Augmented Reality Navigation-Guided Core Decompression for Osteonecrosis of Femoral Head

Our system can improve the success rate and the efficiency in core decompression surgery for femoral head necrosis. It also significantly reduces the intraoperative positioning time and the fluoroscope source. With VR technology, we can utilize the puncture process, reduce the difficulty of the operation, and it cause less additional damage to the patient than traditional surgical results.

The system can be extended to other orthopedic surgery involving puncture procedures. It has been used to get percutaneous endoscopic transforaminal discectomy procedure. This system is specially designed for the early osteonecrosis of the femoral head, since traditional surgery is not precise enough, and may bring more secondary damage to the patient, such as normal tissue damage or excessive radiation.

The protocol should be and the operation carefully observed to understand the principles and the steps of the system, to minimize the risk indication. And the technical points of core decompression of the femoral head will prove helpful for successful excursion. Begin by dividing the planned surgical frontal area into upper and lower levels.

This spatial information will be automatically entered into the software system. Allocate every level with 10 matching points and divide it into three equal parts with two parts having three points each, and the remaining part having four points. Ask the assistant to place the noninvasive body surface marking frame according to the points.

Once done, click on match. The system's special image for registration will be automatically super imposed on the marking frame. Move the puncture device randomly in the surgical area to detect the matching degree of virtual needle and tracking delay.

In the operating room, ask the patient to lie down in a supine position and fix the lower limb of the affected side. Prepare the surgical site with iodine and 75%alcohol. Move the C-arm fluoroscope to the side of the operating table and position the source above the hip joint.

Align the source with the depth camera and record the position of the surgical table as position one. In the AR-assisted orthopedic surgery system, click file front x-ray image and select image one. The system will automatically identify the marking frame and superimpose this image to the hip joint in the surgical video.

Using the AR display of the x-ray image and based on the real time video, plan the puncture path. Stand on the affected side for performing the procedure, hold the puncture device, and determine the best insertion angle. Mark the insertion point on the skin surface, guided by the virtual Kirschner wire and the x-ray image of the hip joint in the surgical video.

Using a Kirschner wire, pierce through the insertion point. Observe the insertion depth and angle in the video, and adjust it timely. When the virtual needle has reached the target area of necrosis, stop the puncture process and retain the screenshot as image two for subsequent puncture accuracy evaluation.

After the puncture, pull out the drill, leaving the Kirschner wires in the bone temporarily. Move the operating table to position one for the second fluoroscopy to verify the actual puncture condition of the Kirschner wire. Record the image file.

Puncture is successful when the location of the Kirschner wire meets all of the surgeon's requirements. Then, use the Lancet to cut the skin around the needle and separate every level of soft tissue until the subtrochanter bone is exposed to approximately a depth of three centimeters. Drill into the necrotic area along the Kirschner wire with a five millimeter trephine to complete the subsequent operations.

After finishing all the procedures, close the skin with three oh silk thread and cover it with sterile dressing. The surgical navigation system was applied in continuative ten hips of nine patients. With an average total positioning time of 10.1 minutes during the surgery, the mean C-arm fluoroscopies were 5.5 times.

The mean error of puncture accuracy was 1.61 millimeters. By the hips evaluated, two hips were in ARCO I stage, four hips were in ARCO IIA stage, and four in ARCO IIB stage. The mean preoperative VAS score was six, and the mean postoperative score was 3.75.

The average preoperative Harris score was 77.5, and the mean postoperative score was 85.5. No postoperative complications such as infection, hematoma, or nerve damage were found. It is also possible to combine the procedure with CT three dimensional reconstruction technology so that the puncture can be realized from a three dimensional perspective, which is our future work.

We provide an innovative idea of combining AI technology and orthopedic surgery. This idea can also be used to improve the precision of other orthopedic operations in the future.