Lower Limb Defects Using the Keystone Technique

Abstract

The applications of the Keystone in the lower limb provide an excellent aesthetic repair for major melanoma defects and especially in the closure of major groin defects for secondary deposits. The oncological defects in this series vary from 14 × 10 cm and up to 22 × 10 cm are readily reconstructed using Keystone principles. Yes, the architectural design is almost rectangular covering the tissues of the anterior thigh covering the quadriceps muscles. The dermatomal mark out extends to the suprapatellar region. In the repair using the anterior thigh in the L1, L2 dermatome, the Keystone island flap mark out extends down the lateral side dividing tensa fascia lata down to the suprapatellar region. The skin epidermal incision transversely across the suprapatellar region then up the medial side of the thigh dividing the deep fascia. This fascial plane must be divided to achieve maximum upward and medial movement. The Keystone consists only of skin and subcutaneous tissue and preserving longtitudenal running neurovascular structures like the saphenous vein. Thus, this island flap repeats the Keystone clinical characteristics including hyperaemia. This ensures flap viablity to close large groin defects to achieve upward and medial closure. This technique in its application of groin reconstruction certainly overcomes the restrictions of loco-regional island flaps to close large inguinal dissection defects, e.g. rectus abdominous and the consequent sequalae of patients in the pre-terminal phase in their lives having major groin defects treated by topical dressings or loco-regional flaps. The Keystone island flap for groin reconstruction is a pre-eminent application for closing major defects on the lower limb, as illustrated.

The morbid restrictions of sartorious transfers and/or skin grafts mean weeks in hospital. This island flap, employing Keystone principles, sticks mainly within the L1 dermatome of the anterior thigh but may encroach on L2, L3 mark outs but the patient’s good clinical response and rapid healing has to be seen to be appreciated while the Keystone characteristics are all illustrated.

This simple technique compares favourably with the antero lateral thigh flap with its pedicle island support. The tensa fasica lata flap again has restrictions and the complex rectus abdominus flap is all avoided.

In the lower limb, the Keystone has pertinent applications as shown in the case series and of course the lady’s skirt line is the indicator for a higher density of melanoma below the knees. To have a skin graft divot is unbecoming and the lady is forced to wear trousers as a means of disguise in any social outing. How often the aesthetic outcome of reconstructive surgery does not paint the full picture of such devastating deformity below the hemline.

Intransit metastesis of Grade II, III melanomas can likewise be treated by Keystones as in cases 54, 55, 56 and 57. The alternatives of excision and graft do not compare favourably of what can be used as a disguise for such intransit metasteses which usually indicate a limited potential lifespan let alone the delays in healing (Marenco et al. Dermatol Surg 35(8):1282–5, 2009).

As we have done with Keystones replacing like with like, the fact we have intact neural supply is a distinct advantage compared with other forms of reconstruction. In the heel reconstructions in cases 63 and 68 melanoma of the heel, the patients retained full topical somatic sensation which is an important aspect to minimise any subsequent trophic ulceration, particularly in the elderly, in this weight bearing site of the foot.

Each of the cases below substantiates the findings, and accompanied by slides with a video PowerPoint supplement in the operative procedure and the outcome achieved.