Fig. 9.1
Injury of the beak ligament of the CMJC, with stretching of the dorsal ligaments, may results in subluxation of the joint, adduction of the metacarpal, hyperextension of the MCPJ. In time, degenerative changes will develop
Radiographs of the thumb are often of normal appearance. However, on occasion they can show a dorso-radial displacement of the metacarpal. Stress radiographs may show displacement of the base of the metacarpal, [6], which correlates with joint laxity. MRI has been recommended to image the beak ligament [7]. Arthroscopy of the CMCJ can show ligament damage and also, importantly, assess the joint surface for any degenerative changes that may be present.
In the acute situation, CMCJ instability can be treated conservatively with activity modification and splints with the metacarpal in palmar abduction-extension for 4–6 weeks. However in chronic cases, these measures often only help in the short term and symptoms recur later on. Recommended surgical treatments include metacarpal osteotomy or ligament reconstruction. Currently, there is good experimental evidence for the use of either.
Extension osteotomy of the thumb metacarpal by 15° decreases joint laxity in radio-ulnar, dorsal-volar and pronation-supination directions, and may stabilise the thumb to a degree or at least similar to that of a standard ligament reconstruction [8].
There is also evidence that stabilisation of the joint decreases symptoms and slows down the development of degenerative changes. Several techniques to stabilise the CMCJ of the thumb have been described, most of them are effectively a tenodesis, using either palmaris longus, extensor carpi radialis longus, APL or flexor carpi radialis. The commonly used techniques are those described by Eaton and by Brunelli.
After a meticulous anatomical study, Brunelli described a method of stabilisation of the CMCJ using just one of the tendons of abductor pollicis longus (98 % of thumbs have several APL tendons) which is passed through a drill hole placed in the base of the first and second metacarpals to reconstruct the intermetacarpal ligament. This new ligament provides a pivot point for the joint allowing movement, but preventing radial displacement of the base of the metacarpal.
In the classic technique described by Eaton and Littler, a modified Wagner approach is used, taking care to protect the branches of the radial nerve. The radial border of the thenar muscle is incised and the muscles elevated extraperiosteally to expose the CMCJ capsule. Blunt dissection is extended dorsally to expose the metacarpal cortex. The capsule is incised and the joint can be inspected. If there are degenerative changes, it may be better to proceed to an arthroplasty procedure rather than a stabilisation.
Half the FCR tendon is harvested for a length of 9 cm. A tunnel is drilled from dorsal to volar in the thumb metacarpal, 1 cm distal to its base and the hemi-tendon is passed from palmar to dorsal through the tunnel and sutured to the metacarpal periosteum. The graft is then passed under the APL tendon, then sutured to the APL, before passing underneath and around the ulnar half of the remaining FCR tendon. The graft is sutured as it loops around. If there is enough length, the graft can be brought back dorsally and sutured to APL again. A Kirschner wire is then drilled from the metacarpal into the trapezium and kept for 5 weeks until the soft tissues have healed.
If on lateral pinch there is 30° of hyperextension at the MCPJ, either a MCPJ capsulodesis or arthrodesis is recommended (Fig. 9.2).
Fig. 9.2
Hyperextension of the MCPJ can be secondary to adduction of the metacarpal. This in turn accentuates the dorsal subluxation at the CMCJ, contributing to degeneration of the joint and thumb collapse
After surgery, the thumb is kept immobilised for 5 weeks in a thumb spica splint. Active range of movement exercises are started after removal of the wire, and strengthening exercises can start 2 months after surgery.
Clinical Pearl
Stability of the CMC joint of the thumb is uncommon. Generally, a significant force is required to de-stabilize this joint. Diagnosis is based on clinical suspicion, but can be aided by stress x-rays. MRI scans can also be increasingly useful. Treatment by tendon reconstruction is generally effective.
The outcomes are generally good, with only 17 % of patients reporting pain with activities of daily living, and 54 % reporting pain with strenuous activities, 10 years after surgery. When tested against stress, 87 % demonstrated joint stability at the CMCJ.
MCPJ Thumb Instability
The MCPJ of the thumb has little intrinsic stability and depends on its ligaments and muscle attachments. The range of motion is the most variable of any joint in the body, with a wide spectrum; some thumbs can flex to 90° degrees, while others have hardly any movement.
The collateral ligaments arise from the lateral condyles of the metacarpal and pass obliquely to insert on the volar third of the proximal phalanx. They are tight in flexion and loose in extension. The accessory collateral ligaments originate from a more volar site on the metacarpal head and insert onto the volar plate and sesamoid bones on each side of the joint, being tight in extension and loose in flexion. The volar plate has a strong insertion into the proximal phalanx, and with the collateral and accessory collateral ligaments forms three sides of a box, stabilising the joint. In contrast to the PIPJ, the volar plate of the MCP has not got strong check rein ligaments.
The adductor pollicis muscle inserts on to the ulnar sesamoid, and the flexor pollicis brevis and abductor pollicis brevis insert onto the radial sesamoid. These muscles have secondary insertions into the extensor mechanism via the abductor and adductor aponeurosis, providing additional stability.
Injuries to the ligaments of the MCPJ of the thumb are common, often related to sport (50 %) or to work (38 %), and more prevalent in the young male population. The ulnar collateral ligament is injured more often (84 %) than the radial collateral ligament. There is some evidence that joints with a lesser range of movement are more prone to injury [9].
Ulnar Collateral Chronic Instability
Ulnar collateral chronic instability, often referred to as skier’s or gamekeeper’s thumb, may represent as a pure avulsion of the ligament; or an avulsion of a fragment of bone, usually from its distal insertion in the proximal phalanx; or it may represent a midsubstance rupture or attenuation. The term gamekeeper’s thumb was used initially to describe the chronic instability of the MCPJ caused by repetitive trauma as seen in Scottish gamekeepers that often stressed this joint undertaking a manoeuvre to kill a wounded rabbit by twisting its neck [10].
Skier’s thumb reflects the incidence of acute UCL injuries associated with a fall while grasping a ski pole in the hand, forcing the thumb into radial deviation; this term is now often used for acute injuries.
Stener described the displacement of the avulsed edge of the ligament, with interposition of the adductor aponeurosis preventing healing of the ligament (Fig. 9.3). If in doubt, an ultrasound scan can often demonstrate the presence of a Stener lesion.
Fig. 9.3
Stener lesion. The adductor aponeurosis covers the ulnar collateral ligament. When the MCPJ is pushed into radial deviation, it can rupture this ligament, and the proximal end of the ruptured UCL can become superficial to the aponeurosis, while the distal insertion is deep to it, preventing healing and causing chronic instability
Failure to diagnose or treat a complete tear of the UCL often results in chronic instability. Patients present with pain in the thumb, often exacerbated by activity. The pinch and grip are weak and some tasks, like opening a jar or holding a large bottle, become increasingly difficult. There is often a history of intermittent swelling of the joint and the patients may report a feeling of instability. Crepitus of the joint on movement indicates degenerative changes are present.
On examination, it is important to inspect the thumb for volar subluxation of the MCPJ and for radial deviation of the thumb. Pushing the phalanx in a radial direction will cause deviation at the joint, indicating instability (Fig. 9.4). When this is done in flexion, the true collateral ligament is tested, when done in extension, the accessory collateral ligament and the volar plate are tested. Increased deviation compared to the contralateral thumb, and lack of a firm end point are diagnostic of instability. In contrast with an acute injury, in most patients with chronic instability it is not necessary to inject local anaesthetic before examination to elicit instability.
Fig. 9.4
(a) Testing the UCL of the MCPJ clinically shows increased radial deviation, without a firm end point. Stressing the MCPJ under fluoroscopy shows the displacement in the left thumb, diagnostic of ulnar collateral ligament insufficiency (b). Compare with the right side, with a normal competent ulnar collateral ligament (c). It is important when testing under fluoroscopy to try to avoid radiation to the fingers of the examiner, as far as possible
Radiographs may show volar subluxation and radial deviation. It is, however, important to assess any degenerative changes in the joint. Further imaging is not required, since the indication for treatment is based on symptoms and degree of clinical instability.
Treatment
In most cases of symptomatic chronic UCL insufficiency, surgery is indicated. As the period since injury increases, it is less likely that a direct repair is feasible, although if the delay is less than a few weeks it may be possible to identify and repair or reattach the ligament. Degenerative changes or a MCPJ that had very little movement before the injury, would be indications for joint arthrodesis rather that a reconstruction.
Commonly used techniques recommended for MCPJ instability without degenerative changes include reconstruction using a tendon graft or adductor advancement. There are also reports of bone-ligament-bone reconstruction. Some patients, however, may prefer a MCPJ arthrodesis because it is more durable and predictable, although at the cost of losing movement.
Adductor pollicis inserts on the ulnar side of the MCPJ and is a dynamic stabiliser of the joint. Neviaser proposed the advancement of the insertion of the adductor onto the ulnar side of the base of the proximal phalanx, combined with suture of the ligament, to act as a dynamic tendon transfer [11]. The advantage of this technique is that it provides a strong dynamic stabiliser during pinch that prevents radial deviation at the MCPJ. This technique involves an incision on the ulnar side of the MCPJ, protecting the sensory branches of the radial nerve, exposing the ulnar side of the joint. The adductor aponeurosis is incised and reflected volarly and after identifying the scarred ligament and capsule, the joint is exposed. The adductor pollicis tendon is then detached from its insertion in the ulnar sesamoid.
Provided there are no degenerative changes, the ligament and capsule are reefed. The adductor tendon is attached to the base of the proximal phalanx with the use of a bone anchor or a pull-out wire. In the postoperative period, the thumb is immobilised for 4 weeks in a cast or splint, thereafter range of movement exercises are started.
An alternative procedure is reconstruction using a free tendon graft. The MP joint is exposed through a mid-axial incision to expose its ulnar aspect. The adductor aponeurosis is mobilised and a hole is drilled on the ulnar side of the base of the proximal phalanx, in the area of insertion of the UCL. A tendon graft is obtained, usually palmaris longus, and a figure of eight suture is placed at the end of the graft. The two ends of the suture are placed on needles and passed through the tunnel at the base of the proximal phalanx and through the radial cortex where sutures are tied over a button. Alternatively, a bone anchor or an interference screw can be used. The ligament is identified and dissected and used to suture the tendon graft to the metacarpal. If the remains of the ligament are not strong enough, the graft can be passed through a tunnel in the metacarpal head (Fig. 9.5). The adductor aponeurosis is sutured over the repair. A thumb spica is recommended for 4 weeks and a splint for a further 5 weeks.
Fig. 9.5
(a–f) Stabilisation of MCPJ using a tendon graft. Two holes are drilled in the proximal phalanx to make a tunnel to pass the tendon graft, and one transverse hole is drilled into the metacarpal to anchor the graft. The graft is passed through the tunnel in the phalanx. The graft is anchored in the metacarpal using an interference screw
The main contraindication to these reconstructive procedures is osteoarthritis of the joint. A relative contraindication is marked volar subluxation or supination of the joint, which may not be improved by these procedures. On occasions MCPJ instability is diagnosed as an incidental finding, with very few symptoms; no surgical treatment is required in these cases.
Radial Collateral Chronic Instability
Although injuries to the RCL of the MCPJ are less common (16 %), they can present with similar symptoms and disability. They are caused by forced adduction of the thumb or by a torsional force on the flexed thumb. The principles of diagnosis and management are similar to those described above.
There are some anatomical differences between the radial and the ulnar sides of the joint. On the radial side, the abductor aponeurosis is wider, and there is little potential to have a lesion, similar to the Stener on the ulnar side of the joint. The RCL is torn in about equal frequency from its proximal and distal insertions and, it is more common that it presents as a mid-substance tear. A rupture of the RCL allows the joint to rotate, pivoting around the intact UCL, giving the typical appearance of a dorso-radial prominence of the metacarpal head. The tear often extends into the dorsal capsule.
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