Comparison of an all-inside suture technique with traditional pull-out suture and suture anchor repair techniques for flexor digitorum profundus attachment to bone

Abstract

Purpose: One goal in repairing zone 1 flexor digitorum profundus (FDP) injuries is to create a tendon-bone construct strong enough to allow early rehabilitation while minimizing morbidity. This study compares an all-inside suture repair technique biomechanically with pull-out suture and double-suture anchor repairs.

Methods: Repairs were performed on 30 cadaver fingers. In all-inside suture repairs (n = 8), the FDP tendon was attached to bone with two 3-0 Ethibond sutures and tied over the dorsal aspect of distal phalanx. Pull-out suture repairs (n = 8) were performed with 2-0 Prolene suture and tied over a dorsal button. There were 2 suture anchor repair groups: Arthrex Micro Corkscrew anchors preloaded with 2-0 FiberWire suture (n = 7) and Depuy Micro Mitek anchors preloaded with 3-0 Orthocord suture (n = 7). Repair constructs were tested using a servohydraulic materials testing system and loaded until the repair lost 75% of its strength.

Results: There were no statistically significant differences in tensile stiffness, ultimate load, or work to failure between the repairs. Failure mode was suture stretch and gap formation greater than 2 mm at the repair site for all pull-out suture repairs and for 7 of 8 all-inside suture repairs. Two of the Arthrex Micro Corkscrew repairs and 5 of the Depuy Micro Mitek repairs failed by anchor pull-out.

Conclusions: This cadaveric biomechanical study showed no difference in tensile stiffness, ultimate load, and work to failures between an all-inside suture repair technique for zone 1 FDP repairs and previously described pull-out suture and suture anchor repair techniques. The all-inside suture technique also has the advantages of avoiding an external button and the cost of anchors. Therefore, it should be considered as an alternative to other techniques.

Clinical relevance: This study introduces a new FDP reattachment technique that avoids some of the shortcomings of current techniques.

Figure 1

Clinical example of the all-inside suture technique with A) Ethibond sutures placed in tendon and Keith needles in position and B) at the initiation of the pull through of the sutures.

Figure 1

Clinical example of the all-inside suture technique with A) Ethibond sutures placed in tendon and Keith needles in position and B) at the initiation of the pull through of the sutures.

Figure 2

Mechanical Testing Setup with all-inside suture repair. Sandpaper was affixed with cyanoacrylate to the distal 3 millimeters of the distal phalanx and to the proximal 10 millimeters of the tendon stump. Pressure clamps were used to secure the proximal end of the tendon and the distal end of the distal phalanx.

Figure 3

Force versus Displacement Curve. Representative force versus displacement curve depicting the applied preload (inset) and the stiffness (K), ultimate force (F_Ult) and work to failure (E).

Figure 4

Example of Failure by Gap Formation. This is a picture of one of the pull-out suture samples after testing. The gap between the bone and the tendon measures greater than 2mm.

Figure 5

Failure Mode for the Repairs. After mechanical testing, the failure mode of the FDP repairs were characterized as either gap formation, suture breakage, or anchor pull out. Suture breakage occurred in 12.5% (1 out of 8) of the all-inside suture repairs and was not seen in any of the other repair types. Anchor pull out occurred in 28.6% of the Arthrex Micro Corkscrew anchors repairs and 71.4% of the DePuy Micro Mitek Anchor repairs.

Figure 6

Mechanical Properties of the Repairs. The mean (A) tensile stiffness and (B) ultimate load of the repairs were calculated. No significant difference (p > 0.10) was found between groups.

Figure 6

Mechanical Properties of the Repairs. The mean (A) tensile stiffness and (B) ultimate load of the repairs were calculated. No significant difference (p > 0.10) was found between groups.

Figure 7

Work to Failure of the Repairs. The mean and standard deviations of the work to failure were plotted and a one-way ANOVA was used to determine differences between groups. No significant differences (p > 0.10) were found between the repair types.

Figure 8

Clinical radiograph demonstrating position of Keith needles for all-inside suture repairs