Metallic humeral and glenoid lateralized implants in reverse shoulder arthroplasty for cuff tear arthropathy and primary osteoarthritis

Clinical and radiological comparison of three different reverse shoulder arthroplasty designs for patients with primary osteoarthritis

AIMS

In reverse shoulder arthroplasty (RSA), different implant designs range from medializing implants to strongly lateralizing onlay designs with different neck-shaft-angles (NSA). Thus different degrees of lateralization are currently used. Aim of this study was to compare clinical and radiological outcomes of three different implant designs in a homogeneous patient cohort with primary osteoarthritis (OA).

METHODS

Patients with OA who underwent RSA between 03/2014 and 01/2020 were included and categorized into three groups based on RSA design: group MD (medialized-distalized design: eccentric glenosphere, 155° NSA), group L (lateralized design: + 4 mm centric glenosphere, 135° NSA), group LD (lateralized-distalized design: eccentric glenospheres, + 3 mm baseplate, curved onlay stem 145° NSA). Inclusion criteria were complete clinical and radiological 24 months follow-up (FU) including range of motion (ROM), Constant-Murley score (CS), Subjective Shoulder Value (SSV). In addition, scapular notching and adverse events were recorded.

RESULTS

Group MD including 26 patients (81% female; mean age: 77.9 years) reached 71 (range: 60-85) points in CS and 90% (range: 40-100) in SSV. In group L, 46 patients (98% female; mean age: 75.2 years) achieved a CS of 75 (59-85) points and SSV was 95% (60-100). In group LD, 25 patients (68% female; mean age: 76.3 years) presented a CS of 79 (30-100) points and SSV of 93% (50-100). Group L and group LD achieved significantly better abduction, internal and external rotation (p < 0.001), forward flexion (p = 0.023) and SSV (p = 0.046). Scapular notching was present in 22% of MD patients (13% grade 1; 4% grade 2; 4% grade 4), 16% in group L (all grade 1) and 9% in group LD (all grade 2). No prosthesis related complication occurred in any group.

CONCLUSION

In patients with primary OA, the lateralized and lateralized-distalized designs result in superior subjective satisfaction in SSV and improved ROM in all planes compared to the traditional distalized-medialized implant designs. In all three groups, no implant related complications were noted.

Clinical and radiological results of reverse total shoulder arthroplasty with or without lateralization as revision procedure for failed arthroplasty

Background

As reverse total shoulder arthroplasty (rTSA) becomes a common treatment option in the revision setting, common problems associated with Grammont's design such as scapular notching, instability, and rotator cuff weakening occur. Design changes associated with superior outcomes in primary rTSA, such as glenoid or humeral lateralization have not yet been examined in the revision settings. The purpose of this consecutive series of revision rTSA is to evaluate the clinical and radiological short-term results after aseptic and septic revision rTSA and explore potential benefits of metallic glenoid and humerus lateralization.

Methods

In this study, patients treated with an rTSA between 2014 and 2020 after failed shoulder arthroplasty were included. Forty-five consecutive patients were divided into comparative groups using lateralized rTSA with metallic baseplate augmentation (latrTSA) and additional humeral lateralization using a 145° onlay curved stem (bi-latrTSA); or no baseplate offset with a Grammont-type 155° stem (non-latrTSA). Further, outcome of postinfection revision rTSAs was compared to aseptic loosening. Constant-Murley-Score, subjective shoulder value, shoulder range of motion including Apley's scratch test, abduction strength, and pain levels were assessed. Radiographs were reviewed for implant loosening, scapular notching, fractures, and osteolysis. Lateralization and distalization shoulder angle were measured at the final follow-up.

Results

Thirty-eight patients showed significant improvement in all functional measurements at the final 2-year follow-up compared to the baseline (P < .01). There were no significant differences in favor of glenoid or bipolar lateralization. However, no scapular notching was seen in patients with both humeral and glenoid lateraliazion (non-latrTSA: 33%; latrTSA: 8%; bi-latrTSA: 0%; P = .103), with no signs of implant loosening. Patients with bi-latrTSA showed significantly greater lateralization shoulder angle (P = .017); distalization shoulder angle was lower, but not significantly (P = .230). Postinfectious rTSA after aseptic loosening (n = 19; 55%) presented better internal rotation (P = .036) compared to postinfectious rTSA. The overall complication rate was 16% and 8% leading to revision.

Conclusion

rTSA is a viable option for revision cases and presents good results after failed shoulder arthroplasty, including the infected shoulder. The effect of metallic augmentation on clinical results is not comparable to those in literature in primary rTSA setting due to advanced preoperative medialization. However, scapular notching was prevented in all cases with bipolar lateralization.

Lateralization has minimal biomechanical impact on tuberosity fixation with the use of a stem-based repair and a 135° humeral implant in reverse shoulder arthroplasty for 4-part proximal humerus fracture

Background

Lateralization in reverse shoulder arthroplasty (RSA) has many proven and potential benefits. Concern over the increase in tension on the tuberosities imparted by glenoid lateralization and the subsequent effect on tuberosity healing may limit its use in the setting of RSA performed for fracture. This study evaluated whether glenoid lateralization increased tuberosity fracture gapping in a biomechanical model of a 4-part proximal humerus fracture with a stem-based tuberosity repair. We hypothesized that increased lateralization would increase fracture gapping.

Methods

Eight cadaveric shoulders (mean age, 62 +/- 2.4 years; range 52-70 years) were tested with a custom testing system that permits loading of rotator cuff muscles and humerothoracic muscles. A 4-part proximal humerus fracture was simulated and then repaired with a stem-based tuberosity repair. The repaired tuberosities were cycled in internal and external rotation with 1.1-Nm torque at 2 mm and 6 mm of glenoid lateralization. For the 6-mm lateralization RSA, the torque was then increased to reach the range of motion (ROM) values achieved with the 2-mm lateralized RSA and cycled 10 times, followed by doubling the torque values for 10 cycles. ROM, muscle length and fracture gapping were assessed at 2 mm and 6 mm of glenoid lateralization.

Results

Internal rotation and total ROM demonstrated a significant decrease in the 6-mm RSA when compared to the 2-mm RSA (P < .05). The 6-mm lateralized RSA significantly increased rotator cuff muscle lengths when compared to the 2-mm lateralized RSA condition except for infraspinatus by an average of 2.7 ± 1.9 mm (P < .05). There was no significant gapping of the proximal fracture for any condition. There was a significant increase in the gapping of the distal fracture gap in the 6-mm lateralized component condition only after 10 cycles of doubled rotational torque, which measured 1.9 ± 1.5 mm (P = .031).

Discussion

We hypothesized that lateralization would increase fracture gapping. Fracture gapping did not occur proximally and only occurred at a slight amount distally after 10 cycles of doubled rotational torque. This may have implications on the choice of glenoid components when performing a RSA for fracture.

Reverse Shoulder Arthroplasty Baseplate Stability Is Affected by Bone Density and the Type and Amount of Augmentation

OBJECTIVE

This study evaluated the effects of bony increased offset (BIO) and metallic augments (MAs) on primary reverse shoulder arthroplasty (RSA) baseplate stability in cadaveric specimens with variable bone densities.

METHODS

Thirty cadaveric specimens were analyzed in an imaging and biomechanical investigation. Computed tomography (CT) scans allowed for preoperative RSA planning and bone density analysis. Three correction methods of the glenoid were used: (1) corrective reaming with a standard baseplate, which served as the reference group (n = 10); (2) MA-RSA (n = 10); and (3) angled BIO-RSA (n = 10). Each augment group consisted of 10° (n = 5) and 20° (n = 5) corrections. Biomechanical testing included cyclic loading in an articulating setup, with optical pre- and post-cyclic micromotion measurements in a rocking horse setup.

RESULTS

There were no differences in bone density between groups based on CT scans (p > 0.126). The BIO-RSA group had higher variability in micromotion compared to the MA-RSA and reference groups (p = 0.013), and increased total micromotion compared to the reference group (p = 0.039). Both augmentations using 20° corrections had increased variance in rotational stability compared to the reference group (p = 0.043). Micromotion correlated with the subchondral bone density in the BIO-RSA group (r = -0.63, p = 0.036), but not in the MA-RSA (p > 0.178) or reference (p > 0.117) groups.

CONCLUSIONS

Time-zero baseplate implant fixation is more variable with BIO-RSA and correlates with bone density. Corrections of 20° with either augmentation approach increase variability in rotational micromotion. The preoperative quantification of bone density may be useful before utilizing 20° of correction, especially when adding a bone graft in BIO-RSAs.

Glenoid lateralization in reverse shoulder arthroplasty: metal vs. bone offset in different implant designs

Background

Higher bone or metal glenoid offset in reverse shoulder arthroplasty (RSA) reduces scapular notching, improves range of motion (ROM), and reduces postoperative instability. This retrospective multicenter study compared two implant designs to evaluate the short-term clinical and radiologic results of bone increased offset RSA (BIO-RSA) and metal increased offset RSA (MIO-RSA) in reverse shoulder. We hypothesized no difference between groups.

Methods

This study analyzed n = 62 BIO-RSA and n = 90 MIO-RSA cases with a mean follow-up of 29.7 ± 6.0 months (BIO-RSA, range 24-49 months) and 24.0 ± 1.1 months (MIO-RSA, range 22-28 months). A 145°-onlay humeral stem was utilized in BIO-RSA cases, while a 135°-semi-inlay humeral stem was implanted in all MIO-RSA cases. Preoperative and postoperative radiologic imaging was reviewed to identify signs of scapular notching. Additionally, lateralization was evaluated according to Erickson et al. The constant score, subjective shoulder value, and ROM were evaluated during the baseline and follow-up consultations, and the findings of both groups were subsequently compared.

Results

Scapular notching was observed in 7.0% (n = 8) of MIO-RSA cases and 8.1% (n = 5) of BIO-RSA cases (P = .801). MIO-group had a higher lateralization angle (P = .020) and the BIO-group had a higher distalization angle (P = .005). At baseline, mean constant score in the MIO-RSA group was higher than in the BIO-RSA group (P < .001), and it significantly increased to 67.8 ± 12.1P (MIO-RSA) and 69.5 ± 12.3P (BIO-RSA) to a similar level (P = .399). ROM improved in both groups with no significant difference between the two groups at follow-up.

Conclusion

BIO-RSA and MIO-RSA in two distinct implant designs provide comparable short-term outcomes with a similar increase in shoulder function with notable variations in the lateralization and distalization angles between both implants. Scapular notching was rarely seen and unaffected by the method of glenoid lateralization. Follow-up investigations of both techniques are necessary to complement and track changes in the long-term outcome.

Metallic Lateralized-Offset Glenoid Reverse Shoulder Arthroplasty

Background

Metallic lateralized-offset glenoid reverse shoulder arthroplasty (RSA) for cuff tear arthropathy combines the use of a metallic augmented baseplate with a metaphyseally oriented short stem design that can be applied at a 135° or 145° neck-shaft angle, leading to additional lateralization on the humeral side. Lateralization of the center of rotation decreases the risk of inferior scapular notching and improves external rotation, deltoid wrapping, residual rotator cuff tensioning, and prosthetic stability1-4. Metallic increased-offset RSA (MIO-RSA) achieves lateralization and corrects inclination and retroversion while avoiding graft resorption and other complications of bony increased-offset RSA (BIO-RSA)5-8. Reducing the neck-shaft angle from the classical Grammont design, in combination with glenoid lateralization, improves range of motion9,10 by reducing inferior impingement during adduction at the expense of earlier superior impingement during abduction2,11. Lädermann et al.12 investigated how different combinations of humeral stem and glenosphere designs influence range of motion and muscle elongation. They assessed 30 combinations of humeral components, as compared with the native shoulder, and found that the combination that allows for restoration of >50% of the native range of motion in all directions was a 145° onlay stem with a concentric or lateralized tray in conjunction with a lateralized or inferior eccentric glenosphere. In addition, the use of a flush-lay or a slight-onlay stem design (like the one utilized in the presently described technique) may decrease the risk of secondary scapular spine fracture13,14. The goal of this prosthetic design is to achieve an excellent combination of motion and stability while reducing complications.

Description

This procedure is performed via a deltopectoral approach with the patient in the beach-chair position under general anesthesia combined with a regional interscalene nerve block. Subscapularis tenotomy and capsular release are performed, the humeral head is dislocated, and any osteophytes are removed. An intramedullary cutting guide is placed for correct humeral resection. The osteotomy of the humeral head is performed in the anatomical neck with an inclination of 135° and a retroversion of 20° to 40°, depending on the anatomical retroversion. The glenoid is prepared as usual. The lateralized, augmented baseplate is assembled with the central screw and the baseplate-wedge-screw complex is placed by inserting the screw into the central screw hole. Four peripheral screws are utilized for definitive fixation. An eccentric glenosphere with inferior overhang is implanted. The humerus is dislocated, and the metaphysis is prepared. Long compactors are utilized for proper stem alignment, and an asymmetric trial insert is positioned before the humerus is reduced. Stability and range of motion are assessed. The definitive short stem is inserted and the asymmetric polyethylene is impacted, resulting in a neck-shaft angle of 145°. Following reduction, subscapularis repair and wound closure are performed.

Alternatives

BIO-RSA is the main alternative to MIO-RSA. Boileau et al.15 demonstrated satisfactory early and long-term outcomes of BIO-RSA for shoulder osteoarthritis. A larger lateral offset may also be achieved with a thicker glenosphere2,16. Mark A. Frankle developed an implant that addressed the drawbacks of the Grammont design: a lateralized glenosphere combined with a 135° humeral neck-shaft angle. The 135° neck-shaft angle provides lateral humeral offset, preserving the normal length-tension relationship of the residual rotator cuff musculature, which optimizes its strength and function. The lateralized glenosphere displaces the humeral shaft laterally, minimizing the potential for impingement during adduction2,9,17,18. The advantage of BIO-RSA and MIO-RSA over lateralized glenospheres is that the former options provide correction of angular deformities without excessive reaming, which can lead to impingement19.

Rationale

BIO-RSA has been proven to achieve excellent functional outcomes15,20,21; however, the bone graft can undergo resorption, which may result in early baseplate loosening. Bipolar metallic lateralized RSA is an effective strategy for achieving lateralization and correction of multiplanar defects while avoiding the potential complications of BIO-RSA6,7,22-24. MIO-RSA also overcomes another limitation of BIO-RSA, namely that BIO-RSA is not applicable when the humeral head is not available for use (e.g., humeral head osteonecrosis, revision surgery, fracture sequelae).

Expected Outcomes

A recent study evaluated the clinical and radiographic outcomes of metallic humeral and glenoid lateralized implants. A total of 42 patients underwent primary RSA. Patients were documented prospectively and underwent follow-up visits at 1 and 2 years postoperatively. That study demonstrated that bipolar metallic lateralized RSA achieves excellent clinical results in terms of shoulder function, pain relief, muscle strength, and patient-reported subjective assessment, without instability or radiographic signs of scapular notching23. Kirsch et al.25 reported the results of primary RSA with an augmented baseplate in 44 patients with a minimum of 1 year of clinical and radiographic follow-up. The use of an augmented baseplate resulted in excellent short-term clinical outcomes and substantial deformity correction in patients with advanced glenoid deformity. No short-term complications and no failure or loosening of the augmented baseplate were observed. Merolla et al.7 compared the results of 44 patients who underwent BIO-RSA and 39 patients who underwent MIO-RSA, with a minimum follow-up of 2 years. Both techniques provided good clinical outcomes; however, BIO-RSA yielded union between the cancellous bone graft and the surface of the native glenoid in <70% of patients. On the other hand, complete baseplate seating was observed in 90% of MIO-RSA patients.

Important Tips

When performing subscapularis tenotomy, leave an adequate stump to allow end-to-end repair.Tenotomize the superior part of the subscapularis tendon in an L-shape, sparing the portion below the circumflex vessels.As glenoid exposure is critical, perform a 270° capsulotomy.Continuously check the orientation of the baseplate relative to the prepared hole and reamed surface to ensure accurate implantation of the full wedge baseplate to achieve a proper fit.Aim for 70% to 80% seating of the baseplate onto the prepared glenoid surface. Avoid overtightening or excessive advancement of the baseplate into the subchondral bone. Gaps between the baseplate and glenoid surface should also be avoided.In order to avoid varus or valgus malpositioning of the final implant, obtain proper diaphyseal alignment by following "the three big Ls": large, lateral, and long. Use a large metaphyseal component to fill the metaphysis. Place the guide pin for the reaming of the metaphysis slightly laterally into the resected surface of the humerus. Use long compactors for diaphyseal alignment to avoid varus or valgus malpositioning of the final implant.Use an intramedullary cutting guide for correct humeral resection.Utilize the correct liner in order to obtain proper tensioning and avoid instability.

Acronyms and Abbreviations

K wire = Kirschner wireROM = range of motion.

[Reverse Shoulder Arthroplasty - Current Concepts]

Due to first promising long term outcome data, reverse shoulder arthroplasty experienced an immense increase of usage during the past decade. Moreover, the initial Grammont concept has constantly been refined and adapted to current scientific findings. Therefore, clinical and radiological problems like scapular notching and postoperative instability were constantly addressed but do still remain an area of concern.This article summarises current concepts in reverse shoulder arthroplasty and gives an overview of actual indications like cuff tear arthropathy, severe osteoarthritis, proximal humerus fractures, tumours, fracture sequelae as well as revision surgery and their corresponding clinical and radiological results.

Analysis of three different reverse shoulder arthroplasty designs for cuff tear arthropathy - the combination of lateralization and distalization provides best mobility

BACKGROUND

The two major reverse shoulder arthroplasty (RSA) designs are the Grammont design and the lateralized design. Even if the lateralized design is biomechanically favored, the classic Grammont prosthesis continues to be used. Functional and subjective patient scores as well as implant survival described in the literature so far are comparable to the lateralized design. A pure comparison of how the RSA design influences outcome in patients has not yet been determined. The aim of this study was a comparison focused on patients with cuff tear arthropathy (CTA).

METHODS

We analyzed registry data from 696 CTA patients prospectively collected between 2012 and 2020 in two specialized orthopedic centers up to 2 years post-RSA with the same follow-up time points (6,12 24 months). Complete teres minor tears were excluded. Three groups were defined: group 1 (inlay, 155° humeral inclination, 36 + 2 mm eccentric glenosphere (n = 50)), group 2 (inlay, 135° humeral inclination, 36 + 4 mm lateralized glenosphere (n = 141)) and group 3 (onlay, 145° humeral inclination, + 3 mm lateralized base plate, 36 + 2 mm eccentric glenosphere (n = 35)) We compared group differences in clinical outcomes (e.g., active and passive range of motion (ROM), abduction strength, Constant-Murley score (CS)), radiographic evaluations of prosthetic position, scapular anatomy and complications using mixed models adjusted for age and sex.

RESULTS

The final analysis included 226 patients. The overall adjusted p-value of the CS for all time-points showed no significant difference (p = 0.466). Flexion of group 3 (mean, 155° (SD 13)) was higher than flexion of group 1 (mean, 142° (SD 18) and 2 (mean, 132° (SD 18) (p < 0.001). Values for abduction of group 3 (mean, 145° (SD 23)) were bigger than those of group 1 (mean, 130° (SD 22)) and group 2 (mean, 118° (SD 25)) (p < 0.001). Mean external rotation for group 3 (mean, 41° (SD 23)) and group 2 (mean, 38° (SD 17)) was larger than external rotation of group 1 (mean, 24° (SD 16)) (p < 0.001); a greater proportion of group 2 (78%) and 3 (69%) patients reached L3 level on internal rotation compared to group 1 (44%) (p = 0.003). Prosthesis position measurements were similar, but group 3 had significantly less scapular notching (14%) versus 24% (group 2) and 50% (group 1) (p = 0.001).

CONCLUSIONS

Outcome scores of different RSA designs for CTA revealed comparable results. However, CTA patients with a lateralized and distalized RSA configuration were associated with achieving better flexion and abduction with less scapular notching. A better rotation was associated with either of the lateralized RSA designs in comparison with the classic Grammont prosthesis.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

How common is nerve injury after reverse shoulder arthroplasty? A systematic review

BACKGROUND

Nerve injury following reverse shoulder arthroplasty (RSA) is a known risk factor with wide ranging incidences reported. This systematic review evaluates the overall incidence of nerve injury following primary and revision RSA and summarizes the characteristics of the nerve injuries reported in the current literature.

METHODS

A systematic review was performed using separate database searches (Pubmed, Embase, Web of Science, Cochrane) following the PRISMA guidelines. Search criteria included the title terms "reverse shoulder," "reverse total shoulder," "inverted shoulder," and "inverted total shoulder" with publication dates ranging from 01/01/2010 to 01/01/2022. Studies that reported neurological injuries and complications were included and evaluated for primary RSA, revision RSA, number of nerve injuries, and which nerves were affected.

RESULTS

After exclusion, our systematic review consisted of 188 articles. A total of 40,146 patients were included, with 65% female. The weighted mean age was 70.3 years. The weighted mean follow-up was 35.4 months. The rate of nerve injury after RSA was 1.3% (510 of 40,146 RSAs). The rate of injury was greater in revision RSA compared to primary RSA (2.4% vs. 1.3%). Nerve injury was most common in RSAs done for a primary diagnosis of acute proximal humerus fracture (4.0%), followed by cuff tear arthropathy (3.0%), DJD (2.6%), and inflammatory arthritis (1.7%). Massive rotator cuff tears and post-traumatic arthritis cases had the lowest nerve injury rates (1.0% and 1.4%, respectively). The axillary nerve was the most commonly reported nerve that was injured in both primary and revision RSA (0.6%), followed by the ulnar nerve (0.26%) and median nerve (0.23%). Brachial plexus injury was reported in 0.19% of overall RSA cases.

CONCLUSION

Based on current English literature, nerve injuries occur at a rate of 1.3% after primary RSA compared with 2.4% after revision RSA. The most common nerve injury was to the axillary nerve (0.64%), with the most common operative diagnosis associated with nerve injury after RSA being acute proximal humerus fracture (4.0%). Surgeons should carefully counsel patients prior to surgery regarding the risk of nerve injury.