Successful use of a 3D-printed surgical guide to facilitate transiliosacral fixation in a cat with bilateral sacroiliac luxation

Abstract

Case summary: A 7-year-old male castrated domestic shorthair cat was presented for treatment of a bilateral sacroiliac luxation (SIL). CT was performed and the data were extracted in a stereolithography (STL) file, after which a 3D-printed drill guide (3DPDG) was devised, using computer-aided design (CAD) software, and printed. Using an open surgical approach, the guide was used as an aid for drilling the sacrum. The ilial wings were drilled free-hand later and a transiliosacral pin (TP) was inserted to realign and stabilise the SIL. The cat exhibited an early return to normal limb function and a CT scan performed at the postoperative follow-up showed early signs of bone remodelling at the sacroiliac joint.

Relevance and novel information: To the authors' knowledge, this is the first report using a 3DPDG for implant placement in the feline sacrum without intraoperative imaging.

Keywords: 3D-printed drill guide; computer-aided design; sacroiliac fracture/luxation; stereolithography; transiliosacral pin.

Figure 1

(a) 3D reconstruction of the pelvis and sacrum, showing bilateral ventral sacroiliac luxation (grey arrow) and (b) 3D reconstruction of the pelvis and sacrum, showing bilateral caudal sacroiliac luxation (grey arrow)

Figure 2

Virtual planning of the sacral model and 3D guide in computer-aided design software, shown in (a) right lateral and (b) axial views, and (c) an additional view of the 3D guide. The angle of the corridor in relation to the articular surface of the sacrum was 106° on the dorsal plane and 107° on the transverse plane

Figure 3

Intraoperative image illustrating the placement of the 3D-printed drill guide on the sacrum

Figure 4

Gras adapted classification system: (a) secure placement within the cancellous bone; (b) secure placement, with contact to cortical bone structures; (c1) ventral malposition, involving penetration of the cortical bone; and (c2) dorsal malposition, involving penetration of the cortical bone

Figure 5

Coronar (a) and axial images (b) of the sacroiliac stabilisation at the 6-week follow-up, confirming secure placement of the implant in cancellous bone, without any signs of implant loosening. Note the left ilium is slightly misaligned dorsally

Figure 6

Comparison between the 6-week postoperative implant placement trajectory (red) and virtual implant (grey). The irregular shape of the postoperative implant (red) is due to CT artefacts. The preoperative and postoperative images of the sacrum were precisely aligned for a comprehensive evaluation