[version 3; peer review: 2 approved]
No competing interests were disclosed.
In this version we integrated the reviewers suggestions, which are: - Exclusion criteria with robotic devices - Data extraction details - New draft of the data extraction table
The shoulder or glenohumeral joint is one of the most complex joints in the human body. The size of the glenoid fossa is much smaller than the articulating humeral head thereby facilitating a large range of motion but also making the joint prone to instability. Different tissues are present in the shoulder to provide more stability including, most importantly, the rotator cuff muscles. Furthermore, the glenohumeral capsule and some other muscles play a minor role in stabilizing the joint
The glenohumeral joint and its stability has been studied in various conditions. Because joint load cannot be measured directly in the living person, previous studies have used
Existing simulators usually consist of a clamping mechanism for the scapula and a cable pulley system that is attached to the tendons inserting at the humerus
We performed a preliminary search in Pubmed and
In this scoping review, we intend to broaden the search from experimental setups for rotator cuff repair and instability to glenohumeral joint experiments. Specifically, we will describe differences and commonalities of
This scoping review seeks to identify methodological and experimental studies that describe or involve glenohumeral joint simulators. The characteristics of these simulators will then be assessed to highlight their strengths and limitations. Particularly, the strengths and limitations will be described by answering the following research questions:
• What is the state of art of glenohumeral simulators in research where the muscles are explicitly modeled?
• How accurate are muscle insertion, glenoid fossa and other soft tissues replicated?
• How are the muscles actuated?
• How is the system controlled?
The proposed scoping review will be conducted in accordance with the Joanna Bricks Institute (JBI) methodology for scoping reviews
A medical information specialist (HE) drafted the full search for PubMed using text words with synonyms and word variations as well as subject headings around the topic areas
In addition to the database search, we will conduct backward and forward citation tracking of the included studies using Scopus.
All retrieved references will be exported to Endnote 20 (Clarivate Analytics, 2020) and database duplicates removed according to the Bramer method (which includes using customized import/export filters and several rounds of manually changing the deduplication configuration to reduce the risk of false duplicate removal)
Following a pilot test, titles and abstracts will then be screened by two independent reviewers for assessment against the inclusion criteria for the review. Potentially relevant sources will be retrieved in full and their citation details imported into Endnote 20 and retrieved from Endnote and through the University library Basel.
The full text of selected citations will be assessed in detail against the inclusion criteria by two reviewers. Reasons for exclusion of sources of evidence at full text that do not meet the inclusion criteria will be recorded and reported in the scoping review.
Any disagreements that arise between the reviewers at each stage of the selection process will be resolved through discussion, or with an additional reviewer. The results of the search and the study inclusion process will be reported in full in the final scoping review and presented in a PRISMA-ScR flow diagram
The data extracted will include specific details about the ability of the shoulder simulators to simulate physiological conditions and motions. The data will be qualitatively summarized using five categories: (i) mechanical aspects of the shoulder simulator; (ii) sensors used; (iii) research question; (iv) specimen preparation; and (v) control strategies, because most studies will use different methodologies. In category (i) the mechanical will be summarized including scapular actuation and how and how many muscles are actuated. In category, (ii) we will summarize what measurements were performed for data acquisition and for feedback control. In category (iii), we will present what kind of studies were performed with these simulators. In category (iv), we will present which parts of the specimen was used and how they were prepared. Furthermore, we will specify how the scapula was oriented in the simulator. In category (v), the control strategies will be presented. As the glenohumeral joint is an under-deterministic system (i.e., a system with more muscles than degrees of freedom (DOF)) we will elaborate on the researcher’s strategy to solve this problem. A draft extraction form is provided (see
| General | Mechanical System | Control System | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| ID | Country | Specimen
|
Research
|
DOF | Active
|
Passive
|
Muscle
|
Measurements | Sensors | Control
|
Motion |
Within the framework of this scoping review, no quality appraisal is planned.
This data will be listed in a tabular form and the studies will be ordered from most to least physiological according to available data. If the physiological level is the same, then the studies will be ordered alphabetically.
In addition to the tabular view, we will narratively analyse the results in the review text. Together, these results will provide a comprehensive scope of past research methodologies on this topic and likely identify opportunities on how to further develop such simulators.
The completed review will be published in an open access peer-reviewed journal.
Start date of search: June 2021; anticipated completion date of review: February 2022.
Current study status: preliminary searches, yes; piloting of the study selection process, yes; formal screening of search results against eligibility criteria, no; data extraction, no; data analysis, no.
No underlying data are associated with this article.
Zenodo:
This project contains the following file:
DOKU_Search-strat_
Data are available under the terms of the
Approved with no further comments.
Is the study design appropriate for the research question?
Yes
Is the rationale for, and objectives of, the study clearly described?
Yes
Are sufficient details of the methods provided to allow replication by others?
Yes
Are the datasets clearly presented in a useable and accessible format?
Yes
Reviewer Expertise:
Shoulder surgery, shoulder biomechanics, rotator cuff lesions
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.
No further comments.
Is the study design appropriate for the research question?
Partly
Is the rationale for, and objectives of, the study clearly described?
Yes
Are sufficient details of the methods provided to allow replication by others?
Yes
Are the datasets clearly presented in a useable and accessible format?
Not applicable
Reviewer Expertise:
In-vitro joint motion simulation; shoulder biomechanics; orthopaedic basic research.
We confirm that we have read this submission and believe that we have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
This scoping review aims to benchmark the most advanced glenohumeral simulators. As reviews focusing on unconstrained simulators are scarce, this review provides a good overview of the development of such simulators and their limitations. Thus, it markedly contributes to the improvement of simulators of the next generation. In general, this may be of interest to orthopaedic surgeons and researchers of the shoulder joint, but especially to the biomechanical engineering community, as many aspects of developing and improving such a sophisticated device are being investigated.
I agree with the authors to choose the design of a scoping review, since the literature provides a wide range of simulators and yields heterogenous data. Furthermore, this scoping review provides a good overview of simulators that avoid the usual simplification of constraining the humerus. Many simulators in the literature constrain the humerus to the abduction plane. This reduces the activation of the stabilizing muscles. On one hand this reduces the complexity to control the humerus, but on the other hand it reduces the importance of the rotator cuff muscles as well.
The systematic search is well set up and managed by an information specialist and a wide range of synonyms is used which should identify most relevant simulators.
Current reviews lack the aspect of the control concept, whereas this scoping review aims to identify it. Another strength is that the preparation methods are looked at and how the setup is mechanically designed.
Although I endorse this scoping review, some aspects should be considered. First, I agree with the previous reviewer that the scapula orientation and motion should be identified, as the joint reaction force varies with the orientation of the glenoid. Second, I also agree with the other reviewer that the robotic involvement should have been closer looked at. Although, I suspect there are only a few or no studies that only include a robot to perturbate the humerus.
Lastly, this review is a scoping review and not a systematic review but can be justified as there are too few simulators in the literature to be examined in a meta-analysis. Furthermore, the data is too heterogenous to be included in a statistical analysis.
Overall, the study is thoroughly designed and well described, and relevant previous publications are referenced. In summary, I recommend publication of this scopiong review with some minor revisions.
Is the study design appropriate for the research question?
Yes
Is the rationale for, and objectives of, the study clearly described?
Yes
Are sufficient details of the methods provided to allow replication by others?
Yes
Are the datasets clearly presented in a useable and accessible format?
Yes
Reviewer Expertise:
Shoulder surgery, shoulder biomechanics, rotator cuff lesions
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.
Thank you for highlighting the importance of this scoping review.
Regarding your suggestion:
Thank you for pointing out that the scapula orientation should be consider. We have amended this in section: Data extraction, where we elaborated how we plan to extract this data.
We agree with you that a scoping review is the right choice of methodology.
Thank you for recommending for publication of our protocol
The authors present the rationale and protocol for a review of current ex-vivo experimental methodologies used to study shoulder biomechanics. The main objectives of this study are to determine the state of art of glenohumeral simulators that explicitly model the muscles of the shoulder. The authors intend to determine the accuracy of tissue replication while highlighting how many muscles each system actuates and how those muscles are actuated. Study selection criteria is outlined, and search methodology is described. The authors provide a template that will be used to extract key data from each study reviewed.
I commend the authors for performing this scoping review, which I believe will make it easier to place simulators in the landscape and understand where any gaps in the literature may be. The rationale for this study is clearly outlined. The objectives are clearly described and the need for this review is discussed given the limitations of existing literature review studies.
The authors’ study design is partly appropriate for the research question. Although the study design is largely appropriate for the research question, some adjustments to the data extraction form are recommended.
Firstly, although a previous review has been conducted that examined scapular orientation, it is still important to consider scapular orientation/motion when reviewing simulators that replicate shoulder motion since scapular motion plays a significant role in shoulder biomechanics. The rhythm between the humerus and scapula is important to shoulder stability because as the arm abducts, the scapula rotates under to provide support against the gravity load vector. Some simulators offer simple uni-planar scapular rotation and others offer more complex six-axis scapular mobility. Therefore, I suggest that scapular motion methods also be included in the review of functionality.
Secondly, in the “Muscle force estimation” and “Control concept” sections of the form, the questions appear to be tailored towards simulators that operate using force-based control. Although force-based control is the most common method of control, other control schemes exist that may be difficult to categorize based on the questions being asked about the control method. Control methods might be broadly categorized in a four-square in which tendon actuation is either force-based or excursion-based, and the control scheme is either closed-loop or open-loop. There are hybrids to these, but that would cover most. Therefore, I recommend to include some broader questions about the controller design to highlight the differences between control techniques.
I agree with the authors approach that “a study should be excluded if the motion is constrained through something other than anatomical structures”. Some simulators use a rail or other passive guide to constrain the humerus within a particular elevation plane; however, the authors should be careful that some of these simulators use such a guide device as an adjunct which is removed for some protocols. It will be important not to exclude these simulators entirely, but I agree that if the complete motion pathway is not achieved without the guide then they should be excluded. The authors also state that “passive movements of the humerus such as guidance through a robotic device are thus generally excluded”. This is potentially more difficult to determine. Some simulators are augmented with a robot in order to generate varying external loads during motion, such as forces experienced in activities of daily living. In this scheme, the robot is supposed to be transparent in every other direction – meaning that it should impart zero forces other than the simulated load. In practice, this is very difficult to achieve because it requires near perfect real-time force response. Typically, the robot’s presence adds dampening to the whole system which provides a false stability to the motion controller. I suggest that if such a simulator is reported to produce the full motion without the robot, then it might be included; however, I suspect that this will be a difficult criteria to meet. I agree with the authors’ general strategy that if anything is in contact with the arm, then the first choice should be to exclude the simulator; though sometimes external augments are added for a purpose, so I would still search for other papers of that same simulator to determine whether it does have the ability to run unconstrained or unassisted.
I see that the search term ‘in-vitro’ is included in the search strategy. This is important, as some groups use that term instead of ex-vivo. The applicability of the term ‘in-vitro’ is debatable but it is still important to give it equal weight in the search because some important simulators are not described by their authors as ex-vivo.
The study design is clearly described, and relevant papers are referenced to further describe the methodology. There is sufficient detail to allow replication by others.
Is the study design appropriate for the research question?
Partly
Is the rationale for, and objectives of, the study clearly described?
Yes
Are sufficient details of the methods provided to allow replication by others?
Yes
Are the datasets clearly presented in a useable and accessible format?
Not applicable
Reviewer Expertise:
in-vitro joint motion simulation; shoulder biomechanics; orthopaedic basic research.
We confirm that we have read this submission and believe that we have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
Thank you for commending us to perform this scoping review.
Regarding your first adjustment recommendation:
In the extraction sheet, we will record this under DOF and constraints, although we agree it could be more clearly stated. Therefore, we amended the extraction sheet and elaborated how we plan to extract the data in section: Data extraction.
Regarding your second adjustment recommendation:
Thank you for pointing this out. We have amended the extraction sheet and elaborated how we plan to extract the data in section: Data extraction.
Regarding your suggestion on constraint motion and robotic assistance:
Thank you for this suggestion. There are indeed some simulators that constrain the motion in their first-generation of the simulator. We will still exclude these studies, but if the same simulator is unconstraint in another study, it then will be included. We agree that if an external force is applied with the sole purpose to perturb or induce an additional external load the study should be included. We have amended this in the exclusion subsection.
Regarding the search terms:
We agree that "in vitro" and "ex vivo" should be included, thank you.