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Clinical Features, Debates & Research / Débats, recherche et articles cliniques

Navigating Orthopaedic Spine Surgery Kyle Stampe1, M.D. Daipayan Guha2,3, M.D. Victor X.D. Yang2,3,4, MD, PhD, P Eng, FRCSC Albert Yee1, M.D., MSc, FRCSC 1. Holland MSK Program, Division of Orthopaedic Surgery, Sunnybrook Health Sciences Centre and Division of Orthopaedic Surgery, Department of Surgery, University of Toronto, Toronto, ON 2. Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, ON 3. Biophotonics and Bioengineering Laboratory, Sunnybrook Health Sciences Centre, Toronto, ON 4. Department of Electrical and Computer Engineering, Ryerson University, Toronto, ON

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urgical navigation falls under the broader umbrella of “computer-assisted surgery” (CAS), which is defined as a suite of devices, methodologies, and technologies for assisting surgical planning, intra-operative guidance, and actuation (i.e. robotics) in surgery. The current utilization of surgical navigation in orthopaedic surgery varies tremendously amongst our subspecialties for a variety of reasons1.

The concept of navigation for spine surgery requires matching of a computer-generated spine imaging reconstruction (i.e. XR/ CT/MRI) with bony anatomy intra-operatively. It requires the use of modern intra-operative camera technologies in order to track the movement of ‘tagged’ surgical instruments to the reference points attached to the patient. This is required in order The practice of orthopaedic surgery continues to evolve. We to align the patient with imaging are faced with an explosion of information stemming from and to validate related patient published cutting-edge research (bench and clinical). Likewise, radiographic images. An interacan increasingly informed public has rapid access to information tive computer display monitor about novel therapies and surgical techniques. Oftentimes the then visualizes the tracked surgibest way to integrate evidence-based practice and innovative cal tools relative to the patienttreatments is unknown or challenging. To add some perspective specific imaging. Where indion how to approach emerging and/or controversial topics, we vidual commercially available systems differ is in how the spine have developed this Horizons feature in the COA Bulletin. imaging is acquired (e.g. imagIn the Horizons articles, thought leaders from various ing time, resolution) and how subspecialties will provide insights based on their extensive the patient-to-image registraclinical experience and ongoing research. The goal of this feature tion is performed/validated (i.e. ease of the surgical workflow). is to “shed some light” on the best way forward.

Horizons

Spine surgery is one area where navigation and robotics have Femi Ayeni, M.D., FRCSC complemented well with cliniScientific Editor, COA Bulletin cal needs, becoming more commonplace. This is largely motivated by the need for accuracy and precision when placing implants in and around critical neurologic structures. The ‘safe’ placement of pedicle screws in the spine is a current ‘standard of care’, whether this placement is guided by non-navigated or navigated surgical techniques. Pedicle screw/rod constructs are helpful in the spine to restore vertebral mechanical stability. Biomechanically sound orthopaedic constructs may be necessary for longer-term osseous fusion and procedural success. Several stereotactic navigation techniques are now available, which facilitate the insertion of pedicle screws with real-time 3D image guidance in order to improve accuracy as may be beneficial to both short- and longer-term patient outcomes. The most common use of surgical navigation in the spine is to guide pedicle screw placement. Pedicle screws are most commonly inserted in the thoracic and lumbar spine, although there is some experience on its select application in the cervical spine. Options available to Canadian spinal surgeons currently include a ‘free-hand’ pedicle screw insertion technique, 2D fluoroscopy guided insertion, or CAS-navigated. A free-hand pedicle screw insertion technique is performed using open/ surgically exposed bony landmarks. Surgical experience of anatomy is necessary to identify the correct starting location COA Bulletin ACO - Summer / Été 2017

and trajectory for the pedicle screw. The success of this technique depends largely on surgical experience and comes with a steep learning curve, with the reported accuracy between 75–98%3. The lowest accuracy rates for free-hand techniques have been associated with the mid thoracic area and in patients with spinal deformities. For lower thoracic and lumbar pedicles and in patients with no pre-existing deformity, the accuracy rating of free-hand placed screws is 92%4.

Presently, the two most common spine surgical navigation techniques (Figure 1) are to either:

Figure 1 Comparison of current surgical navigation techniques registering to preop CT (left), intra-op 3D fluoroscopy (middle) and intra-op cone beam CT (right). Pros and cons (italics) of each technique are highlighted.

COA Bulletin #117, Summer 2017  

The Summer 2017 edition of the COA Bulletin