How are deformities of the metacarpophalangeal (MP) joint in rheumatoid arthritis (RA) treated?

Updated: Jun 11, 2021
  • Author: Michael Neumeister, MD, FRCSC, FACS; Chief Editor: Joseph A Molnar, MD, PhD, FACS  more...
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Conservative treatment is advised for RA of the MP joints to see if control can be gained with medication therapy alone. [4] Recurrence is always a possibility postsynovectomy, and approximately 30-50% of patients may undergo spontaneous remission. Synovectomy is indicated in the RA patient whose MP joint RA is refractory to 6-9 months of medical treatment and has persistent MP joint synovitis with minimal joint deformity and minimal radiographic evidence of RA. Additionally, extensor tendon relocation with synovectomy is indicated for an RA patient who also has early volar subluxation and ulnar drift, especially if the patient is young and the disease is not rapidly progressing. Subluxed extensor tendons fall into the ulnar gutters of the MP joint. The patient may not be able to extend this finger once it is in the flexed position. However, the finger can maintain extension if passively placed into this position.

The arthroplasties of the MP joint can incorporate reconstruction of the soft tissues only or involve complete joint replacement. Soft-tissue arthroplasty usually incorporates an element of synovectomy with MP joint stabilization, such as reconstruction of the radial collateral ligament or tendon realignment. Joint replacement is indicated for MP joint deformity or subluxation when pain is not controlled or function is impaired. Various MP joint implants are available for joint replacement. [11]

The MP joint replacement procedure involves making either a transverse incision across the entire dorsum of the hand at the MP level or individual longitudinal incisions over each MP joint. Less chance of interference with the lymphatics and venous outflow occurs with the individual longitudinal incisions, but the transverse incision is most commonly used for ease of access. The dissection is carried down to the paratenon level. An incision is made on the ulnar aspect of the extensor tendon, and the tendon is reflected radially. Care is taken to not breach the integrity of the capsule at this time. An incision is made longitudinally in the capsule of the MP joint. Using a periosteal elevator, the metacarpal head is freed of any soft-tissue attachments to the metaphyseal flare.

Using an oscillating saw, a true cut is made, maintaining 90° in line with a long access of the metacarpal and in the coronal plane. The metacarpal head is then discarded. An electrical burr or a Christmas-tree type of rasp can be used to ream the medullary canal. The medullary canal of the proximal phalanx is then identified through a burr hole on the articular surface of the base of the phalanx. Osteophytes are removed from the proximal phalanx at this time with a rongeur. The intramedullary canal of the proximal phalanx is reamed. Care is taken so that the rectangular opening for both the metacarpal and the proximal phalanx are square in line with the axial direction of both the metacarpal and phalanx. Appropriate sizes are then placed inside the medullary canals.

Using a no-touch technique, the definitive prosthesis is then introduced. The capsule is repaired, and the extensor tendon is subsequently aligned. Some authors prefer to reconstruct the collateral ligaments at this time. Care is taken at the initial dissection to preserve as much of the collateral ligament as possible. The skin is then closed using nylon suture, and a splint is applied with the fingers in extension and in a neutral position.

Approximately 4-5 days after the procedure, the patient is fitted for a dynamic outrigger splint that maintains extension in an appropriate anatomic position of the fingers while the patient undergoes active flexion exercises. Night splints are manufactured to maintain the fingers in extension. Splinting is required for the next 4-8 weeks. Follow-up radiographs are obtained to confirm the appropriate positioning of the implants.

Crossed intrinsic transfer of the extensor tendons from the ulnar side to the radial side of the adjacent finger to increase stability is another surgical option. Intrinsic release to alleviate intrinsic tightness eliminates the dorsal digital expansion tightness that is one of the subluxing forces on the MP joint.

Finally, MP joint arthroplasties can provide long-term relief. A patient with good hand function in the absence of pain is not a candidate for arthroplasty, even if obvious MP joint deformity is present, because surgery may not improve the hand function and could decrease grip strength.

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