Common Fractures of Carpal
Bones
Introduction
The diagnosis of fractures and dislocations of
the carpal bones can be difficult for several reasons. The outlines of the
eight tightly packed bones are inevitably superimposed in most radiographic
views. Even in the anteroposterior view at least one bone overlies another.
All views must be interpreted with a thorough understanding of the normal
bone contours and the relationships between the bones. Furthermore, the carpal
bones normally shift in their relationship to one another during the various
arcs of wrist motion.
Because of the difficulty
in recognizing fractures in acute injuries, many fractures in this region
are not found at initial examination. Articular damage and ligament injuries
are even more difficult to evaluate. The latter may permit abnormal rotations
and subluxations of the various bones. Special radiographic techniques are
helpful. Prognosis is often uncertain because of the peculiarities of the
blood supply of these bones, especially of the scaphoid and lunate.
SCAPHOID FRACTURES
Fracture of the scaphoid
bone is the most common fracture of the carpal bones, and diagnosis is frequently
delayed. A delay in diagnosis and treatment of this fracture may alter the
prognosis for union. A wrist sprain that is sufficiently severe to require
radiographic examination initially should be treated as a possible fracture
of the scaphoid, and radiographs should be repeated in 2 weeks even though
initial radiographs may be negative.
Etiology
This fracture has been reported in people from
10 to 70 years of age, although it is most common in young adult men. It is
caused by a fall on the outstretched palm, resulting in severe hyperextension
and slight radial deviation of the wrist. The scaphoid usually fractures in
tension. The proximal pole locks in the scaphoid fossa of the radius and the
distal pole moves excessively dorsal. Seventeen
percent of patients have other fractures of the carpus and forearm, including
transscaphoid perilunar dislocations, fractures of the trapezium, Bennett
fractures, fractures of the radial head, dislocations of the lunate, and fractures
at the distal end of the radius.
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Figure. Mechanism of carpal fractures from falls on outstretched hand with wrist going into marked dorsiflexion.
(From Stein F, Siegel MW: J Bone Joint Surg 51A:391, 1969.) |
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Anatomy
and Blood Supply of Scaphoid Bone
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The unique anatomy of the scaphoid predisposes fracture of this carpal bone to delayed union or nonunion and to disability of the wrist. Because it articulates with the distal radius as well as with four of the remaining seven carpal bones, the scaphoid moves with nearly all carpal motions, especially volar flexion. Any alteration of its articular surface through fracture, dislocation, or subluxation or any alteration of its stability by ligamentous rupture can cause severe secondary changes throughout the entire carpus.
The blood supply of the scaphoid is precarious. Only 67% of scaphoid bones have arterial foramina throughout their length, including the distal, middle, and proximal thirds. Of the remaining bones, 13% have blood supply predominantly in the distal third and 20% have most of the arterial foramina in the waist area of the bone with no more than a single foramen near the proximal third. This suggests that one third of scaphoid fractures occurring in the proximal third may be without adequate blood supply, and this seems to be borne out clinically; the prevalence of avascular necrosis can be as high as 35% in fractures at this level. Vessels enter the scaphoid from the radial artery laterovolarly, dorsally, and distally. The laterovolar and dorsal systems share in the blood supply to the proximal two thirds of the scaphoid. |
Diagnosis
and Treatment
Treatment of scaphoid fractures is determined by
displacement and stability of the fracture. Cooney, Dobyns, and Linscheid
classified scaphoid fractures as either undisplaced and stable or displaced
and unstable. Although this classification remains useful, fractures of the
tuberosity, the distal articular surface, and the proximal pole may require
special management decisions. For nondisplaced fractures, radiographic diagnosis
can be difficult initially. A posteroanterior plain radiograph with the wrist
slightly extended in ulnar deviation is helpful. Although repeating radiographs
after 2 weeks of immobilization in a cast is a time-honored method for evaluation
of a suspected nondisplaced scaphoid fracture, the technetium bone scan and
computed axial tomography (in the sagittal plane of the scaphoid) provide
diagnostic information sooner.
Nondisplaced,
Stable Scaphoid Fractures
Nonoperative treatment usually is successful for
acute nondisplaced, stable fractures without other bony or ligamentous injury
and for scaphoid fractures in children. The prognosis is better if the fracture
is diagnosed early. We use either a forearm cast, or a Munster-type cast,
from just below the elbow proximally to the base of the thumbnail and the
proximal palmar crease distally (thumb spica) with the wrist in slight radial
deviation and in neutral flexion. The thumb is maintained in a functional
position, and the fingers are free to move from the metacarpophalangeal joints
distally. Using nonoperative casting techniques, the expected rate of union
is 90% to 95% within 10 to 12 weeks. Fractures at and distal to the scaphoid
waist are expected to heal sooner than those in the proximal pole. During
this time, the fracture is observed radiographically for healing. If collapse
or angulation of the fractured fragments occurs, surgical treatment usually
is required.
If the diagnosis is delayed, or the fracture is
in the proximal third, the prognosis is less favorable and an initial long
arm thumb spica cast for 6 weeks may be justified.
Because of the potential for joint stiffness, muscle
atrophy, or the inability to use the hand during and after prolonged immobilization,
special nonoperative or operative treatment may be considered in certain patients
(e.g., young laborers or athletes). Operative techniques, including percutaneous
fixation with cannulated screws, may shorten the time in cast. For some athletes,
the use of padded casts during competition may be considered. The advantages
and disadvantages of various treatment modifications should be considered
in each patient. When making the diagnosis of scaphoid fractures or nonunions,
a bipartite scaphoid is considered so rare as to be of little or no clinical
significance.
Displaced,
Unstable Scaphoid Fractures
A different course of treatment is required for
a displaced, unstable fracture in which the fragments are offset more than
1 mm in the anteroposterior or oblique view, or if lunocapitate angulation
is greater than 15 degrees, or the scapholunate angulation is greater than
45 degrees in the lateral view (range, 30 to 60 degrees). Other criteria for
evaluating displacement include a lateral intrascaphoid angle greater than
45 degrees, an anteroposterior intrascaphoid angle less than 35 degrees (Amadio
et al.), and a height-to-length ratio of 0.65 or more (Bain et al.). Because
the range of lunocapitate and scapholunate angulation can vary, comparison
views of the opposite wrist can be helpful. Reduction can be attempted initially
by longitudinal traction and slight radial compression of the carpus. If the
reduction attempt is successful, percutaneous fixation with a cannulated screw,
or pins and application of a long arm thumb spica cast, may suffice. Otherwise,
open reduction and internal fixation may be required.
For a displaced or unstable recent fracture of
the scaphoid, the best method of fixation depends on the surgeon's experience
and the equipment available. In some fractures, adequate internal fixation
can be obtained with Kirschner wires. The Warner compression staple, the AO
cannulated screw, and the Herbert differential pitch bone screw have been
used to advantage in displaced and unstable scaphoid fractures. In a comparison
study of two groups of patients with scaphoid fractures, Trumble and associates
noted 100% union in both groups, one treated with AO cannulated screws and
the other with Herbert-Whipple cannulated screws. Cannulated bone screws are
useful because the screw can be placed accurately over a guide pin with video
fluoroscopic control. The advantages of the Herbert screw, according to Sprague
and Howard, are that it (1) reduces the time of external immobilization, (2)
provides relatively strong internal fixation, and (3) produces compression
at the fracture site. In addition, because the headless screw remains below
the bone surface, removal usually is unnecessary. These screws can be used
with a bone graft to correct scaphoid angulation. Use of the cannulated design
can minimize the disadvantages of the noncannulated screw, which include the
use of a jig for insertion and the demanding surgical technique. Contraindications
include (1) avascular crumbling of the proximal pole of the scaphoid, (2)
extensive trauma or osteoarthritis involving the adjacent carpals or articular
surface of the radius, and (3) gross carpal collapse.
Regardless of the fixation device used, careful
attention to the details of the procedure, achieving as near an anatomical
reduction as possible, and precise placement of the fixation device are of
utmost importance.
Malpositioned
Nonunion of Scaphoid Fractures (Humpback Deformity)
Established nonunions of scaphoid fractures can
be seen in preoperative radiographs to have resorption or comminution, with
resulting shortening and angulation, with its convexity dorsal and radial
(“humpback” deformity). Preoperative computer-assisted tomography in the sagittal
and coronal planes demonstrates this deformity. The deformity includes extension
of the proximal pole of the scaphoid, resulting extension of the lunate, and
a form of dorsal intercalated instability (DISI) pattern seen on lateral plain
radiographs. Interposition bone grafting allows restoration of length and
correction of malalignment. Anterior wedge grafting for angulation has been
proposed to create a scapholunate angle of more than 60 degrees or an intrascaphoid
angle of more than 45 degrees. Fernandez' modifications emphasized careful
preoperative planning, comparison radiographs of the uninjured side, the use
of a bone graft fitted to the defect, and Kirschner wire fixation. Tomaino
et al. treated persistent lunate extension after interposition grafting of
the scaphoid by radiolunate pinning to stabilize the lunate in a neutral position
before correcting the scaphoid “humpback” deformity. The cannulated Herbert-Whipple
screw was found to be effective fixation. According to Manske, McCarthy, and
Strecker, the double-threaded Herbert screw was most effective in nonunions
with evidence of avascular necrosis, those involving the proximal third, or
those having had previous failed bone grafts. Stark et al. recommended Kirschner
wire fixation with an iliac bone graft for all nonunions because judging stability
with bone grafting alone was difficult and because the technique was technically
easy and added little to the operating time. They achieved union in 97% of
151 old ununited fractures of the scaphoid.
HAMATE
BONE
FRACTURES
Fractures of the hamate can involve the hamulus,
or hook, the body, and various articular surfaces. Fractures of the hook can
be treated with casting, open reduction, or excision of the hook. Fractures
of the body usually are treated with casting, unless displacement is significant.
Articular fractures require open reduction and internal fixation if displacement
of the articular surface is 1 mm or more.
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A fracture of the hook of the hamate is sometimes
difficult to demonstrate. Pain is elicited at the heel of the hand with
firm grasp and with pressure against the bony prominence just lateral
and slightly distal to the pisiform. A carpal tunnel view may show the
fracture (A), but some are better demonstrated by CT (B). When using
the latter technique, placing the patient's hands together in the praying
position makes the diagnosis easier because the view of both wrists
rules out congenital variation of the hamate, which usually is bilateral.
Occasionally the body of the hamate is fractured, but this rarely requires
surgery. |
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A stress fracture may develop in the hook of the
hamate with some repetitive activities, such as golf. Initial diagnosis can
be difficult. Transient ulnar nerve motor palsy can be caused by an undiagnosed
stress fracture of the hook of the hamate. In most instances, unless the diagnosis
is delayed, union is likely after immobilization, but excision of the fragment
may be necessary for nonunion, persistent pain, or ulnar nerve palsy.
TRAPEZIUM
AND TRAPEZOID FRACTURES
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Fractures of the trapezium and trapezoid are rare and may be comminuted when seen in conjunction with radial fracture-dislocations. Displaced trapezial fractures require open reduction. These fractures can be seen radiographically on the carpal tunnel view of the wrist and with tomography or CT scanning. Palmer classified trapezial fractures into two types: Type I is a fracture of the base of the ridge, and it may heal when treated by immobilization in plaster; Type II is an avulsion at the tip of the ridge, and it usually fails to heal when immobilized |
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Fractures of the trapezium and trapezoid are rare
and may be comminuted when seen in conjunction with radial fracture-dislocations.
Displaced trapezial fractures require open reduction. These fractures can
be seen radiographically on the carpal tunnel view of the wrist and with tomography
or CT scanning. Palmer classified trapezial fractures into two types: type
I is a fracture of the base of the ridge, and it may heal when treated by
immobilization in plaster; type II is an avulsion at the tip of the ridge,
and it usually fails to heal when immobilized
FRACTURES
OF LUNATE AND KIENBÖCK DISEASE
Fractures of the lunate can be difficult to detect
on plain roentgenography. Tomography and CT scanning may be required to see
the fracture. Fractures of the lunate may be nondisplaced, displaced with
large fragments, avulsed, especially the dorsal pole, or comminuted. Nondisplaced
and nondisplaced comminuted fractures can be treated with cast immobilization.
Fractures with more than 1 mm offset and avulsion fractures usually require
open reduction. Internal fixation techniques vary depending on the requirements
of the individual situation and may include Kirschner wires, small cannulated
screws, and suture anchors. Trauma to the lunate may be sufficient to damage
the circulation, leading to avascular necrosis of the lunate.
Kienböck disease is a painful disorder of the wrist
of unknown cause in which radiographs show avascular necrosis of the carpal
lunate. It occurs more frequently between the ages of 15 and 40 years and
in the dominant wrist of men engaged in manual labor. In 75% of patients the
disorder is preceded by severe trauma, usually with the wrist in severe dorsiflexion.
Armistead et al., using CT, demonstrated in some patients occult fractures
of the lunate. Untreated, the disease usually results in fragmentation of
the lunate, collapse with shortening of the carpus, and secondary arthritic
changes throughout the proximal carpal area. Symptoms can develop as early
as 18 months before radiographs show evidence of the disease. The use of MRI
can be helpful in the diagnosis of early avascular changes in the lunate.
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Figure. Common fracture pattern in Kienböck disease is so-called anterior pole type, isolating anterior pole of lunate from remaining portion of bone. A. Distraction of fracture caused by compressive force exerted by capitate diminishes likelihood of fracture healing. This detail usually is not visible on routine roentgenograms because radial styloid process is superimposed on fracture gap. As dorsal portion of lunate collapses further, anterior pole may be extruded volarly. B. Ratio of height of carpus to length of third metacarpal is reduced in this patient with Kienböck disease. Youm et al. determined that this ratio in normal wrists is 0.54:0.03 and that significantly reduced ratios indicate overall carpal collapse. (From Armistead RB, Linscheid RL, Dobyns JH, Beckenbaugh RD: J Bone Joint Surg 64A:170, 1982) |
Treatment
Lichtman and Degnan's classification of lunate
changes is useful in discussing treatment.
Stage I—Normal architecture with evidence
of a linear or compression fracture
Stage II—Normal outline but definite
density changes within the lunate
Stage III—Collapse or fragmentation
of the lunate and proximal migration of the capitate (carpal height ratio
is less than 0.54 ± 0.03)
Stage IV—Generalized degenerative
changes within the carpus
The treatment of established Kienböck disease is
not standardized. Some have preferred simple casting if the disease is considered
to be quite early (stage I or II, before sclerosis, fragmentation, or collapse
occurs). Such management includes casting of the wrist for several weeks,
if warranted, followed by repeated radiographs in search of occult fracture
or avascular changes of the lunate or other disorders that become apparent
later, including previously undiagnosed fractures of the carpal scaphoid.
This treatment generally has been unacceptable because it requires 4 or more
months of immobilization with an uncertain outcome. A study by Mikkelsen and
Gelineck, in which 25 wrists were observed for
Stage I - II.
Some authors recommend ulnar lengthening early in the disease (stage I or
II). Hultén has described a condition known as the ulna-minus variant.
He found in 78% of patients with Kienböck disease that the ulna was shorter
than the radius at their distal articulation. This was true in only 23% of
normal wrists. In no patient with Kienböck disease was the ulna longer than
the radius at the distal articulation, but 16% of the control group had a
so-called ulna-plus variant.
Persson in 1950 reported a series of patients in
whom he lengthened the ulna for this disease. These patients were observed
for several years by Axelsson and Moberg. They found 16 who had been operated
on some 20 years previously, and all but one had been able to continue with
manual labor after the operation. Even in one who had pain, the disease process
appeared to have been halted. Because of these findings, Armistead et al.
have performed the ulnar lengthening operation for Kienböck disease, reporting
20 cases in 1982. Three nonunions required a second plating and bone grafting;
18 of the 20 had pain relief. The technique is detailed below. The ulna should
not be lengthened enough to impair ulnar deviation of the wrist; usually most
wrist movement can be retained. Strong plate fixation of the distal ulna is
recommended.
In addition to ulnar lengthening, the radius can
be shortened to provide a level distal radioulnar articular surface for the
lunate. Of 12 patients reported by Almquist and Burns, all but one had pain
relief, and 10 of 12 showed radiographic revascularization of the lunate.
Their indications for radial shortening include negative ulnar variance and
lunate compression fracture without fragmentation or flattening (stage II).
Earlier studies by Kelven, Axelsson, and Eiken and Niechajev reported similar
satisfactory results. Shortening of the radius consists of making a transverse
osteotomy about 3 inches (7.6 cm) proximal to the distal articular surface,
shortening the radius by 2 mm, and fixing the bone with a compression plate.
Edelson, Reis, and Fuchs reported development of Kienböck disease in a patient
16 months after surgery in a lunate that appeared to have reconstituted normally.
However, in a series of 35 patients, Schattenkerk, Nollen, and van Hussen
reported satisfactory results in two thirds of those treated by both ulnar
lengthening and radial shortening. In addition, Weiss et al. reported 30 wrists
with Kienböck stages I and II treated with radial shortening of an average
of 2.8 mm. At an average 3-year follow-up, 87% had decreased pain, improved
motion and grip strength, and no appreciable change in the amount of lunate
collapse.
Stage III.
In late cases (stage III) in which the lunate has collapsed but secondary
arthritic changes are absent, the ulnar lengthening operation is advocated
by Armistead et al. Stark, Zemel, and Ashworth recommended use of a hand-carved
silicone rubber spacer in the absence of significant alteration in the shape
of the bone, including absence of collapse as measured by the three kinematic
indices of McMurtry et al. The carved prosthetic device is substituted for
the lunate, which is excised through a dorsal approach. Both Swanson and Lichtman
and their associates advocated replacement with a previously molded lunate-shaped
silicone block followed by careful repair of the capsule to avoid dislocation
of the block. This ligamentous and capsular reconstruction is extremely important
and has been emphasized by many authors.
The patient should be warned of the possibility
of silicone synovitis and the formation of foreign body cysts. These complications
are more likely if the implant is oversized or malpositioned, if carpal instability
is present, or if motion or occupational stress of the wrist is excessive.
Because of this possibility, some surgeons have abandoned or limited this
technique and have suggested intercarpal fusion (scaphoid-capitate, capitate-hamate,
or hamate-triquetrum). Simple excision of the lunate, although controversial,
has been shown in a study by Kawai et al. to produce satisfactory results
with continued relief of pain at an average follow-up of 12 years. In 18 patients
the carpus rearranged itself with proximal migration of the capitate, triquetrum,
and palmar-flexed scaphoid, but a good range of motion was preserved and degenerative
changes were less than anticipated. However, the procedure is not recommended
for those who do heavy work. Triscaphe arthrodesis for Kienböck disease has
been advocated by Watson. Sennwald and Ufenast evaluated 11 patients treated
with scaphocapitate arthrodesis, with an average follow-up of 36 months. They
found this procedure effective for pain relief and recommended it for patients
with advanced stages of Kienböck disease.
Stage IV.
When secondary arthritic changes have developed throughout the wrist (stage
IV), treatment usually is proximal carpal row resection or wrist arthrodesis.
