Outcomes of Acetabular Reconstructions for the Management of Chronic Pelvic Discontinuity: A Systematic Review

Journal Pre-proof Outcomes of Acetabular Reconstructions for the Management of Chronic Pelvic Discontinuity: A Systematic Review Michael-Alexander Malahias, MD/PhD, Qian-Li Ma, MD, Alex Gu, BS, Sarah E. Ward, MD, FRCSC, Michael M. Alexiades, MD, Peter K. Sculco, MD PII:

S0883-5403(19)31034-4

DOI:

https://doi.org/10.1016/j.arth.2019.10.057

Reference:

YARTH 57612

To appear in:

The Journal of Arthroplasty

Received Date: 5 September 2019 Revised Date:

11 October 2019

Accepted Date: 29 October 2019

Please cite this article as: Malahias M-A, Ma Q-L, Gu A, Ward SE, Alexiades MM, Sculco PK, Outcomes of Acetabular Reconstructions for the Management of Chronic Pelvic Discontinuity: A Systematic Review, The Journal of Arthroplasty (2019), doi: https://doi.org/10.1016/j.arth.2019.10.057. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.

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Outcomes of Acetabular Reconstructions for the Management of Chronic Pelvic

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Discontinuity: A Systematic Review

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Abstract

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Background: A number of papers have been published reporting on the clinical

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outcomes of various acetabular reconstructions for the management of chronic pelvic

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discontinuity (PD). However, no systematic review of the literature has been published to

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date comparing the outcome and complications of different approaches to reconstruction.

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Methods: The US National Library of Medicine (PubMed/MEDLINE), and EMBASE

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were queried for publications from January 1980 to January 2019 utilizing keywords

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pertinent to total hip arthroplasty, pelvic discontinuity, acetabular dissociation, clinical or

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functional outcomes, and revision THA or postoperative complications.

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Results: Overall, 18 articles were included in this analysis (569 cases with chronic PD).

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The overall survival rate of the acetabular components used for the treatment of chronic

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PD was 84.7% (482 out of 569 cases) at mid-term follow-up, while the most common

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reasons for revision was aseptic loosening (54 out of 569 hips, 9.5%), dislocations (45

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out of 569 hips, 7.9%), PJI (30 out of 569 hips, 5.3%), and periprosthetic fractures (11

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out of 569 hips, 1.9%). Pelvic distraction technique (combined with highly-porous shells)

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and custom triflanges both resulted in less than 5% failure rates (96.2% and 95.8%

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respectively) at final follow-up.

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cages and highly-porous shells with/without augments with 92% survivorship free of

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revision for aspetic loosening for both reconstruction methods. Inferior outcomes were

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reported for conventional cementless shells combined with acetabular plates (72.7%) as

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well as ilioischial cages and reconstruction rings (66.7% and 60.6% survivorship

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respectively).

Also, highly effective in the treatment of PD were cup-

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Conclusion: The current literature contains moderate quality evidence in support of the

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use of custom triflange implants and pelvic distraction techniques for the treatment of

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chronic pelvic discontinuity, with a less than 5% all-cause revision rate and low

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complication rates at mean mid-term follow-up. Cup-cages and highly-porous shells with

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or without augments could also be considered for the treatment of PD, since both resulted

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in greater than 90% survival rates. Finally, there is still no consensus regarding the

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impact of different types of acetabular reconstruction methods on optimizing the healing

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potential of PD and further studies are required in this area to better understand the

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influence of PD healing on construct survivorship and functional outcomes with each

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reconstruction method.

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Keywords: pelvic discontinuity; total hip arthroplasty; acetabular bone loss; custom

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triflange; acetabular reconstruction; systematic review

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Introduction

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Pelvic discontinuity (PD), which represents complete disassociation of the superior and

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inferior hemipelvis, is one of the most challenging reconstructions cases for the hip

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arthroplasty surgeon [1]. While pelvic discontinuity currently represents only 0.9% to

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2.1% of revision cases [2,3], the projected increase in total hip arthroplasty (THA) in a

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younger patient population, the greater demands of activity placed on implants, and

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increasing life expectancy of patients will likely lead to increasing number of PDs

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requiring surgical management [4].

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PD may occur secondary to excessive acetabular reaming, trauma, infection, stress

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fracture, but most commonly occurs in the setting of osteolysis leading to massive bone

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loss and eventual aseptic loosening [5]. Massive osteolysis leading to chronic pelvic

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discontinuity often indicates disruption of the anterior and posterior columns of the

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acetabulum and complete disassociation of the superior and inferior hemipelvis [6].

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Acetabular component fixation is particularly challenging in cases of chronic PD as the

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inherent stability of the acetabulum is compromised and persistent micromotion and the

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superior and inferior hemipelvis often leads to eventual implant-loosening [7].

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The American Academy of Orthopedic Surgeons’ classification (AAOS) includes a sub-

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classification for PD [8] and defines PD as type IV and sub-classifies it into type IVa,

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IVb and IVc [3]. 4

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Although various surgical options have been proposed for the management of chronic PD,

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there is still no consensus regarding the optimal type of treatment. The most commonly

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applied techniques for treating a chronic PD include pelvic plating with a hemispherical

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shell, reconstruction with reinforcement devices (cages, rings), cup-cage constructs,

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acetabular distraction with hemispherical shell, hemispherical shells combined with

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modular acetabular augments, and custom triflange implants [9–11]. The complication

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rate after chronic PD reconstruction is high including recurrent dislocations, sciatic nerve

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injury, periprosthetic joint infection (PJI), and aseptic loosening of the acetabular

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construct [12].

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A number of papers have been published on the clinical performance of various types of

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acetabular reconstruction for the management of chronic PD. However, no systematic

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review of the literature has been published to date. For this reason, the aim of this study

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was two-fold: 1) to determine the re-revision rate for the most common types of

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acetabular reconstruction performed for the treatment of chronic PD and 2) to evaluate

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the overall complication rate for each type of acetabular reconstruction.

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Methods

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Search Criteria

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The US National Library of Medicine (PubMed/MEDLINE), and EMBASE were queried

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for publications from January 1980 to January 2019 utilizing keywords pertinent to total 5

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hip arthroplasty, pelvic discontinuity, acetabular dissociation, clinical or functional

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outcomes, and revision THA or postoperative complications. The specific search terms

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are further shown in Figure 1.

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Inclusion and Exclusion Criteria

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The inclusion criteria were: 1) Clinical trials dealing with patients suffering from chronic

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PD as an independent population for research, 2) Articles exclusively dealing with the

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management of chronic PD during acetabular revision, 3) Clinical trials investigating the

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clinical and/or functional and/or radiographic outcomes of different types of acetabular

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reconstruction, 4) Full-text English publications, and 5) Minimum 2-year follow-up.

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Primary outcomes recorded and assessed included: 1) implant survivorship free of

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acetabular component revision and 2) overall rate of postoperative complications.

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Secondary outcomes included clinical outcome functional scores, and radiographic

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assessments including radiological evidence of component migration and non-progressive

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radiolucent lines.

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The exclusion criteria were: 1) Non clinical study, 2) General review and systematic

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review, 3) Non-English articles, 4) Studies dealing in general with acetabular bone loss

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cases without further stratifying their results on the presence of PD, 5) Number of cases

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being less than 10, 6) Studies dealing with acetabular revision without acetabular bone

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loss, 7) Studies with results including mixed types of acetabular constructs without

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stratification per type of acetabular reconstruction, 8) Non full text articles, 9) Studies

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without clinical and/or functional and/or radiographic results, 10) Studies with less than 2

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years follow-up, 11) Studies dealing with acetabular fractures or acute PD and not with 6

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chronic PD, 12) Studies examining oncological patients with acetabular bone defects due

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to tumor excisions, and 13) Articles published after January 2019.

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Data Collection

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Two authors independently conducted the search [MQ, MM]. All authors compiled a list

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of articles after application of the inclusion and exclusion criteria. The discrepancies

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between the authors were resolved by discussion. During initial review of the data, the

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following information was collected for each study: title, author, year published, study

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design, gender, age, follow-up time, number of patients, number of hips treated for PD,

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gender, PD classification system, type of PD, number of cases per PD type, type of

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acetabular constructs used, reason for re-revision, survivorship of acetabular constructs,

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clinical outcome score, and postoperative complications.

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The level of evidence in the included studies was determined using the Oxford Centre for

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Evidence-Based Medicine-Levels of Evidence [13]. The methodological quality of each

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study and the different types of detected bias were assessed independently by each

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reviewer with the use of modified Coleman methodology score [14].

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Results

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Study Selection

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The literature search identified 523 abstracts related to the treatment of PD (Fig. 1). After

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duplicate articles were identified and removed from the search, 227 articles remained for

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further assessment. Based on the predetermined inclusion and exclusion criteria, 26

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articles were subjected to a full text screening process. After screening the full text,

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another 8 articles were found non-eligible and they were excluded. Ultimately, 18 articles

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were included for analysis in the present study [3,9,11,15–21, 22–29]. (Fig.1)

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General characteristics

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There were 15 Level IV retrospective cases series (83.3%) and 3 Level III retrospective

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case-control studies (16.7%) [21,22,27]. The mean modified Coleman score was 50.0 and

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it ranged from 36 [21] to 64 [27] indicating a moderate level for overall methodological

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quality. (Table 1)

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In total, 569 cases with chronic PD were reported in the studies included in this review.

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Amongst them, there were 377 females (78.5%) and 103 males (21.5%), while the mean

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age of patients varied between 58 [29] and 72 years old [28]. The mean follow-up per

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study ranged from 25.2 months [21] to 162 months [15]. (Table 2)

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Acetabular components

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Cup-cage constructs were the most commonly used reconstruction method for chronic

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PD (7 studies, 172 out of 569 cases; 30.2%) [18,19,22,23,27–29]. Ilioischial spanning 8

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cages were used in 8 studies (114 out of 569 cases; 20.0%) [3,15,18,20–22,27,29], while

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acetabular non-ilioischial spanning cage including reinforcement rings were used in

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3studies (33 out of 569 cases; 5.8%) [20,21,24]. Acetabular custom triflange constructs

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were reported in 3 studies (95 out of 569 cases; 16.7%) [9,17,25]. A combination of

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pelvic plate (bridging the acetabular columns) and highly-porous coated hemispherical

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cup (66 out of 569 cases; 11.6%) was assessed in 4 studies [3,18,27,29]. Furthermore, use

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of highly-porous coated cementless cups with or without metallic augments to reconstruct

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the acetabulum and without associated pelvic distraction was reported in 4 studies (37

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hips; 6.5%) used [11,21,27,29]. The pelvic distraction technique combined with highly-

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porous coated cups with or without metallic augments was reported in 2 studies (52 hips;

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9.1%) [16,26].

(Table 1)

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Classification of acetabular defects associated with chronic PD

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The most common acetabular bone loss classification was Paprosky (7 studies, 135/569

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cases; 23.7%) and graded acetabular defects before surgery [11,16,20,23,25,26,29].

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Acetabular bone loss grading was IIB in 1 case (1/135 cases; 0.7%), IIC in 16 cases

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(11.9%), IIIA in 24 cases (17.8%), and IIIB in 94 cases (69.6%). The AAOS

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classification was used in 6 studies (247 out of 569 cases; 43.4%) [3,15,17,24,27,29] and

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3 studies (152/569 cases; 26.7%) applied the AAOS sub-classification for acetabular PD

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[3,27,29]. According to this AAOS sub-classification, PD was graded as IVa in 6 cases

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(6/152; 3.9%), IVb in 138 cases (138/152; 90.8%) and IVc in 8 cases (8/152; 5.3%).

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(Table 1) 9

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One study [3] correlated failure rates with the different AAOS PD subtypes. Berry et al [3]

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found that the results were best in patients who did not have severe segmental acetabular

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bone loss (type Iva; a satisfactory result in three of three hips) and worse in those who

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had severe segmental or combined segmental and cavitary bone loss (type IVb; a

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satisfactory result in ten of nineteen hips).

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Finally, one study (24 out of 569 cases; 4.2%) made use of the Gross classification [23].

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All patients with PD in this study [23] were graded as V according to Gross classification.

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(Table 1)

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Clinical outcomes, revision and complication rates

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All mean clinical/functional subjective scores used in the studies reviewed demonstrated

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significant postoperative improvement compared to preoperative mean values (Appendix

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A). The overall acetabular construct re-revision rate patients with chronic PD at time of

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initial revision was 15.3% (87/569 cases), while the revision rate of the femoral

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component after acetabular reconstruction of chronic PD was 3.5% (20 out of 569 hips).

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The most common reasons for failure requiring revision were aseptic loosening (54 out of

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569 hips, 9.5%), dislocation (45 out of 569 hips, 7.9%), PJI (30 out of 569 hips, 5.3%),

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and periprosthetic fracture (11 out of 569 hips, 1.9%). Complications not requiring

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reoperation were reported in 12.3% of patients (70 out of 569 cases). The most common

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complications not requiring reoperation were sciatic nerve palsy (17 out of 569 cases;

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3.0%) and superficial hematoma or seroma (10 out of 569 cases; 1.8%). (Table 3) 10

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Healing rate of chronic PD

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Ten studies calculated the radiographic healing rate of chronic PD at last follow-up visit

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(range 3 to 13 years) [3,9,15,17,22–24,26,27,29]. Healed PD cases were considered

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those in which the acetabular bone stock of the medial wall (at the discontinuity site)

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looked incorporated radiologically, in contrast to non-healed PD cases where the medial

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bone continuity was never restored. The overall healing rate of chronic PD at the last

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follow-up was 74.4% (258 out of 347 cases), ranging between 16.7% [29] and 91.7%

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[23]. Seven out of these ten studies [3,9,15,17,22,23,27] reported healing rates of PD

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higher than 70%, while another study noted that the PD healing rate was slightly lower

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than 70% [26]. In contrast, Martin et al [29] reported a PD healing rate of 16.7% (2 out

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of 12 patients) after 72 months mean follow-up, while Hourscht et al found that the

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healing rate was 45% (9 out of 20 patients) [24]. Overall, the higher healing rates were

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noted in studies in which cup-cage [23] or custom triflange components [9] were used,

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whereas reinforcement rings correlated with the lowest rate of PD union [24]. (Table 1)

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Analysis of PD outcomes based on type of acetabular reconstruction

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Cup-cage constructs

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The overall survival rate of cup-cage constructs in PD cases was 91.9% (158 out of 172

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hips). The revision rate for the acetabular component was 8.1% (14 out of 172).

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Reasons for reoperation after cup-cage reconstruction were dislocation (11 out of 172

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cases; 6.4%), PJI (7 out of 172 cases; 4.1%), aseptic loosening (6 out of 172 cases; 3.5%),

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and periprosthetic fracture (2 out of 172 cases; 1.2%). The mean follow-up per study of

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this type of acetabular reconstruct ranged from 35 months [18] to 72 months [28,29].

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Custom triflange acetabular components

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The overall survival rate of custom triflange acetabular components in patients suffering

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from PD was 95.8% (91 out of 95 cases). The revision rate of the acetabular component

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was 4.2% (4 out of 95 cases) with one re-revision for aseptic loosening, one for late

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recurrent dislocation and two for PJI.

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Reasons for reoperation were dislocation (17 out of 95 cases; 17.9%), PJI (6 out of 95

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cases; 6.3%), periprosthetic fracture (3 out of 95 cases; 3.2%) and aseptic loosening (1

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out of 95 cases; 1.1%). One dislocation (out of 95 cases, 1.1%) was treated

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conservatively with closed reduction. The mean follow-up per study of this type of

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acetabular reconstruct ranged from 30 months [25] to 123 months [9].

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Highly-porous coated hemispherical cup with or without augments (no distraction

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technique)

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The overall survival rate of highly-porous coated hemispherical shells (either with or

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without augments) in patients suffering from PD was 91.9% (34 out of 37 cases) and the

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revision rate of the acetabular component only was 5.4% (2 out of 37 cases).

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The most common reasons for reoperation were aseptic loosening (3 out of 37 cases;

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8.1%) and dislocation (4 out of 37 cases; 10.8%). Twenty out of 37 hips (54.1%) were

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treated with highly-porous coated hemispherical cups combined with augments, while 17

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out 37 hips (45.9%) were treated with highly-porous coated hemispherical cups without

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augments. However, there was no further stratification in the results based upon the

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additional use (or not) of augments. The mean follow-up per study of this type of

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acetabular reconstruct ranged from 25.2 months [21] to 72 months [29].

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Pelvic distraction technique combined with highly-porous coated hemispherical cup with

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or without augment

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The overall survival rate of these pelvic distraction-treated patients who were suffering

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from PD was 96.2% (50 out of 52 cases), while the revision rate of the acetabular

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component only was 3.8% (2 out of 52 cases).

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Reasons for reoperation were aseptic loosening (2 out of 52 cases; 3.8%) and PJI (1 out

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of 52 cases; 1.9%). One dislocation (out of 52 cases, 1.9%) was treated conservatively

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with closed reduction. In the pelvic distraction-treated patients, there were 31 hips (out of

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52 cases; 59.6%) which were reconstructed with the use of metallic augments and 21 hips

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(out 52 cases; 40.4%) in which no metallic augments were used. However, there was no 13

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further stratification in the results based upon the additional use (or not) of augments. The

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mean follow-up per study of this type of acetabular reconstruct ranged from 54 months

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[16] to 62 months [26].

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Ilioischial spanning cage

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The overall survival rate of ilioischial spanning cages in patients suffering from PD was

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66.7% (76 out of 114 cases), while the revision rate of the acetabular component only

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was 29.8% (34 out of 114 cases).

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Reasons for reoperation were aseptic loosening (21 out of 114 cases; 18.4%), dislocation

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(9 out of 114 cases; 7.9%), PJI (7 out of 114 cases; 6.1%), and periprosthetic fracture (1

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out of 114 cases; 0.9%). The 3 dislocations (out of 114 cases; 2.6%) were treated

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conservatively with closed reduction. The mean follow-up per study of this type of

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acetabular reconstruct ranged from 35 months [18] to 162 months [15].

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Non-ilioischial spanning cage

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The overall survival rate of non-ilioischial spanning cages (including reinforcement rings

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among others) in patients suffering from PD was 60.6% (20 out of 33 cases), while the

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revision rate of the acetabular component only was 39.4% (13 out of 33 cases).

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The most common reasons for reoperation were aseptic loosening (13 out of 33 cases;

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39.4%) and PJI (3 out of 33 cases; 9.1%). The 5 dislocations (out of 33 cases; 15.2%) 14

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were treated conservatively with closed reduction. The mean follow-up per study of this

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type of acetabular reconstruct ranged from 54 months [20,21] to 74 months [24].

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This type of acetabular reconstruction devices included 21 Ganz reinforcement rings

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[20,24] and 12 Gap II restoration cages [20,21].

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Cementless non-highly-porous acetabular cup with pelvic plate

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The overall survival rate of non-highly-porous acetabular cup with pelvic plate in patients

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suffering from PD was 72.7% (48 out of 66 cases), while the revision rate of the

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acetabular component only was 27.3% (18 out of 66 cases).

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The most common reasons for reoperation were aseptic loosening (7 out of 66 cases;

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10.6%), PJI (6 of 66 cases; 9.1%), periprosthetic fracture (5 out of 66 cases; 7.6%) and

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dislocation (5 out of 66 cases; 7.6%). The other 5 dislocations (out of 33 cases; 6.5%)

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were treated conservatively with closed reduction. The mean follow-up per study of this

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type of acetabular reconstruct ranged from 34 months [18] to 72 months [29].

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Comparisons between different implants

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Acetabular highly-porous coated cups with/without augments versus cage

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In this analysis, one study compared highly-porous (trabecular metal) cups versus Burch-

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Schneider or Gap II cages [21]. This case-control study examined 24 cases of chronic PD

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divided into two groups: 1) patients who received TM cups with or without metallic

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augments and, 2) patients who were treated with a reconstruction cage [21]. In a mean

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follow-up which was slightly longer than 2 years (range 1 to 3 years), the survival rate of

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the highly-porous cups was 100%, whereas the survival rate of those who were treated

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with reconstruction cage was 33.3% [21].

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Cup-cage versus ilioischial cage

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One study compared ilioischial cage reconstruction (19 patients, 69 months mean follow-

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up) for PD with the cup-cage technique [22]. They found that four of the cup-cage group

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(15%) and 13 (68%) of the cage group failed due to septic or aseptic loosening. As a

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result, the seven-year survivorship was 87.2% (95% confidence interval (CI) 71 to 103)

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for the cup-cage group and 49.9% (95% CI 15 to 84) for the cage-alone group (p = 0.009)

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[22].

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One study compared four different reconstruction techniques for the management of PD:

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1) cementless hemispherical cup alone (10 out of 113 hips; 9%), 2) cup-cage construct

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(27 out of 113 hips; 24%), 3) antiprotrusio cage with or without posterior column plate

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(26 hips; 23%), and 4) cementless cup with posterior column plate (50 out of 113 hips;

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44%) [27]. The 5-year revision-free survivorship curves for each implant were 100% for

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the 20 cup-cage constructs, 95% (95% CI, 88% to 100%) for the 22 cage constructs, 89% 16

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(95% CI, 72% to 100%) for the 9 cups, and 83% (95% CI, 72% to 95%) for the 42

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posterior column plates (p = 0.08) [27].

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Acetabular component stability was highest in the group with a cup-cage construct, with

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100% of those patients' components meeting the study’s definition of stability (absence

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of progressive radiolucent lines, absence of radiolucent lines in all 3 zones, and no

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measurable migration of the cup) [27]. In contrast, only 80% of the patients with a

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posterior column plate and an uncemented cup, 80% of uncemented cups, and 81% of

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isolated cage constructs had a stable construct [27].

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Discussion

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In this systematic review of the literature of 569 cases of chronic PD treated with THA

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revision, we found a high survivorship and low rate of complications (mid-term follow-

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up) for patients treated either with the pelvic distraction technique (96.2% survival rate)

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or custom triflange acetabular implants (95.8% survival rate). Excellent outcomes were

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also found with the use of cup-cage constructs (91.9% survival rate), which showed

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improved survivorship [27]. In addition, highly-porous coated hemispherical cups with or

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without augments demonstrated similar survivorship to cup-cage constructs (91.9%) and

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improved survivorship compared to cementless cups with posterior column plates

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(72.7%). Finally, ilioischial spanning cages (66.7% survivorship) and non-ilioischial

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cages (60.6% survivorship), such as reinforcement rings, showed the inferior results.

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PD has been proposed to occur more often in females when there is severe pelvic bone

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loss, after pelvic radiation, or in association with rheumatoid arthritis [3]. Our results are

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consistent with this statement as we found a high proportion of both female patients

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(78.5%) and patients with rheumatoid arthritis (22.1%) in this cohort of PD patients.

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In our analysis, both the Paprosky and the AAOS classification systems were used to

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grade acetabular bone defects. Interestingly, almost one out of three cases (30.4%) with

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PD was not classified as Paprosky type 3B. Taking into consideration that the Paprosky is

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not specific for PD, while cases with PD can be classified with different Paprosky grades

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(2C, 3A, 3B), we feel that this classification should not be the only one used to describe

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these cases. On the other hand, although AAOS classification system is the only one

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which divides PD in different subtypes, it is not clinically useful and, therefore, it is not

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used often in practice. Regarding our analysis, the vast majority (90.8%) of the cases

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which were graded with the AAOS classification system were reported as AAOS grade

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IVb. This means that most cases with PD included segmental or combined acetabular

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defects (IVb), while mild cavitary defects (type IVa) and irradiated cases (IVc) were

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rather uncommon.

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Amongst various types of acetabular reconstruction for the treatment of chronic PD, there

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was no one technique used by the majority of physicians in the studies included in this

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review. Overall, the most popular acetabular reconstruction technique was the cup-cage

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(30.2% of the cases of this review) followed by ilioischial spanning cages (20%) and

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custom triflange acetabular components (16.7%). Finally, the pelvic distraction technique

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was used in less than one out of ten patients (9.1%) and even lesser used techniques 18

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included the highly-porous cup with or without augments (6.5%) and the non-ilioischial

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cages (5.8%). As reconstruction techniques evolve and continue to emphasize biologic

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fixation with hemispherical shells, it is likely that the percentage of cage-only

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reconstructions will decline.

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Overall, all mean functional outcome scores were significantly improved after surgery in

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patients treated for chronic unilateral PD. Interestingly, Martin et al did not report any

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significant improvement in the few patients who were suffering from bilateral PD [29].

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Bilateral PD is rare but presents the surgeon with a major reconstructive challenge, since

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continued motion of the contralateral pelvic dissociation may result in high failure rates

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[29]. Therefore, further investigations into alternative treatment modalities may benefit

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patients with this difficult problem.

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Achieving healing of a chronic PD is challenging because of the technical difficulties

376

associated with gaining rigid fixation of the transverse acetabular fracture in the setting of

377

bone loss and limited host bone-implant contact across the discontinuity site [27]. There

378

is also likely limited biologic potential for healing due to reduced ingrowth surface area

379

as well as compromised biology and limited vascularity after prior surgical procedures

380

and likely osteolysis. In our analysis, there was no consensus regarding the impact of

381

different types of acetabular reconstruction on the healing rate of PD. Although the

382

overall healing rate was good (74.4%) for a chronic condition with limited healing

383

potential assumed, there were wide variations amongst studies in both the reported

384

healing rates (17% to 92%) and for duration of follow-up (1.5 to 13 years). Healing

385

across the PD was not associated with increased risk of failure if biologic fixation 19

386

occurred into the hemispherical shell both above and below the discontinuity. For this

387

reason, biologic constructs do not necessitate PD healing to be successful. Taking into

388

consideration the conflicting evidence regarding the healing rate of chronic PD, we

389

recommend further studies of higher quality to clarify the healing potential of PD in

390

different types of PD, acetabular reconstruction techniques, and host bone quality and the

391

influence of PD healing on outcomes with different construct designs.

392

The pelvic distraction technique combined with highly-porous shells demonstrated the

393

highest survival rate (96.2%) amongst the various types of chronic PD treatment.

394

However, this is a relatively new technique, having been originally described only in

395

2012 [16]. As a result, there is only limited mid-term data [16,26]. In addition, the

396

clinical outcomes of this technique were mainly obtained from two studies [16, 26] with

397

authors declaring relevant financial conflicts of interest that might result in potential bias.

398

Therefore, although this technique could be considered as a promising alternative, more

399

studies of non-conflicted, independent investigators with longer follow-up are required to

400

clarify its role in the treatment of chronic PD.

401

Custom triflange acetabular implants had similar survival rates (95.8%) compared to the

402

pelvic distraction technique and these have been widely used for a longer time. Based on

403

these results and taking into consideration the complex nature of chronic PD, custom

404

triflange acetabular implants offer an excellent reconstruction solution for complex PD

405

cases with excellent outcomes in regards to aseptic loosening. However, custom triflange

406

implants are associated with high rates of dislocation [30]. Therefore, when using a

407

custom triflange implant, efforts to reduce impingement, avoid injury to the superior 20

408

gluteal nerve, use smaller constructs to minimize dissection in the ilium and ischium, and

409

consider dual mobility or constrained bearing options should all be considered to

410

minimize the risk of dislocation.

411

This analysis showed that both cup-cages and highly-porous coated cups with/without

412

augments have high survival rates (91.9% survivorship for both types of constructs) in

413

the treatment of chronic PD. On the contrary, both ilioischial and non-ilioischial spanning

414

cages were associated with significantly lower survival rates (66.7% and 60.6%,

415

respectively). Paprosky et al [21] showed that reconstruction cages were correlated with

416

significantly inferior short-term results (33% survival rate) compared to highly-porous

417

coated cups (100% survival rate) in the treatment of PD. In addition, Abolghasemian et al

418

[22] reported much inferior results with the use of ilioischial cages (49.9% survival rate)

419

compared to cup-cage constructs (87.2% survival rate). Based on these findings, it is

420

suggested that both ilioischial and non-ilioischial spanning cages should be used with

421

caution when treating chronic PD.

422

The studies assessed in this review had several limitations including a lack of prospective

423

studies, randomization, blinding, and a potential that a small number of patients overlap

424

across certain studies. Specifically, there were no levels I or II controlled trials, and all

425

but three studies included in this review were level IV retrospective case series. The

426

quality of the included studies was found to be moderate based on the modified Coleman

427

methodology score and potential bias in the retrospective design in combination with

428

financial conflicts of interest that many authors have in regards to the techniques

429

described might influence the results. While 13 [3, 9, 11, 16-22, 26, 27, 29] out of the 18 21

430

papers were found with some combination of common authors, we found that they

431

majorly included separate distinct patient populations. Specifically, based on an

432

evaluation of institutions, surgical treatments, and recruitment’s dates, only a very small

433

portion of patients (estimated at 1.55% of the total patient population) was included in

434

more than one paper. Another limitation was that the studies varied widely in regards to

435

follow-up (from short to long term) and number of patients. However, the type of

436

treatment and indication for surgery was clearly defined among studies.

437

438

Conclusions

439

Both custom triflange and pelvic distraction techniques showed promising results in the

440

treatment of chronic PD, with less than 5% all-cause revision rate and low complication

441

rates at mean mid-term follow-up. Cup-cages and highly-porous shells with or without

442

augments could also be considered for the treatment of chronic PD, since they resulted in

443

higher than 90% survival rates. Finally, there is still no consensus regarding the impact of

444

different types of acetabular reconstruction methods on optimizing the healing potential

445

of PD and further studies are required in this area to better understand the influence of PD

446

healing on construct survivorship and functional outcomes with each reconstruction

447

method.

448

449

References

450

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451

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Moreland JR, Bernstein ML. Femoral revision hip arthroplasty with uncemented,

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revision total hip arthroplasty. J Bone Jt Surg 1999;81:1692–702.

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Ghanem M, Zajonz D, Nuwayhid R, Josten C, Heyde C-E, Roth A. Management

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Della Valle CJ, Berger RA, Rosenberg AG, Galante JO. Cementless acetabular

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D’Antonio JA, Capello WN, Borden LS, Bargar WL, Bierbaum BF, Boettcher WG,

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Stiehl JB, Saluja R, Diener T. Reconstruction of major column defects and pelvic

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Sporer SM, Paprosky WG. Acetabular revision using a trabecular metal acetabular

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Atkins D, Eccles M, Flottorp S, Guyatt GH, Henry D, Hill S, et al. Systems for

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Regis D, Sandri A, Bonetti I, Bortolami O, Bartolozzi P. A minimum of 10-year

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pelvic discontinuity. J Arthroplasty 2012;27:1057-63.e1.

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Sporer SM, Bottros JJ, Hulst JB, Kancherla VK, Moric M, Paprosky WG.

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Taunton MJ, Fehring TK, Edwards P, Bernasek T, Holt GE, Christie MJ. Pelvic

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Rogers BA, Whittingham-Jones PM, Mitchell PA, Safir OA, Bircher MD, Gross

506

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Kosashvili Y, Backstein D, Safir O, Lakstein D, Gross AE. Acetabular revision

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using an anti-protrusion (ilio-ischial) cage and trabecular metal acetabular

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Paprosky W, Sporer S, O’Rourke MR. The treatment of pelvic discontinuity with 25

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Paprosky WG, O’Rourke M, Sporer SM. The treatment of acetabular bone defects

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Abolghasemian M, Tangsaraporn S, Drexler M, Barbuto R, Backstein D, Safir O,

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Hipfl C, Janz V, Löchel J, Perka C, Wassilew GI. Cup-cage reconstruction for

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Hourscht C, Abdelnasser MK, Ahmad SS, Kraler L, Keel MJ, Siebenrock KA, et

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Sheth NP, Melnic CM, Brown N, Sporer SM, Paprosky WG. Two-centre 26

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De Martino I, Strigelli V, Cacciola G, Gu A, Bostrom MP, Sculco PK.

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Survivorship and clinical outcomes of custom triflange acetabular components in

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550

27

Table 1: Type of study, modified Coleman methodology score, level of evidence, acetabular defect classification, type of implant and healed PD

Author(s)

Type of study

Modified Coleman score 58

Level of evidence

Hipfl et al (2018)

Retrospective case series

Hourscht et al (2017) Sporer et al (2006)

Retrospective case series

44

IV

Retrospective case series

45

IV

Friedrich et al (2014) Sheth et al( 2018)

Retrospective case series

38

IV

Paprosky 3B(PD) n:18

Retrospective case series

63

IV

Paprosky 2C(PD) n:7 3A(PD) n:5 3B(PD) n:20

Martin et al (2017)

Retrospective case-control

64

III

AAOS IVa n:2 IVb n:108 IVc n:3

Konan et al (2017)

Retrospective case series

50

IV

PD n:24

IV

Acetabular defect classification Paprosky 2C n:3 3A n:7 3B:25 Gross IV n:11 V n:24(PD*) AAOS III n:26 IV(PD) n:20 Paprosky 3B(PD) n:13

Type of Implant

Healed PD * (%)

All 35 hips are cup-cage construct 24(PD),2 mm larger TM revision shell 9 Cage with Long Iliac Flange 7 TM augment between the flange and iliac wing 46 Ganz reinforcement ring with structural and morselized bone graft 5 acetabular TM shell alone 4 acetabular TM shell and 1 augment 4 acetabular TM shell and 2 augment 18 Custom-made multiflange acetabular component Acetabular distraction technique 12 Acetabular TM shell with augments 20 Acetabular TM shell without augment 50 Cementless Cup with posterior column plate 27 Cup-cage construct 26 Cage construct 10 Cup alone

22/24(91.7 %)

4 Cup-cage construct with long iliac flange 20 Standard Cup-cage

20/27(74.1 %) Cupcage

9/20(45.0% ) N/R

N/R

22/32(68.8 %)

37/50(74.0 %) Cup with pelvic plate

Martin et al (2016)

Retrospective case series

47

IV

AAOS IVa n:1 IVb n:11 Paprosky 2B n:1 2C n:1 3A n:5 3B n:5

5 Cementless Cup with posterior column plate 3 Cage construct 2 Cup-cage construct 2 Cementless cup alone

23/26(88.5 %) Cage construct

Regis et al (2012)

Retrospective case Series

57

IV

AAOS IVb n:18

5/10(50.0% ) Cup alone

Sporer et al (2012)

Retrospective Case series

59

IV

Paprosky 2C n:4 3A n:3 3B n:13

Taunton et al (2012)

Retrospective case series

61

IV

AAOS IV n:57

18 Burch-Schneider antiprotrusion cage and bulk graft Distraction method 9 Porous acetabular component alone 8 Porous acetabular component with 1 augment 3 Porous acetabular component with 2 augments 57 Custom tri-flange acetabular component

Rogers et al (2012)

Retrospective case series

43

IV

Chronic PD(>12 week) n:62

0/3(0%) Cage construct

Kosashvil i et al (2009) DeBoer et al (2007)

Retrospective case series

39

IV

PD n:26

42 Chronic PD used Cupcage constructs 7 Chronic PD used ZCA Reconstruction Roof and Ring 13 Chronic PD used Burch-Schneider Cage 26 Cup-cage Construct

Retrospective case series

45

IV

PD n:20

20 Custom Tri-flange acetabular component

0/2(0%) Cup alone

Paprosky et al (2006)

Retrospective case series

44

IV

Paprosky 2C(PD) n:2 3A(PD) n:6 3B(PD) n:8

13/18(72.2 %)

Paprosky et al

Retrospective case-control

36

III

PD n:24

6 Gap II Restoration cage 5 Reconstruction cage( Depuy) 4 Burch-Schneider Cage 1 Ganz ring 11 Posterior column plate in combination with structural allograft or non-ilioischial spanning device EG: TM acetabular component with or

N/R

0/4(0%) Cup with pelvic plate

2/3(66.7%) Cup-cage

N/R

without augmentation CG: Structural allograft and either Gap II cage, reconstruction cage or Burch-Schneider cage 43 IV AAOS 13 Burch-Schneider cage 46/57(80.7 Berry et Retrospective IVa n:3 5 Cementless socket and %) al (1999) Case Series IVb n:19 posterior column plate IVc n:5 5 Cemented socket and Chronic PD dual plates for anterior n:25 and posterior columns 2 Cementless socket and dual plates for anterior and posterior columns 64 III N/R 6 Burch-Schneider cage Cup-cage: Abolghas Retrospective (Protek) emian et case-control 23/26 6 ZCA cage (Zimmer) al (2014) (88.4%) 7 Contour Acetabular Ring (Smith & Nephew, Memphis, Tennessee) 26 TM cup-cage *PD: Pelvic discontinuity. Value expressed as n/n. Number of hips with healed PD is before slash. Number of hips with PD in the article is after slash. Percentage in following brackets is healed rate of PD. (2005)

study

Table 2: Number of patients, sex, mean age, mean follow-up, and etiology Author(s)

Patients/Hips

Sex

Mean age (years)

Mean follow-up

Etiology

Hipfl et al (2018)

34/35

F* :27 M*:7

70

47 months PD 46 months

Hourscht et al (2017)

45/46

F:26 M:19

68

74 months

16 Loose Acetabular Component 13 Loose Cage 6 Second-Stage re-implantation for infection N/R

Sporer et al (2006)

13/13

63

31.2 months

N/R

Friedrich et al (2014)

18/18

68

30 months

Sheth et al( 2018)

32/32

67

62 months

4 aseptic loosening 14 2-stage procedure due to PJI N/R

Martin et al (2017)

113/113

F:10 M:3 F:11 M:7 F:28 M:4 F:95 M:18

63

51 Osteoarthritis 25 Rheumatoid arthritis 14 Hip dysplasia 11 Trauma 8 Osteonecrosis 3 Previous radiation 1 Infection

Konan et al (2017)

24/24

72

Cup-cage 46.8 months cementless cup and posterior column plate 67.2 months Anti-protrusion cage 86.4 months Cementless cup alone 63.6 months 72 months

Martin et al (2016)

6/12

58

72 months

Regis et al (2012)

18/18

F:16 M:2

63

162 months

Sporer et al (2012)

20/20

N/R

67.5

54 months

Taunton et al (2012)

57/57

61

76 months

Rogers et al (2012)

62/62

F:51 M:6 F:47 M:15

3 Rheumatoid arthritis 2 Osteonecrosis of femoral head 1 Hip displasia 5 Primary osteoarthritis 2 Avascular necrosis of femoral head 8 Developmental dysplasia 2 Rheumatoid arthritis 1 Posttraumatic 10 Osteoarthritis 9 Rheumatoid arthritis 1 Developmental dysplasia N/R

67.5

Chronic PD 35 months

62 Secondary to periprosthetic bone loss

Kosashvili et al (2009)

24/26

64.9

44.6 months

4 Osteoarthritis 5 Rheumatoid arthritis 4 Hip dysplasia 1 Avascular necrosis 1 Paget's disease 1 Crohn's disease N/R

F:7 M:17 F:6 M:0

N/R

DeBoer et al (2007)

18/20

N/R

N/R

123 months

Paprosky et al (2006)

15/16

F:11 M:4

N/R

54 months

Paprosky et al (2005)

EG* n:12/12 CG* n:12/12

EG 61 CG N/R

EG: 25.2 months CG: 54 months

Berry et al (1999)

23/25

EG F:9 M:3 CG N/R F:22 M:3

61

35.8 months

N/R

7 Osteoarthritis 3 Rheumatoid arthritis 2 Post traumatic arthritis 1 Hip dysplasia 1 Tumor 1 Osteonecrosis 1 Pelvic irradiation N/R

13 Osteoarthritis 7 Rheumatoid arthritis 4 Hip dysplasia

Abolghasemian et al (2014)

43/45

F:38 M:5

65 (cupcage) 70 (cage)

82 months (cupcage) 69 months (cage)

F:Female. M: Male. EG: Experimental group. CG: Control group

2 Osteonecrosis 1 Tumor N/R

Table 3: A summary of different types of acetabular constructs in the treatments for pelvic discontinuity Total Number of Cases

Num ber of Paper s

Aseptic loosening(Re vision needed)(%)

Radiologi c aseptic loosening (No revision needed)( %)

PJI(%)

Dislocatio n(%)

Sciatic nerve palsy( %)

Other Complicatio ns(%)

Rerevision (%)

Survival acetabular cup(%)

172(29. 7%) 95(16.4 %) 37(6.4 %)

7

6 (3.5%) 1 (1.1%)

4

3 (8.1%)

7(4.1 %) 6(6.3 %) 0(0.0 %)

16(9.3 %) 18(1.9 %) 4(10.8 %)

5(2.9 %) 2(2.1 %) 0(0.0 %)

8 (4.7%)

3

6 (3.5%) 9(9.5% ) 0(0.0% )

14(8.1 %) 4(4.2% ) 2(5.4% )

158(91. 9%) 91(95.8 %) 34(91.9 %)

52(9.0 %)

2

2 (3.8%)

20(38. 5%)

1(1.9 %)

1(1.9%)

1(1.9 %)

6(11.5%)

2(3.8% )

50(96.2 %)

Ilioischial spanning cage(e.g. BurchSchneider cage)

114(19. 7%)

8

21 (18.4%)

5(4.4% )

7(6.1 %)

11(9.6 %)

3(2.6 %)

12(10.5 %)

34(29. 8%)

76 (66.7%)

Non-ilioischial spanning cage(e.g. GanZ and Gap II )

33(5.7 %)

3

13 (39.4%)

2(6.1% )

3(9.1 %)

5(15.2 %)

3(9.1 %)

10(30.3 %)

13(39. 4%)

20(60.6 %)

66(11.6 %)

4

7 (10.6%)

2(3.0% )

6(9.0 %)

10(15.2 %)

3(4.5 %)

8(12.1%)

18(27. 3%)

59(89.4 %)

Cup-Cage Tri-flange TM Cup with or without augment(Distraction method not utilized) TM Cup with or without augment(Distraction method) Anti-Protrusion Cage

Acetabular shell with plates

10(10.5 %) 2(5.4%)

Value expressed as n/n in this column. Number before slash is the quantity of hips with healed PD. Number after slash is the quantity of hips treated by this type of acetabular component. Percentage in following brackets is healed rate of PD.

Fig. 1: Workflow of search and selection of articles Pubmed/Medline

Ovid/Embase

(((pelvic) OR (acetabular)) AND ((discontinuity) OR (disassociation))

(((pelvic) OR (acetabular)) AND ((discontinuity) OR (disassociation))

Automatic search result with above query: 242

Automatic search result with above query: 281

227 articles that were be related to the topic after manual refinement

Final paper for review based on the predetermined inclusion and exclusion criteria: 18