Invited Discussion

The case report by Nakamasu and colleagues presents an extremely complex reconstructive problem involving the proximal femur, which was elegantly resolved with the use of a double-barrel fibula microvascular transfer. This graft subsequently proved able to support a complex corrective osteotomy. Several important features of segmental long bony reconstruction using vascularized fibula transfers are highlighted in this article.

By virtue of its length, biomechanical stability, limited donor-site morbitity, and predictable vascular pedicle, the fibula has become well-accepted as an excellent donor bone for microvascular transfers. Due, in part, to its relative similarity in size and ease of internal stabilization, it has proven very effective for tibial, forearm, and even humeral reconstructions. However, when faced with a segmental bony defect bordered by a wide metaphyseal region at one end and a narrower cortical diaphyseal zone at the other, the reconstructive procedure becomes decidedly more complicated. The disparity of the cross-sectional area of the fibula shaft with the wide femoral neck and medullary canal of the femoral diaphysis will subject the intercalary graft to substantial mechanical stresses; thus, it was not surprising to learn that a stress fracture was observed in this report. It became evident to us, as well as others, that a more predictable outcome would be realized using adjuvant stable internal fixation. This is nowhere more evident than in the region of the proximal femur.

The second significant feature of this article lies in the authors' use of a “double-barrel” fibula construct. The beneficial biomechanical effect of this in the femur was also recognized by us some time ago. This will substantially increase the cross-sectional area of the transferred bone graft. One must bear in mind that, when dividing the fibula into two struts, the “proximal” segment will have a dual vascular supply from both periosteal and endosteal circulation, while the “distal” strut will involve only the periosteal circulation.

The third, and perhaps most interesting, aspect of this case, is the successful response of the revascularized fibula to the corrective valgus osteotomy. The two issues that posed a concern to us when we considered similar procedures included (1) whether the hypertrophied fibula now consisting primarily of dense cortical bone would have the same healing response as a normal fibula; and (2) whether the bone remained dependent on its vascular pedicle or had creeping substitution occurring. We learned, as did the authors, that these concerns proved less worrisome.

In summary, this report would offer support for stabilizing complex microvascular bony transfers with a rigid internal fixation, creating a “double-barrel” fibula when faced with the potential of major mechanical stresses on the graft; and emphasizing that bony reconstructive procedures can be performed through a hypertrophied vascularized bony transfer.

SUGGESTED READINGS

• 1 Jones N F, Swartz W M, Mears D C, Jupiter J B, Grossman A. The “double barrel” free vascularized fibular bone graft.  Plast Reconstr Surg. 1988;  81 378-385
• 2 Jupiter J B, Palumbo M A, Nunley J A, Aulicino P L, Herzenberg J E. Secondary reconstruction after vascularized fibular transfer.  J Bone Joint Surg Am. 1993;  75 1442-1450
• 3 Jupiter J B, Bour C J, May Jr J W. The reconstruction of defects in the femoral shaft with vascularized transfers of fibular bone.  J Bone Joint Surg Am. 1987;  69 365-374