 Good day everybody. This is Dr. Sanjay Sanyal, Professor and Department Chair. I'm going to give you a quick demonstration of the components of the spectral girdle, the clinical functional correlations and some clinical applications. I'm holding up the right clavicle for you and you can see this is the sternal end of the clavicle. This is the medial two-thirds of the clavicle, which is curved anteriorly and this is the necromial end of the clavicle. And we can see that the lateral one-third of the clavicle is curved posteriorly. So this is the right side. So this is the one which forms the sternoclavicular joint and this is the one which forms the acromeoclavicular joint. We don't have the sternum, but I will show you the acromeoclavicular joint. So I'm holding up this scapula here and you can see that this is the acromeone process. An acromeone process then continues as the spine of the scapula. So you can see that this is the smooth portion here. This smooth portion is the one which forms the acromeoclavicular joint and it articulates with this smooth portion. of the clavicle. So therefore, this is the acromio-clavicular joint. Both of them are sliding joints, the sternoclavicular and the acromio-clavicular. They are enclosed in a fibrous capsule and they are synobium joints and there is an intra-articular disc, a fibro-cartilage, which partially or completely separates the joint and both of them are uniaxial joints. The sternoclavicular joint is reinforced by several sets of ligaments. We have anterior sternoclavicular ligament, posterior sternoclavicular ligament. We have the inter-clavicular ligament and the costoclavicular ligament attaching to the first strip. So therefore, the sternoclavicular joint is very strong, very stable and during dissection we have a lot of difficulty trying to disarticulate the sternoclavicular joint and in clinical practice also the sternoclavicular joint hardly ever dislocates. Acromio-clavicular joint, on other hand, is also reinforced by many ligaments but it is more likely to either dislocate or separate but that will come to a little later. The ligaments attached to this one is the ligament itself connecting the clavicle to the acromion process that is called the acromio-clavicular ligament. Then we have some supporting ligaments. One of them is the coraco-clavicular ligament which extends on the corokite process to the clavicle. This has got two components, a medial component which is called the conoid part which is attached to the conoid tubercle and a lateral component called the trapezoid part which is attached to the trapezoid line on the clavicle and then we have a coraco-acromial arch which extends from the corokite process to the acromion process. With these two are extrinsic ligaments which indirectly support the acromio-clavicular joint therefore the true ligament of the acromio-clavicular joint is the acromio-clavicular ligament itself. Now let's take a look at the amount of excursions that are possible. As I said both the joints are sliding joints they are uniaxial joints. When my arm is in the neutral position so that is the position when this clavicle is like this. When I flex my shoulder the lateral end of the clavicle moves forward by 30 degrees it slides. So therefore at that position there is sliding movement at the sternoclavicular joint and at the same time there is sliding movement at the acromio-clavicular joint also. When I push my arm back extended the lateral end of the clavicle moves back by another 30 degrees. So therefore the total excursion is 30 degrees forward 30 degrees backwards. From the neutral position when I do overhead abduction. Then again the same sliding movement occurs here and the lateral end of the clavicle moves up by 60 degrees and comes back to the neutral position. So therefore the total excursion in this axis is 60 degrees and the total excursion in this axis is also 60 degrees 30 plus 30 and all of them are sliding. Now let's take a look at the scapula itself. The scapula as you know is on the surface of the chest wall and in between we have the serratus anterior muscle here and sub scapularis. This forms what is known as a functional scapula thoracic articulation. It is not a true joint. The scapula can rotate on the chest wall. It can move forward during protraction. It can move back during retraction of the shoulder. When we are doing overhead abduction the glenoid can rotate up and down. This is referred to as a scapula humoral rhythm and it's a fixed ratio of one is to two. That means for a full 180 degrees of abduction 60 degrees is constituted by the rotation of the scapula and 120 degrees is contributed by the movement of the humerus. So this is what is meant by scapula humoral rhythm one is to two. 60 degrees of this plus 120 degrees of this contribute to the total 180 degrees of overhead abduction. At this juncture I will remind you that the humerus and the glenoid fossa this is the true shoulder joint. This is not part of the pectoral girdle. However every movement of the shoulder joint is accompanied by movements of the pectoral girdle. The actual pectoral girdle on the bones are the glavicle and the scapula and the actual joints are the sternoclavicular joint and the acrobioclavicular joint. Now let's take a look at some clinical correlations pertaining to these joints. As I mentioned the sternoclavicular joint is very stable. It does not dislocate in clinical practice so easily and if it has to dislocate there will be much more serious injuries to the chest and the neck. In contrast we can have separation of the acrobioclavicular joint. If a person falls on his elbow then he can have tear of the acrobioclavicular ligament but the coraco-clavicular ligament will be intact and therefore there will be separation of the acrobioclavicular joint and you can see this in the accompanying radiological image which I am going to put in this video. This is an x-ray of the chest on the right side showing acrobioclavicular joint separation. On the other hand if a person falls on his shoulder then he can have a more serious injury and that is acrobioclavicular joint dislocation as opposed to separation and in clinical terms it is often quite erroneously referred to as shoulder separation but it is actually strictly speaking not shoulder separation but it's a complete dislocation of the acrobioclavicular joint and what happens in this acrobioclavicular ligament as usual is torn. Additionally the coraco-clavicular ligament which I said has got two components the conoid and the trapezoid part they are also torn and therefore the lateral end of the clavicle moves up and it forms a distinct bulge on the tip of the shoulder of course accompanied by severe pain. This is acrobioclavicular joint dislocation. This is another x-ray of the chest shoulder joint to show acrobioclavicular dislocation. Now let's take a look at some fractures of the clavicle. The most common type of fracture is at the junction of the medial two-third which I said is curved posteriorly and the lateral one third which I said is curved posteriorly. The most common fracture is at the junction of this and this usually occurs when a person falls on his outstretched hand and this occurs when a person is suffering from osteoporosis or it can happen in children because of the indirect blow transmitted from the hand to the shoulder to the clavicle the fracture occurs here so therefore this is an indirect blow there's no direct blow to the clavicle. When this fracture occurs then what happens the distal portion of the clavicle it sags down with the weight of the arm and the proximal portion of the clavicle moves up by the pull of the sternocleidomastere muscle which is usually occurs in all types of fractures of the clavicle and you can see that in the accompanying x-ray. We can get yet much less common but we can get if there's a direct blow to the clavicle then we can get a fracture somewhere in the middle of the clavicle and then also the distal portion of the clavicle the lateral portion sags down because of the weight of the arm and the proximal portion moves up by the pull of the sternocleidomastere muscle which is attached here this is the plain x-ray of the left side of the chest to show fracture of the clavicle showing upward elevation of the proximal fragment that makes me to an important point what are the secondary injuries which are possible when there's a fracture of the clavicle if you remember that the clavicle forms one of the boundaries of the cervical axillary canal other boundary is being formed by the first rib and the scapula upper border of the scapula and through the cervical axillary canal passes the brachial plexus the divisions of the brachial plexus which continue to the axilla and of course the axillary artery and the axillary vein when there is a fracture of the clavicle then it can injure the lower trunk of the brachial plexus more specifically the branch the fibers which contribute to the ulnar nerve so therefore ulnar nerve injury is a possibility in a fracture of the clavicle that will produce radial claw hand and loss of sensation on the major side of the hand another secondary injury that can happen is injury to the supra scapular nerve because the supra scapular nerve runs like this across the supra scapular notch supplies the supra's monitors in the supra's minus fossa and then it goes round and then supplies the infraspinus muscle in the infraspinus fossa and the clavicle is located right here so therefore fracture of the clavicle can injure the supra scapular nerve which produce paralysis of the supra's pinus and infraspinus muscle which are the rotated calf muscles so therefore the person will have difficulty in initiating abduction which is the action of the supra's pinus running on the skin cutaneous on the surface of the clavicle we have a series of nerves they are referred to as the supra clavicular nerves and usually there are three branches a medial intermediate and lateral they usually look like this in front they are a branch of the cervical plexus rarely they can go through the clavicle itself they run under the platysma and then they pierce the platysma and supply the skin in this region in a fracture of the clavicle one or more branches of the supra clavicular nerve can also be injured with loss of sensation in the appropriate region of the front of the upper chest or the front of the shoulder so these are the three associated injuries secondary injuries that you can get in a fracture of the clavicle so these are some of the points which I want to mention to you about the sternoclavicular acromuclavicular joint the clinical correlations their functional implications and some aspects of the fracture of the clavicle thank you very much for watching Dr. Sanjay Sanyal signing out if you have any questions or comments please put them in the comment section below have a nice day