Infraspinatus Research Articles

Anatomical analysis of the motor endplate zones of the suprascapular nerve to the infraspinatus muscle and its clinical significance in managing pain disorder.

Myofascial pain syndrome caused by myofascial trigger points is a musculoskeletal disorder commonly encountered in clinical practice. The infraspinatus muscle is the region most frequently involved in the myofascial pain syndrome in the scapular region. The characteristics of the myofascial trigger points are that they can be found constantly in the motor endplate zone. However, localizing myofascial trigger points within the motor endplate zone and establishing an accurate injection site of the infraspinatus muscle has been challenging because the anatomical position of the motor endplate zone of the infraspinatus muscle is yet to be described. Therefore, this cadaveric study aimed to scrutinize the motor endplate zone of the infraspinatus muscle, propose potential myofascial trigger points within the muscle, and recommend therapeutic injection sites. Twenty specimens of the infraspinatus muscle for nerve staining and 10 fresh frozen cadavers for evaluation of the injection were used in this study. The number of nerve branches penetrating the infraspinatus muscle and their entry locations were analyzed and photographed. Modified Sihler's staining was performed to examine the motor endplate regions of the infraspinatus muscle. The nerve entry points were mostly observed in the center of the muscle belly. The motor endplate was distributed equally throughout the infraspinatus muscle, but the motor endplate zone was primarily identified in the B area, which is approximately 20-40% proximal to the infraspinatus muscle. The second-most common occurrence of the motor endplate zone was observed in the center of the muscle. These detailed anatomical data would be very helpful in predicting potential pain sites and establishing safe and effective injection treatment using botulinum neurotoxin, steroids, or lidocaine to alleviate the pain disorder of the infraspinatus muscle.

Investigation of pain sensitivity following 3 nights of disrupted sleep in healthy individuals.

Poor quality sleep is a common complaint among people with chronic pain. The co-occurrence of poor sleep quality and chronic pain often comes with increased pain intensity, more disability and a higher cost of healthcare. Poor sleep has been suggested to affect measures of peripheral and central pain mechanisms. To date, sleep provocations are the only models proven to affect measures of central pain mechanisms in healthy subjects. However, there are limited studies investigating the effect of several nights of sleep disruption on measures of central pain mechanisms. The current study implemented three nights of sleep disruption with three planned awakenings per night in 30 healthy subjects sleeping at home. Pain testing was conducted at the same time of day at baseline and follow-up for each subject. Pressure pain thresholds were assessed bilaterally on the infraspinatus and gastrocnemius muscles. Using handheld pressure algometry, suprathreshold pressure pain sensitivity and area were also investigated on the dominant infraspinatus muscle. Cuff-pressure pain detection and tolerance thresholds, temporal summation of pain and conditioned pain modulation were investigated using cuff-pressure algometry. Temporal summation of pain was significantly facilitated (p= 0.022), suprathreshold pain areas (p= 0.005) and intensities (p< 0.05) were significantly increased, and all pressure pain thresholds were decreased (p< 0.005) after sleep disruption compared to baseline. The current study found that three consecutive nights of sleep disruption at home induced pressure hyperalgesia and increased measures of pain facilitation in healthy subjects, which is consistent with previous findings. Poor quality of sleep is often experienced by patients with chronic pain, with the most common complaint being nightly awakenings. This exploratory study is the first to investigate changes in measures of central and peripheral pain sensitivity in healthy subjects after sleep disruptions for three consecutive nights without any restrictions on total sleep time. The findings suggest that disruptions to sleep continuity in healthy individuals can induce increased sensitivity to measures of central and peripheral pain sensitization.

Strain distribution in the bursal rotator cuff based on whole-muscle and muscle subregion-specific loading: A cadaveric study.

Rotator cuff (RC) tears are common injuries leading to significant dysfunction of the shoulder. Rotator cuff tears alter tension and strain in muscles and tendons. Anatomical studies demonstrated that rotator cuff muscles are comprised of anatomical subregions. However, the strain distribution within the rotator cuff tendons generated from the tension from each anatomical subregion is unknown. We hypothesized that subregions would present distinct 3-dimensional (3D) strain distributions within the rotator cuff tendons, and that the anatomical insertion configuration of the supraspinatus (SSP) and infraspinatus (ISP) tendons might dictate strain, thus tension, transmission. 3D-strains in the bursal side of the SSP and ISP tendons of eight fresh-frozen cadaveric intact shoulders were obtained by applying tension on the whole SSP and ISP muscles, and on their subregions using an MTS system. Strains in the anterior region of the SSP tendon were higher than in the posterior region with whole-SSPanterior-region (p < 0.05) and whole-SSP muscle loading. Higher strains were observed in the inferior half of the ISP tendon with whole-ISP muscle (p < 0.05), middle-subregion (p < 0.01), and superior-subregion (p < 0.05) loading. Tension generating from the posterior-region of the SSP was primarily transmitted to the middle facet via an overlap between the SSP and ISP tendons insertions, while the anterior-region mainly distributed its tension into the superior facet. Tension generating from the middle and superior-regions of the ISP was distributed into the inferior portion of the ISP tendon. These results emphasize the importance of the distinct anatomical subregions of the SSP and ISP muscles in distributing the tension to the tendons.

Relationship between rotator cuff posterior delamination and subscapularis tear: a large cross-sectional analysis

Rotator cuff posterior delamination and subscapularis tear are commonly observed in rotator cuff injuries. However, there are very few studies on the relationship between posterior delamination and subscapularis tendon tear. This study aimed to investigate the relationship between posterior delamination and subscapularis tendon tear. The study was conducted from March 2018 to June 2021 with 553 patients who underwent rotator cuff repairs at two institutions. The age and gender, size of rotator cuff tear, duration of symptoms, range of motion of shoulder joint, visual analog scale score, Korean Shoulder Scale score, gap and width of rotator cuff tear, and fatty degeneration of the supraspinatus and infraspinatus muscles were compared to confirm the differences between a delaminated and nondelaminated rotator cuff tear. Moreover, the proportions of the subscapular tendon rupture and subscapularis tendon rupture according to the size of the rotator cuff tear were analyzed in both the delaminated and nondelaminated rotator cuff tear groups. Compared to the nondelaminated rotator cuff tear group, the age of the delaminated rotator cuff tear group was significantly higher, and as the size of the rotator cuff tear increased, the proportion of delaminated tear increased (P<.001). Furthermore, the duration of symptoms was longer, visual analog scale score was higher, Korean Shoulder Scale score was lower, gap and width of rotator cuff as well as fatty degeneration of the supraspinatus and infraspinatus were more severe in the group with posterior delamination than that without. In the nondelaminated rotator cuff tear group, 212 subjects (84.46%) had no subscapularis tear, and 39 subjects (15.54%) had subscapularis tear. In the delaminated rotator cuff tear group, 103 subjects (34.11%) had no subscapular tendon tear while 199 subjects (65.89%) had a subscapular tendon tear (P<.001). Furthermore, as the size of the rotator cuff tear increased, the rate of subscapular tendon tear increased in both the delaminated and nondelaminated rotator cuff tear groups. The results suggest that there is a high probability of concomitant rupture of the subscapularis tendon in the patient group with posterior delamination tear. Therefore, it should be noted that if a posterior delamination is confirmed during surgery, it is necessary to carefully check for rupture of the scapular tendon.

Validation of the Measuring Protocol for the Infraspinatus Muscle with M-Mode Ultrasound in Asymptomatic Subjects. Intra- and Inter-examiner Reliability Study

M-mode ultrasound is a reliable and valid instrument for assessing muscle activity. However, it has not been studied in any of the muscles belonging to the shoulder joint complex, particularly in the infraspinatus muscle. The aim of this study is the validation of the infraspinatus muscle activity measurement protocol with the M-mode ultrasound in asymptomatic subjects. Sixty asymptomatic volunteers were evaluated by two physiotherapists who were blinded; each of them carried out three measurements with the M-mode ultrasound in infraspinatus muscle and analysed the muscle thickness at rest and contraction, velocity of muscle activation and relaxation and Maximum Voluntary Isometric Contraction (MVIC). Intra-observer reliability was significant in both observers, showing good thickness at rest (ICC = 0.833-0.889), thickness in contraction (ICC = 0.861-0.933) and MVIC (ICC = 0.875-0.813); moderate in the activation velocity (ICC = 0.499-0.547) and relaxation velocity (ICC = 0.457-0.606). The inter-observer reliability also had good thickness at rest (ICC = 0.797), thickness in contraction (ICC = 0.89) and MVIC (ICC = 0.84); poor in relaxation time variable (ICC = 0.474) and not significant at the activation velocity (ICC = 0). The muscle activity measurement protocol of the infraspinatus muscle measured with M-mode ultrasound has been found to be reliable in asymptomatic subjects, for both the intra-examiner and inter-examiner.

Arm Function After Arthroscopic Decompression of the Suprascapular Nerve at the Spinoglenoid Notch and Suprascapular Notch in Volleyball Players.

Suprascapular nerve (SSN) entrapment in volleyball players leads to infraspinatus (ISP) muscle atrophy and weakness of abduction and external rotation (ER) of the shoulder. To assess functional outcome after arthroscopic extended decompression of SSN in the spinoglenoid notch and suprascapular notch in a group of volleyball athletes. Case series; Level of evidence, 4. Volleyballers who underwent arthroscopic SSN decompression were analyzed retrospectively. Assessment tools consisted of range of motion and ER strength on Lovett scale and postoperative ER strength measured by dynamometer, Constant-Murley score (CMS), and visual evaluation of ISP muscle recovery by assessing muscle bulk. The study included 10 patients (9 male and 1 female). The mean age was 25.9 years (range, 19-33) and mean follow-up was 77.9 months (range, 7-123). The mean range of postoperative ER at 90° of abduction (ER2) was 105.6° (88°-126°) and 108.5° (93°-124°) for the contralateral side, while ER2 strength was 8 ± 2.6 and 12.65 ± 2.8 kg (P < .01) respectively. Mean CMS was 89.9 (84-100). In 5 cases, there was complete recovery of ISP muscle atrophy whereas 2 patients had partial recovery and 3 had none. Arthroscopic SSN decompression in volleyball players improves shoulder function, but results of ISP recovery and ER strength are variable.

Does the Fatty Infiltration Influence the Re-tear Rate and Functional Outcome After Rotator Cuff Repair? A Systematic Review and Meta-analysis.

Fatty infiltration (FI) of the rotator cuff muscles occurs after rotator cuff tears (RCTs), which may affect the outcome of the repair procedure. This study aimed to determine the relationship between preoperative FI and the rate of re-tear and functional outcomes after rotator cuff repair. Computerized databases, including PubMed, EMBASE, Web of Science, and Cochrane Library database were searched for studies published from the inception date to January 2022. Two reviewers independently screened the titles and abstracts using prespecified criteria. Articles were included if they clearly stated the effect of varying degrees of FI on the outcome after shoulder cuff repair. Comparison was performed by different degrees of FI analysis: no FI is grade 0-1, FI is grade 2 and above. Statistical analysis was performed using Review Manager 5.4.1 software. A total of 16 articles involving 1383 patients from 8 countries were included. The follow-up period ranged from 8 to 121months. In terms of re-tear rate: patients with preoperative FI had significantly higher rates of re-tear compared with patients without FI (OR 4.60, 95% CI 2.22-9.54, p < 0.0001), supraspinatus FI VS no FI (OR 2.06, 95% CI 1.00-4.24, p = 0.05), infraspinatus FI VS no FI (OR 2.42, 95% CI 1.19-4.91, p = 0.01). In terms of functional scoring: patients without FI had higher postoperative Constant-Murley (Constant) scores than those with FI (MD -5.06, 95% CI -9.40 to -0.72, p = 0.02), there was no clear evidence that preoperative FI was related to postoperative American Society of shoulder and elbow physicians scores and the University of California at Los Angeles scores and range of motion. FI after RCTs significantly increases the risk of postoperative re-tear and leads to worse functional scores, especially FI of the infraspinatus muscle. However, FI does not seem to reduce postoperative range of motion. The online version contains supplementary material available at 10.1007/s43465-022-00807-0.

Evaluation of the anterior shoulder instability using ultrasound shear wave elastography.

This study aims to evaluate the soft tissue stiffness which has a prominent role in shoulder instability using ultrasound (US) shear wave elastography (SWE) and to compare the results with healthy shoulders. Between December 2018 and January 2020, a total of 33 male patients (mean age: 26±4.3 years; range, 18 to 35 years) who underwent arthroscopic repair for traumatic isolated anterior glenohumeral instability were included in this prospective study. The shoulder girdle was evaluated with US SWE in patients with traumatic anterior instability. Deltoid (D), supraspinatus (SS), infraspinatus (IS), subscapularis (SSC), and long head of biceps (LHB) tendons forming the shoulder girdle and anterior labrum (L) were evaluated with SWE. The elasticity and velocity of the tissues were quantitatively measured. The operated shoulders of 33 patients due to isolated traumatic anterior instability were named Group 1, while the healthy shoulders of these patients were named Group 2. Thirty volunteers with healthy shoulders were considered as the control group (Group 3, n=30). All three groups were compared in terms of SS, D, LHB, and SSC tendon velocity and elasticity; however, no statistically significant difference was observed among the groups (p<0.05). The anterior labrum of these three groups did not significantly differ in terms of SWE measurements (p<0.05). The stiffness of shoulder girdle muscle tendons and labrum measured with US SWE does not constitute a risk factor for traumatic anterior shoulder instability.

Anatomical feasibility study of the infraspinatus muscle neurotization by lower subscapular nerve

ABSTRACT Objectives To investigate the anatomical feasibility of the infraspinatus branch of the suprascapular nerve (IB-SSN) reconstruction by lower subscapular nerve (LSN) transfer. Methods The morphological study was performed on 18 adult human cadavers. The length of the distal stump of the IB-SSN, the length of the LSN available for reconstruction and diameter of both stumps were measured. The feasibility study of the LSN to IB-SSN transfer was performed. Results The mean length of the IB-SSN to the end of its first branch was 40.9 mm (±4.6). Its mean diameter was 2.3 mm (±0.3). The mean length of the LSN stump, which was mobilized from its original course and transferred to reach the distal stump of the IB-SSN was 66.5 mm (±11.8). Its mean diameter was 2.1 mm (±0.3). The mean ratio between LSN and IB-SSN diameters was 0.9 (±0.1). The nerve transfer was feasible in 17 out of 18 cases (94.4%). Conclusion This study demonstrates that direct LSN to IB-SSN transfer is anatomically feasible in most cases in the adult population. It may be used in cases of complex scapular fractures resulting in severe suprascapular nerve injury.

Shoulder and Upper Arm Surgery Anaesthesia with Interscalene Approach of Brachial Block and Sedation versus Same Method Adjunct with Additional Suprascapular Nerve Block: A Randomised Controlled Study

Introduction: Interscalene Brachial Plexus Block (ISBPB) block provides optimal analgesia for shoulder and upper arm surgery. However, higher incidence of phrenic nerve palsy limits the application of ISBPB for patients with limited pulmonary reserve. The Supplemented Suprascapular Nerve Block (SSNB) is a landmark based technique that is believed to block the sensory fibres supplying major part of shoulder joint, as well as, supraspinatus and infraspinatus muscles. Aim: To compare the analgesic effect and duration of sensory block in interscalene versus interscalene with SSNB block for shoulder and upper arm surgery. Materials and Methods: This double-blinded randomised controlled study was conducted in a Tertiary Care Institute, from April 2021 to march 2022. Eighty patients posted for shoulder and upper arm surgery were divided into two equal groups (group A and B). In group A (n=40), 30 mL 0.5% levobupivacaine in ISBPB and in group B (n=40), 15 mL 0.5% levobupivacaine in ISBPB+15 mL 0.5% levobupivacaine in SSNB were administered. Demographic data, sensory and motor block, onset times and durations, time to administer first rescue analgesic, total analgesic requirement, indications of upper arm surgeries, surgical bleeding and surgeon’s satisfaction score, postoperative Visual Analogue Scale (VAS) score were recorded for each patient. Results: The onset and duration of sensory and motor block was significantly faster and longer in group B. Consequently, time to administer first rescue analgesic in group A vs group B (325.88±33.23 vs. 348.34±37.12) minutes were significantly delayed and in lesser in amount in group B respectively. On the other hand, suprascapular block reduced the odds of block-related respiratory (group A vs group B are 14 and 10, respectively) complications. In group B postoperative VAS score at 24 hour was significantly lower (p-value &lt;0.05) than group A was (3.5 vs 4.5). Intraoperative haemodynamic parameters were comparable among two groups throughout the study period. Conclusion: SSNB when supplemented with Interscalene Block (ISB) could be an effective adjunct for shoulder and upper arm surgery. This combination prolongs the sensory blockade duration, reduces requirement of analgesics and side-effects in postoperative period.

Effect of 8-week Shoulder External Rotation Exercise with Low Intensity and Slow Movement on Infraspinatus.

Generally, low-intensity training is recommended as selective training of the infraspinatus muscle. This study aimed to investigate whether an 8-week intervention of low-intensity, slow-movement, external rotation exercise of the shoulder led to an increase in muscle strength with shoulder external rotation and cross-sectional area (CSA) infraspinatus muscle. Sixteen healthy male volunteers were randomly assigned to the low-intensity and slow-movement (LS) group (N = 8) or the normal-intensity and normal-speed (NN) group (N = 8). The LS and NN groups performed shoulder external rotation exercises with low intensity and slow movement, and normal intensity and normal speed, respectively. The exercise session consisted of three sets of 10 repetitions, which were performed three times per week for 8 weeks. We measured the CSA of the infraspinatus and muscle strength of the shoulder external rotation before and after the 8-week intervention. A significant increase in infraspinatus CSA from baseline to 8 weeks was found in the LS group (7.3% of baseline) but not in the NN group. No significant differences were found in the muscle strength of shoulder external rotation. Our results suggest that low-intensity exercise of the infraspinatus is effective for muscle hypertrophy when performed with slow movement. This finding may help patients who should avoid excessive stress in the early phase of rehabilitation.

Prevalence of Upper Quadrant Musculoskeletal Disorders among Healthcare Professionals in a Tertiary Care Hospital

Background: Healthcare professionals (HCPs) are vulnerable to acquire musculoskeletal disorders during theirwork routine. Shortage of HCPs, long working hours and mandatory overtime results in overburden on thoseavailable, especially during pandemic such as in COVID -19. Objective of the study was to evaluate the prevalenceof upper quadrant musculoskeletal disorders (UQMSDs) among HCPs.Methodology: A total of 370 HCPs including doctors, dentists, physiotherapists and nurses were evaluated forthe presence of trigger points (TrPs) in upper trapezius, levator scapula, infraspinatus and sternocleidomastoidmuscles, severity of pain (NPRS), neck disability (NDI) and cervical and shoulder ROM (goniometer).Results: The prevalence rate of UQMSDs was found to be high among HCPs. TrPs were more prevalent in uppertrapezius muscle (46.21%) followed by levator scapulae, infraspinatus and sternocleidomastoid muscles. 4.1% ofHCPs reported severe pain, 16.7% reported moderate pain and 48.36% reported mild pain in upper quadrant.0.8% of HCPs had complete, 1.2% had severe, 5.3% had moderate and 37.6% had mild neck disability. The cervicalrotation and shoulder horizontal adduction ROM were found to be more restricted among HCPs.

Appropriate Resistance Intensity for Activation of Infraspinatus and Control of Anterior Translation of the Humeral Head

Background In general, external rotation (ER) exercises are commonly used in rotator cuff retraining programs to improve stabilization ability. ER exercises at 90° of shoulder abduction are common and effective in strengthening the infraspinatus (ISP). However, if the ISP is weak during ER at 90° shoulder abduction, the posterior deltoid muscle (PD) is overactivated, which can lead to anterior translation of the humeral head. Therefore, the selective activation of ISP muscles is an important factor in rehabilitation. Objectives We investigated the muscle activities of the ISP, PD, and middle trapezius (MT), the ratio of the ISP to PD muscle activities, and the anterior translation of the humeral head in response to three resistance intensities during sitting external rotation (SITER) exercises. Methods A total of 12 healthy women recorded changes in the anterior translation of the humeral head using a load cell, the muscle activities of the ISP, PD, and MT, the ratio of the ISP to PD muscle activities using surface electromyography (EMG) during SITER under three different intensities [low (10-20%) medium (45-55%) high (60-70%)]. Results The ISP, PD, and MT amplitudes were highest at high intensity, followed by medium and low intensities during SITER (p < 0.001). The muscle activity ratio was significantly highest at medium intensity compared with low and high intensities (p = 0.031). The anterior translation of the humeral head was highest at high intensity, followed by medium and low intensities during SITER (p < 0.001). Conclusions Medium intensity (45-55%) was the most appropriate intensity during the SITER exercise. However, anterior gliding of the humeral head was the lowest at low intensity. Therefore, during ER exercises, we should think about how to control the anterior gliding of the humeral head.

A Descriptive Study on the Carcass, Muscle, and Offal Yields of the Plains Zebra (Equus quagga) Harvested in Two Seasons

This study presents descriptive data on the meat and offal production of Plains zebras harvested in the winter (n = 8) and summer (n = 12) seasons, at different respective locations in the Western Cape Province of South Africa. The cold dressing percentages were numerically higher for the winter (58.0 ± 0.60%) than for the summer-harvested animals (56.60 ± 0.70%). Heavier internal offal yields were reported for the winter-harvested group (70.76 ± 21.8 kg) compared to the summer-harvested animals (66.13 ± 3.78 kg). As harvest season had no influence, pooled data of the percentage contribution of each muscle to cold carcass weight indicated that the Longissimus et lumborum (3.5 ± 0.18%), semimembranosus (1.6 ± 0.04%), biceps femoris (2.7 ± 0.05%) and semitendinosus (0.9 ± 0.02%) muscles differed significantly in their respective contributions to cold carcass weight. No significant differences were recorded between the contribution of the infraspinatus (0.6 ± 0.02%), supraspinatus (0.4 ± 0.03%) and psoas major (0.6 ± 0.02%) muscles. Carcass and muscle yields, as well as low-cost protein offal yields from this study indicate that the Plains zebra has the potential to be used and distributed as an alternative protein source.

Comparison of the EMG Activity of Shoulder Muscles according to Arm Position during Prone Arm Lift Exercise

Background Full-can exercise was associated with a significantly higher scapulohumeral rhythm than empty-can exercise. These findings suggest that the movements of the scapula and glenohumeral joint are affected by the position of the arm. Purpose We investigated the effect of arm position on the muscle activity of scapular upward rotators during prone arm lift exercise. Study design Cross-sectional study Methods Thirty-two healthy subjects were participated in this study. The muscle activity of the serratus anterior (SA), upper trapezius (UT), lower trapezius (LT), and infraspinatus (IS) were measured using a surface electromyography device. All subjects were asked to perform prone arm lift exercise according to the three arm positions: palm down (PD), neutral (NT), and palm up (PU). One-way repeated analysis of variance was conducted. Results The EMG activities of the UT, LT, and SA were significantly different among three conditions (PU vs. NT vs. PD; <italic>p</italic>&lt;0.05). The muscle activities of the UT and LT were significantly higher in the PD than in the PU (<italic>p</italic>&lt;0.017). The muscle activity of SA was significantly higher in the PU than in the PD (<italic>p</italic>&lt;0.017). However, the activity of the IS muscle was not significantly different among the three conditions (<italic>p</italic>&gt;0.05). Conclusions Prone arm lift exercise for SA strengthening is recommended to be performed in a PU position.

Effect of Fatty Infiltration of the Infraspinatus Muscle on Outcomes and Graft Failure After Arthroscopic Superior Capsule Reconstruction for Irreparable Posterosuperior Rotator Cuff Tears

Background: Superior capsule reconstruction (SCR) was developed as an alternative treatment for irreparable rotator cuff tears to restore superior stability of the glenohumeral joint. Although fatty infiltration (FI) of the rotator cuff muscles, especially the infraspinatus, has been implicated as a predictor of outcomes and graft integrity after rotator cuff repair, it has not been fully investigated in cases of SCR. Purpose: To evaluate the effect of FI of the infraspinatus muscle on clinical and radiological outcomes after SCR. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 55 consecutive patients with irreparable posterosuperior rotator cuff tears who underwent SCR between January 2013 and August 2020 were included retrospectively. Preoperative and postoperative clinical and radiological findings (median follow-up of >2 years), including magnetic resonance imaging results, were thoroughly reviewed. The patients were divided into 2 groups: group 1 with mild FI of the infraspinatus (Goutallier grades 0-2) and group 2 with severe FI of the infraspinatus (Goutallier grades 3-4). The American Shoulder and Elbow Surgeons score, Constant score, visual analog scale score for pain, and range of motion were evaluated. Acromiohumeral distance and rotator cuff tear arthropathy using the Hamada classification were assessed on plain radiography. Postoperative graft integrity was evaluated by magnetic resonance imaging. Graft failure was defined as complete discontinuity. Univariate and multivariable logistic regression analyses were performed to evaluate clinical and radiological findings that might be associated with successful SCR. Results: Clinical and radiological outcomes significantly improved after SCR. Graft failure was noted in 15 (27.3%) patients and was more frequent in group 2 than in group 1 (50.0% vs 14.3%, respectively; P = .004). Univariate analysis indicated a significant association between severe FI in the infraspinatus (group 2) and graft failure after SCR (odds ratio, 6.00 [95% CI, 1.65-21.80]; P = .006). Multivariable analysis indicated that FI of the infraspinatus was the only factor associated with graft failure (odds ratio, 6.37 [95% CI, 1.63-24.90]; P = .008). Conclusion: Severe FI of the infraspinatus muscle was a factor indicating a poor prognosis for graft integrity after SCR. Preoperative evaluation of FI in the rotator cuff muscles can help predict postoperative outcomes and may help guide therapeutic options.

The internal structure of the infraspinatus muscle: a magnetic resonance study

PurposeThis study aimed to describe the internal structure of the infraspinatus muscle. A secondary aim was to explore differences in internal structure between genders, sides, and correlations to demographic data.MethodsIn total, 106 shoulder MRI examinations of patients between 18 and 30 years of age seeking care in 2012–2020 at The Sahlgrenska University Hospital in Gothenburg, Sweden were re-reviewed.ResultsThe number of intramuscular tendons centrally in the infraspinatus muscle varied between 3 and 8 (median = 5). Laterally, the number of intramuscular tendons varied between 1 and 5 (median = 2). There was no difference in the median between the genders or sides. No correlations between the number of intramuscular tendons and demographic data were found. The muscle volume varied between 63 and 249 ml with a median of 188 ml for males and 122 ml for females. There was no significant difference in volume between the sides. The muscle volume correlated with body weight (Pearson’s correlation coefficient, r = 0.72, p < 0.001) and height (r = 0.61, p < 0.001).ConclusionThe anatomical variations of the infraspinatus muscle are widespread. In the medial part of the muscle belly, the number of intramuscular tendons varied between 3 and 8, while the number of intramuscular tendons laterally varied between 1 and 5. Results of our study may help to understand the internal structure of the infraspinatus muscle and its function in shoulder stabilization.

Humeral head coverage in arthroscopic partial repair of massive rotator cuff tears improves functional outcomes: an analysis of influential factors.

Although partial rotator cuff repair has shown good outcomes, differences in clinical outcomes remain concerns. This study was performed to determine whether patients with humeral head coverage would show better functional outcomes than patients without humeral head coverage and to identify the factors for humeral head coverage after arthroscopic partial repair of massive tears. We performed a retrospective study of 63 patients with massive rotator cuff tears who underwent arthroscopic partial repair between 2012 and 2018. Two to four margin convergences were first performed; then, the Mason-Allen technique was performed. The patients were divided into 2 groups: those with humeral head coverage (38 cases) and those without humeral head coverage (25 cases). The following factors were evaluated: age; sex; hypertension; diabetes; osteoporosis; preoperative and postoperative pseudoparalysis, visual analog scale (VAS) pain score, Constant score, acromiohumeral distance, and subacromial bony spur; and subscapularis tear and repair. Muscle atrophy and fatty degeneration were evaluated by magnetic resonance imaging preoperatively, and the integrity of the repaired cuff was evaluated by ultrasonography at a minimum of 2 years after surgery. Compared with preoperative values, significant improvements in VAS pain scores (from 6.27 to 2.32 in patients with humeral head coverage and from 7.00 to 2.81 in those without humeral head coverage) and Constant scores (from 51.35 to 75.95 and from 44.62 to 69.81, respectively) were observed in both groups (P<.001). Statistical analysis revealed that postoperative VAS pain scores (2.32 vs. 2.81) and Constant scores (75.95 vs. 69.81) in patients with humeral head coverage were superior to those in patients without humeral head coverage (P=.044 and P=.003, respectively). The integrity of the repaired cuff was evaluated by ultrasonography, and partial tears were found in 4 of 37 patients with humeral head coverage and 2 of 26 patients without humeral head coverage (P=.816). Univariable logistic regression analysis revealed that age (P<.001), comorbidity (P=.005), symptom duration (P=.023), preoperative shoulder mobility (P<.001), maintained acromiohumeral distance (P=.006), subscapularis tear (P=.026), and less preoperative supraspinatus and infraspinatus muscle atrophy (P=.001 and P=.010, respectively) had significant correlations with humeral head coverage. Overall satisfactory results were achieved in most patients regardless of high retear rates, but patients with partial repair covering the humeral head were associated with better outcomes than patients without humeral head coverage. Multivariable regression analysis revealed that age (<70 years, P=.003), capability of shoulder mobility (P=.005), maintenance of the acromiohumeral space (>7 mm, P=.016), and less atrophy of the rotator cuff muscles (P=.021) were favorable factors to achieve humeral head coverage during surgical partial repair of massive rotator cuff tears.

Intersession Repeatability of Diffusion-Tensor Imaging in the Supraspinatus and the Infraspinatus Muscles of Volunteers.

Quantifying the rotator cuff (RC) muscles' viscoelasticity could provide outcome relevant information in patients with RC tears. MR-elastography requires robust diffusion-tensor imaging (DTI) to account for tissue anisotropy in muscles stiffness computation. To assess the repeatability of DTI parameters in the supraspinatus and infraspinatus muscles and to explore DTI tractography conformity with the muscles' anatomy. Prospective. Six healthy volunteers underwent three consecutive shoulder MRI sessions about 10 minutes apart. 3T/T1-vibe Dixon and Spin echo EPI DTI (12 gradient encoding directions, b-values 500 and 800 sec/mm2 ). Supraspinatus and infraspinatus muscles were segmented on the T1-vibe Dixon sequence. DTI image quality was assessed using a quantitative threshold based on the signal-to-noise ratio (SNR). The eigenvalues ( ), fractional anisotropy (FA) and mean diffusivity were calculated. DTI tractography was visually assessed. DTI parameters within-subject intersession repeatability was assessed with Bland-Altman analysis and the coefficient of variation (CV). Repeatability was considered good for CV < 10%. The SNR between diffusion-weighted and non-diffusion-weighted images was greater than 3, which aligns with standards for estimating DTI parameters. The FA showed the lowest mean bias (-0.007; 95% confidence interval [CI] -0.031 to 0.018) whereas the λ1 had the highest mean bias (0.146 × 10-3 mm2 /sec; CI -0.034 to 0.326 × 10-3 mm2 /sec). CVs of the DTI parameters varied between 3.5% (FA) and 8.4% (λ3 ) for the supraspinatus and between 3.2% (λ1 ) and 6.8% (λ3 ) for the infraspinatus. Tractography provided muscle fiber representations in three-dimensional space concordant with RC anatomy. DTI of the supraspinatus and infraspinatus muscles achieved an adequate SNR, allowing the measurement of the DTI metrics with good repeatability, and thus can be used for optimizing stiffness estimation in these anisotropic tissues. 2 TECHNICAL EFFICACY: Stage 2.

A Functional Electromechanical Dynamometer – Testing Isokinetic Shoulder Rotators Strength

The torque in internal and external rotation of the shoulder is frequently utilized to suspected glenohumeral joint diseases or abnormalities, as well as to monitor the patient's condition and improve over a period of time. The teres major, pectoralis major, subscapularis, latissimus dorsi, and anterior deltoid are the key muscles that internally rotate the GH joint. The supraspinatus muscle is a pennate muscle that rotates and adducts the humerus externally. The infraspinatus muscle abducts and externally rotates the shoulder; it is a pennate muscle that performs best as a rotator in the prone position.Muscular growth and strength development is a multi-step physiologic process that necessitates both muscle activity and rest.While testing the strength of the internal and external shoulder rotator muscles concentrically provided early isokinetic normative values, researchers increasingly recognised the need to test the strength of the external shoulder rotator musculature eccentrically, which is the dominant mode of external shoulder rotator muscle activation during overhead motions . The shoulder rotator musculature was isokinetically tested concentrically, revealing that shoulder muscular imbalance is frequently caused by an adaptation to repeated overhead motions, resulting in bigger gains in concentric internal rotator strength than concentric external rotator strength . The major goal of this research was to find out how reliable internal and external shoulder rotators (concentric and eccentric) were in uprightposture usingFunctional electromechanical dynamometry.