CAS helps to improve the limb alignment of the TKA. Furthermore, it also seems to diminish the presence of systemic emboli  and to lessen the risk of transfusion [4, 5]. Other authors have found that navigation-assisted patients showed statistically significant better results in the flexion range, HSS score, and WOMAC scores, when compared with conventional surgery patients . A recent meta-analysis confirms that CAS improves the leg axis, although the numbers used in many of these studies were far too small to discriminate any other results.
The disadvantages related to the CAS are a longer surgery time and the possibility of complications and adverse effects due to tracker fixing. During the initial use of the navigation system, the placement of the trackers and the performance of the anatomic survey added approximately 15 to 20 minutes. Once the surgeon became familiar with these methods, the placement of the trackers and the anatomic survey added approximately 10–15 minutes [5, 7].
There were a few complications related either to the computer software or the tracker pins inserted in the bones . The placement of the pins and screws in the bone is inevitably associated with some risk. Using pins for tracker fixation creates potential damage issues to neurovascular structures and may cause the breakage of the devices inside the bone, although we did not experience any of these problems in our study. Another issue related to the pins required for fixation of the trackers was the use of a pin in the iliac crest with a separately prepared and draped area. Although there had been no known problems with this technique, it has been abandoned, since it is no longer necessary for the procedure thanks to the updated software. When the iliac crest tracker was used, Sikorski and Blythe  found a 6% of injuries to the lateral cutaneous nerve of the thigh with some persistent numbness, three pin-tract infections (3%), and two periprosthetic fractures, both of which occurred to elderly, osteoporotic patients and after major falls. One was through the site of the screw (the teeth produced an 'apple-corer' effect and a fracture of the shaft of the femur was associated with its use) and the other through a medial femoral condyle well away from the site of the screw. These authors also report a 4% of pin-tract infections in the tibia. Specific navigation complications were observed in two cases of the study undergone by Jenny et al : one broken pelvic drill and one femoral screw forgotten; the authors, however, did not consider that these complications had any significant adverse effects. Three (5%) complications were related to the navigation process in another study ; in these three cases, rigid bodies were contaminated with blood, which led to tracking problems with the navigation system's camera. After cleaning the rigid bodies, the operations could be finished without any further problems.
A potential source of error can be a poor fixation of the locator to the bone, especially in the case of porotic bone. The accuracy of the system is totally dependent on the stability of the beacon or reflector arrays. Any movement altered the results. We consider that the tracker was firm enough when no movement was possible with the strength of one's hands although we admit that it is a subjective finding.
Throughout the years, bone fixation systems have been modified to allow for a more secure fixation. The new OrthoLock system allows for a faster fixation, a percutaneous placement and a more versatile positioning of the femoral emitters.