Closure of an ischial pressure sore using a free gastrocnemius musculocutaneous flap with a long venous pedicle

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  • British JournnlcfP/osrie Surgery(l995),48,50~506 0 1995 The British Association of Plastic Surgeons

    Closure of an ischial pressure sore using a free gastrocnemius musculocutaneous flap with a long venous pedicle

    G. G. Hallock

    Division of Plastic Surgery, The Lehigh Valley Hospital, Allentown, Pennsylvania, USA

    SUMMARY. The recurrent pressure sore in an active paraplegic can become a frustrating challenge as available simple flap options become depleted. The medial gastrocnemius musculocutaneous free flap is an alternative that offers the benefits of muscle from an expendable donor site and still preserves the remainder of the donor limb for future use. Inclusion of an intact greater saphenous vein could augment venous drainage and potentially might be the sole means of oufflow if veins at the recipient site were inadequate.

    This case report describes the closure of a recurrent ischial pressure sore with a free medial gastrocnemius flap, including a greater saphenous vein pedicle.

    Prevention may be the best cure for pressure sores but like most other forms of treatment often proves only to be palliative. Unfortunately, surgery is no panacea as the long-term recidivism rate after operative inter- vention exceeds two-thirds.l Therefore, the precious few simple local flap options available must be jealously guarded in case further pressure sores de- velop.2 When all reasonable alternatives have been depleted, a fillet of the leg could be considered as the final source of tissue to provide wound closure.3l4 This may prove objectionable to the patient, who might instead be willing to accept the risks of a free tissue transfer, as has been done previously using the latissimus dorsi muscle5 or using a partial leg fillet6 while still saving the leg. Although staged transfer of a pedicled soleus muscle flap has been used,7 a better solution if a free flap were seriously considered would be to use only a single donor site from either lower limb* so that as much tissue as possible remains banked for inevitable future requirements. The familiar gastrocnemius musculocutaneous flap as a microsurgical transfer can satisfy these prerequisites and deserves greater emphasis.

    Case report

    A 46-year-old, active, tennis playing, T8 level paraplegic over the course of the past 15 years has had at least 6 operations for a recurrent left ischial pressure sore (Fig. 1). All local possibilities had been exhausted, leaving a scarred buttock with little soft tissue padding in the vicinity of the sore. He sought elimination of the embarrassment of persistent wound drainage and was amenable to having a leg fillet, although his legs helped balance him in his vigorous athletic pursuits. A compromise plan was made to use a medial gastrocnemius musculocutaneous free flap from the right leg, which would otherwise be preserved for future considerations. His left calf had multiple surgical scars following his original injury and was not suitable as a flap donor site.

    After adequate debridement of the sore with the patient in a prone position, the ipsilateral inferior gluteal vessels were isolated and found to be of excellent quality in spite of a

    previous gluteus maximus rotation flap. The sore dimensions were measured and marked on the calf overlying the medial gastrocnemius muscle (Fig. 2). Since the medial sural vessels arise from the popliteal vessels at a level just above the axis of the knee joint,ga10 a flap pedicle with length from this point to the superior edge of the muscle skin paddle was designed to at least equal the distance from the recipient vasculature to the uppermost aspect of the ischial sore (Fig. 3).

    Using a thigh tourniquet, bloodless dissection was begun at the inferior cutaneous margin of the flap to identify the Achilles tendon and medial head of the gastrocnemius muscle. Because a large skin paddle was required, the anterior border was extended to include the greater saphenous vein. The vein was ligated distally and kept intact to exit superiorly from the skin flap (Fig. 3). A few sutures were used to tack the skin paddle to the atrophic muscle to minimise the risk of inadvertent tearing of musculo- cutaneous perforators. The anterior border and the belly of the medial gastrocnemius were then easily separated from the underlying soleus muscle. As the knee joint was approached, more meticulous care was observed along the undersurface of the muscle until the vascular pedicle was identified. This was traced proximally, in this case to an independent source from the popliteal vessels. Division of the muscle origin from the condyle of the femur facilitated this exposure and completed the creation of an island flap (Fig. 3).

    Release of the tourniquet verified adequate flap circulation with normal capillary refill in the skin paddle. A 27 cm long venous pedicle of the greater saphenous vein was elevated up to the upper thigh and included for secondary venous outflow (Fig. 4). The greater saphenous vein was eventually buried in the subcutaneous tissues via an additional incision extending to the left ischium. The sural vessels were first divided, the flap was elevated with its saphenous vein pedicle and inset to cover the sore, and end-to-end microana- stomoses completed to the recipient vessels (Fig. 2). A skin graft was needed to cover the calf donor site. No pressure was allowed on the anastomotic area and routine pre- cautions maintained as for any pressure sore patient.

    Eight days later, the patient somehow obtained an overhead trapeze and while swinging on it disrupted the flap vessels, causing a massive haemorrhage. Emergency tedious repair of the torn flap pedicle necessitated interpositional vein grafts for both artery and vein, which re-established

    504

  • Medial gastrocnemius free flap 505

    Fig. 1 Fig. 2

    Fig. 3

    Fig. 4

    Fig. 5

    Figure l-Recurrent left ischial pressure sore surrounded by atrophic, scarred remnants of multiple flaps from the buttock and upper posterior thigh. Figure 2-A template of the left ischial defect was drawn on the right calf overlying the medial gastrocnemius muscle. The axis of the knee joint closely corresponds to the origin of the medial sural vessels. The greater saphenous vein can be included and left attached in the upper thigh as a secondary venous pedicle following rotation and insetting of the flap. Figure 3-Island medial gastrocnemius musculocutaneous flap still attached (medial sural vessels surrounded by vascular loops) to the popliteal vessels and the greater saphenous vein, which extends above the skin paddle (white and black arrows). Figure 4-Debrided left ischial pressure sore and greater saphenous vein pedicled right medial gastrocnemius musculocutaneous flap, now remaining attached only at the upper posterior thigh. Figure 5-Goad padding ultimately achieved over the left ischium 2 months later allowed the patient to return to a wheelchair.

    blood flow. One month after the initial surgery, the patient was discharged. On his first night home, he fell out of bed dehiscing the superior part of the flap but this eventually healed spontaneously and has remained so, at least for the time being (Fig. 5).

    Discussion

    In spite of intense efforts to educate this patient in the proper treatment and prevention of future pressure

  • 506 British Journal of Plastic Surgery

    sores, considering his history it is highly likely that a recurrence is inevitable, as is true for most post- traumatic parap1egics.l The choice of a medial gastro- cnemius musculocutaneous free flap accomplished at least temporary closure of his ischial sore, while preserving the limb so that a conventional leg or thigh fillet could still be a future option.3,4 The benefits of healthy muscle introduced into a contaminated field and bulk obtained by inclusion of a cutaneous paddle are important to obliterate the void so characteristic of pressure s0res.l As with most free flaps, the gastro- cnemius muscle is well vascularised and tension-free inset with suitable flap design is possible, both qualities sometimes compromised with local flaps or even regional fillet flaps. Of course, an added bonus is that no functioning muscle was sacrificed.

    In spite of our great familiarity with the gastro- cnemius muscles, only rarely has this donor site been used specifically as a free flap9 even though the artery (diameter 2-3 mm) and vein (diameter 2.5-5 mm) are of extremely large calibre. g, l1 A tremendous potential exists for its greater use in treating pressure sore patients where this muscle is always absolutely ex- pendable. The argument that an indisputable and significant donor defect l results from the use of the cutaneous version of the gastrocnemius flap has relevance in the paraplegic only in that the calf becomes more at risk itself for development of a pressure sore.

    Although the cutaneous territory dependent on the gastrocnemius muscle can extend almost to the Achilles tendon insertion,l the exact safe dimensions are unknown. It is well recognised that the greater saphenous vein can also readily be incorporated in such flaps. What exactly is the longest yet safest venous pedicle also is unknown, although the cephalic vein has been used without compromise with a radial forearm flap for scalp coverage and similarly the internal mammary vein with a rectus abdominis flap for facial reconstruction.14 In both cases, the recipient sites were devoid of veins suitable for a venous anastomosis. Even though the inferior gluteal vein in this case was satisfactory for venous anastomosis and outflow, it is possible that a greater saphenous venous pedicled gastrocnemius musculocutaneous flap might alone prove adequate. Some concern might be raised that dissecting out this vein could compromise future local thigh flap options but usuall