Aims. Navigation devices are designed to improve a surgeon’s accuracy in positioning the acetabular and femoral components in total hip arthroplasty (THA). The purpose of this study was to both evaluate the accuracy of an optical computer-assisted surgery (CAS) navigation system and determine whether preoperative spinopelvic mobility (categorized as hypermobile, normal, or stiff) increased the risk of acetabular component placement error. Methods. A total of 356 patients undergoing primary THA were prospectively enrolled from November 2016 to March 2018. Clinically relevant error using the CAS system was defined as a difference of > 5° between CAS and 3D radiological reconstruction measurements for acetabular component inclination and anteversion. Univariate and multiple logistic regression analyses were conducted to determine whether hypermobile (. Δ. sacral slope(SS). stand-sit. > 30°), or stiff (. ∆. SS. stand-sit. < 10°) spinopelvic mobility contributed to increased error rates. Results. The paired absolute difference between CAS and postoperative imaging measurements was 2.3° (standard deviation (SD) 2.6°) for inclination and 3.1° (SD 4.2°) for anteversion. Using a target zone of 40° (± 10°) (inclination) and 20° (± 10°) (anteversion), postoperative standing radiographs measured 96% of acetabular components within the target zone for both inclination and anteversion. Multiple logistic regression analysis controlling for BMI and sex revealed that hypermobile spinopelvic mobility significantly increased error rates for anteversion (odds ratio (OR) 2.48, p = 0.009) and inclination (OR 2.44, p = 0.016), whereas stiff spinopelvic mobility increased error rates for anteversion (OR 1.97, p = 0.028). There were no dislocations at a minimum three-year follow-up. Conclusion. Despite high reliability in acetabular positioning for inclination in a large patient cohort using an optical CAS system, hypermobile and stiff spinopelvic mobility significantly increased the risk of clinically relevant errors. In patients with abnormal spinopelvic mobility, CAS systems should be adjusted for use to avoid acetabular component misalignment and subsequent risk for long-term dislocation. Cite this article: Bone Jt Open 2022;3(6):475–484

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

Aims

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

A total hip replacement (THR) patient's spinopelvic mobility might predispose them to an increased risk of impingement, instability and edge-loading. This risk can be minimised by considering their preoperative movement during planning of component alignment. However, the question of whether the preoperative, arthritic motion is representative of the postoperative mobility has been raised. We aimed to determine the change in functional pelvic tilt in a series of THR patients at one-year. Four-hundred and eleven patients had their pelvic tilt and lumbar lordotic angle (LLA) measured in the standing and flexed-seated (position when patients initiate rising from a seat) positions as part of routine planning for THR. All measurements were performed on lateral radiographs. At 12-months postoperatively, the same two lateral images were taken and pelvic tilt measured. Pearson correlation was used to investigate the linear relationship between pre-and post-op pelvic tilt. Furthermore, a predictive model of post-op pelvic tilt was developed using machine learning algorithms. The model incorporating four preoperative inputs – standing pelvic tilt, seated pelvic tilt, standing LLA and seated LLA. In the standing position, there was a mean 2° posterior rotation after THR, with a maximum posterior change of 13°. The Pearson correlation coefficient between pre-and post-op standing pelvic tilt was 0.84. This prediction of post-op standing tilt improved to 0.91 when the three further inputs were incorporated to the predictive model. In the flexed-seated position, there was a mean 7° anterior rotation after THR, with a maximum anterior change of 45°. The Pearson correlation coefficient between pre-and post-op seated pelvic tilt was 0.54. This prediction of post-op seated tilt improved to 0.71 when the three further inputs were incorporated to the predictive model. The best predictor of post-operative spinopelvic mobility, is the patients pre-operative spinopelvic mobility, and this should routinely be measured when planning THR. The predictive model will continue to improve in accuracy as more data and more variables (contralateral hip pathology, pelvic incidence, age and gender) are incorporated into the model

Spinopelvic mobility describes the change in lumbar lordosis and pelvic tilt from standing to sitting position. For 1° of posterior pelvic tilt, functional cup anteversion increases by 0.75° after total hip arthroplasty (THA). Thus, spinopelvic mobility is of high clinical relevance regarding the risk of implant impingement and dislocation. Our study aimed to 1) determine the proportion of OA-patients with stiff, normal or hypermobile spino-pelvic mobility and 2) to identify clinical or static standing radiographic parameters predicting spinopelvic mobility. This prospective diagnostic cohort study followed 122 consecutive patients with end-stage osteoarthritis awaiting THA. Preoperatively, the Oxford Hip Score, Oswestry Disability Index and Schober's test were assessed in a standardized clinical examination. Lateral view radiographs were taken of the lumbar spine, pelvis and proximal femur using EOS© in standing position and with femurs parallel to the floor in order to achieve a 90°-seated position. Radiographic measurements were performed for the lumbar lordosis angle (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI) and pelvic-femoral-angle (PFA). The difference in PT between standing and seated allowed for patient classification based on spino-pelvic mobility into stiff (±30°). From the standing to the sitting position, the pelvis tilted backwards by a mean of 19.6° (SD 11.6) and the hip was flexed by a mean of 57° (SD 17). Change in pelvic tilt correlated inversely with change in hip flexion. Spinopelvic mobility is highly variable in patients awaiting THA and we could not identify any clinical or static standing radiographic parameter predicting the change in pelvic tilt from standing to sitting position. In order to identify patients with stiff or hypermobile spinopelvic mobility, we recommend performing lateral view radiographs of the lumbar spine, pelvis and proximal femur in all patients awaiting THA. Thereafter, implants and combined cup inclination/anteversion can be individually chosen to minimize the risk of dislocation. No predictors could be identified. We recommend performing sitting and standing lateral view radiographs of the lumbar spine and pelvis to determine spinopelvic mobility in patients awaiting THA

Aims. Our study aimed to 1) Describe the changes in spinopelvic mobility when transitioning from standing, to ‘relaxed-seated’ and thereafter to ‘deep-seated’ position and 2) Determine the change in spinopelvic mobility types 1 year post-THA compared to preoperatively. Methods. This prospective diagnostic cohort study followed 100 consecutive patients 1 year post-THA. Preoperatively and one year postoperatively, radiographic measurements were performed for the lumbar-lordosis-angle, pelvic tilt and pelvic-femoral-angle on lateral radiographs in the standing, ‘relaxed-seated’ and ‘deep-seated’ position (torso maximally leaning forward). Patients were classified according to their spinopelvic mobility type, according to the change in PT between the standing and relaxed-seated position (stiff:ΔPT<±10°, normal:10°≤ΔPT≤30°, hypermobile:ΔPT>±30°). Results. Compared to preoperatively, when moving from a standing to a relaxed-seated position, hip flexion increased by 10°±18, leading to less posterior pelvic tilt by 6°±11 and reduced lumbar spine flexion by 6°±11 (all p<0.001). Similarly, when moving from the standing to deep-seated position, hip flexion improved by a mean of 8°±22, leading to reduced lumbar spine flexion by a mean of 5°±8, whereas the change in pelvic tilt did not change compared to preoperatively (p=0.016, p<0.001, p=0.46). The distribution of spinopelvic mobility types 1 year postoperatively was significantly different compared to preoperatively, as the percentage of patients with stiff spinopelvic mobility increased from 16% to 43% (p<0.001). Conclusion. Hip flexion improved by 10° on average 1 year after total hip arthroplasty. Thus, slightly less compensatory posterior pelvic tilt and lumbar spine flexion was needed when taking a relaxed-seated position. When taking a deep-seated position, improved hip flexion required less lumbar spine flexion. However, these changes were small when being compared to preoperative variability of these parameters. Thus, individual spinopelvic mobility remains relatively unchanged 1 year after THA compared to preoperatively

Introduction. Patients with abnormal spinopelvic mobility are at increased risk for hip instability. Measuring the change in sacral slope (ΔSS) with standing and seated lateral radiographs is commonly used to determine spinopelvic mobility pre-operatively. Sacral slope should decrease at least 10 degrees to demonstrate adequate accommodation. Accommodation of <10 deg necessitates acetabular component position change or use of a dual mobility implant. There is potential for different ΔSS measurements in the same patient based on sitting posture. Methods. 78 patients who underwent THA were reviewed to quantify the variability in pre-operative spinopelvic mobility when two different seated positions (relaxed sitting v. pre-rise sitting) were used in the same patient. Results. 34 patients had standardized pre-rise sitting x-rays, while 44 patients had standardized relaxed sitting x-rays. Of the 44 patients with relaxed sitting x-rays, the mean ΔSS (ΔrSS) was 20.4 degrees. No patients exhibited an increase in sacral slope when sitting (ie; reverse accommodation). Of the 34 patients with pre-rise sitting x-rays, the mean pre-rise sit-stand change (ΔprSS) was only 1.85 degrees with 47% (16/34) showing reverse accommodation, actually increasing the seated sacral slope compared to standing sacral slope. 18 patients had both pre-rise and relaxed sitting x-rays. In patients with both seated x-rays, the mean relaxed sit-stand change in sacral slope (ΔrSS) was 18.1 ± 6.1 degrees and only 3.0 ± 10.5 degrees for pre-rise sit-stand (ΔprSS), with a mean ΔSS difference of the 15.1 degrees (p <0.0001). Conclusion. A 15 degrees error could be made in pre-operative planning depending on the seated posture of the patient. Since decisions on component position or use of dual-mobility are made on pre-operative lateral sit-stand radiographs, postural standardization is critical. The relaxed seated radiograph is the preferred posture at the time of the seated lateral radiograph. For any tables or figures, please contact the authors directly

Introduction. Spinopelvic mobility has been associated with THA outcome. To-date spine assessments have been made quasi-statically, using radiographs, in standing and seated positions but dynamic spinopelvic mobility has not been well explored. This study aims to determine the association between dynamic (motion analysis) and quasi-static (radiographic) sagittal assessments and examine the association between axial and sagittal spinal kinematics in hip OA patients and controls. Methods. This is a prospective, IRB approved, cohort study of 12 patients with hip OA pre-THA (6F/6M, 67±10 years) and six healthy controls (3F/3M, 46±18 years). All underwent lateral spinopelvic radiographs in standing and seated bend-and-reach (SBR) positions. Pelvic tilt (PT), pelvic-femoral-angle (PFA) and lumbar lordosis (LL) angles were measured in both positions and the differences (Δ) in angles between SBR and standing were computed. All participants performed two dynamic tasks at the motion laboratory: seated maximal trunk rotation (STR) and seated bend and reach (SBR). Three-dimensional joint motion data were collected and processed by a 10-camera infrared motion analysis system (Vicon, Nexus 2.10, UK). Total axial and sagittal spine (mid-thoracic to lumbar) range of motion (ROM) were calculated for STR and SBR, respectively. Results. ΔLL for SBR and motion analysis spinal flexion for SBR moderately correlated (ρ=0.4, p=0.007). Dynamic spinal rotation and flexion significantly, strongly, correlated (ρ=0.6 p=0.007). OA patients compared to healthy participants showed significant less ΔPFA (53°±21° vs. 77°±14°; p<0.001); ΔPT (−17°±8° vs. 9°±15°; p<0.001), ΔLL (35°±15° vs. 43° ±9°; p<0.001), axial spinal rotation during STR (62° ±12°vs. 79° ±8°, p<.001) and less, but not significant, spine flexion during SBR (36° ±15° vs. 44° ±10°, P=.1). Conclusion. Dynamic sagittal and axial spinal ROM showed moderately correlated. Motion analysis can provide valid assessments for spine mobility. OA patients compared to healthy participants showed significant less ΔPFA, ΔPT, ΔLL, axial spinal rotation during STR. Surgeons should be aware that patients with less spine mobility that could affect the stability of THA and increase the risk of poor outcomes

Aims. Our study aimed to 1) determine if there was a difference for the HOOS-PS score between patients with stiff/normal/hypermobile spinopelvic mobility and 2) to investigate if functional sagittal cup orientation affected patient reported outcome 1 year post-THA. Methods. This prospective diagnostic cohort study followed 100 consecutive patients having received unilateral THA for end-stage hip osteoarthritis. Pre- and 1-year postoperatively, patients underwent a standardized clinical examination, completed the HOOS-PS score and sagittal low-dose radiographs were acquired in the standing and relaxed-seated position. Radiographic measurements were performed for the lumbar-lordosis-angle, pelvic tilt (PT), pelvic-femoral-angle and cup ante-inclination. The HOOS-PS was compared between patients with stiff (ΔPT<±10°), normal (10°≤ΔPT≤30°) and hypermobile spinopelvic mobility (ΔPT>±30°). Results. Preoperatively, 16 patients demonstrated stiff, 70 normal and 14 hypermobile spinopelvic mobility without a difference in the HOOS-PS score (66±14/67±17/65±19;p=0.905). One year postoperatively, 43 patients demonstrated stiff, 51 normal and 6 hypermobile spinopelvic mobility. All postoperative hypermobile patients had normal spinopelvic mobility preoperatively and showed significantly worse HOOS-PS scores compared to patients with stiff or normal spinopelvic mobility (21±17/21±22/35±16;p=0.043). Postoperatively, patients with hypermobile spinopelvic mobility demonstrated no significant difference for the pelvic tilt in the standing position compared to the other two groups (19±8°/16±8°/19±4°;p=0.221), but a significantly lower sagittal cup ante-inclination (36±10°/36±9°/29±8°;p=0.046). Conclusion. The present study demonstrated that patients with normal preoperative and postoperative spinopelvic hypermobility show worse HOOS-PS scores than patients with stiff or normal spinopelvic mobility. The lower postoperative cup ante-inclination seems to force the pelvis to tilt more posteriorly when moving from the standing to seated position (spinopelvic hypermobility) in order to avoid anterior impingement. Thus, functional cup orientation in the sagittal plane seems to affect postoperative patient reported outcome

Introduction. Cross table lateral (CTL) radiographs are commonly used to measure acetabular component anteversion after total hip arthroplasty (THA). CTL measurements may differ by >10 degrees from CT scan measurements, but the reasons for this discrepancy are poorly understood. We compare anteversion measurements made on CTL radiographs and CT scans to identify spinopelvic parameters predictive of inaccuracy. Methods. THA patients (n=47) with preoperative spinopelvic radiographic analysis and postoperative CT scans were retrospectively reviewed. Acetabular component anteversion was measured on post-operative CTL radiographs, and CT scans using 3D reconstructions of the pelvis. Patients were grouped by error (CTL-CT)>10° (n=11) or <10° (n=36), and spinopelvic mobility parameters were compared using t-tests. Correlation between error and mobility parameters was assessed with Pearson coefficient. Results. Patients with CTL error >10° (range 10–14) had stiffer lumbar spines with less lumbar flexion (38° vs 47°, p=0.03), greater sagittal imbalance measured by pelvic incidence-lumbar lordosis mismatch (6° vs −2°, p=0.04), more pelvic extension when seated (pelvic tilt −10° vs −2°, p=0.05), and greater change in pelvic tilt between supine and seated positions (13° vs 4°, p=0.04). The error of CTL measurements showed a positive correlation with increased CTL anteversion (r=0.5, p=0.001), standing lordosis (r=0.23, p=0.05), seated lordosis (r=0.4, p=0.01) and pelvic tilt change between supine and step-up positions (r=0.34, p=0.01). Discussion. Differences in spinopelvic mobility patterns may explain the variable accuracy of acetabular anteversion measurements on CTL radiographs. Patients with stiff spines and increased compensatory pelvic motion have less accurate measurements on CTL radiographs. Flexion of the contralateral hip is required to obtain clear CTL radiographs. In patients with a stiff lumbar spine, this movement may extend the pelvis and increase anteversion of the acetabulum on CTL views. Reliable analysis of acetabular component anteversion in this patient population may require advanced imaging with a CT scan

Adverse spinopelvic mobility (SPM) has been shown to increase risk of dislocation of primary total hip arthroplasty (THA). In patients undergoing THA, prevalence of adverse SPM has been shown to be as high as 41%. Stiff lumbar spine, large posterior standing pelvic tilt and severe sagittal spinal deformity have been identified as risk factors for increased hip instability. Dislocation rates for dual mobility articulations have been reported to be 0% to 1.1%. The aim of this study was to determine the early survivorship from the Australian National Joint Replacement Registry (AOANJRR) of patients with adverse SPM who received a dual mobility articulation. A multicentre study was performed using data from 229 patients undergoing primary THA, enrolled consecutively. All the patients who had one or more adverse spine or pelvic mobility parameters had a dual mobility articulation inserted at the time of their surgery. Average age was 76 (22 to 93) years and 63% were female. At a mean of 2.1 (1 – 3.3) years post-op, the AOANJRR was analysed for follow-up. Reasons for revision and types of revision were identified. 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 was 99.3% (CI 98.3% − 100%) at 2 years. DM bearings reduce the risk of dislocation of primary THA in patients with adverse spine and pelvic mobility

Aims. The aims of the study were to determine the differences in spinopelvic mobility between a cohort of hip OA patients and a control group for the 1) standing to relaxed-seated and 2) standing to deep-seated task. Methods. A cohort of 40 patients with end-stage hip OA and a control group of 40 subjects, matched for age, gender and BMI were prospectively studied. Clinical data and lateral view radiographs in different positions were assessed. Sagittal spinopelvic mobility was calculated as the change when moving from the standing to relaxed-seated and standing to deep-seated positions for the lumbar lordosis angle, pelvic tilt and pelvic-femoral angle. Results. When moving from the standing to sitting position, hip OA patients demonstrated less hip flexion (52±18 vs. 69±11, p<0.001), an increased posterior pelvic tilt (23±13 vs. 12±9, p<0.001) and more flexion of the lumbar spine (22±15 vs. 14±11, p=0.01). Similarly, when moving from the standing to deep-seated position, hip OA patients demonstrated also less hip flexion (64±21 vs. 84±18, p<0.001), accompanied by a posterior and not an anterior pelvic tilt as in the control group (10±16 vs. −3±17, p<0.001). No difference could be found for lumbar spine flexion (40±15 vs. 43±13, p=0.28). The percentage of subjects with stiff spinopelvic mobility was significantly lower in the patient group (15% vs 48%; p=0.002) and there was a trend towards a higher percentage in spinopelvic hypermobility in patients (20% vs 2%; p=0.08). Conclusions. Decreased hip flexion due to OA leads to an increased posterior pelvic tilt when taking a relaxed-seated position. Less than 10° of posterior pelvic tilt from the standing to relaxed seated position (spinopelvic ‘stiffness’) is more frequent in controls without hip OA and results from hip mobility and not from stiffness of the lumbar spine

A stiff spine leads to increased demand on the hip, creating an increased risk of total hip arthroplasty (THA) dislocation. Several authors propose that a change in sacral slope of ≤10° between the standing and relaxed-seated positions (ΔSSstanding→relaxed-seated) identifies a patient with a stiff lumbar spine and have suggested use of dual-mobility bearings for such patients. However, such assessment may not adequately test the lumbar spine to draw such conclusions. The aim of this study was to assess how accurately ΔSSstanding→relaxed-seated can identify patients with a stiff spine. This is a prospective, multi-centre, consecutive cohort series. Two-hundred and twenty-four patients, pre-THA, had standing, relaxed-seated and flexed-seated lateral radiographs. Sacral slope and lumbar lordosis were measured on each functional X-ray. ΔSSstanding→relaxed-seated seated was determined by the change in sacral slope between the standing and relaxed-seated positions. Lumbar flexion (LF) was defined as the difference in lumbar lordotic angle between standing and flexed-seated. LF≤20° was considered a stiff spine. The predictive value of ΔSSstanding→relaxed-seated for characterising a stiff spine was assessed. A weak correlation between ΔSSstanding→relaxed-seated and LF was identified (r2= 0.15). Fifty-four patients (24%) had ΔSSstanding→relaxed-seated ≤10° and 16 patients (7%) had a stiff spine. Of the 54 patients with ΔSSstanding→relaxed-seated ≤10°, 9 had a stiff spine. The positive predictive value of ΔSSstanding→relaxed-seated ≤10° for identifying a stiff spine was 17%. ΔSSstanding→relaxed-seated ≤10° was not correlated with a stiff spine in this cohort. Utilising this simplified approach could lead to a six-fold overprediction of patients with a stiff lumbar spine. This, in turn, could lead to an overprediction of patients with abnormal spinopelvic mobility, unnecessary use of dual mobility bearings and incorrect targets for component alignment. Referring to patients ΔSSstanding→relaxed-seated ≤10° as being stiff can be misleading; we thus recommend use of the flexed-seated position to effectively assess pre-operative spinopelvic mobility

Evaluation of patient specific spinopelvic mobility requires the detection of bony landmarks in lateral functional radiographs. Current manual landmarking methods are inefficient, and subjective. This study proposes a deep learning model to automate landmark detection and derivation of spinopelvic measurements (SPM). A deep learning model was developed using an international multicenter imaging database of 26,109 landmarked preoperative, and postoperative, lateral functional radiographs (HREC: Bellberry: 2020-08-764-A-2). Three functional positions were analysed: 1) standing, 2) contralateral step-up and 3) flexed seated. Landmarks were manually captured and independently verified by qualified engineers during pre-operative planning with additional assistance of 3D computed tomography derived landmarks. Pelvic tilt (PT), sacral slope (SS), and lumbar lordotic angle (LLA) were derived from the predicted landmark coordinates. Interobserver variability was explored in a pilot study, consisting of 9 qualified engineers, annotating three functional images, while blinded to additional 3D information. The dataset was subdivided into 70:20:10 for training, validation, and testing. The model produced a mean absolute error (MAE), for PT, SS, and LLA of 1.7°±3.1°, 3.4°±3.8°, 4.9°±4.5°, respectively. PT MAE values were dependent on functional position: standing 1.2°±1.3°, step 1.7°±4.0°, and seated 2.4°±3.3°, p< 0.001. The mean model prediction time was 0.7 seconds per image. The interobserver 95% confidence interval (CI) for engineer measured PT, SS and LLA (1.9°, 1.9°, 3.1°, respectively) was comparable to the MAE values generated by the model. The model MAE reported comparable performance to the gold standard when blinded to additional 3D information. LLA prediction produced the lowest SPM accuracy potentially due to error propagation from the SS and L1 landmarks. Reduced PT accuracy in step and seated functional positions may be attributed to an increased occlusion of the pubic-symphysis landmark. Our model shows excellent performance when compared against the current gold standard manual annotation process

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

Introduction. The prevalence of the various patterns of spinopelvic abnormalities that increase the risk for prosthetic impingement is unknown. While prior surgery or lumbar fusion are recognized as a risk factors for postoperative dislocation, many patients presenting for THA do not have obvious radiographic abnormalities. The purpose of this study is to determine the prevalence of large posterior pelvic tilt (PPT) when standing, stiff lumbar-spine (SLL) and spino-pelvic sagittal imbalance (SSI) in patients undergoing primary THA. Methods. A consecutive series of 1592 patients (56% female) over 2 years underwent functional analysis of spinopelvic mobility using CT, standing, and flexed seated lateral radiographs as part of pre-operative THA planning. The average age was 65 (20–93). We investigated the prevalence of these 3 validated spinopelvic parameters known to increase the risk for impingent and correlated them to the patient's age and gender using Chi squared analysis. Finally, the risk of flexion and extension impingement was modeled for each patient at a default supine cup orientation (DSCO) of 40°/20° (±5°). Results. Overall, 221 hips (14%) had at least 1 risk factor for impingement, while 64 (4%) had 2, and 18 (1 %) had all 3 risk factors. The most common risk factor was large PPT (10%) followed by SLL (4%) and SSI (4%). Female gender was not associated with increased spinopelvic abnormalities (p = 0.64), but age > 75 years increased the likelihood of at least having 1 risk factor (p<0.01) (Table-1). Placing the cup within the DSCO resulted in observed prosthetic impingement in 792 patients (50%) (Fig-1). 158 hips (20%) had at least 1 risk factor, while 56 (7%) had 2, and 16 (2 %) had all 3 risk factors for impingement. Posterior pelvic tilt was associated with extension impingement risk, while SLL and SSI increased flexion impingement risk. Conclusion. Spinopelvic risk factors that increase impingement risk are not infrequent in THA patients. We observed 50% prosthetic impingement when a single target for acetabular orientation target was applied. For any figures, tables, or references, please contact the authors directly

Introduction & aims. Apparently well-orientated total hip replacements (THR) can still fail due to functional component malalignment. Previously defined “safe zones” are not appropriate for all patients as they do not consider an individual's spinopelvic mobility. The Optimized Positioning System, OPS. TM. (Corin, UK), comprises preoperative planning based on a patient-specific dynamic analysis, and patient-specific instrumentation for delivery of the target component alignment. The aim of this study was to determine the early revision rate from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) for THRs implanted using OPS. TM. . Method. Between January 4. th. 2016 and December 20. st. 2017, a consecutive series of 841 OPS. TM. cementless total hip replacements were implanted using a Trinity acetabular cup (Corin, UK) with either a TriFit TS stem (98%) or a non-collared MetaFix stem (2%). 502 (59%) procedures were performed through a posterior approach, and 355 (41%) using the direct superior approach. Mean age was 64 (range; 27 to 92) and 51% were female. At a mean follow-up of 15 months (range; 3 to 27), the complete list of 857 patients was sent to the AOANJRR for analysis. Results. There were 5 revisions: . a periprosthetic femoral fracture at 1-month post-op in a 70F. a ceramic head fracture at 12-months post-op in a 59M. a femoral stem loosening at 7-months post-op in a 58M. a femoral stem loosening at 16-months post-op in a 64M. an anterior dislocation in a 53M, that was revised 9 days after the primary procedure. CT analysis, prior to revision surgery, revealed acetabular cup orientation of 46°/31° (inclination/anteversion) and femoral stem anteversion of 38°. Conclusions. These preliminary findings suggest the OPS. TM. dynamic planning and delivery system provides good early results, with a low rate of revision for dislocation. Limitations of the study will be discussed

Background. It is not always clear why some patients experience recurrent dislocation following total hip arthroplasty (THA). In order to plan appropriate revision surgery for such patients, however, it is important to understand the specific biomechanical basis for the dislocation. We have developed a novel method to analyse the biomechanical profile of the THA, specifically to identify edge loading and prosthetic impingement, taking into account spinopelvic mobility. In this study we compare the results of this analysis in THA patients with and without recurrent dislocation. Methods. Post-operative CT scans and lateral standing and seated radiographs of 40 THA patients were performed, 20 of whom had experienced postoperative dislocation. The changes in pelvic and femoral positions on the lateral radiographs were measured between the standing and seated positions, and a 3D digital model was then generated to simulate the movement of the hip when rising from a chair for each patient. The path of the joint reaction force (JRF) across the acetabular bearing surface and the motion of the femoral neck relative to the acetabular margin were then calculated for this “sit-to-stand” movement, in order to identify where there was risk of edge loading or prosthetic impingement. Results. For every patient it was possible to model the path of the JRF and the femoral neck relative to the acetabular component. The analysis predicted either edge loading or prosthetic impingement in significantly more patients in the “dislocating” group compared to the “non-dislocating” group (figure 1). Conclusions. This method of biomechanical simulation may be able to identify edge loading and / or prosthetic impingement in THA patients who have experienced recurrent dislocation. This may be helpful in planning appropriate revision surgery. For any figures or tables, please contact the authors directly

Introduction. Interactions between hip, pelvis and spine, as abnormal spinopelvic movements, have been associated with inferior outcomes following total hip arthroplasty (THA). Changes in pelvis position lead to a mutual change in functional cup orientation, with both pelvic tilt and rotation having a significant effect on version. Hip osteoarthritis (OA) patients have shown reduced hip kinematics which may place increased demands on the pelvis and the spine. Sagittal and coronal planes assessments are commonly done as these can be adequately studied with anteroposterior and lateral radiographs. However, abnormal pelvis rotation is likely to compromise the outcome as they have a detrimental effect on cup orientation and increased impingement risk. This study aims to determine the association between dynamic motion and radiographic sagittal assessments; and examine the association between axial and sagittal spinal and pelvic kinematics between hip OA patients and healthy controls (CTRL). Methods. This is a prospective study, IRB approved. Twenty hip OA pre-THA patients (11F/9M, 67±9 years) and six CTRL (3F/3M, 46±18 years) underwent lateral spinopelvic radiographs in standing and seated bend-and-reach (SBR) positions. Pelvic tilt (PT), pelvic-femoral-angle (PFA) and lumbar lordosis (LL) angles were measured in both positions and the differences (Δ) between standing and SBR were calculated. Dynamic SBR and seated maximal-trunk-rotation (STR) were recorded in the biomechanics laboratory using a 10-infrared camera and processed on a motion capture system (Vicon, UK). Direct kinematics extracted maximal pelvic tilt (PT. max. ), hip flexion (HF. max. ) and (mid-thoracic to lumbar) spinal flexion (SF. max. ). The SBR pelvic movement contribution (ΔPT. rel. ) was calculated as ΔPT/(ΔPT+ΔPFA)∗100 for the radiographic analysis and as PT. max. /(PT. max. +HF. max. ) for the motion analyses. Axial and sagittal, pelvic and spinal range of motion (ROM) were calculated for STR and SBR, respectively. Spearman's rank-order determined correlations between the spinopelvic radiographs and sagittal kinematics, and the sagittal/axial kinematics. Mann-Whitney U-tests compared measures between groups. Results. Radiograph readings correlated with sagittal kinematics during SBR for ΔPT and PT. max. (ρ=0.64, p<0.001), ΔPFA and HF. max. (ρ=0.44, p<0.0002), and ΔLL and SF. max. (ρ=0.34, p=0.002). Relative pelvic movements (ΔPT. rel. ) were not different between radiographic (11%±21) and biomechanical (15%±29) readings (p=0.9). Sagittal SRB spinal flexion correlated with the axial STR rotation (ρ=0.43, p<0.0001). Although not seen in CTRL, sagittal SRB pelvic flexion strongly correlated with STR pelvic rotation in OA patients (ρ=0.40, p=0.002). All spinopelvic parameters were different between the patients with OA and CTRL. CTRLs exhibited significantly greater mobility and less variability in all 3 segments (spine, pelvis, hip) and both planes (axial and sagittal) (Table 1). Conclusion. Correlation between sagittal kinematics and radiographical measurements during SBR validates the spinopelvic mobility assessments in the biomechanics laboratory. Axial kinematics of both pelvis and spine correlated significantly in OA patients, suggesting that patients with abnormal sagittal mobility are likely to also exhibit abnormal axial mobility, which can further potentiate any at-risk kinematics. Significantly lower OA ROM must be investigated post-THA. Pre-THA variability of both sagittal and axial movements indicates that both planes must be considered ahead of surgical planning with navigation and/or robotics. For any figures or tables, please contact the authors directly

The unparalleled events of the year 2020 continue to evolve and challenge the worldwide community on a daily basis. The COVID-19 pandemic has had a major impact on all aspects of our lives, and has caused major morbidity and mortality around the globe. The impact of COVID-19 on the practice of orthopedic surgery has been substantial with practice shutdowns, elective surgery restrictions, heightened utilization of telemedicine platforms and implementation of precautionary measures for in-person clinic visits. During this transition period the scholarly and educational pursuits of academic surgeons have been de-emphasized as the more immediate demands of clinical practice survivorship have been the priority. This unavoidable focus on clinical practice has heightened the importance of orthopedic subspecialty societies in maintaining an appropriate level of attention on research and educational activities. Under the outstanding presidential leadership of Robert Barrack, MD, The Hip Society adapted to the profound challenges of 2020, and maintained strong leadership in the realms of education and research. The recent 2020 summer meeting of the Hip Society was a testimonial to the resilience and dedication of the Society members to ongoing innovation in research and education. Due to travel and social distancing restrictions the 2020 summer meeting was transitioned from an in-person to a virtual meeting format. Dr Barrack and Program Chair Dr John Clohisy assisted with oversight of the meeting, while Olga Foley and Cynthia Garcia ensured the success of the meeting with remarkable planning and organization. These collaborative efforts resulted in an organized, well-attended, high level scientific meeting with engaging discussion and a remarkable virtual conference environment. The Bone & Joint Journal is very pleased to partner with The Hip Society to publish the proceedings of this very unique virtual meeting. The Hip Society is based in the United States and membership is granted to select individuals for leadership accomplishments in education and research related to hip disease. The Society is focused on the mission of advancing the knowledge and treatment of hip disorders to improve the lives of patients. The vision of the Hip Society is to lead in the discovery and dissemination of knowledge related to disorders of the hip. The annual closed meeting is one of the most important events of the society as this gathering highlights timely, controversial and novel research contributions from the membership. The top research papers from The Hip Society meeting will be published and made available to the wider orthopedic community in The Bone & Joint Journal. This partnership with The Bone & Joint Journal enhances the mission and vision of The Hip Society by international dissemination of the meeting proceedings. Given the far-reaching circulation of The Bone & Joint Journal the highest quality work is available to an expanding body of surgeons, associated healthcare providers and patients. Ultimately, this facilitates the overarching Hip Society goal of improving the lives of our patients. The 2020 virtual Hip Society meeting was characterized by outstanding member attendance, high quality paper presentations and robust discussion sessions. The meeting was held over two days and encompassed 58 open paper presentations divided into ten sessions with moderated discussions after each session. All papers will be presented in this issue in abstract form, while selected full papers passing our rigorous peer review process will be available online and in The Bone & Joint Journal in a dedicated supplement in 2021. The first session of the meeting focused on issues related to complex primary THA and osteonecrosis of the femoral head. Dr Gross presented on the conversion of hip fusion to THA in 28 patents at a mean 7 years. He reported a high clinical success rate, yet complications of heterotopic ossification and neurologic injury were relatively common. Consideration of heterotopic ossification prophylaxis and the selective use of a constrained liner were recommended. Dr Pagnano summarized the use of various contemporary porous acetabular components in 38 hips in the setting of prior pelvic radiation. The mean follow-up was 5 years and 10 year survivorship was 100% with all implants radiographically fixed. Dr Bolognesi's study demonstrated that THA in solid organ transplant patients is associated with higher risk for facility placement, transfusions and readmissions. This patient population also has increased mortality risk (4.3% risk at 1 year) especially lung transplant patients. The second group of papers focused on femoral head osteonecrosis. Dr Iorio presented single center data demonstrating that CT scan was a useful adjunct for diagnosis in the staging work-up for cancer, yet was not useful for ARCO staging and treatment decision-making. On the basic science side, Dr Goodman utilized a rabbit model of steroid-induced femoral head osteonecrosis to determine that immunomodulation with IL-4 has the potential to improve bone healing after core decompression. The session was concluded by Dr Nelson's study of ceramic-on-ceramic THA in 108 osteonecrosis patients. The median 12 year results were outstanding with marked increases in PROs, maintenance of high activity levels, and a 3.7% revision rate. In the second session attention was directed to THA instability and spinopelvic mobility. Dr Sierra presented a machine learning algorithm for THA dislocation risk. Two modifiable variables (anterior/lateral approach, elevated liner) were most influential in minimizing dislocation risk. Dr Taunton's study demonstrated a deep learning artificial intelligence model derived from postoperative radiographs to predict THA dislocation risk. High sensitivity and negative predictive value suggest that this model may be helpful in assessing postoperative dislocation risk. In reviewing a large single-center, multiple surgeon cohort of 2,831 DAA procedures, Dr Moskal noted a very low dislocation rate (0.45%) at minimum 2 years. Importantly, spinopelvic pathology or prior spinal instrumentation was not associated with an increased dislocation risk (0.30%). Dr Huo and colleagues analyzed pelvic tilt during functional gait in patients with acetabular dysplasia. They detected variable pelvic tilt on different surfaces with the data suggesting that patients with more anterior pelvic tilt while standing tend to have greater compensatory posterior pelvic tilt during gait. Dr Lamontagne reported on the sagittal and axial spinomobility in patients with hip OA, and highlighted reductions in pelvic tilt, pelvic-femoral-angle, lumbar lordosis and seated maximal trunk rotation when compared to controls. Dr Dennis showed that differences in spinopelvic mobility may explain the variable accuracy of acetabular version measurements on the cross-table lateral radiographs. Dr Gwo-Chin presented on a comprehensive functional analysis of 1,592 patients undergoing THA and observed that spinopelvic abnormalities are not infrequent (14%) in THA patients. Consistent with these findings Dr Murphy and collaborators identified a low prevalence of previous spinal instrumentation (1.5%), yet a high prevalence of spine stiffness (27.6%) in 149 patients undergoing THA. Session three highlighted various aspects of treating hip disease in young patients. Dr Peters investigated the need for subsequent hip arthroscopy in 272 patients treated with an isolated PAO. Only 4.8% of these patients required subsequent arthroscopy calling into question the routine use of combined arthroscopy and PAO. Three papers addressed questions related to THA in young patients. Dr Berend's study of 2532 hips demonstrated that high activity level was not associated with an increased risk of midterm aseptic or all cause failure. Dr Nunley presented on 43 young patients with an average age of 52 years treated with a cementless stem and modular dual mobility articulation. Stress shielding was minimal and no concerning metal ion release detected. Dr Garvin summarized minimum 15 year data of THA with highly cross-linked polyethylene in patient less than 50 years. These hips performed exceptionally well with no mechanical loosening or radiographic osteolysis. Dr Engh examined 10 year results of the Birmingham Hip Resurfacing implant and reported a 92.9 % overall survivorship, with males less than 55 years achieving a 98.3% survivorship. The session was concluded by long-term data on the Conserve Plus hip resurfacing arthroplasty. Dr Amstutz presented an impressive dataset depicting an 83.1% 20 year survivorship for this early resurfacing cohort. Direct anterior approach total hip arthroplasty was the focus of session four. Dr Meneghini reported on the anesthesia and surgical times of direct anterior and posterior approaches from a large healthcare system database. These data suggested longer OR and surgical times for the DAA both in the inpatient and ASC environments. Dr Clohisy introduced the technique and early outcomes of lateral decubitus position DAA. In a learning curve experience of 257 hips. 96% of acetabular components were in the Lewinneck safe zone, the aseptic revision rate was 0.9% and there were no dislocations. Dr Beaule analyzed femoral stem cement mantle with the DAA and posterior approaches by comparing two matched cohorts. Stem alignment and cement mantle quality were equivalent with both approaches. Similarly, Dr Emerson demonstrated technical feasibility and fewer cemented femoral stem failures when compared to cementless stems in a series of 360 DAAs THAs. The final paper of the session presented by Dr Hamilton examined the impact of surgical approach on dislocation after isolated head and liner exchange. Neither the posterior nor the anterior approach was superior in reducing the dislocation rate for these high dislocation risk procedures. The fifth session explored contemporary topics related to anesthesia and pain management. Dr Byrd opened the session with a comparative study evaluating general versus spinal anesthesia for hip arthroscopy. This preliminary study was provoked by the desire to minimize aerosolized exposure early in the COVID-19 pandemic by transitioning to spinal anesthesia. Both anesthetic methods were effective. Dr Austin presented a randomized, double-blind controlled trial comparing spinal anesthetic with mepivacaine, hyperbaric bupivacaine and isobaric bupivacaine. Mepivacaine patients ambulated earlier and were more likely to be discharged the same day. Dr Mont provided a very timely study on the effects of “cannabis use disorder” and THA outcomes. This administrative database study of 44,154 patients revealed this disorder to be associated with longer hospital stays, increased complications rates and higher costs. Dr Bedair investigated whether a highly porous acetabular component submerged in an analgesic solution could enhance perioperative pain management. Interestingly, this novel strategy was associated with a reduction of postoperative pain scores and opioid consumption in 100 experimental patients compared to 100 controls. The concluding paper of the session by Dr Della Valle examined whether decreased discharge opioids led to increased postoperative opioid refills. A large single-center study of 19,428 patients detected a slight increase (5%) in opioid refills but a reduction in total refill morphine milligram equivalents. The final, sixth session of day one considered various challenging aspects of revision hip arthroplasty. Dr Nam started the session with review of preliminary results from a randomized control trial comparing closed incision negative-pressure therapy with a silver-impregnated dressing for wound management in 113 hips undergoing revision arthroplasty. Unlike previous reports, the negative pressure therapy was associated with a higher reoperation rate for wound-related complications. Dr Bostrom highlighted the potential clinical impact of basic biological interventions by establishing the presence of Neutrophil Extracellular Traps (NETS) in fibrotic tissue from human aseptic loosening specimens and in a murine model of unstable tibial implantation. NET inhibition in the murine model prevented the expected tibial implant osseointegration failure. Dr Lombardi presented early 3.3 year clinical results of a highly porous Ti6al4v acetabular component in complex primary and revision arthroplasty. Survivorship for aseptic loosening was 96.6 % and 95.3% for the primary and revision cases, respectively. Dr Schwarzkopf and colleagues explored the impact of time to revision arthroplasty on clinical outcomes. Analysis of 188 revision cases revealed early revisions (less than 2 years from primary) were associated with worse outcomes, longer hospitalizations and higher reoperation rates. Mid-term results for modular dual mobility implants in revision arthroplasty were reviewed by Dr Lachiewicz who reported on 126 hips at a mean 5.5 years. 11% of hips dislocated and the 6 year survival was 91%. An outer head diameter of 48mm or greater was associated with a lower risk of dislocation. Dr Berry concluded the session by discussing the outcomes of treating the challenging problem of interprosthetic femur fractures. A single-center study of 77 cases treated over 32 years demonstrated a 79% success rate free of reoperation at 2 years with 95% of patients being ambulatory. The second day commenced with the seventh session evaluating recent strategies to improve short-term THA outcomes. Dr Bozic and colleagues investigated the association of quality measure public reporting with hip/knee replacement outcomes. Annual trend data from 2010–2011 and 2016–2017 indicate that hospital-level complication and readmission rates decease after the start of public reporting, yet it is difficult to prove a direct effect. Dr Slover reviewed his institutions experience with the Comprehensive Care for Joint Replacement (CJR) model and emphasized that lower CJR target prices make it increasingly difficult for programs to meet target price thresholds. Cost saving strategies including same day discharge and reduction of home health services may result in smaller losses of positive margins. Dr Barsoum reported on the influence of patient and procedure-related risk factors of length of stay after THA. Patient-related risk factors provided substantial predictive value yet procedure-related risk factors (hospital site and surgical approach) remain the main drivers of predicting length of stay. Dr Hozack reviewed an impressive, single surgeon cohort of 3,977 DAA THAs and analyzed adverse events and 90 day perioperative outcomes. Simultaneous bilateral DAA THA was comparable with unilateral or staged bilateral procedures in regards to complications, readmission rate and home discharge rate but with an increased risk of transfusion. To examine the risk of complications with outpatient joint arthroplasty, Dr Della Valle performed a single-surgeon matched cohort analysis comparing outpatient and inpatient hip and knee arthroplasties. Outpatient procedures were not associated with an increased risk of any postoperative complications and actually experienced fewer emergency department visits. The eighth session covered various contemporary challenges in hip arthroplasty care. Dr Griffin began the session with an analysis of the timing of complications associated with two-stage exchange procedures for periprosthetic joint infection (PJI). Of the 189 hips included, 41.6% had a complication and the mortality was 14.1% at 2.5 years, highlighting the morbidity of this treatment method. Dr Fehring provided data assessing the fate of two-stage reimplantation after failed debridement, antibiotics and implant retention (DAIR) for a prosthetic hip infection. This analysis of 114 hips yielded concerning results demonstrating a 42.9% treatment failure of patients treated with a previous DAIR compared to a 12.3% failure rate in patients treated with an initial 2-stage procedure. Dr Jacobs reviewed the analysis of 106 femoral heads with severe corrosion and identified a chemically dominated etching process termed “column damage” to be a detrimental damage mode within CoCr femoral heads that is directly linked to banding within its microstructure. These data indicate that implant alloy microstructure must be optimized to minimize the release of fretting-corrosion products. Simon Mears presented retrospective data from 184 THAs with a dual modular femoral stem. A subgroup of hips with a modular, cobalt chromium femoral neck had a pseudotumor visualized in 15% with only 55% of these having elevated CoCr levels. These findings may support the use of routine follow-up MARS MRI for modular CoCr femoral neck prostheses. The final two studies explored timely issues related to viral illness and hip surgery. Dr Browne analyzed three large administrative databases to elucidate whether patients are at increased risk for viral illnesses following total joint replacement. The incidence of postoperative influenza after total joint replacement was not increased compared to patients not undergoing total joint replacement surgery suggesting that arthroplasty procedures may not heighten the risk of viral illness. In the final paper of the session Dr Haddad presented important data regarding perioperative complications in coronavirus positive patients undergoing surgical treatment of femoral neck fractures. In this multicenter cohort study from the United Kingdom 82 coronavirus positive patients were shown to have longer hospital stays, more critical care unit admissions, higher risk of perioperative complications and an increased mortality compared to 340 coronavirus negative patients. The eighth session had two papers on alternative femoral stem designs and three presentations more focused on femoral fracture treatments. Dr Mihalko focused on the European and US experiences with the Metha femoral neck retaining stem. The US experience mirrored the encouraging results from Europe with a 94% all cause femoral survivorship and a 99.1% femoral aseptic loosening survivorship at 5 years. Dr Kraay summarized dual energy x-ray absorptiometry (DEXA) evaluation of 16 low modulus composite femoral components at long-term follow-up of a mean 22 years. The bone mineral density associated with the implant increased in Gruen zones 2–6 and showed limited decreases in zones 1 and 7. These data support the concept that a low modulus femoral stem may more effectively load the proximal femur. Dr Springer provided data from the American Joint Replacement Registry (AJRR) and by evaluating outcomes of exact matched cohorts of 17,138 patients treated with cementless or cemented femoral implants for femoral neck fractures. Cemented implants were associated with marked reduction in early revision and periprosthetic fractures. However, cemented fixation was associated with an increased mortality at 90 days and 1 year. Additional data from the AJRR was presented by Dr Huddleston who investigated the risk factors for revision surgery after arthroplasty in a cohort of 75,333 femoral neck fractures. THA when compared to hemiarthroplasty was associated with higher early and overall revision rates. Cementless femoral fixation and increased age were also associated with higher rates of any revision. Both of these studies from the AJRR suggest that further consideration should be given to femoral fixation preferences in the femoral neck fracture population. Dr Vail summarized his institution's experience with an interdisciplinary hip fracture protocol for patients undergoing arthroplasty for acute femoral neck fractures. His study compared 157 cases prior to protocol implementation with 114 patients treated after the protocol was established. The impact of the interdisciplinary protocol was impressive as evidenced by a reduced time to operative treatment, length of stay, complication rate and one-year mortality. All being achieved without an increase in readmissions or facility discharges. The final session of the meeting addressed innovations in perioperative care of THA patients. Dr Barrack started the session with an interesting study examining the feasibility and patient preferences regarding telemedicine. A cross-sectional telephone survey of 163 arthroplasty patients indicated that 88% of patients use the internet and 94% own a device capable of videoconferencing. Nevertheless, only 18% of patients preferred a video visit over an in-person clinic visit due to concerns of inferior care. Dr Barnes quantified preoperative optimization work in 100 arthroplasty patients by using EMR activity logs and determined the surgical team spends an average 75 minutes per case on preoperative work activities. Dr Duwelius reported the early outcomes of primary THA with a smartphone-based exercise and educational platform compared to standard of care controls. A randomized control trial design with 365 patients demonstrated similar outcomes and non-inferiority of the smartphone platform relative to complications, readmissions, emergency room/urgent care visits. The association of controlled substance use with THA outcomes was assessed by Dr Higuera Rueda. A quantitative assessment using the NarxCare score identified 300 and above as a score associated with adverse outcomes after THA. Dr Macaulay reviewed data from a large retrospective study of 1,825 THAs indicating that discontinuation of intermittent pneumatic compression devices does not increase the risk of venous thromboembolism in standard risk patients being treated with 81mg ASA BID as prophylaxis. Dr Antoniou presented the final paper of the meeting investigating potential changes in patient health status as an indication for surgery over time. Data from this large systematic review of the literature found patients undergoing THA at similar health status to the past with no influence form patient age, gender, year of enrollment or geographic region. As summarized above, the 2020 virtual Hip Society Summer Meeting was rich in scientific content, productive discussion and a collaborative spirit. This collective body of work will result in impactful scientific contributions and will serve as a foundation for future innovation and advancements in the treatment of hip disease