- See:
- Phalangeal Injury
- Thumb Swan Neck Deformity
- Transverse Retinacular Ligament
- Discussion:
- deformity involves hyperextension of PIP Joint w/ flexion of DIP joint;
- deformity may start at either the PIP or DIP;
- at PIP joint, there is obligatory attunuation of the volar plate;
- at DIP joint there is elongation or rupture of attachment of the extensor tendon to the base of the distal phalanx;
- this results in mallet deformity of distal joint & in addition, an extensor tendon imbalance, which leading to hyperextension
deformity at PIP jont;
- summation of pathology:
- stretching of the volar plate at PIP joint;
- intrinsic tightness;
- collateral ligament contracture
- DIP laxity;
- inciting causes:
- in contast to the boutonniere deformity, swan neck deformities may begin and the DIP, PIP, or MP joints, causing swan neck
deformities in the remaining joints;
- MP joint pathology:
- intrinsic and central tendon tightness leads to MP joint subluxation;
- even before MPJ subluxation develops, the intrinsic tendon tightness may lead to PIP hyper-extension deformity;
- once the MPJ subluxation develops (w/ MPJ flexion deformity), there will be a secondary PIP hyperextension deformity as
a result of altered balance;
- PIP joint pathology:
- PIP Joint hyperextension from lax volar capsule secondary to synovitis;
- FDS rupture (loss of dynamic PIP Joint stabilization)
- complete excision of the FDS;
- DIP joint pathology:
- mallet deformity (common cause)
- in RA, there may be stretching or disruption of the distal extensor mechanism, resulting in mallet deformity;
- as a result of the mallet deformity, there will be eventual PIP hyperextension deformity (the DIP will therefore show
more advanced deformity than the PIP joint);
- terminal tendon ruptures w/ secondary hyperextension PIP Joint;
- misc:
- swan neck following excision of FDS
- following tight repair of FDP or free tendon grafting;
- esp likely to occur in pts w/ hyperextensible PIP joints;
- intrinsic contracture:
- has the effect of causing PIP hyperextension which eventually causes volar plate attenuation;
- Non Operative Treatment:
- extension block splint (Figure of eight or Murphy ring);
- Treatment Based on Classification
- Operative Techniques
- splinting and synovectomy:
- in swan neck deformity, flexor synovitis is treated first;
- FDS sling: (Urbaniak)
- FDS is transected in the palm and is brought over the A2 pulley and sutured back to itself;
- this acts as a checkrein against PIP hyperextension;
- hemitenodesis of FDS:
- indicated if articular surfaces are OK;
- hemitenodesis of FDS tendon to base of middle phalanx will limit hyper-extension deformity of the PIP joint;
- one slip of the FDS is separated from the other and is divided about 1.5 to 2 cm proximal to the PIP joint;
- the tendon slip can be sutured into the flexor tendon sheath with the finger held in slight flexion;
- the joint should be held in 20 deg of flexion for 6 weeks;
- extensor mechanism:
- it is usually not necessary to lengthen central slip;
- required releases include:
- dorsal capsule;
- collateral ligaments;
- palmar plate;
- dermadesis:
- indications: mild flexible deformity in weak hands;
- involves excision & closure of ellipse of loose skin over flexor aspect of PIP Joint;
- preserve underlying vessels and nerves;
- long term results are poor;
- intrinsic tenodesis:
- indicated for intrinsic tightness in RA (especially when ulnar drift is not present);
- releases PIP extension contracture and improves DIP flexion contracture;
- arthrodesis: (see phalangeal arthrodesis)
- if joint surface is not OK, then fuse PIP Joint;
- arthrodesis of index finger provides the greatest amount of f(x) w/ the least amount of morbidity;
- note that arthrodesis of long & ring fingers can produce quadriga effect due to the tethering of the profundus tendons;
- fusion of the DIP joint is performed only if swan neck deformity originates at this joint (ie the DIP deformity should be
more advanced than the PIP joint deformity);
- the joint should be fused in full extension;
- technique:
- curvilinear incision over the dorsum of the DIP joint;
- divide the extensor apparatus transversely;
- currette out the articular cartilage;
- mold bony surfaces to allow good opposition;
- fixation is achieved w/ a longitudinal K wire;
- mark or predrill the surface of the middle phalanx before the K wire is driven retrograde out the distal phalanx and then
back into the middle phalanx;
- a second obliquely placed wire is inserted if necessary;
- implant arthroplasty is rarely indicated;
- MCP is adressed at same time (arthroplasty) to balance extensor mechanism;
- there is a high incidence of recurrance;
- note that dorsal skin is tight from hyper-extension contraction, and wound closure will be difficult if digit is placed in flexion;
- in necessary leave the distal portion of the wound open, in order to avoid skin tension;
- littler procedure: (ORL reconstruction)
- involves creation of an oblique retinacular ligament using a lateral band;
- this procedure involves releasing a lateral band which may be necessary in any case due to when intrinsic tightness;
- this procedure is better suited for primary PIP deformity (w/ secondary DIP deformity);
- w/ primary DIP deformity, the PIP hyper-extension will be corrected, but the DIP deformity will not be corrected;
- prior to any reconstructive procedure full passive motion of the PIP and DIP joints needs to be restored;
- to address abnormal arc of flexion, checkrein at PIP Joint needs to be recreated;
- one lateral band is transected distally (distal to the transverse fibers);
- ulnar lateral band is transected proximal to PIP joint but is left attached distally;
- it is mobilized & transferred volar to Cleland's ligament, so that it is volar to the axis of motion at the PIP joint;
- it sutured to a pulley at base of PIP w/ appropriate tension, ie there is sufficient DIP extension and correction of PIP hyper-extension;
- tranposed tendon should function similar to the oblique retinacular ligament, hence when the PIP joint extends the DIP will
extend as well;
- place K wire across PIP Joint, which is held in sl flexion,
- references:
- The spiral oblique retinacular ligament (SORL).
Superficialis Sling (Flexor Digitorum Superficialis Tenodesis) for Swan Neck Reconstruction
Correction of rheumatoid swan-neck deformity by lateral band mobilization.
The spiral oblique retinacular ligament (SORL).
Surgical Treatment of Swan Neck Deformity in Rheumatoid Arthritis.