Aims. It is important to consider sagittal pelvic rotation when introducing the acetabular component at total hip arthroplasty (THA). The purpose of this study was to identify patients who are at risk of unfavourable pelvic mobility, which could result in poor outcomes after THA. Patients and Methods. A consecutive series of 4042 patients undergoing THA had lateral functional radiographs and a low-dose CT scan to measure supine pelvic tilt, pelvic incidence, standing pelvic tilt, flexed-seated pelvic tilt, standing lumbar lordotic angle, flexed-seated lumbar lordotic angle, and lumbar flexion. Changes in pelvic tilt from supine-to-standing positions and supine-to-flexed-seated positions were determined. A change in pelvic tilt of 13° between positions was deemed unfavourable as it alters functional anteversion by 10° and effectively places the acetabular component outside the safe zone of orientation. Results. For both men and women, the degree of lumbar flexion was a significant predictor of risk in hip flexion (p < 0.0001) with increased odds of unfavourable pelvic mobility in those with lumbar flexion of < 20° (men, odds ratio (OR) 6.74, 95% confidence interval (CI) 3.83 to 11.89; women, OR 2.97, 95% CI 1.87 to 4.71). In women, age and standing pelvic tilt were significant predictors of risk in hip extension (p = 0.0082 and p < 0.0001, respectively). The risk of unfavourable pelvic mobility was higher in those aged > 75 years (OR 2.28, 95% CI 1.56 to 3.32) and those with standing pelvic tilt of < -10° for extension risk (OR 7.10, 95% CI 4.10 to 10.29). In men, only standing pelvic tilt was significant (p < 0.0001) for hip extension with an increased risk of unfavourable pelvic mobility (OR 8.68, 95% CI 5.19 to 14.51). Conclusion. Patients found to have unfavourable pelvic mobility had limited lumbar flexion and more posterior standing pelvic tilt in both men and women, as well as increasing age in women. We recommend that patients undergo preoperative functional radiographic screening to determine specific parameters that can affect the functional orientation of the acetabular component. Cite this article: Bone Joint J 2018;100-B:845–52

Aims. The aim of this study was to review the current evidence surrounding curve type and morphology on curve progression risk in adolescent idiopathic scoliosis (AIS). Methods. A comprehensive search was conducted by two independent reviewers on PubMed, Embase, Medline, and Web of Science to obtain all published information on morphological predictors of AIS progression. Search items included ‘adolescent idiopathic scoliosis’, ‘progression’, and ‘imaging’. The inclusion and exclusion criteria were carefully defined. Risk of bias of studies was assessed with the Quality in Prognostic Studies tool, and level of evidence for each predictor was rated with the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. In all, 6,286 publications were identified with 3,598 being subjected to secondary scrutiny. Ultimately, 26 publications (25 datasets) were included in this review. Results. For unbraced patients, high and moderate evidence was found for Cobb angle and curve type as predictors, respectively. Initial Cobb angle > 25° and thoracic curves were predictive of curve progression. For braced patients, flexibility < 28% and limited in-brace correction were factors predictive of progression with high and moderate evidence, respectively. Thoracic curves, high apical vertebral rotation, large rib vertebra angle difference, small rib vertebra angle on the convex side, and low pelvic tilt had weak evidence as predictors of curve progression. Conclusion. For curve progression, strong and consistent evidence is found for Cobb angle, curve type, flexibility, and correction rate. Cobb angle > 25° and flexibility < 28% are found to be important thresholds to guide clinical prognostication. Despite the low evidence, apical vertebral rotation, rib morphology, and pelvic tilt may be promising factors. Cite this article: Bone Joint J 2022;104-B(4):424–432

Aims. Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation. Methods. Intraoperative pelvic radiographs of 50 patients who underwent THA were collected retrospectively. The 3D pelvic bone model and the acetabular component were image-matched to the intraoperative pelvic radiograph. The radiological anteversion (RA) and radiological inclination (RI) of the acetabular component were calculated and those measurement errors from the postoperative CT data were compared relative to those of the 2D measurements. In addition, the intra- and interobserver differences of the image-matching analysis were evaluated. Results. Mean measurement errors of the image-matching analyses were significantly small (2.5° (SD 1.4°) and 0.1° (SD 0.9°) in the RA and RI, respectively) relative to those of the 2D measurements. Intra- and interobserver differences were similarly small from the clinical perspective. Conclusion. We have developed a computational analysis of acetabular component orientation using an image-matching technique with small measurement errors compared to visual evaluations regardless of the pelvic tilt or rotation. Cite this article: Bone Joint Res 2020;9(7):360–367

Aims. Adverse spinal motion or balance (spine mobility) and adverse pelvic mobility, in combination, are often referred to as adverse spinopelvic mobility (SPM). A stiff lumbar spine, large posterior standing pelvic tilt, and severe sagittal spinal deformity have been identified as risk factors for increased hip instability. Adverse SPM can create functional malposition of the acetabular components and hence is an instability risk. Adverse pelvic mobility is often, but not always, associated with abnormal spinal motion parameters. Dislocation rates for dual-mobility articulations (DMAs) have been reported to be between 0% and 1.1%. The aim of this study was to determine the early survivorship from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) of patients with adverse SPM who received a DMA. Methods. A multicentre study was performed using data from 227 patients undergoing primary total hip arthroplasty (THA), enrolled consecutively. All the patients who had one or more adverse spine or pelvic mobility parameter had a DMA inserted at the time of their surgery. The mean age was 76 years (22 to 93) and 63% were female (n = 145). At a mean of 14 months (5 to 31) postoperatively, the AOANJRR was analyzed for follow-up information. Reasons for revision and types of revision were identified. Results. The AOANJRR reported two revisions: one due to infection, and the second due to femoral component loosening. No revisions for dislocation were reported. One patient died with the prosthesis in situ. Kaplan-Meier survival rate was 99.1% (95% confidence interval 98.3 to 100) at 14 months (number at risk 104). Conclusion. In our cohort of patients undergoing primary THA with one or more factor associated with adverse SPM, DM bearings conferred stability at two years’ follow-up. Cite this article: Bone Joint J 2022;104-B(7):820–825

Aims. The aim of this study was to investigate the impact of the level of upper instrumented vertebra (UIV) in frail patients undergoing surgery for adult spine deformity (ASD). Methods. Patients with adult spinal deformity who had undergone T9-to-pelvis fusion were stratified using the ASD-Modified Frailty Index into not frail, frail, and severely frail categories. ASD was defined as at least one of: scoliosis ≥ 20°, sagittal vertical axis (SVA) ≥ 5 cm, or pelvic tilt ≥ 25°. Means comparisons tests were used to assess differences between both groups. Logistic regression analyses were used to analyze associations between frailty categories, UIV, and outcomes. Results. A total of 477 patients were included (mean age 60.3 years (SD 14.9), mean BMI 27.5 kg/m. 2. (SD 5.8), mean Charlson Comorbidity Index (CCI) 1.67 (SD 1.66)). Overall, 74% of patients were female (n = 353), and 49.6% of patients were not frail (237), 35.4% frail (n = 169), and 15% severely frail (n = 71). At baseline, differences in age, BMI, CCI, and deformity were significant (all p = 0.001). Overall, 15.5% of patients (n = 74) had experienced mechanical complications by two years (8.1% not frail (n = 36), 15.1% frail (n = 26), and 16.3% severely frail (n = 12); p = 0.013). Reoperations also differed between groups (20.2% (n = 48) vs 23.3% (n = 39) vs 32.6% (n = 23); p = 0.011). Controlling for osteoporosis, baseline deformity, and degree of correction (by sagittal age-adjusted score (SAAS) matching), frail and severely frail patients were more likely to experience mechanical complications if they had heart failure (odds ratio (OR) 6.6 (95% CI 1.6 to 26.7); p = 0.008), depression (OR 5.1 (95% CI 1.1 to 25.7); p = 0.048), or cancer (OR 1.5 (95% CI 1.1 to 1.4); p = 0.004). Frail and severely frail patients experienced higher rates of mechanical complication than ‘not frail’ patients at two years (19% (n = 45) vs 11.9% (n = 29); p = 0.003). When controlling for baseline deformity and degree of correction in severely frail and frail patients, severely frail patients were less likely to experience clinically relevant proximal junctional kyphosis or failure or mechanical complications by two years, if they had a more proximal UIV. Conclusion. Frail patients are at risk of a poor outcome after surgery for adult spinal deformity due to their comorbidities. Although a definitively prescriptive upper instrumented vertebra remains elusive, these patients appear to be at greater risk for a poor outcome if the upper instrumented vertebra is sited more distally. Cite this article: Bone Joint J 2024;106-B(11):1342–1347

Aims. The aims of this study were to compare clinically relevant measurements of hip dysplasia on radiographs taken in the supine and standing position, and to compare Hip2Norm software and Picture Archiving and Communication System (PACS)-derived digital radiological measurements. Methods. Preoperative supine and standing radiographs of 36 consecutive patients (43 hips) who underwent periacetabular osteotomy surgery were retrospectively analyzed from a single-centre, two-surgeon cohort. Anterior coverage (AC), posterior coverage (PC), lateral centre-edge angle (LCEA), acetabular inclination (AI), sharp angle (SA), pelvic tilt (PT), retroversion index (RI), femoroepiphyseal acetabular roof (FEAR) index, femoroepiphyseal horizontal angle (FEHA), leg length discrepancy (LLD), and pelvic obliquity (PO) were analyzed using both Hip2Norm software and PACS-derived measurements where applicable. Results. Analysis of supine and standing radiographs resulted in significant variation for measurements of PT (p < 0.001) and AC (p = 0.005). The variation in PT correlated with the variation in AC in a limited number of patients (R. 2. = 0.378; p = 0.012). Conclusion. The significant variation in PT and AC between supine and standing radiographs suggests that it may benefit surgeons to have both radiographs when planning surgical correction of hip dysplasia. We also recommend using PACS-derived measurements of AI and SA due to the poor interobserver error on Hip2Norm. Cite this article: Bone Joint J 2021;103-B(11):1662–1668

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. The aim of this study was to determine the influence of pelvic parameters on the tendency of patients with adolescent idiopathic scoliosis (AIS) to develop flatback deformity (thoracic hypokyphosis and lumbar hypolordosis) and its effect on quality-of-life outcomes. Patients and Methods. This was a radiological study of 265 patients recruited for Boston bracing between December 2008 and December 2013. Posteroanterior and lateral radiographs were obtained before, immediately after, and two-years after completion of bracing. Measurements of coronal and sagittal Cobb angles, coronal balance, sagittal vertical axis, and pelvic parameters were made. The refined 22-item Scoliosis Research Society (SRS-22r) questionnaire was recorded. Association between independent factors and outcomes of postbracing ≥ 6° kyphotic changes in the thoracic spine and ≥ 6° lordotic changes in the lumbar spine were tested using likelihood ratio chi-squared test and univariable logistic regression. Multivariable logistic regression models were then generated for both outcomes with odds ratios (ORs), and with SRS-22r scores. Results. Reduced T5-12 kyphosis (mean -4.3° (. sd. 8.2); p < 0.001), maximum thoracic kyphosis (mean -4.3° (. sd. 9.3); p < 0.001), and lumbar lordosis (mean -5.6° (. sd. 12.0); p < 0.001) were observed after bracing treatment. Increasing prebrace maximum kyphosis (OR 1.133) and lumbar lordosis (OR 0.92) was associated with postbracing hypokyphotic change. Prebrace sagittal vertical axis (OR 0.975), prebrace sacral slope (OR 1.127), prebrace pelvic tilt (OR 0.940), and change in maximum thoracic kyphosis (OR 0.878) were predictors for lumbar hypolordotic changes. There were no relationships between coronal deformity, thoracic kyphosis, or lumbar lordosis with SRS-22r scores. Conclusion. Brace treatment leads to flatback deformity with thoracic hypokyphosis and lumbar hypolordosis. Changes in the thoracic spine are associated with similar changes in the lumbar spine. Increased sacral slope, reduced pelvic tilt, and pelvic incidence are associated with reduced lordosis in the lumbar spine after bracing. Nevertheless, these sagittal parameter changes do not appear to be associated with worse quality of life. Cite this article: Bone Joint J 2019;101-B:1370–1378

Aims. Pelvic tilt (PT) can significantly change the functional orientation of the acetabular component and may differ markedly between patients undergoing total hip arthroplasty (THA). Patients with stiff spines who have little change in PT are considered at high risk for instability following THA. Femoral component position also contributes to the limits of impingement-free range of motion (ROM), but has been less studied. Little is known about the impact of combined anteversion on risk of impingement with changing pelvic position. Methods. We used a virtual hip ROM (vROM) tool to investigate whether there is an ideal functional combined anteversion for reduced risk of hip impingement. We collected PT information from functional lateral radiographs (standing and sitting) and a supine CT scan, which was then input into the vROM tool. We developed a novel vROM scoring system, considering both seated flexion and standing extension manoeuvres, to quantify whether hips had limited ROM and then correlated the vROM score to component position. Results. The vast majority of THA planned with standing combined anteversion between 30° to 50° and sitting combined anteversion between 45° to 65° had a vROM score > 99%, while the majority of vROM scores less than 99% were outside of this zone. The range of PT in supine, standing, and sitting positions varied widely between patients. Patients who had little change in PT from standing to sitting positions had decreased hip vROM. Conclusion. It has been shown previously that an individual’s unique spinopelvic alignment influences functional cup anteversion. But functional combined anteversion, which also considers stem position, should be used to identify an ideal THA position for impingement-free ROM. We found a functional combined anteversion zone for THA that may be used moving forward to place total hip components. Cite this article: Bone Jt Open 2021;2(10):834–841

Aims. This study aimed to analyze the correlation between transverse process (TP) fractures of the fourth (L4) and fifth (L5) lumbar vertebrae and biomechanical and haemodynamic stability in patients with a pelvic ring injury, since previous data are inconsistent. Patients and Methods. The study is a retrospective matched-pair analysis of patients with a pelvic fracture according to the modified Tile AO Müller and the Young and Burgess classification who presented to a level 1 trauma centre between January 2005 and December 2014. Results. A total of 728 patients with pelvic ring injuries were included, of whom 183 (25.1%) had a biomechanically unstable pelvic fracture. Of these patients, 84 (45.9%) had a fracture of a TP of L4 and/or L5. A total of 73 patients (13.4%) with a stable pelvic ring injury (p < 0.001) had a fracture of a TP. Patients with a fracture of a TP of L4 and/or L5 had a 5.5-fold risk (odds ratio (OR)) of having a biomechanically unstable pelvic injury. TP fractures (OR 1.6, p = 0.2) could not be confirmed as an independent predictor of haemodynamic instability. Conclusion. This is the first study that has demonstrated a positive correlation between a TP fracture of L4 and/or L5 and a biomechanically unstable pelvic ring injury. The presence of transverse process fractures of L4 and/or L5 indicates increased severity of pelvic injury and therefore can help in the planning of emergency treatment. Cite this article: Bone Joint J 2018;100-B:1214–19

Aims. To describe the clinical, radiological, and functional outcomes in patients with isolated congenital thoracolumbar kyphosis who were treated with three-column osteotomy by posterior-only approach. Methods. Hospital records of 27 patients with isolated congenital thoracolumbar kyphosis undergoing surgery at a single centre were retrospectively analyzed. All patients underwent deformity correction which involved a three-column osteotomy by single-stage posterior-only approach. Radiological parameters (local kyphosis angle (KA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), C7 sagittal vertical axis (C7 SVA), T1 slope, and pelvic incidence minus lumbar lordosis (PI-LL)), functional scores, and clinical details of complications were recorded. Results. The mean age of the study population was 13.9 years (SD 6.4). The apex of deformity was in thoracic, thoracolumbar, and lumbar spine in five, 14, and eight patients, respectively. The mean operating time was 178.4 minutes (SD 38.5) and the mean operative blood loss was 701.8 ml (SD 194.4). KA (preoperative mean 70.8° (SD 21.6°) vs final follow-up mean 24.7° (SD 18.9°); p < 0.001) and TK (preoperative mean -1.48° (SD 41.23°) vs final follow-up mean 24.28° (SD 17.29°); p = 0.005) underwent a significant change with surgery. Mean Scoliosis Research Society (SRS-22r) score improved after surgical correction (preoperative mean 3.24 (SD 0.37) vs final follow-up mean 4.28 (SD 0.47); p < 0.001) with maximum improvement in self-image and mental health domains. The overall complication rate was 26%, including two neurological and five non-neurological complications. Permanent neurological deficit was noted in one patient. Conclusion. Deformity correction employing three-column osteotomies by a single-stage posterior-only approach is safe and effective in treating isolated congenital thoracolumbar kyphosis. Cite this article: Bone Joint J 2021;103-B(7):1309–1316

Aims. The purpose of this study was to evaluate spinopelvic mechanics from standing and sitting positions in subjects with and without femoroacetabular impingement (FAI). We hypothesize that FAI patients will experience less flexion at the lumbar spine and more flexion at the hip whilst changing from standing to sitting positions than subjects without FAI. This increase in hip flexion may contribute to symptomatology in FAI. Patients and Methods. Male subjects were prospectively enrolled to the study (n = 20). Mean age was 31 years old (22 to 41). All underwent clinical examination, plain radiographs, and dynamic imaging using EOS. Subjects were categorized into three groups: non-FAI (no radiographic or clinical FAI or pain), asymptomatic FAI (radiographic and clinical FAI but no pain), and symptomatic FAI (patients with both pain and radiographic FAI). FAI was defined as internal rotation less than 15° and alpha angle greater than 60°. Subjects underwent standing and sitting radiographs in order to measure spine and femoroacetabular flexion. Results. Compared with non-FAI controls, symptomatic patients with FAI had less flexion at the spine (mean 22°, . sd. 12°, vs mean 35°, . sd. 8°; p = 0.04) and more at the hip (mean 72°, . sd. 6°, vs mean 62°, . sd. 8°; p = 0.047). Subjects with asymptomatic FAI had more spine flexion and similar hip flexion when compared to symptomatic FAI patients. Both FAI groups also sat with more anterior pelvic tilt than control patients. There were no differences in standing alignment among groups. Conclusion. Symptomatic patients with FAI require more flexion at the hip to achieve sitting position due to their inability to compensate through the lumbar spine. With limited spine flexion, FAI patients sit with more anterior pelvic tilt, which may lead to impingement between the acetabulum and proximal femur. Differences in spinopelvic mechanics between FAI and non-FAI patients may contribute to the progression of FAI symptoms. Cite this article: Bone Joint J 2018;100-B:1275–9

Aims. The aim of this study is to test the hypothesis that three grades of sagittal compensation for standing posture (normal, compensated, and decompensated) correlate with health-related quality of life measurements (HRQOL). Methods. A total of 50 healthy volunteers (normal), 100 patients with single-level lumbar degenerative spondylolisthesis (LDS), and 70 patients with adult to elderly spinal deformity (deformity) were enrolled. Following collection of demographic data and HRQOL measured by the Scoliosis Research Society-22r (SRS-22r), radiological measurement by the biplanar slot-scanning full body stereoradiography (EOS) system was performed simultaneously with force-plate measurements to obtain whole body sagittal alignment parameters. These parameters included the offset between the centre of the acoustic meatus and the gravity line (CAM-GL), saggital vertical axis (SVA), T1 pelvic angle (TPA), McGregor slope, C2-7 lordosis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), PI-LL, sacral slope (SS), pelvic tilt (PT), and knee flexion. Whole spine MRI examination was also performed. Cluster analysis of the SRS-22r scores in the pooled data was performed to classify the subjects into three groups according to the HRQOL, and alignment parameters were then compared among the three cluster groups. Results. On the basis of cluster analysis of the SRS-22r subscores, the pooled subjects were divided into three HRQOL groups as follows: almost normal (mean 4.24 (SD 0.32)), mildly disabled (mean 3.32 (SD 0.24)), and severely disabled (mean 2.31 (SD 0.35)). Except for CAM-GL, all the alignment parameters differed significantly among the cluster groups. The threshold values of key alignment parameters for severe disability were TPA > 30°, C2-7 lordosis > 13°, PI-LL > 30°, PT > 28°, and knee flexion > 8°. Lumbar spinal stenosis was found to be associated with the symptom severity. Conclusion. This study provides evidence that the three grades of sagittal compensation in whole body alignment correlate with HRQOL scores. The compensation grades depend on the clinical diagnosis, whole body sagittal alignment, and lumbar spinal stenosis. The threshold values of key alignment parameters may be an indication for treatment. Cite this article: Bone Joint J 2020;102-B(10):1359–1367

Aims. This study of patients with osteoarthritis (OA) of the hip aimed to: 1) characterize the contribution of the hip, spinopelvic complex, and lumbar spine when moving from the standing to the sitting position; 2) assess whether abnormal spinopelvic mobility is associated with worse symptoms; and 3) identify whether spinopelvic mobility can be predicted from static anatomical radiological parameters. Patients and Methods. A total of 122 patients with end-stage OA of the hip awaiting total hip arthroplasty (THA) were prospectively studied. Patient-reported outcome measures (PROMs; Oxford Hip Score, Oswestry Disability Index, and Veterans RAND 12-Item Health Survey Score) and clinical data were collected. Sagittal spinopelvic mobility was calculated as the change from the standing to sitting position using the lumbar lordosis angle (LL), sacral slope (SS), pelvic tilt (PT), pelvic-femoral angle (PFA), and acetabular anteinclination (AI) from lateral radiographs. The interaction of the different parameters was assessed. PROMs were compared between patients with normal spinopelvic mobility (10° ≤ ∆PT ≤ 30°) or abnormal spinopelvic mobility (stiff: ∆PT < ± 10°; hypermobile: ∆PT > ± 30°). Multiple regression and receiver operating characteristic (ROC) curve analyses were used to test for possible predictors of spinopelvic mobility. Results. Standing to sitting, the hip flexed by a mean of 57° (. sd. 17°), the pelvis tilted backwards by a mean of 20° (. sd. 12°), and the lumbar spine flexed by a mean of 20° (. sd. 14°); strong correlations were detected. There was no difference in PROMs between patients in the different spinopelvic mobility groups. Maximum hip flexion, standing PT, and standing AI were independent predictors of spinopelvic mobility (R. 2. = 0.42). The combined thresholds for standing was PT ≥ 13° and hip flexion ≥ 88° in the clinical examination, and had 90% sensitivity and 63% specificity of predicting spinopelvic stiffness, while SS ≥ 42° had 84% sensitivity and 67% specificity of predicting spinopelvic hypermobility. Conclusion. The hip, on average, accounts for three-quarters of the standing-to-sitting movement, but there is great variation. Abnormal spinopelvic mobility cannot be screened with PROMs. However, clinical and standing radiological features can predict spinopelvic mobility with good enough accuracy, allowing them to be used as reliable screening tools. Cite this article: Bone Joint J 2019;101-B:902–909

Aims. Concurrent hip and spine pathologies can alter the biomechanics of spinopelvic mobility in primary total hip arthroplasty (THA). This study examines how differences in pelvic orientation of patients with spine fusions can increase the risk of dislocation risk after THA. Patients and Methods. We identified 84 patients (97 THAs) between 1998 and 2015 who had undergone spinal fusion prior to primary THA. Patients were stratified into three groups depending on the length of lumbar fusion and whether or not the sacrum was involved. Mean age was 71 years (40 to 87) and 54 patients (56%) were female. The mean body mass index (BMI) was 30 kg/m. 2. (19 to 45). Mean follow-up was six years (2 to 17). Patients were 1:2 matched to patients with primary THAs without spine fusion. Hazard ratios (HR) were calculated. Results. Dislocation in the fusion group was 5.2% at one year versus 1.7% in controls but this did not reach statistical significance (HR 1.9; p = 0.33). Compared with controls, there was no significant difference in rate of dislocation in patients without a sacral fusion. When the sacrum was involved, the rate of dislocation was significantly higher than in controls (HR 4.5; p = 0.03), with a trend to more dislocations in longer lumbosacral fusions. Patient demographics and surgical characteristics of THA (i.e. surgical approach and femoral head diameter) did not significantly impact risk of dislocation (p > 0.05). Significant radiological differences were measured in mean anterior pelvic tilt between the one-level lumbar fusion group (22°), the multiple-level fusion group (27°), and the sacral fusion group (32°; p < 0.01). Ten-year survival was 93% in the fusion group and 95% in controls (HR 1.2; p = 0.8). Conclusion. Lumbosacral spinal fusions prior to THA increase the risk of dislocation within the first six months. Fusions involving the sacrum with multiple levels of lumbar involvement notably increased the risk of postoperative dislocation compared with a control group and other lumbar fusions. Surgeons should take care with component positioning and may consider higher stability implants in this high-risk cohort

Aims. The aims of this study were to measure sagittal standing and sitting lumbar-pelvic-femoral alignment in patients before and following total hip arthroplasty (THA), and to consider what preoperative factors may influence a change in postoperative pelvic position. Patients and Methods. A total of 161 patients were considered for inclusion. Patients had a mean age of the remaining 61 years (. sd. 11) with a mean body mass index (BMI) of 28 kg/m. 2. (. sd. 6). Of the 161 patients, 82 were male (51%). We excluded 17 patients (11%) with spinal conditions known to affect lumbar mobility as well as the rotational axis of the spine. Standing and sitting spine-to-lower-limb radiographs were taken of the remaining 144 patients before and one year following THA. Spinopelvic alignment measurements, including sacral slope, lumbar lordosis, and pelvic incidence, were measured. These angles were used to calculate lumbar spine flexion and femoroacetabular hip flexion from a standing to sitting position. A radiographic scoring system was used to identify those patients in the series who had lumbar degenerative disc disease (DDD) and compare spinopelvic parameters between those patients with DDD (n = 38) and those who did not (n = 106). Results. Following THA, patients sat with more anterior pelvic tilt (mean increased sacral slope 18° preoperatively versus 23° postoperatively; p = 0.001) and more lumbar lordosis (mean 28° preoperatively versus 35° postoperatively; p = 0.001). Preoperative change in sacral slope from standing to sitting (p = 0.03) and the absence of DDD (p = 0.001) correlated to an increased change in postoperative sitting pelvic alignment. Conclusion. Sitting lumbar-pelvic-femoral alignment following THA may be driven by hip arthritis and/or spinal deformity. Patients with DDD and fixed spinopelvic alignment have a predictable pelvic position one year following THA. Patients with normal spines have less predictable postoperative pelvic position, which is likely to be driven by hip stiffness. Cite this article: Bone Joint J 2018;100-B:1289–96

Aims. A flexed knee gait is common in patients with bilateral spastic cerebral palsy and occurs with increased age. There is a risk for the recurrence of a flexed knee gait when treated in childhood, and the aim of this study was to investigate whether multilevel procedures might also be undertaken in adulthood. Patients and Methods. At a mean of 22.9 months (standard deviation 12.9), after single event multi level surgery, 3D gait analysis was undertaken pre- and post-operatively for 37 adult patients with bilateral cerebral palsy and a fixed knee gait. Results. There was a significant improvement of indices and clinical and kinematic parameters including extension of the hip and knee, reduction of knee flexion at initial contact, reduction of minimum and mean knee flexion in the stance phase of gait, improved range of movement of the knee and a reduction of mean flexion of the hip in the stance phase. Genu recurvatum occurred in two patients (n = 3 legs, 4%) and an increase of pelvic tilt (> 5°) was found in 12 patients (n = 23 legs, 31%). Conclusion. Adult patients with bilateral cerebral palsy and a flexed knee gait benefit from multilevel surgery including hamstring lengthening. The risk of the occurence of genu recurvatum and increased pelvic tilt is lower than has been previously reported in children. Cite this article: Bone Joint J 2017;99-B:1256–64

Aims. This study aims to: determine the difference in pelvic position that occurs between surgery and radiographic, supine, postoperative assessment; examine how the difference in pelvic position influences subsequent component orientation; and establish whether differences in pelvic position, and thereafter component orientation, exist between total hip arthroplasties (THAs) performed in the supine versus the lateral decubitus positions. Patients and Methods. The intra- and postoperative anteroposterior pelvic radiographs of 321 THAs were included; 167 were performed with the patient supine using the anterior approach and 154 were performed with the patient in the lateral decubitus using the posterior approach. The inclination and anteversion of the acetabular component was measured and the difference (Δ) between the intra- and postoperative radiographs was determined. The target zone was inclination/anteversion of 40°/20° (± 10°). Changes in the tilt, rotation, and obliquity of the pelvis on the intra- and postoperative radiographs were calculated from Δinclination/anteversion using the Levenberg–Marquardt algorithm. Results. The mean postoperative inclination/anteversion was 40° (± 8°)/23° (± 9°) with Δinclination and/or Δanteversion > ± 10° in 74 (21%). Intraoperatively, the pelvis was anteriorly tilted by a mean of 4° (± 10°), internally rotated by a mean of 1° (± 10°) and adducted by a mean of 1° (± 5°). Having Δinclination and/or Δanteversion > ± 10° was associated with a 3.5 odds ratio of having the acetabular component outside the target zone. A greater proportion of THAs that were undertaken with the patient in the lateral decubitus position had Δinclination and/or Δanteversion > ± 10° (35.3%, 54/153) compared with those in the supine position (4.8%, 8/167; p < 0.001). A greater number of acetabular components were within the target zone in THAs undertaken with the patient in the supine position (72%, 120/167), compared with those in the lateral decubitus position (44%, 67/153; p < 0.001). Intraoperatively, the pelvis was more anteriorly tilted (p < 0.001) and more internally rotated (p = 0.04) when the patient was in the lateral decubitus position. Conclusion. The pelvic position is more reliable when the patient is in the supine position, leading to more consistent orientation of the acetabular component. Significant differences in pelvic tilt and rotation are seen with the patient in the lateral decubitus position. Cite this article: Bone Joint J 2018;100-B:1280–8

Aims. Our aim was to evaluate the radiographic characteristics of patients undergoing total hip arthroplasty (THA) for the potential of posterior bony impingement using CT simulations. Patients and Methods. Virtual CT data from 112 patients who underwent THA were analysed. There were 40 men and 72 women. Their mean age was 59.1 years (41 to 76). Associations between radiographic characteristics and posterior bony impingement and the range of external rotation of the hip were evaluated. In addition, we investigated the effects of pelvic tilt and the neck/shaft angle and femoral offset on posterior bony impingement. Results. The range of external rotation and the ischiofemoral length were significantly lower, while femoral anteversion, the ischial ratio, and ischial angle were significantly higher in patients with posterior bony impingement compared with those who had implant impingement (p <  0.05). The range of external rotation positively correlated with ischiofemoral length (r = 0.49, p < 0.05), and negatively correlated with ischial length (r = -0.49, p < 0.05), ischial ratio (r =- 0.49, p < 0.05) and ischial angle (r = -0.55, p < 0.05). The range of external rotation was lower in patients with posterior pelvic tilt (p < 0.05) and in those with a high offset femoral component (p < 0.05) due to posterior bony impingement. Conclusion. Posterior bony impingement after THA is more likely in patients with a wider ischium and a narrow ischiofemoral space. A high femoral offset and posterior pelvic tilt are also risk factors for this type of impingement. Cite this article: Bone Joint J 2017;99-B:1140–6

Aims. Long-term clinical outcomes for ceramic-on-ceramic (CoC) bearings are encouraging. However, there is a risk of squeaking. Guidelines for the orientation of the acetabular component are defined from static imaging, but the position of the pelvis and thus the acetabular component during activities associated with edge-loading are likely to be very different from those measured when the patient is supine. We assessed the functional orientation of the acetabular component. Patients and Methods. A total of 18 patients with reproducible squeaking in their CoC hips during deep flexion were investigated with a control group of 36 non-squeaking CoC hips. The two groups were matched for the type of implant, the orientation of the acetabular component when supine, the size of the femoral head, ligament laxity, maximum hip flexion and body mass index. . Results. The mean functional anteversion of the acetabular component at the point when patients initiated rising from a seated position was significantly less in the squeaking group than in the control group, 8.1° (-10.5° to 36.0°) and 21.1° (-1.9° to 38.4°) respectively (p = 0.002). . Conclusion. The functional orientation of the acetabular component during activities associated with posterior edge-loading are different from those measured when supine due to patient-specific pelvic kinematics. Individuals with a large anterior pelvic tilt during deep flexion might be more susceptible to posterior edge-loading and squeaking as a consequence of a significant decrease in the functional anteversion of the acetabular component. . Cite this article: Bone Joint J 2016;98-B:910–16