Arthroscopic Resection of Distal Scaphoid and Tendon Interposition for Isolated Scaphotrapeziotrapezoid Arthritis

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RATIONALE FOR THE PROCEDURE

Basal thumb arthritis may involve one or both of the trapeziometacarpal (TM) or scaphotrapeziotrapezoid (STT) joints. STT arthritis is more commonly associated with TM arthritis. Isolated STT arthritis is reported to occur in 2% to 16% of the population.

The recalcitrant painful degenerate STT joint may be treated with STT fusion, open excision of the distal scaphoid with or without interposition of soft tissue, silicon, or pyrocarbon. Although STT fusion is effective for pain relief, it may be associated with nonunion, wrist stiffness, radial styloid impingement, and secondary degenerative arthritis of the radioscaphoid or TM joints. The reported complication rates vary from 13% to 53%. Open excision of the distal scaphoid with or without soft tissue interposition has similarly resulted in pain relief; however, there has been some concern about the possible development of a nondissociative dorsal intercalated segmental instability (DISI) pattern in these wrists.

Excision of the distal scaphoid for treatment of STT arthritis appealed as a treatment modality because it negated the risks of nonunion associated with STT fusion (with a reported incidence between 4% and 25%), retained STT motion, and allowed load sharing through the base of the thumb if an interposition material was inserted into the created space. The joint reactive forces across the basal thumb joints may be 13 to 15 times that of the grip strength. Open excision of the distal scaphoid disrupts the palmar STT ligaments and perhaps also the distal limb of the dorsal intercarpal ligament. It is becoming increasingly clear that the integrity of the palmar STT ligaments and the dorsal intercarpal ligaments plays a role in carpal stability. Garcia-Elias and associates reported the development or worsening of a DISI pattern of carpal malalignment in 12 of 21 patients after distal scaphoid excision through either a dorsolateral or palmar approach after a mean follow-up of 29 months. Similar concerns have been raised by Ashwood and associates and Tay and coworkers.

The capsuloligamentous complex of the STT joint has been well described. Our anatomic dissections showed that the capsuloligamentous complex of the STT joint is attached to the proximal margin of the trapezium and trapezoid distally, but that it is attached up to 4 to 5 mm proximal to the distal articular surface of the scaphoid ( Fig. 42-1 ). Arthroscopic resection of the articular surface of the distal pole of the scaphoid can preserve these important palmar ligaments including the subsheath of the flexor carpi radialis if the resection is confined to the articular surface distal to the capsuloligamentous attachment.

The arthroscopic portals used for assessment of the STT joint are well documented and include the radial midcarpal portal (between the extensor carpi radialis brevis and extensor digitorum communis tendons) and the dorsal STT portals (between the extensor pollicis brevis [EPB] and extensor pollicis longus [EPL] tendons or between the EPL and the extensor carpi radialis longus tendons). Since the normal scaphoid posture is that of flexion, the STT joint is located palmar to the coronal axis of the radiocarpal joint. For this reason, arthroscopic visualization of the STT joint from a dorsal portal, particularly the radial midcarpal portal, is limited to the dorsal surface of the joint ( Fig. 42-2 ). We have experienced difficulty establishing the dorsal STT portal because of the lack of defined anatomic landmarks.

A palmar portal has been described to take advantage of the flexed position of the scaphoid and STT joint. We have found this portal to the STT joint easier to establish because of the palpable anatomic landmarks, and it has improved our visualization of the joint except for the dorsal articular surface of the scaphoid ( Fig. 42-3 ). This portal, together with the dorsal radial midcarpal and dorsal STT portals, established with an inside-out technique, are our working portals for arthroscopic resection of 2 to 3 mm of the distal scaphoid articular surface and insertion of a tendon spacer without disrupting the soft tissue stabilizers of the STT joint.

INDICATIONS

Isolated STT joint arthritis is uncommon, and its diagnosis may be considered because of pain arising from the palmar and radial aspects of the wrist. In the diagnostic workup, arthritis of the TM joint must be excluded. If the radiologic investigations of the TM joint are normal—including radiographs and computed tomography—but clinical examination points to tenderness at the TM joint, it is our experience that arthroscopy of the joint will show at least a grade 2 chondromalacia and often small areas devoid of articular cartilage. For patients to be considered for an arthroscopic excision of the distal scaphoid, the TM joint should be clinically and radiographically free of degenerative disease. We do not routinely evaluate the TM joint arthroscopically in these groups of patients.

We recommend routine radiographs of both the basal thumb joint and the wrist, since there is an association between STT arthritis and a DISI malalignment of the wrist. We would be very cautious about recommending this procedure for patients with radiolunate angles greater than 15 degrees, since there is a risk of worsening this angle after distal scaphoid excision.

Diagnostic arthroscopy of the STT joint can be considered when radiologic investigations are inconclusive. In these cases with early arthritis, arthroscopic debridement alone may result in symptom relief.

CONTRAINDICATIONS

Once obvious radiologic changes are present, our experience with arthroscopic debridement of the STT joint has not been very rewarding.

As with all surgical procedures for degenerative arthritis, a reasonable trial of conservative management should be considered before surgery, and it includes one or a combination of activity modifications, anti-inflammatory medication, resting splint, and cortisone injection.

SURGICAL TECHNIQUE

The position of the patient for STT arthroscopy is similar to that for wrist arthroscopy with the patient supine and with the use of traction. More recently, we have used a finger trap to the thumb alone. There must be open access to both the palmar and dorsal surfaces of the wrist.

The palmar portal to the STT joint is identified by first palpating for the prominent scaphoid tubercle by alternately radially and ulnarly deviating the wrist ( Figs. 42-4 and 42-5 ). The scaphotrapezial joint is usually easily palpated just distal to the scaphoid tubercle with the wrist slightly ulnar-deviated, since it causes the scaphoid to extend and diminishes the prominence of the scaphoid tubercle. A 25-gauge needle is inserted into the scaphotrapezial joint ulnar (palmar) to the abductor pollicis longus tendon. The joint is inflated with irrigation fluid. It is important to note the direction of entry of the needle before its removal. A small longitudinal skin incision is made and soft tissue dissection performed with a hemostat to the capsule. A 1.9-mm trocar and cannula are inserted in a direction similar to that of the 25-gauge needle directed toward the fifth carpometacarpal joint. Unlike the palmar portal to the wrist, there is no interligamentous plane at the STT joint.