Swan Neck Deformity

- 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

The rheumatoid swan-neck deformity.

Treatment of chronic, traumatic hyperextension deformities of the proximal interphalangeal joint with flexor digitorum superficialis tenodesis.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, June 20, 2016 7:38 am