Designing patient-specific solutions using biomodelling and 3D-printing for revision lumbar spine surgery.

Purpose: Despite the variety of "off-the-shelf" implants and instrumentation, outcomes following revision lumbosacral surgery are inconstant. Revision fusion surgery presents a unique set of patient-specific challenges that may not be adequately addressed using universal kits. This study aims to describe how patient-specific factors, surgeon requirements, and healthcare efficiencies were integrated to design and manufacture anatomically matched surgical tools and implants to complement a minimally invasive posterior approach for revision lumbar fusion surgery.

Methods: A 72-year-old woman presented with sciatica and a complex L5-S1 pseudoarthrosis 12 months after L2-S1 fixation surgery for symptomatic degenerative scoliosis. Patient computed tomography data were used to develop 1:1 scale biomodels of the bony lumbosacral spine for pre-operative planning, patient education, and intraoperative reference. The surgeon collaborated with engineers and developed a patient-specific 3D-printed titanium lumbosacral fixation implant secured by L2-L5, S2, and iliac screws. Sizes and trajectories for the S2 and iliac screws were simulated using biomodelling to develop a stereotactic 3D-printed drill guide. Self-docking 3D-printed nylon tubular retractors specific to patient tissue depth and bony anatomy at L5-S1 were developed for a minimally invasive transforaminal approach. The pre-selected screws were separately sourced, bundled with the patient-specific devices, and supplied as a kit to the hospital before surgery.

Results: At 6-month follow-up, the patient reported resolution of symptoms. No evidence of implant dysfunction was observed on radiography.

Conclusion: Pre-operative planning combined with biomodelling and 3D printing is a viable process that enables surgical techniques, equipment, and implants to meet patient and surgeon-specific requirements for revision lumbar fusion surgery.