Anteroposterior (AP) radiographs remain the standard of care for pre- and post-operative imaging during total hip arthroplasty (THA), despite known limitation of plain films, including the inability to adequately account for distortion caused by variations in pelvic orientation. Of specific interest to THA surgeons are distortions associated with pelvic tilt, as unaccounted for tilt can significantly alter radiographic measurements of cup position. Several authors have proposed methods for correcting for pelvic tilt on radiographs but none have proven reliable in a THA population. The purpose of our study was to develop a method for correcting pelvic tilt on AP radiographs in patients undergoing primary or revision THA. CT scans from 20 patients/cadaver specimens (10 male, 10 female) were used to create 3D renderings, from which synthetic radiographs of each pelvis were generated (Figure 1). For each pelvis, 13 synthetic radiographs were generated, showing the pelvis at between −30° and 30° of pelvic tilt, in 5° increments. On each image, 8 unique parameters/distances were measured to determine the most appropriate parameters for calculation of pelvic tilt (Figure 2). The most reliable and accurate of these parameters was determined via regression analysis and used to create gender-specific nomograms from which pelvic tilt measurements could be calculated (Figure 3). The accuracy and reliability of the nomograms and correction method were subsequently validated using both synthetic radiographs (n=50) and stereoradiographic images (n=58). Of 8 parameters measured, the vertical distance between the superior margin of the pubic symphysis and the transischial line (PSTI) was determined to be the most reliable (r=−0.96, ICC=0.94). Mean tilt calculated from synthetic radiographs (0.6°±18.6°) correlated very strongly (r=0.96) with mean known tilt (0.5°±17.9°, p=0.98). Mean pelvic tilt calculated from AP EOS images (3.2°±9.9°) correlated strongly (r=0.77) with mean tilt measured from lateral EOS images (3.8°±8.2°, p=0.74). No gender differences were noted in mean tilt measurements in synthetic images (p=0.98) or EOS images (p=0.45). Our method of measuring PSTI and POD on AP images and applying these measurements to nomograms provides a validated and reliable method for estimating the degree of pelvic tilt on AP radiographs during THA. For any figures or tables, please contact authors directly

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

Introduction. The pelvis is not a static structure. It rotates in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic tilt have a substantial effect on the functional orientation of the acetabulum. The aim of this study was to quantify the changes in sagittal pelvic position between three functional postures. Methodology. Pre-operatively, 90 total hip replacement patients had their pelvic tilt measured in 3 functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair), Fig 1. Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography, Fig 2. Results. The mean standing pelvic tilt was −2.1° ± 7.4°, with a range of −15.2° – 15.3°. Mean supine pelvic tilt was 4.1° ± 5.5°, with a range of −9.7° – 17.9°. Mean pelvic tilt in the flexed seated position was −1.8° ± 14.1°, with a range of −31.8° – 29.1°, Fig 3. The mean absolute change from supine to stand, and stand to flexed seated was 6.9° ± 4.1° and 11.9° ± 7.9° respectively. 86.6% of patients had a more anteriorly tilted pelvis when supine than standing. 52.2% of patients had a more anteriorly tilted pelvis when seated than standing. Conclusions. The position of the pelvis in the sagittal plane changes significantly between functional activities. The extent of change is specific to each patient. Planning and measurement of cup placement in the supine position can lead to large discrepancies in orientation during more functionally relevant postures. As a result of the functional changes in pelvic position, cup orientations during dislocation and edge-loading events are likely to be significantly different to that measured from standard CT and radiographs. Optimal cup orientation is likely patient-specific and requires an evaluation of functional pelvic dynamics to pre-operatively determine the target angles

Pelvic tilt (PT) is always described as the pelvic orientation along the transverse axis, yet four PT definitions were established based on different radiographic landmarks: anterior pelvic plane (PT. a. ), the centres of femoral heads and sacral plate (PT. m. ), pelvic outlet (PT. h. ), and sacral slope (SS). These landmarks quantify a similar concept, yet understanding of their relationships is lacking. Some studies referred to the words “pelvic tilt” for horizontal comparisons, but their PT definitions might differ. There is a demand for understanding their correlations and differences for education and research purposes. This study recruited 105 sagittal pelvic radiographs (68 males and 37 females) from a single clinic awaiting their hip surgeries. Hip hardware and spine pathologies were examined for sub-group analysis. Two observers annotated four PTs in a gender-dependent manner and repeated it after six months. The linear regression model and intraclass correlation coefficient (ICC) were applied with a 95% significance interval. The SS showed significant gender differences and the lowest correlations to the other parameters in the male group (-0.3< r <0.2). The correlations of SS in scoliosis (n = 7) and hip implant (female, n = 18) groups were statistically different, yet the sample sizes were too small. PT. m. demonstrated very strong correlation to PT. h. (r > 0.9) under the linear model PT. m. = 0.951 × PT. h. - 68.284. The PT. m. and PT. h. are interchangeable under a simple linear regression model, which enables study comparisons between them. In the male group, SS is more of a personalised spinal landmark independent of the pelvic anatomy. Female patients with hip implant may have more static spinopelvic relationships following a certain pattern, yet a deeper study using a larger dataset is required. The understanding of different PTs improves anatomical education

Introduction. The optimal goal for cup positioning in hip arthroplasty in individual patients is affected by many factors including surgical exposure, femoral anteversion, and pelvic tilt. Some navigation systems ignore pelvic tilt and are based strictly on the anterior pelvic plane while others incorporate pelvic tilt, as measured in the supine position on the operating table. Neither approach incorporates knowledge of preoperative spino-pelvic flexibility or predictions of the change in spino-pelvic attitude or flexibility following surgery. While prior studies have shown little change in pelvic tilt postoperatively, one recent study based on gait analysis, suggested that changes in pelvic tilt are not predictable. The current study aims to assess changes in pelvic tilt following surgery. Methods. 24 patients, 12 male and 12 female, underwent THA using CT-based navigation. Each patient had supine and standing AP pelvis radiographs both pre-operatively and at a minimum of 1 year post-operatively. Pelvic tilt on each radiograph was measured using a noncommercial two-dimensional/three-dimensional matching application. (HipMatch; Institut for Surgical Technology and Biomechanics, Bern, Switzerland). This software application uses a fully auto- mated registration procedure that can match the three- dimensional model of the preoperative CT with the projected pelvis on a postoperative radiograph. This method has been validated and for measurement of cup position for example showed a mean accuracy of 1.7° +/− 1.7° (rang-4.6° to 5.5°) in the coronal plane and 0.9° +/− 2.8° (rang-5.2° to 5.7°) in the sagittal plane compared with postoperative CT measurements. The software showed a good consistency with an intraclass correlation coefficient (ICC) for inclination of 0.96 (95% confidence interval [CI]: 0.93 to 0.98) and for anteversion of 0.95 (95% CI: 0.91 to 0.98). A good reproducibility and reliability for both inclination and anteversion was found with an ICC ranging from 0.95 to 0.99. No systematic errors in accuracy were detected with the Bland- Altman analysis. Using the HipMatch 2D/3D application, changes in pelvic tilt before and after surgery were assess in both the supine and standing positions. Results. Preoperatively, the mean standing pelvic tilt was .9 degrees (range 10.9 to −9.2) and the mean supine pelvic tilt was 3.7 degrees (range 11.8 to −7.7). Postoperatively, the mean standing pelvic tilt was 1.1 degrees (range 13.8 to −12.3) and the mean supine pelvic tilt was 5.9 degrees (−4.0 to 16.5). The maximum change following surgery in individual patients was −4.9 degrees standing and −8.5 degrees supine. Pre-operative supine pelvic tilt predicts post-operative supine pelvic tilt with an r. 2. of .67. Pre-operative standing pelvic tilt predicts post-operative standing pelvic tilt with an r. 2. of 0.91. Discussion. Overall, in both the standing and supine positions, pelvic tilt changed very little as a result of total hip arthroplasty in this sample of patients and pre-operative pelvic tilt is clearly predictive of post-operative pelvic tilt. Preoperative assessment of pelvic tilt, as measured either in the supine or standing position, may be useful information when determining optimal cup positioning goals for total hip arthroplasty. We recommend that both preoperative assessment of pelvic tilt and preoperative or intraoperative assessment of femoral anteversion should be considered when determining optimal acetabular component positioning

Human error is usually evaluated using statistical descriptions during radiographic annotation. The technological advances popularized the “non-human” landmarking techniques, such as deep learning, in which the error is presented in a confidence format that is not comparable to that of the human method. The region-based landmark definition makes an arbitrary “ground truth” point impossible. The differences in patients’ anatomies, radiograph qualities, and scales make the horizontal comparison difficult. There is a demand to quantify the manual landmarking error in a probability format. Taking the measurement of pelvic tilt (PT) as an example, this study recruited 115 sagittal pelvic radiographs for the measurement of two PTs. We proposed a method to unify the scale of images that allows horizontal comparisons of landmarks and calculated the maximum possible error using a density vector. Traditional descriptive statistics were also applied. All measurements showed excellent reliabilities (intraclass correlation coefficients > 0.9). Eighty-four measurements (6.09%) were qualified as wrong landmarks that failed to label the correct locations. Directional bias (systematic error) was identified due to cognitive differences between observers. By removing wrong labels and rotated pelves, the analysis quantified the error density as a “good doctor” performance and found 6.77°-11.76° maximum PT disagreement with 95% data points. The landmarks with excellent reliability still have a chance (at least 6.09% in our case) of making wrong landmark decisions. Identifying skeletal contours is at least 24.64% more accurate than estimating landmark locations. The landmark at a clear skeletal contour is more likely to generate systematic errors. Due to landmark ambiguity, a very careful surgeon measuring PT could make a maximum 11.76° random difference in 95% of cases, serving as a “good doctor benchmark” to qualify good landmarking techniques

Introduction. The pelvis is not a static structure. It rotates in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic tilt have a substantial effect on the functional orientation of the acetabulum. The aim of this study was to quantify the changes in sagittal pelvic position between three functional postures. Methodology. Pre-operatively, 1,517 total hip replacement patients had their pelvic tilt measured in 3 functional positions – standing, supine and flexed seated (point when patients initiate rising from a seated position). Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography. Results. The mean supine pelvic tilt was 4.2°, with a range of −20.5° to 24.5°. The mean standing pelvic tilt was −1.3°, with a range of −30.2° to 27.9°. Mean pelvic tilt in the flexed seated position was 0.6°, with a range of −42.0° to 41.3°. The mean absolute change from supine to stand, and supine to flexed seated was 6.0° (SD = 3.8°) and 10.7° (SD = 8.1°) respectively. 6% of patients rotated posteriorly by more than 13° from supine to stand, consequently putting them at risk of excessive functional anteversion in extension. 11% of patients rotated anteriorly by more than 13° from supine to seated, consequently retroverting their cup and putting them at risk in flexion. Therefore, 17% of patients had sagittal pelvic rotations that could lead to functional cup malorientation even with a supposedly ideal orientation of 40°/20°. Factoring in an intraoperative delivery error of ± 5° extends this risk to 51% of patients. Conclusions. The position of the pelvis in the sagittal plane changes significantly between functional activities. The extent of change is specific to each patient. 17% of patients had sagittal pelvic rotations that could lead to functional cup malorientation in functional flexion or extension, even with an apparently perfectly-orientated component. This number extended to 51% when an intra-operative delivery error of ± 5° was considered. Planning and measurement of cup placement in the supine position can lead to large discrepancies in orientation during more functionally relevant postures. Optimal cup orientation is likely patient-specific and requires an evaluation of functional pelvic dynamics to pre-operatively determine the target angles

Background. Over 10% of total hip arthroplasty (THA) surgeries performed in England and Wales are revision procedures. 1. Malorientation of the acetabular component in THA may contribute to premature failure. Yet with increasingly younger populations receiving THA surgery (through higher incidences of obesity) and longer life expectancy in general, the lifetime of an implant needs to increase to avoid a rapid increase in revision surgery in the future. The Evaluation of X-ray, Acetabular Guides and Computerised Tomography in THA (EXACT) trial is assessing the pelvic tilt of a patient by capturing x-rays from the patient in sitting, standing and step-up positions. It uses this information, along with a CT scan image, to deliver a personalised dynamic simulation that outputs an optimised position for the hip replacement. A clinical trial is currently in place to investigate how the new procedure improves patient outcomes. 2. . Our aim in this project was to assess whether accurate functional assessment of pelvic tilt could be further obtained using inertial measurement units (IMUs). This would provide a rapid, non-invasive triaging method such that only patients with high levels of tilt measured by the sensors would then receive the full assessment with x-rays. Methods. Recruited patients were fitted with a bespoke device consisting of a 3D-printed clamp which housed the IMU and fitted around the sacrum area. A wide elastic belt was fitted around the patient's waist to keep the device in place. Pelvic tilt is measured in a standing, flexed seated and step-up position while undergoing X-rays with the IMU capturing the data in parallel. Patients further completed another five repetitions of the movements with the IMU but without the x-ray to test repeatability of the measurements. Statistical analysis included measures of correlation between the X-ray and IMU measurements. Results. Data on 30 patients indicated a moderate-strong correlation (R. 2. =0.87) between IMU and radiological measures of pelvic tilt. Key message. A novel device has been developed that can suitably track pelvic movements to stratify patients into risk categories for post-operative dislocations

The position of the pelvis influences acetabular orientation. In particular, pelvic tilt in the sagittal plane may lead to inaccurate interpretation of plain pelvic radiographs. We therefore quantified the relationship between this pelvic tilt and acetabular orientation in native hips, and determined whether pelvic tilt affects femoral head cover. We analysed computed tomography scans of 93 hips (36 normal, 31 dysplastic, 26 with acetabular retroversion) and measured acetabular anteversion, inclination, and femoral head cover at pelvic tilt angles ranging from −20° to 20° in relation to the anterior pelvic plane using 5° increments. The effect of pelvic tilt on version was similar in the normal, dysplastic, and retroverted groups, with a drop in anteversion ranging from 2.5° to 5° for every 5° of forward tilt. There was a tendency for the inclination angle to decrease when the pelvis was tilted forward from a position of extension, and in normal hips, this produced a reduction in inclination of about 4° for every 8° of pelvic tilt; but once neutral pelvic tilt was reached, further forward rotation of the acetabulum had rather a small effect on the inclination angle. In normal and dysplastic hips pelvic tilt increased apparent femoral head cover; in the retroverted group the effect was less marked and tended to be negligible at higher tilt angles. Anterior cover increased with increasing forward tilt in all three groups of hips. Posterior cover, on the other hand, decreased by just 2% for the dysplastic hips, 3.5% for the normal hips, and 6% for the retroverted hips over the whole range of tilt from −20° to 20°. A greater understanding of the influence of pelvic tilt may allow improvements in the radiological diagnosis and surgical treatment of acetabular abnormalities, particularly in relation to acetabular reorientation procedures and femoroacetabular impingement

Sagittal pelvic tilt (PT) has been shown to effect the functional position of acetabular components in patients with total hip replacements (THR). This change in functional component position may have clinical implications including increased likelihood of wear or dislocation. Surgeons can use computer-assisted navigation intraoperatively to account for a patient's pelvic tilt and to adjust the position of the acetabular component. However, the accuracy of this technique has been questioned due to the concern that PT may change after THR. The purpose of this study was to measure the change in PT after THR, and to determine if preoperative clinical and radiographic parameters can predict PT changes after THR. 138 consecutive patients who underwent unilateral THR by one surgeon received standing bi-planar lumbar spine and lower extremity radiographs preoperatively and six weeks postoperatively. Patients with prior contralateral THR, conversion THR and instrumented lumbosacral fusions were excluded. PT and pelvic incidence (PI) were measured preoperatively for each patient, and PT was measured on the postoperative imaging. A negative value for PT indicated posterior pelvic tilt. Patient demographics were collected from the chart. Average age was 56.8±10.9 years, average BMI was 28.3±6.0 kg/m2, and 67 patients (48.6%) were female. Mean preoperative pelvic tilt was 0.6°±7.3° (range: −19.0° to 17.9°). We found greater than 10° of sagittal PT in 23 out of 138 (16.6%) patients in this sample. Mean post-operative pelvic tilt was 0.3°±7.4° (range: −18.4° to 15.0°). Mean change in pelvic tilt was −0.3°±3.6° (range: −9.6° to 13.5°). PT changed by less than 5° in 119 of 138 patients (86.2%). The mean difference in pre-operative and post-operative PT is not statistically significant (p = 0.395). Pre-operative PT was strongly correlated with post-operative PT (r2 = 0.88, p = 0.0001) (Figure 1). There was not a statistically significant relationship between PI and change in PT (r2 = −0.16, p = 0.06). In conclusion, based on the variability in pelvic tilt in this study population and the relatively small change in pelvic tilt following THA tilt-adjustment of the acetabular component position based on standing pre-operative imaging is likely to be of benefit in the majority of patients undergoing navigated THA. However, we have been unable to predict the relatively rare occurrence of a large change in pelvic tilt, which would confound tilt-adjusted component position

The position of the pelvis has been shown to influence acetabular orientation. However there have been no studies quantifying that effect on the native acetabulum. Our aims were to investigate whether it is possible to quantify the relationship between pelvic tilt and acetabular orientation in native hips, and whether pelvic tilt affects acetabular cover of the femoral head. Computerized tomography scans of 93 hips (36 normal, 31 dysplastic and 26 with acetabular retroversion) were analyzed. We used a CT technique that allows standardised three-dimensional (3D) analysis of acetabular inclination and anteversion and calculation of femoral head cover in relation to the anterior pelvic plane and at different degrees of forward and backward tilt. Acetabular anteversion, inclination and cover of the femoral head were measured at pelvic tilt angles ranging from −20° to 20° in relation to the anterior pelvic plane using 5° increments. The effect of pelvic tilt on version was similar in the normal, dysplastic and retroverted groups, with a drop in anteversion ranging from 2.5° to 5° for every 5° of forward tilt. The effect on inclination was less marked and varied among the three groups. Pelvic tilt increased femoral head cover in both normal and dysplastic hips. The effect was less marked, and tended to be negligible at higher positive tilt angles, in the retroverted group. This study has provided benchmark data on how pelvic tilt affects various acetabular parameters which in turn may be helpful in promoting greater understanding of acetabular abnormalities and how pelvic tilt affects the interpretation of pelvic radiographs

Introduction. Traditional methods of component positioning in total hip replacement (THR) utilize mechanical alignment guides which estimate position relative to the plane of the operating room table. However, variations in pelvic tilt alter the relationship between the anatomic plane of the pelvis and that of the table such that components placed in optimal position relative the table may not land within the classic anatomic “safe zone” described by Lewinnek. It has been suggested that navigation software should incorporate adjustments for the degree of pelvic tilt. Current imageless navigation software has this capability, however there is a paucity of data regarding the accuracy of this technology. Purpose. We aimed to assess the accuracy of intra-operative pelvic tilt adjusted anteversion measurements as compared to unadjusted measurements. Methods. 6-week post-operative Anteroposterior Pelvis radiographs from 27 consecutive primary THR were measured utilizing Ein-Bild-Roentgen-Analyse (EBRA-Cup®) hip analysis software (Figure 1) and a cross-table lateral radiograph (Figure 2). Inclination and anteversion values were recorded and direction of version was confirmed by assessment of cross-table lateral images. Values were compared with intra-operative measurements obtained via BrainLab® imageless navigation. Pelvic tilt adjusted and unadjusted anteversion measurements were recorded. Mean measurement error and standard error of the mean were determined and Pearson correlation coefficients were calculated. Results. Navigated component inclination correlated with EBRA-Cup® derived inclination measurements (r = 0.4308, p = 0.02) with a mean error of 3.8°. Similarly, pelvic tilt adjusted anteversion correlated with EBRA-Cup® derived measurements (r = 0.65, p < 0.001). The mean difference between anteversion measurements was 3.58° and the standard error of the mean was 0.58°. 24 of 27 patients had <6° of difference between the two measurements. Post-operative component position correlated more closely with pelvic tilt adjusted anteversion than with unadjusted values (r = 0.3, p = 0.12). As expected, this was most pronounced in patients with greater than 10 degrees of pelvic tilt (mean error of 11.2° vs. 4.5°). Conclusions. Imageless navigation based anteversion measurements are more accurate when adjusted for pelvic tilt

Background. Proper positioning of the acetabular component is critical for prevention of dislocation and excessive wear for total hip arthroplasty (THA) and hip resurfacing. Consideration of preoperative pelvic tilt (PT) may aid in acetabular component placement. The purpose of this study was to investigate how PT changes after hip resurfacing, via pre and post-operative radiographic analysis of anterior pelvic plane (APP), and whether radiographic analysis of the APP is a reproducible method for evaluating PT in resurfaced hips. Methods. A consecutive group of 228 patients from a single surgeon who had hip resurfacing were evaluated. We obtained x-rays from an institutional database for these patients who had their surgeries between January 1. st. , 2014 to December 31. st. , 2016. Pelvic tilt (PT) was measured by two observers before and after resurfacing utilizing a standardized radiographic technique. Correlation coefficients were calculated for PT measurements between observers, and pre- and post-surgery. Results. Mean preoperative PT was 0.7° (SD ± 6.6°) and 0.4° (SD ± 6.1°). Mean post-operative PT was −1.2° (SD ± 6.2°) and −1.2° (SD ± 6.0°). Correlations between pre and post-operative PT were R=.829 (p<.001) and R = .837 (p<.001). 80.6% to 82.5% of patients had variation <5°, 15.8% to 17.8% had variation between 5–10°, and 1.6 to1.8% had a variation >10°. Intraclass correlation coefficients between observers were R = .987 (95% CI, .963–.981; p<.001) preoperatively, and R=.985 (95 CI, .963–.981; p<.001) postoperatively. (See Fig 1). Conclusion. After hip resurfacing arthroplasty, the mean difference between preoperative and postoperative PT was less than 1°. These results suggest that near-native PT is maintained with consistency after hip resurfacing, a finding that is variable following THA. Since variations in PT affect functional acetabular position, these results support the use of pelvic tilt measurement in pre-operative planning for hip arthroplasty with a high degree of inter-observer reliability. For any figures or tables, please contact the authors directly

Accurate measurement of pelvic tilt (PT) is critical in diagnosing hip and spine pathologies. Yet a sagittal pelvic radiograph with good quality is not always available. Studies explored the correlation between PT and sacro-femoral-pubic (SFP) angle from anteroposterior (AP) radiographs yet demonstrated conflicting conclusions about its feasibilities. This study aims to perform a cohort-controlled meta-analysis to examine the correlation between the SFP angle and PT and proposes an application range of the method. This study searched PubMed, Embase, Cochrane, and Web of Science databases for studies that evaluated the correlation between SFP angle and PT. The Pearson's correlation coefficient r from studies were tabulated and compared. Pooled r for overall and gender/age (teenage or adult) controlled subgroup were reported using Fisher's Z transformation. Heterogeneity and publication bias were evaluated using Egger's regression test for the funnel plot asymmetry. Eleven studies were recruited, with nine reported r (totalling 1,247 patients). The overall pooled r was 0.61 with high inter-study heterogeneity (I2 = 75.95%). Subgroup analysis showed that the adult group had a higher r than the teenage group (0.70 versus 0.56, p < 0.001). Although statistically insignificant (p = 0.062), the female group showed a higher r than the male group (0.72 versus 0.65). The SFP method must be used with caution and should not be used in the male teenage group. The current studies did not demonstrate that the SFP method was superior to other AP landmarks correlating to PT. Identical heterogeneity was observed among studies, indicating that more ethnicity-segregated and gender-specific subgroup studies might be necessary. More data input analysing the errors will be useful

Purpose. Change of the pelvic tilt is an important factor affecting walking after total hip arthroplasty (THA). There are many reports of static evaluation of pelvic tilt by X-ray, however, there are few reports of dynamic evaluation during walking. In this study, we investigated change of pelvic tilt of THA subjects before and after operation during walking using an optical position sensor. Subjects and Methods. 5 normal volunteers (mean age 26.6 years old, Control group) and 10 patients who underwent primary THA due to unilateral osteoarthritis of the hip (mean age 61 years old, THA group) were enrolled. We have measured angle of the hip and inclination of the pelvis in the mid-stance phase of the affected limb during walking using a motion analyzer (MAC3D system) and acquired physical assessment of the hip preoperatively, 3 weeks postoperatively and 3 months postoperatively. The acquired data of inclination of the pelvis was classified as Duchenne or Trendelenburg type compared with that of normal volunteers. Result. Trendelenburg type in 6 patients and Duchenne type in 4 patients were found preoperatively with THA group. Trendelenburg type showed abductor muscle weakness and limited range of motion (ROM) in hip abduction, and Duchenne type showed a limited ROM in hip adduction with physical examination. At 3 weeks after surgery, 9 of 10 THA patients resulted in the Duchenne type. At 3 months after surgery, the inclination angle of the pelvis showed the same as that of healthy subjects in 5 of the 9 patients, in which hip abduction ROM increased and abductor muscle strength recovered among Trendelenburg type and hip adduction ROM increased among Duchenne type (Figure 1). The pelvic inclination returned to preoperative state in 4 patients, in which limitation of hip abduction ROM and abductor muscle weakness remained in Trendelenburg type preoperatively and limitation of hip adduction ROM remained in Duchenne type preoperatively (Figure 2). Discussion. As a risk factor for limping after THA, preoperative limitation of ROM in hip abduction or adduction can be related, leading to necessity of systematical estimation for ROM of the hip with physical assessment and pelvic tilt type in the mid-stance during walking prior to surgery. In addition, preoperative maximum hip adduction angle and abduction muscle strength can be affected to change of the pelvic tilt after THA. It is important to recover of these ROM and muscle strength with physical therapy for prevention of postoperative limping

Introduction. Although pelvic tilt does not significantly change after primary total hip arthroplasty (THA) at a short term, can vary over time due to aging and the possible appearence of sagittal spine disorders. Cup positioning relative to the stem can be influenced due to these changes. Purpose. We assessed the evolution of pelvic tilt and cup position after THA for a minimum follow-up of five years and the possible appearence of complications. Materials and methods. 47 patients underwent same single THA between 2008 and 2012. All were diagnosed with primary osteoarthritis and their mean age was 70.2 years (range, 63 to 75). There were 28 male patients, 19 had a contralateral THA, 17 were studied for lumbar pathology and three were operated for lumbo-sacral fusion. Radiological analysis included sacro- femoral-pubic and acetabular abduction angles on the anteroposterior pelvic view; and cup anteversion angle on the lateral cross-table hip view according to Woo and Morrey. All assessments were done pre-operatively and at 6 weeks, one, two and five years post-operatively. Three measurements were recorded and mean was obtained at all intervals All radiographs were evaluated by the same author, who was not involved in surgery. Results. There were four dislocations: one early and two contralateral dislocations which were solved wiith closed reduction, and one late recurrent dislocation five years after surgery which required cup revision. No other revision surgeries were performed. Mean sacro-femoral pubic angle decreased at all intervals from 60.6º preoperatively, to 60.0º at one year and 58.8 º at five years. This decrease was more significant in female, 63.3º preoperatively to 59.3º, than in male patients, 58.7º to 58.3º at five years. Mean acetabular abduction angle increased from 47.3º at 6 weeks to 48.2º at five years. Mean cup anteversion increased from 24.3º at 6 weeks to 26.4º at one year and 34.3º at five years. Conclusions. Posterior pelvic tilt increased with aging over time, particularly in women. These changes increased cup inclination and anteversion which may result in more dislocations after primary THA

Tracking of the anterior pelvic plane is of interest for medical interventions such as total hip arthroplasty, for which it is used as a reference for the positioning of the acetabular cup. We introduce and evaluate a new portable ultrasound device for the measure of the pelvic tilt in different positions of daily living. This device consists of two ultrasound probes articulated with respect to each other in order to visualise simultaneously the bony landmarks of interest that are one of the anterior superior iliac spine and the pubic symphysis. A series of sensors and the calibration of the ultrasound probes allow the measurement of the relative position of the landmarks with respect to a vertical line. The accuracy of the device has been investigated through a simulation study and showed errors (mean ± standard deviation [minimum; maximum]) as 0.18° ± 0.96° [−3.85°; 4.33°], with 99% of measurements within a ± 2.5° with respect to the actual pelvic tilt. This level of accuracy is similar to what can be found in the literature for the same purposes. Our device gathers advantages such as being portable and user friendly in order to be used during the pre-operative consultation. It is also non invasive and non irradiant. Further investigations will be run to assess this accuracy in vitro and in vivo

Introduction. Deciding the acetabular cup inclination and anteversion is an important step in total hip arthroplasty. Despite numerous studies focusing on enhancement of precise positioning into anatomical safe zone, problem remains regarding which is the “optimal anteversion” and what is the proper anatomical reference during the surgery. Objectives. The purpose of this study is to evaluate pelvic tilt angle measured in standing lateral view of pelvis in patients with hip osteoarthritis, and to find out the correlations between pelvic tilt angle (on Lewinnek anterior pelvic plane) and optimal anteversion position in total hip arthroplasty surgery. Results. The average pelvic tilt angle is 8.79 degree with standard deviation 8.25 degree. There have no statistically significant difference between the pelvic tilt angles of male and female patients, or patients received total hip arthroplasty and patients did not received surgery. The pelvic tilt angle significantly greater in patients older than 60 years old compared with patients younger than 60 years old (12 degree Vs 4 degree, p<0.005). Conclusions. There are large variations in the pelvic AP tilting between individuals, and the posterior tilting of pelvis increased with aging. Our findings suggested that instead of body axis measured when patient is in decubitus position on the table, cup positioning during total hip arthroplasty should be based on the functional position when patients is in upright position. The difference between functional position and bony axis might increase with age; hence increase the risk of over anteversion in cup positioning. This might lead to impingement between cup and femur prosthesis and cause early failure or dislocation. While positioning the patient using lateral position, surgeons should pay attention to anterior pelvic plane and pelvic tilt angle (taking from lateral standing position) for estimation of anteversion of cup

Introduction. Pelvic tilt can vary over time due to aging and the possible appearance of sagittal spine disorders. Cup position in total hip arthroplasty (THA) can be influenced due to these changes. We assessed the evolution of pelvic tilt and cup position after THA and the possible appearance of complications for a minimum follow-up of ten years. Materials and methods. 343 patients received a cementless THA between 2006 and 2009. All were diagnosed with primary osteoarthritis and their mean age was 63.3 years (range, 56 to 80). 168 were women and 175 men. 250 had no significant lumbar pathology, 76 had significant lumbar pathology and 16 had lumbar fusion. Radiological analysis included sacro-femoral-pubic (SFP), acetabular abduction (AA) and anteversion cup (AV) angles. Measurements were done pre-operatively and at 6 weeks, and at five and ten years post-operatively. Three measurements were recorded and the mean obtained at all intervals. All radiographs were evaluated by the same author, who was not involved in the surgery. Results. There were nine dislocations: six were solved with closed reduction, and three required cup revision. All the mean angles changed over time; the SFP angle from 59.2º to 60º (p=0.249), the AA angle from 44.5º to 46.8º (p=0.218), and the AV angle from 14.7º to 16.2º (p=0.002). The SFP angle was lower in older patients at all intervals (p<0.001). The SFP angle changed from 63.8 to 60.4º in women and from 59.4º to 59.3º in men, from 58.6º to 59.6º (p=0.012). The SFP angle changed from 62.7º to 60.9º in patients without lumbar pathology, from 58.6º to 57.4º in patients with lumbar pathology, and from 57.0º to 56.4º in patients with a lumbar fusion (p=0.919). The SFP cup angle was higher in patients without lumbar pathology than in the other groups (p<0.001), however, it changed more than in patients with lumbar pathology or fusion at ten years after THA (p=0.04). Conclusions. Posterior pelvic tilt changed with aging, influencing the cup position in patients after a THA. Changes due to lumbar pathology could influence the appearance of complications at mid and long-term

The functional pelvic tilt when standing and sitting forward of 7402 cases on the OPS, Optimized Ortho, Australia Data Base were reviewed. All patients had undergone lateral radiographs when standing simulating extension of the hip, and sitting forward when the hip is near full flexion. Pelvic tilt was measured as the angle of the Anterior Pelvic Plane to the vertical Sagittal Plane, rotation anteriorly being given a positive value. Pelvises that had rotated more than 13 degrees anteriorly (+ve) when sitting forward or posteriorly (-ve) when standing were considered to place the hip at increased risk of dislocation or edge loading when flexed or extending respectively. This degree of rotation has the effect of changing the acetabular version by approximately10. 0. Most safe zones that have been described have given a range of anteversion of 20. 0. as safe. A change of 10. 0. would potentially place the acetabular orientation outside this range. Further, clinical studies have supported this concept. All lateral radiographs were reviewed to confirm that 281 had undergone instrumented spinal fusion at some level between T12 and S1. There was a large variability in the number and the levels arthrodesed. The range of pelvic mobility in the non-arthrodesed group in extension was −37. 0. to 31. 0. (mean −0.9. 0. , Standard deviation 7.49) and in flexed position was −70. 0. to 49. 0. (mean −1.9. 0. , Standard deviation 14.01). For the group with any fusion the range of pelvic tilt in extension was −31. 0. to 22. 0. (mean −4. 0. , Standard deviation 8.21) and flexed −32. 0. to 46. 0. (mean 4.4. 0. , Standard deviation 13.79). Of the 7121 cases without instrumented fusion, 15.5% were considered to be at risk when in flexion and 6.1% when extended. The risk for those with any fusion was approximately doubled in both flexion and extension. Further, those with extensive arthrodesis from T12 to S1 had a range of pelvic tilts similar to the non-fused group, although they had a significantly higher percentage of cases in the ‘at risk’ zones. The proportion of the cases in the ‘at risk’ zones decreased progressively as the arthrodesed levels moved from L5/S1 to the upper lumbar spine, and with decreasing number of levels fused. Conclusion. Spinal fusion is not just one group as there are many combinations of different levels fused. Patients with instrumented spinal fusions do have a proportionately high risk of failure of their THR than the majority of cases with no instrumentation, though the risk varies significantly with the number of levels and actual levels arthrodesed. Further approximately 21% of cases with no spinal fusion have functional pelvic movements that would potentially place them ‘at risk’ of edge loading or dislocation. For any figures or tables, please contact authors directly