Swan Neck Deformity

Educational Objectives

The goal of this program is to improve the management of injuries to the finger. After hearing and assimilating this program, the clinician will be better able to:

1. Select patients most likely to benefit from operative or nonoperative treatment of swan-neck deformity. 

Summary

Extensor mechanism: extrinsic component composed of extensor digitorum communis tendon; intrinsic component composed of lumbricals and dorsal and volar interossei; primary function of extrinsic extensor system to extend metacarpophalangeal (MP) joint; main insertion on base of middle phalanx; extends MP joint through sagittal bands extending from dorsal to volar and inserting on volar plate; primary function of intrinsic component to flex MP joint and extend proximal interphalangeal (PIP) joint; position of PIP joint controls distal interphalangeal (DIP) joint; imbalance at one joint induces compensatory deformity at adjacent joint; relationship between tendon and axis of joint critical in formation of boutonnière and swan neck deformities; tolerance for small changes in length of tendon on extensor side minimal; on flexor side, some changes in length can be tolerated

Swan neck deformity: PIP hyperextension and DIP flexion; starts as dynamic imbalance of extensor mechanism; can progress to rigid deformity with alterations of joint; caused by pathology of MP, PIP, or DIP joint; etiologies include laxity of PIP volar plate and extensor lag of DIP joint; rheumatoid arthritis causes synovitis of PIP joint that leads to attenuation of volar plate; volar subluxation of MP joint can increase tension on central tendon and hyperextend PIP joint; if PIP joint hyperextended, lateral bands shift dorsal to axis of PIP joint

Pathophysiology: dorsal shift of lateral bands slackens tension on DIP joint because of fixed attachment of central tendon to base of middle phalanx; DIP joint droops because of unopposed pull of flexor digitorum profundus tendon; hold PIP joint in neutral position, and ask patient to extend DIP joint; ability to extend it indicates pathology of PIP joint; inability to extend it implies extension lag at DIP joint; inability to extend it with PIP joint held in extension indicates DIP extension lag primary pathology; deformity starts as supple deformity (full passive range of motion); can progress to rigid deformity, joint contracture, and articular degeneration

Nonoperative treatment: swan neck deformity typically does not respond to splinting once established; splinting appropriate for soft tissue or bony mallet deformity in patient with laxity of PIP volar plate; splinting DIP joint in extension with treatment of mallet deformity can prevent development of swan neck deformity; ring splints do not cure swan neck deformity but can improve function

Surgical treatment: depends on primary etiology; treatment of primary PIP volar plate laxity designed to create passive restraint to hyperextension of PIP

Superficialis hemitenodesis: leave one slip of flexor digitorum superficialis tendon attached distally; divide it proximally, mobilize it, and insert it into hole in proximal phalanx or suture it to flexor tendon sheath proximally; in small finger, both slips may remain attached distally; flex PIP joint minimally (≈15°), create transverse drill hole in proximal phalanx, pass tendon through hole, set tension, tie tendon in knot, and suture knot to adjacent periosteum

Reconstruction of oblique retinacular ligament (ORL): requires intact lateral band and terminal tendon; divide shelving or volar margin of lateral band proximally; mobilize from proximal to distal; pass slip through hole in proximal phalanx, or suture it to flexor tendon sheath with PIP joint in gentle flexion; ORL — origin fan-shaped from lateral margin of terminal tendon; extends deep proximally to transverse retinacular ligaments volar to axis of PIP joint and inserts on periosteum of proximal phalanx and flexor tendon sheath; distally dorsal to axis of joint; proximally volar to axis of PIP joint; anatomic specimens vary; function debatable; appears to serve as dynamic tenodesis; extension of PIP joint tightens ORL and leads to coordinated extension of DIP

Spiral ORL reconstruction: use free tendon graft; create hole in base of distal phalanx from dorsal to volar; insert tendon graft through hole, bring it proximally to one side of finger, and cross to opposite side on volar aspect of PIP joint; proximally insert tendon into hole in proximal phalanx at metaphyseal-diaphyseal junction; fix graft proximally with button, or tie it in knot and suture it to periosteum; set tension by pulling tendon distally; appropriate tension extends finger

Intrinsic muscle spasticity: options for treatment include intrinsic muscle origin slide and fractional lengthening of intrinsic muscles; adjuncts include superficialis hemitenodesis

Rheumatoid arthritis: different types of swan neck deformity characterized; type 1 — PIP joints flexible in all positions; type 2 — flexion of PIP joint limited in certain positions and dependent on position of MP joint; type 3 — flexion of PIP joint limited in all positions; type 4 — PIP joint stiff, and degeneration present

Treatment: type 1 — PIP dermodesis characterized by excision of ellipse of skin on volar aspect of PIP joint and suturing; tight skin creates passive restraint to hyperextension; other options superficialis hemitenodesis or ORL reconstruction; type 2 — MP intrinsic release and same techniques used for type 1; type 3 — shorten skeleton and rebalance extensor mechanism with MP arthroplasty; treatment at PIP joint determined by degree of suppleness; type 4 — MP arthroplasty combined with PIP arthroplasty or PIP arthrodesis

Readings

Fox PM et al: Treating the proximal interphalangeal joint in swan neck and boutonniere deformities. Hand Clin 2018 May;34(2):167-76; Kiziridis G et al: Volar tenodesis for the treatment of swan neck deformity; a systematic review. J Hand Surg Asian Pac Vol 2017 Sep;22(3):267-74; Thompson JS et al: The spiral oblique retinacular ligament (SORL). J Hand Surg Am 1978 Sep;3(5):482-7.

Disclosures

For this program, members of the faculty and planning committee reported nothing to disclose.

Acknowledgements

Dr. Glickel was recorded at the NYU Langone Hand Surgery Update 2018, held December 15, 2018, in New York, NY, and presented by the NYU School of Medicine, Office of Continuing Education. For information about upcoming CME opportunities from the NYU School of Medicine, Office of Continuing Education, please visit med.nyu.edu/education/continuing-medical-education. The Audio Digest Foundation thanks the speakers and the NYU School of Medicine, Office of Continuing Medical Education, for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

OR420601

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.