[[$INHEADTAG]]Copyright © 1999 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective by Hill Hastings II, MD*,
Department of Orthopaedic Surgery, Indiana University Medical Center, Indianapolis, Indiana
Currently there are no reconstruction methods for the treatment of painful arthritic deformity of the trapeziometacarpal joint that can restore normal function. The normal joint achieves the seemingly impossible combination of unusual motion and stability through its unique saddle-shaped anatomy and supporting ligaments. Rotatory motion derives from a combination of translation and axial motion. In opposition, rotation occurs automatically as the result of the force couple formed between opposing opposition muscles and the restraint of the radiovolar or beak ligaments1,2. Resection of the trapezium with ligament reconstruction and tendon interposition invariably leads to shortening (approximately 43%) of the trapezium from its original height3. Furthermore, this procedure fails to restore normal kinematics to the basilar joint. The normal instantaneous center of rotation is shifted such that the center of flexion-extension is shifted palmarly and the center of abduction-adduction is shifted ulnarly1. Fusing the joint fixes it in a balanced position, which results in dependence upon the surrounding joints for motion.
There are numerous treatment options for instability and painful trapeziometacarpal arthrosis. These include tenotomy of the accessory tendons4; extension osteotomy of the first metacarpal5; ligament reconstruction for instability without severe arthrosis6; ligament reconstruction without tendon interposition; replacement arthroplasty; and the two methods reported here, ligament reconstruction with tendon interposition (LRTI)7 and arthrodesis8. The last two are the most commonly used and, accordingly, the most important to compare.
Both ligament reconstruction with tendon interposition and arthrodesis are procedures that attempt to eradicate pain, the single most important factor and indication for surgery. Both must address the high loads that the trapeziometacarpal joint experiences, which approach ten times the tip pinch force of the thumb1. Resection removes painful joint contact and may provide improved or preserved motion through the resultant increased space. Fusion definitively repositions the thumb metacarpal from its flexed and adducted position and removes motion as a source of pain.Variables That May Have Influenced Treatment Selection and Functional Results
Several variables may have affected the choice of procedure. First, severe pantrapezial deformity cannot be treated by trapeziometacarpal arthrodesis alone. The scaphotrapezial joint must be free of significant arthritic involvement. Radiographs do not fully reveal the severity of disease at both the trapeziometacarpal and scaphotrapezial joints9. True arthritic involvement, which might preclude arthrodesis, however, is less common than radiographs may suggest. When arthritis affected the trapeziometacarpal joint, North and Eaton found concomitant radiographic arthritis at the scaphotrapeziotrapezoid joint 73% of the time10 but anatomic pantrapezial arthritis in only 46% of the same specimens. Some of the patients treated in this study with ligament reconstruction and tendon interposition could not have been treated with arthrodesis because of pantrapezial involvement.
Long-standing deformity typically leads to an adduction and flexion deformity of the first metacarpal and compensatory hyperextension of the metacarpophalangeal (MCP) joint. Intraoperative assessment of the metacarpophalangeal joint should be performed following resection arthroplasty. When the metacarpophalangeal joint hyperextends more than 15º, volar capsulodesis is needed to prevent the hyperextended joint from postoperatively levering the metacarpal into a flexion deformity. Volar capsulodesis, when performed with resection arthroplasty will affect the final range of motion. When trapeziometacarpal arthritis is associated with an arthritic hyperextension of the metacarpophalangeal joint, that joint must be fused in 20º to 30º of flexion in order to maintain a similar proper balance at the thumb carpometacarpal (TMC) joint. Capsulodesis or arthrodesis of the metacarpophalangeal joint will further prevent the thumb from compensating for the motion lost in the thumb carpometacarpal arthrodesis. In this situation, resection arthroplasty also is necessarily a better treatment choice.Expected Outcomes Following These Procedures
Most surgeons have felt that resection with ligament reconstruction and tendon interposition (LRTI) offers better motion but less predictable strength than does arthrodesis, which achieves better strength at the expense of motion. If one accepts this assumption, as I have in the past, it follows that one will usually advise LRTI for older patients with lesser strength demands and those with significant arthritic change at the scaphotrapezial joint and one will recommend fusion for patients with maximum strength demands and those with surrounding joints free of significant arthritic involvement. This paper provides important information to evaluate more accurately this very basic assumption. It suggests that both treatment recommendations following from this assumption are essentially incorrect.
There is little difference between the functional results of arthroplasty and those of arthrodesis. Both procedures provide comparable pain relief, functional improvement, time of return to work, overall patient satisfaction, and tip pinch strength. Motion was marginally better following arthroplasty, and lateral pinch strength was better after fusion. This has also been reported in similar but smaller studies. Peng, Low, and Looi reported that arthrodesis on one side and arthroplasty on the other provided equal pain relief in a single patient with bilateral primary osteoarthritis of the first carpometacarpal joint11. Amadio and DeSilva found that the choice of procedure—resection, arthroplasty, or arthrodesis—had little effect on strength and patient satisfaction in forty-seven thumb reconstructions performed in thirty-five men with disabling trapeziometacarpal osteoarthritis12. Two patients had arthrodesis on one side and arthroplasty on the other, with no reported difference in functional outcome between the two sides.
Complications are twice as common with arthrodesis as with ligament reconstruction with tendon interposition and most consist of nonunion. The literature also indicates a nonunion rate of nearly 50% after arthrodesis of the thumb metacarpophalangeal joint, yet few persistent symptoms despite nonunion.How Do We Minimize the Complications of Nonunion?
The difficulty in obtaining union arises from the long lever arm and high forces in the thumb that lead to micromotion. Kirschner wires have been shown to be far less effective than a 2.0-mm condylar plate. Tension-band wiring makes little sense, at least when performed dorsally, since there is not a consistent tension or compression side of the thumb metacarpophalangeal joint. In active flexion, the dorsal aspect of the thumb metacarpophalangeal joint experiences tension. When pressure is applied to the palm to flatten the thumb into retroposition, the palmar side experiences tension and may gap. Kirschner wires, dorsal tension-band wires, and even a fairly weak 2.0-mm condylar dorsal plate may not resist such passive extension forces. I have found that a 2.7-mm condylar plate is more appropriately suited to the task. In addition, fixation should also be attempted to lag the palmar portion of the joint. This is most easily achieved with use of a separate screw inserted dorsoradially and directed palmarly and ulnarly, which substantially inhibits volar gapping of the joint (Figs. 1-a and 1-b.). Matching, crescent-shaped, decorticated surfaces provide better contact than do flat, opposing surfaces.
Figure 1-a. Anteroposterior radiograph of the thumb metacarpophalangeal joint in hyperpronation, after TMC arthrodesis with a 2.7-mm condylar plate. Note the screw inserted dorsoradially and directed palmarly and ulnarly, to provide added palmar resistance to gap formation.
Figure 1-b. Lateral radiograph of thumb metacarpophalangeal fusion.The Bottom Line: So How Should We Choose?
When the scaphotrapeziotrapezoid and/or metacarpophalangeal joints are arthritic, ligament reconstruction with tendon interposition is clearly, in my opinion, a more reasonable choice of treatment than arthrodesis. In the absence of arthritic involvement of the metacarpophalangeal and scaphotrapeziotrapezoid joints, both methods of reconstruction are comparable. Until we have a more anatomic reconstruction, I believe that the results allow for choice according to individual surgeon preference. With improved and more predictable fixation techniques, I would opt for an arthrodesis when repetitive motions and high forces are expected.
*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.
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