A Critical Review on Prosthetic Features Available for Reversed Total Shoulder Arthroplasty

Reverse Shoulder Arthroplasty for Proximal Humeral Fractures: Is the Bigliani-Flatow Stem Suitable for Tuberosity Fixation and Healing?

Background/Objectives: The aim of the study was to investigate the clinical, functional, and radiographic results of patients affected by three- or four-part proximal humeral fractures treated with reverse total shoulder arthroplasty, to investigate whether a prosthetic stem nonspecifically designed for fractures (i.e., the Bigliani-Flatow stem) promotes tuberosities' healing, and to evaluate the impact of tuberosity fixation and healing on the outcomes. Methods: Patients' data such as gender, age, side and dominancy, comorbidities, complications during or after surgery, and time lapse between trauma and surgery were prospectively collected. The type of fixation of the stem, the thickness and type of liner, and whether the tuberosities were fixed or not were also recorded. The Constant score weighted on the contralateral limb, QuickDASH, Oxford Shoulder Score, and Subjective Shoulder Value were collected. Tuberosities' healing was assessed with X-rays (anteroposterior, Grashey, and axillary views). Results: Overall, 34 patients were included, with an average follow-up of 42 months. Tuberosities were reinserted in 24 cases and their healing rate was 83%. The mean values were the following: a Constant score of 64, Oxford Shoulder Score of 39, Subjective Shoulder Value of 71, and QuickDASH score of 27. There were no significant differences in the scores or range of motion between patients with tuberosities healed, reabsorbed, or not reattached. There was a better external rotation in the group with healed tuberosities and a longer duration of surgery to reattach tuberosities. Conclusions: The treatment of proximal humerus fractures with the Bigliani-Flatow stem is associated with good clinical and functional results. The healing rate of the tuberosities was high and comparable, if not even better, than the mean rates reported for the stems dedicated to fractures of the proximal humerus and was, therefore, also appropriate for this indication.

Modification of Humeral Component Results in Increased Impingement Free Range of Motion in a Reverse Shoulder Arthroplasty Model

Introduction

Shoulder arthroplasties have been demonstrated to provide reliable pain relief as well as functional benefits. The advent of the reverse shoulder arthroplasty allowed for expanded indications for shoulder replacement. Several studies comparing the outcomes of anatomic and reverse total shoulder arthroplasties have demonstrated decreased range of motion in the reverse arthroplasty cohort, especially in internal rotation. The authors hypothesized that slight modifications to the humeral component of a reverse shoulder arthroplasty could result in increased impingement free range of motion without significant sacrifices to stability.

Methods

A reverse shoulder arthroplasty model was fashioned to mimic a setting of anterior mechanical impingement after replacement. Sequential resections were taken from the anterior aspect of the polyethylene up to a resection of 10 mm. A solid modeling software was utilized to compare the experimental group to the control group with regard to impingement free motion. Finite element analysis was subsequently utilized to assess stability of the construct in comparison to the nonmodified polyethylene.

Results

Impingement free internal rotation increased minimally at 3 mm of resection but considerably at each further increase in resection. A resection of 10 mm resulted roughly 30% improvement in impingement free internal rotation. Instability in this model increased with modifications beyond 7 mm.

Conclusion

Slight alterations to the geometry of the humeral tray and polyethene components can result in improvements in impingement-free internal rotation without substantial increased instability in this model. Further work is needed to determine in vivo implications of modifications to the humeral tray and polyethylene.

Functional outcome and CEUS-assessed deltoid muscle vitality after fracture-specific versus standard prosthetic design in reverse shoulder arthroplasty for trauma

Functional outcome after reverse-shoulder-arthroplasty (RSA) in proximal humerus fractures (PHF) depends on deltoid muscle integrity and successful reattachment of the tuberosities for best possible recovery of rotator-cuff function. In this monocentric, prospective, randomized, controlled trial we investigated whether a reverse-fracture-prosthesis (RFP) with a metaphyseal fenestrated stem achieved superior shoulder and muscle function compared to a common reverse-prosthesis (RP) design for patients with PHF. Our hypothesis was that patients with RFP may achieve a superior healing rate of the greater tuberosity (GT) compared to patients receiving RP, which translates to significantly higher clinical outcome and functional scores as well as differences in deltoid muscle microperfusion. Forty-four patients with PHF were randomized preoperatively to one of the prosthesis types in RSA between 2018 and 2020 (22 with RFP and 22 with RP) and prospectively assessed 6 months after surgery. We assessed osteointegration of the GT with radiographs 1 day and 6 months postoperatively and examined shoulder function and patient satisfaction by using established shoulder scores. A contrast-enhanced ultrasound (CEUS) examination of both shoulders was performed to quantify intramuscular blood flow and evaluate vitality of the deltoid muscle. None of the functional and psychosocial scores or radiographs and ultrasound examinations showed significant differences between the RSA designs. The constant-Murley score (p = 0.384) and active anterior-elevation-abduction, and external rotation were comparable between the RFP and RP group. Similar healing rates of the GT were observed (p = 0.655). CEUS-assessed deltoid microperfusion revealed equivalent muscle vitality for both groups (p = 0.312). Level of evidence: Level II; Randomized Controlled Trial; Treatment Study. Clinical significance: The radiographic evaluation for the investigation of the GT healing rate indicates that the proclaimed benefits of the fracture prosthesis with fenestration design might not be as great as expected.

Influence of neck shaft angle of humerus in prosthesis design

Background

A better understanding of the proximal humerus is essential for anatomical reconstruction of the glenohumeral joint during prosthetic replacement. The neck-shaft angle is critical for correct calcar screw positioning when fixing a proximal humeral fracture with a locking plate. It's essential for exact implant placement and treatment of any soft-tissue or bone pathology. Improper implants cause discomfort and post-operative complications, therefore understanding the humeral neck shaft angle is fundamental in the design and manufacturing of prostheses. This study looked into the necessity regional data of the humeral neck shaft angle (NSA) and its importance in shoulder prosthesis manufacturing.

Method

This cross-sectional investigation was conducted on 300 dry cadaveric humeri of unknown gender and age that were free of damage or deformity. The Goniometer was used to measure the neck shaft angle. The data was analysed using SPSS software. The standard deviation and mean were calculated. The statistical difference between the right and left humeri was assessed using the students' t' test.

Observations

The NSA of the humerus was 131.265.82° on average. The NSA mean values were substantially higher on the right side. A statistically significant difference between the right and left humeri was revealed by a P value of 0.001.

Conclusion

Success of the shoulder arthroplasty demands anatomical reconstruction of the normal neck-shaft angle of the humerus. Racial variations in the morphometry of the neck-shaft angle needs to be considered in prosthesis design.

Treatment of proximal humerus fractures using reverse shoulder arthroplasty: do the inclination of the humeral component and the lateral offset of the glenosphere influence the clinical outcome and tuberosity healing?

INTRODUCTION

The employment of reverse shoulder arthroplasty for dislocated proximal humerus fractures of elderly patients becomes increasingly relevant. The standard inclination angle of the humeral component was 155°. Lately, there is a trend towards smaller inclination angles of 145° or 135°. Additionally, there has been an increased focus on the lateralization of the glenosphere. This retrospective comparative study evaluates clinical and radiological results of patients treated for proximal humerus fractures by reverse shoulder arthroplasty with different inclination angles of the humeral component, which was either 135° or 155°. Additionally, a different lateral offset of the glenosphere, which was either 0 mm or 4 mm, was used.

METHODS

For this retrospective comparative analysis, 58 out of 66 patients treated by reverse total shoulder arthroplasty for proximal humerus fractures were included. The minimum follow-up was 24 months. Thirty (m = 3, f = 27; mean age 78 years; mean FU 35 months, range 24-58 months) were treated with a standard 155° humeral component and a glenosphere without lateral offset (group A), while 28 patients (m = 2, f = 26; mean age 79 years; mean FU 30 months, range 24-46 months) were treated with a 135° humeral component and a glenosphere with a 4 mm lateral offset (group B). We determined range of motion, Constant score, and the American Shoulder and Elbow Surgeons Shoulder score as clinical outcomes and evaluated tuberosity healing as well as scapula notching.

RESULTS

Neither forward flexion (A = 128°, B = 121°; p = 0.710) nor abduction (A = 111°, B = 106°; p = 0.327) revealed differences between the groups. The mean Constant Score rated 63 in group A, while it was 61 in group B (p = 0.350). There were no differences of the ASES Score between the groups (A = 74, B = 72; p = 0.270). There was an increased risk for scapula notching in group A (47%) in comparison to group B (4%, p = 0.001). Healing of the greater tuberosity was achieved in 57% of group A and in 75% of group B (p = 0.142). The healing rate of the lesser tuberosity measured 33% in group A and 71% in group B (p = 0.004).

CONCLUSIONS

Both inclination angles of the humeral component are feasible options for the treatment of proximal humerus fractures in elderly patients. Neither the inclination angle nor the lateral offset of the glenosphere seem to have a relevant influence on the clinical outcome. The healing rate of the lesser tuberosity was higher in implants with a decreased neck-shaft angle. There is an increased risk for scapula notching, if a higher inclination angle of the humeral component is chosen.

LEVEL OF EVIDENCE

III. Retrospective comparative study.

Comparative study of 145° onlay curved stem versus 155° inlay straight stem reverse shoulder arthroplasty: clinical and radiographic results with a minimum 2-year follow-up

BACKGROUND

Lateralized onlay reverse shoulder arthroplasty (RSA) is designed to ensure better clinical functional recovery and lower rate of complications compared with Grammont medialized inlay RSA. The purpose of the present study was to compare the clinical and radiographic outcomes between these 2 different designs.

METHODS

Eighty-five consecutive patients who underwent RSA were retrospectively analyzed. Nine patients were lost to follow-up, 34 received a curved onlay with a 145° neck-shaft angle (Ascend Flex group), and 42 received a long straight inlay stem with a 155° neck-shaft angle (Delta Xtend group). Patients were reviewed at an average follow-up of 46.8 ± 13.2 months (Ascend Flex group) and 36 ± 10.8 months (Delta Xtend group). Clinical outcome measures included active range of motion, strength, visual analog scale, Constant-Murley score, and the American Shoulder and Elbow Surgeons score. Radiographic evaluation at the final follow-up was performed to assess scapular notching, stress shielding, acromial or scapular fractures, heterotopic ossification, and radiolucent lines or implant loosening.

RESULTS

No differences emerged between the 2 groups in terms of visual analog scale, American Shoulder and Elbow Surgeons and Constant-Murley scores, pain, function, strength, mobility, active forward elevation, active internal rotation, active external rotation at 0° and 90° of abduction, abduction, forward elevation, and external rotation strength (P = n.s.). Statistically superior active abduction was observed in the Delta Xtend group (P = .0017). Scapular notching was observed in 12 shoulders (35.2%) in the Ascend Flex group (a grade 1) and in 10 shoulders (23.8%) in the Delta Xtend group (P = n.s.). No differences emerged between the 2 groups in terms of humeral or glenoid radiolucency (P = n.s.). Higher rate of humeral stress shielding rate was observed in the Ascend flex cohort (P = n.s.).

CONCLUSIONS

No statistically significant difference emerged between the 145° onlay curved stem vs. the 155° inlay straight stem according to most of the evaluated parameters. Statistically superior active abduction was observed in the 155° group although it did not affect patients' satisfaction.

Reverse Total Shoulder Arthroplasty for Treatment of Massive, Irreparable Rotator Cuff Tear

Massive tears of the rotator cuff can result in severe functional deficits due to loss of the axial force couple and effective fulcrum that the intact cuff normally provides. For massive, irreparable rotator cuff tears, especially in the setting of early to moderate degenerative changes, reverse total shoulder arthroplasty functions to modify the center of joint rotation, allowing the deltoid and intact components of the cuff to carry out shoulder function more effectively. Our preferred technique uses a standard open deltopectoral shoulder approach with a 3-dimensional glenoid baseplate model and a 135° prosthesis in an onlay configuration to reduce the risk of scapular notching and increase lateralization of the humerus.

The Evolution of Reverse Total Shoulder Arthroplasty-From the First Steps to Novel Implant Designs and Surgical Techniques

Purpose of Review: The purpose of this review is to summarize recent literature regarding the latest design modifications and biomechanical evolutions of reverse total shoulder arthroplasty and their impact on postoperative outcomes. Recent findings: Over the past decade, worldwide implantation rates of reverse total shoulder arthroplasty have drastically increased for various shoulder pathologies. While Paul Grammont’s design principles first published in 1985 for reverse total shoulder arthroplasty remained unchanged, several adjustments were made to address postoperative clinical and biomechanical challenges such as implant glenoid loosening, scapular notching, or limited range of motion in order to maximize functional outcomes and increase the longevity of reverse total shoulder arthroplasty. However, the adequate and stable fixation of prosthetic components can be challenging, especially in massive osteoarthritis with concomitant bone loss. To overcome such issues, surgical navigation and patient-specific instruments may be a viable tool to improve accurate prosthetic component positioning. Nevertheless, larger clinical series on the accuracy and possible complications of this novel technique are still missing.

Clinical and radiographic outcomes of reverse shoulder arthroplasty using a hybrid baseplate fixation mechanism

Background

Despite the success of reverse shoulder arthroplasty (RSA), complication rates remain high (13% to 25%), due to instability, infection, and glenoid component loosening, which can lead to revision. The aim of the present study was to report the early clinical outcomes of RSA using a new hybrid baseplate design, in comparison with the literature on other common RSA baseplates.

Methods

The authors retrospectively analyzed the records of 142 patients (142 shoulders) who underwent primary RSA using a hybrid baseplate design by the senior surgeons between May 2014 and December 2018. Preoperative and postoperative assessments included the Constant score (CS) and range of motion, including active forward elevation, external rotation, and internal rotation.

Results

Of the initial cohort of 142 patients, 13 were lost to follow-up (8.6%), 2 died (1.3%), and 8 required reoperations with implant removal (5.3%). The remaining 119 patients comprised 71 women (60%) and 48 men (40%), aged 73.6 ± 7.3 years at index surgery, 43 of whom required bony increased offset (36%). At a minimum follow-up of 2 years, the CS improved by 37.3 ± 16.1, active forward elevation increased by 51.2° ± 38.1°, external rotation increased by 16.4° ± 25.0°, and internal rotation increased by 1.5 ± 3.2.

Conclusion

At a minimum follow-up of 2 years after RSA using a new hybrid baseplate system, the CS and range of motion were satisfactory and comparable to those in recent systematic reviews. The findings of this study suggest that this hybrid baseplate system provides satisfactory outcomes in the short term, although longer follow-up studies are needed to validate its long-term efficacy.

Biomechanics of anatomic and reverse shoulder arthroplasty

The biomechanics of the shoulder relies on careful balancing between stability and mobility. A thorough understanding of normal and degenerative shoulder anatomy is necessary, as the goal of anatomic total shoulder arthroplasty is to reproduce premorbid shoulder kinematics.With reported joint reaction forces up to 2.4 times bodyweight, failure to restore anatomy and therefore provide a stable fulcrum will result in early implant failure secondary to glenoid loosening.The high variability of proximal humeral anatomy can be addressed with modular stems or stemless humeral components. The development of three-dimensional planning has led to a better understanding of the complex nature of glenoid bone deformity in eccentric osteoarthritis.The treatment of cuff tear arthropathy patients was revolutionized by the arrival of Grammont's reverse shoulder arthroplasty. The initial design medialized the centre of rotation and distalized the humerus, allowing up to a 42% increase in the deltoid moment arm.More modern reverse designs have maintained the element of restored stability but sought a more anatomic postoperative position to minimize complications and maximize rotational range of motion. Cite this article: EFORT Open Rev 2021;6:918-931. DOI: 10.1302/2058-5241.6.210014.

Concept and simulation of an alternative design for an orthopaedic shoulder implant

For a first-time glenohumeral arthritis patient, total shoulder arthroplasty (TSA) is an option where the shoulder joint is replaced with an artificial humeral head that articulates against a cup attached to the glenoid. A patient with rotator cuff deficiency can undergo reverse total shoulder arthroplasty (RTSA) where the components are switched. Presented here is a concept design at simulation stage which offers a platform-based implant where either a system can be assembled and implanted for TSA or a reverse system for RTSA. Platform components and the glenoid baseplate have been designed as part of this concept stage. Modular components are also described as part of the concept, which can influence a patient's range of motion (ROM), as well as the effect of implant positioning within the patient. A 42 mm hemisphere is used as the articulating component providing a good balance between ROM, joint load and deltoid force. The most suitable material concluded for the concept design TSA was as follows: grade 5 Ti-6Al-4V for the humeral stem and baseplate and CoCrMo with cross-linked polyethylene (XLPE) for the metal-on-polymer bearing surface. Finite element analysis concluded that the concept prosthesis is able to withstand an impact force of six times bodyweight from a forward fall. A dynamic fatigue test concluded that the expected lifetime of the concept polymer bearing surface is 33 years.

Case Report: Watching and Waiting? A Case of Incomplete Glenosphere Seating With Spontaneous Reversal in Reverse Shoulder Arthroplasty

Introduction: Reverse shoulder arthroplasty is a useful procedure with broadening applications, but it has the best outcomes when used for rotator cuff tear arthropathy. However, this procedure is not without complications. While scapular notching and aseptic loosening are more common complications that have been extensively studied in the literature, dissociation of the glenoid component and incomplete glenosphere seating has not received much attention. Specifically, little research has explored appropriate management of incomplete seating of the glenosphere component, and no gold standard for treatment of this complication has emerged.

Methods: In the case described here, an elderly patient with an incompletely seated glenosphere component post-operatively opted to pursue conservative management in order to avoid revision surgery if possible.

Results: The partially engaged, superiorly directed components in this case exhibited spontaneous complete and symmetric seating of the glenosphere between six and twelve months post-operatively, indicating that conservative management of this complication in low-demand patients may be a viable option to avoid the risks associated with revision surgery.

Conclusion: Further research should be pursued to explore what patient and prosthesis design factors may be suited to observation with serial radiographs when incomplete seating of the glenosphere component occurs.

Treating cuff tear arthropathy by reverse total shoulder arthroplasty: do the inclination of the humeral component and the lateral offset of the glenosphere influence the clinical and the radiological outcome?

PURPOSE

Reverse total shoulder arthroplasty is widely used for the treatment of cuff tear arthropathy. Standard implants consist of a humeral component with an inclination angle of 155° and a glenosphere without lateral offset. Recently, lower inclination angles of the humeral component as well as lateralized glenospheres are implanted to provide better rotation of the arm and to decrease the rate of scapular notching. This study investigates the clinical and radiological results of a standard reverse total shoulder in comparison with an implant with an inclination angle of 135° in combination with a 4 mm lateralized glenosphere in context of cuff tear arthropathy.

MATERIAL AND METHODS

For this retrospective comparative analysis 42 patients treated by reverse total shoulder arthroplasty for cuff tear arthropathy were included. Twenty-one patients (m = 11, f = 10; mean age 76 years; mean follow-up 42 months) were treated with a standard 155° humeral component and a standard glenosphere with caudal eccentricity (group A), while twenty-one patients (m = 5, f = 16; mean age 72 years; mean follow-up 34 months) were treated with a 135° humeral component and 4 mm lateral offset of the glenosphere (group B). At follow-up patients of both groups were assessed with plain X-rays (a.p. and axial view), Constant Score, adjusted Constant Score, the subjective shoulder value and the range of motion.

RESULTS

The clinical results were similar in both groups concerning the Constant Score (group A = 56.3 vs. group B = 56.1; p = 0.733), the adjusted CS (group A = 70.4% vs. group B = 68.3%; p = 0.589) and the SSV (group A = 72.0% vs. group B = 75.2%; p = 0.947). The range of motion of the operated shoulders did not differ significantly between group A and group B: Abduction = 98° versus 97.9°, p = 0.655; external rotation with the arm at side = 17.9° versus 18.7°, p = 0.703; external rotation with the arm positioned in 90° of abduction = 22.3° versus 24.7°, p = 0.524; forward flexion = 116.1° versus 116.7°, p = 0.760. The rate of scapular notching was higher (p = 0.013) in group A (overall: 66%, grade 1: 29%, grade 2: 29%, grade 3: 10%, grade 4: 0%) in comparison to group B (overall: 33%, grade 1: 33%, grade 2: 0%, grade 3: 0%, grade 4: 0%). Radiolucency around the humeral component was detected in two patients of group B. Stress shielding at the proximal humerus was observed in six patients of Group A (29%; cortical thinning and osteopenia in zone M1 and L1) and two patients of group B (10%; cortical thinning and osteopenia in zone M1 and L1). Calcifications of the triceps origin were observed in both groups (group A = 48% vs. group B = 38%).

CONCLUSION

Theoretically, a lower inclination angle of the humeral component and an increased lateral offset of the glenosphere lead to improved impingement-free range of motion and a decreased rate of scapular notching, when compared to a standard reverse total shoulder implant. This study compared two different designs of numerous options concerning the humeral component and the glenosphere. In comparison to a standard-fashioned implant with a humeral inclination of 155° and a standard glenosphere, implants with a humeral inclination angle of 135° and a 4 mm lateralized glenosphere lead to comparable clinical results and rotatory function, while the rate of scapular notching is decreased by almost 50%. While the different implant designs did not affect the clinical outcome, our results indicate that a combination of a lower inclination angle of the humeral component and lateralized glenosphere should be favored to reduce scapular notching.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Factors Influencing Appropriate Implant Selection and Position in Reverse Total Shoulder Arthroplasty

Reverse shoulder arthroplasty has increased in popularity and has provided improved but somewhat variable results. These variable outcomes may be related to many factors, including implant design, component positioning, specific indication, and patient anatomy. The original Grammont design provided a solution to the high failure rate at the time but was found to have a high rate of scapular notching and poor restoration of rotation. Modern lateralized designs are more consistent in reducing scapular notching while improving range of motion, especially in regards to external rotation. This review article summarizes the effects of modern reverse shoulder prostheses on outcomes.

Effect of RSA glenoid baseplate central fixation on micromotion and bone stress

Background

In reverse shoulder arthroplasties (RSA), osseous in-growth is promoted if glenoid micromotion does not exceed 150 μm. The purpose of this study was to determine whether the configuration of central fixation for RSA glenoid baseplates reduces implant micromotion or changes scapula bone stresses.

Methods

Using finite element analysis, glenoid baseplate fixation was tested in a cohort of 3 male and 2 female patients who were to undergo RSA. Computer models were created for 3 different RSA glenoid baseplate and 84 glenosphere designs, a central threaded peg (1 variant, D-TP), a central unthreaded peg (2 variants, I- 85 P(15) and I-P(25)), and a central peg with a screw (2 variants, A-PS and I-PS). A compressive and shear force of 756 N was distributed across the glenosphere with the scapula anchored.

Results

Displacement was within 20-130 μm at the glenosphere baseplate-bone interface for all baseplates. The glenospheres with unthreaded pegs had intermediate displacement values (I-P(15): median, 89 μm; range, 32-112 μm; and I-P(25): median, 93 μm; range, 31-109 μm). The von Mises stresses were 1.8-7.0 MPa within cortical bone and 0.6-1.6 MPa within trabecular bone. Cortical bone stresses were similar with unthreaded pegs (I-P(15): median, 4.2 MPa; range, 1.8-6.0 MPa; and I-P(25): median, 4.2 MPa; range, 1.8-6.1 MPa), whereas mean trabecular stresses were similar for all configurations.

Conclusions

All configurations yielded adequate stability, with micromotions being below 150 μm. The unthreaded pegged designs provided a valid alternative to the stable threaded pegged convex baseplates in terms of micromotions and bone stresses.

Preoperative deltoid assessment by contrast-enhanced ultrasound (CEUS) as predictor for shoulder function after reverse shoulder arthroplasty: a prospective pilot study

INTRODUCTION

Although the deltoid represents the main motor muscle after reverse shoulder arthroplasty (RSA), its standardized preoperative assessment regarding morphology and function is still not established. Its clinical relevance and interactions with major biomechanical parameters like the medialization of the center of rotation (COR) regarding shoulder function after RSA are yet unknown. We evaluated contrast-enhanced ultrasound (CEUS) of the deltoid as possible surrogate marker for individual deltoid properties of patients receiving an RSA, and its predictive value for postoperative shoulder function.

MATERIALS AND METHODS

35 patients were prospectively assessed. Before and 6 months after RSA, dynamic deltoid perfusion, caliber and a combination of both (PE*caliber, named DeltoidEfficacy) was quantified by CEUS. Changes of deltoid properties and the predictive value of preoperative CEUS-based deltoid properties for shoulder function after RSA were assessed. To analyze interrelating effects with deltoid properties, COR-medialization and deltoid lengthening were quantified.

RESULTS

Deltoid caliber and perfusion significantly increased after RSA (p = 0.0004/p = 0.002). Preoperative deltoid caliber, perfusion and the combined value DeltoidEfficacy significantly correlated with shoulder function after RSA within the whole study cohort (caliber: r = 0.445, p = 0.009; perfusion: r = 0.593, p = 0.001; DeltoidEfficacy: r = 0.66; p = 0.0002). The predictive value of DeltoidEfficacy for shoulder function after RSA varied among patient subgroups: Multivariate regression analysis revealed the strongest prediction in patients with either very high or very low deltoid properties (Beta = 0.872, r = 0.84, p = 0.0004), independent from COR-medialization or deltoid lengthening. Contrary, in patients with intermediate deltoid properties, COR-medialization revealed the strongest predictive value for shoulder function after RSA (Beta = 0.660, r = 0.597; p = 0.024).

CONCLUSION

Deltoid CEUS seems to allow an assessment of individual deltoid properties and deltoid adaptations after RSA. Deltoid CEUS seems to predict shoulder function after RSA and might support an identification of patients requiring special attention regarding COR positioning.

Effect of humeral stem and glenosphere designs on range of motion and muscle length in reverse shoulder arthroplasty

PURPOSE

To determine how different combinations of humeral stem and glenosphere designs for reverse shoulder arthroplasty (RSA) influence range of motion (ROM) and muscle elongation.

METHODS

A computed tomography scan of a non-pathologic shoulder was used to simulate all shoulder motions, and thereby compare the ROM and rotator cuff muscle lengths of the native shoulder versus 30 combinations of humeral components (1 inlay straight stem with 155° inclination and five onlay curved stems with 135°, 145° or 155° inclinations, using concentric, medialized or lateralized trays) and glenospheres (standard, large, lateralized, inferior eccentric and bony increased-offset (BIO-RSA)).

RESULTS

Only five of the 30 combinations restored ≥ 50% of the native ROM in all directions: the 145° onlay stem (concentric tray) combined with lateralized or inferior eccentric glenospheres and the 145° stem (lateralized tray) combined with either a large, lateralized or inferior eccentric glenosphere. Lengthening of the supraspinatus and infraspinatus, observed for all configurations, was greatest using onlay stems (7-30%) and BIO-RSA glenospheres (13-31%). Subscapularis lengthening was observed for onlay stems combined with BIO-RSA glenospheres (5-9%), while excessive subscapularis shortening was observed for the inlay stem combined with all glenospheres except the BIO-RSA design (> 15%).

CONCLUSIONS

The authors suggest implanting 145° onlay stems, with concentric or lateralized trays, together with lateralized or inferior eccentric glenospheres.

Reverse total shoulder arthroplasty: an imaging overview

Although not as common as hip or knee arthroplasty, shoulder arthroplasty is becoming a more common procedure. Reverse total shoulder arthroplasty (RTSA) is known to be an effective surgical procedure for massive irreparable rotator cuff tears, comminuted proximal humerus fractures, and revision shoulder arthroplasty. The utilization of RTSA has been increasing, and although complications following reverse arthroplasty have been reported, there are few reports in the literature that focus on the imaging features of RTSA. Herein, we demonstrate the biomechanics of RTSA, prosthesis components, indications, and imaging features of the normal postoperative appearance and various complications after RTSA. Familiarization with the normal and abnormal imaging appearances after RTSA can be helpful for appropriate management of patients.

Reverse Total Shoulder Arthroplasty: Implant Design Considerations

PURPOSE OF REVIEW

Our understanding of the reverse total shoulder arthroplasty (RTSA) has grown exponentially since Grammont first introduced his design in 1985. There are a multitude of implant-related variables to consider when performing RTSA. The purpose of this article is to provide a review of these design considerations.

RECENT FINDINGS

Current literature demonstrates that the traditional Grammont prosthesis has over 90% survivorship at 10 years. Despite these promising results, there have been concerns raised over the significant rate of scapular notching observed. As a result, the traditional RTSA design has been modified to minimize this complication and maximize impingement-free motion. Modern RTSA designs with a cementless, curved, short-stemmed eccentric onlay humeral component combined with a large, lateralized glenosphere placed in 10° of inferior tilt with > 3.5 mm of inferior overhang have been found to provide excellent results. However, all implant design features must be considered on a case-by-case basis to optimize outcome for each patient. Humeral and glenoid implant design variables have evolved as the biomechanics of RTSA have been further elucidated. Consideration of these variables allows the surgeon to maximize joint efficiency, improve impingement-free range of motion, decrease the risk of scapular notching, preserve bone stock, and minimize the risk of instability.

Reverse shoulder arthroplasty has higher perioperative implant complications and transfusion rates than total shoulder arthroplasty

Background

Indications for reverse total shoulder arthroplasty (RTSA) have expanded. The purpose of this retrospective cohort study was to evaluate national trends in shoulder arthroplasty utilization and to compare national perioperative complication rates for hemiarthroplasty (HA), total shoulder arthroplasty (TSA), and RTSA in a matched cohort.

Methods

The National Inpatient Sample was queried from 2011-2013 to identify patients who underwent HA, TSA, or RTSA. Age, sex, race, insurance type, Elixhauser comorbidity index, and perioperative complications were identified. A coarsened exact matching algorithm was used to match RTSA patients with TSA and HA patients to compare medical and implant-related perioperative in-hospital complications. Multivariable logistic regression analysis was performed on unmatched data to identify risk factors for development of perioperative complications.

Results

Overall, 42,832 shoulder arthroplasties were identified (44% TSAs, 34% RTSAs, 19% HAs). After matching, RTSAs had 6.2 times the odds of a perioperative implant-related complication (P < .001) and 2 times the odds of a red blood cell transfusion compared with TSAs (P < .001). The logistic regression model showed that prior shoulder arthroplasty (odds ratio [OR], 15.1; P < .001), younger age (OR, 0.98; P = .006), earlier year of index surgery (OR, 0.83; P = .002), history of illicit drug use (OR, 6.2; P = .008), and depression (OR, 2.3; P = .003) were risk factors for development of in-hospital implant-related complications after RTSA.

Conclusion

The perioperative implant-related complication rate and postoperative transfusion rate of RTSAs were significantly higher than those of TSAs. In addition, prior shoulder surgery, younger age, earlier year of index surgery, history of illicit drug use, and depression were risk factors for implant-related complications after RTSA. However, the perioperative RTSA implant-related complications did decline each year, suggesting a growing national proficiency with performing RTSA.