Arthroscopic treatment of trapeziometacarpal osteoarthritis

Biomechanics and anatomy

One longitudinal radiographic study of 751 patients over a 24-year period showed that in those without osteoarthritis (OA) at baseline, women had more incidence of disease than men in almost all hand joints, but the joints most frequently affected were the same in both sexes: the distal interphalangeal (DIP), followed by the base of the thumb. In another radiographic study of 3327 men and women between the ages of 40 and 80 +, 21% had involvement of the trapeziometacarpal (TM) joint. The age-adjusted prevalence of carpometacarpal (CMC) arthritis based on radiographic evidence has been reported to be 15% for the female population and 7% for the male population. The prevalence increases to 33% for the postmenopausal female population.

OA is not merely a wear-and-tear or age-related phenomenon; it is a common disease of articular cartilage that becomes more prevalent with advancing age. The deep anterior oblique ligament (dAOL) and the dorsoradial ligament (DRL) have been shown to be the principal checkreins to dorsal subluxation during physiologic motion of the TM joint. During key pinch, the incongruity of the articular surfaces causes apex loading on the volar articular surface of the trapezium, which transmits loads that are as high as 13 times the joint reactive force. In a biomechanical study, Cooney and Chao demonstrated that a pinch force of 1 kilograms at the thumb tip was amplified to 3.68 kilograms at the interphalangeal (IP) joint, 6.61 kilograms at the metacarpophalangeal (MCP) joint, and up to 13.42 kilograms at the TM joint. The typical joint compression forces averaged 3 kilograms of force at the IP joint, 5.4 kilograms at the MCP joint, and 12.0 kilograms at the TM joint during simple pinch. Compression forces of as much as 120 kilograms can occur at the TM joint during strong grasp. Because of the repeated eccentric loading, osteoarthritic changes begin volarly. Any laxity or incompetence to the anterior oblique ligament (AOL) allows this fulcrum to move dorsally and adds to the eccentric force concentration. The alterations in the contact forces, which may occur after injury or surgery to the TM joint due to ligamentous insufficiency, can lead to even higher forces that can accentuate the wear on the articular cartilage. Posttraumatic OA can also be seen after malreduced intraarticular fractures or sepsis.

Imaeda et al. from the Mayo clinic biomechanics lab dissected the TM joint of 30 cadaver specimens and described the anatomy and properties of three major ligaments. Bettinger et al. from the Mayo group revisited this and further described 16 ligaments stabilizing the TM joint. The AOL is a two-part ligament that consists of a superficial portion and an intraarticular deep portion. The superficial anterior oblique capsular ligament (sAOL) is immediately deep to the thenar musculature, which overlies the volar aspect of the TM joint and is superficial to the dAOL. The ligament originates 0.5 mm proximal to the articular surface at the volar tubercle of the trapezium, and inserts broadly over the volar ulnar tubercle of the thumb metacarpal base, 2 mm distal to the volar styloid process. The sAOL is lax throughout most of the TM range of motion and becomes taut at the extremes of thumb pronation and extension. In a biomechanical study of 17 cadaver hands, Colman et al. found that the broad, loose, and curtainlike superficial portion of the ligament plays only a minor role in joint stability, does not prevent dorsal metacarpal subluxation, and limits the joint’s motion only in pronation.

The dAOL, formerly known as the volar beak ligament, is an intraarticular ligament that lies deep to the sAOL. It originates from the volar central apex of the trapezium, ulnar to the ulnar edge of the trapezial ridge, and inserts into the articular margin ulnar to the volar styloid process (volar beak) of the thumb metacarpal base. The dAOL becomes taut with increasing thumb abduction, pronation, and extension. Colman et al. found the intraarticular dAOL to be a major stabilizer of the joint. Because it is the closest ligament to the center of the joint, it acts as a pivot point to guide the metacarpal during the pronation that occurs as a part of thumb opposition. Its intraarticular fibers run obliquely from distal-ulnar to proximal-radial; thus this ligament is positioned to prevent an ulnar shift of the metacarpal, which would tighten the oblique fibers whereas a radial shift would slacken them. The sulcus between the sAOL and dAOL can often be palpated with an arthroscopic probe. Fenestrations of tears of the AOL permit arthroscopic views of the flexor carpi radialis (FCR).

The ulnar collateral ligament (UCL) is an extracapsular ligament that is slightly ulnar to and superficial to the sAOL. It originates from the flexor retinaculum, then runs obliquely from a palmar-proximal position and attaches to the palmar-ulnar tubercle of the first metacarpal base. It is taut in extension, abduction, and pronation, and helps prevent volar subluxation of the metacarpal base. Arthroscopically, it is identified by its oblique fibers running ulnarly to the AOL. Tears of the UCL will reveal the thenar muscle fibers that run behind it.

The dorsal aspect of the thumb is covered by two main ligaments. The posterior oblique ligament (POL) is an intracapsular ligament that originates from a fan-shaped base on the dorsoulnar side of the trapezium immediately ulnar to the DRL. It runs obliquely to insert into the dorsoulnar aspect and palmar-ulnar tubercle of the first metacarpal base. This ligament is taut at the extremes of abduction, opposition, and supination, which prevent ulnar translation of the thumb metacarpal base during opposition and abduction.

The DRL is the shortest, thickest, and widest ligament that spans the joint. The DRL is a fan-shaped capsular ligament that arises from the dorsoradial tubercle of the trapezium and has a broad insertion into the dorsal base of the thumb metacarpal. It is believed to be the most important stabilizer that resists dorsal translation of the thumb metacarpal base and is a checkrein against radial subluxation. In a biomechanical study by Bettinger et al. the ultimate load to failure of the DRL (205.5 ± 60.2 N) was significantly greater than the other ligaments, which they believed was due to the size and bulk of the ligament. The stiffness for the DRL (78.3 ± 21.9 N/mm) was significantly higher than for the AOL (24.1± 13.3 N/mm), and therefore likely to be the most significant restraint to lateral dislocation. The AOL demonstrated the least stiffness and the greatest hysteresis, and was thought to be a poor stabilizer of the TMC joint.

Edmunds emphasizes the point that in the static resting position, the prominent volar beak of the thumb metacarpal is disengaged from its recess in the trapezium, the TM joint space is relatively large, and both the dAOL and the dorsal ligament complex are lax. In the final phase of opposition, during either active or passive screw-home torque rotation, the dorsal ligament complex tightens, the dAOL becomes even more lax and redundant, the TM joint is compressed, and the volar beak of the thumb metacarpal is tightly compressed into its recess area in the trapezium. This dynamic force couple changes the TM joint from incongruity to congruity and from laxity to rigid stability. It changes a normally lax TM joint into a stable TM joint to support the powerful forces on the thumb in power pinch and grasp. If the dorsal ligament complex is cut or torn (as occurs in a pure TM dislocation) gross instability of the TM joint results, and the joint dislocates even if the dAOL is intact.

Trapeziometacarpal joint portals ( video 25-1 )

Menon initially presented his work on arthroscopy of the TM joint at a meeting exhibit in 1994. He then published his experience with the arthroscopic management of TM arthritis in 1996. He described two working portals, a volar portal just radial to the abductor pollicis longus (APL) tendon and a dorsal portal that is just ulnar to the APL along the line of the joint. Berger independently developed his technique for arthroscopic evaluation of the first carpometacarpal joint, which he first presented as an instructional course in 1995. He then published his clinical work in 1997. He named the volar radial portal the 1-R portal and the dorsoulnar portal the 1-U ( Fig. 25.1 A–D). Orrellana and Chow described a modified radial portal (RP) for improving the radial view of the TM joint. The RP is located just distal to the oblique ridge of the trapezium following a line along the radial border of the FCR tendon rather than the APL ( Fig. 25.2 A–C). A thenar portal was subsequently described by Walsh et al. This portal is placed by illuminating the thenar eminence with the arthroscope in the 1-U portal, and then inserting an 18-gauge needle through the bulk of the thenar muscles at the level of the TM joint, approximately 90 degrees from the 1-U portal. Access to medial osteophytes may sometimes be difficult; hence I have found the use of a distal-dorsal (D-2) accessory portal to be of some value. Its main utility is that it allows one to look down on the trapezium rather than across it, which facilitates resection of medial osteophytes ( Fig. 25.3 A–E). This accessory portal allows views of the dorsal capsule (DC) with rotation of the scope, and it facilitates triangulation of the instrumentation. It is situated in the dorsal aspect of the first web space. An anatomical study of 5 cadaver hands revealed that the D-2 portal surface landmark is ulnar to the extensor pollicis longus (EPL) tendon and 1 cm distal to the V -shaped cleft at the juncture of the index and thumb metacarpal bases. The portal lies just distal to the dorsal intermetacarpal ligament (DIML). There is no true safe zone for the D-2 portal due to the first dorsal metacarpal artery and its branches, and branches of the superficial radial nerve (SRN); therefore wound-spread technique is paramount. Hugging the ulnar border of the thumb metacarpal and moving 1 cm distal to the thumb/index metacarpal juncture increases the space between the portal and the radial artery.

Diagnosis

The patient who presents with basal joint arthritis may complain of palmar-sided pain, which is frequently localized to the thenar eminence and may radiate up the radial wrist. Complaints of thumb weakness and clumsiness with fine manipulation tasks are common. On inspection, one may see a prominent TM joint due to lateral subluxation of the thumb metacarpal base with or without marginal osteophytes and synovitis. There is often a loss of joint motion, especially thumb retropulsion, and a contracted first web space that interferes with grasping large objects. MCP joint hyperextension may occur as an adaptive response to increase the first web space span. Thenar muscle weakness and atrophy due to misuse might be present. A concomitant carpal tunnel syndrome, however, should be sought by history of sensory loss in the median nerve distribution and through physical findings, which include a Tinel sign over the carpal tunnel, and a positive Phalen test or median nerve compression test. On palpation, the patient will often have tenderness localized to the TM joint and the scaphoid tuberosity, and a positive scaphoid shift test, but this may also occur with scapholunate (SL) instability or scaphotrapeziotrapezoidal (STT) OA, which should be ruled out. FCR tendinitis can also present with tenderness over the scaphoid tuberosity. The TM grind test will be positive in the face of TM OA and can help to distinguish these entities. The test is performed by applying an axial load to the thumb metacarpal combined with manipulation of the metacarpal in a dorsal and volar direction. A positive test produces variable degrees of crepitus and pain depending on the stage of arthritis. Alterations in grip and pinch strengths are documented to gauge the effects of treatment, but are nonspecific findings.

The radiographic evaluation of the thumb CMC joint includes a true anteroposterior (AP) view, which is performed by placing the forearm in maximum pronation with the dorsal aspect of the thumb resting on the radiograph table and taking a true lateral view. A radial stress view of the thumb can be performed by asking the patient to push the radial borders of their thumbs together. This can demonstrate the degree of joint laxity by the amount of lateral subluxation of the metacarpal base. Littler and Eaton described a radiographic staging classification of TM OA. Stage I comprises normal articular surfaces without joint space narrowing or sclerosis. Less than one-third subluxation of the metacarpal base might be present. Stage II reveals mild joint space narrowing, mild sclerosis, or osteophytes <2 mm in diameter. Instability is evident on stress views with greater than one-third subluxation. The STT joint is normal. In stage III, there is significant joint space narrowing, subchondral sclerosis, and peripheral osteophytes >2 mm in diameter but a normal STT joint. In stage IV there is pantrapezial OA with narrowing, sclerosis, and osteophytes involving both the TM and STT joints. Badia proposed a more specific classification based upon the arthroscopic changes. Stage I included intact articular cartilage, stage II included eburnation on the ulnar one-third of the metacarpal base and central trapezium, and stage III comprised widespread full-thickness cartilage loss on both surfaces.

Treatment