Do Modern Designs of Metal-Backed Glenoid Components Show Improved Clinical Results in Total Shoulder Arthroplasty? A Systematic Review of the Literature

Abstract

Background:

Despite the increased popularity of reverse total shoulder arthroplasty, total shoulder arthroplasty is the standard treatment for advanced shoulder arthritis in young adult patients. Conventional metal-backed glenoid (MBG) designs result in more loosening and revision surgery compared with cemented polyethylene glenoid components. However, modern MBG designs have been recently devised to overcome such drawbacks.

Purpose:

To compare the radiolucency, loosening, and failure rates of modern MBG designs with those of conventional designs.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A search for relevant articles was carried out using the PubMed, Cochrane Library, and Embase databases using MeSH (Medical Subject Headings) terms and natural keywords. A total of 362 articles were screened. We descriptively analyzed numerical data between the groups and statistically analyzed categorical data, such as the presence of loosening, failure, and revision surgery. The main outcome was the rate of revision surgery or failure. Subgroup analysis according to follow-up duration was performed to reduce heterogeneity.

Results:

A total of 25 articles (2036 shoulders) were included; 15 articles (1579 shoulders) involved a conventional MBG design, and 10 (457 shoulders) involved a modern design. The mean age of the patients was 64.2 and 66.5 years in the conventional and modern design groups, respectively, with a mean follow-up duration of 102.0 and 56.1 months, a mean gain of forward elevation of 35.1° and 61.7°, and a mean gain of external rotation of 24.2° and 39.2°. The rate of radiolucency was 48.0% and 16.7%, the rate of loosening was 11.2% and 4.9%, and the rate of revision was 15.9% and 2.4%, for the conventional and modern design groups, respectively. Subgroup analysis according to follow-up duration showed that the rates of loosening and revision were significantly lower in the modern design group (P < .001).

Conclusion:

Our findings suggest that modern MBG designs showed significantly lower loosening and failure rates than conventional designs. The overall results of the comparison, including loosening, failure, change in range of motion, and clinical scores, indicate that modern MBG designs are promising. More long-term follow-up studies on modern MBGs should be conducted.

Keywords

shoulder arthroplasty glenoid component metal-backed

First-generation shoulder arthroplasty was developed by Frederik Krueger¹⁵ in 1951. This was followed by modular-type, second-generation shoulder arthroplasty with various humeral head diameters; however, the clinical results were not significantly improved. In the third generation, shoulder prostheses could be adapted to the individual patient so that the patient’s anatomic structure could be reconstructed.^22,30,31 Despite the increased popularity of reverse total shoulder arthroplasty (rTSA), TSA is the standard treatment for advanced shoulder arthritis in young adult patients with an intact rotator cuff. TSA consists of a glenoid component, humeral head, and humeral component, and each of these parts can vary in material, modularity, length, and design. Numerous studies have attempted to optimize the design for each component, but no clear conclusions have yet been drawn, and the matter is still being actively researched.²⁶

Neer et al^23,24 first introduced glenoid implants in shoulder arthroplasty to treat glenohumeral arthritis. The glenoid component can have a keel- or rod-type shape, and it can be composed of all-polyethylene (PE) materials or have a metal-backed design. Metal-backed glenoid (MBG) components usually have metal base plates, metal screws or rods, and PE liners. In the initial design, the PE liner was thin, resulting in high rates of wear and failure.¹ According to a systematic review conducted in 2014, MBGs have a higher failure rate than all-PE components.²⁹ Advanced designs were devised to overcome these shortcomings.^4,10,18

This systematic review aimed to summarize the results of TSA using MBGs and to compare the radiolucency, loosening, and failure rates of modern MBG designs with those of conventional MBG designs. The main outcomes were radiolucency, loosening, other complications, and failure or revision. Additionally, we compared range of motion (ROM) improvements and clinical scores for some of the studies that presented these data. We hypothesized that modern MBG designs would show lower rates of radiolucency, loosening, and failure than conventional MBG designs.

Methods

This systematic review was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.¹⁹ Additionally, it was registered on the PROSPERO website (CRD42019131822).

Inclusion and Exclusion Criteria

The inclusion criteria for this systematic review were as follows: (1) human adult participants, (2) presentation of the outcomes of TSA using an MBG component to treat any type of arthritis, (3) mean follow-up duration of more than 2 years, and (4) publication in English. The exclusion criteria were as follows: (1) case report or inclusion of fewer than 5 cases, (2) conference abstract or biomechanical study, (3) use of an implant that was not truly metal backed (eg, a glenoid component with only the rod made of metal), and (4) inclusion of glenoid revision or bone grafts.

Search Strategy and Study Selection

PubMed, Embase, and Cochrane Library were searched to find articles related to the topic. The search terms were determined through a group discussion and included a natural language search as follows: total AND shoulder AND (replacement OR arthroplasty) AND (metal OR backed OR (cementless glenoid)). After excluding duplicate documents, 2 independent reviewers (F.A., M.A.) screened the articles by title and abstract. They then made the final selection through a full-text review. This study also conducted citation tracking to find additional articles and checked newly published articles by performing a search update just before completing the review. All disagreements were solved by a group discussion involving ≥3 investigators.

Methodological Assessment and Data Extraction

Levels of evidence were assessed according to the Oxford Centre for Evidence-Based Medicine.¹³ A methodological assessment was performed using the MINORS (Methodological Index for Non-Randomized Studies) tool, which has been validated.³⁴ Noncomparative studies are evaluated by 8 items and comparative studies by 12 items, and each item is scored as 0, 1, or 2 points. Thus, noncomparative studies can have a total score of 0-16 and comparative studies of 0-24. A study that scored ≥60% of the total score was considered a high-quality article.

The terms “modern design” and “conventional design,” which were the main themes of this study, were defined through a group discussion, during which the latest review articles on glenoid components were evaluated. The 3 advanced designs presented in the 2019 review by Castagna and Garofalo³ were defined as modern designs: (1) the second-generation Systema Multiplana Randelli (SMR) MBG (LimaCorporate); (2) the first-generation trabecular metal (TM) glenoid, which consists of a soft MBG (Sulmesh; Zimmer Biomet); and (3) the second-generation TM glenoid (Zimmer Biomet). The second-generation SMR MBG had the following characteristics: curved back and less conforming shape, stiff and thick metal back (5 mm) to minimize wear, hydroxyapatite coating on a peg, and stable fixation through 2 screws and 1 central peg. The first- and second-generation TM glenoids were selected as modern designs because they were monoblock systems; they used porous tantalum or titanium to stabilize the initial fixation and reduce backside wear. The Sulmesh, one of the first-generation TM glenoids, consists of several layers of titanium mesh and has 4 pegs made of Protasul-Ti (Zimmer), which allows stable initial fixation without screws.¹⁰ The second-generation TM glenoid exhibits a further improved design: a porous tantalum keel. The remaining designs were regarded as conventional designs.

Two independent reviewers (F.A., M.A.) extracted the following data from selected articles: publication year, number of patients and shoulders, months of follow-up, age, sex, surgery, history of disease or surgery, rehabilitation program, diagnosis, name of implant and manufacturer, clinical score, ROM, radiolucency, loosening, other complications, and revision surgery (failure). Radiolucency was defined as a radiolucent line of ≥1 mm, grade ≥2 on the Lazarus radiolucency scoring system, or at least 7 points of a total 18 points.²⁰ “Loosening” included both clinical and radiological loosening, and failure was defined as revision surgery because of an implant-related problem.

Statistical Analysis

We could not perform a meta-analysis on numerical data such as ROM and clinical scores because important data, such as the standard deviation, were often absent. Also, there was no specific patient-reported outcome that all articles used in common. Therefore, a descriptive analysis of the numerical data was conducted to compare the modern and conventional designs. Regarding categorical variables, such as the presence of radiolucency, loosening, and failure or revision surgery, statistical analysis was performed on the difference between modern and conventional designs. If preoperative factors, such as age or follow-up duration, differed between the 2 groups, we planned to minimize bias using a subgroup analysis of these factors. All statistical analyses were conducted using SPSS for Windows (Version 24.0.0.0; IBM), and P values <.05 were considered statistically significant.

Results

Search Results

A total of 177 articles in PubMed, 324 in Embase, and 29 in the Cochrane Library were found. After removal of duplicates, 362 titles and abstracts were screened, and 33 articles underwent full-text review. There were 24 articles that were included in the systematic review after the full-text review, and 1 article was added through citation tracking of the included articles. No additional articles were found in the search update. Figure 1 shows the entire process using a PRISMA flow diagram. Overall, 15 studies used conventional MBG components,^¶ and 10 studies used modern MBG components.^#

Figure 1.

PRISMA (Preferred Reporting Items for Systematic Meta-Analyses) flow diagram showing the selection of appropriate articles.

Assessment of Methodological Quality and Heterogeneity

Levels of evidence were determined by an agreement between 2 researchers (D.M.K., K.H.K.), and no disagreements occurred. There was 1 randomized controlled trial (level 1), 1 study with level 3 evidence, and 23 studies with level 4 evidence. The mean MINORS score was 9.43 ± 1.35 for noncomparative studies and 19 ± 0 for comparative studies. Also, 9 of 15 articles (60.0%) that used conventional designs and 6 of 10 articles (60.0%) that used modern designs were high quality. The distribution of age and follow-up duration in each study is shown using a summary plot (Figures 2 and 3) to determine the heterogeneity between the 2 groups. In the summary plot, age showed a similar pattern between the 2 groups, but the conventional design group had a longer follow-up period than the modern design group.

Figure 2.

Summary plots for age.

Figure 3.

Summary plots for follow-up duration.

Summary of Outcomes of Each Article

The demographic data and outcome measurements of each study are summarized in Table 1. The TSA outcomes were presented using various items and measurement methods; the following were the most common: ROM (10 and 6 articles for conventional and modern designs, respectively), the visual analog scale for pain (3 and 7 articles, respectively), the Constant score (6 and 3 articles, respectively), the American Shoulder and Elbow Surgeons score (1 and 6 articles, respectively), complications (all articles), and revision surgery or failure (all articles). The results of each article with regard to these commonly used items are shown in Table 2.

TABLE 1

Demographic Data and Outcome Measurements of Individual Studies ^a

Author (Year)	LOE	Design	No. of Cases	Age, ^b y	Follow-up, ^b mo	ROM	Outcome Measures
Conventional design
Figgie et al⁸ (1992)	4	Custom-fit model	27	55 (25-75)	60 (36-84)	FE, ABD, ER	Shoulder score
Wallace et al³⁹ (1999)	3	Neer II ^c	26	64 (25-87)	64 (46-90)	FE, IR, ER	VAS, SF-36, complications, loosening, and revision (failure)
Boileau et al¹ (2002)	1	Aequalis ^d	20	69 (56-89)	38	ER	Constant
Levy and Copeland¹⁶ (2004)	4	Copeland CSRA ^e	39	71.5 (50-87)	91.2 (48-156)	FE, ABD, IR, ER	Constant
Martin et al¹⁷ (2005)	4	Kirschner II-C ^f	140	63.3 ± 13 (22-92)	90 ± 30 (63-159)	FE, IR, ER	ASES
Rosenberg et al³² (2007)	4	Mixed ^g	227	60.1	82.5	NR	NR
Taunton et al³⁷ (2008)	4	Neer I ^h	83	68 (41-87)	114	FE, ABD, IR, ER	VAS, Neer rating, survival estimate
Tammachote et al³⁶ (2009)	4	Neer II ^c	95	68 ± 8	129.6	ABD, IR, ER	VAS, Neer rating
Fox et al⁹ (2009)	4	Mixed ⁱ	561	65	118.7	NR
Clement et al⁶ (2010)	4	Biomodular TSR ^j	46	55 (35-86)	132 (96-168)	FE, ABD, ER	Constant
Clement et al⁵ (2013)	4	Biomodular TSR ^j	33	67	95 (60-173)	FE, ABD, ER	Constant
Montoya et al²¹ (2013)	4	Univers ^k	65	66 (54-85)	64 (26-85)	FE, ABD, ER	Constant
Katz et al¹⁴ (2013)	4	ARROW ^l	143	NR	NR	NR	NR
Vuillermin et al³⁸ (2015)	4	Univers ^k	51	70.4 (51-90)	65.5 (44-97)	NR	NR
Gauci et al¹¹ (2018)	4	Aequalis ^d	23	54 (35-60)	108 (60-156)	Only preoperative	Constant
Modern design
Castagna et al⁴ (2010)	4	2nd-generation SMR ^m	35	62.7 (55.3-70.1)	75.4	NR	VAS, Constant, SST
Fucentese et al¹⁰ (2010)	4	Sulmesh ⁿ	22	68.5 (49-84)	50 (24-89)	NR	Constant
Budge et al² (2013)	4	Tantalum TM ^o	19	62.8 ± 14.6	31 (24-64)	ER	VAS, ASES
Styron et al³⁵ (2016)	4	Tantalum TM ^o	66	66.2 (31-88)	50.2	FE, IR, ER	NR
Sandow and Schutz³³ (2016)	4	Tantalum TM ^o	10	60-79	24	FE	VAS, Oxford, ASES
Panti et al²⁸ (2016)	4	Tantalum TM ^o	76	69.6 (52-81)	43.2 (24-72)	FE, ABD, ER	VAS, ASES
Endrizzi et al⁷ (2016)	4	Tantalum TM ^o	73	67.5 ± 8.6 (46-85)	50.8 (24-68)	NR	VAS, ASES
Merolla et al¹⁸ (2016)	4	Tantalum TM ^o	40	63.8 (40-75)	38 (24-42)	FE, ABD, ER	Health state, Constant, ASES
Gurin and Seitz¹² (2017)	4	Tantalum TM ^o	80	NR	100	NR	VAS
Watson et al⁴⁰ (2018)	4	Tantalum TM ^o	36	66.36 (50-85)	34.1 (23-61)	FE, ER	VAS, SANE, Penn, ASES

^a ABD, abduction; ASES, American Shoulder and Elbow Surgeons; ER, external rotation; FE, forward elevation; IR, internal rotation; LOE, level of evidence; NR, not recorded; ROM, range of motion; SANE, Single Assessment Numeric Evaluation; SF-36, 36-Item Short Form Health Survey; SMR, Systema Multiplana Randelli; SST, Simple Shoulder Test; TM, trabecular metal; VAS, visual analog scale.

^b Data are shown as mean, mean ± SD, mean ± SD (range), mean (range), or range.

^c Neer II metal-backed polyethylene component (Kirschner Medical).

^d Aequalis metal-backed glenoid (Tornier).

^e Copeland CSRA (Cementless Surface Replacement Arthroplasty; Zimmer Biomet).

^f Kirschner II-C uncemented glenoid component (Kirschner Medical).

^g BioModular TSR prosthesis (Zimmer Biomet), initial Nottingham TSR prosthesis, and Nottingham TSR prosthesis (Zimmer Biomet).

^h Neer I metal-backed polyethylene component (Kirschner Medical).

ⁱ Neer II metal-backed polyethylene component and Cofield 1 and 2 metal-backed polyethylene components (Smith & Nephew).

^j BioModular TSR prosthesis.

^k Univers metal-backed, uncemented glenoid implant (Arthrex).

^l ARROW universal shoulder prosthesis (FH Orthopedics).

^m Second-generation SMR system (Systema Multiplana Randelli; LimaCorporate).

ⁿ Sulmesh titanium metal-backed glenoid component (Zimmer Biomet).

^o Second-generation, porous, tantalum trabecular metal glenoid (Zimmer Biomet).

TABLE 2

Clinical Outcomes of Studies Using Conventional and Modern Designs of MBG Components ^a

Author	No. of Cases	FE Gain, deg	ER Gain, deg	Radiolucency ^b	Loosening ^b	Revision Surgery ^b	No. of Other Reoperations
Conventional design
Figgie et al⁸	27	40	20	7 (26)	0 (0)	0 (0)	2: RC repair
Wallace et al³⁹	26	NR	NR	6 (23)	6 (23)	5 (19)	NR
Boileau et al¹	20	NR	42	1 (5)	4 (20)	4 (20)	NR
Levy and Copeland¹⁶	39	62	41	18 (46)	18 (46)	4 (10)	0
Martin et al¹⁷	140	45	14	105 (75)	14 (10)	19 (14)	NR
Rosenberg et al³²	227	NR	NR	NR	21 (9)	43 (19)	0
Taunton et al³⁷	83	33	29	50 (60)	33 (40)	26 (31)	NR
Tammachote et al³⁶	95	NR	34	69 (73)	2 (2)	5 (5)	NR
Fox et al⁹	561	NR	NR	NR	36 (6)	95 (17)	0
Clement et al⁶	46	–4	10	4 (9)	1 (2)	5 (11)	0
Clement et al⁵	33	31.8	22.9	6 (18)	1 (3)	3 (9)	0
Montoya et al²¹	65	27.5	23	4 (6)	5 (8)	6 (9)	NR
Katz et al¹⁴	143	NR	NR	NR	NR	3 (2)	0
Vuillermin et al³⁸	51	NR	NR	NR	13 (25)	17 (33)	NR
Gauci et al¹¹	23	NR	NR	NR	5 (22)	16 (70)	0
Modern design
Castagna et al⁴	35	NR	NR	8 (23)	0 (0)	0 (0)	0
Fucentese et al¹⁰	22	NR	NR	NR	3 (14)	3 (14)	0
Budge et al²	29	NR	44	7 (37)	4 (21)	3 (16)	NR
Styron et al³⁵	66	70	36	NR	13 (20)	1 (2)	NR
Sandow and Schutz³³	10	NR	NR	0 (0)	0 (0)	0 (0)	0
Panti et al²⁸	76	54.4	40.8	5 (7)	0 (0)	0 (0)	1: RC repair
Endrizzi et al⁷	73	NR	NR	24 (33)	1 (1)	1 (1)	0
Merolla et al¹⁸	40	NR	NR	2 (5)	0 (0)	0 (0)	0
Gurin and Seitz¹²	80	NR	NR	NR	0 (0)	2 (3)	0
Watson et al⁴⁰	36	NR	NR	1 (3)	1 (3)	1 (3)	NR

^a ER, external rotation; FE, forward elevation; MBG, metal-backed glenoid; NR, not recorded; RC, rotator cuff.

^b Data are shown as n (%).

Comparison Between Conventional and Modern MBG Designs

Table 3 shows the results of our comparison of modern versus conventional MBG designs based on the studies reviewed. The mean gain in forward elevation was 35.1° and 61.7° and the mean gain in external rotation was 24.2° and 39.2° for conventional and modern designs, respectively. The respective rates of radiolucency, loosening, and revision surgery (failure) were 48.0%, 11.2%, and 15.9% in the conventional design group and 16.7%, 4.9%, and 2.4% in the modern design group. A scatter plot was used to graph the rates of loosening and failure of each study according to the follow-up duration (Figure 4). The graphs showed that the modern design group tended to have lower loosening and failure rates than the conventional design group. In addition, a subgroup analysis according to follow-up duration was performed (Table 4). The rates of radiolucency, loosening, and revision surgery were significantly lower in the modern design group (P < .001 in all cases), with the exception of radiolucency in cases with a follow-up duration of ≤6 years. The findings of the subgroup analysis concurred with the overall comparison between the 2 groups.

TABLE 3

Comparison Between Conventional and Modern Designs of MBG Components ^a

	Conventional Design (n = 1579)	Modern Design (n = 457)
Age, y
No. of cases/articles	1436/14	377/9
Mean (range)	64.2 (25-90)	66.5 (31-88)
Follow-up duration, mo
No. of cases/articles	1436/14	457/10
Mean (range)	102.0 (26-173)	56.1
FE gain, deg
No. of cases/articles	433/7	142/2
Mean	35.1	61.7
ER gain, deg
No. of cases/articles	548/9	161/3
Mean	24.2	39.2
Radiolucency, n (%)
Present	270 (48.0)	47 (16.7)
Absent	292 (52.0)	235 (83.3)
Not reported	1017	175
Loosening, n (%)
Present	159 (11.2)	22 (4.9)
Absent	1265 (88.8)	427 (95.1)
Not reported	155	8
Revision surgery (failure), n (%)
Present	251 (15.9)	11 (2.4)
Absent	1328 (84.1)	446 (97.6)
Not reported	0	0
Other complications
No. of cases/articles	1579/15	457/10
n (%)	91 (5.8)	14 (3.1)

^a ER, external rotation; FE, forward elevation; MBG, metal-backed glenoid.

Figure 4.

(A) Rate of loosening or wear according to design and follow-up duration. (B) Rate of revision surgery or failure according to design and follow-up duration. MBG, metal-backed glenoid.

TABLE 4

Subgroup Analysis of Radiolucency, Loosening, and Revision Surgery (Failure) According to Follow-up Duration ^a

	Conventional Design	Modern Design	P Value
Follow-up duration ≤6 y
Radiolucency			.762
Present	18 (14.3)	39 (15.8)
Absent	108 (85.7)	208 (84.2)
Loosening			.001
Present	28 (15.8)	22 (6.6)
Absent	149 (84.2)	312 (93.4)
Revision surgery (failure)			<.001
Present	32 (16.9)	9 (2.6)
Absent	157 (83.1)	333 (97.4)
Follow-up duration >6 y
Radiolucency			<.001
Present	252 (57.8)	8 (22.9)
Absent	184 (42.2)	27 (77.1)
Loosening			<.001
Present	131 (10.5)	0 (0.0)
Absent	1116 (89.5)	115 (100.0)
Revision surgery (failure)			<.001
Present	219 (14.2)	2 (1.7)
Absent	1328 (85.8)	113 (98.3)
Follow-up duration ≤100 mo
Radiolucency			<.001
Present	147 (42.0)	47 (16.7)
Absent	203 (58.0)	235 (83.3)
Loosening			<.001
Present	82 (13.1)	22 (4.9)
Absent	546 (86.9)	427 (95.1)
Revision surgery (failure)			<.001
Present	101 (16.1)	11 (2.4)
Absent	527 (83.9)	446 (97.6)

^a Data are shown as n (%).

The causes of revision surgery are summarized in Figure 5. The most common cause of failure in cases that used conventional designs was loosening (118 cases; 47.0%), while in cases that used modern designs, the most common cause was fracture of the glenoid component (6 cases; 54.5%). Other complications, excluding implant problems, occurred in 91 cases (5.8%) that used a conventional design and in 14 cases (3.1%) that used a modern design (Figure 6). Such complications in the conventional design group included instability (33 cases; 36.3%), wound problems (22 cases; 24.2%), and rotator cuff tears (20 cases; 22.0%). The most commonly seen complications in the modern design group were stiffness (5 cases; 35.7%), rotator cuff tears (3 cases; 21.4%), and instability (2 cases; 14.3%).

Figure 5.

Graph showing the causes of revision surgery. Fx, fracture; PE, polyethylene.

Figure 6.

Other complications in the conventional and modern design groups.

Discussion

A systematic review carried out in 2014 compared complications and revision surgery rates between MBG and all-PE glenoid components and found that MBGs showed significantly higher rates of complications and reoperations. That review included all MBG implants in the same group.²⁹ After MBGs were abandoned by many surgeons, attempts were made to improve the design, altering the shape of the implant, the design of the peg and keel, and the angle of the screws or peg. The second-generation SMR MBG is representative of the modern design. Castagna et al⁴ reported good results using this device, citing the following reasons: (1) the shape of the glenoid—the implants have a curved back and are less conforming; (2) a stiff and thick metal back (5 mm), which reduces stress on the PE component and reduces wear; (3) hydroxyapatite on the peg as well as the base plate; and (4) the presence of 2 screws and 1 central peg, which ensures stable fixation.

Another representative modern design is Zimmer Biomet’s tantalum or titanium TM. The first-generation TM glenoid—the Sulmesh soft MBG—consists of several titanium meshes, and 4 pegs protect the metal back. The second-generation TM glenoid shows an improved design with a porous tantalum keel. Recent clinical studies on these modern MBG designs have reported good results.^** Future improvements in these modern designs may further minimize negative outcomes and improve overall results.³

In the current review, after comparing variables such as ROM change, loosening, and revision surgery (failure), the modern designs of MBG components seem promising compared with the conventional designs. Our hypothesis was supported by the results. Statistical analysis of numerical data such as ROM was not possible because many studies did not provide the standard deviation. However, most studies presented information regarding radiolucent lines on plain radiography, loosening, and revision (failure). Furthermore, because these data were presented in a categorical fashion, such as present versus absent, they were analyzed able to be using crosstab analysis. The scatter plot and subgroup analysis showed that loosening and failure were less common in the modern design group than in the conventional design group (P < .001 for each item).

MBGs were designed to allow strong fixation by inducing bone ingrowth using a porous-coated component at the glenoid interface. The joint surface was designed to induce smooth ROM using a PE component. Various types of MBGs have been developed, most of which are cementless and are fixed to the glenoid using screws or rods. General advantages of MBGs over cemented PE glenoids are as follows: (1) bone ingrowth that provides greater stability, (2) easy conversion to reverse TSA, (3) concomitant bone graft procedure in case of severe glenoid bone loss, and (4) no complications related to cement. Conventional MBGs were expected to be an ideal design, but the results of clinical studies were disappointing.^†† The following reasons were given for this: (1) PE wear, which occurs because the metal back necessitates a thin PE liner⁹; (2) overstuffing of joints, which was often done to ensure sufficient PE thickness, resulting in loosening and rotator cuff tears and eventually leading to joint instability; and (3) failure of rods and screws, which are not used in cemented, all-PE glenoid components.

A 2018 study by Page et al²⁷ analyzed glenoid revision rates using the Australian Orthopaedic Association National Joint Replacement Registry, which was begun in 2004. Cementless MBGs were classified into a modular and fixed type in the study, and SMR L1, L2, and TM glenoids were included in the analysis. Cementless glenoids showed a significantly higher revision rate compared with cemented glenoids. Contrary to the results of the study by Castagna et al,⁴ which used SMR L1 glenoid, the SMR L2 design showed a higher revision rate than other designs according to Page et al. Based on the result, SMR L2 was withdrawn from the market. Only L1 glenoid has been used since 2012. TM glenoids, on the other hand, showed the same low revision rate in the current review and in the study by Page et al. Results of this review and the study by Page et al suggest that surgeons be cautious in their selection of MBG because different designs can produce different results. TM glenoids are promising and comparable with cemented glenoids. However, TM glenoids cannot be easily converted to reverse TSA because of the monoblock design. SMR glenoids can be easily converted to reverse TSA and can be used even in case of glenoid bone loss. More reports regarding the results of the SMR are needed.

This study has several limitations. First, although we carried out a systematic search using predefined criteria and search terms, we may have missed some articles. Second, there is no clear consensus about the distinction between modern and conventional designs. We based our definitions on the study by Castagna and Garofalo,³ which was the most up-to-date review article presenting the rationale for glenoid components. Third, a meta-analysis or Kaplan-Meier analysis could not be carried out because the current study failed to acquire all the appropriate data. It is for this reason that the numerical data, such as clinical scores and ROM, were not significant, even though the difference was quite large. Fourth, the follow-up duration in the modern design group was relatively short; this was the main heterogeneity against the conventional design group. However, we minimized this heterogeneity through the scatter plot and subgroup analysis according to the follow-up duration. Also, most of the modern designs were TM glenoids. This made it difficult to generalize on the advantages of modern MBG designs.

Conclusion

Our findings suggest that modern MBG designs, especially the TM glenoid, showed significantly lower loosening and failure rates than conventional designs. The overall results of the comparison, including loosening, failure, change in ROM, and clinical scores, indicate that the modern MBG designs are promising. More long-term follow-up studies on modern MBGs should be conducted.

Footnotes

Acknowledgment

The authors thank Minkyu Han, PhD, for analyzing and interpreting data and processing them into meaningful results. They also thank Editage () for English language editing.

Final revision submitted March 7, 2020; accepted April 10, 2020.

Notes

One or more of the authors has declared the following potential conflict of interest or source of funding: This study was supported by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Education (NRF-2018R1D1A1A02086025). AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

References

Boileau

Avidor

Krishnan

Walch

Kempf

Mole

. Cemented polyethylene versus uncemented metal-backed glenoid components in total shoulder arthroplasty: a prospective, double-blind, randomized study. J Shoulder Elbow Surg. 2002;11(4):351–359.

Budge

Nolan

Heisey

Baker

Wiater

. Results of total shoulder arthroplasty with a monoblock porous tantalum glenoid component: a prospective minimum 2-year follow-up study. J Shoulder Elbow Surg. 2013;22(4):535–541.

Castagna

Garofalo

. Journey of the glenoid in anatomic total shoulder replacement. Shoulder Elbow. 2019;11(2):140–148.

Castagna

Randelli

Garofalo

Maradei

Giardella

Borroni

. Mid-term results of a metal-backed glenoid component in total shoulder replacement. J Bone Joint Surg Br. 2010;92(10):1410–1415.

Clement

Duckworth

Colling

Stirrat

. An uncemented metal-backed glenoid component in total shoulder arthroplasty for osteoarthritis: factors affecting survival and outcome. J Orthop Sci. 2013;18(1):22–28.

Clement

Mathur

Colling

Stirrat

. The metal-backed glenoid component in rheumatoid disease: eight- to fourteen-year follow-up. J Shoulder Elbow Surg. 2010;19(5):749–756.

Endrizzi

MacKenzie

Henry

PDG

. Early debris formation with a porous tantalum glenoid component radiographic analysis with 2-year minimum follow-up. J Bone Joint Surg Am. 2016;98(12):1023–1029.

Figgie

Inglis

Figgie

3rd Sobel

Burstein

Kraay

. Custom total shoulder arthroplasty in inflammatory arthritis: preliminary results. J Arthroplasty. 1992;7(1):1–6.

Fox

Cil

Sperling

Sanchez-Sotelo

Schleck

Cofield

. Survival of the glenoid component in shoulder arthroplasty. J Shoulder Elbow Surg. 2009;18(6):859–863.

10.

Fucentese

Costouros

K ühnel

Gerber

. Total shoulder arthroplasty with an uncemented soft-metal-backed glenoid component. J Shoulder Elbow Surg. 2010;19(4):624–631.

11.

Gauci

Bonnevialle

Moineau

Baba

Walch

Boileau

. Anatomical total shoulder arthroplasty in young patients with osteoarthritis: all-polyethylene versus metal-backed glenoid. Bone Joint J. 2018;100(4):485–492.

12.

Gurin

Seitz

. The emerging role of the non-cemented glenoid in total shoulder arthroplasty. Semin Arthroplasty. 2017;28(3):128–133.

13.

Howick

Chalmers

Glasziou

, et al. The Oxford 2011 levels of evidence. http://www.cebm.net/index.aspx?o=5653. Accessed April 13, 2019.

14.

Katz

Kany

Valenti

Sauzieres

Gleyze

El Kholti

. New design of a cementless glenoid component in unconstrained shoulder arthroplasty: a prospective medium-term analysis of 143 cases. Eur J Orthop Surg Traumatol. 2013;23(1):27–34.

15.

Krueger

. A vitallium replica arthroplasty on the shoulder: a case report of aseptic necrosis of the proximal end of the humerus. Surgery. 1951;30(6):1005–1011.

16.

Levy

Copeland

. Cementless surface replacement arthroplasty (Copeland CSRA) for osteoarthritis of the shoulder. J Shoulder Elbow Surg. 2004;13(3):266–271.

17.

Martin

Zurakowski

Thornhill

. Uncemented glenoid component in total shoulder arthroplasty: survivorship and outcomes. J Bone Joint Surg Am. 2005;87(6):1284–1292.

18.

Merolla

Chin

Sasyniuk

Paladini

Porcellini

. Total shoulder arthroplasty with a second-generation tantalum trabecular metal-backed glenoid component. Bone Joint J. 2016;98(1):75–80.

19.

Moher

Liberati

Tetzlaff

Altman

; PRISMA Group. Preferred Reporting Items for Systematic Reviews and Meta-Analyses: the PRISMA statement. PLoS Med. 2009;6(7):e1000097.

20.

Molé

Roche

Riand

L évigne

Walch

. Cemented glenoid component: results in osteoarthritis and rheumatoid arthritis. In: Walch

Boileau

, eds. Shoulder Arthroplasty. Springer; 1999:163–171.

21.

Montoya

Magosch

Scheiderer

Lichtenberg

Melean

Habermeyer

. Midterm results of a total shoulder prosthesis fixed with a cementless glenoid component. J Shoulder Elbow Surg. 2013;22(5):628–635.

22.

Neer

2nd . Articular replacement for the humeral head. J Bone Joint Surg Am. 1955;37(2):215–228.

23.

Neer

2nd . Replacement arthroplasty for glenohumeral osteoarthritis. J Bone Joint Surg Am. 1974;56(1):1–13.

24.

Neer

2nd Watson

Stanton

. Recent experience in total shoulder replacement. J Bone Joint Surg Am. 1982;64(3):319–337.

25.

Obermeyer

Cagle

Jr Parsons

Flatow

. Midterm follow-up of metal-backed glenoid components in anatomical total shoulder arthroplasties. Am J Orthop (Belle Mead NJ). 2015;44(9):e340–e342.

26.

Song

. The current state of total shoulder arthroplasty. Clin Shoulder Elbow. 2011;14(2):253–261.

27.

Page

Pai

Eng

Bain

Graves

Lorimer

. Cementless versus cemented glenoid components in conventional total shoulder joint arthroplasty: analysis from the Australian Orthopaedic Association National Joint Replacement Registry. J Shoulder Elbow Surg. 2018;27(10):1859–1865.

28.

Panti

Tan

Kuo

Fung

Walker

Duff

. Clinical and radiologic outcomes of the second-generation trabecular metal glenoid for total shoulder replacements after 2-6 years follow-up. Arch Orthop Trauma Surg. 2016;136(12):1637–1645.

29.

Papadonikolakis

Matsen

3rd . Metal-backed glenoid components have a higher rate of failure and fail by different modes in comparison with all-polyethylene components: a systematic review. J Bone Joint Surg Am. 2014;96(12):1041–1047.

30.

Pearl

Volk

. Coronal plane geometry of the proximal humerus relevant to prosthetic arthroplasty. J Shoulder Elbow Surg. 1996;5(4):320–326.

31.

Roberts

Foley

Swallow

Wallace

Coughlan

. The geometry of the humeral head and the design of prostheses. J Bone Joint Surg Br. 1991;73(4):647–650.

32.

Rosenberg

Neumann

Modi

Mersich

Wallace

. Improvements in survival of the uncemented Nottingham total shoulder prosthesis: a prospective comparative study. BMC Musculoskelet Disord. 2007;8:76.

33.

Sandow

Schutz

. Total shoulder arthroplasty using trabecular metal augments to address glenoid retroversion: the preliminary result of 10 patients with minimum 2-year follow-up. J Shoulder Elbow Surg. 2016;25(4):598–607.

34.

Slim

Nini

Forestier

Kwiatkowski

Panis

Chipponi

. Methodological Index for Non-Randomized Studies (MINORS): development and validation of a new instrument. ANZ J Surg. 2003;73(9):712–716.

35.

Styron

Marinello

Peers

Seitz

Jr . Survivorship of trabecular metal anchored glenoid total shoulder arthroplasties. Tech Hand Up Extrem Surg. 2016;20(3):113–116.

36.

Tammachote

Sperling

Vathana

Cofield

Harmsen

Schleck

. Long-term results of cemented metal-backed glenoid components for osteoarthritis of the shoulder. J Bone Joint Surg Am. 2009;91(1):160–166.

37.

Taunton

McIntosh

Sperling

Cofield

. Total shoulder arthroplasty with a metal-backed, bone-ingrowth glenoid component: medium to long-term results. J Bone Joint Surg Am. 2008;90(10):2180–2188.

38.

Vuillermin

Trump

Barwood

Hoy

. Catastrophic failure of a low profile metal-backed glenoid component after total shoulder arthroplasty. Int J Shoulder Surg. 2015;9(4):121–127.

39.

Wallace

Phillips

MacDougal

Walsh

Sonnabend

. Resurfacing of the glenoid in total shoulder arthroplasty: a comparison, at a mean of five years, of prostheses inserted with and without cement. J Bone Joint Surg Am. 1999;81(4):510–518.

40.

Watson

Gudger

Jr Long

Tokish

Tolan

. Outcomes of trabecular metal-backed glenoid components in anatomic total shoulder arthroplasty. J Shoulder Elbow Surg. 2018;27(3):493–498.