The vascular anatomy of the forehead related to forehead flaps and its application in plastic and reconstructive surgery
Thesis (PhD (Surgical Sciences))—University of Stellenbosch, 2007.
Aims: The goal of this study was to identify arterial variations by cadaveric dissection, in the forehead, in order to validate the practicality and implementation of planned forehead flaps and to increase the safety of forehead flaps in plastic and reconstructive surgery. Hypothesis tested: Unique frontal forehead flaps can be safely based on anatomical dissection and on the presence of the central vein and the anastomosing branches of the frontal ramifications of the angular artery (AA). Materials & methods: The study had two strategic components: an anatomical cadaveric study and a clinical study, based on the newly described forehead vasculature. The anatomical study consisted of a) dissection of 30 latex infused cadavers and 20 non-latexed cadavers; b) histological assessment of forehead vasculature of 20 cadavers. The clinical applicability study consisted of a cohort of 12 plastic and reconstructive surgery cases, undergoing nasal rhinoplasty, based on the cadaveric study and anatomical vasculature. The research was conducted within an ethical protocol and all patients gave informed consent. The follow-up period is 2 years. Results: In the cadaveric dissection, the following vessels, relevant to forehead flaps and nasal reconstruction, were consistently identified: DNA, FBSTA, STrA, TFA, AA, CA, CV, PCA, SOA and OV. Side branch analysis of STrA (N = 43) showed: MCB (60%), LCB (23%), SPA (26%), OB (19%), single VB (47%), medial and lateral VB (53%). Side branches of the supra-orbital artery (SOA) were: LRB (91%), OB (91%), VB (100%), MB (44%), BB (5%) and SVB (9%). Side branch profile of the angular artery (AA) was: DNA (96%), CB (67%) and PCA (47%). In 71% of cases the origin of the PCA was from the angular artery (AA). Individual artery side branches of the forehead were as follows: STrA (9), SOA (6), FBSTA (4), DNA (4), AA (3/4), CA (2) and PCA (2). Average diameter of the small arteries at point of entry ranged from 1 – 2mm (CA < 1mm, PCA < 1mm). The central vein was a constant finding in all dissections and an important landmark. Other constant veins detected included the nasofrontal, ophthalmic, angular, supra-trochlear and facial veins. Twelve prospective randomized patients met inclusion criteria for nasal flap reconstruction, based on the cadaveric vascular study. Race profile was white (6), mixed (4) and black (2). There were 8 males and 4 females. Disease demographics included cancer (6; melanoma 2, basal cell cancer 5), trauma (3), infections (1) and congenital (1). Post-operative grading was as follows: defects corrected (12/12), subjective improvement (12/12), objective improvement (12/12), partial flap necrosis (1/12) and secondary interventions (debulking or revision 2/12). Doppler assessment for pedicle vasculature showed identification of the following arteries: TFA (85%), STrA (65%), PCA (20%) and AA (25%). Doppler studies further indicated the following small side branches: TFA (49%), STrA (30%), PCA (9%), AA (12%). The central vein was identified in 9/12 (75%) by macroscopic examination. In one female with a basal cell carcinoma (BCC), modest dermal stock loss was demonstrated by the application of high frequency dermal ultrasound (Dermascan®). The results of the cadaveric anatomy study show the existence of various important subtle arterial variations in the forehead that are not described in the literature. Many arterial side branches not clearly named and others not described before, were highlighted in this anatomical study. Other observations regarding the anatomical relationships of the forehead nerves were of practical surgical value, the most important being to reduce sensory neuropraxia. The histological study endorsed the cadaver dissection observations and showed the importance of the flap vasculature at the proximal level of the pedicle. The clinical study with follow-up period of 24 months, illustrates an evolving refinement in surgical technique based on the findings of the anatomic vasculature study. A new method of planning a “2500-year-old operation” was confidently developed based on the anatomical vasculature observations detected during the cadaver study. The Doppler study suggests that crude arterial variations of the central forehead, in the region of the intended flap pedicle, can not be diagnosed and highlighted accurately pre-operatively. The macroscopic anatomy of the central vein (clinical landmark) is an accurate predictor of underlying arterial variations and may be more valuable clinically than the hand-held Doppler examination. Conclusion: Comprehensive vascular anatomical detail of the forehead was not described accurately or completely by clinical anatomists in the past and does not appear in classic text books of anatomy and morphology. This has led to one-dimensional (arterial) application of the midline forehead flap planning and eventually the introduction of the para-median forehead flap, which has become the modern “work horse” of forehead flaps for nasal reconstruction. Now that in a definitive cadaveric study of the forehead blood supply has been demonstrated, the results show that surgeons will once again be able to embrace the midline forehead flap, only this time there will be possibly no inconsistent descriptions of unnamed blood vessels or ill-defined landmarks for flap planning. New flaps and reconstructive options in or around the forehead will be hopefully planned and executed more effectively and safer based on a more comprehensive understanding of the forehead anatomy and vasculature. The subjective and objective end-point analysis of the clinical study show favourable measured outcomes in the interim follow-up period (24 months) and benefit to the patients, in the presence of a low percentage of flap loss (1/12; 8.3%). The use of pre-operative Doppler assessment helped with flap planning. In one patient, the application of high frequency ultrasound facilitated long term follow-up regarding recurrent tumour formation and enhancement of dermal consistency with anti-aging creams, vitamin A derivations and sunscreens. Recommendations: The classic anatomy text books and clinical plastic surgery works with their inconsistent descriptions of the central forehead blood supply (arterial and venous) need to be updated. The evolution of the midline forehead flap method is far from complete. The refinement of the one-stage midline forehead flap method without an island is in progress and can clinically be implemented, based on a sound anatomical dissection study.