Contemporary anesthetic management for lower extremity surgical procedures has established regional techniques as fundamental therapeutic modalities, demonstrating clinical superiority over general anesthesia in selected patient populations. The evolution of regional anesthetic methodologies has broadened the therapeutic armamentarium, encompassing neuraxial and peripheral nerve block modalities. Spinal anesthesia and the Sciatic-Obturator-Femoral Technique (SOFT) represent contrasting approaches with distinct pharmacodynamic characteristics [1].

Spinal anesthesia remains the preferred regional technique for lower extremity procedures due to its procedural simplicity, reproducible efficacy, and extensive clinical validation. This neuraxial approach involves intrathecal administration of local anesthetic agents, producing temporary neural transmission blockade. Clinical preference derives from its reliability, rapid onset, dense surgical anesthesia, and minimal equipment requirements [2].

However, spinal anesthesia involves predictable physiological consequences. Concurrent sympathetic blockade precipitates significant hemodynamic alterations, particularly hypotension and bradycardia, posing clinical risks for vulnerable populations including geriatric patients, those with poorly controlled diabetes or hypertension, patients on anticoagulation, those with ischemic heart disease, and polytrauma patients with hemodynamic compromise [3].

Ultrasonographic guidance has accelerated peripheral nerve block advancement, transforming precision, safety, and clinical reliability. Real-time visualization of neuroanatomical structures has enhanced procedural accuracy while expanding applicability to complex scenarios and diverse patient populations [4].

Peripheral nerve blocks offer multiple advantages including preserved hemodynamic stability, reduced urinary retention risk, early mobilization, and prolonged postoperative analgesia. The SOFT technique provides comprehensive lower extremity anesthesia through systematic sciatic, obturator, and femoral nerve blockade while avoiding sympathetic blockade associated with neuraxial approaches [5].

Clinical utility extends to emergency scenarios, patients with comorbidities, and those receiving anticoagulation where neuraxial techniques are contraindicated. Optimized local anesthetic dosing has enhanced safety while maintaining efficacy [6,7]. Despite expanding evidence supporting peripheral nerve blocks, direct comparative studies between SOFT block and spinal anesthesia for tibial fracture management remain limited. This represents a significant gap considering tibial fracture prevalence, associated pain burden, and potential anesthetic technique impact on perioperative outcomes.

This investigation addresses this knowledge deficit through direct comparative evaluation of SOFT block versus spinal anesthesia efficacy and safety in tibial fracture repair. Research outcomes may influence clinical practice by providing evidence-based guidance for anesthetic selection, potentially improving hemodynamic stability, optimizing pain management, reducing opioid consumption, enhancing patient satisfaction, and facilitating functional recovery.

This prospective comparative study was conducted at the Department of Anesthesia, A.C.S medical college and hospital, Chennai, from January 2024 - August 2024. Institutional Ethics Committee approval was obtained and written informed consent was secured from all participants prior to enrollment.

The study population comprised young adults aged 18-60 years of both sexes with ASA physical status I-II, scheduled for elective or emergency tibial fracture repair. Exclusion criteria included injection site infection, coagulopathy or active anticoagulation, known hypersensitivity to study medications, and contraindications to neuraxial anesthesia.

Sample size calculation was based on findings by Shokri H et al.[3], where analgesic duration was 9.43 ± 2.7 hours for SOFT block versus 3.15 ± 1.83 hours for spinal anesthesia. With 95% confidence level and 80% power, the calculated sample size was 82 participants (n=41 per group).

Randomization employed computer-generated random numbers in 1:1 allocation ratio. Group assignments were concealed in sequentially numbered opaque envelopes opened immediately before procedures. Both participants and data collectors remained blinded to group allocation throughout the study period.

Preoperative evaluation included comprehensive history, physical examination, and routine laboratory investigations. Standard monitoring encompassed non-invasive blood pressure, electrocardiography, and pulse oximetry. Intravenous access was established using 18G cannula with Ringer's lactate preloading (10 ml/kg).

Group S1 participants received SOFT block in supine position under sterile conditions using SonoSite M-Turbo ultrasound system. Femoral nerve block utilized high-frequency linear probe placement at the inguinal crease with 15 ml of 0.25% bupivacaine injected lateral to the femoral nerve via in-plane technique. Obturator nerve block involved 10 ml of 0.25% bupivacaine injection into the fascial plane between pectineus and adductor longus muscles. Sciatic nerve block employed curvilinear probe for anterior approach identification with 20 ml of 0.25% bupivacaine injection.

Group S2 participants underwent spinal anesthesia in sitting position. A 25G Quincke needle was inserted at L3-L4 intervertebral space with intrathecal injection of 15 mg (3 ml) 0.5% hyperbaric bupivacaine following correct needle placement confirmation.

Intraoperative monitoring recorded heart rate, blood pressure, oxygen saturation, and respiratory rate at baseline, 5 minutes post-anesthesia, then every 15 minutes. Hypotension (>20% systolic blood pressure decrease from baseline or <90 mmHg) was managed with intravenous fluid bolus and phenylephrine if persistent. Bradycardia (<50 beats/minute) received atropine treatment.

Postoperative surveillance continued with vital parameters and pain scores documented at 30 minutes, 1, 2, 6, 12, and 24 hours. Pain assessment utilized Visual Analog Scale (VAS). Rescue analgesia with intravenous diclofenac 75 mg was administered for VAS scores ≥4. Time to first rescue analgesia and total 24-hour analgesic consumption were recorded.

Statistical analysis employed SPSS version 29.02. Continuous variables were expressed as mean ± standard deviation, categorical variables as frequencies and percentages. Independent t-test or Mann-Whitney U test was applied for continuous variables as appropriate. Categorical variables were compared using Chi-square or Fisher's exact test. Statistical significance was defined as p<0.05.

The demographic characteristics including age, gender, ASA physical status, BMI, and fracture type distribution were comparable between the two groups (Table 1). The mean age was 42.3 ± 8.7 years in the SOFT block group and 41.8 ± 9.2 years in the spinal anesthesia group.

Table 1: Demographic characteristics and type of surgery

*Statistically significant(p<0.05)

Males predominated in both groups (SOFT block: 75.6%, spinal anesthesia: 80.5%). The majority of patients had ASA I status (SOFT block: 78.0%, spinal anesthesia: 73.2%). The mean BMI was similar in both groups (SOFT block: 23.4 ± 2.8 kg/m², spinal anesthesia: 23.6 ± 2.7 kg/m²). Regarding fracture types, tibial shaft fractures were the most common (SOFT block: 46.3%, spinal anesthesia: 43.9%), followed by proximal tibial fractures and distal tibial fractures.

Table 2: Comparison of Block Characteristics and Analgesia Parameters Between Groups

There were significant differences in the onset times for both sensory and motor blockade between the two groups (Table 2). The onset of sensory blockade was significantly slower in the SOFT block group (14.7 ± 3.8 minutes) compared to the spinal anesthesia group (4.2 ± 1.6 minutes, p<0.001). Similarly, the onset of motor blockade was longer in the SOFT block group (16.2 ± 3.5 minutes) compared to the spinal anesthesia group (5.7 ± 2.1 minutes, p<0.001).

The duration of analgesia was markedly longer in the SOFT block group (9.8 ± 2.1 hours) compared to the spinal anesthesia group (3.2 ± 1.4 hours, p<0.001). Similarly, the time to first rescue analgesia was significantly delayed in the SOFT block group (10.1 ± 2.0 hours vs. 2.8 ± 1.3 hours, p<0.001). The total dose of rescue analgesia (diclofenac) required in the first 24 hours was substantially lower in the SOFT block group (63.4 ± 38.2 mg) compared to the spinal anesthesia group (176.8 ± 31.5 mg, p<0.001).

Table 3: Comparison of Hemodynamic Parameters and Adverse Effects between Groups

Groups

The SOFT block group demonstrated superior hemodynamic stability compared to the spinal anesthesia group (Table 3). The incidence of hypotension was significantly lower in the SOFT block group (7.3%) compared to the spinal anesthesia group (46.3%, p<0.001). Similarly, bradycardia occurred less frequently in the SOFT block group (2.4% vs. 34.1%, p<0.001).

Management of hypotensive episodes primarily involved intravenous fluid boluses, which were required in 43.9% of spinal anesthesia patients versus only 4.9% of SOFT block patients (p<0.001). Vasopressor support with phenylephrine was needed in 19.5% of spinal anesthesia patients compared to 2.4% of SOFT block patients (p=0.014). The spinal anesthesia group also experienced higher rates of nausea/vomiting (14.6% vs. 0%, p=0.011) and urinary retention (9.8% vs. 0%, p=0.041).

Detailed temporal monitoring of hemodynamic parameters revealed that systolic blood pressure, diastolic blood pressure, and mean arterial pressure were all significantly lower in the spinal anesthesia group at 30 minutes, 1 hour, and 2 hours postoperatively, with differences resolving by 6 hours. Similarly, heart rates were significantly lower in the spinal anesthesia group during the same period.

Table 4: Comparison of Visual Analog Scale (VAS) Pain Scores at Different Time Intervals

Visual Analog Scale (VAS) pain scores showed no significant differences during the first 2 hours postoperatively (Table 4). However, significant differences emerged at 6 hours, with the SOFT block group reporting substantially lower pain scores (1.1 ± 1.0) compared to the spinal anesthesia group (4.2 ± 1.6, p<0.001). This difference persisted at 12 hours (SOFT block: 2.3 ± 1.1, spinal anesthesia: 3.8 ± 1.5, p<0.001) and remained statistically significant even at 24 hours (SOFT block: 2.0 ± 0.9, spinal anesthesia: 2.6 ± 1.2, p=0.016).

Table 5: Distribution of Pain Intensity at 6 Hours Postoperatively

 At 6 hours postoperatively, 90.2% of patients in the SOFT block group reported minimal pain (VAS 0-2), compared to only 14.6% in the spinal anesthesia group (Table 5). In contrast, 22.0% of patients in the spinal anesthesia group reported moderate pain (VAS 6-8) at this time point, while no patients in the SOFT block group experienced this level of pain.

This prospective randomized study compared the efficacy and safety of SOFT block versus spinal anesthesia for tibial fracture surgeries in a broader adult population aged 18-60 years. The findings demonstrate significant differences between the two techniques across multiple parameters including onset characteristics, hemodynamic stability, postoperative analgesia, and analgesic requirements.

Our findings revealed a significantly longer onset time for both sensory and motor blockade in the SOFT block group compared to the spinal anesthesia group (14.7 ± 3.8 vs. 4.2 ± 1.6 minutes for sensory blockade; 16.2 ± 3.5 vs. 5.7 ± 2.1 minutes for motor blockade, p<0.001). This difference in onset kinetics is consistent with the known pharmacodynamic properties of neuraxial versus peripheral nerve blockade. Spinal anesthesia produces rapid onset due to direct access of local anesthetics to nerve roots and the spinal cord, while peripheral nerve blocks require time for local anesthetic diffusion through various tissue planes to reach the neural targets[8].

Sviggum et al. reported similar findings when comparing femoral-sciatic nerve blocks to spinal anesthesia for lower extremity surgery, with mean onset times of 15.3 ± 4.2 minutes versus 4.7 ± 1.8 minutes respectively[9]. This more gradual onset with SOFT block necessitates appropriate timing of block administration in relation to surgical scheduling, typically requiring block performance 20-30 minutes before anticipated surgical start to ensure adequate surgical conditions.

One of the most striking differences observed in our study was the substantially prolonged duration of effective analgesia in the SOFT block group compared to the spinal anesthesia group (9.8 ± 2.1 vs. 3.2 ± 1.4 hours, p<0.001). This extended analgesic duration translated directly to significantly later times to first rescue analgesic requirement (10.1 ± 2.0 vs. 2.8 ± 1.3 hours, p<0.001) and markedly lower total rescue analgesic consumption in the first 24 hours (63.4 ± 38.2 vs. 176.8 ± 31.5 mg of diclofenac, p<0.001).

This superior analgesic profile of SOFT block is consistent with findings by Rodriguez et al., who demonstrated that combined femoral and sciatic nerve blocks provided effective analgesia for 8-12 hours following lower limb orthopedic procedures, compared to 2-4 hours with spinal anesthesia using bupivacaine[10]. The extended analgesic duration with peripheral nerve blocks can be attributed to several factors including the relatively lower vascularity of peripheral nerve tissues compared to epidural and intrathecal spaces, resulting in slower systemic absorption and prolonged local action of anesthetics[11].

The VAS pain scores showed no significant differences during the first 2 hours postoperatively, reflecting adequate analgesic coverage with both techniques during this initial period. However, significant differences emerged at 6 hours (1.1 ± 1.0 vs. 4.2 ± 1.6, p<0.001) and persisted at 12 hours (2.3 ± 1.1 vs. 3.8 ± 1.5, p<0.001), demonstrating the substantial analgesic advantage of SOFT block after spinal anesthesia effects had dissipated. Even at 24 hours, a small but statistically significant difference in pain scores remained (2.0 ± 0.9 vs. 2.6 ± 1.2, p=0.016), suggesting a persistent benefit that extended beyond the expected pharmacological duration of the local anesthetic.

This protracted analgesic benefit might be explained by the "preemptive analgesia" phenomenon, wherein effective blockade of nociceptive input during surgery and the immediate postoperative period may attenuate central sensitization processes, resulting in reduced pain intensity even after block resolution[12]. Kuthiala and Chaudhary postulated that early and effective pain control with peripheral nerve blocks might interrupt the pain-inflammation-hyperalgesia cycle and reduce secondary hyperalgesia, explaining the extended benefits observed beyond the pharmacological action of local anesthetics[13].

Our study demonstrated significant hemodynamic advantages with SOFT block compared to spinal anesthesia across our adult population aged 18-60 years. The incidence of hypotension was markedly lower in the SOFT block group (7.3% vs. 46.3%, p<0.001), as was the incidence of bradycardia (2.4% vs. 34.1%, p<0.001). The hemodynamic instability in the spinal anesthesia group was primarily managed with intravenous fluid boluses (43.9% vs. 4.9%, p<0.001), with vasopressor support required in 19.5% of patients compared to only 2.4% in the SOFT block group (p=0.014).

This vasopressor requirement rate of 19.5% in our spinal anesthesia group aligns well with reported incidences in the literature for 15mg hyperbaric bupivacaine. Carpenter et al. reported vasopressor requirements in 15-25% of patients receiving similar spinal anesthetic doses for lower extremity surgery[14]. The relatively moderate vasopressor requirement in our study reflects the typical clinical response to standard spinal anesthesia doses, where initial management with fluid resuscitation is often effective, with phenylephrine reserved for persistent or severe hypotension.

The comprehensive adverse effect profile revealed additional benefits of SOFT block beyond hemodynamic stability. The spinal anesthesia group experienced higher rates of nausea and vomiting (14.6% vs. 0%, p=0.011) and urinary retention (9.8% vs. 0%, p=0.041). These complications, while manageable, contribute to patient discomfort and may delay discharge or prolong recovery room stays.

The fundamental physiological difference between the techniques explains these findings: spinal anesthesia produces sympathetic blockade along with sensory and motor effects, while peripheral nerve blocks like SOFT preserve sympathetic tone and cardiovascular stability. The absence of sympathetic blockade with SOFT technique eliminates the risk of neurogenic hypotension while maintaining normal cardiovascular homeostasis.

The superior hemodynamic profile of SOFT block becomes particularly relevant when considering the broader age range (18-60 years) included in our study. While younger patients typically tolerate spinal anesthesia-induced hypotension well, middle-aged patients may have underlying cardiovascular risk factors or reduced physiological reserve that makes hemodynamic stability more crucial. Singh et al. demonstrated that patients over 40 years receiving spinal anesthesia had a higher incidence of clinically significant hypotension requiring intervention compared to younger cohorts[15].

These findings are consistent with those reported by Vendittoli et al., who documented a 42% incidence of hypotension with spinal anesthesia versus 7% with peripheral nerve blocks for lower limb surgery[16]. The hemodynamic stability associated with SOFT block represents a significant clinical advantage, particularly for patients with limited cardiovascular reserve or those at risk for adverse consequences from hypotensive episodes.

The superior analgesic efficacy and hemodynamic stability associated with SOFT block has several important clinical implications across the adult age spectrum. The reduced requirement for rescue analgesics not only reflects improved pain control but also potentially minimizes analgesic-related complications. Non-steroidal anti-inflammatory drugs like diclofenac are associated with gastric irritation, renal dysfunction, and platelet inhibition, while opioids frequently cause nausea, vomiting, sedation, and respiratory depression. Reducing exposure to these agents through effective regional anesthesia represents a meaningful clinical benefit, particularly in middle-aged patients who may be more susceptible to these adverse effects.

The extended duration of analgesia with SOFT block may facilitate earlier and more effective participation in physical therapy and rehabilitation, which is crucial for optimizing functional outcomes following tibial fracture surgery across all age groups. Chelly et al. demonstrated that peripheral nerve blocks allowing effective pain control were associated with greater distances walked during physical therapy sessions and earlier achievement of rehabilitation milestones following lower extremity orthopedic procedures[17].

From a resource utilization perspective, the reduced requirement for management of hemodynamic instability and breakthrough pain may translate to more efficient use of nursing resources and potentially shorter post-anesthesia care unit stays. The 19.5% vasopressor requirement and 43.9% fluid bolus requirement in the spinal anesthesia group, while clinically manageable, represent additional interventions and monitoring requirements compared to the minimal hemodynamic support needed in the SOFT block group.

The technique's safety profile across the 18-60 year age range supports its applicability for the diverse population of tibial fracture patients. Younger patients benefit from the excellent analgesia and minimal side effects, while middle-aged patients particularly benefit from the hemodynamic stability and reduced risk of cardiovascular complications.

While our study was not powered to detect differences in outcomes based on fracture location, the comprehensive coverage provided by SOFT block makes it suitable for all tibial fracture types across the adult age spectrum. The technique's versatility and safety profile make it an excellent choice regardless of patient age within our study

range.

The SOFT block technique demonstrates superior postoperative analgesia, extended pain relief, and improved hemodynamic stability compared to spinal anesthesia in tibial fracture surgeries across the adult population aged 18-60 years. Despite slower onset, SOFT block provides markedly longer analgesic duration (9.8 vs. 3.2 hours), reduced rescue analgesic requirements, and significantly lower incidences of hypotension (7.3% vs. 46.3%) and vasopressor requirements (2.4% vs. 19.5%).

This approach offers a promising alternative for patients requiring comprehensive pain management with minimal cardiovascular complications, making it particularly valuable for enhanced recovery protocols in tibial fracture repair.

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