18 months old boy with 
Congenital pseudarthrosis 
in the right leg showing non 
union following illizarov treatment

Micovascular Free Fibula transfer done

After two years - showing good hypertrophy

Post traumatic soft tissue and bone loss

Patient walking well without support

Bone grafting is one of the most  frequently  performed  procedure in orthopaedic surgery in a variety of clinical situations. Conventional  bone  grafting  can be used in the vast majority of cases, but their efficacy in treating large, segmental defects is limited.

Advances in microvascular surgery has now made it possible to bridge large bony  defects. With the blood supply preserved , the bone cells in the grafts can survive hostile environment like infection with ease and allow rapid healing.

The major objective of a vascularised bone transfer is the immediate restoration of blood supply so that the  cells in the bone graft can survive. In conventional bone grafting the cells in the bone graft first  have to pick up blood supply, survive and then unite with the bone ends.  When microsurgical transfer of bone is done, the bone cells are already alive and the graft unites with bone ends just as a fracture heals.  That is a greatest advantage of a vascularised bone graft. 
The commonly used donor sites of bone for microsurgical transfer are fibula(smaller of the two bone in the leg) and the bone from the iliac crest( bone around the groin).

Clinical application of microvascular bone grafting

Congenital pseudoarthrosis of tibia - It is a rare disease and one of the most difficult conditions to treat.  The problem lies in the poor knowledge we have about the disease and the severe complications of conventional techniques of reconstruction.  In the past large number of patients have gone amputation of the limb because of complications. 
In this condition  the major bone of the leg is diseased and hence fractures.  Since the fractured ends do not have healthy   bone it cannot unite. The  removal of large segment of diseased bone results in a significant bone gap which is very difficult to bridge by conventional technique like illizarov.
Micro surgery offers a reliable technique of cure, as any length of bone gap can be safely reconstructed.  In out experience involving 8 cases, 5 underwent microsurgical free fibula transfer (fig 1).  All the 5 cases went on to unite at an average time of 10 - 14 weeks. 

Large bone gaps due to accidents - 
Traumatic bone loss usually resulting from high intensity trauma and highly comminutted open fracture.  In such cases the extend to which the soft tissue is lost, devitalised will influence the complexity of the reconstructive plan.  Microsurgery is a boon in reconstructing extensive soft tissue and bony defects.