Silicon foil patching for blast tympanic membrane perforation: a retrospective study

The Dorsal Skinfold Chamber as a New Tympanic Membrane Wound Healing Model: Intravital Insights into the Pathophysiology of Epithelialized Wounds

BACKGROUND

Tympanic membrane perforations (TMPs) are a common complication of trauma and infection. Persisting perforations result from the unique location of the tympanic membrane. The wound is surrounded by air of the middle ear and the external auditory canal. The inadequate wound bed, growth factor, and blood supply lead to circular epithelialization of the perforation's edge and premature interruption of defect closure. Orthotopic animal models use mechanical or chemical tympanic membrane laceration to identify bioactive wound dressings and overcome premature epithelialization. However, all orthotopic models essentially lack repetitive visualization of the biomaterial-wound interface. Therefore, recent progress in 3D printing of customized wound dressings has not yet been transferred to the unique wound setup of the TMP. Here, we present a novel application for the mice dorsal skinfold chamber (DSC) with an epithelialized full-thickness defect as TMP model.

METHODS

A circular 2-mm defect was cut into the extended dorsal skinfold using a biopsy punch. The skinfold was either perforated through both skin layers without prior preparation or perforated on 1 side, following resection of the opposing skin layer. In both groups, the wound was sealed with a coverslip or left unclosed (n = 4). All animals were examined for epithelialization of the edge (histology), size of the perforation (planimetry), neovascularization (repetitive intravital fluorescence microscopy), and inflammation (immunohistology).

RESULTS

The edge of the perforation was overgrown by the cornified squamous epithelium in all pre-parations. Reduction in the perforation's size was enhanced by application of a coverslip. Microsurgical preparation before biopsy punch perforation and sealing with a coverslip enabled repetitive high-quality intravital fluorescence microscopy. However, spontaneous reduction of the perforation occurred frequently. Therefore, the direct biopsy punch perforation without microsurgical preparation was favorable: spontaneous reduction did not occur throughout 21 days. Moreover, the visualization of the neovascularization was sufficient in intravital microscopy.

CONCLUSIONS

The DSC full-thickness defect is a valuable supplement to orthotopic TMP models. Repetitive intravital microscopy of the epithelialized edge enables investigation of the underlying pathophysiology during the transition from the inflammation to the proliferation phase of wound healing. Using established analysis procedures, the present model provides an effective platform for the screening of bioactive materials and transferring progress in tissue engineering to the special conditions of tympanic membrane wound healing.

A Systematic Review of Nonautologous Graft Materials Used in Human Tympanoplasty

OBJECTIVES

Nonautologous graft materials may solve several dilemmas in tympanoplasty by obviating the need for graft harvest, facilitating consistent wound healing, and permitting graft placement in the clinical setting. Prior studies of nonautologous grafts in humans have shown variable outcomes. In this systematic review, we aim to 1) summarize clinical outcomes and 2) discuss limitations in the literature regarding nonautologous grafts for tympanoplasty in humans.

METHODS

A literature review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. The study size, etiology and duration of perforation, type of nonautologous graft, and postoperative closure rate were assessed.

RESULTS

The PRISMA approach yielded 61 articles, including 3,247 ears that met inclusion criteria. Studies evaluated nonautologous grafts including paper patch, gelatin sponge, growth factors, porcine small-intestinal submucosa, among others. Traumatic perforations (62.3%) were most commonly studied, whereas postinfectious perforations (31.9%) and other etiologies (5.8%) comprised a minority of cases. Acute perforations of <8 weeks duration constituted just over half of all treated ears. Overall closure rate was 82.1%, with significantly higher closure rates in acute (89.9%) versus chronic perforations (64.9%, P < .01), regardless of material. A median postoperative air-bone gap of 5.6 dB was found in the 23% of studies reporting this metric.

CONCLUSIONS

The majority of publications reviewing nonautologous materials in tympanoplasty evaluate acute or traumatic perforations, and few rigorously report hearing outcomes. Given available data, porcine submucosa and basic fibroblast growth factor may hold promise for chronic perforation closure. Future studies should report closure rates and hearing outcomes in perforations >8 weeks duration. Laryngoscope, 131:392-400, 2021.