**4. Computer navigation-assisted arthroscopic osteochondroplasty**

The planning data are transferred directly to a CT-based navigation system (Orthomap 3D; Stryker, Kalamazoo, MI). The technical details of computer navigation-assisted arthroscopic surgery have been published previously [7]. The most important and challenging aspect is point-to-point matching under fluoroscopic guidance (**Figure 5**). After matching five or six landmark points, surface matching of 40–50 points is performed. It is important to add several distal femur points to ensure accurate registration, and to add points from as large an area as possible. The final mean deviation error after registration must be <1 mm. After registration, an instrument tracker device is attached to the abrader burr. The tracker device must be fixed securely to the abrader burr, as any loosening of the device will result in variance in the navigation. Computer navigation-assisted osteochondroplasty is then initiated, during which time fluoroscopic guidance is not required.

The most notable advantage of navigation assistance is that it provides information on the actual depth and range of the resected area in real-time, seen as the tip of abrader burr (**Figure 6**). In addition, the planned resection area can also be seen as a red zone. It is, therefore, possible to accurately resect a cam lesion, without deficiency or excess. Using a pointer device, the resected region can be reliably

**57**

**Figure 6.**

*burr located in the planned resection area (red area).*

**Figure 5.**

*(arrow) (B).*

*The Practice of Computer-Assisted Planning and Navigation for Hip Arthroscopy*

*Point matching under fluoroscopic guidance (A) and surface matching (B) during navigation system registration. Point matching is performed under fluoroscopic guidance for 5–6 landmark points (A). Thereafter, surface matching is performed without fluoroscopic guidance for 40–50 points, including on the distal femur* 

verified (**Figure 7**). Occasionally, it may be necessary to use pincer resection. In these cases, it is also possible to plan the pincer resection and to use navigation assistance once pelvic registration has been completed (**Figure 8**). Particularly in pincer resection, it is difficult to identify the acetabular rim three-dimensionally by fluoroscopy, while navigation assistance can clearly identify the actual point on acetabula rim. Thus, the navigation assistance may contribute to the reduction of operative time during lower limb traction. This is important in terms of reducing the complication such as neurological disturbance caused by perineal post.

*Navigation assistance during osteochondroplasty. The center of the cross (arrow) indicates the tip of the abrader* 

*DOI: http://dx.doi.org/10.5772/intechopen.89502*

*The Practice of Computer-Assisted Planning and Navigation for Hip Arthroscopy DOI: http://dx.doi.org/10.5772/intechopen.89502*

#### **Figure 5.**

*Essentials in Hip and Ankle*

**Figure 4.**

*developmental dysplasia of the hip.*

cam morphology [6], demonstrating that the improvement in the range of motion is dependent on the extent of bone resection. An interesting clinical implication in this study is that borderline dysplasia with cam morphology showed the most significant improvement by virtual osteochondroplasty. Therefore, even in cases of borderline dysplasia, the co-existence of cam morphology should be considered.

*Improvement in the internal rotation angle after each type of resection. The mean improvement in the internal rotation angle in the DDH with cam group after slight resection was significantly greater than that in the DDH without cam group (P = 0.046), as was that after sufficient resection (P = 0.002). The improvement in the cam-FAI group was significantly greater than that in the DDH without cam group (P = 0.043). DDH:* 

**4. Computer navigation-assisted arthroscopic osteochondroplasty**

then initiated, during which time fluoroscopic guidance is not required.

The most notable advantage of navigation assistance is that it provides information on the actual depth and range of the resected area in real-time, seen as the tip of abrader burr (**Figure 6**). In addition, the planned resection area can also be seen as a red zone. It is, therefore, possible to accurately resect a cam lesion, without deficiency or excess. Using a pointer device, the resected region can be reliably

The planning data are transferred directly to a CT-based navigation system (Orthomap 3D; Stryker, Kalamazoo, MI). The technical details of computer navigation-assisted arthroscopic surgery have been published previously [7]. The most important and challenging aspect is point-to-point matching under fluoroscopic guidance (**Figure 5**). After matching five or six landmark points, surface matching of 40–50 points is performed. It is important to add several distal femur points to ensure accurate registration, and to add points from as large an area as possible. The final mean deviation error after registration must be <1 mm. After registration, an instrument tracker device is attached to the abrader burr. The tracker device must be fixed securely to the abrader burr, as any loosening of the device will result in variance in the navigation. Computer navigation-assisted osteochondroplasty is

**56**

*Point matching under fluoroscopic guidance (A) and surface matching (B) during navigation system registration. Point matching is performed under fluoroscopic guidance for 5–6 landmark points (A). Thereafter, surface matching is performed without fluoroscopic guidance for 40–50 points, including on the distal femur (arrow) (B).*

#### **Figure 6.**

*Navigation assistance during osteochondroplasty. The center of the cross (arrow) indicates the tip of the abrader burr located in the planned resection area (red area).*

verified (**Figure 7**). Occasionally, it may be necessary to use pincer resection. In these cases, it is also possible to plan the pincer resection and to use navigation assistance once pelvic registration has been completed (**Figure 8**). Particularly in pincer resection, it is difficult to identify the acetabular rim three-dimensionally by fluoroscopy, while navigation assistance can clearly identify the actual point on acetabula rim. Thus, the navigation assistance may contribute to the reduction of operative time during lower limb traction. This is important in terms of reducing the complication such as neurological disturbance caused by perineal post.

#### **Figure 7.**

*Verification of resected area and depth using a pointer device. The pointer device indicates the distal margin of the resected area from the anterolateral portal view with the pointer via the mid-anterior portal (A), which is also identified by the computer navigation monitor (B). The lateral margin of the resected area is clearly verified from the mid-anterior portal view with the pointer via the anterolateral portal (C, D).*

#### **Figure 8.**

*Navigation assistance for pincer resection. The purple colored area shows the planned resection for a pincer lesion. The center of the cross indicates the tip of the abrader burr.*
