The holy grail of tracheal replacement

Total tracheal replacement has remained an unresolved challenge since Grillo formulated its 5 criteria for ideal tracheal substitute 50 years ago [1]. Today, 4 main solutions are investigated: composite autologous tissues construct, decellularized aortic allograft, 2 steps chimeric tracheal allograft and complete bioengineered construct [2]. Decellularized aortic allografts and cartilage-armed free flaps are the only 2 solutions with the largest clinical experience [3–5]. Both have limitations that should be reminded when confronted to diseases involving the entire trachea. Over the last 16 years, our team explored the autologous flap solution and described an original 1-stage reconstructive technique using a forearm free flap armed with custom-carved costal cartilage grafts. A total of 40 cases have been performed so far. Our 1st case was a non-circumferential defect after the resection of a thyroid cancer that preserved the carina. Today, patient is alive, cancer free, stent free, with patent trachea. However, our construct lacks respiratory ciliated epithelium lining, the only missing Grillo’s criteria. By progressively extending our indications to the entire tracheal length, including the carina, we could measure how crucial this imperfection was. The lack of mucociliary airway clearance led to bronchial secretions accumulation and fatal repeated lung infections. We learnt to limit our indications to entire tracheal defects preserving the carina as the capacity to cough, actively breath and move is a prerequisite for a successful outcome. In this article, De Fremicourt et al. [6] must be congratulated for exploring an innovative technique belonging to the autologous tissue family. They describe a tubulated internal mammary perforator flap combined with Ravitch procedure, incorporating the right cartilage breastplate and adjacent pleura. Three major improvements are postulated: avoidance of microsurgery, pleura as internal lining rather than skin and vascularized perichondrium to recreate cartilage ring. This cadaveric work pledge for exhilarating translational research as it brings into light multiple unresolved questions. First, pleura is presented as a better lining that will be replaced overtime by adjacent respiratory ciliated epithelium. This hypothesis requires to be demonstrated by an in vivo animal model. In addition, this replacement is time sensitive. Early mucociliary clearance restitution is needed to avoid pulmonary infection and is critical in case of distal carinal defects. At last, pleura remains a thinner and less resistant lining than skin and may show limit in resisting to stent or canulation trauma as well as airway infections. Second, the assertion that perichondrium may induce hyalin cartilage rings with biomechanical properties able to withstand respiratory depression forces needs to be proven. Third, free flap, in the hand of trained microsurgeons, is not a disadvantage and has a comparable success rate than loco-regional solutions. In addition, the forearm flap can be harvested during tracheal resection allowing for a comparable operative time. Avoiding microsurgery could be beneficial in patients with high risk for flap failure, and in democratizing tracheal replacement in cardiothoracic teams with no plastic surgery collaboration. As stated by the authors, pedicle positioning and length may be a matter of concern as care must be paid to avoid kink or stretch. In cadaveric condition, the impact of dynamic situation, such as respiratory movements or cough, could not be evaluated. In addition, this flap may not be adapted to all tracheal resection length, considering the anatomy of the internal mammary pedicle, and shape, such as the carina division. Work is still needed to define which indications may benefit from a pedicle flap solution. Finally, chest wall defect represents the last major concern. Bronchial clearance is ‘life keeping’ during postoperative course as conserving the capacity to cough and move is correlated to the clinical success of the tracheal replacement. Having mesh and bars at the level of the chest may hamper the capacity to recover and may complicate a theoretically simplified surgical procedure. Clinical translation research is critical for surgical technique addressing such complicated and life-threatening condition. This excellent anatomic work has a lot to demonstrate and prove before being adopted as a surgical solution for tracheal replacement. As a reminder, obtaining a construct with a respiratory ciliated epithelium lining on the day of the surgery represents the next predominant improvement towards extended airway reconstruction.

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