Glenoid version and inclination are not static descriptive parameters but active determinants of glenohumeral joint mechanics, acting alongside the fundamental disproportion between the small glenoid and the much larger humeral head established in foundational cadaveric anatomical work22. The concavity-compression model of glenohumeral stability2 establishes that joint stability depends on the orientation of the glenoid concavity relative to the compressive force generated by the rotator cuff, such that even small angular deviations displace the point of peak contact pressure toward the glenoid rim. Because these angular relationships depend on a reproducible reference axis, considerable methodological effort has been devoted to optimising axis definition, from early goniometric technique4 to CT-based optimised-axis methods3.

These parameters carry direct clinical translation. The glenoid track concept5, subsequently formalised into the on-track/off-track classification of Hill-Sachs lesions6, converts glenoid width directly into individualised instability risk assessment. The Walch classification of osteoarthritic glenoid erosion and version change7 underpins modern preoperative planning for total and reverse shoulder arthroplasty1,8-9, and recent biomechanical work has shown that native glenoid concavity and version independently predict anterior shoulder stability13 and that graft positioning in bone-block augmentation surgery has a measurable effect on restored stability12. Separately, the glenopolar angle (GPA) carries established prognostic value in scapular trauma, with a markedly reduced angle indicating severe glenoid fragment displacement warranting operative fixation in floating shoulder injuries10.

Because all of these applications depend on population-appropriate reference values, and because glenoid angular parameters, like linear dimensions, are known to vary between populations18-19, locally derived data are required for safe clinical translation. An Indian population reference for GPA has been reported11, and version/inclination reference values exist from optimised-axis cadaveric work3, but no dedicated dataset combining all three angular parameters had previously been generated for Central India. This study reports glenoid version, inclination, and GPA in an adult dry-bone sample from the Malwa region of Madhya Pradesh and interprets these findings against the concavity-compression2 and glenoid track5-6 frameworks.

2.1 Study design and specimens This observational, cross-sectional osteometric study examined 150 fully ossified, intact adult human dry scapulae (75 right, 75 left) from the departmental bone bank, Department of Medical Anatomy, Index Medical College, Hospital and Research Center, Indore. Sample size was estimated using the standard formula for estimating a population mean with specified precision21, yielding a target of 150 specimens consistent with comparable published series. Scapulae with unfused epiphyses, gross pathology, fracture, or ambiguous laterality were excluded. Institutional Ethics Committee clearance was obtained; as specimens were previously accessioned, unclaimed osteological material, individual informed consent was not applicable. 2.2 Measurement protocol Glenoid version (retroversion/anteversion) and inclination (superior/inferior tilt) were measured using the optimised scapular- and glenoid-axis method3, in which the glenoid axis is defined as the normal to a least-squares plane fitted to the glenoid rim and the reference scapular axis by the spinoglenoid root and lateral border ridge, cross-checked against the axis conventions of Churchill et al.4. The glenopolar angle was measured as the angle subtended between a line joining the supero-lateral and infero-lateral glenoid margins and a line joining the supero-lateral glenoid margin to the inferior angle of the scapula, following the technique described for an Indian population11. Maximum scapular length and breadth were measured on an osteometric board. All measurements were taken in triplicate by two independent examiners using a digital goniometer/protractor, with repeat measurement triggered by inter-observer discrepancy exceeding 5% of the mean value. 2.3 Statistical analysis Data were analysed in SPSS v26.0. Normality was assessed with the Shapiro-Wilk test, and all three angular parameters were normally distributed (p > .05). Right-left comparisons used the independent-samples t-test. Pearson correlation and simple linear regression examined associations between angular parameters and scapular dimensions. Two-tailed p < .05 was considered significant throughout.

Descriptive statistics for all angular parameters are presented in Table 1. Mean glenoid version was 5.16 ± 1.82° of retroversion (range 0.79-11.75°), mean inclination was 15.39 ± 2.17° of superior tilt (range 10.11-21.22°), and mean GPA was 42.58 ± 2.02° (range 37.99-47.96°).

Table 1.

Descriptive Statistics of Glenoid Angular Parameters and Scapular Dimensions (N = 150)

Right-left comparison is shown in Table 2. No angular parameter differed significantly between sides (all p > .05).

Table 2.

Side-Wise Comparison of Glenoid Angular Parameters

Note. Version comparison used Welch-corrected t-test following Levene's test for unequal variances. None of the three parameters reached statistical significance.

Figure 1. Mean glenoid version and inclination by side, with error bars representing ±1 SD.

None of the correlations examined between angular parameters and scapular dimensions reached statistical significance: glenoid version vs. inclination (r = -0.030, p = .711), GPA vs. scapular length (r = -0.063, p = .443). A simple linear regression of GPA on scapular length explained under 1% of variance. The present GPA value (42.58 ± 2.02°) closely replicated an independently reported Indian population value of 42.6°¹¹ (Figure 2), and both values fall well above the 20° threshold conventionally used to indicate severe rotational glenoid fragment displacement warranting operative fixation in floating shoulder injuries¹⁰.

Figure 2. Mean glenopolar angle in the present study compared with an independently reported Indian population value, relative to the 20° operative threshold for floating shoulder management.

Table 3.

Comparison of Glenoid Version and Inclination with Published Reference Values

Note. Superscript numbers refer to the reference list. Em-dash indicates sample size not directly comparable across cadaveric series.

The version and inclination values recorded here closely match the optimised-axis reference values reported by Amadi et al.3, and are consistent with the near-neutral version and mild superior inclination described using goniometric technique4 (Table 3). The substantially narrower standard deviations obtained here most plausibly reflect the triplicate, dual-examiner protocol applied to a single regional population rather than a true reduction in underlying anatomical variability, since angular measurements are recognised as particularly sensitive to the precise reference axis used3,8. These findings carry direct translation through the concavity-compression model2: because joint stability depends on the alignment between the compressive force and the glenoid concavity, and because a joint reaction force inclined by only a few degrees from the glenoid axis has been shown computationally to displace peak contact pressure toward the glenoid rim15, the version and inclination values reported here represent the baseline orientation of this mechanism in the present population. This baseline, measured in non-diseased dry bone, plausibly approximates the pre-arthritic, concentric glenoid configuration in the Walch classification7 used to grade pathological glenoid erosion in preoperative arthroplasty planning, and is directly relevant to glenoid-track width estimation and individualised instability risk assessment through the on-track/off-track framework5-6. The intact glenoid labrum further contributes a direction-specific "suction cup" stabilising effect additive to bony concavity14, underscoring that native glenoid geometry, rather than bone alone, governs stability. The glenopolar angle recorded here (42.58 ± 2.02°) is remarkably closely replicated against an independently measured Indian population value (42.6°)11 - the smallest numerical discrepancy of any parameter compared in this study - and falls centrally within the normal 30-45° range used in the orthopaedic trauma literature, well above the 20° threshold associated with severe rotational glenoid fragment displacement warranting operative management of floating shoulder injuries10. This close agreement between an independently derived pan-Indian value and the present region-specific measurement strengthens the case for using an Indian-derived GPA reference range, rather than one imported from Western trauma literature, in clinical decision-making for patients from this population. No angular parameter differed significantly between sides, consistent with radiological evidence of excellent glenoid side-to-side symmetry20 and with the specific bilateral comparison reported for a North Indian population16, supporting pooling of side for reference-value generation in this population; this pattern of bilateral symmetry has similarly been assumed, if not always formally tested, in the nearest published regional comparator series from Western Rajasthan17. Similarly, the absence of significant correlation between angular parameters and scapular dimensions is consistent with population-comparative evidence that shoulder morphology does not scale uniformly with overall body or bone size18-19, reinforcing those biomechanical parameters as independent determinants of joint mechanics that cannot be inferred from gross scapular measurements and must continue to be assessed directly in preoperative planning1,9. 4.1 Limitations Glenoid depth, directly relevant to the concavity term of the concavity-compression model2, was not measured. Age and sex of individual specimens were unknown, precluding stratified analysis. Findings derive from a single institutional bone bank and would benefit from future multi-centric and living-patient CT-based validation.

Glenoid version, inclination, and glenopolar angle in this Central Indian population are bilaterally symmetrical, independent of scapular size, and closely consistent with existing Indian and optimised-axis reference values. These population-specific angular data support their direct clinical application to glenoid component positioning in shoulder arthroplasty, glenoid-track-based instability risk stratification, and glenopolar-angle-based prognostication in scapular trauma management for patients from this region.

Declarations

Ethics approval and consent to participate: Institutional Ethics Committee, Malwanchal University (Ref: MU/IEC/2026/xxx). As the study used previously accessioned, unclaimed osteological specimens, individual consent was not applicable.

Consent for publication: Not applicable.

Availability of data and materials: The datasets analysed are available from the corresponding author upon reasonable request.

Competing interests: The authors declare no competing interests.

Funding: This research received no specific grant from any funding agency.

Authors' contributions (CRediT): Shailendra Singh: Conceptualization, Methodology, Data curation, Formal analysis, Investigation, Writing - original draft. Avantika Bamne: Supervision, Conceptualization, Methodology, Writing - review & editing, Project administration.

Acknowledgements: The authors thank the Department of Medical Anatomy, Index Medical College, Hospital and Research Center, Indore, for access to the departmental bone bank.

Reporting guideline: This study is reported in accordance with the STROBE statement for cross-sectional studies.

Note on related work: This study forms part of a larger doctoral thesis examining glenoid cavity morphometry in the Malwa region; linear dimensions, glenoid cavity index, and shape distribution from the same specimen set are reported in a companion publication..

1. Neer CS 2nd. Replacement arthroplasty for glenohumeral osteoarthritis. J Bone Joint Surg Am. 1974;56(1):1-13.
2. Lippitt SB, Vanderhooft JE, Harris SL, Sidles JA, Harryman DT, Matsen FA. Glenohumeral stability from concavity-compression: a quantitative analysis. J Shoulder Elbow Surg. 1993;2:27-35.
3. Amadi HO, Banerjee S, Hansen UN, Wallace AL, Bull AM. An optimised method for quantifying glenoid orientation. Int J Shoulder Surg. 2008;2(2):25-9.
4. Churchill RS, Brems JJ, Kotschi H. Glenoid size, inclination, and version: an anatomic study. J Shoulder Elbow Surg. 2001;10(4):327-32.
5. Yamamoto N, Itoi E, Abe H, Minagawa H, Seki N, Shimada Y, Okada K. Contact between the glenoid and the humeral head in abduction, external rotation, and horizontal extension: a new concept of glenoid track. J Shoulder Elbow Surg. 2007;16(6):649-56.
6. Di Giacomo G, Itoi E, Burkhart SS. Evolving concept of bipolar bone loss and the Hill-Sachs lesion: from "engaging/non-engaging" lesion to "on-track/off-track" lesion. Arthroscopy. 2014;30(1):90-8.
7. Walch G, Mesiha M, Boileau P, Edwards TB, Levigne C, Moineau G, Young A. Three-dimensional assessment of the dimensions of the osteoarthritic glenoid. Bone Joint J. 2013;95(10):1377-82.
8. Gustas-French C, Petscavage-Thomas J, Bernard SA. Imaging of shoulder arthroplasties. AJR Am J Roentgenol. 2018;211(3):485-95.
9. Flatow EL, Harrison AK. A history of reverse total shoulder arthroplasty. Clin Orthop Relat Res. 2011;469(9):2432-9.
10. Yadav V, Khare GN, Singh S, Kumaraswamy V, Sharma N, Rai AK, Ramaswamy AG, Sharma H. A prospective study comparing conservative with operative treatment in patients with a 'floating shoulder' including assessment of the prognostic value of the glenopolar angle. J Bone Joint Surg Br. 2013;95(6):815-9.
11. Kumari N, Subhash A, Panchal P. Morphometric analysis of glenopolar angle of the scapula in Indian population. Cureus. 2024;16(7):e65189.
12. Oenning S, Wermers J, Köhler A, Sußiek J, Wiethölter M, Raschke MJ, Katthagen JC. The biomechanical importance of bone block positioning in glenoid augmentation: every millimeter matters. Am J Sports Med. 2025;53(5):1164-70.
13. Oenning S, de Castillo C, Jacob E, Riegel A, Michel PA, Wermers J, Raschke MJ, Katthagen JC. The clinical impact of glenoid concavity and version on anterior shoulder stability. JSES Int. 2025;9(1):62-9.
14. Ishikawa H, Henninger HB, Kawakami J, Zitnay JL, Yamamoto N, Tashjian RZ, Itoi E, Chalmers PN. A stabilizing role of the glenoid labrum: the suction cup effect. J Shoulder Elbow Surg. 2023;32(5):1095-104.
15. Daniel M, Proboštová M, Šika Z, Fulín P. The most common glenoid cavity morphotype confers the lowest shoulder stability: a computational analysis. Biomechanics. 2026;6(3):65.
16. Singh R. Surgical anatomy of the glenoid cavity and its use in shoulder arthroplasty among the North Indian population. Cureus. 2020;12(12):e11940.
17. Kataria SK, Shekhawat M, Gehlot K, Goyal S. Morphological and morphometric study of glenoid cavity and its clinical application in Western Rajasthan population. Int J Health Clin Res. 2022;5(1):222-6.
18. Cabezas AF, Krebes K, Hussey MM, Santoni BG, Kim HS, Frankle MA, Oh JH. Morphologic variability of the shoulder between the populations of North American and East Asian. Clin Orthop Surg. 2016;8(3):280-6.
19. Matsuki K, Sugaya H, Hoshika S, Ueda Y, Takahashi N, Tokai M, Banks SA. Three-dimensional measurement of glenoid dimensions and orientations. J Orthop Sci. 2019;24(4):624-30.
20. Shi L, Griffith JF, Huang J, Wang D. Excellent side-to-side symmetry in glenoid size and shape. Skeletal Radiol. 2013;42(12):1711-5.
21. Cochran WG. Sampling Techniques. 3rd ed. New York: John Wiley & Sons; 1977.
22. Iannotti JP, Gabriel JP, Schneck SL, Evans BG, Misra S. The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders. J Bone Joint Surg Am. 1992;74(4):491-500.