Introduction of a new repair technique in bony avulsion of the FDP tendon: A biomechanical study

Abstract

The purpose of this study was to determine the biomechanical characteristics of an innovative surgical technique based on a tension banding principle using a suture anchor in the repair of bony avulsions of the flexor digitorum profundus tendon. After injury simulation in 45 fresh frozen distal phalanges from human cadavers, repair was performed with minifragment screws, interosseous sutures and the innovative technique (15 per group). All repairs were loaded for a total of 500 cycles. Subsequently the specimens were loaded to failure. Load at failure, load at first noteworthy displacement (>2 mm), elongation of the system, gap formation at the avulsion site, and the mechanism of failure were assessed. The new techniques' superior performance in load at failure (mean: 100.5 N), load at first noteworthy displacement (mean 77.4 N), and gap formation (median 0 mm) was statistically significant, which implies a preferable rigidity of the repair. No implant extrusion or suture rupture during cyclic loading were recorded when the new technique was applied. This innovative repair technique is superior biomechanically to other commonly used surgical tendon reattachment methods, particularly with respect to an early passive mobilisation protocol. Further, due to its subcutaneous position, reduction of complications may be achieved.

Figure 1

(A) Suture insertion into the avulsed fragment and securing the tendon with the Bunnell technique in a cadaver specimen. (B) Graphical illustration of the new repair technique.

Figure 2

Illustration of the interosseous sutures to reattach a bony avulsion of the FDP tendon.

Figure 3

(A) Bony tendon avulsion repair using minifragment screws. (B) Screw positioning in a cadaver specimen. (C) Reduced articular line of the distal phalanx after repair with minifragment screws.

Figure 4

(A) Specimen holding device with a semicircumferrential window. The ball-joint is situated at the top of the cylinder. (B) Testing unit with the DP cylinder. The tendon is secured in the inferior clamp using abrasive paper to prevent tendon slipping.

Figure 5

A specimen repaired with the new technique (A) prior to cyclic loading, (B) after 500 cycles, and when loaded to failure with a displacement of 3 mm (C). Distance (r) is the main length reference and measures exactly 10 mm.

Figure 6

Graphs (A–C) are representing exemplary load versus displacement curves for each particular repair method. Abb. LND indicates the point of measurement of the load at the first noteworthy displacement (>2 mm). Abb. LF marks the point of measurement of the load at failure.

Figure 7

Boxplots of load at failure data. *Statistically significant difference compared to our novel technique.