Gauging the Tension: A Simple and Reliable Method to Quantify the Forces Generated on Fascial Closures in Hernia Repair and Component Separation

Introduction: Ventral hernias are a common complication after open abdominal surgery. Excessive tension on the fascial line of closure is an established and major cause of recurrence. Although hernias in the literature are most commonly characterized by area, almost no clinical literature exists that describes the actual tension experienced by the fascia at closure. Thus, small hernias surrounded by less compliant tissue may actually be at higher risk for recurrence than larger hernias with more elastic tissues. Here we aim to develop an accurate and simple technique for intra-operatively measuring the tension of the fascia on closure during hernia repair.

 

Methods: A simple device (tensiometer) was created using a spring with a known recoil constant (k) hooked to a Kocher clamp, which was attached to a fascial defect and pulled until the fascia reached midline. By measuring the change in length of the spring, the resulting tension on the fascia could be calculated by Hooke’s Law (Force=kX; k=spring constant, x=spring displacement). This method was applied first to a synthetic skin secured on one end to test validity over a range of forces by two independent observers. Next, the model was tested on the anterior abdominal fascia of 4 fresh cadavers(8 hemi-abdomens) over a range of simulated hernia defects from 0 to 18cm wide. When the fascia could no longer be approximated to midline, a components separation(CS) was performed and measures repeated. Measurements were taken in triplicate for each defect size by 2 observers for each hemi-abdomen at the midpoint and 1/3 from the inferior and superior most points. All measurements were plotted as force versus defect size, allowing calculations of tissue stiffness. Given our novel methodology, pearson’s correlation was calculated to validate the reliability of our technique. P-values less than 0.05 were considered significant.

 

Results: When the synthetic skin edge was pulled to 3, 5, and 8 cm, the spring length was increased to 8.6, 9.3, and 10.4 cm, respectively, resulting in a force of 10.44, 14.12, and 19.90 N (SD 0.1). In cadavers, defects ranged from 1 to 18cm in diameter with average midline force prior to release 36.1N(range 17-48) and 8.2N (range 5-11) after CS, a mean 436% decrease(range 327 to 677). Mean R² values between defect size and tension for the synthetic and cadaver models were 0.99 (p<0.01) and 0.91(p=0.01; all values significant), demonstrating the precision of this methodology in quantifying fascial tension. Inter-rater pearson’s correlation between observers consistently found R² values >0.95(p<0.01) for each hemi-abdomen, showing this model to be highly reproducible.

Conclusion: We have developed a low cost, simple, and precise method of assessing fascial tension on the hernia suture line. This technique may be rapidly translated into the operating room, requiring only a Kocher and a spring made of medical grade stainless steel that can easily be sterilized using an autoclave. Quantifying the fascial tension at the time of hernia repair would provide significant objective data to surgeons critical for intraoperative decision-making, leading to improved outcomes and reduced incidence of recurrent hernia.