Fractional Fowler Tenotomy for Chronic Mallet Finger: A Cadaveric Biomechanical Study

Purpose 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. Methods 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. Results In these models, the average extensor lag of the DIP joint was 44 degrees (range, 40 degrees to 50 degrees). 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 degrees (range, 0 degrees to 40 degrees). With one-half detachment, the average lag was 13 degrees (range, 0 degrees to 35 degrees), and with two-thirds detachment, the average lag was 6 degrees (range, 0 degrees to 15 degrees). Extensor lag at the proximal interphalangeal joint occurred in 4 fingers, with an average lag of 8 degrees (range, 5 degrees to 15 degrees). Conclusions 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.