A New Accurate, Simple and Less Radiation Exposure Device for Distal Locking of Femoral Intramedullary Nails

Fast and accurate distal locking of interlocked intramedullary nails using computer-vision and a 3D printed device

INTRODUCTION

Distal locking is a challenging and time-consuming step in interlocked intramedullary nailing of long bone fractures. Current methods have limitations in terms of simplicity, universality, accuracy, speed, and safety. We propose a novel device and software for distal locking using computer vision.

METHODS AND MATERIALS

The device consists of an universal ancillary clamp, a telescopic arm, a viewfinder clamp, and a radio-opaque cross. The software uses a camera photo from the C-arm intensifier and adjusts for geometric projection deformities. The software employs edge detection, Hough transform, perspective interpolation, and vector calculation algorithms to locate the distal hole center. The device and software were designed, manufactured, and tested using 3D CAD, FEM, DRR, and performance testing on phantom bones.

RESULTS

The device and software showed high accuracy and precision of 98.7% and 99.2% respectively in locating the distal hole center and calculating the correctional vector. The device and software also showed high success ratio in drilling the hole and inserting the screw. The device and software reduced the radiation exposure for the surgeon and the patient. The success ratio of the device and software was validated by the physical testing, which simulated the real clinical scenario of distal locking. The radiation exposure was as low as 5 s with a radiation dose of 0.2mSv, drastically reducing radiation exposure during distal locking.

DISCUSSION

Our device and software have several advantages over other distal locking methods, such as simplicity, universality, accuracy, speed, and safety. Our device and software also have some disadvantages, such as reliability and legislation. Our device and software can be compared with other distal locking methods based on these criteria. Our device and software have some limitations and challenges that need to be addressed in the future, such as clinical validation, and regulatory approval.

CONCLUSION

The device showed promising results in terms of low-cost, reusability, low radiation exposure, high accuracy, fast distal locking, high stiffness, and adaptability. The device has several advantages over other distal locking techniques, such as free-hand technique, mechanical aiming devices, electromagnetic navigation systems, and computer-assisted systems. We believe that our device and software have the potential to revolutionize the distal locking technique and to improve the outcomes and quality of life of the patients with long bone fractures.

[Research progress on distal interlocking screws of cephalomedullary nails in intertrochanteric fractures]

Objective

To summarize the new research progress in distal interlocking screws of cephalomedullary nails for the treatment of intertrochanteric fractures.

Methods

Relevant domestic and foreign literature was extensively reviewed to summarize the static/dynamic types of distal interlocking screw holes, biomechanical studies, clinical studies and application principles, effects on toggling in the cavity, and related complications of distal interlocking screws.

Results

The mode of the distal interlocking screw holes can be divided into static and dynamic. Distal interlocking screws play the role of anti-rotation, maintaining femur length, resisting compression stress, increasing torque stiffness, resisting varus stress, etc. The number of the screws directly affects the toggling of the main nail in the cavity. At present, regardless of whether long or short nails are used, distal interlocking screws are routinely inserted in clinical practice. However, using distal interlocking screws can significantly increase the duration of anesthesia and operation, increase fluoroscopy exposure time, surgical blood loss, and incision length. There is a trend of trying not to use distal interlocking screws in recent years. No significant difference is found in some studies between the effectiveness of dynamic and static interlocking for AO/Orthopaedic Trauma Association (AO/OTA) 31-A1/2 fractures. At present, the selection of the number and mode of distal interlocking screws is still controversial. When inserting distal interlocking screws, orthopedists should endeavor to minimize the occurrence of complications concerning miss shot, vascular injuries, local stress stimulation, and peri-implant fractures.

Conclusion

Distal interlocking screws are mainly used to prevent rotation. For stable fractures with intact lateral walls, long cephalomedullary nails can be used without distal interlocking screws. For any type of intertrochanteric fractures, distal interlocking screws are required when using short cephalomedullary nails for fixation. Different interlocking modes, the number of interlocking screws, and the application prospects of absorbable interlocking screws may be future research directions.

Comparison of freehand technique and a novel laser-guiding navigation system in femoral neck-cannulated screw fixation: a randomized controlled trial

Cannulated screw fixation is essential in treating femoral neck fractures, and the widely used freehand technique has several limitations. Therefore, we designed a new laser-positioning and navigation system and compared its efficacy with that of the traditional freehand technique in the cannulated screw fixation of femoral neck fractures. This randomized controlled single-blind trial recruited patients with femoral neck fracture, who were treated using either the newly designed laser-navigation device or the freehand technique. In in-vitro experiments, using the femoral neck model, the laser group was better than the freehand group in terms of operation time (P = 0.0153) and radiation exposure time (P < 0.001). In in-vivo experiments, involving 30 patients (15 in each group), the laser group was better than the freehand group in terms of operation time (P < 0.001), radiation exposure time (P < 0.001), blood loss (P < 0.001) and first success rate (P = 0.03). There was no difference in visual analog scale score, Harris score, and fracture-healing time between the two groups. In conclusion, the novel laser-guiding navigation system resulted in shorter operation time, less radiation exposure, and higher first success rate compared with the freehand technique. Further qualified investigations with a larger number of patients and longer follow-up are required in the future.

Intramedullary nail holes laser indicator, a non-invasive technique for interlocking of intramedullary nails

Interlocking of intramedullary nails is a challenging procedure in orthopedic trauma surgery. Numerous methods have been described to facilitate this process. But they are exposed patient and surgical team to X-rays or involves trial and error. An accurate and non-invasive method has been provided to easily interlocking intramedullary nails. By transferring a safe visible light inside the nail, a drilling position appears which use to drilling bone toward the nail hole. The wavelength of this light was obtained from ex-vivo spectroscopy on biological tissues which has optimal transmission, reflectance, and absorption properties. Moreover, animal and human experiments were performed to evaluate performance of the proposed system. Ex-vivo performance experiments were performed successfully on two groups of cow and sheep samples. Output parameters were procedure time and drilling quality which there were significant differences between the two groups in procedure time (P < 0.05). But no significant differences were observed in drilling quality (P > 0.05). Moreover, an In-vivo performance experiment was performed successfully on a middle-aged man. To compare the provided method, targeting-arm, and free-hand techniques, two human experiments were performed on a middle-aged and a young man. The results indicate the advantage of the proposed technique in the procedure time (P < 0.05), while the drilling quality is equal to the free-hand technique (P = 0.05). Intramedullary nail holes laser indicator is a safe and accurate method that reduced surgical time and simplifies the process. This new technology makes it easier to interlocking the intramedullary nail which can have good clinical applications.