# Orthopedics-Related Applications of Ultrafast Laser and Its Recent Advances
## 5 Future Direction and Conclusions
### Future Directions  
In the scenarios envisioned where ultrafast lasers would potentially be of benefit, there are number of future directions that should be addressed and examined. Firstly, a method to stop laser ablation as soon as the bone is cut through to prevent a similar laser-induced 'plunge' into tissue such as dura or nervous tissue would need to be developed, similar to the mechanical chuck that has been integrated into cranial perforators [107]. Plunging into inferior tissues such as the dura and/or brain would be of greater detriment compared to any gains made from reduced thermal deposition and reduced thermal damage from either direct brain damage or CSF leakage. A high degree of pre-planning using CT or MRI to determine bone thickness as well as depth control during the procedure would need to be achieved to prevent overcutting at any given volume currently being ablated. This degree of intraoperative control of cutting/ablation would, at a minimum, require a guidance platform demonstrated in procedures such as pedicle screw placement whereby IR based navigation is used to track the screw in real time with combined CT guidance [108], and the laser tip/front could be tracked in real time. A second approach would be to combine the ultrafast laser cutting tool with an optical approach such as diffuse reflectance spectroscopy (DRS) where optical properties of incoming tissue can be measured in real time. In combining DRS with ultrafast laser cutting/ablation, the relatively slower speed of laser-based ablation would allow for DRS measurements in combination with real-time optical property measurements, enabling in-line tissue differentiation. Nonetheless, a system of external tracking, such as IR navigation, or with fiber measurements of optical properties, such as DRS, would need to be implemented to prevent overcutting of tissue, leading to dural laceration or nerve/vessel injury that would provide no appreciable benefit to conventional surgical techniques. Secondly, we propose that in the transition of the use of ultrafast lasers into bone surgery, integration either within a robotic or navigation platform will be necessary to allow for higher success chance in the proposed applications [109]. As mentioned previously, cutting depth is an important parameter in the procedures such as laminectomy or transsphenoidal placement. Surgeons currently use a combination of auditory cues and haptic feedback when assessing depth while drilling, and would not be able to use a laser-based cutting/ablation approach. We propose that a robotic platform could be developed, including either a navigation device or optical 'guidance' system such as DRS. The addition of these platforms can overcome the loss of haptic feedback and auditory cues normally used by surgeons while maintaining the safety of the procedure. This can be expanded to include semi-autonomous or AI-driven robotic platforms where surgeons design cutting paths in conjunction with a robotic laser-based system that could perform cutting procedures, such as removal of the spinenoid bone or lamina with minimal surgeon oversight. This type of platform is appealing as it would lead to a reduction in exposure to X-rays to both patient and operators, commonly encountered in many orthopedic procedures and secondly, increase overall outcomes due to increased osteointegration and reduced thermal deposition. Finally, laser systems and fibers need to be developed that can provide both high ablation rates and flexibility that would allow for integration into currently existing minimally invasive surgical devices. In terms of ablation rates, the rate would need to at least approximate the ablation rate of mechanical drills (4-5 mm/s) as well as approximating the ablation volume. For example, in orthopedic surgery the drill bit size would be 6-8 mm with the aforementioned ablation rate in procedures such as hip and knee arthroplasty.