Spinal anaesthesia is one of the most widely used regional anaesthetic techniques, particularly for infra-umbilical surgeries of a predetermined duration.1 It offers several advantages over general anaesthesia, including lower rates of venous thromboembolism, reduced incidence of myocardial infarction, decreased postoperative analgesic requirements and attenuation of the sympathetic response to surgical stimulation.2 However, the success of spinal anaesthesia largely depends on the ease of performing a lumbar puncture, which can sometimes be challenging due to anatomical and physiological variations among patients.3 Multiple attempts at needle insertion can lead to increased procedural time, patient discomfort, and heightened anxiety.4 More importantly, repeated attempts are associated with a higher incidence of complications such as post-dural puncture headache, spinal hematoma, nerve damage, and transient or persistent neurological deficits.5 The risk of encountering a difficult lumbar puncture is particularly high in patients with certain predisposing factors such as obesity, osteoarthritis, ankylosing spondylitis, kyphoscoliosis, previous spinal surgeries, and degenerative disc diseases.6 These conditions may contribute to anatomical alterations, reduced intervertebral space, or difficulty in palpating spinal landmarks, all of which can hinder needle access to the subarachnoid space.7 Accurate preoperative identification of patients at risk for a difficult spinal puncture could help anaesthesiologists prepare in advance, take necessary precautions, and consider alternative approaches such as ultrasound-guided neuraxial techniques or alternative anaesthesia modalities.8 This predictive capability could improve overall procedural success, minimize patient discomfort, and reduce complications related to failed or multiple lumbar puncture attempts. Several studies have sought to establish predictive scoring systems for assessing the likelihood of difficult lumbar puncture.9,10 Some of these scoring systems are based on patient characteristics such as age, body mass index, spinal deformities, and anatomical spinal landmark assessments.11 Others incorporate radiological findings or operator experience as additional factors influencing procedural difficulty.12 However, despite the existence of these studies, a universally accepted and practically implementable scoring system that can be easily used at the bedside in routine clinical practice remains elusive. Many of the existing models require complex calculations, specialized imaging modalities, or are not adequately validated in diverse patient populations.13 In this context, our study aims to assess the correlation of the grade of lumbar puncture with a bedside scoring system in patients scheduled for elective infra-umbilical surgeries under spinal anaesthesia. By evaluating five key patient variables, namely age, abdominal circumference, spinal deformity (as measured by axial trunk rotation value)14, anatomical spine assessment (based on spinous process landmark grading system)15 and patient positioning, we seek to develop a reliable and user-friendly tool for predicting lumbar puncture difficulty. If validated successfully, this scoring system could serve as a valuable tool in the preoperative assessment of patients undergoing spinal anaesthesia, enabling anaesthesiologists to anticipate potential challenges and modify their approach accordingly

This prospective randomised study was conducted during January 2024 to December 2024 after obtaining approval from the Institutional Ethics Committee (Ref.No.337/MC/EC/2023) and registered with the Clinical Trial Registry of India (CTRI/2024/07/071495). The written informed consent was obtained from all participants of the study. A total of 157 patients belonging to American Society of Anaesthesiologist (ASA) physical status I and II and aged between 20 to 80 years, who were scheduled for elective infra-umbilical surgeries under spinal anaesthesia were included in the study, based on a sample size calculation derived from prior research9. The patients refusing spinal anaesthesia, known allergy to LA agent, pregnant women, patients who were unable to perform Adam’s forward bend test, any contraindication to spinal anaesthesia were excluded from the study . The study was double blinded. Two anaesthesiologists was assigned for the study. During pre anaesthetic evaluation, patients were assessed for 5 variables by one anaesthesiologist. Another anaesthesiologist with more than 5 years experience, who was not involved in the pre-anaesthetic assessment of patient variables, performed the lumbar puncture. During preoperative assessment, each patient underwent a detailed preoperative evaluation, which included: 1. Age (in years) 2. Abdominal circumference measurement (in cm) using a non-stretchable measuring tape, taken at the level of the umbilicus at the end of expiration while the patient was in a standing position. 3. Spinal deformity assessment using the Axial Trunk Rotation (ATR) value, measured using smartphone application Scoliometer. At least two values were recorded at each level, and the maximum degree of ATR obtained was noted. 4. Anatomical spine assessment using the Spinous Process Landmark Grading System (SLGS) to classify the visibility and palpability of spinal landmarks. 5. Patient positioning assessment, based on the posture assumed by the patient during lumbar puncture, which was categorized and scored accordingly. A total bedside difficulty score (ranging from 0 to 15) was calculated based on the summation of individual patient variable scores (0-15). In operating room, NBM status, PAC and consent were checked. Standard vital monitors (Heart Rate, Systolic Blood Pressure, Diastolic Blood Pressure, Mean Arterial Pressure, and SpO₂) were attached, and baseline parameters were recorded. An 18G intravenous cannula was secured, and Ringer’s lactate solution was administered at 5 ml/kg before the subarachnoid block. The second anaesthesiologist, who was blinded to the preoperative score, performed the lumbar puncture in sitting position under strict aseptic precautions. The spinal space was identified using the landmark palpation technique. A 25G Quincke’s spinal needle was used to perform the lumbar puncture and 3 ml of 0.5% hyperbaric Bupivacaine was injected after confirming clear and free flow of cerebrospinal fluid (CSF). The lumbar puncture was graded as easy, moderate, or difficult based on: The number of attempts required and the number of spinal levels attempted. Each new skin puncture was considered a new attempt. If an additional spinal level was required for successful puncture, it was recorded. After the procedure, the patient was placed in supine position and hemodynamic monitoring was continued throughout the surgery. Lumbar puncture difficulty grading was documented as Easy: CSF obtained on the first attempt. Moderate: CSF obtained after 2-4 attempts at one or more spinal levels. Difficult: CSF obtained after ≥5 attempts or shifting to a third spinal level. The primary objective was to predict the difficulty of lumbar puncture using five patient-related variables: Age (in years), Abdominal circumference (in cm), Spinal deformity (assessed using axial trunk rotation (ATR) value), Anatomical spine assessment (evaluated using the spinous process landmark grading system (SLGS)), Patient position (based on the posture assumed by the patient during lumbar puncture). The secondary objective was to grade the difficulty of lumbar puncture as easy, moderate or difficult based on: The number of attempts required and the number of spinal levels attempted. The sample size was calculated with a 95% confidence level and 95% power, considering an 11% prevalence of difficult lumbar puncture based on patient positioning, as per seed article9. This sample size was also adequate to cover all other study variables. The patients were recruited using a consecutive sampling method. All collected data were entered into Microsoft Excel. Descriptive statistics (mean, standard deviation and frequency distributions) were used to summarize baseline patient characteristics. Inferential statistical methods were applied to determine the correlation between bedside difficulty scores and actual lumbar puncture outcomes. A p-value < 0.05 was considered statistically significant. Table 1: Pre-operative assessment tool SCORE PATIENT VARIABLE 0 1 2 3 ASSIGNED SCORE AGE(years) 20-39 40-59 60-69 > 70 ABDOMINAL CIRCUMFERENCE (cm) < 80 80-99 100-120 > 120 ANATOMICAL SPINE ASSESSMENT Spinous process visible Spinous process palpable and not visible Spinous process not visible and not palpable, but interval between them is palpable as a low landmark under the thumb None of the previous case SPINE DEFORMITY (ATR VALUE) No (<5 degree) Mild (5-7.5 degree) Moderate (7.5-10 degree) Severe (>10 degree) PATIENT POSITION / ATTITUDE Can sit with flexed back Lateral position with flexed back Sitting with stiff back Right or left lateral position with stiff back DIFFICULTY SCORE No. of attempts : No. of spinal level attempted : Grade of difficulty of lumbar puncture ( easy/ moderate/ difficult

A total of 157 patients undergoing elective infra-umbilical surgeries under spinal anaesthesia were enrolled in the study, out of which 54.14% were females (n=85) and 45.86% were males (n=72). The near-equal distribution of gender indicates that both male and female patients were well represented in the study, allowing for an unbiased assessment of gender-related anatomical differences that may affect lumbar puncture difficulty. All participants were evaluated for demographic parameters, bedside difficulty score, number of lumbar puncture attempts, number of spinal levels attempted and incidence of complications. The bedside scoring system was assessed preoperatively and lumbar puncture difficulty was graded based on procedural outcomes. Table. 2 Distribution of patients according to each variable Variables Category / Range Frequency (n) Percentage (%) Age (years) 20–39 88 56.05 40–59 48 30.57 ≥60 21 13.38 Abdominal Circumference (cm) <80 12 07.64 80–99 107 68.15 100-119 35 22.29 >120 3 1.91 Spinal Deformity (ATR value) No deformity (<5°) 121 77.07 Mild (5–7.4°) 25 15.92 Moderate (7.5–9.9°) 6 3.82 Severe (≥10°) 5 3.18 SLGS (Spinous Landmark Grade) Spinous process visible 56 35.67 Spinous process palpable and not visible 51 32.48 Spinous process not visible and not palpable 44 28.03 None of the previous 6 3.82 Patient position Sitting with flexed back 120 76.43 Lateral with flexed back 18 11.46 Sitting with stiff back 16 10.19 Lateral with stiff back 3 1.91 Table. 3 Distribution of patients according to no. of attempts and no. of spinal level attempted Parameters Range Frequency (n) Percentage (%) No. of attempts 1 102 64.97 2 11 7.01 3 15 9.55 4 15 9.55 >=5 14 8.92 No. of spinal levels attempted 1 113 71.97 2 30 19.11 3 12 7.64 4 2 1.27 All patient variables—including age, abdominal circumference, spinal deformity, anatomical spine assessment (SLGS), and patient positioning—showed statistically significant differences (p < 0.001) when compared across easy, moderate, and difficult lumbar puncture grades. The median total difficulty score increased progressively from easy to difficult grades, suggesting that higher scores are predictive of increased lumbar puncture difficulty. A strong positive correlation was observed between patient variables and lumbar puncture grading, with the highest correlation seen with anatomical spine assessment (r = 0.722, p < 0.001), followed by patient positioning (r = 0.598, p < 0.001) and abdominal circumference (r = 0.586, p < 0.001). These findings indicate that anatomical factors play a crucial role in predicting lumbar puncture difficulty

This study validates bedside scoring system as a reliable predictor of difficult lumbar puncture in patients undergoing infra umbilical surgeries under spinal anaesthesia. Age The mean age of participants was 42.03 ± 12.48 years, with 56.05% of patients in the 20-39 years group, 30.57% in the 40-59 years group, and 13.38% in the 60-79 years group. A significant correlation (p < 0.001) was observed between increasing age and lumbar puncture difficulty, as 50% of patients aged ≥60 years experienced a difficult lumbar puncture. This aligns with Gvalani et al., where patients aged ≥60 years had a 42.8% failure rate in achieving spinal anaesthesia on the first attempt, compared to 15.2% in the 20-39 age group (p = 0.001). Khoshrang et al., however, reported no significant association between age and spinal anaesthesia difficulty, with first-attempt success rates of 49.5%, 35.6%, and 14.9% for easy, moderate, and difficult groups, respectively (p = 0.12), suggesting that other anatomical factors might be stronger predictors. Chien et al. found that spinal landmark visibility declined with age, leading to a 25% increase in technical difficulty for patients ≥60 years compared to younger groups. Abdominal Circumference In the present study, a significant correlation (p < 0.001) was found between abdominal circumference and lumbar puncture difficulty. Patients with an abdominal circumference of <80 cm had a 100% easy lumbar puncture rate, while those in the 80-99 cm group had 78.43% easy LPs, 58.54% moderate LPs, and 21.43% difficult LPs. However, in the 100-119 cm group, only 9.80% had an easy LP, while 39.02% had moderate difficulty and 64.29% had difficult LPs. Among those with an abdominal circumference ≥120 cm, none had an easy LP, 2.44% had moderate difficulty, and 14.29% had a difficult LP. These findings confirm that increasing abdominal circumference is strongly associated with increased procedural difficulty, which aligns with Zhou et al., who found that higher abdominal girth (≥100 cm) significantly increased the required bupivacaine dose and lumbar puncture failure rate (p < 0.0001). Subramanian et al. demonstrated that patients with an abdominal circumference >100 cm had a median lumbar puncture difficulty score of 7, compared to 3 in those with a circumference <100 cm (p < 0.0001). Spinal deformity A significant correlation (p < 0.001) was found between spinal deformity (assessed by axial trunk rotation (ATR) value) and lumbar puncture difficulty. In patients with mild deformity, 26.83% had moderate difficulty, while 28.57% experienced difficult LPs. Among patients with moderate deformity, 7.32% had moderate difficulty, while 14.29% had a difficult LP, and those with severe deformity had the highest difficulty rate, with only 0.98% classified as easy LPs, 4.88% as moderate, and 14.29% as difficult. These findings are consistent with Chien et al., who found that patients with spinal deformities required an average of 3.1 puncture attempts compared to 1.7 in those with normal spinal anatomy (p = 0.002), reinforcing the notion that deformities complicate spinal needle insertion. Shah et al. similarly reported that among 148 patients undergoing lumbar puncture, 41% of those with spinal deformities required multiple puncture attempts compared to 18% in those with normal spines (p = 0.01). Gvalani et al. also confirmed that patients with spinal deformities had an overall LP success rate of 68%, compared to 92% in patients with normal spine curvature (p = 0.005). Spinal landmark grading system (SLGS) A significant correlation (p < 0.001) was found between the spinal landmark grading system (SLGS) and lumbar puncture difficulty. Patients with visible spinous processes had a 50% easy lumbar puncture success rate, while those with palpable but not visible spinous processes had 34.31% easy LPs and 31.71% moderate LPs. Among patients whose spinous processes were neither visible nor palpable, 50% experienced difficult LPs, while 28.57% of those categorized as “none of the previous” had a difficult LP. These findings align with Chien et al., who found that patients with poor spinal landmark visibility had a 40% lower first-attempt success rate compared to those with visible landmarks (p = 0.001). Similarly, Shah et al. reported that patients in whom spinal processes were not identifiable by palpation had a 60% higher likelihood of requiring multiple LP attempts (p = 0.002). Patient position A significant correlation (p < 0.001) was found between patient positioning and lumbar puncture difficulty. The sitting position with flexed back was associated with the highest success rate, with 91.18% classified as easy LPs, 60.98% as moderate, and only 14.29% as difficult. In contrast, patients in sitting position with stiff back had significantly higher difficulty rate, with 57.14% experiencing difficult LP. Similarly, patients in lateral position with stiff back had a high rate of difficult LPs (14.29%) compared to those in lateral position with flexed back, where only 5.88% had difficult LPs. These results align with Subramanian et al. who found that patients positioned in sitting flexed posture had a median LP difficulty score of 2, compared to 7 in those with stiff back (p < 0.0001). Berg et al. confirmed that proper patient positioning reduced the required number of attempts by 1.5 per procedure (p = 0.009). Lumbar puncture difficulty score A significant correlation (p < 0.001) was found between various patient factors and lumbar puncture difficulty. Among the study population, 64.97% of patients had an easy LP, 26.11% had a moderate LP, and 8.92% had a difficult LP. The distribution of LP difficulty across different patient characteristics demonstrated clear trends: patients with higher age, increased abdominal circumference, spinal deformities, poor spinal landmark visibility (SLGS), and suboptimal positioning had higher rates of moderate and difficult LPs. These findings align with Chien et al., who found that patients with anatomical variations had a 42% higher rate of difficult LPs compared to those with normal spinal landmarks (p < 0.001). Grade of difficult lumbar puncture In the present study, a statistically significant correlation (p < 0.001) was found between patient variables and both total scores and grades of lumbar puncture (LP) difficulty. The strongest correlation was observed between spinal landmark grading system (SLGS) and total scores (r = 0.722, p < 0.001), followed by patient position (r = 0.598, p < 0.001) and abdominal circumference (r = 0.586, p < 0.001). Age (r = 0.576, p < 0.001) and spinal deformity (ATR values) (r = 0.457, p < 0.001) also demonstrated a strong association with LP difficulty. When comparing total scores with LP difficulty grades, a strong correlation (r = 0.707, p < 0.001) was found, indicating that higher scores were predictive of more difficult lumbar punctures. These findings align with Subramanian et al., who demonstrated that patients with total scores ≥6 had a 5-fold higher likelihood of experiencing moderate or difficult LPs (p < 0.0001). Similarly, Chien et al. reported that the SLGS had the strongest correlation with LP success (r = 0.68, p < 0.001), followed by age and BMI (p = 0.002 and p = 0.004, respectively). Limitations The study was conducted at a single institution, limiting the generalizability of the findings. Multicentre studies with diverse patient populations are needed to validate the results. Our study had small sample size, a larger study population may provide more robust conclusions and improve the power of the study.

Financial Assistance Nil Conflict of Interest Declaration The authors declare no conflicts of interest related to this study Author Contribution Kanchan Chauhan contributed in conception of work and study design, Sneha Mishra performed experimental work and collected data. Kanchan Chauhan and Ragini Keswani performed statistical analysis and interpreted the data. Sneha Mishra and Ragini Kashan drafted the manuscript and interpreted the collected data. All authors read and approved the final manuscript

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