A biomechanical study of the aponeurotic inguinal hernia repair

The aponeurotic inguinal hernia repair is essentially a union of the aponeuroses of the external oblique and transversus abdominis muscles in the groin. Its tension-free status and resistance to intra-abdominal stress were measured in a biomechanical study. Comparative studies were made with the American Bassini procedure. Suture tensions were measured at three sites in six aponeurotic repairs and the mean tension was 3.9 +/- 2.9 grams, which was within the accuracy of the combined transducer and recorder measurement. Similar measurements in six American Bassini operations registered 633 +/- 230 grams mean tension. A relaxing incision in the Bassini repair reduced but did not eliminate tension. Mean tension figures remained at 401 +/- 198 grams. Specimens of external oblique aponeuroses in six random patients were tested, counter to their parallel fibers, in a tensiometer. The thickness of the specimens varied from 0.21 to 1.2 millimeters. The tissue mean stress capacity under tension was 4.1 +/- 1.9 x 10(6) pascals with a range of 2.5 to 6.5 x 10(6) pascals. An analysis was made of the impact of intra-abdominal pressure at five possible sites of failure in the aponeurotic repair. Established values of suture bite tissue tear resistance and our values of external oblique aponeurosis stress tension were used to calculate the resistance of the aponeurotic repair to established values of intra-abdominal pressure. The maximum reported intra-abdominal pressure is 26.6 kilopascals. In this series, the largest reconstructed inguinal floor was 5 square centimeters and supported a load of 1,360 grams force. There was a safety margin of 2.4 against a failure of tissue of minimal thickness (0.2 millimeter) in the aponeurotic repairs when subjected to maximum intra-abdominal pressure. With average thickness of specimen (0.45 millimeter) there was a safety margin of 5.4. The 2-0 polypropylene suture had a requirement of 1,590 grams force maximum knot pull strength, which was much greater than our measured tensions. The added suture-line tension created by the assumed intra-abdominal pressure with sutures spaced one-half centimeter apart was calculated to be 65 grams force. This figure is well below the reported tensions of 5,300 and 9,100 grams force resisting tissue pull through failure in the external oblique and transversus aponeurosis, respectively. The transversalis aponeurosis component of the repair had shown in the proceeding study a tensile strength greater than the external oblique aponeurosis, and by analogy, a competence to resist intra-abdominal pressure.(ABSTRACT TRUNCATED AT 400 WORDS)