Management of complications after reverse shoulder arthroplasty

Reliable technique for acromion density assessment on CT

INTRODUCTION

Acromial stress fracture (ASF) is an uncommon but acknowledged complication of reverse total shoulder arthroplasty (RTSA). There is no standardised method to directly measure the bone mineral density of the acromion to allow a detailed analysis of the potential mechanism of ASF. The aim is to establish a reliable and reproducible technique for measurement of acromial density on computer tomography (CT).

METHODS

A retrospective review on CT scans obtained for three groups of patients: those planned for RTSA (n = 26); age and gender-matched non-operative (n = 26); and young non-operative patients (n = 28) were performed. Standardised axial images of 1 mm thickness at 1 mm increments were created following horizontal straightening on the coronal and sagittal views. To assess inter-rater reliability, two senior CT radiographers performed density measurements using standard region of interest (ROI) tool on the CTs with the ROI placed on the mid (ROI 1) and posterior (ROI 2) acromion. ROIs were selected as the most common locations for acromion fracture post RTSA. Measurements were repeated at least 6 weeks apart. Intra-class coefficients (ICC) were used to determine intra- and inter-rater reliability.

RESULTS

ICCs demonstrated good to high intra-rater and inter-rater reliability for both ROI 1 and ROI 2 across all three groups. The lower margin of 95% confidence intervals was more than 0 for all intra-class coefficients.

CONCLUSION

This study demonstrates a reliable method of measuring acromion density on CT. This method can be used to assess bone mineral density in the clinical setting and in future studies investigating ASF following RTSA.

Global trends and research hotspots of reverse total shoulder arthroplasty: a bibliometric analysis from 1991 to 2022

Reverse total shoulder arthroplasty (rTSA) has been demonstrated to be an effective intervention for various shoulder disorders. The number of rTSA-related studies performed has increased annually over the past three decades. The Journal of Shoulder and Elbow Surgery had the highest number of publications and citations in the rTSA-related research domain and is therefore considered to be the most influential journal in this field. The USA published the most publications and established a high degree of cooperation with many countries worldwide. The University of Florida, the Hospital for Special Surgery, and Rush University, Mayo Clinic were representative and active institutions in this field. It is anticipated that advancements in prosthesis design, specifically with regards to lateralized design concepts, expanding indications for rTSA, a trend toward younger patient populations, and the management of postoperative complications will emerge as research hotspots in the following years. The most valuable publications, influential journals, major researchers, and leading countries were analyzed. The findings of our study will help researchers gain insights into current research hotspots and frontiers and shape their research focus in the field of rTSA.

Managing rotator cuff tear arthropathy: a role for cuff tear arthropathy hemiarthroplasty as well as reverse total shoulder arthroplasty

BACKGROUND

Disabling cuff tear arthropathy (CTA) is commonly managed with reverse shoulder arthroplasty (RSA). However, for patients with CTA having preserved active elevation, cuff tear arthropathy hemiarthroplasty (CTAH) may offer a cost-effective alternative that avoids the complications unique to RSA. We sought to determine the characteristics and outcomes of a series of patients with CTA managed with these procedures.

MATERIALS AND METHODS

We retrospectively reviewed 103 patients with CTA treated with shoulder arthroplasty, the type of which was determined by the patient's ability to actively elevate the arm. Outcome measures included the change in the Simple Shoulder Test (SST), the percent maximum improvement in SST (%MPI), and the percentage of patients exceeding the minimal clinically important difference for the change in SST and %MPI. Postoperative x-rays were evaluated to assess the positions of the center of rotation and the greater tuberosity for each implant.

RESULTS

Forty-four percent of the 103 patients were managed with CTAH while 56% were managed with RSA. Both arthroplasties resulted in clinically significant improvement. Patients having RSA improved from a mean preoperative SST score of 1.7 (interquartile range [IQR], 0.0-3.0) to a postoperative score of 6.3 (IQR, 2.3-10.0) (P < .01). Patients having CTAH improved from a preoperative SST score of 3.1 (IQR, 1.0-4.0) to a postoperative score of 7.6 (IQR, 5.0-10.) (P < .001). These improvements exceeded the minimal clinically important difference. Instability accounted for most of the RSA complications; however, it did not account for any CTAH complications. The postoperative position of the center of rotation and greater tuberosity on anteroposterior radiographs did not correlate with the clinical outcomes for either procedure.

CONCLUSION

For 103 patients with CTA, clinically significant improvement was achieved with appropriately indicated CTAH and RSA. In view of the lower cost of the CTAH implant, it may provide a cost-effective alternative to RSA for patients with retained active elevation.

Impact of constrained humeral liner on impingement-free range of motion and impingement type in reverse shoulder arthroplasty using a computer simulation

BACKGROUND

Dislocation is a major complication of reverse total shoulder arthroplasty (RSA). The humeral liner may be changed to a constrained type when stability does not improve by increasing glenosphere size or lateralization with implants, and patients, particularly women with obesity, have risks of periprosthetic instability that may be secondary to hinge adduction on the thorax, but there are few reports on its impact on the range of motion (ROM). This study aimed to determine the influence of humeral liner constraint on impingement-free ROM and impingement type using an RSA computer simulation model.

METHODS

A virtual simulation model was created using 3D measurement software for conducting a simulation study. This study included 25 patients with rotator cuff tears and rotator cuff tear arthropathy. Impingement-free ROM and impingement patterns were measured during flexion, extension, abduction, adduction, external rotation, and internal rotation. Twenty-five cases with a total of 4 patterns of 2 multiplied by 2, making a total of 100 simulations: glenosphere (38 mm normal type vs. lateralized type) and humeral liner constraint (normal type vs. constrained type). There were 4 combinations: normal glenosphere and normal humeral liner, normal glenosphere and constrained humeral liner, lateralized glenosphere and normal humeral liner, and lateralized glenosphere and constrained humeral liner.

RESULTS

Significant differences were found in all impingement-free ROM in 1-way analysis of variance (abduction: P = .01, adduction: P < .01, flexion: P = .01, extension: P = .02, external rotation: P < .01, and internal rotation: P < .01). Tukey's post hoc tests showed that the impingement-free ROM was reduced during abduction, external rotation, and internal rotation with the combination of the normal glenosphere and constrained humeral liner compared with the other combinations, and improved by glenoid lateralization compared with the combination of the lateralized glenosphere and constrained humeral liner. In the impingement pattern, the Pearson χ2 test showed significantly greater proportion of impingement of the humeral liner into the superior part of the glenoid neck in abduction occurring in the combination of the normal glenosphere and constrained humeral liner group compared with the other groups (P < .01). Bonferroni post hoc tests revealed that the combination of the normal glenosphere and constrained humeral liner was significantly different from that of the lateralized glenosphere and constrained humeral liner (P < .01). Using constrained liners resulted in early impingement on the superior part of the glenoid neck in the normal glenosphere, whereas glenoid lateralization increased impingement-free ROM.

CONCLUSION

This RSA computer simulation model demonstrated that constrained humeral liners led to decreased impingement-free ROM. However, using the lateralized glenosphere improved abduction ROM.

Three-Dimensional Finite Element Analysis of a Notched Insert Design for Reverse Total Shoulder Arthroplasty to Prevent Scapular Notching

Purpose

Reverse total shoulder arthroplasty (RSA) is an effective treatment option for rotator cuff arthropathy. Scapular notching following RSA remains a major complication and has a high incidence. This finite element analysis (FEA) study provides a future reference for the optimal design of the insert component of RSA. This study aims to clarify the effect of a new design RSA with a notched insert on the range of adduction, scapular notching, and stress variation of its insert component using three-dimensional (3D) FEA.

Methods

3D nominal Grammont-type monobloc RSA implant components are modeled on the sawbones glenohumeral joint. The polyethylene insert is redesigned with notching of the inferior part. The comparison of standard and notched designs was performed by FEA for stress pressure of scapular notching and the degree of adduction. 3D mesh models are created for stress analysis to compare the results between standard and notched inserts for the adduction.

Results

The redesigned notched inserts had an additional ~ 11.2° on adduction and prevented scapular notching. The stress analysis results for the notched insert design were lower than the standard ones (4.7 vs 22.4 Kpa).

Conclusions

Notched insert design of Grammont-type RSA could provide additional adduction with lower stress on the glenoid, leading to less scapular notching. Further experimental and clinical studies on different RSA types are needed to verify this effect.

Study Design

Basic Science Study; Biomechanics and Computer Modeling.

Fracture Dislocations of the Glenohumeral Joint

PURPOSE OF REVIEW

Proximal humerus fracture dislocations typically result from high-energy mechanisms and carry specific risks, technical challenges, and management considerations. It is vital for treating surgeons to understand the various indications, procedures, and complications involved with their treatment.

RECENT FINDINGS

While these injuries are relatively rare in comparison with other categories of proximal humerus fractures, fracture dislocations of the proximal humerus require treating surgeons to consider patient age, activity level, injury pattern, and occasionally intra-operative findings to select the ideal treatment strategy for each injury. Proximal humerus fracture dislocations are complex injuries that require special considerations. This review summarizes recent literature regarding the evaluation and management of these injuries as well as the indications and surgical techniques for each treatment strategy. Thorough pre-operative patient evaluation and shared decision-making should be employed in all cases. While nonoperative management is uncommonly considered, open reduction and internal fixation (ORIF), hemiarthroplasty, and reverse total shoulder replacement are at the surgeon's disposal, each with their own indications and complication profile.

Iatrogenic Ulnar Nerve Neuropathy Following Reverse Total Shoulder Arthroplasty: Electrodiagnostic Findings in 18 Patients

Background A reverse total shoulder arthroplasty (RTSA) is often recommended for rotator cuff pathology and may be associated with a myriad of complications, including prosthetic instability, infection, humeral problems, and glenoid loosening. Neurological injuries following an RTSA are infrequent and are usually related to brachial plexus or proximal nerve injury in the affected arm. Iatrogenic ulnar nerve neuropathy is exceedingly rare. Aims This study describes the clinical and electrodiagnostic (EDX) features of 18 patients with ulnar nerve neuropathy complicating RTSA. Materials and methods All patients underwent EDX studies, and 14 had an ultrasound (US) study. Results All patients complained of numbness, tingling, hyperalgesia, and/or allodynia in the distribution of the ulnar nerve. Eight (44%) patients reported hand weakness, and one (6%) noted wasting of the intrinsic hand muscles. Decreased pinprick sensation in the ulnar nerve distribution was detected in all patients. Seventeen (94%) patients had weakness of the ulnar nerve-innervated intrinsic hand muscles. All patients had focal slowing of the motor conduction of the ulnar nerve across the elbow. Sensory potentials were either absent or of a low amplitude over the digital and/or dorsal cutaneous branch of the ulnar nerve in all patients. Twelve (86%) patients showed an increase in the cross-sectional area (CSA) of the ulnar nerve at the elbow; six (43%) had a hypoechoic ulnar nerve. Ulnar nerve neuropathy was confirmed at the elbow in all 18 patients. Of the 14 (78%) patients who underwent surgical intervention for ulnar nerve neuropathy following an RTSA, only four had complete symptom resolution. Conclusions Surgeons should be cognizant of ulnar nerve neuropathy as a potential complication of an RTSA and take precautions to avoid damage to the ulnar nerve intraoperatively. EDX and US studies should be performed to confirm and assess the site and severity of the injury.

A narrative review of non-infected painful total shoulder arthroplasty: evaluation and treatment

Background and Objective

The prevalence of shoulder arthroplasty has increased significantly over the past two decades outpacing both total hip and total knee arthroplasty. Total shoulder arthroplasty (TSA) has been shown to significantly improve function and pain in most patients, however, complications after shoulder arthroplasty have been reported to be greater than 10% in anatomic shoulder arthroplasty and 10-47% in reverse shoulder arthroplasty leading to a painful shoulder. As the number of performed primary shoulder arthroplasty increases, the incidence of painful total shoulders and the need for revision shoulder arthroplasty will see a similar trend. Management of post-operative shoulder arthroplasty pain and complications will be even more essential for the orthopedic surgeon in this growing population. Potential sources of pain after shoulder arthroplasty are variable and include infection, implant related complications, hematoma, nerve injury, rotator cuff failure, instability, fracture, among other less prevalent complications. Treatment options for the painful shoulder arthroplasty differ depending on the source of pain, thus early identification of the cause will lead to expedited and appropriate definitive management. The objectives of this narrative review are to highlight the common causes of pain after TSA, provide surgeons an algorithmic approach for working up the painful total shoulder, and discuss treatment options for each source of pain.

Methods

A database search of PubMed and Google Scholar was conducted including studies relating to painful shoulder arthroplasty evaluation, management, and treatment.

Key Content and Findings

This review presents an in-depth evaluation to the non-infected, painful shoulder arthroplasty, providing treatment options for each source with the goal of assisting practicing physicians in the management of painful post-operative shoulder arthroplasty.

Conclusions

With increasing numbers of TSA being performed, a thorough understanding of the potential complications and their treatments is essential. A systematic approach to working up the painful TSA can help identify the source of symptoms more readily. Knowledge of the common complications and their specific causes can help surgeons avoid the painful TSA. This knowledge will also help to successfully treat the painful TSA when it is inevitably encountered.

Reverse shoulder replacement versus hemiarthroplasty for proximal humeral fracture in elderly patients: a systematic review

This systematic review of the literature aims to analyse current knowledge to inform choice between hemiarthroplasty (HA) and reverse total shoulder arthroplasty (rTSA) for managing proximal humerus fractures (PHF) in elderly patients; the aim is to understand if rTSA can be considered the gold standard for treating PHF in the elderly when surgical fixation or conservative treatment is not viable options. Studies reporting outcomes and complications of PHF treated with shoulder arthroplasty in the elderly were included. Studies were in English and published after 2008. Evidence levels I, II, III and IV were included. According to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a comprehensive literature search was conducted using Medline, CINAHL (Cumulative Index to Nursing and Allied Health Literature) and PubMed search engines, as well as the Cochrane Central Register of Controlled Trials. General data collected were study design, number of patients treated with HA and rTSA, age of patients (mean, mean and SD, mean and range), length of follow-up, type of implant, and clinical outcomes. rTSA can be regarded as the gold standard for surgical management of displaced 3 and 4-part fractures in the elderly. However, the literature offers mostly low-quality studies, thereby requiring further work to achieve a full understanding of this important topic.

Bone density and its relation to the development of acromial stress fracture following reverse total shoulder arthroplasty

BACKGROUND

Postoperative acromial stress fracture is a troublesome postoperative complication after reverse shoulder arthroplasty. Our study aims to utilize routinely performed preoperative computed tomography scans to identify differences in the material properties of the acromion in patients who did and did not develop a postoperative acromial stress fracture.

METHODS

Treatment records and computed tomography scans for 99 reverse shoulder arthroplasties were collected. Scans were calibrated using a phantom and transferred for post-processing where the acromion, full scapula, and humeral head were isolated. The final segmented model was used to assess acromial volume and volumetric bone mineral density for each region of interest.

RESULTS

There was no association between age and volumetric bone mineral density in any region of interest (all R ² ≤ 0.048, all p > 0.082). Patients who developed an acromial stress fracture were not significantly different from those who did not in terms of age, acromial volume, or acromial volumetric bone mineral density (all p > 0.559). Patients with known osteoporosis or osteopenia had slightly lower volumetric bone mineral density, but the differences were not significant (all p ≥ 0.072).

CONCLUSION

Postoperative acromial fractures following reverse shoulder arthroplasty cannot be predicted by computed tomography-derived volumetric bone mineral density or volume. These mechanical characteristics also do not predictably decrease with age or osteoporosis diagnosis.

Factors Influencing Acromial and Scapular Spine Strain after Reverse Total Shoulder Arthroplasty: A Systematic Review of Biomechanical Studies

BACKGROUND

Acromial and scapular spine fractures after reverse total shoulder arthroplasty (RTSA) can be devastating complications leading to substantial functional impairments. The purpose of this study was to review factors associated with increased acromial and scapular spine strain after RTSA from a biomechanical standpoint.

METHODS

A systematic review of the literature was conducted based on PRISMA guidelines. PubMed, Embase, OVID Medline, and CENTRAL databases were searched and strict inclusion and exclusion criteria were applied. Each article was assessed using the modified Downs and Black checklist to appraise the quality of included studies. Study selection, extraction of data, and assessment of methodological quality were carried out independently by two of the authors. Only biomechanical studies were considered.

RESULTS

Six biomechanical studies evaluated factors associated with increased acromial and scapular spine strain and stress. Significant increases in acromial and scapular spine strain were found with increasing lateralization of the glenosphere in four of the included studies. In two studies, glenosphere inferiorization consistently reduced acromial strain. The results concerning humeral lateralization were variable between four studies. Humeral component neck-shaft angle had no significant effect on acromial strain as analysed in one study. One study showed that scapular spine strain was significantly increased with a more posteriorly oriented acromion (55° vs. 43°; p < 0.001). Another study showed that the transection of the coracoacromial ligament increased scapular spine strain in all abduction angles (p < 0.05).

CONCLUSIONS

Glenoid lateralization was consistently associated with increased acromial and scapular spine strain, whereas inferiorization of the glenosphere reduced strain in the biomechanical studies analysed in this systematic review. Humeral-sided lateralization may increase or decrease acromial or scapular spine strain. Independent of different design parameters, the transection of the coracoacromial ligament resulted in significantly increased strains and scapular spine strains were also increased when the acromion was more posteriorly oriented. The results found in this systematic review of biomechanical in-silico and in-vitro studies may help in the surgical planning of RTSA to mitigate complications associated with acromion and scapular spine fracture.

Outcome and complications following revision shoulder arthroplasty : a systematic review and meta-analysis

AIMS

It is important to understand the rate of complications associated with the increasing burden of revision shoulder arthroplasty. Currently, this has not been well quantified. This review aims to address that deficiency with a focus on complication and reoperation rates, shoulder outcome scores, and comparison of anatomical and reverse prostheses when used in revision surgery.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) systematic review was performed to identify clinical data for patients undergoing revision shoulder arthroplasty. Data were extracted from the literature and pooled for analysis. Complication and reoperation rates were analyzed using a meta-analysis of proportion, and continuous variables underwent comparative subgroup analysis.

RESULTS

A total of 112 studies (5,379 shoulders) were eligible for inclusion, although complete clinical data was not ubiquitous. Indications for revision included component loosening 20% (601/3,041), instability 19% (577/3,041), rotator cuff failure 17% (528/3,041), and infection 16% (490/3,041). Intraoperative complication and postoperative complication and reoperation rates were 8% (230/2,915), 22% (825/3,843), and 13% (584/3,843) respectively. Intraoperative and postoperative complications included iatrogenic humeral fractures (91/230, 40%) and instability (215/825, 26%). Revision to reverse total shoulder arthroplasty (TSA), rather than revision to anatomical TSA from any index prosthesis, resulted in lower complication rates and superior Constant scores, although there was no difference in American Shoulder and Elbow Surgeons scores.

CONCLUSION

Satisfactory improvement in patient-reported outcome measures are reported following revision shoulder arthroplasty; however, revision surgery is associated with high complication rates and better outcomes may be evident following revision to reverse TSA. Cite this article: Bone Jt Open 2021;2(8):618-630.

The effect of load and plane of elevation on acromial stress after reverse shoulder arthroplasty

BACKGROUND

Acromial fractures are a substantial complication following reverse shoulder arthroplasty, reported to affect up to 7% of patients. Previous studies have shown that implant placement affects acromial stress during elevation of the arm in the scaption plane. The purpose of this study was to investigate the results of arm loading and variation in plane of elevation on acromial stresses.

METHODS

Nine elevation angles (0°-120°), in three planes of elevation (abduction (0°), scaption (30°), and forward elevation (60°)), and three hand loads (0, 2.5, 5 kg) were investigated. Finite element models were generated using computed tomography data from 10 cadaveric shoulders (age 68 ± 19 yrs) to determine acromial stress distributions. Models were created for a lateralized glenosphere (0, 5, 10 mm), inferiorized glenosphere (0, 2.5, 5 mm), and humeral offset (-5, 0, 5 mm).

RESULTS

For all planes of elevation (0°, 30°, 60°) and hand loads (0, 2.5, 5 kg) investigated, glenoid lateralization consistently increased acromial stress, glenoid inferiorization consistently decreased acromial stress, and humeral offset proved to be insignificant in altering acromial stress. Abduction resulted in significantly higher peak acromial stresses (p = 0.002) as compared to scaption and forward elevation.

CONCLUSIONS

In addition to implant position and design, patient activity, such as plane of elevation and hand loads, has substantial effects on acromial stresses.

LEVEL OF EVIDENCE

Basic science study.

The role of acromial morphometry in the development of acromial stress fracture following reverse total shoulder arthroplasty

BACKGROUND

Indications for reverse total shoulder arthroplasty are expanding, and postoperative acromial stress fractures are a troubling postoperative complication. The purpose of this study was to determine if differences in acromial morphometry were present between cohorts with and without this complication.

METHODS

A retrospective review of 101 reverse total shoulder arthroplasty procedures met criteria for the study. A total of eight acromial measurements on preoperative computed tomography scans were performed in axial, coronal, and sagittal views. Postoperative acromial stress fractures were confirmed by computed tomography scan on six patients and classified by fracture type. Statistical analysis was performed using a Mann-Whitney U test.

RESULTS

The median acromial thickness at the posterior and lateral half was significantly thinner in the fracture cohort compared to the non-fracture cohort. Fracture and non-fracture cohort measurements demonstrated a median lateral thickness of 6.8 and 8.7 mm (p = 0.010), respectively, and median posterior thickness of 7.6 and 9.5 mm (p = 0.008), respectively. There were no demographic differences between cohorts.

DISCUSSION

Two acromial measurements (lateral and posterior thickness) were associated with the development of postoperative acromial stress fracture following reverse total shoulder arthroplasty. These findings suggest that a thinner acromion in the lateral and posterior half is a risk factor for an acromial stress fracture following reverse total shoulder arthroplasty.

Complications of reverse shoulder arthroplasty: a concise review

Reverse shoulder arthroplasty is an ideal treatment for glenohumeral dysfunction due to cuff tear arthropathy. As the number of patients treated with reverse shoulder arthroplasty is increasing, the incidence of complications after this procedure also is increasing. The rate of complications in reverse shoulder arthroplasty was reported to be 15%-24%. Recently, the following complications have been reported in order of frequency: periprosthetic infection, dislocation, periprosthetic fracture, neurologic injury, scapular notching, acromion or scapular spine fracture, and aseptic loosening of prosthesis. However, the overall complication rate has varied across studies because of different prosthesis used, improvement of implant and surgical skills, and different definitions of complications. Some authors included complications that affect the clinical outcomes of the surgery, while others reported minor complications that do not affect the clinical outcomes such as minor reversible neurologic deficit or minimal scapular notching. This review article summarizes the processes related to diagnosis and treatment of complications after reverse shoulder arthroplasty with the aim of helping clinicians reduce complications and perform appropriate procedures if/when complications occur.

Acromial fracture after reverse total shoulder arthroplasty: a systematic review

BACKGROUND

The reverse total shoulder arthroplasty has become the most common method of arthroplasty of the shoulder. The complication of acromial or scapular stress fracture deserves consideration to describe incidence and determine whether prosthetic design or patient factors act as risk factors.

METHODS

A systematic review of the literature was performed including the EMBASE, Medline and the Cochrane Library in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

The search returned 565 articles. After exclusion, 25 papers remained. In total, 208 fractures were reported in the literature, with an overall incidence of 5% and stress fractures were more common than post-traumatic ones; 24 fractures underwent osteosynthesis and there were nine revision arthroplasty surgeries. Outcomes worsened after fracture - whether treated with surgery or not. In patients with scapular base fractures, there was an improvement in functional outcome scores after surgery. Heterogeneous reporting of the risk factors prior to fractures, treatment methods and outcomes made recommendations weak.

DISCUSSION

Acromial stress fracture after reverse total shoulder arthroplasty occurs relatively commonly but is poorly reported in the literature. It is unclear whether immobilisation, fixation or revision arthroplasty is the best treatment, although fixation may offer a better outcome. In future, reports should aim for greater consistency to allow a better understanding of this condition.

Polyethylene Liner Dissociation after Reverse Shoulder Arthroplasty Dislocation: a Case Series

Reverse shoulder arthroplasty is a common procedure. While dislocation is a common complication, there are few reports documenting dislocation with associated polyethylene liner dissociation from the humeral tray. There have been 4 instances of this occurrence over 9 years at our institution, and there are specific radiographic clues for diagnosis. Recognizing polyethylene liner dissociation on imaging is important prior to treatment. In a "routine" dislocation, closed reduction may be attempted but when the polyethylene is dissociated, open reduction is the only treatment option, as closed reduction can damage the components. Dislocations with polyethylene dissociation may not be initially recognized, prompting a non-operative period leading to wear and metallosis. These 4 cases demonstrate key findings present on imaging to recognize the difference between a dislocation with and without polyethylene liner dissociation, namely the subluxation appearance rather than dislocation.

Clinical implications of scapular notching at 2 and 5-year follow-up after reverse total shoulder arthroplasty

Objective

Scapular notching is a unique radiographic sequela of reverse total shoulder arthroplasty (rTSA) with unclear long-term clinical consequences.

Methods

Our retrospective review of a single surgeon, single implant, primary rTSA database investigates the incidence of scapular notching at 2 and 5-year follow-up. Various patient outcome scores were also obtained.

Results

Of 158 primary rTSAs performed, 82 (52%) patients completed 2-year and subsequent 5-year follow-up. The incidence of scapular notching at 2 and 5-years was 11.9% and 19.5%, respectively.

Conclusion

Scapular notching negatively affects validated post-operative outcome scores, active range of motion and total complications, and furthermore increases with time.

Management of Painful Shoulder Arthroplasty: A Narrative Review

Despite the recent advances in surgical techniques, the percentage of painful shoulder arthroplasties is still high (more than 10%). The causes of residual pain after shoulder arthroplasty, and the resulting treatment solutions, are many and different. The most common complications of shoulder prosthesis are infections, aseptic loosening, modular components disassembling, metal hypersensitivity, and instability. There are also implant-related complications such as glenoid wear in hemiarthroplasty, rotator cuff tear in anatomical total shoulder arthroplasty, scapular notching, and acromion fracture in reverse shoulder arthroplasty. Several of these complications can be avoided with a careful selection of the implants, a proper surgical technique and a precise implant positioning. The execution of a more accurate preoperative planning and the possible use of patient-specific implants are expected to translate into better clinical results in the future. We provide the reader with recent evidence on the causes and therapeutic options of this condition.

Neurologic deficit after reverse total shoulder arthroplasty: correlation with distalization

BACKGROUND

Neurologic problems after reverse total shoulder arthroplasty (RTSA) have been reported, but there are a lack of studies regarding which nerve(s) are damaged and the outcomes for the patients who had neurologic complications after RTSA. The purpose of this study was to assess the prevalence and outcomes of neurologic deficit after RTSA and to evaluate the correlation between nonanatomic rearrangement of the shoulder joint and neurologic complications after RTSA. We hypothesized that the neurologic deficit was associated with excessive distalization or lateralization of the humerus after RTSA.

METHODS

RTSA was performed on 182 consecutive shoulders with cuff tear arthropathy. Comparative analysis was performed on 34 shoulders with (group 1) and 148 shoulders without (group 2) neurologic deficit.

RESULTS

The mean follow-up period in the study was 58.5 months (range: 24-124). The mean age was 71.5 ± 7.7 years in group 1 and 73.1 ± 7.2 years in group 2. Neurologic deficit after RTSA was found in 34 shoulders (19%). The mean postoperative acromiohumeral distance was 34.1 ± 11.0 mm in group 1 and 29.4 ± 7.6 mm in group 2 (P = .015). Significant differences in terms of postoperative distalization of the humerus were seen between group 1 (24.5 ± 9.4 mm) and group 2 (20.5 ± 8.3 mm) (P = .009). The most common forms of neurologic deficit after RTSA were axillary nerve (41.2%) and radial nerve (15%) injuries. Thirty shoulders (88%) had neuropraxia, and 4 shoulders (12%) had axonotmesis. By conservative treatment, all patients with neurologic complications achieved complete recovery without any additional surgery; the mean recovery period was 7.4 months (range: 2-38 months).

CONCLUSION

Neurologic deficit occurred in 19% of patients who underwent RTSA, and it was significantly correlated with humeral distalization after surgery. Axillary nerve was mostly involved, and all patients with neurologic deficit achieved complete recovery without any additional surgery.

Is subscapularis repair associated with better outcome compared to non-repair in reverse total shoulder arthroplasty? A systematic review of comparative trials

We aimed to investigate whether combined reverse total shoulder arthroplasty (RTSA) and subscapularis repair leads to improved clinical and functional outcome in comparison with RTSA alone. Two reviewers independently conducted a systematic search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) using the MEDLINE/PubMed database and the Cochrane Database of Systematic Reviews. These databases were queried with the terms "reverse" AND "shoulder" AND "arthroplasty" AND "with" AND "subscapularis" AND "repair". From the 72 initial studies, we finally chose five studies which were eligible to our inclusion-exclusion criteria. The total mean modified Coleman methodology test was 55/100 (range: 47/100 to 60/100). The eligible studies included 1087 patients, in total. Regarding the subjective functional scores as well as range of motion (ROM), the differences amongst groups were insignificant in almost all studies. The mean complications' rate of the repair group was 10.4%, whereas the respective rate of the nonrepair group was 10.2%. All studies concluded that the repair of subscapularis did not affect the complications' rate of patients who were treated with RTSA. The mean dislocations' rates of the repair and the nonrepair group were 1.5% and 2.3%, respectively. Although subscapularis repair was proven safe and effective for the augmentation of RTSA, it did not offer any additional clinical or functional benefit in the outcome of patients treated with lateralized RTSA. Therefore, it is not supported its routine use for patients who have a preoperatively sufficient subscapularis tendon.

Reverse shoulder arthroplasty has a higher risk of revision due to infection than anatomical shoulder arthroplasty

Aims

The aim of this study was to use national registry database information to estimate cumulative rates and relative risk of revision due to infection after reverse shoulder arthroplasty.

Patients and Methods

We included 17 730 primary shoulder arthroplasties recorded between 2004 and 2013 in The Nordic Arthroplasty Register Association (NARA) data set. With the Kaplan–Meier method, we illustrated the ten-year cumulative rates of revision due to infection and with the Cox regression model, we reported the hazard ratios as a measure of the relative risk of revision due to infection.

Results

In all, 188 revisions were reported due to infection during a mean follow-up of three years and nine months. The ten-year cumulative rate of revision due to infection was 1.4% overall, but 3.1% for reverse shoulder arthroplasties and 8.0% for reverse shoulder arthroplasties in men. Reverse shoulder arthroplasties were associated with an increased risk of revision due to infection also when adjusted for sex, age, primary diagnosis, and year of surgery (relative risk 2.41 (95% confidence interval 1.26 to 5.59); p = 0.001).

Conclusion

The overall incidence of revision due to infection was low. The increased risk in reverse shoulder arthroplasty must be borne in mind, especially when offering it to men. Cite this article: Bone Joint J 2019;101-B:702–707.

The Influence of Different Rotator Cuff Deficiencies on Shoulder Stability Following Reverse Shoulder Arthroplasty

BACKGROUND

The primary indication for reverse shoulder arthroplasty (RSA) is rotator cuff arthropathy caused by a deficient rotator cuff. Cuff deficiency in patients is highly variable in its distribution and extent, with mechanical implications that may significantly affect post-operative recovery. This study investigated the effects of variable cuff deficiency on the propensity for impingement between the scapula and humeral component and resulting subluxation, the source of two common complications (scapular notching and instability).

METHODS

Five different finite element models of an RSA were analyzed with varying degrees of rotator cuff deficiency: (1) baseline, with intact subscapularis, infraspinatus and teres minor, (2) no subscapularis, (3) no subscapularis or infraspinatus, (4) no infraspinatus, and (5) no infraspinatus or teres minor. The supraspinatus was not included in any models, as it is absent in rotator cuff arthropathy. Each model was moved through a prescribed arc of 45° internal/ external rotation originating from neutral.

RESULTS

Greater rotator cuff deficiency was associated with more impingement and larger magnitudes of subluxation. The largest subluxation (7.5 mm) and highest impingement-related contact stress (479 MPa) was in the model lacking all rotator cuff muscle groups. Posterior subluxation was present in most models lacking the infraspinatus, while anterior subluxation was present in all models lacking the subscapularis.

CONCLUSIONS

This study helps clarify how different rotator cuff deficiencies influence shoulder stability following RSA and can ultimately help predict which patients may be at greater risk for impingement-related scapular notching and subluxation.

CLINICAL RELEVANCE

Surgeons should carefully consider the nature of the rotator cuff deficiency and its influence on impingement and instability when planning for RSA.Level of Evidence: V.

Analysis of impingement-free range of motion of the glenohumeral joint after reverse total shoulder arthroplasty using three different implant models

BACKGROUND

This study aimed to investigate impingement-free range of motion (ROM) of the glenohumeral joint following reverse total shoulder arthroplasty (RTSA) with three types of implant models using computational motion analysis.

METHODS

Three-dimensional (3D) scapulohumeral models were created from preoperative computed tomography (CT) images of seven patients by using visualization and computer-aided design software. Three types of implant designs, namely, typical medialization, in between, and lateralization implants, were used for the reconstruction of 3D model; each design was designated as group I, II, and III, respectively. All possible combinations of virtual surgeries were evaluated for impingement-free ROM in all three groups. Maximal ROMs were compared. The effect of implant positions on ROM of the shoulder joints were investigated in each group.

RESULTS

The all lateralization group (group III) showed significantly greatest maximal adduction, abduction and external rotation (ER). Adduction and abduction were significantly increased by the glenoid component inferior translation in all three groups. (In group I, p < 0.001 for adduction, p = 0.002 for abduction, respectively; in group II, p = 0.025, p < 0.001, respectively; in group III, p = 0.038, p = 0.011, respectively). Increasing humerus retroversion might have some effect on increasing abduction. In group II and III, internal rotation (IR) and ER were significantly affected by the humerus retroversion (in group II, p = 0.033 for IR, p = 0.007 for ER, respectively; in group III, p = 0.004, p < 0.001, respectively). In group III, ER was also significantly affected by the glenoid component inferior translation (p = 0.003).

CONCLUSIONS

Lateralization design model showed greatest ROM of the shoulder joint. The effects of implant positions on impingement-free ROM exhibited different tendencies between medialization and lateralization implant models. Humerus retroversion affected both IR and ER, especially in lateralization design. Increasing glenoid inferior translation increases both adduction and abduction regardless of implant designs.

Outcomes of an anatomic total shoulder arthroplasty with a contralateral reverse total shoulder arthroplasty

BACKGROUND

It is common for patients to require staged bilateral shoulder arthroplasties. There is a unique cohort of patients who require an anatomic total shoulder arthroplasty (TSA) and a contralateral reverse shoulder arthroplasty (RSA). This study compared the outcomes of patients with a TSA in 1 shoulder and an RSA in the contralateral shoulder.

METHODS

Our institutional database was queried to identify all patients with a TSA and a contralateral RSA. Data collection included patient demographics, preoperative and latest follow-up shoulder range of motion, radiographic analysis, and postoperative complications. Identified patients were assessed at follow-up visits or contacted by phone for functional outcome scores.

RESULTS

Nineteen patients met our inclusion/exclusion criteria. There was statistically significant greater internal rotation in the TSA shoulder (P= .044) but no significant difference in forward elevation (P = .573) or external rotation (P= .368). There was no radiographic evidence of humeral or glenoid component loosening of any arthroplasty implants. There were no significant differences between TSA and RSA shoulders for the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment (P= .381), Simple Shoulder Test (P = .352), Single Assessment Numerical Evaluation (P = .709), and visual analog scale satisfaction (P= .448) or pain scores (P= .305). Thirteen patients (68.4%) preferred the RSA side, 1 patient (5.3%; z = 4.04, P < .001) patient preferred the TSA side, and 5 patients expressed no preference.

CONCLUSION

Despite known limitations and differences between TSA and RSA designs, patients who have received both implants are highly satisfied with both. The only parameter in which the TSA had superior outcomes was internal rotation.

Scapula fracture incidence in reverse total shoulder arthroplasty using screws above or below metaglene central cage: clinical and biomechanical outcomes

BACKGROUND

Reverse total shoulder arthroplasty (RTSA) is a viable treatment option for rotator cuff tear arthropathy but carries a complication risk of scapular fracture. We hypothesized that using screws above the central glenoid axis for metaglene fixation creates a stress riser contributing to increased scapula fracture incidence. Clinical type III scapular fracture incidence was determined with screw placement correlation: superior screw vs. screws placed exclusively below the glenoid midpoint. Cadaveric RTSA biomechanical modeling was employed to analyze scapular fractures.

METHODS

We reviewed 318 single-surgeon single-implant RTSAs with screw correlation to identify type III scapular fractures. Seventeen cadaveric scapula specimens were matched for bone mineral density, metaglenes implanted, and fixation with 2 screw configurations: inferior screws alone (group 1_INF) vs. inferior screws with one additional superior screw (group 2_SUP). Biomechanical load to failure was analyzed.

RESULTS

Of 206 patients, 9 (4.4%) from the superior screw group experienced scapula fractures (type III); 0 fractures (0/112; 0%) were identified in the inferior screw group. Biomechanically, superior screw constructs (group 2_SUP) demonstrated significantly (P < .05) lower load to failure (1077 N vs. 1970 N) compared with constructs with no superior screws (group 1_INF). There was no significant age or bone mineral density discrepancy.

CONCLUSION

Clinical scapular fracture incidence significantly decreased (P < .05) for patients with no screws placed above the central cage compared with patients with superior metaglene screws. Biomechanical modeling demonstrates significant construct compromise when screws are used above the central cage, fracturing at nearly half the ultimate load of the inferior screw constructs. We recommend use of inferior screws, all positioned below the central glenoid axis, unless necessary to stabilize the metaglene construct.

Implant positioning in reverse shoulder arthroplasty has an impact on acromial stresses

BACKGROUND

Acromial fractures after reverse shoulder arthroplasty (RSA) have been reported to occur in up to 7% of patients. Whereas RSA implant parameters can be configured to alter stability, range of motion, and deltoid mechanical advantage, little is known about the effect of these changes on acromial stresses. The purpose of this finite element study, therefore, was to evaluate the effect of RSA humeral and glenoid implant position on acromial stresses.

METHODS

Solid body models of 10 RSA reconstructed cadaveric shoulders (38-mm glenosphere, 155° neck-shaft angle) were input into custom software that calculated the deltoid force required to achieve an abduction arc of motion (0°-120°). The resulting forces were applied to a finite element study model of the scapula to ascertain the acromial stress distribution. This process was repeated for varying glenoid inferiorizations (0, +2.5, +5.0 mm), lateralizations (0, +5.0, +10.0 mm), and humeral lateralizations (-5.0, 0, +5.0 mm).

RESULTS

Glenosphere inferiorization decreased maximum principal stress in the acromion by 2.6% (0.7 ± 0.2 MPa; P = .007). Glenosphere lateralization produced a greater effect, increasing stress by 17.2% (4.1 ± 0.9 MPa; P = .001). Humeral lateralization caused an insignificant increase in stress by 1.7% (0.5 ± 0.2 MPa; P = .066), and humeral medialization decreased stress by 1.4% (0.8 ± 0.3 MPa; P = .038). The highest acromial stresses occurred in the region where fractures most commonly occur, Levy type II, at 33.7 ± 3.81 MPa (P < .001).

CONCLUSIONS

Glenosphere positioning has a significant effect on acromial stress after RSA. Inferior and medial positioning of the glenosphere serves to decrease acromial stress, thought to be primarily due to increased deltoid mechanical advantage. The greatest effect magnitudes are seen at lower abduction angles, where the humerus is more frequently positioned.

Indications and outcomes of shoulder arthroscopy after shoulder arthroplasty

BACKGROUND

Arthroscopy is a widely used intervention in the treatment of a variety of shoulder conditions. Arthroscopy has also been selectively used in symptomatic patients after shoulder arthroplasty. The purpose of this systematic review was to determine indications for shoulder arthroscopy in patients after shoulder arthroplasty and to report patient outcomes after these procedures.

MATERIALS AND METHODS

The electronic databases MEDLINE, EMBASE, and PubMed were searched and screened in duplicate for studies involving shoulder arthroscopy in shoulder arthroplasty patients. A full-text review of eligible studies was conducted in duplicate, and references were searched using predetermined inclusion and exclusion criteria.

RESULTS

The review included 11 studies containing 84 patients. All were Level IV evidence. The most common indications for shoulder arthroscopy in the setting of shoulder arthroplasty were pain or loss of range of motion without a clear diagnosis, suspected periprosthetic infection, and rotator cuff assessment. Although 92% of patients were satisfied with the procedure and standardized shoulder scores increased in all studies that reported them, 44% of patients still went on to additional revision surgery after arthroscopy.

CONCLUSIONS

Shoulder arthroscopy in patients after arthroplasty is most frequently used as a diagnostic tool; however, it has utility in treating a number of predetermined pathologies. Despite the low sample size and quality of evidence in our review, patient satisfaction after arthroscopy is high because standardized outcome scores improve, and the risk of complications is low. However, a high percentage of patients who receive arthroscopy later require further surgery.

Safety and efficacy of arthroscopy in the setting of shoulder arthroplasty

Shoulder arthroplasty has become a reliable and reproducible method of treating a range of shoulder pathologies including fractures, osteoarthritis, and rotator cuff arthropathy. Although most patients experience favorable outcomes from shoulder arthroplasty, some patients suffer from persistent symptoms post-arthroplasty and it is these patients who present a unique diagnostic and therapeutic challenge. The role of arthroscopy in assessing and treating patients with symptomatic prosthetic joints elsewhere in the body has been established in recent literature. However, the range of pathology that can affect a prosthetic shoulder is distinct from the knee or the hip and requires careful and considered assessment if an accurate diagnosis is to be made. When used alongside other investigations in a comprehensive assessment protocol, arthroscopy can play an important role in the diagnosis and treatment of the problematic shoulder arthroplasty.