Reliability of the pelvis and femur anatomical landmarks and geometry with the EOS system before and after total hip arthroplasty

Abstract

Bi-plane X-ray provides 3D measurements of the lower limb based on the identification of anatomical landmarks in sagittal and frontal X-rays. In clinical practice, such measurements involve multiple operators and sessions. This study aimed at evaluating the reliability of anatomical landmarks identification and geometric parameters of the pelvis and femur measured with bi-plane X-rays before and after total hip arthroplasty (THA). Twenty-eight patients undergoing primary THA were selected retrospectively. Two operators performed three reconstructions for each patient before and after THA. Intraclass correlation (ICC) and smallest detectable change (SDC) were computed for intra-operator, inter-operator, and test–retest conditions. Most anatomical landmark positions had good to excellent SDC (< 5 mm) apart from the centre of the sacral slope, greater trochanter, and anterior superior iliac spines (up to 7.1, 16.9, and 21.5 mm respectively). Geometric parameters had moderate to excellent SDC, apart from femoral and stem torsion, pelvic incidence, and APP inclination with poor SDC (9–12°). The sagittal view had significantly higher measurement errors than the frontal view. Test–retest and inter-operator conditions had no significant differences suggesting a low influence of patient posture. Osteoarthritis and the presence of implants did not seem to influence reliability and measurement error. This study could be used as a reference when assessing lower limb structure with bi-plane X-rays.

Definition and reliability of 3D acetabular and global offset measurements from bi-plane X-rays

“…The combination of the anatomical coordinate system defined by the acetabula and centre of the sacral slope (A2) with the medio-lateral axis defined by the acetabula (ML1) reached the same reliability, despite slightly higher measurement error, as the femoral offset approved for clinical use for both acetabular and global offsets. Indeed, the femoral offset presented ICCs between 0.853 and 0.916 and a mean SDC of 4.8 mm with the same dataset 3 while, with the selected definition, the ICC were between 0.858 and 0.953 with mean SDCs of 6.3 mm and 6.2 mm for the acetabular and global offsets, respectively.…”

“…Two operators performed three reconstructions at each session for each patient using a research version of the dedicated sterEOS software (EOS imaging, Paris, France). Details of the protocol and statistical method are outlined in a previous study 3 and data is shared on the online repository Yareta 4 . This study was approved by the local ethics committee (CCER Geneva, Switzerland).…”

“…Between the pre- and post-THA bi-plane X-rays, the operated acetabulum is the only affected landmark so the others can be used. However, the antero-superior iliac spines position have poor reliability 3 , thus the anterior pelvic plane will not be used as a plane of reference. The available landmarks with good reliability therefore include the centre of the sacral slope, the pubic symphysis, and the contralateral acetabulum.…”

“…The ICCs were classified as follow: poor (< 0.5), moderate (0.5–0.75), good (0.75–0.9), and excellent (> 0.9) 10 . The SDCs were classified as follow: poor (> 10 mm/°), moderate (5 to 10 mm/°), good (3 to 5 mm/°), and excellent (< 3 mm/°) 3 .…”

“…The target for an acceptable measurement was to achieve similar or better ICC and SDC as the femoral offset approved for clinical use. These reliability outcomes of the femoral offset were evaluated with the same database in a previous study 3 and resulted in a good to excellent ICC (0.853 to 0.916) and an average SDC of 4.8 mm (4.3–5.7 mm).…”