Title & Abstract

International Journal of Anatomy and Research

Morphometric Evaluation of Wedging Index, Pedicle Index, Canal-to-Body Ratio, and Canal Spinal Index in Dry Human Lumbar Vertebrae: Anatomical Implications for Lumbar Instrumentation and Spinal Canal Assessment

DOI: 10.16965/ijar.2026.196

Rohilla, Swati ¹

Saha, Susmita ¹

Aneja, Prachi Saffar ¹

Kapur, Neeru ²

Roy, Tara Sankar ³

1,2,3 Department of Anatomy, SGT Medical College, Gurugram-122505, India.

⁴ Department of Radiology, SGT Medical College, Gurugram-122505, India.

⁵ Department of Anatomy, NDMC Medical College, Delhi, India.

ABSTRACT

Background.

This study aims to evaluate the anatomical and surgical significance of the Wedging Index (WI), Pedicle Index (PI), Canal-to-Body Ratio (CBR), and Canal Spinal Index (CSI) in dry human lumbar vertebrae.

Methods.

A total of 100 dried adult lumbar vertebrae (L1-L5) were analysed using a digital Vernier caliper. Measurements of the spinal canal, pedicle, and vertebral body were obtained, and the Wedging Index (WI), Pedicle Index (PI), Canal-to-Body Ratio (CBR), and Canal Spinal Index (CSI) were calculated using standard formulas. Descriptive statistics, Pearson correlation, and one-way ANOVA were employed for data analysis.

Results.

The WI increased from L1 (0.93 ± 0.07) to L4 (1.08 ± 0.15), indicating level-specific variation in vertebral body wedging. The PI increased slowly from L1 (0.53 ± 0.18) to L4 (1.13 ± 0.27), then dropped at L5 (0.51 ± 0.14). The CBR declined from L1 (0.53 ± 0.07) to L4 (0.40 ± 0.07), suggesting reduced canal capacity at lower lumbar levels. The CSI varied significantly between vertebral levels (ANOVA, p < 0.001). There was a strong positive correlation between CSI and CBR.

Conclusion.

Lumbar vertebrae exhibit significant morphometric differences across levels. L4 demonstrated the lowest relative canal dimensions among the studied levels, which may have anatomical relevance to assessment of spinal canal adequacy. These findings may assist with implant design, radiograph interpretation, and spinal instrumentation planning.

Keywords: Lumbar vertebra; Wedging index; Pedicle index; Canal spinal index; Canal to body ratio

INTRODUCTION

The lumbar spine is the major load-bearing axis of the human skeletal system which sustains maximum biomechanical and complex kinematic forces [1]. As a result, the region is prone to degenerative diseases like lumbar spinal stenosis, spondylolisthesis and vertebral compression fractures [2]. Knowledge of regional morphometry is immensely important for decompressive laminectomies and for transpedicular screw fixation [3]. Even a deviation of a millimetre during pedicle instrumentation may result in pedicle breach, neurological injury or dural rupture [4]. Therefore, establishing accurate, population-specific anatomical baselines has immense importance in the safety of these procedures and in designing implants accordingly [5].

Standardised structural indices are essential for translating anatomical data into clinical practice. These indices represent quantitative measurements used to convert anatomical data into the language of the practising orthopaedic surgeon and to assist in clinical diagnosis. The Wedging Index (WI) is a parameter for calculating the severity of compression fracture and is the primary element of lumbar lordosis [6]. The Pedicle Index (PI) describes the 'safe zone' for screw courses, though it measures the cortical-cancellous structure [4,7]. The Canal Spine Index and Canal Body Ratio (CBR) are subtle measures of osseous three-dimensional capacity [6]. These ratios help clinicians differentiate between secondary narrowing from soft-tissue hypertrophy and primary osseous stenosis by comparing the vertebral foramen area to the overall vertebral frame [8].

There is a lack of morphometric data on the Asian population, because most conventional morphometric data is derived from Western populations or from imaging techniques such as MRI and CT [5,9]. Plain radiographs can magnify images by 10 to 15% due to radiation divergence [10]. CT may obscure cortical borders secondary to slice thickness averaging and partial-volume effects leading to inaccurate pedicle measurements [11]. MRI gives limited detail of cortical bone, so perimeter delineation is subject to observer interpretation. Examining direct dry lumbar vertebrae using digital calipers is considered the gold standard as it offers unconfounded anatomical precision [7,11].

This study aims to determine the Wedging Index, Pedicle Index, Canal Body Ratio, and Canal Spine Index in dry human lumbar vertebrae on the basis of precise measurements, eliminating the artifacts of imaging technologies to provide population-specific baselines for pre-operative planning, radiological interpretations, and transpedicular implant design.

MATERIALS AND METHODOLOGY

Study Design and Specimen Selection

This cross-sectional osteological study was conducted on 100 dried adult human lumbar vertebrae from the Department of Anatomy collection. Ethical clearance was obtained from the Institutional Review Committee (IEC/FMHS/PhD/2024-09). All intact and well-preserved lumbar vertebrae, both typical (L1-L4) and atypical (L5), were included irrespective of sex.

Data Acquisition and Primary Morphometric Parameters

Linear parameters of dried lumbar vertebrae were measured using a digital Vernier caliper with an accuracy of 0.01 mm (Figure 1). Primary measured parameters are defined in Table 1.

Figure 1

Table 1

Morphometric parameters measured in the present study.

S. No. | Parameter | Definition
1 | Ha | Anterior vertebral body height
2 | Hp | Posterior vertebral body height
3 | APVB | AP diameter of vertebral body
4 | TVB | Transverse diameter of vertebral body
5 | PW | Pedicle width
6 | PH | Pedicle height
7 | APC | AP canal diameter
8 | TC | Transverse canal diameter

Morphometric Indices Calculation

Four established morphometric indices—Wedging Index (WI), Pedicle Index (PI), Canal-to-Body Ratio (CBR), and Canal Spinal Index (CSI)—were calculated using standard formulas (Table 2).

Table 2

Morphometric indices calculated in the present study.

S. No. | Index | Formula
1 | WI | Hp / Ha
2 | PI | PW / PH
3 | Canal Body Ratio [12] | A-P canal / mean A-P of body
4 | Canal Spinal Index [13] | (T canal X A-P canal) / (T body X A-P body)

Statistical Analysis

Data were analyzed using SPSS version 28 (IBM Corp.). Descriptive statistics (mean, standard deviation, range) were calculated by lumbar level. Paired Student's t-tests (p < 0.05) assessed bilateral differences in pedicle dimensions, one-way ANOVA (p < 0.001) evaluated level-wise variation (L1-L5), and Pearson correlation evaluated inter-index relationships.

RESULTS

A total of 100 dry lumbar vertebrae (L1: n=32, L2: n=24, L3: n=23, L4: n=10, L5: n=11) were examined. Primary morphometric measurements of vertebral body height, diameters, canal diameters, and pedicle dimensions are presented in Tables 3 to 6.

Morphometric indices varied significantly across lumbar vertebral levels (Table 7). The Wedging Index increased from L1 (0.93 ± 0.07) to L4 (1.08 ± 0.15; Figure 2). Pedicle Index increased from L1 (0.53 ± 0.18) to L4 (1.13 ± 0.27), changing from a vertical oval to transverse oval configuration, before falling at L5 (0.51 ± 0.14; Figure 3). Canal-to-Body Ratio declined progressively from L1 (0.53 ± 0.07) to a minimum at L4 (0.40 ± 0.07, ANOVA F=8.47, p < 0.001; Figure 4), recovering at L5 (0.48 ± 0.06). Canal Spinal Index reached its nadir at L4 (0.20 ± 0.05, ANOVA F=8.98, p < 0.001; Figure 5).

Figure 2

Figure 3

Figure 4

Figure 5

Pearson correlation demonstrated a moderate positive relationship between Wedging Index and Pedicle Index (r = 0.69, R2 = 0.481, p = 0.196; Figure 6). A very strong, statistically significant positive correlation was identified between Canal-to-Body Ratio and Canal Spinal Index (r = 0.96, R2 = 0.928, p < 0.001; Figures 7 and 8), confirming morphometric synergy across lumbar levels.

Figure 6

Table 3

Descriptive statistics of anterior and posterior vertebral body height.

S. No. | Parameter | Min (mm) | Max (mm) | Mean (SD) (mm) | t-value | p-value
1a | Vertebral Body Height Ant. | 15.2 | 28.3 | 22.92 (2.37) | 0.671 | 0.503
1b | Vertebral Body Height Post. | 17.6 | 29.1 | 23.14 (2.11) | 0.671 | 0.503

Table 4

Descriptive statistics of transverse diameter (vertebral body width) and anteroposterior vertebral body diameter at superior and inferior levels.

S. No. | Parameter | Min (mm) | Max (mm) | Mean (SD) (mm) | t-value | p-value
1a | Transverse diameter Sup. | 30.02 | 55.5 | 41.46 (5.46) | 3.006 | 0.003*
1b | Transverse diameter Inf. | 31.9 | 58 | 43.74 (5.25) | 3.006 | 0.003*
2a | A-P vertebral diameter Sup. | 22.3 | 35.3 | 28.48 (3.15) | 1.089 | 0.278
2b | A-P vertebral diameter Inf. | 23.5 | 39.8 | 28.95 (2.91) | 1.089 | 0.278

Table 5

Descriptive statistics of transverse and anteroposterior diameters of the vertebral canal.

S. No. | Parameter | Min (mm) | Max (mm) | Mean (SD) (mm)
1 | Transverse diameter of vertebral canal | 14.7 | 28.34 | 20.60 (2.72)
2 | A-P diameter of vertebral canal | 9.3 | 18.48 | 13.32 (2.18)

Table 6

Descriptive statistics of pedicle width and pedicle height on right and left sides.

S. No. | Parameter | Min (mm) | Max (mm) | Mean (SD) (mm) | t-value | p-value
1a | Width of pedicle Right | 4.1 | 17.43 | 8.25 (3.25) | 0.534 | 0.594
1b | Width of pedicle Left | 4.1 | 19.12 | 8.50 (3.41) | 0.534 | 0.594
2a | Height of pedicle Right | 6.4 | 17.1 | 13.09 (1.47) | 0.976 | 0.33
2b | Height of pedicle Left | 5.5 | 18.1 | 12.87 (1.67) | 0.976 | 0.33

Table 7

Mean values and standard deviations of calculated morphometric indices across human lumbar vertebral levels (L1-L5).

S. No. | Vertebral level | n | Wedging index | Pedicle index | Canal to body ratio | Canal Spine index
1 | L1 | 32 | 0.93 ± 0.07 | 0.53 ± 0.18 | 0.53 ± 0.07 | 0.27 ± 0.05
2 | L2 | 24 | 1.03 ± 0.11 | 0.62 ± 0.16 | 0.43 ± 0.06 | 0.20 ± 0.05
3 | L3 | 23 | 1.00 ± 0.08 | 0.74 ± 0.29 | 0.45 ± 0.10 | 0.21 ± 0.06
4 | L4 | 10 | 1.08 ± 0.15 | 1.13 ± 0.27 | 0.40 ± 0.07 | 0.20 ± 0.05
5 | L5 | 11 | 1.03 ± 0.04 | 0.51 ± 0.14 | 0.48 ± 0.06 | 0.23 ± 0.03

DISCUSSION

This osteometric study establishes normative baselines for Wedging Index, Pedicle Index, Canal-to-Body Ratio, and Canal Spinal Index in dry human lumbar vertebrae [15]. Regional and ethnic anthropometric variations necessitate population-specific osteometric data for accurate forensic, orthopedic, and neurosurgical applications.

The progressive increase in WI from L1 (0.93) to L4 (1.08) demonstrates the transition from anterior wedging to posterior wedging, supporting the sagittal alignment and load-transfer mechanics of lumbar lordosis [15]. Pedicle Index expansion peaking at L4 (1.13) reflects functional adaptation to increasing caudal biomechanical loads before transitioning toward the sacrum [16,17].

Canal-to-Body Ratio and Canal Spinal Index both reached a spatial nadir at L4 (CBR = 0.40, CSI = 0.20), providing an anatomical basis for the high clinical incidence of degenerative lumbar canal stenosis at the L4 level [6,14,18,19]. The very strong correlation between CBR and CSI (r = 0.96, R2 = 0.928, p < 0.001) confirms coordinated developmental and biomechanical adaptation between the spinal canal and vertebral body (Tables 8 and 9) [20].

Table 8

Comparison of the present study with previous studies on lumbar vertebral morphometry.

S. No. | Author (Year) | Population / Material | Parameter Studied | Main Findings | Comparison with Present Study
1 | Zindrick MR et al. (1987) [3] | Human lumbar vertebrae | Pedicle dimensions | Progressive increase in pedicle width from L1 to L5; important for pedicle screw fixation | Similar trend observed. Present study showed increasing PI from L1 to L4, confirming adaptation of pedicles to increasing biomechanical load.
2 | Mitra SR et al. (2002) [7] | Indian population | Pedicle morphometry | Lower lumbar pedicles wider than upper lumbar pedicles | Present findings support gradual increase in pedicle dimensions toward lower lumbar levels.
3 | Verma V et al. (2023) [4] | Dry lumbar vertebrae | Pedicle width and height | Significant regional variation in pedicle dimensions with surgical implications | Consistent with our findings of level-specific PI variation and maximal pedicle expansion at L4.
4 | Been E & Kalichman (2014) [15] | Review of lumbar lordosis | Vertebral wedging | Lumbar lordosis results from cumulative vertebral and disc wedging | Present study demonstrated progressive increase in WI from L1 to L4, supporting their biomechanical explanation of lordosis formation.
5 | Abbas J et al. (2010) [6] | Radiological lumbar spine analysis | Canal morphology and lumbar configuration | Vertebral shape influences spinal canal dimensions and stenosis | Present study also demonstrated reduced canal dimensions at L4, supporting anatomical predisposition to stenosis.
6 | Shrestha I (2022) [14] | Dry lumbar vertebrae | Canal-to-Body Ratio (CBR) | Higher CBR in upper lumbar vertebrae and lower values in mid-lumbar levels | Strong agreement with present study, where CBR decreased from L1 (0.53) to L4 (0.40).
7 | Bajwa NS et al. (2013) [18] | 420 postmortem lumbar vertebrae | Lumbar Torg ratio | Smaller canal-body ratios associated with reduced canal area and stenosis risk | Present study similarly identified L4 as the segment with the lowest relative canal capacity.
8 | Qudsieh H et al. (2022) [19] | MRI-based lumbar spine study | Torg-Pavlov Ratio | Significant variation with vertebral level and canal size | Present osteometric findings corroborate level dependent changes in canal adequacy.
9 | Present Study (2026) | 100 dry lumbar vertebrae | WI, PI, CBR, CSI | L4 showed highest PI (1.13), lowest CBR (0.40), lowest CSI (0.20); strong CSI-CBR correlation (r = 0.96) | Demonstrates a morphometric bottleneck at L4 and introduces the concept of morphometric synergy between CSI and CBR.

Table 9

Novel findings of the present study compared with previous literature.

S. No. | Morphometric Observation | Previous Literature | Present Study Contribution
1 | Lumbar vertebral wedging contributes to lordosis | Reported by Been and Kalichman [15] | Quantified using WI across L1-L5 in dry vertebrae
2 | Pedicle dimensions increase caudally | Reported by Zindrick, Mitra, Verma [3,4,7] | Confirmed through Pedicle Index analysis with peak at L4
3 | Canal-body ratio decreases in lower lumbar spine | Reported by Shrestha and Bajwa [14,18] | Demonstrated lowest value at L4, indicating stenosis-prone segment
4 | Canal morphology varies by vertebral level | Reported in radiological studies by Abbas J et al. (2010) [6] | Confirmed osteometrically through CSI analysis
5 | Relationship between CSI and CBR | Rarely investigated | Demonstrated very strong positive correlation (r = 0.96) suggesting coordinated vertebral canal adaptation

CONCLUSION

This study indicates significant level-wise variations in lumbar vertebrae morphometry, with the Canal Spinal Index and Canal-to-Body Ratio exhibiting strong morphometric synergy. The identification of a structural bottleneck at L4—characterized by maximal pedicle expansion and minimal relative canal capacity—provides an anatomical rationale for vulnerability to spinal stenosis. These findings provide baseline osteometric parameters essential for pre-operative planning, transpedicular instrumentation, and implant design.

Abbreviations & Declarations

DECLARATIONS

Ethical Approval: Ethical clearance was obtained from the Institutional Review Committee (IEC/FMHS/PhD/2024-09).

Conflicts of Interest: There is no competing interests between authors.

Author Contributions: All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Swati Rohilla, Susmita Saha, Prachi Saffar Aneja and Neeru Kapur. The first draft of the manuscript was written by Swati Rohilla, and all authors commented on previous versions of the manuscript and Tara Sankar Roy has done the data analysis and critical revision. All authors read and approved the final manuscript.

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