Movement of the Sacroiliac (SI) Joint, Comparing Conventional RSA With the Sectra Implant Movement Analysis
Movement of the Sacroiliac (SI) Joint, Comparing Conventional RSA With the Sectra Implant Movement Analysis
Movement of the Sacroiliac (SI) Joint, comparing conventional RSA with the Sectra Implant
 Movement analysis using a low dose CT for high accuracy measurement
Abstract Background: Radiostereometric analysis (RSA) is a high precision in vivo measuring
 method and regarded as the gold standard for motion analysis. RSA has been around for over 40
 years and its accuracy is properly evaluated. The CT technics have evolved and now low dose
 CT scans can reproduce 3-D models of bone and joints. The Sectra Implant Movement analysis
 (IMA) is a new method using a low dose CT for high accuracy measurement. There is no study
 evaluating the precision and accuracy of the new CT based method.The investigator want to
 compare the accuracy of the two methods.

 Method/design: The RSA method will be tested in patients that already have tantalum markers
 inserted around the SI joints from earlier studies conducted at Ullevål University Hospital.
 There are 2-6 patients in the age of 40-50 years available for RSA analysis with and without
 provocation of the SI joints. Some are fused in one SI joint after insertion of the tantalum
 markers, but the contralateral joint can then be used for the analysis. At the same time,the
 investigator will perform low dose CT with and without provocation of the SI joints. The
 results of the analysis will be compared.

 Discussion: The conventional RSA is an invasive method using tantalum markers inserted in to
 bone. If the CT method has the same accuracy, then the tantalum markers will become obsolete
 and future studies can easily be performed using non-invasive low dose CT scans.

 Keywords: RSA, CT method, low dose CT, IS joint, movement

 Introduction:

 Because of the high accuracy and precision, radiostereometric analysis (RSA), has become a
 well- established method for three-dimensional (3-D) measurements of micro motion in joints.
 The implantation of tantalum markers is invasive, but no reports of patient injuries are
 reported. The markers might be inserted through the approach used during a surgical
 intervention or in an extra stab incisions in the skin to get the markers to the necessary
 position in the bony structures. The placements of the markers are of outmost importance to
 achieve good quality measurements. At least three no collinear markers in each segment and a
 good distance and distribution in all three axes (X, Z, Y) is essential for a good 3-D
 configuration.

 The CT techniques have evolved and now low dose CT scans can reproduce 3-D models of bone and
 joints. The Sectra Implant movement analysis (IMA) is a non-invasive method using a low dose
 CT scan. No tantalum markers are needed and joint provocation can easily be conducted in the
 CT. The CT scan is then sent to the Sectra AB for analysis.

 Method:

 Patients and methods:

 The RSA method will be tested in patients that already have tantalum markers inserted around
 the SI joints from earlier studies , approximately five years ago, conducted at Ullevål
 University Hospital. These are patients with long lasting severe sacroiliac joint pain. There
 are six patients in the age of 40-50 years available for RSA analysis with and without
 provocation of the SI joints, at the same time the investigator will perform low dose CT with
 and without provocation of the SI joints. For the non-provocation, the patient will be in a
 supine-position. The provocation x-ray/low dose CT will be performed; 1: anterior straight
 leg raise 2: One side figure of four position, both with 1kg of load. Some are fused in one
 SI joint after insertion of the tantalum markers, but the contralateral joint can then be
 used for the analysis. The investigators will also measure eventual movement in the fused
 joint and the symphysis (if tantalum markers present). The Center for Implant and
 Radiostereometric Research Oslo has extensive experience with RSA and established state of
 the art measuring method of movement in the SI joint. They will perform the RSA measurements.
 The CT scan is send to the Sectra AB for analysis.

 Statistical analysis:

 Null hypothesis (H0): There is no difference in the accuracy Alternate Hypothesis (H1): There
 is a difference in the accuracy Continuous variables will be described with mean and standard
 deviation\, and the normality of the data will be checked using the histograms, QQ-plots and
 the Kolmogorov-Smirnov-Test of normality. The differences of motion will also be tested for
 normality. The paired sample T-test will be used to detect possible significance in the
 difference between the two groups. Non-parametric tests are used if the assumption of
 normality does not hold. All analysis will be conducted using commercially available software
 (SPSS version 24, IBM Inc.) and the level of significance is set to p<0.05 in a two-sided
 test.

 Participants Project leader and responsible institution Stephan M. Röhrl, PhD, MD, Ass.
 Professor, Head of Center for Implant and Radiostereometric Research Oslo, President of Knee
 and Hip Register, Oslo University Hospital, Oslo, Norway.

 PhD candidate Vinjar Myklevoll, MD, Haukeland University Hospital, Bergen. Collaborating
 partner Thomas Kibsgård, Ass. Professor, PhD, MD, President Pelvic Girdle Pain Society, Head
 of Department Rikshospitalet, Oslo, OUS.
Inclusion Criteria:

 -  The RSA method will be tested in patients that already have tantalum markers inserted
 around the SI joints from earlier studies, approximately five years ago, conducted at
 Ullevål University Hospital.

 Exclusion Criteria:

 -  The patients that can not perfome the provocation images of the SI joints.

 -  Pregnancy

 -  Not able to or do not want to participate