This prospective study, upon approval by the institutional review board, was conducted in the authors’ affiliated institution from August 2017 to December 2018. Ethical clearance was obtained from the ethical committee and approval was obtained from the Institutional review board. Hundred and twenty subjects who were scheduled for elective unilateral TKA by a single orthopaedic surgeon were included in this study. Patients were randomly divided into three groups, with 40 subjects in each group. Group I (LIA group) Group II (ACB group) and Group III (LIA + ACB group). The patients were informed in detail about the study and written consent to participate in this study was obtained.
Eligibility criteria included (1) primary unilateral TKA, (2) age between 18 to 85 years, (3) no contraindications for either of the analgesic method, and (4) subjects were mentally sound and functionally rated grade I–III on the American Society of Anesthesiologists (ASA) scale. Exclusion criteria included (1) contraindications for peripheral nerve or neuraxial blockade, (2) history of allergy to drugs used in this study, (3) chronic pain requiring opioid medications, (4) psychiatric illness, and (5) patients receiving bilateral TKA and subjects refusing to be involved in the study.
After consent was obtained, participants’ baseline demographic information was collected and patients were randomly assigned to one of the three groups (Group I, II and III). All patients were operated under spinal anesthesia with 3 ml 0.5% heavy bupivacaine at L3–5 level. Surgery was performed using a femoral tourniquet. All surgeries were done through the same medial parapatellar approach to knee joint. All patients received posterior stabilized cemented implants. The LIA cocktail was prepared in operating room and was composed of 100 ml 0.2% Ropivacaine + Morphine 5 mg + 1 ml Adrenaline (1:1000) + Ketorolac 30 mg.
The LIA was given in two stages. The prepared solution (50% of total volume) was first injected, after bone surface preparation and before component placement, into posteromedial capsule, attachment of residual posterior meniscal rim and posterior capsule, ACL femoral attachment and PCL tibial attachment, residual rim of the medial meniscus, posterolateral capsule, attachment of residual posterior rim of the lateral meniscus and posterior capsule, residual rim of lateral meniscus (Fig. 1). During the injection into the posterior areas of the knee, care was taken not to inject into popliteal artery. Aspiration was performed prior to any injection into the posterior region of the knee. Second injection of LIA cocktail (remaining 50% of total volume) was injected after component insertion but before wound closure while the cement was curing into the suprapatellar pouch, fat pad and retinacular tissues and subcutaneous tissues. Drain was used in all patients. At the end of surgery, the surgeon applied compression bandages covering the entire knee.
In the ACB group, ACB was usually administered after the surgery by the anesthesia team (Fig. 2). This block typically was performed with the patient in the supine position, with the thigh abducted and externally rotated to allow access to the medial thigh. It was performed using a high frequency ultrasound transducer. The goal was to place the needle tip just anterior to the femoral artery, deep to the sartorius muscle, and to deposit up to 20 ml of local anesthetic until its spread around the artery was confirmed with ultrasound visualization. The skin was disinfected and the transducer was placed antero-medially, approximately at the junction between the middle and the distal third of the thigh or somewhat lower. Once the pulsation of femoral artery had been identified, the probe was moved distally to trace the artery until it passed through the adductor hiatus to reach the popliteal artery. Then the probe was moved cephalad about 3–4 cm to obtain a good view in the axis of superficial femoral artery and the adjacent saphenous nerve. An adductor canal block was typically performed at this level. The needle was inserted in a lateral-to-medial orientation and advanced toward the femoral artery. Once the needle tip was visualized anterolaterally to the artery and after careful aspiration, 1–2 ml of local anesthetic was injected to confirm the right injection site which showed its spread around the femoral artery. Then 10–12 ml of Ropivacaine was injected at a rate of 5 ml/hr.
In the third group (LIA + ACB group), a single shot of 50 ml LIA was given intraoperatively after bone surfaces had been prepared into the posteromedial capsule, attachment of residual posterior meniscal rim and posterior capsule, residual rim of the medial meniscus, posterolateral capsule, attachment of residual posterior rim of the lateral meniscus and posterior capsule, residual rim of lateral meniscus and before components were inserted. Postoperatively ACB was given as in group II.
There was not substantial difference in the operating time among the three methods, which lasted for about 45 to 55 mins. LIA had the shortest time, taking approximately 50 mins as 50 ml of LIA was injected after preparation of bone surfaces and the injection of the rest 50 ml after the final implantation. With the group II (ACB), when the surgeons operating time was lesser than the group I, the operating room time was longer as the procedure of ACB took roughly 10–15 min for our anesthesia team. The group III had the longest operating room as the surgeon had to deliver 50 ml of LIA after preparation of bone surfaces and the anesthesia team had to perform ACB.
The postoperative pain control regime consisted of a PCA (patient controlled analgesia). In the intensive care unit, all patients were intravenously administered PCA fentanyl. At the outset, a bolus of 3 ml (30 mcg) was given. It was later given at a lockout interval of 20 mins and administered over a period of 48 h postoperatively.
The primary outcome of the analgesic effectiveness was measured in terms of Numerical Pain Rating Scale (NPRS) scores by assessing and asking the patients in the first 24 h of surgery at fixed intervals of 6, 12 and 18 h. The total amount of fentanyl consumed as rescue analgesia to support primary block was recorded at the start, 6, 12 and 24 h. Numerical Pain Rating Scale score (NPRS) is a measure of pain intensity, which is a whole number (0–10 integers) a respondent selects. The pain was rated on a 0-to-10 scale, with 0 representing no pain and 10 indicating extreme pain. It is effective, reliable and takes only few minutes to complete.
On the first post-operative day, ambulation ability and mobilization achieved by patients were assessed in terms of ability to stand, distance covered and range of knee flexion measured by goniometer. Adverse effects resulting from analgesics in the form of nausea, vomiting episodes, pruritus, quadriceps weakness, any unwanted cardiovascular and neurological events, DVT (deep vein thrombosis) and falls were noted. The patients were discharged on the 4th post-operative day, the criteria for discharge included that (1) the patients were ambulatory and (2) were able to manage their day-to-day activities with minimal pain. The primary outcome was based on the postoperative pain control and the amount of fentanyl consumed. Further functional assessment of patients was done 2 and 6 weeks after operation in terms of WOMAC (Western Ontario & McMaster Universities Osteoarthritis Index) score.
The analysis included profiling of patients on different demographic data. Quantitative data were presented as means and standard deviation. Qualitative/categorical data were expressed as absolute numbers and proportions. Cross tables were generated and chi square test was used for testing of significance. Student t test was used for comparison of quantitative parameters of outcomes. A P value < 0.05 was considered statistically significant. SPSS software package (Version 24.0) was used for statistical analysis.