Title: Acellular Dermal Matrix for Chest Wall Reconstruction in a Rabbit Model

Authors: Luther H. Holton III, MD, Thomas L. Chung, DO, Ronald P. Silverman, MD, Hafez Haerian, BA, Nelson H. Goldberg, MD, Whitney M. Burrows, MD, Andrea Gobin, PhD, and Charles E. Butler, MD

Full-thickness defects of the lateral chest wall requiring surgical reconstruction can occur as a result of trauma, infection, radiation, resection to treat a malignancy, or a combination of these causes. The goals of chest wall reconstruction procedures include maintaining an airtight seal of the pleural cavity, reestablishing chest wall integrity to protect the contents of the thorax from trauma and infection, restoring sufficient rigidity to prevent paradoxical chest wall motion, and, when possible, providing an acceptable cosmetic result. Synthetic mesh is frequently used for chest wall reconstruction but infection or exposure can occur and necessitate removal.1 Human acellular dermal matrix (ADM) has been used to reconstruct musculofascial defects in the trunk with low infection and herniation rates.2 ADM may have advantages over synthetic mesh for chest wall reconstruction. This study compared outcomes and repair strengths of ADM to expanded polytetrafluoroethylene (ePTFE) mesh used for repair of chest wall defects.

Methods:A3cm2 full-thickness right lateral chest wall defects was created in each rabbit by removing the central 3cm of the 6th through 8th ribs including the intervening intercostal musculature and underlying parietal pleura. The defects were then repaired with either ePTFE(n=8) or ADM (n=9). At 4 weeks, the animals were euthanized and evaluated for: lung herniation/dehiscence; strength of adhesions between the implant and intrapleural structures, and breaking strength of the implant materials and the implant-fascial interface. Tissue sections were analyzed with standard histology to evaluate cellular infiltration/repopulation. Frozen sections were procured and processed for immunohistochemical staining with anti-CD31 antibody, a marker for vascular endothelium.

Results:No animals experienced respiratory complications and no paradoxical chest wall motion was detected for any animal. Additionally, no herniation or dehiscence occurred with either material. The incidence and strength of adhesions was similar between materials (Table I and Figure 1). The mean breaking strength of the ADM-fascia interface (14.2 ± 8.7 N) was greater than the ePTFE-fascia interface (10.0 ± 5.7 N; p=0.028) and similar to the rib-intercostal-rib interface of the contralateral native chest wall (13.6 ± 5.1 N) (Tables II and III). The ADM grafts became infiltrated with cells and vascularized after implantation.

Conclusions:ADM appears to be a reasonable option for reconstruction of lateral chest wall defects. ADM used for chest wall reconstruction results in greater implant-defect interface strength than ePTFE with a similar adhesion profile. The ability of ADM to become vascularized and remodeled by autologous cells and to resist infection may be advantageous for chest wall reconstruction. Further studies will be important to determine the long-term outcome of biologic materials used in chest wall reconstruction.

TableI. General Wound Complications Stratified by Type of Graft Material

No. Cases (%) by Graft Type
ADM (n= 9) / ePTFE (n = 8)
Complications+
Seroma / 3 (33%) / 2 (25%)
Dehiscence / 0 / 0
Abscess / 0 / 0
Herniation / 0 / 0
Adhesions+
Incidence / 8 (89%) / 8 (100%)
Mean grade* / 1.3 ± 0.9 / 2.0 ± 1.0

+ No significant difference between ADM and ePTFE for any complication or for the incidence or grade of adhesions.

* Adhesion grade: 0 = none, 1 = easily freed with gentle tension, 2 = freed with blunt dissection, and 3 = freed with sharp dissection. P = 0.16 for difference between ADM and ePTFE.

Table II. Results of Tensile Strength Testing

Material Tested / No.
Strips Tested / Mean Ultimate Tensile Strength ± SD, N / Range, N
Native chest wall / 24 / 13.6 ± 5.1 / 4.1-21.8
ePTFE-fascial junction / 30 / 10.0 ± 5.7 / 1.5-27.7
ADM-fascial junction / 32 / 14.2 ± 8.7 / 2.3-36.3
Explanted ADM / 9 / 71.0 ± 22.9* / 39.7-107.7
Non-implanted ADM / 18 / 68.1 ± 16.5 / 32.9-100.1
Non-implanted ePTFE / 24 / 62.5 ± 4.1 / 56.2-71.5

* The values for this group may be artificially low because 6 of 9 samples slipped from the clamps before the force required to cause failure could be reached.

Table III. Comparison of Ultimate Tensile Strength between Groups

Groups Compared / p Value *
ADM-fascial group vs. ePTFE-fascial group / 0.028
ADM-fascial group vs. native chest / 0.744
ePTFE-fascial group vs. native chest / 0.018
Explanted ADM vs. non-implanted ADM / 0.748
Non-implanted ePTFE vs. non-implanted ADM / 0.170

Two-tailed Student’s t-test.

Figure 1. Mean breaking strength (Newtons) of ADM-fascia (A-F) interface (n=32), ePTFE-fascia (G-F) interface (n=30), and native chest wall (NC) (n=24).

References

  1. Szczerba, S. R., Dumanian, G. A. Definitive surgical treatment of infected or exposed ventral hernia mesh.Ann. Surg. 237(3): 437, 2003.
  2. Butler, C. E., Langstein, H. N., and Kronowitz, S. J. Pelvic, abdominal, and chest wall reconstruction with alloderm in patients at increased risk for mesh-related complications. Plast. Reconstr. Surg. (in press).

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