Swan Neck Deformity following Excision of FDS - Wheeless' Textbook of Orthopaedics

- Discussion:
- may result from complete excision of the flexor digitorum sublimis;
- it is especially likely to occur in patients with a hyperextensible PIP joint;
- major vinculum exists at the insertion of the sublimis tendon;
- when tendon is exised to to its insertion, the vinculum is violated,
creating major source of adhesion formation for reconstructed tendon;
- checkrein effect on the joint is lost, allowing hyperextension;
- this creates a relative lengthening of the extensor apparatus, causing terminal phalanx to drop into flexion;
- lateral bands displace dorsally;

- Prevention:
- do not excise sublimis distally farther than neck of middle phalanx or just proximal to vinculum;
- if possible, the remaining sublimis should be left even longer;