Keys To Intraoperative Positioning For Subtalar Joint Procedures
This desired final position of the heel is a reproducible “distance” (or amount of pronation/supination) relative to both the neutral calcaneal stance position and the maximally pronated position. Therefore, as long as the examiner can determine both the neutral position and the maximally pronated position intraoperatively, the examiner can reproduce the ideal final position of the heel by measuring or accurately estimating the same amount of pronation/supination that he or she obtained preoperatively. It will be the predetermined position from the neutral position and/or from the maximally pronated position.
Ensuring Optimal Intraoperative Positioning
One may place the patient in the supine or lateral decubitus position intraoperatively. It is not necessary for the patient to be prone in order to reproduce the ideal position of the heel that the surgeon obtained during the preoperative examination. Ensure that the patient’s leg is prepped and draped to the knee in order to allow visualization of the lower leg.
First draw a line along the distal, anterior leg parallel to the longitudinal axis of the tibia. Then determine the neutral subtalar joint position by manual manipulation and palpation of the talar head. Extend the leg line onto the dorsum of the foot with the foot in its neutral position. Draw a line parallel to and in line with the mark on the distal anterior leg. In the same manner, shift the patient’s foot to a maximally pronated position of the subtalar joint and extend the leg line once again onto a corresponding mark placed on the dorsum of the foot.
The surgeon has now reproduced the same two reference points he or she obtained in the preoperative examination (i.e. the neutral subtalar position and the maximally pronated subtalar joint position). One can now easily identify the ideal subtalar joint position for fusion or arthroereisis by pronating or supinating the foot the desired amount relative to the two previous marks. The surgeon can usually mark this position with a dotted line.
This ideal position, which surgeons would determine preoperatively, should be equal to the same relative amount of heel eversion from the neutral position or heel inversion from the maximally pronated position that he or she measured during the weightbearing preoperative exam.
The surgeon can now proceed with the surgical procedure, taking care to refer back to the marks for final positioning of the foot. He or she can be assured of the proper positioning of the foot to the ground postoperatively when the final placement of the foot allows the dotted line to be a straight line extension of the leg line intraoperatively.
Subtalar joint arthrodesis and arthroereisis can be powerful surgical procedures to reduce pain and disability, and restore or improve functionality of the foot.
However, successful outcomes depend on correct and accurate intraoperative positioning of the foot. A surgeon should always perform a preoperative weightbearing exam to determine the ideal position of the heel for fusion or arthroereisis relative to the ground. Failure to take weightbearing into account can lead to frontal plane deformities and an undesirable final position of the foot.
By preoperatively determining the ideal heel position relative to the neutral position and maximally pronated position, the surgeon can accurately reproduce the proper foot position intraoperatively and ensure the best possible outcome.
Dr. Wallin is a second-year resident with the Scripps Mercy Kaiser Podiatric Residency Program at the Scripps Mercy Medical Center in San Diego.