Normal wrist alignment:
- Distal radius articular surface palmar tilt (~11deg), ulnar inclination (20-25deg).
- Distal ulnar few mm shorter than distal radius (not longer).
- Proximal and distal carpal rows in smooth carpal/Gilula’s arcs on PA.
- Approximate colinear alignment of distal radius, lunate, capitate, 3rd metacarpal when in neutral position. Lunate within 10-20deg of capitate on lateral. In neutral position lunate straddles junction of radius and TFC, volar angulation of at least 10deg.
- Scaphoid palmar tilt with scapholunate angle 30-60deg on lateral (line between most volar projections of scaphoid to capitate long axes).
- CMCJs zig-zag on PA.
Acro-osteolysis (resorption of terminal tufts):
- Arthritis – Psoriatic arthritis (DIP erosions), neuroarthropathy (diabetes, congenital indifference to pain, syringomyelia, myelomeningocoele).
- Collagen vascular disease – Scleroderma (soft tissue calcifications), Raynaud, dermatomyositis.
- Metabolic – Hyperparathyroidism, Lesch-Nyhan disease.
- Inherited – Inherited acroosteolysis, pyknodysostosis (dense bones, transverse fractures), progeria, pachydermoperiostosis, Hajdu-Cheney syndrome, epidermolysis bullosa.
- Thermal injury – Burns (contractures, soft tissue calc), frostbite (usually spares thumb which is protected in fist).
- Infection – Leprosy (linear calcification of digital nerves, flexion contractures).
- Environmental – Polyvinylchloride (PVC) exposure.
Imaging Techniques and Applications
- Lateral in neutral position for carpal alignment
- Scaphoid views – Semi-pronated oblique PA, semi-supinated oblique AP with ulnar deviation, PA in ulnar deviation, true lateral in neutral position.
- Ball catcher’s/Norgaard view – AP oblique.
- Hook of hamate view – Wrist on plate, fingers pulled dorsally, beam angled 45deg parallel to palm of hand.
- Functional views for carpal instability – Stress, PA ulnar deviation, PA clenched fist.
- Distal radioulnar joint instability views
- Pisotriquetral view
- Carpal boss view
- Anterior ridge of trapezium
Ultrasound for joint/tendon sheath effusion. Tendon pathology or carpal tunnel mass.
- T2 coronal or GRE for interosseous ligmanets, TFCC
- T1 for bone marrow abnormalities, fracture
- T2FS or STIR for bone marrow oedema
- Transverse for nerves and tendons esp carpal tunnel
Bone scan for suspected scaphoid fracture
Soft tissue signs of fracture:
- Pronator quadratus fat plane displacement – Only seen in ~1/3 of distal radius fractures.
- Scaphoid fat pad displacement – Distortion or obliteration of fat stripes lateral to scaphoid. Not sensitive or specific.
Carpal bone fractures:
- Scaphoid/navicular fracture – Most nondisplaced through waist. Radiographically occult, if trauma and pain over snuffbox then MR/CT or cast with re-XR in 7-10 days (fracture seen from disuse osteoporosis and hyperaemia, cyst-like bone resorption, faint sclerosis). Avascular necrosis (AVN) of proximal pole is common causing increasd density (doesn’t always mean AVN); Tx surgery with screw and bone grafting. Other Cx delayed union, nonunion, humpback deformity (dorsal tilt of proximal pole, palmar tilt of distal pole), scaphoid non-union advanced collapse (SNAC) wrist.
- Triquetral avulsion of dorsal wrist ligaments/capsule which all attach onto the triquetrum. Small bony fragment dorsal wrist on lateral (virtually pathognomonic). Assocociated with lunate/perilunate dislocation, transverse fracture of capitate and proximal hamate.
- Lunate fracture – rare.
- Hook of the Hamate (hamulus) fracture – FOOSH, overswinging of club/bat/racket with butt levering off hook of hamate (usually only professionals). Radiographically occult. Normal dence C (hook) over mid-distal hamate not seen. Improved sensitivity with carpal tunnel view (wrist on plate, fingers pulled dorsally, beam angled 45deg parallel to palm of hand). CT if XR N.
- Pisiform fracture
- Capitate fracture
- Trapezium anterior ridge fracture
Greater and lesser arcs run perpendicular to Gilula’s arcs, trauma concentrates forces along these.
- Greater arc injruy – Through radial styloid, scaphoid, proximal capitate, hamate, triquetrum, ulnar styloid (or the ligaments adjacent to these bones). Includes trans-scaphoid perilunate fracture-dislocation, trans-scaphoid transcapitate perilunate fracture-dislocation. Ligmanet damage usually causes abnormal carpal motion.
- Lesser arc injury (rotary subluxation of the lunate) – Confined to ligaments around lunate. From forced extension to thenar eminence. Stage 1 injury interrupts scapholunate ligament (scapholunate dissociation); stage 2 luno-capitate (capitolunate instability or perilunate dislocation); stage 3 luno-triquetrum (midcarpal dislocation with palmar tilt/subluxation of lunate and carpal dorsal dislocation); stage 4 complete perilunate ligament disruption (volar lunate dislocation)
- Perilunate dislocation (stage 2) – Capitate and surrounding bones dislocate dorsally from line through radius and lunate (volar dislocation uncommon).
- Lunate dislocation (stage 4) – Capitate pushes lunate volarly tipping it over, with capitate aligned normally with radius. On AP, triangular or pie-shaped lunate (usually rhomboid). Cx median nerve impairment (impinged by lunate).
From ligament injury in trauma or inflammatory arthritis (esp RA). Scapholunate (SL) and lunotriquetral (LT) ligaments the most important of intrinsic/interosseous ligaments (esp dorsal SL), can stretch 50-100% before tear. Perforation of central ligaments is usually incidental (esp older patients), don’t indicate ligament failure. Extrinsic/capsular ligaments are complex, palmar/volar stronger and more important than dorsal.
- Translocation – Shift of entire carpus relative to radius.
- Dissociation – Abnormal motion between bones of same carpal row (often interosseous ligament disruption).
- Intercalated segment instability – Between carpal rows (esp refering to lunate and capitate).
- Carpal columns include central (radius-lunate-capitate, most important), ulnar (ulna-triquetrum-hamate) and radial (radius-scaphoid-trapezoid/trapezium).
- Static carpal instability is abnormal alignment in neutral position; dynamic instability on fluoroscopy or special XRs (eg cleched fist view).
Scapholunate dissociation (rotary/rotatory subluxation of the scaphoid) – Most common, disruption of SL and extrinsic ligaments. Greater palmar flexion of scaphoid with scapholunate angle >60deg and shortening on PA. Dorsal rotation of the lunate with the normal PA trapezoidal shape transformed to triangular/wedged shape with incongruence of dorsal and volar margins of the distal aspects. Widening of scapholunate interval >2-4mm (Terry Thomas sign), exaccerbated with PA clenched fist or PA in ulnar deviation. Independent scaphoid and lunate movement on fluoroscopy. Watson’s test (scaphoid shift test) wrist in neutral with pressure to palmar distal scaphoid in radial tilt; causes further palmar rotation of scaphoid in normal, but not in scapholunate dissociation.
- Scapholunate advanced collapse (SLAC) – Collapse of capitate into medial scaphoid, lateral lunate and radiocarpal joint causing degeneration and OA.
Dorsal intercalated segment instability (DISI, dorsiflexion instability) – Derrangement of radial-sided ligaments with lunate tilting dorsally, increasing lunocapitate angle >20-30deg. Usually associated with scapholunate dissocation (scahpolunate angle >60deg). Lateral fluoroscopy shows lunate failing to flex (wrt radius) or capitate failing to flex (wrt lunate).
Volar intercalated segment instability (VISI, volar flexion instability) – Derrangement of ulnar-sided ligaments with lunate tilting volarly and capitolunate angle >20-30deg. Lunate <10deg plantarflexed wrt radius. Usually associated with lunotriquetral dissociation with scapholunate angle <30deg. Asymmetric movement of radiolunate and lunocapitate joints on fluoroscopy. Much less common than DISI, more frequent in RA.
Lunotriquetral dissociation/instability – Subtle interruption of carpal arcs, scapholunate angle <30deg, lunotriquetral gap usually not widened. Clenched fist rolls scaphoid and lunate into palmar flexion. Usually associated with VISI.
Capitolunate instabiilty pattern (CLIP wrist) – Dynamic instability of central column. CLIP maneuver – lateral fluoroscopy alternating dorsal and volar force holding metacarpals causing at least 50% capitolunate subluxation.
Triquetrohamate instability – Dynamic instability of medial column. Reproducible click from abnormal motion between hamate and triquetrum. On ulnar deviation proximal carpal row should smoothly swing into dorsiflexion, but in instability this is delayed until later with a painful clunk.
Carpal translocation – In any direction. Ulnar translocation of entire carpus associated with RA. Radial and dorsal translocation is associated with previous Colles fracture. Palmar translocation is asssociated with previous Barton’s fracture.
Metatarsals and Phalanges
Thumb extra-articular MC fractures maintain alignment due to muscle attachments, but intra-articular fractures may displace and are usually unstable.
- Bennett’s fracture – Fracture-dislocation base of thumb MC into CMCJ. From axial loading of partially flexed 1st CMCJ (eg fist-fight). Almost always requires ORIF due to strong adductors causing dorsal displacement. Frequently small volar avulsion fragment retains normal position.
- Rolando fracture – Communuted Bennet’s fracture, restoration of alignment often impossible. Tx usually cast or traction.
- Pseudo-Bennet’s fracture – Without joint involvement.
- Gamekeeper’s/Skier’s thumb – Avulsion ulnar collateral ligament proximal 1st MCPJ. From valgus stress ± hyperextension. Tx internal fixation. Stener lesion – thumb adductor tendon aponeurosis interposed between torn edges of UCL, Tx surgical correction and reattachment.
- Boxer’s fracture – MC fracture usually neck of 5th ± 4th MC from abrupt axial loading. Commonly dorsal angulation with volar comminution.
- Mallet/baseball finger – Tear or avulsion fracture of lateral slips extensor digitorum tendon at base distal phalanx causing flexion deformity. From baseball striking distal phalanx causing forced flexion in extended finger. Tx surgery. Associated with volar plate fracture.
- Boutonniere/buttonhole deformity – Tear or avulsion of middle slip extensor tendon (inserting into base middle phalanx) with preservation of lateral slips. PIPJ may slip between lateral tendon slips like buton through buttonhole causing fixed deformity.
- Volar plate fracture – Fracture base proximal or middle phalanx from avulsion of volar plate (dense fibrocartilaginous band covering volar joint of PIPJ and MCPJ), which may get interposed into joint. Tx often requires surgery.
- Jersey finger – Avulsion of flexor digitorum profundus from insertion onto volar base distal phalanx. From forced extension while in flexion (eg grabbing jersey of excaping football player).
- Flexor annular pulley injury – Pulley usually holds flexor tendons against phalanges, may be torn in repetitive flexion of fingers under extreme load (eg rock climbers). Flexor tendons displace from phalanges like bowstring of violin.
- Extra-articular phalanx fracture esp tufts – From blunt or sharp trauma.
- CMCJ disclocations usually dorsal, often associated with small fracture. Adjacent fracture fragment suggests dislocation is/was present. May be subtle, check normal zig-zag line on PA.
- PIPJ dislocation usually dorsal or lateral, often spontaneously reduced or by patient. Commony collateral ligament injury, small lateral/medial avulsion fragments. Ligament injury may be revealed on lateral/medial stress views.
Requires proper positied PA in neutral alignment; dorsiflexion and pronation may simulate ulnar plus and vice versa.
- Ulnar plus/positive variance – Distal ulnar extends distal to radius. May impact against TFCC and medial lunate increasing risk of TFCC tears.
- Ulnar impaction/abutment syndrome – Impingement of distal lateral ulna against TFCC and proximal carpal row (proximal medial lunate), may cause degeneration of TFC and lunate cartilage. Ulna positive variance, subchondral cyst, sclerosis, osteophytes. Tx shortening of ulna.
- Ulnar minus/negative variance – Distal ulnar > few mm shorter than radius. From ulnar growth arrest, surgical shortening, trauma. Causes ulnar impaction syndrome (impaction against distal radial metaphysis), associated with Kienbock’s malacia.
(Lunatomalacia, avascular necrosis of the lunate). From trauma or idiopathic. Associated with negative ulnar variance (ulnar shorter than radius). Increasd density of lunate, may -> collapse and fragmentation. Tx bone grafting, removal or proximal carpal row fusion.
Triangular Fibrocartilage Complex (TFCC) Injuries
Tears cause ulnar wrist pain and weakness, click/pop with motion. Arthrography or MRI may show TFC defect, communication between radiocarpal joint and DRUJ. DDx age-related degeneration.
Type I hamate doesn’t articulate with lunate whereas type II does (V50%). Type II increases risk of chondromalacia, subchondral marrow oedema at proximal pole of hamate or lunate.
De Quervain’s Disease
Stenosing tenosynovitis of extensor pollicis brevis and abductor pollicis longus tendons
(Palmar fibromatosis). Fibromatosis of palmar hand with fibrotic bands tethering flexor tendons causing flexion contractures.
Ganglion cysts are common, usually incidental. Free water, well-circumscribed uni/multi-locular. May have peripheral ehancement. From areas of relative weakness in joint capsule, some from tendon sheaths. Recur if neck is not removed.
Carpal Tunnel Syndrome
Increased pressure in carpal tunnel causing median nerve dysfunction, between trapezium, trapezoid, capitate, hamate, hook of hamate, flexor retinaculum. Median nerve oedema (otherwise not usually well seen on FS image). From fracture, tenosynovitis, RA, gout, amyloid, TB, tumours, pregnancy, diabetes, anomalous muscles, repetitive stress, idiopathic. Most believe it is a clinical or electromyographic diagnosis. MRI and US may identify surgically correctable causes.
Guyon’s Canal Syndrome
Compression of ulnar nerve (and a) between pisiform and hook of hamate (dorsally). Same causes as carpal tunnel syndrome.
- VACTERL associated with agenesis/hypoplasia.
- Madelung deformity – Distal radius bowing to volar and ulnar direction with shortening, ulnar usually dorsally dislocated, widened DRUJ, reduced ROM. DDx trauma, infection, growth disturbance (osteochondromas, enchondromas), Leri-Weill disease, Turner syndrome, or sporadic.
- Holt-Oram syndrome – AD congenital heart disease (esp ASD) and thumb or radius abnormal. Triphalangeal thumb, hypoplasia or bifid. Radius absent, hypoplastic or normal.
- TAR syndrome (thrombocytopenia-absent radius) – Severe thrombocytopenia. Absent radius and ulna shortening with hand at 90deg, usually bilateral.
- Radial club hand – Absent radius with ulnar shortening and hand at 90deg, absent thumb and scaphoid.
- Fanconi anaemia – Brown skin, late childhood pancytopenia. Congenital radial ray and thumb abnormality in 1/2 esp hypoplastic thumb.
- Congenital radioulnar synostosis – Proximal failed segmentation with radius displaced posterior and bowed laterally. May be associated with abnormal karyotype or acquired after infection or Caffey’s disease.
- Congenital radial head dislocation.
Congenital fusion of MCs and phalanges.