Quiz 3: Shoulder Complex

Brushing/combing your hair on the back of your head requires full shoulder external rotation because this movement involves reaching behind the head and extending the arm to comb or brush the hair at the back. This action requires the shoulder joint to rotate externally to allow the arm to move in that direction. Tying a tie, brushing your teeth, and buttoning a polo shirt do not require the same range of motion in the shoulder as brushing/combing the hair on the back of the head.

Shoulder depression refers to the action of lowering or depressing the shoulders. Pushing down on arm rests of a chair in order to stand up requires the action of shoulder depression because it involves lowering the shoulders in order to generate the necessary force to push down on the arm rests and lift the body up from a seated position.

Shoulder sublaxation refers to an incomplete or partial separation of the GH joint, specifically when the head of the humerus has partially slipped out of the glenoid fossa. Unlike a complete separation, this type of sublaxation does not involve tearing or rupturing of the soft tissue structures.

Shoulder retraction refers to the movement of pulling the shoulder blades back towards the spine. This action is necessary when scratching your back, as it requires reaching behind the body and extending the arm to reach the itchy area. Reaching an object on top of the refrigerator, pushing down on arm rests, and lifting a cup to take a drink do not specifically involve shoulder retraction.

Shoulder protraction is the movement of the shoulder blades away from the spine, towards the front of the body. This movement is required when reaching forward to grab an object in front of you, as it helps to extend the reach and bring the object closer to the body. In the other activities mentioned, different movements such as shoulder elevation or depression, or shoulder flexion, are required.

The correct answer is Serratus Anterior. Winging of the scapula refers to the abnormal protrusion or prominence of the scapula bone on the back. This condition occurs when there is weakness or paralysis in the Serratus Anterior muscle, which is responsible for stabilizing the scapula against the rib cage. When the Serratus Anterior muscle is weak or dysfunctional, it cannot properly hold the scapula in place, causing it to wing outwards. Therefore, weakness in the Serratus Anterior muscle is the cause of scapular winging.

To test the middle deltoid against gravity for a muscle grade of 4 or 5, the shoulder needs to be positioned at 90 degrees of shoulder humeral flexion or shoulder humeral abduction. This position allows for optimal activation and resistance against gravity for the middle deltoid muscle. Any other position, such as 180 degrees, 45 degrees, or 120 degrees, would not provide the same level of challenge and activation for the middle deltoid.

The GH joint, also known as the glenohumeral joint, is the most likely component of the shoulder girdle to undergo degenerative changes over time. This joint is a ball-and-socket joint that allows for a wide range of motion in the shoulder. Due to its complex structure and constant use, it is susceptible to wear and tear, leading to degenerative changes such as osteoarthritis. Over time, the cartilage in the GH joint may wear down, causing pain, stiffness, and limited mobility.

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The middle traps are not involved in the motion of shoulder flexion. The anterior deltoid, upper traps, coracobrachialis, subscapularis, and biceps brachii all contribute to shoulder flexion, but the middle traps primarily function to retract and stabilize the scapula.

The closed packed position for the GH joint is when the shoulder is maximally abducted and externally rotated. This means that the arm is lifted away from the body and rotated outwards. The joint end feel for this position is firm, indicating that there is limited range of motion and resistance when trying to move the joint further.

Excessive loading of the hanging limb, especially in situations where muscle function has been impacted by stroke or other brain injury, can lead to shoulder subluxation. This occurs when the head of the humerus partially comes out of the shoulder joint. The weakened muscles are unable to adequately support the weight of the limb, causing the shoulder joint to become unstable and resulting in subluxation.

The serratus anterior muscle is not involved in the motion of shoulder girdle elevation. The other three muscles listed (upper & middle traps, levator scapulae, and rhomboid major & minor) are all involved in this motion. The serratus anterior muscle is primarily responsible for protracting the scapula and assisting in scapular upward rotation, but it does not directly contribute to shoulder girdle elevation.

The correct answer is GH and AC joints. The glenohumeral (GH) joint, also known as the shoulder joint, is a ball-and-socket joint that allows for a wide range of motion in the shoulder. The acromioclavicular (AC) joint is the joint between the acromion process of the scapula and the clavicle. These two joints work together to allow for shoulder abduction or flexion in the range of 90-110 degrees. The GH joint provides the majority of the movement, while the AC joint provides stability and helps to control the movement of the scapula.

Upward rotation refers to the movement of the scapula (shoulder blade) upward and away from the spine. This action is required when reaching for an object on top of the refrigerator, as it involves lifting the arm overhead and extending it upwards. Pushing down on arm rests, lifting a cup, and putting a hat on top of your head do not involve upward rotation of the scapula.

The serratus anterior muscle is not involved in the motion of shoulder horizontal abduction. The serratus anterior muscle is responsible for protraction of the scapula and is involved in movements such as pushing and punching. In contrast, the posterior deltoid and middle traps are both involved in shoulder horizontal abduction. The posterior deltoid assists in shoulder horizontal abduction along with other muscles, while the middle traps help to stabilize the scapula during this motion.

The anterior deltoid muscle is not involved in the motion of shoulder adduction. Shoulder adduction refers to the movement of bringing the arm towards the midline of the body. The muscles that are involved in this motion are the pectoralis major, latissimus dorsi, teres major, and subscapularis. The anterior deltoid muscle is responsible for shoulder flexion and medial rotation, not adduction.

The middle deltoid muscle is not involved in the motion of shoulder girdle depression. Shoulder girdle depression refers to the downward movement of the shoulder blades. The pectoralis major, lower traps, and serratus anterior muscles are all involved in this motion. However, the middle deltoid muscle is primarily responsible for shoulder abduction, not depression.

Brushing your teeth requires full shoulder flexion/adduction because it involves reaching the toothbrush to the back of the mouth. This movement requires raising the arm in front of the body and bringing it closer to the midline, which is achieved through shoulder flexion/adduction. Tying a tie, buttoning a polo shirt, and brushing/combing the hair on the back of the head do not require the same level of shoulder movement as brushing teeth.

Bringing the head down to the shoulder by tipping the head to the side is a motion that can substitute or trick the movement of scapular elevation. This motion involves tilting the head to the side and bringing it down towards the shoulder, which can create the illusion of scapular elevation without actually performing the correct movement. This substitution or trick movement can be used to deceive or confuse observers or opponents in certain situations.

Full shoulder internal rotation is needed to reach behind the head to brush or comb hair. This motion involves rotating the shoulder joint inward, allowing the hand to reach the back of the head to perform the task. The other activities mentioned (tying a tie, brushing your teeth, buttoning a polo shirt) primarily involve shoulder flexion, extension, abduction, and/or external rotation, but not necessarily full internal rotation.

If the clavicle were unable to rotate on its axis due to injury at the SC joint, it would limit the range of motion in shoulder flexion and abduction. The clavicle plays a crucial role in allowing the scapula to move freely, and without its ability to rotate, the shoulder girdle complex would be restricted in its movement. This would result in a limited range of approximately 90 to 110 degrees for shoulder flexion and abduction, causing functional movement issues in the shoulder girdle complex.

The pectoralis major muscle is not involved in the dynamic stabilization of the GH joint when the arm is in a dependent position. The rotator cuff muscles (which include the supraspinatus, infraspinatus, teres minor, and subscapularis) work together to stabilize the joint and prevent dislocation. The upper trapezius muscle helps to elevate and stabilize the shoulder girdle. The long head of the biceps muscle also contributes to stabilizing the GH joint by providing dynamic stability during movement.

If the GH joint is immobilized by osteoarthritis, only 20 degrees of motion would be available at the joint. Additionally, the movement from the AC joint is unavailable. However, there is still 30 degrees of motion available from the SC joint. Therefore, the total range of shoulder flexion and abduction would be approximately 50 degrees.

The shoulder girdle is made up of three joints: the glenohumeral (GH) joint, the acromioclavicular (AC) joint, and the sternoclavicular (SC) joint. In order to perform shoulder abduction or flexion from 0-90 degrees, the GH joint and the SC joint combine to allow for this range of motion. The GH joint is responsible for the movement of the humerus, while the SC joint allows for the movement of the clavicle. The AC joint, on the other hand, is not directly involved in this specific range of motion.

The given answer is correct because bringing the head down to the shoulder by tipping the head to the side is not a substitution or trick movement for shoulder abduction to 90 degrees. The other options listed, such as shoulder shrug, scapular extension, and contralateral or ipsilateral trunk side flexion, can all be used as alternative movements to achieve shoulder abduction to 90 degrees.

The question asks for the muscle that is not involved in the motion of shoulder external rotation. The infraspinatus and teres minor muscles are both involved in shoulder external rotation. The supraspinatus muscle also assists in this motion. However, the posterior deltoid muscle is not involved in shoulder external rotation, as its primary function is shoulder extension and horizontal abduction. Therefore, the correct answer is the posterior deltoid.

Lifting a cup to take a drink requires the action of shoulder elevation. When lifting a cup, the arm needs to be raised towards the mouth, and this movement involves the elevation of the shoulder joint.