Warren C. Hammert and Matthew M. Tomaino
DEFINITION
Osteoarthritis, or more appropriately termed osteoarthrosis, is a common problem in the hand.
The trapeziometacarpal joint is frequently affected, second in frequency only to the distal interphalangeal joint, but much more disabling due to pain and weakness of grip and pinch strength.
The surgical management of symptomatic basilar joint arthrosis depends on anatomy, radiographic staging, and patient requirements, followed by intraoperative confirmation of the stage of disease.
Arthrodesis of the thumb carpometacarpal (CMC) joint was initially described by Muller over 50 years ago.6 With refinements in arthroplasty procedures, arthrodesis of the basal joint of the thumb has become less popular, but the procedure still can provide an excellent result in the right circumstances; it is a valid treatment option for stage II or stage III disease only.
ANATOMY
The thumb CMC joint is a biconcave joint, allowing for motion in three planes: flexion-extension, abduction-adduction, and pronation-supination.
There are minimal osseous constraints, making the ligamentous structures extremely important stabilizers of the thumb base.
A total of 16 ligaments have been described around the thumb CMC joint.
Seven are primary stabilizers of the thumb metacarpal:
Superficial and deep anterior oblique (sAOL and dAOL)
Dorsal radial
Posterior oblique
Ulnar collateral
Intermetacarpal
Dorsal intermetacarpal
The remainder stabilize the trapezium, providing a stable foundation for the thumb.2
PATHOGENESIS
The pathogenesis of CMC joint arthrosis is multifactorial, involving biochemical and biomechanical influences. The synovial fluid within the joints contains cytokines, which invariably play a role in cartilage degradation and decreased ability to withstand the loads generated at the joint during daily activities.10
Although not clearly delineated, there probably is some protective role played by estrogen or estrogen-related compounds, which may explain the increased incidence of osteoarthritis in postmenopausal women (10 to 15:1).
The anterior (palmar) oblique ligament, or so-called beak ligament, has been shown to be the most important stabilizing ligament of the thumb, and its degeneration or functional incompetence leads to laxity, followed by abnormal translation of the metacarpal on the trapezium, resulting in increased shear forces and abnormal wear patterns. This eventually leads to eburnation of the articular cartilage, initially along the palmar aspect of the joint.9 With progression of disease, osteophytes develop and eburnation progresses throughout the entire joint surface.
Osteoarthrosis can also develop from disruption of the articular cartilage. Any fracture involving the articular surfaces (most commonly the base of the thumb metacarpal) will predispose to or accelerate the development of arthrosis.
Anatomic restoration of the joint surface can minimize this progression but not eliminate it completely.
Paradoxically, a Bennett fracture may protect the joint from the development of osteoarthritis (assuming subluxation is not present) by virtue of consequential unloading of the volar aspect of the joint.
NATURAL HISTORY
Arthrosis of the thumb CMC joint begins along the palmar aspect of the metacarpal secondary to laxity of the AOL.
The entire base of the metacarpal and the distal trapezium experience eburnation of the cartilage, which progresses to develop osteophytes.
The thumb metacarpal assumes an adducted position and the metacarpophalangeal (MCP) joint may compensate by becoming hyperextensile, resulting in hyperextension.
Finally, the entire surface of the trapezium becomes involved, resulting in degeneration between the proximal trapezium and the distal scaphoid.
Disease can involve all the trapezial articulations as well as the scaphotrapezoidal joint.8,11
PATIENT HISTORY AND PHYSICAL FINDINGS
Thumb CMC joint arthrosis will often present with pain at the base of the metacarpal.
The pain will be exacerbated with activities involving loading the thumb metacarpal base, such as turning a doorknob, twisting a lid off a jar, or turning a key.
Pain at rest may or may not be present.
Symptoms do not always correlate with the clinical or radiographic appearance. A patient may have advanced clinical and radiographic disease but be minimally symptomatic. Conversely, a patient may have significant symptoms with minimal radiographic changes and no clinical deformity at rest.
Physical examination of the patient with advanced disease reveals deformity.
The thumb subluxates in a dorsal direction and becomes fixed in adduction, manifesting as a prominence at the base of the thumb and decreased ability to abduct the thumb away from the palm.
In an effort to compensate for this limitation, the MCP joint will often hyperextend, creating a zig-zag deformity.
Asking the patient to place one finger on the point that is most symptomatic helps localize the point of maximal tenderness to the CMC joint or another area.
CMC grind test: Reproduction of symptoms confirms the CMC joint as a site of disease.
CMC distraction test: Reproduction of symptoms confirms the CMC joint as a site of disease.
Finkelstein maneuver: Maximal tenderness indicates that DeQuervain disease may be a greater source of symptoms.
Phalen test: Reproduction of symptoms indicates carpal tunnel syndrome as a more likely etiology.
Carpal tunnel compression test: Reproduction of symptoms indicates carpal tunnel syndrome as a more likely etiology.
Trigger evaluation: Reproduction of pain, triggering, or locking of the thumb indicates trigger thumb as an etiology.
Allen test: The radial and ulnar arteries are compressed and the hand is exsanguinated. The ulnar artery is released and the circulation of the hand is assessed. The process is repeated, releasing the radial artery while the ulnar artery is occluded. Surgical procedures often involve mobilization of the radial artery in the snuffbox. Damage to this artery will require reconstruction if the ulnar artery cannot compensate.
Other conditions causing pain at the base of the thumb must be eliminated, such as DeQuervain disease, trigger thumb, and carpal tunnel syndrome. Although more than one condition may exist, the physical examination can usually determine the most problematic area.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs are the imaging modality of choice for evaluation of thumb CMC joint arthrosis (FIG 1).
These include a pronated AP (Robert view), lateral, and a 30-degree posteroanterior stress view.
Eaton and Littler3 have described a radiographic staging system that is commonly used, but Tomaino et al11 have emphasized routine assessment of the scaphotrapezoidal joint, both radiographically and intraoperatively, to rule out scaphotrapezoidal arthritis, or what they termed “stage V disease.”
FIG 1 • AP radiograph of the thumb carpometacarpal joint.
Stage I: normal-appearing or widened joint space secondary to synovitis
Stage II: joint space narrowing and osteophyte formation smaller than 2 mm
Stage III: joint space narrowing with osteophytes larger than 2 mm
Stage IV: stage III appearance with the addition of narrowing or osteophytes in the scaphotrapezial joint
The scaphotrapezoid joint is not specifically addressed in this system and may be difficult to assess radiographically, but this joint should always be assessed at the time of surgery because it may be a source of continued pain.
DIFFERENTIAL DIAGNOSIS
Thumb CMC arthrosis
DeQuervain disease
Trigger thumb or stenosing tenosynovitis
Carpal tunnel syndrome
Intramuscular (thenar) processes, such as vascular or tumor etiologies
NONOPERATIVE MANAGEMENT
Most patients with symptomatic thumb CMC joint arthrosis benefit from a trial of conservative therapy, which may include corticosteroid injection, thenar isometric strengthening exercises, and splinting.1
Although this will not eliminate the problem or alter the underlying disease process, it often reduces symptoms, at least transiently, allowing the patient the opportunity to plan for surgical treatment at the most opportune time.
Steroid injections can also be helpful in determining how much of a patient's symptoms are coming from the thumb CMC joint versus other areas (carpal tunnel or De Quervain disease).
SURGICAL MANAGEMENT
The indications for surgical intervention for symptomatic thumb basilar joint arthrosis include pain and weakness not responsive to conservative treatments.
There are multiple procedures used to treat symptomatic CMC thumb arthritis, many of which have merit depending on several factors. Consideration should be given to the age of the patient and the demands placed on the thumb (specifically looking at the patient's occupation) as well as the radiographic stage and the condition of surrounding joints.
The best candidates for thumb CMC arthrodesis are young, active patients who need to maintain power grip and pinch, and regularly place high demand on their thumb. These are typically young male manual laborers with stage II or III disease.
Special consideration should be given to the thumb MCP joint. If hyperextension and laxity are present, arthrodesis of the CMC joint is not an appropriate option, because fusion of both the thumb CMC and MCP joints will result in significant functional impairment.
Pan-trapezial involvement represents a contraindication for CMC arthrodesis because of the risk of incomplete pain relief.
Preoperative Planning
The patient should be made aware of the decreased mobility, inability to flatten the palm on the table, potential difficulty in placing the hand in tight confined spaces, and possible difficulty placing the hand in a glove.
Patients also should understand the risks of nonunion, potential for hardware complications, and potential for developing degenerative changes at adjacent joints.
Positioning
The procedure is performed under regional or general anesthesia with the use of a pneumatic tourniquet.
The patient is in supine position with the arm extended on an armboard.
Approach
The procedure can be performed through a Wagner-type incision, along the junction of the glabrous and dorsal skin, or through a dorsal incision.
The dorsal incision can be oriented in a longitudinal fashion, along the radial aspect of the first dorsal compartment tendons, or in a transverse direction, with the incision oriented in the resting skin tension lines centered over the trapeziometacarpal joint.
TECHNIQUES
THUMB CMC (TRAPEZIOMETACARPAL) ARTHRODESIS
Incision and Dissection
Make a dorsal longitudinal incision along the radial aspect of the first dorsal compartment tendons (TECH FIG 1A).
Identify and protect sensory branches of the radial nerve and the lateral antebrachial cutaneous nerve (TECH FIG 1B).
Identify the first dorsal compartment tendons and release the compartment along the ulnar aspect to allow for better exposure (TECH FIG 1C).
Identify the dorsal branch of the radial artery deep to the abductor pollicis longus and extensor pollicis brevis tendons running in a dorsal and ulnar direction (TECH FIG 1D). Carefully mobilize and protect it.
Identify the base of the metacarpal, and complete a longitudinal capsulotomy to expose the base of the metacarpal, the entire trapezium, and the distal aspect of the scaphoid.
Fluoroscopy is used to confirm the location of the CMC joint if necessary.
Preparation of the Joint
Inspect the scaphotrapeziotrapezoid joints (TECH FIG 2A).
If there is evidence of arthrosis, consideration is given to alternative procedures.
Then inspect the CMC joint (TECH FIG 2B).
By freeing the surrounding capsular attachments, the base of the metacarpal can be flexed to allow better access to the joint.
Use a rongeur to remove osteophytes (TECH FIG 2C), any remaining articular cartilage, and subchondral bone. Shape the metacarpal base in a cone fashion to provide a larger surface area and greater freedom for obtaining the ideal position for arthrodesis (TECH FIG 2D).
Decorticate the distal aspect of the trapezium in a similar fashion, creating a cup for placement of the prepared metacarpal base.
Positioning and Fixation
The position for arthrodesis should allow the tip of the thumb to rest against the radial aspect of the index middle phalanx when the hand is placed in the fisted position.
The exact angles to accomplish this position are debated, but in general there should be about 45 degrees of palmar abduction and adequate pronation to allow positioning.
Place three 0.045-inch smooth Kirschner wires through the decorticated metacarpal base in a antegrade manner, exiting the dorsal aspect of the metacarpal until the tip of the wires are just beneath the prepared proximal metacarpal (TECH FIG 3A).
TECH FIG 1 • A. Surgical outline for the longitudinal incision along first dorsal compartment. B. Surgical incision with identification of the radial sensory nerve. C. Release of the first dorsal compartment with exposure of the abductor pollicis longus and the extensor pollicis brevis tendons through an incision along dorsal ulnar aspect (retinaculum is held in forceps). D. Identification of the radial artery deep to the first compartment tendons (tendons are retracted to volar).
TECH FIG 2 • A. Inspection of the scaphotrapeziotrapezoid (STT) joint for arthrosis (probe is in the scaphotrapezial joint). B. Exposure of the carpometacarpal (CMC) joint (forceps are around trapezium and probe is in CMC joint). C. Closeup view of small dorsal osteophyte along base of thumb metacarpal. D. View of the CMC joint after removal of articular cartilage in preparation for arthrodesis.
The metacarpal is then aligned with the trapezium, properly positioned, and compressed with axially directed force (TECH FIG 3B).
Advance the Kirschner wires retrograde across the joint into the trapezium, anchoring in the subchondral bone.
The wires can be advanced into the carpus (TECH FIG 3C).
Fluoroscopy is used to confirm reduction and Kirschner wire placement (TECH FIG 3D). If there is inadequate bony apposition, distal radius bone graft can be harvested and used to fill any voids.
Close the capsule with a nonabsorbable suture and close the skin with buried absorbable sutures.
Bend the Kirschner wires and cut them external to the skin.
If mild thumb MCP joint hyperextension is noted at this juncture, pin the MCP joint in 20 degrees of flexion. If dynamic collapse accompanies pinch, then perform volar capsulodesis.
Apply a well-padded short-arm thumb spica splint.
TECH FIG 3 • A. Preliminary placement of Kirschner wire to check alignment before compression of the arthrodesis site. B. Final inspection of the prepared surfaces before compression and advancement of the Kirschner wires across site of arthrodesis. C. Appearance of the arthrodesis site after compression and advancement of the Kirschner wires. D. Radiograph of the thumb carpometacarpal arthrodesis with the Kirschner wires in place.
VARIATIONS
Bony Preparation
Rather than the “cup and cone” technique, an oscillating saw can be used to create two flat surfaces that can be apposed, allowing a large contact area.
Make the cuts in the exact plane desired, or the position of the thumb will be compromised.
This is a much less forgiving technique than the cup and cone method, which allows for correction by rotation of the metacarpal while positioning it on the trapezium.
Fixation Devices
Single or multiple smooth Kirschner wires, tension band wiring, cerclage wiring, staples, compression screws, and plates and screws have all been used with documented success.
Union rates are comparable for Kirschner wires and more rigid fixation devices, but plates and screws result in a higher rate of additional procedures, typically due to hardware prominence or tendon irritation.
Kirschner wires are associated with the fewest complications and are the simplest method of fixation.
FIG 2 • Final radiograph, demonstrating fusion of the carpometacarpal joint.
POSTOPERATIVE CARE
The patient is seen in the office at 10 to 14 days to check the wound and the Kirschner wires and to obtain radiographs.
If fixation is secure and the Kirschner wires are not advanced through the trapezium, a well-molded short-arm thumb spica splint is applied and removed for hygiene purposes only. If the Kirschner wires are advanced into the carpus, the patient is placed in a thumb spica cast.
If there is any concern about fixation, a short-arm thumb spica cast is applied and the patient is seen at 2to 3-week intervals until clinical tenderness subsides and there is radiographic evidence of fusion (FIG 2). This typically occurs by 6 to 8 weeks after surgery.
Once healing is documented, the pins are removed and range-of-motion exercises are begun under the direction of a hand therapist. The splint is continued for protection.
At 3 months, strengthening exercises are begun, the splint is discontinued, and the patient is allowed to return to unrestricted activities.
OUTCOMES
The outcomes of trapeziometacarpal arthrodesis are generally good, with predictable pain relief and patient satisfaction.
Hartigan et al5 retrospectively reviewed patients who had arthrodesis and compared them to those having trapezial excision and ligament reconstruction. At 6 to 9 months there were no significant differences in pain, function, patient satisfaction, or grip strength. The arthrodesis group had greater key pinch and three-point pinch but more difficulty with opposition and the ability to flatten the hand, all of which were statistically significant. The arthrodesis group also had a higher complication rate, most of which was attributable to nonunion. Interestingly, all patients with nonunion had improvement in their pain and were satisfied with their outcomes.
Forseth and Stern4 compared the complication rate with Kirschner wire fixation to that with plates and screws and found similar nonunion rates (less than 10% in their small series), but there were higher rates of secondary procedures and lower patient satisfaction in the plate and screw group.
Despite Hartigan et al's report, which found that the ligament reconstruction and tendon interposition (LRTI) arthroplasty and arthrodesis resulted in high levels of patient satisfaction, Mureau et al7 found less subjective improvement with arthrodesis in comparison to arthroplasty and no significant differences in pinch strength. They also found a higher incidence of complications in the arthrodesis group.
COMPLICATIONS
Complications from thumb CMC arthrodesis are generally related to nonunion or hardware problems, including malposition (screws in the trapeziotrapezoid joint), prominence and tendon irritation, and rupture.
The patient should be made aware of the possible need for secondary procedures.
REFERENCES
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