Deltoid muscle activity in patients with reverse shoulder prosthesis at 2-year follow-up

Anatomic Versus Reverse Total Shoulder Arthroplasty for Primary Osteoarthritis With an Intact Rotator Cuff: A Midterm Comparison of Early Top Performers

BACKGROUND

Several surgeons state that their best anatomic total shoulder arthroplasty (aTSA) outperforms their best reverse total shoulder arthroplasty (rTSA) when performed for rotator cuff-intact glenohumeral osteoarthritis. We identified the top-performing aTSAs and rTSAs at short-term follow-up and compared their clinical performance at midterm follow-up to validate this common claim.

METHODS

A retrospective review of a multicenter shoulder arthroplasty database was conducted. All shoulders undergoing primary aTSA or rTSA for rotator cuff-intact glenohumeral osteoarthritis between 2007 and 2020 were reviewed. Shoulders with a follow-up clinical visit between 2 and 3 years and a clinical follow-up of minimum 5 years were included. Two separate cohorts were identified: patients with a top 20% (1) American Shoulder and Elbow Surgeons (ASES) score and (2) Shoulder Arthroplasty Smart (SAS) score at 2 to 3 years of follow-up. Clinical outcomes including range of motion, outcome scores, and rates of complications and revision surgeries were compared at minimum 5-year follow-up.

RESULTS

The ASES score cohort comprised 185 aTSAs (mean age 67 years, 42% female) and 49 rTSAs (mean age 72 years, 45% female). The SAS score cohort comprised 145 aTSAs (mean age 67 years, 59% female) and 42 rTSAs (mean age 71 years, 57% female). Active external rotation (ER) was greater after aTSA at midterm follow-up in both ASES and SAS score cohorts; however, preoperative to postoperative improvement was equivalent. Postoperative ER and SAS scores were greater after aTSA in both cohorts (P < 0.05); however, no other significant differences in any preoperative or postoperative clinical outcomes were present (P > 0.05), and patients achieved the minimal clinically important difference and substantial clinical benefit at similar rates for all outcomes. No difference was found in the incidence of complications and revision surgeries between top-performing aTSAs and rTSAs.

CONCLUSION

Among top-performing shoulder arthroplasties at early follow-up, aTSA does not appear to outperform rTSA, except superior ER at midterm follow-up.

LEVEL OF EVIDENCE

Retrospective comparative cohort study, Level Ⅲ.

Inlay vs. onlay humeral components in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study

BACKGROUND

Both inlay and onlay humeral implants are available for reverse total shoulder arthroplasty (rTSA), but biomechanical data comparing these components remain limited. This study investigated the effects of inlay and onlay rTSA humeral components on shoulder biomechanics using a biorobotic shoulder simulator.

METHODS

Twenty fresh-frozen cadaveric shoulders were tested before and after rTSA with either an inlay or onlay humeral implant. Comparisons were performed between the most commonly implanted configurations for each implant (baseline) and with a modification to provide equivalent neck-shaft angles (NSAs) for the inlay and onlay configurations. Specimens underwent passive range-of-motion (ROM) assessment with the scapula held static, and scapular-plane abduction was performed, driven by previously collected human-subject scapulothoracic and glenohumeral kinematics. Passive ROM glenohumeral joint angles were compared using t tests, whereas muscle force and excursion data during scapular-plane elevation were evaluated with statistical parametric mapping and t tests.

RESULTS

Maximum passive elevation was reduced for the inlay vs. onlay humeral components, although both implants caused reduced passive elevation vs. the native joint. Inlay rTSA also demonstrated reduced passive internal rotation at rest and increased external rotation at 90° of humerothoracic elevation vs. the native joint. All preoperative planning estimates of ROM differed from experiments. Rotator cuff forces were elevated with an onlay vs. inlay humeral implant, but simulated muscle excursions did not differ between systems. Compared with the native joint, rotator cuff forces were increased for both inlay and onlay implants and deltoid forces were reduced for inlay implants. Muscle excursions were dramatically altered by rTSA vs. the native joint. Comparisons of inlay and onlay humeral implants with equivalent NSAs were consistent with the baseline comparisons.

CONCLUSIONS

Rotator cuff forces required to perform scapular-plane abduction increase following rTSA using both inlay and onlay implants. Rotator cuff forces are lower with inlay implants compared with onlay implants, although inlay implants also result in reduced passive-elevation ROM. Deltoid forces are lower with inlay implants in comparison to the native joint but not with onlay implants. The differences between inlay and onlay components are largely unaffected by NSA, indicating that these differences are inherent to the inlay and onlay designs. In those patients with an intact rotator cuff, decreased rotator cuff forces to perform abduction with an inlay humeral implant compared with an onlay implant may promote improved long-term outcomes owing to reduced deltoid muscle fatigue when using an inlay implant.

Electromyographic analysis of selected shoulder muscles during shoulder rehabilitation exercises in patients after reverse total shoulder arthroplasty

BACKGROUND

Reverse shoulder arthroplasty (RSA) aims to restore function in patients with rotator cuff failure and joint arthropathy. After surgery, patients are routinely referred to a rehabilitation specialist to regain range of motion, strength, and function. A key element in these programs is active exercises. The exercises are often selected based on assumed muscle activity, investigated by electromyography (EMG). In particular, in this patient population, activation of the deltoid and the scapular muscles is the focus of exercise therapy. Currently, most studies investigating muscle activity levels during exercises are performed on healthy individuals. To our knowledge, no study exists analyzing EMG activity during exercises in a population of shoulder arthroplasty patients. Therefore, the study aimed to analyze activity in the shoulder girdle muscles during 6 commonly used rehabilitation exercises 12 weeks after reverse shoulder arthroplasty surgery.

METHODS

Forty-four patients (50 shoulders) participated in this cross-sectional study, 12 weeks postoperatively (mean 99.18 ± 12.8 days), aged 68.9 ± 7.75 years. Surface EMG activity was measured in 10 shoulder girdle muscles: the 3 trapezius parts, serratus anterior, the 3 deltoid parts, latissimus dorsi, and 2 pectoralis major parts during 6 exercises, 3 in a closed chain, and 3 open chain elevation exercises.

RESULTS

Gravity-minimized exercises (horizontal plane) show low activity for almost all muscles. Vertical closed kinetic chain exercises show an increased activity compared to horizontal plane exercises. Open kinetic chain exercises against gravity showed the greatest activity in deltoid and upper trapezius. For the other muscles, no consistency in progression was found.

CONCLUSION

This study offers a progression of exercises for patients after reverse shoulder arthroplasty based on increased muscle activity.

Postoperative complications of reverse total shoulder arthroplasty: a multicenter study in Japan

Background

Reverse total shoulder arthroplasty (RSA) has been approved since 2014 in Japan, and the number of RSA cases has been accumulating. However, only short-to medium-term outcomes have been reported, with a small number of case series, because of its short history in Japan. This study aimed to evaluate complications after RSA in hospitals affiliated with our institute, with comparison to those in other countries.

Methods

A multicenter retrospective study was performed at 6 hospitals. In total, 615 shoulders (mean age: 75.7 ± 6.2 years; mean follow-up: 45.2 ± 19.6 months) with at least 24 months of follow-up were included in this study. The active range of motion was assessed pre-and postoperatively. The 5-year survival rate was evaluated for reoperation for any reason in 137 shoulders with at least 5 years of follow-up using Kaplan-Meier analysis. Postoperative complications were evaluated, including dislocation; prosthesis failure; deep infection; periprosthetic, acromial, scapular spine, and clavicle fractures; neurological disorders; and reoperation. Furthermore, imaging assessments, including scapular notching, prosthesis aseptic loosening, and heterotopic ossification were evaluated on postoperative radiography at the final follow-up.

Results

All range of motion parameters were significantly improved postoperatively (P < .001). The 5-year survival rate was 93.4% (95% confidence interval: 87.8%-96.5%) for reoperation. Complications occurred in 256 shoulders (42.0%), with reoperation in 45 (7.3%), acromial fracture in 24 (3.9%), neurological disorders in 17 (2.8%), deep infection in 16 (2.6%), periprosthetic fracture in 11 (1.8%), dislocation in 9 (1.5%), prosthesis failure in 9 (1.5%), clavicle fracture in 4 (0.7%), and scapular spine fracture in 2 (0.3%). Regarding imaging assessments, scapular notching was observed in 145 shoulders (23.6%), heterotopic ossification in 80 (13.0%), and prosthesis loosening in 13 (2.1%).

Conclusion

This is the first large case series to investigate the complications after RSA in Japan, and the overall frequency of complications after RSA was similar to that in other countries.

Deltoid fatigue part 2: a longitudinal assessment of anatomic total shoulder arthroplasty over time

BACKGROUND

Gradual loss of overhead range of motion (ROM) has been observed after reverse shoulder arthroplasty (RSA). It remains unclear if this is caused by the effect of RSA design on muscle fiber lengthening or is part of the natural aging process of the shoulder musculature. Although studies have attempted to evaluate deltoid fatigue after RSA, there is a paucity of literature evaluating this effect after anatomic shoulder arthroplasty (aTSA), which would be expected to occur due to aging alone. The purpose of this study is to evaluate the effect of time on overhead ROM after aTSA and compare this with previous data on a similar cohort of RSAs. We hypothesized that overhead ROM would decrease gradually over time in both groups without differences between prosthesis types.

METHODS

A retrospective review of 384 aTSAs without complications was performed over a 10-year period. All shoulders were treated for primary osteoarthritis using a single implant system. Patients were evaluated longitudinally at multiple postoperative time points. At least 1 follow-up visit was between 1 and 2 years postoperatively and another at least 5 years after surgery. ROM and patient reported outcome measures (PROMs) were evaluated using linear-mixed models for repeated measures. These results were compared with a previously evaluated cohort of 165 well-functioning RSAs analyzed using the same methodology.

RESULTS

Primary aTSA shoulders were observed to lose 0.7° of abduction per year starting 1 year postoperatively (P = .001). Smaller losses were observed in external rotation (-0.3°/yr, P = .06) and internal rotation (-0.04/yr, P < .001). However, no significant losses were observed in forward elevation (P = .8). All PROMs diminished slowly over time, but these changes did not exceed the minimally clinically important difference when modeled over 10 years (Simple Shoulder Test -0.08/yr, P < .001; American Shoulder Elbow Surgeons -0.5/yr, P < .001; University of California Los Angeles Shoulder Score -0.2/yr, P < .001). When compared with a similarly analyzed cohort of RSAs, overhead ROM decreased at a slower rate in the aTSA cohort (abduction -0.7° vs. -0.8°/yr, P = .9; FE -0.06° vs. -0.8°/yr, P = .05).

DISCUSSION

In the well-functioning aTSA, gradual loss of ROM occurs in all planes of motion except forward elevation. However, these losses are small and have little meaningful impact relative to minimally clinically important difference thresholds on PROMs. Progressive loss of abduction seen in both aTSA and RSA is likely secondary to aging of the periscapular and rotator cuff musculature. When compared with RSA, loss of motion after aTSA was statistically similar, calling into question the belief that RSA-induced deltoid fatigue leads to loss of overhead motion over time.

Maximizing Muscle Function in Cuff-Deficient Shoulders: A Rehabilitation Proposal for Reverse Arthroplasty

Purpose

The purpose of this review is to describe the role of altered joint biomechanics in reverse shoulder arthroplasty and to propose a rehabilitation protocol for a cuff-deficient glenohumeral joint based on the current evidence.Methods and Materials: The proposed rehabilitation incorporates the principles of pertinent muscle loading while considering risk factors and surgical complications.

Results

In light of altered function of shoulder muscles in reverse arthroplasty, scapular plane abduction should be more often utilized as it better activates deltoid, teres minor, upper trapezius, and serratus anterior. Given the absence of supraspinatus and infraspinatus and reduction of external rotation moment arm of the deltoid in reverse arthroplasty, significant recovery of external rotation may not occur, although an intact teres minor may assist external rotation in the elevated position.

Conclusion

Improving the efficiency of deltoid function before and after reverse shoulder arthroplasty is a key factor in the rehabilitation of the cuff deficient shoulders. Performing exercises in scapular plane and higher abduction angles activates deltoid and other important muscles more efficiently and optimizes surgical outcomes.

Rate of improvement in shoulder strength after anatomic and reverse total shoulder arthroplasty

Background

Methods

Results

Conclusion

Magnetic resonance imaging of deltoid muscle/tendon tears: a descriptive study

OBJECTIVE

To describe the MRI features of deltoid tears and to evaluate tear characteristics in patient groups based on history of trauma and rotator cuff tear (RCT).

MATERIALS AND METHODS

The records of patients who underwent shoulder MRI at our institution between July 2007 and June 2018 were retrospectively reviewed to identify deltoid tears, and patients were divided into groups based on history of recent trauma and presence of RCT. Images were reviewed to identify the location and size of the deltoid tear; the presence or absence of RCT, muscle atrophy, tendon retraction, humeral head subluxation, soft tissue edema, and additional pathologies were also noted. Medical records were reviewed for information about history of steroid injection, previous rotator cuff surgery, and treatments used.

RESULTS

Among 69 patients with deltoid tears (45 men; mean age, 65.2 years; range, 19-89 years), patients with RCTs and no trauma had the highest frequency of deltoid tears in the middle portion (p = 0.005). Only patients with RCTs had undergone steroid injection or rotator cuff surgery. Two patients had deltoid tear without RCT and without recent trauma; these patients demonstrated evidence of calcific tendinopathy and chronic subacromial-subdeltoid bursitis.

CONCLUSION

The middle (acromial) portion of the deltoid is more frequently affected in patients with RCTs than in those with trauma. Although deltoid tears are commonly associated with RCT, calcific tendinopathy and chronic bursitis may also be seen in patients with deltoid tears.

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.

The effect of glenosphere lateralization and inferiorization on deltoid force in reverse total shoulder arthroplasty

BACKGROUND

A medialized center of rotation (COR) in reverse total shoulder arthroplasty (RTSA) comes with limitations such as scapular notching and reduced range of motion. To mitigate these effects, lateralization and inferiorization of the COR are performed, but may adversely affect deltoid muscle force. The study purposes were to measure the effect of RTSA with varying glenosphere configurations on (1) the COR and (2) deltoid force compared with intact shoulders and shoulders with massive posterosuperior rotator cuff tears (PS-RCT). We hypothesized that the highest deltoid forces would occur in shoulders with PS-RCT, and that RTSA would lead to a decrease in required forces that is further minimized with lateralization and inferiorization of the COR but still higher compared with native shoulders with an intact rotator cuff.

METHODS

In this study, 8 cadaveric shoulders were dissected leaving only the rotator cuff muscles and capsule intact. A custom apparatus incorporating motion capture and a dynamic tensile testing machine to measure the changes in COR and deltoid forces while simultaneously recording glenohumeral abduction was designed. Five consecutive testing states were tested: (1) intact shoulder, (2) PS-RCT, (3) RTSA with standard glenosphere, (4) RTSA with 4 mm lateralized glenosphere, and (5) RTSA with 2.5 mm inferiorized glenosphere. Statistical Parametric Mapping was used to analyze the deltoid force as a function of the abduction angle. One-way repeated-measures within-specimens analysis of variance was conducted, followed by post hoc t-tests for pairwise comparisons between the states.

RESULTS

All RTSA configurations shifted the COR medially and inferiorly with respect to native (standard: 4.2 ± 2.1 mm, 19.7 ± 3.6 mm; 4 mm lateralized: 3.9 ± 1.2 mm, 16.0 ± 1.8; 2.5 mm inferiorized: 6.9 ± 0.9 mm, 18.9 ± 1.7 mm). Analysis of variance showed a significant effect of specimen state on deltoid force across all abduction angles. Of the 10 paired t-test comparisons made between states, only 3 showed significant differences: (1) intact shoulders necessitated significantly lower deltoid force than specimens with PS-RCT below 42° abduction, (2) RTSAs with standard glenospheres required significantly lower deltoid force than RTSA with 4 mm lateralized glenospheres above 34° abduction, and (3) RTSAs with 2.5 mm inferiorized glenospheres had significantly lower deltoid force than RTSA with 4 mm of glenosphere lateralization at higher abduction angles.

CONCLUSIONS

RTSA with a 2.5 mm inferiorized glenosphere and no additional lateralization resulted in less deltoid force to abduct the arm compared with 4 mm lateralized glenospheres. Therefore, when aiming to mitigate downsides of a medialized COR, an inferiorized glenosphere may be preferable in terms of its effect on deltoid force.

A kinematic and electromyographic comparison of a Grammont-style reverse arthroplasty combined with a l'Episcopo transfer compared to a lateralized humeral component reverse for restoration of active external rotation

PURPOSE

To assess kinematic and electromyographic findings of two designs of reverse total shoulder arthroplasty (RTSA). We tested two hypotheses: (H₁) Grammont-style (RTSA) with l'Episcopo tendon transfer gains similar postoperative kinematic findings of a lateralized humeral component RTSA without a tendon transfer; (H₂) RTSA with lateralized humeral component induces earlier shoulder muscle activation during shoulder motion compared with standard Grammont prosthesis with l'Episcopo transfer.

METHODS

Twenty-five patients with a cuff tear arthropathy, pseudoparalysis, and a positive dropping sign were sequentially included. A Grammont-style RTSA with a l'Episcopo tendon transfer was implanted in 13 patients (medialized humerus and transfer group) and an on-lay curved-stem RTSA in 12 (lateralized humerus group). Constant score; the disabilities of the arm, shoulder, and hand (DASH) score; and active shoulder range of motion (flexion, abduction, external rotation, and internal rotation) were measured pre- and postoperatively. Upper limb kinematic and surface electromyography (EMG) (anterior and posterior deltoid; upper, middle, and lower trapezius; and the upper and lower latissimus dorsi muscles) were recorded during active range of motion.

RESULTS

At > 24 months of follow-up, the Constant and DASH scores and active shoulder range of motion improved in both groups (p < 0.0001). Internal rotation was significantly higher in the lateralized humerus group than in the medialized humerus and transfer group (p = 0.004). The dropping sign was found in 0/12 patients in the lateralized humerus group and in 5/13 patients in the medialized humerus and transfer group (p < 0.001). Kinematic findings were similar between groups (p = 0.286). A pattern of earlier muscle activation in the lateralized humerus group was found as compared to the transfer group as follows: (i) posterior deltoid during external rotation (p = 0.004); (ii) upper latissimus dorsi and middle and lower trapezius during flexion (p = 0.004, p = 0.005, and p = 0.042, respectively); (iii) lower latissimus dorsi during abduction (p = 0.016).

CONCLUSION

RTSA with a lateralized humeral component provided similar active external rotation restoration to a Grammont-style RTSA with a l'Episcopo procedure in patients with a dropping sign. The posterior deltoid muscle underwent earlier activation during active external rotation in the lateralized humerus RTSA group as compared to the tendon transfer group. Our findings demonstrated the H₁ and only partially demonstrated the H₂ of the study.

Deltoid fatigue: a longitudinal assessment of reverse shoulder arthroplasty over time

BACKGROUND

Studies evaluating the mid-term performance of reverse shoulder arthroplasty (RSA) have identified a drop in the Constant-Murley score between 6 and 8 years after surgery, which is most affected by a loss of forward elevation and strength. Alterations of the deltoid length and moment arm after RSA lead to nonphysiological stress on the deltoid muscle. Concern has arisen that the long-term implications of increased deltoid work may be causing "deltoid fatigue." The purpose of this study was to evaluate the long-term effects of RSA on overhead range of motion (ROM) and validate the hypothesis of deltoid fatigue.

METHODS

We performed a retrospective review of 165 RSAs over a 5-year period. Diagnoses were limited to cuff tear arthropathy, osteoarthritis with rotator cuff deficiency, and irreparable rotator cuff tear. All procedures were performed using a single implant system. Patients were evaluated longitudinally at multiple time points. They were required to undergo a minimum of 3 follow-up visits, with at least 1 visit at >5 years. ROM and patient-reported outcome measures were evaluated using linear mixed models for repeated measures to evaluate changes in outcome measures over time. A secondary analysis was performed to assess the influence of patient demographic factors on observed changes in ROM and patient-reported outcome measures.

RESULTS

Primary RSA shoulders were observed to lose 0.8° of forward elevation and abduction per year starting at 1 year postoperatively (P = .006), without a significant drop at mid-term follow-up. No significant change in external or internal rotation was observed. Male patients and patients with a diagnosis of osteoarthritis with rotator cuff deficiency showed greater baseline overhead ROM at 1 year postoperatively, but the subsequent rates of functional decline were similar regardless of age, sex, or indication.

DISCUSSION

This study challenges the previous theory of deltoid fatigue resulting in a significant loss of overhead ROM beginning 6-8 years after index arthroplasty. However, a slower progressive decline in overhead ROM in well-functioning RSA shoulders was observed, averaging 0.8° of overhead ROM per year. This progressive deterioration occurs at a slightly greater rate than that observed in the natural shoulder. The observed rate of functional decline was found to be independent of age, sex, and preoperative diagnosis.

The effect of metaglene lateralization on joint mobility of reverse shoulder arthroplasty: A cadaveric biomechanical study

Introduction

Lateralization of the metaglene reduces scapular notching or impingement. However, the effect on joint mobility remains unclear. With increased attention to reverse shoulder arthroplasty over the past years, the aim of this biomechanical study is to analyze the effect of metaglene lateralization on range of motion in reverse shoulder arthroplasty.

Methods

Reverse shoulder arthroplasty (DeltaXtend; Fa. Depuy/Synthes) was performed in 7 cadaveric shoulders. Lateralization of the metaglene was performed in increments, using spacers of +0 mm (subgroup I), +5 mm (subgroup II), +10 mm (subgroup III). Deltoid muscle (pars clavicularis, acromialis and spinalis), teres minor (TMI), infraspinatus (IF) and subscapularis muslces (SSC) were loaded separately. Range of motion was measured by using a motion capture system (Optotrak Certus) in the sagittal plane (z-axis), coronar plane (x-axis) and transversal plane (y-axis). A custom-made biomechanical test set up was used to test the samples with a constant preload with additional testing load up to 4 kg on each muscle.

Results

Specimens showed a tendency towards increased range of motion in abduction (deltoid, pars acromialis), external rotation (IS/TMI) and internal rotation (SSC) in subgroup II, compared to subgroups I and III, without reaching the level of significance Abduction at maximum used load was 46° (subgroup I), 62° (subgroup II) and 22° (subgroup III). The mean external rotation (ISF) at maximum used load was 25° (I), 28° (II) and 24° (III). Mean internal rotation was 22° (subgroup I), 48° (subgroup II) and 26° (subgroup III).

Conclusion

Moderate lateralization of the glenosphere of +5 mm has improved the range of motion in our experimental cadaveric setup. Especially a higher internal and external rotation can be reached with less load.Level of evidence III.

Clinical Importance of Graft Integrity in Arthroscopic Superior Capsular Reconstruction Using a Minimally Invasively Harvested Midthigh Fascia Lata Autograft: 3-Year Clinical and Magnetic Resonance Imaging Outcomes

BACKGROUND

The clinical importance of graft type and integrity in arthroscopic superior capsular reconstruction (ASCR) remains controversial.

PURPOSE

To assess 3-year clinical and magnetic resonance imaging (MRI) outcomes of ASCR using a minimally invasively harvested fascia lata autograft (FLA) for irreparable rotator cuff tears (IRCTs) and to determine the clinical importance of graft integrity and whether the results change from year 2 to 3.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 22 consecutive patients who underwent ASCR with a minimally invasively harvested FLA were enrolled in a prospective single-arm study. At 3 years, the patients answered a satisfaction questionnaire and underwent a clinical examination and MRI. The MRI scans were independently reviewed by 3 raters to determine the graft integrity, acromiohumeral interval, supraspinatus atrophy, and fatty degeneration of the rotator cuff muscles. Reliability statistics were calculated, and the outcomes were compared across subgroups of patients with and without complete graft tears.

RESULTS

Overall, 21 patients (95.5%) answered the questionnaire, 20/21 (95.2%) were satisfied, 4/20 (20.0%) reported donor site pain, and 19 patients (86.4%) underwent examinations. From preoperatively to 3 years, the mean improvement was 73.68° in elevation (95% CI, 47.59°-99.77°), 89.21° in abduction (95% CI, 66.56°-111.86°), 24.74° in external rotation (95% CI, 4.72°-34.75°), 3.00 in internal rotation (95% CI, 2.36-3.64), 2.61 kg in abduction strength (95% CI, 1.76-3.45 kg), 50.79 on the Constant score (CS; 95% CI, 41.99-59.58), 7.47 on the Simple Shoulder Test (SST; 95% CI, 5.19-9.75), and 36.05% on the subjective shoulder value (SSV; 95% CI, 23.19%-48.92%), which were all significant (P < .05). From 2 to 3 years, the mean improvement in abduction was 20.26° (95% CI, 5.44°-35.09°), which was significant (P = .010). At 3 years, the raters perfectly agreed (kappa = 1; P = .000013) that 4 patients (21.1%) had complete graft tears; this subgroup of patients had decreased external rotation strength at 90° of abduction (1.77 ± 0.17 vs 4.45 ± 2.55 kg, respectively; P = .027) and increased grades of infraspinatus (3.50 ± 0.58 vs 2.20 ± 1.01, respectively; P = .030) and teres minor fatty degeneration (3.25 ± 0.96 vs 1.53 ± 0.64, respectively; P = .005) compared with those without a complete graft tear, but the mean CS, SST, and SSV scores did not differ from those of the overall group (69.50 ± 5.20 vs 69.63 ± 18.25; 9.00 ± 2.31 vs 9.74 ± 4.73; and 72.50 ± 15.00 vs 71.58 ± 26.70, respectively).

CONCLUSION

The 3-year clinical outcomes of ASCR using a minimally invasively harvested FLA for IRCTs were good, despite donor site morbidity. Active abduction improved significantly from 2 to 3 years. Complete graft tears were correlated with significantly decreased external rotation strength at 90° of shoulder abduction and increased grades of infraspinatus and teres minor fatty degeneration.

REGISTRATION

NCT03663036 (ClinicalTrials.gov identifier).

Shoulder Muscle Strength and Neuromuscular Activation 2 Years after Reverse Shoulder Prosthesis-An Experimental Case Control Study

Although reverse shoulder arthroplasty (RSA) has shown successful postoperative outcomes, little is known about compensatory activation patterns of remaining shoulder muscles following RSA. The purpose of this experimental case control series was to investigate shoulder muscle strength and neuromuscular activation of deltoid and teres minor muscles 2 years after RSA. Humerus lengthening, center-of-rotation medialization, maximal voluntary strength, and electromyographic (EMG) activity were compared between the operated and the non-operated side of 13 patients (mean age: 73 years). Shoulder muscle strength was significantly lower on the operated side for external rotation (−54%), internal rotation (−20%), and adduction (−13%). Agonist deltoid EMG activity was lower on the operated side for shoulder flexion, extension, and internal and external rotation (p < 0.05). Antagonist deltoid coactivation was higher on the operated side for external rotation (p < 0.001). Large correlation coefficients were observed between shoulder adductor strength asymmetry and both center-of-rotation medialization (r = −0.73) and humerus lengthening (r = 0.71). Shoulder abduction strength and neuromuscular activation were well preserved 2 years after RSA, while persistent strength and activation deficits were observed for shoulder adduction and internal and external rotation. Additional studies are required to elucidate shoulder neuromuscular activation patterns before and after RSA to support decision making for surgical, implant design, and rehabilitation choices.

Relation between preoperative electromyographic activity of the deltoid and upper trapezius muscle and clinical results in patients treated with reverse shoulder arthroplasty

BACKGROUND

If patients susceptible to poor clinical outcomes could be predicted before reverse shoulder arthroplasty (RSA), it would help to set reasonable postsurgical patient expectations in the preoperative setting. Our hypothesis was that the preoperative electromyographic (EMG) activity of the deltoid and upper trapezius muscles would be correlated with clinical outcomes of patients undergoing RSA.

METHODS

EMG activity of the deltoid and upper trapezius muscles was measured in 25 patients scheduled to undergo RSA during 3 motions: shrugging, forward flexion, and abduction. Their postoperative clinical results were assessed prospectively during regular outpatient visits, including strength, active range of motion (ROM), pain, and functional scores. The correlations between the preoperative EMG activities and clinical results were analyzed.

RESULTS

Postoperative shoulder strength after RSA was increased in patients with greater preoperative EMG activity of the middle deltoid and upper trapezius. Preoperative EMG activity of the anterior or middle deltoid muscle was associated with active ROM in flexion or abduction, whereas EMG activity of the posterior deltoid was associated with active ROM in external rotation.

CONCLUSIONS

Shoulder strength after RSA was positively correlated with preoperative EMG activity of the deltoid and upper trapezius. Active ROM after RSA was positively correlated with preoperative EMG activity of the deltoid. Therefore, preoperative EMG measurements of the deltoid and upper trapezius may predict clinical outcomes after RSA.