Use of a titanium cutting guide to assist raising the composite radial forearm free flap

Abstract

The use of composite radial free tissue transfer has been overtaken by other composite flaps. This is due to donor site morbidity and the poor volume of bone yielded. The advantages and potential complications of composite radial flaps are well described. Use of the composite radial forearm free flap has been largely superseded in mandible reconstruction, but applications such as a salvage option still exist. Additionally it may be used in the reconstruction of midface defects. The use of a cutting guide to reduce the donor site complications and yet produce a maximal yield of bone is described herein. With the use of a skilled maxillofacial laboratory, the planning allows precise cuts and placement of the free flap and allows accurate prophylactic plating of the radius. A precise titanium cutting guide and custom distal radius plate are used. Details of three cases where these techniques have been implemented are described. The paper demonstrates the significant advantages of using laboratory-based technology to assist in performing composite radial free flaps. This paper reveals that composite radial free tissue transfer still has a place in the reconstruction of very selective defects of the head and neck. In particular, its use in reconstruction of Class 5 and 6 maxillary defects (Brown classification) is illustrated. Correct case selection and planning results in increased confidence to use this flap.

The radial free flap was first described by Yang over 30 years ago . It was soon recognized as a versatile flap for intraoral reconstruction . The radial osteocutaneous flap initially became established as the first reliable free flap for reconstruction of continuity defects of the mandible . Although the volume of available bone was limited, it provided sufficient length to reconstruct many defects. In the maxilla, the bone and soft tissue characteristics of the radial composite flap allow reconstruction of Class 2 defects (Brown classification) . The advantage of the radial forearm flap is the relative ease in raising the flap and the excellent pedicle length.

However, the composite radial flap carries significant drawbacks. It has been criticized for the quantity and quality of bone available for harvest. This means that the bone is often unsuitable for the placement of dental implants . Additionally, the composite radial flap carries a significant risk of morbidity at the donor site. The main cause of morbidity is fracture following osteotomy . The incidence of fracture of the distal radius has been quoted as being between 23% and 31% . The incidence of fractured radius may also be reduced by limiting the amount of bone removed to 40% of the cross-sectional area . However, accurate assessment of this bony depth can be difficult in practice . The use of prophylactic plating of the radius to reduce the risk of fracture following the osteotomy has also been described.

Recognition of these drawbacks and the development of alternative reconstructive options have meant that the radial composite flap is frequently disregarded as a genuine reconstructive option for mandibular and maxillary defects. This was confirmed in 2006 in a 10-year review of free flap selection .

In spite of this, the composite radial flap remains a useful option in selected clinical circumstances. The composite radial forearm flap is suitable for low-level maxillary defects (Class 2) and for Class 5 and 6 defects. In the Class 5 and 6 defects, only a small volume of bone is usually required and the soft tissue component becomes more important. Additionally, the length of the pedicle is exceptionally important in these cases. The fibula flap is an alternative for these defects, but often yields too much bone and a shorter pedicle length.

This note describes the use of a novel cutting guide to enable swift and safe harvest of the radial bone ensuring maximal bone yield (40%). The paper also illustrates the use of a pre-bent prophylactic osteosynthesis plate to prevent fracture of the radius at the donor site.

Materials and methods

Patients requiring composite radial free flap reconstruction undergo a three-dimensional (3D) computerized tomogram (CT) of the maxilla and forearm (non-dominant arm is used if the Allen’s test is favourable). Using DICOM (Digital Imaging and Communication in Medicine) data from the CT scan, a stereolithographic model of the maxilla and the radius is created. The printer used is an Objet 3D Printer with 27 μm slices, which provides a highly accurate model.

Using the stereolithographic model of the maxilla/mandible, preoperative planning of the anticipated resection is conducted. This allows the surgeon planning the case to determine the volume of bone required. The size of the anticipated resection is recorded.

On the model of the radius, a template is used to outline the amount of bone required. Care is taken to mark less than 40% of the cross-sectional width of the bone. This is measured manually on the model.

A cutting guide is constructed out of 0.4-mm titanium sheet with locators and screw holes to allow accurate placement intraoperatively. The anatomical area exposed to apply the guide is not significantly greater than when not using the guide. The screw holes drilled will match the holes required for placement of the prophylactic distal radius plate. The cutting guide allows the reciprocating saw to osteotomize the bone with confidence. The osteofasciocutaneous flap can then be raised.

The stereolithographic model of the radius also allows a 3.5-mm steel dynamic compression plate (Synthes Co.) to be pre-contoured to fit perfectly with utilization of the holes made to secure the cutting template. This allows prophylactic plating of the radius to give strength in both torsion and bending. The plate is then secured along the anterior aspect with bicortical screws. The defect is closed with a full thickness abdominal skin graft covering the cutaneous donor site. The forearm is supported in a below-elbow cast for 6 weeks in total. A backslab is used for the first 14 days. This is then changed to a complete cast (with a window over the skin graft site) for 4 weeks.

Figures 1–4 illustrate the techniques and materials.

Jan 20, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Use of a titanium cutting guide to assist raising the composite radial forearm free flap
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