Types of Studies and inclusion criteria:
This systematic review will follow recommendations proposed by the Cochrane Handbook of Interventions Reviews [10, 11] and PRISMA protocols [12, 13]. Our study will include only randomized or quasi-randomized controlled clinical trials, comparing metal-backed glenoid designs and polyethylene (keeled or pegged) design in Total Shoulder Arthroplasties.
This study has been approved by the Research Ethics Committee of Universidade Federal de São Paulo (protocol 0725/2017, 2.157.415 and 70473017.5.0000.5505) (document attached).
Types Of Participants (inclusion And Exclusion Criteria):
The inclusion eligibility studies that assessed adults that underwent TSA due to idiopathic and inflammatory OA [14, 15, 16, 17]. The following exclusion criteria were adopted: Patients with previous surgery, neurological diseases (Charcot's Arthropathy, Parkinson's disease), Revision surgeries of arthroplasty and Reverse Total Arthroplasty.
Functional results, complications and failure represented by new surgical intervention, will be our main outcomes. We will consider the Constant-Murley (CM) , American Shoulder and Elbow Surgeons (ASES)  and University of California at Los Angeles (UCLA)  to measure function as a validated score. Complications like deep infection affecting prosthesis components, persistence or worsening of pain (Visual Analogue Scale - VAS) , loosening or breakage of implanted materials, dislocation, surgical revision.
Clinical and radiographic outcomes will be assessed by range of motion (forward flexion, lateral and internal rotation) and indirect radiographic signs that evidence the loosening of the glenoid implant. The Lazarus classification for keeled components and Franklin classification for pegged components were the systems selected to assess radiolucency concerning those all-polyethylene components [22, 23].
Quality of life analysis validated short form scores 36 , will also be assessed.
Search Methods And Strategy:
The electronic search will be carried out in the MEDLINE (PubMed), Cochrane Central Register of Controlled Trials [25, 26], EMBASE, Web of Science, International Clinical Trials Registry Platform, ClinicalTrials.gov and Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS for randomized or quasi-randomized RCTs). The grey literature will also be searched through Google Scholar, OpenGrey and GreyNet .
We are going to use the following terms in different combinations and combinations for our search: “total shoulder arthroplasty”, “glenoid”, “keeled”, “pegged”, “loosening”, “metal-backed” and “radiolucency”. No restriction on language or publication status.
Data Collection And Analysis:
Two independent reviewers will access the selected studies, as well as the data extracted from these studies using EndNote X9, in order to facilitate collaboration among them during the selection process.
Two authors will select independently and analyze the eligible studies for this systematic review through the title and abstract. The selected studies will be entirely reviewed. Any disagreement will be resolved through discussion and, when necessary, will be judged by a third author in an attempt to resolve a possible conflict.
Data Extraction And Handling:
Data extraction will be performed by two reviewers will extract the data using an appropriate extraction form based on methodological characteristics, including design and duration, whether the protocol was published prior the recruitment of the patients, possible funding sources and study registration; characteristics of the participants including location, number of recruits, their evaluation, inclusion and exclusion criteria, age and classification relevant to the disease addressed; characteristics of the intervention like duration, surgery type and complications; results through time and loss of follow-up; methodological domains and risk of bias.
The extracted data will be also classified according to the time of follow-up into early and late, establishing 1 year as the cutoff for this division.
Access To Risk Of Bias:
Two authors will independently evaluate various aspects of methodological quality of the included studies using a modified version of the Cochrane Bone Joint and Muscle Trauma Group tool form . Some items will be considered: random sequence generation, allocation concealment, participant blinding, outcome assessment blinding, selective reporting and potential influence of incomplete outcome data, in each trial, will also be carried out. After judgment and classification, these criteria will produce three levels of bias: low, high or unclear. Disagreements will be solved by the analysis of a third reviewer [29, 30].
Measures Of Treatment Effect:
The resulting dichotomous data will be analyzed with relative risk (RR) with a 95% confidence interval. When appropriate, we will express the estimated effects as numbers that need treatment (NNTs). Data on continuous outcomes will be expressed as an average difference of 95% in the confidence interval (CI). We intend to group the results with the mean difference (MD) if two or more trials reveal results from the same valid instrument of evolution (with the same units of measurement). If primary studies measure the same variables using different instruments (as well as different units of measurement), Cochrane Review Manager on its 5.3 version will be used for the statistical analyze.
Dealing With Missing Data:
We will perform an intention-to-treat analysis in order to include all randomized participants of any intervention. Insufficient information according to the estimated effects, as well as the number of participants, mean, uncertainty measurement (standard deviation or error) or number of events; we will contact the authors of the selected trials.
An analysis will be carried out independently of the lost data, submitting them to the worst and best scenarios.
The heterogeneity of the estimated effects between the included studies will be evaluated through visual inspection of the forest plots and the statistical I² test (significant > 50%).
The results of comparable tests will be grouped using the fixed-effect model and a 95% CI. However, the variable model will be used when there is a diversity in clinical or methodological characteristics.
Subgroup Analysis and Heterogeneity Investigation:
Where appropriate, subgroups will be analyzed in order to explore the difference in side effect related to the type of glenoid selected.
Confidence in Cumulative Evidence:
We will apply GRADE (www.gradepro.org) in order to describe and rate the quality of evidence and the strength of the recommendations, classifying them as high, moderate, low and very low [31, 32, 33].