance, or contraindication to local anesthetics (ropivacaine)
• Pre-existing significant neurological deficit or neuropathy in the operative limb
• Coagulopathy or anticoagulation that contraindicates peripheral nerve blocks (e.g., INR >1.5, platelets <100,000/µL, or therapeutic anticoagulation that cannot be safely paused)
• Infection at or near the planned needle insertion sites
• Severe hepatic or renal impairment
• Chronic opioid therapy (>30 days of daily opioid use before surgery)
• Cognitive impairment or delirium preventing reliable pain assessment BMI > 40 kg/m² (optional - if chcesz ograniczyć ze względu na trudność USG)
• Previous knee arthroplasty on the same side or revision TKA (jeśli chcesz tylko primary TKA)
• Pregnancy or breastfeeding
• Participation in another interventional clinical trial within 30 days

12 months after publication, available for 5 years

upon reasonable request; de-identified data; DSA if needed

Study blocks will be performed by an anesthesiologist who is not involved in intraoperative management or postoperative outcome assessment. Study medications and syringes will be prepared by a clinician not involved in patient care. All participants will receive identical appearing syringes, and all blocks will be performed under ultrasound guidance in a standardized fashion. Patients, surgeons, ward staff, investigators, and outcome assessors will remain blinded to group allocation.