Neurovascular Anatomy at the "Box Junction": Considerations in the Anterolateral Thigh Flap.

BACKGROUND:  The anterolateral thigh (ALT) perforator flap is one of the most widely used flaps in reconstructive microsurgery. This study investigated a previously unexplored and clinically relevant aspect of perforator anatomy: the "box junction" (BxJn), the point at which the perforator arises from its source vessel. Negotiating the BxJn can be a challenging and time-consuming step in flap harvest, due to the neurovascular structures in the area which must be protected from injury. However, as the presence and location of these structures have yet to be clearly defined, painstaking exploration is necessary on each occasion. Knowledge of BxJn anatomy could allow surgeons to harvest the ALT flap more rapidly and safely.

METHODS:  We dissected 20 cadaveric thighs and identified perforators to the ALT region and investigated the neurovascular anatomy at their BxJns.

RESULTS:  In 51 BxJns, two clinically relevant vascular structures were identified: an intramuscular artery arising from the perforator (23, 45% of cases) and a "deep" artery to the underlying muscle arising from the source vessel (29, 57% of cases). We confirmed the consistent presence of motor nerve branches and describe one previously unreported, clinically significant variation, in which the nerve to vastus lateralis crosses the BxJn (12, 24% of cases); 36, 71% of BxJns contained at least one vascular and one neural structure.

CONCLUSION:  Our study confirms that the BxJn is a site of potentially complex and challenging neurovascular anatomy for the surgeon. Based on these results, we propose an algorithm to guide inexperienced surgeons in negotiating this area.