Biomechanical and histological outcomes of a cervical expander capsule.

[BACKGROUND] An expander capsule is a fibrous membrane that forms around a tissue expander. However, its outcome is still unclear. Here we investigated the biomechanical and histological outcomes of cervical capsules that were left in vivo after expanders were removed.

[METHODS] The deep and superficial capsules of 29 human cervical expanders were collected to serve as an experimental group. All 29 patients sustained facial and neck burn scars and underwent scar excision and expanded skin flap transfer. These capsules were divided into four groups based on the in vivo persistence time of the capsules following expander removal. The control group featured skin from five normal subjects. We investigated the biomechanics and histology of each group of capsules.

[RESULTS] Capsule thickness, Young's modulus, collagen content, type I/III collagen ratio and α-SMA expression level were significantly related to the layer and the persistence time of the capsule in vivo (p＜0.05). Capsules persisted for more than 24 months following expander removal, the Young's modulus of the capsules remained greater than that of normal skin, limiting neck mobility. Moreover, some patients experience cord-like capsular contracture and a cervical pulling sensation, which may be attributable to the fusion of the deep expander capsules and platysma muscle.

[CONCLUSIONS] Following the removal of neck expanders, the capsules can persist in vivo for a long time, affecting cervical contours and mobility.