Effectiveness of Reverse Total Shoulder Arthroplasty for Primary and Salvage Fracture Care Clinical and Radiological Outcome in Mid-term Follow-up in a Single-Center Experience

The introduction of reverse total shoulder arthroplasty (RSA) as a treatment option in complex proximal humeral fractures, including patients with poor bone quality, has signicantly extended the surgical armamentarium. The aim of this study was to investigate the mid-term outcome following fracture RSA (FRSA) in acute or sequelae, as well as salvage procedures. It was hypothesized that revision FRSA (SRSA) leads to similar mid-term results as primary fracture treatment by RSA (PRSA). This retrospective case-series study describes the radiological and clinical mid-term outcome in a standardized single-center and one-material Inlay design. Patients who underwent FRSA between 2008 and 2017 were matched (minimum follow-up: two years, minimum age at the time of operation: 60 years). Statistically, signicant positive tubercle changes were evaluated in the PRSA group; radiological changes contained dislocations and (partial) resorptions in this group. In the SRSA group, only postoperative partial resorptions were detected. Signicant values are bold-marked. in percent, other scores in points. Signicant results are bold-marked. The values are presented on average.


Trial Registration
Not applicable, level of evidence III.
Meanwhile, recent trends show that RSA has become the treatment of choice for complex proximal humeral fractures, especially in patients with poor bone quality (21). The RSA was primarily designed to treat patients with massive rotator cuff defects (22)(23)(24)(25). Thus, indications have been extended to further pathologies, such as cuff tear arthropathy (26,27) , and proximal humeral fractures (PHFs) (17,28) or revision arthroplasty (29). Moreover, RSA is used as a salvage procedure in cases of symptomatic mal-or non-unions following (failed) primary osteosynthesis or HA of PHFs (1,13,29).
The keypoint in clinical practice is to perform a stable osteosynthesis after meticulous, gentle reduction without denudation of fracture fragments in complex fracture situations. Various treatment options and expectations for acute PHFs lead to vivid discussions among surgeons and patients. To address this focus, we hypothesized that a failed joint preserving strategy treated by revision RSA might achieve similar clinical results as the primary joint replacement approach. Therefore, the aim of the study was to evaluate the functional outcome following primary RSA (PRSA) for PHFs compared to secondary RSA (SRSA) performed as a salvage procedure.

Study design and patient recruitment
This retrospective case-series study characterizes a single-center evaluation in a standardized setting following reverse total shoulder arthroplasty in primary (PRSA) or secondary / sequelae (SRSA) fracture care.
All consecutive patients older than 60 years at the time of surgery were included after the treatment by either PRSA or SRSA between January 2008 and December 2017 at a level-III trauma center (AUVA -Trauma Hospital Styria | Graz). The time-line was chosen based on data accessibility. Only patients with the Inlay (Grammont) design (155° humeral neck-shaft angle) were included; two different implants were involved {Delta Xtend, DePuy Synthes; Warsaw, USA | Anatomical Reverse, Zimmer; Warsaw, USA}.
The PRSA group included patients that received RSA implantation as primary treatment for three-or fourpart and articular segment fractures according to Neer's classi cation (30,31). In this group, all cases have been treated with a reverse shoulder arthroplasty within ten days after trauma. For the SRSA group, a minimum time interval from index to revision surgery of three months has been de ned. This group comprised subgroups of patients that underwent RSA implantation in cases of humeral head necrosis following angular stable plate osteosynthesis (HHN), as following failed open reduction and internal xation (fORIF) and after trauma hemiarthroplasty (THA). For detailed study design, see Figure 1.

Patient characteristics
Data were collected prospectively in the respective hospital database. Patient characteristics and pathological as well as course of treatment data were summed up and analyzed retrospectively. All postoperative adverse events were evaluated via the hospital database and their medical history in the nal patient investigation. Major complications were speci ed by requiring an unplanned revision, all others were classi ed as minor complications. The follow-up (FU) time was de ned as an interval between surgery and last assessment. The minimum FU was xed by two years.
Speci c details in operative and postoperative procedure The operative procedure and rehab protocol were equivalent in the entire sample according to the standardized work-up at our center. A deltopectoral approach was performed in the beach-chair position in every case. Further, all humeral monobloc components were cemented. For glenoid preparation, a full 360° release was accomplished under axillary nerve visualization. If necessary, an additive arthrolysis and scar release was performed.
All tubercles were xed via non-resorbable transosseous and cerclage sutures and circular sutures around the prosthesis neck. If a detachment of the subscapularis tendon was necessary, a double-row transosseous re xation was realized. Passive physiotherapy with a free range of motion (ROM) in a painfree interval was started two days postoperatively. The active-assistive motion was initiated ve weeks postoperatively, deltoid muscle mass improvement was fostered at the beginning of the seventh week.

Clinical outcome assessment
Patients were assessed to determine their current clinical level via the following scores: Visual Analog Scale (VAS), absolute Constant Score (CS) (32), normative Constant Score (nCS) (33), Subjective Shoulder Value (SSV) (34), and Quick DASH (QD) (35). ROM was evaluated in degrees for exion, abduction, and external rotation (ER). The internal rotation (IR) was characterized in points based on the functional shoulder-speci c CS (32). Patient-speci c assessment was carried out via the modi ed valuation of the CS, which is based on age-and gender-related characteristics (nCS) (33).
The SSV symbolizes a Single Assessment Numeric Evaluation (SANE) of the shoulder, representing a shoulder self-assessment by the patient him-/ herself. The score is expressed as a percentage of an entirely healthy shoulder, which would score 100% (34). The QD is a self-assessment instrument and includes eleven questions concerning complaints regarding the upper extremity and activities of daily living (35). The preoperative CS, which was available in their prospective documentation in the hospital database, was compared to their respective postoperative values. Further analysis in the SRSA group was performed by differentiation in early (<12 months) and late (>12 months) time intervals from index surgery to revision RSA implantation regarding their mid-term outcome in CS.

Radiological outcome assessment
During follow-up, X-rays in three planes (anterior-posterior, axial, and supraspinatus outlet view) were performed. The nal X-rays were analyzed under comparison to index and interim radiological data. They were evaluated by three trauma and orthopedic surgeons (AS, GH, and MN) regarding implant dislocation, grade of notching according to Sirveaux (36), resorption of the major and/or minor tubercles, and radiological signs of loosening of the prosthesis.
To assess clinical correlations and the radiological outcome, the CS and nCS were chosen for evaluation in the following focuses: tubercle bone stock healing and scapular notching. Analyzing the ROM results, the strongest relationship was found for exion and abduction with a correlation coe cient of ρ = .901 (p < .001).

Scores
The outcome values of PRSA and SRSA did not reveal any statistically signi cant differences, as displayed in Table 3. Thus, no signi cant differences were observed in CS (p = .204) and nCS (p = .211), for details see Figure 2. Similarly, no signi cant associations were evaluated in both scores when comparing the PRSA values with individual subgroups within the SRSA (see Table 4).
When comparing the VAS and QD score amongst primary and secondary care, homogeneous results were observed in PRSA and SRSA (p = .573 and .291), as cited in Table 3 and Figure 3 (QD). Regarding the SRSA subgroups, no statistical signi cance could be evaluated concerning VAS and QD scores (p ≥ .05, see Table 4). Assessing the patient satisfaction, equivalent SSV results in PRSA and SRSA were observed, which was statistically not signi cant (p = .558), see Figure 4. For speci c details, see Table 3 plus 4.
Of the score data analyzed, the most substantial relationship was found for the CS and QD with a correlation coe cient of ρ = -.785 (p < .001).
A signi cant improvement in CS could be validated in the SRSA group; the preoperative mean CS was 23 (SD: 9.7), whereby a postoperative average CS of 56 (SD: 13.9) resulted in nal FU (p = .001), see Figure  5. Additional SRSA differentiation in early (<12 months) and late (>12 months) time of operative revision did not reveal a statistical signi cance; all scores were comparable (p ≥ .05) -see Table 5.

Radiological ndings and their functional correlations
No implant dislocations, as well as no glenoid loosenings, were observed. In one patient, who suffered from rheumatoid arthritis, a humeral component's loosening had to be noticed.
When comparing the healed with unhealed tubercles like resorption zones or dislocations, statistically signi cant values were documented in all scores. (all: p = <0.05). The ROM analysis veri ed a signi cant negative ER in unhealed situations (p = .019); see Table 7 for details.
A total rate of scapular notching of 23% (n = 16/68) without any correlation regarding PRSA or SRSA was evaluated (p = .687, ρ = .70; see Table 8). Only one case was classi ed with a higher grade of notching

Complications
The overall rate of adverse events was 13% (n = 9/68). Six percent (n = 4/68) were classi ed as major, seven percent (n = 5/68) as minor complications. There were fewer complications in the SRSA group when compared to the PRSA group without any statistically signi cance (p = .196). The seven complications (in 6 patients) in the PRSA group included two patients requiring revision surgery. This represents a rate of adverse events of 17% in PRSA (n = 7/42). The two complications in the SRSA group were a single major and minor complication, which led into one revision surgery. Hence, a rate of 8% (n = 2/26) was observed in SRSA group. Listed details of all adverse events are depicted in Table 9.

Discussion
The aim of the study was to analyze the effectiveness of FRSA via a standardized setting in mid-term outcome. While RSA signi cantly improved the treatment of patients with rotator cuff disorders, we focused on the value and better understanding of RSA in fracture management.
The PRSA and SRSA groups did not show statistically signi cant differences in the range of motion and functional scores, which con rms our hypothesis. Only the subgroup following fORIF showed signi cantly decreased values regarding exion and abduction compared to the PRSA.
Signi cant improvements between pre-and postoperative CS could be proven in SRSA. Furthermore, the time from index to revision surgery demonstrated no in uence on the functional outcome, which indicates that RSA implantation represents a successful treatment strategy in salvage care. However, radiographic changes regarding the tubercles and the overall complication rate were increased in the PRSA compared to the SRSA sample. Association registry data from the interval between 2004 and 2016, whereby 1523 implantations could be included in the study. Only two percent of these (33/1523) required revision surgery with instability as the most common reason (11/1523). The nine adverse effects (13%) and six percent major complication rate of the present study have to be re-evaluated regarding their incidence. Implant-related major complications concern in only one solely case of instability and dislocation. A shaft loosening had to be attributed to an underlying disease. All other adverse events were not implant-related or fateful events. These facts lead to a major complication rate of three percent in total collective, comparable to Lehtimäki et al. (2). Moreover, the rate of adverse events was similar in primary and secondary care.
Common agreements exist regarding decreasing notching rates in modern prosthesis designs (45). The clinical impact of scapular notching appears controversial in the literature. Some authors report a signi cant decrease in outcome by notching; others declare no important in uences (46)(47)(48). A recent systematic review (49), including 2,222 shoulder arthroplasties, found that 155° implants had a total notching rate of 16.8%. The authors reported that the notching rate is signi cantly higher at the 155° as in the 135° design. These values are comparable to our results of a 23% notching rate.
Jain et al. (50) identi ed a tubercle healing rate of 70.5%, which is equivalent to our results of 72% in a meta-analysis of 382 shoulder arthroplasties and a similar FU period. Acceptable functional results in non-healed or (partial) resorption tubercle patients (28% of the total collective) substantiate that a fracture RSA implantation allows predictable postoperative results. Nevertheless, statistically signi cant correlations by healed tubercles were shown in all functional scores and patient satisfaction characteristics, as well as in ER -an essential aspect for the daily processes. Based on these data in midterm clinical outcome, we recommend that surgeons make a strict effort on tubercle re xation.

Strengths and limitations
This study investigated the combined effect of radiological events and tubercle bone stock associated with clinical outcome in primary and secondary fracture care and may allow preoperative assessments in order to estimate the postoperative processes. Due to changes in patient requirements and the increasing demand for salvage procedures, this study reinforces our understanding with mid-term results in an assimilable patient number. The clinical signi cance is forti ed by continuously increasing implantation rates of RSA in fracture care in a modern material design. Future research is needed to establish potential superiorities and the best surgical option in younger patients.
However, there are several limitations to this study. First, the study design was retrospective, and our preoperative documentation (except SRSA) did not collect all the tests and scores used in our follow-up study. Therefore, we argue with the term amelioration only in the SRSA group with CS and nCS.
Second, the follow-up period is mid-term, and the complication rate might increase with time. Next, group sizes regarding patient numbers and FU were inconstant; this aspect is well comparable to literature data in this patient sample. Furthermore, the study was conducted only using reverse total shoulder systems with cemented humeral components, and direct comparisons to its contemporaries the cementless RSA systems cannot be drawn. Lastly, multiple surgeons (four experienced trauma and orthopedic surgeons) were involved, and no comparisons regarding their personal experiences and outcome were performed.

Conclusions
The similar mid-scale/-term ndings of both strategies con rm the value of RSA in complex shoulder fracture management as a primary or secondary / salvage care to maintain autonomy. Predictable, promising mid-term functional results, a high patient satisfaction, and excellent pain reliefs could be demonstrated.
In SRSA, signi cant postoperative improvements could be stated.

Declarations
Ethics approval and consent to participate The study protocol was approved by the local ethics committee (Votum EK 32/2017) of the Austrian Social Insurance for Occupational Risks (AUVA), and was performed in agreement with the protocol. The study was performed in accordance with the principles of the Declaration of Helsinki and the ICH-GCP Guidelines. Informed consent was written obtained from all individual participants included in the study.

Consent for publication
Not applicable.
Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author at a reasonable request.

Competing interests
The authors declare that they have no competing interests.

Funding
The authors declare that there was no funding source.

Authors contributions
AS was responsible for the initiation of the study, analysis of the data, the rst draft of the manuscript and contributed signi cantly with the input from MP to the nal draft of the manuscript. MP had the original idea of the study, initiated the study, participated in critical revision of the article for important intellectual content and supervision. AS and MP worked out the study design, all authors conceived the study protocol.
All authors were involved in drafting of the manuscript and approved the nal version to be submitted for publication.  (ER -external rotation, IR -internal rotation, po -points ROM -range of motion, FRSA -fracture reversed total shoulder arthroplasty, PRSA -primary reversed total shoulder arthroplasty, SRSAsecondary reversed total shoulder arthroplasty, SD -standard deviation)  (ER -external rotation, fORIF SRSA -reversed total shoulder arthroplasty following failed open reduction and internal xation, HHN RSA -reversed total shoulder arthroplasty following humeral head, IRinternal rotation, po -points, ROM -range of motion, SD -standard deviation, THA -SRSA -reversed total shoulder arthroplasty following trauma hemiarthroplasty) (CS -absolute Constant Score, nCS -normative Constant Score, FRSA -fracture reversed total shoulder arthroplasty, PRSA -primary reversed total shoulder arthroplasty, QD -Quick DASH, SD -standard deviation, SRSA -secondary reversed total shoulder arthroplasty, SSV -Subjective Shoulder Value, VAS -Visual Analog Scale)    (PRSA -primary reversed total shoulder arthroplasty, SD -standard deviation, SRSA -secondary reversed total shoulder arthroplasty)  In total 21% (n = 9/42) 27% (n = 7/26) .687 Similar notching rates without statistical relevance were observed in both groups.