The benefits of computer-assisted surgery

Nicolas Dea

Surgical technologies are becoming more diverse and more easily accessible. Most do not have true added value, but others, like neuromonitoring for complex deformity procedures, are now incorporated in day-to-day practice, and have become standard of care, writes Nicolas Dea.

Surgical navigation systems have been integrated in cranial neurosurgery practice for years, but have only recently became readily accessible for spinal surgery. The computer-assisted surgery (CAS) technique involves the use of intraoperative navigation that necessitates preoperative or intraoperative 2D or 3D imaging linked to a navigation unit. It allows the surgical team to increase pedicle screw placement accuracy, create precise osteotomies in deformity and tumour cases, and achieve post-implantation screw assessment, among other applications.

Multiple systematic reviews have demonstrated the superiority of CAS technique compared to others for pedicle screw placement.1 Accuracy rates of above 95% are commonly reported with CAS compared to rates as low as 50% for the free-hand technique. Yet, most misplaced screws do not cause any problems and are totally asymptomatic. Misplaced screws can, however, result in irreversible neurological damage, biomechanically weaker constructs, lower fusion rates, vascular injuries and higher reoperation rates. We must therefore aim for proper screw placement; something CAS has proven its superiority for. 

There are not only better accuracy rates with the CAS technique. The ability to obtain a confirmatory intraoperative computed tomography scan may also obviate the need for a postoperative scan. Less postoperative imaging can not only reduce costs, but can also limit radiation exposure to patients. CAS has furthermore been shown to significantly reduce the amount of radiation delivered to operating room staff ,2 a problem that we should be particularly aware of, especially given the rising usage of minimally-invasive techniques which rely heavily on intraoperative guidance. CAS also constitutes an invaluable teaching tool for surgeons working with residents and fellows. Moreover, it can allow for tumour-free osteotomy creation in primary tumour cases, promoting appropriate margins and lower recurrence rates. Computer-assisted surgery could also potentially obviate litigation issues for surgeons and hospitals.

So why has CAS not yet become the standard of care? An interesting survey revealed that high acquisition costs and longer operative time were the main obstacles against a more widespread usage of this technology.3 As many physicians have experienced, there is definitely a learning curve associated with the use of CAS in surgery. However, once we become familiar with using computer-assisted techniques, navigated cases may actually be even shorter to perform.4

And what about the cost-effectiveness? In an era when health expenditure is rising exponentially, cost-effectiveness analyses are mandatory to responsibly manage scarce healthcare resources. To answer this question, we recently conducted a cost-effectiveness analyses comparing CAS to traditional fluoroscopy-guided techniques.5 We performed a full economic evaluation using rigorous patient-level data outcomes and methodology, and showed that acquisition costs might not be as prohibitive as previously anticipated. Based on lower surgical revision rates, computer-assisted surgery can even be cost-saving in high volume centres. An incremental cost-effectiveness ratio of US$23,288 per reoperation avoided was calculated for the computer-assisted surgery group. Based on a reoperation cost of US$27,768 this new technology becomes cost-saving for centres performing more than 168 instrumented spinal procedures per year.

For most cases, especially less demanding interventions, computer-assisted surgery might not change outcomes—traditional techniques may remain completely appropriate. However, with no concrete disadvantages, I do not see any reason why we should not embrace this new technology with the ultimate goal of making surgery safer for our patients.


  1. Mason A, Paulsen R, Babuska JM, Rajpal S, Burneikiene S, Nelson EL,etal. The accuracy of pedicle screw placement using intraoperative image guidance systems. JournalofNeurosurgery:Spine 2014;20:196–203 doi:10.3171/2013.11.SPINE13413.
  2. Mendelsohn D, Strelzow J, Dea N, Ford NL, Batke J, Pennington A, etal. Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation. SpineJ 2015. doi:10.1016/j.spinee.2015.11.020
  3. Härtl R, Lam KS, Wang J, Korge A, Kandziora F, Audigé L. Worldwide survey on the use of navigation in spine surgery. WorldNeurosurgery 2013; 79:162–72. doi:10.1016/j.wneu.2012.03.011
  4. Shin BJ, James AR, Njoku IU, Härtl R. Pedicle screw navigation: a systematic review and meta-analysis of perforation risk for computer-navigated versus freehand insertion. Journal of Neurosurgery: Spine 2012;17:113–22. doi:10.3171/2012.5.SPINE11399
  5. Dea N, Fisher CG, Batke J, Strelzow J, Mendelsohn D, Paquette SJ, etal. Economic evaluation comparing intraoperative cone beam CT-based navigation and conventional fluoroscopy for the placement of spinal pedicle screws: a patient-level data cost-effectiveness analysis. SpineJ2016;16:23–31. doi:10.1016/j.spinee.2015.09.062

Nicolas Dea is a neurosurgeon at the Centre Hospitalier Universitaire de Sherbrooke, as well as director of the neurosurgery program at the Université de Sherbrooke (both Sherbrooke, Canada)