Ann Thorac Surg 2002;74:209-212
© 2002 The Society of Thoracic Surgeons
Original article: general thoracic
Reconstruction of diaphragm using autologous fascia lata: an experimental study in dogs
Kazuya Suzuki, PhD*a,
Tsuyoshi Takahashi, MDa,
Yasushi Itou, MDa,
Katsuyuki Asai, MDa,
Hiroshi Shimota, MDa,
Teruhisa Kazui, PhDa
a First Department of Surgery, Hamamatsu University School of Medicine, Handayama, Hamamatsu, Japan
Accepted for publication March 21, 2002.
* Address reprint requests to Dr Suzuki, Hamamatsu University School of Medicine, 1-20-1 Handayama, 431-3192 Hamamatsu, Japan
e-mail: kazuya36{at}hama-med.ac.jp
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Abstract
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Background. We investigated whether fascia lata is an appropriate material for reconstruction of the diaphragm.
Methods. A diaphragmatic defect (2 cm by 5 cm) was reconstructed with a patch of autologous fascia lata in the experimental group (n = 12) and with expanded polytetrafluoroethylene in the control group (n = 12). Maximal tensile strength at the sutured region was measured serially.
Results. The maximal tensile strength at the sutured region reconstructed with the fascia lata was 1.14 ± 0.50 kgf 15 days and 2.04 ± 0.94 kgf 30 days after operation. The values were higher than those of expanded polytetrafluoroethylene (p < 0.0001). These values of fascia lata were close to the original maximal tensile strength of the muscular region of the diaphragm (1.52 to 1.66 kgf).
Conclusions. Reconstruction of diaphragm using autologous fascia lata is safe, easy, and inexpensive, and provides smooth wound healing. The only disadvantage is the necessity of a femoral incision for harvest; nevertheless, it may be worthwhile to use fascia lata in clinical trials to further assess its suitability as a reconstruction material.
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Introduction
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Invaded diaphragm is excised in operations for intrathoracic malignant tumors such as lung cancer and pleural mesothelioma [1, 2]. When the excised area is wide, the diaphragm cannot be directly sutured and prosthetic reconstruction is necessary. Applicable artificial materials include expanded polytetrafluoroethylene (ePTFE) sheet, Dacron mesh, and polypropylene mesh [3]. However, artificial materials are weak against infection and induce foreign body reactions, and they are expensive. As biological materials, bovine pericardium and dura mater are commercially available, but these materials have risks of immune response and infection, and are also expensive [4]. As a result, autologous tissues, pedicled latissimus dorsi muscle flap and pedicled rectus abdominis muscle flap, have been used [5, 6]. Because these tissues are autologous and contain blood flow, there is no concern about infection or allergic reaction, and wound healing is smooth. However, the surgical procedure is complex and requires technical skill [7]. Because the fascia lata is one of the strongest fasciae in the body and is easy to obtain, free fascia lata has been used in a variety of operations [8–10]. However, there has been no detailed study other than a case report regarding use of fascia lata in the reconstruction of diaphragm [11]. In this study, we experimentally investigated whether free fascia lata is applicable as a prosthesis for the reconstruction of the diaphragm, compared to ePTFE, which is used most frequently.
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Material and methods
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Twenty-four beagles weighing 8 to 12 kg were used. Under general anesthesia induced by intravenous injection of 30 mg/kg pentobarbital, respiration was controlled using an intratracheal tube and a respirator. A 5-cm skin incision was made on the lateral side of the left thigh, the subcutaneous tissue was separated, and a piece of fascia lata (2 cm by 5 cm) covering the vastus lateralis muscle was excised. This fascia lata was used as a patch to reconstruct the diaphragm in the experimental group, and in the control group a portion of the fascia was used in a traction test.
Left thoracotomy was performed at the seventh intercostal space and a 2-cm by 5-cm patch of the central diaphragm was excised. In the experimental group, the defect of diaphragm was reconstructed by patching with autologous fascia lata with continuous sutures using a 4-0 polypropylene thread. In the control group, the defect was reconstructed by patching with ePTFE (0.4-mm thickness) using the same procedure. Antibiotic (cefmetazole sodium, 0.3 g) solution was dispersed over the thigh wound as well as in the left thoracic cavity. After a thoracic drain was indwelled, the incision was closed, and the thoracic drain was removed after about 1 hour.
Two animals on postoperative days 4 and 7, and four animals on postoperative days 15 and 30 from each group (a total of 24 animals) underwent left thoracotomy, and the reconstructed diaphragms were excised. The excised diaphragmatic specimens with pleura and peritoneum were used for histopathologic examination and for a traction test performed within 30 minutes after harvest. The nontreated (right) sides of the diaphragm were harvested in 12 animals. In the traction test, strips measuring 2-cm by 0.5-cm were prepared from the specimens and ePTFE, and both ends of each strip were held and gradually pulled by an extensometer (Extensometer for Soft Specimens SES-1000, Shimadzu Corporation, Tokyo, Japan). Because the traction test was continued until tearing, each strip could only be used once. The tensile strength was continuously measured using a polygraph. In the patch-reconstructed specimens, strips were prepared using the suture line as the center point, and measurement taken as per the protocol. Six strips from each fascia lata (a total of 72 strips; 36 perpendicular, 36 parallel to fibers), one strip of each central tendon (a total of 12 strips), four strips (two perpendicular, two parallel to fibers) of the muscular portion of each right diaphragm (a total of 48 strips), and four strips from each reconstructed specimen (a total of 96 strips) were prepared. The maximal tensile strength (in kilogram-force) immediately before tearing was regarded as the maximum measured value. These values were averaged, represented by mean ± standard deviation, and were compared by unpaired t test. Two-thirds of the strips (48 strips) from the excised fascia lata were cultured in a medium (RPMI-1640, 10% fetal bovine serum) at 37°C in 5% CO2 for 3 days (24 strips) and for 10 days (24 strips) to examine their degeneration after excision, and the maximal tensile strength was measured over time.
The experiment was conducted in conformity with the Guidelines for Animal Experimentation of Hamamatsu University School of Medicine, which is in compliance with the "Guide for the Care and Use of Laboratory Animals" published by the National Institutes of Health.
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Results
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Different numbers of strips were used in each group during the traction test, because some strips tore at the ends where they were held, and as a result data from these strips were abandoned. In the central tendon group, the maximal tensile strength of the nontreated diaphragm, immediately after excision, was higher than that in muscular region, as shown in Table 1.
The maximal tensile strengths of the fascia lata were equivalent to that of ePTFE, and these values were significantly higher than those of the nontreated native diaphragm (p < 0.0001). Table 2
shows the results of the traction test of the cultured fascia lata. The maximal tensile strength, both in the longitudinal direction and in the short axial direction, showed no significant decrease after incubation.
The maximal tensile strengths at the sutured region of the diaphragm with fascia lata were 0.10 ± 0.07 kgf (n = 8), 0.15 ± 0.04 kgf (n = 8), 1.14 ± 0.50 kgf (n = 16), and 2.04 ± 0.94 kgf (n = 16) after 4, 7, 15, and 30 days, respectively. The maximal tensile strength at the sutured region of the diaphragm with ePTFE were 0.09 ± 0.04 kgf (n = 8), 0.12 ± 0.05 kgf (n = 8), 0.41 ± 0.10 kgf (n = 14), and 0.49 ± 0.26 kgf (n = 15) after 4, 7, 15, and 30 days, respectively. There were significant differences between the experimental and control groups after 15 and 30 days (p < 0.0001) (Fig 1). These values of fascia lata (15 and 30 days after operation) were close to the original maximal tensile strength of the muscular region of the diaphragm.
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Fig 1. Changes in tensile strength at suture line. Sutured region using fascia lata shows higher tensile strength (as strong as original diaphragm) than that using expanded polytetrafluoroethylene (ePTFE) on 15 and 30 days after reconstruction.
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All animals were alive after operation, and complications such as hernia, infection, and bleeding were not observed. On macroscopic observation during thoracotomy, the surface of the fascia was covered by the surrounding tissue, and was continuous with the native diaphragm in the experimental group after 1 week. In the control group, adherent fibrin was observed, but surrounding tissues did not cover the ePTFE patch at 1 week after operation.
On histopathologic examination, cells from the surrounding tissues invaded the fascial patch, and both thoracic and abdominal sides of the patch were covered by the tissue, and were continuous with the original diaphragmatic tissue after 7 days in the experimental group. New capillaries developed in the tissue, and the removal of only the fascia lata was not possible any more. The specimens reconstructed with ePTFE were not unified with the surrounding tissue, even after 2 and 4 weeks. Foreign body reactions were observed and removal of only the ePTFE patch was easy (Fig 2).
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Fig 2. Pathologic findings 30 days after reconstruction (hematoxylin and eosin-stained section, x20). (A) A specimen reconstructed with expanded polytetrafluoroethylene (ePTFE) is not unified with the surrounding tissue even after 4 weeks. Foreign body reactions (white arrows) are observed, and the expanded polytetrafluoroethylene patch could be easily detached (black arrows). (B) Autologous fascia lata is buried in the tissue as if it is a part of the original diaphragm. Viable cells and vessels are present, and no inflammatory reaction is observed.
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Comment
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When a large area of the diaphragm is excised, it is necessary to use a material for reconstruction [1–3]. Artificial materials, animal-derived materials, and autologous pedicled muscle flaps have been used. Artificial materials are easy to use, but are weak against infection. If an infection occurs, the artificial material has to be removed. Foreign body reactions or allergic reactions may also occur. Moreover, artificial materials are expensive [4]. Animal-derived materials have risks of immune response and infection, and are also expensive. The use of autologous pedicled muscle flap generates no concerns regarding foreign body response or infection, but the surgical procedure is complex [5, 6]. Meticulous attention must be paid to preserve adequate blood flow. Moreover, muscular injury or functional loss is incurred at the site of the harvest [7]. Thus, an autologous material that can be used as a free graft without concerns of foreign body response, allergic reaction, or infection would be very useful.
On the basis of our experience of using autologous fascia lata as a patch material for pericardium [12, 13], we considered that fascia lata is also useful for reconstruction of the diaphragm and undertook this study [11]. The fascia lata is one of the strongest fasciae in the body, but no comparative study with the diaphragm regarding its strength has been reported. If the fascia lata is weaker than diaphragm, it cannot be used as a material for the reconstruction of diaphragm. Therefore, at first, we measured the maximal tensile strength of diaphragmatic tissue and fascia lata [14]. The maximal tensile strength of the fascia lata was same as that of ePTFE (0.4-mm thickness), and was higher than that of any region of the diaphragm. When the fascia lata was cultured in a culture medium, the maximal tensile strength did not decrease and it retained a strength that was not less than that of the diaphragm. These findings suggest that the fascia lata, even in the free form, maintains an adequate strength and is applicable as a prosthesis for the diaphragm as with ePTFE. The fascia lata mostly consists of fibrous component, and even if the constituent cells are lost in the excised specimen, its strength may not change. In the experimental group, the maximal tensile strength of the sutured site of the diaphragm gradually increased after operation, and reached the original maximal tensile strength of the muscular region of the diaphragm 2 to 4 weeks after operation. Thus, the sutured region may have acquired a satisfactory strength by the time the strength of the suture materials decreased. Histopathologically, cells invaded the fascia lata from the surrounding tissues and the patch was unified with the native diaphragm 2 to 4 weeks after operation, and thus, the wound healing was judged to be smooth.
When ePTFE was used, the maximal tensile strength of the sutured region did not reach the original strength of the diaphragm, even 4 weeks after operation. Pathologically, the patch was not unified with the surrounding tissue, and therefore, a decrease in strength of the suture that may occur and infection is likely to cause dehiscence. Because complications after operation using artificial materials often occur within 4 weeks, in this study we evaluated the tissue response after 4 weeks [15, 16]. Some recent studies reported that fascia lata used in a variety of operations showed good long-term results [17]. However, more long-term studies will be necessary to further clarify the properties of the materials used, and to apply them clinically. We studied the most commonly used ePTFE in this experiment. As found in many previous reports concerning prosthetic materials, artificial materials other than ePTFE seem to be exhibiting a similar reaction in comparison with autologous fascia lata.
As for the expense, harvesting of fascia lata costs only about 15 to 20 dollars excluding the personnel cost, whereas a sheet of ePTFE measuring about 15 cm by 15 cm costs about 350 dollars in the United States and more than 100 dollars in Japan. Therefore, fascia lata may be one of the most inexpensive sheet materials worldwide.
Reconstruction materials are required to have the following properties: (1) fulfill the objective function (for reconstruction of the diaphragm, the material is required to separate the thoracic and abdominal cavities); (2) not induce foreign body response or allergic reaction; (3) provide smooth wound healing and unification with the surrounding tissue; (4) be resistant to infection; (5) be easy to handle; (6) be inexpensive; and (7) not degenerate in the long term.
Although there is a disadvantage in making an incision in the femoral region, which is necessary to obtain the fascia, autologous fascia lata seems to fulfill all the conditions described [17]. No other material fulfilling all these conditions has been found to date. In our clinical experience of using fascia lata for the reconstruction of pericardium [12], no dyskinesia at the femoral region was observed, and patients did not have pain, suggesting that excision of the fascia lata inflicted no extra invasiveness. Anatomically, the fascia lata covering the vastus lateralis muscle in dogs is not as wide as in humans. Therefore, a small size patch was used in this study in which wound healing around the sutured region was the focus of our investigation. On the other hand, it is easy to excise a patch of fascia lata measuring about 25 cm by 15 cm from adult humans [11]. Although there are many useful artificial prosthetic materials available, surgeons sometimes do not want to use them for a variety of reasons such as susceptibility to infection, delayed wound healing, aggressive surgical intervention, and sometimes the necessity of concomitant chemoradiation therapy. Judging from the original strength and good wound healing, we believe that it is worthwhile to use the autologous fascia lata in clinical trials to further evaluate its usefulness as a reconstruction material.
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References
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Abstract
Introduction
