A combined use of a free vascularised flap and an external fixator for reconstruction of lower extremity defects in children

Journal of Orthopaedic Surgery, Aug 2007 by Segev, E, Wientroub, S, Kollender, Y, Meller, I, Et al

ABSTRACT

Purpose. To describe a combined use of a free vascularised flap and an external fixator for reconstruction of lower extremity defects in children, and correction of equinus contracture developed after removal of the external fixator using a circular dynamic frame.

Methods. Seven children (4 males) aged 4 to 12 (mean, 8) years were treated with 9 free vascularised flaps for 8 limbs (bilaterally in one patient and for a failed flap in another). Patient pathologies included: 3 soft tissue degloving injuries, one soft tissue and bone avulsion, one severe burn contracture, one resurfacing of soft tissue and bone necrosis, and one osteosarcoma resection defect. Free flap reconstruction was delayed in 6 patients (range, 3 weeks to 4 years). Static external fixators were used to stabilise the free vascularised flaps at the time of reconstruction, with the ankle in a neutral position.

Results. The mean follow-up was 5 (1-10) years. All flaps but one survived; the failed one was immediately reconstructed with a contralateral, latissimus dorsi flap. One anastomosis following a Kirschner-wire injury was successfully revised. Six patients had pin tract infections and were treated with oral antibiotics. Two patients developed equinus contracture 6 and 3 years later, after removal of the external fixator, and were corrected by distraction, using a dynamic Ilizarov frame.

Conclusion. The combined use of a free flap and an external fixator for salvage of lower extremities is useful in children. Late development of equinus contracture can be safely corrected by distraction, without compromising flap viability.

Key words: equinus deformity; fixators, external; Ilizarov technique; surgical flaps

INTRODUCTION

In children, combined use of an external fixator and a free vascularised flap can successfully salvage lower extremities after trauma or cancer ablation.1,2 However, in patients with severely traumatised limbs, bone loss and shortening remains a challenge. There are reports of limb lengthening after compound tibial fractures with bone loss following vascular flap incorporation.3,4 Corticotomy was carried out either above or below the flap for bone transport, in order to bridge the gap. All flaps remained viable, and the tibia was successfully lengthened. During bone distraction following flap reconstruction, incorporation of the vascular anastomosis with the flap in the moving fragment has been recommended, so as to prevent stretching of the anastomosis.5

Moreover, use of the Ilizarov apparatus for correction of joint contractures using a gradual distraction technique for stretching ankles and knee contractures due to congenital or acquired pathologies has produced favourable results.6,7

MATERIALS AND METHODS

Between 1996 and 2005, 7 children (4 male, 3 female) aged 4 to 12 (mean, 8) years underwent reconstruction of lower extremity defects, using a combination of a free vascularised flap and an external fixator. Nine free vascularised flaps were applied in 8 limbs (bilaterally in one patient, and for a failed flap in another). Three patients with soft tissue degloving injuries and bone fracture due to motor vehicle accidents underwent a latissimus dorsi flap reconstruction. Two others underwent an anterolateral thigh fasciocutaneous flap reconstruction (one for soft tissue and bone avulsion due to a lawnmower injury, and another for severe burn contractures of both feet). Another patient underwent a free gracilis flap reconstruction for resurfacing soft tissue and bone necrosis due to surgery and in one other a fibular osseocutaneous flap was reconstructed for a 15-cm intercalary tibial defect due to osteosarcoma resection. The free flap reconstruction was delayed in 6 patients (range, 3 weeks to 4 years; Table). Static external fixators were used to stabilise the free vascularised flaps at the time of reconstruction; the ankle was in a neutral position for 3 to 6 (mean, 4) months.

RESULTS

The mean follow-up was 5 (1-10) years. All but one of the flaps survived. The failure was due to venous thrombosis, not related to the fixation, and was immediately reconstructed with a contralateral latissimus dorsi flap. In another patient, one arterial anastomosis was immediately revised due to misinsertion of a Kirschner wire during external fixator application. Six patients had pin tract infections and were treated with oral antibiotics.

Patients 2 and 6 developed rigid equinus contractures 6 and 2.5 years respectively, after removal of their external fixator. Their ankles gradually contracted to an equinus position, despite continuous use of an orthosis. Patient 2 was treated with distraction using an Ilizarov dynamic frame inserted directly via the free flap spanning the ankle and foot posteriorly, without recourse to soft tissue release or osteotomy. Patient 6 was first treated with Achilles tendon lengthening that failed. Distraction using an Ilizarov dynamic frame inserted distal to the flap was subsequently used, also without soft tissue release or osteotomy. For both patients, the distraction lasted 2 months and was applied at a rate of 1 mm per day, until the foot achieved 10� of overcorrected dorsiflexion. The frames were removed after 3 and 3.5 months respectively and there was no ischaemia to the flap or adjacent soft tissues (Fig.).