Soo Y. Kim

Investigation of the static and dynamic musculotendinous architecture of supraspinatus

To date, the architecture of supraspinatus (SP) and its relation to joint position has not been investigated. The purpose of this study was to quantify the dynamic architecture of the distinct regions of SP using ultrasound (US). Seventeen subjects (8 M/9 F), mean age 36.4 ± 12.7 years, without tendon pathology were recruited. The SP was scanned in relaxed and contracted states. For the contracted state, SP was scanned with the shoulder actively abducted to 60° and the glenohumeral joint in neutral rotation; 80° external rotation; 80° internal rotation. Fiber bundle length (FBL) and pennation angle (PA) of distinct regions, and muscle thickness were computed. Measurements of the posterior region were limited because of acromion shadowing. Parameters between regions and changes between relaxed and contracted states were analyzed using paired t‐tests and repeated measures ANOVA (P < 0.05). On contraction in the anterior region, mean percentage of FBL shortening ranged between 9% and 21%. However, in the posterior region, shortening of approximately 2% only occurred in two of the three positions; lengthening of approximately 2.5% occurred in internal rotation. For the anterior region, the mean PA increased the least in the externally rotated position, and the mean PA of the middle part was smaller than the deep part for all states. Findings suggest changes in the architecture are not uniform throughout the muscle and joint position may play an important role in force production. The US protocol may serve as an outcome measure of adaptive changes of muscle function following surgery, training, and rehabilitation. Clin. Anat. 23:48–55, 2010.

Investigation of supraspinatus muscle architecture following concentric and eccentric training

OBJECTIVES To investigate the effects of concentric or eccentric abduction strength training on supraspinatus fiber bundle architecture and strength. DESIGN A pre-post single-subject design. METHODS Thirteen participants were randomized to concentric (n=6) or eccentric (n=7) training groups. Participants completed an eight week shoulder abduction training program in the scapular plane using an isokinetic dynamometer. Resistance training, requiring maximal effort on contraction, consisted of 4 sets of 8 reps at 60°/s in weeks 1-4, and 6 sets of 6 reps at 60°/s in weeks 5-8 with a frequency of 3×/week. Primary outcome measures included fiber bundle length, pennation angle, and muscle thickness of supraspinatus and these were quantified using ultrasound. Secondary outcome measures included isometric, eccentric and concentric abduction strength and these were evaluated using the isokinetic dynamometer. RESULTS Mean fiber bundle length in the relaxed (p=0.033) and contracted (p=0.036) states significantly decreased with concentric training but remained unchanged with eccentric training. A significant increase in pennation angle, muscle thickness, and peak torque were found with training but no significant differences were detected between concentric and eccentric groups. CONCLUSIONS Training mode has a significant impact on fiber bundle length changes of the supraspinatus. Eccentric training of shoulder abduction leads to similar strength gains as concentric, but it may also have the added advantages of maintaining fiber bundle lengths and promoting tendon healing. Study is needed to confirm fiber bundle changes in a clinical population which would further support the use of eccentric abduction strength training in rehabilitation settings.

Musculotendinous Architecture of Pathological Supraspinatus: A Pilot In Vivo Ultrasonography Study

Architectural changes associated with tendon tears of the supraspinatus muscle (SP) have not been thoroughly investigated in vivo with the muscle in relaxed and contracted states. The purpose of this study was to quantify the geometric properties within the distinct regions of SP in subjects with full‐thickness tendon tears using an ultrasound protocol previously developed in our laboratory, and to compare findings with age/gender matched normal controls. Twelve SP from eight participants (6 male/2 female), mean age 57 ± 6.0 years, were investigated. Muscle geometric properties of the anterior region (middle and deep parts) and posterior region (deep part) were measured using image analysis software. Along with whole muscle thickness, fiber bundle length (FBL) and pennation angle (PA) were computed for architecturally distinct regions and/or parts. Pathologic SP was categorized according to the extent of the tear in the tendon (with or without retraction). In the anterior region, mean FBL of the pathologic SP was similar with normal controls; however, mean PA was significantly smaller in pathologic SP with retraction compared with normal controls, in the contracted state (P < 0.05). Mean FBL in the posterior region in both relaxed and contracted states was significantly shorter in the pathologic SP with retraction compared with normal controls (P < 0.05). Findings suggest FBL changes associated with tendon pathology vary between the distinct regions, and PA changes are related to whether there is retraction of the tendon. The ultrasound protocol may provide important information on architectural changes that may assist in decision making and surgical planning. Clin. Anat., 2013.

Innervation pattern of the suprascapular nerve within supraspinatus: A three-dimensional computer modeling study

The relationship between the innervation pattern of the suprascapular nerve (SSN) and the muscle architecture of supraspinatus has not been thoroughly investigated. The supraspinatus is composed of two architecturally distinct regions: anterior and posterior. Each of these regions is further subdivided into three parts: superficial, middle and deep. The purpose of this study was to investigate the course of the SSN throughout the volume of supraspinatus and to relate the intramuscular branches to the distinct regions and parts of the supraspinatus. The SSN was dissected in thirty formalin embalmed cadaveric specimens and digitized throughout the muscle volume in six of those specimens. The digitized data were modeled using Autodesk® Maya® 2011. The three‐dimensional (3D) models were used to relate the intramuscular innervation pattern to the muscle and tendon architecture defined by Kim et al. (2007, Clin Anat 20:648–655). The SSN bifurcated into two main trunks: medial and lateral. All parts of the anterior region were predominantly innervated by the medial trunk and its proximal and medial branches, whereas all parts of the posterior region predominantly by the lateral trunk and its posterolateral and/or posteromedial branches. The posterior region also received innervation from the proximal branch of the medial trunk in half of the specimens. These findings provide evidence that the anterior and posterior regions are distinct with respect to their innervation. The 3D map of the innervation pattern will aid in planning future clinical studies investigating muscle activation patterns and provide insight into possible injury of the nerve with supraspinatus pathology and surgical techniques. Clin. Anat. 622–630, 2014.

At-home resistance tubing strength training increases shoulder strength in the trained and untrained limb.

The purpose was to determine if an at‐home resistance tubing strength training program on one shoulder (that is commonly used in rehabilitation settings) would produce increases in strength in the trained and untrained shoulders via cross‐education. Twenty‐three participants were randomized to TRAIN (strength‐trained one shoulder; n = 13) or CONTROL (no intervention; n = 10). Strength training was completed at home using resistance tubing and consisted of maximal shoulder external rotation, internal rotation, scaption, retraction, and flexion 3 days/week for 4 weeks. Strength was measured via handheld dynamometry and muscle size measured via ultrasound. For external rotation strength, the trained (10.9 ± 10.9%) and untrained (12.7 ± 9.6%) arm of TRAIN was significantly different than CONTROL (1.6 ± 13.2%; −2.7 ± 12.3%; pooled across arm; P < 0.05). For internal rotation strength, the trained (14.8 ± 11.3%) and untrained (14.6 ± 10.1%) arm of TRAIN was significantly different than CONTROL (6.4 ± 11.2%; 5.1 ± 8.8%; pooled across arm; P < 0.05). There were no significant differences for scaption strength (P = 0.056). TRAIN significantly increased muscle size in the training arm of the supraspinatus (1.90 ± 0.32 to 1.99 ± 0.31 cm), and the anterior deltoid (1.08 ± 0.37 to 1.21 ± 0.39 cm; P < 0.05). This study suggests that an at‐home resistance tubing training program on one limb can produce increases in strength in both limbs, and has implications for rehabilitation after unilateral shoulder injuries.

Fiber type composition of the architecturally distinct regions of human supraspinatus muscle: a cadaveric study.

The human supraspinatus muscle is clinically important as it is frequently injured in older adults and the elderly. We have previously shown that the supraspinatus has a complex architecture with two distinct regions each consisting of three parts. Further we have found dynamic changes in architectural parameters such as fiber bundle length markedly vary between these regions. Fiber types of the supraspinatus have not been thoroughly investigated throughout its volume and are of interest to clinicians treating supraspinatus pathologies. In this study we investigated the distribution of fiber types within the distinct regions and parts of supraspinatus. Samples of supraspinatus were excised from six distinct parts of each muscle from five formalin embalmed specimens (one male, four female; mean age 77±11.1 years) free of tendon pathology. Samples were frozen in liquid nitrogen and then cryosectioned. Serial sections were labeled using immunohistochemical techniques and antibodies against fast or slow myosin heavy chain isoforms. The mean percentage of Type I (slow) fibers ranged from 56.73% to 63.97%. Results demonstrated significant variations in fiber type distribution. The middle part of the anterior region has a significantly greater percentage of Type I fibers compared to that of the posterior. The superficial part of the anterior region has a greater percentage of Type II (fast) fibers compared to the middle and deep parts. Findings aid in highlighting the distinct functions of the anterior and posterior regions, and prompt the need to re-evaluate assessment and treatment techniques established on a limited understanding of the fiber type distribution.

Upper limb and trunk muscle activation during an unexpected descent on the outstretched hands in young and older women

Falling on the outstretched hands (FOOSH), a protective mechanism to arrest the body and avoid injury, requires upper limb and trunk motor control for effective body descent. The purpose of this study was to investigate muscle activity during three phases of an unexpected FOOSH in healthy older and younger women. Twenty young (mean age 22.9yrs, SD±3.7) and 20 older females (mean age 68.1yrs, SD±5.0) performed five trials of unexpected FOOSHs. Surface electromyography (EMG) determined muscle activations for left shoulder girdle, elbow and abdominal muscles during an unexpected FOOSH. Root mean squared EMG data were calculated during three phases: (1) baseline (BL; 500msprior to release), (2) the preparatory phase (PRE; time between release and impact) (mean 257±37ms) and post-impact (POST; 200msafter impact). A mixed MANOVA determined differences between phases and age groups. There was a significant multivariate interaction effect of age and time phase on muscle activity (p=0.001). Younger women had significantly higher internal oblique/transversus abdominus activity during PRE (p=0.006) as well as variations in muscle activity of shoulder girdle and elbow muscles. The age differences observed may lead to poorer preliminary trunk activation and greater arm bracing in older women, potentially increasing risk of fallrelated injury.

Angelman syndrome: A review highlighting musculoskeletal and anatomical aberrations

Angelmans syndrome (AS) is a genetic neurodevelopment disorder. The cause is a known abnormality involving the maternal inherited ubiquitin‐protein ligase (UBE3A) gene. Clinical characteristics universal to the disorder are well documented in the literature and include developmental delay, seizures, ataxia, altered tone, severely impaired speech and intellect, as well as an overall happy demeanor, frequent bouts of laughter, and hypermotoric behavior. Associated with this disorder are several musculoskeletal aberrations. To date, a review of case studies reporting on these musculoskeletal changes has not been carried out. Thus, the purpose of this paper was to provide an overview of the musculoskeletal changes present in individuals with AS. In our review of 21 case reports from 1965–2013, the most consistently reported anatomical changes were of the craniofacial region. These include microcephaly, brachycephaly, a palpable occipital groove, prognathism, and wide spaced teeth. Other musculoskeletal abnormalities less frequently reported in the literature include scoliosis, excessive lumbar lordosis, and pes planus. Given that the majority of the case reports reviewed was of young children, the possibility of underreporting musculoskeletal changes which may manifest in the later years of life may be present. Early diagnosis and interventions to minimize secondary complications are crucial to maintain quality of life. An overall multidisciplinary approach is emphasized to maximize developmental potential for these individuals. Future prospective studies that follow patients into adulthood are needed to better understand the prevalence and development of secondary musculoskeletal changes, which in turn can inform intervention techniques and preventative measures. Clin. Anat. 29:561–567, 2016.

Electromyographic investigation of anterior and posterior regions of supraspinatus: a novel approach based on anatomical insights

Abstract Supraspinatus is composed of anterior and posterior regions that are distinct. To date, the relative electromyographic (EMG) activity of these regions during different tasks has not been investigated. This work, thus, evaluated activity of the anterior and posterior regions of supraspinatus during isometric actions in different postures. Data were analyzed from 11 healthy participants. Fine-wire electrodes were inserted into the anterior and posterior regions of supraspinatus. EMG activity was recorded during isometric abduction and external rotation exertions against 5% of body weight resistance. Three postures for abduction (30°, 60°, and 90° of humeral abduction, scapular plane) and two for external rotation (0° and 90° humeral abduction) were tested. Each participant’s data were normalized to the peak root mean square (RMS) values for the corresponding region. The RMS of the anterior region was divided by that of the posterior to calculate muscle activation ratios. Non-parametric statistics were used for analyses. The median ratio was lower during external rotation at 90° abduction compared to abduction at 30° (P = 0.003). These results suggest that the two regions of supraspinatus are functionally distinct during isometric tasks. The posterior region may play a more dominant role in postures with higher degrees of abduction and during external rotation exertions.

Change in the Pathologic Supraspinatus: A Three-Dimensional Model of Fiber Bundle Architecture within Anterior and Posterior Regions.

Supraspinatus tendon tears are common and lead to changes in the muscle architecture. To date, these changes have not been investigated for the distinct regions and parts of the pathologic supraspinatus. The purpose of this study was to create a novel three-dimensional (3D) model of the muscle architecture throughout the supraspinatus and to compare the architecture between muscle regions and parts in relation to tear severity. Twelve cadaveric specimens with varying degrees of tendon tears were used. Three-dimensional coordinates of fiber bundles were collected in situ using serial dissection and digitization. Data were reconstructed and modeled in 3D using Maya. Fiber bundle length (FBL) and pennation angle (PA) were computed and analyzed. FBL was significantly shorter in specimens with large retracted tears compared to smaller tears, with the deeper fibers being significantly shorter than other parts in the anterior region. PA was significantly greater in specimens with large retracted tears, with the superficial fibers often demonstrating the largest PA. The posterior region was absent in two specimens with extensive tears. Architectural changes associated with tendon tears affect the regions and varying depths of supraspinatus differently. The results provide important insights on residual function of the pathologic muscle, and the 3D model includes detailed data that can be used in future modeling studies.