The Histological Characteristics Of Slow Expanded Human Tissue Expander Capsule And The Clinical Application

Objectives:This research was to explore the relationship between the thickness and the composition in different parts of tissue expander capsules,and to clarify the relationship between the thickness of the tissue expander capsule and the expression of collagen,elastic fiber and a-SMA.Analysis was made about the residue of tissue expander capsule after the removal.The relationship between the thickness,composition of the tissue expander capsule and the retraction,contracture of the expanded flap was discussed from the histological point of view.The results of this study were used to provide guidance for clinical surgery operation.Methods:The specimens were harvested from the capsules when removing the expanders and divided into two groups:the middle group and the marginal group,which were collected at the central part of the dome and annular thickening ring at the edge of tissue expander capsules.Besides,the samples were devided into two groups according to the original position of the expanders,and the patients were also divided into two groups according to their age.The residual group specimens were harvested underneath the expanded flap while debulking or revision procedure.The specimens were divided into 1-3 months after flap transferring operation group;3-6 months'group;6-12 months' group and more than one-year group.After routine fixation,HE staining,MASSON trichrome staining,elastic fiber EvG staining and a-SMA immunohistochemical staining were performed.The thickness of the capsules,the amount of collagen fiber,elastic fiber,and a-SMA in the capsule were calculated and analyzed.11 patients underwent cheek reconstruction with expanded flaps that originated from the cervicoperiauricular area using round expanders.During the flap transfer procedures,based on our previous laboratory findings,the edge and thicken parts of the capsules were removed primarily in order to minimize the possibility of flap retraction and contracture.Results:1.There was difference in thickness between the central part and the edge of the capsule.The marginal part of the capsule was thicker than the central part remarkably.No difference was found between adult patients and underage patients,no difference was found between the limbs group and trunk group either.2.The content of collagen fibers,elastic fibers and ?-SMA in different parts of the capsule were different.The marginal part contained more collagen fibers and a-SMA than the central part.while the central part had more elastic fibers.No difference was found in the content of collagen fibers,elastic fibers and a-SMA in the marginal part between two age groups,but the underage patients group had more a-SMA in the central part of their capsules.No difference was found in the content of collagen fibers,elastic fibers and a-SMA between two position groups.3.The thickness of expanded capsule was significant positively correlated with the content of collagen fiber and medium positively correlated with the IOD of a-SMA.4.As time passed by,the capsule in the body gradually degraded.The thickness decreased,the content of collagen fibers decreased and arranged in a more disorder way.The content of alpha SMA decreased too.5.No extra risks would occur in the surgery of cheek reconstruction with expanded cervicoperiauricular flaps by removing the thickening edge of the capsules.The risks of post-surgery scar contracture underneath the flap or flap retraction would be reduced in this way.Conclusion:There were significant differences in thickness and composition between the central and the marginal part of the expander capsule,the thickness and the content of collagen fiber and the IOD of ?-SMA of the central part were less than the marginal part.The thickness of expanded capsule was significant positively correlated with the content of collagen fiber and medium positively correlated with the IOD of a-SMA.The thickened marginal part had higher possibility causing long-term contracture.The long-term effect and the stability of the expanded flap would be benefit from the removal of all the marginal and thickening part of the capsule during the flap transfer procedures.