OTA 1997 Posters - Foot & Ankle Fractures

Vascularity of the Lateral Calcaneal Flap

Joseph Borrelli, Jr., MD, Cyrus Lashgari, MD

St. Louis, Missouri, USA

Displaced intraarticular fractures of the calcaneus are more and more commonly being managed with open reduction and internal fixation. Utilization of an extensile lateral incision necessitates the development of a full thickness, proximally based fasciocutaneous flap. The vascular supply to this flap has been referred to as an "angiosome" by some authors. The purpose of this investigation was to characterize the primary blood supply to this flap and relate the position of the primary arteries to the recommended position of the surgical incision.

Twenty-four fresh hip disarticulation specimens were utilized. Digital pulp incisions were created and each specimen underwent cleansing of the arterial system with sterile water by manual injection of the superficial femoral artery. In twenty specimens this cleansing was followed by injection of India ink, using firm manual pressure, followed by Ward's blue latex solution (60-80cc). The injection was stopped and the arterial system considered filled when the injected material could be seen exiting the digital pulp incisions. The specimens were then placed in the freezer (-80°C) for 48 hours to assure consolidation of the latex. The specimens were defrosted and transected at the mid-tibial region and the proximal limb discarded. Metallic skin staples were placed 1/2 finger's-bredth anterior to the palpable edge of the achilles tendon and along the junction of the lateral and plantar skin to the level of the base of the fifth metatarsal. This staple line represented the ideal lateral extensile incision. A mechanical debridement of the skin was carried out followed by chemical debridement of the subcutaneous fat of the foot and ankle, using full strength bleach (sodium hypochlorite). During the chemical debridement, the specimens were inspected every half hour to determine the amount of soft tissue debridement. Once exposed, the position of the Lateral Canal Artery (LCA), Lateral Malleolar Artery (LMA) and the Lateral Tarsal Artery (LTA) was determined by direct measurements from the lateral malleolus, posterosuperior corner of the calcaneus and the base of the fifth metatarsal using cardiac calipers and metric ruler. Metallic vascular clips were then placed along the path of each artery and a lateral radiograph taken.

The remaining four specimens underwent selective arterial injections. The distal aspect of the anterior tibial artery was cannulated and injected just proximal to the take off of the lateral malleolar artery and the distal peroneal artery was injected just proximal to the branch of the lateral calcaneal artery with India ink. Visual changes of the skin of the lateral foot and ankle supplied by these arteries was observed and photographed.

The lateral fasciocutaneous flap was consistently found to be supplied by three primary arteries. These arteries included the Lateral Calcaneal Artery, (LCA a branch of the peroneal artery), the Lateral Malleolar Artery, (LMA, a branch of the anterior tibial artery), and the Lateral Tarsal Artery (LTA, branch of dorsalis pedis artery). All three of these arteries anastomosed laterally, anterior and distal to the tip of the fibula and proximal to the base of the fifth metatarsal, forming a leash of vessels which extended from posterior to the lateral malleolus to the base of the fifth metatarsal.

The LCA was found to exit from beneath the deep fascia 15mm proximal to the tip of the lateral malleolus and 36mm posterior to the mid coronal plane of the fibula. It proceeded distally, passing 14mm anterior to the posterior superior corner of the calcaneus and then 32mm below the tip of the fibula. The LMA branched from the anterior tibial artery and descended distally, 5mm anterior to the anterior border of the distal fibula passing over the peroneal tendons and anastomosing with the LCA. The LTA branched from the dorsalis pedis artery 52mm from the midpoint of the fibula on the dorsum of the midfoot and traveled distally over the cuboid and beneath the peroneal brevis tendon 28mm proximal to the base of the fifth metatarsal, before anastomosing with the LCA and LMA.

Radiographs of the prepared doubly-clipped specimens delineated the relationship between the LCA and its anastomotic vessels, and the typical surgical incision. The origin of the lateral calcaneal artery was found to lie 8mm from the posterior limb of the typical incision. The major portions of the LMA and LTA were no closer than 3cm of the typical surgical incision.

Selective injection of the distal peroneal artery (LCA) caused visual discoloration of the lateral skin from 2cm above the tip of the malleolus to the base of the fifth metatarsal. Selective injection of the distal aspect of the dorsalis pedis artery (LMA, LTA) caused visual discoloration of the anterolateral skin of the hindfoot. An area of demarcation between these two areas could be seen extending from the tip of the fibula to the base of the fifth metatarsal.

The "angiosome" responsible for providing the lateral fasciocutaneous flap created during operative stabilization of calcaneal fractures is actually made up of three arteries: Lateral Calcaneal Artery, Lateral Malleolar Artery and the Lateral Tarsal Artery. The LCA is responsible for supplying the area around the lateral malleolus and the angle of the lateral flap with its blood supply. The LMA and LTA are important contributors to the vascularity of the anterior 1/3 of the flap, and the peroneal tendons. The proximal portion of the LCA lies within 8mm of the posterior limb of the typical incision and it is in this area that injury to this artery may occur, jeopardizing the vascularity of a portion of the flap.

Although the blood supply of the lateral calcaneal flap is provided by three arteries, the LCA appears to be most vulnerable to injury. Injury to this vessel proximally could jeopardize the viability of the flap and lead to wound complications. An understanding of the vasculature of the flap and placement of the incision is crucial in avoiding direct injury to the blood supply of the lateral calcaneal flap.