Embryology and surgical anatomy of the auricle

Objective quantitative methods to evaluate microtia reconstruction: A scoping review

Background

Commonly used methods to evaluate auricles are subjective and are therefore not specific, comprehensive, and precise nor effective in the assessment of microtia reconstruction outcomes. This scoping review aimed to summarize the objective methods for the accurate evaluation of microtia reconstruction.

Methods

We performed a scoping review of publications that used objective measurement methods to evaluate outcomes of microtia reconstruction according to the PRISMA-ScR guidelines. A systematic literature search was conducted in the Embase, PubMed, Cochrane, CNKI, and VIP databases, and literature references were screened for additional records. Studies that evaluated auricles after microtia reconstruction using quantitative anthropometric methods were included, and data on these methods were collected.

Results

Twenty-five publications reported on quantitative objective outcome measurements. Thirteen studies evaluated auricular protrusion, three articles assessed the position or symmetry, and twelve studies reported on auricle size. The quantitative measurements of fine structures, such as the tragus and concha, were described in three studies. All described measurements used manual landmarking, where fifteen studies described well-defined landmarks, fifteen studies described poorly defined landmarks, and four studies used a combination of well and poorly defined landmarks.

Conclusion

The objective evaluation of microtia reconstruction outcomes is hindered by significant heterogeneity of measurement methods. The measurement methods used for general auricular measurements (auricular protrusion, auriculocephalic angle, and size) used in microtia reconstruction were abundant, while measurements of auricular position and the fine structures of the auricle were limited. Three-dimensional imaging combined with computer analyses poses promising future alternatives.

Auricular Protrusion After the Postauricular Approach: A Review of the Current Literature

The postauricular approach is a widely adopted surgical technique for the ear due to its unique access to the middle ear, mastoid, and other internal structures, while adeptly concealing the surgical incision for aesthetic superiority. Despite its advantages, concerns have emerged regarding the potential for auricular protrusion following the procedure. While the exact mechanisms underlying this phenomenon remain under debate, it is worth noting that comprehensive literature on this topic is scant. Nevertheless, available studies predominantly indicate no association between the postauricular approach and lasting auricular protrusion. In the few reports that do note its occurrence, the protrusion appears transient, resolving over time. These findings suggest that surgeons should continue using the postauricular approach without concerns regarding auricular protrusion. Nonetheless, it is recommended to take all precautionary measures, including appropriate patient selection, engagement of an experienced surgeon, and meticulous postoperative dressing.

Auricular cartilage configuration: A histological study using late-stage human fetuses and adult cadavers

The auricular cartilage is considered to develop from a funnel-like arrangement of six embryonic hillocks. However, there is little information as to when and how the initial cartilage plate differentiates into the major three hollows or caves: the concha, the scapha and the triangular fossa. We examined semiserial histological sections from 42 human fetuses as well as from seven cadavers of elderly individuals. Tangential sections from adults suggested that three ring-like cartilages were combined to provide a single auricular cartilage and that the external auditory meatus was attached to the lowest ring or concha. All of the fetuses studied carried the three major hollows delineated by skin folds. These skin folds often contained a cartilage loop as a core in place of a thickening or tubercle. Conversely, some of the skin folds corresponded to a highly wavy cartilage plate without looping. According to whether the cartilage loop was present or absent in horizontal sections from 35 fetuses, we classified the cartilage morphology into four patterns, the most frequent of which was absence of the triangular fossa loop (27 fetuses), followed by absence of the scapha loop (11 fetuses). Each pattern was evenly distributed among small and large fetuses. This suggested that some form of cartilage correction or reconstruction was likely to occur after birth, especially at the triangular fossa and/or scapha. Infants appear to show significant region-specific variation in the postnatal growth of the auricular cartilages, especially at the triangular fossa and/or scapha.

Development and growth of auricular cartilage and muscles: A study using human fetuses

OBJECTIVES

The auricle is a key target in pediatric plastic surgery and is considered to develop from a ring- or funnel-like arrangement of six hillocks in the embryo. However, there has been no report showing the morphologies of the auricular muscle and cartilage after midterm in humans.

METHODS

We examined histological sections of 20 near-term human fetuses (29-40 weeks) and those from 7 midterm fetuses (15-16 weeks).

RESULTS

At midterm, the auricular cartilage was a single wavy plate with the helicis major muscle (HMM). The superior and posterior auricular muscles (SAM, PAM) were inserted into the middle parts, and the anterior auricular muscle (AAM) was inserted into the lowest part of the cartilage plate, while the tragus and antitragus were not clearly identified. In near-term fetuses, the cartilage plate varied in size and shape between specimens. The scapha and antihelix were separated from the cartilage plate with major or minor involvement of the HMM from the initial mass along the helix. The SAM inserted to the crus helix or the developing scapha, while the insertion sites of the AAM and PAM into the helix were stable. The tragus-antitragus cartilages were well-developed and they sandwiched a deep notch of skin below the helix tail. The antitragicus muscle was more evident than the tragicus muscle. An unnamed muscle was evident along the external acoustic meatus. The other intrinsic muscles, including the transverse and oblique muscles, might develop from the HMM after birth.

CONCLUSIONS

Development of the auricle was advanced after midterm. However, a single wavy plate-like cartilage was maintained until late-stage. Near term, the antihelix and scapha developed from the plate-like core of the auricle and the tragus and antitragus were added in the antero-inferior side of the cartilage plate. Establishment of muscle arrangements was markedly delayed compared to cartilage development. Altogether, the classical concept of an initial funnel-like arrangement of cartilage anlagen might have been biased by studies of adult morphology.

[The interdisciplinary approach to the rehabilitation of the patients presenting with congenital atresia of the external auditory canal and the concomitant microtia]

The objective of the present study was to develop and introduce into the clinical practice the method for the combined aesthetic and functional rehabilitation of the patients presenting with congenital atresia of the external auditory canal (CAEAC) and the concomitant microtia. A total of 8 patients at the age from 6 to 21 years with unilateral CAEAC and microtia were given the surgical treatment. During the intervention, atresia was resolved using the trans-mastoid approach, tympanoplasty of autofasciae and ossiculoplasty making use of the partial titanium prosthesis and the placement of cranial osteointegratable titanium implants. At the second stage of the surgical intervention the 3D silicone prosthesis of the auricle shaped on an individual basis were used. The long-term follow-up observations have demonstrated the stable formation of the tube of the external auditory canal, with the bone-air interval amounting to 15-20 dB. The auricular prosthesis was the mirror image of the natural ear and completely concealed the congenital defect.

The Protruding Ear: Cosmetic and Reconstruction

Ear prominence is a relatively common cosmetic deformity with no associated functional deficits, but with profound psychosocial impact, especially in young patients. Protruding ears in children have propagated surgical advances that incorporate reconstructive techniques. Here we outline a systematic framework to evaluate the protruding ear and present various reconstructive surgical options for correction. Both cosmetic and reconstructive perspectives should be entertained when addressing this anatomical deformity.

The estimation of the time since death using temperatures recorded from the external auditory canal : Part I: Can a temperature be recorded and interpreted from this site?

In this first paper of two, two experimental models are used to revisit and expand upon the question as to whether a temperature can be recorded from the external auditory canal (EAC) and used to estimate a time since death using the largest data series for this site to date. The behaviour of the temperature within the EAC after death is investigated and compared to that of the rectum. The temperatures are then applied to previously published algorithms to estimate the time since death. The choice of thermometer and the algorithm to be used are considered as well as why the time since death will be overestimated if consideration is not given to the differences between the rectal and EAC temperature in life or after death.