FINGER DEFORMITIES CAUSED BY RHEUMATOID ARTHRITIS
– varying spectrum of deformities, caused by intrinsic tightness, lateral band displacement, rupture of the central slip, or abnormalities of the flexor or extensor tendons, including rupture or tenosynovitis
Intrinsic Plus Deformity (Intrinsic Tightness)
– with the intrinsics tending to flex the MCPï¿½s and extend the IPï¿½s, when the intrinsics are tight, they PIP joint cannot flex when the MCP is extended (The MCP extension tightens up the intrinsics even further so that the PIP cannot be flexed fully). When the MCPï¿½s are flexed, the intrinsics are slackened, and the PIP can flex. This is the basis of the Bunnell test.
– be careful when doing the Bunnell test in rheumatoids – it must be done with the proximal phalanx in line with the metacarpal. If it is ulnarly deviated (which is common), the test will not be accurate.
Littler – release of intrinsic muscle contractures (Fig 75-10, page 3669)
– basically, incises the oblique fibers of the extensor aponeurosis into the extensor tendon. The transverse fibers are preserved to avoid hyperextension of teh MCP joints
– after the oblique fibers have been cut, the PIP joints should have full passive flexion with the MCPï¿½s in extension.
– described as a hyperextension deformity of the PIP and flexion deformity of the DIP, with flexion at Phillip E. 2
times of the MCP
– there seems to be a number of different ways for this deformity to form
– Start at the DIP: may begin with the disruption of the extensor tendon at the DIP, causing a mallet deformity; then, with secondary overpull of the central tendon, the PIP is hyperextended
– Start at the PIP: may begin with synovitis at the PIP causing tightening of the lateral bands and central tendon, and adherence of the lateral bands in a fixed dorsal position – thus, the PIP is hyperextended. With the lateral bands stuck in this dorsal position, they are unable to extend the DIP, and a mallet deformity may develop without actual rupture of the extensor tendon at the DIP. This requires synovectomy of the PIP, mobilization of the lateral bands, and release of the skin distal to the PIP.
Lateral band release is shown and described on page 3620
Nalebuff, Feldon, Millender – categorized swan-neck deformities into four types
Type I: flexible deformities
– require dermodesis, flexor tenodesis of the PIP, fusion of the DIP, reconstruction of the retinacular ligament
Type II: intrinsic muscle tightness
– require intrinsic release, plus one or more of the above procedures
Type III: stiff deformities but without joint destruction
– require joint manipulation, lateral band mobilization, and dorsal skin release
Type IV: stiff deformities with joint destruction
– require arthrodesis of the PIP or, in the ring and small fingers, Swanson arthroplasties
– consider flexor sublimis tenodesis at the PIP joint in addition to the release of the lateral bands. Beckenbaugh thinks that sublimis laxity due to tenosynovitis is a contributor to the development of these deformities, and he treats them with this sublimis tenodesis, brining the PIP down into about 30 degrees of flexion.
Arthroplasty of the PIP joint can only be undertaken when there is near normal function at the MCP joint proximally
– common but not unique to rheumatoid arthritis
– caused by synovitis at the PIP causing the central slip to stretch out and the lateral bands to sublux volarly to a position where they maintain the flexion deformity at the PIP and cause the secondary hyperextension at the DIP. A compensatory hyperextension of the MCP may develop, but this is usually not fixed.
– if flexible, with normal x-rays, the lateral bands may be repositioned after PIP synovectomy and extensor tenotomy over the middle phalanx (Dolphin Fowler procedure)
– for moderate deformities with satisfactory xrays, the central slip can be reconstructed using the lateral bands or a tendon graft
– for severe deformities, the long,