Michael Swank

Role of navigation in total hip arthroplasty.

Current uses of computed tomography-based and imageless navigation systems for total hip arthroplasty include proper placement of the acetabular component, measurement of limb-length changes, enablement of minimally invasive surgery, and proper placement of components for hip resurfacing procedures. This article provides an overview of the rationale for computer-assisted surgery in total hip arthroplasty and hip resurfacing. The experience of the senior author (M.L.S.) with computer-assisted surgery for hip arthroplasty has demonstrated improved position of the acetabular component as compared with the position attainable with use of mechanical instruments, maintenance of appropriate position of the acetabular component during minimally invasive surgery, and appropriate positioning of the femoral and acetabular components during the learning curve for hip resurfacing procedures.

Imageless navigation in hip resurfacing: avoiding component malposition during the surgeon learning curve.

BACKGROUND Studies suggest that hip arthroplasty procedures performed in specialty hospitals or by physicians in practices with a high surgical volume are associated with a decreased rate of adverse outcomes related to component malpositioning. Little is known, however, about the influence of imageless computer navigation systems on the procedural experience of the surgeon and the subsequent alignment of implants in the setting of hip resurfacing arthroplasty. METHODS Seventy-one consecutive hip resurfacing arthroplasties in which the components were placed with use of computer-assisted navigation were reviewed retrospectively. Intraoperative femoral and acetabular component parameters were compared with postoperative radiographic alignment values. Within this single surgeon series, operative time, intraoperative cup inclination and femoral stem-shaft angles, and postoperative cup inclination and femoral stem-shaft angles were measured and compared over the course of three discrete, sequential operative time periods. Patient demographic data and surgical parameters, including blood loss, surgical approach, and anesthesia time, were recorded. RESULTS No significant difference was seen between the intraoperative and postoperative cup inclination angles. A significant difference was noted between the intraoperative and postoperative femoral stem-shaft angles; however, the mean angles in all groups had a valgus orientation when compared with the mean native neck angles. Over three sequential operative time periods, computer-assisted navigation produced consistent values with regard to intraoperative cup inclination (43 degrees , 44 degrees , and 40 degrees ) and postoperative radiographic alignment of the cup (46 degrees , 44 degrees , and 43 degrees ) and femoral stem (148 degrees , 147 degrees , and 144 degrees ), despite different levels of surgeon experience. Operative times significantly decreased with surgeon experience, showing the largest decrease after the first sequence interval (110, ninety-eight, and ninety-five minutes, respectively). There was a significant difference with evolving surgeon experience concerning intraoperative stem placement (144 degrees , 142 degrees , and 138 degrees , respectively) despite the mean values remaining well-clustered. No femoral notching occurred throughout the series. CONCLUSIONS Computer-assisted navigation is a dependable and accurate method of positioning hip resurfacing components during arthroplasty, as measured by cup inclination, and a reliable technique for valgus stem placement and avoidance of notching. Furthermore, computer navigation allows for consistency of component alignment independent of procedural experience.

Low Incidence of Postoperative Complications Due to Pin Placement in Computer-Navigated Total Knee Arthroplasty

Computer-navigated joint arthroplasty surgery using optical tracking systems requires arrays fixated to bone via pins. Reports of fractures at pin sites have raised concern about safety. We reviewed the postoperative complications occurring in a single-surgeon series of 984 consecutive primary total knee arthroplasties. All pins were placed unicortically and connected by a dual pin array. Femoral pins were placed into the medial epicondyle, and tibial pins were placed in the shaft 10 cm inferior to the joint line. There were no fractures. Seventeen (1.7%) patients had minor pin-related complications. Twelve patients had a superficial infection around the tibial pin sites, which resolved with antibiotics. None of the infections required readmission or reoperation. We believe pin placement to be safe and effective with proper technique.

Variability in Distal Femoral Anatomy in Patients Undergoing Total Knee Arthroplasty: Measurements on 13,546 Computed Tomography Scans

Proper mechanical and rotational alignment plays an important role in achieving the success of the total knee arthroplasty (TKA). The purpose of the present study was to retrospectively determine with computed tomography (CT) the distal femoral valgus angle (DFVA) and femoral rotation angle (FRA). Our cohort included 13,546 CT scans of patients undergoing TKA. The average DFVA was 5.7 ± 2.3° (range from 1 to -16°) with 13.8% of patients identified as outliers. The distal FRA angle average was 3.3 ± 1.5° (range from -3 to 11°) with 2.8% of patients identified as outliers. These data can be useful in making orthopedic surgeons aware of the variability of femoral anatomy. Using the same cutting angle may lead to malposition of the femoral component.

Section VIII: Novel approaches to imaging and tracking of hip topology.

While magnetic resonance imaging remains a standard tool in the radiologic diagnosis of disorders about the hip joint, challenges remain with regard to assessment of cartilage damage secondary to the spherical contour of the joint and relative thinness of the articular cartilage. Despite these difficulties, magnetic resonance arthrography is the recommended study for the assessment of chondral and labral pathology of the hip. Magnetic resonance imaging technology will benefit from increased field strength, improved coils, and the development of fast isotropic high-resolution sequences. These improvements will allow detection of subtle cartilage abnormalities. Additionally, …