Mucous cysts of the DIPJ

Mucous cyst DIPJGanglion cyst of the DIPJ Usually occurs between the fifth and seventh decadesAssociated with osteophytes or spurring of the DIPJOsteoarthritis in other joints

Ganglion/Mucous cystSingle or multiloculated cyst which appears smooth, white & translucentWall is made up of compressed collagen fibres and is sparsely lined with flattened cells without evidence of an epithelial or synovial liningMucin-filled clefts from the capsular attachment of the main cyst interconnect with the adjacent underlying joint via tortuous continuous ductsStroma may show tightly packed collagen fibres or sparsely cellular areas with broken fibres and mucin-filled intercellular & extracellular lakesNo inflammatory reaction or mitotic activity has been noted

Ganglion/Mucous cystContents of cyst characterized by a highly viscous, clear, sticky, jelly-like mucin made up of glucosamine, albumin, globulin, & high concentrations of hyaluronic acidAetiology & pathogenesis remain obscureMost widely accepted theory - mucoid degeneration associated with degeneration of joint capsule or tendon sheathInjury & mechanical irritation may stimulate production of hyaluronic acid to form mucin, which may penetrate joint ligaments and capsules and then coalesce to form cyst

Clinical signsLongitudinal grooving of the nail - earliest sign without a visible mass, caused by pressure on the nail matrix

Clinical signsEnlarged cyst with attenuated overlying skin

Clinical signsCyst (3-5mm) usually lies to one side of the extensor tendon and between the dorsal distal joint crease & the eponychium

Clinical signsOften has Heberdens nodes and radiographic evidence of osteoarthritic changes in the joint

TreatmentPrimarily surgicalNumerous alternative treatment reported in the past with moderate success:Intralesional injection - eg. Sodium morrhuate, triamcinoloneOcclusive flurandrenolone tape

Surgical ManagementExcision of the cyst aloneWide excision of the cyst along with surrounding adjacent structures - eg.the overlying skin, osteophyte debridementsDebridement of the DIPJ osteophytes only, without excision of the cyst itself or overlying skin

Operative techniqueL-shaped / H-shaped / curved incisionElliptical excision of attenuated or involved skin

Operative techniqueCyst mobilized, traced to the joint capsule & excised with the joint capsuleAll tissue excised between the extensor tendon & the adjacent collateral ligamentsInsertion of the extensor tendon and the nail matrix must be protected

Operative techniqueExcison of osteophytesSkin closure may require rotation / advancement dorsal skin flap or a full-thickness graft

Alternative approachTransverse incision centred over DIPJBase of mucous cyst identified & excised while leaving the distal & superficial portion of the cyst intactExcision of osteophtyes & joint capsule with direct skin closureAllow several weeks for involution of the remaining cyst

ComplicationsResidual nail deformitiesStiffnessSkin necrosisRecurrence:- inadequate excision- ganglion extension to the other side of extensor tendon- persistent underlying arthritic process

*************