Prospective multicentre mid-term clinical and radiological outcomes of 159 reverse total shoulder replacements and assessment of the influence of post-operative complications

Abstract

Background

The aim of our prospective multicentre study is to evaluate the five-year follow-up outcomes of primary reverse shoulder replacement utilizing two different designs of glenoid baseplates.

Methods

There were 159 reverse shoulder replacements (91 cemented and 68 uncemented stems, 67 Trabecular Metal baseplates and 92 Anatomical Shoulder baseplates in 152 patients (99 women) with a mean age of 74.5 (58–90) years. The principal diagnosis was rotator cuff arthropathy in 108 shoulders.

Results

Clinical and functional results improved significantly overall; the adjusted Constant Murley score improved from 28.2 ± 13.3 pre-operatively to 75.5 ± 22.8 (p < 0.0001) and the mean Subjective Shoulder Value improved from 27.5 ± 20 to 73.8 ± 21.3 points (p < 0.0001). Radiologically, there was good bony stability in 88% and 86% of cemented and uncemented stems without significant impact on the Constant Murley score and Subjective Shoulder Value at one, two and five years post-surgery. There were no significant clinical differences between Trabecular Metal and Anatomical Shoulder baseplates at five years. There were four cases of intraoperative shaft fractures that were managed with cables. Although the Trabecular Metal baseplates showed better integration radiologically, there was no significant difference in the mean of Constant Murley, Subjective Shoulder Value and the range of motion depending on the grade of inferior scapular notching at one-, two- and five-year intervals.

Conclusions

Reverse total shoulder arthroplasty restores the function in shoulder with significant improvements in function and moderate complications with minor differences between both designs of baseplates that were not reflected clinically.

Introduction

Reverse total shoulder arthroplasty (RTSA) has evolved over the last two decades to become a commonly performed procedure managing various pathologies including rotator cuff arthropathy,^1–5 irreparable rotator cuff tear without glenohumeral arthritis,^1,6 rheumatoid arthritis,^7,8 proximal humeral fractures in the elderly,^9–11 revision arthroplasty,^1,12 revision of another RTSA, ¹³ failed fixation of fractures ¹⁴ and malignancy.^15,16

The concept of RTSA is not new. Several similar RTSA devices were developed in the 1970s, when Neer devised the initial design of a shoulder replacement with the geometry reversed. ¹⁷ The major change occurred in the mid-eighties,^17,18 which transformed the historic reversed out-of-favour fixed-fulcrum prosthesis into the currently more successful designs of RTSA.^2,19 The biomechanical aim of the design is to place the deltoid into an optimal position to act as an abductor by increasing its lever arm through the medialized and distalized centre of rotation (COR), thus successively increasing deltoid efficiency. Analogous to the COR, the humerus with the insertion sites of the rotator cuff is shifted medially and inferiorly. There are other parameters that can affect stability of RTSAs; these include convex baseplate versus flat baseplate, subchondral bone sparing versus reaming, difference in bone/prosthesis contact area of the baseplates. This lengthening of the humerus increases the stability of RTSA as well as the deltoid tension.

As such, we report the mid-term multicentre follow-up of the outcomes of RTSA using the Anatomical Shoulder™ Inverse/Reverse stems (Zimmer GmbH, Switzerland) utilizing either the Anatomical Shoulder (AS) or the Trabecular Metal™ (TM) glenoid baseplates. TM (Zimmer Biomet, Parsippany, New Jersey, USA) was introduced with the intended purpose of improving early and long-term stability of the baseplate; both designs have similar COR. This is achieved by a distinctive combination of screw fixation and ingrowth into a porous tantalum baseplate. There are only limited previous reports published on the clinical and radiological outcomes of TM baseplates.^20–22

This study specifically evaluated clinical outcome measures and assessment of radiological signs that may be considered complications of the reverse geometry design. Specifically, we assessed whether the presence of notching or radiolucency affects the final outcomes.

Patients and methods

Between September 2005 and February 2012, 159 reverse shoulder replacements were completed in 152 patients (99 women and 53 men) with a mean age of 74.5 (58–90) years at operation; these included 91 cemented and 68 uncemented and 67 TM baseplates and 92 AS baseplates. Clinical and radiological follow-up assessments were performed at six weeks or six months (depending on the routine care at the hospital), one year, two years and five years. Seven patients had bilateral RTSA. The pre-operative diagnosis was cuff-tear arthropathy in 108 shoulders (68%) and osteoarthritis in 45 shoulders (28%). The indication for surgery in the remainder of patients was avascular necrosis (one shoulder), post-traumatic arthritis (one shoulder), instability (two shoulders) and rheumatoid arthritis (two shoulders). The rotator cuff tendons were deficient in all 157 shoulders; there were small, medium, large and massive tears in 8, 9, 54 and 86 shoulders, respectively.

The study was carried out as a prospective multicentre clinical trial. Surgeries were performed at five hospitals by five consultant shoulder surgeons or directly under their supervision. All patients included in the study satisfied predefined eligibility criteria. The inclusion criteria included: (1) 18 years of age or older, (2) medically fit to undergo surgery, (3) willingness to participate in the planned follow-up programme, (4) willingness to undergo standardized post-operative rehabilitation, (5) capable of providing informed consent (or by patient’s legal representative), (6) pre-operative diagnosis of cuff-tear arthropathy or failure of prior rotator cuff surgery or irreparable rotator cuff tears associated with loss of glenohumeral stability with the indication for RTSA and (7) an entirely intact deltoid (clavicular, acromial and spinal) prior to surgery. Exclusion criteria included: (1) patients having a previous history of ipsilateral septic arthritis, (2) chronic fracture, (3) acute fracture, (4) pre-existing axillary nerve lesion, (5) severe loss of humeral or glenoid bone, (6) paralysis of the deltoid muscle, (7) patient requires one of the following medical interventions: implant revision, glenoid bone grafting or simultaneous autografts, (8) women who are pregnant, (9) subjects who are skeletally immature and (10) those unwilling or unable to cooperate with the proposed follow-up programme.

All potential participants were screened for eligibility by the surgical team. The local research review board at each centre approved the study prior to ethical approval. This study received approval by the relevant research ethics board before recruiting any of the study patients. The Ethics Committee approved the informed consent as well as the patient information form. All participants were encouraged to remain in the study up to 10 years after surgery. Participants were given the right to withdraw from the study at any time for any reason. The confidentiality of every patient was maintained at all times. To anonymize the data, a specific study number was allocated to each subject.

Clinical evaluation

In each centre, the operating surgeon or a qualified, independent, designated clinical research assistant examined patients prior to surgery and at each time point after surgery. Functional and clinical outcomes were evaluated by both the Constant Murley (CM) score ²³ and the Subjective Shoulder Value (SSV) score. ²⁴ Patients were asked to rate their pain on a visual analogue scale of 0 (none) to 10 (maximal). Using a goniometer, the range of motion (ROM) was assessed and documented at each time point. This included active external rotation, active forward elevation (FE), lateral elevation (LE) and active internal rotation (IR). Data were collected pre-operatively and then at either six weeks or six months (according to the hospital’s standard care plan) and thereafter at one, two and five years after hospital discharge according to the study protocol. Surgical and medical complications that occurred after surgery were also recorded. Clinical outcomes between both TM and AS groups were compared and the influence of complications and radiographic adverse findings on the final outcomes assessed.

Radiographic evaluation

Serial anteroposterior and lateral radiographs were obtained at each follow-up visit at six weeks or six months (depending on the routine care at the hospital), one year, two years and five years. Because this was a multicentre analysis conducted in different countries, an independent review of radiographs was not performed. Participating investigators reviewed the early post-operative radiograph and each successive radiograph for any evidence of post-surgical radiological complications. These included subsidence or tilt in the humeral component, osteolysis, presence of radiolucent lines in Gruen zones. ²⁵ Evidence of spot welding, pedestal formation and reactive lines, relatively thinner cortices surrounding the implant compared with the native humerus distal to the stem, failure of components and scapular notching were documented in each of the Gruen zones on successive radiographs as well. Scapular notching was graded according to the system of Nerot-Sirveaux. ²⁶ Four grades were recorded based on the extent of notching: 1: involving only the lateral pillar; 2: contacting the inferior screw; 3: extending beyond the inferior screw; and 4: when notching extends under the baseplate.

Migration was determined from serial measurement of the vertical distance between the most proximal aspect of the implant within the greater tuberosity and the apex of the greater tuberosity itself. Pre-operative computed tomography (CT) scans were assessed.

Statistical analysis

CM score and SSV were analysed by comparing them to the pre-operative state with paired t-test. For FE, LE and IR, the post-operative distribution was compared to the pre-operative distribution by using Bowker’s Test of Symmetry. The relationship/association between ROM and notching at each follow-up exam was evaluated by Fisher exact test. The impact of notching on the CM score and SSV at each follow-up exam was evaluated by one-way ANOVA model. The α-level of significance for all tests was 0.05. We then compared the two subgroups TM versus AS in regards to the clinical and radiological outcomes at five years post-surgery. Also, we compared the presence of radiolucency in both the cemented and uncemented groups and assessed its influence on clinical outcomes with the Wilcoxon rank-sum test. The survival rate was calculated using Kaplan–Meier survival curves with 95% confidence intervals (CI).

Results

All 159 primary RTSAs using the AS Inverse Reverse Shoulder System or the TM baseplate were included into the analysis. For the minimum five-year follow-up, a maximum number of 100 data sets were available (6 × revision, 9 × death, 15 × withdrawal and 29 × patient unavailable for five-year data collection). Clinical and functional results of the treated shoulders improved significantly (Table 1). The adjusted CM score improved significantly from 28.2 ± 13.3 pre-operatively to 75.5 ± 22.8 post-operatively at five years follow-up (p < 0.0001). The mean SSV prior to surgery was 27.5 ± 20 points. At five-year review, the mean SSV was 73.8 ± 21.3 points (p < 0.0001). There were no significant differences in clinical outcomes comparing TM and AS baseplates in regards to CM score. The AS baseplates showed superior SSV initially; however, it was not evident at five years post-surgery (Table 2). There were no significant differences between the two groups regarding FE (p = 0.77), abduction (p = 0.16) and IR (p = 0.22) ROM at five years post-surgery.

Table 1.

Summary of CM score and SSV at different time points.

Variable	Examination period	Mean	SD	Min	Max	p value
Age and gender adjusted CM score	Pre-operative	28.17	13.31	0	76
	1 year	76.14	21.96	14	123	<0.0001
	2 year	78.98	22.06	17	116	<0.0001
	5 year	75.45	22.81	21	117	<0.0001
Subjective Shoulder Value	Pre-operative	27.47	20.06	0	90
	1 year	73.95	18.44	0	100	<0.0001
	2 year	75.3	18.94	0	100	<0.0001
	5 year	73.8	21.31	20	100	<0.0001

CM: Constant Murley; SSV: Subjective Shoulder Value; SD: standard deviation; Min: minimum; Max: maximum.

Table 2.

Comparison of CM score and SSV between both AS and TM baseplates.

Variable	Visit	p value	AS Mean ± SD (n, range)	TM Mean ± SD (n, range)
Age and gender adjusted CM score	Pre-operative	0.0984	29.7 ± 14.6 (84, 0–76)	26.1 ± 11.0 (60, 3–55)
	1 year	0.1640	78.3 ± 21.7 (80, 14–113)	72.7 ± 22.1 (50, 24–123)
	2 year	0.2167	80.9 ± 19.9 (76, 25–113)	75.9 ± 24.9 (49, 17–116)
	5 year	0.3465	77.4 ± 24.0 (53, 25–117)	72.8 ± 21.1 (39, 21–106)
Subjective Shoulder Value	Pre-operative	0.1003	25.2 ± 18.4 (88, 0–90)	30.8 ± 22.1 (60, 0–85)
	1 year	0.0366	76.5 ± 16.4 (84, 25–100)	69.6 ± 20.9 (49, 0–100)
	2 year	0.0201	78.4 ± 18.4 (77, 0–100)	70.4 ± 18.9 (49, 25–100)
	5 year	0.8918	74.1 ± 20.6 (57, 20–100)	73.5 ± 22.5 (40, 20–100)

CM: Constant Murley; SSV: Subjective Shoulder Value; SD: standard deviation; n: number; AS: Anatomical Shoulder System; TM: Trabecular Metal.

The ROM of all patients can be found in Figure 1. The distributions for FE and LE increased significantly at one, two and five years post-operatively (p < 0.0001). IR only demonstrated a statistically significant increase at five years post-operative (p = 0.007). There were no significant differences in ROM between the AS and TM baseplates at five years post-surgery regarding FE (p = 0.77), abduction (p = 0.16) and IR (p = 0.22). All expired subjects died with their RTSA in situ with uneventful history regarding their prosthesis at their last assessment.

Figure 1.

Summary of range of motion variables in the whole cohort. (a) Forward elevation distribution, (b) lateral elevation distribution and (c) ROM internal rotation summary.

ROM: range of motion.

Radiological analysis

A complete radiographic series was available for 136 shoulders before and after surgery. Of the 23 remaining shoulders, one glenoid could not be classified while the other 22 shoulders did not have pre-operative CT scans. At final review, 88% of the cemented humeral components demonstrated no signs of radiological loosening and 86% of the uncemented humeral components demonstrated good bony ingrowth. There was no radiographic evidence of osteolysis or subsidence (considered present if the component settled by ≥3 mm) in any shoulder. At five years, 80% of the AS baseplates demonstrated no radiolucent lines, compared to 97.5% of the TM baseplates (p = 0.13).

The presence of radiolucency was not associated with inferior clinical scores (Table 3). For cemented stems, the presence of radiolucency at five years did not show significant impact on the CM score (p = 0.31) or SSV (p = 0.36). The same was observed in uncemented stems (Table 4). The presence of radiolucency was not associated with inferior FE (p = 0.12) and LE (p = 0.52) in cemented components at five years post-operative. Additionally, the presence of radiolucency was not associated with inferior FE (p = 0.21) and LE (p = 0.32) in uncemented components at five years post-operative.

Table 3.

CM score and SSV comparison in relation to presence of radiolucency: cemented cases.

	Have radiolucency at 5 years?
Variable	Visit	p value	NO Mean ± SD (n, range)	YES Mean ± SD (n, range)
Age and gender adjusted CM score	Pre-operative	0.7687	26.0 ± 10.6 (41, 6–55)	30.3 ± 14.6 (6, 17–54)
	1 year	0.8535	71.8 ± 18.9 (36, 38–99)	75.3 ± 21.5 (6, 51–111)
	2 year	0.9539	76.2 ± 22.2 (38, 17–112)	78.5 ± 15.9 (6, 63–108)
	5 year	0.3108	75.9 ± 22.1 (43, 25–113)	69.8 ± 14.2 (6, 51–86)
Subjective Shoulder Value	Pre-operative	0.2001	31.5 ± 22.7 (42, 0–85)	19.0 ± 11.4 (5, 0–30)
	1 year	0.0960	69.7 ± 15.5 (36, 40–95)	81.7 ± 11.7 (6, 60–90)
	2 year	0.2168	69.9 ± 16.8 (36, 30–90)	77.5 ± 15.4 (6, 50–90)
	5 year	0.3611	71.7 ± 21.9 (44, 20–100)	62.5 ± 26.4 (6, 20–90)

CM: Constant Murley; SSV: Subjective Shoulder Value; SD: standard deviation; n: number.

Table 4.

CM score and SSV comparison in relation to presence of radiolucency: uncemented cases.

	Have radiolucency at 5 years?
Variable	Visit	p value	NO Mean ± SD (n, range)	YES Mean ± SD (n, range)
Age and gender adjusted CM score	Pre-operative	0.9078	32.6 ± 13.8 (35, 6–76)	34.0 ± 14.9 (6, 18–54)
	1 year	0.4862	81.8 ± 22.7 (36, 31–113)	89.0 ± 17.5 (5, 65–106)
	2 year	0.3344	82.4 ± 22.3 (33, 25–113)	92.4 ± 15.2 (5, 71–108)
	5 year	0.5301	76.8 ± 25.8 (33, 21–117)	71.3 ± 19.8 (6, 42–92)
Subjective Shoulder Value	Pre-operative	0.7601	26.8 ± 17.4 (36, 0–65)	29.2 ± 3.8 (6, 25–35)
	1 year	0.2845	79.9 ± 21.2 (37, 0–100)	78.3 ± 9.3 (6, 60–85)
	2 year	0.2906	81.4 ± 22.1 (35, 0–100)	78.3 ± 11.3 (6, 60–90)
	5 year	0.0693	79.4 ± 18.7 (37, 25–100)	65.0 ± 16.4 (6, 40–80)

CM: Constant Murley; SSV: Subjective Shoulder Value; SD: standard deviation; n: number.

Notching was seen in 57 shoulders, all cases stabilized by two years post-surgery (Figure 2). However, there was no significant difference in the mean CM score or SSV at one, two or five years post-surgery in shoulders demonstrating inferior notching compared to the rest of the cohort (Table 5). We did not find a correlation to prove that notching had significant impact on the CM and SSV scores. Even severe grades of notching were not associated with inferior clinical outcomes. Our analysis did not generate sufficient evidence to prove the notching grade had significant impact on CM score and SSV. Similarly, notching was not associated with inferior FE (p = 0.298), abduction (p = 0.198) or IR (p = 0.797) at five years follow-up.

Figure 2.

Scapular notching of an AS (a) and TM (b) baseplate fully established at two years post-surgery without effect on the ROM and functional scores.

AS: Anatomical Shoulder; TM: Trabecular Metal; ROM: range of motion.

Table 5.

Summary of CM score and SSV comparison based on notching status.

		Comparing test p value	Having notching?
Variable	Visit		NO Mean ± SD (n, range)	Yes Mean ± SD (n, range)
Age and gender adjusted CM score	1 year	0.0681	79.4 ± 21.2 (76, 14–123)	72.6 ± 22.4 (49, 24–113)
	2 year	0.3043	81.1 ± 21.3 (66, 18–116)	76.5 ± 23.1 (54, 17–112)
	5 year	0.7362	78.0 ± 22.7 (46, 33–117)	75.0 ± 22.8 (38, 21–108)
Subjective Shoulder Value	1 year	0.3891	75.5 ± 17.0 (76, 0–100)	71.9 ± 19.8 (52, 20–100)
	2 year	0.5861	74.5 ± 19.6 (68, 0–100)	77.0 ± 17.3 (54, 30–100)
	5 year	0.2631	76.7 ± 21.2 (49, 20–100)	72.5 ± 20.2 (40, 20–100)

CM: Constant Murley; SSV: Subjective Shoulder Value; SD: standard deviation; n: number.

Complications

Axillary nerve palsy was reported in two patients. Expectant therapy was undertaken in both subjects in the form of physiotherapy and medication. Four patients had documented haematoma formation. The haematomas were either evacuated or spontaneously disappeared; none required revision. Acromial fracture occurred in one patient and was managed conservatively. There were four intraoperative fractures of the humerus (three cemented components and one uncemented component), all of which were secured with cerclage cables and showed complete healing and stability at radiological review. All fractures were associated with worse clinical outcomes and worse forward flexion and abduction. The mean CM and SSV scores were 76 and 74, respectively, in patients without intraoperative fractures compared with 57.7 and 66.7, respectively, in those with intraoperative fractures. No statistical test was performed as the sample size is small (N = 5) and the power too low to calculate a reliable p value.

In the whole cohort, six cases were revised (Table 6). Three shoulders were revised because of glenoid implant loosening, one was revised because of humeral implant loosening, one was revised because of humeral side pain and one was revised because of post-operative instability. Using revision for any reason, the total survival for this series was 95.6% (95% CI: 90.50, 98.03) at five years (Figure 3). A summary of the used components in the cohort is summarized in Table 7.

Table 6.

Complications.

Surgery date	Operative side	Revision date	Revised at year	Event	Treatment
15 December 2008	Right	02 July 2009	1	Humeral pain	Revision of the humeral component
20 June 2006	Right	16 January 2007	1	Glenoid implant loosening (AS)	Conversion to hemiarthroplasty
15 March 2011	Left	16 November 2012	2	Dislocation	Revision of the glenoid component
05 September 2008	Right	06 October 2009	2	Glenoid implant loosening (AS)	Revision of the whole component
09 March 2010	Right	13 June 2013	4	Glenoid implant loosening (AS)	Revision of the humeral component
21 May 2008	Right	08 December 2011	4	Humeral implant loosening	Revision of the whole component

AS: Anatomical Shoulder System.

Figure 3.

Kaplan–Meier survival curve for any of the components with “revision for any reason” as the endpoint. Highlighted area represents 95% confidence intervals.

Table 7.

Summary of the used components in this cohort. ^a

	Cemented			Uncemented
	Diameter (mm)	Length (mm)	N (%)	Diameter (mm)	Length (mm)	N (%)
Humeral stem	7	100	12 (7.8)	7	100	1 (0.7)
	9	110	39 (25.3)	9	110	3 (2.0)
	12	110	26 (16.9)	10.5	110	15 (9.7)
	14	110	8 (5.2)	12	110	27 (17.5)
	9	210	1 (0.6)	14	110	22 (14.3)
	Diameter (mm)	AS glenosphere		TM glenosphere
Glenoid head	36	70 (44.6%)		52 (33.1%)
	40	21 (13.4%)		14 (8.9%)

AS: Anatomical Shoulder System; TM: Trabecular Metal.

^aSome operative notes were lacking the sizes used so were excluded.

Discussion

This prospective multicentre series demonstrates favourable mid-term clinical and radiological results of a reverse shoulder replacement at five years post-surgery using two different baseplate designs. Each group had statistically significant improvements in functional scores, pain scores and functional ROM. There was no significant difference in regards to clinical outcomes when comparing the AS baseplates with the TM baseplates even though the TM baseplates demonstrated superior bony integration at five years. There were no significant differences between cemented and uncemented components in either clinical outcomes or ROM. Finally, although the presence of intraoperative fractures was associated with inferior outcomes, notching did not affect the clinical scores significantly at any time point.

RTSA represents one of the most significant advances in shoulder arthroplasty in recent decades with satisfactory outcomes.^2,3,27 Excellent outcomes are achievable, yet they are reliant on indications and appropriate patient selection. ²⁸ Our results demonstrated significant improvements in functional and clinical outcomes at a minimum of five years follow-up. Indications continue to evolve and the number of prostheses implanted globally is rapidly expanding. Indications for RTSA in our cohort included all common pathologies with rotator cuff pathology and osteoarthritis representing the main indication in more than two-thirds of the cohort. Similar results were reported for the use of RTSA for managing rotator cuff tears,^1–5 osteoarthritis^28–30 and rheumatoid arthritis.^7,8 Surgeons need to be aware not only of potential benefits but also of complications of this prosthesis.^2,31,32

Notwithstanding the few encouraging long-term outcomes,^27,33 the rate of loosening of the stem is thought to be high with RTSA compared to total shoulder arthroplasty. ³⁴ This observation could be related to the semi-constrained nature of the prosthesis causing increased shear stress at the stem-bone interface. ³⁵ This was not observed in the current study. Historically, this was avoided by the use of cemented humeral components; hence, many studies reported the outcomes of RTSA with cemented humeral component.^5,36–38 However, in our cohort, we found no significant differences between cemented and uncemented components of which 88% and 86%, respectively, demonstrated no radiolucencies. The presence of radiolucencies had no observed negative impact on the clinical scores at five years post-surgery. Similarly, Wiater et al. ²² did not show significant difference in functional clinical outcomes between the cemented and uncemented RTSA (p > 0.05).

In our series, notching of the scapular pillar occurred in 36% of the implanted RTSA at five years follow-up, and all cases of notching manifested by two years post-surgery. Notching is initiated by the impingement of the cup against the scapular neck and is a common radiologic finding that is specific to RTSA.^39–42 Levigne et al. ⁴³ reported notching in 68% of cases at two years follow-up. We have observed no significant difference in CM score or SSV in association with the grade of inferior scapular notching at various time points. This finding is similar to others who reported no clinical significance of notching.^{5,20,36,42,44,45} Others, however, demonstrated that severe notching is associated with inferior outcomes.^26,46,47 Regarding the ROM, we also did not observe inferior outcomes in shoulders with the presence of notching.

To the best of our knowledge, there is paucity in reports on the outcomes of TM baseplate in shoulder arthroplasty literature. TM implants have shown superiority in providing secure fixation in both basic science applications and in short-term analysis in hip⁴⁸ and knee ⁴⁹ arthroplasty. Biomechanical properties that can increase the stability of the glenoid components include design and materials used. ⁵⁰ Clinically, we observed superior osteointegration of the glenoid baseplate at five years post-surgery. Bogle et al. ²¹ reported radiographic results of uncemented TM RTSA at two years’ follow-up. Similar to the results of the present study, their data advocate that TM RTSA is associated with inherent stability of the glenoid at one, two and five years.

Radiolucency, in both cemented and uncemented components, at five years post-operative visit did not have significant impact on the CM score, SSV or ROM at any follow-up visits. However, due the small sample size of shoulders with radiolucency, the exact Wilcoxon rank-sum tests did not have good power. Thus, the inferences based on these p values might not be very reliable.

Using revision of the components as the endpoint for failure, the survival rate of the components was 96% at five years. This is significantly superior than that reported by Guery et al. ⁵¹ who showed a survival rate of 84% at 10 years follow-up of 80 Delta RTSA. Four of their revisions took place due to glenoid aseptic loosening. Cuff et al. ⁵² reported RTSA survivorship, with the end point being revision for any reason, was 90.7%. Favard et al. ²⁷ reported survivorship of 89% at 10 years with a marked break occurring at two and nine years. Survivorship to a CM score of less than 30 was 72% at 10 years with a marked break observed at eight years. They observed progressive radiographic changes after five years and an increasing frequency of large notches with long-term follow-up.

Similar complications have been previously reported in literature. Anticipated complications after RTSA include glenoid loosening, dislocation, infection, glenoid notching, humeral periprosthetic fracture, neurologic problems, acromion fracture and haematoma formation.^5,26,28,32 We report acromial fracture in one patient, which has been linked to the increase in the passive tension of the deltoid.^2,53 with reported rate up to 3% ³⁴ compared with less than 1% in our study. In the present study, intraoperative fractures were associated with inferior clinical results over the five years follow-up. Fractures on the humeral side may happen during exposure in patients with either severe osteopenia or marked fibrosis, as seen in revision cases.^54,55 The rate of intraoperative fractures during shoulder arthroplasty is as high as 3.3%. ⁵⁶

We report haematoma formation in 4% of patients in our cohort, which does not appear to affect the outcome of RTSA^2,53 and may be attributed to the under-reporting of haematoma formation. Nevertheless, haematoma formation is purported to be a substantial risk factor for the occurrence of infection after shoulder arthroplasty as reported by Cheung et al. ⁵⁷ In our study, none of the four shoulders with haematoma demonstrated signs of infection.

There are limitations in our study. Due to the multicentre nature of the study, independent observers could not evaluate the radiographs from different centres. Also, because of the nature of comparing two different types of glenoid implants, specifics regarding radiographic evaluation of the COR lateralization compared to the native glenoid as well as arm lengthening using the distance between the acromion and greater tuberosity should have been performed. However, there was a standardized protocol in all participating centres by which all clinical and radiological analyses were performed. Moreover, a total of 59 datasets were missing at the five-year follow-up time point. In addition to the six revision and nine death cases, 15 patients withdrew from the analysis and 29 patients could not be reached for their five-year’s follow-up. This could be a source of bias in the reported outcomes. ⁵⁸ We are reporting the clinical outcomes of a single humeral prosthesis; although these findings can be applied to other implants, however, this is beyond the scope of this publication.

Conclusions

RTSA restores the function in shoulder with significant improvements in function and moderate complications with minor differences between both designs of baseplates that were not reflected clinically.

Ethical Review and Patient Consent

For all the study participants, written informed consent was obtained. The Ethics Committee approved the informed consent as well as the patient information forms.