8 Carpal bone ossification The capitate ossifies first and the pisiform lastBut the order and timing of the ossification of the other bones is variableExcluding the pisiform, they ossify in a clockwise direction from capitate to trapezoid as follows:CapitateHamateTriquetral at 3 yearsLunate bone at 5 yearsScaphoid, trapezium and trapezoid at 6 yearsThe pisiform ossifies at 11 years of ageat 4 months
9 Supernumery bonesBe sure not to confuse the lanula with a styloid process fracture
11 CompartmentsImportant because these compartments can point to pathology on arthrography if the ligaments are disrupted. For example: contrast can be injected into the Radiocarpal compartmentand if it spreads into the midcarpal compartment, it can point to fractures etc.
13 Compartments, joints and ligaments The midcarpal and radiocarpal joint are seperated by interosseous ligaments No communication Complex palmar and dorsal ligaments provide support Arthrogaphy – ideally conducted in 3 stages
16 Osseous structures - joints • Distal (inferior) radioulnar joint:Pivot joint; ROM: Distal radius rotates around distal ulna• Radiocarpal joint:Ellipsoid joint created by proximal carpal row articulating with distal radius & ulnaROM:Flexion, extension, abduction, adduction,circumduction, no rotation
17 Osseous structures - joints • Pisotriquetral:Gliding joint created by pisiform and triquetrum;Discretely separate from radiocarpal joint in 10-25%;ROM: Minimal• Midcarpal:Gliding joint created by articulation ofproximal & distal carpal rowsROM: Some extension, abduction, minimal rotation
18 Osseous structures - joints • Intercarpal:Gliding joints created by interface of individual carpal bonesROM: Complex• Carpometacarpal- First CMC (thumb base): Saddle joint, highlymobile; ROM: Flexion, extension, abduction,adduction, circumduction, rotation, opposition- Intermetacarpals 2nd-5th: Gliding joints; ROM:Limited mobility of 2nd & 3rd CMC, increasingmobility of 4th & 5th CMC
19 ArthrographyGood evaluation for integrity of scapho-lunate, lunotriquetral ligaments & TFCLimited value for extrinsic ligamentsInjections spaced to allow contrast resorptionRadiocarpal joint injected first (most likely to document with single injection);If no tear, wait minutes & proceed sequentially with distal radio-ulnar and midcarpal injectionDigital subtraction allows dynamic evaluation of ligament status and sequential compartment injection without delayInjectate: Iodinated contrast ( mg I/ml);Volumes: Midcarpal, 4-5 cc; radiocarpal, 2-3 cc; DRU, 1-2 cc; pisotriquetral, 1-2 cc
21 ArthrogramsIntact radiocarpal compartment - contrast filling pisotriquetral joint via prestyloid recess. Triangular fibrocartilage distal surface is outlined.Scapholunate & lunotriquetral ligaments are intact, with no evidence of spillinto midcarpal joint.
40 Triangular fibro-cartiliginous complex The term "triangular fibrocartilage complex of the wrist" was first coined by Palmer and Werner in 1981,1 Describes the cartilaginous and ligamentous structures that bridge the distal radius and ulna,Provides articulation with the adjacent lunate and triquetrum.Important stabilizer of the distal radioulnar jointProvides important shock absorption to the carpus.
41 TFCC The components of the TFCC include: The articular disc The dorsal and volar radioulnar ligamentsThe meniscus homologueThe extensor carpi ulnaris tendon sheathThe ulnocarpal ligaments
42 TFCCIt is the articular disc and the radioulnar ligaments that are the most important to evaluate.Characteristic triangular shapeThe articular disc may be only 1-2 millimeters thick within its central portion, but the TFC thickens considerably at its dorsal and volar aspects, as well as at the ulnar attachments.The thickened dorsal and volar components are what comprise the dorsal and volar radioulnar ligaments.
43 TFCA 3D depiction of the TFC (arrow) demonstrates its triangular shape and relatively thin central region.Viewed from above, the thickened peripheral components that represent the dorsal and volar radioulnar ligaments (arrows) are readily apparent.
44 Normal tfcA T1-weighted coronal image demonstrates a normal TFC. Normal intermediate signal intensity is evident at the ulnar attachment (arrow). The normal interface with articular cartilage at the radial side is also apparent (arrowhead), and should not be mistaken for a vertical tear.
46 TFCC – mriInjuries to the TFCC are a frequent cause of ulnar sided wrist pain.MRI allows accurate pre-treatment evaluation of patients with suspected TFCC pathologyProvides excellent characterization of TFCC tears and their associated wrist pathology.Such information is invaluable for the proper management of patients with TFCC tears.
50 Neurovascular structures Radial arteryOrigin:Terminal branch of brachial arteryCourse:Superficial to pronator quadratusContinues dorsally around radial styloid processPasses deep to APL & EPBAcross anatomic snuffbox & deep to EPL
52 Neurovascular structures Ulnar artery:Course in wrist:Superficial to pronator quadratusContinues between FCU & FDS tendonsBranches:Common interosseousAnterior interosseousPosterior interosseous arteryPalmar carpal branchDorsal carpal branchDeep palmar branchSuperficial palmar branch
53 Neurovascular structures Ulnar nerve:Origin: Brachial plexus-medial cordCourse in wrist:Radial to FCU, close to ulnar arteryAt proximal pisiform: Nerve proximal to bifurcation; nerve deep to FCU, ulnar to ulnar artery & veinsAt distal pisiform: Nerve bifurcates into deep (motor) & superficial (sensory) branchesAt hook of hamate: Superficial branches volar to hook of hamate & ADM; nerve ulnar to ulnar artery & veins; deep branches are dorsal & ulnar to hook of hamate, deep to abductor digiti minimi, superficial to pisometacarpal ligament
54 Neurovascular structures Radial nerveOrigin: Brachial plexus-posterior cordCourse in wrist: Branches into superficial & deep branches in distal forearm- Branches:• Superficial branch passes under brachioradialis tendon into dorsal wrist; divides into lateral branch (supplies radial wrist & thumb skin) & medial branch (supplies mid & ulnar wrist skin); divides to dorsal digital nerves supplying ulnarthumb, index, middle & radial ring fingers• Deep branch enters supinator volarly; exitsdistally & posteriorly as posterior interosseousnerve; supplies ECRB, supinator, ED, EDM, ECU,EPL, APL & El
55 Nutrient arteries of the scaphoid In 13% of subjects these enter the scaphoid exclusively in its distal half.Fractures across scaphoid midportion - problematicThe blood supply to the proximal portion is cut offIschaemic necrosisOccurs in 50% of patients with displaced scaphoid fractures
57 Vascular supply of the lunate The large majority of the lunate is covered with articular cartilage, leaving only small areas accessible to nutrient vessels along the dorsal and volar poles. These "bare areas" correspond to ligamentous insertion sites, and thus trauma may result in avulsion injuries to the entering arteries. Internally, the lunate blood supply forms patterns resembling a Y (59%), an I (31%), or an X (10%).
58 Kienbock’s diseaseDiffusely decreased signal intensity is present within the lunate (arrow). Negative ulnar variance with compensatory thickening of the triangular fibrocartilage (arrowhead) is also present.DiagnosisKienbock's Disease (avascular necrosis of the lunate).
59 Osteonecrosis of the lunate Negative ulnar variance Kienbock
61 A few anatomical variants Examples from one study:Hypoplasia of the hook of the hamate boneAnomalous muscles inside the carpal tunnelUnusual location and double branching of the median nerveAberrant median artery
62 A few anatomical variants Accessory abductor digiti minimi
67 BibliographyDiagnostic and Surgical Imaging Anatomy – Muskuloskeletal – ManasterApplied Radiological Anatomy - ButlerAnatomy for Diagnostic Imaging 3rd ed – RyanVariations of the arterial pattern in the upper limb revisited: a morphological and statistical study, with a review of the literature – Rodrigues et al; J. Anat. (2001) 199, pp. 547±566Accessory Muscles: Anatomy, Symptoms, and Radiologic Evaluation – Sookur et al - RadioGraphics 2008; 28:481–499