· posture of finger where
· PIP jt hyperextended
· DIP jt flexed
· initially is dynamic
· when patient tries to maximally extend finger
· later becomes fixed
· may develop joint changes
· volar plate tear at PIP jt
· mallet finger with coexisting PIP volar plate laxity
· fractures of P2 healed in hyperextension
· stroke
· cerebral palsy
· MCP jt subluxation
· PIP jt volar plate laxity
· FDS tendon rupture
· mallet finger
· FDS sacrifice for tendon transfer or reconstruction
Extension
· most important insertion of extensor mechanism is into base of P2
· central slip
· extension requires competent PIP jt volar plate
· to avoid hyperextension as full extension obtained
· if volar plate incompetent, lateral bands sublux dorsally
· decreased tension on lateral bands
· because of fixed attachment of central slip
· results in DIP jt droop
· slackened distal tension
· unopposed pull of FDP
· FDP tightened by PIP jt hyperextension
· may be precipitated by failure of extensor mechanism at DIP jt
· leads to extensor lag of distal phalanx (mallet deformity)
· causes extensor mechanism to shift proximally
· causes increased tone at PIP jt
· if PIP jt volar plate lax, PIP hyperextends as secondary deformity
Flexion
· flexion normally starts at PIP jt
· in swan-neck, flexion starts at DIP jt
· under action of FDP
· PIP jt blocked in hyperextension
· when DIP jt fully flexed, PIP can flex
· often accompanied by characteristic click
Extrinsic
· enhanced action of EDC on base of P2
· ischaemic or spastic contracture of EDC
· laxity or detachment of terminal slip (mallet finger)
Intrinsic
· enhanced action of intrinsics on P2
· ischaemic or spastic contracture of interossei
· ulnar deviation with ulnar interossei shortening
· volar subluxation of MCP jt with dorsal displacement of intrinsics and increased extensor action on PIP jt
Articular
· loss of stabilisation of PIP jt
· volar plate
· FDS
· Nalebuff
· joints have full ROM
· prevention of hyperextension of PIP jt corrects flexion deformity of DIP jt
· function normal except flexion of DIP jt precedes flexion of PIP jt
· intrinsic tightness
· flexion of PIP jt influenced by position of MCP jt
· if MCP jt extended, PIP jt cannot be flexed
· if MCP jt flexed, PIP jt can be flexed
· PIP jt stiffness
· due to contracture of
· extensor mechanism
· collateral ligaments
· intrinsics
· skin
· destruction of PIP jt
· if secondary to mallet deformity, only this need be corrected
· if secondary to fracture of P2, treated with osteotomy
· if secondary to rheumatoid arthritis, MCP jt must be addressed first
· intrinsic release must be accompanied by correction of PIP jt volar laxity
· treatment consists of preventing hyperextension of PIP jt
· options are
· spiral oblique retinacular ligament reconstruction (modified Littler)
· superficialis tenodesis (Littler)
SORL procedure
· curved ulnar dorsolateral incision
· free tendon graft harvested
· usually palmaris longus
· two bony holes made
· AP in base of distal phalanx
· transverse in base of proximal phalanx
· graft spiralled around digit
· subcutaneously deep to NV bundle
· dorsum of PIP jt
· ulnar side of P2, volar to PIP jt
· radial side of P1
· attached by pull-out sutures
· volar surface of P3 distally
· ulnar side of P1 proximally
· tension adjusted until PIP jt flexed 20o
Superficialis tenodesis
· middle limb of Brunner incision
· one slip of FDS detached proximally
· passed through AP drill hole in P1
· sutured to button over dorsum
· PIP jt stabilised in 20o flexion with K wire
Postoperative
· 4 weeks with finger at 20o flexion
· PIP flexion exercises with extension blocking splint for further 2-4 weeks
· flexion limited by tightness of ulnar intrinsics
· treated by relief of intrinsic tightness
· intrinsic release
· may need to address MCP jt flexion deformity
· with interosseous advancement
Intrinsic release
· dorsomedial incision over PIP jt
· longitudinal incision in oblique fibres of extensor expansion
Advancement of interossei
· for associated MCP jt flexion
· interossei partially released from MC origin
· allowed to slide distally
· aim is to restore passive ROM
· best treated with exercise and splinting programme
· may require lateral band mobilisation
Lateral band mobilisation
· dorsomedial incision over PIP jt
· extensor expansion exposed
· lateral bands freed from central slip by excision of oblique and lateral bands of extensor hood
· arthrodesis
· arthroplasty
· flexion of PIP joint with hyperextension of DIP joint
· due to disruption of extensor mechanism over PIP jt
· central slip damaged by
· closed rupture
· open division
· PIP jt synovitis with stretching and attrition of central slip
· originates at PIP joint
· unlike swan-neck deformity which may originate at MCP, PIP or DIP joints
· basic pathology is disruption of
· central extensor tendon over PIP joint or off dorsal base of middle phalanx
· transverse retinacular bands
· result is prolapse of lateral bands volar to PIP joint axis
· lateral bands now act as flexors of PIP joint
· bands become shortened and secondary hyperextension of DIP joint occurs
· initially, full active flexion and full passive extension of PIP joint possible
· with time, central tendon continues to lengthen and lateral bands shorten and deformity becomes fixed
· as flexion deformity of PIP joint increases, patient compensates by hyperextending the MP joint
· dynamic imbalance
· lateral bands volarly subluxed but not adherent
· slight lag of PIP joint (10-15o)
· DIP joint may or may not be hyperextended
· can be passively corrected
· established extensor tendon contracture
· cannot be completely passively corrected
· PIP joint flexed 30-40o
· DIP joint hyperextended and MP joint often hyperextended
· flexion contracture of PIP joint not correctable
· secondary changes present
· volar plate and collateral ligament scarring
· joint degeneration
· effective if recognised and treated before established contracture occurs
· in the form of exercises and splints
· may require treatment for 2-3 months
Exercises
· two sequential manoevres
1. active assisted PIP joint extension
· stretches tight volar structures
2. forced flexion of DIP joint while PIP joint held in maximal extension
· stretches lateral bands and oblique retinacular ligaments
Splints
· active PIP extension splints during day
· static splints at night
Stage 1
· Eaton-Littler extensor tenotomy
· decreases extensor tone at DIP by complete transection of extensor mechanism
· extensor mechanism divided over dorsum of middle phalanx
· oblique retinacular ligaments preserved
Stage 2
· Littler-Eaton reconstruction of extensor mechanism
· separates PIP and DIP flexion by transferring lateral bands to only flex PIP jt (DIP jt flexed by oblique retinacular ligaments)
· lateral bands divided at middle phalanx
· sutured to central tendon insertion
Stage 3
· arthrodesis of PIP joint
· PIP joint arthroplasty