Pelvic organ prolapse (POP) is known to be one of the most common reasons for submission of woman in hospital and indication for surgery. The uterine prolapse is described to affect up to 14.2% of woman. Our society is ageing, and life expectancy is growing. Furthermore, age and obesity are considered the main risks for POP. The incidence of POP is therefore likely to get higher in the future. Almost 11 to 19 % women will likely undergo POP surgery. In the US approximately 300.000 surgeries are performed each year in order to treat POP. Abdominal sacrocolpopexy is currently considered to be the gold standard of treatment. Since POP is affecting a large number of women and surgery is considered the gold standard optimizing surgery techniques will hopefully reduce time for surgery and therefore morbidity of the patients. 
The main problem remains the point of fixation as well as the manner in which sutures are implemented. There is no biomechanical analysis available in this area. 
In a previous biomechanical analysis we evaluated the value of combining several sutures compared to a single suture with or without artificial mesh interponation  (1). Our Results showed that a single suture may at times be sufficient for adequate suspension. Further biomechanical analyses were required in order to evaluate the choice of suspension ligament as well as suture placement in relation to ligamental fiber orientation.
The goal of this biomechanical analysis was to evaluate three main parameters. 
1)	Establish a baseline for the sacrospinal ligament biomechanical parameters for a single suture including: Maximum Load (N), Displacement and Failure (mm) and Stiffness (N/mm).
2)	Evaluate Data for in-line suturing and orthogonal suturing.
3)	Compare these findings to current literature.

The evaluation procedure has been established in a previous publication. Similar to this method we performed all experiments on human non-embalmed, fresh, female cadaver pelvices. Preparation of the sacrospinous ligament was performed by an experienced gynecological surgeon. An Instron test frame was used for load/displacement analysis. The average patient age was 75 years and ligament preparation resulted in 14 available ligaments for testing.  A total of 14 trials were performed. 
Following analysis groups may be differentiated:
Group 1 (n=7) evaluated the sacrospinal ligament with an orthogonal suture (S O). Group 2 (n=7) evaluated the sacrospinal ligament with an in-line suture (S IL).
A synthetic, braided, non-absorbable Ethibond suture 0, FSLX needle, 75 cm green filament (Ethicon / Johnson & Johnson, Somerville, NJ, USA) was used in all trials. 
Analysis was performed on an Instron 5565® test frame using the Bluehill 2 Software®. All tests were transient evaluations of the individual fixation methods at 5 N/s load increase. Recorded parameters were ultimate load (N) and displacement at failure (mm). These resulted in calculated parameters such as stiffness (N/mm) and load at 2 mm displacement. The latter being considered as fixation failure in biomechanical evaluations since stability may be lost as dehiscence exceeds 2 mm. 
Statistics
Statistics Statistical analysis was performed using the VassarStats1 (Vassar College, Poughkeepsie, NY, USA) statistics program. ANOVA analysis and t-tests were used in order to evaluate significances when appropriate.

This in-vitro analysis of different suturing methods showed the main difference between an orthogonal and an in-line approach to be the ultimate load. Orthogonal sutures showed an ultimate load of 80 N while in-line suturing showed to yield only 57 N (p<0.05). No significant difference could be established for the parameter’s displacement at failure and stiffness.

Our results show that an orthogonal suture is superior to an in-line suture.

This is the first biomechanical data to this extent. Orthogonal sutures should be preferred to in-line suture whenever possible.

Sauerwald et al., 2016