Abstract
The MP joint is the key joint for function of the fingers. Rheumatoid arthritis involvement of this joint is frequent (1/3 of patients), and results in severe painful deformity and functional loss. The factors leading to the classic ulnar drift and volar luxation are multiple but the permanent pathophysiological element is synovitis of the joint. No deformation will occur in the MP joint without synovitis.
Etiopathogenesis: The causes of MP joint deformity in Rheumatoid arthritis are anatomical, pathological and indirect.
The asymmetry of the metacarpal heads with a slight ulnar tilt induce the deformation in this direction. The weakness and the length of the radial collateral ligaments compared to the ulnar collateral ligament makes the laxity to occur on the radial side of the joint. The obliquity of the extensor tendons pull the fingers ulnarly with a tendency of dislocation over the MP joints.
Synovitis is at the origin of elongation, rupture or destruction of the ligaments, attrition of the cartilage and bone resorption. The distention of the extensor hood predominate radially and accentuate the extensor tendon obliquity. The destruction of the A1 pulley of the flexor tendon participate to the volar luxation of the joints. The ulnar sliding and radial tilt of the carpus, the tension of Abductor Digiti Minimi and the contracture of the intrinsic muscle participate indirectly or aggravate the deformation. The thumb force in pinch grip and the ulnar deviation of the finger in heavy prehension participate also to the deformation.
Classification: Without prognostic factor the following classification gives information on the stage of the deformation and the treatment that can be proposed.
synovitis without deformation, normal radiographs
synovitis with ulnar deviation, normal radiographs
synovitis with ulnar deviation and volar subluxation, volar luxation on radiographs with almost normal cartilage
ulnar deviation and volar luxation with or without active synovitis, destroyed cartilage and more or less bone erosion on radiographs
Synovectomi with stabilization and realignment procedures can only be used in stage 1 and 2. In stage 3 and 4 arthroplasty is more appropriate.
Treatment: Indication are pain, loss of function and cosmesis.
Synovectomy. The prophylactic effect of synovectomy is still subject to debate. The almost impossible total synovectomy, the difficulties to control the effect of the procedure and the different stage in disease of each patient make the synovectomy unpredictable as a real prophylactic procedure.
Stabilization and realignment procedures has always to be part of a synovectomy. If the destruction of the cartilage and the bone erosion are irreversible process, the elongation of the ligaments or the destruction of their bony insertions can always be reconstructed. For this purpose different techniques can be used. Suture of the extensor hood on the radial side enables reorientation of the extensor tendons. The radial collateral ligaments can be strengthened or their attachments reinserted, the Abductor Digiti Minimi or the intrinsic tendons can be divided. Some tendon transfers (intrinsic, Extensor Indicis Proprius) can also be proposed.
Arthroplasty. The choice of the procedure depends most of the surgeon preferences. The silicon arthroplasties are the most often used. They associate a reduction of the ulnar and volar deformation and opened the hand with very good results on the aspect of the hand and on pain. The mobility of the MP joints is variable and depends of the mobility of the finger joints. The bone erosion and the rupture of these devices are in favor of autologous interposition arthroplasties which, on the other hand, gives lesser mobility and stability. For these reasons silicon and interposition arthroplasties are often indicated late in the MP joint destruction process. More recently, new non constrained implants have been proposed in order to offer an earlier treatment. When used with good ligament reconstruction and tendon rebalancing these devices have good results on pain, cosmesis and function. If the preliminary results are confirmed in the long term, these non constrained devices will have a good indication as early MP joint replacement in the active young rheumatoid patient.
Conclusion: MP joint deformity in rheumatoid arthritis is complex. The Etiopathogenesis will guide the treatment most appropriate in each patient. However some principles has to be respected in all cases. A good stabilization and recentralization is the key stone of the surgical procedure. The ulnar deviation can be reduced and corrected by ligaments and tendon procedures. The volar subluxation/luxation indicates an advanced deformity of the MP joint that requires arthroplasty.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
