Scalp Avulsion Injuries

Recently a post by Scalpel about a successful scalp replantation, after a 11 year old girl somehow gets her hair caught in a ferris wheel. Pictures of the case (and photo credit) can be seen here (not for the faint-of-heart). So I thought I'd share more about this injury.

The nature and mechanism of scalping injury have been reported by Koss et al. They emphasized "that it requires an oblique force to produce scalping, thus giving rise to the theory that the scalp tears at either of the bony ridges. The actual extent depends on the site, amount of hair caught, and the direction of the force." This was reemphasized by Bhattacharya et al. In all these descriptions, the extent of avulsion was from the supraorbital ridge to the nuchal line posteriorly. A case of avulsion of the face in continuity with the scalp reported by Dr. Abraham Thomas (1998) broke this pattern and showed that the actual extent depended on the speed and force of injury from the mechanical device and also the attitude and protective movements of the patient (successfully replanted--face and scalp). It was 1976 when the first successful replantation of a totally avulsed scalp was reported by Miller & others with return of normal hair growth and frontalis muscle funtion.

Scalp Anatomy:
The layers of the scalp are easily remembered by the mnemonic SCALP:
S (skin) is the thickest in the body, measuring between 3-8 mm,
C (subcutaneous tissue)- The vessels, lymphatics, and nerves course through the subcutaneous layer just superficial to the galea.
A (aponeurotic layer) --The galeal aponeurosis, the strength layer of the scalp, is contiguous with the paired frontalis muscles anteriorly, the paired occipitalis muscles posteriorly, and the temporoparietal fascia laterally,
L (loose areolar tissue) is also known as the subgaleal fascia, the innominate fascia, and the subaponeurotic plane. The loose areolar tissue of this plane allow for scalp mobility. Scalp avulsions routinely occur through this layer, leaviing pericranium intact.
P (pericranium) is tightly adherent to the skull and should be left intact in scalp reconstruction to allow for "back-grafting" of the donor site or for a means of alternative recontruction in the event of a failed local tissue transfer.

The scalp is supplied by arterial branches and vena comitantes of the internal and external carotid systems into four distinct vascular territories. Extensive collateralization (connections between the four territories) of these vascular territories allows total scalp replantation based on a single vascular anastomosis. The scalp is innervated by branches of the three divisions of the trigeminal nerve, cervical spinal nerves, and branches from the cervical plexus.

Replantation is the treatment of choice in scalping injuries and should always be considered, even in case of a badly damaged scalp. Specific procedures regarding pre-, intra- and postoperative care are crucial to success in replantation. These include: haemodynamic stabilization of the patient without causing damage to possible donor vessels; cooling, cleaning and further proper care of the avulsed specimen; use of antibiotics and haemodilution to optimize the intra- and post-operative situation.

When replantation is not possible then as in the past the goals are to obtain calvarial (bone) coverage to prevent calvarial desiccation, sequestration, and sepsis. However, today, the reconstructive surgeon should also strive for a cosmetically appealing result in addition to merely achieving coverage. The best replacement for scalp tissue is scalp tissue. There is no other donor site in the body that will approximate the same hair-bearing qualities of scalp tissue. A wide variety of techniques has been used to close scalp defects. They include:

• Primary Closure--For small defects this is often the best option. Defects less than 3 cm in diameter can be closed primarily, but this varies depending on location. If primary closure is selected, any defect in the galea should be closed first with buried resorbable sutures, and skin edges should be reapproximated using suture or staples.


• Skin Grafting and Tissue Expansion--Placing split-thickness skin grafts can provide a quick and effective means of defect closure. Skin grafts require an adequately vascularized wound bed and are not successful if applied directly to exposed bone. Intact pericranium is typically sufficient to support a skin graft. Tissue expansion usually provides ample tissue with preservation of scalp sensation, color, thickness, and hair; however, it ultimately requires a minimum of 2 operative procedures. Patients should understand beforehand that this requires a commitment of at least 1-2 months


• Local Flaps--Local flaps are the workhorses of small to midsized scalp reconstructions. These flaps consist of skin, subcutaneous tissue, and galea, although occasionally small superficial defects may be adequately reconstructed using a flap elevated in the subcutaneous plane. Any local flap is best raised over named arterial systems. Raising a large flap and then covering the donor site with a skin graft is probably safest. One should avoid suture lines in areas where prosthetic material might be exposed.


• Free-tissue transfers--Before the advent of free-tissue transfers, closure of scalp defects covering more than 15-20% of the scalp was essentially impossible with a single procedure. Free flaps provide for single-procedure closure of large defects or complicated wounds involving scalp and bone. They can also provide improved wound healing in the setting of radiation or infection. However, they are time-consuming and expensive, and they all involve at least some donor site morbidity. Therefore, they should be reserved for appropriate situations when local flaps, skin grafting, or healing by secondary intent is not an option.


• Vacuum assisted Closure Device (VAC)--A vacuum assisted closure device has been used for large defects over the dura to promote the growth of granulation tissue. This tissue is then covered with a skin graft. The device works by applying uniform subatmospheric pressure to the wound, allowing it to develop a better blood supply, decreased bacterial counts, and robust granulation tissue.

References:

Reconstruction of Acquired Scalp Defects: An Algorithmic Approach; Plastic & Reconstr Surg, Vol 116(4):54e-72e, September 15, 2005. Leedy, Jason E. M.D.; Janis, Jeffrey E. M.D.; Rohrich, Rod J. M.D.
Psychological Sequelae of Failed Scalp Replantation; Plastic & Reconstr Surg.; Vol 113(6):1573-1579, May 2004. Mowlavi, Arian M.D.; Bass, Michael J. B.S.; Khurshid, Khurshid A. M.D.; Milner, Stephen M.D.; Zook, Elvin G. M.D.
Total Face and Scalp Replantation [Case Report]; Plastic and Reconstructive Surgery, Vol 102 (6) November 1998, pp 2085-2087; Thomas, Abraham M.S., M.A.M.S., M.Ch., F.A.I.S., F.I.C.S.; Obed, Vijay M.S., M.Ch.; Murarka, Anil M.S., M.Ch.; Malhotra, Gopal M.S., M.Ch.
Scalping Injury; Plast. Reconstr. Surg., Vol 55: 439, 1975; Koss, N, Robson, M, and Krizek, TJ
Successful Replantation of an Avulsed scalp by Microvascular Anastomoses; Plast. Reconstr. Surg. Vol 58: 133, 1976.; Miller, G D H, Anstee, E J, and Snell, J A