3D Free Scapula, Clavicle, and Humerus Models in 3D-Printable STL Format

Shoulders are comprised of three main bones. These include humerus (bone in the upper arm), scapula (shoulder blade), and the clavicle, which we commonly refer to as the "collarbone." Bones of the shoulder work together with the transverse humeral ligament, synovial membrane of the bicep, bursa sac, and the superior transverse ligament to perform a complex range of motions. In fact, the shoulder has the most extended pivot range of any joint within the body. Your glenohumearal joint (shoulder) is a ball-and-socket joint that is able to move in so many positions due to the relatively small size of the glenoid fossa, as well as the laxity ("wiggle room") of the joint capsule. But, these features also make the shoulder prone to overuse injuries, subluxation, dislocation, and ligament tears.

In this week's embodi3D® Top Ten, we are bringing you some of the best 3D scapula, clavicle, and humerus models which comprise the majority of the human shoulder joint. 

Before you dive into this week's Top 10 and start printing your own 3D anatomical models, you must first register with embodi3D®. It's absolutely free to sign up and you can take advantage of many of the features found on the embodi3D® website, including standard resolution democratiz3D® conversions. Register with embodi3D® today! Technologies like these were recently featured in the journal Société Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT), where models of a 3D scapula, humerus, and soft tissues are being used in preoperative planning. If you are interested in uploading your CT scans and converting these to 3D-printable STL format, the democratiz3D® Quick Start Guide will help you to quickly get up and running.

How Shoulders Achieve Their Range of Motion

Flexion, extension, abduction, adduction, circumduction, medial rotation, and lateral rotation.
* Flexion: Pectoralis major, deltoid, coracobrachialis, & biceps muscles
* Extension: Deltoid & teres major muscles.
– If against resistance, also latissimus dorsi & pectoralis major.
* Abduction: Deltoid & supraspinatus muscles.
– Subscapularis, infraspinatus, & teres minor exert downward traction
– Supraspinatus contribution controversial 
* Medial rotation: Pectoralis major, deltoid, latissimus dorsi, & teres major muscles.
– Subscapularis when arm at side
* Lateral rotation: Infraspinatus, deltoid, & teres minor muscles.

#1. An Incredible 3D Model of the Shoulder in STL Format

This articulation is maintained by overlying soft tissue structures. The posterosuperior acromion process of the scapula provides one half of the AC joint. It also forms most of the osseous portion of the coracoacromial arch, the roof over the rotator cuff. The acromion process is connected to the body of the scapula by the spine. 

The osseous structures of the shoulder girdle are the clavicle, scapula, and humerus. Medially, the clavicle articulates with the manubrium of the
sternum at the sternoclavicular (SC) joint. This joint serves as the only true articulation between the shoulder girdle and the axial skeleton. Laterally, the clavicle articulates with the acromion process of the scapula at the acromioclavicular (AC) joint

#2. STL File Showing Scapular Notch and Shoulder

Variations in the shape of the clavicle are considered normal and are not usually pathologic. These variations may range from an almost straight bone to one with exaggerated curves. Another variation of the clavicle that is present in 6-10% of the population is termed the canalis nervi supraclavicularis. In this variation, a foramen forms through the clavicle, and the medial supraclavicular nerve passes through this accessory osseous canal.

The scapular notch varies in size and shape. The notch is bridged by the superior transverse scapular ligament. This ligament ossifies in 10% of patients, producing a bony foramen for the suprascapular nerve.

#3. A 3D Model of the Shoulders of the Muscle

Rotator cuff: 4 muscles arising on scapula and inserting on humerus
* Supraspinatus: From supraspinatus fossa of scapula to greater tuberosity
– Abducts humerus, also depresses humeral head.
* Infraspinatus: From posterior surface of scapula to greater tuberosity.
– Externally rotates humerus
* Teres minor: From lateral border of scapula to greater tuberosity
– Externally rotates humerus
* Subscapularis muscle: From anterior surface of scapula to lesser tuberosity
– Superficial fibers extend across to anterior margin of greater tuberosity as part of transverse ligament 
– Internally rotates, adducts humerus

#4. 3D Model (STL Format) of the Muscles Connecting the Arm to Axial Skeleton

4. Various muscles also serve to connect the arm to the axial skeleton. Anteriorly, the pectoralis major and minor muscles extend from the sternum and clavicle to the proximal humeral shaft. Posteriorly, the latissimus dorsi muscle arises from the thoracic cage to attach onto the proximal humeral shaft. The great range of motion provided for by the glenohumeral joint is executed in large part by the muscles of the rotator cuff. The supraspinatus muscle arises superior to the scapular spine and attaches to the superior facet of the greater tuberosity. The more posterior infraspinatus muscle arises below the spine and inserts onto the posterior facet of the greater tuberosity. The teres minor muscle originates and inserts just caudal to the infraspinatus. The subscapularis muscle arises from the anterior scapular body to insert onto the lesser tuberosity. The long head of the biceps originates at the superior glenoid rim, passes through the rotator cuff interval at the anterosuperior glenohumeral joint, and then follows the bicipital groove between the tuberosities into the upper arm. The deltoid muscle has a broad origination along the lateral aspect of the
acromion from anterior to posterior. It covers the lateral portion of the upper arm before inserting on to the lateral proximal humeral shaft at the  deltoid tuberosity.

#5. 3D Model of the Skin around the Shoulder, Arm, and Upper Chest  

A 3D model of the skin of the shoulder where the soft tissue of the shoulder and arm are shown. 

Trapezius: is responsible for the smooth contour of the lateral side of the neck and over the superior aspect of the shoulder. It can be seen and felt throughout its entirety when the shoulder girdles are retracted against resistance; the superior part can be palpated when the shoulders are elevated against resistance.

Posterior axillary fold: is formed by the latissimus dorsi winding around the lateral border of the teres major muscle. Latissimus dorsi forms much of the muscle mass underlying the posterior axillary fold extending obliquely upward from the trunk to the arm. Teres major passes from the inferior angle of the scapula to the upper humerus and contributes to the fold laterally. Both muscles can be palpated on resisted shoulder adduction.

Pectoralis major: can be seen and felt throughout its entire extent when it is contracted against resistance as in pressing the palm together in front of the body. Clavicular fibers can be felt if the shoulder is flexed against resistance to a position midway between flexion and extension, while the sternocostal fibers can be felt if the shoulder is extended against resistance starting in a flexed position. The inferior border of the pectoralis major muscle forms the anterior axillary fold.

Deltoid: forms the muscular eminence inferior to the acromion and around the glenohumeral joint. The anterior, middle, and posterior fibers of the deltoid can be palpated. When the arm is abducted against resistance, the anterior border of the deltoid can be felt.

The clavipectoral triangle (deltopectoral triangle) is the depressed area just inferior to the lateral part of the clavicle, bounded by the clavicle superiorly, the deltoid laterally, and the clavicular head of the pectoralis major medially.

#6. CT Scan Showing a Fracture in the Proximal Humeral

A computed tomography (CT) is recommended for complex fracture situations although those situations were not clearly defined. Therefore, precise indications for CT in proximal humeral fractures are not established.

#7. Connection of Scapula, Humerus, and Clavicle Shown in 3D STL File

The scapula is a spade-shaped bone comprised of a thin triangular body and a semi-ovoid cavity known as the glenoid fossa (glenoid cavity). The glenoid fossa faces lateral and slightly anterior and cranial. A bony spine runs across the dorsal surface of the scapular body and terminates in the acromion. The scapula articulates with two bones, the humerus and clavicle. The scapula does not directly contact the bony rib cage: the two structures are separated by muscle and other soft tissue.

#8. Right Shoulder Injury Revealed by CT Scan

On CT acute trauma may result of bony, labral, ligamentous or musculotendinous damage. The shoulder may be injured following repetitive injury or as part of systemic inflammatory conditions or infection. Moreover, the bones around the shoulder may be affected by benign or malignant bony lesions, and associated pathological fracture.

#9. Right Shoulder with Pleomorphic Spindle Cell Sarcoma (3D-Printable STL File)

Pleomorphic sarcoma composed of fibroblasts, myofibroblasts and histiocyte-like cells. Historically considered the most common adult soft tissue sarcoma. Usually older adults (age 50+ years) with slight male predominance; more common in lower extremities, rarely retroperitoneum, head and neck, breast. Large and deep-seated with progressive enlargement. Sarcomas adjacent to orthopedic implants or post-radiation are usually osteosarcoma or MFH.

#10. 3D-Printable Model of Right Shoulder Bones 

The humerus is the large single bone of the upper arm. Proximally, it articulates with the glenoid fossa of the scapula forming the glenohumeral joint. The humeral head is large and globular. Just ventral to the articular surface is the lesser tubercle, where the subscapularis attaches. Lateral to the articular surface is the greater tubercle. The rotator cuff muscles of the shoulder insert on the proximal humerus.

References

1. Manaster, B. J., & Crim, J. R. (2016). Imaging Anatomy: Musculoskeletal E-Book. Elsevier Health Sciences.

2. Bahrs, C., Rolauffs, B., Südkamp, N. P., Schmal, H., Eingartner, C., Dietz, K., ... & Helwig, P. (2009). Indications for computed tomography (CT-) diagnostics in proximal humeral fractures: a comparative study of plain radiography and computed tomography. BMC musculoskeletal disorders, 10(1), 33.

3. Duke University Medical School - Anatomy. (2018). Web.duke.edu. Retrieved 4 August 2018, from https://web.duke.edu/anatomy/

4. Shoulder Joint Anatomy: Overview, Gross Anatomy, Microscopic Anatomy. (2018). Emedicine.medscape.com. Retrieved 4 August 2018, from https://emedicine.medscape.com/article/1899211-overview#a1

5. The Radiology Assistant : Shoulder MR - Anatomy. (2012). Radiologyassistant.nl. Retrieved 4 August 2018, from http://www.radiologyassistant.nl/en/p4f49ef79818c2/shoulder-mr-anatomy.html