Extract
The distal radioulnar joint is inherently unstable. Pathologic instability
can be acute or chronic; it can be dorsal, palmar, or multidirectional; and it
can result primarily from soft-tissue injury or osseous malunion. Recognition
of the type and cause of instability is fundamental in order to provide
effective treatment.
The distal radioulnar joint is inherently unstable. Pathologic instability
can be acute or chronic; it can be dorsal, palmar, or multidirectional; and it
can result primarily from soft-tissue injury or osseous malunion. Recognition
of the type and cause of instability is fundamental in order to provide
effective treatment.
The distal radioulnar joint is a distal articulation in the biarticulate
rotational arrangement of the forearm. This articulation allows only one
degree of motion: pronation and supination. The sigmoid notch of the radius is
concave and is shallow with a radius of curvature of 15 mm. The ulnar head is
semicylindrical and has an articulate convexity of 220° with a radius of
curvature of 10 mm1.
The ulnar head is surrounded by an ulnar carpal ligament complex. This
consists of the ulnolunate and ulnotriquetral ligaments, which originate from
the palmar radioulnar ligament near the ulnar styloid process. When seen
through an arthroscope, these ligaments appear to be continuous with the
triangular fibrocartilage.
The triangular fibrocartilage is a fibrocartilaginous disk originating at
the junction of the lunate fossa and the sigmoid notch and inserting at the
base of the ulnar styloid. Its central portion is cartilaginous, and it is
designed for weight-bearing. It is also avascular. The peripheral margins are
composed of thick lamellar cartilage designed for tensile loading and are
called the dorsal and palmar radioulnar ligaments. The peripheral
margins of the triangular fibrocartilage are well vascularized from the palmar
and dorsal branches of the anterior interosseous artery and from the ulnar
artery. The ulnar styloid is the continuation of the subcutaneous ridge of the
ulnar shaft, and it stands as a strut on the end of the ulna to stabilize the
ulnar soft tissues of the wrist. The sheath of the extensor carpi ulnaris, the
ulnocarpal ligaments, and the triangular fibrocartilage help to maintain the
congruency of the distal radioulnar joint with attachments at the base of the
ulnar styloid; together, they are known as the triangular fibrocartilage
complex2-6.
The radius of curvature of the ulna does not equal that of the sigmoid
notch. Full congruity of two articulating surfaces is therefore not possible.
The shallow sigmoid cavity and the difference between the radii of curvature
of the sigmoid notch and the ulnar head cause the ulna to translate volarly in
supination and dorsally in pronation. In the extremes of forearm rotation,
<10% of the ulnar head may be in contact with the
notch1. Translation
is normal. In pronation, the ulna translates 2.8 mm dorsally from a neutral
position; in supinaton, the ulna translates 5.4 mm volarly from a neutral
position7. The
stability of the distal radioulnar joint is provided by the joint surface
morphology, the joint capsule, the dorsal and palmar radioulnar ligaments, the
interosseous membrane, and the musculotendinous units, primarily the extensor
carpi ulnaris and the pronator
quadratus8,9.
The pronator quadratus and the extensor carpi ulnaris are dynamic stabilizers
of the distal part of the ulna. The pronator quadratus has a superficial head
that is a prime mover in forearm pronation and a deep head that helps to
stabilize the distal radioulnar
joint10. The
pronator quadratus actively stabilizes the joint by coapting the ulnar head in
the sigmoid notch, particularly in pronation, and it passively stabilizes the
joint by viscoelastic forces in
supination11,12.
The extensor carpi ulnaris is maintained in its position over the dorsal
aspect of the distal part of the ulna by a separate fibro-osseous tunnel deep
to and separate from the extensor retinaculum. This separate arrangement
allows unrestricted rotation of the radius and ulna. An intact extensor carpi
ulnaris and fibro-osseous tunnel partially stabilize the distal radioulnar
joint even after the triangular fibrocartilage and other ligaments are
sectioned13. The
important role of the distal radioulnar joint capsule as a restraint and as a
contributor to stability was demonstrated by Ward et
al.14, Watanabe et
al.15, and Marangoz
and
Leblebicioglu16.
Its complementary role in posttraumatic limitations of forearm rotation was
described by Kleinman and
Graham17.
The triangular fibrocartilage, the ulnar carpal ligaments, the
infratendinous extensor retinaculum, the pronator quadratus, and the
interosseous membrane provide additional key soft-tissue constraints. The
triangular fibro-cartilage attaches to the fovea in the ulna by way of the
dorsal and palmar radioulnar ligaments. The fibers that insert into the fovea
are separated from those that insert into the styloid by an areolar vascular
tissue known as the ligamentum
subcruentum18.
There is a debate in the literature regarding the radioulnar ligaments.
According to Schuind et al., in pronation the dorsal radioulnar ligament
tightens as the ulna translates dorsally and in supination the palmar
radioulnar ligament tightens as the ulna translates
palmarly19
(Table I). In contrast,
Ekenstam showed that in pronation the palmar radioulnar ligament becomes taut
(although the dorsal capsule tightens) as the ulna translates dorsally, and in
supination the dorsal radioulnar ligament tightens (although the palmar
capsule becomes tight) as the ulna translates
volarly20. Ekenstam
believed that stability in pronation depends on the tension in the volar
radioulnar ligament and compression between the contact areas of the dorsal
aspect of the sigmoid notch and the ulna, whereas stability in supination
depends on the tension in the dorsal radioulnar ligament and the triangular
fibrocartilage articular disk as well as compression between the contact areas
of the volar aspect of the sigmoid notch and the ulna.
Adams and Holley measured strain on the surface of the triangular
fibrocartilage articular disk and calculated the strain at the dorsal and
palmar margins of the
disk21. In
supination, strain increased dorsally; in pronation, strain increased
palmarly. In a biomechanical study of eleven fresh cadavers, Ward et al.
measured tension in the dorsal and palmar radioulnar ligaments, joint
rotation, and radial translation after sequential excision of the disk,
interosseous membrane, joint capsule, and radioulnar
ligaments14. This
experiment confirmed that the dorsal ligament tightens during pronation while
the palmar ligament becomes progressively lax, whereas the converse occurs
during supination.
The preponderance of biomechanical evidence supports the findings reported
by Schuind et
al.19, and the
inconsistency between their observations and those presented by
Ekenstam20 can be
resolved because, in pronation, the dorsal radioulnar ligament tightens and
tends to displace the ulna dorsally. Left unconstrained, this dynamic
tensioning would lead to subluxation and dislocation of the joint. The palmar
radioulnar ligament checks that force and keeps the joint reduced. If the
interosseous membrane is disrupted and the palmar radioulnar ligament is
sectioned, the distal part of the ulna dislocates dorsally in pronation. If
the interosseous membrane is disrupted and the dorsal radioulnar ligament is
sectioned, the distal part of the ulna dislocates palmarly in supination.
Disorders of the distal radioulnar joint can be classified into four
categories: (1) impaction, (2) incongruity, (3) inflammation, and (4)
instability. All of these disorders can produce pain around the distal
radioulnar joint and should be considered when a patient reports symptoms at
the distal radioulnar joint. Ulnar impaction is due to a positive ulnar
variance that causes the distal part of the ulna to abut against the lunate,
often leading to thinning of the triangular fibrocartilage and eventually to a
central tear. Some surgeons also refer to this as ulnar abutment
syndrome. Incongruity refers to the lack of a smooth interface between
the ulnar head and the sigmoid notch. Incongruity can be due to a
posttraumatic condition such as a distal radial fracture into the sigmoid
notch, or it can be secondary to osteoarthritis or rheumatoid arthritis.
Inflammation around the distal radioulnar joint is usually due to extensor
carpi ulnaris tendinitis dorsally or flexor carpi ulnaris tendinitis palmarly,
and sometimes these disorders can be of a calcific variety.
Instability of the distal radioulnar joint may be acute or chronic and may
be related to osseous changes after a fracture or to soft-tissue injury.
Soft-tissue injury of the triangular fibrocartilage, dorsal radioulnar
ligament, palmar radioulnar ligament, interosseous membrane, joint capsule, or
any combination of those structures is capable of producing instability of the
distal radioulnar joint. Fractures of the distal part of the radius or distal
part of the ulna alter the biomechanics of the distal radioulnar
joint22. It is
important to keep in mind that instability can occur alone or in conjunction
with impaction, incongruity, or inflammation. Treatment must be directed at
each component of the disease complex.
To examine the ulnar styloid, one should follow the superficial border of
the ulnar shaft distally while the wrist is in radial deviation. The ulnar
styloid can be found more volarly than anticipated. This maneuver should be
done with the wrist in a pronated position. The distal radioulnar joint is the
most complex structure to evaluate. The most common pathological finding is
radioulnar incongruity secondary to a malunited distal radial fracture with
loss of the pronation-supination arc. With loss of the volar tilt of the
radius, the distal part of the ulna appears to be more prominent. With ulnar
impaction, ulnar deviation and extension are limited and can be painful. The
areas of pronation, supination, and flexion-extension should be determined. To
test for instability of the distal radioulnar joint, the examiner should
supinate the wrist while supporting the hand, perform a ballottement maneuver
of the distal part of the ulna, and compare the affected side with the normal
side. During this maneuver, he or she should feel for crepitus and ask the
patient if pain occurs. To check for instability of the extensor carpi ulnaris
tendon, the patient should be asked to flex the elbow and pronate and supinate
the forearm with the hand in slight ulnar deviation while the examiner looks
for abnormal motion of the extensor carpi ulnaris tendon. Peripheral tears of
the triangular fibrocartilage complex can produce instability of the distal
radioulnar joint with the wrist in supination. With the patient's forearm in
supination, the examiner should hold the distal part of the ulna between the
thumb and index finger and test for dorsal and volar displacement of the
distal part of the ulna. The so-called press-test is a simple assessment. The
patient is asked to push himself or herself up from a seated position with use
of the affected wrist. This test creates an axial ulnar load and has a high
sensitivity for detecting a tear of the triangular fibrocartilage
complex23. Pain
with this maneuver suggests that there is a lesion in the triangular
fibrocartilage complex.
Standard radiographs of the distal part of the ulna should be made with
comparison views of the unaffected side. The images should include a true
lateral radiograph made with the forearm in neutral rotation. Any deviation of
>10° from a true lateral view will greatly reduce the accuracy of the
examination. Ulnar variance should be measured and compared with that on the
contralateral side on radiographs made with the forearm in neutral rotation
and the shoulder and elbow in 90° of flexion with the x-ray beam directed
from posterior to
anterior24. Ulnar
variance changes by up to a millimeter as the forearm moves from full
supination to full pronation; therefore, this standard position should be
used. Ulnar variance is measured by drawing a transverse line at the level of
the lunate fossa and a second transverse line at the level of the ulnar head,
and determining the distance between the two lines. On the posteroanterior
radiograph, one should look for a fleck fracture demonstrating an avulsion of
the triangular fibrocartilage complex, an ulnar styloid nonunion, and joint
widening between the radius and ulna (Fig.
1). Radiographic signs of injury to the distal radioulnar joint
include a fracture at the base of the ulnar styloid, widening of the distal
radioulnar joint space seen on the posteroanterior radiograph, >20° of
dorsal radial angulation, and >5 mm of proximal displacement of the distal
part of the radius.
Computed tomography scanning is the technique of choice for evaluating
congruity of the distal radioulnar joint, but the same information can be
obtained with magnetic resonance imaging
(Figs. 2-A and 2-B). There are
several methods for evaluating subluxation of the distal radioulnar joint,
including the method described by Mino et
al.25,26,
the congruency
method27, the
epicenter method27,
and the RUR (radioulnar ratio)
method28. Magnetic
resonance imaging is useful for identifying tears of the triangular
fibrocartilage (Fig. 3), but
its specificity and sensitivity
vary29. It is
necessary to use high-resolution magnetic resonance imaging with a dedicated
wrist coil to obtain accurate
scans30-32.
Arthrography is still a valuable examination, and it is even more useful when
it is combined with magnetic resonance imaging. Arthroscopy is a sensitive
method for evaluating tears of the triangular fibrocartilage complex and is
considered the gold standard with which to compare the accuracy of other
examinations.
By convention, the ulna is considered to dislocate with respect to the
radius, but it is the radius that moves and therefore is displaced. With
dorsal subluxation, the head of the ulna becomes prominent dorsally,
particularly in pronation, and may snap during wrist rotation. This is usually
associated with a weak and painful wrist. With complete dislocation, the ulnar
head is locked in position, most commonly dorsally but on occasion palmarly.
Supination is restricted with either type of dislocation because the radius
cannot slip dorsally over the ulnar head.
The mechanism of action for a dorsal subluxation or dislocation of the ulna
is extreme pronation and extension with the coiled and tightened extensor
carpi ulnaris and ulnar carpal ligaments acting as a sling to lift the ulnar
head through the dorsal capsule. Weakening of the triangular fibrocartilage
complex secondary to its avulsion (or a fracture of the ulnar styloid) and
attenuation of the palmar radioulnar ligament will allow the dislocation.
Sheer stress during this mechanism may produce associated chondral defects.
The clinical appearance of a dorsal dislocation of the ulna is a tender
prominent dorsally displaced ulna and a forearm with limited supination or
locked in pronation. Direct pressure may reduce the dislocation, but the ulnar
head usually springs back into a dorsal position if the forearm remains
pronated. There is increased anteroposterior translation of the distal
radioulnar joint with passive motion. Routine radiographs may be
nondiagnostic. A posteroanterior radiograph can show the ulna overlapping the
distal part of the radius. The best study with which to visualize a
subluxation or dislocation is a computed tomography examination of both wrists
performed in both pronation and
supination25,26,33-35.
Treatment of Acute Dislocations
Dorsal Subluxation and Dislocation
An acute dorsal dislocation can be reduced with digital pressure on the
distal part of the ulna and forceful supination. The reduction should be
maintained for six weeks. Some
authors36 have
advocated full supination, whereas
others37 have
recommended the neutral position. Nonoperative methods of treatment should be
used only when there is congruity of the distal radioulnar joint in two
planes. Open reduction with repair of the triangular fibrocartilage complex
should be performed if the joint is locked and cannot be reduced, or if it is
incongruous following reduction. Open repair of the triangular fibrocartilage
complex is done with a dorsal incision through the fifth compartment with the
extensor digiti minimi reflected radially and the extensor carpi ulnaris
reflected ulnarly, thereby exposing the triangular fibrocartilage complex and
visualizing the dorsal radioulnar ligament. Nonabsorbable sutures should be
used to reattach the triangular fibrocartilage complex to the ulnar
styloid38.
Ulnar styloid fractures have an important effect on the stability of the
triangular fibrocartilage complex. These fractures commonly occur together
with fractures of the distal part of the radius and can be a sign of
instability of the triangular fibrocartilage complex. Symptomatic nonunions of
the styloid can occur. Hauck et al. classified these nonunions as type 1 when
the distal radioulnar joint is stable and as type 2 when it is
unstable2. Type-1
fractures occur through the tip of the styloid, and when they become
symptomatic they are often treated successfully with excision. Type-2
fractures occur through the base of the styloid, creating a much larger
fragment, and usually open reduction and internal fixation and restoration of
the integrity of the triangular fibrocartilage complex is recommended even if
there is a nonunion.
The distal part of the ulna can dislocate or subluxate palmarly as a result
of a fall on a supinated hand or from exertional lifting in supination, with
failure of the dorsal radioulnar ligament being the critical event.
Clinically, patients present with the forearm held in a supinated position.
Pronation is painful and
restricted39. The
ulnar head is palpable volarly, and ulnar dysesthesias may develop from
pressure on the ulnar nerve. Once again, a diagnosis can be made on the basis
of good standard radiographs (Figs. 4-A and
4-B) and can be confirmed by comparing computed tomography scans
of the affected and normal wrists. A fracture or erosion of the palmar lip of
the sigmoid notch may lead to persistent instability. An acute palmar
dislocation can be reduced with digital pressure on the distal part of the
ulna in a dorsal direction combined with forceful pronation. The treatment for
an acute palmar dislocation is closed reduction with immobilization for six
weeks in an above-the-elbow cast in a neutral or slightly pronated position.
Open treatment is reserved for patients for whom closed reduction has failed.
The approach is volar with careful retraction of the volar neurovascular
bundle in an ulnar direction.
Triangular fibrocartilage tears can occur without causing instability of
the distal radioulnar joint. The most common tear occurs within the articular
disk of the triangular fibrocartilage, near its attachment to the radius, and
is not associated with instability of the distal radioulnar
joint40-44.
The tears themselves, however, can be unstable and symptomatic. Despite the
recognition of specific types of triangular fibrocartilage
lesions45, the
exact mechanisms of injury remain uncertain. Adams et al., using a laboratory
model to simulate distraction of the radius and ulna through the distal
radioulnar joint, postulated that such a distraction force may result from a
violent axial load on the
forearm40. This
model did not, however, produce the types of tears of the triangular
fibrocartilage complex that are seen clinically. Probably, a combination of
compression across the wrist trapping the disk in the ulnocarpal joint with
distraction or twisting of the distal radioulnar joint then creates enough
shear forces to tear the disk.
Symptomatic instability and tears of the triangular fibrocartilage complex
require surgical treatment. The peripheral rim of the triangular
fibrocartilage is well vascularized and has good healing potential. Repair of
these lesions with a variety of techniques can lead to healing. Historically,
open repair was
advocated38, but
currently most peripheral tears can be treated arthroscopically. This
arthroscopic approach repairs only the superficial fibers of the triangular
fibrocartilage complex to the joint capsule and not the deep portion that
inserts onto the fovea. There is much less chance that central tears of the
triangular fibrocartilage complex will heal because they are in areas of
hypovascularity or avascularity. Arthroscopic débridement of these
lesions is
recommended46.
Dorsal, Palmar, or Bidirectional Instability
Chronic distal radioulnar joint instability is a painful and often
disabling condition. Functional bracing, which has been tested in a cadaveric
model47, can be
used for patients who do not wish to have surgery, but most patients prefer
surgical treatment. It is necessary to check the osseous anatomy in patients
with chronic palmar dislocation. Many patients have had a fracture of the
wrist or forearm, sometimes many years before symptoms developed at the distal
radioulnar joint. Bilateral radiographs of the entire wrist and forearm, made
in the same position, should be compared. Osseous malalignment should be
corrected. The status of the triangular fibrocartilage complex is evaluated
with either magnetic resonance imaging or arthroscopy. If the triangular
fibrocartilage complex is not repairable, a tendon reconstruction is needed
and should be tightened in
supination48,49.
Illustrative Case Report
An eighteen-year-old, right-hand-dominant man presented with pain in the
left wrist and forearm that had been increasing during the previous two years.
He had sustained a fracture of the distal third of the left radius at the age
of twelve years and had been treated nonoperatively. One month later, he fell
and sustained a refracture of the radius as well as an ulnar styloid fracture.
The fracture of the radius was treated with open reduction and internal
fixation through a volar approach. It healed without complication, and the
patient returned to full participation in volleyball, weight-lifting, soccer,
and snowboarding.
Three years later, he noticed swelling about the wrist and had pain at the
distal part of the left ulna in association with many activities. Volar
angulation of the radius could be seen on radiographs
(Figs. 5-A and 5-B). The
triangular fibrocartilage complex appeared normal on the magnetic resonance
imaging scan. The symptoms were attributed to malunion of the fracture and
angular overgrowth of the radius resulting in palmar subluxation of the distal
part of the ulna and instability of the distal radioulnar joint. The hardware
was removed, and a dome osteotomy of the left radius with iliac crest
bone-grafting was done. A closing-wedge osteotomy of the radius was not
performed because of the potential that it could further destabilize the
distal radioulnar
joint50. Eight
months after the surgery, the osteotomy site had healed and the patient had
regained the preoperative range of wrist motion. The distal radioulnar joint
was stable on examination. He resumed all of his previous activities,
including volleyball and weight-lifting, without any symptoms in the left
upper extremity, and he was discharged from our clinic. He subsequently joined
the Marine Corps and wrote to say that he had remained asymptomatic throughout
all physical endeavors involved in his strenuous active
training51.
Galeazzi Fractures
A Galeazzi fracture is a diaphyseal fracture of the radius associated with
a dislocation of the radioulnar
joint52. A Galeazzi
fracture has also been called the "fracture of necessity" because
nonoperative treatment so often yields a poor result. The radioulnar joint may
be dislocated or subluxated, and it is always affected
(Figs. 6-A through 6-D).
Detection of the disorder of the distal radioulnar joint in a patient with a
radial shaft fracture requires a high level of suspicion. Radiographs of the
contralateral side may be helpful. Rettig and Raskin found that twelve of
twenty-two fractures of the distal third of the radius (within 7.5 cm of the
midarticular surface of the distal part of the radius) were associated with
intraoperative instability of the distal radioulnar joint, whereas only one of
eighteen fractures in the middle third of the radial shaft (>7.5 cm from
the midarticular surface of the distal part of the radius) was associated with
intraoperative instability of the distal radioulnar
joint53. Open
reduction with internal fixation of the radial fracture is the first stage of
treatment of a Galeazzi fracture. If the distal radioulnar joint is stable,
early motion can be initiated. If it is unstable and reducible, the wrist
should be immobilized in slight supination for four to six weeks. If a sizable
ulnar styloid fracture is present, fixation may allow early mobilization and
should be considered. If the distal radioulnar joint is irreducible, open
reduction of the joint is necessary; this usually requires repair of the
triangular fibrocartilage or fixation of the ulnar styloid fragment. Six weeks
of immobilization in slight supination is recommended if the distal radioulnar
joint requires surgical treatment. Rarely, the extensor carpi ulnaris is
interposed and prevents reduction; if it is, it needs to be removed from the
joint (Figs. 6-C and
6-D)54.
Essex-Lopresti Injuries
Essex-Lopresti injuries, which are severe and disrupt the entire
forearm55, consist
of a radial head fracture with proximal migration of the radius. The migration
indicates complete disruption of the interosseous ligament and the triangular
fibrocartilage complex. These injuries are usually caused by a fall on the
outstretched hand with axial loading. The primary stabilizer preventing
proximal migration of the radius is the radial head, and the secondary
stabilizers are the interosseous ligament and the triangular fibrocartilage.
Diagnosing the wrist injury in this complex is important. Treatment consists
of open reduction and internal fixation of the radial head if possible, with
immobilization of the forearm in supination. Pinning of the distal radioulnar
joint is an option, but if the pins break they can be difficult to retrieve.
Comminuted radial head fractures often are not repairable and require
replacement, usually with a metallic prosthesis. Silicone radial head
replacements have not performed well in this situation because they fracture,
causing particulate synovitis, when they are placed under load. The operation
is best done early as delayed treatment can lead to poorer results. The
options for delayed surgery include radial head replacement with a prosthesis
or allograft56, or
a Sauvé-Kapandji procedure.
The axis of forearm motion passes through the fovea of the distal part of
the ulna. The deep fibers of the distal radioulnar ligaments, the palmar
radioulnar ligament, the triangular fibrocartilage, the ulnolunate ligament,
the ulnotriquetral ligament, and the ulnocapitate ligament all insert onto the
fovea57. These
ligamentous attachments are key to the stability of the distal radioulnar
joint. The distal radioulnar joint can be stabilized surgically in one of
three ways: (1) a repair of the triangular fibrocartilage complex and the
distal radioulnar ligaments, (2) an extrinsic soft-tissue reconstruction
either with a direct link (i.e., a radioulnar tether) or an indirect link
(i.e., an ulnar carpal sling tenodesis), or (3) a distal radioulnar ligament
reconstruction.
The first option for stabilizing the distal radioulnar joint is to repair
the triangular fibrocartilage complex to the fovea, from which it is usually
found to be ruptured. When repair is not possible, reconstruction is
indicated. There are several procedures for stabilization of the distal
radioulnar joint, as described by Hui and
Linscheid58, Tsai
and Stilwell59,
Breen and
Jupiter60,
Fulkerson and
Watson61, and
Ellison, Boyes, and
Bunnell1, just to
mention a few. The above are all indirect stabilization procedures through an
ulnocarpal sling or tenodesis, or a direct radioulnar tether extrinsic to the
joint (the technique described by Fulkerson and Watson). Johnson described a
dynamic muscle transfer involving use of the pronator
quadratus11. Other
distal radioulnar stabilization procedures involving reconstruction of the
radioulnar ligaments were described by Scheker et
al.62, Sanders and
Hawkins63, and
Bowers64. We are
not aware of any long-term follow-up study of an adequate series of patients
treated with such procedures. In a biomechanical cadaver model,
reconstructions of the radioulnar ligaments were found to be superior to
radioulnar tethering procedures although the results of capsular repair alone
most closely matched the kinematics of an intact distal radioulnar
joint65.
I recommend the procedure described by Adams et al. to reconstruct the
ligamentous anatomy (Fig.
7)48,49.
Their indications and criteria for ligament reconstruction include
unidirectional or bidirectional chronic instability of the distal radioulnar
joint, absence of substantial arthritis, and a competent sigmoid notch rim
with no residual axial instability of the forearm. Any malunion should be mild
or corrected concurrently. Adams and Divelbiss cautioned that, if the volar or
dorsal lip of the sigmoid notch is incompetent (shallow), ligament
reconstruction may not be sufficient and an opening-wedge osteotomy of the
distal part of the radius may be
required48. The
procedure is done with use of a dorsal approach through the fifth extensor
compartment, which provides direct access to the distal radioulnar joint.
Typical findings are a triangular fibrocartilage complex that is torn from the
ulna, a torn extensor carpi ulnaris sheath, concomitant carpal ligament
injuries, and perhaps an ulnar styloid fracture. Adams and Berger reported
that, of twenty patients (twelve with bidirectional instability and eight with
unidirectional instability) followed for a minimum of one year after the
procedure, eighteen recovered stability, with an 80% recovery of supination,
84% recovery of pronation, and 88% recovery of grip
strength49.
If there is residual instability after a distal ulnar resection, a flexor
carpi ulnaris and extensor carpi ulnaris tenodesis, as described by Breen and
Jupiter60,66,
can be considered. Wolfe et al. reported that the distal part of the ulna will
remain stable even after removal of more than a third of
it67. This may be
true after a tumor resection, but it is not a reliable assumption after
traumatic injuries. Wide resections of the distal part of the ulna usually
require some additional form of stabilization, and tenodesis of the flexor
carpi ulnaris and extensor carpi ulnaris tendons is recommended. Implantation
of a metallic prosthesis to replace the distal part of the ulna can also be
considered as a salvage procedure for treatment of this difficult
problem68. The
Sauvé-Kapandji procedure is a useful salvage technique when there is
instability of the distal part of the ulna and arthritic changes
(Fig. 8). The
Sauvé-Kapandji procedure involves fusion of the distal radioulnar joint
and creation of a pseudarthrosis of the ulna just proximal to the arthrodesis
to allow forearm
rotation69. There
can be subluxation of the proximal ulnar stump, which can be symptomatic,
after a Sauvé-Kapandji procedure, and this can be stabilized with
either an extensor carpi ulnaris tenodesis, as described by Minami et
al.70, or a flexor
carpi ulnaris tenodesis, as described by Lamey and
Fernandez71.
Acute dislocations of the distal radioulnar joint should be reduced
promptly and treated with cast immobilization. If the dislocation is
irreducible, open reduction is warranted. The first attempts to treat chronic
instability should be directed at repairing the triangular fibrocartilage
complex, but only after careful assessment for any osseous malunions along the
forearm axis, which must also be corrected. If it is not possible to repair
the triangular fibrocartilage complex, the osseous architecture is normal, and
no arthritis is present, a ligament reconstruction can be considered, but the
competency of the sigmoid notch must be evaluated carefully. If there are
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