114 Upper Limb: Bones, Ligaments, Joints The Free Upper Limb The humerus is twisted at its proximal end, i.e., the head is posteriorly rotated at about The bones of the free upper limb are 20Њ in relation to the transverse axis of the – The humerus distal end (torsion). The angle between the – The radius and ulna long axis of the humerus and that of the – The carpal bones head averages 130Њ, and at the distal end, – The metacarpal bones between the transverse axis of the joint – The phalanges and the long axis of the shaft of the humerus, there is an angle of 76Њ to 89Њ. Bone of the Arm The proximal epiphysial line (23) runs trans- Humerus (A–H) versely through the lesser tubercle and in- The humerus articulates with the scapula ferior to the greater tubercle. It crosses the and the radius and ulna. It consists of the zone of attachment of the capsule (see body and upper (proximal) and lower (distal) p. 117) in such a way that a small part of the ends. The proximal end is formed by the Upper Limb shaft comes to lie within the capsule. At head (1), adjoining the anatomical neck (2). the distal end there are two epiphyses and On the anterolateral surface of the proxi- two epiphysial lines (24). One epiphysis car- mal end lies laterally the greater tubercle ries the medial epicondyle and the other (3), and medially is the lesser tubercle (4). the joint surfaces and the lateral epicon- Between these tubercles begins the inter- dyle. tubercular sulcus (5), which is bounded dis- tally by the crests of the lesser (6) and Ossification: In general, development of the ossification centers and fusion of the epiphyses greater (7) tubercles. The surgical neck (8) occur somewhat earlier in females than in males. lies proximally on the body of the The perichondral bone anlage in the shaft ap- humerus. In the middle of the body lies pears in the 2nd– 3rd intrauterine month. The laterally the deltoid tuberosity (9). The body endochondral ossification centers in the may be divided into an anteromedial sur- epiphyses appear between the 2nd week of life face (10) with a medial border (11), and an and the 12th year. Three centers appear proxi- anterolateral surface (12) with a lateral mally soon after birth, and distally four ossifica- border (13), which becomes sharpened dis- tion centers develop later. The distal epiphysial tally and is called the lateral supracondylar disks fuse during puberty and the proximal disks at the end of puberty. ridge. The groove for the radial nerve (14) lies on the posterior surface of the body. Variants: Just above the medial epicondyle a The distal end of the humerus bears on its supracondylar process (25) is occasionally found, medial side the large medial epicondyle and above the trochlea there may be a su- (15) and on the lateral side the smaller pratrochlear foramen (26). lateral epicondyle (16). The trochlea (17) and the capitulum (18)of Clinical tip: 50% of fractures of the humerus the humerus form the humeral condyles for occur in the shaft. There is a risk of damage to articulation with the bones of the forearm. the radial nerve! The radial fossa (19) lies proximal to the capitulum and proximal to the trochlea is the somewhat larger coronoid fossa (20). Medial to the trochlea (D) there is a shal- low groove, the groove for ulnar nerve (21). On the posterior surface above the trochlea is a deep pit, the olecranon fossa (22). aus: Platzer, Locomotor System (ISBN 9783135333069), ᮊ 2009 Georg Thieme Verlag KG Humerus 115 2 2 1 1 3 3 4 5 2 2 886 8 12th15th 8 15 months 2nd3rd 21 years 7 D Medial view of distal 2nd4th end of humerus years Upper Limb 2nd3rd i.u.m. 14 9 15 26 E Supratrochlear 8th13th 5th year foramen years 1st 12 th year year 13 12 10 11 C Ossification of humerus 25 16 19 16 20 22 15 15 18 17 17 A Anterior view of right humerus B Posterior view of right humerus F Supracondylar process 24 23 24 23 24 24 G Anterior view of epiphyseal lines H Posterior view of epiphyseal lines aus: Platzer, Locomotor System (ISBN 9783135333069), ᮊ 2009 Georg Thieme Verlag KG 130 Upper Limb: Bones, Ligaments, Joints Radiocarpal and Midcarpal Joints Ligaments in the Region of the Wrist (A–E) (A–E) Four groups of ligaments can be distin- The radiocarpal or wrist joint is an ellip- guished: soid joint formed on one side by the radius (1) and the articular disk (2) and on the Ligaments which unite the forearm bones with other by the proximal row of carpal bones.Not the carpal bones (violet). These include the all the carpal bones of the proximal row are ulnar collateral ligament (8), the radial col- in continual contact with the socket- lateral ligament (9), the palmar radiocarpal shaped articular facet of the radius and the ligament (10), the dorsal radiocarpal liga- disk. The triquetrum (3), only makes close ment (11), and the palmar ulnocarpal liga- contact with the disk during ulnar abduc- ment (12). tion and loses contact on radial abduction. Ligaments which unite the carpal bones with The capsule of the wrist joint is lax, dorsally one another,orintercarpal ligaments (red). These comprise the radiate carpal ligament Upper Limb relatively thin, and is reinforced by numer- ous ligaments. The joint space is un- (13), the pisohamate ligament (14), and the branched and sometimes contains synovial palmar intercarpal (15), dorsal intercarpal folds. Often the wrist joint is in continuity (16), and interosseous intercarpal ligaments with the midcarpal joint. (4). Ligaments between the carpal and metacarpal The midcarpal joint is formed by the proxi- bones,orcarpometacarpal ligaments (blue). mal and distal row of carpal bones and has an To this group belongs the pisometacarpal S-shaped joint space. Each row of carpal ligament (17), the palmar carpometacarpal bones can be considered as a single articu- ligaments (18), and the dorsal carpometa- lar body, and they interlock with each carpal ligaments (19). other. Although there is a certain limited Ligaments between the metacarpal bones,or degree of mobility between members of metacarpal ligaments (yellow). These are or- the proximal row of carpal bones, this is ganized into dorsal (20), interosseous (21), not true of the distal row because they are and palmar (22) metacarpal ligaments. joined one to another (4), as well as to the metacarpal bones by strong ligaments. Almost all of these ligaments strengthen Thus, the distal row of carpal bones and the the joint capsules and partly guide the metacarpals form a functional entity. movements of the joints of hand. The joint capsule is tense on the palmar sur- The joints between the carpal bones of a face and lax dorsally. The joint space is row are designated as intercarpal joints. branched and has connections with the Only the joint between the triquetrum and radiocarpal joint, and around the the pisiform, the pisiform joint deserves trapezium (5) and trapezoid (6) there are special attention. also connections with adjacent carpometa- carpal joints. Clinical tip: Several more ligaments are de- Sometimes the joint space contains scribed in hand surgery. They are important in numerous synovial folds (7). The space be- cases of surgical intervention. tween the lunate and triquetrum and the capitate and hamate is padded by synovial folds which may be visible in radiographs. aus: Platzer, Locomotor System (ISBN 9783135333069), ᮊ 2009 Georg Thieme Verlag KG Radiocarpal and Midcarpal Joints 131 1 1 8 8 11 10 9 9 10 12 3 15 16 14 16 13 17 16 13 18 19 19 Upper Limb 19 20 22 20 20 22 22 A Ligaments of right wrist, B Ligaments of right wrist, dorsal surface palmar surface 1 2 D Diagram of ligaments of right wrist, dorsal surface 3 7 4 5 7 4 6 21 21 21 21 C Section through right wrist, E Diagram of ligaments dorsal view of right wrist, palmar surface aus: Platzer, Locomotor System (ISBN 9783135333069), ᮊ 2009 Georg Thieme Verlag KG 140 Upper Limb: Muscles, Fascias, and Special Features Shoulder Muscles The latissimus dorsi (12) is broad and flat, and is the largest muscle in humans. It Inserted on the Humerus arises from the spinous processes of the Dorsal Muscle Group, continued (A–D) seventh to twelfth thoracic vertebrae (13)as the vertebral part,fromthethoracolumbar Insertion on the lesser tubercle and its crest fascia (14) and the posterior third of the subscapularis, teres major and latissimus dorsi iliac crest (15) as the iliac part, from the The subscapularis (1) arises in the sub- 10th– 12th ribs (16) as the costal part, and, in scapular fossa (2) and is inserted on the addition, very often from the inferior angle lesser tubercle (3) and the proximal part of of the scapula as the scapular part (17). The its crest. Near to its attachment between latissimus dorsi thus usually arises in four the subscapularis and the joint capsule oc- parts which have different functions. It curs the subtendinous bursa of the sub- develops embryologically with the teres scapularis (4), and between it and the base major, with which it is inserted on the crest of the coracoid process lies the subcoracoid of the lesser tubercle (18). The subtendinous Upper Limb bursa (5). Both bursae are connected with bursa of the latissimus dorsi lies immedi- the joint space. It produces medial (inter- ately before the junction of both muscles. nal) rotation of the arm. The latissimus dorsi provides the muscular Nerve supply: subscapular nerve (C5–C8).