A Study on Morphometric Changes of the Pinna Following Ear Surgery

Abstract

Morphometry of pinna may change following ear surgeries. This study gives information about postoperative changes following ear surgeries. This study aims to measure the variation of ear morphology following surgery and to correlate the type of surgery with post-operative variations. Eighty patients with Chronic Otitis Media(COM) undergoing surgery by post aural approach were grouped into Modified Radical Mastoidectomy (MRM), Cortical Mastoidectomy + Tympanoplasty (CM + TM) and Tympanoplasty groups(TM). The MRM, CM + TM and TM groups had 14, 46 and 20 participants respectively. Various morphometric measurements were taken pre and post operatively. In all groups, the mean Concho-Mastoid Angle (CMA) was increased post operatively, with increase of 11.1 degrees in MRM (p value-0.002), 8.9 degrees in CM + TM (p value-0.000) and 4.8 degrees (p value- 0.657) in TM group. Similarly, the Cepahlo-auricular distances (D1 and D2) showed statistically significant changes in MRM and CM + TM groups (p value < 0.05). Mean CMA of MRM group compared with other groups did not show any statistically significant difference. However, when the CMA of CM + TM group was compared with TM group showed significant difference of 14.53 degree (p value 0.002). Similarly, the D1 and D2 showed statistically significant changes between the CM + TM and TM groups (p value 0.005 and 0.000 respectively). Prominence of pinna following ear surgery is a not a myth. It happens mostly in cases requiring drilling of the mastoid, rather than Tympanoplasty alone. This needs to be explained to the patient beforehand to prevent any confusion post operatively.

Introduction

As man is becoming more and more active on social media, the looks have a great influence in one’s life. Human ear is defining feature of face and is an important key in the natural, harmonious, aesthetically pleasing face. Its shape and size is influenced by age sex and ethnic origin [1–3].

William Wilde’s curvilinear incision in post auricular groove is the most preferred incision for ear surgeries [4]. This incision plays very important role in the final post-operative position of pinna and the cosmetic outcome [5]. This study aims to measure the variations of the ear morphology following different ear surgeries.

Materials and Methodology

This is a prospective observational study done on 80 patients with Chronic Otitis Media (COM) undergoing surgery. The study was conducted from February 2019 to February 2020. The purpose of this study was explained to the patient and written informed consent was taken. Institutional Ethical Committee approval was also obtained. All the patients included in the study were above 18 years. Patients undergoing revision surgeries, patients with congenital ear anomalies and ear malignancies were excluded from the study.

Participants were grouped into Tympanoplasty (TP), Cortical Mastoidectomy with Tympanoplasty (CM + TP) and Modified Radical Mastoidectomy (MRM) groups based on the surgery they underwent. All the patients were subjected to detailed history and examination. Various measurements of ear were recorded using Vernier's caliper and goniometer. The ear morphometry was measured preoperatively. All procedures were done under general anesthesia. A curved post aural incision was made in all the cases and did not extend the highest point of pinna superiorly and the mastoid tip inferiorly. After incising into the subcutaneous tissue, the post auricular muscles were divided and periosteum overlying the mastoid bone was cut. After the surgery, the post aural incision was repaired in 2 layers with interrupted sutures and was removed on Post-Operative Day (POD) 7. The measurements were taken again on post-operative follow ups on 7th day (POD 7), 30th day (POD 30) and 3 months (POD 90). The morphometric measurements included in the study are:

Morphometric Measurements

1. DISTANCE -1 (Cephalo-auricular Distance -1/ D1)–distance between the highest point of the pinna to the adjacent temporal bone (Fig. 1B).

2. DISTANCE -2 (Cephalo-auricular Distance-2/D2)–distance between midpoint of the pinna to the adjacent mastoid (Fig. 1C, Fig. 2)

3. LENGTH–measured from highest point of ear pinna to the lowest (Fig. 1D).

4. WIDTH–a horizontal distance between the root of the helix to the point of maximum convexity of the helix posteriorly (Fig. 1D).

5. CONCHO-MASTOID ANGLE–angle between the conchal bowl and the mastoid. It is measured at the highest point of the helix in all the cases (Fig. 3).

Fig. 1.

Schematic representation of various morphometric measurements

Fig. 2.

Measuring the Cephalo-auricular Distance 2/ D2

Fig. 3.

Measuring the Concho-mastoid angle

Results

A total 80 patients were included in the study, of which 37(46.25%) were females and 43(53.75%) were males (Table 1). Of the 80 participants, 14(17.5%) underwent MRM, 46(57.5%) underwent cortical mastoidectomy with tympanoplasty and the remaining 20(25%) underwent tympanoplasty alone.

Table 1.

Demographic data of the study subjects

Demography		SURGERY
		MRM		CM + Tympanoplasty		Tympanoplasty		Total
		N	%	N	%	N	%	N	%
AGE	< 20	2	14.3	6	13.0	0	0	8	10.0
	21–30	7	50.0	9	19.6	5	25.0	21	26.3
	31–40	1	7.1	17	37.0	6	30.0	24	30.0
	41–50	1	7.1	9	19.6	5	25.0	15	18.8
	> 50	3	21.4	5	10.9	4	20.0	12	15.0
	Total	14	100	46	100.0	20	100	80	100
SEX	F	5	35.75	18	39.1	14	70.0	37	46.3
	M	9	64.25	28	60.9	6	30.0	43	53.8
	Total	14	100	46	100	20	100	80	100
Side	R	5	35.7	27	58.7	13	65.0	45	56.3
	L	9	64.3	19	41.3	7	35.0	35	43.8
	Total	14	100	46	100	20	100	80	100

MRM- Modified Radical Mastoidectomy; CM- Cortical Mastoidectomy

In the MRM group, the mean preoperative value of Concho-Mastoid Angle (CMA) was 60.07 degrees (standard deviation-13.86) which showed an increase of 18 degrees on POD 7 and 17.1 degrees on POD 30. It stood at elevated 11.1 degrees at POD 90 when compared to the baseline value. This is statistically significant change (p value-0.002). Similarly, the Mean Distance 1 (D1) showed increase in 2.0 mm & 1.7 mm at POD 7 and POD 30 respectively. At POD 90 it averaged at 1.3 mm (p value–0.001) more than baseline. The mean Distance 2 (D2) at POD 90 measured 1.6 mm more than baseline (p value–0.004) which is statistically significant. Length and Width showed no changes following surgery (Table 2).

Table 2.

Morphometric analysis of MRM group

MRM	BASELINE		POD-7			POD 30			POD 90
	Mean	SD	Mean	SD	Variation	Mean	SD	Variation	Mean	SD	Variation	P value
CMA	60.07	13.86	78.07	18.1	− 18	77.21	17.45	− 17.1	71.14	14.20	− 11.1	0.002
D1	11.29	2.30	13.29	2.33	− 2.0	13	2.22	− 1.7	12.57	1.83	− 1.3	0.001
D2	14.50	2.41	17.50	2.35	-3.0	17.43	1.9	-2.9	16.07	1.64	− 1.6	0.004
L	60.07	3.41	60.07	3.41	0	60.07	3.41	0	60.07	3.41	0	–
W	26.43	3.39	26.43	3.39	0	26.43	3.39	0	26.43	3.39	0	–

Bold signifies statistically significant results

SD-Standard Deviation; POD-Post-Op day; MRM-Modified Radical Mastoidectomy; CMA- Concho-Mastoid Angle; D1 Distance 1; D2- distance 2;L-Length; W- Width

In the CM + TM group, the mean baseline CMA was 70.57 degrees, which showed an increase of 17.8 degrees on POD 7, 16.3 degrees on POD 30. On the 90th POD the mean CMA stabilized at 8.9 degrees more than the baseline value. This is highly significant change (p value- 0.000). Similarly, the Mean values of both D1 & D2 at POD 90 were 1.3 mm more than the baseline (p value-0.000) (Table 3).

Table 3.

Morphometric analysis of Cortical Mastoidectomy + Tympanoplasty group

CM + TM	BASELINE		POD-7			POD 30			POD 90
	Mean	SD	Mean	SD	Variation	Mean	SD	Variation	Mean	SD	Variation	P-value
CMA	70.57	18.28	88.39	17.3	17.8	86.89	16.86	16.3	79.48	16.14	8.9	0.000
D1	11.72	2.24	13.80	2.33	2.1	13.72	2.25	2.0	13.02	2.14	1.3	0.000
D2	16.39	2.97	19.67	3.51	3.3	19.43	3.28	3.0	17.72	3.00	1.3	0.000
L	59.85	3.53	57.78	3.41	0.1	59.78	3.41	0.1	59.78	3.41	0.1	–
W	28.41	4.05	28.24	3.95	0.2	28.24	3.95	0.2	28.24	3.95	0.2	–

Bold signifies statistically significant results

In the TM group, the mean value of CMA was 4.8 degree more than baseline on POD 90 (p value- 0.657). At POD 90, the D1 showed increase in 0.6 mm (p value–0.580) and D2 showed increase in 0.3 mm more than baseline (p value- 1.000) which was not statistically significant (Table 4).

Table 4.

Morphometric analysis of Tympanoplasty group

TM	BASELINE		POD-7			POD-30			POD-90
	Mean	SD	Mean	SD	Variation	Mean	SD	Variation	Mean	SD	Variation	P-value
CMA	60.20	18.38	74.50	15.30	-14.3	73.50	15.31	-13.3	64.95	14.14	-4.8	0.657
D1	10.75	1.74	12.20	1.40	-1.5	12.25	1.39	-1.4	11.35	1.31	-0.6	0.580
D2	13.75	2.81	15.75	3.27	-2.0	15.55	3.17	-1.8	14.05	2.46	-0.3	1.000
L	57.70	4.16	57.70	4.16	0	57.70	4.16	0	57.70	4.16	0	–
W	27.70	2.15	27.70	2.15	0	27.70	2.15	0	27.70	2.15	0	–

At POD 90, the mean Concho-Mastoid angle of MRM group compared with other two groups did not show any statistically significant difference. However, when the CMA of CM + TM group was compared with TM group, it showed mean difference of 14.53 degree with standard error of 4.11 which was statistically significant (p value 0.002). Again, like the CMA, the D1 and D2 showed statistically. The Length and width showed no significant variation between any two groups.

Discussion

Ear is the most prominent feature in human face. The shape, size and angles of the ear have a great deal of significance aesthetically. The morphology of ear can vary in congenital conditions, trauma, infections, tumours or following ear surgeries. Chronic otitis media is a common otological condition and surgery is the mainstay of the treatment options. The surgeries can be done through various approaches, including (a) William Wilde’s post aural approach, (b) Lempert’s endaural approach and (c) Rose’s endomeatal approach. The commonly noted pinna abnormality following ear surgery is ear protrusion, either over- or under-protrusion [6]. Low set ears is another possible deformity following Mastoidectomy [7]. Any change in the morphology can have profound impact on patient psychologically [7].

We compared the morphometric values taken preoperatively with the post-operative recordings done at POD 7, POD 30 and POD 90 following various post aural ear surgeries. Although various parameters were studied here, measuring the CMA was the most challenging. Great care was taken during the measurements and was done by the same person in all the cases. Since the CMA can vary by 10–15 degrees depending at site of measurement [1], utmost care was taken to measure it at the same levels postoperatively. Most of the measurement was modified from Alexander & Farkas methods [1, 8].

The final position of pinna was assumed after 3 months of surgery. Length and width of the pinna did not show any changes after surgeries. Ear prominence or over-protrusion was the only deformity we encountered in our study. Since ear prominence is subjective entity, there was no clear-cut value to call it prominent. We relied totally on statistical analysis to call prominence as none of the patients complained of any cosmetic defects. Ear prominence was detected by measuring the Concho-Mastoid angle and Cephalo-auricular distances. In all the 3 groups, an increase in CMA, D1 and D2 was noted. Although the 3 values were much higher in the immediate post-operative period (POD7), the values declined at POD 30 and stabilised at POD 90 in all the three groups. It is logical to assume that the D1 and D2 would increase in case of any increase in CMA.

Our study showed significant increase in CMA values in patients who underwent MRM and CM + TM than patients requiring Tympanoplasty alone (Fig. 4). Similar significant increments were noted in D1 and D2 of CM + TM group (Figs. 5, 6). These changes may be attributed to the fact that in Tympanoplasty the mastoid bone is left untouched, whereas in other 2 procedures the mastoid periosteum is elevated and mastoid process is drilled.

Fig. 4.

Concho-Mastoid Angle (CMA) values in different ear surgeries

Fig. 5.

Cephalo-auricular distance 1 (D1) values in different ear surgeries

Fig. 6.

Cephalo-auricular distance 2 (D2) values in different ear surgeries

Shekhar and Bhavana in their study series concluded that post-operative deviation of pinna was more in Mastoidectomy when compared to tympanoplasty [5]. This was consistent with our results. However, we fail to explain why the deviation of pinna was more in CM + TM group than MRM in spite of the fact that more bone is drilled in MRM. Shekhar and Bhavana also stated that when the incision was given slightly behind the groove showed minimal deviation of pinna with better cosmetic result. In our study this observation was not made, as all the incisions were made slightly behind the groove.

Study done by Ali MS, shows that low set pinna can be a sequelae of canal wall down Mastoidectomy; however, we did not encounter any such situation [7]. Even though our study shows deviation in all our cases, none of our patients showed any dissatisfaction about it.

Conclusion

Although not much research is done in the field some amount of deviation of pinna should be anticipated in all cases of ear surgeries with post aural incision and should be explained to the patient beforehand. The deviation of pinna is more common in Modified Radical Mastoidectomy and Cortical Mastoidectomy than Tympanoplasty and we believe that this is due to elevation of periosteum and drilling of the mastoid bone.

Funding

No funding was received for conducting this study.

Declarations

Conflict of interest

The authors have no relevant financial or non-financial interests to disclose.