Indian Journal of Plastic Surgery Medknow Publications on behalf of Indian Journal of Plastic Surgery ISSN: 0970-0358 EISSN: 1998-376x Vol. 39, Num. 1, 2006, pp. 22-28

Indian Journal of Plastic Surgery, Vol. 39, No. 1, January-June, 2006, pp. 22-28

Original Article

The effect of tissue expanders on the growing craniofacial skeleton

Awad MohamedM.S

Department of Surgery, Zagazig University Hospitals, Zagazig
Correspondence Address:Department of Surgery, Zagazig University Hospitals, Zagazig
dadlahm@yahoo.com

Code Number: pl06006

Abstract

Keywords: Tissue expansion, cranium, pediatric, growing skeleton-scalp

INTRODUCTION

Tissue expansion allows adjacent soft tissue to be incorporated into the reconstruction of a large defect that cannot be closed primarily without undue tension. Since the donated tissue is from the same region as the defect site, appropriate color match and texture of the donor tissues are maintained. Additionally, tissue expansion can circumvent the need for more extensive surgeries including distant pedicled or free tissue flaps.[1] Tissue expansion can safely be considered one of the major advances in reconstructive plastic surgery. The merits of the technique are supplying skin adjacent to the defect of similar color and texture with minimal donor site morbidity. However, in order to achieve the best possible result, the expanded flap must be mobilized maximally. Inability to perform this may impair the final result.[2]

Currently, a host of shapes and sizes of silicone expanders is available and custom-made expanders can be manufactured when unique situations are encountered. The single self-sealing filling port may be incorporated into the body of the expander or it may be connected to the body of the expander by silicone tubing. This remote port may be placed subcutaneously away from the body of the expander or it may be passed externally. These ports allow injection of isotonic sodium chloride solution and removal of it if overexpansion occurs.[3] The aim of this study is to demonstrate the effect of expander on the bony aspect in infants.

MATERIALS AND METHODS

Scalp and facial expansions for 30 pediatric patients (14 males and 16 females) were performed during the period from May 2003 to 2005 at Plastic department of Zagazig University Hospital. The mean age of the patients studied was 3,8 years, with a range from 2 to 10 years. Thirty four expanders were implanted, 30 in the scalp and 4 in the face. In four patients, 2 expanders were used [Table - 1]. Our patients were classified as burn scars (n=20), post-traumatic scars (n=4), haemangioma (n=3), large congenital nevi (n=2) and congenital aplasia cutis (n=1) [Table - 2], All patients underwent routine clinical and laboratory assessments; two staged operation (expander insertion, regular intermittent (conventional) inflation and reconstruction). Computed tomography (CT) was done on three occasions: pre-expansion; post-expansion and 3 to12 months after reconstruction.

Surgical technique

Preoperative planning; The expanders which were chosen were larger than the length of the defect. These were inserted in the appropriate adjacent sites. Some sites were smaller than the defects, so we used 2 expanders. We used round expanders (n=23), rectangular expanders (n=8) and crescentic expanders (n=4). Their bases were semisolid (n=18), soft (n=10) and hard (n-6). All expanders had remote filling ports. In 4 patients, 2 expanders were used [Table - 3].

Procedure

Prophylactic anti-staphylococcal antibiotic was administered intravenously at the start of the procedure and then a small marginal incision was made enough to introduce the expander and its valve. The same incision was used to remove the expander and advance the expanded flap. The pocket for the tissue expander was dissected 2 cm larger than the dimensions of the expander in the subgaleal plane in the scalp (facilitated by the use of a urethral dilator) and in the subcutaneous plane in the face, superficial to the superficial muscloaponeurotic system with great care to avoid injury of facial nerve. The pocket was copiously irrigated with an isotonic saline solution, prior to insertion of the expander. Expansion was done till the expander was tense without pain or skin blanching. All patients were expanded twice weekly. Overexpansion by nearly twice normal was done in all cases which complete the procedure. Expansion proceeded uneventfully in 6 cases however, reconstruction were performed immediately in 2 cases.

Reconstruction: The expander and its valve were removed through the original incision. All flaps were designed as random flaps except in 2 patients where axial flaps based on the superficial temporal artery were used to reconstruct the right ear and the left eye brow. All CT examinations (pre-expansion, post-expansion and after reconstruction) were done correspondingly with each other to be able to compare: bone thickness and bone density under the expander; certain intracranial dimensions under the center and the edge of the expander and to observe the contour of the skull in the 3D reconstruction.

RESULT

DISCUSSION

Tissue expansion plays an integral role in pediatric plastic surgery. Surgeons have been using this technique for years in the treatment of large congenital nevi, haemangioma, burn and post-traumatic scars, meningomyelocoeles, congenital aplasia cutis and other congenital deformities. We used the expanders for different causes mainly burn scar in [n=20]. When applying tissue expansion to the pediatric population, there are certain unique variables, which differ from adults making this type of surgery even more complex. These include body size, tissue tensile strength and thickness and patient cooperatively.[1] Expansion in infants and children is controversial. Possible complications include thinning and deformation of underlying bone and subsequent scar widening with growth.[4]

Johnson et al[5] stated that tissue expansion may cause temporary thinning in outer skull in children and is contraindicated in children less than 3 years because of open cranial suture.

Our study was done for patients aged between 2 and 10 years. Osseous changes in the age group below 5 years were more than in those above 5, with more risk of bone thinning and inward bone displacement. Suture widening that occurred in this group may necessitate delay of the procedure until above five years; but with no significant differences between patients below five years from those above with respect to the CT changes after and before expansion

A few studies have investigated the effect of tissue expansion on the craniofacial bone. They demonstrated bone growth inhibition under the expander with apposition zone at the periphery. It can not be determined whether the bony changes are caused by pressure related erosive changes or whether they are due to complex growth changes Also, it can not be determined whether rapid expansion may lead to fewer bony changes,[6] Penoff,[7] reported a case of outer table as well as a portion of inner table erosion during scalp expansion in a child. In our study of the effect of tissue expander on skull bones, the bone appeared thinner and had a reduced convexity. At 9 months post-operatively, in most cases, a complete normalization was confirmed by computed tomography.[8]

We report in this work two cases with erosion of the outer and inner table of the skull away from the sites of pressure, of unknown aetiology that may be due to growth inhibition or traction on a nutrient vessel of the skull. All these effects were relieved after six months as a complete normalization confirmed by CT.

Inward bone displacement had occurred in 15 [44%] patients. Suture widening had occurred in 4 patients [11.5%] and no effects were noticed on the superior sagittal sinuses for patients who had expanders inserted over the anterior fontanel, unlike the study done by Keith et al .[1] who reported laceration of superior sagittal sinus in infants with expander inserted on anterior fontanel. In this study, after scalp expansion, bone resorption was observed in 7 patients under the expansion [Figure - 2] and in two patients the resorption had occurred away from sites of expansions [Figure - 3]. Bone resorption during scalp expansion was observed on occasion and consisted of thinning of outer table of the calvarium according to CT examination post operatively. Apposition at the edge of the expanders also occurred in 23 patients, rapid inflation and expansion had occurred in 7 patients with no differences between those with rapid and those with slow expansion. Prolonged expansion with large volume expanders did not lead to significant CT changes. Full thickness erosion of the skull secondary to tissue expansion has been recorded with prolonged expansion using large volume expanders.[9] Tissue expansion involves at least 3 stages: insertion, expansion and reconstruction. The ultimate success or failure of the reconstructive effort is largely based on the preoperative planning, selection of appropriate expander(s) and the placement of the expander(s) at the initial operation.[10] If the defect is large and cannot be completely excised after the initial expansion, the defect is only partially excised and the expander is deflated but left in place. After the wound has healed, expansion is initiated again. A third operation is then necessary to remove the expander and accomplish the final reconstruction. This process is termed sequential expansion.[10] We did not prefer the sequential expansion, as it is time consuming and preferred only if the donor area is so small so as to insert only one expander. We inserted two expanders in four patients to reconstruct a big defect, with good results but it was more painful and one of them necessitated removal of the expander before over filling.

The widely used type of tissue expanders is the Radovan prosthesis. It consists of a silicon bag and a self sealing inflation reservoir connected by a silicon tube. There are different volumes (from 25 ml up to 1000 ml) and different shapes (round, rectangular, elliptical and crescent). It may be baseless or have a woven dacron semi hard or hard base to direct the expansion force away from the base [Figure - 7][Figure - 8]. The reservoir may be built-in or remote.[11] Conventional inflation is conducted on a weekly basis, however rapid expansion at 48 hours interval is developed. Usually within 8-10 weeks expansion becomes sufficient to allow reconstruction.

Don and Marion,[12] enumerated 10 simple rules to reduce the risk of complications occurring with tissue expansion and they preferred the use of the largest expander possible and use rectangular expanders-these "harvest" more tissue. We used rounded expanders [Figure - 9][Figure - 5] for most of our patients [n=23], Crescent type in 4 and rectangular expanders in 7 patients. The rounded type was preferable as it easy to harvest and easy to plane the tissue flap for scalp reconstruction after its removal.

Some authors overfill the expander and allow the final volume to remain in the expander for several months to stabilize the expansion and counteract the tendency of the expanded flap to contract once the expander is removed. If expansion proceeds uneventfully, reconstruction may be performed immediately. The expander is removed through the original incision. If necessary, incisions may be made in the capsule surrounding the expander to gain additional flap length. This should be performed with extreme caution because of the delicate network of new blood vessels present just superficial to the capsule; these should be avoided if at all possible.[2] We did not need the incisions through the capsule for lengthening of the flaps due to overfilling of the expanders to gain tissue excess and utilized it.

Tissue expansion creates a three-dimensional structure. This tissue must be converted to a flat sheet or two-dimensional flap. Hence the 'excess'tissue present in the three dimensions must be maximally converted to a two-dimensional flap, so that all the additional tissue available is utilised rather than wasted.[2] Any type of rotation, advancement or transposition flap may be designed with the expanded tissue. All flaps in our study were designed as random flaps except in 2 patients where axial flaps based on the superficial temporal artery were used to reconstruct the right ear and the left eye brow [Figure - 10]. Because of the increased vascularity of expanded tissue, much larger flaps may be designed while maintaining adequate blood flow. However, a word of caution is necessary regarding the use of epinephrine.

We had never used epinephrine during reconstruction in all patients. Evidence exists that the increased vascularity of expanded flaps may be exquisitely sensitive to the vasoconstrictive effects of epinephrine; therefore, it should not be used.[13]

Complications were divided into major and minor categories [Table - 7]. Major complication was defined as that resulting in premature loss of expander that required additional surgery or when preoperative plan was not completed, thus yielding a poor result. The minor complication were defined as those resulting in only partial accomplishment of the preoperative plan and thus defined as a fair result. Cunha et al .[14] reported that complications rates for tissue expansion have been as low as zero and as high as 48% when expanding the head and neck region in Pediatric patients (Keith et al . 2005). Tissue expansion is associated with a learning curve. Also, the use of multiple expanders is associated with a higher complication rate. With respect to the complications, we noticed that haematoma occurred in 23 patients as we avoid the use of epinephrine in all patients. However, this complication was avoided through application of tube drain for three days and application of a light pressure bandage. Skin tissue necrosis with plugging of the expanders was noticed in three cases due to rapid inflation. We proceeded with expansion in two of them after delaying the inflation rate; in one case the expander failed and we delayed the procedure. The pain and neuropraxia in all our patients were tolerable without analgesia except in two cases, where the pain continued in spite of analgesia that necessitated removal of the expander due to associated uncontrolled pus collection. No major complications were recorded in our patients.

References

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