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.

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).

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.

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].

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.