Analysis of techniques and complications of soft tissue expander in the treatment of facial and neck scars

Da-yong WEI,Guang-zhao HE, Jia LIU

Department of Burns and Plastic Surgery,the First Affiliated Hospital of Chongqing Medical University,Chongqing City,400016,China

ABSTRACT Tissue expansion is a naturally-occurring phenomenon.Human skin will stretch and expand naturally under continuous pressure,resulting in extra skin,which is the theoretical basis of expander reconstruction and repair.Tissue expansion technique is of great value in the reconstruction of various parts of the human body,especially in the treatment of facial and neck scars.The related complications are as follows:infection,hematoma,seroma,exposure,necrosis,displacement ,skin flap retraction and so on.Patient selection,surgical design and technical control are all indispensable for obtaining good aesthetic results and reducing the incidence of complications.

KEY WORDS tissue expansion,scar,complication,technique

Tissue expansion has been widely confirmed and applied.At present,the generally accepted principle of tissue expansion is that the skin is damaged repeatedly under pressure and tension during the expansion,while immune cells such as macrophages and lymphocytes gather at the damaged site to clear the necrosis and repair the defect[1].Skin tissue expansion can regenerate new skin and blood vessels,rather than simply elongate tissue cells,and unlike wound healing that causes scar tissue hyperplasia.Because of the peculiarity of the face and neck,the aesthetic result is very important in the scar repair of the face and neck.Traditional surgical methods (such as skin grafting)can not meet people’s needs for beauty.Soft tissue expansion surgery has certain advantages in the reconstruction and repair of facial and neck scars because it has a more matching color,structure and thinner flap,can reduce the defect of the donor area and even retain the sensation[2-5].However,due to the high incidence of complications and the long reconstruction process,the development of this technique is hindered to some extent.

ANALYSIS OF EXPANSION TECHNIQUE

Patient selection

When the area of facial scar is small and can be resected and sutured directly or when the local free flap is designed,the tissue expansion technique is not recommended for the repair and reconstruction,but for the large scar defect,it is the first choice.However,because this technique requires two or more surgeries,the whole treatment process lasts for a long time,and during the skin expansion,it will lead to face and neck deformity,to a certain extent,it will increase the psychological pressure of patients and some patients may not be able to accept the treatment process with declined compliance,which will eventually bring adverse effects to the expansion and increase the contradictions between doctors and patients[6].Therefore,the patient’s psychological stability and good compliance are the guarantee of successful surgery.In addition,the patient’s donor area must be complete and have good blood supply to ensure sufficient expansion to satisfy the defect repair.At the same time,the donor area must be healthy,because the expander,as an implant,any existing infection may lead to the occurrence of its related infection,as well as the failure of the expansion process.

Expander selection:the expander is mainly analyzed from its size,shape and expansion mode.

Selection of expander size:the general principle is to select the expander according to the size of scar and defect.The expander with matching size can not only meet the needs of scar repair area,but also minimize the expansion time and the incidence of complications.Fochtmann A,KarimiI H,et al.[2,7]mentioned in their study that the larger the expander ,the greater the expansion degree,and the higher the incidence of complications.However,Di Mascio D[8]believed that there is no significant statistical difference between the expander size and the incidence of complications,and a large expander or over expansion should be selected as much as possible,so as to get better aesthetic effect in the second-stage repair surgery.

Selection of expander shape:at present,there are circular,elliptical and square expanders available on the market[9].In foreign studies,the square expander is mostly selected;in China,because of some specific factors,the circular expander is basically used.Khalatbari B[3]believed that the square expander has a larger surface area,which can obtain a larger area of skin flap under the same volume.And compared with the circular expander,it is not easy to shift in the expansion process.But it should be noted that the square expander has a higher incidence of edge necrosis of skin flap.As for the oval expander,it is generally used for the reconstruction of microtia.

Selection of expander expansion mode:self-expanding expander,as the continuation and development of traditional expander,to a certain extent,increases the selection of expander and brings some advantages,but it can not replace the traditional expander.The traditional expander is expanded by the periodic injection through the injection valve,each of which inevitably brings needle pricking and increases the risk of infection.Selfexpanding expander has no such concerns,but the uncontrollability of expansion speed and degree and the increase of cost limit its wide application[10].

Expander implantation

Incision design:during the preoperative visit,the location of the donor area can be confirmed,the expandable tissue closest to the scar area of the face and neck is the conventional selection,and the selected tissues must have the maximum expansion ability to repair the burn scar tissue[11].After the donor area is confirmed,the incision design can be accomplished easily.If an advancement skin flap is used,the incision position where healthy skin can pass through the scar should be considered,that is,the junction between healthy skin and scar should be selected,and the distance between the healthy skin and the scar is 1-2cm[11-12].If a rotation skin flap is used,the factors for determining the incision site are as follows:guaranteed pedicle blood supply,undisturbed flap expansion and sufficient concealment of the incision[13].Healthy skin is selected for the incision to ensure that the expander is implanted under the healthy tissue to reduce the incidence of infection,exposure and other complications.In some cases with few healthy tissues,some scholars have performed the repair surgery by implanting an expander under the scar to increase the expansion area,and good results have been achieved[14,15].

Selection of expander implantation site for face and neck :according to the division of the face,the face is divided into the upper face (trichion to NFA),the middle face (NFA to subnasion),and the lower face ( subnasion to gnathion).The upper face is mainly the forehead.The expander for the forehead is implanted in the deep surface of the frontal muscle,and the incision line is designed at hairline.After the expander is implanted,the direct advancement skin flap can be designed,which can generally advance 3-4cm.If the transposition skin flap is used,it can repair large area of scar defect,but it is necessary to be wary of the formation of “cat ear” at the anastomosis of incision.For the scar in the middle face,the expander is directly implanted in the superficial surface of SMAS to ensure its stability.After the expansion is completed,the direct advancement skin flap or rotation skin flap is designed to repair the scar.When repairing the scar in the lower part,an expander can be implanted in the deep cervical fascia.After the expansion,the direct advancement skin flap is designed to repair.When the facial defect is large,the expander can be implanted in the neck,the transposition skin flap can be used for repair,and the pedicle can be medial or lateral.Because of the peculiarity of the face,it is necessary to be alert to eyelid ectropion and labial angle ectropion.The fundamental solution lies in reducing the retraction of the expanded flap and the tension at the suture,paying attention to the design of the expanded flap and ensuring sufficient expansion[7,16].Behzad[3]proposed that the dermal layer of the expanded skin flap could be sutured and fixed on the periosteum of the orbital margin to avoid ectropion.

Separation of expansion cavity:after the incision is established,the expansion cavity is separated bluntly and sharply.The size of the expansion cavity depends on the size of the expander,and the designed cavity is 10-20%larger than the tissue expander under the donor tissue[12,17].Before implanting the tissue expander,the cavity is washed with normal saline,and its safety and leakage are checked.The combination of electrocoagulation,ligation and other methods to achieve full hemostasis is the key to avoid postoperative hematoma complications ,which should not be compromised in pursuit of smaller incision.As’adi K et al.[18,19]proposed to implant the expander under the assistance of endoscope,which also proves the importance of hemostasis,and their hemostasis strategies that magnify the surgical field of vision can achieve twice the result with half the effort.As for the location selection of water injection valve,the following principles should be followed:there is enough distance between the water injection valve and the expander to avoid the difficulty of water injection or expander rupture caused by the pressure on the water injection valve after expansion; the water injection valve can be touched easily to facilitate the water injection and reduce the risk of tube rupture caused by needling; the water injection valve is located in a relatively hidden and healthy tissue to ensure facial beauty and reduce the risk of infection[20].

1.3.4 Embedment of drainage tube:after the expander is implanted,it is first necessary to confirm that the expander is flat and unfolded to ensure that the water injection tube is not bent and the head of the water injection valve is upward.The next step is to embed the drainage tube instead of suture.After the surgery,the negative pressure drainage tube is normally placed under the expander,contrary to the low drainage incision,and in the deepest part of the high incision to avoid the distortion and compression of the drainage tube,and keep the negative pressure drainage tube unobstructed[21].Finally,the incision is sutured in layers and the implantation of expander is completed.

Expansion duration and expansion volume

After the expander is sutured,initial water injection is required.Under normal circumstances,saline containing methylene blue is injected until the expander fills the expansion cavity (about 1 / 10 of the expander volume)[2]to ensure that the cavity is compressed with the help of drainage,thereby reducing the incidence of seroma or hematoma.The wound is covered with sterile gauze and the first-stage surgery is completed.

Start time and volume of water injection for expansion:the first water injection for expansion can be carried out after the incision is completely healed (about 15 days).The water injection needs to be done in line with the principle of sterile operation and is conducted by an experienced clinician.After the water injection valve is touched,an adequate disinfection is performed,a scalp needle or butterfly needle is used for injection to reduce the trauma,and the needle position should be determined by pumping back before injection.The interval of water injection for expansion is one week.The water injection volume can be evaluated according to the following principles:(1)the enlarged dome is palpated to evaluate the water injection volume,which is still soft (more salt water can be added)or tight (the water injection is finished); (2)the signs of skin burning under the continuous expansion pressure are evaluated,and the pressure release test shows that the capillary is well filled,indicating that the tissue is tolerant to the test; (3)the patient’s tolerance is evaluated,the feeling of over tightness or even pain and discomfort means the end of the expansion.It is suggested to apply standard expansion.In Saxby’s study,the survival length of the skin flap after standard expansion is 50% larger than that of the control group with delayed skin flap and nearly 150% higher than that of the rapidly expanded skin flap[22].

Facial expansion volume and second-stage surgery:the water injection for expansion should be carried out once a week,the expansion volume that the expander can tolerate is 9 times the rated volume of the expander.In practical application,we often use over expansion( 3-6 times the rated volume),and the selection of facial expansion volume is determined by the formula (Mohammad Reza ashab Yaminn[23]believed that the tissue width in the exposed part of the expander minus the base width should be greater than 10-20% of the scar width.Hamid Karimi[2]considered that the ideal width is that the expanded flap is 2cm wider than the scar.),and the sufficient flap expanded area can guarantee the complete coverage of the scar tissue.The stable expansion lasts for 2-3 weeks after the completion of water injection to ensure the stability of the expanded flap and prevent its retraction[24].After the accomplishment of expansion,the expander is taken out along the original incision,the scar excision area is covered by the expanded flap for repair,and the designed skin flap is direct advancement skin flap,rotation skin flap,transposition skin flap and so on[25].The incision is sutured in layers and the repair surgery is completed.

Brief introduction of over expansion:a technique in which tissue is expanded beyond the prescribed expansion volume of the expander to obtain more skin flap.Dimcio D[8]mentioned in his study that 59 patients received over expansion with an average expansion volume of 3.6 times that provided by the manufacturer and an average expansion time of 172.6 days.All patients completed the reconstruction,3 of them had complications,and there was no statistical difference with the incidence of conventional expansion complications.This provides the basis for clinical application of over-expansion technique.Under the perfect design and operative conditions,over expansion can provide more flaps for tissue reconstruction without increasing the incidence of complications,and reduce the times of surgery in the repair of large-area defects.However,the longer expansion time can not be ignored.

COMMONLY USED EXPANSION TECHNIQUES AND VASCULAR UTILIZATION FOR FACE

In the process of facial scar repair,a water injection expander is often selected.The expansion cavity is a semi-permeable membrane,the skin flap is expanded by injecting isotonic normal saline,and the location of the expander is determined by the scar location.The commonly used expansion techniques include conventional expansion technique,flap delaying expansion technique and flap prefabrication technique.

Conventional expansion technique

It is suitable for the small burn scars on the face and neck.The main implant site is the neck,because its healthy skin has the greatest similarity with the facial skin.The incision is designed beside the scar and parallel to the edge of the scar.The expander for the forehead is placed on the deep surface of the frontal muscle,the one for the cheek is implanted on the superficial surface of SMAS,and the one for the neck is put under the deep cervical fascia.And the conventional water injection is used to expand the skin flap enough to cover the scar defect,which has been described in detail above.

Flap delaying expansion technique

When the facial scar reaches nasolabial groove,inner canthus and upper lip,the common expansion flap may not be able to completely repair the scar,and may cause eyelid ectropion and lip ectropion due to the flap retraction.The flap expansion delaying technique can effectively solve this defect.It is a combination of flap delaying technique and expansion technique.The flap that has been expanded is designed with incision line on the surface of the expander flap according to the shape and size of the repair site.After the flap is cut to the superficial layer of the expanded flap envelope,all the visible vessels should be cut off,the incision is sutured intermittently,the expansion is maintained for 1-2 weeks,and then the second-stage repair and reconstruction is carried out.The delaying of expansion flap can reposition the pedicle and facilitate the transfer of the flap.And for the large length-to-width ratio expansion flap (≥ 3:1),it can increase the directional blood supply of the flap and reduce the possibility of necrosis.Wu Haojun[37]achieved good results in the repair of large area scar of cheek in 17 cases by using the flap delaying expansion technique and pointed out that the flap delaying expansion technique can change the direction and diameter of blood vessels,make blood vessel metastasis safer and prevent blood circulation obstruction.Zhu Lin[38]used piglet model to point out that the flap delaying expansion technique can change the blood flow direction of the skin flap and increase the blood flow volume of the functional blood vessels,thereby alleviating the ischemia reperfusion injury and increasing the survival rate of the skin flap.

Flap prefabrication technique

When the scar area of the face and neck is large or the contracture is serious,and there is no healthy skin flap around the scar for expansion,the pre-expanded distant or ortho-position axial flap can provide an effective solution.Xianjie M[39]achieved good aesthetic effect in the repair of large area defects by using the prefabricated deltopectoral flap and pointed out that if the deltopectoral flap is used,the thoracoacromial artery and the descending branches of cervical cutaneous branch of transverse cervical artery should be ligated when the expander was placed,so that the second and third branches of the internal thoracic artery could be the main blood supply of the expansion flap.On the contrary,if the cervical cutaneous branch flap of transverse cervical artery was used ,the second and third branches of the internal thoracic artery and the thoracoacromial artery were ligated when the expander was implanted.It should be noted that the vascular anastomosis of the thoracic triangle area is located in the superficial layer of the deep fascia,and the dissection of the expansion cavity should be done under the deep fascia.Ling Zhang et al.[40]took the vessels of superficial temporal artery and the surrounding fascia as the vessel carrier when using the superficial temporal artery ,the temporoparietal fascial flap was sutured to the deep cervical fascial layer,the prefabricated island flap was made to repair large area burn scar on the face and neck,and good results were achieved.

ANALYSIS OF COMPLICATIONS

In terms of overall complications,the implant site of expander,gender,the repaired scar area ,and the expander volume have all been proved to be independent factors for the occurrence of complications.Christian Smolle[31]proved in her study that the implantation of expander in female limbs could lead to a significant increase in complications.Yeong and A.Fochtmann[7][37]believed that the repaired scar area is an independent factor of overall complications (P = 0.0258).The complications are divided into minor complications and major complications.Hamid Karimi[2],A.Fochtmann[7],and Bozkurt A[11]have classified the complications in their literatures.The complications that do not affect the surgical results and can continue to expand after treatment are called minor complications,while the complications that need to be interrupted or cannot complete the reconstruction are called major complications.The common complications are discussed separately as follows:

Hematoma and seroma

Hematoma refers to the phenomenon of congestion and blood clot aggregation in the expansion area after the implantation of expander ,which is a common complication with an incidence of 5-10%.And it will not affect the process of expansion after timely and appropriate treatment.Ashall g,Quaba A[30]proposed that hematoma may be considered as an iatrogenic complication to some extent,and its main cause is incomplete hemostasis.When implanting the expander in the face,it is necessary to pay attention to the blood vessel route,for example,there is a blood vessel in the zygomatic ligament that runs from the deep part to the skin.The route and cutaneous branch distribution of the thoracoacromial artery,the transverse cervical artery and the internal thoracic artery should also be noticed.And postoperative hematoma is often caused by cutting without ligation.For patients with normal coagulation function,the solution such as complete hemostasis after dissecting expansion cavity during surgery,placement of drainage strip and preliminary water injection can avoid the occurrence of hematoma.The commonly used tumescent fluid in the surgery contains a higher concentration of epinephrine,which can cause vasospasm and vasoconstriction,so that there is no obvious bleeding during the surgery .But after the effect of epinephrine is lost,rebound bleeding occurs.In case of hematoma,the incision should be opened immediately,the expander should be taken out,the hemostasis should be fully performed,a new expander should be replaced,and the drainage tube should be placed.An antibiotics should be used for 5-7 days after the surgery,and tissue expansion can be carried out normally after the incision is healed[31].

Infection

As the most common and serious complication of repair surgery related to tissue expander ,it can cause wound healing delay,flap necrosis,expander exposure,capsule formation,etc.The occurrence of infection often means the failure of expansion surgery.Therefore,the importance of infection prevention and control has been mentioned in many studies.In Christian smolle’s[31]study,the infection rate is 12.7%,in other studies,it is 1.22%and 4%[32][33].The causes of infection are summarized as follows:the first-stage surgery violates the rules of sterile operation; the treatment of hematoma is not timely,the blood as a natural medium increases the risk of infection;the disinfection is not thorough in the process of water injection expansion,leading to infection; the condition of skin flap in the donor area is poor,such as folliculitis.In the early stage of infection,the skin flap may be red,swollen and scalded,which should be treated with broadspectrum antibiotics in time.If it is serious,surgical intervention is needed,the expansion cavity should be fully flushed,the expander should be relocated,and an antibiotic treatment should be given for 5-7 days after the surgery,a close observation and prevention of reinfection should be performed[34],or the expander should be taken out to terminate the reconstruction process.

Expander exposure

The time of expander exposure is mainly about 20-60 days after the first-stage surgery,and the incidence is the second in all complications,accounting for about 7%.The implant site is the independent factor for the expander exposure.The neck tissue is soft and tends to expand in two directions when expanding,which compresses the blood vessels,trachea and other tissues in the neck.Moreover,because the neck is very active,it is easy to cause complications.However,the expander for the head is implanted under the galea aponeurotica,because the dissection in the surgery is in one layer,the galea aponeurotica is relatively tough and the scalp is relatively thick,even though the local tension after expansion is large,the occurrence of expansion exposure is still less[35][36][37].Christiaccn Smolle,A.Bozkurt et al.[31][11]found that the incidence of complications in the lower extremities is significantly higher than that in other parts in their study.This paper mainly discusses the treatment of facial and neck scars,so there is no further description of the extremities.In addition,the expander volume may be the risk factor for the expander exposure,the larger the expander,the larger the scope of dissection required by the surgery,the longer the incision length,the longer the surgery time and the longer the exposure time of the wound,the increase of adverse factors may lead to a higher complication rate of the large-capacity expander.The dissection lacune is not large enough,the expander is not fully flattened when it is implanted,the sharp angle is formed during the first-stage expansion,and the tension is too large to puncture the normal skin during water injection,all of which may cause the expander to be exposed [38].This is also the reason why the lacune should be 1-2cm larger than the outer edge of the expander[39].

Flap ischemia and expander rupture

The main reason of the flap ischemia is that the expansion speed is too fast.In the process of rapid expansion,the blood supply of the flap may be blocked,which may lead to the ischaemic necrosis of flap.For the ischaemic necrosis of distal flap caused by large lengthto-width ratio flap (3:1),the flap delaying expansion technique can reduce the flap ischemia reperfusion injury and necrosis.The face and neck are exposed parts,which may be frostbitten due to poor warmth in winter.The expansion leads to the skin expansion at the scar site,because of the poor blood supply and elasticity of the scar tissue,it is easy to lead to ischaemic necrosis and even rupture,but this complication is not common[40].The rate of expander rupture is even lower.The poor quality of expander ,external force stimulation,and improper operation in water injection for expansion are all the direct causes of the rupture.Careful care and operation can avoid the rupture[21].

SUMMARY

The reason why the soft tissue expander can achieve good aesthetic results in the reconstruction and repair of facial scars is that the expanded flap has the characteristics of matching color,similar structure and the possibility of retaining sensation.But these should be based on reasonable flap design,careful patient selection and careful nursing,otherwise,the related complications may bring incalculable losses.The disadvantages such as high incidence of complications,multiple surgeries and relatively long expansion time still hinder the development of expander.However,it is undeniable that the expander has its unique advantages and is still one of the irreplaceable solutions for the treatment of facial and neck scars.