This article from the Hand Unit at the Bristol Royal Infirmary (United Kingdom) uses the case of a 42-year-old woman with an early swan neck deformity (SND) to review the evidence for current surgical procedures to correct the problem. Since there is no clear consensus on which one is the best, surgeons must use available studies to make the most appropriate decision for each patient.
What is a swan neck deformity? Sounds elegant but in fact, it can be very limiting. Basically, it is a crooked finger. The tip of the finger is bent at the distal interphalangeal (DIP) joint while the middle joint (proximal interphalangeal or PIP) is hyperextended. To see what this looks like, see our publication Swan Neck Deformity of the Finger. Human anatomy is not simple and that description does not begin to tell you how complex a “crooked finger” can be.
In the proximal interphalangeal (PIP) joint, (that is the middle joint between the main knuckle and the tip of the finger), the strongest ligament is the volar plate. This ligament connects the proximal phalanx (bone closest to the palm) to the middle phalanx on the palm side of the joint. The ligament tightens as the joint is straightened and keeps the PIP joint from bending back too far (hyperextending). Swan neck deformity can occur when the volar plate loosens from disease or injury.
Rheumatoid arthritis (RA) is the most common disease affecting the PIP joint. Chronic inflammation of the PIP joint puts a stretch on the volar plate. As the volar plate becomes weakened and stretched, the PIP joint becomes loose and begins to easily bend back into hyperextension. The extensor tendon gets out of balance, which allows the tip of the finger to get pulled downward into flexion. As the tip of the finger bends down and the PIP joint hyperextends, the swan neck deformity occurs.
Gripping objects and picking things up becomes very difficult when this deformity is present. Conservative care (often with splinting) is tried first but if it is unsuccessful (as in the case of this patient), then surgery may be needed. But that brings us back to the question of which surgical procedure works best to prevent a fixed-extension deformity?
There are four basic surgical choices: 1) Dermodesis, 2) Flexor Tendon Tenodesis, 3) Retinacular Ligament Reconstruction, and 4) Lateral Band Tenodesis/Translocation. Each technique has benefits and drawbacks. Some are easier to perform than others. Some seem to work better than others for certain individuals. Currently, there are no large studies comparing one method to another and most studies are very small in size.
The authors describe each one in detail outlining when it is most appropriate and how the technique has been modified by different surgeons over time. Some of the decisions about which method to use depend on how much joint stiffness is present in the proximal interphalangeal (PIP) joint. Earlier deformities may be more supple (not as stiff as the more advanced or severe cases) and have not been studied as much so evidence for outcomes remains limited.
Future research is needed to compare newer methods of volar ligament repair (attaching to the bone versus soft tissue fixation). Long-term follow-up to report on late failures is also needed. Patient satisfaction (not just surgeon satisfaction) should always be taken into account when measuring results. Appearance, range-of-motion, grip strength, and hand function are all important outcomes to the patients. Degree of deformity correction may be the surgeon’s primary measure of success.