Objectives. The spinopelvic relationship (including pelvic incidence) has been shown to influence pelvic orientation, but its potential association with femoroacetabular impingement has not been thoroughly explored. The purpose of this study was to prove the hypothesis that decreasing pelvic incidence is associated with increased risk of cam morphology. Methods. Two matching cohorts were created from a collection of cadaveric specimens with known pelvic incidences: 50 subjects with the highest pelvic incidence (all subjects > 60°) and 50 subjects with the lowest pelvic incidence (all subjects < 35°). Femoral version, acetabular version, and alpha angles were directly measured from each specimen bilaterally. Cam morphology was defined as alpha angle > 55°. Differences between the two cohorts were analysed with a Student’s t-test and the difference in incidence of cam morphology was assessed using a chi-squared test. The significance level for all tests was set at p < 0.05. Results. Cam morphology was identified in 47/100 (47%) femurs in the cohort with pelvic incidence < 35° and in only 25/100 (25%) femurs in the cohort with pelvic incidence > 60° (p = 0.002). The mean alpha angle was also greater in the cohort with pelvic incidence < 35° (mean 53.7°, . sd. 10.7° versus mean 49.7°, . sd. 10.6°; p = 0.008). Conclusions. Decreased pelvic incidence is associated with development of cam morphology. We propose a novel theory wherein subjects with decreased pelvic incidence compensate during gait (to maintain optimal sagittal balance) through anterior pelvic tilt, creating artificial anterior acetabular overcoverage and recurrent impingement that increases risk for cam morphology. Cite this article: W. Z. Morris, C. A. Fowers, R. T. Yuh, J. J. Gebhart, M. J. Salata, R. W. Liu. Decreasing pelvic incidence is associated with greater risk of cam morphology. Bone Joint Res 2016;5:387–392. DOI: 10.1302/2046-3758.59.BJR-2016-0028.R1

Aims

The effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?

Abstract. OBJECTIVES. Cam femoroacetabular impingement (FAI – femoral head-neck deformity) and developmental dysplasia of the hip (DDH – insufficient acetabular coverage) constitute a large portion of adverse hip loading and early degeneration. Spinopelvic anatomy may play a role in hip stability thus we examined which anatomical relationships can best predict range of motion (ROM). METHODS. Twenty-four cadaveric hips with cam FAI or DDH (12:12) were CT imaged and measured for multiple femoral (alpha angles, head-neck offset, neck angles, version), acetabular (centre-edge angle, inclination, version), and spinopelvic features (pelvic incidence). The hips were denuded to the capsule and mounted onto a robotic tester. The robot positioned each hip in multiple flexion angles (Extension, Neutral 0°, Flexion 30°, Flexion 60°, Flexion 90°); and performed internal-external rotations to 5 Nm in each position. Independent t-tests compared the anatomical parameters and ROM between FAI and DDH (CI = 95%). Multiple linear regressions determined which anatomical parameters could predict ROM. RESULTS. The FAI group demonstrated restricted ROM in deep hip flexion, with DDH showing higher ROM in Flexion 30° (+20%, p = 0.03), 60° (+31%, p = 0.001), and 90° (+36%, p = 0.001). In Neutral 0° and Flexion 30°, femoral neck and version angles together predicted ROM (R. 2. = 60%, 58% respectively); whereas in Flexion 60°, pelvic incidence and femoral neck angle predicted ROM (R. 2. = 77%). In Flexion 90°, pelvic incidence and radial alpha angle together predicted ROM (R. 2. = 81%), where pelvic incidence alone accounted for 63% of this variance. CONCLUSIONS. Pelvic incidence is essential to predict hip ROM. Although a cam deformity or acetabular undercoverage can elevate risks of labral tears and progressive joint degeneration, they may not be primary indicators of restrictive hip impingement or dysplastic instability. Better delineating additional spinopelvic characteristics can formulate early diagnostic tools and improve opportunities for nonsurgical management. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Objectives. Sagittal alignment of the lumbosacral spine, and specifically pelvic incidence (PI), has been implicated in the development of spine pathology, but generally ignored with regards to diseases of the hip. We aimed to determine if increased PI is correlated with higher rates of hip osteoarthritis (HOA). The effect of PI on the development of knee osteoarthritis (KOA) was used as a negative control. Methods. We studied 400 well-preserved cadaveric skeletons ranging from 50 to 79 years of age at death. Each specimen’s OA of the hip and knee were graded using a previously described method. PI was measured from standardised lateral photographs of reconstructed pelvises. Multiple regression analysis was performed to determine the relationship between age and PI with HOA and KOA. Results. The mean age was 60.2 years (standard deviation (. sd. ) 8.1), and the mean PI was 46.7° (. sd. 10.7°). Multiple regression analysis demonstrated a significant correlation between increased PI and HOA (standardised beta = 0.103, p = 0.017). There was no correlation between PI and KOA (standardised beta = 0.003, p = 0.912). Conclusion. Higher PI in the younger individual may contribute to the development of HOA in later life. Cite this article: Dr J. J. Gebhart. Relationship between pelvic incidence and osteoarthritis of the hip. Bone Joint Res 2016;5:66–72. DOI: 10.1302/2046-3758.52.2000552

Aims. The risk factors for abnormal spinopelvic mobility (SPM), defined as an anterior rotation of the spinopelvic tilt (∆SPT) ≥ 20° in a flexed-seated position, have been described. The implication of pelvic incidence (PI) is unclear, and the concept of lumbar lordosis (LL) based on anatomical limits may be erroneous. The distribution of LL, including a unusual shape in patients with a high lordosis, a low pelvic incidence, and an anteverted pelvis seems more relevant. Methods. The clinical data of 311 consecutive patients who underwent total hip arthroplasty was retrospectively analyzed. We analyzed the different types of lumbar shapes that can present in patients to identify their potential associations with abnormal pelvic mobility, and we analyzed the potential risk factors associated with a ∆SPT ≥ 20° in the overall population. Results. ΔSPT ≥ 20° rates were 28.3%, 11.8%, and 14.3% for patients whose spine shape was low PI/low lordosis (group 1), low PI anteverted (group 2), and high PI/high lordosis (group 3), respectively (p = 0.034). There was no association between ΔSPT ≥ 20° and PI ≤ 41° (odds ratio (OR) 2.01 (95% confidence interval (CI)0.88 to 4.62), p = 0.136). In the multivariate analysis, the following independent predictors of ΔSPT ≥ 20° were identified: SPT ≤ -10° (OR 3.49 (95% CI 1.59 to 7.66), p = 0.002), IP-LL ≥ 20 (OR 4.38 (95% CI 1.16 to 16.48), p = 0.029), and group 1 (OR 2.47 (95% CI 1.19; to 5.09), p = 0.0148). Conclusion. If the PI value alone is not indicative of SPM, patients with a low PI, low lordosis and a lumbar apex at L4-L5 or below will have higher rates of abnormal SPM than patients with a low PI anteverted and high lordosis. Cite this article: Bone Jt Open 2023;4(9):668–675

Purpose. Spinopelvic parameters are associated with the development of symptomatic femoroacetabular impingement and subsequent osteoarthritis. Pelvic incidence (PI) characterizes the sagittal profile of the pelvis and is important in the regulation of both lumbar lordosis and pelvic orientation (i.e. tilt). The purpose of this imaging-based study was to test the association between PI and acetabular morphology. Methods. Measurements of the pelvis and acetabulum were performed for 96 control patients and 29 hip dysplasia patients using 3D-computed topography (3D-CT) scans. Using previously validated measurements the articular cartilage and cotyloid fossa area of the acetabulum, functional acetabular version/inclination, acetabular depth, pelvic tilt, sacral slope, and PI were calculated. Non-parametric statistical tests were used; significance was set at p<0.05. Results. Of the 125 scans analyzed in this study, 65% were females and the average age was 24.8±6.0 years old. Thirty-six (14.4%) hips had acetabular retroversion; 178 (71.2%) had normal acetabular version; and 36 (14.4%) had high acetabular anteversion. Acetabular version moderately correlated with pelvic incidence; (Sρearman= 0.4; p<0.001). Patients with acetabular retroversion had significantly lower PI (44.2. °. ; 95% CI 41.0–47.4. °. ), compared to those with normal acetabular version (49.4. °. ; 95% CI 47.8–51.0. °. ) (p=0.004). Patients with normal version had significantly lower PI compared to those with high acetabular anteversion (56.4. °. ; 95% CI 52.8–60.0. °. ) (p<0.001). A significant difference in pelvic tilt between the groups (retroversion: 3±7; normal: 9±6; high version: 17±7) (p<0.001) was noted. Acetabular depth inversely and weakly correlated with pelvic incidence (ρ= −0.2; p=0.001). No other of the acetabular parameter correlated with the spinopelvic parameters tested. Conclusion. This is the first study to demonstrate the association between PI and functional acetabular version using 3D-CT scans. The results of this study illustrate the importance of PI as a descriptor of both pelvic and acetabular morphology and function

The aim was to evaluate the Intraobserver and Interobserver reliability of Pelvic Incidence as a fundamental parameter of sagittal spino-pelvic balance in patients with spondylolisthesis compared to controls with Idiopathic Adolescent Scoliosis. A blinded test retest study including multi-surgeon assessment of Pelvic Incidence in patients with spondylolisthesis and Idiopathic Adolescent Scoliosis was carried out. We assessed the agreement between the pelvic incidence measurements using the Bland and Altman method and mean differences (95% confidence interval) are reported. Forty patients seen at Starship Children’s Hospital between 1992 – 2003 by two spinal surgeons were retrospectively identified. The main group had 20 patients with spondylolisthesis (Isthmic and/or Dysplastic types) and the control group consisted of 20 patients with Idiopathic Adolescent Scoliosis. Five observers with different levels of experience included the two orthopaedic surgeons, one fellow, one senior trainee and one non-trainee registrar. Prior to the initial test phase, a consensus-building session was carried out. All five observers arrived at a standardised method for measuring the Pelvic Incidence. In the test phase randomly ordered lateral lumbosacral radiographs were independently evaluated by the five observers and pelvic incidence was measured. Assessment of the Pelvic Incidence was repeated one week later in the re-test phase. The radiographs were presented in a randomly pre-assigned order. Bland and Altman plots were constructed and mean differences (95% confidence interval) reported to evaluate the agreement between the Pelvic Incidence measurements among the five independent observers. All analysis was performed on the statistical software package SAS. P-value of 0.05 was considered statistically significant. The spondylolisthesis group had 11 (55%) males and 9 (45%) females with an average age of 14 ± 4.2. 2 patients had high-grade (Meyerding Class III, IV, V) and 16 had low-grade (Meyerding Class I, II) spondylolisthesis. 2 patients were post-reduction of spondylolisthesis. In the Scoliosis group there were 2 (10%) males and 18 (90%) females with an average age of 15 ± 2.9. There was no significant difference between male and females pelvic incidence measurement (60° ± 18.7° vs. 57° ± 14.6°, p=0.540) or age (15 ± 2.9 vs. 14 ± 3.8, p=0.181). There was no difference in pelvic incidence across the Meyerding groups, p=0.257. There was a significant difference between spondylolisthesis and scoliosis pelvic incidence measurements 65° ± 15.6° vs. 51° ± 12.8°, p=0.003. In the . Spondylolisthesis Group. the interobserver reliability between five clinicians, expressed as the mean difference in pelvic incidence measurement was 0.6° (95%CI −0.81, 1.91) and was not significantly different from zero p=0.423. The agreement limits were from −12.8° to 13.9°. The intraobserver reliability of pelvic incidence showed the mean difference ranging from −2.1° to 1.4° (p=0.129 and 0.333 with 95% CI). One had marginal evidence of a significant difference of 3.3° (95% CI 0.05° to 6.55°, p=0.047). In the . Scoliosis Group. the interobserver reliability was 0.3° (95% CI −0.81, 1.49) and was not significantly different from zero p=0.726. The agreement limits were from −11.0° to 11.6°. The intraobserver reliability among four observers ranged from −1.7° to 0.5° (p=0.178 and 0.661). One had a significant difference in readings of 4.1° (95% CI of 0.70° to 7.40°, p= 0.020). Scoliosis patients had a significantly smaller pelvic incidence than spondylolisthesis patients. The interobserver reliability of the pelvic incidence measurement was excellent across both groups. The intraobserver reliability was good with only one observer in each group demonstrating a marginally significant difference. Pelvic incidence is therefore a reliable measurement which can be used as a predictor in progression of spondylolisthesis

Purpose. Minimally invasive anterolateral approach (ALA) for total hip arthroplasty (THA) has gained popularity in recent years as better postoperative functional recovery and lower risk of postoperative dislocation are claimed. However, difficulties for femur exposure and intraoperative complications during femoral canal preparation and component placement have been reported. This study analyzes the anatomical factors likely to be related with intraoperative complications and the difficulties of access noted by the surgeons through a modified minimally invasive ALA. The aim is to define the profile for patient at risk of intraoperative complications during minimally invasive ALA. Methods. We retrospectively included 310 consecutive patients (100 males, 210 females) who had primary unilateral THA using the same technique in all cases. The approach was performed between the tensor fascia lata and the gluteus medius and minimus, without incising or detaching muscles and tendons. Posterior translation was combined to external rotation for proximal femur exposure (Fig. 1). All patients were reviewed clinically and radiologically. For the radiological evaluation, all patients underwent pre- and postoperative standing and sitting full-body EOS acquisitions. Pelvic [Sacral slope, Pelvic incidence (PI), Anterior pelvic plane angle] and femoral parameters were measured preoperatively. We assessed all intraoperative and postoperative complications for femoral preparation and implantation. Intraoperative complications included the femoral fractures and difficulties for femoral exposure (limitations for exposure and lateralization of the proximal femur). The patients were divided into two groups: patients with or without intraoperative complications. Results. Ten patients (3.2%) had intraoperative femoral fractures (greater trochanter: 2 cases, calcar: 8 cases). Five fractures required additional wiring. Difficult access to proximal femur was reported in the operative records for 10 other patients (3.2%). There was no difference in diagnosis, age, sex, BMI between the patients with or without intraoperative complications. No significant group differences were found for surgical time, and blood loss. Patients with intraoperative complication, presented a significantly lower pelvic incidence than patients without intraoperative complications (mean PI: 39.4° vs 56.9°, p<0.001). The relative risk of intraoperative complications in patients with low PI (PI<45°) was more than thirteen times (relative risk; 13.3, 95% CI= 8.2 to 21.5. p<0.001) the risk for patients with normal and high PI (PI>45°). Conclusions. Anterolateral approach for THA implantation in lateral decubitus is reported to have anatomical and functional advantages. Nevertheless, the exposure of the femur remains a limitation. This study highlights a significant increased risk in case of low PI less than 45°. This specific anatomical pattern reduces the local working space as the possibility for posterior translation and elevation of the proximal femur is less on a narrow pelvis. This limitation is due to the length and the orientation of the hip abductor and short external rotator muscles related to the relative positions of iliac wing and greater trochanter (Fig. 2). This study points out the importance of pelvic incidence for the detection of anatomically less favourable patients for THA implantation using ALA. For any figures or tables, please contact the authors directly

Aim:. To determine if patients with coronal plane deformity in the lumbar spine have a higher grade of lumbar spine subtype compared to controls. Method:. This was a retrospective case/control study based on a review of radiological investigations in 250 patients aged over 40 years who had standing plain film lumbar radiographs with hips present. Measurements of lumbar coronal plane angle, lumbar lordosis, sacral slope, pelvic tilt and pelvic incidence were obtained. “Cases” with degenerative scoliosis (n=125) were defined as patients with a lumbar coronal plane angle of >10°. Lumbar spine subtype was categorised (1–4) using the Roussouly classification. Lumbar spine subtype was dichotomised into low (type 1,2) or high (type 3,4). Prevalence of lumbar spine subtype in cases versus controls was compared using the Chi squared test. Pelvic incidence was compared using an unpaired T-test. Predictors of lumbar coronal plane angle were identified using stepwise multiple regression. Significance was accepted at P<0.05. Results:. The prevalence of type 1–4 lumbar spine subtypes in the case group were 12.8%, 20.8%, 30.4% and 36% respectively and in the control group were 10.4%, 38.3% and 28% and 23.3% respectively. Types 3 and 4 lumbar spine subtypes were more prevalent in the cases group (66.4% vs 51.2% respectively, P=0.0207). Pelvic incidence was not significant different between groups (P=0.0594). No significant predictors of lumbar coronal plane angle were determined. Lumbar spine subtype (P=0.969), pelvic incidence (P=0.740), sacral slope (P=0.203) pelvic tilt (P=0.167) and lumbar lordosis (P=0.088) were not significant. Discussion:. Results show that neither the lumbar spine subtype nor pelvic parameters appear to have a significant influence on determining the coronal plane angle in the degenerative lumbar spine. Conflict Of Interest Statement: No conflict of interest

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

Introduction. Post op cup anatomical and functional orientation is a key point in THP patients regarding instability and wear. Recently literature has been focused on the consequences of the transition from standing to sitting regarding anteversion, frontal and sagittal inclination. Pelvic incidence (PI) is now considered as a key parameter for the analysis of sagittal balance and sacral slope (SS) orientation. It's influence on THP biomechanics has been suggested. Interestingly, the potential impact of this morphological angle on cup implantation during surgery and the side effects on post op functional orientation have not been studied. Our study explores this topic from a series of standing and sitting post-op EOS images. Material and methods. 310 patients (mean age 63,8, mean BMI 30,2) have been included prospectively in our current post-operative EOS protocol. All patients were operated with the same implants and technique using anterior approach in lateral decubitus. According to previous literature, 3 groups were defined: low PI less than 45° (57 cases), high PI if more than 60° (63 cases), and standard PI in 190 other cases. Results. Mean PI was 55,8° (SD 11,5). -In High PI, postop SS in standing was significantly higher than in Low and Medium PI. In Medium PI, postop SS in standing was significantly higher than in Low PI. -In High PI, postop SS in sitting was significantly higher than in Low and Medium PI. -In Low PI, postop Functional anteversion in sitting was significantly higher than in Medium PI, but not different from High PI. -In Low PI, Anatomical anteversion was significantly higher than in Medium and High PI. Discussion, Conclusion. This preliminary study points out the potential influence of pelvis morphology expressed by PI on per-operative cup orientation. As surgeons are accustomed to follow bony landmarks during cup implantation, unexpected variations for cup adjustment may be observed if PI is not standard. For any figures or tables, please contact authors directly

Aim:. To simplify sagittal plane spinal assessment by describing a single novel angle in the lumbar spine equivalent to the difference between pelvic incidence (PI) and lumbar lordosis (LL) and evaluate its reliability. Methods:. New sagittal modifiers in the classification of adult degenerative spinal deformity have been shown to be valid and reliable with the greatest variability being for pelvic incidence minus lumbar lordosis (PI-LL). This measurement can be simplified to a new angle (alpha) without the need to determine either PI or LL. This angle is between a line intersecting the bicoxofemoral centre and perpendicular to the L1 endplate (alpha line) and a line from the bicoxofemoral centre to the centre of the sacral endplate. Two readers graded 40 non-premarked cases twice each, approximately 1 week apart. Inter- and intra-rater variability and agreement were determined for PI-LL and alpha angle separately. Fleiss' kappa was used for reliability measures. Results:. Inter-rater kappa for PI-LL showed substantial reliability and alpha angle showed almost perfect agreement. Intra-rater kappa showed substantial reliability for PI-LL but almost perfect agreement for alpha angle across both readers. Discussion:. Alpha angle can be used as a surrogate for PI-LL and is easier and more reliable to measure. When PI=LL, alpha angle is 0, so the alpha line bisects the sacral plate. Conflict Of Interest Statement: No conflict of interest

Aims. Spinopelvic characteristics influence the hip’s biomechanical behaviour. However, to date there is little knowledge defining what ‘normal’ spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals. Methods. This systematic review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines to identify English studies, including ≥ 18-year-old participants, without evidence of hip or spine pathology or a history of previous surgery or interventional treatment, documenting lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). From a total of 2,543 articles retrieved after the initial database search, 61 articles were eventually selected for data extraction. Results. When all ethnicities were combined the mean values for LL, SS, PT, and PI were: 47.4° (SD 11.0°), 35.8° (SD 7.8°), 14.0° (SD 7.2°), and 48.8° (SD 10°), respectively. LL, SS, and PT had statistically significant (p < 0.001) changes per decade at: −1.5° (SD 0.3°), −1.3° (SD 0.3°), and 1.4° (SD 0.1°). Asian populations had the largest age-dependent change in LL, SS, and PT compared to any other ethnicity per decade at: −1.3° (SD 0.3°) to −0.5° (SD 1.3°), –1.2° (SD 0.2°) to −0.3° (SD 0.3°), and 1.7° (SD 0.2°) versus 1.1° (SD 0.1°), respectively. Conclusion. Ageing alters the orientation between the spine and pelvis, causing LL, SS, and PT to modify their orientations in a compensatory mechanism to maintain sagittal alignment for balance when standing. Asian populations have the largest degree of age-dependent change to their spinopelvic parameters compared to any other ethnicity, likely due to their lower PI. Cite this article: Bone Joint Res 2023;12(4):231–244

Aims

Precise implant positioning, tailored to individual spinopelvic biomechanics and phenotype, is paramount for stability in total hip arthroplasty (THA). Despite a few studies on instability prediction, there is a notable gap in research utilizing artificial intelligence (AI). The objective of our pilot study was to evaluate the feasibility of developing an AI algorithm tailored to individual spinopelvic mechanics and patient phenotype for predicting impingement.

The lordosis distribution index (LDI) describes distribution of lumbar lordosis, measured as the % of lower lumbar lordosis (L4-S1) compared to global lordosis (L1-S1) with normal value 50–50%. Maldistributed LDI is associated with higher revision in short lumbar fusions, 4 vertebrae1. We hypothesise maldistributed LDI is also associated with mechanical failure in longer fusions. Retrospective review of 29 consecutive ASD patients, aged 55+, undergoing long lumbar fusion, 4 levels, with >3-years follow-up. LDI, pelvic incidence (PI) and sagittal vertical axis (SVA) were measured on pre- and post-op whole spine standing X-rays (Fig A and B). Patients were categorized according to their pelvic incidence (PI) and postoperative LDI: Normal (LDI 50 80), Hypolordotic (LDI < 50), or Hyperlordotic (LDI > 80) and assessed for failure rate compared to normal LDI and PI <60. Mean follow-up 4.5 years. 19 patients had mechanical failures including junctional failure and metalware fracture. PI >60o was associated with higher mechanical failure rates (Chi^2 p<0.05). Hypolordotic LDI was associated with 82% mechanical failure (Chi^2 p<0.001), Hyperlordotic 88% mechanical failure (Chi^2 p<0.001) and Normal 8% mechanical failure (Table 1). Maldistributed LDI, whether Hyperlordotic or Hypolordotic, correlated with 10× greater mechanical failure rate compared to Normal LDI in long fusions. LDI is a useful measurement that should be considered, especially in high PI patients

Intra-Discal Vacuum Phenomenon (IDVP) represents an intradiscal nitrogen gas accumulation where a cavity opens in a supine position, lowering intra-discal pressure and generating a bubble. IDVP has been observed in up to 20% of elderly patients and reported in almost 50% of chronic LBP patients. With a highly accurate detection on CT, its significance lacks clarity and consideration within normative data. IDVP occurs with patterns of lumbar and/or lumbopelvic morphology and associated diagnoses. Over-60s population based sample of 2020 unrelated CT abdomen scans without acute spinal presentations, with sagittal reconstructions, inclusive of T12 to femoral heads, were analyzed for IDVP and pelvic incidence (PI). Subjects with diagnostic morphological associations of the lumbar spine, including previous fracture, autofusion, transitional vertebra and listhesis, were selected out and analyzed separately. Subjects were then equally grouped into low, medium and high PI. Prevalence of lumbar spine IDVP is 41.3%. 125 cases were excluded. 1603 subjects yielded 663 IDVP. This was increased in severity towards the lumbosacral junction (L1L2 9.4%, L2L3 10.9%, L3L4 13.7%, L4L5 19.9%, L5S1 28.5%) and those with low PI, while distribution was more even with high PI. 292 had positive diagnostic associations, which were more likely to occur at the level of isthmic spondylolisthesis, adjacent to a previous fracture or suprajacent to lumbosacral transitional vertebra (p<0.05). This study has identified normative values for prevalence and severity of IDVP in a normal aging population. Morphological patterns that influence the pattern of IVDP such as pelvic incidence and diagnostic associations provide novel insights to the function of the aging spine

Aims. The aim of this study was to evaluate the reliability and validity of a patient-specific algorithm which we developed for predicting changes in sagittal pelvic tilt after total hip arthroplasty (THA). Methods. This retrospective study included 143 patients who underwent 171 THAs between April 2019 and October 2020 and had full-body lateral radiographs preoperatively and at one year postoperatively. We measured the pelvic incidence (PI), the sagittal vertical axis (SVA), pelvic tilt, sacral slope (SS), lumbar lordosis (LL), and thoracic kyphosis to classify patients into types A, B1, B2, B3, and C. The change of pelvic tilt was predicted according to the normal range of SVA (0 mm to 50 mm) for types A, B1, B2, and B3, and based on the absolute value of one-third of the PI-LL mismatch for type C patients. The reliability of the classification of the patients and the prediction of the change of pelvic tilt were assessed using kappa values and intraclass correlation coefficients (ICCs), respectively. Validity was assessed using the overall mean error and mean absolute error (MAE) for the prediction of the change of pelvic tilt. Results. The kappa values were 0.927 (95% confidence interval (CI) 0.861 to 0.992) and 0.945 (95% CI 0.903 to 0.988) for the inter- and intraobserver reliabilities, respectively, and the ICCs ranged from 0.919 to 0.997. The overall mean error and MAE for the prediction of the change of pelvic tilt were -0.3° (SD 3.6°) and 2.8° (SD 2.4°), respectively. The overall absolute change of pelvic tilt was 5.0° (SD 4.1°). Pre- and postoperative values and changes in pelvic tilt, SVA, SS, and LL varied significantly among the five types of patient. Conclusion. We found that the proposed algorithm was reliable and valid for predicting the standing pelvic tilt after THA. Cite this article: Bone Joint J 2024;106-B(1):19–27

Abstract. Introduction. Recent reports show that spinopelvic mobility influences outcome following total hip arthroplasty. This scoping review investigates the relationship between spinopelvic parameters (SPPs) and symptomatic femoroacetabular impingement (FAI). Methods. A systematic search of EMBASE, PubMed and Cochrane for literature related to SPPs and FAI was undertaken as per PRISMA guidelines. Clinical outcome studies and prospective/retrospective studies investigating the role of SPPs in symptomatic FAI were included. Review articles, case reports and book chapters were excluded. Information extracted pertained to symptomatic cam deformities, pelvic tilt, acetabular version, biomechanics of dynamic movements and radiological FAI signs. Results. The search identified 42 papers for final analysis out of 1168 articles investigating the link between SPPs and pathological processes characteristic of FAI. Only one (2.4%) study was of level 1 evidence, five (11.9%) studies) were level 2, 17 (40.5%) were level 3 and 19 (45.2%) were level 4. Three studies associated FAI pathology with a greater pelvic incidence (PI), while four associated it with a smaller PI. Anterior pelvic tilt was associated with radiographic overcoverage parameters of FAI. In dynamic movements, decreased posterior pelvic tilt was a common feature in symptomatic FAI patients at increased hip flexion angles. FAI patients additionally demonstrated reduced sagittal pelvic ROM during dynamic hip flexion. Six studies found kinematic links between sagittal spinopelvic movement and sagittal and transverse plane hip movements. Conclusions. Our study shows that spinopelvic parameters can influence radiological and clinical manifestations of FAI, with pelvic incidence, acetabular version and muscular imbalances being aetiologically implicated. These factors may be amenable to non-surgical therapy. Individual spinopelvic mechanics may predispose to the development of FAI. If FAI pathoanatomy already exists, sagittal pelvic parameters can influence whether FAI symptoms develop and is an area of further research interest

Aims. This study aimed to evaluate sagittal spinopelvic alignment (SSPA) in the early stage of rapidly destructive coxopathy (RDC) compared with hip osteoarthritis (HOA), and to identify risk factors of SSPA for destruction of the femoral head within 12 months after the disease onset. Methods. This study enrolled 34 RDC patients with joint space narrowing > 2 mm within 12 months after the onset of hip pain and 25 HOA patients showing femoral head destruction. Sharp angle was measured for acetabular coverage evaluation. Femoral head collapse ratio was calculated for assessment of the extent of femoral head collapse by RDC. The following parameters of SSPA were evaluated using the whole spinopelvic radiograph: pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), sagittal vertical axis (SVA), thoracic kyphosis angle (TK), lumbar lordosis angle (LL), and PI-LL. Results. The HOA group showed higher Sharp angles compared with the RDC group. PT and PI-LL were higher in the RDC group than the HOA group. SS and LL were lower in the RDC group than the HOA group. No difference was found in PI, SVA, or TK between the groups. Femoral head collapse ratio was associated with PT, SS, SVA, LL, and PI-LL. A PI-LL > 20° and a PT > 30° correlated with greater extent of femoral head destruction by RDC. From regression analysis, SS and SVA were significantly associated with the femoral head collapse ratio within 12 months after disease onset. Conclusion. Compared with HOA, RDC in the early stage correlated with sagittal spinopelvic malalignment. SS and SVA may partially contribute to the extent of femoral head destruction by RDC within 12 months after the onset of hip pain. The present study indicates a potential role of SSPA assessment in identification of RDC patients at risk for subsequent bone destruction. Cite this article: Bone Jt Open 2022;3(1):77–84

Aims. Our objective was describing an algorithm to identify and prevent vascular injury in patients with intrapelvic components. Methods. Patients were defined as at risk to vascular injuries when components or cement migrated 5 mm or more beyond the ilioischial line in any of the pelvic incidences (anteroposterior and Judet view). In those patients, a serial investigation was initiated by a CT angiography, followed by a vascular surgeon evaluation. The investigation proceeded if necessary. The main goal was to assure a safe tissue plane between the hardware and the vessels. Results. In ten at-risk patients undergoing revision hip arthroplasty and submitted to our algorithm, six were recognized as being high risk to vascular injury during surgery. In those six high-risk patients, a preventive preoperative stent was implanted before the orthopaedic procedure. Four patients needed a second reinforcing stent to protect and to maintain the vessel anatomy deformed by the intrapelvic implants. Conclusion. The evaluation algorithm was useful to avoid blood vessels injury during revision total hip arthroplasty in high-risk patients. Cite this article: Bone Jt Open 2022;3(11):859–866