Fractional Fowler tenotomy for chronic mallet finger: a cadaveric biomechanical study

The Fowler tenotomy, adjusting the balance of the extensor mechanism by central slip and lateral band detachment, is a common surgical technique for chronic mallet finger. The purpose of this study was to determine how much tendon to detach from the middle phalanx by measuring the extensor lag of the distal interphalangeal (DIP) joint following the procedure and to quantify how often a boutonniere deformity occurred as a consequence of the procedure.

Sixteen fingers were obtained from 8 fresh-frozen cadaver hands. We made mallet finger deformity models by terminal tendon elongation. We detached the central slip and lateral band from the middle phalanx by one-third, one-half, and two-thirds of the phalangeal length and measured extensor lag of the DIP and proximal interphalangeal joints before and after this procedure.

In these models, the average extensor lag of the DIP joint was 44° (range, 40° to 50°). After central slip and lateral band detachment over one-third of the phalangeal length, the average residual extensor lag of the DIP joint was 19° (range, 0° to 40°). With one-half detachment, the average lag was 13° (range, 0° to 35°), and with two-thirds detachment, the average lag was 6° (range, 0° to 15°). Extensor lag at the proximal interphalangeal joint occurred in 4 fingers, with an average lag of 8° (range, 5° to 15°).

In the Fowler tenotomy models, detachment of the central slip and lateral band from the middle phalanx reduced extensor lag of the DIP joint. Detachment of up to two-thirds of the phalangeal length was effective in this model and did not cause any boutonniere deformity.

Controlled clinical application of our cadaveric results might yield improved active motion for chronic mallet extensor lag.