Fractional Dolphin Tenotomy for Boutonniere Deformity: A Cadaveric Study

Terminal extensor tenotomy or Dolphin tenotomy, is a described treatment for the management of distal interphalangeal (DIP) joint hyperextension in chronic boutonniere deformity. The purpose of this study was to investigate the effects of incremental partial Dolphin tenotomy in correcting boutonniere deformity, with a focus on evaluating the improvement in DIP joint hyperextension deformity and documenting the development of iatrogenic mallet finger.

Thirty-eight fingers from 10 cadaveric hands were used. We created a boutonniere deformity in each digit by transecting the central slip and repairing it with a 3-mm gap. We performed incremental fractional terminal extensor tenotomy by detaching one-third, one-half, two-thirds, and complete transection. The positions of the proximal interphalangeal (PIP) and DIP joints were measured in the extended position following each subsequent tenotomy.

The model produced an average DIP joint hyperextension deformity of -15 ± 1°. The DIP joint position sequentially improved with one-third (-11 ± 1°), one-half (-9 ± 1°), and two-thirds (-5 ± 1°) tenotomy. Complete tenotomy resulted in an average 25° extensor lag. There was no significant improvement in PIP joint flexion deformity with any degree of fractional tenotomy (P > 0.05), and only mild improvement after complete tenotomy (48 ± 2° to 41 ± 2°, P < 0.05).

Fractional terminal extensor tenotomy demonstrated incremental improvement in DIP joint hyperextension deformity with increasing degree of tenotomy performed. There were no cases of iatrogenic mallet finger with fractional tenotomy involving up to two-thirds of the tendon.

Clinical application of fractional terminal extensor tenotomy may be an effective treatment option for patients with chronic boutonniere deformity in whom PIP joint deformity is mild and DIP joint hyperextension accounts for the primary functional deficit. Fractional tenotomy may allow the surgeon to tailor the degree of correction to the existing preoperative deformity.