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Detailed notes about the human shoulder

1. SHOULDER/GLENO-HUMERAL JOINT DR. G. KAMAU

2. Classification & stability Synovial, Multiaxial , Ball&socket joint between the humeral head & small , shallow glenoid fossa of scapula which is pear- shaped .The articular surface of humeral head is four times that of the glenoid,&only 1/3 of it articulates with the glenoid cavity. This marked disproportion between the head & glenoid allows wide range of movements at the expense of stability making the joint most unstable. Glenoid labrum a triangular fibro- cartilage whose base is attached to the rim of glenoid fossa peripherally >deepens & widens >enlarging the glenoid fossa >increasing the joint stability. The labrum edge is thin &sharp. Labral tears & glenoid defects ( Bankart lessions ) are frequent cause of anterior shoulder instability & recurrent dislocation of the shoulder. The angle of inclination of humeral head &shaft is 130-150 degrees & is also retroverted about 30 degrees posteriorly lmost same orientation as the medial epicondyle & condyle .

3. Fibrous capsule & ligaments Fibrous capsule attached to anatomical neck around the articular cartilage margin except inferiorly where it is attached below the articular surface about 1” below the articular margin at the surgical neck.This makes the capsule lax & loose inferiorly which is necessary to give the joint greater mobility. Tapping of the shoulder can be done from inferior part of the shoulder ,where fluid collect due to loose capsule & synovium . Since part of inferior medial part of surgical neck of humerus is intra- articular , osteomyelitis of this area> septic arthritis. The fibrous fibres of the capsule are tough and arranged transversely at the joint. Anteriorly the fibrous capsule is thickened to form intrinsic ligaments from glenoid & supra- glenoid tubercle to anatomical neck of humerus . The intrinsic ligaments are well seen intra- articular , especially during arthroscopy - 1)superior gleno -humeral ligament -2)middle gleno -humeral ligament -3)inferior gleno -humeral ligament (often the middle &inferior ligaments are joined together)

4. Extrisic Shoulder ligaments Coraco -humeral ligament to the greater tuberosity . Occassionally P.Minor sends a slip to it. Transverse ligament is formed from capsule between LT &GT between the inter-tubercular / bicipital groove containing long head of biceps tendon. Coraco-acromial arch :-extrinsic & prevents upward displacement of humeral head.The arch formed by the overhanging smooth inferior surfaces of coracoid & acromion process and the bridging coraco-acromial ligament. Coraco-acromial ligament is strong ,triangular & flat from the broader medial border of acromion to smaller lateral border of coracoid . Below the arch is subacromial bursa which prevents impingement of the head & supraspinatus tendon on to the arch during abduction,& is continous with sub-deltoid bursa which is below the deltoid &communicates with it.

5. Other Stability factors Rotator cuff muscles (SITS) which blend intimately with the capsule posterioly , superiorly & anteriorly . Supraspinatus (most important) together with T.Minor & Infraspinatus are attached to greater tuberosity . Subscapularis is attached to lesser tuberosity anteriorly . RC prevents nipping of the capsule during abduction & further thicken the capsule. Long head of biceps tendon which passes at bicipital groove between the lesser & greater tuberosities below the transverse ligament, becomes intra- articular , to be attached to supra- glenoid tubercle. It is invested by synovium & prevents upwards head displacement, steadying it during shoulder movements. Long head of triceps inferiorly especially in abduction preventing the head subluxating /dislocating through loose lax inferior capsule. Other distantly related long muscles acting on the shoulder are deltoid,P.Major,T.Major , Lattismus dorsi . Negative intra- artcular pressure has been suggested as contributing to stability

6. Shoulder synovium & surrounding bursae The synovium lines the capsule & is attached to glenoid labrum & articular margin of the head of humerus.It invests the long head of biceps in a tubular sleeve at the bicipital groove which it also covers together with inferior surface of transverse ligament.An opening on anterior part between the superior &middle glenohumeral ligaments at the base of coracoid , to communicate with subscapularis bursa , beneath the tendon of subscapularis .A similar opening posteriorly may communicates with infraspinatus bursa.Sub-acromial bursa does not communicate with the shoulder,but is continous with sub-deltoid bursa. It lies below subacromial arch & above supraspinatus tendon which it protects from attrition &impingement.

7. Movements of the shoulder joint. Shoulder movements occur at anatomical glenohumeral joint & at physiological scapulo -thoracic joint between the chest&scapula.Supraspinatus initiates the first 25-30 degrees of abduction after which the middle acromial part of deltoid continues with abduction until 90 degrees when the greater tuberosity impinges on the glenoid rim & no further articular surface is available on the humerus.This can be increased further by external / lateral rotation of the arm by T.minor & Infraspinatus , to delay impingement up to 120 degrees.Further abduction is entirely scapulothoracic even up to 180 degrees. Even when the shoulder is arthrodesed at ~ 20 degrees of abduction, the scapulo-thoacic movements allow reasonable use of the shoulder. Another view is that for every 15 degrees of abduction, 10 degrees is at gleno -humeral joint, & 5 degrees scapulo -thoracic.

8. Adduction 0-50 degrees Abduction 0- >170 Forward flexion 0-165 degrees Backward extension 0-60 degrees Internal &external rotation 0-70 degrees Circumduction

9. Principle muscles acting on the shoulder joint Abductors :-1) supraspinatus (initiates) -2)Deltoid (middle acromial part) Adductors :-1) P.Major -2) Lattismus dorsi Flexors :-1) P.Major -2)Deltoid (anterior clavicular part) -3) Coracobrachialis Extensors :-1) Lattismus Dorsi .2)Deltoid (posterior scapular part). 3) T.Major . Medial rotators :-1) Subscapularis . 2) T.Major . 3)P. Major. -4) L.Dorsi . Lateral rotators :-1) infraspinatus . 2) Teres Minor * What is “triangle of ascultation ” & “Lumbar triangle of Petit “in relation to Lattismus Dorsi ? What is LD called?

10. Neuro -vascular supply Hilton’s law that the nerves supplying the muscles acting on a joint also supply the joint. Axillary nerve, Suprascapular nerve, musculo-cutaneous & lateral pectoral. Anterior & posterior humeral circumflex vessels

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12. Some clinical shoulder conditions Acute traumatic dislocation:- Very common because of inherent shoulder instability. Anterior/sub- coracoid commonest but Posterior & inferior ( subglenoid / Luxatio Erecta ). *(the theory is that the dislocation is initially inferior before becoming anterior or posterior) Axillary view xray of the shoulder, can differentiate anterior & posterior types. Reccurrent anterior shoulder dislocation where the shoulder easily dilocates with minor force usually after acute dislocation causing anterior labral tears & glenoid defects.It is recurrent if dislocation is >4times.It could be due to ligament laxity > joint hypermobility .Epilepsy may trigger the dislocation . They may have a postero -lateral defect of humeral head (Hill Sachs lession ) with anterior glenoid / labral defects ( Bankart Lession ) Habitual dislocation:- Usually by mentally unstable patient with ligament laxity or shoulder instability who dislocates &reduces the shoulder voluntarily. Paralytic dislocation due brachial plexus palsy. Shoulder instability causing “dead arm syndrome” Anterior is commonest but posterior,inferior or multiaxial .

13. When the shoulder is dislocated ,the head is adducted & internally rotated by subscapularis.In dislocated shoulder the shoulder bulge is lost > shoulder flatenning with coraco-acromial arch becoming prominent. Hence in Kocher’s manouvre of reducing, the arm is rotated externally to stretch the subscapularis.This is followed by adduction of the flexed elbow across the chest to relocate the head back to the glenoid . Hippocratic method by longitudinal traction & adduction of the arm. Reduction by gravity.

14. Supraspinatus tendinitis > “painful arch syndrome” between 60-120 degrees of abduction when the tendon become impinged between the coraco-acromial arch & humeral head. Subacromial bursitis

15. Painful Arc Syndrome due to impingement of rotator cuff at subacromial space between 70-120 degrees range of abduction. Due to subacromial bursitis or RC tendinitis.Pain in the last 30 degrees of abduction is often due to A/C joint pathology. RC tears:- Common in the elderly due to degeneration &attrition of RC especially supraspinatus tendon. Acute Tear occur in the young often from shoulder sports injuries Calcific tendinitis of supraspinatus tendon. Rupture of long head of biceps tendon /Biceps tendinitis at bicipital groove. Adhesive capsulitis /Frozen shoulder :- May be autoimmune or associated with DM

16. UPPER ARM The upper arm is enclosed by brachial fascia which give medial & lateral intermuscular septum that divide the muscles into anterior /flexor &adductor compartment and posterior/extensor compartment. The medial intermuscular septum is attached to medial supracondylar ridge of humerus &medial epicondyle.It is pierced by ulnar nerve.The lateral intermuscular septum is attached to lateral supracondylar ridge of humerus & lateral epicondyle.It is pierced by radial nerve & profunda brachii artery.The nerve for anterior compartment is musculocutenous . For posterior compartment is radial nerve.

17. Muscles of anterior/flexor &adductor compartment. -1) coracobrachialis :- Arises from coracoid process.Inserted to upper medial border of humerus.Very weak adductor.Nerve supply musculocutenous .(the muscle is the counterpart of three adductors of lower limb.The upper two heads have fused together enclosing musculocutenous nerve between them.The ligament of Struthers when present is a remnant of lower head).

18. 2)Biceps:-Short head arises from coracoid . Long head arises from supraglenoid tubercle> Intra- articular in the shoulder>enclosed with Synovium at bicipital groove where it is covered by transverse humeral ligament.Attached to Biceps tuberosity of radius &by bicipital Aponeurosis to subcutenous of upper ulna & deep fascia. Flexor of elbow& powerful supinator of forearm. Nerve supply- musculocutanous . 3) Brachialis :- Broad flat muscle arising from the front of lower 2/3 of humerus.Inserted to coronoid process & tuberosity of ulna. Nerve supply:-lateral ½ by radial nerve,medial ½ by musculocutenous . Elbow flexor.

19. Triceps is the only extensor/posterior compartment of upper arm. Long head from infraglenoid tubercle. Lateral head from lateral lip of spiral groove. Medial head from medial lip of spiral groove.Nerve supply-radial nerve . Attached to olecranon process of ulna.Elbow Extensor.Long head is important stabiliser of abducted shoulder *but is not intra- articular . Brachioradialis Arising from lateral supra- condylar ridge.Attached to radial styloid process. Elbow flexor ECRL From lower part of lateral supracondylar ridge &lateral intermuscular septum .Attached to back of base of 2 nd metacarpal. Wrist extensor *NB Brachioradialis , ECRL & anconius are supplied by radial nerve above the elbow > hence spared in elbow injuries involving the posterior interrosseous nerve between the supinator heads >the patient can extend the wrist with radial deviation, but still can not extend the Mpjoints . Anconius triangular small muscle covering the radial head from lateral condyle to lateral aspect of proximal ulna olecranon process

20. Arteries of upper limb Axillary artery:- Continuation of subclavian artery at outer border of 1 st rib to end as brachial artery at lower border of T.Major . Divided into three parts by P.Minor . 1 st part:- Medial to P.Minor.Its only branch is superior thoracic artery which pierces clavipectoral fascia to supply both P.Minor&P.Major 2 nd Part branches are:- 1) Lateral thoracic descending along axillary border of P.Minor to supply it together with P.Major,Serratus anterior and the breast. 2) Acromial Thoracic Pierces clavipectoral fascia to give four branches that radiate from each other:- acromial,pectoral,clavicular &humeral(deltoid)

21. 3 rd Part:- 1) Subscapular- Largest.Descends along posterio axillary wall to supply LD &SA. It gives a dorsal circumflex scapular artery. 2)Anterior humeral circumflex 3) Posterio humeral circumflex-larger

22. Brachial artery:- C ontinuation of axillary artery Initially is medial to humerus > anteriorly at Cubital fossa where it can be palpated midpoint Between medial & lateral epicondyles . Proximally, the median nerve is lateral to the artery. The nerve later crosses infront of the artery obliquely to lie medial to the artery at cubital fossa . The ulnar nerve is medial to brachial artery proximally before it leaves its company after piercing medial intermuscular septum to be in posterior comparment as it goes into cubital canal. The arte ends 1cm below the elbow where it is covered by Bicipital aponeurosis to become radial & ulnar Arteries. Other branches are 1) Profunda brachii Largest branch.Follows radial nerve passing through triangular space to be between long &medial heads of triceps above >spiral groove of humerus.It gives ascending deltoid branch to anastomose with descending branch from posterior circumflex humeral. Radial collateral &middle collateral for elbow anastomosis . 2) Superior & inferior ulna collaterals to form elbow anastomosis

23. Arterial anastomosis around the shoulder Large posterior circumflex humeral artery from 3 rd part of axillary artery Small anterior circumflex humeral artery from 3 rd part of axillary artery. Both form a ring around the surgical neck and Send ascending branches which anastomose with acromial branches around the shoulder From:-1) suprascapular artery from subclavian 2) Thoraco-acromial artery Descending branch which anastomose with ascending branch from profunda brachii .

24. Cephalic & Basilic veins of arm interconnected by median cubital vein at cubital fossa . Cephalic , Basilic & median veins of forearm.