Discussion

The use of the combined graft procedure is based on observations of the intrinsic properties of the allograft and of the vascularized fibula graft. By combining the two, the advantages of each technique can be fused into a single procedure. In fact there are no limits to the size of the allograft, which allows for stable bone fixation. However, progressive resorption, the long period of time necessary for fusion and the high rate of nonunion8,3,4 are among the limits when only this procedure is used. The addition of vascularized fibula graft can eliminate these disadvantages. The live bone heals quickly, hypertrophy occurs progressively and maintains the allograft when it is weakened by biological phenomena (Fig. 10C.3). In addiction the VFG seems to be able to induce osteointegration of the allograft and facilitates bone union at the level of osteotomy at a significantly shorter period of time. These clinical observations require further experimental study to better understand the reasons for these phenomena and to confirm the benefits.

This technique has both optional and absolute indications. Intercalary resection is an optional indication. When combined graft is carried out recovery time and the incidence of complication are reduced. Absolute indications are defined as those which involve metaepiphyseal resections, growth plate salvaging and arthrodesis of the ankle.

Metadiaphyseal tumors of the knee joint are commonly treated by intra-articu-lar resection even when the articular surface and the subchondral bone are not involved in the tumoral processes. In these cases, an intraepiphyseal resection can be performed. A thin fragment of articular surface should be preserved, and intercalary reconstruction is feasible with the combined allograft procedure. Minimal fixation is necessary at the epiphyseal osteotomy, while rigid osteosynthesis is required at the diaphyseal level. The union at the junction sites is achieved into the first 3-4 months. Initial stability of the implant is provided by the allograft, and later stability is supplied by the hypertrophied fibula.

Fig. 10C.3. Reconstruction of the tibia. Hypertrophy of the VFG progressively occurs while the allograft is resorpted.

In growing patients, if the metadiaphyseal tumor does not involve the growth plate and resection can be performed preserving the epiphysis, combined allograft reconstruction with minimal fixation of the graft (Kirschner wires or screws) can avoid epiphysiodesis (Fig. 10C.4). Our experience has shown that, in spite of the relatively less rigid fixation, the vascularized fibula provides the necessary biological activity to enhance bone union and a rapid recovery of the patient.

When distal tibial resection is performed, arthrodesis reconstruction with combined allograft procedure, is feasible. With minimal screw fixation of the grafts ar-throdesis can be achieved with the talus preserving the subtalar joints (Fig. 10C.5). In this situation, especially in children, subtalar joint function permits a flexion-extension range of up to 60°.

In conclusion the procedure with hybrid combined bone graft (VFG+allograft) is an innovative technique. The advantages of mechanical resistance by a massive allograft are associated with the biological properties of the vascularized bone graft. With this technique an early recovery of the patient and a progressively increasing strength of the reconstructed bone are obtained. Combined bone grafts represent an elective reconstructive option in such particular situations as juxta articular resections, juxta epiphyseal resections in growing patients and resections of distal tibia requiring ankle arthrodesis.

Fig. 10C.5. Distal tibia reconstruction. Arthrodesis performed with the talus. The minimal screws fixation of the grafts preserves the subtalar joint.

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