Effective Technique for Periosteal Removal During Mohs Micrographic Surgery
A 75-year-old man presented to the Mohs surgery unit for treatment of a 3 × 2 cm biopsy-proven squamous cell carcinoma (SCC) on his left vertex scalp. One Mohs layer was removed and involved soft tissue down to but not including the periosteum. Histologic frozen section evaluation revealed residual tumor along the deep margin with no involvement of the lateral margins. When the defect was clinically evaluated, a thin layer of the periosteum was still present encasing the underlying bone. The following method was used to evaluate for tumor invasion of the underlying periosteum.
The tip of a small bore needle (1/2 inch 30-gauge needle on a 3 mL syringe) was introduced just beneath the level of the periosteum with the bevel facing upward (Figure 1). One milliliter of normal saline was then slowly injected to separate or “tent up” the periosteum from the underlying bone. Immediately afterward and before dissipation of the injected fluid into the surrounding tissue, a #15 blade on a scalpel was used to circumferentially incise the edges of the periosteum around the area of interest. One pole of the tissue was then gently gripped with Adson tissue forceps, whereas a freer elevator was introduced beneath the periosteum further releasing any remaining attachments from the underlying bone (Figure 2) This resulted in rapid and complete removal of an even and adequate sample of the underlying periosteum (Figures 3 and 4) that was very amenable to frozen section processing. No tumor was found within the sampled periosteum providing histologic confirmation of complete removal.
In the dermatologic surgery literature, a similar technique has been reported for the perichondrium of the ear.2(p108) Furthermore, the use of a disposable curette has been reported as a means of periosteal removal.3(p46) However, this was used more as a means of removing the periosteum and not for preparing a histologic tissue sample. Dermatologic surgery has borrowed from techniques used by plastic surgery and otolaryngology such as use of the double-edged Freer elevator for this purpose but not in a way intended to preserve the removed tissue for histologic evaluation.4(p47)
Squamous cell carcinomas frequently occur on the scalp and are therefore commonly encountered in Mohs surgery. When these tumors invade within or beyond the periosteum, they are more difficult to treat and may necessitate interdisciplinary management.5(p1) Hence, histologic evaluation of the periosteum can be an important factor in patient care.
Mohs surgery has a very high reported cure rate. Given unique obstacles encountered in various bodily locations, innovative methods and techniques may need to be used to ensure tumor extirpation. Mohs micrographic resection of aggressive scalp tumors may require full-thickness wounds down to or including the level of the periosteum. The periosteum's inherent adherence to the underling bone poses a unique challenge as the Mohs surgeon must find a way to efficiently and atraumatically excise a tissue sample suitable for frozen section processing. The authors believe that the described technique can be useful in addressing this challenge. Limitations to the described technique include the requirement of intact periosteum, which is needed for the initial fluid bolus to lift the tissue.