#12. Joint نبيل خوري

Transcription

1 #12 30 Anatomy Joint هيام الر جال 9/10/2015 نبيل خوري

2 Salam Awn Some notes before starting : ** Not all slides are included, so I recommend having a look at the slides beside this sheet ** If you find any differences between the slides and the sheet, I advise you to follow the slides because the Dr. sometimes made mistakes, I corrected as much as I could ** personally, I don t recommend listening to the record while studying this sheet; because it is so modified and much more organized than the record. So please if you are interested in the record, don t follow the sheet literally ** I did my best ; forgive me for any accidental mistake 1

3 Elbow joint is the Synovial Hinge Joint that occurs between the lower extremity of the humerus and the upper extremity of both forearm bones; radius and ulna. This is somehow complex because in some matter the radioulnar joint is inside the capsule of the elbow joint, so therefore some anatomists consider it as a part of the joint, and others don't. Therefore there are 2 different joints that are located within the same area enveloped by one capsule, so it is like if you remember when we talked about the shoulder joint having the long head of the biceps goes inside the capsule of the shoulder joint; it is something like that, but still that is a tendon and this is another joint, so there is always some differences between book, articles and other sources, that's why they are unclear. Now if you look over here, the participation of the humerus is through Capitulum which is lateral and through Trochlea. Capitulum is a round head that articulate with the head of the radius (the part of the radius that participate in this joint), and the trochlear notch which is formed by the coronoid process and the olecranon in a U/L shape that fits the whole aspect. 2

4 We also talk about the radial fossa and olecranon fossa and so on. Those are parts of the joint that all are covered by the capsule, and we will see how this capsule is attached to the borders of these fossae and to the portion of the bones, and we will see that the exclusion part of this capsule (outside the capsule) that is obvious to have this; is the lateral and medial epicondyles, because most of these muscles that go into the forearm extremity whether they are extensor or flexor they can't be inside the capsule at all. So if we look over here, these are the joint articular surfaces: The capitulum and trochlea of the humerus "above". The head of the radius "below" and you will observe that the head of the radius has this radial notch and around this head there is an angular ligament which allows this bone to make this specific joint at the radioulnar level together with the supinator and pronator muscles; which is the supination and pronation of the forearm and hand. Trochlear notch "below" that is between the two processes of the upper extremity of the ulna. And all of those are covered by hyaline cartilage which is similar to hyaline cartilage at the level of any joint in the body. 3

5 Now if you look at the capsule, you will see that it is distributed in a different way. In this picture, you will see that the capsule is cut anteriorly to show you the superior and inferior borders. The superior border goes to the humerus (excluding the medial and the lateral epicondyles), it covers the radial fossa and the coronoid fossa AND the synovial membrane covers these fossae, so these fossae are included inside the joint because of the movement. The coronoid process will enter into the coronoid fossa, so therefore it has to be completed and covered by the synovial membrane as well. The capsule from below as you see it will cover the coronoid process of the ulna in the anterior vision and cover the head of the ulna toward the middle distance between the head and the body which is the neck of the radius. So practically the capsule is very tough and tight laterally and it is loose anteriorly and posteriorly and that will allow the flexion and extension to occur. There are certain things which are found within the cubital fossa and within this joint that prevent the hyper flexion of this bone. 4

6 The posterior view of the capsule : it is more limited and looser. If you let your hand and the forearm extend onto the arm and you feel your joint posteriorly, you will be able to notice that there is an amount of fat and skin, and the skin has the capsule attached to it. Again the capsule is loose posteriorly and it will permit the complete extension but the hyper extension is prevented by the olecranon process. Note that The posterior of the capsule is less stretched than the anterior. (The anterior is wider that gives flexibility to the joint anteriorly but limits the flexibility posteriorly). If you look around the olecranon fossa, the articular cartilage is attached to its border. There is some amount of fat pads within the capsule (inside it) so the separation between the capsule and the synovial membrane that is adherent to the deeper layer of the fat pad is to prevent the friction and erosion between the capsule and the synovial membrane as when we are putting our elbow on the table. So from the posterior view we can see : 1) The articular cartilage that covers the lower extremity of the humerus. 2) The head of the radius 5

7 3) The articular cartilage of the ulna. The upper margin of this capsule at the level of the lower aspect it will go all the way surrounding the olecranon, leaving the olecranon exposed and it is covered by the skin. The capsule is surrounding most of the structures that are delineated by the bones. The lateral and medial epicondyles are very exposed and they hold the ligaments which are : Lateral (Radial Collateral) Ligament Medial (Ulnar Collateral) Ligament The radial collateral ligament is triangular in shape; it goes and fuses anteriorly with the annular ligament around the head of the radius, extending from the anterior aspect of the radial notch of the ulna to the posterior aspect of the fossa. Lateral (Radial Collateral) Ligament This annular ligament goes all the way to the ulna and the medial aspect covering the radial roof of the ulna. This triangular shape comes immediately from underneath the lateral epicondyle and goes all the way to be inserted and enforce the capsule as well as the neck of the radius. 6

8 It has an apex and a base because it is triangular shape and the base fuses the annular ligament. Medial (Ulnar Collateral) Ligament This ligament is more of slip like structure, it has a triangular aspect with two slips; one slip is straight forward and it is called anterior band and posterior band. The anterior and posterior bands are 2 bands that aren't triangular, but when you look at them from the medial aspect you will see that they are triangular!! :P They are overlapped : the medial one is the anterior and the lateral one is the posterior They take origin from inferior aspect of the medial epicondyle and they will go all the way to the margin of the olecranon fossa covering the capsule. and together they are united at the base where they have transverse band which goes all over the olecranon fossa in the medial aspect, so that it will hold and cover most of the capsule that is around the olecranon fossa of the ulna. ** form the slides ** Anterior strong cord-like band: Between medial epicondyle and the coronoid process of ulna Posterior weaker fan-like band: Between medial epicondyle and the olecranon process of ulna Transverse band: 7

9 Passes between the anterior and posterior bands holding them together in position. **** **** **** **** The presence of the biceps brachii tendon prevents the hyper flexion, so together the capsule and this tendon prevent the hyper flexion of the joint. Beside the biceps brachii tendon there is the bicipital aponeurosis which is a band at the insertion of the biceps brachii that goes to the ulna, it covers and enforce the anterior aspect of the capsule of this joint. Synovial Membrane It is a membrane that follows the entire capsule and covers most of joint, leaving it sterile and it doesn t allow any thing to go in there. It exactly follows the inner aspect of the capsule, so anteriorly and posteriorly have it the same, except that in the posterior where the capsule is loose this will form a bag and as we said before: " at the level of the olecranon process we have fat pads that separate this synovial membrane from the capsule to prevent the friction in that region ". Note that : the posterior fat pad is bigger and has more specific role than the anterior one. 8

10 ** form the slides ** This lines the capsule and covers fatty pads in the floors of the coronoid, radial, and olecranon fossae. Is continuous below with synovial membrane of the superior radioulnar joint **** **** **** **** Bursae around the elbow joint: 1) Subcutaneous olecranon bursa : between the lateral collateral ligament and the insertion as well as between the origin of these extensor muscles and the bones. This bursa prevents the extensor muscle form friction over the posterior aspect of the ulna because the ulna is bigger posteriorly, so that it needs more potential. 2) Subtendinous olecranon bursa : which is a continuation, and it is between the origin of the extensors. *************************** What are the relations of this joint? Anterior: Brachialis and biceps brachii ( they both provide protection to the capsule anteriorly) Tendon of Biceps Median nerve Brachial artery 9

11 The presence of the Brachialis enforces the joint laterally, where the biceps brachii enforces the capsule anteriorly and prevents the hyper flexion. Posterior: Triceps muscle Small bursa intervening Triceps muscle and the subcutaneous fat and the bursa will hold the friction and enforce the loose capsule posteriorly even though the muscle insertion is tough, but still we have this olecranon bursa that prevent the friction between the tendon of the insertion of the triceps and the posterior olecranon surface. Lateral: Common extensor tendon The supinator Medial: Ulnar nerve The clinical aspect of the ulnar nerve is very important, when ever you want to palpate this nerve; you go into the lateral aspect there is a groove immediately under the medial epicondyle as when we hit our hand and feel electricity goes into the forearm and hand. The radial nerve is the most dangerous and exposable part of the brachial plexus and it is the only thing that is weak in the elbow joint. Movements Flexion Is limited by the anterior surfaces of the forearm and arm coming into contact. Extension Is limited by the tension of the anterior ligament and the brachialis muscle which prevents the hyper extension. 10

12 The joint is supplied by branches from the: Median Ulnar Musculocutaneous Radial nerves The flexion is made by the brachialis and biceps brachii The extension is made by the triceps brachii Carrying Angle Angle Between the long axis of the extended forearm and the long axis of the arm Opens Laterally more than medially About 170 degrees in male and 167 degrees in females Disappears When the elbow joint is flexed

13 This carrying angle is very important in radiology by measuring it. Some people have larger carrying angle which is abnormal situation and it might be deformity. We said once don t think about holding a child from his hands upward because that will increase the angle and practically what will happen is that the dislocation of the radius help more because it is laterally more open, so the dislocation of the head of the radius that occurs at that level will allow the angle to be more, and you will see the hand of the child after he was injured goes with the carrying angle which is widely opened in the lateral aspect. Articulations The elbow joint is stable because of the: Wrench-shaped articular surface of the olecranon and the pulley-shaped trochlea of the humerus. Strong medial and lateral ligaments. Elbow dislocations are common & most are posterior because the anterior aspect of the joint is having the coronoid process that might slip posteriorly and the olecranon can be fractured, and when it is fractured the dislocation occurs posteriorly. So the most common site for fracture is the olecranon process of the ulna. (Not sure about this; unclear in the record) Posterior dislocation usually follows falling on the outstretched hand. Posterior dislocations of the joint are common in children because the parts of the bones that stabilize the joint are incompletely developed 12

14 Avulsion of the epiphysis of the medial epicondyle is also common in childhood There is a line on this bone which is the Epiphyseal plate it is a line that connects between the epiphysis and the diaphysis and that region of the bone it is called the metaphysis. This Epiphyseal plate is a layer of hyaline cartilage that provides elongation of the bone (the bone will grow in there), and after the age of seventeen this line will disappear, you will not be able to see it anymore. "you can see it only below the age of seventeen". When there is a fracture in the bone, you have to look for the epiphysis because this line extends from the upper part of the lateral to the upper part of the medial epiphysis. So practically when the bone is broken; it will be broken at the weakest part which is in the Epiphyseal line. So the breakage of the lower end of the humerus occurs at the level of the epiphysis; the lower fracture will happen at the level of the epicondyle lateral 13

15 and medial and in the lower of the Epiphyseal line that is weak at this part and there is no bony structure. CUBITAL FOSSA Now we will come to the 2 nd part of this lecture which is the cubital fossa or antecubital fossa "we will call it the cubital fossa " The cubital fossa is a triangular space that is located between the muscles and delineated superiorly by an imaginary line that goes from the lateral to the medial epicondyles. The lateral border is made by the medial border of the brachioradialis. The medial border is made by the lateral border of pronator teres. The superior border is made by the imaginary line between the epicondyles. The brachioradialis + pronator teres + imaginary line = form what we call it the triangular depression which is very important clinically for many things. 14

16 When doctors want to measure the blood pressure, they put the cuff and then listen with the stethoscope placed over the brachial artery in the cubital fossa. The presence of the biceps brachii muscle is very important, it has a tendon and an aponeurosis; this aponeurosis goes over the pronator teres muscle and fuses with fascia of the hand, it is very tough and you can feel it in the medial aspect if you flex your hand and partially flex your forearm on arm. Laterally this tendon goes and insert in the upper portion of the radius. Again the biceps brachii is a guideline for palpitation and taking the pulse, and that pulse is located medial to the border of the biceps brachii, you have to look at the upper border of the bicipital aponeurosis and feel the pulse. So find the pronator teres, find the biceps brachii ; and between these two muscles you can find the brachial artery at the level of the apex (it is triangular so it has a base superior and an apex inferior ), and the apex is made by the meeting of the brachioradialis and the pronator teres. Now at this level the brachial artery will break down into radial and ulnar arteries. Medial to the brachial artery there is the median nerve that goes in the back and you can see it in the medial posterior to the medial epicondyle. 15

17 In the surface anatomy you observe the cubital fossa (you can draw it), so if you want to palpate the pulse, you have to go lateral to the upper medial corner, you will see the medial cubital vein and lateral to that you can push your hand between the biceps brachii and pronator teres and feel the pulse. Notice the cephalic vein and basilic vein and between them there is a connection which is the median cubital vein (very big vein), and when you hold your arm tightly, these veins will pop up and you can see them and introduce your IV or insert a needle and draw blood. The roof of the cubital fossa is formed by superficial fascia and skin. The most important structure within the roof is the median cubital vein, which passes diagonally across the roof and connects the cephalic vein on the lateral side of the upper limb with the basilic vein on the medial side. The bicipital aponeurosis (which is superficial) separates the median cubital vein from the brachial artery and median nerve. 16

18 The median cubital vein is above the bicipital aponeurosis * it is the most superficial after the skin *, where as the brachial artery is deeper. Order from superficial to deep : Skin median cubital vein bicipital aponeurosis brachial artery Other structures within the roof are cutaneous nerves-the medial cutaneous and lateral cutaneous nerves of the forearm. The medial and lateral cutaneous nerves together with the veins they are located more superficially to the bicipital tendon. The brachial artery can't be seen unless you remove the bicipital aponeurosis because it is the 2 nd deeper part after the median cubital vein and the bicipital aponeurosis. The brachial artery normally bifurcates into the radial and ulnar arteries in the apex of the fossa, although this bifurcation may occur much higher in the arm, even in the axilla. (There is variation in the site of bifurcatation). 17

19 The median nerve lies immediately medial to the brachial artery and leaves the fossa by passing between the ulnar and humeral heads of the pronator teres muscle. The brachial artery and the median nerve are covered and protected anteriorly in the distal part of the cubital fossa by the bicipital aponeurosis. This flat connective tissue membrane passes between the medial side of the tendon of the biceps brachii muscle and deep fascia of the forearm. It holds the superficial flexor muscles of the forearm in position (there is no overlapping). The sharp medial margin of the bicipital aponeurosis can often be felt. **** **** **** **** The radial nerve can't be considered as a part of the cubital fossa because it lies under (masked by) the brachioradialis (lateral margin of the fossa). It gives off deep branch of the radial nerve and continues as superficial radial nerve there is a deep and superficial branch of the radial nerve that goes into the forearm. Contents of the cubital fossa Superficially, in the subcutaneous tissue overlying the fossa median cubital vein, medial and lateral antebrachial cutaneous nerves basilic and cephalic veins. 18

20 Mnemonic for order of structures from lateral to medial : TAN : Tendon - artery nerve The major contents of the cubital fossa, from lateral to medial, are: The tendon of the biceps brachii muscle The terminal part of brachial artery The median nerve The End 19