Advances in the Measurement and Interpretation of Intervertebral Motion in the Lumbar Spine: A Scoping Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This scoping review aims to map 25 years of research on intervertebral motion measurement and interpretation. While the topic is relevant, the manuscript has substantial methodological, conceptual, and interpretive weaknesses. The narrative is largely descriptive, lacks analytical depth, and frequently presents published findings uncritically. There are major issues with rigor, structure, transparency of methods, and validity of several conclusions.

Major comments

1. The search strategy is insufficiently detailed and does not meet typical scoping review standards (e.g., no explicit search strings, no database date limits, no justification for exclusions).
2. The review lacks a PRISMA flow diagram or equivalent, making it impossible to verify how studies were screened, excluded, or categorized.
3. The methods do not provide a clear operational definition for what qualifies as “intervertebral motion studies,” leading to a heterogeneous and sometimes arbitrary set of included papers.
4. The classification into “study types” appears subjective and post-hoc, without transparent criteria or inter-reviewer agreement.
5. The taxonomy is presented as a major contribution, yet it is not directly derived from systematic methodology and seems more speculative than evidence-based.
6. Many included studies are summarized without any critical appraisal of their methodological quality, sample size limitations, or measurement validity.
7. The manuscript frequently presents findings from extremely small studies (n < 10) without contextualizing their limited generalizability.
8. Several statements imply causal interpretations, although the underlying studies are observational, cross-sectional, or technically constrained.
9. The narrative often restates results from primary studies without synthesizing or evaluating how reliable or comparable these results actually are.
10. The review does not address publication bias or selective reporting, which is highly relevant given the small and fragmented research landscape.
11. The discussion of imaging modalities lacks a structured comparison of accuracy, reliability, temporal resolution, and clinical feasibility.
12. The review heavily favors 2D quantitative fluoroscopy without adequately questioning its limitations (projection errors, boundary detection, planar approximation).
13. The authors do not address potential confounding factors such as posture standardization, participant training, movement variability, or inter-operator differences.
14. The review fails to critically evaluate the validity of dynamic imaging for capturing true intervertebral motion, given known issues of vertebral tracking accuracy.
15. Soft tissue artifact is described as “largely complete,” which is an overstatement and not justified by only three highly constrained studies.
16. The presentation of normative kinematic databases is uncritical; important issues such as reproducibility, cohort representativeness, and cross-device comparability are not addressed.
17. The interpretation of disc degeneration kinematics is overly reliant on a few dated studies without acknowledging substantial advances in recent MRI-based biomechanics.
18. Several citations are treated as definitive despite major methodological weaknesses (e.g., small sample sizes, invasive designs, limited frame rates).
19. The claim that implanted marker systems have “waning interest” is speculative and does not consider broader reasons such as ethics, cost, or alternative technologies.
20. The aerospace kinematics section is extremely brief and lacks any substantive biomechanical synthesis; its inclusion seems forced rather than logically integrated.
21. The review repeatedly conflates “motion abnormalities” with “biomarkers” without providing criteria for what constitutes a valid biomarker.
22. The identification of MSI as a potential biomarker is presented as a key insight but without critical assessment of measurement error, inter-rater variability, or construct validity.
23. The conclusions suggest major clinical implications, yet the preceding sections do not provide robust enough evidence to justify such claims.
24. The manuscript overstates the degree to which technological “advances” have resolved issues of accuracy and reliability; the evidence presented does not support this optimism.
25. The review does not sufficiently consider the impact of harmonizing different coordinate systems, tracking algorithms, or imaging geometries across studies.
26. Terminology such as “phase lag,” “instability,” and “attenuation rate” is used inconsistently and sometimes without clear biomechanical definitions.
27. Several sections merely list studies chronologically, which reads more like an annotated bibliography than a coherent biomechanical synthesis.
28. The paper lacks a conceptual framework linking intervertebral kinematics to functional outcomes, pathology progression, or neuromuscular control.
29. The discussion frequently generalizes beyond the actual evidence base, especially concerning clinical relevance and measurement precision.
30. The limitations section acknowledges missing studies but does not propose concrete methodological improvements or explain how these limitations bias results.
31. Many claims about “research trajectories” or “prevailing priorities” are speculative and not quantitatively supported (e.g., no evidence of trends over time).
32. The manuscript lacks critical evaluation of the validity of fluoroscopic tracking algorithms, particularly regarding digitization noise and smoothing artifacts.
33. No consideration is given to translational issues such as cost, required expertise, or patient burden, limiting the practical relevance of the review.
34. The recommendation for standardization is generic and not supported by specific proposals, metrics, or implementation pathways.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Since there is currently a lack of standardization and thorough understanding in the measurement and interpretation of intervertebral motion, the review aims to provide a structured taxonomy to enhance clinical practice and research in this area. The introduction of the paper provides a solid and well-developed justification for the review.

This review was conducted following the PRISMA guidelines. The search strategy and eligibility criteria for inclusion are adequately described. 

Forty-nine studies were finally included and categorized into 11 distinct study types, which were further grouped into 6 overarching categories (Normal biomechanical mechanisms, Pathological and injury mechanisms, Direct kinematic measurement, Spinal stabilization, Dynamic radiography, and Clinical markers). The authors claim that the  paper's primary practical implication is to bring order and clarity to a complex and often disparate field. By offering a robust taxonomy and highlighting key areas of progress and challenge, it provides essential guidance for improving the consistency, comparability, and clinical utility of research into lumbar intervertebral motion.

The discussion is inclusive and wide ranging. The authors acknowledge that although this scoping review is thorough, it has a number of limitations such as potential bias for missed or excluded studies, and the prevalence of studies with small sample size.

Although it was not the author's intention, this scoping review does not offer any new evidence in this field of study. The review arranges and categorizes different facets of the field's knowledge and seems very interesting to experts.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

excellent and well conducted research

please add kappa agreement in study selection phase

explain better why quality assesment was not performed

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Editor, thank you for the opportunity to review this interesting review on Advances in the Measurement and Interpretation of Intervertebral Motion in the Lumbar Spine. Congratulations to the authors for their work, which is well structured overall and presented in an appropriate format. However, before it is considered for publication, in my opinion, some aspects should be addressed and improved.

Specific comments:

Introduction: In my opinion, Figure 1 is useful but should be discussed and better integrated into the text.

Methods:

• The authors chose a time frame of 2000–2025, but then cite studies from the 1990s, such as Kanayama 1996, which creates a fundamental inconsistency.
• The classification categories are not mutually exclusive, and therefore some studies may fall into more than one category (e.g., “technology development” vs. “dynamic radiography”). Furthermore, I imagine they were derived post hoc from a manual and qualitative grouping rather than from a systematic analysis (e.g., cluster analysis). This should be stated for the reasons of transparency. Furthermore, some categories are not of the same type. For example, “Normative lumbar kinematics” is a type of study, while “Dynamic radiography” is a technique. The taxonomy could be reconstructed by clearly distinguishing between: Purpose of the studies, Methodology applied, and Target population.

Results:

• Many of the studies come from the group of authors. This is acceptable, but there is a risk that the results reflect more what is being done by a single group than the state of the art. Therefore, it is suggested that the research be expanded by including other external references.
• Some fields such as MRI-based, machine learning landmarking, and wearable inertial sensors are rarely discussed and could be given greater consideration.
• The very small sample sizes in most studies; this could be further emphasized in the limitations section.

Discussion:

• In my opinion, the discussion section is a bit limited. The studies found could be discussed in greater detail here, and some cases could be reported and compared in more detail. This section should not simply repeat the contents of the results, but should clearly explain the added value of the work.
• Furthermore, I think it would be very interesting if the authors could indicate in a subsection of the discussions some practical applications and uses of these systems in postural treatments, for example (D'Amanti, Alfredo, et al. "Effective treatment of adolescent idiopathic scoliosis with the PosturalSpine® D’Amanti method and Chêneau brace. A pediatric patient case report demonstrating postural and orthotic synergy." European Journal of Translational Myology 2025 ; Leinonen, Ville, et al. "Lumbar paraspinal muscle function, perception of lumbar position, and postural control in disc herniation-related back pain." Spine 28.8 2003)

Some other suggested references:

• Lee, Sai-wing, et al. "Development and validation of a new technique for assessing lumbar spine motion." Spine 27.8 (2002): E215-E220.
• Vergari, Claudio, et al. "Lumbar annulus fibrosus biomechanical characterization in healthy children by ultrasound shear wave elastography." European radiology 26.4 (2016): 1213-1217.
• Gajny, Laurent, et al. "Quasi-automatic 3D reconstruction of the full spine from low-dose biplanar X-rays based on statistical inferences and image analysis." European Spine Journal 28.4 (2019): 658-664.
• Lee, Raymond. "Measurement of movements of the lumbar spine." Physiotherapy Theory and Practice 18.4 (2002): 159-164.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

thank you for your comments, paper is now ready for publication

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

I confirm what was said during the first round of review regarding the quality of the work, and in my opinion, there are some points that should be improved, which I will pay attention to.

- Comment 1. The authors did not make changes to the manuscript in the introduction section, and Figure 1, inserted at the beginning of the manuscript, could be described more in the text (and the authors could improve its quality).

- Comment 2. If older references such as Kanayama (1996) were not included in the curation as the authors state, they should not be presented in the results of the paper, and they might be discussed in the introduction and discussions.

- Comment 8. Although the examples provided were not considered of interest by the authors, I think it would still be interesting (not mandatory) if the authors could indicate in a subsection of the discussions some practical applications and uses of the systems in the discussion section (even citing other papers not included for some reason, but that they evaluate to be relevant).

Author Response

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Author Response File: Author Response.pdf