3D Volumetric Modeling and Microvascular Reconstruction of Irradiated Lumbosacral Defects after Oncologic Resection

Abstract

Background: Locoregional flaps are sufficient in most sacral reconstructions. However, large sacral defects due to malignancy necessitate a different reconstructive approach, with local flaps compromised by radiation and regional flaps inadequate for broad surface areas or substantial volume obliteration. In this report, we present our experience using free muscle transfer for volumetric reconstruction, in such cases, and demonstrate three-dimensional (3D) haptic models of the sacral defect to aid preoperative planning.

Methods: Five consecutive patients with irradiated sacral defects secondary to oncologic resections were included, surface area ranging from 143-600 cm². Latissimus dorsi (LD)-based free flap sacral reconstruction was performed in each case, between 2005 and 2011. Where the superior gluteal artery was compromised, the subcostal artery (SA) was used as a recipient vessel. Microvascular technique, complications, and outcomes are reported. The use of volumetric analysis and 3D printing is also demonstrated, with imaging data converted to 3D images suitable for 3D printing with Osirix software (Pixmeo, Geneva, Switzerland). An office-based, desktop 3D printer was used to print 3D models of sacral defects, used to demonstrate surface area and contour and produce a volumetric print of the dead space needed for flap obliteration.

Results: The clinical series of LD free flap reconstructions is presented, with successful transfer in all cases, and adequate soft-tissue cover and volume obliteration achieved. The original use of the SA as a recipient vessel was successfully achieved. All wounds healed uneventfully. 3D printing is also demonstrated as a useful tool for 3D evaluation of volume and dead space.

Conclusion: Free flaps offer unique benefits in sacral reconstruction where local tissue is compromised by irradiation and tumor recurrence, and dead space requires accurate volumetric reconstruction. We describe for the first time the use of the SA as a recipient in free flap sacral reconstruction. 3D printing of haptic bio-models is a rapidly evolving field with a substantial role in preoperative planning.

Keywords: free flap; model; planning; preoperative imaging; volumetric analysis.

Figure 1

Preoperative computed tomography scan, showing the three-dimensional nature of a sacral defect.

Figure 2

Surface-rendered reconstruction images derived from a preoperative computed tomography scan, showing the three-dimensional nature of a sacral defect (A–C: three dimensional rotating views).

Figure 3

Three-dimensional (3D) printed model of the sacral defect shown in Figure 2, produced using a 3D printer (Cube 2 printer, 3D Systems, Rock Hill, SC, USA) (A–C: three dimensional rotating views).

Figure 4

A 25 cm × 10 cm surface area sacral defect requiring reconstruction.

Figure 5

A free latissimus dorsi myocutaneous flap was selected for reconstruction of the defect, with donor site marked.

Figure 6

Free latissimus dorsi myocutaneous flap harvested, with templated skin paddle and muscle for volumetric filling.

Figure 7

Flap inset into sacral defect, with adjacent remnants of previous locoregional reconstructive flaps.

Figure 8

An 18 cm × 20 cm surface area sacral defect requiring reconstruction.

Figure 9

Free latissimus dorsi muscle only flap inset into the defect.