Swan Neck Deformity
Swan neck deformity. The volar plate is torn, causing the joint to
open abnormally under the pull of the extensor ligaments
.
Swan-Neck Deformity
• Typically defined as:
– proximal interphalangeal (PIP) joint
hyperextension
– with concurrent distal interphalangeal (DIP)
joint flexion
• Not necessarily unique to RA but rather an
end result of muscle and tendon
imbalance caused by RA.
Swan-Neck Deformity
• Not necessarily unique to RA but rather an
end result of muscle and tendon
imbalance caused by RA
Nalebuff Classification
1989
• Type I - PIP joints flexible in all positions
– No intrinsic tightness or functional loss
• Type II - PIP joint flexion limited in certain positions
– Intrinsic tightness
– Limited PIP motion with extended MCP with ulnar deviation
• Type III - PIP joint flexion limited in all positions
– Near normal radiograph
• Type IV - PIP joints stiff with poor radiographic
appearance
Pathophysiology
• The intercalated joint collapse concept of
Landsmeer means that collapse of a joint
in one direction will result in deformity of
the next distal joint in the opposite
direction.
– Z deformity
Pathophysiology
• In a normal finger, intrinsic muscles serve
as:
– flexors of the MCP joint
– extensors of the PIP and DIP joints
• By being located volar to the MCP joint
axis and dorsal to the PIP and DIP joint
axes
Pathophysiology
• Intrinsic tightness increases the flexor pull on the
MCP joint and hyperextension of PIPJ
• Weak flexor power aggravates this by being
unable to pull the middle phalanx.
– DIPJ and MCPJ hyperextension follows
• Constant efforts to extend the finger against this
pull then leads to stretching of the collateral
ligaments and weakening of the volar plate at
the PIPJ.
Pathophysiology
• the lateral bands are constrained in their dorsal
position with the extensor apparatus migrating
proximally
– therefore upsetting the flexor-extensor balance,
• The lateral bands in this position act to increase
the pull of the central slip that attaches to the
dorsal base of the middle phalanx.
– Leading to hyperextension of PIPJ
Pathophysiology
• The increase of FPL tension resulting from
hyperextension of the PIP joint leads to a
reciprocal flexion of the DIP joint.
• DIP mallet deformity also from:
– Joint erosion
– Extensor tendon attentuation or rupture
• Progressive disease leads to joint
destruction and fixed contracture.
Hashemi-Nejad and Goddard (1994)
-multidisciplinary approach is best
-an affected joint will affect other joints
-early synovectomy is worthwhile after a 6-month trial of
non-operative treatment
-tenosynovectomy decreases the risk of tendon rupture,
-the wrist is the key in the RA hand
-the thumb is a very important source of disability
-silastic MCPJ arthroplasty is successful in reducing pain
and improving function
Feldon (1993) lists the aims of
surgery in the RA hand:
1.
2.
3.
4.
pain relief
functional improvement
preventing disease progression
cosmetic improvement
Note that the presence of a painless
deformity with minimal function deficit is
not an indication for surgery.
Management
• Millender and Nalebuff staging system
(1975) is a good guideline for identifying
treatment options in RA
Principles
• Prevention
• Correct PIPJ hyperextension
• Restore DIPJ extension
Type1
–
–
–
–
–
Silver ring splint to flex PIPJ
Volar dermatodesis
Correction of any MCPJ abnormality first
Flexor tenosynovectomy (if synovitis is present)
Flexor tenodesis - FDS slip through A2 pulley then
looped back to itself
– Retinacular ligament reconstruction
– Release ulnar lateral band proximally and pass volar
to PIPJ axis  sheath
Silver Ring Splint
• Permit active PIP
flexion and limit
hyperextension of the
PIP joint
•
DIP Fusion
• Difficult and unreliable to restore the
extensor apparatus at DIP level cause
underlying RA disease will destroy the
repair
• Also secondary arthritis within DIP may
make attempts to mobilise joint unwise
•
Dermadesis
• Used to prevent PIP hyperextension bu
creating a skin shortage volarly
• Elliptical skin wedge (4-5mm at widest) is
removed from volar aspect of PIP
• Care not too disturb venous drainage or
violate the flexor sheath
• Skin closed with PIP in flexion
• Only useful if done in conjunction with
other procedures ie DIP fusion
Flexor Tendon Tenodesis
“sublimis sling”
• Used as checkrein against hyperextension ie
restoration of strong volar support
• One slip of FDS is divided ~1.5cm proximal to
PIP
• This is then separated from its corresponding
slip bit left attached distally
• With joint at 20-30 degrees the detached slip is
fixed proximally
– Anchored to thickened margin of sheath, distal edge
of A2 or Mitek
• Nalebuff did simpler procedure whereby he
passed split tendon around A1 pulley
Reticular Ligament
Reconstruction
• Credited to Littler
• Ulnar lateral band is freed from extensor
mechanism proximally but left attached distally
• Passed volar to Cleland’s fibres to bring it volar
to axis of PIP
• Band is sutured to the fibrous tendon sheath
under enough tension to restore DIP extension
and prevent hyperextension at PIP
• However, in RA may have destruction of
terminal tendon so no amount of tension applied
to the relocated tendon will achieve DIP
extension
Type 2
• Looks like Type 1 but PIP movement is limited in
certain positions related to position of MCPJ
– MCPJ extended/radial deviation then limited passive
PIP ROM
– MCPJ flexed/ulnar deviated then PIP ROM increased
• As MCPJ subluxates and the intrinsics get tight
a secondary swan neck develops as a result of
muscular imbalance
• Not sufficient to restrict PIPJ hyperextension,
intrinsics must be released plus MCPJ
subluxation must be corrected +/- arthroplasty
Intrinsic Release
• Photo on camera
• A rhomboid portion of the ulnar extensor
aponeurosis is then resected
• This procedure resects the lateral band
through which the abnormally tight
intrinsics have caused MP flexion and PIP
hyperextension
Type 3
• unlike type 1 & 2 have significant functional
disability due to inability to grasp objects
• Not joint destruction but restriction due to:
– Extensor mechanism
– Collateral ligaments
– Skin
• First goal is to restore passive ROM
–
–
–
–
PIPJ manipulation
Skin release
Lateral band mobilisation
Then correction of deformity after motion restored
PIPJ Manipulation
• MUA possible up to 80-90 degrees
• Usually in conjunction with intrinsic
release, arthroplasty or tenosynovectomy
Skin Release
• Dorsal skin may limit the amount of
passive flexion that is achieved during
manipulation
• Tension minimised with an oblique incision
just distal to the PIPJ
– Allowing skin edges to spread
– Closes 2-3 weeks by secondary intention
– PHOTO 2112
Lateral Band Mobilisation
• Lateral bands are displaced dorsally
• Free lateral bands from central slip using 2
parallel incisions allows flexion without
releasing lateral bands or lengthening
central slip
• PHOTO 2113
Type 4
• Patients with stiff PIPJ and radiographic
evidence of advanced intra-articular
changes require salvage procedure
– Fusion or arthroplasty
• PHOTO 2114