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Surgery on the anterior cruciate ligament (ACL) in the knee is a complex procedure that demands precision and control. In order to repair or replace an ACL, the surgeon removes any remnants of the natural ACL and then attaches a replacement ligament (a graft usually taken from elsewhere in the patient’s body) to the tibia and femur. The positioning of the grafted ligament is critical, as it should accurately mimic that of the natural ACL.

To help make this precise surgery easier, orthopedic surgeon Dr. Dana Piasecki designed a two-part system consisting of a flexible pin (drill) and a guide for positioning the pin inside the knee. This guide is the key to a less invasive surgery, as it allows the surgeon to move and hold the pin without opening the knee or contorting it to place the new ligament.

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Though 95 percent of the guide is made up of a simple shaft, the end of the device is the critical part. The shape of the neck is intended to follow the ligament’s normal path to ensure that it is placed at the right location and angle, and the tip is precisely sized to hold the 2.2-mm pin.

To machine this guide tool from a block would have required many setups with multiple angles and undercuts. Instead, Dr. Piasecki and his business partner Jim Duncan of DanaMed worked with Stratasys Direct Manufacturing to have the device manufactured with direct metal laser sintering (DMLS). This powder-bed additive process allowed the device to be built at the correct angle and build orientation to accommodate the critical features, without any machining necessary. Producing the guide additively also saved on material and reduced its overall cost, while enabling ongoing design changes.

Learn more about this device—including its design, manufacture and postprocessing— from Additive Manufacturing magazine.