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| REVIEW ARTICLE |
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| Year : 2019 | Volume
: 2
| Issue : 4 | Page : 119-124 |
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Tension measurements in abdominal wall hernia repair: Concept and clinical applications
Paul L Tenzel, Jordan A Bilezikian, Frederic E Eckhauser, William W Hope
Department of Surgery, New Hanover Regional Medical Center, Wilmington, North Carolina, USA
| Date of Submission | 04-Sep-2019 |
| Date of Acceptance | 11-Sep-2019 |
| Date of Web Publication | 22-Oct-2019 |
Correspondence Address:
Dr. William W Hope
Department of Surgery, New Hanover Regional Medical Center, 2131 South 17th Street, PO Box 9025, Wilmington 28401, North Carolina
USA
 Source of Support: None, Conflict of Interest: None  | 3 |
DOI: 10.4103/ijawhs.ijawhs_37_19
Tension has always been and remains an important concept in hernia repair. Revolutionary techniques in the field of hernia repair have generally aimed to reduce tension and thereby reduce recurrence rates. Despite the uniformly agreed upon idea that tension is an important part of hernia repair, little is known about this subject in ventral and incisional hernias. We reviewed all published journal articles related to abdominal wall tension. Articles were organized into basic science and clinical reports, and results were evaluated for type and technique of tension measurement and implications for clinical practice. Several cadaveric and clinical studies relate to the measurement of abdominal wall tension. Despite similar methods of measuring, there is no uniformly agreed upon device or measurement. Abdominal wall tension has not been correlated with hernia width, and abdominal wall tension measurement has shown to be a useful adjunct intraoperatively. Abdominal wall tension measurements likely have a role in both the research and clinical practice of hernia surgery.
Keywords: Abdominal, hernia, measurements, tension
How to cite this article:
Tenzel PL, Bilezikian JA, Eckhauser FE, Hope WW. Tension measurements in abdominal wall hernia repair: Concept and clinical applications. Int J Abdom Wall Hernia Surg 2019;2:119-24 |
| Introduction | |  |
Abdominal wall hernias affect nearly one million Americans each year and can result in serious complications and disability. Nearly 350,000 surgical repairs are completed annually in the United States, making it one of the most common general surgery operations.[1] Because of suboptimal outcomes using autologous repair techniques, a radical shift in philosophy relating to the repair of hernias came about with the concept of tension-free repairs and the use of mesh, first popularized in inguinal hernia by Stoppa et al.,[2] Usher et al.,[3] and Lichtenstein et al.[4] Mesh materials were developed and quickly adopted by surgeons worldwide to reduce recurrence rates. Using mesh materials improved surgical outcomes; however, vexing problems persist including pain, infection, and hernia recurrence which necessitates revision surgery in up to 30% of patients.[1] Mismatches between biomaterials and host tissue contribute to many of these failures. Other important contributing factors include our lack of understanding of the fundamental mechanical properties of the abdominal wall and/or the nature and effects of stresses created by surgical intrusions.
One of the main tenets of a successful open incisional/ventral hernia is closure of the midline fascia without undue tension and mesh reinforcement. Several techniques commonly referred to as myofascial releases have been developed in attempts to reduce tension at the midline closure. These techniques have been well described and involve incising different layers of the abdominal wall fascia and/or musculature.[5] Despite these well-described techniques and the commonly used tension-free repairs, very little is known about abdominal wall tension. This review paper summarizes the current literature related to the role of tension in abdominal wall hernia repair and extrapolates how measurements of tension can be used to potentially improve surgical outcomes and reduce recurrence rates.
| Methods | | |
We reviewed all published journal articles related to abdominal wall tension as it relates to hernia repair. Relevant articles were reviewed and grouped in basic science/cadaveric studies and clinical studies. Results related to tension measurements, use in operative decision making, and techniques and methods of measurement were summarized.
| Results | | |
Mechanical properties of the abdominal wall
The anatomy and structure of the abdominal wall is complex and has been described in detail elsewhere.[6],[7] The primary role of the abdominal wall is mechanical in nature, and each of the lateral myofascial layers contributes to provide stability, flexibility, and support. The linea alba is a vertical midline band of connective tissue that consists of a complex network of predominantly type I collagen, intermixed with elastic fibers. The linea alba and the lateral layers of the abdominal wall together create a composite structure that envelops intra-abdominal contents in a semirigid cylinder that exhibits both compliance (distensibility related to volume) and elasticity (having the capacity to stretch and return to its original shape). Tension on the intact abdominal wall can be calculated using La Place's law which states that “in an elastic spherical vessel,” tension equals diameter times pressure divided by four times wall thickness.[8] Tension is commonly defined as the force generated by muscle contractions. Even at rest, muscle is contracted slightly without producing movement to create tone which, in turn, continually stabilizes joints and maintains posture. At present, there is no simple, reliable, and reproducible methodology to characterize the mechanical behavior of the healthy abdominal wall and its response to intra-abdominal pressure changes that accompany fundamental activities of daily living. One study using computed tomography to numerically model global passive behavior of the abdominal wall showed that pressures as high as 170 mmHg (0.0223 MPa) can be generated with strenuous activity such as jumping.[9] To better understand linea alba biomechanics, Konerding et al. conducted a human cadaver study using progressive balloon inflation to simulate intra-abdominal pressure.[10] At a maximum balloon inflation pressure of 200 mbar, they measured forces acting transversely on the linea alba at between 41.6 and 52.2 N/cm (mean 45.9 N/cm). These experimental studies provide fascinating insights into abdominal wall biomechanics but are costly and have limited ability to reproduce natural and pathological situations, especially related to abdominal wall hernia repair.
Measurement of tension
A variety of experimental and computer-based modeling studies of the abdominal wall have been conducted to better define the properties of the abdominal wall and the mechanical behavior of biomedical materials.[11],[12] While not inclusive, [Table 1] summarizes the findings of many such studies related to abdominal wall tension measurements. Such studies typically are categorized as ex vivo testing of cadaveric abdomens or in vivo testing in live human subjects.[13],[14],[15],[16],[17] The results are difficult to interpret because of confounding variables such as the tools and methodology used to measure tensions, the site(s) and number of measurements obtained, and whether the study was conducted in cadaveric or living tissue. | Table 1: A summary of techniques and measurements of studies evaluating abdominal wall tension
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Cadaveric studies
Cadaveric study results are inherently flawed because the musculature of the abdominal wall has no dynamic tone, and while distensible in response to increasing pressure, has lost its elasticity. Nonetheless, several studies are noteworthy. Silveira et al. conducted a cadaveric study in specimens with an intact and surgically unaltered abdominal wall.[13] They incised and resected the linea alba from the level of the tenth rib to the inguinal ligament. Traction loops of nylon were placed 10 mm from the aponeurotic line at seven sites, including four below and three above the level of the umbilicus. An analog dynamometer was used to obtain measurements, and a traction index in kg/cm was calculated using traction force times mobilization distance from the aponeurotic point. The authors demonstrated no differences in traction index along the linea alba, suggesting it is subject to uniform forces along its entire length. In another, Barbosa et al. performed a similar study but measured traction index at 8 sites before and after incising and undermining the rectus muscles (Stage 1) and then incising and undermining the external oblique aponeurosis bilaterally (Stage 2).[14] The authors demonstrated a significant reduction in regional traction index after separating the anterior rectus muscles from their sheaths (Stage 1). Similar results were obtained after incising and undermining the external oblique muscles, with a more striking reduction in tension measured by the traction index. They suggested that this technology might be applicable for objectively measure tension during abdominal wall hernia repair and showed that medial traction at the midline aponeurosis can be reduced progressively by staged mobilization of the layers of the abdominal wall.
Clinical studies
Clinical studies employing tensiometry as a decision-making tool in abdominal wall hernia repair date back to Klein et al. and Reingruber and colleagues in 1996 and 2001.[18],[19] Dragu and associates in 2009 published a report of 23 patients who underwent reconstruction of the abdominal wall in the manner described by Ramirez et al.,[20] combined in some cases with the use of alloplastic material.[15] Intraoperatively, they measured tension using the method of tensiometry described earlier by Klein et al.[18] Tensiometry was used to determine the need for component separation versus autologous repair and to judge the need for mesh implantation. Based on previous studies and personal experience, a tensiometry value of 1.5 kilopounds (kp) at closure was considered critical with the patient completely relaxed. Ramirez-type component separation was performed in all patients. Following component separation, 14 patients (61%) had kP <1.5 and underwent primary reconstruction without alloplastic reinforcement. In nine patients (39%), kp values were > 1.5 and alloplastic material was implanted. After 56 months of follow-up, 17 of the original 23 patients (74%) were evaluable. Hernia recurrence was detected in three patients (18%). In addition to tension, the authors cited two additional predictors of outcome, including nature of the defect and size.
Afifi et al. in 2017 published an interesting study in which they used tensiometry to measure tension after each surgical step in component separation.[16] Following initial cadaver studies, 26 patients underwent surgical reconstruction of large midline abdominal wall defects. A dynamometer was used to measure the force needed bring the edge of each hemiabdominal wall to the midline as described by Reingruber et al.,[19] before dissection and at three points along the length of the abdominal defect after each stage of the dissection. After quantitative measurements had been obtained, the defects were closed in a standard fashion. Mesh was implanted at the discretion of the operating surgeon. The authors determined that the percentage change in tension was highest after release of the external oblique (>30%), and further improved by release of the internal oblique, dissection between the muscles, and finally, dissection of the subcutaneous tissues. The authors also noted that the percentage reduction rates in tension in the lower abdominal wall were comparable to those observed in the upper abdominal wall. While interesting, the study has several serious limitations. It is a small study, and results may therefore not be generalizable to a larger study population. While conclusively demonstrating that staged component separation decreases tension in midline closure, the authors intentionally made no mention of clinical outcomes. Thus, we cannot conclude from this study that reducing midline closure tension reduces hernia recurrences.
Tenzel et al. in 2019 published a preliminary assessment of abdominal wall tension in 45 patients undergoing retromuscular hernia repair.[2],[21] The study's purpose was to assess the effect of cutting the posterior rectus sheath on midline closure tension. This approach was originally described by Rives et al. and Stoppa et al.[2],[21] and allows placement of alloplastic material outside of the abdominal cavity in a well-vascularized space. The authors obtained tension measurements using Kocher clamps attached to a mechanical analog linear spring scale that measured tension in pounds and demonstrated a significant decrease in tension after bilateral posterior rectus sheath incision (5.6 vs. 31 lbs, P < 0.0001). All patients underwent retromuscular implantation of alloplastic material(s). This study was the first to measure changes in tension in patients following a retrorectus release. With an average follow-up of 268 days, three patients (6.7%) had hernia recurrences. This study was well conceived and executed but also has limitations. Because there was nonuniformity of alloplastic material implanted and a relatively short average follow-up (<1 year), it is difficult to generalize conclusions.
Hope et al. evaluated abdominal wall tension in 59 patients undergoing hernia repair.[22] They reported no correlation between width of the hernia defect and abdominal wall tension measurements.[22] This important finding highlights the common thought among surgeons that abdominal wall compliance varies among patients and you cannot rely on width of hernia defect only in hernia repair. It also means that abdominal wall tension measurement may be a useful technique in hernia repair, and hernia width is likely not the most important surrogate for tension.
| Discussion | | |
Tension is likely one of the most common terms used when discussing ventral and incisional hernias. Despite the common belief among all surgeons that tension is a very important factor in hernia repair, the concepts of passive and dynamic abdominal wall tension, particularly as they apply to abdominal wall hernia repair, are incompletely understood. It is intuitive that excessive tension can disrupt a midline aponeurotic closure and lead to hernia recurrence. This concern is certainly valid and has led, in conjunction with our improved understanding of the anatomy and biomechanics of the abdominal wall, to formulate better operations specifically designed to reduce tension. The importance of tension in this context is incontrovertible. However, we continue to struggle with developing reliable and inexpensive methods to measure tension and remain unsure about what the values mean in terms of intraoperative decision-making. Simple dynamometers or tensiometers are now readily available and inexpensive. The methodology for using them, however, is incomplete and nonstandardized. Many questions remain unanswered. How many points of reference should be measured, in what locations, and at which stages of the procedure? What is a critical tension value, above which alloplastic reinforcement should be considered? Should all abdominal wall hernia patients undergo concomitant and routine component separation procedures with repeat tension measurements before deciding on primary suture closure versus mesh-reinforced closure. Once we better understand the mechanical properties of the abdominal wall, not only as individual layers but as a composite, what biomaterials should be used to optimize reinforcement? What constitutes an “ideal” mesh, where should it optimally be placed, and in what orientation relative to the native tissues? These questions remain unanswered and are beyond the scope of this review.
There are likely several factors why measuring abdominal wall tension has not propagated in the hernia community. First, although there are several publications on the topic, many of these are in cadaveric studies and there are few published studies evaluating the clinical usefulness of this technique. Second, there is no universally agreed upon way to measure abdominal wall tension and no standard device used to measure it. While many published reports' methods of measuring abdominal wall tension are very similar, there has been no universally accepted method, and in a clinical scenario, the technique may be cumbersome and not easily adopted by a busy surgeon. In addition, there is no current description of measuring abdominal wall tension in laparoscopic or robotic repairs which may limit the use of tension measurements in minimally invasive surgery. There has been a description of measuring crural tension in minimally invasive foregut surgery, and this technology could likely be applicable to the abdominal wall.[23] Lastly, there may be some surgeons who do not see the benefit of measuring abdominal wall tension. Despite the proposed advantages for research and better understanding of the physiology of the abdominal wall, the routine use of abdominal wall tension may not be deemed as important by surgeons, especially surgeons dealing with smaller hernias. For increased use of abdominal wall tension measurements, several things must likely happen. First, increased exposure through publications and presentations at scientific meetings should occur. Second, there should be an agreed upon method and standard for measuring abdominal wall tension so that all surgeons are using the same technique and using the same “language.” Ideally, abdominal wall tension measurements could be embedded in hernia registries so that these objective measures can be studied and see how they affect surgical outcomes.
Another poorly studied concept is that of physiologic tension. Although described in some articles, the physiologic tension of the abdomen has not been well described. Moving forward, this will be an important measure and may help surgeons further understand the mechanics of the abdominal wall and may help intraoperative decision-making regarding when and what types of myofascial releases to perform.
There is now good evidence to suggest that further studies are warranted to improve our understanding of tension and how it relates to intraoperative decision-making in patients undergoing abdominal wall hernia repair. As surgeons interested in achieving better hernia repair outcomes, we now have new tools and methodology to better understand the concept of tension in abdominal wall reconstruction and apply it to improving our intraoperative decision-making. More standardized protocols and clinical studies are needed to generate meaningful data that can objectively guide improved intraoperative decision-making.[28]
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Table 1]
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