Checklist for response to neuromonitoring changes. (From Vitale et al. [51], with permission)
It is important that surgeons understand that this technology is not a substitute for clinical judgment. The overwhelming majority of literature illustrates that neuromonitoring can provide the surgical team with both sensitive and specific info regarding the patient’s neurologic status. However, several initial publications have described instances where the intra-operative neuromonitoring data came back as “normal’ whereas the patient suffered significant neurologic deficits. This has been observed mostly in cases where the surgical team relied only on SSEPs data [20–22]. There are also relatively infrequent instances of false positives whereby data from intra-neuromonitoring techniques indicate a negative neurologic status yet the patient awakens with normal sensory and motor functions – which are reported at around 5–8% [23]. The key is to have a standardized integrated team using multiple platforms including SSEP, MEP, and EMG. This breaks into the notion of, in order to be safe, the surgeon must understand, integrate, and use the proper leading technology.
Again, a constant theme, this information is an adjunct to the surgeon’s clinical decision. Technology is not a substitute. It merely provides more information to the surgeon to improve the safety of surgery. The surgeon must integrate this information with expertise, clinical-decision making, and a standardized-response format. Ignoring a change in neuromonitoring can be disastrous, but this has very different implications for an elective anterior cervical discectomy with fusion as compared to the non-ambulatory neuromuscular scoliosis with multiple medical co-morbidities.
Minimally Invasive Surgical (MIS) Techniques
Minimally invasive surgical (MIS) approaches are mainly utilized to ensure patients incur minimal damage to soft tissues during surgery. The MIS technique has several specific advantages including decreased muscle and tendon stripping, muscle function preservation and integrity, less blood loss, and smaller incisions. MIS techniques have also been reported to improve patient safety since it potentially lowers the infection rates, and the time to recovery aftersurgery [24, 25].
MIS and Safety in Spine
Adongwa et al. demonstrated that patients who underwent MIS trans-foraminal lumbar interbody fusion (TLIF), as opposed to open TLIF, had shorter hospital stay (3 vs. 5.5 days), decreased duration of narcotics post-op (2 vs. 4 weeks), and resumed work faster (8.5 vs. 17 weeks). Both groups showed similar improvements in pain and back related disability at 2 years [26]. This has significant patient and societal cost-related impact. Results of a meta-analysis comparing open TLIF to MIS TLIF showed that the latter has less blood loss, and since the intra- and post-operative transfusion rates were not availed, it could not be determined whether the differences were clinically significant. What was confirmed, however, was that both approaches (open TLIF and MIS TLIF) had similar re-operation rates, operative times, and complication rates [27]. Moreover, other studies have confirmed similar operative time (182 minutes Open TLIF, 166 minutes MIS, p > 0.05), less blood loss (447 ml vs. 50 ml), longer fluoroscopic time (17.6 s open, 49 s MIS), less morphine requirements (33.5 mg open vs. 3.4 mg MIS), less post-operative drainage (open 528 ml, MIS 0 ml), and shorter hospital stay (6.8 days open, 3.2 days MIS) with MIS surgery. Additionally, similar improvements for visual analogue pain scale improvement, overall health improvement on the Short-Form 36 (SF-36) questionnaires, Oswestry Disability Index (ODI), and similar fusion rates between both groups at 2 years (98 vs. 97%) for both groups [28, 29].
Adverse events in open- and MIS lumbar fusion have been analyzed using large meta-analysis and systematic reviews. In a study comparing 806 open patients and 856 MIS patients, the results showed MIS fusion was associated with lower blood loss (260 ml less), 3.5 days faster time to ‘normal’ ambulation, and shorter hospitalization (2.9 days) [30]. In the meta-analysis, there was no difference in intra-operative complications, operative time, or adverse events. Additionally, between MIS and open lumbar fusion, there was no significant difference noted in non-union or revision surgery rates. MIS cases were significantly less likely to experience medical adverse events (risk ratio [MIS vs. open] = 0.39, 95% confidence interval 0.23–0.69, p = 0.001). However, it is important to note some nuances of the data. All studies included in the meta-analysis were considered to be low or very low quality with inherent bias. This remains an interest and important evolving field within spine surgery.
While the science of minimally invasive spine surgery is progressing and evolving to improve outcomes and patient safety, it comes with a steep learning curve. Investigation has clearly indicated that surgeons find it quite challenging to master MIS techniques because they require in-depth understanding of the anatomy of the spine and exemplary three-dimensional spatial-visual skills [31]. The learning curve can be even be steep with experienced surgeons. Nevertheless, it is proven in a peer-reviewed format that MIS techniques reduces hospital stays, lower infection rate, has less blood loss, and provides faster recovery time.
It is important to recognize the synergy of technological advancement that has allowed MIS techniques to flourish. An electronically moveable radiolucent operating table, the ability to use high-quality fluoroscopy intraoperatively, and the ability to now integrate intra-operative navigation of CT scans are just a sample. However, it remains important that surgeons again remain in realistic ownership of the operative theatre and operative outcome. That is, true MIS surgery requires a learning curve and a safety paradigm that is somewhat different for each surgeon. There is a tremendous difference in undertaking technology guided advancement for better patient outcomes and a competition-based marketing approach relying technological adjuncts.
Intra-Operative CT and Three-Dimensional Navigation
As outlined earlier in the chapter, pedicle screws are an indispensable asset to a spine surgeon, but only if they are safely inserted. And, pedicle screw insertion can be challenging, despite widespread adoption, breaches can still occur. The key to the safe placement of the pedicle screw is contingent on the surgeon’s comprehension of the dorsal spine bony anatomy and the relative orientation of the pedicle in relation to the posterior column [32] Not only should surgeons be knowledgeable on the landmarks that define the dorsal anatomy, they also need to be familiar with the three-dimensional orientation of pedicles at each level in the spine. Pedicle screws should be accurately placed within the bony channel of the pedicle to ensure maximum pullout strength of the screw, avoid neurologic injury, leakage of the cerebrospinal fluid, and spinal cord or nerve root irritation.
Studies have reported significant variations in accuracy levels of plain radiographs and intra-operative fluoroscopy in determining pedicle screw placement. A study by Parker et al. reported a pedicle breach rate of 1.7% of pedicle screws placed using true free-hand technique and the radiographs obtained after the screw is in place [33]. Based on reports from several meta-analyses, spine experts generally agree that pedicle screw malposition rate is around 10–15% [34]. Several factors, such as differences in surgical experience and technique, limitations of fluoroscopy, and limitations of 2-dimensional assessment to accurately assess screw placement into a pedicle, can be partially used to elucidate the difference in variation rates [35].
As such, intraoperative CT and 3D navigation of have developed to support improved accuracy of pedicle screw placement. These are two separate adjuncts that can be linked into application. Compared to plain radiography, computerized-tomography (CT) is much more sensitive in assessing the accuracy of pedicle screw placement [36]. Thus, the introduction of intra-operative CT technology in posterior spinal fixation procedures can greatly enhance the process in such a way that surgeons can accurately determine pedicle screw placement during the immediate intraoperative course. Surgeons are able to reposition misaligned screws without having to perform another surgery on the patient. As the intra-operative CT scans continue to evolve, they may be coupled with computer navigation technology, which gives the surgery team a live, real-life view of the pedicle and cannulation tools in the axial, sagittal, and coronal plane. This technology creates a variety of technological workflows for the spine surgeon. It allows the CT imaging platform to function as an adjunct of confirmation after free-hand or fluoroscopic guided placement of pedicle screws or as direct CT guidance.
Empirical data confirms that computer-assisted navigation technology enhances safety in spinal instrumentation by increasing accuracy. A systematic and meta-analysis of spine literature indicates that, compared to the other methods of assessing the accuracy of pedicle screw placement, instances of pedicle violation was much lower when the surgical team used CT-based navigation systems to determine if the screws were accurately placed (Odds ratio 0.32–0.60, p < 0.01) [37]. At the margins, there are reports of accurate pedicle cannulation in 68% of “convectional” cases as compared to 95% accuracy when navigation technology was utilized in the procedure [36].
It is important to also recognize the challenge in comparing different modalities for the accurate placement of pedicle screws. Variations in the reported accuracy of the free-hand technique may be the likely difference between surgeons in terms of surgical capabilities and operative experience. A novice surgeon may report a larger discrepancy in accuracy between free-hand and navigated techniques of placing pedicle screws as compared to a surgeon with many years of experience whose variation between the two techniques might not show a large difference. Therefore, it can be argued that CT-navigation closes the gap separating experienced surgeons from the novices- novice surgeons [38]. Each surgeon must integrate technology at the appropriate level for their practice. As per theme, technology should be integrated into technical mastery but substituted for it.
This creates an open challenge to academic surgeons and surgeons-in-training. As navigational systems become more ubiquitous, it remains vitally important that senior mentors and trainees take an active role to remain fluent in free-hand and fluoroscopic techniques. Technology works with the surgeon and not for the surgeon. It is obvious that, as is the case with every technological surgical tool, CT-navigation works best in situations with the highest level of competency, sound clinical judgment and careful attention to details on the part of the surgical team. The surgeon cannot maximize patient’s safety when these attributes are missing in the operating room. The surgeon must be prepared when (not if) the technology stops working.
In summation, intraoperative CT imaging and navigation are valuable technological adjuncts. Both have been illustrated to be both effective and safe. Each individual surgeon must best develop a technological integration platform that fits their needs and the realities of their hospital and local community practice.
Robotic Spine Surgery
Surgeons in all field, are now pivoting to robotic surgery in an effort to increase efficiency and safety. In spine surgery, for instance, techniques such as the robotic-assisted pedicle cannulation was developed to assist in quick and accurate placement of pedicle screws using both open and MIS techniques. Using a pre-operative CT scan, this technology is able to first create a digital “map” of the patient’s spinal anatomy; then as the surgical team begins the procedure, they obtain fluoroscopic radiographs, which are juxtaposed by the robotic software on the CT scan to determine where the elements of the spinal cord are in space. A reference point is then secured on the patient and the surgeon is then guided by a robotic arm to the correct starting point and the trajectory of the desired pedicle. The surgeon uses the Seldinger technique to drill into the pedicle and place a guide wire, tap the screws to the desired caliber, and finally insert the pedicle screw. In theory, this procedure should be quite effective at reducing large discrepancies in accurate placement of pedicle screws among surgeons while enhancing patient’s safety. When compared to CT navigation the robotic technology is able to use a segmental navigation points that aren’t interrupted by wholesale changes to spinal anatomy or navigation.
Several studies have examined the accuracy of robot-assisted pedicle screw cannulation. For example, a retrospective study by Kantelhardt et al. in 2011 established that 94.5% of pedicle screws that were placed with the guidance of robotic arms were accurately placed as compared with the success rate of 91.4% in the freehand group, a statistical significant difference. The same study also found no significant difference in accuracy when it compared the application of the robotic arm in both percutaneous and open (midline incision) screw placement [39]. Schatlo et al., using the Gertzbein-robbins classification, reported 83.6% “perfect” placement in robotic insertion compared to 79% with freehand technique [39, 40]. New studies continue to demonstrate high accuracy rate in robotic cohorts, ranging from 85% to nearly 100%, of robotic-assisted pedicle and S2-Alar-illiac cannulation [41–43]. Meanwhile, Gao and Yu do not concur with these reports via their meta-analyses and systematic reviews concede that the available evidence is hardly enough to determine the superiority of robotic pedicle cannulation over other placement techniques such as CT-Navigation and the freehand [44, 45]. Indeed, the debate is in its primary stages regarding the accuracy of robotic assisted cannulation. Larger and systematic studies need to be undertaken to compare this technology with more conventional approaches to pedicle placement.
An interesting caveat to this technology is that it allows the surgical team to precisely plan the pedicle screw start point and essentially avoid violating the superior facet joint in fusion constructs, which in turn may decrease iatrogenic instability of the adjacent level. Kim et al. proved that indeed this was the case in their randomized trial of free-hand versus robot-assisted pedicle screw fixation. From their study, they observed that although there was hardly any perceivable difference in accuracy of pedicle cannulation, but the robotic sample enjoyed a 0% superior facet violations compared to the 15% reported in the open freehand group [46]. These findings by Kim et al. have been corroborated by Gao et al. in their meta-analysis of robotic freehand screw placement [44]. It is imperative to understand that the benefits associated with bypassing the cephalad facet joint with pedicle screw placement and are only theoretical. Park et al. established that there were no differences in clinical outcomes or adjustment segment degeneration after studying two-year results of MIS-Robotic fusion patients compared to freehand fusion techniques, despite fewer facet violations in the robotic-assisted group [47]. Park et al. admit that their sample size for the study was limited and consequently they cannot authoritatively determine whether or not the cranial facet avoidance is clinically relevant.
Another advantageous application of robotic-assisted spine instrumentation is that it reduces the amount of radiation being exposed by the surgical team and the patient in the operating room, thereby enhancing safety. This can be non-trivial, especially in MIS cases. Using the same meta-analysis that assessed both robotic and freehand techniques Gao and Yu illustrated the radiation difference between the two techniques . These studies associated robot-assisted pedicle cannulation with reduced radiation time (mean difference = 12.38). The radiation dosage exposed to the surgeon was also significantly lower (64% less). Obviously, the amount of fluoroscopy is variable by surgeon and surgeon technique.
Spine literature notes that robotic instrumentation technology can be of tremendous benefit in the situations of distorted spinal anatomy. Placement of instrumentation through either severe deformity or previous fusion mass can be extremely challenging. Robotic surgery can serve as an adjunct in those particular cases. It also has a strong potential for superiority during the placement of S2 Alar-iliac screws (S2A-I). Bederman et al. point out that a nearly 100% accuracy rate was achieved with 31 robot-guided S2A-I screws with free-hand palpation, although there were 6 lateral iliac protrusions >4 mm in this cohort [43]. At the author’s institution, a 94% success rate for accurate placement was achieved in the first 72 robotic S2A-I screw attempts. Shilingford et al., however, conducted a retrospective review of robotic versus free-hand S2A-I and found no perceivable difference between the two techniques with regard to accuracy [48]. Shilingford et al. however integrate data from top spinal experts which could distort the data as compared to the general spine surgeon. Surgeon specific factors remain vitally important.
Although robotic-assisted spine surgery is still at its infancy, it has been shown to be effective and safe as a pedicle screw placement technique. More evidence, in terms of large prospective comparative studies, is needed to prove the superiority of robotic-assisted spine surgery over computer-assisted navigation and free-hand techniques since the available data suggests equipoise between the three techniques of pedicle cannulation. Thus, large, carefully controlled prospective studies comparing the overall accuracy and safety of robotic-assisted cannulation with the other techniques is warranted. The surgeon’s training and experience should always be considered as well. It is largely established that surgeons who are conversant with all spinal instrumentation techniques are unlikely to report large differences in accuracy between the techniques.
In the same breath, again, many young surgeons have trained in programs that exclusively utilize CT-navigation, MIS, or robotic techniques and, consequently, are likely to report significant discrepancy between one of the aforementioned techniques and a true freehand technique. It is, therefore, crucial that available data on the techniques be interpreted in a cautious manner. Surgeons must identify and acknowledge their abilities and limitations with each technique so as to enhance patient safety. We predict that more surgeons will embrace this technology as it becomes more prevalent due to reduced cost of acquiring and operating surgical robotic technology.
Cost Consideration
A realistic appreciation for the cost of technology is applicable. There are several barriers to the integration of technology at the hospital, provider, and third-party level. Hospital systems are concerned about overhead expenditures with a greater focus on the immediate fiscal period. Different technologies will have different fixed and variable cost structures. Private insurance companies are concerned about the immediate cost of something only during the period in which they are to cover the patient. Long-term savings over the lifetime of a patient are generally not of immediate concern. Surgeons are focused chiefly on patient related outcomes and healing the person to the best of their ability. Meanwhile government agencies focus within a budget, a budget that disproportionately is responsible for coverage in patients over the age of 65. This triangularization of priorities can make new technology adaptation difficult.
Technology in spine surgery
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