# Orthopedics-Related Applications of Ultrafast Laser and Its Recent Advances
## 5 Future Direction and Conclusions
### Applications  
In terms of pre-surgical applications of ultrafast lasers in orthopedic surgery, the main benefit would be the preparation of implants or materials for integration within bone. For instance, [PERSON] et al. [89] and [PERSON] et al. [86] have demonstrated how ultrafast laser machining increases osteointegration and biocompatibility. Taking these into consideration, it could be envisioned that implants in total hip arthroplasty and total knee arthroplasty would be patterned to increase osteointegration of the implants without necessitating the use of bone cement or other anchors, such as intramedullary nailing or percutaneous screws. Although an uncommon complication, early failure of implants occurs in both knee and hip arthroplasty, either due to failure of bone cement to anchor the implant causing loosening and loss of stability, or contact with surrounding bone when using a cementless implant, leading to a similar outcome [97; 98]. Revision surgeries in these cases provide worse outcomes compared to the primary surgery, with higher rates of infection, worse overall prognosis and delayed healing, especially in patients with preexisting comorbidities and poor overall health [99]. Thus, ultrafast laser machining of the implant surface could mitigate failure rates and improved overall outcomes. However, it should be noted that during many of these surgeries, it is not known a priori what implant or which size the surgeon will choose as it is dependent on the size of bored hole in the femur/tibia or the size of the acetabulum. In these cases of furthering the osteointegrative potential of hip and knee arthroplasty implants, there are two approaches in which femtosecond laser surface modification could  
Figure 3: SEM image comparison of a pre-anodized titanium-based bone screw without femtosecond laser treatment (**left**) showing osteoblast growth and adhesion, and the same screw with femtosecond laser treatment (**middle**) showing cell-free areas, and details at higher magnification (**right**). Adapted from [86]. be used. In the first use case, all implants have surface preparation performed with ultrafast lasers at the time of manufacturing prior to shipment to various orthopedic centers. If the cost or time of surface preparation is not a feasible option, a second approach would be for the surgeon to identify high-risk patients where implant failure may occur and prepare these devices accordingly. Furthermore, many medical device manufacturers have explored the use of 3D printing of custom implants based on preoperative imaging where ultrafast laser surface modification in combination with custom 3D-printed joint implants could provide an overall increase in mobility and function following surgery for these high-risk patients. Thus, ultrafast laser surface preparation in conjunction with custom implant manufacturing, where an increase in osteointegration contributes to the overall well-being of the patient, provides a greater impetus for both custom implant manufacturing as well as increases in overall outcome. Future work would examine the use of ultrafast laser patterning on materials outside of the traditional knee arthroplasty and hip arthroplasty components, as 3D-printed joint replacement can use highly porous materials that are prone to heat damage and warping [100]. Additionally, recent studies have demonstrated higher migration rates (implant slides 'upwards' from where it was set) for cementless 3D-printed joint'stems' in knee and hip arthroplasty [101]. This migration of the implant away from where it is set is an indicator of impending aseptic loosening, which normally necessitates a revision procedure, whereby surface preparation and increased implant anchoring provides a tangible benefit to both patients and operators, since, as discussed, revision surgery is a costly and detrimental procedure. Secondly, to preparation of implants or materials, a large area of research for the use of ultrafast lasers is cutting of hard surfaces, specifically dentine, enamel and bone.