Figures & data
Table I. Patient demographics
Figure 1. The specially developed burr attached to the navigation probe in order to monitor its location within the tumor cavity.
Figure 2. Articular involvement was evaluated by measuring subchondral bone thickness on the pre- and post-operative CT images. A representative case of punctured articular cartilage during burring is shown (case No. 4). The thickness of the subchondral bone between the tumor (or cement) and the outer cortex was measured via pre- and post-operative three-plane CT images. The distance between the two arrows indicates the subchondral bone thickness for each section of the matched CT images. On pre-operative sagittal and coronal images, the subchondral bone was extremely thin like paper (less than 1 mm) (B and C). This thin subchondral bone was punctured during surgery, and bone cement invaded to approximately 1 mm beyond the articular surface (E and F).
Figure 3. Representative pre- and post-operative CT scans and fusion images. All axial and coronal pre- and post-operative images were matched using a program of the Stryker Navigation System (iNtellect Navigation System version 1.0). Pre-operative images were converted to a green color, and post-operative images were red. The two images were then merged to compare the curetted margins of the benign bone tumors.
Figure 4. An accessory cavity over a sclerotic wall was successfully treated using the navigation system. Pre-operative CT images (A to C) showed that the accessory tumor cavity was located medial to the main cavity over the sclerotic wall. In post-operative CT images (D to F), not only the accessory cavity but also the main cavity were completely filled with bone cement. We could easily localize the accessory cavity in three dimensions using the specially designed burr equipped with a navigation probe (G).
Figure 5. A 21-year-old man presented at our outpatient clinic with vague knee pain. A chondroblastoma was detected in the medial femoral condyle close to the articular cartilage on pre-operative CT and MRI coronal images (A and B). The articular cartilage (arrow) was intact on the pre-operative MRI image (B). Following navigation-guided curettage, the tumor was removed and the cavity filled with cement (C). The articular cartilage (arrow) was intact after surgery (D).
Figure 6. Subchondral bone thickness was measured on pre- and post-operative CT images as shown in . The results for axial (A), sagittal (B), and coronal (C) CT image sections for case No. 1 are shown separately. All three-plane (axial, sagittal, and coronal) images were measured and graphed. Each thickness value was depicted on the graph according to the serial section number of the CT image. The horizontal axis represents consecutive section numbers of the CT image, and the vertical axis is the thickness of the subchondral bone (mm) as measured in . The gray shaded area indicates a subchondral thickness of less than 0 mm. The dashed red horizontal line indicates the thickest pre-operative subchondral bone when the articular joint was punctured.
Figure 7. All five of the punctured articular cases are summarized in three graphs (one each for axial [A], sagittal [B], and coronal [C] images). The post-operative thickness of the subchondral bone is plotted against the pre-operative thickness. When all the measured values of the five cases were analyzed together, a strong positive correlation was observed between the pre- and post-operative subchondral bone thicknesses. We also found that a pre-operative subchondral bone thickness of 3 mm was the upper limit for puncture of the articular cartilage. The gray shaded area indicates a post-operative subchondral thickness of less than 0 mm. The dotted straight line indicates points where the subchondral thickness on pre- and post-operative CT images is identical. The black vertical line indicates the thickest pre-operative subchondral bone in which the articular joint was punctured after curettage.
![Figure 7. All five of the punctured articular cases are summarized in three graphs (one each for axial [A], sagittal [B], and coronal [C] images). The post-operative thickness of the subchondral bone is plotted against the pre-operative thickness. When all the measured values of the five cases were analyzed together, a strong positive correlation was observed between the pre- and post-operative subchondral bone thicknesses. We also found that a pre-operative subchondral bone thickness of 3 mm was the upper limit for puncture of the articular cartilage. The gray shaded area indicates a post-operative subchondral thickness of less than 0 mm. The dotted straight line indicates points where the subchondral thickness on pre- and post-operative CT images is identical. The black vertical line indicates the thickest pre-operative subchondral bone in which the articular joint was punctured after curettage.](/cms/asset/acb2de63-eb75-41a8-bef3-a93d64f2911b/icsu_a_655780_f0007_b.gif)
Figure 8. A representative case of benign fibrous histiocytoma on the proximal tibia. The tumor was shown to be located very close to the popliteal artery and tibial nerve on preoperative MRI (A and B). There was no neurovascular compromise after navigation-guided curettage, and post-operative MRI showed successful integration of the allogenic bone graft (C and D). Since we used a specially designed burr attached to the navigation apparatus, it was possible to monitor the burr tip in real time, thereby avoiding damage to the neurovascular bundle (E).
Table II. Clinical results