Background: : As per the previous studies, the line that connects the highest portion of iliac crests crosses at L4–L5 intervertebral disc space level in midline posteriorly. This line on palpation and imaging have different relationships, especially in the L4–L5 interspace. Purpose: The purpose of this study is to determine whether the level at the highest iliac crest on palpation and in the c-arm is are same or not. Materials And Methods: Admitted patients with lower back pain who are all accepted for injection steroid epidural route at our hospital, between July 2022 to November 2022. The authors drew the iliac crest line posteriorly on palpation and later in the C-arm, the level identified and was compared. Results: Thirty-four patients were included in our study with basic anthropometric variables (mean) are age 20-65 years (42 year), sex 12 males and 22 females, weight 50-95 kg (73.6 kg), height 145-185 cm (165.6 cm), body mass index 19-38 kg/m2 (26.8 kg/m2). On palpation, the intercrestal line crosses the midline 8.8% at L3 spinous process, 55.9% at L3-L4 interspinous space, 29.4% at L4 spinous process, 5.9% at L4-L5, and in no case at L5 spinous process. The C-arm imaged line crossed at L4 in 70.5% and L4-5 in 29.5% of patients with normal spinal anatomy. Conclusion: Our research found that using the iliac crest line to locate spinal levels is more accurate with imaging than palpation. On palpation, the line at the highest level of the iliac crest is at L3–4 and L4 spinal levels rather than the L4 or L4–5 levels.
Accurate identification of the intervertebral level is crucial for epidural injections in orthopedics, anesthesiology, and neurosurgery.(1,2) The iliac crest is a common landmark, with the intercrestal line typically aligning with the L4-L5 level.(3-5) However, studies show that using the iliac crest alone for palpation is unreliable (only 29% accuracy).(6) While adding the 10th rib as a landmark improves accuracy, palpation methods remain generally inaccurate.(7) This study compares spinal level identification using iliac crest palpation and C-arm fluoroscopy to determine the effectiveness of palpation.
This observational study, conducted from July to November 2022 at MVJ Medical College and Research Hospital, compared two methods for identifying the L4-L5 spinal level: palpation of the iliac crests and fluoroscopic imaging. After obtaining informed consent and ethical approval, patients (aged over 15) with lower back pain receiving epidural steroid injections were included. Patients with scoliosis, spondylolisthesis, or prior spinal trauma were excluded. Basic anthropometric data (age, sex, height, weight, BMI) were collected. Experienced examiners palpated the iliac crests, marking the postero-superior aspect. The line was measured using a radiopaque rod, and its corresponding spinal level (L4 spinous process or L4-L5 interspinous space) was determined via fluoroscopy. Statistical analysis (SPSS version 17.0) was used to compare the two methods, testing the null hypothesis of no difference. Descriptive statistics (mean, standard deviation) and correlations between anthropometric variables and intercristal line assessment were calculated. Statistical significance was set at P<0.05.
Thirty four patients were included in our study with basic anthropometric variables (mean) are age 20-65 years (42 year), sex 12 males and 22 females, weight 50-95 kg (73.6 kg), height 145-185 cm (165.6 cm), body mass index 19-38 kg/m2 (26.8 kg/m2)
Table 1. The distribution of population in different age groups and gender.
Gender |
Number of patients |
Male |
12 |
Female |
22 |
Age |
Number of patients |
20 – 30 yrs |
4 |
31 – 40 yrs |
13 |
41 – 50 yrs |
15 |
51 – 60 yrs |
2 |
On palpation, the intercrestal line crosses the midline 8.8% at L3 spinous process, 55.9% at L3-L4 interspinous space, 29.4% at L4 spinous process, 5.9% at L4-L5 and no case at L5 spinous process.
Table 2. Clinical and C-arm Findings of the lines
(SP = spinous process, IS = inter-spinous space)
|
L3 SP |
L3-4 IS |
L4 SP |
L4-5 IS |
L5 SP |
Total |
Clinical |
|
|||||
Male |
0 |
7 |
3 |
2 |
0 |
12 |
Female |
3 |
12 |
7 |
0 |
0 |
22 |
C-arm |
|
|||||
Male |
0 |
0 |
10 |
2 |
0 |
12 |
Female |
0 |
0 |
14 |
8 |
0 |
22 |
Table 3. Clinical and C-arm Findings of the lines correlation
(SP = spinous process, IS = interspinous space)
Palpation |
Imaging |
|||||
|
L3 SP |
L3-4 IS |
L4 SP |
L4-5 IS |
L5 SP |
TOTAL |
L3 SP |
0 |
0 |
3 |
0 |
0 |
3 |
L3-4 IS |
0 |
0 |
14 |
2 |
0 |
16 |
L4 SP |
0 |
0 |
2 |
8 |
2 |
12 |
L4-5 IS |
0 |
0 |
0 |
2 |
1 |
3 |
L5 SP |
0 |
0 |
0 |
0 |
0 |
0 |
TOTAL |
|
|
19 |
12 |
3 |
34 |
On no occasions did the palpated line identify a lower level than the imaging.
The palpated ICL identified the higher spinal levels in patients with higher BMI, the difference between the median values reach statistically significance (p=0.04) shown in table 4. With the imaged ICL there was no significant difference between the spinal level and BMI.
Table 4: Correlation coefficient between the levels of intersection and patients’ characteristics
Variable |
Correlation coefficient |
95% Confidence Interval |
P value |
Weight (kg) |
0.21 |
0.12-0.56 |
0.28 |
Height (cm) |
0.29 |
0.39-0.08 |
0.16 |
Body mass index (kg/m2) |
0.38 |
0.03-0.63 |
0.04 |
Accurate spinal level identification is crucial in orthopedics, anesthesiology, and neurosurgery. Various methods exist, including using a vertical line from the iliac crest (Ievins et al.), a line between the posterior superior iliac spines (Borley et al.), or a line between the lowermost margins of the tenth ribs (Jung et al.). The intercrestal line (ICL), palpated between the iliac crests, is a popular method, often cited as intersecting L4 or L4-5.
However, studies using imaging (X-rays and MRI) reveal inconsistencies. Our study showed that on palpation, the intercrestal line crosses the midline 8.8% at L3 spinous process, 55.9% at L3-L4 interspinous space, 29.4% at L4 spinous process, 5.9% at L4-L5 and no case at L5 spinous process.
The c-arm imaged line crossed at L4 in 70.5% and L4-5 in 29.5% of patients with normal spinal anatomy. Palpation's accuracy is limited, with inter-clinician agreement around 60% (Broadbent et al., 2000). While Ievins et al. (1991) reported higher accuracy (78.3%) using cadavers, this contrasts with the lower accuracy (59.3%) of half-Tuffier's line. Factors influencing inaccuracy include high lumbar level selection, obesity, and the difference between palpated and imaged ICL. Palpated ICL most often identifies L3-4 (48.2%), while imaged ICL identifies L4 and L4-5 (96.4%). This discrepancy is significant except at L4. Subcutaneous tissue thickness affects palpation accuracy, with higher BMI and body fat percentage in females leading to higher level identification (Bartali et al., Gallagher et al.). While our study focused on normal anatomy, conditions like sacralization, lumbarization, spondylolisthesis, scoliosis, and vertebral height loss can affect accuracy. Limitations include our small sample size; larger studies are needed.
Our research found that using the iliac crest ine to locate spinal levels is more accurate with imaging than palpation. Palpation most often identifies the L3-L4 space, while imaging shows the L4 spinous process and L4-L5 space. While both methods aim to pinpoint the exact spinal level, palpation is less reliable in people with high BMIs. Imaging is the preferred method for these individuals.