Brirish JournalofPIastic Surgery (1988), 41,221-227 0 1988 The Trustees of British Association of Plastic Surgeons

The distally based island posterior interosseous flap

H. COSTA and D. S. SOUTAR

West of Scotland Regional Plastic and Oral Surgery Unit, Canniesburn Hospital, Glasgow

Summary-The posterior interosseous vessels give a significant contribution to the fascial plexus which supplies the skin of the forearm. This vascular arrangement forms the basis for an island fasciocutaneous flap which can be based either proximally or distally. Twenty-two dissection studies have been carried out to demonstrate the vascular anatomy of the posterior interosseous arteryand its contribution to the fascial plexus. Based on this information, the design and usage of an island fasciocutaneous flap is described.

A distally based island fasciocutaneous flap appears to have a reliable vascular basis and its role in covering soft tissue defects in the hand is illustrated in three clinical cases.

Soft tissue reconstruction of the hand remains a challenge for the plastic and reconstructive surgeon. The choice lies between using a distant flap, pedicled to the trunk, or a free flap using microvas- cular techniques, or a local flap. The advent of the radial and ulnar forearm flaps has significantly increased the safety and reliability of local flaps (Song et al., 1982; Biemer and Stock, 1983; Soutar and Tanner, 1984; Foucher et al., 1984; Lovie et af., 1984; Lin et al., 1984) but involves sacrificing a major artery to the hand.

The forearm skin is supplied by perforating subcutaneous and musculocutaneous arteries which originate from the radial, ulnar, anterior and posterior interosseous arteries (Lamberty and Cor- mack, 1982). The posterior interosseous artery supplies multiple small vessels to this fascial plexus (Penteado et al., 1986).

To investigate the value and contribution of the posterior interosseous artery to the fascial plexus, a series of cadaveric injections was performed. These injection studies have shown three main vascular patterns which can form the basis of an island fasciocutaneous flap based on the posterior inter- osseous artery, either proximally or distally.

Material and methods

Twenty-two preserved cadaveric limbs were in- jected with latex (Tompsett, 1956) and dissected to demonstrate the course of the posterior interosseous artery and its vascular branches. The vessel lay in the intermuscular septum between extensor carpi ulnaris and extensor digiti minimi. The artery

entered the septum between supinator and abductor pollicis longus and this point of entry was measured from the lateral epicondyle proximally and the ulnar styloid distally. Septocutaneous branches from the artery were dissected and preserved and their origin again marked by measuring the distance from the lateral epicondyle and ulnar styloid. The termination of the artery was dissected and its anastomoses with the anterior interosseous artery and the dorsal carpal arch were identified.

In a further four fresh cadavers the posterior interosseous artery was cannulated. The whole skin of the forearm was raised in the sub-fascial plane via circumferential incisions at the level of the interepicondylar line and at the wrist, and a vertical incision in the middle of the volar surface of the forearm. This large fasciocutaneous unit was left attached only by the fascial septum between extensor carpi ulnaris and extensor digiti minimi. In this septum lay the posterior interosseous artery and its septocutaneous branches. All the muscular branches from the artery were coagulated using bipolar diathermy. Methylene blue was injected into the cannula and the extent of skin colouration was noted.

Results

The posterior interosseous artery was located in all the 22 cadaveric forearm dissections in the septum between the extensor carpi ulnaris and extensor digiti minimi muscles and its origin from the common interosseous artery was also confirmed. After passing between the chorda obliqua and the

221

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interosseous membrane, the artery enters the intermuscular septum from underneath the supi- nator at a distance of between 7.5 and 9.5 cm from the lateral epicondyle of the humerus and between 12.3 and 16 cm from the ulnar styloid. At this level the interosseous recurrent artery originates and runs proximally and, in 9 out of 22 dissections, a septocutaneous perforator was identified as a distinct branch coming from the interosseous recurrent artery distal to its origin.

The main trunk of the posterior interosseous artery passes distally in the intermuscular septum and in all of the 22 cadaveric forearm dissections the artery was found to run distally as far as the wrist, lateral to the ulnar head. Here, underneath the extensor tendons, the anastomosis between the posterior interosseous and anterior interosseous arteries was a constant finding. The artery gives off

Lateral Supinator

fasciocutaneous perforators along its length through the above mentioned septum. Three distinct pat- terns of these septocutaneous vessels have been identified (Fig. 1) :

In Pattern I the septocutaneous branches are distributed in two sub-groups, one proximal and the other distal, each containing three or four vessels (6 cases).

Pattern II comprises multiple small branches arising at 1-2 cm intervals along the total length of the posterior interosseous artery (13 cases).

Pattern III shows a large proximal perforator in the proximal group sharing the same origin as the interosseous recurrent artery. This perforator has a larger diameter than the remaining septocutaneous vessels and fans out into several branches (3 cases).

All the septocutaneous vessels anastomose in the superficial layer of the deep fascia to form rich

PAmERN

PIA

Lateral Supinator

. P

Ulnar Head

Lateral

Ulnar Head Ill

(3122 cases)

i 9.2 Lb.2 .I *a 9.2 7.1 7.8 3.0

I I 1 1 I I I

Fig. 1

Figure l-The three patterns of septocutaneous vessels identified in the anatomical dissections. IRA-interosseous recurrent artery. PIA-posterior interosseous artery.

THE DISTALLY BASED ISLAND POSTERIOR INTEROSSEOUS FLAP 223

vascular arcades with longitudinal anastomoses. The largest septocutaneous perforator is found proximally and is most commonly the first vessel identified distal to the supinator. In the deep posterior forearm, the posterior interosseous artery is only 1.5 mm in external diameter (range 1.2- 2.1 mm), but sometimes the artery becomes smaller in the lower third of the forearm, reaching 1.2 mm in diameter. The anastomotic branch has a diameter of 0.9 mm (range 0.9-1.2 mm). We were always able to identify two venae comitantes accompany- ing the artery in the fascial septum.

The cadaveric methylene blue injections show staining of the posterior skin of the forearm which extends from the wrist to 4 cm below the interepi- condylar line. The most proximal posterior skin of the forearm near the elbow remains unstained.

The cadaveric injection studies show that the posterior interosseous vessels can readily be found in a constant position lying in the intermuscular septum between extensor carpi ulnaris and extensor digiti minimi. It gives abundant branches which pass into the fascial plexus and supply an area of skin on the posterior aspect of the forearm. An island flap can be raised based proximally and the arc of rotation allows the skin to be used for soft tissue cover around the elbow. A distally based island flap can similarly be raised and will easily reach the dorsum of the hand to the level of the metacarpophalangeal joints and the first web-space of the thumb. This flap survives on a retrograde arterial flow from the dorsal carpal arch, via the anastomosis between the posterior interosseous and the anterior interosseous arteries. This anastomosis was a constant finding in all the cadaveric forearm dissections. Based on these anatomical findings, three clinical cases are described, using this island flap pedicled distally.

Operative technique The surface marking of the posterior interosseous artery lies between the lateral epicondyle and the ulnar head, with the forearm in full pronation. A point 9 cm (range 7.5-9.5) distal to the lateral epicondyle marks the centre of the fasciocutaneous island distally based flap to be raised (Figs 2C and 4B).

The flap is outlined and the distal incision extended to the level of the deep fascia. The septum between extensor carpi ulnaris and the extensor digiti minimi is identified and preserved. The fascia is incised on each side of the septum and the posterior interosseous artery identified. Dissection

proceeds from distal to proximal up to the distal border of the supinator. At this level the posterior interosseous nerve is identified and preserved where it lies on the lateral side of the artery. The origin of the interosseous recurrent artery is identified and a portion of this artery can be included in cases where a septocutaneous perforator is present. The outline of the skin paddle is completed by incising through the deep fascia to raise the fasciocutaneous flap (Figs 2D and 4D).

Clinical case reports

Case 1 A 7-year-old boy presented with a post-bum contracture to the flexor aspect of the right forearm and wrist. There was restriction of movement of both the wrist and thumb. On release of the scarring a sizeable defect was created. This was repaired using a distally based posterior interosseous island flap and all wounds closed directly (Fig. 2).

Case 2 An 84-year-old man presented with an extensive squa- mous cell carcinoma on the dorsum of the hand. Excision included the paratenon and fascia covering the extensor tendons. The defect was reconstructed using a distally based posterior interosseous artery island flap. There was evidence of oedema and venous congestion postopera- tively, but this gradually subsided and the Rap healed uneventfully (Fig. 3).

Case 3 An g-year-old boy presented with a severe post-bum contracture of his right hand, involving the flexor aspect of all the fingers as well as the first web. The fingers were released and thick split thickness skin grafts were applied. K-wires were inserted through the distal and proximal interphalangealjoints tomaintain extension. Three weeks later, the first web contracture was extensively released and a distally based posterior interosseous island flap was used for reconstruction. The donor area was closed directly and the flap healed uneventfully (Fig. 4).

Discussion

Fasciocutaneous flaps in the forearm have proved an effective and reliable method of reconstructing soft tissue defects of the hand (Lamberty and Cormack, 1982). The most popular and widely used is the radial forearm flap, either as a free flap or as a distally based island flap. This versatile flap has been described to provide skin cover (Foucher et al., 1984; Soutar and Tanner, 1984), vascularised bone for thumb reconstruction (Biemer and Stock,

BRITISH JOURNAL OF PLASTIC SURGERY

Fig. 2

Figure 2-Case 1. (A) Post-bum contracture to the flexor aspect of the right forearm and wrist. (B) The defect after scar release. (C)A line is drawn between the lateral epicondyle and the ulnar head with the forearm in full pronation. The skin paddle is marked on this line, see text. (D) The flap is raised based on the septum between extensor carpi ulnaris and extensor digiti minimi. (E and F) The flap is transposed via a subcutaneous tunnel. (G and H) Postoperative appearance at 6 weeks.

THE DISTALLY BASED ISLAND POSTERIOR INTEROSSEOUS FLAP 225

c Fig. 3

Figure 3-Case 2. (A) An infiltrating squamous cell carcinoma involving the dorsum of the right hand. (B) A distally based posterior interosseous island flap has been transposed and all wounds closed directly. (C and D) Appearance at one month after operation. The thin skin adequately replaces the tissue loss and gives a good contour result.

1983), and vascularised tendons (Reid and Moss, 1983). Its major disadvantage lies in the cosmetic deformity that results, particularly when skin is removed, and from disruption of the radial artery (Kamienski and Barnes, 1976 ; Fenton and Roberts, 1985; Timmons et al., 1986). The cosmetic deform- ity can be minimised by using a purely fascial flap so that the forearm wound can be closed directly. Similarly the ulnar artery forearm flap can be used as a distally based pedicle flap, although this has not gained such widespread popularity as the radial forearm flap. The major problem with these techniques is that they require disruption of a major arterial supply to the hand. Although problems following division of the radial artery are rare, cases have been described (Jones and O’Brien, 1985).

The posterior interosseous fasciocutaneous flap has been described by Penteado et al. (1986). These authors undertook a similar anatomical study to ours with 70 cadaveric dissections. In that study they found, in 5 out of 70 dissections, either the disappearance of the posterior interosseous artery in the middle third of the forearm (4 cases) or absence altogether of anastomosis at the wrist (1

case). In our study, the posterior interosseous artery was always located in the fascial septum between the extensor carpi ulnaris and extensor digiti minimi until it reached the level of the ulnar head, and its anastomosis to the anterior interosseous artery was constant. Care must be taken to preserve the deep branches of the radial nerve and its branches. Both studies agree that the motor branch to extensor carpi ulnaris crosses superficial to the interosseous recurrent artery when it arises proximally or the posterior interosseous artery when it arises distally to the supinator. When the motor nerve branch to the extensor carpi ulnaris is found to cross the posterior interosseous artery, the artery must be ligated distal to the supinator, deep to this motor nerve branch. Whatever the pattern of vascularis- ation, however, perforators were always found just distal to this motor branch so that a retrograde flap can safely be raised with preservation of this nerve branch.

The posterior interosseous artery appears to be constant in position and provides a reliable blood supply to the skin of the posterior aspect of the forearm. A moderate-sized flap can be raised to

226 BRITISH JOURNAL OF PLASTIC SURGERY

Fig. 4

Figure 4-Case 3. (A) Severe post-bum contracture involving flexor aspect of all the fingers and lirst web. (B) The flap is outlined. (C) The contractures have been released and skin grafts applied to the flexor aspect of the fingers. (D, E and F) A distally based island flap has been raised and via a subcutaneous tunnel easily reaches the first web. (G and H) Postoperative appearances at 3 weeks. The pliable and soft skin allows good mobility of the thumb.

THE DISTALLY BASED ISLAND POSTERIOR INTEROSSEOUS FLAP 227

allow the donor defect to be closed primarily. A distally based flap can be transposed to cover defects on the dorsum of the hand, first web-space and the region of the wrist. The main advantage of this technique is that it preserves the major arterial supply to the hand intact. The distally based posterior interosseous island flap is a useful addition to reconstructive hand surgery and is most effective when dealing with the small defect, particularly those in the proximity of the base of the thumb.

Acknowledgements

The authors would like to thank the Anatomy Department of Glasgow University, particularly Dr J. Shaw-Dunnforproviding the anatomical specimens used in this study. Our sincere thanks to Mrs Jean Leiper in the preparation and typing of this manuscript.

References

Biemer, E. and Stock, W. (1983). Total thumb reconstruction: a one-stage reconstruction using an osteocutaneous forearm flap. British Journalof Plastic Surgery, 34,52.

Fenton. 0. M. and Roberts. J. O-11985). Imnroving the donor site df the radial forearm flap. British JournalofPlak Surgery, 38,504.

Foucker, G., van Gene&ten, F., Merle, N. and Michon, J. (1984). A compound radial artery forearm flap in hand surgery: an original modification of the Chinese forearm flap. British Journal of Plastic Surgery, 37, 139.

Jones, B. M. and O’Brien, C. J. (1985). Acute ischaemia of the hand resulting from elevation of a radial forearm flap. British Journal of Plastic Surgery, 30, 396.

Kamienski, W. and Barnes, W. (1976). Critique of the Allen Test for continuity of the palmar arch assessed by Doppler ultrasound. Surgery, Gynecology and Obstetrics, 142, 861,

Lamberty, B. G. H. and Cormack, G. C. (1982). The forearm angiotomes. British Joumalof Plastic Surgery, 35,420.

Lii, S-D., Lai, C-S. and Ckiu, C-C. (1984). Venous drainage in the reverse forearm flap. Plastic and Reconstructive Surgery, 74,508.

Lotie, M. J., Duncan, G. M. and Glasson, D. W. (1984). The ulnar artery forearm free flap. British Journalof Plastic Surgery, 37,486.

Penteado, C. V., Masquelet, A. C. and Ckevrel, J. P. (1986). The anatomic basis of the fasciocutaneous flap OF the posterior interosseous artery. Surgicaland Radiologic Anatomy, 8,209.

Reid, C. D. and Moss, A. L. H. (1983). One-stage flap repair with vascularised tendon grafts in a dorsal hand injury using the “Chinese” forearm flap. British Journaiof Plastic Surgery, 36, 473.

Song, R., Gao, Y., Song, Y. and Yu, Y. (1982). The forearm flap. Plastic and Reconstructive Surgery, 70,343.

Soutar, D. S. and Tanner, N. S. B. (1984). The radial forearm flap in the management of soft tissue injuries of the hand. British Journalof Plastic Surgery, 37, 18.

Thmoas, M. J., MZiswtten, F. E. M., Poole, M. 1). and Davies, D. M. (1986). Complications of radial forearm flap donor sites. British Joumalfo Plastic Surgery, 39, 176.

Tompsett, D. H. (1956). Anatomical Techniques. Edinburgh: E. and S. Livingstone.

The Authors

Horatio Costa, MD, British Council Research Fellow in Plastic Surgery.

David S. Soutar, CkM, FRCSEd, Consultant Plastic Surgeon.

West of Scotland Regional Plastic and Oral Surgery Unit, Canniesburn Hospital, Bearsden, Glasgow G61 I QL.

Requests for reprints to Mr D. S. Soutar at the above address.

Paper received 21 April 1987. Accepted 9 September 1987 after revision.