Array pin placement in robotic-assisted total hip arthroplasty: Optimal trajectory to avoid neurovascular injury

Background

Array pin placement into the pelvis is a necessary step for robotic-assisted total hip arthroplasty (RATHA). Despite the increase in RATHA being performed, there is limited literature investigating safe zones and pin trajectory to avoid neurovascular injury.

Methods

This study utilized lower extremity magnetic resonance images of nine patients. The trajectory of three array pins placed at caudal angles of 35, 45, and 55 were recreated, and each pin was divided into four equidistant zones. For each pin, the distance was determined from each zone to nearby neurovascular structures: lateral femoral cutaneous nerve (LFCN), internal iliac artery (IIA), superior gluteal artery (SGA), superior gluteal nerve (SGN).

Results

Pin 3 placed at a caudal angle of 35° was the furthest distance away from the IIA compared to pins 1 and 2 (p = 0.005). Pin 1 placed at a caudal angle of 55° was the furthest distance away from the SGA (p = 0.009) and SGN (p = 0.012) and was associated with the most distal portion of the pin being in bone compared to other caudal angles (p = 0.002). There were no statistically significant differences in distances from pins to neurovascular structures based on gender.

Conclusion

Pin placement is a required step for RATHA, and the results of this study show that caudal angle trajectory is important for placement of specific array pins to ensure the distal aspect is in bone as well as far away from important neurovascular structures to avoid injury.