Total knee arthroplasty (TKA) is among the most frequently performed orthopedic procedures worldwide, offering substantial improvements in pain relief, joint function, and quality of life for patients with end-stage degenerative joint disease [1]. However, the procedure is also associated with considerable postoperative pain, particularly during the initial 48–72 hours, which can hinder early mobilization, increase the risk of thromboembolic events, delay discharge, and reduce patient satisfaction [2][3]. Effective pain control is therefore a cornerstone of successful postoperative recovery and rehabilitation in TKA. In recent years, there has been growing emphasis on regional anesthesia techniques as part of enhanced recovery after surgery (ERAS) protocols to minimize opioid use and its associated complications—such as nausea, sedation, respiratory depression, and prolonged ileus [4]. Among the most widely used regional anesthetic approaches in TKA are spinal anesthesia, epidural anesthesia, and femoral nerve blocks (FNB), each with distinct mechanisms, durations of action, and side effect profiles. The choice among these techniques often depends on patient comorbidities, surgeon preference, and institutional protocols [5].

Spinal anesthesia, involving intrathecal administration of local anesthetics, offers the advantage of rapid onset, dense neural blockade, and minimal drug requirement. It has been associated with reduced intraoperative blood loss, lower rates of thromboembolic events, and shorter hospital stays compared to general anesthesia [6]. Importantly, spinal anesthesia also provides excellent postoperative analgesia for the first 6–8 hours but often requires supplementary analgesia thereafter. Epidural anesthesia, in contrast, enables continuous infusion of anesthetics and opioids through a catheter, allowing titration to the patient’s needs [7]. While it provides extended pain relief, especially useful in bilateral procedures or patients with high pain sensitivity, its use has declined due to concerns over urinary retention, hypotension, delayed ambulation, and risk of epidural hematoma in anticoagulated patients [8]. Femoral nerve blocks, particularly when delivered as continuous infusions, have become a popular choice for TKA pain management due to their targeted analgesia of the anterior thigh and knee. However, since they do not reliably anesthetize the posterior knee, supplementary blocks such as sciatic or adductor canal blocks are sometimes added. FNBs have demonstrated superiority over systemic opioids in reducing pain and opioid consumption, though at the cost of temporary quadriceps weakness that may delay mobilization [9][10].

Several comparative studies have attempted to identify the optimal regional anesthetic approach. Some have reported superior analgesia and patient satisfaction with spinal anesthesia compared to femoral nerve blocks [11], while others found no significant differences in pain scores but noted varying rates of complications and recovery milestones [12][13]. However, most studies have been limited by small sample sizes, lack of standardized pain assessment timing, or inconsistency in anesthetic drug combinations used. In this context, the present study aims to directly compare the postoperative analgesic effectiveness of spinal anesthesia, epidural anesthesia, and femoral nerve block in patients undergoing unilateral total knee arthroplasty. By analyzing Visual Analogue Scale (VAS) scores at fixed intervals, total opioid consumption, time to first analgesic requirement, and incidence of side effects, this study will provide evidence to guide anesthesia choice and pain protocols in knee replacement surgery. Such comparative evaluation is especially critical for optimizing outcomes within resource-constrained or high-volume healthcare settings where cost-effectiveness and rapid recovery are paramount.

Objective:

To compare the effectiveness of different regional anesthesia techniques on postoperative pain control and opioid requirement in patients undergoing total knee arthroplasty.

A comparative analytical study was enrolling 126 patients undergoing total knee arthroplasty to evaluate postoperative pain control with regional anesthesia, using non-probability consecutive sampling.

Inclusion Criteria:

• Patients aged 40–80 years.
• Scheduled for elective unilateral total knee arthroplasty.
• ASA (American Society of Anesthesiologists) physical status I–III.
• Provided informed written consent for participation.

Exclusion Criteria:

• Known allergy to local anesthetics or opioids.
• Coagulopathy or ongoing anticoagulant therapy.
• Neurological disorders affecting the lower limbs.
• Revision knee surgeries or bilateral procedures.
• Cognitive impairment precluding accurate pain assessment.

Data Collection Procedure

Data were collected from 126 patients undergoing unilateral total knee arthroplasty who met the eligibility criteria and consented to participate in the study. Each participant was assigned to one of three groups based on the regional anesthesia technique administered: spinal anesthesia, epidural anesthesia, or femoral nerve block. Preoperative demographic data including age, gender, body mass index (BMI), and comorbidities were recorded. Postoperative pain intensity was assessed using the Visual Analogue Scale (VAS) at 6, 12, and 24 hours after surgery. Additionally, total opioid consumption in the first 24 hours, time to first analgesic request, and the incidence of adverse effects such as nausea, urinary retention, and hypotension were documented.

All data were recorded in a structured proforma and verified by two independent researchers for accuracy.

Statistical Analysis

Data were entered and analyzed using SPSS version 26.0. Continuous variables such as age, VAS scores, time to first analgesic request, and total opioid consumption were expressed as means with standard deviations and compared across groups using one-way ANOVA. Categorical variables like gender and adverse effects were summarized as frequencies and percentages and compared using the Chi-square test or Fisher’s exact test as appropriate. A p-value of less than 0.05 was considered statistically significant. Subgroup analyses were also conducted to assess variations in outcomes based on age and comorbidity status.

The mean age across groups was similar: 65.3 years in the spinal anesthesia group, 66.1 years in the epidural group, and 64.7 years in the femoral nerve block group (p = 0.74). BMI ranged from 27.9 to 29.1 kg/m² across groups (p = 0.56). Males made up 54.8% of the spinal group, 50% of the epidural group, and 52.4% of the femoral group (p = 0.91). Hypertension was reported in 38.1% to 42.9% of patients across groups, while diabetes ranged from 28.6% to 33.3% (p-values > 0.78), indicating no significant demographic differences.

Table 1: Demographic and Baseline Characteristics

Spinal anesthesia provided the lowest pain scores at 6 hours (mean 3.2), compared to 4.6 for epidural and 4.2 for femoral blocks (p = 0.01). At 12 hours, pain remained lower in the spinal group (3.8) than in epidural (4.8) and femoral groups (4.5), with statistical significance (p = 0.03). At 24 hours, scores were similar across all groups (4.1–4.4), with no significant difference (p = 0.67).

Table 2: Postoperative Pain Scores (VAS)

Total opioid use was lowest in the spinal anesthesia group (28.6 mg), followed by femoral nerve block (32.4 mg) and epidural anesthesia (35.2 mg), with a significant difference (p = 0.01). The spinal group also had the longest time to first analgesic request (mean 7.8 hours), compared to 6.1 hours for femoral block and 5.6 hours for epidural group (p = 0.04), suggesting prolonged analgesia with spinal anesthesia.

Table 3: Opioid Use and Time to First Analgesia

Nausea was most common in the epidural group (28.6%), followed by femoral nerve block (16.7%) and spinal anesthesia (11.9%) (p = 0.04). Urinary retention occurred in 9.5% of spinal, 19% of epidural, and 7.1% of femoral cases (p = 0.12). Hypotension was reported in 14.3% of epidural cases, 7.1% in spinal, and 4.8% in femoral groups, though the differences were not statistically significant (p = 0.29).

Table 4: Side Effects Profile

Patients receiving spinal anesthesia reported the highest satisfaction score (mean 8.7/10), followed by femoral block (8.1) and epidural anesthesia (7.9) (p = 0.02). High satisfaction (score ≥ 8) was achieved by 81% of spinal group, 74% of femoral, and only 67% of epidural patients (p = 0.03). Moderate and low satisfaction scores were more frequent in the epidural group, though these differences were not statistically significant.

Table 5: Patient Satisfaction Scores

This study evaluated the effectiveness of spinal anesthesia, epidural anesthesia, and femoral nerve block in managing postoperative pain, reducing opioid use, minimizing complications, and improving patient satisfaction following total knee arthroplasty. The findings highlight notable differences in outcomes among these anesthetic approaches. Demographic and baseline characteristics were well-balanced across the three groups, ensuring comparability. Mean age and BMI showed no statistically significant differences, and comorbid conditions such as hypertension and diabetes were evenly distributed. This demographic parity supports the reliability of observed outcome differences being attributable to the type of anesthesia rather than confounding baseline variables. Postoperative pain scores were significantly lower in the spinal anesthesia group at both 6- and 12-hours post-surgery. At 6 hours, spinal anesthesia achieved a mean VAS score of 3.2 compared to 4.6 for epidural and 4.2 for femoral nerve block (p = 0.01). Similar patterns were observed at 12 hours (p = 0.03), indicating superior early analgesia with spinal anesthesia. These results are consistent with findings from previous research, which also demonstrated that spinal anesthesia provides more effective short-term pain control following knee arthroplasty compared to other regional blocks [14][15].

In terms of opioid consumption, the spinal group required significantly fewer opioids (mean 28.6 mg) compared to the epidural (35.2 mg) and femoral nerve block groups (32.4 mg, p = 0.01). Moreover, time to first analgesic request was longer in the spinal group (7.8 hours) than in the epidural (5.6 hours) and femoral nerve block groups (6.1 hours), indicating prolonged analgesic effect. These findings echo previous research demonstrating that spinal anesthesia is associated with reduced opioid requirements and delayed need for rescue analgesia in postoperative orthopedic surgery [16]. The safety profile showed that spinal anesthesia had the lowest rates of complications. Nausea was reported in only 11.9% of spinal cases, compared to 28.6% in the epidural group (p = 0.04), and hypotension was also least frequent in the spinal group. These outcomes are in line with previous research suggesting that spinal anesthesia is associated with fewer systemic side effects compared to epidural anesthesia, which can lead to a higher incidence of hypotension and urinary retention [17][18]. Patient satisfaction, a critical endpoint in postoperative care, was highest in the spinal anesthesia group. A satisfaction score of ≥8 was reported by 81% of patients in the spinal group compared to 74% in the femoral nerve block group and 67% in the epidural group (p = 0.03). This aligns with earlier studies reporting that improved pain control and reduced complications with spinal anesthesia contribute to higher patient-reported satisfaction scores [19]. Taken together, these findings support the preferential use of spinal anesthesia in total knee arthroplasty, particularly when the goal is to optimize early pain control, reduce opioid burden, and enhance patient satisfaction. Although femoral nerve block also showed favorable outcomes, spinal anesthesia appears superior in multiple domains. Epidural anesthesia, while still effective, was associated with more complications and comparatively lower satisfaction levels.

It is concluded that among the regional anesthesia techniques evaluated, spinal anesthesia offers the most effective postoperative pain control in total knee arthroplasty. It was associated with lower pain scores at 6 and 12 hours, reduced opioid consumption, and longer time to first analgesic requirement compared to epidural anesthesia and femoral nerve block. Furthermore, spinal anesthesia demonstrated a better safety profile with fewer side effects such as nausea and hypotension, and higher patient satisfaction. While femoral nerve block showed relatively favorable outcomes, epidural anesthesia was comparatively less effective and had a higher incidence of complications. These findings suggest that spinal anesthesia may be the preferred regional anesthetic technique for patients undergoing knee replacement surgery when aiming to enhance analgesia, minimize opioid reliance, and improve overall patient experience.

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