Subchondral and Osteochondral Unit Bone Damage in the Fetlock Region of Sport Horses Using Low-Field MRI: Case Series

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,

It is a well written manuscript and an interesting retrospective study, particularly your findings regarding the prognosis differences related to age.

I have only one suggestion regarding the introduction. It would be wise to further develop the difference between "subchondral plate unit" and osteochondral unit". What I mean is to have a better definition of both, and which parameters were used to discriminate one from the other, maybe include a figure to differentiate both definitions and criteria use on the images. 

KR

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The study reviewed evaluates the medical history, and outcome of 35 adult sport horses that were diagnosed with a subchondral or osteochondral unit lesion by low-field MRI. The study nicely shows how useful is MRI in the detection and differentiation of the 2 kinds of lesions. It also states that horses that did not return to soundness all had osteochondral unit lesions instead of subchondral, and that age might be the only factor affecting the return to soundness.

General comments:

In the discussion it would be nice to have a paragraph saying “X% of cases with the only finding of a subchondral lesion by low-field MRI returned to soundness after diagnosis. In contrast, Y% of cases returned to soundness where an osteochondral unit lesion was present on MRI. The presence of a fissure did not worsen the prognosis to return to soundness.” And why you think it is worse prognosis (lines 329-334).

Specific comments:

Line 22-23: The sentence “magnetic resonance examination should be suggested in horses with acute onset of lameness…” Not all horses had an acute onset, so this should not be a conclusion of the study. You can say that it may be suggested in horses with inconclusive radiographs alone and erase acute onset.

Same in lines 40-42. Acute onset is recommended to be erased.

Line 39:  recommend correcting a mistake in sentence style that affects understanding: suggest erasing “and lesions”, reading “either the whole osteochondral unit or only the subchondral bone plate…”

Line 43: recommend erase the word “unit”.

Line 73-74: recommend sentence rewording to improve understanding: “highlighted how cartilage lesions higher than mild grade can be appreciated with low-field MRI systems, whereas…”

Line 96-101: inclusion criteria is not correct as you say that you only accept horses that had response to analgesic blocks, and radiographic findings (when available), and not all cases included were blocked or radiographed. Hence, this is not an inclusion criteria of the study. I would suggest rephrase with the only inclusion criteria:  “horses with complete clinical history were included in the study when MRI findings suggested primary injuries involving subchondral or osteochondral unit of the third metacarpal/tarsal or proximal phalanx. Exclusion criteria for the study were the presence of primary concomitant orthopedic lesions, horses with an incomplete clinical record, or horses for which it was not possible to obtain data concerning the follow-up.

Clinical data recorded reviewed included lameness degree and duration, lameness onset, response to analgesic blocks by referring, radiographic findings, treatments, and outcome.”

Line 115:  correct error, double punctuation “obtained..”

Line 142: correct spelling error, “all analyses were performed…”

Table 1 heading, lines 161-165: Maybe include also BML: bone marrow lesion in your list of abbreviations for the table.

Table 1 content, line 166: in the table all 3 columns fall under the heading or title MRI features. I suggest changing the heading to “MRI consistent lesion features” only over the second column, and include another heading for the third column like “additional possible/inconsistent MRI features/findings”.

Line 207: Recommend reword sentence for better understanding location of lesion: “radiolucent lesion was observed affecting the medial groove? Or medial aspect of the sagittal groove? Or medial articular surface of the proximal phalanx?”

Figure 1, line 218: Just a comment here. In my experience there are horses with small fissures in this location without any lameness and are found on survey radiographs. I am not suggesting that this is not the cause of the lameness in your cases, but for me it would be beneficial to have evidence of subchondral damage in the STIR sequence. Do you think it would be valuable to add to the figure an image C with the corresponding STIR sequence? They usually don’t have any abnormalities in that sequence, and they usually do not have uptake on bonescan/petscan when not lame. Thus, differentiate which of these fissures is clinically relevant just by MRI alone when there is no STIR evidence of subchondral lesion is for me difficult.

Figure 2 heading, line 257-270: It would read better with the following sentence rewording: ”…used for high-level show jumping competition diagnosed with and osteochondral lesion involving the subchondral bone of the medial articular surface of the proximal phalanx. A), Sagittal plane short tau inversion recovery; B), Dorsal plane short tau inversion recovery; C), Dorsal plane Turbo 3DT1 image. A linear transverse hyperintense area is present in the subchondral bone plate in all sequences. The perilesional trabecular bone is characterized by a very mild high signal on STIR images and a heterogeneous low signal on Turbo 3DT1 images. D), E), F), Magnetic resonance images of a 10-year-old Selle Français horse used in medium-level show jumping competition diagnosed with a lesion involving the osteochondral unit of the dorso-central aspect of the medial condyle. The horse was referred for 2/5 lameness of the left front fetlock, which was abolished by intra-articular block of the metacarpophalangeal joint. D), Sagittal plane Turbo 3DT1; E), Dorsal plane Turbo 3DT1 and F), Dorsal plane STIR image…”

Line 309:  I am having trouble understanding why, and how did you do the analysis for the statement “The treatment had no influence on the outcome (p=0.77)”. Of 35 horses, you report only 6 having any treatment other than rest so any analysis is very poor, and difficult. I don’t know if what you meant here was “the number of months of resting period did not influence outcome”?

Table 2, line 326: It would be clinically beneficial for the reader to add in the list of cases a column of treatment: how many weeks resting and which ones were the ones receiving the bisphosphonate treatment or IA injections.

Line 362-366: recommend reword sentence for better understanding: “Similarly to Dyson, the present study reported an overall soundness of 66% **correct 23/25 for 23/35**. However, another study reported a worse prognosis with a lower percentage of soundness (32%), which was attributed to development of osteoarthritis or underestimated cartilage lesion severity in low-field MRI [8].”

Line 381: reference [7] should go at the end of the sentence as [7,15].

Line 382-383: recommending rewording sentence for better understanding: “although bone scintigraphy  can allow an early recognition of bone remodeling and also of increased bone activity caused by exercise-induced stresses, it has a poor specificity”

Line 400-403: This is the most confusing statement in the publication to me. In lines 306-307 of the results you report “On the other hand, both the involvement of the subchondral plate (p = 0.002) or of the osteochondral unit (p = 0.007) were significantly associated to the outcome.”, and also in line 42-43 “Our results suggest that lesions limited to the sub-42 chondral bone unit are associated with a better prognosis and outcome”. But then here you say, “no correlation observed between subchondral versus osteochondral lesions… the lack of statistical correlation could be due to the limited number of cases included in the study.” I understand that only age was significant in the regression model, but I am missing a sentence in the results that says there was no difference in outcome of subchondral versus osteochondral lesions (p>0.05).

Line 438: erase the word “hence”.

Line 439: again, sudden onset of lameness should not be one of your conclusions as they were not all acute onset and it is rather a progressive repetitive stress injury. Probably owners did not realize that horse was mildly off until it progressed to a point where was more noticeable in some cases. I would recommend erase sentence starting from based on the results…inconsistent radiographic findings”, or say only “mri examination should be recommended when subchondral damage of the fetlock joint is suspected despite inconclusive or absence of findings on radiographs.”

Line 442: “associated with a negative outcome when treated only with stall rest” should not be a conclusion and should be erased as you state in your results “The treatment had no influence on the outcome (p=0.77)”. You may say something like “lesions involving osteochondral unit had a worse prognosis to return to soundness than lesions when only the subchondral bone is injured.” If it was not statistically significant (line 400-403), then you can just say had less percentage of horses returning to soundness than wen unit involved”.

Comments on the Quality of English Language

Overall English is very good. Just minor adjustments of style would improve readability.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents a retrospective study on a population of sport horses with osteochondral/subchondral pathology in the metacarpo/metatarsophalangeal joint region using low-field MRI. Due to the small number of horses and the relatively heterogeneous horse population, the results do not present a significant scientific contribution. However, they may still be useful for improving understanding of these pathologies, particularly in show jumping horses. Additionally, the study contains numerous limitations as noted. 

The term “bone damage” should be replaced with 'bone lesion

Line 70- the term “paper” should be changed to "study" or "article"

Line 98 “analgesic blocks” should be changed to "diagnostic analgesia"

Inclusion criteria should not be defined as “when available”. If certain data were not available, those cases should not have been included in the study. Please clarify and revise accordingly.

Please specify the duration of follow-up and how the follow-up data were obtained.

Line 118-9- It is unclear whether the diagnostic analgesia was performed by the authors or by the referring veterinarians. Please specify.

The methodology for assessing the outcome is not clearly described. The criteria for determining the time of return to work are unclear and may have been influenced by the severity and/or type of lesion. Over what period was the recurrence of lameness evaluated?

The table description should include more detail to link its contents to the context of this study clearly. Abbreviations should be explained in footnotes.

The term “palmar digital nerve block” typically refers to the administration of local anaesthetic at the level of the ungular cartilages. If the same nerve is desensitised at the level of the base of the proximal sesamoid bones, the correct term is “abaxial sesamoid nerve block”. Using the same terminology for both techniques may be confusing.

Considering that diagnostic analgesia was not performed in one of the cases, it should not be listed as an inclusion criterion.

Unusually, radiographs were not available, especially considering that all other clinical data were included. Could you please clarify why radiographic images were not obtained in all the horses?

Line 216-term osteochondral fracture should be changed into osteochondral fissure or incomplete osteochondral fracture.

Had the horses that had the lameness been abolished with the PDNB, and had all had negative MRI findings in the distal limb? It is mandatory to locate the cause of lameness in the fetlock region.

The use of bisphosphonates in the treatment of subchondral bone fissures is controversial, considering their inhibitory effects on bone remodelling.  Could you explain the scientific rationale behind selecting this therapeutic approach in such cases?

Table 2 presents results for individual horses, which makes it difficult to extract key findings and does not add significant value to the manuscript. I recommend introducing the relationship between clinical outcome and MRI findings more clearly, as this represents the most relevant result of this retrospective study.

Line 361- Were data regarding the volume of local anaesthetic used for the PDNB reported? If more than 2 mL was administered, what was the rationale behind this choice?

Lie 366. “no signs of osteoarthritis” Could you clarify what criteria were used to determine this? Were the horses re-evaluated following their return to work, and if so, at what time point?

Line 400. Since correlations were not performed in the statistical analysis, the term should be revised accordingly.

Line 437-444. The conclusion is insufficiently supported by the methodology and results presented in the study, and reflects the authors' opinion. The conclusion should be revised to more accurately reflect the findings of the study.

There is no information regarding ethical approval for the study. Although it was not an experimental study, and written consent from the owners was obtained, retrospective studies should still be reviewed by an ethical committee.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The study reviewed evaluates the medical history, and outcome of 35 adult sport horses that were diagnosed with a subchondral or osteochondral unit lesion by low-field MRI. The study nicely shows how useful is MRI in the detection and differentiation of the 2 kinds of lesions. It also states that horses that did not return to soundness all had osteochondral unit lesions instead of subchondral, and that age might be the only factor affecting the return to soundness.

General comments:

All specific comments were addressed.

Specific comments:

 - Line 167: in the heading of the table when I suggested the column title, you may choose your favorite in between the two synonyms separated by "/". (E.g. Additional possible MRI features, or Additional inconsistent MRI features...).

 - Line 319: there is a dot "." at the beginning of the sentence.

  - Line 392: there is a double space in the sentence.

Author Response

 Comment 1:- Line 167: in the heading of the table when I suggested the column title, you may choose your favorite in between the two synonyms separated by "/". (E.g. Additional possible MRI features, or Additional inconsistent MRI features...).

Answer 1: Sorry for the misunderstanding. We modify the column title in "Additional possible MRI findings"

 Comment 2:- Line 319: there is a dot "." at the beginning of the sentence.

Answer 2: corrected as suggested

Comment 3:  - Line 392: there is a double space in the sentence.

Answer 3: corrected as suggested 

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript is significantly improved, and the methodology is clearer and more precise. However, I kindly ask the authors to review the statistical section once more, as the current description does not make it entirely clear how and for what purpose the correlation analyses were applied. Additionally, I do not consider it necessary to emphasize the years of experience of the author that performed the statistical analysis.

Author Response

The manuscript is significantly improved, and the methodology is clearer and more precise. However, I kindly ask the authors to review the statistical section once more, as the current description does not make it entirely clear how and for what purpose the correlation analyses were applied. Additionally, I do not consider it necessary to emphasize the years of experience of the author that performed the statistical analysis.

 

Authors’ response – We thank the reviewer for the comments. We clarified how and for what purpose the anlyses reported were performed (lines 146-148; 152-162); for the same reason, we tried to better organize the Results Outcome section (lines 305-311;324-332). We deleted the years of experience of the author performing the statistical analysis, as requested.

The manuscript has been carefully re-examined and revised to enhance the clarity of the English language and the overall editorial quality.