AbsorbaTack™ vs. ProTack™ vs. sutures: a biomechanical analysis of cervical fixation methods for laparoscopic apical fixations in the porcine model

Abstract

Purpose: Treatment of pelvic organ prolapse (POP) often requires the use of synthetic mesh. In case of a novel and standardized bilateral apical fixation, both uterosacral ligaments are replaced by polyvinylidene-fluoride (PVDF) tapes. One of the main problems remains the fixation method, which should be stable, but also simple and quick to use. The current study evaluated biomechanical differences between the cervical tape fixation with sutures (group 1), non-absorbable tacks (group 2) and absorbable tacks (group 3) in an in vitro porcine model.

Methods: A total of 28 trials, conducted in three groups, were performed on porcine, fresh cadaver uteri. All trials were performed until mesh, tissue or fixation device failure occurred. Primary endpoints were the biomechanical properties maximum load (N), displacement at failure (mm) and stiffness (N/mm). The failure mode was a secondary endpoint.

Results: There was a significant difference between all three groups concerning the maximum load. Group 1 (sutures) supported a maximum load of 64 ± 15 N, group 2 (non-absorbable tacks) yielded 41 ± 10 N and group 3 (absorbable tacks) achieved 15 ± 8 N. The most common failure mode was a mesh failure for group 1 and 2 and a fixation device failure for group 3.

Conclusion: The PVDF-tape fixation with sutures supports 1.5 times the load that is supported by non-absorbable tacks and 4.2 times the load that is supported by absorbable tacks. Nevertheless, there was also a stable fixation through tacks. Sutures are the significantly stronger and cheaper fixation device but may prolong the surgical time in contrast to the use of tacks.

Keywords: Apical fixation; Biomechanical analysis; Cervicosacropexy; Mesh fixation; Pelvic organ prolapse; Polyvinylidene-fluoride; Uterosacral ligaments.

Fig. 1

Intraoperative cervical fixation. Cervical fixation of the central part of the PVDF ligament-replacement structure (DynaMesh CESA, FEG Textiltechnik mbH Aachen, Germany) with three non-absorbable sutures (white arrows), PremiCron (HR26s, braided, coated, non-absorbable sutures, Braun Surgical, S.A. Rubi. Spain). The two black asterisks mark each arm of the PVDF-replacement structure for USL replacement. Note that both parts of the PVDF structure already run below the peritoneal fold of the left and right USL

Fig. 2

Schematic view of the PVDF-tape in the small pelvis. Position of the specially designed polyvinylidene-fluoride (PVDF) tape (DynaMesh CESA, FEG Textiltechnik mbH Aachen, Germany) for cervicosacropexy (CESA) in the small pelvis. These tapes were attached distally on the cervical stump and proximal to the prevertebral fascia on the sacral vertebra in the level of S1/S2. The two black arrows show the arms of the PVDF-tape, which are intended for bilateral uterosacral ligament (USL) replacement. S sacrum; C cervix, V vagina, B bladder, P pubic bone

Fig. 3

Overview of the different fixation methods. Fixation of the central part of the PVDF-tape (DynaMesh CESA, FEG Textiltechnik mbH Aachen, Germany) with three different fixation devices. a Group 1 (three interrupted sutures) used PremiCron (HR26s, braided, coated, non-absorbable sutures, Braun Surgical, S.A. Rubi. Spain). b Group 2 (three titanium tacks) used a fixation device (ProTack, Auto Suture 5 mm, Covidien, Mansfield, MA, USA) c Group 3 (three violet absorbable tacks) used a different fixation device (AbsorbaTack^™ Covidien, Mansfield, MA) (ProTack^™)

Fig. 4

Displacement–force diagram. Shown is a representative displacement–force diagram, exemplary for the tape fixation with sutures (Group 1). On the Y-axis, the Load is recorded in Newton (N), on the X-axis the Displacement is recorded in mm. At the beginning, the diagram has a part with low stiffness which changes to a part with high stiffness. In this work, stiffness was calculated as the slope in the part with high stiffness. The black box shows the maximum load that the cervical tape fixation could withstand until a mesh failure occurred

Fig. 5

Testing set-up. Shown are representative images of the complete testing set- up for the in vitro experiments with the porcine cervices. a There are 5 cm between the surgical clamp and the central part of the PVDF ligament-replacement structure (DynaMesh CESA, FEG Textiltechnik mbH Aachen, Germany) that is fixed on the cervix and 7 cm from this fixation point to the metal bar. b Shown is the testing setup for the porcine cervices using the Instron 5565^®

Fig. 6

Failure modes for all three groups. Shown are the most common failure modes for the three different fixation devices used with the PVDF-tape (DynaMesh CESA, FEG Textiltechnik mbH Aachen, Germany) on the porcine cervices after the experiments have been performed. a Mesh failure in group 1 after the fixation with three single sutures, PremiCron (HR26s, braided, coated, non-absorbable sutures, Braun Surgical, S.A. Rubi. Spain). b Mesh failure in group 2 after the fixation with three titanium tacks (ProTack, Auto Suture 5 mm, Covidien, Mansfield, MA, USA). c Fixation Device Failure in group 3 after the fixation with three absorbable tacks (AbsorbaTack^™ Covidien, Mansfield, MA)