Systematic Review of Radiological Analysis of Total Hip Replacement Via Direct Anterior Approach in Comparison to Other Approaches – Study Protocol

Total hip arthroplasty (THR) is considered as the most effective available method of treatment of end-stage hip osteoarthritis (OA). This surgery can be performed via many different approaches. One of the newly developed technique is called direct anterior approach (DAA). It gains popularity and recognition as the least traumatic to the soft tissues, thus quickening rehabilitation and improving joint stability in the early postoperative period. There are no systematic reviews covering this subject in terms of potential differences in radiological prosthesis placement, and while there is still unsatisfactory evidence concerning long-term outcomes of DAA, such review may prove useful in the debate. The objective of our study was to systematically collect and review available data from randomized-controlled trials (RCTs) regarding radiographic assessment of prosthesis placement after total hip arthroplasty using direct anterior approach compared to other common approaches. with the radiological two following: femoral mean radiographic cup inclination, mean radiographic cup anteversion, mean radiographic cup abduction, position in Lewinnek's safe zone. Study selection and the will by for RCTs.


Abstract Background
Total hip arthroplasty (THR) is considered as the most effective available method of treatment of endstage hip osteoarthritis (OA). This surgery can be performed via many different approaches. One of the newly developed technique is called direct anterior approach (DAA). It gains popularity and recognition as the least traumatic to the soft tissues, thus quickening rehabilitation and improving joint stability in the early postoperative period. There are no systematic reviews covering this subject in terms of potential differences in radiological prosthesis placement, and while there is still unsatisfactory evidence concerning long-term outcomes of DAA, such review may prove useful in the debate. The objective of our study was to systematically collect and review available data from randomized-controlled trials (RCTs) regarding radiographic assessment of prosthesis placement after total hip arthroplasty using direct anterior approach compared to other common approaches.

Methods
A systematic review of randomized controlled trials (RCTs) will be conducted. SciFinder, Scopus, ScienceDirect, PubMed, Embase, Clinical Key and The Cochrane Library databases will be searched without restriction to date up to June 2020. Primary outcomes will include measurements related with the radiological analysis of trials comparing use of DAA to other approaches used for THR, containing at least two of the following: femoral stem alignment, mean radiographic cup inclination, mean radiographic cup anteversion, mean radiographic cup abduction, position in Lewinnek's safe zone. Study selection will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and the methodological appraisal of the studies will be assessed by the Cochrane Risk-of-Bias Tool for RCTs.

Discussion
This systematic review will provide missing information regarding in uence of differences between DAA and other surgical approaches in total hip replacement on prosthesis implants placement in case of femoral stem and cup. This may result in improving knowledge and awareness of surgeons, improving patients satisfaction and functional outcome and lowering the risk of hip dislocations and other complications.

Trial registration
International Registration of Systematic reviews (PROSPERO) numberCRD42019122675 Background Total joint arthroplasty is considered the most effective way of treating the end-stage osteoarthritis (OA) of hip and knee joints (1, 2). It is estimated that every year more that one million total joint replacements are performed in Europe, while in Poland about 100000 annually. It is believed that our community is getting older and that is the reason why the number of total joint replacements will be growing, as well as patients expectations towards it. Even though total knee and hip replacement have wonderful outcome and are improving signi cantly patients, there is still place for improvement. This surgery can be performed via many different approaches. (3,4) However, there is continuous dispute regarding the optimal choice of techniques, implants and approaches. The direct anterior approach (DAA) utilizes the intermuscular plane between sartorius and rectus muscles and tensor fascia lata, without the need to division of any tendon attachment of mentioned muscles. (5,6). A direct anterior approach (DAA) gains popularity and recognition as the least traumatic to the soft tissues, thus probably quickening rehabilitation and improving joint stability in the early postoperative period and due to the shorter incision better cosmetic outcome. (4, 7-9) On the other side it is also considered to have steep learning curve and suspected to have higher risk of complications. (10) We believe that the di culty of this approach might also have a negative effect on prosthesis placement, which could be assessed radiographically. It was previously proved, that proper prosthesis implants placement might be crucial for lowering the possibility of postoperative hip dislocations. (11,12) Still, to our knowledge there are no systematic reviews covering this subject, and while there is still unsatisfactory evidence concerning long-term outcomes of DAA, such review may prove useful in the debate. There has been recently published meta-analysis of (13), in which authors analyzed outcomes of RCTs comparing DAA to other approaches in terms of postoperative analgesic requirements and pain scores, hospitalization time, length of incision, surgical time, complications such as: infection, wound healing problems, neurovascular damage, fractures, thrombosis, dislocations, component malpositioning, heterotopic ossi cation and death, but did not report analysis of radiological assessments in included studies. The objective of our study was to systematically collect and review available data regarding radiographic assessment of prosthesis placement after total hip arthroplasty using direct anterior approach compared to other common approaches.

Protocol design and registration
We will perform systematic review to summarize results from randomized controlled trials published with no restriction to date up to the June 2020. The development of this study protocol and the reporting of results will be performed accordingly to the Preferred Reporting Items for Systematic Reviews and Metaanalyses Protocol (PRISMA). (14) We used the PRISMA-P checklist when writing our report (15). This study protocol was previously registered with the International Registration of Systematic reviews (PROSPERO) and registration number CRD42019122675 was assigned.
(https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=122675) Such registration lowers the risk of duplicating systematic reviews and allows researchers to keep up with proper review process, resulting in minimizing of reporting bias.

Eligibility criteria
We will include only randomized clinical trials involving patients over 18 years old (with primary hip osteoarthritis treated operatively), comparing DAA with other approaches and consisting of radiological analysis in at least of two of the following terms: femoral stem alignment, mean radiographic cup inclination, mean radiographic cup anteversion, mean radiographic cup abduction, position in Lewinnek's safe zone. We will exclude non-English studies, with full text not available, review or non-comparative studies, studies analyzing bilateral total hip replacement or hemiarthroplasty, and analyzing robotassisted surgeries.

Data extraction (selection and coding)
A summary of the participants, interventions, comparators and outcomes considered, as well as the type of studies included according to PICOS strategy, is provided in Table 1. (16) Two independent researchers (BM, KR) will evaluate nal set of studies in terms of: rst author's name, country, publication year, type of surgical approach being compared to direct anteror approach, any signi cant differences at baseline, sample size, radiographic analysis. Revised Cochrane risk-of-bias tool for randomized trials (RoB 2) will be used (17). Disagreements between the review authors over the risk of bias in particular studies will be resolved by discussion, with involvement of a third review author (AS) where necessary. We will provide a narrative synthesis of the ndings from the included studies, structured around the type of intervention, the target population characteristics, the type of outcome and the intervention content. Cohen's kappa coe cient will be calculated for interrater agreement between reviewers following assessment of study eligibility. (18) Kappa values ≤ 0 will be interpreted as indicating no agreement, 0.01-0.20 as none to slight, 0.21-0.40 as fair, 0.41-0.60 as moderate, 0.61-0.80 as substantial, and 0.81-1.00 as almost perfect agreement.

Data synthesis
We expect signi cant differences between studies in reporting radiological analysis with different values being assessed, therefore statistical data synthesis and exploration of consistency will probably be impossible to perform. However mean values of different prosthesis implant placement angles will be possible to analyzed between subgroups comparing DAA to single other approach.

Discussion
This systematic review will provide missing information regarding in uence of differences between DAA and other surgical approaches in total hip replacement on prosthesis implants placement in case of femoral stem and cup. This may result in improving knowledge and awareness of surgeons, improving patients satisfaction and functional outcome and lowering the risk of hip dislocations and other complications. To the strengths of this study protocol belong the fact that it is the rst systematic review of radiological analysis, comparing direct anterior approach to other used approaches for total hip replacement. It offers the highest level of evidence as only randomized controlled trials will be included.
Direct anterior approach as more innovative and younger technique for performing total hip replacement might be described and analyzed in small number of randomized controlled trials. Ethics approval and consent to participate No institutional review board approval was required for this systematic review because the study included data that had been published previously. Results of this systematic review will be widely disseminated through publication in the valuable scienti c peer-reviewed journal, concerning orthopaedic surgery.

Consent for publication Not applicable
Availability of data and materials The datasets used and/or analysed during the current study will be available from the corresponding author on reasonable request.