The multifocal procedure, in which two osteotomies are performed, is indicated in the presence of large bone defects, extreme shortening, shortening combined with metaphyseal deformity where lengthening takes place in more than one site, and fractures with soft tissue defects and exposed bone. The application technique of the external device is quite similar to that for bone transport, with the only difference being that in this procedure two compression-distraction units are used simultaneously.
In the case of extreme shortening, with no instability, no bony defect, and no angular deformity that may require realignment, the bifocal procedure is performed with the application of an external device – e.g. a monolateral frame such as the Limb Reconstruction System (LRS) by Orthofix – where the proximal and distal screw-clusters must be positioned within the metaphyseal regions so that both the two osteotomies are within the metaphyseal bone. The alignment of the rail should be along the limb’s mechanical axis (which is the line drawn from the center of the femoral head to the middle of the ankle joint). The middle clamp should be positioned in the middle of the intermediate segment, and two compression-distraction units should be used.
In the presence of shortening associated with metaphyseal deformity, bone realignment is achieved at the osteotomy site at the level of the deformity. Some lengthening may be necessary in order to achieve progressive, controlled correction of deformity. Further lengthening, when required, may be aimed through an osteotomy in the healthy metaphysis. When this procedure is performed in the tibia, about 1cm of the middle third of the fibula must be resected.
Multifocal procedure may be used to treat fractures with major soft tissue defects or exposed bone, delayed unions, or nonunions with osteomyelitis and soft tissue necrosis. The shortening-lengthening technique involves primary resection of sufficient bone to permit closure of the soft tissues, followed by callotasis(1) at a healthy methaphyseal site to recover segment length and is generally used to reduce significant bone defects – from 4 to 12cm.(2) (3)
References
- Saleh M, Donnan L 2000. The technique of Callotasis and its Application to Monofocal Limb Lengthening, in: De Bastiani G. Apley AG, Goldberg AAJ. Orthofix External Fixation in Trauma and Orthopaedics. London: Springer.
- Giebel G 1992. In Callus Distraction: Clinical Application. New York, Stuttgart: Georg Thieme Verlag.
- Mahajan Ravi K, Srinivasan K et al. 2019. Management of Post-Traumatic Composite Bone and Soft Tissue Defect of Leg. Indian J Plast Surg: 52(1):45-54.
