S U M M A R Y Background In clinical routine, preoperative radiographic assessment of lower extremity geometry relies on conventional X-rays. However, the plane goniometric measuring has several limitations in accurately locating anatomical landmarks. The purpose of this study is to propose a fast and accurate 3D-reconstruction-method based on biplanar X-rays with clinical measurements assessment in standing position. Methods 50 candidates for HTO or DFO with deformity of the lower extremities were included in this study. Biplanar X-rays were performed using the EOS imaging system in conventional double-stance full weight-bearing position (DS) and shifted-foot standing position (SF). The results of hip-knee-ankle angle (HKAA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) were evaluated by either 2D manual goniometer (MG) based on X-ray in DS standing position or 3D-reconstruction goniometer based on X-rays in SF standing position. Results For the reproducibility study, MG and EOS goniometer were both reliable in repeated measures of HKAA, LDFA, and MPTA, with average concordance correlation coefficients (CCCs) all above 0.910. The agreements between MG and EOS measurements were high for HKAA and LDFA with CCCs all above 0.90, while the agreement was low for MPTA with CCC below 0.75. Further linear regression model analysis also revealed a significant correlation between MG and EOS measurements for HKAA (all R 2 ≥ 0.93) and LDFA (all R 2 ≥ 0.90), but not for MPTA (all R 2 ≤ 0.522). Conclusion In comparison with the traditional 2D manual goniometer, EOS 3D reconstruction based goniometric measuring could provide equivalent results of HKAA and LDFA, and potentially a more accurate result of MPTA. These findings suggest that EOS 3D reconstruction based goniometric measuring is suitable for preoperative evaluation and planning for HTO/DFO. However, future improvements of the 3D reconstruction method are needed for better detection of the femoral condyles and tibial plates without the requirement of shifted-foot standing position. The translational potential of this article EOS 3D reconstruction based goniometric measuring could provide equivalent or even more accurate results of HKAA, LDFA, and MPTA, in comparison with the traditional 2D manual goniometer, making it suitable for preoperative evaluation and planning for HTO/DFO.

Background: Accurate preoperative planning for total hip arthroplasty (THA) relies on conventional anteroposterior radiographs. The difficulty of determining the magnification factor of radiographs is a major limitation. Despite the use of markers for calibration, identifying the plane of the hip joint is a major challenge. The aim of this study was to evaluate the accuracy of a novel method for image calibration and preoperative planning in THA involving the use of a biplanar radiographic (EOS imaging) system and a self-designed coin device. Methods: Biplanar radiographs (with the self-designed coin device) and a conventional anteroposterior radiograph (with a coin) were made for 26 patients after primary THA. The agreement between the actual and calculated diameters for each method was assessed using the concordance correlation coefficient (CCC) and Bland-Altman plots. In addition, 15 patients undergoing primary THA were prospectively enrolled to evaluate the EOS imaging-based method (EOS method), with biplanar radiographs made with use of the coin device. The accuracy of the preoperative predicted size of the implants was evaluated. Results: Both the EOS and conventional anteroposterior radiograph-based methods were reliable in repeated measurements of the diameter of the artificial femoral head in the reproducibility study, with the average CCCs for both methods >0.990. The agreement between the actual and EOS-based calculated diameters of the artificial femoral head was excellent, with a CCC of >0.990, while the agreement was poor between the actual and anteroposterior radiograph-based calculated diameters, with a CCC of <0.75. The EOS method exhibited a lower absolute difference (0.09 ± 0.07 mm) between the actual and calculated diameters compared with conventional anteroposterior radiography (1.26 ± 0.86 mm) (p < 0.001). EOS-based preoperative plans also exhibited excellent performance on the accuracy of the planning of the cups and stems; only 1 patient (6.7%) had a final implanted cup that differed by 1 size from the predicted size. Two patients (13.3%) had final implanted stems that differed by 1 size from the predicted size, and for 1 patient (6.7%), the stem size was off by ≥2 sizes. Conclusions: We describe a novel and easy-to-use method for the accurate calibration of radiographs and preoperative planning for THA. The EOS method evaluated in this study is an alternative method for preoperative planning in clinical practice.

Background Orthostatic state is maintained by harmonizing the spine, pelvis and lower extremities. In the past few decades, several studies have demonstrated the associations between spinal imbalance and generalized osteoarthritis. The compensatory mechanisms of pelvis translation and knee flexion, however, have not been fully assessed. Methods A total of 213 volunteers, over 40 years of age, were recruited. Radiological measurements were performed by EOS imaging system. Pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), sagittal vertical axis (SVA), global tilt (GT), hip-knee-angle (HKA), knee flexion angle (KFA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) were measured. On the basis of SRS-Schwab, the subjects were classified into decompensated group (PI-LL > 20°), compensated group(10° ≤ PI-LL ≤ 20°), and normal group (PI-LL < 10°). Differences in radiographic parameters among groups were evaluated. Data of Knee Society Score (KSS) and Oswestry Disability Index (ODI) score were collected via questionnaires. Results Decompensated group showed larger pelvic parameters (PT) and low extremity parameters (LDFA, MPTA, HKA and KFA) than normal group (P < 0.05). Pelvic parameter was larger in the compensated group (median = 31°) compared to the normal group (median = 17°) (P < 0.05). There was no difference in low extremity parameters between the compensated and normal groups. At the sagittal plane, the radiological parameters of spine were greater in subjects with patellofemoral joint pain (PFP) than without PFP (P = 0.058). Higher PI-LL values were observed in women (P < 0.05). Conclusions A correlation between sagittal spinal imbalance and knee joint angles was recognized. The progression of knee and low back pain was associated with the severity of sagittal spinal imbalance. Pelvic retroversion was considered to be the probable compensatory mechanism.

Objective The classical approaches for total hip arthroplasty (THA) are the direct lateral approach (DLA) and posterior lateral approach (PLA). There are few studies comparing implant orientation with these two approaches, and the impact of surgical approaches on implant orientation remains controversial. With the rise of the EOS imaging system, we aimed to use it to identify the differences between and factors associated with implant orientation after THA using DLA and PLA. Methods In our department from January 2019 to December 2021, 321 primary unilateral THAs that used PLA and DLA were enrolled. A total of 201 patients who received PLA and 120 patients who received DLA were included in this study. Two blinded observers measured each case using EOS imaging data. Postoperative imaging metrics and other relevant influencing factors of the two surgical approaches were compared. Postoperative imaging metrics, including the anteversion and inclination of the cup, anteversion of the stem, and combined anteversion were measured based on EOS. Other relevant influencing factors included age, approach, gender, laterality, BMI, anterior pelvic plane inclination, femoral head diameter, femoral offset, lateral pelvic tilt, pelvic incidence, pelvis axial rotation, sacral slope, sagittal pelvic tilt, and surgery time. Multiple linear regression analyses were performed to identify the predictors of acceptability for each imaging data point. Results No dislocation was found in the 321 patients who underwent primary THA during this period. The mean anteversion and combined anteversion of the cups using the DLA were 21.33° ± 17.31° (−51.7°–60.8°) and 33.71° ± 20.85° (−38.8°–77.6°) and PLA were 25.34° ± 12.76° (−5.5°–57.0°) and 42.37° ± 18.85° (−8.7°–84.7°), respectively. The DLA group had smaller anteversion ( p = 0.038) and combined anteversion ( p < 0.001). We found that surgical approach ( p < 0.05), anterior pelvic plane inclination ( p < 0.001), gender ( p < 0.001), and femoral head diameter ( p < 0.001) were important factors affecting acetabular cup anteversion ( R 2 = 0.375) and combined anteversion ( R 2 = 0.525). Conclusions In total hip arthroplasty, different prosthesis installation directions should be made according to different surgical approaches. Compared with the direct lateral approach, the acetabular anteversion can be intentionally enlarged when using the posterolateral approach. Surgical approach, anterior pelvic plane inclination (APPI), gender, and femoral head diameter were significant predictors of prosthesis orientation. The anterior pelvic plane inclination may be a useful standard for assessing the position of the prosthesis using EOS.