Measurement of Lower Extremity Alignment Using a Smartphone Application

Round 1

Reviewer 1 Report

The work presented is interesting and novel. It has many useful applications. the paper is well-written 

Author Response

We thank the reviewers for positively receiving our manuscript. We are grateful to receive constructive and useful suggestions.

Thank you.

Reviewer 2 Report

This study conducted a validity and reliability analysis of a smartphone application developed for identifying lower-extremity misalignment. This may help people with lower-extremity misalignment reduce the need for radiation exposure, hospital visits, and specialized equipment. Therefore, this was a very interesting investigation, but several problems remain:

 

1.      Line 40-49. These lines illustrate the importance of lower-extremity alignment using knee osteoarthritis disease, but neither the title nor subject selection mention knee osteoarthritis. This can easily lead to misunderstandings by readers.

2.      This study detailed the predicted lower-extremity alignment angle (PLEAA) in the Results and Discussion section, but not in the Introduction section. It is necessary to supplement the relevant content of PLEAA in the Introduction section.

3.      Line 87-88. The author explained that the subjects selected people with lower extremity joint pain, but there are many diseases that cause lower extremity joint pain. Please elaborate on the selection criteria for subjects.

4.      Line 161-164. The smartphone application still requires the assessor to use a finger or touch pens to adjust the identification points on the joint in the app, which means that the app's data results can be influenced by the user. Please explain in details.

5.      Line 174-176. This study used only two evaluators to collect data. As mentioned in the previous question, the subjective actions of the evaluator may have an impact on the data results. Does using only two evaluators eliminate this effect? Please provide details.

6.      All tables for this study do not meet the formatting requirements. Please revise.

7.      Line 202. K-L grade is a commonly used method for grading the severity of knee osteoarthritis, but the selection of subjects does not only include patients with knee osteoarthritis. Please add details.

8.      Among the 45 subjects selected for this study, four levels of injury were included. Is the sample size sufficient to account for validity and reliability? Does the degree of damage affect the results? Please provide additional explanation.

9.      Line 259-261. "The intra-rater reliability was within .93" does not appear to appear in the results. Please, clarify it.

Author Response

We thank the reviewers for positively receiving our manuscript. We are grateful to receive constructive and useful suggestions.

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Reviewer 3 Report

in this study, an app able to measure varus/valgus angle was tested.

the study is quite interesting, however, some info and details need to be further added to improve the scientific value of the study.

In particular, the following questions were raised after reading:

- How to discriminate between a varus/valgus due to tibia or femur or both?

- how is it possible, using the app, to evaluate the varus/valgus angle in patients that have a bone deformity or trauma?

The technique considers a perfectly balanced and symmetric pelvis, also if this is not the case the technique is not able to demonstrate this. 

how the position of the patient and the position of the cellphone could alter the results?

it is not clear how the population used for the validation of the test is close to a real case of a patient under investigation.

please comment and add to the limitations

It is clear that the inter and intra-operator reliability of the results is quite high; however,  to prove the real efficacy and validation of the use of the app as a clinical tool it is important to compare the real values with the values obtained by the app. however, the authors do not report a scatter plot of the true/measured (x-ray/app) values but limited to a Pearson correlation coefficient that it is not extremely high as it is close to 0.6. moreover, it is important to report the max/min difference between  true and measured and comment htis values. 

Author Response

We thank the reviewers for positively receiving our manuscript. We are grateful to receive constructive and useful suggestions.

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

all the main concerns were covered in the reviewed version of the paper