Spine, Pelvis and Hip Kinematics—Characterizing the Axial Plane in Healthy and Osteoarthritic Hips

Round 1

Reviewer 1 Report

This topic is very interesting for hip and spine surgeons, but please look at these points to improve the paper:

• Lines 36-41. Although it is possible to understand what authors want to say and what they want to introduce, but these first lines are very confusing and need to be improved.
• In this first part of the introduction it is necessary to consider also the cervical spine. Please consider these 3 veryimportant papers: Regional and experiential differences in surgeon preference for the treatment of cervical facet injuries: a case study survey with the AO Spine Cervical Classification Validation Group. Eur Spine J. 2021 Feb;30(2):517-523. doi: 10.1007/s00586-020-06535-z.    ----   The Y-shaped trabecular bone structure in the odontoid process of the axis: a CT scan study in 54 healthy subjects and biomechanical considerations. J Neurosurg Spine. 2019 Feb 1:1-8. doi: 10.3171/2018.9.SPINE18396.  ----  Cervical sagittal balance: a biomechanical perspective can help clinical practice. Eur Spine J. 2018 Feb;27(Suppl 1):25-38. doi: 10.1007/s00586
• Lines 83-85. How did authors choose controls?
• Lines 253-255: "Our findings show that assessments of spinopelvic characteristics in the motion analysis laboratory can produce reliable assessments of spinopelvic characteristics, albeit with certain inherent limitations." With what limitations? please define.
• Lines 303-313. Report limitations of the study but also strengths.

Overall a good paper.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Review for applied sciences

Title: Spine, Pelvis and Hip Kinematics – Characterizing the Axial 2 Plane in Healthy and Osteoarthritic Hips

Summary:

The authors present a manuscript about spinopelvic kinematics in a prospective setting. This topic is of great interest for spine, pelvic and hip surgeons, because of the influence of the kinematics in all three “joints”. The study gives important information in the comparison of healthy and OA patients and in the relationship of sagittal and axial plane kinematics.

General notes:

• I cannot evaluate the 3D-analysis of the Seated Maximal Trunk Rotation in the Methods-section, because I have no experience in the used programs and calculations.
• In the exclusion criteria patients over the age of 75 years are excluded. In Table 1 the range in the OA-group is 48-84 years. Can you explain this discrepancy?
• Both groups have an unequal size, more controls would have been interesting for the comparison. In general, both groups are relatively small.

Summarised assessment:

The manuscript provides important information in the relationship of sagittal and axial kinematics and in the comparison of OA patients and healthy controls. The knowledge of the relationship of these parameters is important for all surgeons, who interfere in this system with spinal arthrodesis or THA. Especially in cases with unsatisfying outcome like THA dislocations these parameters should be considered to in the search fort he underlying problem. There are no major flaws in the methodology or interpretation of the study. I recommend to accept the manuscript after minor revision of the question seen above.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf