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Pearls for Perfecting the Mastoid Interpolation Flap

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Pearls for perfecting the mastoid interpolation flap
Hilda Justiniano MD1, Daniel B Eisen MD2
Dermatology Online Journal 15 (6): 2

1. Procedural Dermatology Fellow
2. Assistant Professor of Dermatology, Director Procedural Dermatology Fellowship and Aesthetic Dermatology.
University of California, Davis, School of Medicine, Department of Dermatology, Sacramento, California


Helical rim ear defects can present a reconstructive challenge to the Mohs surgeon. Multiple options exist including wedge excision, helical rim advancement flaps, bilobed flap, and grafts, to name a few. Wedge excision of the ear may result in a noticeable anteverted, smaller ear, and disrupts auricular cartilage with the possibility of chondritis and excess pain. Helical rim advancements can result in anteversion of the ear and a smaller lobule. Mastoid interpolation flaps, which are also called retroauricular to auricular flaps, can be a useful alternative in patients who are willing to return for a second procedure. They are easy to perform and can result in a highly aesthetic reconstruction in which the ear size and form are maintained. The donor skin comes from an area that is hidden from view and heals with minimal complications. We present our suggestions for performing these reconstructions. Ways to optimize results, potential pitfalls, and postoperative care instructions are discussed. Step by step videos are included with this manuscript.


Helical rim ear defects can be problematic for the patient and surgeon. The skin is very thin with little subcutaneous tissue to protect the underlying cartilage. As a result surgery patients are at risk for chronic chondritis, slow healing time, and pain. Reconstruction options range from second intention healing, full or split thickness grafting, helical rim advancement flaps, wedge excisions, and banner flaps, to name a few.

We will describe the technique we use to perform the retroauricular to auricular (mastoid) interpolation flap. This flap is applicable to defects that extend as far forward as the conchae.

Although this is a two-stage procedure, we have found that the relative ease with which it is completed makes it a good alternative to repair defects of the ear that involve the helical rim and are too large to repair with a single stage flap.

Description of procedure

Figure 1
Figure 1. Measuring of the defect prior to flap incision. The flap's width should be equal to or wider than the greatest vertical length of the defect.

After margin control is assured, the length of the surgical defect is measured along the helical rim (Fig. 1). If the defect extends only to the helical rim, the flap can be started at the junction where mastoid skin meets the posterior ear. If the defect extends further medial to the scaphoid fossa or beyond, the flap incision can be started on the posterior ear and extended onto the mastoid area. The flap should be sized slightly larger than the measured width of the defect and be long enough so that excessive tension is not placed on the flap after it is sutured (Fig. 2). The flap is then elevated in the superficial subcutaneous plane (Fig. 3). Meticulous hemostasis is necessary because this site will be difficult to access after the flap is sutured in place.

Figure 2Figure 3
Figure 2. Drawing of the flap prior to incision. The flap's length will depend on the extent of the defect. For defects along the helical rim, the flap can be started where the mastoid skin meets the posterior ear. If the defect extends over the scaphoid fossa, the flap can be started on the posterior ear and extended to the mastoid area.

Figure 3. Once incised, the flap is elevated in the superficial subcutaneous plane. Meticulous hemostasis must be achieved at this stage because this site will be hard to access once the flap is sutured in place.

Figure 4Figure 5
Figure 4. Stage one of the flap is completed once the superficial cutaneous sutures are in place.

Figure 5. Eversion of wound edges is essential when suturing flap in place; failure to do so will result in helical rim notching; A) Mohs defect prior to flap suturing; B) 2 months after flap takedown. Notice the notching along the helical rim that resulted because of inadequate wound edge eversion.

The recipient site is undermined to allow easy eversion of the wound edges. The flap is then anchored in place with buried inverted subcutaneous mattress sutures along the leading edge. The periphery is sutured with fast acting gut to avoid the need for suture removal in the future (Fig. 4). Careful attention to wound edge eversion should be paid in the helical rim area; notching will result if this is not properly executed (Fig. 5). To avoid this, we recommend using vertical mattress sutures in this location.

Figure 6
Figure 6. Bridging of the helix and antihelix resulting in blunting of the scaphoid sulcus; A) Mohs defect; B) Blunting of the scaphoid fossa. This issue may be avoided by aggressively thinning the flap to match the thickness of the surrounding skin and by placing basting sutures along the scaphoid fossa. Alternatively, a third procedure maybe performed to remove more subcutaneous tissue. Intralesional triamcinolone acetonide may also be helpful.

Attention must also be paid to the form of the ear. If any bridging of the flap is observed between the helical rim and antihelix the form of the scaphoid sulcus will be blunted (Fig. 6). This issue can be addressed with basting sutures and by aggressively thinning the flap to match the contour of the surrounding skin. The basting sutures can be carried through the auricular cartilage if it is not possible to grasp the underlying perichondrium. Even with these techniques a third procedure might still be necessary in the future to adequately thin the flap so that it matches the contour of the surrounding skin.

Figure 7Figure 8
Figure 7. Merocel with airway. This device may be used instead of surgifoam to fill the gap between the pedicle and donor skin, thus achieving better hemostasis.

Figure 8. Stage 1 completed. Notice Merocel with airway is placed between the pedicle and the donor skin. Care must be taken not to stretch the pedicle too much; this may compromise its blood supply.

Once the flap is sutured in place, it is important to prevent desiccation of the pedicle and minimize bleeding. Addressing postoperative bleeding can be problematic because getting access to the pedicle or flap donor site is difficult. For this reason, we recommend gel foam to both the donor defect and underside of the exposed pedicle. Alternatively, Merocel nasal packing with airway (Figs. 7 & 8) may be used instead of gel foam; this provides bulk to fill the gap between the pedicle and the donor site, thus helping achieve better hemostasis. However, care must be taken to avoid stretching the pedicle too much because this may compromise its blood supply. If gel foam is used instead of Merocel we wrap the pedicle with petrolatum-impregnated gauze to prevent desiccation.

Figure 9Figure 10
Figure 9. Flap take-down. Notice that the pedicle is incised along its proximal end.

Figure 10. Flap sutured in place. We recommend using fast absorbing gut to avoid the need for suture removal after the procedure.

The pedicle division may be safely done after two weeks by incising along the proximal end of the pedicle (Fig. 9). There is little benefit to cutting the pedicle closer to the ear. Because it is difficult to see how long the flap needs to be cut once it is sewn in place, there is a risk of making the flap too short. Therefore, we prefer to cut it close to its base, as previously mentioned. Once severed, the flap is trimmed to fit the remaining defect. It is helpful to undermine around the flap site to allow easy wound edge eversion. Once the operative site is undermined, the flap may be sewn in place. We recommend using fast absorbing gut to avoid the need for suture removal after the procedure (Fig. 10).

Figure 11Figure 12
Figure 11. Excellent helical rim contour achieved with adequate execution of the flap; A) Mohs defect; B) two weeks after stage one; C) two months after flap take-down. Notice the pinkish color of the flap two weeks after stage 1.

Figure 12. Another example of the excellent results achievable with this flap; A) Mohs defect; B) two weeks after stage 1, notice the partial superficial necrosis and exudation due to infection on the superior portion of the flap; C) two weeks after flap take-down. Acceptable end result obtained despite infection and partial necrosis.

A pressure bandage is applied and left in place for two days. After this time, traditional wound care may be followed. Final results are evident at the two month follow up. The use of this flap results in excellent helical rim contour, color, and texture matching (Figs. 11 & 12).


Auricular surgery is one of the most demanding procedures in the field of dermatologic surgery. The contour of the ear is not easily reproduced and even small changes can cause noticeable deformity. Numerous techniques have been reported to repair helical rim defects. These procedures range in complexity from simple closure, for smaller defects, to chondrocutaneous flaps, for larger defects [1, 2].

Because retroauricular skin is richly vascularized, hidden behind the ear, and very similar in color and texture to the ear and face, it has been considered a "flaps bank" for reconstruction of ear and face defects [3, 4, 5]. The retroauricular to auricular interpolation flap is best suited for defects on the mid and lower helical rim. A similar technique can be used for the upper helical rim, but the flap donor site must be moved from the mastoid area to the area just above the auricle.

Figure 13
Figure 13. Partial flap necrosis as a result of pressure exerted on pedicle; A) Crust over partially necrosed flap; B) crust removed revealing shallow erosion.

Although the flap can be sized and completed with relative ease, it is not without complications. Besides the notching that may occur along the helical rim and blunting of the scaphoid fossa that were described above, we have also faced instances of partial flap necrosis and infection. Partial flap necrosis can occur if pressure is exerted over the pedicle, thus compromising its blood supply. This may occur either when the pedicle is stretched too much or as a result of pressure over the pedicle caused by a hearing aid or eyeglasses (Fig. 13). As with any skin surgery, infections may occur. In our experience, the infection rate after this flap is no greater than for other common surgeries in our clinic. However, infections may result in partial flap dehiscence and necrosis. Nonetheless, the final result in these cases may still be acceptable (Fig. 12).

Figure 14Figure 15
Figure 14. Mastoid flap repair video 1 (QuickTime)

Figure 15. Mastoid flap repair video 2 (QuickTime)

The retroauricular to auricular interpolation flap or mastoid flap is a good tool to have in our armamentarium for the reconstruction of helical rim defects. In our experience, it provides excellent helical contour when performed correctly. It is relatively easy to execute and can be completed in an acceptable amount of time. The flap's first stage usually takes about 20 minutes to position and suture (Fig. 14). The second stage, pedicle division and inset, usually takes no more than 10 minutes to complete (Fig. 15). Given the good cosmetic outcome this flap provides, in our opinion the extra visit is worth it.


1. Mellette, J.R., Jr., Ear reconstruction with local flaps. J Dermatol Surg Oncol, 1991. 17(2): p. 176-82. [PubMed]

2. Skaria, A.M., The modified chondrocutaneous advancement flap for the reconstruction of helical defects of the ear. Dermatol Surg, 2008. 34(6): p. 806-10. [PubMed]

3. Pinho, C., et al., A new retroauricular flap for facial reconstruction. Br J Plast Surg, 2003. 56(6): p. 599-602. [PubMed]

4. Cordova, A., et al., Retroauricular skin: a flaps bank for ear reconstruction. J Plast Reconstr Aesthet Surg, 2008. 61 Suppl 1: p. S44-51. [PubMed]

5. Yotsuyanagi, T., et al., Retroauricular flap: its clinical application and safety. Br J Plast Surg, 2001. 54(1): p. 12-9. [PubMed]

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