The External Oblique Myocutaneous Flap for Extended Hemipelvectomy Reconstruction

B. CHANDRASEKHAR, MD,* GERALD M. SLOAN, MD,t AND J. DAVID BEATTY, MD*

This article documents the first case report of an extended hemipelvectomy defect closure using an ipsilateral external oblique myocutaneous flap. When a hemipelvectomy usually is performed for soft tissue tumor ablation, an anterior or posterior flap can be preserved for immediate coverage of vital structures. When these flaps are also resected to obtain clear tumor margins, closure becomes difficult. In our patient, although the rectus myocutaneous flap was a next logical choice, prior surgical scars precluded its use. The external oblique flap was successfully rotated and solved a difficult problem. This flap should be considered when the rectus abdominis myocutaneous flap is unavailable for extended hemipelvectomy closures.

Cancer 6 2: 1022- 1025, 1 988.

HE EXTERNAL OBLIQUE iS a broad, flat muscle Orig- T inating from the lower eight ribs. The fibers run downward and forward to insert inferiorly into the iliac crest and into the linea alba in the midline. The muscle is anteriorly replaced by an aponeurosis, which forms part of the anterior rectus sheath. The aponeurosis infe- riorly curves on itself to form the inguinal ligament.

The blood and nerve supply is segmental. Muscular branches pierce the internal oblique and supply the ex- ternal oblique and overlying skin by way of perforators (Fig. 1). There is additional cutaneous blood supply by way of the lateral cutaneous branches of the intercostals.

The flaps can be raised from the midline taking the entire anterior rectus sheath (Figs. 1 and 2). The rectus muscle is left intact. A plane between the external and internal oblique is laterally reached and elevation is car- ried out at this level. Small muscular branches are di- vided as they are encountered. Dissection is more cau- tiously performed past the midclavicular line. Larger perforating vessels are here encountered and carefully preserved. The inguinal ligament is detached at the

From the *Department of Plastic and Reconstructive Surgery, City of Hope National Medical Center, Duarte, California, the ?Depart- ment of Plastic Surgery, Children’s Hospital of Los Angeles, Los An- geles, California; and the $Department of Surgical Oncology, City of Hope National Medical Center, Duarte, California.

The authors thank Mr. Randall Howarth for his illustrations and Ms. Margaret Brown for secretarial support.

Address for reprints: B. Chandrasekhar, MD, City of Hope National Medical Center, 1500 E. Duarte Rd., Duarte, CA 9 10 10.

Accepted for publication March 2, 1988.

pubic tubercle if it is still intact. A backcut in the skin paddle is usually necessary to rotate the flap. The origin of the upper muscular fibers are then detached from the ribs. The flap can then be transposed to cover the defect in the pelvis (Fig. 3). The resulting defect over the rectus muscle is skin grafted. Notice that the skin paddle over the rectus fascia is a “random” extension of the true

FIG. 1. Diagrammatic representation of the external oblique vascu- lar supply and plane of flap elevation.

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No. 5 EXTERNAL OBLIQUE FLAP - Chandrasekhar et al. 1023

FIG. 2. Surface marking of the external oblique myocutaneous flap.

myocutaneous part. Incorporating the anterior rectus sheath preserves the delicate vascular plexus and its communications to the large muscular perforators later- ally.

Case Report A 36-year-old Hispanic woman was evaluated for an enlarg-

ing mass on her left thigh (Fig. 4). The mass was first noticed 3 months before the evaluation. A clinical examination revealed

Fbp Ruta)ed. In& Place.

FIG. 3. Completed flap rotation and skin graft over the exposed rectus muscle.

a huge tumor occupying the anterior upper third of the thigh and extending posteriorly into the gluteal musculature. The femoral vessels were encased in tumor. A transverse scar across the right lower abdomen was noticed from a previous appen- dectomy. A biopsy confirmed the diagnosis of fibrosarcoma. A computerized axial tomography (CAT) scan showed no intra- pelvic tumor extension. Lung tomograms were negative.

FIG. 4. Large fibrosarcoma extending posteriorly from upper medial thigh to the glutei. Upper mark is the line of proposed resection.

1024 CANCER September I 1988 VOl. 62

An extended hemipelvectomy was needed to achieve tumor-free margins (Fig. 4). All tissue from just above the inguinal ligament and the gluteus musculature was resected. The right rectus was not available for rotation because of pre- vious abdominal surgery in that area. The external oblique flap with the skin paddle extending to the midline was elevated and rotated into the defect for closure (Fig. 5). The exposed rectus muscle was skin grafted (Fig. 6). The postoperative course was uneventful. The patient's wound remained healed for 8 months when she died from pulmonary metastatic disease.

FIG. 5. Defect after extended hemipel- vectomy; skin paddle marked over the ex- ternal oblique.

Discussion

Wound coverage after hemipelvectomy continues to be associated with a significant degree of morbidity. In the literature there are reports of a 25% to 60% incidence of complications resulting from inadequate wound clo- sure. ' Musculocutaneous flaps are generally more reli- able than random pattern skin flaps and are now more frequently used. Continuous and discontinuous anterior thigh myocutaneous flaps based on the superficial femo-

FIG. 6. Final closure and skin graft over the rectus muscle.

No. 5 EXTERNAL OBLIQUE FLAP - Chandrasekhar et al. 1025

ral vessels have been described to close hemipelvectomy defect^.^-^ However, if the femoral vessels are sacrificed because of tumor involvement, they cannot be used. The rectus abdominis myocutaneous flap with a fascio- cutaneous extension based on the deep inferior epigas- tric vessels is reliable5-* and seems a logical next choice. It is not necessary to delay this flap as de~cribed.~ Liga- tion of the deep inferior epigastric vessels or muscle transection from previous surgery, as seen in our pa- tient, further limits these options. We believe that the external oblique myocutaneous flap is indicated in such a situation. In summary, a number of reliable flaps are available for extended hemipelvectomy reconstruction. The external oblique flap is a useful addition when other flaps are unavailable.

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