Traumatic Thumb Carpometacarpal Joint Dislocations

REVIEW ARTICLE
Traumatic Thumb Carpometacarpal Joint Dislocations
B. Bosmans, MD, M. H. J. Verhofstad, MD, PhD, T. Gosens, MD, PhD
Isolated traumatic dislocation of the thumb carpometacarpal joint, also called the trapeziometacarpal joint, is a rare injury.
Controversy still exists concerning which ligaments are the true key stabilizers for the joint and therefore need to be damaged
to result in dislocation, and optimal treatment strategies for thumb carpometacarpal joint dislocations are the subject of
continuing debate. We give a review of the literature concerning traumatic dislocations of the carpometacarpal joint of the
thumb and propose a treatment algorithm. (J Hand Surg 2008;33A:438–441. Copyright © 2008 by the American Society for
Surgery of the Hand.)
Key words Carpometacarpal, dislocation, pathophysiology, thumb, treatment algorithm.
A
PURE TRAUMATIC DISLOCATION of the first
carpometacarpal joint is very rare, in contrast with
the fracture-dislocation variant, the so-called
Bennett fracture. Carpometacarpal dislocation of the thumb
accounts for less than 1% of all hand injuries.1 It usually
results from axial loading with flexion of the thumb
metacarpal base that forces the joint to dislocate in a dorsal
direction.2,3 Because the volar ligaments are very strong,
avulsion of the metacarpal base is usually seen.
Although for years the volar oblique ligament has been
believed to be the key stabilizer of the thumb
carpometacarpal joint,4 controversy concerning which
ligaments are damaged in joint dislocation and which
ligaments are the true key stabilizers for joint stability still
exists.5
Optimal treatment strategies for thumb carpometacarpal
joint dislocations are still a subject of debate. Strategies have
ranged from closed reduction and immobilization in a
thumb plaster cast to closed or open reduction and
temporary fixation using K-wires with or without
reconstruction of capsule and ligaments.6,7
This article aims to review the relevant literature concerning
traumatic dislocation of the carpometacarpal joint of the
thumb and its treatment.
From the Department of Surgery and the Department of
Orthopaedic Surgery, St. Elisabeth Hospital, Tilburg, The
Netherlands.
Received for publication October 3, 2007; accepted in
revised form November 26, 2007.
No benefits in any form have been received or will be
received from a commercial party related directly or
indirectly to the subject of this article.
Corresponding author: B. Bosmans, MD, St. Elisabeth
Hospital, Hilvarenbeekseweg 60, 5022 GC Tilburg, The
Netherlands; e-mail: [email protected].
0363-5023/08/33A03-0024$34.00/0
doi:10.1016/j.jhsa.2007.11.022
438 䉬 ©  ASSH 䉬 Published by Elsevier, Inc.
ANATOMY OF THE THUMB CARPOMETACARPAL
JOINT
Management of dislocations of the thumb carpometacarpal
joint in a proper way requires a fair understanding of its
anatomy and function. Several authors have reported on the
specific characteristics of the thumb carpometacarpal joint
regarding its surfaces and ligaments. Since as early as 1742,
when Weitbrecht (quoted by Kaplan8) reported on 4
ligaments around the thumb, the anatomy of the thumb
carpometacarpal joint has been studied. It has been called a
saddle joint: the trapezium is convex on anteroposterior
views and concave on lateral views, whereas the metacarpal
is the opposite.9,10
This unique configuration provides a wide range of
motion varying from abduction to opposition while the
joint remains stable. The thumb can thus withstand loading
and yet allow mobility, resulting in powerful pinching and
grasping. This is achieved by means of the so-called screwhome torque mechanism.5 When the thumb is moved into
opposition, a slight internal rotation of the metacarpal takes
place and the dorsoradial ligament tightens. At the same
moment, the volar beak of the thumb metacarpal is
compressed into its recess in the trapezium and the joint
gains articular congruence. As a result, a dynamic force
couple (ie, abducting force through the abductor pollicis
longus in combination with tension on the dorsal ligament
and locking of the volar beak resulting in articular
congruence) for stability is created and the carpometacarpal
joint is converted from an incongruent lax joint in the static
resting position to a congruent rigid and stable joint in
opposition. Normal function of the carpometacarpal
ligaments in this situation is essential.
PATHOPHYSIOLOGY IN THUMB
CARPOMETACARPAL JOINT DISLOCATION
In the late 1960s, the anterior oblique ligament was
considered to be the key stabilizer of the thumb
carpometacarpal joint.4 This observation was subsequently
debated in the following years by Harvey and Bye11 and
Pagalidis et al12 who respectively proposed that the posterior
THUMB CARPOMETACARPAL JOINT DISLOCATIONS
439
FIGURE 1: A A 27-year-old man sustained injury to his left wrist in a motor vehicle accident resulting in dislocation of the left thumb
carpometacarpal joint. A closed reduction with a palpable clunk was performed. B After applying a cast, the joint was and remained congruent.
The cast was removed after 6 weeks and physiotherapy started. More than 3 years after his accident, he was still able to work in construction
with a completely painless thumb carpometacarpal joint. Range of motion in all directions and thumb strength using a pinch gauge (Saehan
hydraulic pinch gauge SH 5005 [also known as Jamar hydraulic pinch gauge]; Saehan Corporation, Korea) were normal.
oblique and intermetacarpal ligaments were the most
substantial contributors to joint stability. Several clinical
reports on the open treatment of thumb carpometacarpal
joint dislocations have described other ligamentous
pathology. Shah and Patel2 found the dorsal structures to be
disrupted in their 4 cases of thumb carpometacarpal
dislocations, while the anterior oblique ligament was intact.
In a large cadaver study by Strauch et al13 studying 38
cadaver thumbs, the dorsoradial ligament complex was
found to be the primary restraint to dorsal dislocation.
When cutting all ligaments of the thumb carpometacarpal
joint except the dorsoradial ligament, the least joint
dislocation was found. On the other hand, when all
ligaments were intact and the dorsoradial ligament was cut,
the largest degree of joint (sub)luxation occurred. This was
confirmed by several anatomic and biomechanical studies of
Bettinger et al,14 van Brenk et al,15 and Colman et al,16 and
also is in accordance with the study of Pieron.10 It has been
shown in his cadaver studies that the ulnovolar capsule is
reinforced by the volar ligament, also called the anterior
oblique ligament, which is short and strong. It is rather close
to the joint margin and runs in an oblique direction from
proximal-radial to distal-ulnar. A second reinforcement
comes from the infratendinous layer of the tendon of the
abductor pollicis longus, which inserts on the volar aspect of
the base of the first metacarpal. The capsule on the
radiovolar and dorsal side is thin and inserts at a distance
from the articular edge, allowing for mobility. An exception
to this is the radiodorsal ligament, which is strong and inserts
closely to the articular cartilage.
Therefore, axial loading with flexion of the thumb
metacarpal base will force the joint to dislocate in a dorsal
direction with a rupture of the thin dorsal capsule. Because
the reinforced volar capsule is strong, an avulsion of the
metacarpal base can be seen frequently.
TREATMENT APPROACH
Because thumb carpometacarpal dislocation results in
ligamentous injury, several surgeons have treated this
condition with ligamentous reconstructions. Already in the
early 1940s, traumatic thumb carpometacarpal dislocations
had been treated with free tendon grafts of various origins
with good to excellent results. Eggers7 used a part of the
extensor carpi radialis longus as a tendon transfer through a
drilled hole on the ulnar side of the thumb metacarpal base,
and Slocum17 and Kestler18 had treated traumatic thumb
carpometacarpal joint dislocations with a palmaris longus
graft or an extensor pollicis brevis graft, respectively. In later
years, several authors have used other ligaments such as the
flexor carpi radialis3,4 and abductor pollicis longus.19,20
Because nonsurgical or minimal invasive (percutaneous
pinning) treatment can result in good outcome,6,21
treatment strategies are still the subject of discussion despite
the earlier reports. Simonian and Trumble22 have tried to
JHS 䉬 Vol A, March 
440
THUMB CARPOMETACARPAL JOINT DISLOCATIONS
FIGURE 2: An 18-year-old man fell on his left hand from his
motorbike. His thumb carpometacarpal joint appeared unstable. The
clinical diagnosis of thumb carpometacarpal joint dislocation was
proved by computed tomography (reconstructed image). The thumb
carpometacarpal joint was stabilized by plication of the dorsal
capsule and was placed in a thumb plaster cast for 4 weeks. At
follow-up after 4 months, the patient had completely recovered
without any pain. Reexamination of the thumb carpometacarpal
joint 3 years later showed normal joint stability with a complete
range of motion in all directions with normal strength.
address this ongoing debate by comparing early ligamentous
reconstruction with closed reduction and pinning. Half of
the group (4 of 8 patients) initially treated with closed
reduction and percutaneous pinning were converted during
follow-up to open reduction with ligamentous
reconstruction because of recurrent instability. Although
their data suggest that early open reduction and ligamentous
reconstruction results in a better outcome, no conclusions
can be drawn from this study (eg, because patient groups are
far too small to allow statistical analysis). However, an
interesting finding was that all patients irrespective of the
treatment were noted to have substantial instability.
Would a nonsurgical treatment (closed reduction and
casting) be an option as definitive treatment if the thumb
carpometacarpal joint was found to be stable after immediate
and anatomic reduction? In their case report, Khan et al23
described a patient with a bilateral thumb carpometacarpal
dislocation. After closed reduction immediately after the
injury, both joints appeared stable and the patient was
treated with thumb spicas for 6 weeks only. At 15 months
of follow-up, the functional result was good. From this case,
other studies,6,21,24,25 and one of our own patients (Fig. 1),
it might be concluded that patients with an acute traumatic
thumb carpometacarpal dislocation showing no gross
instability after proper reduction can be treated with a
thumb cast. After reviewing the results described in the
literature to date, we propose the following treatment
regimen for thumb carpometacarpal dislocations:
FIGURE 3: A 38-year-old man was involved in a motor vehicle accident resulting in a fracture of the left distal radius. A At follow-up 9 weeks
after the accident, a dislocated carpometacarpal joint of the thumb was also found. B Open reduction of the joint using a dorsal approach and
fixation with a 1.6-mm (0.062-in.) K-wire and capsulorrhaphy was performed. The joint was stable, and ligament reconstruction was not
necessary. A cast was applied postoperatively for 4 weeks, and the K-wire was removed after 6 weeks. At follow-up after 2 years, function of the
thumb carpometacarpal joint was normal with a full range of motion.
JHS 䉬 Vol A, March 
THUMB CARPOMETACARPAL JOINT DISLOCATIONS
●
●
Acute dislocation: If the injury is recognized
immediately, a closed reduction should be performed
and a plaster cast with slight abduction of the thumb
should be placed. If the joint remains congruent, it can
be continued for 4 to 6 weeks. Joint congruency must
be established with adequate radiographs in
perpendicular directions or, more likely, computed
tomography scans with reconstructions in various
directions (as illustrated in Fig. 2). However, if the
joint remains unstable or incongruent, one should at
least perform closed reduction and temporary
percutaneous fixation with a K-wire, but it might be
necessary to do an open surgical procedure with
temporary joint fixation and capsulorrhaphy and/or
ligament reconstruction to obtain an absolute anatomic
and stable reduction. An additional plaster cast is
preferable.
Chronic dislocation: In a situation of a neglected injury
(Fig. 3) or secondary dislocation, open reduction, Kwire fixation, capsulorrhaphy, and/or ligament
reconstruction with a plaster cast are mandatory.
In conclusion, an isolated thumb carpometacarpal joint
dislocation is a rare but challenging injury. Controversy on
ligament stability and optimal treatment still exists, but when
studying the literature to date, one must conclude that the
dorsoradial ligament appears responsible for joint stability in
opposition and when torn dislocation occurs. Treatment can
vary from closed reduction and plaster cast to open
reduction and ligament reconstruction. It depends on degree
of instability and anatomic restoration after first reduction. A
very aggressive policy (ie, always open reduction and
ligament reconstruction) cannot be justified from the
literature to date.
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