The repair of flexor tendons continues to be

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Vascular Anatomy of the Dorsum of the Foot

Ruben Garcia-Pumarino, M.D., Ph.D.

Eduardo Moraleda, M.D.

Ander Aburto, M.D.

Jesus A. Barros, M.D.

Lawrence Garro, M.D.

Jose´ F. Salvador, M.D.

Francisco Sanchez, M.D.

Madrid and Alicante, Spain

Background: The authors’ purpose was to study the anatomy of the dorsum of the foot and determine the distribution and caliber of all vascular branches that nourish the skin and the extensor hallucis longus and extensor digitorum longus tendons.

Methods: The authors performed 20 cadaver dissections. The skin paddle was designed within the dorsum of the foot. Dissection continued until all vascular branches that nourished the skin and tendons were identified. The authors measured the caliber of the vascular connections and the distance to the proximal end of the extensor retinaculum.

Results: The dorsalis pedis artery was the continuation of the anterior tibial artery in all cases. A mean of five cutaneous perforators irrigated the cutaneous paddle with a mean caliber of 0.53 mm. The paratenon of the extensor hallucis longus tendon was vascularized by a mean of 8.1 vascular branches with a mean diameter of 0.71 mm. The paratenon of the extensor digitorum longus tendon was nourished by a mean of 5.4 vascular branches, and the mean caliber of those branches was 0.65 mm.

Conclusion: The dorsum of the foot presents a constant vascular anatomy that is well suited for the elevation of different types of compound flaps which, in turn, would adapt to the needs of the defect. (Plast. Reconstr. Surg. 126: 2012, 2010.)

T

he repair of flexor tendons continues to be one of the most difficult problems faced by hand surgeons, especially when the injury is located in the so-called no-man’s land. The formation of adhesions and the possibility of rupture secondary to repair are the two complications that most limit the functional result.

In the past, the formation of adhesions was believed essential for tendon healing processes, because of their relatively avascular and practically acellular nature.^1–3 Later, it was shown that tendons could be nourished through the synovial fluid that surrounds them within the synovial sheath, and that this diffusion mechanism is sufficient for the intrinsic processes of tendon healing.^4,5 On studying in detail the processes that influence the formation of adhesions, it was observed that immobilization was a determining factor.^6,7 Consequently, several studies based on clinical findings propose early mobilization to stimulate the intrinsic repair pro-

cesses and thus improve the functional results of primary tendon repair.^{8 –10}Despite early mobilization, however, only a third of primary repairs in the no-man’s land area reached a near-normal range of movement.¹¹

When primary repair is not possible because of the local conditions of the injury, secondary tendon repair may be undertaken in a one-stage operation, provided that the synovial sheath is preserved in good condition and at least pulleys A2 and A4 are respected. Repair by tendon grafts in two-stage surgery is restricted to patients who have undergone multiple operations and present cicatricial beds, ar- ticular lesions, nerve lesions, or lesions in multiple structures (grades III, IV, and V according to the Boyes classification).¹² Nevertheless, this approach usually results in a high rate of failures because of inadequate nutrition of the graft by the neosheath.

The rate of good functional results associated with the two-stage flexor tendon reconstruction technique is approximately 50 percent.^13,14 Moreover, the final functional result is not obtained until at least 6 months after surgery.^15–18

From the Department of Plastic and Reconstructive Sur- gery, Ramon y Cajal Hospital, and the Department of Histology and Anatomy, Faculty of Medicine, Miguel Hernandez University.

Received for publication March 15, 2010; accepted June 14, 2010.

Disclosure: The authors have no financial interest to declare in relation to the content of this article.

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where skin coverage was precarious.^21,22

Although several authors have used vascularized tendon grafts based on the dorsalis pedis vessels, none has described in detail the number and mea- surement of vascular branches that nourish the tendons. Therefore, the main objective of this study was to examine the vascularization of the different anatomical structures of the dorsum of the foot (skin and extensor hallucis longus and extensor digitorum longus tendons), enabling different combina- tions of compound flaps to be raised.

MATERIALS AND METHODS

Anatomical dissections were performed on 20 feet of 20 cadavers between 62 and 85 years of age preserved using the Thiel-Graft technique. After undertaking the preservation technique, six of 20 cadavers were injected with colored latex. The Thiel-Graft solution consists of a high concentra- tion of salty components that denaturalize the pro- teins of the tissue. The Thiel-Graft technique pre- serves specimens for approximately 2 years. All cadavers in the study were preserved during the first 48 postmortem hours. Specimens used in this study had been preserved for approximately 6 months. To undertake the preservation technique, conservation solution was injected into the left external carotid artery. Saline solution was then injected to eliminate detritus, followed lastly by injection of the colored latex. Dissection was performed under magnification with a 3.6⫻ Zeiss (Carl Zeiss, Oberkochen, Germany) surgical loupe. In the specimens, we used as landmarks the midpoint of the intermalleolar line and the meta- tarsophalangeal joint (Fig. 1). The union of these points coincides approximately with the pathway of the dorsalis pedis vessels. Point 0 was fixed at the proximal end of the extensor retinaculum. A mil- limeter compass was used to measure the vascular branches, and the external diameter of the vessel was recorded. The dissection technique began with skin incisions around the cutaneous paddle, designed on the dorsum of the foot. The superficial fibular nerve was located and preserved. The

line of cutaneous perforators followed the pathway of the dorsalis pedis and first dorsal metatarsal arteries (Fig. 2).

The deep fascia in the space between the extensor hallucis longus and the extensor digitorum longus tendons was opened up. After the retro- grade pathway of the cutaneous perforators, the dorsalis pedis vessels and deep fibular nerve were located. Each of the branches emitted by the dorsalis pedis artery and first dorsal metatarsal was identified, respecting the ones that vascularized the paratenon of the extensor hallucis longus, the extensor digitorum longus, and the perforators that nourished the cutaneous paddle (Figs. 3 through 5). Once the vascular branches were iden-

Fig. 1. The midpoint of the intermalleolar line and the metatar- sophalangeal joint were used as landmarks to localize the dor- salis pedis vessels (black points). The white points indicate the po- sition of the medial and lateral malleolus.

Fig. 2. Lateral view of the foot (distal portion on the left). The skin paddle has been raised showing the cutaneous perforator branches. The superficial fibular nerve has been isolated with four blue markers.

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tified, dissection of the extensor tendons of the foot was completed. The dissection continued proximally, opening the extensor retinaculum on both sides of the tendons to reach the myotendi- nous union and gain length of pedicle, dissecting the anterior tibial vessels (Fig. 6).

RESULTS

After dissecting the specimens, the following observations could be made.

Dorsalis Pedis Vessels

In all cases, the dorsalis pedis artery was the continuation of the anterior tibial artery. Proximal

to the extensor retinaculum, the anterior tibial artery ran between the muscular belly of the anterior tibial and the extensor hallucis longus. At the proximal end of the extensor retinaculum, the mean diameter of the dorsalis pedis artery was 2.67⫾ 0.65 mm. At the level of the extensor retinaculum, the dorsalis pedis artery crossed from medial to lateral under the extensor hallucis longus tendon, to position itself between this tendon and the extensor digitorum longus tendon. The lateral tarsal artery came from the dorsalis pedis artery, 2 to 3 cm distal to the extensor retinaculum, in all feet studied. The first dorsal metatarsal

Fig. 3. Frontal view of the dorsum of the foot. The space between the exten- sor hallucis longus and extensor digitorum longus tendons has been dissected. The vascular branches that nourish the paratenon of both tendons have been isolated with blue markers (extensor hallucis longus tendon at the top). The orange arrowhead point to the deep fibular nerve. The asterisk marks the medial tarsal artery.

Fig. 4. Frontal view of the dorsum of the foot (colored latex). The space between the extensor hallucis longus (EHL) and extensor digitorum longus tendons has been dissected. The blue markers isolate the vascular branches that nourish the extensor hallucis lon- gus paratenon. The orange arrow points to the deep fibular nerve.

The red arrowheads mark two cutaneous perforators. TA, tibialis an- terior tendon.

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artery was absent in four of the specimens (20 percent). The anterior tibial artery, and the dorsalis pedis arteries, the first dorsal intermetatarsal and the lateral tarsal, were accompanied in all specimens by two concomitant veins. The arterial branches that irrigate the cutaneous paddle and paratenon of the extensor hallucis longus and the extensor digitorum longus are always accompanied by two concomitant veins. The caliber of the dorsalis pedis veins varied between 1.9 and 3.4 mm.

Skin Paddle

The cutaneous perforators that were found medial to the extensor hallucis longus tendon, or lateral to the extensor digitorum longus tendon, were rejected, on the understanding that these perforators were subsidiary to the tarsal, medial, or lateral arteries, and that it would be difficult to preserve them during dissection. Only the perforators located between the tendons of the extensor hallucis longus and the extensor digitorum longus were considered. The mean number of perforant branches depending on the dorsalis pedis artery that vascularized the skin of the dorsum of the foot was five, with a range that varied between two and nine perforators. The diameter of the perforators varied between 0.2 and 0.9 mm (mean, 0.53 mm). A total of 65.8 percent of cutaneous perforators were located between 3 and 8 cm distal to the proximal end of the extensor retinaculum.

Extensor Hallucis Longus Tendon

The extensor hallucis longus tendon was cov- ered along its entire length by paratenon. This

with a range that varied between 13 and 18 cm.

Extensor Digitorum Longus Tendon

As in the case of the extensor hallucis longus, this tendon was also surrounded along its entire length by paratenon and presented firm adhesions to the deep surface of the extensor retinaculum. Between four and 10 arterial branches vascularized the paratenon (mean, 5.4). Most of these branches originated in the dorsalis pedis artery (93 percent), whereas the rest were subsid- iaries of the lateral tarsal artery. The mean caliber was 0.65 mm, with a range of 0.3 to 0.95 mm, and 93.61 percent of the branches that vascularized the paratenon of the extensor digitorum longus were located in the first 6 cm distal to the proximal end of the extensor retinaculum. The length of the extensor digitorum longus tendon varied between 12.5 and 20.5 cm (mean, 16.45 cm).

Superficial and Deep Fibular Nerves

In practice, it is very difficult to preserve both structures without sacrificing any vascular branch, because in practically all specimens the nerves passed between those branches. When- ever possible, and depending on the needs of each case, the integrity of both nerves should be preserved. It is possible to provide sensory in- nervation to the cutaneous paddle by means of the superficial fibular nerve.

DISCUSSION

Diverse studies^23–28have demonstrated that the structure of the tendon possesses a reasonable vascular blood flow and that the concept of the tendon as an acellular structure with precarious vascularization is incorrect. Despite these findings, intratendinous vascularization was believed inadequate to replace the metabolic needs of the injured tendon. The fibroblastic activity of ad- jacent tissues was therefore necessary for the processes of tendon repair. This led to the formation of adhesions that could limit tendon excursion.³ Iso-

Fig. 5. Detail of a vascular branch that penetrates the paratenon of the extensor hallucis longus tendon.

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lating the tendon repair in the no-man’s land area by using different biomaterials did not solve the problem; adhesions were limited to the two ends of the insulating material. However, there was a delay in the repair processes and an increased risk of rupture caused by necrosis of the isolated portion of tendon. From that point on, attempts were made to improve the functional result, decreasing the frequency of adhesions.

The findings of Colville et al.²⁹highlighted the importance of the mesotendon for tendinous vascularization. Using Silastic (Dow Corning Corp., Midland, Mich.) sheets, the tendon and its adja- cent tissue were isolated, showing that a tendon could survive solely by means of its mesotendon.

In the digital sheath, this mesotendon is made up of vincula longa and vincula brevis, whereas in the carpometacarpal region, the mesotendon is identified as the common carpal sheath.

When comparing the functional result of vascularized and nonvascularized tendinous grafts in

an experimental model on primates, Singer et al.²⁰ demonstrated that the vascularized tendons had a range of movement greater than the nonvascularized tendons and were less inclined to the formation of adhesions. Therefore, when conserving the vascularization of the connective tissue that surrounds the tendon, vascular blood flow to the tendon is maintained. This avoids the need to establish vascular continuity with surrounding tissues in order for the tendon to survive.²²

The ultrastructure of the connective tissue (paratenon) that surrounds the tendon is made up of filaments running in multiple directions, interlaced, creating separated spaces. The walls serve as support for the blood and lymph vessels.

This system is known as the multimicrovacuolar collagenous dynamic absorbing system³⁰ and al- lows optimal sliding of the tendon, decreasing friction while facilitating deformation and adapt- ability. Histologic continuity is thus established between the common carpal sheath, the mesoten-

Fig. 6. Different types of flaps that can be raised. (Above, left) Vascularized extensor hallucis longus tendon graft. (Above, right) Vascularized extensor hallucis longus tendon graft with a skin paddle. (Below, left) Vascularized extensor digitorum longus tendon graft with a skin paddle. (Below, right) Vascularized extensor hallucis longus and extensor digitorum longus tendon grafts with a skin paddle.

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flexor digitorum profundus in zone II. In complex cases, where several tendons of the flexor digitorum profundus are damaged, or reconstruction of pulleys is required, the technique would enable the palmaris longus tendon and the tendon of the flexor digitorum sublimis of the fifth finger to be raised. This is the authors’ technique of choice in grade III or IV fingers according to the Boyes classification. The main disadvantage of the technique would be sectioning of the cubital artery proximal to the Guyon canal. At the level of the distal third of the forearm, the radial artery is dominant,³¹for which reason it may be considered relatively safe to sacrifice the cubital artery. To decrease the possibility of complications, the artery could be reconstructed with a venous graft or vascular prosthesis.²¹Microvascularized transfer of this tendon graft with anastomosis to the superficial palmar arch has even been described, along with repair of the cubital artery.³²The good functional results of the technique have led their au- thor to undertake allotransplants of the flexor apparatus on the cubital pedicle in two cases.³³

Several authors have used dorsalis pedis flaps that included the extensor digitorum longus tendons.^{19,34 –36} Technical innovations have even been described to preserve the dorsalis pedis artery by using arterialized venous flaps associated with surgical and chemical delay.³⁷However, this has always been described for reconstructing complex defects of the dorsum of the hand, although none of them describes the vascular anatomy of the zone in detail. The main disadvantage associated with the dorsalis pedis flap is the morbidity it produces in the donor area. A careful surgical technique, the use of full-thickness skin grafts, and the preservation of the 2 cm proximal to the meta- tarsophalangeal joints would limit these donor- site complications.³⁸Provided that the integrity of the deep fibular nerve is respected, the action of the extensor hallucis longus and extensor digitorum longus of the second, third, and fourth toes may be compensated by the function of the extensor hallucis brevis and extensor digitorum bre-

each case. In any case, the lack of sensitivity would not have major repercussions.

The main indication would be cases of complex tendon injury associated with precarious skin cover, or where the injured finger presents severe cicatricial retraction. Another possible indication would be failure of tendon repair techniques in two-stage surgery. The extensor hallucis longus could be used in the reconstruction of flexor tendons, whereas the extensor digitorum longus has been used in reconstruction of the common extensor of the fingers from zone V to zone VIII. It would also be possible to elevate the extensor hallucis longus and the extensor digitorum longus of the second toe for reconstruction of two flexor tendons in the hand.

CONCLUSIONS

Our study demonstrates that the dorsum of the foot presents a constant vascular anatomy that enables different types of compound flaps to be elevated that would adapt to the needs of the injury. The tendons, provided with a sliding unit, are sufficiently long to allow reconstruction of complex tendinous defects.

Ruben Garcia-Pumarino, M.D., Ph.D.

Department of Plastic and Reconstructive Surgery Ramon y Cajal Hospital Ctra. Colmenar km. 9,100 28034 Madrid, Spain rgpsruben@yahoo.es

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