Experimental assessment of precision and accuracy of radiostereometric analysis for the determination of polyethylene wear in a total hip replacement model

Background Different techniques have been used to quantify the movement of sacroiliac (SI) joints. These include radiostereometric analysis (RSA), but the accuracy and precision of this method have not been properly evaluated and it is unclear how many markers are required and where they should be placed to achieve proper accuracy and precision. Purpose The purpose of this study was to test accuracy and precision of RSA, applied to the SI joint, in a phantom model and in patients. Methods We used a plastic phantom attached to a micrometer to obtain a true value of the movement of the SI joint and compared this value with the measured value obtained by RSA; the difference represented the accuracy. The precision of the system was measured by double examination in the phantom and in six patients, and was expressed by a limit of significance (LOS). We analyzed different marker distributions to find optimal marker placement and number of markers needed. Results The accuracy was high and we identified no systematic errors. The precision of the phantom was high with a LOS less than 0.25°and 0.16 mm for all directions, and in patients, the precision was less than 0.71°for rotations and 0.47 mm translations. No markers were needed in the pubic symphysis to obtain good precision. Conclusions The accuracy and precision are high when RSA is used to measure movement in the SI joint and support the use of RSA in research of SI joint motion.

Section: Discussionmentioning

confidence: 99%

Precision and Accuracy Measurement of Radiostereometric Analysis Applied to Movement of the Sacroiliac Joint

Kibsgård

Røise

Stuge

et al. 2012

“…Ebramzadeh et al showed that the PolyWare method has a tendency to overestimate the amount of wear by 0.18 mm [10]. Although RSA is an extremely precise method for wear analysis [4,19], its use has been limited by its expense, its requirement for prospective assessment, and the expertise required for analysis [23].…”

Section: Introductionmentioning

confidence: 99%

Wear of a 5 Megarad Cross-linked Polyethylene Liner: A 6-year RSA Study

Callary

Campbell

Mercer

et al. 2013

Background One cross-linked polyethylene (XLPE) liner is manufactured using a lower dose of radiation, 5 Mrad, which may result in less cross-linking. The reported in vivo wear rate of this XLPE liner in patients undergoing THA has varied, and has included some patients in each reported cohort who had greater than 0.1 mm/year of wear, which is an historical threshold for osteolysis. Previous studies have measured wear on plain radiographs, an approach that has limited sensitivity.Questions/purposes We therefore measured the amount and direction of wear at 6 years using Radiostereometric analysis (RSA) in patients who had THAs that included a cross-linked polyethylene liner manufactured using 5 Mrad radiation. Methods We prospectively reviewed wear in 30 patients who underwent primary THAs with the same design of cross-linked acetabular liner and a 28-mm articulation. Tantalum markers were inserted during surgery and all patients had RSA radiographic examinations at 1 week, 6 months, 1, 2, and 6 years postoperatively. Results The mean proximal, two-dimensional (2-D) and three-dimensional (3-D) wear rates calculated between 1 year and 6 years were 0.014, 0.014, and 0.018 mm/per year, respectively. The direction of the head penetration recorded between 1 week and 6 years was in a proximal direction for all patients, proximolateral for 16 of 24 patients, and proximomedial for eight of 24 patients. Conclusions The proximal, 2-D and 3-D wear of a XLPE liner produced using 5 Mrad of radiation was low but measurable by RSA after 6 years. No patients had proximal 2-D or 3-D wear rates exceeding 0.1 mm/year. Further followup is needed to evaluate the effect of XLPE wear particles on the development of long-term osteolysis.

“…An important distinction should be drawn between precision and accuracy. While precision refers to agreement between repeated measurements, accuracy refers to agreement between measurements and a known true standard [3]. Accuracy of a CAS navigation system can be appropriately evaluated in laboratory settings; clinical trials are usually precision studies [13].…”

Section: Discussionmentioning

confidence: 99%

Accuracy of Computer-assisted Navigation for Femoral Head Resurfacing Decreases in Hips with Abnormal Anatomy

Pitto

Malak

Anderson

2009

Computer-assisted navigation systems for hip resurfacing arthroplasty are designed to minimize the chance of implant malposition. However, there is little evidence computer navigation is useful in the presence of anatomical deformity. We therefore determined the accuracy of an image-free resurfacing hip arthroplasty navigation system in the presence of a pistol grip deformity of the head and femoral neck junction and of a slipped upper femoral epiphysis deformity. We constructed an artificial phantom leg from machined aluminum with a simulated hip and knee. The frontal and lateral plane implant-shaft angles for the guide wire of the femoral component reamer were calculated with the computer navigation system and with an electronic caliper combined with micro-CT. There was a consistent disagreement between the navigation system and our measurement system in both the frontal plane and lateral plane with the pistol grip deformity. We found close agreement only for the frontal plane angle calculation in the presence of the slipped upper femoral epiphysis deformity, but calculation of femoral head size was inaccurate. The use of image-free navigation for the positioning of the femoral component appears questionable in these settings.