Accuracy Of Patient-Specific 3D-Printed Drill Guides For Spine Surgery Compared With Computer Assisted Surgery

Accurate screw insertion is essential for safe and optimal spinal fixation
surgery. Screw misplacement may lead to damage to vital structures or failure
of the fixation. Traditionally, screws are inserted free-hand, based on
anatomical landmarks and with the aid of fluoroscopy. There are however
numerous studies reporting high rates of screw misplacement by freehand screw
insertion.

Technical developments in spinal surgery have led to the implementation of
Computer Assisted Surgery (CAS) navigation systems in complex spine surgery.
Initially, CAS was based on preoperative planning, but current systems use an
intraoperatively acquired CT and, therefore, require the surgeon to plan the
screws during surgery. There is a consensus based on clinical experience that
CAS improves the accuracy of screw placement, but unfortunately screw
malposition still occurs. Since modern CAS systems are considered highly
accurate but lack integrated preoperative planning, optimizations of screw
insertion can mainly be achieved by improving the screw planning using
preoperative planning techniques.

Advancements in Computer-Aided Design and Manufacturing have led to 3D virtual
surgical planning techniques and the use of patient specific 3D-printed drill
guides. This technique consist of preoperative virtual screw planning including
screw direction, length and thickness. The corresponding 3D-printed guides are
applied per vertebra and therefore independent to intervertebral motion.
Recently, our research team developed an optimized spinal 3D guide design
during a cadaveric study, which allowed the surgeons to pass through the
learning curve. Nowadays, guides have been implemented into clinical practise
in addition to CAS, to assist in complex cases.

At present, no systematic comparison between guides and CAS has been conducted.
Therefore, the current study will provide a randomized systematic comparison
between guides and CAS by means of a uniform radiological 3D analysis.

In this non-inferiority trial, we aim to demonstrate that 3D-printed guides are
just as good as CAS, regarding the postsurgical radiological screw-insertion
accuracy.

This non-inferiority study will be a prospective, split-spine randomized,
controlled trial.

The intervention in this study is the 3D virtual surgical planning and the use
of patient specific guides for spinal screw insertion in one half of the
patient*s spine.

Research-related burden includes Randomisation of two screw insertion
techniques and the CAS measurements, together resulting in approximate surgery
prolongation of 15 minutes.
The surgical procedure will not be subject to changes for the patient. The
guides are produced under ISO 13485 and ISO 9001:2008, and the printed material
(nylon) is bio-compatible according to the ISO 10993-1 classification. A risk
analysis and approval of Medical Technique UMCG was obtained (DAD17.00001).