Wrist Trauma Fractures and Dislocations of the Wrist

Wrist Trauma

Fractures and Dislocations of the Wrist • Clinically point tenderness over the wrist with >20% loss of grip strength are good physical indicators • Complex anatomy requires four views for interpretation • Neutral PA, PA in ulnar deviation, medial oblique and lateral • Advanced imaging very useful because fractures not always visible

Normal Anatomy http: //uwmsk. org/Rad. Anat/Wrist. PALabelled. html

Distal Radius Fractures • Fractures may be subtle or even occult • Alteration of pronator quadratus fat plane is a useful indicator of fracture • Distal radial fractures include: -Colles’, Smith’s, Barton’s, Chauffer’s, Moore’s, torus, slipped radial epiphysis http: //radiology. rsna. org/content/244/3/927. full

Distal Radius Fractures • Colles’ fracture- fx. of distal radius with posterior angulation of distal fragment – Usually FOOSH – Osteoporosis is risk factor, so increased incidence in women>65 • Smith's fracture (reverse Colles’ fracture)- fracture of distal radius with anterior angulation of distal fragment – Less common than Colles’ – Direct blow or fall on flexed hand http: //imageinterpretation. co. uk/wrist. html

Distal Radius Fractures • Barton’s fracture (rim fx. )- posterior rim fracture of distal radial articular surface with associated proximal dislocation of carpals – Will see overlap of proximal row with articular surface of radius • Chauffeur’s fracture (backfire fx. , Hutchinson's fx. )fracture of radial styloid – Caused by avulsion or impaction by scaphoid – Formerly caused by starting cars with hand cranks http: //radiographics. rsna. org/content/24/4/1009/F 11. expansion. html http: //www. radiologyassistant. nl/en/476 a 23436683 b

Distal Radius Fractures • Moore’s fracture- fracture of ulnar styloid process and dislocation of distal ulna associated with Colles’ fracture • Torus fracture- buckling of cortex after trauma – Happens in children – Can happen in any long bone – Radiographic sign is bump or bulge of cortex

Distal Radius Fractures • Slipped radial epiphysis- childhood equivalent of Colles’ fracture – Hyperextension injury (FOOSH) causes shearing of radial epiphysis, which gets displaced posteriorly – Usually has small metaphyseal fragment (corner sign), which makes it Salter-Harris II http: //www. oha. or. kr/skr/trauma 4. htm

Distal Unlar Fractures • Ulnar styloid process fracture- rare as an isolated fracture – Usually avulsion by ulnar collateral ligament – More frequently found as associate fracture with other injuries • Distal ulnar shaft fracture- see “nightstick fracture” from forearm fracture section

Scaphoid Fractures • Most common carpal bone to fracture – Usually ages 15 to 40; rare in children • FOOSH • Clinical presentation is snuffbox pain with swelling • Most common site for occult fracture • Classified by anatomic location of fracture line – Waist (70%), proximal pole (20%) and distal pole (10%)

Scaphoid Fractures • Initially radiographs may be negative • Repeat x-ray in 10 to 20 days or advanced imaging immediately – MRI makes most sense if US not available • Complications include: – AVN, nonunion, carpal instability and radiocarpal degenerative arthritis

Scaphoid AVN • Scaphoid had 2 blood supplies – Proximal pole is supplied by an artery that enters distally • The more proximal the fracture is, the more likely AVN will occur if untreated • Radiographic signs include increased density (dead bone) and fragmentation

Nonunion • Missed diagnosis may lead to delay in treatment • Over time fracture line will widen and margins will become smooth and sclerotic

Carpal Instability • Follows rupture of scapholunate ligament • Radiographic features include: – Terry Thomas sign- widening of scapholunate jt. space >4 mm – Ring sign- rotation of scaphoid – Loss of parallel joint surfaces

Radiocarpal Degenerative Arthritis • Radiographic signs are that of OA anywhere else in the body • OA signs at the radiocarpal joint in the absence of trauma suggests diagnosis of CPPD • SLAC (Scapho. Lunate Advanced Collapse) wrist may follow if capitate is allowed to migrate proximally

Triquetral Fractures • 2 nd m. c. carpal bone to fracture • Usually by avulsion from dorsal surface by radiocarpal ligament (Fisher fracture) – Small flake dorsally only identifiable on lateral film

Fractures of Other Carpal Bones • All may fracture, but unusual unless directly traumatized • Hamate frequently complicated by nonunion • Lunate frequentlyly complicated by avascular necrosis (Keinböck’s disease) http: //orthoinfo. aaos. org/topic. cfm? topic=a 00017

Dislocations of the Wrist • Two patterns – 1. a single bone that dislocates relative to remaining carpals – 2. a single bone that remains in place with the surrounding carpals dislocating • Evaluation of carpal arcs is a useful tool – Arc 1 - proximal articular surfaces of proximal row – Arc 2 - distal articular surfaces of proximal row – Arc 3 - proximal surfaces of distal carpals (capitate and hamate) – Disruption indicates dislocation http: //www. radiologyassistant. nl/en/42 a 29 ec 06 b 9 e 8

Single Carpal Dislocations • Lunate dislocation- most common carpal bone to dislocate – On PA film dislocated lunate appears triangular (pie sign) – Rows 2 and three disrupted • Scaphoid dislocation– On PA film, see ring sign and Terry Thomas sign as previously described • Other single carpal dislocations unusual and require severe trauma

Multiple carpal dislocations • Perilunate dislocation- dorsal displacement of all carpals except lunate, which stays in place – On lateral, capitate does not sit in the lunate – On PA, capitate overlies lunate http: //www. imageinterpretation. co. uk/wrist. html • Trans-scaphoid perilunate dislocation- same as above, but with associated scaphoid fracture • de Quervaine’s fracture dislocation- anterior dislocation of lunate as well as proximal fragment of fractured scaphoid

Fractures of 2 nd - 5 th Metacarpals • Boxers fracture- transverse fracture of neck of second or third metacarpals – Result of straight jab with fist • Barroom fracture- transverse fracture of neck of fourth or fifth metacarpals – Result of roundhouse blow from inexperienced fighter

First Metatarsal Fractures • Bennett's fracture- intra-articular fracture through base of the first metacarpal with dorsal displacement of the shaft – A small medial fragment remains at its articulation with trapezium • Rolando's fracture (comminuted Bennet’s) same as above but comminuted • Transverse fracture- most common fracture of first metacarpal – Doesn't interfere with articulation

• Distal phalangeal fractures – Described as transverse, longitudinal, comminuted or chip fractures – Chip fractures occur at posterior or anterior corners of phalangeal base • Posterior chip fracture inactivates extension of the DIP joint and produces flexion deformity (mallet or baseball finger) • Middle phalangeal fractures – Chip fracture at anterior aspect of base (Volar plate fracture)

References • Yochum, T. R. (2005) Yochum and Rowe’s Essentials of Skeletal Radiology, Third Edition. Lippincott, Williams and Wilkins: Baltimore.