Aims. Pelvic incidence (PI) is considered an important anatomical parameter for determining the sagittal balance of the spine. The contribution of an abnormal PI to hip osteoarthritis (OA) remains controversial. In this study, we aimed to investigate the relationship between PI and hip OA, and the difference in PI between hip OA without anatomical abnormalities (primary OA) and hip OA with developmental dysplasia of the hip (DDH-OA). Methods. In this study, 100 patients each of primary OA, DDH-OA, and control subjects with no history of hip disease were included. CT images were used to measure PI, sagittal femoral head coverage, α angle, and acetabular anteversion. PI was also subdivided into three categories: high PI (larger than 64.0°), medium PI (42.0° to 64.0°), and low PI (less than 42.0°). The anterior centre edge angles, posterior centre edge angles, and total sagittal femoral head coverage were measured. The correlations between PI and sagittal femoral head coverage, α angle, and acetabular anteversion were examined. Results. No significant difference in PI was observed between the three groups. There was no significant difference between the groups in terms of the category distribution of PI. The DDH-OA group had lower mean sagittal femoral head coverage than the other groups. There were no significant correlations between PI and other anatomical factors, including sagittal femoral head coverage, α angle, and acetabular anteversion. Conclusion. No associations were found between mean PI values or PI categories and hip OA. Furthermore, there was no difference in PI between patients with primary OA and DDH-OA. From our evaluation, we found no evidence of PI being an independent factor associated with the development of hip OA. Cite this article: Bone Joint J 2021;103-B(11):1656–1661

Aims. Pelvic incidence (PI) is a position-independent spinopelvic parameter traditionally used by spinal surgeons to determine spinal alignment. Its relevance to the arthroplasty surgeon in assessing patient risk for total hip arthroplasty (THA) instability preoperatively is unclear. This study was undertaken to investigate the significance of PI relative to other spinopelvic parameter risk factors for instability to help guide its clinical application. Methods. Retrospective analysis was performed of a multicentre THA database of 9,414 patients with preoperative imaging (dynamic spinopelvic radiographs and pelvic CT scans). Several spinopelvic parameter measurements were made by engineers using advanced software including sacral slope (SS), standing anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), lumbar lordosis (LL), and PI. Lumbar flexion (LF) was determined by change in LL between standing and flexed-seated lateral radiographs. Abnormal pelvic mobility was defined as ∆SPT ≥ 20° between standing and flexed-forward positions. Sagittal spinal deformity (SSD) was defined as PI-LL mismatch > 10°. Results. PI showed a positive correlation with parameters of SS, SPT, and LL (r-value range 0.468 to 0.661). Patients with a higher PI value showed higher degrees of standing LL, likely as a compensatory measure to maintain sagittal spine balance. There was a positive correlation between LL and LF such that patients with less standing LL had decreased LF (r = 0.49). Similarly, there was a positive correlation between increased SSD and decreased LF (r = 0.54). PI in isolation did not show any significant correlation with lumbar (r = 0.04) or pelvic mobility (r = 0.02). The majority of patients (range 89.4% to 94.2%) had normal lumbar and pelvic mobility regardless of the PI value. Conclusion. The PI value alone is not indicative of either spinal or pelvic mobility, and thus in isolation may not be a risk factor for THA instability. Patients with SSD had higher rates of spinopelvic stiffness, which may be the mechanism by which PI relates to THA instability risk, but further clinical studies are required. Cite this article: Bone Joint J 2022;104-B(3):352–358

Aims. The aim of the study was to compare two methods of calculating pelvic incidence (PI) and pelvic tilt (PT), either by using the femoral heads or acetabular domes to determine the bicoxofemoral axis, in patients with unilateral or bilateral primary hip osteoarthritis (OA). Methods. PI and PT were measured on standing lateral radiographs of the spine in two groups: 50 patients with unilateral (Group I) and 50 patients with bilateral hip OA (Group II), using the femoral heads or acetabular domes to define the bicoxofemoral axis. Agreement between the methods was determined by intraclass correlation coefficient (ICC) and the standard error of measurement (SEm). The intraobserver reproducibility and interobserver reliability of the two methods were analyzed on 31 radiographs in both groups to calculate ICC and SEm. Results. In both groups, excellent agreement between the two methods was obtained, with ICC of 0.99 and SEm 0.3° for Group I, and ICC 0.99 and SEm 0.4° for Group II. The intraobserver reproducibility was excellent for both methods in both groups, with an ICC of at least 0.97 and SEm not exceeding 0.8°. The study also revealed excellent interobserver reliability for both methods in both groups, with ICC 0.99 and SEm 0.5° or less. Conclusion. Either the femoral heads or acetabular domes can be used to define the bicoxofemoral axis on the lateral standing radiographs of the spine for measuring PI and PT in patients with idiopathic unilateral or bilateral hip OA. Cite this article: Bone Joint J 2021;103-B(8):1345–1350

Aims. The aetiologies of common degenerative spine, hip, and knee pathologies are still not completely understood. Mechanical theories have suggested that those diseases are related to sagittal pelvic morphology and spinopelvic-femoral dynamics. The link between the most widely used parameter for sagittal pelvic morphology, pelvic incidence (PI), and the onset of degenerative lumbar, hip, and knee pathologies has not been studied in a large-scale setting. Methods. A total of 421 patients from the Cohort Hip and Cohort Knee (CHECK) database, a population-based observational cohort, with hip and knee complaints < 6 months, aged between 45 and 65 years old, and with lateral lumbar, hip, and knee radiographs available, were included. Sagittal spinopelvic parameters and pathologies (spondylolisthesis and degenerative disc disease (DDD)) were measured at eight-year follow-up and characteristics of hip and knee osteoarthritis (OA) at baseline and eight-year follow-up. Epidemiology of the degenerative disorders and clinical outcome scores (hip and knee pain and Western Ontario and McMaster Universities Osteoarthritis Index) were compared between low PI (< 50°), normal PI (50° to 60°), and high PI (> 60°) using generalized estimating equations. Results. Demographic details were not different between the different PI groups. L4 to L5 and L5 to S1 spondylolisthesis were more frequently present in subjects with high PI compared to low PI (L4 to L5, OR 3.717; p = 0.024 vs L5 to S1 OR 7.751; p = 0.001). L5 to S1 DDD occurred more in patients with low PI compared to high PI (OR 1.889; p = 0.010), whereas there were no differences in L4 to L5 DDD among individuals with a different PI. The incidence of hip OA was higher in participants with low PI compared to normal (OR 1.262; p = 0.414) or high PI (OR 1.337; p = 0.274), but not statistically different. The incidence of knee OA was higher in individuals with a high PI compared to low PI (OR 1.620; p = 0.034). Conclusion. High PI is a risk factor for development of spondylolisthesis and knee OA. Low pelvic incidence is related to DDD, and may be linked to OA of the hip. Level of Evidence: 1b. Cite this article: Bone Joint J 2020;102-B(9):1261–1267

Aims. Spinopelvic pathology increases the risk for instability following total hip arthroplasty (THA), yet few studies have evaluated how pathology varies with age or sex. The aims of this study were: 1) to report differences in spinopelvic parameters with advancing age and between the sexes; and 2) to determine variation in the prevalence of THA instability risk factors with advancing age. Methods. A multicentre database with preoperative imaging for 15,830 THA patients was reviewed. Spinopelvic parameter measurements were made by experienced engineers, including anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence (PI). Lumbar flexion (LF), sagittal spinal deformity, and hip user index (HUI) were calculated using parameter measurements. Results. With advancing age, patients demonstrate increased posterior APPT, decreased standing LL, decreased LF, higher pelvic incidence minus lumbar lordosis (PI-LL) mismatch, higher prevalence of abnormal spinopelvic mobility, and higher HUI percentage. With each decade, APPT progressed posteriorly 2.1°, LF declined 6.0°, PI-LL mismatch increased 2.9°, and spinopelvic mobility increased 3.8°. Significant differences were found between the sexes for APPT, SPT, SS, LL, and LF, but were not felt to be clinically relevant. Conclusion. With advancing age, spinopelvic biomechanics demonstrate decreased spinal mobility and increased pelvic/hip mobility. Surgeons should consider the higher prevalence of instability risk factors in elderly patients and anticipate changes evolving in spinopelvic biomechanics for young patients. Cite this article: Bone Joint J 2024;106-B(8):792–801

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

Aims. Spinopelvic mobility plays an important role in functional acetabular component position following total hip arthroplasty (THA). The primary aim of this study was to determine if spinopelvic hypermobility persists or resolves following THA. Our second aim was to identify patient demographic or radiological factors associated with hypermobility and resolution of hypermobility after THA. Methods. This study investigated patients with preoperative posterior hypermobility, defined as a change in sacral slope (SS) from standing to sitting (ΔSS. stand-sit. ) ≥ 30°. Radiological spinopelvic parameters, including SS, pelvic incidence (PI), lumbar lordosis (LL), PI-LL mismatch, anterior pelvic plane tilt (APPt), and spinopelvic tilt (SPT), were measured on preoperative imaging, and at six weeks and a minimum of one year postoperatively. The severity of bilateral hip osteoarthritis (OA) was graded using Kellgren-Lawrence criteria. Results. A total of 136 patients were identified as having preoperative spinopelvic hypermobility. At one year after THA, 95% (129/136) of patients were no longer categorized as hypermobile on standing and sitting radiographs (ΔSS. stand-sit. < 30°). Mean ΔSS. stand-sit. decreased from 36.4° (SD 5.1°) at baseline to 21.4° (SD 6.6°) at one year (p < 0.001). Mean SS. seated. increased from baseline (11.4° (SD 8.8°)) to one year after THA by 11.5° (SD 7.4°) (p < 0.001), which correlates to an 8.5° (SD 5.5°) mean decrease in seated functional cup anteversion. Contralateral hip OA was the only radiological predictor of hypermobility persisting at one year after surgery. The overall reoperation rate was 1.5%. Conclusion. Spinopelvic hypermobility was found to resolve in the majority (95%) of patients one year after THA. The increase in SS. seated. was clinically significant, suggesting that current target recommendations for the hypermobile patient (decreased anteversion and inclination) should be revisited. Cite this article: Bone Joint J 2021;103-B(12):1766–1773

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. Patients with spinal pathology who undergo total hip arthroplasty (THA) have an increased risk of dislocation and revision. The aim of this study was to determine if the use of the Hip-Spine Classification system in these patients would result in a decreased rate of postoperative dislocation in patients with spinal pathology. Methods. This prospective, multicentre study evaluated 3,777 consecutive patients undergoing THA by three surgeons, between January 2014 and December 2019. They were categorized using The Hip-Spine Classification system: group 1 with normal spinal alignment; group 2 with a flatback deformity, group 2A with normal spinal mobility, and group 2B with a stiff spine. Flatback deformity was defined by a pelvic incidence minus lumbar lordosis of > 10°, and spinal stiffness was defined by < 10° change in sacral slope from standing to seated. Each category determined a patient-specific component positioning. Survivorship free of dislocation was recorded and spinopelvic measurements were compared for reliability using intraclass correlation coefficient. Results. A total of 2,081 patients met the inclusion criteria. There were 987 group 1A, 232 group 1B, 715 group 2A, and 147 group 2B patients. A total of 70 patients had a lumbar fusion, most had L4-5 (16; 23%) or L4-S1 (12; 17%) fusions; 51 patients (73%) had one or two levels fused, and 19 (27%) had > three levels fused. Dual mobility (DM) components were used in 166 patients (8%), including all of those in group 2B and with > three level fusions. Survivorship free of dislocation at five years was 99.2% with a 0.8% dislocation rate. The correlation coefficient was 0.83 (95% confidence interval 0.89 to 0.91). Conclusion. This is the largest series in the literature evaluating the relationship between hip-spine pathology and dislocation after THA, and guiding appropriate treatment. The Hip-Spine Classification system allows surgeons to make appropriate evaluations preoperatively, and it guides the use of DM components in patients with spinopelvic pathology in order to reduce the risk of dislocation in these high-risk patients. Cite this article: Bone Joint J 2021;103-B(7 Supple B):17–24

We investigated the spinopelvic morphology and global sagittal balance of patients with a degenerative retrolisthesis or anterolisthesis. A total of 269 consecutive patients with a degenerative spondylolisthesis were included in this study. There were 95 men and 174 women with a mean age of 64.3 years (. sd. 10.5; 40 to 88). A total of 106 patients had a pure retrolisthesis (R group), 130 had a pure anterolisthesis (A group), and 33 had both (R+A group). A backward slip was found in the upper lumbar levels (mostly L2 or L3) with an almost equal gender distribution in both the R and R+A groups. The pelvic incidence and sacral slope of the R group were significantly lower than those of the A (both p < 0.001) and R+A groups (both p < 0.001). The lumbar lordosis of the R+A group was significantly greater than that of the R (p = 0.025) and A groups (p = 0.014). The C7 plumb line of the R group was located more posteriorly than that of the A group (p = 0.023), but was no different from than that of the R+A group (p = 0.422). The location of C7 plumb line did not differ between the three groups (p = 0.068). The spinosacral angle of the R group was significantly smaller than that of the A group (p < 0.001) and R+A group (p < 0.001). Our findings imply that there are two types of degenerative retrolisthesis: one occurs primarily as a result of degeneration in patients with low pelvic incidence, and the other occurs secondarily as a compensatory mechanism in patients with an anterolisthesis and high pelvic incidence. Cite this article: Bone Joint J 2013;95-B:1244–9

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

We investigated the relationship between spinopelvic parameters and disc degeneration in young adult patients with spondylolytic spondylolisthesis. A total of 229 men with a mean age of 21 years (18 to 26) with spondylolytic spondylolisthesis were identified. All radiological measurements, including pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, sacral inclination, lumbosacral angle (LSA), and sacrofemoral distance, were calculated from standing lateral lumbosacral radiographs. The degree of intervertebral disc degeneration was classified using a modified Pfirrmann scale. We analysed the spinopelvic parameters according to disc level, degree of slip and disc degeneration. There were significant positive correlations between the degree of slip and pelvic incidence (p = 0.009), sacral slope (p = 0.003) and lumbar lordosis (p = 0.010). The degree of slip and the LSA were correlated with disc degeneration (p < 0.001 and p = 0.003, respectively). There was also a significant difference between the degree of slip (p < 0.001) and LSA (p = 0.006) according to the segmental level of disc degeneration. Cite this article: Bone Joint J 2013;95-B:1239–43

Aims. To compare the rates of sagittal and coronal correction for all-pedicle screw instrumentation and hybrid instrumentation using sublaminar bands in the treatment of thoracic adolescent idiopathic scoliosis (AIS). Methods. We retrospectively reviewed the medical records of 124 patients who had undergone surgery in two centres for the correction of Lenke 1 or 2 AIS. Radiological evaluation was carried out preoperatively, in the early postoperative phase, and at two-year follow-up. Parameters measured included coronal Cobb angles and thoracic kyphosis. Postoperative alignment was compared after matching the cohorts by preoperative coronal Cobb angle, thoracic kyphosis, lumbar lordosis, and pelvic incidence. Results. A total of 179 patients were available for analysis. After matching, 124 patients remained (62 in each cohort). Restoration of thoracic kyphosis was significantly better in the sublaminar band group than in the pedicle screw group (from 23.7° to 27.5° to 34.0° versus 23.9° to 18.7° to 21.5°; all p < 0.001). When the preoperative thoracic kyphosis was less than 20°, sublaminar bands achieved a normal postoperative thoracic kyphosis, whereas pedicle screws did not. In the coronal plane, pedicle screws resulted in a significantly better correction than sublaminar bands at final follow-up (73.0% versus 59.7%; p < 0.001). Conclusion. This is the first study to compare sublaminar bands and pedicle screws for the correction of a thoracic AIS. We have shown that pedicle screws give a good coronal correction which is maintained at two-year follow-up. Conversely, sublaminar bands restore the thoracic kyphosis better while pedicle screws are associated with a flattening of the thoracic spine. In patients with preoperative hypokyphosis, sublaminar bands should be used to restore a proper sagittal profile. Cite this article: Bone Joint J 2020;102-B(3):376–382

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. 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. 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

Spinal deformities are a common feature of Marfan’s syndrome and can be a significant cause of morbidity. The morphology of the scoliosis associated with this condition was previously described by Sponseller, but no correlation with the pelvic parameters has been seen. We performed a retrospective radiological study of 58 patients with scoliosis, secondary to Marfan’s syndrome and related the findings in the thoracolumbar spine to the pelvic parameters, including pelvic version (tilt), pelvic incidence and sacral slope. Our results showed marked abnormalities in the pelvic values compared with those found in the unaffected population, with increased retroversion of the pelvis in particular. In addition we found a close correlation between the different patterns of pelvic parameters and scoliosis morphology. We found that pelvic abnormalities may partially dictate the spinal disorders seen in Marfan’s syndrome. Our results supplement the well-established Sponseller classification, as well as stressing the importance of considering the orientation of the pelvis when planning surgery

Aims

Excessive posterior pelvic tilt (PT) may increase the risk of anterior instability after total hip arthroplasty (THA). The aim of this study was to investigate the changes in PT occurring from the preoperative supine to postoperative standing position following THA, and identify factors associated with significant changes in PT.

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.

Aims

Postoperative complication rates remain relatively high after adult spinal deformity (ASD) surgery. The extent to which modifiable patient-related factors influence complication rates in patients with ASD has not been effectively evaluated. The aim of this retrospective cohort study was to evaluate the association between modifiable patient-related factors and complications after corrective surgery for ASD.