Orientation of the acetabular component influences wear, range of movement and the incidence of dislocation after total hip replacement (THR). During surgery, such orientation is often referenced to the anterior pelvic plane (APP), but APP inclination relative to the coronal plane (pelvic tilt) varies substantially between individuals. In contrast, the change in pelvic tilt from supine to standing (dPT) is small for nearly all individuals. Therefore, in THR performed with the patient supine and the patient’s coronal plane parallel to the operating table, we propose that freehand placement of the acetabular component placement is reliable and reflects standing (functional) cup position. We examined this hypothesis in 56 hips in 56 patients (19 men) with a mean age of 61 years (29 to 80) using three-dimensional CT pelvic reconstructions and standing lateral pelvic radiographs. We found a low variability of acetabular component placement, with 46 implants (82%) placed within a combined range of 30° to 50° inclination and 5° to 25° anteversion. Changing from the supine to the standing position (analysed in 47 patients) was associated with an anteversion change < 10° in 45 patients (96%). dPT was < 10° in 41 patients (87%). In conclusion, supine THR appears to provide reliable freehand acetabular component placement. In most patients a small reclination of the pelvis going from supine to standing causes a small increase in anteversion of the acetabular component.

Cite this article: Bone Joint J 2013;95-B:1326–31.

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. Patients with abnormal spinopelvic mobility are at increased risk for instability. Measuring the change in sacral slope (ΔSS) can help determine spinopelvic mobility preoperatively. Sacral slope (SS) should decrease at least 10° to demonstrate adequate posterior pelvic tilt. There is potential for different ΔSS measurements in the same patient based on sitting posture. The purpose of this study was to determine the effect of sitting posture on the ΔSS in patients undergoing total hip arthroplasty (THA). Methods. In total, 51 patients undergoing THA were reviewed to quantify the variability in preoperative spinopelvic mobility when measuring two different sitting positions using SS for planning. Results. A total of 32 patients had standardized relaxed sitting radiographs, while 35 patients had standardized flexed sitting images. Of the 32 patients with relaxed sitting views, the mean ΔSS was 20.7° (SD 8.9°). No patients exhibited an increase in SS during relaxed sitting (i.e. anterior pelvic tilt or so-called reverse accommodation). Of the 35 patients with flexed sitting radiographs, the mean ΔSS was only 2.1° (SD 9.7°) with 16/35 (45.71%) showing anterior pelvic tilt, or so-called reverse accommodation, unexpectedly increasing the sitting SS compared to the standing SS. Overall, 18 patients had both relaxed sitting and flexed sitting radiographs. In patients with both types of sitting radiographs, the mean relaxed sit to stand ΔSS was 18.06° (SD 6.07°), while only a 3.00° (SD 10.53°) ΔSS was noted when flexed sitting. There was a mean ΔSS difference of 15.06° (SD 7.67°) noted in the same patient cohort depending on sitting posture (p < 0.001). Conclusion. A 15° mean difference was noted depending on the sitting posture of the patient. Since decisions on component position can be made on preoperative lateral sit-stand radiographs, postural standardization is crucial. If using ΔSS for preoperative planning, the relaxed sitting radiograph is preferred. Cite this article: Bone Joint J 2020;102-B(7 Supple B):41–46

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. It has been well documented in the arthroplasty literature that lumbar degenerative disc disease (DDD) contributes to abnormal spinopelvic motion. However, the relationship between the severity or pattern of hip osteoarthritis (OA) as measured on an anteroposterior (AP) pelvic view and spinopelvic biomechanics has not been well investigated. Therefore, the aim of the study is to examine the association between the severity and pattern of hip OA and spinopelvic motion. Methods. A retrospective chart review was conducted to identify patients undergoing primary total hip arthroplasty (THA). Plain AP pelvic radiographs were reviewed to document the morphological characteristic of osteoarthritic hips. Lateral spine-pelvis-hip sitting and standing plain radiographs were used to measure sacral slope (SS) and pelvic femoral angle (PFA) in each position. Lumbar disc spaces were measured to determine the presence of DDD. The difference between sitting and standing SS and PFA were calculated to quantify spinopelvic motion (ΔSS) and hip motion (ΔPFA), respectively. Univariate analysis and Pearson correlation were used to identify morphological hip characteristics associated with changes in spinopelvic motion. Results. In total, 139 patients were included. Increased spinopelvic motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.05). Loss of hip motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.001). A decreased joint space was associated with a decreased ΔPFA (p = 0.040). The presence of disc space narrowing, disc space narrowing > two levels, and disc narrowing involving the L5–S1 segment were associated with decreased spinopelvic motion (all p < 0.05). Conclusion. Preoperative hip OA as assessed on an AP pelvic radiograph predicts spinopelvic motion. These data suggest that specific hip osteoarthritic morphological characteristics listed above alter spinopelvic motion to a greater extent than others. Cite this article: Bone Joint J 2023;105-B(5):496–503

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. 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

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. 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. 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. 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

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

We describe 13 patients with cerebral palsy and lordoscoliosis/hyperlordosis of the lumbar spine who underwent a posterior spinal fusion at a mean age of 14.5 years (10.8 to 17.4) to improve sitting posture and relieve pain. The mean follow-up was 3.3 years (2.2 to 6.2). The mean pre-operative lumbar lordosis was 108. °. (80 to 150. °. ) and was corrected to 62. °. (43. °.  to 85. °. ); the mean thoracic kyphosis from 17. °. (-23. °. to 35. °. ) to 47. °. (25. °. to 65. °. ); the mean scoliosis from 82. °. (0. °. to 125. °. ) to 22. °. (0. °. to 40. °. ); the mean pelvic obliquity from 21. °. (0. °. to 38. °. ) to 3. °. (0. °. to 15. °. ); the mean sacral slope from 79. °. (54. °. to 90. °. ) to 50. °. (31. °. to 66. °. ). The mean pre-operative coronal imbalance was 5 cm (0 cm to 8.9 cm) and was corrected to 0.6 cm (0 to 3.2). The mean sagittal imbalance of -8 cm (-16 cm to 7.8 cm) was corrected to -1.6 cm (-4 cm to 2.5 cm). The mean operating time was 250 minutes (180 to 360 minutes) and intra-operative blood loss 0.8 of estimated blood volume (0.3 to 2 estimated blood volume). The mean intensive care and hospital stay were 3.5 days (2 to 8) and 14.5 days (10 to 27), respectively. Three patients lost a significant amount of blood intra-operatively and subsequently developed chest or urinary infections and superior mesenteric artery syndrome. An increased pre-operative lumbar lordosis and sacral slope were associated with increased peri-operative morbidity: scoliosis and pelvic obliquity were not. A reduced lumbar lordosis and increased thoracic kyphosis correlated with better global sagittal balance at follow-up. All patients and their parents reported excellent surgical outcomes. Lordoscoliosis and hyperlordosis are associated with significant morbidity in quadriplegic patients. They are rare deformities and their treatment is challenging. Sagittal imbalance is the major component: it can be corrected by posterior fusion of the spine with excellent functional results. Cite this article: Bone Joint J 2014;96-B:800–6

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

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.

Understanding spinopelvic mechanics is important for the success of total hip arthroplasty (THA). Despite significant advancements in appreciating spinopelvic balance, numerous challenges remain. It is crucial to recognize the individual variability and postoperative changes in spinopelvic parameters and their consequential impact on prosthetic component positioning to mitigate the risk of dislocation and enhance postoperative outcomes. This review describes the integration of advanced diagnostic approaches, enhanced technology, implant considerations, and surgical planning, all tailored to the unique anatomy and biomechanics of each patient. It underscores the importance of accurately predicting postoperative spinopelvic mechanics, selecting suitable imaging techniques, establishing a consistent nomenclature for spinopelvic stiffness, and considering implant-specific strategies. Furthermore, it highlights the potential of artificial intelligence to personalize care.

Cite this article: Bone Joint J 2024;106-B(11):1206–1215.

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

Achieving accurate implant positioning and restoring native hip biomechanics are key surgeon-controlled technical objectives in total hip arthroplasty (THA). The primary objective of this study was to compare the reproducibility of the planned preoperative centre of hip rotation (COR) in patients undergoing robotic arm-assisted THA versus conventional THA.

Aims

The aim of this study was to assess the ability of morphological spinal parameters to predict the outcome of bracing in patients with adolescent idiopathic scoliosis (AIS) and to establish a novel supine correction index (SCI) for guiding bracing treatment.

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).

Aims

To report the surgical outcome of patients with severe Scheuermann’s kyphosis treated using a consistent technique and perioperative management.

Aims

Cross-table lateral (CTL) radiographs are commonly used to measure acetabular component anteversion after total hip arthroplasty (THA). The CTL measurements may differ by > 10° from CT scan measurements but the reasons for this discrepancy are poorly understood. Anteversion measurements from CTL radiographs and CT scans are compared to identify spinopelvic parameters predictive of inaccuracy.

Aims

The complex relationship between acetabular component position and spinopelvic mobility in patients following total hip arthroplasty (THA) renders it difficult to optimize acetabular component positioning. Mobility of the normal lumbar spine during postural changes results in alterations in pelvic tilt (PT) to maintain the sagittal balance in each posture and, as a consequence, markedly changes the functional component anteversion (FCA). This study aimed to investigate the in vivo association of lumbar degenerative disc disease (DDD) with the PT angle and with FCA during postural changes in THA patients.

In recent years, machine learning (ML) and artificial neural networks (ANNs), a particular subset of ML, have been adopted by various areas of healthcare. A number of diagnostic and prognostic algorithms have been designed and implemented across a range of orthopaedic sub-specialties to date, with many positive results. However, the methodology of many of these studies is flawed, and few compare the use of ML with the current approach in clinical practice. Spinal surgery has advanced rapidly over the past three decades, particularly in the areas of implant technology, advanced surgical techniques, biologics, and enhanced recovery protocols. It is therefore regarded an innovative field. Inevitably, spinal surgeons will wish to incorporate ML into their practice should models prove effective in diagnostic or prognostic terms. The purpose of this article is to review published studies that describe the application of neural networks to spinal surgery and which actively compare ANN models to contemporary clinical standards allowing evaluation of their efficacy, accuracy, and relatability. It also explores some of the limitations of the technology, which act to constrain the widespread adoption of neural networks for diagnostic and prognostic use in spinal care. Finally, it describes the necessary considerations should institutions wish to incorporate ANNs into their practices. In doing so, the aim of this review is to provide a practical approach for spinal surgeons to understand the relevant aspects of neural networks.

Cite this article: Bone Joint J 2021;103-B(9):1442–1448.

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).

Dislocation following total hip arthroplasty (THA) is a well-known and potentially devastating complication. Clinicians have used many strategies in attempts to prevent dislocation since the introduction of THA. While the importance of postoperative care cannot be ignored, particular emphasis has been placed on preoperative planning in the prevention of dislocation. The strategies have progressed from more traditional approaches, including modular implants, the size of the femoral head, and augmentation of the offset, to newer concepts, including patient-specific component positioning combined with computer navigation, robotics, and the use of dual-mobility implants. As clinicians continue to pursue improved outcomes and reduced complications, these concepts will lay the foundation for future innovation in THA and ultimately improved outcomes.

Cite this article: Bone Joint J 2022;104-B(1):8–11.

Aims

While previously underappreciated, factors related to the spine contribute substantially to the risk of dislocation following total hip arthroplasty (THA). These factors must be taken into consideration during preoperative planning for revision THA due to recurrent instability. We developed a protocol to assess the functional position of the spine, the significance of these findings, and how to address different pathologies at the time of revision THA.

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.

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.

There remains confusion in the literature with regard to the spinopelvic relationship, and its contribution to ideal acetabular component position. Critical assessment of the literature has been limited by use of conflicting terminology and definitions of new concepts that further confuse the topic. In 2017, the concept of a Hip-Spine Workgroup was created with the first meeting held at the American Academy of Orthopedic Surgeons Annual Meeting in 2018. The goal of this workgroup was to first help standardize terminology across the literature so that as a topic, multiple groups could produce literature that is immediately understandable and applicable. This consensus review from the Hip-Spine Workgroup aims to simplify the spinopelvic relationship, offer hip surgeons a concise summary of available literature, and select common terminology approved by both hip surgeons and spine surgeons for future research.

Cite this article: Bone Joint J 2019;101-B:808–816.

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.

Aims

Whether a combined anteroposterior fusion or a posterior-only fusion is more effective in the management of patients with Scheuermann’s kyphosis remains controversial. The aim of this study was to compare the radiological and clinical outcomes of these surgical approaches, and to evaluate the postoperative complications with the hypothesis that proximal junctional kyphosis would be more common in one-stage posterior-only fusion.

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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).

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The primary aim of this study was to analyse the position of the acetabular and femoral components in total hip arthroplasty undertaken using an anterior surgical approach.

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Patients with multiple myeloma (MM) develop deposits in the spine which may lead to vertebral compression fractures (VCFs). Our aim was to establish which spinopelvic parameters are associated with the greatest disability in patients with spinal myeloma and VCFs.

Adolescent idiopathic scoliosis (AIS) is a complex 3D deformity of the spine. Its prevalence is between 2% and 3% in the general population, with almost 10% of patients requiring some form of treatment and up to 0.1% undergoing surgery. The cosmetic aspect of the deformity is the biggest concern to the patient and is often accompanied by psychosocial distress. In addition, severe curves can cause cardiopulmonary distress. With proven benefits from surgery, the aims of treatment are to improve the cosmetic and functional outcomes. Obtaining correction in the coronal plane is not the only important endpoint anymore. With better understanding of spinal biomechanics and the long-term effects of multiplanar imbalance, we now know that sagittal balance is equally, if not more, important. Better correction of deformities has also been facilitated by an improvement in the design of implants and a better understanding of metallurgy. Understanding the unique character of each deformity is important. In addition, using the most appropriate implant and applying all the principles of correction in a bespoke manner is important to achieve optimum correction.

In this article, we review the current concepts in AIS surgery.

Cite this article: Bone Joint J 2018;100-B:415–24.

Cardiac disease in patients with ankylosing spondylitis (AS) has previously been studied but not in patients with a kyphosis or in those who have undergone an operation to correct it.

The aim of this study was to measure the post-operative changes in cardiac function of patients with an AS kyphosis after pedicle subtraction osteotomy (PSO).

The original cohort consisted of 39 patients (33 men, six women). Of these, four patients (two men, two women) were lost to follow-up leaving 35 patients (31 men, four women) to study. The mean age of the remaining patients was 37.4 years (22.3 to 47.8) and their mean duration of AS was 17.0 years (4.6 to 26.4). Echocardiographic measurements, resting heart rate (RHR), physical function score (PFS), and full-length standing spinal radiographs were obtained before surgery and at the two-year follow-up.

The mean pre-operative RHR was 80.2 bpm (60.6 to 112.3) which dropped to a mean of 73.7 bpm (60.7 to 90.6) at the two-year follow-up (p = 0.0000). Of 15 patients with normal ventricular function pre-operatively, two developed mild left ventricular diastolic dysfunction (LVDD) at the two-year follow-up. Of 20 patients with mild LVDD pre-operatively only five had this post-operatively. Overall, 15 patients had normal LV diastolic function before their operation and 28 patients had normal LV function at the two-year follow-up.

The clinical improvement was 15 out of 20 (75.0%): cardiac function in patients with AS whose kyphosis was treated by PSO was significantly improved.

Cite this article: Bone Joint J 2015;97-B:1405–10.

The interaction between the lumbosacral spine and the pelvis is dynamically related to positional change, and may be complicated by co-existing pathology. This review summarises the current literature examining the effect of sagittal spinal deformity on pelvic and acetabular orientation during total hip arthroplasty (THA) and provides recommendations to aid in placement of the acetabular component for patients with co-existing spinal pathology or long spinal fusions. Pre-operatively, patients can be divided into four categories based on the flexibility and sagittal balance of the spine. Using this information as a guide, placement of the acetabular component can be optimal based on the type and significance of co-existing spinal deformity.

Cite this article: Bone Joint J 2015;97-B:1017–23.

A review of the current literature shows that there is a lack of consensus regarding the treatment of spondylolysis and spondylolisthesis in children and adolescents. Most of the views and recommendations provided in various reports are weakly supported by evidence. There is a limited amount of information about the natural history of the condition, making it difficult to compare the effectiveness of various conservative and operative treatments. This systematic review summarises the current knowledge on spondylolysis and spondylolisthesis and attempts to present a rational approach to the evaluation and management of this condition in children and adolescents.

Aims

The pelvis rotates in the sagittal plane during daily activities. These rotations have a direct effect on the functional orientation of the acetabulum. The aim of this study was to quantify changes in pelvic tilt between different functional positions.

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.

This review of the literature presents the current understanding of Scheuermann’s kyphosis and investigates the controversies concerning conservative and surgical treatment. There is considerable debate regarding the pathogenesis, natural history and treatment of this condition. A benign prognosis with settling of symptoms and stabilisation of the deformity at skeletal maturity is expected in most patients. Observation and programmes of exercise are appropriate for mild, flexible, non-progressive deformities. Bracing is indicated for a moderate deformity which spans several levels and retains flexibility in motivated patients who have significant remaining spinal growth.

The loss of some correction after the completion of bracing with recurrent anterior vertebral wedging has been reported in approximately one-third of patients. Surgical correction with instrumented spinal fusion is indicated for a severe kyphosis which carries a risk of progression beyond the end of growth causing cosmetic deformity, back pain and neurological complications. There is no consensus on the effectiveness of different techniques and types of instrumentation. Techniques include posterior-only and combined anteroposterior spinal fusion with or without posterior osteotomies across the apex of the deformity. Current instrumented techniques include hybrid and all-pedicle screw constructs.