RADIOGRAPHIC ANATOMY OF THE SKELETAL YSYTEM.pptx

Gross anatomy and radiographic anatomy of the skeletal system

1. RADIOGRAPHIC ANATOMY OF THE SKELETAL YSYTEM BY DR. MOHAMMED SIDI DEPARTMENT OF MEDICAL RADIOGRAPHY, FACULTY OF ALLIED HEALTH SCIENCES, BAYERO UNIVERSITY, KANO

2. UPPER LIMB The scapula T his flat triangular bone has three processes, borders and angles. The 3 processes are: The glenoid process, which is separated from the remainder by the neck of the scapula. The glenoid cavity forms part of the shoulder joint.

3. UPPER LIMB…. The spine, which arises from the posterior surface of the scapula and separates the supraspinous and infraspinous fossae . The spine extends laterally over the shoulder joint as the acromium . The coracoid process, which projects anteriorly from the upper border of the neck of the scapula.

4. UPPER LIMB…. Radiological features of the scapula Plain radiographs The inferior angle of the scapula lies over the seventh rib or interspace This is a useful guideline in identifying ribs or thoracic vertebral levels. The scapula lies over the ribs and obscures some of the lung fields in PA chest radiographs unless the shoulders are rotated forwards.

5. UPPER LIMB…. In AP views it is not usually possible to rotate the scapulae off the lung fields. Similarly, in AP views of the scapula the beam is centred over the head of the humerus to project the thoracic cage away from the scapula.

6. UPPER LIMB…. In lateral chest radiographs, the lateral border of the scapula may be confused with an oblique fissure. The inferior angle of the scapula may be slightly bulbous and simulate a mass on this view. Isotope bone scan The inferior angle of the scapula overlying the seventh rib may appear as a 'hot spot'.

7. UPPER LIMB…. Ossification The scapula ossifies in the eighth week of fetal life. An ossification centre appears in the middle of the coracoid process in the first year of life and fuses at 15 years of age.

8. UPPER LIMB…. Secondary centres appear in the root of the coracoid process. The medial border and the inferior angle of the scapula between 14 and 20 years. And fuse between 22 and 25 years of age.

9. UPPER LIMB…. The Clavicle The clavicle lies almost horizontally between the sternoclavicular and the acromioclavicular joints. It is also attached to the first costal cartilage by the costoclavicular ligament, which arises from the rhomboid fossa on its inferomedial surface.

10. UPPER LIMB…. It is connected to the coracoid process by the coracoclavicular ligament at the conoid tubercle and the trapezoid line on its inferolateral surface. The subclavian vessels and the trunks of the brachial plexus pass behind its medial third.

11. UPPER LIMB…. Radiological features of the clavicle Chest radiograph The clavicle overlies the apices of the lungs in chest radiographs. Apical or lordotic views are used to project the clavicles above the lungs to evaluate this area further.

12. UPPER LIMB…. In portable AP chest radiography, if the patient is inclined backwards from a true vertical position the horizontal beam projects the clavicles above the lungs. On a chest radiograph, the distance between the medial end of the clavicle and the spine of the vertebrae is equal on both sides unless the patient is rotated.

13. UPPER LIMB…. The rhomboid fossa is seen in 0.6% of normal chest X-rays and 33% are bilateral. Ossification The clavicle begins to ossify before any other bone in the body. It ossifies in membrane from two centres that appear at the fifth and sixth fetal weeks, and fuses in the seventh week.

14. UPPER LIMB…. A secondary centre appears at the sternal end at 15 years in females and 17 years in males, and fuses at 25 years of age. The humerus The hemispherical head of the humerus is separated from the greater and lesser tubercles by the anatomical neck. Between the tubercles is the bicipital groove for the long head of the biceps.

15. UPPER LIMB…. The shaft just below the tubercles is narrow and is called the surgical neck of the humerus . The shaft is marked by a spiral groove where the radial nerve and the profunda vessels run. The deltoid tuberosity on the lateral aspect of the midshaft is the site of insertion of the deltoid muscle.

16. UPPER LIMB…. The lower end of the humerus is expanded and has medial and lateral epicondyles . The articular surface for the elbow joint has a capitellum for articulation with the radial head and a trochlea for the olecranon fossa of the ulna. Above the trochlea are fossae , the coronoid anteriorly and the deeper olecranon fossa posteriorly .

17. UPPER LIMB…. Radiological features of the humerus Plain radiographs The lower epiphysis of the humerus lies at a 25° angle to the shaft so that a vertical line down the front of the shaft on a lateral radiograph - the anterior humeral line - bisects the capitellum .

18. UPPER LIMB…. An olecranon foramen may replace the olecranon fossa . A hook-shaped projection of bone - termed the supracondylar process - occasionally occurs about 5 cm above the medial epicondyle . It varies in length between 2 and 20 mm and may be continuous with a fibrous band.

19. UPPER LIMB…. The ligament of Struthers, attached above the epicondyle to form a foramen that transmits the median nerve and the brachial artery. Avulsion of the medial epicondyle The flexor muscles of the forearm arise from the medial epicondyle of the humerus .

20. UPPER LIMB…. Repeated contractions or a single violent contraction of these muscles in a child can result in avulsion of the apophysis (a secondary ossification centre occurring outside a joint) of the medial epicondyle .

21. UPPER LIMB…. Ossification The primary centre for the humerus appears at the eighth week of fetal life. Secondary centres appear in the head of the humerus at 1 year, the greater tuberosity at 3 years, and the lesser tuberosity at 5 years of age. These fuse with one another at 6 years and with the shaft at 20 years of age.

22. UPPER LIMB…. Secondary centres appear in the capitellum at 1 year The radial head at 5 years The internal epicondyle at 5 years Trochlea at 10 years Olecranon at 10 years and external epicondyle at 10 years. These fuse at 17-18 years of age.

23. UPPER LIMB…. The radius and ulna The radius has a cylindrical head that is separated from the radial tubercle and the remainder of the shaft by the neck. Its lower end is expanded and its most distal part is the radial styloid . The radius is connected by the interosseus membrane to the ulna.

24. UPPER LIMB…. The upper part of the ulna - the olecranon - is hook shaped, with the concavity of the hook - the trochlear fossa - anteriorly . A fossa found laterally at the base of the olecranon is for articulation with the radial head. The shaft of the ulna is narrow. The styloid process at the distal end is narrower and more proximal than that of the radius.

25. UPPER LIMB…. Radiological features of the radius and ulna Plain radiographs The head of the radius has a single cortical line on its upper surface and is perpendicular to the neck in the normal radiograph. Angulation of the head or a double cortical line are signs of fracture of the radial head.

26. UPPER LIMB…. The triceps muscle is inserted into the tip of the olecranon . Fracture of the olecranon is therefore, associated with proximal displacement by the action of this muscle. The ulnar styloid is proximal to the radial styloid , with a line joining them on an AP radiograph lying at an angle of 110° with the long axis of the radius.

27. UPPER LIMB…. Ossification of the radius The primary ossification centre of the radius appears in the eighth week of fetal life. Secondary centres appear distally in the first year and proximally at 5 years of age. These fuse at 20 years and 17 years, respectively.

28. UPPER LIMB…. Ossification of the ulna The shaft of the ulna ossifies in the eighth week of fetal life. Secondary centres appear in the distal ulna at 5 years In the olecranon at 10 years of age. These fuse at 20 and 17 years, respectively.

29. UPPER LIMB…. The carpal bones. The carpal bones are arranged in two rows of four each. In the proximal row, from lateral to medial, are the scaphoid , lunate and triquetral bones, with the pisiform on the anterior surface of the triquetral . The trapezium, trapezoid, capitate and hamate make up the distal row.

30. UPPER LIMB…. Together the carpal bones form an arch, with its concavity situated anteriorly . The flexor retinaculum is attached laterally to the scaphoid and the ridge of the trapezium, and medially to the pisiform and the hook of the hamate .

31. UPPER LIMB…. It converts the arch of bones into a tunnel, the carpal tunnel, which conveys the superficial and deep flexor tendons of the fingers and the thumb (except flexor carpi ulnaris and palmaris longus tendons) and the median nerve.

32. UPPER LIMB…. The extensor retinaculum on the dorsum of the wrist attaches to the pisiform and triquetrum medially and the radius laterally Six separate synovial sheaths run beneath it.

33. UPPER LIMB…. Radiological features of the carpal bones Radiography These are radiographed in the anteroposterior , lateral and oblique positions. Carpal tunnel views are obtained by extending the wrist and taking an inferosuperior view that is centred over the anterior part of the wrist.

34. UPPER LIMB…. Supernumerary bones These may be found in the wrist and include the os centrale found between the scaphoid , trapezoid and capitate , which may represent the tubercle of the scaphoid that has not fused with its upper pole The os radiale externum , which is found on the lateral side of the scaphoid distal to the radial styloid .

35. UPPER LIMB…. Nutrient arteries of the scaphoid In 13% of subjects these enter the scaphoid exclusively in its distal half. If such a bone fractures across its midportion , the blood supply to the proximal portion is cut off and ischaemic necrosis is inevitable. This occurs in 50% of patients with displaced scaphoid fractures.

36. UPPER LIMB…. Ossification of the carpal bones These ossify from a single centre each. The capitate ossifies first and the pisiform last But, the order and timing of the ossification of the other bones is variable. Excluding the pisiform , they ossify in a clockwise direction from capitate to trapezoid as follows:

37. UPPER LIMB…. The capitate at 4 months The hamate at 4 months The triquetral at 3 years The lunate bone at 5 years The scaphoid Trapezium trapezoid at 6 years. The pisiform ossifies at 11 years of age

38. UPPER LIMB…. The metacarpals and phalanges The five metacarpals are numbered from the lateral to the medial side. Each has a base proximally that articulates with that of the other metacarpals, except in the case of the first metacarpal, which is as a result more mobile and less likely to fracture.

39. UPPER LIMB…. The third metacarpal has a styloid process extending from its base on the dorsal aspect. Each metacarpal has a rounded head distally, which articulates with the proximal phalanx. The phalanges are 14 in number, three for each finger and two for the thumb. Like the metacarpals, each has a head, a shaft and a base.

40. UPPER LIMB…. The distal part of the distal phalanx is expanded as the tuft of the distal phalanx. Radiological features of the metacarpals and phalanges Bone age A radiograph of the left hand is used in the determination of bone age.

41. UPPER LIMB…. Standards of age determined by epiphyseal appearance and fusion have been compiled for the left hand and wrist by Greulich and Pyle, and by Tanner and Whitehouse (TW2 method). The metacarpal sign A line tangential to the heads of the fourth and fifth metacarpals does not cross the head of the third metacarpal in 90% of normal hands - this is called the metacarpal sign.

42. UPPER LIMB…. This line does, however, cross the third metacarpal head in gonadal dysgenesis . The carpal angle This is formed by lines tangential to the proximal ends of the scaphoid and lunate bones. In normal hands the average angle is 138°. It is reduced to an average 108° in gonadal dysgenesis .

43. UPPER LIMB…. The metacarpal index This is calculated by measuring the lengths of the second, third, fourth and fifth metacarpals and dividing by their breadths taken at their exact midpoint. The sum of these divided by four is the metacarpal index, which has a normal range of 5.4-7.9.

44. UPPER LIMB…. An index greater than 8.4 suggests the diagnosis of arachnodactyly . Sesamoid bones Two sesamoid bones are found related to the anterior surface of the metacarpophalangeal joint of the thumb in the normal radiograph. A single sesamoid bone in relation to this joint in the little finger is seen in 83% of radiographs.

45. UPPER LIMB…. At the interphalangeal joint of the thumb in 73%. These are occasionally found at other metacarpal and distal interphalangeal joints. The incidence of sesamoid bones is increased in acromegaly .

46. UPPER LIMB…. Tendons of the extensors of the fingers These are inserted into the base of the dorsum of the phalanges. Avulsion fractures of this part of the phalanx are associated with proximal displacement of the fragment if the extensor tendon is attached to it, and may need internal fixation.

47. UPPER LIMB…. Small fractures of the base of the distal phalanx without displacement do not need fixation. Ossification of the metacarpals and phalanges These ossify between the ninth and twelfth fetal weeks.

48. UPPER LIMB…. Secondary ossification centres appear in the distal end of the metacarpals of the fingers at 2 years and fuse at 20 years of age. Secondary centres for the thumb metacarpal and for the phalanges are at their proximal end and appear between 2 and 3 years, and fuse between 18 and 20 years of age.

49. THE JOINTS OF THE UPPER LIMB The sternoclavicular joint Type The sternoclavicular joint is a synovial joint divided into two parts by an articular disc. Articular surfaces The sternal end of the clavicle, the clavicular notch of the manubrium and the upper surface of the first costal cartilage.

50. THE JOINTS …. Ligaments These are: The anterior and posterior sternoclavicular ligaments The costoclavicular ligament The interclavicular ligament.

51. THE JOINTS …. The acromioclavicular joint Type The acromioclavicular joint is a synovial joint. Articular surfaces These are the outer end of the clavicle and the acromium . In health the undersurface of the acromion will align with the undersurface of the clavicle.

52. THE JOINTS …. Ligaments These are as follows: Acromioclavicular ligament, which is a thickening of the fibrous capsule superiorly Coracoclavicular ligament, which has conoid and trapezoid parts.

53. THE JOINTS …. The shoulder ( glenohumeral ) joint Type The glenohumeral joint is a ball-and-socket synovial joint. Articular surfaces These are as follows: Head of the humerus and the glenoid cavity of the scapula, which is made deeper by a fibrocartilaginous ring - the labrum glenoidale .

54. THE JOINTS …. The articular surface of the humeral head is four times the area of the glenoid cavity. Capsule This is attached to epiphyseal line of glenoid and humerus , except inferiorly where it extends downwards on the medial aspect of the neck of the humerus as the axillary pouch.

55. THE JOINTS …. Synovium In addition to lining the capsule of the joint The synovium extends along the tendon of the long head of the biceps and beneath the tendon of subscapularis muscle as the subscapular bursa. The long head of the biceps is therefore extrasynovial but intracapsular attaching to the supra¬ glenoid tubercle.

56. THE JOINTS …. Ligaments These are as follows: Three glenohumeral ligaments: Anterior thickenings of the capsule passing from the upper part of the glenoid to the lesser tuberosity and And the inferior part of the head of the humerus ; These are weak ligaments And not supported by overlying muscles

57. THE JOINTS…. Unlike the posterior capsule which is reinforced by the infraspinatus muscle The coracohumeral ligament The transverse humeral ligament Between the greater and the lesser tuberosities of the humerus .

58. THE JOINTS…. Stability In addition to ligaments The stability of the shoulder joint depends upon the surrounding muscles. These are: The short muscles known as the rotator cuff muscles (i.e. subscapularis , infraspinatus and teres minor muscles)

59. THE JOINTS…. The longer muscles, including the long head of biceps, pectoralis major, latissimus dorsi , teres major and deltoid muscles. The inferior part of the joint is least well protected by either ligaments or muscles.

60. THE JOINTS…. Radiological features of the shoulder joint Plain radiographs The supraspinatus muscle passes on the superior aspect of the shoulder joint to the greater tuberosity of the humerus . Calcification occurs in this muscle owing to degenerative change and may be visible on radiographs.

61. THE JOINTS…. The supraspinatus muscle is separated from the acromium by the subacromial-subdeltoid bursa The largest bursa in the body. This bursa does not communicate with the shoulder joint unless supraspinatus is ruptured by trauma or degeneration. This communication is then visible on arthrography .

62. THE JOINTS…. MRI can also be used to detect this rupture. The capsule of the shoulder joint is lax and relatively unprotected by ligaments or muscles inferiorly. This is the site of accumulation of fluid in effusion or haematoma of the joint.

63. THE JOINTS…. Similarly, dislocation of the joint occurs most often inferiorly, with the head of the humerus coming to lie inferior to the coracoid process. Arthrography with or without CT In the shoulder joint, arthrography is achieved by injection of contrast into the joint below and lateral to the coracoid process.

64. THE JOINTS…. It shows the features of the joint as outlined above. In particular, the axillary pouch can be seen inferior to the humeral head on external rotation of the arm, and the subscapular ( subcoracoid ) bursa can be seen on internal rotation of the arm. The subacromial ( subdeltoid ) bursa is not filled unless the supraspinatus tendon is completely ruptured.

65. THE JOINTS…. The tendon of the long head of biceps is seen as a filling defect within the joint and its synovial sheath is opacified outside the joint along the bicipital groove of the humerus . Magnetic resonance imaging MRI with surface coils is used increasingly to image the shoulder joint.

66. THE JOINTS…. The rotator cuff Four muscles comprise the rotator cuff: the supraspinatus , the infraspinatus , the teres minor and the subscapularis (mnemonic - SITS) and are readily identified in the coronal oblique (plane parallel to the axis of the supraspinatus tendon), sagittal oblique and axial planes

67. THE JOINTS…. The coracoacromial arch This represents the osseous, ligamentous arch composed of the tip of the coracoid , the coracoacromial ligament, the acromion and the acromioclavicular articulation. Three typical acromial shapes are described: type 1 curved, type 2 flat, and type 3 flat with a marginal hook.

68. THE JOINTS…. Type 1 acromion is identified in 75% of the normal population; type 3 is least common but often produces symptomatic impingement of the supraspinatus tendon. The glenoid labrum The osseous glenoid is angled 10-20° volarly preventing posterior dislocation following a fall on the outstretched hand.

69. THE JOINTS…. And increasing the likelihood of anterior dislocation following a fall with direct lateral trauma to the shoulder. Hyaline cartilage overlies the osseous glenoid , facilitating smooth articulation. Stability is afforded by the presence of a rim of fibrocartilage , the glenoid labrum, which marginates the osseous glenoid and overlies the hyaline cartilage.

70. THE JOINTS…. Typically the glenoid labrum is more rounded posteriorly and more triangular anteriorly . The configuration of the superior labrum reflects its association with the insertion of the long head of the biceps tendon, the so-called bicipitolabral complex.

71. THE JOINTS…. Three forms of bicipitolabral complex are described, which include type 1, in which the long head of the biceps inserts to the osseous glenoid immediately above the labrum; type 2, in which the biceps tendon inserts to the superior surface of the labrum; and type 3, where the long head of the biceps inserts into the labrum to produce a meniscoid -type insertion.

72. THE JOINTS…. The type 3 insertion predisposes to superior labral tears (SLAP, superior labral anteroposterior tear or injury) following applied traction forces. Coronal MR images with intra- articular contrast allow the identification of a sulcus along the anterior margin of the superior labrum, the sublabral sulcus , which parallels the configuration of the osseous glenoid in contrast to superior labral tears.

73. THE JOINTS…. The sublabral sulcus becomes more prominent with age. A relative deficiency of the anterior labrum is occasionally identified in less than 0.5% of the population between 12 and 3 o'clock on MR arthrography in association with a cord-like middle glenohumeral ligament, the so-called Bufort complex.

74. THE JOINTS…. In the axial plane it is quite normal to identify hyaline cartilage undercutting the fibrocartilaginous labrum at the level of the coracoid to produce the sublabral foramen.

75. THE JOINTS…. The anteroinferior labrum is identified as a triangular structure in both the coronal and axial planes and is continuous with a fold of the joint capsule termed the inferior glenohumeral ligament.

76. THE JOINTS…. Injury at this site following anterior dislocation, with both blunt trauma and traction stresses imposed by the inferior glenohumeral ligament. May result in simple disruption of the labrum (a Perthes ' lesion). In disruption of the labrum and associated bone (a Bankaart lesion).

77. THE JOINTS…. In medialization of the labrum beneath a rind of periosteum (an ALPSA lesion anterior labral periosteal sleeve avulsion) Or merely produce avulsion of the inferior glenohumeral ligament from the humerus , A HAGL injury (humeral avulsion of the glenohumeral ligament).

78. THE JOINTS…. The joint space is enveloped by joint capsule. Posteriorly the capsule is inserted on cortex immediately behind the posterior labrum. Anteriorly three patterns of capsular insertion are described.

79. THE JOINTS…. Type 1, when the capsule inserts immediately behind the labrum Type 2, when the capsule inserts 1 cm behind the labrum. Type 3, when it inserts more than 2 cm behind the labrum on the neck of the glenoid .

80. THE JOINTS…. Three folds in the anterior capsule give rise to the superior, middle and inferior glenohumeral ligaments Which result in local strengthening of the capsule and promote stability

81. THE JOINTS…. Shoulder stability Superior stability - of the glenohumeral joint is afforded by the; superior labrum, the long head of the biceps the joint capsule, the supraspinatus tendon the subacromial bursa the structures of the coracoacromial arch.

82. THE JOINTS…. Posterior stability - of the glenohumeral joint is afforded by the; Angulation of the osseous glenoid The posterior labrum The capsule The posterior tendons of the rotator cuff The infraspinatus and the teres minor

83. THE JOINTS…. Anterior stability - of the glenohumeral joint is afforded by the; Labrum The capsule and its associated folds or glenohumeral ligaments The subscapularis muscle

84. THE JOINTS…. The elbow joint Type The elbow joint is a synovial hinge joint which incorporates the humeroulnar , the humeroradial and superior radioulnar joints as one cavity.

85. THE JOINTS…. Articular surfaces These are; The trochlea and capitellum of the humerus The head and ulnar notch of the radius and the trochlear fossa The radial notch of the ulna.

86. THE JOINTS…. Capsule This is attached to the margins of the articular surfaces of the radius and ulna but more proximally on the humerus to include the olecranon , coronoid and radial fossae within the joint.

87. THE JOINTS…. Ligaments These are: The radial and ulnar collateral ligaments, which are lateral and medial thickenings of the capsule The annular ligament, which surrounds the head of the radius and rotates within it. It is attached to the anterior and posterior edges of the radial notch on the ulna.

88. THE JOINTS…. The development of the elbow At birth, the distal humerus is composed of a single cartilaginous epiphysis separated from the metaphysis by an arched physis . Injury at this time results in complete epiphyseal separations.

89. THE JOINTS…. The primitive epiphysis differentiates into four ossification centres : Two epiphyses, the capitellum and the trochlea And two apophyses , the medial and lateral epicondyles .

90. THE JOINTS…. Following such a division, subsequent injury is usually confined to individual ossification centres In contrast to the gross injury or displacement that occurs in infancy.

91. THE JOINTS…. The cartilage of the proximal ulna develops a single ossification centre, the olecranon , which eventually leads to mineralization of the coronoid . The cartilage of the radial head develops into a further single ossification centre.

92. THE JOINTS…. Ossification The appearance of ossification centres occurs 1-2 years earlier in girls than in boys and follows an orderly progression. With appearance of the capitellar ossification centre first at 1-2 years.

93. THE JOINTS…. The radial head at 3-6 years The inner or medial epicondyle at 4 years The trochlea at 8 years The olecranon at 9 years The external epicondyle at 10 years.

94. THE JOINTS…. In adolescence, usually between 10 and 12 years, the three lateral ossification centres fuse, followed by closure of their associated physes at 13-16 years. The medial epicondyle physis is the last to close, at between 16 and 18 years.

95. THE JOINTS…. Inappropriately treated injury to any of the ossification centres around the elbow may lead to deformity However, as the elbow physes contribute to only 20% of final length, shortening is often subtle.

96. THE JOINTS…. Radiological features of the elbow joint Plain radiographs The capsule of the elbow joint is lax anteriorly and posteriorly so that effusion within the joint causes distension of the capsule anteriorly and posteriorly .

97. THE JOINTS…. Fat pads anterior and posterior to the joint are displaced away from the joint by an effusion and become visible as linear lucencies that are separated by soft-tissue densities from the bones on a lateral radiograph. Anterior fat pad may be normally seen.

98. THE JOINTS…. A posterior fat pad, when seen, is pathological. Arthrography Arthrography of the elbow joint is achieved by injection of contrast medium between the radial head and the capitellum .

99. THE JOINTS…. The synovial cavity of the joint is outlined and seen to extend proximal to the articular surfaces on the humerus With a configuration on AP views that has been likened to rabbit ears and called the 'Bugs Bunny' sign.

100. THE JOINTS…. On lateral views, a coronoid recess is seen anterior to the lower humerus and an olecranon recess posteriorly . Distally the synovial cavity is seen to extend anterior to the radius as the preradial recess. This is indented where the annular ligament of the radius surrounds it.

101. THE JOINTS…. Magnetic resonance imaging Relevant anatomy The ulnar collateral ligament The ulnar collateral ligament is responsible for medial elbow joint stability And resistance to valgus strain.

102. THE JOINTS…. It is composed of three discrete tendon bundles; The anterior bundle, The posterior bundle The transverse bundle Despite anatomic complexity

103. THE JOINTS…. The anterior bundle is the most important contributor to stability and is therefore most frequently injured. Fortuitously, the anterior bundle (the A-UCL) is taut in the extended elbow position.

104. THE JOINTS…. And is therefore readily visualized on direct coronal images running from the undersurface of the medial epicondyle . Just deep to the common flexor tendon origin, distally to its attachment to the medial aspect of the ulnar coronoid process.

105. THE JOINTS…. The anterior bundle blends with the fibres of the overlying flexor digitorum superficialis muscle. The posterior and transverse bundles may be identified in the axial plane forming the floor of the cubital tunnel.

106. THE JOINTS…. At MRI, similar to other tendons with an organized structure, the ulnar collateral ligament is hypointense on all sequences. Following injury, intrasubstance haemorrhage and oedema result in localized signal changes or loss of hypointensity .

107. THE JOINTS…. Tendon strain following valgus injury results in associated oedema both within and without the collateral ligament, often extending to the overlying flexor digitorum superficialis muscle belly. In severe injury complete rupture occurs, which is most frequently midsubstance (87%). Avulsion is extremely uncommon

108. THE JOINTS…. The sensitivity of MR imaging to complete collateral ligament injury is reported to be as high as 100%. Its sensitivity to partial tears, particularly undersurface tears, is considerably less, surgically proven undersurface partial tears being identified in as few as 14% of cases.

109. THE JOINTS…. When partial tears are suspected, MR arthrography dramatically improves the sensitivity to almost 86%. Partial tears being manifest by extension of fluid along the medial margin of the coronoid process.

110. THE JOINTS…. The inferior radioulnar joint. Type The inferior radioulnar joint is a synovial pivot joint. Articular surfaces These are the head of the ulna and the ulnar notch of the lower end of the radius and the upper surface of the articular disc (the triangular cartilage).

111. THE JOINTS…. This is triangular, with its apex attached to the styloid process of the ulna and the base to the ulnar notch of the radius. It separates the inferior radioulnar and radiocarpal joints. Capsule This is slightly thickened anteriorly and posteriorly .

112. THE JOINTS…. It is lax superiorly and extends upwards as a pouch, the recessus sacciformis , in front of the lower part of the interosseus membrane. The radiocarpal joint Type This is a synovial joint.

113. THE JOINTS…. Articular surfaces These are the distal radius and distal surface of the triangular cartilage and the proximal surfaces of the scaphoid , lunate and triquetral bones. The articular surface of the radius is divided into a scaphoid and lunate facet.

114. THE JOINTS…. Following a fall on the outstretched hand, differential shear imposed by impaction of the lunate against the lunate facet results in extension of intra- articular fractures of the distal radius to the junction of the lunate and scaphoid articular facets.

115. THE JOINTS…. Capsule This is attached around the articular surfaces, except where it extends proximally as the palmar radial recess over the proximal radius to a variable degree.

116. THE JOINTS…. Ligaments These are; The Palmar Dorsal radiocarpal ligaments Palmar ulnocarpal ligament Ulnar and radial collateral ligaments.

117. THE JOINTS…. The intercarpal joints A midcarpal joint is found between the proximal and distal rows of carpal bones. This is separated from the radiocarpal and the carpometacarpal joints by interosseus ligaments between carpal bones.

118. THE JOINTS…. The carpometacarpal joint of the thumb between the trapezium and the metacarpal of the thumb is separate from the other carpometacarpal joints. The carpometacarpal joint of the medial four metacarpals has a single synovial cavity and is also continuous with the intermetacarpal joints of the bases of these bones.

119. THE JOINTS…. Radiological features of the joints of the wrist and hand Wrist biomechanics – Stable versus unstable equilibrium The biomechanics of the wrist are complex and involve the integrated motion of two intercalated segments (carpal bones linked by intercarpal ligaments)

120. THE JOINTS…. The proximal and distal row of carpal bones, which articulate with the bases of the metacarpals and the distal radius at the radiocarpal articulation Facilitating wrist flexion and extension Ulnar and radial deviation and minimal pronation and supination (although this is most marked at the distal radiocarpal articulation

121. THE JOINTS…. Within the proximal carpal row there is a delicate balance between the opposing forces of the volarly angulated scaphoid and the mildly dorsally angulated lunate , transmitted through the scapholunate ligament. Such a balance allows smooth integrated movement of the proximal intercalated segment.

122. THE JOINTS…. In such a way, in the sagittal or lateral plane the scapholunate angle, or the angle between the volarly angulated scaphoid and the mildly dorsally angulated lunate , is 30-60° Whereas that between the lunate and the capitate is 0-30°.

123. THE JOINTS…. The angle of the distal radial articular surface is 10° volar . Although slightly decreasing the range of dorsiflexion at the radiocarpal articulation. This is an evolutionary attempt to stabilize the radiocarpal articulation and limit the tendency to dislocate dorsally at the radiocarpal articulation following a fall and dorsally oriented impaction forces.

124. THE JOINTS…. Following a fall on an outstretched hand, combined dorsal shear and axial loading forces are applied to the wrist, the induced deformity depending on whether the forces are applied in radial or ulnar deviation. Depending on the balance between axial load and dorsal shear, applied forces may result in a range of both displaced and undisplaced carpal bone fractures including;

125. THE JOINTS…. Perilunate dislocation (in which all bones distal to the midcarpal articulation sublux dorsally) lunate dislocation (in which axial loading, against the volarly angulated distal radial articular surface, forces the lunate to sublux volarly ).

126. THE JOINTS…. Rupture of intrinsic ligaments and stabilizing fibrocartilage within the wrist, and both displaced or undisplaced fractures in the distal radius. Plain radiographs The normal alignment of the joints of the wrist and hand is visible on PA, lateral and oblique radiographs.

127. THE JOINTS…. Damage to any of the interosseus ligaments can cause displacement of one or more bones. The pisiform is the most anterior carpal bone on a true lateral X-ray of the wrist. Scaphoid views Recognizing its volarangulation Direct PA radiographs will project the distal pole of the scaphoid over the midbody and result in foreshortening and the radiographic ring sign.

128. THE JOINTS…. The scaphoid may be elongated by imaging in ulnar deviation, which minimizes the amount of volar angulation , and by tilting the incident beam to 20-25°. Evaluating the scaphoid in the absence of an angled tube in ulnar deviation is poor practice and likely to lead to erroneous diagnoses.

129. THE JOINTS…. Arthrography Arthrography of the radiocarpal or intercarpal or carpometacarpal joints may be achieved by injecting the appropriate space with contrast medium. The synovial cavity extends proximally anterior to the radius as the volar radial recess.

130. THE JOINTS…. The prestyloid recess is medial to the ulnar styloid process. The inferior radioulnar , the radiocarpal , the midcarpal and carpometacarpal joints are not usually connected to one another.

131. THE JOINTS…. Studies of arthrograms on cadavers have, however, shown communication between the radiocarpal and inferior radioulnar joints in up to 35% of subjects, between the radiocarpal and midcarpal joints in up to 47%.

132. THE JOINTS…. And between the pisiform triquetral joint and the radiocarpal joint in more than 50%. The incidence of these communications increases with age and with force of injection, and probably reflects degenerative change.

133. THE JOINTS…. Magnetic resonance imaging . Relevant anatomy The scapholunate ligament In health, the scapholunate ligament balances opposing forces of the volarly angulated scaphoid and the dorsally angulated lunate .

134. THE JOINTS…. At MRI, the ligament is delta-shaped in 75% of cases and linear in approximately 25%, and is hypointense in approximately 75% versus heterogeneous with areas of isointensity in 25% of cases. The ligament is usually less than 3 mm in maximal transverse diameter in the coronal plane.

135. THE JOINTS…. And is interposed between the scaphoid and lunate in the axial plane as thick dorsal (responsible for stability) and volar fibres , and an interposed membranous portion. Following a fall on the outstretched hand, impaction forces through the long axis of the capitate are transmitted to the scapholunate interspace and the scapholunate ligament.

136. THE JOINTS…. Under the action of such forces the scapholunate ligament may rupture acutely, most commonly from the proximal pole of the scaphoid , or it may stretch before rupture, in both cases resulting in widening of the scapholunate interspace . In the absence of restraint the scaphoid tilts volarly whereas the lunate tilts dorsally.

137. THE JOINTS…. Induced changes in biomechanics following ligament rupture produce commonly identified radiographic signs: widening of the scapholunate interspace more than 4 mm, the 'Terry Thomas' sign.

138. THE JOINTS…. Volar angulation and flattening of the scaphoid producing the 'ring' sign (the distal pole of scaphoid projected over the waist and proximal pole), and dorsal tilt of the lunate relative to both the capitate and scaphoid producing a dorsal intercalated segmental instability pattern (DISI).

139. THE JOINTS…. On MR imaging following injury, the delta configuration of an intact ligament is lost as the ligament elongates prior to rupture, and frequently intrasubstance oedema results in apparent swelling or thickening of the ligament. The lunate attachment has more Sharpey's fibres and hence, when it occurs, tear is usually from the base of the scaphoid .

140. THE JOINTS…. Following rupture, hyperintense fluid is noted to pass freely between radiocarpal and midcarpal joint spaces. Although MR imaging may accurately detect scapholunate ligament disruption, the clinical significance of observed abnormalities must always be established before intervention.

141. THE JOINTS…. As central perforations through the membranous portion of the ligament may not result in biomechanical changes. And fenestration, establishing contact between radiocarpal and midcarpal joint spaces, may occur in health

142. THE JOINTS…. Aware that in many circumstances fenestrations are symmetrical, some advocate imaging both symptomatic and asymptomatic wrists simultaneously using an extended surface coil in patients with suspected injury. Lunatotriquetral ligament

143. THE JOINTS…. Lunatotriquetral ligament The lunatotriquetral ligament, similar to the scapholunate , is comprised of both volar and dorsal components that attach directly to bone, rather than to hyaline cartilage overlying carpal bones. The ligament establishes continuity between radial and ulnar structures of the proximal carpal row of bones or intercalated segment.

144. THE JOINTS…. Following a fall in ulnar deviation, impaction forces are transmitted through the ulnar side of the wrist, with acute shear manifest as rupture of the lunatotriquetral ligament, disruption of components of the triangular fibrocartilage complex, as subluxation of the distal radioulnar joint or as fracture.

145. THE JOINTS…. Shearing forces lead to acute tear of the lunatotriquetral ligament which, in contrast to the scapholunate ligament, does not stretch and widen the interspace before actual rupture. Identification of acute rupture requires high- reso imaging, And even with meticulous attention to detail the sensitivity of MRI in this setting is as low as 50%

146. THE JOINTS…. Triangular fibrocartilage complex (TFCC) The triangular fibrocartilage complex is a complex anatomical structure composed predominantly of a triangular wedge-shaped fibrocartilaginous disc bridging the distal radioulnar joint, supported anteriorly .

147. THE JOINTS…. Posteriorly by radioulnar ligaments Distally by attachments to the lunate through the volar ulnocarpal ligaments (the ulnolunate and ulnotriquetral ligaments) Laterally by the ulnar collateral ligament and the extensor carpi ulnaris . The complex is completed by an additional fold in the lateral capsule interposed between the ulnar styloid and the triquetrum , termed the meniscal homologue.

148. THE JOINTS…. The meniscal homologue is interposed between the prestyloid recess and the trique ¬ tropisiform recess. The triangular fibrocartilage is a biconcave disc separating the radiocarpal from the distal radioulnar joint spaces. It has attachments to both the ulnar styloid and the lunate fossa of the radius.

149. THE JOINTS…. En bloc, the triangular fibrocartilage complex functions to buttress forces transmitted to the distal ulnar and distal radioulnar articulations secondary to impaction during ulnar deviation. As such, injury is manifest as atypical pain and tenderness localized to the region of the ulnar styloid , often worse in ulnar deviation.

150. THE JOINTS…. Such discomfort often limits pronation and supination at the distal radioulnar articulations. In old age, as a result of cartilage degeneration, asymptomatic tears of the triangular fibrocartilage are common.

151. THE JOINTS…. At MR imaging the triangular fibrocartilage is the only structure of the TFC complex consistently identified, although three-dimensional gradient echo sequences now allow visualization of both the volar and dorsal radioulnar ligaments.

152. THE JOINTS…. MR imaging has a reported sensitivity of between 72% and 100% in the detection of tears, with associated specificities of 89-100%. Tendon injury at the wrist Extensor carpiulnaris tendon Extensor carpi ulnaris tenosynovitis usually complicates chronic occupational overuse, presenting as ulnar -sided wrist pain mimicking TFC tear, in chronicity commonly accompanying TFC tear.

153. THE JOINTS…. At MR imaging the tendon sheath is noted to be thickened, associated with peritendinous hyperintense fluid on T2- weighted sequences. In chronicity , foci of mineralization within the tendon are often noted to be hyperintense .

154. THE JOINTS…. Extension of chronic synovitis at the level of the radiocarpal articulation often leads to TFC degeneration in chronicity . First extensor compartment syndrome - de Quervain's tenosynovitis

155. THE JOINTS…. Repetitive wrist flexion and extension, particularly repetitive extension of the thumb, may promote chronic tenosynovitis in the first dorsal compartment or a fibro-osseous tunnel at the level of the radial styloid surrounding the extensor pollicis brevis and abductor pollicis longus tendons.

156. THE JOINTS…. At MR imaging there is focal peritendinous fluid and apparent soft tissue thickening. Changes are noted to resolve following immobilization and treatment with anti- inflammatories .

157. THE JOINTS…. Median nerve injury Median nerve injury commonly accompanies distal radial fractures, either secondary to the tension of forceful hyperextension or secondary to direct impaction by fracture fragment in forced flexion injury - Smith's fracture.

158. THE JOINTS…. In one study chronic median neuropathy was identified in 23% of 536 patients with fractures of the distal radius. Compression of the median nerve, or carpal tunnel syndrome, has been extensively studied using MRI.

159. THE JOINTS…. Neuropathy is accompanied by swelling of the median nerve, best evaluated at the level of the pisiform ; flattening of the median nerve, best evaluated at the level of the hamate ; increased signal within the nerve on T2-weighted images; and volar bulging of the retinaculum .

160. THE JOINTS…. Scaphoid and associated injury The scaphoid is the second most commonly fractured bone of the wrist Typically complicating a fall on a dorsiflexed hand.

161. THE JOINTS…. Undisplaced fractures heal without complication in up to 95% of cases. Displaced fractures occur in up to 30% of cases, and when displacement is greater than 1 mm approximately 50% of cases develop either non-union, avascular necrosis or both.

162. THE JOINTS…. Fractures are classified by site and orientation into those affecting the proximal pole, the waist and the distal pole. Fractures of the distal pole rarely develop either non-union or avascular necrosis. In contrast, fractures of the proximal pole develop non-union in almost all cases.

163. THE JOINTS…. Healing of fractures through the midzone or waist is variable. Complications are more common in fractures with displacement or humpback angulation at the fracture margin.

164. THE JOINTS…. Vascular integrity of fracture fragments There are three patterns of blood supply to the carpal bones. Single vessels supply the scaphoid , capitate and lunate in 20%. The trapezium, triquetrum and pisiform and 80% of the lunate receive nutrient arteries through two non- articular surfaces, with a consistent intraosseous anastomosis .

165. THE JOINTS…. The trapezoid and hamate lack an intraosseous anastomosis and after fracture are at risk of ischemic necrosis. The proximal 70-80% of the scaphoid is supplied by the dorsal branch of the radial artery.

166. THE JOINTS…. Disruption of this vessel invariably occurs in fracture through the proximal pole, and occasionally in fracture through the wrist, resulting in ischaemic necrosis ( atraumatic interruption of the vascular supply to the proximal pole is termed Preiser's disease).

167. THE JOINTS…. The tuberosity and distal pole are supplied by the volar branches, rarely interrupted by fracture. Guyon's canal Guyon's canal is a fibro-osseous canal superficial to the flexor retinaculum , intimately related to both the pisiform and the hook of the hamate .

168. THE JOINTS…. The canal contains the ulnar nerve, artery and vein. At the level of the hook of hamate the nerve divides to a superficial palmar branch and a deep motor unit, such that fracture may disrupt either or both branches by direct contusion or persistent compression.

169. THE JOINTS…. Anatomy of the thumb and associated injury Gamekeeper's thumb derives its name from an injury to the metacarpophalangeal articulation acquired by Scottish gamekeepers attempting to kill rabbits by strangulation.

170. THE JOINTS…. A contemporary term, skier's thumb, is now more frequently employed as it is in this group that the injury is now more frequently recognized. The injury is characterized by disruption of the ulnar collateral ligament at the base of the thumb, integrity of which dictates the ability to successfully appose the thumb and digits.

171. THE JOINTS…. Two forms of injury are recognized, one in which a small ossific fragment is avulsed at the insertion of the ligament Type 1, readily identified on radiographs And the second, which is radiographically occult, is characterized by intrasubstance rupture without avulsion of bone (type 2).

172. THE JOINTS…. Similar collateral ligaments are responsible for radial and ulnar stability in all the interphalangeal joints and, using MRI, may be imaged following suspected trauma. The volar plate The volar plate represents the ligamentous thickening of the volar capsule that bridges and stabilizes the volar aspect of the interphalangeal and metacarpophalangeal joints.

173. THE JOINTS…. The volar plate is primarily responsible for passive resistance to hyperextension at these articulations, active resistance being provided by contraction of flexor muscle groups. Volar pain on induced hyperextension with local tenderness suggests the injury, which can be clearly visualized in both passive and stressed sagittal views of the digits using MRI.

174. THE JOINTS…. Extensor tendon injury – Mallet finger The term mallet finger is used to describe the flexion deformity of the DIP joint resulting from loss of extensor tendon continuity to the distal phalanx. The term 'mallet finger of bony origin' is used to describe the same deformity occurring secondary to intra- articular fracture of the dorsal lip of the distal phalanx.

175. THE JOINTS…. Three patterns of tendon-related mallet finger are recognized, and include Type 1 injury resulting from stretching of the ligament Type 2 injury characterized by rupture of the tendon at its insertion Type 3 injury characterized by a subtle avulsion at the site of tendon insertion.

176. THE JOINTS…. Extensor tendon injury : Boutonniere deformity Boutonniere or buttonhole deformity Is caused by disruption of the central slip of the extensor tendon combined with tearing of the triangular ligament on the dorsum of the middle phalanx Allowing the lateral bands of the extensor tendon to slip below the axis of the PIP articulation.

177. THE JOINTS…. Although clinically apparent, MR imaging allows detailed evaluation of tendon position and integrity, triaging patients into surgical and non-surgical groups. Flexor digitorum profundus tendon injury - jersey finger Avulsion of the flexor digitorum profundus tendon from its insertion into the base of the distal phalanx is a relatively uncommon injury

178. THE JOINTS…. Usually occurring during active sports, typically when a football or rugby player attempts to tackle the opposition but ends up grabbing a handful of jersey, hence the term 'jersey finger.