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

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

In 2021, Vigdorchik et al. published a large multicentre study validating their simple Hip-Spine Classification for determining patient-specific acetabular component positioning in total hip arthroplasty (THA). The purpose of our study was to apply this Hip-Spine Classification to a sample of Australian patients undergoing THA surgery to determine the local acetabular component positioning requirements. Additionally, we propose a modified algorithm for adjusting cup anteversion requirements. 790 patients who underwent THA surgery between January 2021 and June 2022 were assessed for anterior pelvic plane tilt (APPt) and sacral slope (SS) in standing and relaxed seated positions and categorized according to their spinal stiffness and flatback deformity. Spinal stiffness was measured using pelvic mobility (PM); the ΔSS between standing and relaxed seated. Flatback deformity was defined by APPt <-13° in standing. As in Vigdorchik et al., PM of <10° was considered a stiff spine. For our algorithm, PM of <20° indicated the need for increased cup anteversion. Using this approach, patient-specific cup anteversion is increased by 1° for every degree the patient's PM is <20°. According to the Vigdorchik simple Hip-Spine classification groups, we found: 73% Group 1A, 19% Group 1B, 5% Group 2A, and 3% Group 2B. Therefore, under this classification, 27% of Australian THA patients would have an elevated risk of dislocation due to spinal deformity and/or stiffness. Under our modified definition, 52% patients would require increased cup anteversion to address spinal stiffness. The Hip-Spine Classification is a simple algorithm that has been shown to indicate to surgeons when adjustments to acetabular cup anteversion are required to account for spinal stiffness or flatback deformity. We investigated this algorithm in an Australian population of patients undergoing THA and propose a modified approach: increasing cup anteversion by 1° for every degree the patient's PM is <20°

Aims. Some patients presenting with hip pain and instability and underlying acetabular dysplasia (AD) do not experience resolution of symptoms after surgical management. Hip-spine syndrome is a possible underlying cause. We hypothesized that there is a higher frequency of radiological spine anomalies in patients with AD. We also assessed the relationship between radiological severity of AD and frequency of spine anomalies. Methods. In a retrospective analysis of registry data, 122 hips in 122 patients who presented with hip pain and and a final diagnosis of AD were studied. Two observers analyzed hip and spine variables using standard radiographs to assess AD. The frequency of lumbosacral transitional vertebra (LSTV), along with associated Castellvi grade, pars interarticularis defect, and spinal morphological measurements were recorded and correlated with radiological severity of AD. Results. Out of 122 patients, 110 (90.2%) were female and 12 (9.8%) were male. We analyzed the radiographs of 122 hips (59 (48.4%) symptomatic left hips, and 63 (51.6%) symptomatic right hips). Average age at time of presentation was 34.2 years (SD 11.2). Frequency of LSTV was high (39% to 43%), compared to historic records from the general population, with Castellvi type 3b being the most common (60% to 63%). Patients with AD have increased L4 and L5 interpedicular distance compared to published values. Frequency of pars interarticularis defect was 4%. Intraclass correlation coefficient for hip and spine variables assessed ranged from good (0.60 to 0.75) to excellent (0.75 to 1.00). Severity of AD did not demonstrate significant correlation with frequency of radiological spine anomalies. Conclusion. Patients with AD have increased frequency of spinal anomalies seen on standard hip radiographs. However, there exists no correlation between radiological severity of AD and frequency of spine anomalies. In managing AD patients, clinicians should also assess spinal anomalies that are easily found on standard hip radiographs. Cite this article: Bone Joint J 2021;103-B(8):1351–1357

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.

Hip-spine relationships should be better investigated in THP as lumbo-sacral orientation in the sagittal plane plays a critical role in the function of the hip joints. Lateral X-rays showing spine and hips together in standing, sitting or squatting positions characterize the adaptations of the sagittal balance and the functionnal interactions between hips and spine. Acetabular cup implantation has to be planned for frontal inclination, axial anteversion, and sagittal orientation. The later refers to the sacro-acetabular angle, key-point in the spine – hip relationships, and that is redefined by the surgeon at the time of implantation. Usual standard CT-sections are biased for evaluating acetabular anteversion. The conventional CT procedure does not refer to the pelvic bony frame and. the measured anteversion is a projected angle on a transverse plane, depending on the pelvic adaptation in lying position. This measured angle is often considered as anatomical anteversion, leading to some confusion. Therefore this angle is only a “functional” supine anteversion, reflecting the anterior opening angle of the acetabulum in a specific position. According to the sagittal orientation of the pelvis, the true functional acetabular orientation can virtually be assessed in various postures from adjusted CT-scan sections. The EOS. ™. low irradiation 2D-3D X-ray scanner is an innovative technology already used for global evaluation of the spine. This technology allows simultaneously “full body” frontal and lateral X-rays with the patient in standing, sitting or squatting positions; a tridimensionnal patient specific bone recontruction can be performed and the cup anteversion can be directly assessed according to the position. We investigated the lumbo-pelvic parameters influencing the tridimensionnal orientation of the acetabulum. We compared the data obtained for real postural situations using the EOS. ™. system and the measures from plane X Rays and classical CT scan cuts replicating standing, and sitting positions.368 patients with cementless THP were involved in a prospective follow-up protocol. Sacral slope and pelvic tilt, incidence angle, acetabular frontal and sagittal inclination were evaluated on AP and lateral standard XRays. Functionnal anteversion of the cup has been measured using a previously described protocol with CTscan cuts oriented according to standing and sitting sacral slope. The mean difference between CTscan and EOS. ™. system was 4,4° with comparable accuracy and reproductibility. Sacral slope decrease in sitting position was linked to anteversion increase (38,8° SD 5,4°). Sacral slope increase in standing position was linked to lower ante-version (31,7° SD 5,6°). The anatomical acetabular anteversion, the frontal inclination, and the sagittal inclination were functional parameter which significantly varied between the standing, sitting, and lying positions. We noticed that the acetabular parameters in lying position highly correlated to the one in standing position, while poorly correlated with the one in sitting position. The difference between the lying and the sitting positions was about 10°, 25°, and 15° for the cup anteversion (CA) and the frontal and sagittal inclinations (FI,SI) respectively. The poor correlation between the lying and sitting positions suggests that the usual CT scan protocol is biased and not fully appropriate for investigating the cases of posterior THP dislocation and subluxation, which happen in sitting position. On the contrary, a strong correlation was observed between lying and standing measurements with all the acetabular parameters (CA,FI, SI), suggesting that the classical CT assessment of the cup anteversion remains an interesting source of information in case of anterior THP. Each patient is characterized by a morphological parameter, the incidence angle. High incidence angle is linked to low acetabular anteversion, increasing the instability risk and anterior impingement in sitting and squatting position; higher anteversion angles are observed in low incidence angle patients, leading to more internal rotation of the hip in any position. Lumbo-sacral orientation in the sagittal plane influences the tridimensionnal orientation of the acetabulum, especially for anteversion. Aging of the hip-spine complex is linked to progressive pelvic posterior extension. Impingement phenomenons, orientation of stripe wear zones and some instability situations can be interpreted according to those data. This study points out the opportunity to adjust the CT scan sections to the sacral slope in functional position for properly investigating the orientation of the acetabular cup, mainly in case of posterior dislocation. In addition, the mobility of the lumbo-sacral junction could be a crucial parameter in the mechanical functioning and the stability of a THP due to its impact on sacral slope and pelvic tilt. Therefore we also recommend doing dynamic lateral radiographs of the lumbo sacral junction in standing and sitting position for planning a THP implantation in order to detect stiff lumbosacral junction or sagittal pelvic malposition

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. Patients and Methods. Prospectively collected data on 111 patients undergoing revision THA for recurrent instability from January 2014 to January 2017 at two institutions were included (protocol group) and matched 1:1 to 111 revisions specifically performed for instability not using this protocol (control group). Mean follow-up was 2.8 years. Protocol patients underwent standardized preoperative imaging including supine and standing anteroposterior (AP) pelvis and lateral radiographs. Each case was scored according to the Hip-Spine Classification in Revision THA. Results. Survival free of dislocation at two years was 97% in the protocol group (three dislocations, all within three months of surgery) versus 84% in the control group (18 patients). Furthermore, 77% of the inappropriately positioned acetabular components would have been unrecognized by supine AP pelvis imaging alone. Conclusion. Using the Hip-Spine Classification System in revision THA, we demonstrated a significant decrease in the risk of recurrent instability compared with a control group. Without the use of this algorithm, 77% of inappropriately positioned acetabular components would have been unrecognized and incorrect treatment may have been instituted. Cite this article: Bone Joint J 2019;101-B:817–823

The presence of hip osteoarthritis is associated with abnormal spinopelvic characteristics. This study aims to determine whether the pre-operative, pathological spinopelvic characteristics “normalize” at 1-year post-THA. This is a prospective, longitudinal, case-control matched cohort study. Forty-seven patients underwent pre- and post- (at one-year) THA assessments. This group was matched (age, sex, BMI) with 47 controls/volunteers with well-functioning hips. All participants underwent clinical and radiographic assessments including lateral radiographs in standing, upright-seated and deep-flexed-seated positions. Spinopelvic characteristics included change in lumbar lordosis (ΔLL), pelvic tilt (ΔPT) and hip flexion (pelvic-femoral angle, ΔPFA) when moving from the standing to each of the seated positions. Spinopelvic hypermobility was defined as ΔPT>30° between standing and upright-seated positions. Pre-THA, patients illustrated less hip flexion (ΔPFA −54.8°±17.1° vs. −68.5°± 9.5°, p<0.001), greater pelvic tilt (ΔPT 22.0°±13.5° vs. 12.7°±8.1°, p<0.001) and greater lumbar movements (ΔLL −22.7°±15.5° vs. −15.4°±10.9°, p=0.015) transitioning from standing to upright-seated. Post-THA, these differences were no longer present (ΔPFApost −65.8°±12.5°, p=0.256; ΔPTpost 14.3°±9.5°, p=0.429; ΔLLpost −15.3°±10.6°, p=0.966). The higher prevalence of pre-operative spinopelvic hypermobility in patients compared to controls (21.3% vs. 0.0%; p=0.009), was not longer present post-THA (6.4% vs. 0.0%; p=0.194). Similar results were found moving from standing to deep-seated position post-THA. Pre-operative, spinopelvic characteristics that contribute to abnormal mechanics can normalize post-THA following improvement in hip flexion. This leads to patients having the expected hip-, pelvic- and spinal flexion as per demographically-matched controls, thus potentially eliminating abnormal mechanics that contribute to the development/exacerbation of hip-spine syndrome

The study of spinopelvic anatomy and movement has received great interest as these characteristics influence the biomechanical behavior (and outcome) following hip arthroplasty. However, to-date there is little knowledge of what “normal” is and how this varies with age. This study aims to determine how dynamic spino-pelvic characteristics change with age, with well-functioning hips and assess how these changes are influenced by the presence of hip arthritis. This is an IRB-approved, cross-sectional, cohort study; 100 volunteers (asymptomatic hips, Oxford-Hip-sore>45) [age:53 ± 17 (24-87) years-old; 51% female; BMI: 28 ± 5] and 200 patients with end-stage hip arthritis [age:56 ± 19 (16-89) years-old; 55% female; BMI:28 ± 5] were studied. All participants underwent lateral spino-pelvic radiographs in the standing and deep-seated positions to determine maximum hip and spine flexion. Parameters measured included lumbar-lordosis (LL), pelvic incidence, pelvic-tilt (PT), pelvic-femoral angles (PFA). Lumbar flexion (ΔLL), hip flexion (ΔPFA) and pelvic movement (ΔPT) were calculated. The prevalence of spinopelvic imbalance (PI–LL>10?) was determined. There were no differences in any of the spino-pelvic characteristics or movements between sexes. With advancing age, standing LL reduced and standing PT increased (no differences between groups). With advancing age, both hip (4%/decade) and lumbar (8%/decade) flexion reduced (p<0.001) (no difference between groups). ΔLL did not correlate with ΔPFA (rho=0.1). Hip arthritis was associated with a significantly reduced hip flexion (82 ±;22? vs. 90 ± 17?; p=0.003) and pelvic movements (1 ± 16? vs. 8 ± 16?; p=0.002) at all ages and increased prevalence of spinopelvic imbalance (OR:2.6; 95%CI: 1.2-5.7). With aging, the lumbar spine loses its lumbar lordosis and flexion to a greater extent that then the hip and resultantly, the hip's relative contribution to the overall sagittal movement increases. With hip arthritis, the reduced hip flexion and the necessary compensatory increased pelvic movement is a likely contributor to the development of hip-spine syndrome and of spino-pelvic imbalance

Introduction. Hip-Spine syndrome has various clinical aspects. For example, schoolchild with severe congenital dislocation of the hip have unfavorable standing posture and disadvantageous motions in ADL. Hip-Spine syndrome is closely related closely as the adjacent lumbar vertebrae and the hip joint. Furthermore, not only the pelvis and the lumbar spine, but also the neck position might influence on the maximum hip flexion angle. In this study, we examined the maximum hip flexion angle and pelvic movement angle by observing the lumbar spine, the pelvis and the neck in three different positions. Subjects and Methods. The participants were five healthy volunteers (three males and two females) and ranged in age from 16 to 49 years. We measured the hip flexion angle (=∠X) and the pelvic tilt angle (=∠Y), using Zebris WinData and putting the six markers on skin. The positions of the marker are Femur lateral condyle (M1), Greater trochanter (M2), Lateral margin of 10th rib (M3), Anterior superior iliac spine (M4), Superior lateral margin of Iliac (M5), and Acromion (M6). We performed maximum hip flexion three times in three positions and measured ∠X (=∠M1,2,3) and ∠Y (=∠M4,5,6) and calculated the mean and SD of each position. The first position (P1) that we investigated is the regular position specified by the Japanese Orthopedics Association and Rehabilitation Medical Association. The second position (P2) is performed in the limited position of the posterior pelvic tilt and lumbar movement, by placing the tube under the subject's lower back. The third position (P3) is the altered limited position of P2 added by placing the 500ml PET bottle filled water under the back of the subject's neck. Analysis. A two way factorial analysis of variance was used for statistical analysis to examine the difference among three different positions (P1, P2 and P3) in ∠X and ∠Y. A significance level was set at P < 0.05. We also calculated Spearman rank correlation coefficients to determine the correlation between ∠X and ∠Y. Results. There was a statistically significant difference among three different positions (P1, P2 and P3) in both ∠X and ∠Y (p < 0.01). Slight strong correlations were found between ∠X and ∠Y in three different positions. (r =0.5178571). The smallest values of ∠X and ∠Y were obtained in P1. The values of ∠X and ∠Y in P3 were all smaller than those in P2. Conclusions. The limited movement of pelvic and lumbar spine, and neck different positions give the limit to a maximum hip joint flexion angle

Introduction. Stand to sit pelvis kinematics is commonly considered as a rotation around the bicoxofemoral axis. However, abnormal kinematics could occur for patients with musculoskeletal disorders affecting the hip-spine complex. The aim of this study is to perform a quantitative analysis of the stand to sit pelvis kinematics using 3D reconstruction from bi-planar x-rays. Materials and Methods. Thirty healthy volunteers as a control group (C), 30 patients with hip pathology (Hip) and 30 patients with spine pathology (Spine) were evaluated. All subjects underwent standing and sitting full-body bi-planar x-rays. 3D reconstruction was performed in each configuration and then translated such as the middle of the line joining the center of each acetabulum corresponds to the origin. Rigid registration quantified the finite helical axis (FHA) describing the transition between standing and sitting with two specific parameters. The orientation angle (OA) is the signed 3D angle between FHA and bicoxofemoral axis and the rotation angle (RA) represents the signed angle around FHA. Pelvic incidence, sacral slope and pelvic tilt were also measured. After checking normality of distribution, parameters were compared statistically between the 3 groups (p<0.05). Results. The mean value of the orientation angle in control group was −1.8° (SD 10.8°, range −26° to 25°). The mean value of the OA was 0.3° (SD 12.3°, range to −31° to 37°) in Hip group and −4.7° (SD 21.5°, range −86° to 38°) in Spine group. There was no significant difference in mean OA among groups. However, the more subnormal and abnormal patients were in Spine group compared to C and Hip groups. The mean value of the rotation angle in C group was 18.1° (SD 9.1°, range 5° to 43°). There was significant difference in RA between Hip and Spine groups (21.1° (SD 8.0°) and 16.0° (SD 10.7°), respectively) (p=0.04). Conclusion. This study highlights new informations obtained by the quantitative analysis of pelvis rotation between standing and sitting in healthy, hip pathology patients and spine pathology patients using 3D reconstruction from bi-planar radiographs. Hip and spine pathologies affect stand to sit pelvic kinematics. Surgeons should be aware of potential abnormal stand to sit transition in such clinical situations. This improved assessment of the pelvic rotational adaptation could lead to a more personalized approach for the planning of hip prostheses

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.

Introduction. Understanding hip-spine relationships and accurate evaluation of the pelvis position are key- points for the optimization of total hip arthroplasty (THA). Hip surgeons know the importance of pelvic parameters and the adaptation mechanisms of pelvic and sub-pelvic areas. Literature about posture after THA remains controversial and adaptations are difficult to predict. One explanation can be the segmental analysis focused on pelvic parameters and local planning. In a significant number of patients a global analysis may be important as a cascade of compensatory mechanisms is implemented, the hip being only one of the links of this chain reaction. 3 parameters can be measured on full body images:. SVA (sagittal vertical axis) : horizontal distance between the vertical line through the center of C7 and the postero-superior edge of S1. T1 pelvic angle (TPA) : line from femoral heads to T1center and line from the femoral heads to S1center. TPA combines informations from both the sagittal vertical axis and pelvic tilt. Global Sagittal Angle (GSA) : line from the midpoint of distal femoral condyles to C7 center and line from the midpoint between distal femoral condyles to the postero-superior S1corner. The objective of this preliminary study is to report the post-operative evolution of posture after THA. Material and Method. 49 patients (28 women, 21 men, mean age 61 years) were enrolled for full-body standing EOS images before and after THA. The sterEOS software was used to measure pelvic parameters (sacral slope SS, pelvic incidence PI) and global postural parameters (TPA, GSA, SVA). Sub-analysis was made, grouping the sample by TPA (<14°, 14°–22°, >22°), by PI (<55°, 55°–65°, >65°) and by SS (<35°, 35°–45°, >45°). Paired t-test was used to compare differences between preoperative and postoperative parameters within each subgroup. Statistical significance was set at p < 0.05. Results. TPA, SVA and GSA may change independently following THA surgery. In the 2 groups with TPA< 19° and 14° <TPA< 22°, GSA and SVA decreased significantly after THA (p < 0.05). The difference was not significant in the group with TPA>22°. In the group with SS between 35° and 45°, the GSA and SVA decreased after THA (p < 0.05). In the group with SS > 45° only GSA decreased. In the group with PI < 55°, GSA and SVA decreased after THA. There was no significant change in the remaining subgroups. Discussion. This preliminary study confirms a decrease of GSA and SVA after THA. Some preoperative characteristics are observed in patients with significant global sagittal postural modifications: low to standard TPA, low PI or standard to high SS. Conclusion. Planning and prediction of sagittal postural changes after THA implantation is challenging. It is an important topic in patients with stiff and degenerative spine or in case of spinal fusion. In case of complex hipspine cases, the timing of the procedures can be a real concern. The combined analysis of SVA, TPA and GSA may open new perspectives for a more rationale planning of THA

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.

Aims

Spinopelvic characteristics influence the hip’s biomechanical behaviour. However, to date there is little knowledge defining what ‘normal’ spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals.

Introduction. The combination of spinal fusion and THP is not exceptional. Disorders of the pelvic tilt and stiffness of the lumbosacral junction modify the adaptation options while standing or sitting. Adjusting the cup can be difficult and THP instability is a potential risk. This study reports an experience with EOS® simultaneous measurements on AP and lateral views of spine and hips in THP patients. Material and methods. 29 men and 45 women were included in this prospective study. 21cases had bilateral THP. Patients were separated into two groups: long fusions including the thoraco-lumbar junction (group 1) and shorter fusions below L1 (group 2). We analyzed the impact of the arthrodesis on the position of the pelvis by measuring variations of the sacral slope (SS) and APP angle. Cup position was defined by coronal inclination and functional anteversion in the horizontal plane standing and sitting. We compared the data to a previous series of 150 THP patients with asymptomatic and non fused spine. Results. Table1 reports the results of the fusion series. The overall analysis of all patients demonstrates that the values for the cup functional anteversion and coronal inclination are statistically different when comparing standing to sitting (respectively p <0.01and p <0.001). The same results are obtained for SS and APP. This difference is not significant for group 1 patients. The mean range of variation for cup anteversion and inclination is 5° and 7° in the fused cases. Table 2 reports the results of the non fusion series. SS, APP and cup orientation values are statistically significant between standing and sitting. All of the values are statistically different when compared to the fused patients. The mean range of variation for cup anteversion and inclination is 11,6° and 10°. Discussion. The population of THP patients is characterized by pelvic retroversion and a significant reduction of sagittal pelvic mobility when compared to young asymptomatic individuals. Patients combining THP and spine fusion showed significant reduction of adaptation possibilities due to low variations for SS and cup orientation angles. Conclusion. This preliminary study shows the importance of planning THP taking into account not only the orientation of the spine but also its mobility for adaptation in standing and sitting positions. This is a key issue because of the growing number of elderly THP patients whose spine is degenerative or fused. A particular attention must be drawn to the cases with long fusions. The interest of a global vision of the hip-spine relationship is evident in the prevention or in management of dislocations and subluxations, and especially for the indications of dual-mobility prostheses. To view tables/figures, please contact authors directly

Aims

Computer-assisted 3D preoperative planning software has the potential to improve postoperative stability in total hip arthroplasty (THA). Commonly, preoperative protocols simulate two functional positions (standing and relaxed sitting) but do not consider other common positions that may increase postoperative impingement and possible dislocation. This study investigates the feasibility of simulating commonly encountered positions, and positions with an increased risk of impingement, to lower postoperative impingement risk in a CT-based 3D model.

Aims

The aim of this study was to investigate whether anterior pelvic plane-pelvic tilt (APP-PT) is associated with distinct hip pathomorphologies. We asked: is there a difference in APP-PT between young symptomatic patients being evaluated for joint preservation surgery and an asymptomatic control group? Does APP-PT vary among distinct acetabular and femoral pathomorphologies? And does APP-PT differ in symptomatic hips based on demographic factors?

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).