Andrew L. Terrono, Paul Feldon, and Hervey L. Kimball III
DEFINITION
The finger metacarpophalangeal joint (MCP joint) is commonly and characteristically involved in inflammatory arthritis.
The MCP joint is often involved early in inflammatory arthritis and usually presents with ulnar extensor tendon subluxation resulting in ulnar deviation of the fingers.
Occasionally in systemic lupus erythematosus (SLE) radial subluxation of the extensor tendon is seen.
ANATOMY
The normal MCP joint is a condylar joint that allows flexion and extension as well as radial and ulnar deviation and a combination of these movements. Normally there is 90 degrees of flexion, although hyperextension can vary.
The stability of the MCP joint is provided by the radial and ulnar collateral ligaments, the accessory collateral ligaments, the volar plate, the dorsal capsule, and the extensor tendon (FIG 1).
The metacarpal head diameter increases in both the transverse and sagittal planes and therefore has a cam effect, making the collateral ligaments tight in flexion and lax in extension. This allows more radial and ulnar deviation of the MCP joint in extension.
The MCP joint collateral ligaments are asymmetric.
The ulnar collateral ligament is more parallel to the long axis of the fingers.
The radial collateral ligament is more oblique.
This causes supination of the MCP joint with MCP joint flexion.
The collateral ligament also resists volar-directed forces.
The volar plate is fibrocartilaginous distally and has a membranous portion proximally. It limits MCP joint extension.
The transverse intermetacarpal ligament connects the volar plates to each other.
The accessory collateral ligament connects the collateral ligament and volar plate and keeps the volar plate close to the volar aspect of the MCP joint throughout motion.
The A-1 pulley of the flexor tendon sheath is attached to the volar plate.
The extensor digitorum tendon is maintained centrally over the MCP joint by the transverse fibers of the sagittal band that attach volarly to the volar plate and the intermetacarpal ligament. This forms a sling mechanism. The ulnar sagittal band is felt to be stronger and denser than the radial sagittal band.
There is usually no direct extensor tendon insertion into the proximal phalanx. The proximal phalanx is extended through the sling mechanism.
The lumbrical muscle originates from the tendon of the flexor digitorum profundus and is volar to the intermetacarpal ligament. It inserts into the lateral band.
There are three volar (which adduct) and four dorsal (which abduct) interossei that have tendons that all pass dorsal to the transverse intermetacarpal ligament. They have variable insertions into the proximal phalanx and extensor mechanism.
FIG 1 • A. Normal anatomy of the metacarpophangeal joint. B. Abnormal anatomy seen in inflammatory arthritis. The extensor tendon is subluxated ulnarly.
The first dorsal interosseous almost always inserts completely into the radial side of the proximal phalanx of the index finger.
PATHOGENESIS
The pathology of inflammatory arthritis begins with proliferative synovitis.
Selective changes in static and dynamic stabilizers of the MCP joint occur, resulting in alteration in the equilibrium of the joint. The most common deformity produced is ulnar deviation of the fingers (FIG 2A).
Which comes first, the changes to the dynamic or static stabilizers, is unclear and may vary.
The capsule, radial collateral ligament, and radial sagittal band are stretched by the synovitis and allow the equilibrium to move toward ulnar deviation.
FIG 2 • A. Radiograph of a patient with extensor tendon subluxation and ulnar deviation of the metacarpophalangeal (MCP) joints. The joint spaces are maintained and the joints are not subluxated. B. Radiograph of a patient with extensor tendon subluxation and ulnar deviation of the MCP joints with reducible MCP joint subluxation involving the index and middle MCP joints.
The accessory collateral ligament and the membranous portion of the volar plate become lax.
The joint capsule becomes thinned and a defect in the dorsal capsule may occur.
With increasing ulnar deviation, the ulnar intrinsic muscle shortens.
The intrinsic muscle contribution to the deformity is unclear. It may be a primary or secondary change. There is a cycle that is set up as the MCP joint ulnarly deviates and the extensor tendon acts as an ulnar deviator and may even act as a flexor of the MCP joint.
The laxity of the volar plate and accessory collateral ligament causes the flexor tendons to develop a mechanical advantage and increased flexion force. This results in an increase in the deformity.
The combination of changes to the capsule, radial collateral ligament, radial sagittal band, accessory collateral ligament, and the membranous portion of the volar plate and the increased mechanical advantage of the flexor tendon is magnified by the normal ulnar and volar slope of the metacarpal condyles and allows ulnar deviation and volar displacement of the proximal phalanx (FIG 2B).
The wrist may be a contributing factor to the development of the MCP joint deformity, and this must be considered in each case before correcting the MCP joint.
Radial deviation of the wrist can be a compensatory position to the ulnar deviation of the MCP joints to allow the fingers to line up with the forearm.
Ulnar deviation of the digit is more common in patients with radial deviation of the wrist.
At first the deformity is correctable passively, but gradually this mobility is lost and the deformity becomes fixed.
Articular cartilage changes progress from softening of the cartilage to erosion with significant loss of cartilage and bone. This contributes to the deformity.
Once there are significant cartilage and bone changes, extensor tendon realignment alone, without joint resurfacing, is not indicated.
The changes seen in SLE are secondary not to synovitis but rather to alteration in the collagen that results in a change in the equilibrium of the MCP joint and subsequent deformity.
The finger deformity in SLE is often ulnar deviation, but radial deviation is not uncommon.
In SLE it is easy to change one deformity to another (ie, ulnar drift into a radial deviation deformity after surgery) because of the global changes to the supporting structures.
Despite the MCP deformity becoming fixed, the articular cartilage is usually preserved.
NATURAL HISTORY
The natural history of the MCP joint changes in inflammatory arthritis is not known and is probably highly variable and influenced by the new disease-modifying medications.
Mild ulnar deviation of the fingers is normal and increases with MCP joint flexion.
In inflammatory arthritis, such as rheumatoid arthritis, deformity is initially passively correctable.
Mild ulnar deviation of the fingers is seen in less than 10% of the patients in the first 5 years of having rheumatoid arthritis.3
Ulnar deviation has been reported in 30% of patients with rheumatoid arthritis, with palmar subluxation in 20%.3
Palmar subluxation almost always occurs with ulnar deviation.3
PATIENT HISTORY AND PHYSICAL FINDINGS
In a patient with inflammatory arthritis who is being considered for MCP joint surgery, the entire upper extremity is evaluated. Involvement of the lower extremities must also be considered, given that the upper extremities may need to assist in ambulation.
The need to use the upper extremities for weight bearing can significantly affect the durability of the correction obtained after MCP joint surgery.
Ideally MCP joint surgery is performed when the upper extremity is not needed for such support.
The wrist is evaluated for the presence of a static deformity at the time of MCP joint surgery. Presence of a static radial deviation deformity will negatively affect the results of MP joint surgery.
The skin over the MCP joint is evaluated; it should be in good condition.
Motion of the MCP joint is assessed. The surgeon should specifically ensure that ulnar deviation and flexion deformities can be easily corrected passively.
Proximal interphalangeal (PIP) joint motion and alignment must be critically evaluated.
If there is a significant boutonnière deformity, this should be corrected before the MCP joint surgery since the PIP flexion will influence the amount of MCP joint flexion obtained postoperatively.
If there is a swan-neck deformity, this can be treated at the same time or after the MCP joint. A stiff PIP joint in extension will cause the patient to flex the finger at the MCP joint and can help obtain better flexion postoperatively.
Any radial or ulnar deformity at the PIP joint must be corrected before the MCP joint surgery.
The flexor and extensor tendons must be intact before any MCP joint surgery.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs of the hand and wrist are essential before MCP joint surgery to evaluate alignment, congruence, and joint integrity.
DIFFERENTIAL DIAGNOSIS
The most common cause of inflammatory arthritis that affects the MCP joint is rheumatoid arthritis.
SLE is more common in black women, and the deformity is secondary to a collagen abnormality causing ligament and tendon imbalance. Articular cartilage loss is a much less common problem in SLE. Soft tissue realignment can be performed even after the condition has been present for a long time.
Psoriatic arthritis is more common in men and has a characteristic skin rash, although patients may have joint involvement before a clinically obvious skin rash. The patient with psoriatic arthritis often has an asymmetric deformity and more stiffness. The cartilage and bone are also affected.
FIG 3 • A splint used to try to prevent progression of the ulnar deviation. Usually this is not successful and ulnar deviation eventually progresses.
NONOPERATIVE TREATMENT
A team approach to patients with inflammatory arthritis is important.
Splinting in a corrected position (FIG 3) and joint protection may decrease the forces that contribute to the deformity.
This may be helpful, but the effect in the long term is unknown, and we have not noticed significant long-term benefit.
SURGICAL MANAGEMENT
One the most difficult operations to decide to perform is MCP joint synovectomy and realignment.
This is usually best performed early when there is minimal deformity.
However, at this time the patient often has minimal pain and only slight loss of function.
With the use of disease-modifying medications, if the anatomy can be restored and the mechanical problems corrected, salvage procedures may be prevented or significantly delayed.
The ideal patient for surgery is one with increasing deformity and good medical management with control of his or her synovitis.
The deformity should be passively correctable with good active MCP joint motion.
Ideally the MCP joint is not volarly subluxated, since correction and maintenance of correction is more unreliable.
There should be a well-aligned wrist with good PIP joint function without deformity.
If the deformity is passively correctable but cannot be actively corrected, obtaining active ulnar deviation such as by an extensor carpi ulnaris tendon relocation or transfer should be considered.
The radiographs should reveal good preservation of the joint space without volar subluxation.
If all of these criteria are met and the joints are not passively correctable or there is volar subluxation of the MCP joint, surgery can be performed, although the results may not be as reliable.2
A firm diagnosis can help with establishing a prognosis for the maintenance of correction obtained at surgery.
The effect of the new disease-modifying medication is not known.
It is possible that the soft tissue correction obtained at surgery may now last longer and therefore the procedure should be entertained earlier and more often.
Ideally, earlier surgery will solve the correctable mechanical problem and will end the cycle of deformity.
Positioning
The procedure is performed using tourniquet control. The hand is supported by a hand table.
Approach
The procedure usually is performed on all four fingers through a transverse dorsal incision over the MCP joint (FIG 4).
If a single digit is involved, a longitudinal incision should be used.
If not all of the fingers are going to be corrected, the fingers on the side of the deformity (ie, if there is ulnar deviation deformity, the radial involved digits) must be corrected first to limit recurrent deformity.
FIG 4 • A transverse incision is used to expose the metacarpophalangeal joints when performing an extensor tendon centralization.
TECHNIQUES
EXPOSURE
Expose the extensor mechanism at each joint (TECH FIG 1A).
Release the juncture tendineae as needed (TECH FIG 1B).
Develop the interval between the extensor hood and capsule.
Try to relocate the extensor tendon to the midline.
Sometimes this can be done without releasing the ulnar sagittal band.
If the extensor tendon can be relocated to the midline, expose the joint by incising the radial sagittal band.
The radial sagittal band will be reefed at the end of the procedure.
If the extensor tendon cannot be relocated to the midline, release the ulnar sagittal band to expose the capsule.
A central defect in the joint capsule is often present. Open the capsule through this defect using a distally based dorsal capsular flap (TECH FIG 1C).
TECH FIG 1 • A. The extensor tendons are exposed through a transverse skin incision. The extensor tendons are subluxated ulnarly. B. The juncture tendineae are released as needed. C. The capsule is opened by creating a distally based dorsal capsular flap.
SYNOVECTOMY AND TENDON REALIGNMENT
Perform a synovectomy using small rongeurs, curettes, and elevators (TECH FIG 2A).
Evaluate the intrinsics after the extensor tendon is relocated and the joint is in neutral position. Perform an intrinsic tightness test. If positive and intrinsic tightness persists, release the ulnar intrinsics.
Incise the sagittal band and expose the intrinsic tendon on the ulnar side of the joint.
It is superficial to the collateral ligament and capsule.
Pass a curved hemostat beneath the ulnar intrinsic tendon as it inserts into the lateral band (see Fig 1) and divide the tendon.
A section of the oblique fibers may be excised.
If intrinsic tightness continues, release the proximal phalanx insertion by grasping the proximal portion of the tendon with a clamp and sectioning (TECH FIG 2B).
A step-cut lengthening of the ulnar intrinsics may be preferred to complete intrinsic release in patients with SLE to avoid late radial deviation.
If the joint still cannot be corrected, release the ulnar collateral ligament.
If the ulnar intrinsic has been released, an intrinsic transfer can be performed, usually attaching it to the radial collateral ligament (TECH FIG 2C).
The advantage of using the radial collateral ligament as the attachment site is that it does not increase the extensor force at the PIP joint, which could result in a swan-neck deformity.
If the joint was subluxated volarly preoperatively, pin the MCP joint in extension with a Kirschner wire.
After the proximal phalanx is reduced, reef or advance the radial collateral ligament as needed (TECH FIG 2D).
Close the capsule in a pants-over-vest manner so that the MCP joint is in extension (TECH FIG 2E).
The extensor tendon is relocated onto the dorsal midline of the joint.
Strip the periosteum from the dorsum of the proximal phalanx base and tenodese the central tendon to the proximal phalanx using a suture anchor (TECH FIG 2F,G).
Alternatively, place two drill holes in the proximal phalanx to suture the tendon directly to the bone.
2-0 PDS suture is used. Nonabsorbable suture may result in prominent knots in this patient population with thin skin.
Reef the radial sagittal band fibers with a 4-0 nonabsorbable suture to rebalance and support the extensor tendon directly over the joint.
Repair the juncture tendineae.
Traction on the central tendon should result in full MCP joint extension.
A bulky dressing with fluffs between the fingers is applied, followed by a volar splint supporting the MCP joints in extension and in a slightly overcorrected position.
TECH FIG 2 • A. A metacarpophalangeal joint synovectomy is performed. B. The ulnar intrinsic tendon is sectioned and the ulnar collateral ligament is released. The central tendon is centralized and sutured to the proximal phalanx. C. The contracted ulnar sagittal fibers are released and the radial sagittal fibers are reefed (red arrows) to rebalance and support the extensor tendon in the midline. The radial collateral ligament is advanced (green arrow) and the ulnar intrinsic muscle is transferred to the radial collateral ligament (blue arrow) of the adjacent digit. D. The radial collateral ligament is advanced, as in this case, or reefed. E. The capsule is closed in a pants-over-vest manner so that the metacarpophalangeal joint is supported in extension. F. The extensor tendon is sutured directly to the dorsal base of the proximal phalanx using absorbable suture. G. Postoperative radiograph of a patient showing suture anchors in place after extensor tendon centralization.
POSTOPERATIVE CARE
The postoperative dressing is removed at about 10 to 14 days and the sutures are removed.
An Orthoplast splint with the MCP joints extended and slightly overcorrected, usually in slight radial deviation, is applied until 4 weeks postoperatively.
At 4 weeks postoperatively, if Kirschner wires were inserted they are removed. Splinting is then continued for 2 additional weeks.
At 6 weeks postoperatively, hand therapy is started, concentrating on active MCP joint extension. Active MCP flexion is also started. Protective splinting is continued for another 2 weeks in between exercises and at night.
The fingers are splinted together as a unit to maintain alignment and concentrate flexion at the MCP level.
To increase the postoperative flexion, the PIP joint is occasionally splinted in extension, concentrating the flexion force at the MCP joint.
Dynamic splinting can be used to support extension and maintain digital alignment during the early healing stage but is usually not necessary.
At 8 weeks postoperatively daytime splinting is decreased and gradual return to functional activities is encouraged.
Nighttime extension splinting is continued for 3 months.
OUTCOMES
MCP joint extension and ulnar drift are improved postoperatively.
MCP flexion is usually slightly less than it was preoperatively.
Strength is not significantly improved.
Maintenance of correction is usually good with slight increase in ulnar drift, usually without recurrent subluxation.
When the deformity is seen early and is still passively correctable with preserved joints, extensor tendon centralization and MCP joint synovectomy (as needed) is often beneficial, improving patient function.
As with all joint procedures for deformities resulting from inflammatory arthritis, the procedure itself does not stop the progression of the disease. However, the new generation of disease-modifying medications combined with surgery may result in long-lasting correction of joint deformity.
COMPLICATIONS
Infection
Wound healing problems
Loss of motion
Recurrent ulnar drift with tendon subluxation
Radial subluxation of the extensor tendon (seen in SLE)
Progressive joint destruction from the arthritis and need for joint replacement
REFERENCES
1. Abboud JA, Beredjiklian PK, Bozentka DJ. Metacarpophalangeal joint arthroplasty and rheumatoid arthritis. J Am Acad Orthop Surg 2003;11:184–191.
2. Nalebuff EA. Surgery for systemic lupus erythematosus arthritis of the hand. Hand Clin 1996;12:591–602.
3. Wilson RL, Carlblom ER. The rheumatoid metacarpohalangeal joint. Hand Clin 1989;8:223–237.
4. Wood VE, Ichtertz DR, Yahiku H. Soft tissue metacarpophalangeal reconstruction for treatment of rheumatoid hand deformity. J Hand Surg Am 1989;14A:163–174.