Hands-on robotic distal interlocking in intramedullary nail fixation of femoral shaft fractures

Abstract

Introduction: Intramedullary nailing has become the gold standard in the treatment of femoral shaft fractures. This procedure involves the placement of distal interlocking bolts using the freehand technique. Accurate placement of distal interlocks can be a challenging task, especially in inexperienced hands. Misplacement of distal interlocking bolts can lead to iatrogenic fracture, instability of the bone-implant construct, or even malalignment of the extremity. Repeated drilling attempts increase radiation exposure and can cause additional bony and soft tissue trauma. We hypothesize that robot-guided placement of distal interlocks is more accurate, precise, and efficient than the freehand technique.Methods: A custom-designed drill guide was mounted onto the arm of an industrial robot. We developed a special device to secure a generic block (Synbone, Malans, Switzerland) into which an intramedullary nail could be inserted in a standardized way. A metric scale allowed later measurements of the drillings. Digital images were taken from each side of the block for analysis of the drilling trajectories. The fluoroscope was adjusted to obtain perfect circles of the distal interlocking holes. The number of images necessary to achieve this was recorded. The axis was recognized automatically by using the differences in contrast between the matrix of the generic bone and the implant (intramedullary nail). The drill trajectories were then computed. The robot with the mounted drill-guide automatically moved onto the calculated trajectory. The surgeon then executed the drilling. We performed 40 robot assisted drillings in generic blocks. Freehand drilling served as our control group.Results: Analysis of the digital images revealed a mean deviation of 0.94 mm and 2.7 • off the ideal trajectory using robotic assistance. In 100% of the cases (n = 40), the distal locking hole was hit. A mean of 8.8 images was acquired. After manual drilling, 92.5% of the distal interlocks were hit. A mean deviation of 3.66 mm and 10.36 • was measured. A mean of 23.4 fluoroscopic images were needed. The differences between the two methods were statistically significant.Conclusion: Robot-guided drilling increases the accuracy and precision of distal interlocking while reducing irradiation. Considering economical and logistical aspects, this application should be integrated with robot-guided fracture reduction.

Comparison of algorithms for automated femur fracture reduction

“…In an effort to improve outcomes after intramedullary nailing of femur fractures, we have worked on developing a comprehensive roboticassisted operative technique. [6][7][8][9][10]13,14,[17][18][19][20][21][22][23] We have previously shown that surgeon-performed telemanipulated fracture reduction is effective and accurate for simple fracture types. To further improve the accuracy of more complex fractures, we have worked on automated fracture reduction algorithms that are able to rearrange the fracture fragments into their optimal position and plan an efficient and minimally traumatic fracture reduction path.…”

“…We have previously described several components of a computer-assisted robotic framework for intramedullary nailing of the femur, including the successful implementation of telemanipulated 2D and 3D fracture reduction. [6][7][8][9][10] These techniques are highly accurate for simple fractures, but the effectiveness of the procedure decreases in complex fractures with multiple small fragments and without a clear connection between the main ends of the femur segments. Given that smaller fragments cannot be tracked using computer navigation, the surgeon must intuitively guide the reduction using her best guess as to where the fragments should be positioned.…”

Is a Magnetic-Manual Targeting Device an Appealing Alternative for Distal Locking of Tibial Intramedullary Nails?

“…Nevertheless, a new technique will only prevail against the free-hand technique and other targeting systems, if it is precise, reliable and easy to apply. Misplacement of distal interlocking screws can lead to iatrogenic fractures, instability of the bone-implant construct or even misalignment of the extremity; repeated drilling attempts can cause additional bony and soft tissue trauma (19). The Sanatmetal® targeting system is quite simple and easy to learn; our cadaver study revealed a mean duration of 9.6 minutes at the most for the setting of four distal screws.…”

Evidence for robots

“…Robotic systems have also been described in experimental studies to guide intramedullary nailing and assist in distal locking of interlocking femoral nail [31, 32]. …”