Periodically, the drill bit should be withdrawn, cleaned and placed in front of the limb to gauge the penetration depth needed to engage the physis but avoid penetration of the joint.
The hypodermic needle helps to identify the level of the joint.
Another option involves taking of a dorsopalmar/dorsoplantar intraoperative radiographic view with the drill bit in place. If needed, the drill bit can be further advanced until it reaches a level approximately 5-8 mm short of the radiographic articular joint space.
Note: the radiographic articular joint space consists of 2 articular cartilage layers and the microscopic joint space.