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INVITED ARTICLE
J. K. Stanley, MCh Orth, FRCS, FRCS Ed, Consultant in Hand and UpperLimb SurgeryI. A. Trail, MD, FRCS, Consultant in Hand and Upper Limb SurgeryCentre for Hand and Upper Limb Surgery, Wrightington Hospital for JointDisease, Hall Lane, Appley Bridge, Wigan, Lancashire WN6 9EP, UK.
Correspondence should be sent to Mr J. K. Stanley.
©1994 British Editorial Society of Bone and Joint Surgery0301-620X/94/5844 $2.00J Bone Joint Surg [Br] 1994; 76-B:691-700.
VOL. 76-B, No. 5, SEPTEMBER 1994 691
CARPAL INSTABILITY
J. K. STANLEY, I. A. TRAIL
From Wrightington HospitalNHS Trust, Wigan, England
Carpal instability is the term used for a group of conditions
which results from injuries to the carpus, ranging from a
simple sprain to a major fracture-dislocation. In the
English literature Gilford, Bolton and Lambrinudi (1943)were the firstto note the potential for instability, describingthe wrist as a link joint which was stable under tension
because of the position and size of the scaphoid bone, andin 1970 Fisk described carpal instability from nonunion
of a scaphoid fracture as a zig-zag or concertina deformity.
Linscheid et al (1972) proposed a classification and
offered the definition “carpal injury in which a loss ofnormal alignment of the carpal bones develops early or
late”.
INCIDENCE
In 1975 Dobyns et al reviewed their own experience and
that of the B#{246}hlerClinic and reported that 10% of all
carpal injuries resulted in instability. Jones (1988) studied
a consecutive series of 100 wrist injuries with no
radiological evidence of fracture; he took special radio-
graphs of the wrist including a clenched-fist view. In 19
patients there was an increase in the scaphoid-lunate gap
and five of these had scaphoid-lunate instability. Kellyand Stanley (1990) reviewed 98 consecutive wristarthroscopies and identified many ligamentous injuries,
findings that were confirmed by Sennwald, Fischer andJacob (1993) who carried out arthroscopy on 41 injured
wrists and found at least one ligamentous lesion in 25%
and two or more distinct lesions in 75%.
The incidence of carpal instability in association
with other injuries is unclear. In a large series of fractures
of the distal radius, Tang (1992) found radiological
evidence of carpal instability in 30.6%. Nakamura et al( 1991), however, performed arthroscopy on the wrists of
a group of patients with ununited scaphoid fractures and
found that most did not have serious ligamentous injuries.
PATHOMECHANICS
Understanding carpal instability requires a thorough
knowledge of the anatomy and mechanics of the carpus.
The distal row of bones, the trapezium, trapezoid, capitate
and hamate, forms a stable platform upon which the
metacarpals ride and there is very little motion between
these bones. Similarly, the distal radius and ulna, althoughthey move in pronation and supination, are essentially
stable. The proximal row of the carpus, however, is an
intercalated segment with no muscle insertions; its
stability depends entirely on the capsular and interosseous
ligaments between the scaphoid, lunate and triquetrum
(Fig. 1). Flexion and extension of the wrist result from
movements between the radius and the lunate, between
the lunate and the capitate in the centre of the wrist,
between the trapezium, trapezoid and scaphoid on the
lateral side, and between the triquetrum and the hamate
on the medial side (Fig. 2). There is no differential motion
between the medial and lateral sides of the wrist andapproximately half the range of flexion/extension occurs
at the radiocarpaljoint and half at the midcarpal joint.
In radialdeviation the distance between the trapezium
and the radial styloid shortens and in ulnar deviation it
lengthens (Fig. 3). Two principal movements allow this
to occur. First, there is sliding of the scaphoid into the
lunate fossa during radial deviation and sliding of the
lunate into the scaphoid fossa during ulnar deviation.
Secondly, there is a movement which can be described as
simple flexing of the scaphoid under the compression of
the trapezium during radial deviation, and passiveextension during ulnar deviation. The triquetrum passively
follows the other two bones of the proximal row. Mostwrists show both types of motion, but in varying
proportions. Wrists which mainly slide are called ‘row’
types and those in which flexion predominates are called
‘column’ types. The triquetrum articulates with the hamate
at a helicaljoint which allows sliding and flexing to occur.
Flexion of the scaphoid, however, is greater than that of
the triquetrum and the lunate becomes therefore anintercalated torque converter between scaphoid and
triquetrum during radial and ulnar deviation. The lunate
is also an intercalated segment between the radius and the
capitate.
Taleisnik’s (1985) modification ofNavarro’s concept
of longitudinal columns (Fig. 4) has made the collapse
deformities of the wrist much easier to understand. When
the ligamentous supports of the scaphoid are ruptured,
.,1�:i:w? �.
The extrinsic ligaments of the carpus (a) palmar (b) dorsal. 1) radioscaphocapitate ligament, 2) radiolunateligament, 3) ulnar triquetrocapitate ligament, 4) space of Poirier, 5) radiotriquetral ligament, 6) scaphotriquetralligament.
Fig. 2
The normal wrist in flexion and extension.
The normal wrist in radial and ulnar deviation.
692 J. K. STANLEY, I. A. TRAIL
THE JOURNAL OF BONE AND JOINT SURGERY
Fig. 4
The carpal bones shown as (a) three columns: scaphoid; lunate, capitate,hamate, trapezoid and trapezium; triquetrum and as (b) two rows: scaphoid,
lunate and triquetrum; hamate, capitate, trapezoid and trapezium.
Fig. 5
CARPAL INSTABILITY 693
VOL. 76-B, No. 5, SEPTEMBER 1994
compensates by flexing (Fig. 6). Subluxation of the
midcarpal joint is seen at rest on lateral radiographs and
this pattern is termed volar intercalated segment instability
(VlSI).
The normal kinematics of radial/ulnar deviation and
flexion/extension were investigated in detail by Youm et
al (1978). They found that rotation occurred around a
fixed axis in the middle of the head of the capitate and
that this was independent of the position of the hand. The
distance from the base of the third metacarpal to the distal
articular surface ofthe radius (the carpal height), measured
along the axis of the third metacarpal, was constant
throughout radial and ulnar deviation; the perpendicular
distance of the fixed axis of rotation from the distally
projected longitudinal axis of the ulna was also constant.
�
�
� .‘:�� �. �
Anteroposterior and lateral radiographs of a wrist with dorsal intercalated segment instability (DISI). The linesrepresent the long axes of the lunate and the scaphoid.
longitudinal compression forces the scaphoid into a flexed
position. The lunate, being narrower anteriorly than
dorsally, tends to extend under compression. Coincident
extension of the lunate with flexion of the scaphoid can
occur only if the ligamentous connections between themare damaged. Both bones collapse into their ‘default’
positions only when there is severe ligament injury on theradial side of the carpus and this pattern is termed dorsalintercalated segment instability (DISI) (Fig. 5). The
classical mechanism of this injury is a fall on the
outstretched, extended wrist. If the thenar eminencestrikes the ground first, there is an additional supination
element to the extension and compression forces.
If the hypothenar eminence strikes the ground first
the resulting pronation disrupts the dorsal ulnar-triquetral
ligament complex, the triquetrolunate interosseous liga-
ment and the anterior midcarpal capsule. This allows the
capitate to hyperextend in relation to the lunate, which
These measures can be used to quantify respectively
carpal collapse and carpal translocation. Ruby et al (1988)
used a similar but more sophisticated technique to showthat the wrist functions as two carpal rows, the proximal
row acting as an intercalated segment of variable geometry
which was confirmed by Sennwald Ct al(1993). Movement
of the intercarpaljoints in the proximal row accounted for
40% of flexion, 33% of extension and 10% of ulnar
deviation (Seradge et al 1990).
The intercarpal ligaments have been studied by
several authors. The scapholunate ligament was first
investigated by Logan et al (1986) who described its
dorsal and volar components. Hixson and Stewart (1990)
examined the radioscapholunate ligament and found that
it had an abundant blood supply. Berger, Kauer and
Landsmeer (1991) thought that the structure should notbe considered a ligament, but this was disputed by
Taleisnik (1985). The dorsal capsular ligaments were
Fig. 6
694 J. K. STANLEY, I. A. TRAIL
ThE JOURNAL OF BONE AND JOINT SURGERY
Anteroposterior and lateral radiographs of a wrist with volar intercalated segment instability (VlSI).
studied by Mizuseki and Ikuta (1989) who found that
neither the dorsal radioulnar ligament nor the ulnar
collateral ligament could be isolated as discrete conden-
sations.
Viegas et al (1989) considered how loads were
transmitted across the wrist. They found that the scaphoid
fossa constituted 60% of the total contact area and the
lunate fossa 40%. At the midcarpal joint load was
distributed as follows: 23% at the scaphotrapeziotrapezoid
joint, 28% at the scaphocapitate joint, 29% at the
lunocapitate joint and 20% at the triquetrohamate joint
(Viegas et al 1993).
Although the injury which causes carpal instability
is almost always hyperextension, the precise patho-
mechanics are little understood. A study of cadaver wrists
by Mayfield (1984) identified four stages of lunate
instability:
1) Instability limited to the scapholunate joint.
2) Added instability of the capitolunate joint.
3) Added damage to the triquetrolunate joint.
4) Dorsal disruption of the radiocarpal ligament leaving
the lunate totally unstable.
The displacements required to produce this type of
injury were extension, ulnar deviation and intercarpal
Supination.
Other research on specific instabilities has sought to
identify those structures which need to be damaged to
produce the observed radiological appearances. Trumble
et al (1990) found that the pattern of VlSI required rupture
of the triquetrohamate and triquetrolunate ligaments. Hon
et al (1991) concluded that the essential lesion to produce
such an instability pattern was rupture of the dorsalradiotniquetral and dorsal scaphotniquetral ligaments plus
damage to the lunotniquetral ligament and intenosseous
membranes.
The long-term effects of instability on the wrist were
evaluated by Blevens et al (1989) who used pressure-sensitive film to record changes in the radioscaphoid and
radiolunate contact areas after sequential ligament section.
They found that the scapholunate interosseous ligamentwas essential for preventing scapholunate diastasis and
that the change in contact area after its division would
explain the later development of degenerative arthritis.
Benninghaus, Koob and Steffens (1992) showed that
carpal instability does indeed lead to degenerative arthritis.
CLASSIFICATIONS
The International Wrist Investigators Workshop Nomen-
clature Committee was set up to define the terms used to
describe carpal instability but as yet no one system has
been agreed on. The most frequently used terms are those
introduced by Linscheid et al (1972) and Dobyns et al
(1975) who identified four groups of carpal instability:dorsal flexion instability (DISI); volar flexion instability(VlSI); ulnar translocation; and dorsal subluxation.
The radiological appearances of the dorsal flexion
and volar flexion instability patterns have already been
discussed. Ulnar translocation describes ulnar shift of thecarpus on the radius and is commonly seen in patientswith rheumatoid arthritis. Dorsal subluxation describes
dorsal shift of the carpus, often seen after malunion of
distal radial fractures (Dias and McMohan 1988).
Taleisnik (1985) introduced the concepts of static
and dynamic instability. Static instability is an end state,
with marked scapholunate dissociation, fixed flexion of
the scaphoid and fixed extension of the lunate. Dynamic
instability exists when partial ligament injuries cause pain
but with minimal or even no changes on the staticradiograph, the diagnosis being made by dynamic
Fig. 7
Pseudostability test for carpal instability undertaken with the examiner holding the carpus firmly with one hand
and the distal forearm with the other and performing anteroposterior translation. Often in carpal instability this
translation is reduced.
CARPAL INSTABILITY 695
VOL. 76-B, No. 5, SEPTEMBER 1994
radiology or arthroscopy. The terms carpal instabilitydissociative (CID), carpal instability non-dissociative
(CIND) and carpal instability complex (CIC) were
introduced by Dobyns in 1990. CID describes instability
due to loss of linkage between the individual bones of
either row; CIND means that there is no dissociation
between individual carpal bones but instability at theradiocarpal or midcarpal joints; and CIC includes insta-
bilities which were not otherwise classifiable.
DIAGNOSIS
Clinical tests. Of paramount importance in the diagnosis
of carpal instability are a careful history and physical
examination. Attention must be paid to the position of the
wrist at the time of injury and the location of pain.
Swelling and local tenderness are noted and the ranges of
motion and grip strengths of the injured and uninjured
sides are measured. The most important differential
diagnosis for pain on the radial side of the wrist is a
fracture of the scaphoid. The problems of early diagnosis
of this injury are well known, but after two to three weeks
the standard tests for carpal instability can be performed.The pseudoinstability test, described by Kelly and Stanley
in 1990, in which there is loss of the normal forward glide
of the carpus (Fig. 7) is useful. Lack of this motion due to
protective spasm is akin to the positive apprehension sign
of shoulder instability. Other tests include that of Watson,
Ryu and Akelman (1986) which stresses the scapholunate
interosseous ligament (Fig. 8). Scapholunate or lunotn-
quetral ballotment may reveal specific joint instability
and Lichtman et al (1981) described a pivot shift test for
midcarpal instability. All of these are specific for a
particular ligamentous lesion but overlap is not uncommon
and perhaps the most specific and reliable test is point
tenderness over the affected ligament.Imaging. The work of Schernberg (1990) on the
radiological examination of the normal wrist has shown
the importance of the quality and reproducibility of the
films. On the posterior/anterior view, the width of the
scapholunate gap should be no greater than that of the
triquetrolunate gap, and Gilula and Weeks (1978) found
that a scapholunate angle greater than 80#{176}was indicative
of DISI. Schernberg (1990) found that stress views were
needed to diagnose 18 out of 27 cases of wrist injury.
Degreif et al (1990) advocated comparison of both wrists
because of the considerable variations in normal anatomy.
Larsen et al (1991) reported great interobserver variation
in radiographic measurements and recommended the use
of well-defined axes. Other authors (Lichtman et a! 1981;
Stanley 1993) have found that examinations under an
image intensifier are useful for dynamic instabilities.
Special investigations including narrow-bore colli-
mator scintigraphy, ultrasound, MRI and CT may be
useful and three-phase arthrograms and three-dimensional
reconstruction of CTR arthrography can be used to
Fig. 9
696 J. K. STANLEY, I. A. TRAIL
THE JOURNAL OF BONE AND JOINT SURGERY
demonstrate leakage of contrast between the various
intercarpal joints. Herbert et al (1990) showed, however,
that an arthrogram is of little diagnostic value unless it
can be compared with that of the opposite undamaged
wrist.
Fig. 8
In Watson’s test for scapholunate disruption the examinerpresses firmly with his thumb on the anterior aspect ofthe distal tubercle of the scaphoid with the wrist in ulnardeviation. The carpus is then rotated radially in anattempt to flex the scaphoid against resistance. Inscapholunate dissociation, the scaphoid will subluxdorsally resulting in a painful ‘clunk’.
As mentioned above, scintigraphy has been used to
diagnose Preiser’s disease, Kienbock’s disease and avas-
cular necrosis of the capitate but bone scans are not useful
in the diagnosis of carpal instability. CT has now replaced
other forms of tomography in the assessment of complex
injuries of the carpus (Stewart and Gilula 1992).MRI appears to have the greatest potential (Zlatkin
and Greenan 1992) but, like CT, it gives only static
images. Even the use of surface coils, improved software
and the addition of gadolinium contrast have failed to
improve its diagnostic accuracy and the method often
fails to reveal minor tears of the triquetrolunate interos-
seous ligament (Munk et al 1992).
Arthroscopy. Arthroscopy ofthe radiocarpal and midcar-
pal joints is the best method for the diagnosis of carpal
instability. Roth and Haddad (1986), Kelly and Stanley
(1990) and Cooney (1993) have all advocated its use and
there is no doubt that it can provide much informationabout the altered mechanics and pathology of the wrist at
all levels. Kelly and Stanley (1990) and Dautel, Goudot
and Merle (1993) examined groups of patients with
symptoms suggestive of scapholunate interosseous liga-
ment tear but with normal radiographs and established the
diagnosis by dynamic manoeuvres undertaken during
radiocarpal and midcarpal arthroscopy (Fig. 9). Fischer
and Sennwald (1993) detected ligament tears by arthro-
scopy in every wrist in 20 cases of carpal instability.
TREATMENT
Scapholunate dissociation. When this condition is
diagnosed early and treatment is indicated, an attempt
should be made to bring about healing of the torn
interosseous ligament. Palmer, Dobyns and Linscheid(1978) reported good results from immobilisation for
eight weeks in plaster if treatment started within four
weeks of injury and if an anatomical reduction was
Arthroscopic views of scapholunate dissociation from the radiocarpaljoint (a) showing the gap or fissure betweenthe scaphoid and lunate. The view from the midcarpal joint (b) shows an obvious widening between the twobones.
CARPAL INSTABILITY 697
VOL. 76-B. No. 5, SEPTEMBER 1994
maintained. This often required the use of closed pinningwith a Kirschner wire under radiographic control. Cases
that cannot be reduced and held by this technique, and
those diagnosed later, do poorly with immobilisation, and
often require surgery. Ligament reconstruction, whether
undertaken through a volar or a dorsal approach (Taleisnik
1985), often needs supplementary Kirschner-wire fixation
and the results range from good to fair depending on the
quality of the tissue available for repair.If the diagnosis is delayed for three months or more
it becomes even more difficult to repair what is left of the
interosseous ligament. If the disability is minor, with
more than 80% of the range of motion and grip strength
retained, no treatment is required (Dobyns et al 1975),
but if there is a significant disability, a number of surgicalprocedures are available. Dobyns et al (1975) advocated
splitting one of the radial wrist extensor tendons and
passing half of it as a loop through the scaphoid and
lunate; Taleisnik (1985) advocated the use ofa free tendongraft in the same way. Glickel and Millender (1984)reviewed 21 cases so treated and found that range of
motion and grip strength had improved slightly but that
the radiographs showed loss of much of the early
correction. Almquist et al (1991) used a four-bone-
ligament reconstruction and also reported clinical im-provement and radiological recurrence of the deformity;most of the patients returned to their preinjury activities
including heavy labour. Conyers (1990), who performed
imbrication of the palmar ligaments and chondrodesis
between the scaphoid and lunate, reported improvementof the pinch and grip strengths and the range of motion.
Lavernia, Cohen and Taleisnik (1992) advocated direct
scapholunate ligament repair and dorsal radioscaphoid
capsulodesis for most scapholunate dissociations in which
there was no osteoarthritis present, regardless of the time
lapse since injury. Blatt and Nathan (1992) described
dorsal capsulodesis for rotatory subluxation of the
scaphoid. In this procedure palmar flexion ofthe scaphoidis prevented by a dorsal capsular check-rein; a long-term
review of 30 patients showed satisfactory clinical results
and MRI suggested physiological hypertrophy of the
transferred tissue.
The indifferent results of ligament reconstruction
have persuaded many surgeons to perform an intercarpalarthrodesis, the most logical of which is scapholunate
arthrodesis. Hom and Ruby (1991) reported, however,
that of seven patients only one showed radiographic
fusion and three still had significant symptoms; Alnot, De
Cheveigne and Bleton (1992) had similar problems. Inview of these difficulties, attention turned to the scaphoid-
trapezoid-trapezium (SiT) joint. Watson and Hempton(1980) found that 511.’ fusion was readily obtained andwas successful in rotatory subluxation of the scaphoid,
preserving 80% ofthe range of flexion/extension and 66%
of the range of radial and ulnar deviation. These findings
were supported by Kleinman, Steichen and Strickland(1982), nine of their 12 patients returning to preinjury
activities without wrist pain and with 80% of the
preoperative range of motion. More recently, however,
Eckenrode, Louis and Greene (1986) reported less good
results. Voche et al (1991) found that patients maintained
60% of their preoperative range of motion but that the
radiographs revealed styloid impingement in 34% of
cases. Fortin and Louis (1993) showed that 8 out of 14
patients had significant residual symptoms and 1 1 had
complications including radiocarpal and trapeziometacar-
pal arthritis and nonunion.
Scaphocapitate arthrodesis is easier to undertake.
Pisano et al (1991) found that although it reduced wrist
movement, particularly radial deviation, grip strength was
good and only two patients out of 17 required reoperation
for nonunion. Our own experience, and that of Kleinman
(1990) of this procedure, is that a few patients develop
osteoarthritis due to the excessive force between the
scaphoid and the dorsal half of the scaphoid fossa.
Lunotriquetral dissociation. This is a less common
problem than scapholunate dissociation but it occasionally
requires surgical treatment. Reagan, Linscheid and
Dobyns (1984) found that simple immobilisation was
useful only for acute injuries; capsulodesis, tenodesis and
arthrodesis have been used for chronic cases. Pin et al
(1989) had no failure of fusion in 1 1 cases, but three
patients had persistent pain. Most of the range of motion
was preserved but only 59% of grip strength. Kirschen-
baum, Coyle and Leddy (1993) also advocated fusion but
Nelson et al (1992) reported problems of nonunion andrecommended using a Herbert screw as well as a Kirschner
wire for fixation, plus a cast for at least eight weeks.
We recommend triquetrohamate fusion as being
easier to achieve. If, however, on arthroscopy a posterior
triangular fibrocartilaginous complex tear is found but no
midcarpal instability, then a reconstruction of the ulnar
dorsal capsule using half the tendon of extensor carpi
ulnaris is preferred. For combined midcarpal and trique-
trohamate instability the so-called ‘four-corner’ or luno-
triquetrocapitohamate fusion is indicated.
Midcarpal instability. Lichtman et al (1981) described
this instability and investigated its pathomechanics. They
also described a diagnostic test, which causes a painful
click on ulnar deviation, compression and pronation of
the wrist. The radiographs are usually normal but
cin#{233}fluoroscopy can show dissociation between the
proximal and distal carpal rows with volar collapse
deformity. Laboratory studies have shown volar subluxa-
tion of the capitate and hamate on the lunate and
triquetrum. Johnson and Carrera (1986) identified attenu-
ation of the radiocapitate ligament as the cause of this
condition and advocated tightening the ligament to
obliterate the space of Poirier, but soft-tissue reconstruc-
tions have usually failed and midcarpal arthrodesis is
preferred (Lichtman et al 1993).
Carpal instability resulting from malunion of a
fracture of the distal radius in dorsal angulation can be
effectively treated by distal radial osteotomy (Sennwald,
Fig. 10
698 J. K. STANLEY, I. A. TRAIL
THE JOURNAL OF BONE AND JOINT SURGERY
Scapholunate advanced collapse (SLAC), pattern of arthritis.
Fischer and Stahelin 1992) but if the carpal ligamentshave been damaged it is rarely successful.
Post-traumatic ulnar translation of the carpus has not
been successfully treated by soft-tissue repair (Chamay,
Della Santa and Vilaseca 1983; Rayhack et al 1987) and
most authors now advocate radiolunate fusion for thisproblem.
Secondary osteoarthritis. The loss of motion and altered
biomechanics which result from intercarpal arthrodesis
may give rise to osteoarthritis in the long term. The
particular contribution of each intercarpal joint to totalwrist motion was measured by Gellman et al (1988).Palmer et al (1985) measuredJlmctional wrist motion and
found that the normal range was 5#{176}of flexion, 30#{176}of
extension, 10#{176}of radial deviation and 15#{176}of ulnardeviation, values which lie well within the range of mostwrists after intercarpal arthrodesis. Scaphotrapeziotrape-zoidal fusion and scaphocapitate fusion have been found
to produce a similar reduction in range of motion. Both
procedures increased the sliding motion of the lunate on
the radius (Garcia-Elias et al 1989) and Viegas et al
(1990) found that afterwards virtually all the load was
transmitted to the scaphoid fossa. Other fusions, scapho-lunate, scapholunocapitate and capitolunate, all distrib-
uted the load more equally through both the scaphoid and
lunate fossae. The position of the scaphoid in scaphotra-
peziotrapezoid fusions is important; if it is vertical there
is a greater loss of flexion and ulnar deviation; if it is
horizontal, extension and radial deviation are lost. If the
scaphoid is in anatomical alignment scaphotrapeziotra-
pezoid and scaphocapitate fusion result in similar patterns
of motion (Ambrose et al 1992).
The treatment of carpal instability when there are
already arthritic changes in the wrist was described by
Watson and Ballet (1984). They defined scapholunate
advanced collapse (SLAC), a sequential pattern of arthritisaffecting first the radial fossa and then the capitolunate
joint but sparing the radiolunate joint (Fig. 10). They
recommend reduction of the so-called DISI, excision of
the scaphoid and fusion of the capitate, hamate, lunate
and triquetrum. Of the 19 patients treated, 18 had some
pain reliefwhile maintaining an adequate range of motion.
Krakauer, Bishop and Cooney (1992) operated on 55
patients with SLAC and obtained the best results with
scaphoid excision and a ‘four-corner fusion’. Saffar and
Fakhoury (1992) compared proximal row carpectomy
with partial wrist arthrodesis and found that the latter
gave better results.
Conclusions. Carpal instability may result from a varietyof wrist injuries and is important in the differential
diagnosis of chronic wrist pain. Over the last decade,
much has been added to our knowledge about these
injuries but more remains to be understood. Diagnosis
and treatment are often difficult and require special skills.
At this time the authors’ preferred method of investigation
includes a thorough clinical and radiological examination
including stress views. Most patients then undergo
arthroscopy to confirm the provisional diagnosis and toexclude other pathology. Treatment depends on the
patients’ symptoms. For those with little disability andmore than 80% of the range of motion and grip strength,
surgical treatment is not indicated.
For those with more serious problems from acute
scapholunate dissociation (within six weeks of injury),
direct repair and dorsal capsulodesis are recommended;
for cases seen later a full Blatt dorsal capsulodesis is
required. If, however, reduction of the dorsal intercalated
segment cannot be maintained, scaphocapitate fusion ispreferred. For an isolated lunotriquetral disorder arthro-
desis of this joint only is performed; for midcarpalinstability a triquetrohamate arthrodesis is preferred.
Finally, for patients with secondary arthritis either a ‘four-
corner fusion’ with scaphoid excision or a total wrist
arthrodesis is advised depending upon the extent of thearthritis and the patients’ individual requirements.
No benefits in any form have been received or will be received from acommercial party related directly or indirectly to the subject of this article.
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