The most important finding of this prospective randomized controlled study was that simple laser navigation technology can effectively improve the rate of excellent mechanical axis correction, reduce radiation exposure and operation time and cost, reduce the labor required, and reduce postoperative complications. Simple laser navigation technology is therefore advantageous compared with traditional positioning technology.
In our study, knee pain and function, as evaluated by the VAS and WOMAC scores, continued to improve for 12 months after the operation. The main reason for this improvement may be that OWHTO causes significant changes in the load distribution of the knee joint, which could cause early degenerative changes and dysfunction if left untreated. Because the time of bone remodeling of the TomoFix plate is appropriately 6–18 months, we chose to remove the implants at 18 months postoperatively. Therefore, the improvement in knee function from 12 to 24 months postoperatively can be explained by implant removal. Cartilage degeneration has been linked with knee osteoarthritis. It has been reported that varus malalignment is correlated with cartilage damage in the medial compartment on MRI, with a dose effect . The results of this study agree with those of previous clinical studies in the sense that the correction of alignment protects the knee from additional cartilage damage, induces cartilage regeneration, and improves knee pain and function [31–33].
The traditional technology involves the use of a metal pole or cable to correct the lower limb mechanical axis, which inevitably negatively affects the operation. The pole or cable can be deformed by external forces, which ultimately affects the accuracy of the operation. It can also be deformed by other external forces during the disinfection and transportation processes, so it needs to be calibrated regularly, resulting in a high maintenance cost. Although computer navigation technology has basically solved the problem of correction accuracy [34–40], the equipment is expensive; in addition, this technology increases the complexity of the operation and thus is not suitable for implementation in areas with limited medical resources. Simple laser navigation combined with a mesh surgical instrument box can effectively improve the accuracy and stability of surgical correction. Laser navigation technology is easy to operate, and beginners can quickly master its use. Moreover, like other computer navigation technologies, it can effectively reduce the probability of outliers, since the laser has a strong anti-interference ability and will not interfere with the positioning accuracy of the operator. Moreover, an intuitive lower limb mechanical axis can be created when the operator uses the laser beam. The application and maintenance costs are very low, and the operation is simple and convenient to perform. It is suitable for use in hospitals at any level.
Radiation exposure contributes to iatrogenic injury. Iatrogenic radiation injury is becoming a problem of increasing concern in the international medical community [41–47]. The application of metal poles and cables in traditional medial high osteotomy is complicated and requires medical personnel to carry out repeated X-ray fluoroscopies to verify the precision of the mechanical axis correction, which inevitably exposes both medical workers and patients to radiation. Simple laser navigation technology solves the problem of insufficient anti-interference ability of the traditional force pole. The laser cannot deform due to interference from external forces . It has higher precision and stability than traditional poles and cables and can effectively reduce the incidence of undercorrection and overcorrection.
Previous comparisons of computer navigation technology with traditional treatment in terms of operation time and radiation exposure have indicated that the former is advantageous. This study also focused on hospital costs and labor input and determined whether laser navigation can reduce the occurrence of postoperative complications. The findings revealed that the operation time of the laser navigation group was significantly shorter than that of the traditional group, primarily because the time required for positioning the surface references for the lower limb force line and proximal tibial plateau osteotomy decreased when the surgical grid-shaped instrument box was used. Since laser navigation will not affect the operation and its application is simple and convenient, it can reduce the operation time. In addition, the decreased operation time and reduced number of X-ray fluoroscopies indirectly decrease the cost of using a C-arm machine and anesthesia. Because navigation requires less intraoperative fluoroscopy, it can effectively reduce the labor input.
Due to the many X-ray fluoroscopies required in the traditional group, the operation time and the duration of tourniquet use were longer than in the navigation group, which led to an increase in the occurrence of body ischemia-reperfusion injury and the release of inflammatory factors [44–49], thereby increasing the probability of limb swelling after the operation. Moreover, adjusting the mechanical axis repeatedly during the operation increased traction and damage to the surrounding soft tissue, resulting in a higher incidence of postoperative complications in the traditional group.
This study showed that 2 patients in the traditional group underwent knee replacement at 18 and 24 months postoperatively, and 1 patient in the laser navigation group underwent knee arthroplasty at 18 months postoperatively. In the traditional group, the reason for knee replacement was severe tibial plateau compression fracture in 1 patient and no obvious improvement in knee pain in 1 patient. In the laser navigation group, the meniscus and cartilage of the affected knee sustained severe trauma in a traffic accident, and the resulting pain was not relieved by arthroscopic treatment. After consideration, we performed knee arthroplasty in these patients. This investigation suggests that the main reason for knee replacement was unexpected trauma. While the effect in one patient in the traditional group was unsatisfactory, the survival time of the affected knee after OWHTO was satisfactory in most patients, which is consistent with most clinical research results [18, 19].
However, this study has some limitations. First, the sample size was small, and more cases need to be studied to increase the quality of the evidence. Second, the status of the knee cartilage was not observed postoperatively, which requires attention in the next step of the research. Finally and most importantly, the observation period was short, and a longer follow-up period is needed to determine the clinical efficacy of simple navigation technology. A follow-up period of 2 years does not allow us to draw conclusions about the long-term clinical outcomes of our patients, including the need to undergo total knee replacement in the future.