British Journalof Plastic Surgery (1990), 43,236240 0 1990 The Trustees of British Association of Plastic Surgeons

0007-1226/90/0043-0236/$10.00

The deep inferior epigastric artery local musculocutaneous flap: a method of preserving sensation

G. I. MUGUTI and K. KALANGU

Department of Surgery, Mpilo Central Hospital, Bula wa yo, Zimbabwe

Summary-We present a case in which an island extended inferior epigastric artery musculocutaneous flap, used to resurface an amputation stump, retained sensation. The reasons for this are discussed.

Case report A 36-year-old Zimbabwean woman was admitted to Mpilo Central Hospital with extensive gas gangrene of the left lower limb and lower half of the left anterior abdominal wall as a result of a septic abortion.

The patient survived because of aggressive manage- ment by both the gynaecologists and the general surgeons. In addition to heavy doses of intravenous antibiotics, the patient required an emergency hysterectomy, desloughing of the lower half of the left anterior abdominal wall and disarticulation of the left hip joint. She had a stormy course in the Intensive Care Unit but eventually improved and was transferred back to the ward. The resultant extensive soft tissue defect was resurfaced with a split thickness skin graft after about 4 weeks.

At this stage the patient was referred to G.I.M. as it was envisaged that some form of flap would be needed to provide adequate padding for a left lower limb prosthesis. After adequate preparation the patient was taken to theatre and the contralateral thoraco-umbilical deep inferior epigastric artery island musculocutaneous flap was raised and used to resurface the amputation stump (Fig. 1). Apart from a minor wound infection the patient did very well postoperatively. It was noted in the immediate postoperative period that the patient had sensation in the flap. Initially this was perceived in the area of the donor site but within a week the patient could localise sensation to the flap. A few weeks later our neurosurgical colleague (K.K.) was consulted to verify our observation of sensation in the flap. He confirmed that the patient had all modalities of sensation in the flap and was able to record this by carrying out evoked potentials on her. In the meantime she has been discharged from hospital and will soon be fitted with a prosthesis. Sensation in the flap will certainly ensure long-term flap survival.

Operative technique

A right extended deep inferior epigastric artery

island musculocutaneous flap was outlined along the right thoraco-umbilical axis (Fig. 2). Through appropriate skin incisions the cephalad part of the flap above the subcostal margin was raised as a fasciocutaneous flap. The skin incision was then completed as outlined in Figure 2. A right parame- dian incision was made in the rectus sheath and through this incision the rectus abdominis muscle was mobilised laterally. Just below the subcostal margin the anterior rectus sheath and rectus abdominis muscle were divided transversely, leav- ing only the lateral 1.5 cm of the sheath and muscle intact as a narrow strip. Just above the arcuate line the anterior rectus sheath and muscle were again divided transversely, leaving the lateral 1.5 cm of muscle and sheath intact. The division was carried out taking care not to damage the inferior epigastric pedicle. Throughout the dissection the 1.5 cm strip of rectus sheath and muscle was maintained in between the two points of division of the rectus abdominis muscle. This meant that there was a narrow strip of intact rectus abdominis muscle and sheath linking the upper and lower remnants of both the muscle and the sheath. Figure 3 shows the fully mobilised flap lying on the donor site and the distal remnant of the divided rectus abdominis muscle.

The inferior epigastric pedicle was mobilised by cauterising and dividing its peritoneal and muscular branches. This part of the dissection was carried down only for a distance which would allow the flap to reach its destination without stretching the pedicle. As a result of this dissection several muscular and peritoneal branches were spared and in the process the authors believe that some of the branches of the lowermost intercostal nerves were

236

THE DEEP INFERIOR EPIGASTRIC ARTERY LOCAL MUSCULOCUTANEOUS FLAP 237

Fig. 1 Fig. 2

Fig. 3 Fig. 4

Figure I-The amputation stump resurfaced with the flap. The small island of SSC was excised. Figure 2-Design of extended right deep inferior epigastric artery island musculocutaneous flap. Figure %Fully mobilised DIEA flap lying on the donor site. Distal remnant of the divided rectus abdominis flap held by an artery forceps. Figure 4-DIEA flap sutured in place.

also spared and hence found their way to the flap along the inferior epigastric pedicle.

Following adequate preparation of the recipient site, the flap was sutured in place (Fig. 4). The distal remnant of the rectus abdominis muscle was sutured to the posterior rectus sheath above the arcuate line. It was possible to close the entire donor site defect directly.

Assessment of sensation in the flap

The patient was examined clinically and only the sensory aspect could be considered because the left lower limb was disarticulated. The standard method

of grading sensibility in order to compare both sides was that established by the British Medical Re- search Council, the sensibility being graded from SO to S4 (Nicholson and Seddon, 1957). In our patient, sensation to light touch, pin-prick and temperature was scored as S3 + (return of superfi- cial cutaneous pain and tactile sensibility with disappearance of any previous over-response and some recovery of 2-point discrimination). The vibration sense was normal (S4).

Grading of sensory function is difficult because of its subjective nature and the need to score quality of sensation as well as the perception of the primary sensory stimuli and therefore, in addition to the

238 BRITISH JOURNAL OF PLASTIC SURGERY

clinical examination, we carried out somatosensory evoked potentials (Fig. 5). The only difference we observed was in the voltage required to stimulate the flap, which was 3.6 times more than the other. This was in accordance with our clinical examina- tion.

Discussion

The ultimate achievement in the design of any flap is the preservation or the introduction of sensation. It follows, therefore, that any observation or modification in the dissection of a flap which preserves sensation is an important one. The long- term survival of a flap in areas where it may be exposed to injurious agents (e.g. pressure and heat) depends on its sensibility.

LEFT SIDE

Cz - Erb’s point

-2l.W 11 5ms

CVII - cz

‘A i

Certain flaps have excellent nervous sensibility, e.g. biceps femoris, rectus femoris and tensor fasciae latae musculocutaneous flaps. Others, such as the gastrocnemius and gracilis flaps, vary; the latissimus dorsi and pectoral flaps are relatively lacking in sensation. The rectus abdominis flap is said to be devoid of sensation after being elevated (McGraw and Vasconez, 1980).

To date, all the work on the versatile deep inferior epigastric artery musculocutaneous flap has concen- trated on the great variations in size, shape and design that are possible with this flap. In this paper the authors would like to recommend the possibility of dissecting a sensate deep inferior epigastric artery island musculocutaneous flap. In addition to its other advantages of large size, excellent vascu- larity and the possibility of an abdominoplasty, the

RIGHT SIDE

Cz - Erb’s point

-2Pjj 5ms

SOMATOSENSORY EVOKED POTENTIAL: Left side : Electrode placed on the flap Right side : Electrode placed on the posterior aspect of the thigh just below the buttock Stimulation intensity : 55~ on the left side and 15~ on the right

Each trace is the average of 512 clicks Latency on the left side : 13.8 (mean) Latency on the right side : 13.7 (mean)

Fig. 5

Figure %Somatosensory evoked potential. Left side: Electrode placed on the flap. Right side: electrode placed on the posterior aspect of the thigh just below the buttock. Srimulation intensity: 55V on the left side and 15V on the right; each trace is the average of 512 clicks. Lufency: left side 13.8 (mean, right side 13.7 (mean).

THE DEEP INFERIOR EPIGASTRIC ARTERY LOCAL MUSCULOCUTANEOUS FLAP 239

introduction of sensation in this flap will no doubt complete the dream of the reconstructive surgeon’s ideal flap. In our patient the provision of a sensate flap should ensure not only adequate padding for the prosthesis but also long-term survival of the flap.

A detailed understanding of the anatomy of the lowermost six intercostal nerves (i.e. 7-12) is essential to appreciate how it was possible to preserve sensation in our patient’s flap. The upper six intercostal nerves run horizontally on the chest wall whereas the last six run obliquely on the anterior abdominal wall (Fig. 6) (Gray’s Anatomy, 1973). At the lateral edge of the rectus abdominis muscle the intercostal nerves pierce the posterior rectus sheath to get into the muscle, and after supplying it they pass on to supply the anterior rectus sheath and the overlying skin (Gray’s Anatomy, 1973). Another important anatomical observation is that communicating branches link the intercostal nerves to one another in the posterior parts of the intercostal spaces and, in addition, the lower five communicate freely as they traverse the abdominal wall (Davies et al., 1932). The anterior primary ramus of the 12th intercostal nerve is larger than the others and often gives off a communicating branch to the first lumbar nerve (i.e. ilio-hypogastric and ilio-inguinal nerves) (Gray’s Anatomy, 1973).

If it is appreciated that the intercostal nerves and the first lumbar nerve are interconnected it becomes easy to understand why, if a few branches of the lowermost intercostal nerves or the first lumbar nerve are spared, it is possible to preserve sensation in the flap. We believe that this has been achieved in our case by leaving a distal remnant of the rectus abdominis muscle and not disturbing its lateral border, sparing a few small neurovascular bundles between the inferior epigastric pedicle and the rectus abdominis muscle and leaving a narrow strip of rectus abdominis muscle, approximately 1.5 cm wide, completely undivided. It was observed by Terzis and Hamilton (1983) that the rectus abdom- inis muscle has a segmental neurovascular supply. One or more of these pedicles can be preserved along the lateral border of the muscle to provide a functional unit. It appears that certain flaps have a significant portion of sensory innervation traversing the “motor” nerve (McGraw and Vasconez, 1980). In the classical dissection the inferior epigastric pedicle is dissected down to its origin from the external iliac vessels (Taylor et al., 1984). In our case the pedicle was mobilised only for a distance required for the flap to reach its destination

comfortably, thereby sparing a few neurovascular connections between the muscle and the pedicle.

In this report the authors present an aspect of the versatile deep inferior epigastric artery musculocu- taneous flap that has not been investigated in the past. Although more clinical and experimental work needs to be done, a modification of the dissection of the deep inferior epigastric artery musculocutaneous flap has succeeded in preserving sensation in the flap. This is a distinct advantage to the patient as the flap was designed to provide adequate long-term padding for the prosthesis.

Fig. 6

Figure 6-(a) Intercostalis internus; (b) transversus abdominis; (c) obliquus externus; (d) left rectus abdominis without its superficial layers; (e) pyramidalis: (f) obliquus internus; (g) obliquus externus; (h) right rectus abdominis; (7) 9th intercostal nerve and lateral cutaneous branch; (8) 10th intercostal nerves and their lateral cutaneous branches; (9) abdominal branch of the 12th intercostal nerve; (10) abdominal branch of the 1st lumbar nerve; (11) lateral femoral cutaneous nerve; (I 2) medial femoral cutaneous nerve; (13) ilio-inguinal nerve; (14) ilio- hypogastric nerve; (15) anterior cutaneous branch of the 12th intercostal nerve. (From Instituzioni Di Anatomia Dell’uomo: Giulio Chiarugi and Luigi Bucciante. 10th Edition, 1973. Casa Editrice Dr Francesco Vallardi Societa Editrice Libraria Milano.)

240 BRITISH JOURNAL OF PLASTIC SURGERY

Acknowledgements deep inferior epigastric (inferior recurs abdominis) flap. Bri!ish Journalof Plastic Sur~erv. 37. 330.

We are grateful to Mr M. J. Oliver for referring the patient to us Terzis, J. and Hamilton, S-(1%3). Transfer of the rectus and to Mrs N. Sibanda for typing the manuscript. abdominis muscle for facial reconstruction. Presented at the

7th International Meeting of Reconstructive Microsurgery, New York.

References

Davies, F.. Gladstone, R. J. and Stibbe, E. P. (1932). Anatomy of The Authors intercostal nerves. Journalof Anatomy, 66, 323.

Gray’sAnatomy(l973). 35thEdition. Warwick, R. and Williams, G. I. Mu@, FRCSEd, Head of Department of Surgery, Mpilo

P. L. (Eds). Neurology, pp. 1047-1050. Edinburgh: Longman. Central Hospital, P.O. Box 2096, Bulawayo, Zimbabwe.

McGraw, J. B. and Vasconez, L. 0. (1980). Musculocutaneous K. Kalangu, MD, Consultant Neurosurgeon, Mpilo Central

flaps: principles. Clinics in Plastic Surgery, 7,9. Hospital, Bulawayo.

Nicholson, 0. R. and Seddon, H. J. (1957). Nerve repair in civil oractice. Results of treatment of median and ulnar nerve

Requests for reprints to Mr Muguti.

lesions. British Medical Journal, 2, 1065. Paper received 21 March 1989. Taylor, G. I., Corlett, R. J. and Boyd, J. B. (1984). The versatile Accepted 19 June 1989.