Deltoid Muscle Volume After Superior Capsule Reconstruction in Patients With Irreparable Rotator Cuff Tears: A 3-Dimensional Magnetic Resonance Imaging Analysis

Abstract

Background:

Shoulder function improvement after superior capsule reconstruction (SCR) for irreparable rotator cuff tears is thought to be due primarily to increased efficiency of the remaining shoulder muscles and to restoration of glenohumeral superior stability. However, the role of the deltoid muscle after SCR remains unclear.

Purpose:

To investigate deltoid muscle volume change after SCR and its association with clinical outcomes.

Study Design:

Case series; Level of evidence: 4

Methods:

A total of 29 patients who underwent arthroscopic SCR using a fascia lata autograft were included. All received the same postoperative physical therapy. Active shoulder abduction and external rotation and American Shoulder and Elbow Surgeons (ASES) and Japanese Orthopaedic Association (JOA) scores were assessed preoperatively and 2 years postoperatively. Additionally, the acromiohumeral distance (AHD), rotator cuff tear size, and Goutallier/Fuchs and Hamada classifications were evaluated. Preoperative and postoperative deltoid muscle volumes were measured using a 3-dimensional reconstructed model from magnetic resonance imaging scans.

Results:

Across the whole group, active elevation, active external rotation, ASES score, and JOA score were significantly increased 2 years after SCR (P < .001). The change in deltoid muscle volume after SCR was significantly positively correlated with the change in active elevation (P = .004; r = 0.52), ASES score (P = .03; r = 0.42), and JOA score (P = .005; r = 0.51). Deltoid muscle volume was increased after SCR in 18 patients and decreased in 11. Patients in the increased volume group were significantly younger than those in the decreased volume group at the time of surgery (P = .04). Two years after surgery, the increased volume group had a significantly greater AHD than the decreased volume group (P = .04), although before SCR there was no significant between-group difference in AHD.

Conclusion:

The change in deltoid muscle volume was significantly positively correlated with the changes in active elevation, ASES score, and JOA score after SCR. This suggests that deltoid muscle strengthening should be recommended to improve shoulder function after SCR. An increase in AHD, which represents the restoration of glenohumeral superior stability, after SCR may be necessary to improve deltoid function.

Keywords

deltoid irreparable muscle volume superior capsule reconstruction rotator cuff tear

Managing chronic large to massive rotator cuff tears is a continuing challenge in orthopaedics. Several surgical treatment options have been described, including partial and complete tendon repair, tendon transfer, and reverse total shoulder arthroplasty.^{5,10,11,14,16} However, the complete repair of chronic large to massive rotator cuff tears is difficult to achieve and is associated with poor healing rates.^14,36 Reverse total shoulder arthroplasty is a reliable surgical option for improving function and relieving shoulder pain in older patients. However, the procedure is associated with high complication rates in young patients.^12,34 Recently, superior capsule reconstruction (SCR) was developed as an alternative joint-preserving procedure for chronic irreparable rotator cuff tear.^27,29 In this technique, a fascia lata autograft or dermal allograft is attached medially to the superior glenoid and laterally to the greater tuberosity.^4,8,29,31 Several studies have demonstrated favorable short- and midterm clinical results, with significant improvements after SCR in patient-reported scores, shoulder function, and active elevation, as well as reversal of pseudoparalysis in patients with chronic irreparable rotator cuff tear.^4,28-31

The postoperative functional improvement achieved by this technique is thought to be associated primarily with both improved deltoid muscle function and glenohumeral superior stability achieved through SCR.²⁹ However, the change in deltoid muscle volume after SCR, and its relationship with clinical outcomes, remains unclear. Here, we hypothesized that changes in the deltoid muscle affect the clinical outcomes after SCR, as the role of the deltoid muscle after rotator cuff repair has been well established.^{6,9,15,17,23-25,37,38} Our objective was to investigate the changes in deltoid muscle volume after SCR and to assess the relationship between muscle volume changes and clinical outcomes in patients with irreparable rotator cuff tear treated with SCR. We hypothesized that change in the deltoid muscle volume after SCR would be positively correlated with clinical outcomes and would be affected by glenohumeral superior stability after the surgery.

Methods

Patient Selection

The study protocol was approved by the Institutional Review Board of Osaka Medical and Pharmaceutical University (No. 2782). We retrospectively reviewed our database of rotator cuff tear cases. We initially included 39 consecutive shoulders that had been diagnosed at our institution with chronic irreparable rotator cuff tear and treated with arthroscopic SCR between 2013 and 2017. The inclusion criteria were chronic irreparable rotator cuff tear, a minimum follow-up duration of 2 years, and completion of plain radiography and magnetic resonance imaging (MRI) examinations and clinical assessments preoperatively and 2 years postoperatively. The exclusion criteria were insufficient MRI scans, concomitant fracture of the shoulder girdle, graft tear, infection, irreparable subscapularis tear, axillary nerve palsy, or symptomatic cervical radiculopathy based on clinical assessment and MRI. We excluded 10 patients from the study: 4 with insufficient MRI scans, 2 with cervical radiculopathy, 2 with irreparable subscapularis tear, 1 with a fracture of the greater tuberosity, and 1 with infection of the affected shoulder. Consequently, 29 shoulders of 29 patients were included in the study. The patients comprised 16 men and 13 women, with a mean age of 67.9 ± 7.2 years (range, 49-82 years) at the time of surgery.

Clinical Outcome Assessment

All patients were assessed for clinical and structural outcomes preoperatively and 2 years after surgery in our clinic. Active shoulder elevation and external rotation were measured with a goniometer in a seated position. Shoulder function was assessed using the American Shoulder and Elbow Surgeons (ASES) shoulder index and the Japanese Orthopaedic Association (JOA) index. Both are 100-point scoring systems. Acromiohumeral distance (AHD)³³ and Hamada grade¹⁹ were evaluated using standard anteroposterior radiographs. The Goutallier classification (modified for MRI) to assess fatty degeneration of the supraspinatus muscle was evaluated using MRI.^13,18

Surgical Procedures

The SCR surgical procedures were performed arthroscopically by a senior shoulder surgeon (T.M.) using a fascia lata autograft. The surgical procedure used has been described previously.^29,31 Briefly, the graft was folded 2 or 3 times to achieve a thickness of 6 to 10 mm. The prepared graft was then inserted into the subacromial space through the lateral portal. The medial side of the graft was attached to the superior glenoid using 2 suture anchors. The lateral side of the graft was attached to the rotator cuff footprint on the greater tuberosity by using the SpeedBridge technique with SwiveLock anchors and FiberTape sutures (Arthrex) at 30° to 45° of shoulder abduction. Finally, 2 side-to-side sutures with No. 2 FiberWire nonabsorbable sutures (Arthrex) were added between the graft and the infraspinatus tendon or teres minor tendon.

Postoperative Protocol

Each patient wore a shoulder abduction sling (Block Shoulder Abduction Sling; Nagano Prosthetics & Orthotics) for 4 weeks after the surgery. The arm was then immobilized in an arm sling for 1 week. This was followed by passive exercise initiated with the help of physical therapists to promote scapular plane elevation. At 8 weeks after SCR, patients began to perform exercises to strengthen the rotator cuff, deltoid, and scapular stabilizers. Physical therapists assisted all patients.

Deltoid Muscle Volume Measurement

All patients underwent shoulder MRI examination preoperatively and at 2 years postoperatively. The MRI examinations were performed with a 3.0-T scanner (Achieva; Philips Healthcare). None of the 29 shoulders showed signs of graft tear on the MRI scans obtained 2 years after surgery. The MRI scans were stored in the Digital Imaging and Communications in Medicine format and transferred to a dedicated 3-dimensional volume analysis system (Synapse Vincent; Fujifilm Medical Systems) for review and volume measurement of the deltoid muscle.

Muscle volume was measured by reconstructing a 3-dimensional muscle model from MRI cross sections, in accordance with techniques used previously to measure the gluteus medius in osteoarthritis of the hip and free-flap volume changes in head and neck reconstructions.^32,41 The portions of the deltoid and supraspinatus muscles to be measured were determined on the basis of the diameter of the humeral head, because the standard shoulder MRI for rotator cuff tear evaluation did not include the entire deltoid muscle (Figure 1A). To include the maximum muscle volume available on the MRI scan, the deltoid muscle volume was measured on consecutive axial cross sections from the level of the acromion undersurface to 1.1 lengths of the humeral head diameter distally (Figure 1B).

Figure 1.

Humeral head diameter and measurement range determination. (A) Measurement of the humeral head diameter on a midcoronal magnetic resonance imaging slice. (B) Range of the deltoid muscle to be measured (dotted area). A indicates the line connecting the superior and inferior articular margins; B, the line touching the superior point of the humeral head; and C, the line touching the most inferior point of the humeral head. The dashed line represented by D shows the humeral head diameter.

We measured the muscle volumes on T2-weighted MRI sequences, with a slice thickness of 3 mm. We carefully defined the muscle by excluding the surrounding fat and connective tissue. The cross-sectional muscle area on each slice was marked in green (Figure 2). The software reconstructed the 3-dimensional model (Figure 3) and calculated the muscle volume. Two assessors independently analyzed the muscle volume twice. Our muscle volume measurement technique showed excellent reliability, with intra- and interobserver intraclass correlation coefficients of 0.813 and 0.961, respectively.

Figure 2.

Manual tracing of the deltoid muscle on magnetic resonance imaging cross sections. The cross-sectional area of the deltoid muscle was marked in green on each axial section of the T2-weighted images for 3-dimensional muscle model reconstruction.

Figure 3.

Reconstructed 3-dimensional model of the deltoid muscle.

Statistical Analysis

To assess the factors associated with an increase in the deltoid muscle volume, the 29 patients were allocated to 2 groups after a comparison of the deltoid muscle volume between before and 2 years after SCR, namely (1) an increased deltoid muscle volume group and (2) a decreased deltoid muscle volume group. An unpaired t test was used to compare age at the time of surgery, tear size in the anterior-posterior direction, AHD, and clinical outcomes between the increased and decreased deltoid muscle volume groups. Sex, torn tendons, Goutallier classification of the supraspinatus muscle, and Hamada classification were compared between the 2 groups using chi-square tests. A paired t test was used to compare the clinical outcomes before SCR with those 2 years after SCR. We used the Pearson correlation coefficient to analyze the relationship between muscle volume and clinical outcomes. All statistical analyses were performed using Statistica software (Version 6; StatSoft). Values are given as means and standard deviations or ranges, where appropriate. A significant difference was defined as a P value <.05.

We used the G*Power3 package to perform a power analysis after data collection. We calculated the power (1–β) of comparison between the preoperative and postoperative values by defining the sample size as 29, the threshold of significance (α) as .05, and the effect size as 1.80 for active elevation, 0.97 for active external rotation, 3.74 for the ASES score, and 3.74 for the JOA score. According to the power analysis, the comparison between preoperative and postoperative values had a power of 1.0 for active elevation, 0.99 for active external rotation, 1.0 for the ASES score, and 1.0 for the JOA score.

Results

Deltoid Muscle Volume

The mean deltoid muscle volume calculated from the MRI scans preoperatively was 125.3 ± 32.6 mL, whereas that calculated 2 years after surgery was 128.0 ± 38.0 mL (Table 1). The increased deltoid muscle volume group consisted of 18 patients, and the decreased deltoid muscle volume group consisted of 11 patients.

Table 1

Deltoid Muscle Volume ^a

	Before SCR, mL	2 y After SCR, mL
Total (n = 29)	125.3 (87.9-184.5)	128.0 (73.6-189.9)
Increased volume (n = 18)	130.7 (88.7-180.7)	141.0 (92.2-189.9)
Decreased volume (n = 11)	116.6 (87.9-184.5)	106.9 (73.6-183.0)

Values are given as mean (range). SCR, superior capsule reconstruction.

Clinical Outcomes After SCR

In the group as a whole, active elevation (mean, 78°-165°; P< .001) and active external rotation (mean, 20°-40°; P< .001) were significantly increased 2 years after SCR. In the subgroup analysis, both the increased deltoid muscle volume group and the decreased volume group had significant increases in active elevation and external rotation 2 years after SCR (P < .001) (Table 2). The overall ASES (mean, 32°-95°; P < .001) and JOA (mean, 47°-93°; P < .001) scores were also significantly increased 2 years after SCR. Subgroup analysis revealed significant increases in the ASES and JOA scores after SCR in both the increased and decreased deltoid muscle volume groups (P < .001) (Table 2). The increases in the active elevation (P < .001) and JOA score (P = .02) in the increased deltoid muscle volume group were significantly larger than those in the decreased volume group.Both the increased deltoid muscle volume group and the decreased volume group had significant increases in AHD 2 years after SCR (P < .001). Preoperative active elevation (P < .001) and JOA score (P = .006) were significantly different between the increased deltoid muscle volume group and the decreased volume group.When we compared preoperative and postoperative active elevation, active external rotation, ASES score, and JOA score between the younger group (<70 years) and older group (≥70 years), there was no statistically significant difference.

Table 2

Clinical Outcomes After SCR ^a

	Before SCR	2 y After SCR	Increased Values After SCR	P (Before SCR vs 2 y After SCR)
Active elevation, deg
Total (n = 29)	78 ± 53	165 ± 12		<.001
Increased deltoid volume (n = 18)	52 ± 45	161 ± 14	109 ± 43	<.001
Decreased deltoid volume (n = 11)	120 ± 35	172 ± 4	52 ± 35	<.001
P (increased deltoid vs decreased deltoid)			<.001
Active external rotation, deg
Total (n = 29)	20 ± 23	40 ± 17		<.001
Increased deltoid volume (n = 18)	14 ± 24	35 ± 19	21 ± 22	<.001
Decreased deltoid volume (n = 11)	31 ± 16	49 ± 11	18 ± 21	.02
P (increased deltoid vs decreased deltoid)			.73
ASES score
Total (n = 29)	32 ± 19	95 ± 6		<.001
Increased deltoid volume (n = 18)	28 ± 18	95 ± 6	68 ± 18	<.001
Decreased deltoid volume (n = 11)	39 ± 19	94 ± 6	55 ± 18	<.001
P (increased deltoid vs decreased deltoid)			.08
JOA score
Total (n = 29)	47 ± 14	93 ± 5		<.001
Increased deltoid volume (n = 18)	41 ± 12	93 ± 5	51 ± 13	<.001
Decreased deltoid volume (n = 11)	55 ± 13	94 ± 5	39 ± 14	<.001
P (increased deltoid vs decreased deltoid)			.02

Values are given as mean ± SD. ASES, American Shoulder and Elbow Surgeons; JOA, Japanese Orthopaedic Association; SCR, superior capsule reconstruction.

Comparison Between Increased and Decreased Deltoid Muscle Volume Groups

At the time of surgery, patients in the increased deltoid muscle volume group were significantly younger than those in the decreased volume group (P = .04) (Table 3). Two years after surgery, the increased volume group had a significantly larger AHD than the decreased volume group (P = .04), although before SCR there was no significant difference in the AHD between the 2 groups (Table 3). Sex, tear size, torn tendons, Goutallier classification of the supraspinatus muscle, and Hamada classification before or after the surgery did not differ significantly between the 2 groups. There was no significant difference in preoperative muscle volume between the 2 groups.

Table 3

Comparison Between Increased and Decreased Deltoid Muscle Volumes ^a

	Increased Deltoid	Decreased Deltoid	P (Increased vs Decreased)
	(n = 18)	(n = 11)	P (Increased vs Decreased)
Age at surgery, y	65.8 (49-78)	71.3 (64-82)	.04
Sex (shoulders)			.11
Male	12	4
Female	6	7
Tear size in anterior-posterior direction, cm	3.3 (2.5-5)	2.8 (2-4)	.07
Torn tendons (shoulders)			.30
2 tendons: supraspinatus and infraspinatus	12	10
3 tendons: supraspinatus, infraspinatus, and subscapularis	4	1
3 tendons: supraspinatus, infraspinatus, and teres minor	2	0
Goutallier class of supraspinatus muscle			.63
1	0	0
2	1	0
3	6	5
4	11	6
AHD, cm
Preoperative	4.4 (0.9-8.1)	3.8 (0.5-11.0)	.54
2 y after SCR	8.1 (3.9-12.7)	6.2 (3.7-10.0)	.04
Hamada class before surgery			.96
1	4	2
2	5	3
3	9	6
4	0	0
Hamada class at 2 y after SCR			.09
1	15	6
2	2	5
3	1	0
4	0	0

Values are given as mean (range) or n unless otherwise indicated. AHD, acromiohumeral distance; SCR, superior capsule reconstruction.

Relationship Between Deltoid Muscle Volume and Clinical Outcomes

The change in the deltoid muscle volume was significantly positively correlated with the change in active elevation (P= .004; r = 0.52), the ASES score (P = .03; r = 0.42), and the JOA score (P = .005; r = 0.51). There was no significant correlation between the change in the deltoid muscle volume and the change in active external rotation (P = .36) (Figure4).

Figure 4.

Relationships between changes in deltoid muscle volume and clinical outcomes, namely changes in (A) active elevation, (B) active external rotation (ER), (C) American Shoulder and Elbow Surgeons (ASES) score, and (D) Japanese Orthopaedic Association (JOA) score. SCR.

Discussion

We evaluated deltoid muscle volume using a 3-dimensional reconstruction model based on MRI data before SCR and 2 years after SCR to assess changes in deltoid muscle volume after SCR. We found that the change in deltoid muscle volume after SCR varied, and not all patients had an increase in deltoid muscle volume after surgery even though they underwent the same physical therapy, including muscle training. Therefore, we investigated the factors influencing the increase in deltoid muscle volume after SCR by comparing the increased deltoid muscle volume group and the decreased volume group.We found that age at the time of surgery and AHD influenced the change in deltoid muscle volume. The increased deltoid muscle volume group was significantly younger than the decreased volume group.Therefore, muscle strength may improve more after SCR in younger patients, because muscle volume is positively correlated with muscle strength.^1-3,20,21,35 Also, the increased deltoid muscle volume group had a larger AHD after SCR, suggesting that normalized location of the humeral head relative to the glenoid may be necessary to improve deltoid function. Conversely, decreased tension of the deltoid muscle fibers due to a superior shift of the humeral head (ie, decreased AHD) may reduce an improvement in deltoid muscle strength, because decreased AHD represents a decrease in length between the proximal (acromion) and distal (humerus) attachments of the deltoid muscle.

In the current study, active elevation, active external rotation, ASES score, and JOA score were significantly improved 2 years after SCR in both the increased deltoid muscle volume group and the decreased volume group.A possible explanation for this is that restoration of shoulder function in the decreased deltoid muscle volume group after SCR resulted from the restoration of shoulder superior stability, which can improve shoulder function in patients with rotator cuff tears.³⁹ However, we also found that the change in the deltoid muscle volume was significantly positively correlated with changes in active elevation, ASES score, and JOA score after SCR. Furthermore, the increases in active elevation and JOA score in the increased deltoid muscle volume group were significantly larger than those in the decreased volume group.These results suggest that deltoid muscle strengthening may be recommended to obtain better shoulder function, especially better active elevation, even though shoulder function can be improved without increasing deltoid muscle volume.

Clinical studies have postulated that graft healing and an increase in the AHD are important for achieving better clinical outcomes.^22,26 Mihata etal^30,31 emphasized that graft healing was the key to success and reported an AHD increase by a mean of 4.1 or 4.3 mm in patients with healed grafts at last follow-up.Lee and Min²² reported that inadequate AHD improvement was a predictor of graft tear. They reported that the increment between the immediate postoperative and preoperative AHDs was 1.6 mm in a retear-positive group and 3.8 mm in a retear-negative group.Here, all our patients demonstrated graft healing on the basis of their MRI findings 2 years after surgery. Also, radiographic assessment showed that the 2-year postoperative AHD values were significantly larger than the preoperative values. This was consistent with the findings in patients with healed grafts in previous studies, suggesting that superior shoulder stability could be restored in our patients by SCR.^22,31 Furthermore, 2 years after surgery, AHD in the increased deltoid muscle volume group was significantly larger than that in the decreased volume group.According to these results, the increase in AHD after SCR may lead to both improvement of deltoid muscle function and restoration of glenohumeral superior stability, consequently improving shoulder function.

To our knowledge, this study is the first to investigate the effect of SCR on deltoid muscle volume and the resulting effect on clinical outcomes after SCR. A particular strength of our study is that we used 3-dimensional reconstruction for muscle volume analysis. According to recently published studies, muscle atrophy in a single MRI slice does not predict 3-dimensional measurements.^7,40 Chung etal⁷ measured the 2-dimensional cross-sectional area and 3-dimensional volume of the supraspinatus muscle after rotator cuff repair. They reported significant changes in the 3-dimensional volume, despite a lack of change in the 2-dimensional cross-sectional area.⁷ Therefore, we believe that 3-dimensional muscle volume measurement yielded more accurate and reliable information about the muscle mass and volume changes than would a 2-dimensional cross-sectional area measurement.

Nevertheless, our study has several limitations. First, it lacks data from unsuccessful cases, because patients with graft tear, infection, irreparable subscapularis tear, or deltoid muscle dysfunction secondary to axillary nerve or cervical spine pathology were excluded. Further studies with larger sample sizes and including patients with poor clinical outcomes are warranted to identify the factors predictive of clinical outcomes after SCR. Second, we could not measure the volume of the entire deltoid muscle from the MRI scans owing to constraints imposed by the standard shoulder MRI examination settings for rotator cuff injury. However, we included the maximum muscle volume available on the MRI scans and used the humeral head diameter as a reference to eliminate measurement area bias between patients. Therefore, we believe that the measured values reflect the changes in muscle volume in individual patients. Third, we included only patients who had undergone SCR with a 6 to 10 mm–thick fascia lata autograft. Different graft materials, such as human dermal allografts or synthetic grafts, might give different results. Fourth, in the subgroup analysis, preoperative active elevation was significantly different between 2 groups. Therefore, we compared a change in elevation between 2 groups. Fifth, postoperative deltoid muscle volume was variable even though we applied the same postoperative muscle strengthening. Our muscle strengthening protocol may need to be modified to be beneficial for more patients.

Conclusion

The change in deltoid muscle volume was significantly positively correlated with the changes in active elevation, ASES score, and JOA score after SCR. This suggests that effective deltoid muscle strengthening is recommended to improve shoulder function after SCR. After SCR, an increase in the AHD, which represents the restoration of glenohumeral superior stability, may be necessary to improve deltoid function.

Footnotes

Final revision submitted February 10, 2025; accepted March 28, 2025.

The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto

Ethical approval for this study was obtained from Osaka Medical and Pharmaceutical University (No. 2782).

ORCID iDs

Nor Zarini Yusoff

Teruhisa Mihata

References

Audenaert

De Roo

Mahieu

, et al. Deltoid muscle volume estimated from ultrasonography: in vitro validation and correlation with isokinetic abduction strength of the shoulder. Med Biol Eng Comput. 2009;47(5):557-563.

Baek

Kim

SJ.

Increased latissimus dorsi and teres major muscle volume after anterior transfer for irreparable anterior superior rotator cuff tear: correlation with improved internal rotation strength. Arch Orthop Trauma Surg. 2024;144:1491-1502.

Bchini

Hammami

Moussaoui

, et al. Relationship between muscle power, muscle volume and limb length in healthy male and female adolescents. Front Sports Act Living. 2024;6:1457948.

Burkhart

Hartzler

RU.

Superior capsular reconstruction reverses profound pseudoparalysis in patients with irreparable rotator cuff tears and minimal or no glenohumeral arthritis. Arthroscopy. 2019;35(1):22-28.

Burkhart

Nottage

Ogilvie-Harris

Kohn

Pachelli

Partial repair of irreparable rotator cuff tears. Arthroscopy. 1994;10(4):363-370.

Chung

Kim

Tae

Yoon

Choi

JH.

Is the supraspinatus muscle atrophy truly irreversible after surgical repair of rotator cuff tears?

Clin Orthop Surg. 2013;5(1):55-65.

Chung

Moon

, et al. Serial changes in 3-dimensional supraspinatus muscle volume after rotator cuff repair. Am J Sports Med. 2017;45(10):2345-2354.

Denard

Brady

Adams

Tokish

Burkhart

SS.

Preliminary results of arthroscopic superior capsule reconstruction with dermal allograft. Arthroscopy. 2018;34(1):93-99.

Deniz

Kose

Tugay

Guler

Turan

Fatty degeneration and atrophy of the rotator cuff muscles after arthroscopic repair: does it improve, halt or deteriorate?

Arch Orthop Trauma Surg. 2014;134(7):985-990.

10.

Elhassan

Wagner

Werthel

JD.

Outcome of lower trapezius transfer to reconstruct massive irreparable posterior-superior rotator cuff tear. J Shoulder Elbow Surg. 2016;25(8):1346-1353.

11.

Ernstbrunner

Andronic

Grubhofer

Camenzind

Wieser

Gerber

Long-term results of reverse total shoulder arthroplasty for rotator cuff dysfunction: a systematic review of longitudinal outcomes. J Shoulder Elbow Surg. 2019;28(4):774-781.

12.

Ernstbrunner

Suter

Catanzaro

Rahm

Gerber

Reverse total shoulder arthroplasty for massive, irreparable rotator cuff tears before the age of 60 years: long-term results. J Bone Joint Surg Am. 2017;99(20):1721-1729.

13.

Fuchs

Weishaupt

Zanetti

Hodler

Gerber

Fatty degeneration of the muscles of the rotator cuff: assessment by computed tomography versus magnetic resonance imaging. J Shoulder Elbow Surg. 1999;8(6):599-605.

14.

Galatz

Ball

Teefey

Middleton

Yamaguchi

The outcome and repair integrity of completely arthroscopically repaired large and massive rotator cuff tears. J Bone Joint Surg Am. 2004;86(2):219-224.

15.

Gerber

Fuchs

Hodler

The results of repair of massive tears of the rotator cuff. J Bone Joint Surg Am. 2000;82(4):505-515.

16.

Gerber

Rahm

Catanzaro

Farshad

Moor

BK.

Latissimus dorsi tendon transfer for treatment of irreparable posterosuperior rotator cuff tears: long-term results at a minimum follow-up of ten years. J Bone Joint Surg Am. 2013;95(21):1920-1926.

17.

Gladstone

Bishop

Flatow

EL.

Fatty infiltration and atrophy of the rotator cuff do not improve after rotator cuff repair and correlate with poor functional outcome. Am J Sports Med. 2007;35(5):719-728.

18.

Goutallier

Postel

Bernageau

Lavau

Voisin

MC.

Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan. Clin Orthop Relat Res. 1994;304:78-83.

19.

Hamada

Yamanaka

Uchiyama

Mikasa

A radiographic classification of massive rotator cuff tear arthritis. Clin Orthop Relat Res. 2011;469(9):2452-2460.

20.

Alter

Brochard

Pons

Sheehan

FT.

In vivo pediatric shoulder muscle volumes and their relationship to 3D strength. J Biomech. 2014;47(11):2730-2737.

21.

Lanza

Martins-Costa

De Souza

Lima

Diniz

RCR

Chagas

MH.

Muscle volume vs. Anatomical cross-sectional area: different muscle assessment does not affect the muscle size-strength relationship. J Biomech. 2022;132:110956.

22.

Lee

Min

YK.

Can inadequate acromiohumeral distance improvement and poor posterior remnant tissue be the predictive factors of re-tear? Preliminary outcomes of arthroscopic superior capsular reconstruction. Knee Surg Sports Traumatol Arthrosc. 2018;26(7):2205-2213.

23.

Maman

Harris

White

Tomlinson

Shashank

Boynton

Outcome of nonoperative treatment of symptomatic rotator cuff tears monitored by magnetic resonance imaging. J Bone Joint Surg Am. 2009;91(8):1898-1906.

24.

Melis

DeFranco

Chuinard

Walch

Natural history of fatty infiltration and atrophy of the supraspinatus muscle in rotator cuff tears. Clin Orthop Relat Res. 2010;468(6):1498-1505.

25.

Melis

Nemoz

Walch

Muscle fatty infiltration in rotator cuff tears: descriptive analysis of 1688 cases. Orthop Traumatol Surg Res. 2009;95(5):319-324.

26.

Mihata

Editorial commentary: Superior capsule reconstruction: graft healing for success. Arthroscopy. 2018;34(1):100-101.

27.

Mihata

Bui

CNH

Akeda

, et al. A biomechanical cadaveric study comparing superior capsule reconstruction using fascia lata allograft with human dermal allograft for irreparable rotator cuff tear. J Shoulder Elbow Surg. 2017;26(12):2158-2166.

28.

Mihata

Lee

Fukunishi

, et al. Return to sports and physical work after arthroscopic superior capsule reconstruction among patients with irreparable rotator cuff tears. Am J Sports Med. 2018;46(5):1077-1083.

29.

Mihata

Lee

Hasegawa

, et al. Arthroscopic superior capsule reconstruction can eliminate pseudoparalysis in patients with irreparable rotator cuff tears. Am J Sports Med. 2018;46(11):2707-2716.

30.

Mihata

Lee

Hasegawa

, et al. Five-year follow-up of arthroscopic superior capsule reconstruction for irreparable rotator cuff tears. J Bone Joint Surg Am. 2019;101(21):1921-1930.

31.

Mihata

Lee

Watanabe

, et al. Clinical results of arthroscopic superior capsule reconstruction for irreparable rotator cuff tears. Arthroscopy. 2013;29(3):459-470.

32.

Momose

Inaba

Choe

Kobayashi

Tezuka

Saito

CT-based analysis of muscle volume and degeneration of gluteus medius in patients with unilateral hip osteoarthritis. BMC Musculoskelet Disord. 2017;18(1):457.

33.

Petersson

Redlund-Johnell

The subacromial space in normal shoulder radiographs. Acta Orthop Scand. 1984;55(1):57-58.

34.

Sershon

Van Thiel

Lin

, et al. Clinical outcomes of reverse total shoulder arthroplasty in patients aged younger than 60 years. J Shoulder Elbow Surg. 2014;23(3):395-400.

35.

Seto

Yukata

Fujii

, et al. Structural and functional alterations of the deltoid muscle after arthroscopic rotator cuff repair: a 2-year longitudinal observation study. Orthop J Sports Med. 2024;12(10):23259671241275667.

36.

Sugaya

Maeda

Matsuki

Moriishi

Repair integrity and functional outcome after arthroscopic double-row rotator cuff repair. A prospective outcome study. J Bone Joint Surg Am. 2007;89(5):953-960.

37.

Thomazeau

Rolland

Lucas

Duval

Langlais

Atrophy of the supraspinatus belly. Assessment by MRI in 55 patients with rotator cuff pathology. Acta Orthop Scand. 1996;67(3):264-268.

38.

Turkmen

Altun

Increasing the deltoid muscle volume positively affects functional outcomes after arthroscopic rotator cuff repair. Knee Surg Sports Traumatol Arthrosc. 2019;27(1):259-266.

39.

Ueda

Tanaka

Tomita

, et al. Comparison of shoulder muscle strength, cross-sectional area, acromiohumeral distance, and thickness of the supraspinatus tendon between symptomatic and asymptomatic patients with rotator cuff tears. J Shoulder Elbow Surg. 2020;29(10):2043-2050.

40.

Vidt

Santago

II Tuohy

, et al. Assessments of fatty infiltration and muscle atrophy from a single magnetic resonance image slice are not predictive of 3-dimensional measurements. Arthroscopy. 2016;32(1):128-139.

41.

Yamaguchi

Kimata

Onoda

Mizukawa

Onoda

Quantitative analysis of free flap volume changes in head and neck reconstruction. Head Neck. 2012;34(10):1403-1407.