Morphometric study of the lumbar vertebrae in dried anatomical collections

Background The objective of this anatomical study was to perform the morphometry of dried lumbar vertebrae in human cadavers. Methods This study utilized 200 adult human cadaveric dried lumbar vertebrae. The digital Vernier calipers was used to perform the measurements. The height, antero-posterior length, transverse length of the body of the vertebrae, interpedicular distance at the lateral ends, lamina length, height and thickness, superior and inferior articular facet height and width, mid sagittal and transverse diameter of vertebral foramen, height, width and thickness of the pars inter-articularis were measured. Results The vertebral body’s anteroposterior length was more at the lower border than at the superior border ( p < 0.01). The length of lamina was higher over the right in comparison to the left (p < 0.001). The height of lamina, width of inferior articular facet, diameter of lateral recess and thickness of pars inter-articularis were greater for the left sided specimens ( p < 0.01). The statistical significance was not observed for the comparison of the remaining parameters ( p > 0.05). Conclusion This anatomical study offered several dimensions of lumbar vertebrae, which are essential in the surgical practice. The implants at the lumbar vertebrae need to be manufactured based on the anatomical dimensions of that particular sample population.


Introduction
In Latin language, 'lumbus' means 'lion', hence lumbar vertebrae are compared to a lion.They are very flexible and offer stability to the vertebral column.There are few studies available, which offer the morphometric data of the lumbar vertebrae, however there are not many studies available about the dimensions of pars inter-articularis in the anatomical collections.Pars interarticularis is located between the superior and inferior articular facets of the zygapophyseal joints of each vertebra.In the radiographs of the lumbar vertebrae, the pars inter-articularis resembles the neck of a Scottish dog.Since the surgical techniques of the vertebral column involve the utilization of bony anatomical landmarks, the morphometric data of the various parts of the vertebrae are essential.The accurate anatomical dimensional knowledge is important to understand the etiopathogenesis of the lower backache.The bony landmarks like the pars inter-articularis, transverse process, superior and inferior articular facets are particularly important during the internal fixation of the lumbar spine.The pars interarticularis are important parts of lumbar vertebrae, which help during the surgical instrumentation. 1 The anatomical studies help in understanding the detail complex morphometry of the vertebral column. 2,3There is an assumption that the morphometry of the vertebrae play a role in degenerative diseases of the vertebral column. 4The measurements are essential while choosing a suitable implant and this may avoid the intervertebral space exceeding and subsequent injury of the blood vessels. 5In this context, the objective of this anatomical study was to perform the morphometry of dried lumbar vertebrae of the human cadavers in sample Indian population.

Methods
This descriptive anatomical study included 200 adult cadaveric dry lumbar vertebrae.The sample size was calculated by referring the article by Singh et al. 6 The formula applied was Z 1-α/2 =Z value at 'α' level of significance Z 1-β =Z value at (1-β) % power σ=anticipated population standard deviation of the outcome variable (or) common assumed standard deviation between the two groups d=clinically significant difference The protocol of this present research is available online at https://www.protocols.io/view/morphometric-study-of-thelumbar-vertebrae-in-drie-cjqhumt6.The study duration was 6 months from 17.02.2022 to 17.08.2022.The age and sex of the specimens was not taken into consideration.The present study did not segregate the vertebrae into typical or atypical, because of the random collections of the dried vertebrae.We could not number the vertebrae with respect to the lumbar region.Congenitally deformed lumbar vertebrae were excluded from the present study.Measurements of this study are performed by the digital Vernier calipers.All the measurements were performed by one among the authors of this manuscript.The same author performed the measurements to prevent the inter-observer error.Three measurements were performed and the average of it was taken to prevent the intra-observer error.
The data are expressed in millimeters and tabulated as meanAEstandard deviation.The details of the measurements performed in this investigation are represented in Figure 1 and Table 1.The SPSS software (version 26) was utilized to perform the statistical analysis.The paired 't' test was applied to compare the parameters between the right and left sides.
The dimensions given here in this table, are to be correlated with Figure 1.

REVISED Amendments from Version 3
In this revised version, the changes are performed to the scientific content as per the learned reviewer's opinion.Two more recently published literature are cited.The limitations of this study based on the reviewer comments about the statistical analysis, ethnic variations are added.The Table 1 was revised and the clarity was given in correlation to Figure 1 with respect to the measurements.The discussion part is added with one more paragraph.
The ethics committee of our institution has approved this research (Institutional Ethics Committee, Kasturba Medical College, Mangalore, IEC KMC MLR: 02/2022/60, dated 17.02.2022).Since this is a study from the cadaveric dried bones, the consent from the participants is not applicable.This was waived by our institutional ethics committee.This present research is following the guidelines of the international ethical standards.Since this is a cross sectional study from the dried lumbar vertebrae of the donated cadavers and did not reveal the identity of the body donor, the written informed consent was not taken from the body donor's family for the use and publication of this research.

Results
The anatomical data obtained in this study are given in Tables 2 and 3.The vertebral body anteroposterior dimension was more at its lower border than at the upper (p<0.01).The length of lamina was higher over the right side (p < 0.001).The height of lamina, width of inferior articular facet, diameter of lateral recess and thickness of pars inter-articularis were greater for the left side (p<0.01).The remaining parameters, which were compared on the right and left sides did not reveal the difference with respect to the statistical significance (p>0.05).Table 1.Morphometric parameters of the lumbar vertebrae (n=200) performed in this study.

Discussion
If the significant part of vertebral body is involved in a disease, there will be neurological deficits and instability of the back.Internal fixation of vertebral column is the best management available for the traumatic spine injury, lumbar canal stenosis, spondylolisthesis and malignant tumors.The internal fixation offers better stabilization and decreases the duration of the morbidity.The spinal surgery is also performed in prolapsed intervertebral disc and conditions like scoliosis.It was reported that, this is among the hardest surgeries to perform as it is prone for the postoperative complications. 7Krag et al. 8 performed the morphometry of the vertebrae in cadavers, both manually and radiologically.
Characterizing the morphology of the spine among populations, would allow personalizing the conditions under which each individual should be exposed.The morphometric data of the vertebrae are not only useful in the field of neurosurgery, but are also essential to the specialties like neurology and orthopedics.Dimensions of the cervical and thoracic spine were already determined in our collections, few years ago. 9This present study was the continuation of this and here we determined the parameters in the lumbar vertebrae.The morphometrical data of various parts of lumbar vertebrae, procured from this study can be considered as the reference data for our study population.
There are not many studies being performed about the morphometry of pars inter-articularis.It offers structural support to the vertebral column and considered as the main support.Pars inter-articularis is a dense cortical bone and is exposed in the posterior approaches.There are morphometrical studies, which are performed by using the radiological methods like utilizing the radiographs and computed tomogram scans. 10The vertebral column robusticity increased significantly over the time affecting the dimensions of the vertebral body as well. 10According to Kapoor et al., 11 the inter-pedicular distance was 18.5 mm at the first lumbar vertebra, 21.5 mm at the lower lumbar vertebrae.Aly and Amin 12 reported that the interpedicular distance in the lumbar vertebrae varies from 17 to 43.4 mm and this increases towards inferior region.Nayak et al. 13 opined that the dimensions of vertebral foramen are higher in the atypical lumbar vertebrae than in the typical.The height of body of vertebrae was 171 cm in males and 158.2 cm in females. 10 During the neurosurgical procedures like pedicle screw insertion, improper design of the implant, the depth of insertion, morphometry, density of bone and iatrogenic mistakes can lead to complications like injury to the meninges, CSF leakage and injury to the neurovascular structures. 14Best knowledge of human anatomy about the morphometry and angulations of the pedicles in relation to the clinically oriented anatomical landmarks can prevent these complications. 14A South African research studied the ethnic variation in the osseous morphology of the dried lumbar vertebrae. 15In this present study, the ethnic variations were not studied and also the comparison with the previously published data was not possible as there were differences in the method of measurements performed.
In the present study, we could not segregate the vertebrae with respect to their number, age and sex.The segregation of the lumbar vertebrae into typical and atypical groups might have added more clarity and specificity.This can be considered as a limitation of this anatomical research.In this study, repeatability of the measurements by asking a secondary observer was not performed.It would have been better if a subset of the sample was measured by a secondary observer and intraclass correlation was applied statistically.If the measurements are consistently taken by one observer incorrectly and then averaged to one value it still might not be representative of the 'true' dimensions of the vertebrae.
Statistically confirming the agreement between these measurements would strengthen the quality of the research.If the intra-observer error is high, it might suggest the requirement for better measurement definitions or suggest using different tools for them in the field of vertebral morphometry in general.
Since it was just a cross sectional anatomical investigation from the dried vertebrae, the specimens from the same cadaver could not be determined as these are random collections.More studies with larger cohort and validated methods of accurate geometric measurements will be helpful in studying this complex anatomy.However, this study offers data about the pars interarticularis of the lumbar vertebrae, which are scarcely reported in the scientific literature.This makes this study interesting as this is novel in the anatomical literature and different from the previous publications.

Conclusion
We report the measurements of parts of the vertebrae of the lumbar region in sample Indian population.It is believed that, these data will help the operating neurosurgeons and spine surgeons during the surgeries like laminectomy and decompression.They are also essential in planning the accurate sizes of the plates and screws in the internal fixation.
The implants have to be manufactured depending on the anatomical dimensions of that particular sample population.I have some minor comments and suggestions to improve the manuscript:

Data availability
Introduction: 1.When referring to the shape of the pars inter-articularis as resembling the neck of a Scottish dog, please can a clear morphological description be provided instead?

Methods:
1. Please change the reference made to 'gender' to 'sex' instead as this is a biological study, gender is a social denomination and may not always be applicable in the biological context.
2. This study is commendable for including repeatability considerations as a lot of studies in anatomy do not do that, while it is a core premise of reproducibility.However, inter-observer error cannot be prevented entirely by simply having only one observer take the measurements.It would be better practice to test the repeatability of the measurements in a subset of the sample (usually 10-15% of the overall sample) by asking a secondary observer to measure the subset of the sample and using a statistical test (e.g., Intraclass Correlation also known as ICC).While this is not common practice in anatomy, if the physical lumbar vertebrae are still accessible it would improve the reproducibility of the overall study conducting these measurements and statistically testing them.
3. While the majority of morphometric studies tend to follow the same procedure the authors do regarding intra-observer error (i.e, measure 3 times and take the average), it would also be better to confirm this statistically by conducting an ICC on the same data (or a subset of them).If the measurements are consistently taken by one observer incorrectly and then averaged to one value it still might not be representative of the 'true' dimensions of the vertebrae.Statistically confirming the agreement between these measurements would strengthen the quality of the paper.If the intra-observer error is high, it might suggest the requirement for better measurement definitions or suggest using different tools for them in the field of vertebral morphometry in general.
4. In Table 1, please add dashes between the letters of the landmarks referring to Figure 1 (i.e., Vertebral body height (AB) should be: Vertebral body height (A-B)) and clarify in the table these letters refer to Figure 1, as it may be confusing to a reader without that context.

Discussion:
1.The study could benefit from direct comparison to other populations to contextualize the differences between the Indian population and other populations to manufacturers of vertebral implants.An example of a "recent" study from South Africa that may be worth including is: Sani, H.Y., 2018.The morphometric description of the thoracic and lumbar vertebral pedicles in European, African, and mixed populations of South Africa.The Faculty of Health Sciences, University of the Witwatersrand, Johannesburg.Available at: https://wiredspace.wits.ac.za/server/api/core/bitstreams/bcb279ea-d4d3-4301-ad99-062294c1aa12/contentHowever, this is a master dissertation/thesis (grey literature) and not an academic journal publication and may not fit the requirements of the authors or publishing platform for inclusion.
As such this suggestion is by no means a requirement.

Is the work clearly and accurately presented and does it cite the current literature? Yes
Is the study design appropriate and is the work technically sound?Yes Are sufficient details of methods and analysis provided to allow replication by others?Partly

If applicable, is the statistical analysis and its interpretation appropriate? Yes
Are all the source data underlying the results available to ensure full reproducibility?Yes

Are the conclusions drawn adequately supported by the results? Yes
Competing Interests: No competing interests were disclosed.
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
them in the field of vertebral morphometry in general.This is also added as the limitation. 5.The table 1 is revised as per the suggestion, like AB is revised as A-B 6.The given dissertation was referred and since it is a very good scientific literature, it is cited in the revised manuscript with respect to the ethnic variations.
Competing Interests: We do not have competing interests.

Gyanaranjan Nayak
Siksha 'O' Anusandhan Deemed to be University, Bhubaneswar, Odisha, India First of all, I am privileged to review this article.This seems like a well-conducted research.This is approved by the Institution Ethics Committee which is laudable.Despite working on only dried bones, the authors have ventured to get clearance from the said committee.The collection and analysis of the data seem adequate.However, I would like to comment that the segregation of the lumbar vertebrae into typical and atypical groups might have been done by the authors. 1.
I may suggest that segregating the vertebrae in the above manner will add more clarity and specificity to this well-conducted research and aptly written article.

2.
The authors also highlight that they have not done the above-mentioned segregation.But as for me, the criteria for segregating the vertebrae into typical atypical classes are rather lucid.

3.
The criteria can be easily looked up in any standard anatomy text.Apart from this obvious point, the research appears adequate.

Is the work clearly and accurately presented and does it cite the current literature? Yes
Is the study design appropriate and is the work technically sound?Partly

If applicable, is the statistical analysis and its interpretation appropriate? Yes
Are all the source data underlying the results available to ensure full reproducibility?Yes

Are the conclusions drawn adequately supported by the results? Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Human Anatomy, Clinical Anthropology, Cadaveric Anatomy, Histology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

Ravi Kant Narayan ESIC Medical College & Hospital, Bihar, India
The study is a repetition of numerous previous published literature. 1.
There is nothing novel in the manuscript except for the data from the unnamed population.2.
There is a lack of citations for multiple recently published articles on the same topic, such as Priya et al. (2023 1 ).

3.
Further, the discussion part is too thin and could have had much more clinically correlated data.

Introduction
Authors should cite some of the recent articles dealing with the morphometry of lumbar vertebrae.

Methods
It should be stated how many observers were involved in the data collection.

○
This section should explain how the authors avoided observational bias.

○
The time of the study's conduct needs to be mentioned.

○
If possible, provide more information about the lumbar vertebrae, such as whether they are typical or atypical.

○
The statistical test used in the study is missing, though it is mentioned in the data availability file.

○
In Tables 2 and 3, the statistical tests used need to be mentioned in the caption.

○
In Table 2, p value representation for AP length needs to be double-checked.

Discussion
The heading "Implications" in this section may not be appropriate as it deals only with the review of the literature.

○
Including information about how the current study's findings differ from those of previous studies will make the paper more interesting.I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
The benefits of publishing with F1000Research: Your article is published within days, with no editorial bias • You can publish traditional articles, null/negative results, case reports, data notes and more • The peer review process is transparent and collaborative • Your article is indexed in PubMed after passing peer review • Dedicated customer support at every stage • For pre-submission enquiries, contact research@f1000.com

Figure 1 .
Figure 1.Morphometric parameters of the lumbar vertebrae performed in this study (n=200).
length of body at superior border (C-A) 3 Antero-posterior length of the body at inferior border (D-B) 4 Transverse length of the body (E-F) 5 Distance between the lateral most parts of the pedicles (G-H) 6 Lamina length, right and left side (I-J) 7 Lamina height (K-L), right side and left side 8 Lamina thickness (M-N) on right and left sides 9 Superior articular facet height (O-P) and width (Q-R), right and left side 10 Inferior articular facet height (S-T) and width (U-V), right and left side 11 Mid sagittal anteroposterior diameter of vertebral foramen (W-X) 12 Transverse diameter of vertebral foramen (Y-Z) 13 Lateral recess diameter, right and left side (A1-B1) 14 Pars inter-articularis height on the right and left sides (C1-D1) 15 Pars inter-articularis width on the right and left sides (E1-F1) 16 Pars inter-articularis thickness over the right and left sides (G1-H1)

Reviewer Report 20
November 2023 https://doi.org/10.5256/f1000research.152503.r209281© 2023 Nayak G.This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

○
Is the work clearly and accurately presented and does it cite the current literature?PartlyIs the study design appropriate and is the work technically sound?YesAre sufficient details of methods and analysis provided to allow replication by others?YesIf applicable, is the statistical analysis and its interpretation appropriate?Partly Are all the source data underlying the results available to ensure full reproducibility?YesAre the conclusions drawn adequately supported by the results?YesCompeting Interests: No competing interests were disclosed.Reviewer Expertise: Natural products, osteoporosis, cardiovascular research and Bisphenol A associated toxicity and morphological variations.

Table 1 .
The SPSS software (version 26) was utilized to perform the statistical analysis.Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC BY 4.0).
Figshare.LUMBAR VERTEBRAE MORPHOMETRIC DATA.xlsx.DOI: https://doi.org/10.6084/m9.figshare.21307917.v1 16This project contains the following data: -This descriptive anatomical study included 200 adult cadaveric dry lumbar vertebrae.The sample size was as per the previous study by Singh et.al.The age and sex of the specimens was not taken into consideration.Congenitally deformed lumbar vertebrae were excluded from the present study.Measurements of this study are performed by the digital Vernier calipers.The data are expressed in millimeters and tabulated as mean AE standard deviation.The details of the measurements performed in this investigation are represented in Fig. 1 and