- Email: [email protected]
MR imaging of thumb carpometacarpal joint ligament injuries
ARTICLE IN PRESS
MR IMAGING OF THUMB CARPOMETACARPAL JOINT LIGAMENT INJURIES D. A. CONNELL, J. PIKE, G. KOULOURIS, N. VAN WETTERING and G. HOY From the Department of Medical Imaging, Victoria House Hospital, Prahran, Victoria, Australia, the Lifecare Sports Medicine, Croydon Road, Croydon, Victoria, Australia and the Melbourne Orthopaedic Group, 44 The Avenue, Windsor, Victoria, Australia
This study describes the MR imaging appearances of the supporting ligaments of the thumb carpometacarpal joint in asymptomatic volunteers and in a group of patients following joint injury. Fourteen patients with 11 acute and three chronic injuries underwent MR imaging. The anterior oblique ligament was the most commonly injured ligament, usually on the metacarpal side where it was disrupted, or allowed dislocation because of subperiosted stripping from the base of the thumb metacarpal. The dorsal radial ligament was occasionally avulsed or partially torn from the trapezoid. Following chronic injury, MR imaging can evaluate ligamentous laxity, ganglion cyst formation or osteoarthritis. Accurate evaluation of ligament injury may identify patients who would benefit from surgery. Journal of Hand Surgery (British and European Volume, 2004) 29B: 1: 46–54 Keywords: thumb metacarpal joint, MRI, imaging
of ligamentous integrity which may aid in patient management. We performed a study to assess the role of MR imaging for evaluating the supporting ligaments of the thumb carpometacarpal joint.
INTRODUCTION The thumb requires dexterity and precision to handle fine objects and stability and strength to counteract force applied by the fingers when grasping. Large loads are imparted through its carpometacarpal joint (Bettinger et al., 1999) and so it has a complex and strong ligamentous system which can withstand axial loading and yet allow mobility. These ligaments are encased by the tendons and thenar muscles. Acute injury to the thumb carpometacarpal joint usually results from an axial load with flexion to the thumb metacarpal causing dislocation in a dorsal direction (Shah and Patel, 1983; Watt and Hooper, 1987). Fracture to the base of the thumb metacarpal may occur but there is controversy as to which ligaments are damaged (Eaton and Littler, 1973; Harvey and Bye, 1976; Pagalidis et al., 1981; Watt and Hooper, 1987). Many researchers consider the anterior oblique ligament is the primary stabiliser of the thumb carpometacarpal joint and that dislocation results in injury to this structure, which has implications for joint stability (Haines, 1944; Imaeda et al., 1993, 1994; Napier, 1955; Strauch et al., 1994).(Table 1) Assessment of thumb carpometacarpal joint injuries is based upon a clinical examination supplemented by radiographs. Patients commonly present with focal tenderness and pain deep to the thenar eminence following dislocation, but ligamentous instability can be difficult to diagnose clinically particularly when there is pain, swelling and haematoma. Radiographs may demonstrate soft tissue swelling and occasional avulsion of a fragment of bone from the base of the thumb metacarpal (Bennett’s fracture) but, in the absence of a fracture, will be normal (Imaeda et al., 1993). Stress views may show loss of anatomical alignment and provide indirect information about ligament stability. MR imaging allows direct visualisation and assessment
Normal anatomy There are four main ligaments that contribute to stability of the thumb carpometacarpal joint (Fig 1): (1) The anterior oblique ligament. (2) The dorsal radial ligament, which arises from the dorsal and radial aspects of the trapezium and inserts onto the adjacent portion of the thumb metacarpal base. This ligament is reinforced by the abductor pollicis longus tendon (Strauch et al., 1994). (3) The posterior oblique ligament, which runs from the dorsal-ulnar tubercle of the trapezium to the ulnar tubercle of the thumb metacarpal base. (4) The intermetacarpal ligament, which runs from the radial base of the index metacarpal to the ulnar aspect of the thumb metacarpal base. The anterior oblique ligament is a short thick band with fibres running from the palmar tubercle of the trapezium to insert into the base of the thumb metacarpal. The ligament is felt to be composed of two bundles, a superficial component (sAOL) and a deeper component (dAOL), which is intra-articular (Imaeda et al., 1993). The superficial bundle arises from the palmar tubercle of the trapezium and inserts broadly onto the ulnar tubercle of the thumb metacarpal close to the joint capsule, creating a capsular recess. The superficial component measures 9.5 mm in length, 8.5 mm in width, and is 1.4 mm thick, and is found in 46
Age
Sex
Site of injury
Presentation
Clinical history
Anterior oblique ligament
Dorsal radial ligament
Post oblique ligament
Transverse metacarpal ligament
Bone oedema
Other
1
54
F
R
Acute
Fall down stairs
M
R
Acute
Football
No
25
F
R
Acute
Platform diver
Hyperintense thickened Normal
Primary surgical repair Pinning
3
Yes
Primary surgical repair
4
32
M
L
Acute
Football
Hyperintense intact
Yes
Pinning
5
55
F
L
Acute
Netball umpire
Moderate grade partial tear
Complete tear trapezium side High grade partial tear trapezium side High grade partial tear trapezium side Moderate grade partial tear trapezium side Low grade partial tear hyperintense
Yes
22
Complete tear trapezium side Complete tear trapezium side Moderate grade partial tear trapezium side Complete tear trapezium side
Disrupted
2
Complete tear metacarpal side Complete tear metacarpal side Complete tear metacarpal side
Intact low signal
No
Primary surgical repair
6
41
M
R
Acute
Rock-climber
Moderate grade partial tear
Low grade partial tear hyperintense
Intact low signal
No
Primary surgical repair
7
25
M
L
Acute
Basketball
Low grade partial tear
Low grade partial tear hyperintense
Intact low signal
No
Pinning
8
23
M
R
Acute
Tripped over rock
Low grade partial tear
Intact low signal
No
Pinning
9
54
M
R
Acute
Antarctic explorer
Intact
Moderate grade partial tear hyperintense Intact
low
No
—
10
20
M
R
Acute
Fall down stairs
Intact
Intact
low
No
—
11
33
F
F
Acute
Basketball
Yes
43
F
R
Chronic
low
No
Fracture base 1st MCP —
13
52
M
L
Chronic
Fall down stairs 3 months ago Fight 6 months ago
Intact mild increased signal Intact low signal, lax
low
12
Intact mild increased signal Intact low signal, lax Intact lax low signal thickened
Intact low signal lax
Intact signal Intact signal Intact signal Intact signal Intact signal
low
No
Ganglion
14
27
M
L
Chronic
Intact low signal
Intact low signal
Intact low signal
No
Advanced OA
Basketball 30 months ago
High grade partial tear and periosteal stripping Moderate grade partial tear & periosteal stripping Moderate grade partial tear & periosteal stripping Moderate grade partial tear & periosteal stripping Moderate grade partial tear & periosteal stripping Low grade partial tear Low grade partial tear Intact mild increased signal Intact low signal, lax Intact low signal mildly thickened lax Intact low signal
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MR IMAGING OF TRAPEZIOMETACARPAL JOINT
Table 1—Injuries of the thumb carpometacarpal joint – MRI findings
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The AOL therefore acts as a primary stabiliser assisted by the ulnar collateral ligament, which runs in a similar direction though has different attachments.
PATIENTS AND METHODS
Fig 1 The ligaments of the thumb carpometacarpal joint (a) palmar aspect: note the dorsal radial ligament (DRL) reinforced by the abductor pollicis longus (APL) tendon sheath (shaded). (b) Dorsolateral view demonstrating the dorsal radial (DRL), posterior oblique (POL) and intermetacarpal (IML) ligaments.
all of cadaveric specimens (Imaeda et al., 1993). It lies immediately deep to the thenar eminence but superficial to the deep component and blends with the capsule. It is taut at the extremes of joint motion especially extension. The dAOL inserts adjacent to the articular margins of the trapezium and the thumb metacarpal, is intraarticular and lies closest to the centre of the joint. It is shorter than the sAOL and therefore becomes taut first, preventing ulnar subluxation. Owing to its location, the dAOL probably serves as a pivot point for the thumb carpometacarpal joint. It measures approximately 8 mm in length, 5.5 mm in width, and 1 mm thick and is found in 70% of cadaveric specimens (Imaeda et al., 1993).
From January 2000 to May 2002, 14 patients were referred by orthopaedic surgeons, hand surgeons and sports medicine physicians for MR imaging of the base of the thumb following injury. Radiographs were performed to exclude a fracture. There were nine men and five women with an age range from 22 to 55 (mean, 36) years. There were injuries to the thumbs of eight right hands and six left hands. Eleven injuries were acute with the interval from injury to MR imaging ranging from 1 day to 6 weeks (mean, 15 days). There were also three chronic injuries (3 months, 6 months, 2.5 years). Four patients sustained injuries while falling during basketball games, while three patients injured the thumb while playing football. There was also an amateur football player whose thumb was kicked. Two netball players injured their thumbs, one in a fall and the other with a direct knock by the ball. A rock-climber fell as did an Antarctic explorer and a platform diver banged his thumb on the platform. Two patients reported falling down the stairs, one tripping over a rock and one patient dislocated the joint in a fight. One patient fell from a truck landing on his thumb. The spectrum of injury was felt to range from ligamentous sprain to frank dislocation. Seven dislocations were documented by the referring clinician and the dislocated joint was reduced by the time of MR imaging. In addition, five healthy volunteers underwent MR evaluation of the thumb carpometacarpal joint. Patients were examined with a 1.5 T super-conducting unit (Signa Horizon; GE Medical Systems, Milwaukee, Wis, USA). Each was placed in a supine position with the hand by the side and the thumb in a phase array wrist coil (wrist array; Medical Advances, Milwaukee, Wis. USA) with the thumb carpometacarpal joint placed in the centre of the coil. An axial localising image was performed after which the following sequences were taken: (a) Coronal FSE imaging through the base of the thumb carpometacarpal joint (repetition time ms/ echotime ms=4000/45 (effective), 512 320 matrix, two signals acquired, 8 cm field of view, 2.5 mm section thickness with no intersection gap, echotime length of 8). (b) Axial FSE imaging through the base of the thumb carpometacarpal joint (repetition time ms/echotime ms = 4000/45 (effective), 512 320 matrix, two signals acquired, 8 cm field of view, 2.5 mm section thickness with no intersection gap, echotime length of 8).
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(c) Coronal MPGR (TR/TE 460/20, flip 451, 256 256 matrix, three signals acquired, 8 cm field of view, 1.5 mm section thickness with no gap). (d) Coronal STIR (TR/TE/TI 3500/45/120) 256 224 matrix, four signals acquired, 10 cm field of view, 3.0 mm section thickness with no gap. On MR images, the normal anterior oblique ligament appears as a longitudinal band of low signal, which can be followed from the palmar tubercle of the trapezium to insert broadly onto the base of the thumb metacarpal close to the joint capsule (Fig 2a). The dorsal radial, posterior oblique and transverse ligaments also are continuous bands of low signal (Fig 2b). The ligaments were evaluated with respect to morphology and abnormal signal intensity. Disruption of the normal low signal band with or without hyperintensity of a ligament was felt to represent a complete tear. Incomplete disruption with some continuity of the fibres at the site of the injury was interpreted as a partial tear. Partial injuries were considered high grade if more than 70% of fibres were torn, moderate if 30–70% of the fibres were torn and low grade if less than 30% of the fibres were torn. The percentage of injury was quantified by assessing the integrity of fibres arising from the trapezium inserting onto the base of the thumb metacarpal. The trapezium and thumb metacarpal were assessed for periosteal stripping and the ligament edge morphology was assessed for the presence of local haematoma, oedema or ganglion cyst formation. An assessment was made of joint congruity and the surfaces of the joint were assessed for cartilage injury. Any bone contusion or fracture was noted. The MR images were prospectively interpreted by a musculoskeletal radiologist (DC) who produced the original MR imaging report. Later a senior musculoskeletal imaging fellow (GK) independently assessed all the images and any discrepancy was settled by means of consensus. Six months later, and in order to assess reproducibility between their two conclusions, the scans were re-evaluated by the senior author and a third musculoskeletal radiologist. Eight patients subsequently underwent surgical intervention with stabilisation of the joint, the surgeon knowing the original MR imaging results at the time of surgery. The remaining patients were treated conservatively with clinical follow-up. One patient underwent repeat MR imaging 3 months after surgery to demonstrate ligament stability and exclude cartilage injury.
RESULTS In our study cohort, there were 11 patients with acute injuries and three with chronic injuries. Of the 11 with acute injuries, ten had an injury to the anterior oblique ligament, all of which occurred close to, or at, the metacarpal side of the joint (Fig 3). There were three
Fig 2 Ligamentous anatomy of the thumb carpometacarpal joint in an asymptomatic volunteer: (a)coronal FSE (TR/TE 4000/30) image demonstrating the anterior oblique (curved arrow), dorsal radial (straight arrow), and intermetacarpal (small arrow) ligaments. Note the abductor pollicis longus tendon (open arrow). (b) Coronal image taken posteriorly to further define the anatomy
complete tears and seven partial tears, five of which showed stripping of the periosteum from the thumb metacarpal base (Fig 4). The dorsal radial ligament was also injured in eight of the 11 acute cases. Three were avulsions of the dorsal radial ligament on the trapezium side and five were partial tears. There were no injuries to
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Fig 3 Coronal FSE image (TR/TE 4000/30) demonstrating rupture of the anterior oblique ligament in a 25-year-old professional basketballer.
the dorsal radial ligament on the metacarpal side. One patient had, in addition to injuries of the anterior oblique and dorsoradial ligaments, avulsed the posterior oblique ligament from the trapezium (Fig 5). Another patient had a fracture through the base of the thumb metacarpal with the ligaments preserved: this was initially missed on his radiographs although could be seen retrospectively. Four patients, including the patient with a fracture, showed bone contusion on the STIR imaging, and this was evident on both sides of the joint in all four patients. Soft tissue haematoma was commonly seen in the acute setting. No focal chondral defects were seen in the acute setting.(Fig 6) There were three patients with chronic injuries. One demonstrated ligament laxity with mild thickening of both the anterior oblique and dorsal radial ligaments, and another had a small ganglion arising from the site of anterior oblique ligament attachment onto the metacarpal base (Fig 7). The third patient, who had dislocated his thumb 3 years earlier, showed advanced degenerative change of the thumb carpometacarpal joint with chondral loss and subcortical cyst formation (Fig 8). His anterior oblique and dorsal radial ligaments were continuous, but had abnormally thickened bands of low signal. The anterior oblique, dorsal radial, posterior oblique and intermetacarpal ligaments were reliably seen in all the five healthy volunteers. Using our MR technique, these ligaments appeared as continuous bands of low signal which could be followed from origin to insertion. The anterior oblique ligament is a prominent structure that is readily defined although
Fig 4 Twenty-five-year-old platform diver following injury to the thumb carpometacarpal joint:(a) coronal FSE image (TR/TE 4000/30) showing high grade partial tearing of the anterior oblique ligament (straight arrow) with periosteal stripping (small arrows) from the base of the thumb metacarpal.(b) Axial FSE image (TR/TE 4000/30) showing the periosteal stripping (open curved arrow) and the torn anterior oblique ligament (straight arrow).
the superficial and deep components could not be distinguished from each other. The fibres of the dorsal radial and posterior oblique ligaments were intimately related and not clearly separable on sequential scans.
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Fig 6 Thirty-three-year-old woman following a fall playing basketball. Coronal FSE image (TR/TE 4000/30) showing occult fracture line (small arrows) through base of first metacarpal. In retrospect this was seen on radiographs.
Fig 5
Four-year-old woman following a fall down the stairs: (a) coronal FSE image (TR/TE 4000/30) showing a tear of the anterior oblique ligament (straight arrow) with only a few attenuated hyperintense fibres remaining intact. Maceration of the dorsal radial ligament (open curved arrow) is noted. (b)Coronal FSE image (TR/TE 4000/30) further posteriorly demonstrating avulsion of the posterior oblique ligament (curved arrow) from the trapezium.
The initial independent assessments of the musculoskeletal radiologist and senior fellow were in agreement for determining whether the anterior oblique and dorsal radial ligaments were normal or partially or completely
torn, except that in one patient the senior radiologist felt the dorsal radial ligament was completely torn, while fellow felt there was a moderate grade partial tear. However, there was discrepancy in the assessment of the degree of partial tearing (mild, moderate, severe) in 10 of the 14 cases. There was moderate agreement with respect to the posterior oblique ligament (eight of 14 cases) and poor agreement with respect to tears of the transverse metacarpal ligament (five of 14 cases). Six months later, and when blinded to the initial report, the senior radiologist and a third musculoskeletal radiologist independently re-assessed the MR images of the patient cohort and healthy volunteers. Both radiologists were consistent in discriminating normal from abnormal assessments, and the senior radiologist separated partial from complete tears as before in all but two patients. The third radiologist agreed with the initial findings in 11 of the 14 patients. Eight patients underwent surgical intervention, four with pinning of the joint and four with primary ligament repair. The MR findings of a complete anterior oblique ligament disruption (patient No 1) and high grade partial tear (patient No 3) were confirmed in two cases at surgery. Partial detachment and periosteal stripping of the ligament from the metacarpal site was also confirmed in patient No 3. Concomitant injury to the dorsal radial ligament and the intermetacarpal ligament in both these patients was also observed. The MR imaging findings were also validated in the two other patients treated by primary ligament repair.
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Fig 7 Fifty-two-year-old man involved in a fist fight 6 months previously. Coronal FSE image (TR/TE 4000/30) showing continuity but laxity of the anterior oblique (open curved arrow) and dorsal radial (long straight arrow) ligaments. There is a small ganglion cyst (straight arrow) arising from the insertion of the anterior oblique ligament into the thumb metacarpal base.
DISCUSSION Trauma to the carpometacarpal joint of the thumb probably results in a spectrum of ligamentous injury dependent on the rate and direction of the loading force (Strauch et al., 1994). In our study ligamentous injury ranged from disruption of all four major ligaments following dislocation to low grade partial tearing of the anterior oblique ligament alone seen following ligamentous sprain. The anterior oblique ligament was the most common ligament injured, followed by the dorsal radial ligament. The superficial component of the anterior oblique ligament inserts onto the thumb metacarpal distal to the articular margins and this was the most common site for either complete or partial tears. This is in agreement with the findings of Strauch et al (1994). The dorsal radial ligament was the next most common injury with tearing occurring exclusively on the trapezium side. MR imaging has the ability to diagnose the degree of ligamentous injury and differentiate avulsions from partial tears. In the case of a complete tear, MR imaging can confirm the clinical findings as well identifying concomitant pathology such as chondral
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injuries, occult fractures and intra-articular bony fragments or interposed soft tissue. This information could aid in surgical planning. When patients are treated conservatively, MR imaging can be used to monitor healing and resolution of haematoma, and to evaluate ligament quality and joint stability before returning to normal activity. Our three radiologists’ assessment of the anterior oblique and dorsal radial ligaments were consistent, but there was less consistency with the posterior oblique and intermetatarsal ligaments assessments. This is probably because the first two ligaments are relatively large. Our radiologists had no difficulties discriminating normal from abnormal scans, although there was some discrepancy when assessing high grade partial tears from complete tears, and also the degree of partial tearing in individual ligaments. While this study was primarily concerned with acute injuries, three patients had chronic injuries. It has been suggested that degeneration or tearing of the anterior oblique ligament results in hypermobility leading to increased shear forces across the joint, resulting in osteoarthritis (Imaeda et al., 1994; Moore et al., 1978; Pellegrini 1991; Simonian and Trumble, 1996). We demonstrated advanced osteoarthritis in a 27-year-old basketballer who had dislocated his thumb 2.5 years ago and had not sought treatment. MR imaging could be used to assess the integrity of the thumb carpometacarpal ligaments prior to the onset of irreversible joint damage. Certain technical aspects of the study should be considered. The use of a dedicated wrist coil increases the signal-to-noise ratio, enhances spatial resolution and this makes the injury more conspicuous. Fast spin echo techniques decrease imaging time without loss of resolution or contrast and true coronal images centred over the thumb carpometacarpal joint will usually identify both the anterior oblique and dorsal radial ligaments and are the easiest to interpret. In the setting of pain and swelling following acute injury, extreme care and patience is required to place the thumb joint flat within the wrist coil, so that the ligaments could be assessed in the true anatomic plane. Despite being tightly held by soft tissue sponges, some of our studies were degraded by motion artefact, and one patient was immobilised in a plaster case which necessitated imaging in a knee coil. Recognition of abnormal signal intensity surrounding the cortex of the thumb metacarpal is important because this finding is typically due to stripping of the periosteum as the anterior oblique ligament is avulsed from its osseous insertion. Discriminating the dorsal radial from the posterior oblique ligament is best achieved by following the abductor pollicis longus tendon to its insertion on to the thumb metacarpal, where it reinforces the dorsal radial ligament. Among the imitations of study are the facts that surgeons had access to MR imaging reports at the time of surgery and that direct visualisation of the ligaments
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MR IMAGING OF TRAPEZIOMETACARPAL JOINT
Fig 8
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Twenty-seven-year-old basketball player who injured his thumb 30 months previously, now presenting with basal joint pain: (a) delayed radionuclide imaging shows increased uptake in the thumb carpometacarpal joint; (b) coronal FSE image (TR/TE 4000/30) shows marked thickening and diffuse low signal (open curved arrow) of the anterior oblique and dorsal radial (straight arrow) ligaments compatible with chronic injury. Some minor hyperintensity of the anterior oblique ligament (straight arrow) at the thumb metacarpal base is likely to reflect an area of ligament tearing. (c) Coronal gradient echo image (TR/TE 1400/20 flip 201) shows loss of cartilage with pronounced subchondral cyst formation (small arrows) compatible with advanced osteoarthritis.
at surgery was performed in only four cases. The injuries taken to surgery were high grade and we have no correlation with low grade injuries. Treatment of thumb carpometacarpal injuries includes immobilisation in a plaster cast for approxi-
mately 4 weeks, pinning of the joint and primary surgical repair using tendon transfer. MR imaging may have a role in avoiding unnecessary immobilisation in cases where the ligament is shown to be normal. The confirmation of injury can also aid in surgical planning.
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Acknowledgements Thanks to Judy Tan and Nicki Freer for their help in the typing of this manuscript.
References Bettinger PC, Linscheid RL, Berger RA et al. (1999). An anatomic study of the stabilizing ligaments of the trapezium and trapeziometacarpal joint. Journal of Hand Surgery, 24A: 786–798. Eaton RG, Littler JW (1973). Ligament reconstruction of the painful thumb carpometacarpal joint. Journal of Bone and Joint Surgery, 55A(8): 802–806. Haines RW (1944). The mechanisms of rotation at the first carpometacarpal joint. Journal of Anatomy, 78: 44–46. Harvey FJ, Bye WD (1976). Bennett’s fracture. The Hand, 8: 48–53. Imaeda T, An KN, Cooney WP, Linscheid R (1993). Anatomy of the trapeziometacarpal ligaments. Journal of Hand Surgery, 18A(2): 226–231. Imaeda T, Niebur G, An KN et al. (1994). Kinematics of the trapeziometacarpal joint after sectioning of the ligaments. Journal of Orthopaedic Research, 12(2): 205–210. Moore JR, Webb CA, Thompson RC (1978). A complete dislocation of the thumb metacarpal. Journal of Hand Surgery, 3(6): 547–549. Napier JR (1955). The form and function of the carpometacarpal joint of the thumb. Journal of Anatomy, 89: 362–369.
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Pagalidis T, Kuczynski K, Lamb DW (1981). Ligamentous stability of the base of the thumb. Hand, 13: 29–35. Pellegrini Jr. VD (1991). Osteoarthritis of the trapeziometacarpal joint : the pathophysiology of articular cartilage degeneration. Journal of Hand Surgery, 16A: 967–974. Shah J, Patel M (1983). Dislocation of the carpometacarpal joint of the thumb. Clinical Orthopaedics, 175: 166–169. Simonian PT, Trumble T (1996). Traumatic dislocation of the thumb carpometacarpal joint: early ligamentous reconstruction versus closed reduction and pinning. Journal of Hand Surgery, 21A: 802–806. Strauch RJ, Behrman MJ, Rosenwasser MP (1994). Acute dislocation of the carpometacarpal joint of the thumb: an anatomic and cadaver study. Journal of Hand Surgery, 19A(1): 93–98. Watt N, Hooper G (1987). Dislocation of the trapeziometacarpal joint. Journal of Hand Surgery, 12B: 242–245.
Received: 8 October 2002 Accepted after revision: 16 May 2003 Dr David Connell, Department of Medical Imaging, Victoria House Hospital, 316 Malvern Road, Prahran 3181, Australia. Tel.: 03-9529-7333; Fax: 03-9529-7833; E-mail: [email protected] r 2003 The British Society for Surgery of the Hand. Published by Elsevier Ltd. All rights reserverd. doi:10.1016/S0266-7681(03)00170-0 available online at http://www.sciencedirect.com
MR IMAGING OF THUMB CARPOMETACARPAL JOINT LIGAMENT INJURIES D. A. CONNELL, J. PIKE, G. KOULOURIS, N. VAN WETTERING and G. HOY From the Department of Medical Imaging, Victoria House Hospital, Prahran, Victoria, Australia, the Lifecare Sports Medicine, Croydon Road, Croydon, Victoria, Australia and the Melbourne Orthopaedic Group, 44 The Avenue, Windsor, Victoria, Australia
This study describes the MR imaging appearances of the supporting ligaments of the thumb carpometacarpal joint in asymptomatic volunteers and in a group of patients following joint injury. Fourteen patients with 11 acute and three chronic injuries underwent MR imaging. The anterior oblique ligament was the most commonly injured ligament, usually on the metacarpal side where it was disrupted, or allowed dislocation because of subperiosted stripping from the base of the thumb metacarpal. The dorsal radial ligament was occasionally avulsed or partially torn from the trapezoid. Following chronic injury, MR imaging can evaluate ligamentous laxity, ganglion cyst formation or osteoarthritis. Accurate evaluation of ligament injury may identify patients who would benefit from surgery. Journal of Hand Surgery (British and European Volume, 2004) 29B: 1: 46–54 Keywords: thumb metacarpal joint, MRI, imaging
of ligamentous integrity which may aid in patient management. We performed a study to assess the role of MR imaging for evaluating the supporting ligaments of the thumb carpometacarpal joint.
INTRODUCTION The thumb requires dexterity and precision to handle fine objects and stability and strength to counteract force applied by the fingers when grasping. Large loads are imparted through its carpometacarpal joint (Bettinger et al., 1999) and so it has a complex and strong ligamentous system which can withstand axial loading and yet allow mobility. These ligaments are encased by the tendons and thenar muscles. Acute injury to the thumb carpometacarpal joint usually results from an axial load with flexion to the thumb metacarpal causing dislocation in a dorsal direction (Shah and Patel, 1983; Watt and Hooper, 1987). Fracture to the base of the thumb metacarpal may occur but there is controversy as to which ligaments are damaged (Eaton and Littler, 1973; Harvey and Bye, 1976; Pagalidis et al., 1981; Watt and Hooper, 1987). Many researchers consider the anterior oblique ligament is the primary stabiliser of the thumb carpometacarpal joint and that dislocation results in injury to this structure, which has implications for joint stability (Haines, 1944; Imaeda et al., 1993, 1994; Napier, 1955; Strauch et al., 1994).(Table 1) Assessment of thumb carpometacarpal joint injuries is based upon a clinical examination supplemented by radiographs. Patients commonly present with focal tenderness and pain deep to the thenar eminence following dislocation, but ligamentous instability can be difficult to diagnose clinically particularly when there is pain, swelling and haematoma. Radiographs may demonstrate soft tissue swelling and occasional avulsion of a fragment of bone from the base of the thumb metacarpal (Bennett’s fracture) but, in the absence of a fracture, will be normal (Imaeda et al., 1993). Stress views may show loss of anatomical alignment and provide indirect information about ligament stability. MR imaging allows direct visualisation and assessment
Normal anatomy There are four main ligaments that contribute to stability of the thumb carpometacarpal joint (Fig 1): (1) The anterior oblique ligament. (2) The dorsal radial ligament, which arises from the dorsal and radial aspects of the trapezium and inserts onto the adjacent portion of the thumb metacarpal base. This ligament is reinforced by the abductor pollicis longus tendon (Strauch et al., 1994). (3) The posterior oblique ligament, which runs from the dorsal-ulnar tubercle of the trapezium to the ulnar tubercle of the thumb metacarpal base. (4) The intermetacarpal ligament, which runs from the radial base of the index metacarpal to the ulnar aspect of the thumb metacarpal base. The anterior oblique ligament is a short thick band with fibres running from the palmar tubercle of the trapezium to insert into the base of the thumb metacarpal. The ligament is felt to be composed of two bundles, a superficial component (sAOL) and a deeper component (dAOL), which is intra-articular (Imaeda et al., 1993). The superficial bundle arises from the palmar tubercle of the trapezium and inserts broadly onto the ulnar tubercle of the thumb metacarpal close to the joint capsule, creating a capsular recess. The superficial component measures 9.5 mm in length, 8.5 mm in width, and is 1.4 mm thick, and is found in 46
Age
Sex
Site of injury
Presentation
Clinical history
Anterior oblique ligament
Dorsal radial ligament
Post oblique ligament
Transverse metacarpal ligament
Bone oedema
Other
1
54
F
R
Acute
Fall down stairs
M
R
Acute
Football
No
25
F
R
Acute
Platform diver
Hyperintense thickened Normal
Primary surgical repair Pinning
3
Yes
Primary surgical repair
4
32
M
L
Acute
Football
Hyperintense intact
Yes
Pinning
5
55
F
L
Acute
Netball umpire
Moderate grade partial tear
Complete tear trapezium side High grade partial tear trapezium side High grade partial tear trapezium side Moderate grade partial tear trapezium side Low grade partial tear hyperintense
Yes
22
Complete tear trapezium side Complete tear trapezium side Moderate grade partial tear trapezium side Complete tear trapezium side
Disrupted
2
Complete tear metacarpal side Complete tear metacarpal side Complete tear metacarpal side
Intact low signal
No
Primary surgical repair
6
41
M
R
Acute
Rock-climber
Moderate grade partial tear
Low grade partial tear hyperintense
Intact low signal
No
Primary surgical repair
7
25
M
L
Acute
Basketball
Low grade partial tear
Low grade partial tear hyperintense
Intact low signal
No
Pinning
8
23
M
R
Acute
Tripped over rock
Low grade partial tear
Intact low signal
No
Pinning
9
54
M
R
Acute
Antarctic explorer
Intact
Moderate grade partial tear hyperintense Intact
low
No
—
10
20
M
R
Acute
Fall down stairs
Intact
Intact
low
No
—
11
33
F
F
Acute
Basketball
Yes
43
F
R
Chronic
low
No
Fracture base 1st MCP —
13
52
M
L
Chronic
Fall down stairs 3 months ago Fight 6 months ago
Intact mild increased signal Intact low signal, lax
low
12
Intact mild increased signal Intact low signal, lax Intact lax low signal thickened
Intact low signal lax
Intact signal Intact signal Intact signal Intact signal Intact signal
low
No
Ganglion
14
27
M
L
Chronic
Intact low signal
Intact low signal
Intact low signal
No
Advanced OA
Basketball 30 months ago
High grade partial tear and periosteal stripping Moderate grade partial tear & periosteal stripping Moderate grade partial tear & periosteal stripping Moderate grade partial tear & periosteal stripping Moderate grade partial tear & periosteal stripping Low grade partial tear Low grade partial tear Intact mild increased signal Intact low signal, lax Intact low signal mildly thickened lax Intact low signal
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Table 1—Injuries of the thumb carpometacarpal joint – MRI findings
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The AOL therefore acts as a primary stabiliser assisted by the ulnar collateral ligament, which runs in a similar direction though has different attachments.
PATIENTS AND METHODS
Fig 1 The ligaments of the thumb carpometacarpal joint (a) palmar aspect: note the dorsal radial ligament (DRL) reinforced by the abductor pollicis longus (APL) tendon sheath (shaded). (b) Dorsolateral view demonstrating the dorsal radial (DRL), posterior oblique (POL) and intermetacarpal (IML) ligaments.
all of cadaveric specimens (Imaeda et al., 1993). It lies immediately deep to the thenar eminence but superficial to the deep component and blends with the capsule. It is taut at the extremes of joint motion especially extension. The dAOL inserts adjacent to the articular margins of the trapezium and the thumb metacarpal, is intraarticular and lies closest to the centre of the joint. It is shorter than the sAOL and therefore becomes taut first, preventing ulnar subluxation. Owing to its location, the dAOL probably serves as a pivot point for the thumb carpometacarpal joint. It measures approximately 8 mm in length, 5.5 mm in width, and 1 mm thick and is found in 70% of cadaveric specimens (Imaeda et al., 1993).
From January 2000 to May 2002, 14 patients were referred by orthopaedic surgeons, hand surgeons and sports medicine physicians for MR imaging of the base of the thumb following injury. Radiographs were performed to exclude a fracture. There were nine men and five women with an age range from 22 to 55 (mean, 36) years. There were injuries to the thumbs of eight right hands and six left hands. Eleven injuries were acute with the interval from injury to MR imaging ranging from 1 day to 6 weeks (mean, 15 days). There were also three chronic injuries (3 months, 6 months, 2.5 years). Four patients sustained injuries while falling during basketball games, while three patients injured the thumb while playing football. There was also an amateur football player whose thumb was kicked. Two netball players injured their thumbs, one in a fall and the other with a direct knock by the ball. A rock-climber fell as did an Antarctic explorer and a platform diver banged his thumb on the platform. Two patients reported falling down the stairs, one tripping over a rock and one patient dislocated the joint in a fight. One patient fell from a truck landing on his thumb. The spectrum of injury was felt to range from ligamentous sprain to frank dislocation. Seven dislocations were documented by the referring clinician and the dislocated joint was reduced by the time of MR imaging. In addition, five healthy volunteers underwent MR evaluation of the thumb carpometacarpal joint. Patients were examined with a 1.5 T super-conducting unit (Signa Horizon; GE Medical Systems, Milwaukee, Wis, USA). Each was placed in a supine position with the hand by the side and the thumb in a phase array wrist coil (wrist array; Medical Advances, Milwaukee, Wis. USA) with the thumb carpometacarpal joint placed in the centre of the coil. An axial localising image was performed after which the following sequences were taken: (a) Coronal FSE imaging through the base of the thumb carpometacarpal joint (repetition time ms/ echotime ms=4000/45 (effective), 512 320 matrix, two signals acquired, 8 cm field of view, 2.5 mm section thickness with no intersection gap, echotime length of 8). (b) Axial FSE imaging through the base of the thumb carpometacarpal joint (repetition time ms/echotime ms = 4000/45 (effective), 512 320 matrix, two signals acquired, 8 cm field of view, 2.5 mm section thickness with no intersection gap, echotime length of 8).
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(c) Coronal MPGR (TR/TE 460/20, flip 451, 256 256 matrix, three signals acquired, 8 cm field of view, 1.5 mm section thickness with no gap). (d) Coronal STIR (TR/TE/TI 3500/45/120) 256 224 matrix, four signals acquired, 10 cm field of view, 3.0 mm section thickness with no gap. On MR images, the normal anterior oblique ligament appears as a longitudinal band of low signal, which can be followed from the palmar tubercle of the trapezium to insert broadly onto the base of the thumb metacarpal close to the joint capsule (Fig 2a). The dorsal radial, posterior oblique and transverse ligaments also are continuous bands of low signal (Fig 2b). The ligaments were evaluated with respect to morphology and abnormal signal intensity. Disruption of the normal low signal band with or without hyperintensity of a ligament was felt to represent a complete tear. Incomplete disruption with some continuity of the fibres at the site of the injury was interpreted as a partial tear. Partial injuries were considered high grade if more than 70% of fibres were torn, moderate if 30–70% of the fibres were torn and low grade if less than 30% of the fibres were torn. The percentage of injury was quantified by assessing the integrity of fibres arising from the trapezium inserting onto the base of the thumb metacarpal. The trapezium and thumb metacarpal were assessed for periosteal stripping and the ligament edge morphology was assessed for the presence of local haematoma, oedema or ganglion cyst formation. An assessment was made of joint congruity and the surfaces of the joint were assessed for cartilage injury. Any bone contusion or fracture was noted. The MR images were prospectively interpreted by a musculoskeletal radiologist (DC) who produced the original MR imaging report. Later a senior musculoskeletal imaging fellow (GK) independently assessed all the images and any discrepancy was settled by means of consensus. Six months later, and in order to assess reproducibility between their two conclusions, the scans were re-evaluated by the senior author and a third musculoskeletal radiologist. Eight patients subsequently underwent surgical intervention with stabilisation of the joint, the surgeon knowing the original MR imaging results at the time of surgery. The remaining patients were treated conservatively with clinical follow-up. One patient underwent repeat MR imaging 3 months after surgery to demonstrate ligament stability and exclude cartilage injury.
RESULTS In our study cohort, there were 11 patients with acute injuries and three with chronic injuries. Of the 11 with acute injuries, ten had an injury to the anterior oblique ligament, all of which occurred close to, or at, the metacarpal side of the joint (Fig 3). There were three
Fig 2 Ligamentous anatomy of the thumb carpometacarpal joint in an asymptomatic volunteer: (a)coronal FSE (TR/TE 4000/30) image demonstrating the anterior oblique (curved arrow), dorsal radial (straight arrow), and intermetacarpal (small arrow) ligaments. Note the abductor pollicis longus tendon (open arrow). (b) Coronal image taken posteriorly to further define the anatomy
complete tears and seven partial tears, five of which showed stripping of the periosteum from the thumb metacarpal base (Fig 4). The dorsal radial ligament was also injured in eight of the 11 acute cases. Three were avulsions of the dorsal radial ligament on the trapezium side and five were partial tears. There were no injuries to
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Fig 3 Coronal FSE image (TR/TE 4000/30) demonstrating rupture of the anterior oblique ligament in a 25-year-old professional basketballer.
the dorsal radial ligament on the metacarpal side. One patient had, in addition to injuries of the anterior oblique and dorsoradial ligaments, avulsed the posterior oblique ligament from the trapezium (Fig 5). Another patient had a fracture through the base of the thumb metacarpal with the ligaments preserved: this was initially missed on his radiographs although could be seen retrospectively. Four patients, including the patient with a fracture, showed bone contusion on the STIR imaging, and this was evident on both sides of the joint in all four patients. Soft tissue haematoma was commonly seen in the acute setting. No focal chondral defects were seen in the acute setting.(Fig 6) There were three patients with chronic injuries. One demonstrated ligament laxity with mild thickening of both the anterior oblique and dorsal radial ligaments, and another had a small ganglion arising from the site of anterior oblique ligament attachment onto the metacarpal base (Fig 7). The third patient, who had dislocated his thumb 3 years earlier, showed advanced degenerative change of the thumb carpometacarpal joint with chondral loss and subcortical cyst formation (Fig 8). His anterior oblique and dorsal radial ligaments were continuous, but had abnormally thickened bands of low signal. The anterior oblique, dorsal radial, posterior oblique and intermetacarpal ligaments were reliably seen in all the five healthy volunteers. Using our MR technique, these ligaments appeared as continuous bands of low signal which could be followed from origin to insertion. The anterior oblique ligament is a prominent structure that is readily defined although
Fig 4 Twenty-five-year-old platform diver following injury to the thumb carpometacarpal joint:(a) coronal FSE image (TR/TE 4000/30) showing high grade partial tearing of the anterior oblique ligament (straight arrow) with periosteal stripping (small arrows) from the base of the thumb metacarpal.(b) Axial FSE image (TR/TE 4000/30) showing the periosteal stripping (open curved arrow) and the torn anterior oblique ligament (straight arrow).
the superficial and deep components could not be distinguished from each other. The fibres of the dorsal radial and posterior oblique ligaments were intimately related and not clearly separable on sequential scans.
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Fig 6 Thirty-three-year-old woman following a fall playing basketball. Coronal FSE image (TR/TE 4000/30) showing occult fracture line (small arrows) through base of first metacarpal. In retrospect this was seen on radiographs.
Fig 5
Four-year-old woman following a fall down the stairs: (a) coronal FSE image (TR/TE 4000/30) showing a tear of the anterior oblique ligament (straight arrow) with only a few attenuated hyperintense fibres remaining intact. Maceration of the dorsal radial ligament (open curved arrow) is noted. (b)Coronal FSE image (TR/TE 4000/30) further posteriorly demonstrating avulsion of the posterior oblique ligament (curved arrow) from the trapezium.
The initial independent assessments of the musculoskeletal radiologist and senior fellow were in agreement for determining whether the anterior oblique and dorsal radial ligaments were normal or partially or completely
torn, except that in one patient the senior radiologist felt the dorsal radial ligament was completely torn, while fellow felt there was a moderate grade partial tear. However, there was discrepancy in the assessment of the degree of partial tearing (mild, moderate, severe) in 10 of the 14 cases. There was moderate agreement with respect to the posterior oblique ligament (eight of 14 cases) and poor agreement with respect to tears of the transverse metacarpal ligament (five of 14 cases). Six months later, and when blinded to the initial report, the senior radiologist and a third musculoskeletal radiologist independently re-assessed the MR images of the patient cohort and healthy volunteers. Both radiologists were consistent in discriminating normal from abnormal assessments, and the senior radiologist separated partial from complete tears as before in all but two patients. The third radiologist agreed with the initial findings in 11 of the 14 patients. Eight patients underwent surgical intervention, four with pinning of the joint and four with primary ligament repair. The MR findings of a complete anterior oblique ligament disruption (patient No 1) and high grade partial tear (patient No 3) were confirmed in two cases at surgery. Partial detachment and periosteal stripping of the ligament from the metacarpal site was also confirmed in patient No 3. Concomitant injury to the dorsal radial ligament and the intermetacarpal ligament in both these patients was also observed. The MR imaging findings were also validated in the two other patients treated by primary ligament repair.
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Fig 7 Fifty-two-year-old man involved in a fist fight 6 months previously. Coronal FSE image (TR/TE 4000/30) showing continuity but laxity of the anterior oblique (open curved arrow) and dorsal radial (long straight arrow) ligaments. There is a small ganglion cyst (straight arrow) arising from the insertion of the anterior oblique ligament into the thumb metacarpal base.
DISCUSSION Trauma to the carpometacarpal joint of the thumb probably results in a spectrum of ligamentous injury dependent on the rate and direction of the loading force (Strauch et al., 1994). In our study ligamentous injury ranged from disruption of all four major ligaments following dislocation to low grade partial tearing of the anterior oblique ligament alone seen following ligamentous sprain. The anterior oblique ligament was the most common ligament injured, followed by the dorsal radial ligament. The superficial component of the anterior oblique ligament inserts onto the thumb metacarpal distal to the articular margins and this was the most common site for either complete or partial tears. This is in agreement with the findings of Strauch et al (1994). The dorsal radial ligament was the next most common injury with tearing occurring exclusively on the trapezium side. MR imaging has the ability to diagnose the degree of ligamentous injury and differentiate avulsions from partial tears. In the case of a complete tear, MR imaging can confirm the clinical findings as well identifying concomitant pathology such as chondral
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injuries, occult fractures and intra-articular bony fragments or interposed soft tissue. This information could aid in surgical planning. When patients are treated conservatively, MR imaging can be used to monitor healing and resolution of haematoma, and to evaluate ligament quality and joint stability before returning to normal activity. Our three radiologists’ assessment of the anterior oblique and dorsal radial ligaments were consistent, but there was less consistency with the posterior oblique and intermetatarsal ligaments assessments. This is probably because the first two ligaments are relatively large. Our radiologists had no difficulties discriminating normal from abnormal scans, although there was some discrepancy when assessing high grade partial tears from complete tears, and also the degree of partial tearing in individual ligaments. While this study was primarily concerned with acute injuries, three patients had chronic injuries. It has been suggested that degeneration or tearing of the anterior oblique ligament results in hypermobility leading to increased shear forces across the joint, resulting in osteoarthritis (Imaeda et al., 1994; Moore et al., 1978; Pellegrini 1991; Simonian and Trumble, 1996). We demonstrated advanced osteoarthritis in a 27-year-old basketballer who had dislocated his thumb 2.5 years ago and had not sought treatment. MR imaging could be used to assess the integrity of the thumb carpometacarpal ligaments prior to the onset of irreversible joint damage. Certain technical aspects of the study should be considered. The use of a dedicated wrist coil increases the signal-to-noise ratio, enhances spatial resolution and this makes the injury more conspicuous. Fast spin echo techniques decrease imaging time without loss of resolution or contrast and true coronal images centred over the thumb carpometacarpal joint will usually identify both the anterior oblique and dorsal radial ligaments and are the easiest to interpret. In the setting of pain and swelling following acute injury, extreme care and patience is required to place the thumb joint flat within the wrist coil, so that the ligaments could be assessed in the true anatomic plane. Despite being tightly held by soft tissue sponges, some of our studies were degraded by motion artefact, and one patient was immobilised in a plaster case which necessitated imaging in a knee coil. Recognition of abnormal signal intensity surrounding the cortex of the thumb metacarpal is important because this finding is typically due to stripping of the periosteum as the anterior oblique ligament is avulsed from its osseous insertion. Discriminating the dorsal radial from the posterior oblique ligament is best achieved by following the abductor pollicis longus tendon to its insertion on to the thumb metacarpal, where it reinforces the dorsal radial ligament. Among the imitations of study are the facts that surgeons had access to MR imaging reports at the time of surgery and that direct visualisation of the ligaments
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Fig 8
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Twenty-seven-year-old basketball player who injured his thumb 30 months previously, now presenting with basal joint pain: (a) delayed radionuclide imaging shows increased uptake in the thumb carpometacarpal joint; (b) coronal FSE image (TR/TE 4000/30) shows marked thickening and diffuse low signal (open curved arrow) of the anterior oblique and dorsal radial (straight arrow) ligaments compatible with chronic injury. Some minor hyperintensity of the anterior oblique ligament (straight arrow) at the thumb metacarpal base is likely to reflect an area of ligament tearing. (c) Coronal gradient echo image (TR/TE 1400/20 flip 201) shows loss of cartilage with pronounced subchondral cyst formation (small arrows) compatible with advanced osteoarthritis.
at surgery was performed in only four cases. The injuries taken to surgery were high grade and we have no correlation with low grade injuries. Treatment of thumb carpometacarpal injuries includes immobilisation in a plaster cast for approxi-
mately 4 weeks, pinning of the joint and primary surgical repair using tendon transfer. MR imaging may have a role in avoiding unnecessary immobilisation in cases where the ligament is shown to be normal. The confirmation of injury can also aid in surgical planning.
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Acknowledgements Thanks to Judy Tan and Nicki Freer for their help in the typing of this manuscript.
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Pagalidis T, Kuczynski K, Lamb DW (1981). Ligamentous stability of the base of the thumb. Hand, 13: 29–35. Pellegrini Jr. VD (1991). Osteoarthritis of the trapeziometacarpal joint : the pathophysiology of articular cartilage degeneration. Journal of Hand Surgery, 16A: 967–974. Shah J, Patel M (1983). Dislocation of the carpometacarpal joint of the thumb. Clinical Orthopaedics, 175: 166–169. Simonian PT, Trumble T (1996). Traumatic dislocation of the thumb carpometacarpal joint: early ligamentous reconstruction versus closed reduction and pinning. Journal of Hand Surgery, 21A: 802–806. Strauch RJ, Behrman MJ, Rosenwasser MP (1994). Acute dislocation of the carpometacarpal joint of the thumb: an anatomic and cadaver study. Journal of Hand Surgery, 19A(1): 93–98. Watt N, Hooper G (1987). Dislocation of the trapeziometacarpal joint. Journal of Hand Surgery, 12B: 242–245.
Received: 8 October 2002 Accepted after revision: 16 May 2003 Dr David Connell, Department of Medical Imaging, Victoria House Hospital, 316 Malvern Road, Prahran 3181, Australia. Tel.: 03-9529-7333; Fax: 03-9529-7833; E-mail: [email protected] r 2003 The British Society for Surgery of the Hand. Published by Elsevier Ltd. All rights reserverd. doi:10.1016/S0266-7681(03)00170-0 available online at http://www.sciencedirect.com