FRACTURES AND DISLOCATIONS OF THE CARPUS BONE OR WRIST
Introduction and anatomy
BONES OF THE HAND
The articulated bones of the hand are made up of a carpus (eight bones), five metacarpal bones and the phalanges of the five digits The eight carpal bones articulated together form a semi circk, the convexity of which is proximal and articulates with the forearm. The diameter of the semicircles distal and
articulates with the metacarpal bases . The Bexor surface of the carpus is deeply concave to accommodate the flexor tendons. The extensor surface is gently convex and the extensor tendons pass across it
The carpus bones
• Made up of two rows of four bones
• Proximally, lateral to medial-scaphoid, lunate, triquetral plus attached pisiform
• Distally, lateral to medial trapezium, trapezoid, capitate, hamate
• carpus is arched transversely, the palmar aspect being concave
• Arch is maintained by individual bones which are broader posteriorly than anteriorly except the lunate
• Arch is also maintained by the flexor retinaculum passing from the scaphoid and trapezium laterally to the pisiform and hook of the hamate medially
Fractures of carpus bones
It should be consider that the most common injuries of the carpus or wrist including the following injuries
Fracture of scaphoid bone - dislocation of carpal bones - fractures of other carpal bones
Scaphoid fracture
The most commonly fractured wrist bone is the scaphoid, which is involved in both the radiocarpal joint and the joint between the distal and proximal carpal rows
common in males aged 15 to 30 years
The blood supply to the scaphoid is variable. It commonly enters the distal part of the ligamentous ridge between the two main articular surfaces. Thus there is a risk of avascular necrosis( AVN ) of the proximal part of the bone if a fracture of the waist is sustained
Due to the role of the scaphoid in two major joints, movement of fracture fragments is difficult to control. The prognosis is good in stable fractures, but poor in unstable fractures
Mechanism of injury
• Fall onto out-stretched hand in young adults
• Kick-back when using jump-start handles or pulleys
Sites of scaphoid fracture
• Waist of scaphoid bone most common
• Proximal pole high risk of AVN
• Distal half least common
Clinical features
As any fractures history of trauma beside there is tenderness at the anatomic snufbox the hollow between the thumb extensor tendons on the radial aspect of the wrist just dorsal to the styloid process of the radius pain is elicited and symptoms reproduced with direct pressure over the tuberosity of the scaphoid at the palmar base of the thenar eminence and with passive wrist motion
Investigations
Radiogtaphs X rays plain posteroanterior or lateral and oblique views may not appear the fracture so it need for carpal tunnel projection or other view if imaging information is non diagnostic or equivocal CT scan sometimes needing three- dimensional reconstruction will demonstrate the fractures and fragment position, technetium bone scan 72 hours or three days after trauma is also diagnostic, MRI scanning is also extremely sensitive in delineating the presence of a carpal fracture
Management of scaphoid fractures
If initial radiographs are normal but the history and physical examination suggest the possibility of scaphoid fracture continuous immobilization in a thumb spica or cast is advised repeat radiographs in 2 to 3 weeks MRI or technetium bone scan after 72 hours will make the diagnosis
Treatment
Non displaced stable scaphoid fractures
by plaster immobilisation or long arm above elbow thumb spica for 6 weeks followed by a short arm spica cast for another 6 weeks immobilization of the wrist in slight flexion and radial deviation relaxes the volar radioscaphoid ligament
Displaced scaphoid fractures defined as more than or equal to 1.0 mm displacement are commonly associated with avascular necrosis and non union if not reduced and stabilized operatively by open reduction and internal fixation with an interfragmentary lag compression screw this allow early mobilization and more stable
In case of acute fracture but non displaced may used per cutaneous compression screw for immediate internal stabilization
Delayed union eg if not healed by about 3 months may need bone graft and internal fixation
Method of Scaphoid plaster
• Wrist pronated, radially deviated, moderately dorsiflexed
• Extending from MCP joints (including thumb in mid-abduction), extending along forearm but not involving elbow joint For 6 a week
Complications of scaphoid fractures
• Delayed union
• Non-union
• AVN of proximal third
• Osteoarthritis
plaster immobilization
Other carpal bones fractures
They are uncommon as follow
most commonly fractures secondary to idiopathic avascular necrosis or lunatomalacia (Kienbock,s disease) without history of acute trauma
it appear more radiodense on posteroanterior projection view
it appear more radiodense on posteroanterior projection view
Treatment
non displaced by immobilization displaced by open reduction and internal fixation especially if associated with intercarpal misalgnment
Fractures of the capitate
Fractures of the capitate bone are uncommon The proximal pole, like that of the scaphoid, receives its blood supply from vessels that enter distally. Capitate neck fractures are therefore at potential risk for avascular necrosis. When avascular necrosis occurs, usually it is incomplete i.e. temporary Capitate head collapse is uncommon
trapezium and trapezoid fractures
trapezium and trapezoid fractures
These fractures are uncommon. Injuries to these bones are often associated with intra-articular fractures of the base of the first metacarpal. Open reduction is often necessary, with internal fixation by Kirschner wires or small compression screws.
Fractures of the pisiform
Fractures of the pisiform
Fractures of the pisiform are usually secondary to a direct blow to the hypothenar eminence. The fractured pisiform is best seen in carpal tunnel projection radiographs or CT scan. Excision may be required, and is symptomatically curative for displaced fractures nonunion, malunion, and secondary arthritis.
There are two types of fracture of the hamate
Those involving the body and those of the hamulus (hook
.Fractures of the body of the hamate are difficult to diagnose on plain radiographs imaging may require several
oblique projections, or even better, CT scan. The patient may have pain referred to the dorsal hand or wrist with fractures of the body or hook. Most fractures of the body of the hamate heal with immobilization for 4 to 6 weeks. Fractures of the hamulus are more common, and usually are the result of a direct force transmitted into the base of the palm from a grasped object The palm is tender to direct pressure over the hamate, but sometimes the discomfort is reported as being dorsal with such a maneuver or with use. Secondary ulnar neuropathy in the distal third of Guyon's canal may be present. Late flexor tendon ruptures (little and ring finger flexors) may occurs especially in those whose undiagnosed palmar pain syndrome is treated with repeated steroid injections. Routine radiographs and carpal tunnel views may be negative , CT scan will make this diagnosis evident the acute hook fracture should be expected to heal in a short-arm cast (4 weeks), displaced fractures and symptomatic nonunions are most efficiently treated by excision of the hamulus and smoothing of the fracture base, but taking care to visualize and protect the deep motor branch of the ulnar nerve, which courses radially around the distal edge of the hamulus as it goes dorsally into the mid-palm
most carpal dislocation are caused by an acute axial load and wrist hyperextension first occurs at the midcarpal joint with dorsal displacement of the capitate when the capitate displaces the scaphoid must fracture or it is ligaments tear allowing it to rotate into flexion this situation is called dorsal perilunate dislocation these are serious and unstable intra articular injuries with or without associated scaphoid fracture or triquetral fractures and or triquetrolunate separation which require careful realignment most all by open reduction with internal fixation direct trauma to the median nerve from impact and or secondary stretching from dorsal displacement of the carpus blood and swelling within the carpal tunnel should be elucidated by neurovascular examination and pressure measurement
Dislocation of the lunate bone
The lunate is a wedge-shaped bone with its base anteriorly. If it is subjected to excessive force with the hand extended it can be squeezed out of position. In the characteristic displacement the lunate lies anterior to the wrist, rotated through 90 degree or more on a horizontal axis, so that its concave lower articular
Management of dislocation of the lunate
• MUA
• ORIF
Complications of dislocation of the lunate
• Median nerve injury
• Osteoarthritis
Perilunate dislocation of the carpus
The whole carpus is dislocated posteriorly except for the lunate, which remains congruous with the radius
Scapholunate dissociation (rupture of the scapholunate ligament complex) The carpal bones rotate as the hand moves from radial to ulna deviation. The rotational force is transmitted through the intrinsic carpal ligaments. Disruption of the ligaments leads to abnormal carpal biomechanics this may lead to Osteoarthritis( OA )in the long term
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