Navigating the two-incision total hip arthroplasty

Minimally-invasive techniques have gained popularity over the past few years and are changing the practice of orthopedic surgery today. The objectives of minimallyinvasive total hip replacement are to minimize surgical dissection and, as a result, potentially decrease postoperative pain, shorten hospital stay, and accelerate recovery [1-4]. However, it is critical that the present long term success, reliability and safety of total hip arthroplasty is maintained. The two-incision total hip arthroplasty [5, 6] which takes advantage of a tissue-sparing approach offers the potential for a marked decrease in morbidity with a dramatically more rapid recovery. Computer-assisted surgery offers the potential of more accurate component orientation without complete visualization of the bony landmarks [7]. Thus, navigation is a natural complement to accurately performing a truly minimally- invasive surgical procedure. Navigation has been shown to increase the accuracy of component positioning, while decreasing variability of component placement [8, 9]. This technology provides real time measurements of acetabular position such as cup abduction angle and anteversion, which should result in a significant reduction in technical errors and complications related to mal-positioning of the components [10]. Navigation also allows the surgeon to accurately measure leg-lengths and hip offset intra-operatively. It is important to remember that leglength discrepancy and patient dissatisfaction represent one of the most common reasons for litigation against the orthopedic community [11], and hopefully with navigation, this risk can be minimized or eliminated. In addition, navigation may be used as a teaching tool in the early stages of surgeon education so as to limit the admittedly steep learning curve of complex minimally-invasive surgical procedures such as two-incision total hip arthroplasty. Image-guided surgery utilizes high-speed computers coupled with advanced tracking devices to enable more accurate and precise surgery [12]. Navigation technology can be loosely classified as image-guided or imageless technology. Image guided navigation includes CT based, fluoroscopic based, and ultrasonic based technology in which there has been some early work. Although CTguided imaging is accurate and reliable, it is expensive and requires significant patient registration and preoperative planning. Currently it is less popular for joint arthroplasty applications at this time than either fluoroscopically- based or imageless systems. Fluoroscopy is available in any operating room and the vast majority of orthopedic surgeons are familiar with the use of image intensification. In addition, fluoroscopic systems allow intra-operative planning and are relatively inexpensive with the exception of technician time. Fluoroscopy based systems provide the surgeon with a real-time instrument tracking in a multiplanar setting, and provides the surgeon with data in both the AP and lateral planes. Fluoroscopic based navigation is an ideal match for two-incision incision hip arthroplasty because the two-incision total hip arthroplasty is a procedure that currently requires five to 30 seconds of fluoroscopy, depending on the individual surgeon's preference and experience. By utilizing the fluoroscopy-based navigation system, the need for live intra-operative fluoroscopy is eliminated. With only three static fluoroscopic images, the surgeon can plan, visualize intra-operatively and gain valuable real-time information specific to each patient. The navigation system can aid the surgeon in identifying critical points such as proper incision location, neck osteotomy location and angle, cup abduction and anteversion, femoral component version and seating, as well as leg length and offset measurements. By using these simple few static images taken pre-operatively, xray exposure to the surgeon, operating room staff, and patient is minimized.