Techniques in the Safe Use of Polycaprolactone.

Structural Rhinoplasty is a term use by rhinoplastic surgeons wherein the existing structures are reconstructed and strengthened for functional and aesthetic improvement of the nose. The function refers mainly to breathing by correcting septal deviation and enlarging the internal valves.¹

The usual surgical method is open rhinoplasty approach and all anatomical structures are analyzed. The central septal cartilage is removed while the remaining dorsal and caudal strut are reconstructed for better breathing and tip support.² The general concept is to alter the length and height of the existing dorsal and caudal strut by restructuring with the use of the central harvested cartilage. Cartilages used for strengthening the struts are called structural grafts while cartilages used for tip reshaping and projection are called contour grafts.³

Structural grafts commonly include the columellar strut graft, septal extension graft (SEG), spreader graft or extended spreader graft (ESG).1 The columellar strut and SEG are used for lower cartilage and tip support. The spreader graft is used for strengthening the dorsal strut and enlarging the internal valve. The ESG is a spreader graft that is extended beyond the anterior angle of the septum for support of lower cartilage and tip. Among the structural grafts for lower cartilage tip support it is the Septal Extension Graft (SEG) that gives the best longevity.4 The SEG is either placed side-to-side to the caudal strut or end-to-end supported by bilateral extended spreader graft (ESG). (Figures 1 & 2) Sometimes, a combination of ESG with SEG is needed to correct weakness of the struts. (Figure 3) Contour grafts are usually the dorsal graft and tip grafts. (Figure 4)

Because Asian (specifically South East Asian) noses are usually small, the harvested septum is often small and soft.^3,4 Occasionally, the septum may look strong but upon harvest the dorsal and caudal struts weaken. Additional cartilage grafts are usually needed either from the auricle or from the rib. Auricular cartilage is too soft as support graft while the rib cartilage is strong because of its resemblance to septum in its histology. Autologous rib rhinoplasty is not only tedious and invasive but also more expensive which most patients do not prefer. Because of the paucity of septum, there are many substitute commercial materials in the market which can simulate the strength of septal cartilage as support graft. These can be homologous processed human rib cartilage, or alloplastic non-absorbable porous polyethylene. These materials are prone to long term complications e.g. warping, fracture, infection, resorption and extrusion.^5,6 Scientists and bioengineers recently developed polycaprolactone (PCL) which is a new synthetic absorbable porous material. It is marketed as a better material because not only it gives support but it also serves as a scaffold for tissue regeneration.^7-9

Polycaprolactone (PCL) is an absorbable material used in craniomaxillofacial surgery as a scaffold for defects.¹⁰ It is absorbed completely in 2 years. It is also a material used as threads in facial rejuvenation.^11-13 Recently, PCL has been fashioned into mesh for use in septoplasty and rhinoplasty as implants and support.^14,15 Its use is mainly as a scaffold for tissue regeneration and support. It has been shown in studies that osteoblasts, chondroblasts and mesenchymal tissues grow into its pores.^{10, 15} It comes in various shapes and sizes. The ideal ones for use in nasal surgery are the 10 mm x 30-40 mm mesh plate with thickness variety of 0.8-1.2 mm. (Figure 5)

Polycaprolactone is not used routinely; it is still best to use all autologous tissues. The indication of the use of PCL depends on the structure of the nose (mainly the septum). It is best for use in cases of small septum with inadequate septal material for correction of deviation. It is also best for use in cases of weak septum or weak dorsal/ caudal struts after septal harvest to correct any possibility of collapse. Moreover, PCL is not advisable in severe contracted nose because forces of healing may lead to wound dehiscence, extrusion and infection. Extrusion and infection may also happen while PCL is still not completely absorbed in 2 years. 

Since PCL is noted to lose its strength but provide well as a template for tissue regeneration, it is recommended to cover the PCL with septal or conchal cartilages whenever possible for 2 reasons: firstly, for protection against mucosal erosion; and secondly, as cartilage regeneration template for future support. (Figure 6). The decision to use PCL is made intraoperatively. The PCL mesh is fashioned into either an end-to-end SEG or ESG; both techniques of grafting are covered majority with cartilages. Following is the algorithm showing the indications when to use PCL after open rhinoplasty approach and assessment of the strength of the septum:

There are times wherein minimal surgery is needed for tip projection. Since Asian noses have weak medial crura with heavy skin and soft tissue envelope, PCL can be used just as a columellar strut - either floating or fixed to the posterior caudal septum. Fixing to the posterior caudal septum functions similar to a SEG too. However, these techniques may be unstable. (Figures 12 & 13)

Polycaprolactone was commercially available locally in the latter part of 2018. From August 2018 to March 2020, I used PCL in 213 (40.7%) out of 523 cases of septoplasty for structural rhinoplasty for various indications. All outcomes were followed up through calls and/or texts and all results were good with all patients satisfied with their results as of this writing, except for two. One patient developed post-operative deviation of the SEG after a week; the etiology was due to the improper choice of PCL strength. Revision surgery was done with replacement by a thicker PCL. Another patient developed infection after 4 months. Revision surgery involved removal of PCL and placement of columellar strut for support. This initial experience with the use of PCL is promising but it is too early to conclude. Long term follow-up should be done to see changes in structure when the PCL is totally absorbed.

In summary, PCL is a strong absorbable tissue template mesh in septoplasty and rhinoplasty. It is gradually absorbed within 2 yrs. While it is in its early stage as a mesh graft, it gives strength. However, as it is slowly absorbed, it imbibes the surrounding tissue cells for regeneration for future strength. It is highly recommended to cover the PCL with cartilages to prevent erosion to surrounding mucosa. Aside from protection of the PCL against erosion and extrusion, the cartilage also gives the future strength as chondrocytes grow into the PCL mesh.