THE RHEUMATOID THUMB BY ANDREW L. TERRONO, MD The thumb is frequently involved in patients with rheumatoid arthritis. Thumb postures can be grouped into a number of deformities. Deformity is determined by a complex interaction of the primary joint, the adjacent joints, and tendon function and integrity. Joints adjacent to the primarily affected one usually assume an opposite posture. If they do not, tendon ruptures should be suspected. Surgical treatment is individualized for each patient and each joint, with consideration given to adjacent joints. The treatment consists of synovectomy, capsular reconstruction, tendon reconstruction, joint stabilization, arthrodesis, or arthroplasty. Copyright © 2001 by the American Society for Surgery of the Hand he majority of patients with rheumatoid ar- ring between the various joints. Any alteration of thritis will develop thumb involvement.1,2,3 posture at one level has an effect on the adjacent joint. TThe deformities encountered in the rheuma- The 6 patterns of thumb postures described here, toid patient are varied and are the result of changes unfortunately, do not exhaust the deformities one taking place both intrinsically and extrinsically to the encounters in rheumatoid arthritis (Table 1). It is thumb. Synovial hypertrophy within the individual possible, for example, for the patient to stretch the thumb joints leads not only to destruction of articular supporting structures of a joint, causing a flexion, cartilage, but can also stretch out the supporting extension, or lateral deformity. However, instead of collateral ligaments and joint capsules. As a result, the adjacent joint assuming the opposite posture, it each joint can become unstable and react to the may assume an abnormal position secondary to a stresses applied to it both in function against the other tendon rupture. Thus, a patient might have hyperex- digits or as a result of the deforming forces of the tension of both the metacarpophalangeal (MP) and extensor or flexor tendons acting on it. The thumb interphalangeal (IP) joints or flexion at both levels. deformity patterns are the result of imbalances occur- When patients are encountered with adjacent joints deformed in the same direction, it usually implies that a combination of factors have brought about this From the Department of Orthopaedic Surgery, New England Baptist situation. The examiner should check each individual Bone & Joint Institute, New England Baptist Hospital, Hand Surgical Associates, Boston, MA. joint for instability and tendon function. Address reprint requests to Andrew L. Terrono, MD, Associate Disruption of the normal thumb biomechanics of- Clinical Professor, Tufts University School of Medicine, Depart- ten leads to significant loss of the patient’s ability to ment of Orthopaedic Surgery, New England Baptist Bone & Joint carry out activities of daily living (ADL). Activities Institute, New England Baptist Hospital, Hand Surgical Associ- ates, 125 Parker Hill Ave, Boston, MA 02120. E-mail: such as buttoning clothing or manipulating small [email protected] objects are difficult to accomplish if the patient lacks either control or stability of the thumb joints. Surgery Copyright © 2001 by the American Society for Surgery of the Hand 1531-0914/01/0102-0004$35.00/0 can improve thumb function and represents one of the doi:10.1053/jssh.2001.23906 most effective procedures for patients with rheuma- JOURNAL OF THE AMERICAN SOCIETY FOR SURGERY OF THE HAND ⅐ VOL. 1, NO. 2, MAY 2001 81 82 THE RHEUMATOID THUMB ⅐ TERRONO TABLE 1 Rheumatoid Thumb Deformities Type CMC Joint MP Joint IP Joint I (Boutonniere) Not involved Flexed Hyperextended II (Uncommon) CMC flexed and adducted Flexed Hyperextended III (Swan neck) CMC subluxed, flexed, and Hyperextended Flexed adducted IV (Gamekeeper’s) CMC not subluxed, flexed, 1°, Radially deviated, ulnar Not involved and adducted collateral ligament unstable V May or may not be involved 1°, Hyperextended, volar plate Not involved unstable VI (Arthritis mutilans) Bone loss at any level Bone loss at any level Bone loss at any level toid arthritis. The goals of thumb surgery for patients the base of the proximal phalanx. The extensor pollicis with rheumatoid arthritis are pain relief, enhanced longus (EPL) tendon displaces ulnarly and volar to the function, prevention of disease progression and im- axis of rotation (Fig 2). The patient loses the ability to proved appearance.3,4 Before discussing treatment, a actively extend the MP joint, although passive exten- review of the most common thumb deformities and sion may be maintained early on. At the same time, factors leading to their development will be high- articular erosion and collateral ligament laxity occur lighted. to varying degrees. Hyperextension of the IP joint is the result of the TYPE 1(BOUTONNIERE DEFORMITY) altered pull of both the intrinsic muscles and the EPL and occurs secondarily.5 Each time the patient pinches The boutonniere deformity is the most common the thumb, a cycle of MP joint flexion and IP joint rheumatoid thumb deformity.5 This consists of MP hyperextension is initiated.5,6 In time, the IP joint joint flexion and IP joint hyperextension (Fig 1). The deformity approximates the MP joint deformity, and pathology in this deformity usually starts with MP the result is often a 90°/90° deformity.5,6 joint synovitis stretching the dorsal capsule.5 The Other less common mechanisms for a boutonniere overlying extensor hood and extensor pollicis brevis thumb deformity include MP flexion secondary to (EPB) tendon insertion become attenuated, resulting rupture of the EPL tendon at the wrist and IP hyper- in loss of MP joint extension and volar subluxation of extension from volar plate stretching or rupture of the flexor pollicis longus (FPL) tendon. After EPL func- tion is lost, the MP joint assumes a flexed position and the cycle is started. Stretching of the volar plate of the FIGURE 1. This is an example of a boutonniere thumb de- FIGURE 2. This is an example of a type I thumb deformity formity with MP joint flexion and IP joint hyperextension. with EPL tendon subluxation ulnarly and volarly. THE RHEUMATOID THUMB ⅐ TERRONO 83 distal joint or rupture of the FPL tendon causes IP joint hyperextension. In this case, the distal joint hyperextension can be primary, and MP joint flexion is secondary. Therefore, when faced with a patient having a type I deformity, one should evaluate the extensor tendons controlling the MP joint and also the flexor tendon controlling the distal joint to determine the primary site of imbalance. Usually the joint with the most deformity is the joint that initiated the deformity. Treatment includes MP joint synovectomy and increasing the extensor force (EPL rerouting) for early correctable deformities or MP fusion or arthro- plasty for late involvement. Capsulodesis/sesamoidesis FIGURE 3. This is an example of a swan neck deformity with is used for MP joint hyperextension deformities with CMC joint subluxation, narrowed first web space, MP joint good flexion, and ligament reconstruction is used for hyperextension, and IP joint flexion. lateral deformities as needed. Hyperextension of the MP joint results from a com- TYPE II AND TYPE III DEFORMITY bination of volar plate laxity and the metacarpal ad- duction/flexion contracture. Metacarpal abduction and In the original classification of thumb deformities, extension become limited with a fixed CMC joint type II and type III deformities were described.5 In deformity. Thus, as the patient attempts to open the both, the deformity starts at the carpometacarpal first web space to grasp an object, the extension forces (CMC) joint with subluxation of the first metacarpal, are transmitted to the MP joint, resulting in the which then assumes an adducted and flexed position. secondary hyperextension deformity of this joint. In the type II deformity the MP joint and IP joint Any attempt to correct the type III deformity re- assume positions identical to the type I deformity in quires that the first metacarpal adduction be cor- that the MP joint is flexed and the distal joint hyper- rected. If the CMC joint is subluxed, abduction usu- extended. This particular combination of metacarpal ally can be accomplished only by salvage surgery. adduction with MP joint flexion and distal joint hy- With restoration of metacarpal abduction, the MP perextension (type II) is not common and assumes joint hyperextension deformity may correct itself. importance only in that it should be recognized as However, if hyperextension persists, this joint also different from the type I deformity because of the must be treated—by capsulodesis, sesamoidesis,9 or CMC involvement and subsequent metacarpal adduc- arthrodesis (if fixed deformity or minimal active flex- tion. ion is present)— in a slightly flexed position. A much more common sequence of events after CMC joint subluxation and metacarpal flexion and TYPE IV DEFORMITY adduction is MP joint hyperextension and distal joint flexion (type III) (Fig 3). This deformity is the oppo- The type IV, or gamekeeper’s, deformity results site of the common type I deformity in all respects. It from stretching out of the ulnar collateral ligament of has been called a swan neck deformity of the thumb.5 the MP joint from synovitis7 (Fig 4). As the proximal In the type III deformity synovitis and articular phalanx deviates laterally at the MP joint, the first erosion occur initially at the CMC level. Dorsoradial metacarpal secondarily assumes an adducted position. subluxation and eventually dislocation occurs as the Subsequently, the first dorsal interosseous and adduc- thumb is pinched during daily activities. With the tor muscles may become shortened and the web space metacarpal base subluxed radially, the abduction between the thumb and index finger may become forces are reduced and a progressive adduction and contracted. Although the first metacarpal is adducted flexion contracture of the metacarpal develops. in these patients, there is no subluxation at the CMC As the CMC joint subluxation progresses, the like- joint.