Introduction. Spatial orientation of the pelvis in the sagittal plane is a key parameter for hip function. Pelvic extension (or retroversion) and pelvic flexion(or anteversion) are currently assessed using Sacral Slope (SS) evaluation (respectively SS decrease and SS increase). Pelvic retroversion may be a risk situation for THA patients. But the magnitude of SS is dependant on the magnitude of pelvic incidence (PI) and may fail to discriminate pelvic position due to patient's anatomy and the potential adaptation mechanisms: a high PI patient has a higher SS but this situation can hide an associated pelvic extension due to compensatory mechanisms of the pelvic area. A low PI patient has a lower SS with less adaptation possibilities in case of THA especially in aging patients. The individual relative pelvic version (RPV) is defined as the difference between « measured SS » (SSm) minus the « normal SS »(SSn) described for the standard population. The aim of the study was to evaluate RPV in standing and sitting position with a special interest for high and low PI patients. Materials and Methods. 96 patients without THA (reference group) and 96 THA patients were included. Pelvic parameters (SS and PI) were measured on standing and sitting EOS images. RPV standing (SSm-SSn) was calculated using the formula SSm – (9 + 0.59 × PI) according to previous publications. SSn in sitting position was calculated according to PI using linear regression: RPV sitting was calculated using the formula RPV = SS – (3,54+ 0,38 × PI). Three subgroups were defined according to pelvic incidence (PI): low PI <45°, 45°<normal PI<65° or high PI>65°. Results. For THA patients, pelvic parameters were:. SSm standing 41° (SD 11°; 8°.73°). SSm sitting 25° (SD 12°;−3°.54°). SSm variation 16°(SD 11°; 9°.46°). RPV standing −2°(SD 9°; −27°.21°). RPV sitting 7° (SD 10; −15°.29°). For non THA patients, pelvic parameters were:. SSm standing39° (SD 10°; 13°.63°). SSm sitting 17° (SD 11°;−5°.48°). SSm variation 27°(SD 13°; −27°.46°). RPV standing −1°(SD 7°; −29°.12°). RPV sitting 0° (SD 10,5; −29.35). Standing-sitting SS variations and RPV were not correlated with PI. Low PI incidence patients had very low RPV standing and sitting. In non THA patients RPV standing and sitting were very low. In THA patients standing-sitting SS variations and RPV were higher than for non THA patients. Sitting RPV was higher than in standing position. Discussion, Conclusion. The overall analysis of SS has limitations: higher or lower SS may be linked to 2 factors: pelvic morphology (PI) and sagittal orientation of the pelvis. RPV and PI were not correlated: a higher or lower value of RPV directly represents the sagittal orientation of the pelvis. Low PI patients have a specific postural pattern with low pelvic adaptability. THA patients specificity for RPV needs further studies for understanding the impact on postoperative rebalancing and instability problems

Introduction. Understanding hip-spine relationships and accurate evaluation of the pelvis position are key- points for the optimization of total hip arthroplasty (THA). Hip surgeons know the importance of pelvic parameters and the adaptation mechanisms of pelvic and sub-pelvic areas. Literature about posture after THA remains controversial and adaptations are difficult to predict. One explanation can be the segmental analysis focused on pelvic parameters and local planning. In a significant number of patients a global analysis may be important as a cascade of compensatory mechanisms is implemented, the hip being only one of the links of this chain reaction. 3 parameters can be measured on full body images:. SVA (sagittal vertical axis) : horizontal distance between the vertical line through the center of C7 and the postero-superior edge of S1. T1 pelvic angle (TPA) : line from femoral heads to T1center and line from the femoral heads to S1center. TPA combines informations from both the sagittal vertical axis and pelvic tilt. Global Sagittal Angle (GSA) : line from the midpoint of distal femoral condyles to C7 center and line from the midpoint between distal femoral condyles to the postero-superior S1corner. The objective of this preliminary study is to report the post-operative evolution of posture after THA. Material and Method. 49 patients (28 women, 21 men, mean age 61 years) were enrolled for full-body standing EOS images before and after THA. The sterEOS software was used to measure pelvic parameters (sacral slope SS, pelvic incidence PI) and global postural parameters (TPA, GSA, SVA). Sub-analysis was made, grouping the sample by TPA (<14°, 14°–22°, >22°), by PI (<55°, 55°–65°, >65°) and by SS (<35°, 35°–45°, >45°). Paired t-test was used to compare differences between preoperative and postoperative parameters within each subgroup. Statistical significance was set at p < 0.05. Results. TPA, SVA and GSA may change independently following THA surgery. In the 2 groups with TPA< 19° and 14° <TPA< 22°, GSA and SVA decreased significantly after THA (p < 0.05). The difference was not significant in the group with TPA>22°. In the group with SS between 35° and 45°, the GSA and SVA decreased after THA (p < 0.05). In the group with SS > 45° only GSA decreased. In the group with PI < 55°, GSA and SVA decreased after THA. There was no significant change in the remaining subgroups. Discussion. This preliminary study confirms a decrease of GSA and SVA after THA. Some preoperative characteristics are observed in patients with significant global sagittal postural modifications: low to standard TPA, low PI or standard to high SS. Conclusion. Planning and prediction of sagittal postural changes after THA implantation is challenging. It is an important topic in patients with stiff and degenerative spine or in case of spinal fusion. In case of complex hipspine cases, the timing of the procedures can be a real concern. The combined analysis of SVA, TPA and GSA may open new perspectives for a more rationale planning of THA

Introduction. Optimal implant position is critical to hip stability after total hip arthroplasty (THA). Recent literature points out the importance of the evaluation of pelvic position to optimize cup implantation. The concept of Functional Combined Anteversion (FCA), the sum of acetabular/cup anteversion and femoral/stem neck anteversion in the horizontal plane, can be used to plan and control the setting of a THA in standing position. The main purpose of this preliminary study is to evaluate the difference between the combined anteversion before and after THA in weight-bearing standing position using EOS 3D reconstructions. A simultaneous analysis of the preoperative lumbo pelvic parameters has been performed to investigate their potential influence on the post-operative reciprocal femoro-acetabular adaptation. Material and Methods. 66 patients were enrolled (unilateral primary THAs). The same mini-invasive anterolateral approach was performed in a lateral decubitus for all cases. None of the patients had any postoperative complications. For each case, EOS full-body radiographs were performed in a standing position before and after unilateral THA. A software prototype was used to assess pelvic parameters (sacral slope, pelvic version, pelvic incidence), acetabular / cup anteversion, femoral /stem neck anteversion and combined anteversion in the patient horizontal functional plane (the frontal reference was defined as the vertical plane passing through centers of the acetabula or cups). Sub-analysis was made, grouping the sample by pelvic incidence (<55°, 55°–65°, >65°) and by pre-operative sacral slope in standing position (<35°, 35°–45°, >45°). Paired t-test was used to compare differences between preoperative and postoperative parameters within each subgroup. Statistical significance was set at p < 0.05. Results. In the full sample, mean FCA increased postoperatively by 9,3° (39,5° vs 30,2°; p<0.05). In groups with sacral slope < 35° and sacral slope > 45°, postoperative combined anteversion increased significantly by 11,7° and 12,9°, respectively. In the group with pelvic incidence > 65°, postoperative combined anteversion increased significantly by 14,4°. There was no significant change of combined anteversion in the remaining subgroups. Discussion. In this series the FCA increased after THA, particularly in patients with a low or high sacral slope on the pre-operative evaluation in standing position. This may be related to a greater difficulty for the surgeon in anticipating the postoperative standing orientation of the pelvis in these patients, as they were standardly oriented during surgery (lateral decubitus). Interestingly the combined anteversion was also increased in patients with a high pelvic incidence that is commonly associated with a high sacral slope. Conclusion. Post-operative increase of anatomical cumulative anteversion has been previously reported using anterior approach. The FCA concept based on EOS 3D reconstructions brings new informations about the reciprocal femoro-acetabular adaptation in standing position. Differences found in combined anteversion before and after the surgery show that a special interest should be given to patients with high pelvic incidence and low or high sacral slope, to optimize THA orientation in standing position

Purpose. Spinopelvic parameters describe the orientation, shape, and morphology of the spine and pelvis. In children without spinal deformity, these parameters have been shown to change during the first ten years of life; however, spinopelvic parameters have yet to be defined in children with significant Early Onset Scoliosis (EOS). The purpose of this study is to examine the effects of EOS on sagittal spinopelvic alignment. Method. Standing, lateral radiographs of 82 untreated patients with EOS greater than 50 degrees were evaluated. Sagittal spine parameters (sagittal balance, thoracic kyphosis (TK), lumbar lordosis (LL)) and sagittal pelvic parameters (pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), modified pelvic radius angle (PR)) were measured. These results were compared to those reported by Mac-Thiong et al (Spine, 2004) for a group of asymptomatic (i.e. without spinal deformity) children of similar age. Results. These patients had a mean age of 5.17 years and mean scoliosis of 73.3 17.3. Mean sagittal spine parameters were: sagittal balance (+2.4 4.03 cm), TK (38.2 20.8), and LL (47.8 17.7). These values were similar to those reported for asymptomatic subjects. Mean sagittal pelvic parameters were measured for PI (47.1 15.6), PT (10.3 10.7), SS (35.5 12.2), and PR (57.1 21.2). Although PI was similar to age-matched normals, PT was significantly higher and SS trended lower in the study population. Conclusion. Sagittal plane spine parameters in children with EOS were similar to those found in children without spinal deformity. Likewise, pelvic parameters (PI, SS, PR) were similar; however, those children with EOS signs of pelvic retroversion (increased pelvic tilt). This data may be useful as a baseline in determining prognosis for children with EOS who are treated with growing systems

Introduction. A comprehensive understanding of pelvic orientation prior to total hip arthroplasty is necessary to allow proper cup positioning and mitigate the risks of complications associated with component malpositioning. Measurements using anteroposterior (AP) radiographs have been described as effective means of accurately predicting pelvic orientation. The purpose of our study was to describe the inter- and intra-observer reliability and predictive accuracy of predicting pelvic tilt using AP radiographs. Methods. Five fellowship-trained orthopaedic surgeons independently analyzed pelvic tilt, within 10 degrees, for 50 different AP pelvis radiographs. All surgeons were blinded to patient information, diagnosis, and correct measurements prior to analysis. Responses were then compared to correct measurements using sitting-standing AP and lateral stereoradiographs. Results. The average correct predictive value of pelvic tilt between all surgeons was 54%. The intra-observer accuracy of predicting pelvic tilt ranged from 48% to 64%. Discussion. Pelvic tilt cannot be accurately predicted using anteroposterior radiographs. Pre-operative evaluation of pelvic parameters requires multiple views for detailed assessment. Therefore, lateral radiographs are required for accurate prediction of pelvic tilt

Anteroposterior (AP) pelvic radiographs are the standard tool used for pre-operative planning and post-operative evaluation during total hip arthroplasty (THA). The accuracy of this imaging modality is, however, limited by errors in pelvic orientation and image distortion. Pelvic obliquity is corrected for by orienting measurements to a reference line such as the interteardrop line or the interischial line, while several methods for correcting for pelvic tilt have been suggested, with varying levels of success. To date, no reliable method for correcting for pelvic rotation on pelvic imaging is available. The purpose of this study was to evaluate a novel method for correcting pelvic rotation on a standard anteroposterior (AP) radiographs. Computed tomography (CT) scans from 10 male cadavers and 10 female THA patients were segmented using 3D Slicer and used to create 3D renderings for each pelvis. Synthetic AP radiographs were subsequently created from the 3D renderings, using XRaySim. For each pelvis, images representing pelvic rotation of 30° left to 30° right, at 5° increments were created. Four unique parameters based on pelvic landmarks were used to develop the correction method: i) the horizontal distance from the upper edge of the pubic symphysis to the sacroiliac joint midline (PSSI), ii) the ratio of the horizontal distances from the upper edge of the pubic symphysis to the outer lateral border of both obturator foramina (PSOF), iii) the width ratio of the obturator foramina (OFW) and iv) the ratio of the horizontal distance from each anterior superior iliac spine to the sacroiliac joint midline (ASISSI). The relationships between the chosen parameters and pelvic rotation were investigated using a series of 260 (13 per pelvis) synthetic AP radiographs. Male and female correction equations were generated from the observed relationships. Validation of the equations was done using a different set of 50 synthetic radiographs with known degrees of rotation. In males, the PSSI parameter was most reliable in measuring pelvic rotation. In females, PSOF was most reliable. A high correlation was noted between calculated and true rotation in both males and females (r=0.99 male, r=0.98 female). The mean difference from the male calculated rotation and true rotation value was 0.02°±1.8° while the mean difference from the female calculated rotation and true rotation value was −0.01°±1.5°. Our correction method for pelvic rotation using four pelvic parameters provides a reliable method for correcting pelvic rotation on AP radiographs. For any figures or tables, please contact authors directly

Background. Postural change after total hip arthroplasty (THA) is still a matter of discussion. Previous studies have mainly concentrated on the pelvic motions. We report the postoperative changes of the global sagittal posture using pelvic, spinal and lower extremities parameters. Methods. 139 patients (primary THA, without previous spinal or lower extremity surgery) were included. We measured pelvic parameters [SS: Sacral Slope, PI: Pelvic Incidence, PT: Pelvic Tilt, APP angle: Anterior Pelvic Plane angle] and the global posture parameters (SVA: Sagittal Vertical Angle, GSA: Global Sagittal Angle, TPA: T1 pelvic angle). Patients were categorized into low PI group <45°, 45°< medium PI <65° and high PI >65°. Results. Mean GSA and SVA decreased postoperatively (p=0.005 and p=0.004 respectively). The TPA change was not significant (p=0.078). In low PI group, GSA (5.4 ± 5.0 to 4.3 ± 4.0, p=0.005) and SVA (5.4 ± 4.9 to 4.2 ± 4.1, p=0.038) decreased with more posterior pelvic tilt. Postoperative TPA was significantly higher (8.4 ± 10.6 to 9.8 ± 10.7; p=0.048). In medium PI group, SVA decreased (4.2 ± 4.6 to 3.6 ± 4.5, p=0.020) with more posterior pelvic tilt. In high PI group, pelvic and global posture parameters did not evolve significantly. Conclusion. PI is the key determining factor in pelvic tilt modification after THA. Patients with low PI demonstrate significant modification in spine, pelvic and lower extremities. Pelvic tilt is the main adaptation mechanism for medium incidence patients whereas pelvic tilt does not change in high PI patients after surgery

Introduction. Limb length discrepancy after THA can result in medicolegal litigation. It can create discomfort for the patient and potentially cause back pain or affect the longevity of the implant. Some patients tolerate the length inequality better compared to others despite difference in anatomical femoral length after surgery. Methods and materials. We analyzed the 3D EOS images of 75 consecutive patients who underwent primary unilateral THA (27 men, 48 women). We measured the 3D length of the femur and tibia (anatomical length), the 3D global anatomical length (the sum of femur and tibia anatomical lengths), the 3D functional length (center of the femoral head to center of the ankle), femoral neck-shaft angle, hip-knee-ankle angle, knee flexum/recurvatum angle, sacral slopes and pelvic incidence. We correlated these parameters with the patient perception of the leg length. Results. The values for leg length and pelvic parameters are shown in table 1. 37 patients had a perception of the LLD (49.3%). When the global anatomical length was shorter on the operated side, the perception of the discrepancy was observed in 56% of the cases. In case of anatomical length longer on the operated side, the perception of the discrepancy was described by the patients in 46% of the cases. The LLD perception was correlated with difference in functional length (p=0.0001), pelvic obliquity (p=0.003) and sacral slope (p=0.023). The anatomical femoral length was not correlated with the LLD perception (p=0,008). Discussion. The perception of LLD is a multifactorial complication. We found that the anatomical femoral length (that can be directly affected by the position of the stem) is not the only important factor. The functional length of the lower extremity which can also be affected by the knee deformities is better correlated with the LLD. The pelvic obliquity and version also affect the patient perception of the LLD

Introduction. The gold standard for knee surgery is the restoration of the so-called «neutral mechanical alignment ». Recent literature as pointed out the patients with «constitutional varus »; in these cases, restoring neutral alignment could be abnormal and even undesirable. The same situation can be observed in patients with «constitutional valgus alignment ». To date, these outliers cases have only been explored focusing on the lower limb; the influence of the pelvic morphotype has not been studied. Intuitively, the pelvic width could be a significant factor. The EOS low dose imaging technique provides full body standing X-rays to evaluate the global anatomy of the patient. This work explores the influence of the pelvic parameters on the frontal knee alignment. Material and methods. – We included 170 patients (340 lower extremities). 2 operators performed measurements once per patient on AP X-rays. The classical anatomical parameters were:. –. Femoral mechanical angle (FMA). –. Tibial mechanical angle (TMA). –. Hip knee shaft angle (HKS). –. Hip knee ankle angle (HKA). –. Femoral and tibial lengths. The morphotype was evaluated by:. –. the distances between the center of two femoral heads (FHD), between knees (KD) and between ankles (AD). –. the medial neck-shaft angle (MNSA). –. the femoral offset. The horizontal distance between the limb mechanical axis (line passing from center of the femoral head to the center of the ankle) and the center of the knee was called the intrinsic mechanical axis deviation (IMAD) (fig 1). The horizontal distance between the pelvic mechanical axis (line from the center of the sacral plate to the center of the ankle) and the center of the knee was called the global mechanical axis deviation (GMAD) (fig 2). Inter-Operator Reliability was calculated with Intra-class Correlation Coefficient (ICC) and Inter-Reader Agreement was assessed with Bland-Altman test. A relationship between IMAD and GMAD to the other parameters was assessed using Pearson's correlation coefficient. Results. Inter-Operator Reliability was high for femoral offset, TMA and MSNA (ICC > 0,88) and very high for the other parameters (ICC > 0,93). These values are given in table 1 and all the 2D parameters are given in the table 2. IMAD was significantly correlated with HKA (r = 0,99), FMA (r = −0,58), TMA (r = −0,61) and KD (r = 0,72). GMAD was significantly correlated with HKA (r = 0,94), FMA (r = −0,53), TMA (r = −0,60) and KD (r = 0,67). Two groups were identified according to pelvic width (FHD):. Group 1 (standard patients): Pelvic width < 18 cm (164 lower extremities). Group 2 (wide pelvis): Pelvic width ≥ 18 cm (176 lower extremities). For standard patients the FHD is a significant parameter, whereas the proximal femoral anatomy (offset and MNSA) are more relevant for wide pelvis. Conclusion. Accurate analysis of the morphotype of the lower limbs is essential for planning femoral or tibial osteotomy and knee prostheses. Taking into account pelvic morphotype can provide additional informations for the axes restoration and the detection of outliers patients

The anterior pelvic plane (APP) angle is often used as a reference to decide pelvic alignment for hip surgeons. However, Rousseau criticised the validness of the APP angles because the APP angles in standing position measured on conventional standing X-ray films never showed correlation with the other pelvic alignment parameters, such as sacral slope (SS). We measured the APP angles, SS and pelvic tilt (PT) on the non-distorted anteroposterior (AP) and lateral digitally reconstructed radiography (DRR) images in supine position (with CT scans) and AP and lateral X-ray images in standing position (with EOS X-ray machine [EOS imaging, Paris, France]) by using of the same EOS software. Our data showed that the pre- and post-operative APP angles correlated with SS and PT in both supine and standing positions. Our non-distorted high quality images and the EOS software revealed these correlations. Therefore, we can still use the APP angles to decide pelvic alignment for patients who undergo total hip arthroplasty (THA). Recent papers demonstrated positional or chronological dramatic changes of the APP angles between pre- and post-operative states in patients who underwent THA. The EOS system will be a powerful tool to investigate these changes of the pelvic alignments

Pelvic incidence is as a key factor for sagittal balance regulation that describes the anatomical configuration of the pelvis. The sagittal alignment of the pelvis is usually evaluated in two-dimensional (2D) sagittal radiographs in standing position by pelvic parameters of sacral slope, pelvic tilt and pelvic incidence (PI). However, the angle of PI remains constant for an arbitrary subject position and orientation, and can be therefore compared among subjects in standing, sitting or supine position. Such properties also enable the measurement of PI in three-dimensional (3D) images, commonly acquired in supine position. The purpose of this study is to analyse the sagittal alignment of the pelvis in terms of PI in 3D computed tomography (CT) images. A computerised method based on image processing techniques was developed to determine the anatomical references, required to measure PI, i.e. the centre of the left femoral head, the centre of the right femoral, the centre of the sacral endplate, and the inclination of the sacral endplate. First, three initialisation points were manually selected in 3D at the approximate location of the left femoral head, right femoral head and L5 vertebral body. The computerised method then determined the exact centres of the femoral heads in 3D from the spheres that best fit to the 3D edges of the femoral heads. The exact centre of the sacral endplate in 3D was determined by locating the sacral endplate below the L5 vertebral body and finding the midpoint of the lines between the anterior and posterior edge, and between the left and right edge of the endplate. The exact inclination of the sacral endplate in 3D was determined from the plane that best fit to the endplate. Multiplanar 3D image reformation was applied to obtain the superposition of the femoral heads in the sagittal view, so that the hip axis was observed as a straight not inclined line and all anatomical structures were completely in line with the hip axis. Finally, PI was automatically measured as the angle between the line orthogonal to the inclination of the sacral endplate and the line connecting the centre of the sacral endplate with the hip axis. The method was applied to axially reconstructed CT scans of 426 subjects (age 0–89 years, pixel size 0.4–1.0 mm, slice thickness 3.0–4.0 mm). Thirteen subjects were excluded due to lumbar spine trauma and presence of the sixth lumbar segment. For the remaining subjects, the computerised measurements were visually assessed for errors, which occurred due to low CT image quality, low image intensity of bone structures, or other factors affecting the determination of the anatomical references. The erroneous or ambiguous results were detected for 43 subjects, which were excluded from further analysis. For the final cohort of 370 subjects, statistical analysis was performed for the obtained PI. The resulting mean PI ± standard deviation was equal to 46.6 ± 9.2 degrees for males (N = 189, age 39.7 ± 20.3 years), 47.6 ± 10.7 degrees for females (N = 181, age 43.4 ± 19.9 years), and 47.1 ± 10.0 degrees for both genders (N = 370, age 41.5 ± 20.1 years). Correlation analysis yielded relatively low but statistically significant correlation between PI and age, with the correlation coefficient r = 0.20 (p < 0.005) for males, r = 0.32 (p < 0.0001) for females, and r = 0.27 (p < 0.0001) for both genders. No statistically significant differences (p = 0.357) were found between PI for male and female subjects. This is the first study that evaluates the sagittal alignment of the pelvis in terms of PI completely in 3D. Studies that measured PI manually from 2D sagittal radiographs reported normative PI in adult population of 52 ± 10 degrees, 53 ± 8 degrees and 51 ± 9 degrees for 25 normal subjects aged 21–40, 41–60, and over 60 years, respectively [3], and 52 ± 5 degrees for a cohort of 160 normal subjects [4]. The PI of 47 ± 10 degrees obtained in our study is lower than the reported normative values, which indicates that radiographic measurements may overestimate the actual PI. Radiographic measurements are biased by the projective nature of X-ray image acquisition, as it is usually impossible to obtain the superposition of the two femoral heads. The midpoint of the line connecting the centres of femoral heads in 2D is therefore considered to be the reference point on the hip axis, moreover, the inclination of the sacral endplate in the sagittal plane is biased by its architecture and inclination in the coronal plane. On the other hand, the measurements in the present study were obtained by applying a computerized method to CT images that determined the exact anatomical references in 3D. Perfect sagittal views were generated by multiplanar reformation, which aligned the centres of the femoral heads in 3D. The measurement of PI was therefore not biased by acquisition projection or structure orientation, as all anatomical structures were completely in line with the hip axis. Moreover, the range of the PI obtained in every study (standard deviation of around 10 degrees) indicates that the span of PI is relatively large. It can be therefore concluded that an increased or decreased PI may not necessary relate to a spino-pelvic pathology

Aims

The aetiologies of common degenerative spine, hip, and knee pathologies are still not completely understood. Mechanical theories have suggested that those diseases are related to sagittal pelvic morphology and spinopelvic-femoral dynamics. The link between the most widely used parameter for sagittal pelvic morphology, pelvic incidence (PI), and the onset of degenerative lumbar, hip, and knee pathologies has not been studied in a large-scale setting.