Spinopelvic Motion Research Articles

Robotic-assisted Total Hip Arthroplasty and Spinopelvic Parameters: A Review.

Total hip arthroplasty (THA) is an effective treatment for osteoarthritis, and the popularity of the direct anterior approach has increased due to more rapid recovery and increased stability. Instability, commonly caused by component malposition, remains a significant concern. The dynamic relationship between the pelvis and lumbar spine, deemed spinopelvic motion, is considered an important factor in stability. Various parameters are used in evaluating spinopelvic motion. Understanding spinopelvic motion is critical, and executing a precise plan for positioning the implant can be difficult with manual instrumentation. Robotic and/or navigation systems have been developed in the effort to enhance THA outcomes and for implementing spinopelvic parameters. These systems can be classified into three categories: X-ray/fluoroscopy-based, imageless, and computed tomography (CT)-based. Each system has advantages and limitations. When using CT-based systems, preoperative CT scans are used to assist with preoperative planning and intraoperative execution, providing feedback on implant position and restoration of hip biomechanics within a functional safe zone developed according to each patient's specific spinopelvic parameters. Several studies have demonstrated the accuracy and reproducibility of robotic systems with regard to implant positioning and leg length discrepancy. Some studies have reported better radiographic and clinical outcomes with use of robotic-assisted THA. However, clinical outcomes comparable to those for manual THA have also been reported. Robotic systems offer advantages in terms of accuracy, precision, and potentially reduced rates of dislocation. Additional research, including conduct of randomized controlled trials, will be required in order to evaluate the long-term outcomes and cost-effectiveness of robotic-assisted THA.

Spinopelvic Motion: A Simplified Approach to a Complex Subject.

Knowledge of the relationship between the hip and spine is essential in the effort to minimize instability and improve outcomes following total hip arthroplasty (THA). A detailed yet straightforward preoperative imaging workup can provide valuable information on pelvic positioning, which may be helpful for optimum placement of the acetabular cup. For a streamlined preoperative assessment of THA candidates, classification systems with a capacity for providing a more personalized approach to performance of THA have been introduced. Familiarity with these systems and their clinical application is important in the effort to optimize component placement and reduce the risk of instability. Looking ahead, the principles of the hip-spine relationship are being integrated using emerging innovative technologies, promising further streamlining of the evaluation process.

Do 3-dimensional Spinopelvic Characteristics Normalize After THA? A Prospective, Comparative Study Using Motion Capture Analysis.

Spinopelvic stiffness (primarily in the sagittal plane) has been identified as a factor associated with inferior patient-reported outcomes (PROs) and increased dislocation risk after THA. Incorporating preoperative spinopelvic characteristics into surgical planning has been suggested to determine a patient-specific cup orientation that minimizes dislocation risk. Sagittal plane radiographic analysis of static postures indicates that patients exhibit a degree of normalization in their spinopelvic characteristics after THA. It is not yet known whether normalization is also evident during dynamic movement patterns, nor whether it occurs in the coronal and axial planes as well. (1) Does motion capture analysis of sagittal spinopelvic motion provide evidence of normalization after THA? (2) Do changes in coronal and axial plane motion accompany those in the sagittal plane? Between April 2019 and February 2020, 25 patients agreed to undergo motion capture movement analysis before THA for the treatment of hip osteoarthritis (OA). Of those, 20 underwent the same assessment between 8 and 31 months after THA. Five patients were excluded because of revision surgery (n = 1), contralateral hip OA (n = 1), and technical issues with a force plate during post-THA assessment (n = 3), leaving a cohort total of 15 (median age [IQR] 65 years [10]; seven male and eight female patients). A convenience sample of nine asymptomatic volunteers, who were free of hip and spinal pathology, was also assessed (median age 51 years [34]; four male and five female patients). Although the patients in the control group were younger than those in the patient group, this set a high bar for our threshold of spinopelvic normalization, reducing the possibility of false positive results. Three-dimensional motion capture was performed to measure spinal, pelvic, and hip motion while participants completed three tasks: seated bend and reach, seated trunk rotation, and gait on a level surface. ROM during each task was assessed and compared between pre- and post-THA conditions and between patients and controls. Statistical parametric mapping (SPM) was used to assess the timing of differences in motion during gait, and spatiotemporal gait parameters were also measured. After THA, patients demonstrated improvements in sagittal spinal (median [IQR] 32° [18°] versus 41° [14°]; difference of medians 9°; p = 0.004), pelvis (25° [21°] versus 30° [8°]; difference of medians 5°; p = 0.02), and hip ROM (21° [18°] versus 27° [10°]; difference of medians 6°; p = 0.02) during seated bend and reach as well in sagittal hip ROM during gait (30° [11°] versus 44° [7°]; difference of medians 14°; p < 0.001) compared with their pre-THA results, and they showed a high degree of normalization overall. These sagittal plane changes were accompanied by post-THA increases in coronal hip ROM (12° [9°] versus 18° [8°]; difference of medians 6°; p = 0.01) during seated trunk rotation, by both coronal (6° [4°] versus 9° [3°]; difference of medians 3°; p = 0.01) and axial (10° [8°] versus 16° [7°]; difference of medians 6°; p = 0.003) spinal ROM, as well as coronal (8° [3°] versus 13° [4°]; difference of medians 5°; p < 0.001) and axial hip ROM (21° [11°] versus 34° [24°]; difference of medians 13°; p = 0.01) during gait compared with before THA. The SPM analysis showed these improvements occurred during the late swing and early stance phases of gait. When restricted preoperatively, spinopelvic characteristics during daily tasks show normalization after THA, concurring with previous radiographic findings in the sagittal plane. Thus, spinopelvic characteristics change dynamically, and incorporating them into surgical planning would require predictive models on post-THA improvements to be of use. Level II, prognostic study.

Impact of pelvic anteversion on spinopelvic alignment in an asymptomatic population: a dynamic perspective of standing and sitting

BACKGROUND CONTEXTA subgroup of patients with pelvic anteversion can present with an unusually large degree of lumbar lordosis (LL), a highly sloped sacrum, and a relatively small pelvic incidence (PI). Prior to lumbar surgery, it can be important to consider such unique sagittal alignment. However, until now, there has been a lack of a predictive model considering different pelvic alignments. Furthermore, the dynamic characteristics of an anteverted pelvis (AP) subgroup have also been unclear. PURPOSETo build linear predictive formulas for LL that take pelvic anteversion into consideration and to explore the dynamic characteristics of an AP subgroup. STUDY DESIGNMonocentric, cross-sectional study. PATIENT SAMPLEFive hundred sixty-five asymptomatic Chinese men and women between the ages of 18 and 80 years. OUTCOME MEASURESSagittal parameters including LL, lumbar lordosis minus thoracic kyphosis (LL-TK), PI, pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), sacral slope (SS), sacral slope divided by pelvic incidence (SS/PI), sagittal vertical axis (SVA), thoracic kyphosis (TK), and T1 (first thoracic vertebra) pelvic angle (TPA) were measured on whole spine radiographs obtained with participants in standing and sitting positions. METHODSAll participants underwent radiography in the standing position; 235 of them underwent additional radiography in the sitting position to allow measurement of sagittal parameters. The participants with pelvic anteversion were placed in an AP (anteverted pelvis) group. Sagittal parameters were compared between the AP group and the non-AP group, and predictive formulas for LL based on PI were created in both groups. In addition, changes in sagittal parameters from standing to sitting were compared in the AP group and a PI-matched control group. RESULTSOf the 565 participants, 171 (30.3%) had pelvic anteversion. In comparison with the non-AP group, the AP group presented with larger LL, a larger SS, and a smaller PT, with relatively small PI. The predictive formulas for LL were LL=0.60° × PI+21.60° (R2=0.268; p<.001) in the whole cohort, LL=0. 83×PI+18.75° (R2=0.427; p<.001) in AP group, and LL=0.79°×PI+9.66° (R2=0.451; p<.001) in the non-AP group. In moving from standing to sitting, the AP group presented with a larger decrease in SS and LL compared with the control group, indicating different patterns of spinopelvic motion. CONCLUSIONSIn the cohort examined, 30.3% present with pelvic anteversion. Those with AP present with unique characteristics of spinopelvic alignment. In moving from standing to sitting, they exhibit different patterns of spinopelvic motion. We found that identifying the degree of anteversion in each person improves the accuracy of linear models for predicting the degree of LL, which in turn can make plans for spine surgery more accurate.

Virtual range of motion is a safe and acceptable alternative to intra-operative manual range of motion testing in direct anterior robotic total hip arthroplasty

IntroductionIn robotic total hip arthroplasty (THA), virtual range of motion (VROM) modeling allows the surgeon to account for spinopelvic motion and create an impingement-free range of motion that is patient-specific. The primary purpose of this study was to evaluate the risk of dislocation in patients undergoing direct anterior THA using VROM rather than manual ROM trialing. MethodsProspectively collected data was reviewed retrospectively of all consecutive anterior THAs performed by a single fellowship-trained surgeon. No patients were excluded from the study. VROM identified bone and implant impingement, which was recorded in degrees of hip external rotation(ER) at 0° of hip extension (standing), and in degrees of hip internal rotation(IR) at 90° of hip flexion (sitting). No patients had manual ROM trialing performed. Dislocation events were recorded during the first 3 months of follow-up. 362 patients, with a mean age of 67 and mean BMI of 28.8, were included. ResultsThis cohort, including 154 patients (42.5%) with abnormal spinopelvic motion, demonstrated zero dislocations using VROM. The average ER impingement occurred at 60.9° ER (range 20-90°), and 50.8° IR (range 25-90°). Patients with ER impingement <55° had significantly less acetabular anteversion (16.4° ±3.3°, p < 0.001). Compared to the entire cohort, anteversion of the acetabulum was also decreased in the stuck-sitting subgroup (17.4° ±3.3°, p < 0.001) and increased in the stuck standing subgroup (20.5° ±3.6°, p < 0.001). ER impingement was a stronger predictor of acetabular anteversion than spinopelvic motion category (r = 0.458). Patients with ER impingement <45° (6.4%) or IR impingement <35° (6.6%) were “early impingers”. ConclusionIn this cohort of anterior THA patients with a high proportion of abnormal spinopelvic motion, a technique utilizing only VROM produced no dislocations. An impingement-free zone of 45° ER standing and 35° IR sitting is recommended.

Instability in Patients With Lumbar Spine Disease Undergoing Posterior Approach and Lateral Approach Primary Total Hip Arthroplasty.

Dislocation rates in patients who have fixed spinopelvic motion have been reported up to 20%. Few studies have directly compared dislocation rates in patients who have spine pathology undergoing total hip arthroplasty (THA) through different surgical approaches. This study compared postoperative dislocation rates in patients who had lumbar spine disease and underwent primary THA using a posterior or direct lateral approach. Between 2011 and 2017, consecutive cohorts of primary THAs were retrospectively reviewed. One surgeon routinely used a posterior approach, while the other used a direct lateral approach. Chart and radiographic review were conducted to identify patients who had lumbar spine disease. Dislocations among cohorts with and without lumbar spine disease were compared by posterior and direct lateral approaches. The overall dislocation rate was 1.3% (15/1,198). The top four predictors of dislocation were presence of lumbar spine disease (odds ratio [OR] 5.0; P = 0.014), posterior surgical approach (OR, 6.5; P = 0.074), cases performed for fracture (OR, 4.4; P = 0.035), and women (OR, 4.6; P = 0.050). Dislocation rates among direct lateral approach patients who had lumbar spine pathology were significantly lower than posterior approach patients who had lumbar spine pathology (0.0% versus 3.6%; P = 0.011). Although dislocation rates were low in both groups, study results suggest that a direct lateral approach for primary THA may reduce postoperative dislocations for patients who have limited spinopelvic motion due to lumbar spine pathology. Furthermore, surgeons using the posterior approach might consider optimizing the femoral head to acetabular cup ratio in patients who have lumbar spine disease.

Anteroposterior pelvic radiograph findings correlate with sagittal spinopelvic motion

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. A retrospective chart review was conducted to identify patients undergoing primary total hip arthroplasty (THA). Plain AP pelvic radiographs were reviewed to document the morphological characteristic of osteoarthritic hips. Lateral spine-pelvis-hip sitting and standing plain radiographs were used to measure sacral slope (SS) and pelvic femoral angle (PFA) in each position. Lumbar disc spaces were measured to determine the presence of DDD. The difference between sitting and standing SS and PFA were calculated to quantify spinopelvic motion (ΔSS) and hip motion (ΔPFA), respectively. Univariate analysis and Pearson correlation were used to identify morphological hip characteristics associated with changes in spinopelvic motion. In total, 139 patients were included. Increased spinopelvic motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.05). Loss of hip motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.001). A decreased joint space was associated with a decreased ΔPFA (p = 0.040). The presence of disc space narrowing, disc space narrowing > two levels, and disc narrowing involving the L5-S1 segment were associated with decreased spinopelvic motion (all p < 0.05). Preoperative hip OA as assessed on an AP pelvic radiograph predicts spinopelvic motion. These data suggest that specific hip osteoarthritic morphological characteristics listed above alter spinopelvic motion to a greater extent than others.

Preoperative radiographic findings associated with postoperative spinopelvic risk factors for instability following total hip arthroplasty.

Postoperative spinopelvic changes are associated with increased dislocation risk following total hip arthroplasty (THA). The aim of this study was to identify preoperative patient and radiographic factors associated with high-risk postoperative spinopelvic parameters. A retrospective review of consecutive THA patients who received preoperative and postoperative sitting and standing lateral lumbar spine-hip radiographs with minimum radiographic and clinical follow-up of 10 months was performed. Patient demographics were recorded and preoperative standing and sitting sacral slope (SS), anteinclination, pelvic femoral angle (PFA), and combined sagittal index (CSI) were measured. High-risk patients were defined by decreased spinopelvic motion (∆SS from sitting to standing of >10°), increased hip motion (∆PFA from sitting to standing of >10°), or decreased CSI of >10° at final follow-up compared with preoperative measurements. Univariate and multivariate regression analyses were used to identify preoperative demographic and radiographic factors associated with these high-risk categories. One hundred and fifty-three patients were included with an average age of 62 years, average body mass index of 27.8 kg/m2 , and average follow-up of 16.2 months. At 1-year follow-up, 43 (28.1%) patients demonstrated a decreased ∆SS > 10° and 67 (43.7%) patients demonstrated an increased ∆PFA > 10° compared with preoperative values. Sitting CSI decreased by >10° in 17 (11.1%) patients. Preoperative increased sitting PFA (adjusted odds ratio [aOR] 1.057, p < 0.001) and decreased preoperative hip motion (∆PFA) were associated with decreased sitting CSI of >10° at 10-month follow-up. Increased spinopelvic motion (∆SS) and decreased hip motion (∆PFA) preoperatively are associated with postoperative radiographic changes that beassociated with increased dislocation risk.

Variations in lower limb alignments indicate pelvic tilt after total hip arthroplasty

ObjectiveWe sought to correlate various spinopelvic and lower limb alignments, and to examine the current spinopelvic theories on a Chinese cohort.MethodsWe retrospectively reviewed 166 patients undergoing THA. Among them, 138 patients with unilateral THA met the inclusion criteria. Sagittal alignments and cup orientations were measured on standing and sitting lateral EOS images. Patients were categorized into two groups with a scoring system for lumbar spine degeneration. Patients’ demographics including age, sex, lumbar spine degeneration and radiographic measurements were studied.ResultsPT, SS, LL and TK differed significantly between standing and sitting within each group except for TK in degenerative group (32.8 ± 13.9 vs. 32.9 ± 14.2, p = 0.905). Compared with degenerative spine group, non-degenerative spine patients have great pelvic mobility (ΔPT, -24.4 ± 12.5° vs. -17.6 ± 10.7, p = 0.0008), greater lumbar mobility (ΔLL, -34.8 ± 15.2 vs. -21.7 ± 12.2, p = < 0.0001) and compensatory cup orientation changes (ΔRA, -15.5 ± 11.1 vs. -12.0 ± 8.4, p = 0.00920; ΔRI, -10.8 ± 11.5 vs. -5.6 ± 7.5, p = 0.0055). Standing PT and ankle dorsiflexion angle correlated positively (R2 = 0.236, p = 0.005).ConclusionTHA patients in this cohort showed a spinopelvic motion paradigm similar to that from previous studies on Caucasians. Ankle dorsiflexion indicate greater posterior pelvic tilt on standing. Surgeons should beware of risks of instability in patients with lower limb compensations.Advances in knowledgeThis study provides new insights into the clinical relevance of lower limb alignments to spinopelvic motion after THA in a relatively young Chinese population.

Increased dislocation rates following total hip arthroplasty in patients with ankylosing spondylitis.

Patients with ankylosing spondylitis (AS) experience abnormal spinopelvic motion due to chronic inflammation of the axial skeleton, predisposing them to impingement and dislocation. The purpose of this study was to evaluate total hip arthroplasty (THA) dislocation rates in AS patients and evaluate the effects of age and gender on dislocation risk. Patients who underwent primary THA from 2005 to 2014 were identified using the PearlDiver database. AS patients were compared to age- and gender-matched controls without AS. Patients with a history of spine pathology or spine surgery were excluded. Univariate analyses were performed based on age and sex to evaluate dislocation rates at 90 days, 6 months, 1 year, and 5 years postoperatively. A total of 2792 THA patients (59.6% male) with AS were identified and compared to an age- and gender-matched control group of 5582 THA patients (59.5% male) without AS or known spine pathology. At final follow-up, there were 96 dislocations (3.4%) in the AS group and 138 (2.5%) dislocations in the control group (OR 1.40; 95% CI, 1.08-1.83; p = 0.0118). AS patients ⩾70 years old had higher dislocation rates at all time points (OR range, 1.75-2.09; p < 0.05) compared to controls. At 5-year follow-up, dislocation-free survivorship was 95.7% (95% CI, 94.5-96.9%) for AS patients ⩾70 years old compared to 97.3% (95% CI, 96.6-98.0%) for patients ⩾70 years old without AS. Older AS patients have higher dislocation rates following THA. This effect is likely related to decreased spinopelvic motion in the sagittal plane, predisposing patients to impinge and dislocate.

Abnormal Spinopelvic Motion and Spine Deformity are Associated With Native Femoral Retroversion in the Setting of Total Hip Arthroplasty

BackgroundThe effect of spinopelvic pathology on femoral version is unclear. This study investigated variability in native femoral anteversion in patients undergoing total hip arthroplasty (THA) and its relationship to the patient’s underlying spinopelvic pattern. MethodsA retrospective chart review was performed to include in the study all patients undergoing robot-assisted THA over a 3-year period. Native femoral version was measured for each patient using a preoperative computed tomography scan and categorized as excessive, normal, or retroverted. Additionally, a subset analysis was performed for all patients with sit-to-stand dynamic pelvic radiographs available, and cases were classified by spinopelvic pattern. ResultsA total of 119 patients were included in the study with a mean age of 68.6 years; 61 (51%) were female. The median femoral anteversion for the entire study group was 6.0° (−32° to 40°, interquartile range 13.5°). Eleven patients (9.2%) had excessive femoral anteversion, 54 of the 119 (45.4%) had normal femoral version, and 54 of the 119 (45.4%) had native retroversion. Forty-two patients (35.3%) had sit-to-stand radiographs available and were subclassified by femoral version type and spinopelvic parameters. Welch’s analysis of variance demonstrated a significant difference in femoral version among spinopelvic patterns (F = 7.826, P = .003), with Games-Howell post hoc analysis showing increased retroversion in deformity-stiff patients compared to deformity-normal mobility patients (P = .003). ConclusionsThis study demonstrates that native femoral retroversion is present in a significant number of patients undergoing THA and is more common in patients with stiff spine deformities. Based on this observation, currently available spinopelvic classification systems should be modified to account for native femoral version.

Spinopelvic Relationship and Its Impact on Total Hip Arthroplasty

The dynamic, complex interaction among the spine, pelvis, and hip is often underappreciated, yet understanding it is vital for both arthroplasty and spinal surgeons. There is an increasing incidence of degenerative hip and spinal pathologies as a result of the ageing population. Furthermore, hip pathology can cause spine pathology and vice versa through “hip-spine” and “spine-hip syndrome.” Consequently, total hip arthroplasty (THA) and spinal fusion surgery, which both affect spinopelvic mobility, are also on the rise. Alteration in spinopelvic motion can affect the orientation of the acetabulum and, therefore, implant positioning in THA, leading to complications such as dislocation, impingement, aseptic loosening, and wear of components. This makes it imperative to assess spinopelvic motion and pelvic tilt prior to patients undergoing THA. In this paper, we explore how the surgeon should proceed to reduce risk of component malalignment, as well as the role of navigation systems in acetabular cup positioning.

The Effect of Hip Offset and Spinopelvic Abnormalities on the Risk of Dislocation Following Total Hip Arthroplasty.

Previous studies have demonstrated that patients with abnormal spinopelvic motion are at increased risk of dislocation. However, little is known about the effect of hip offset on dislocation risk following total hip arthroplasty (THA) in patients with abnormal spinopelvic motion. The purpose of this study is to investigate the prevalence of under-restored hip offset and spinopelvic abnormalities in a series of THA patients treated for recurrent instability. This is a retrospective review of consecutive patients treated for hip instability following primary THA (THA+I) from 2012 to 2020. Patient demographics, surgical variables, and radiographic parameters were recorded. THA+I patients were compared to an age-matched and gender-matched control THA population without hip instability (THA). Univariate analyses were performed to compare differences between groups. Thirty-three THA+I patients (44 hips) were compared to 44 THA patients (44 hips). THA+I patients had a higher prevalence of spinopelvic pathology (odds ratio [OR] 7.80, 95% confidence interval [CI] 2.59-23.50, P < .001). The majority of acetabular components were placed within the Lewinnek safe zone (86.4% THA+I vs 72.7% THA; P= .119). THA+I patients were at greater risk of markedly under-restored hip offset (Δoffset ≤ 3 mm; OR 6.34, 95% CI 2.20-18.30, P= .001) and small (<32 mm) femoral head diameter (OR 4.38, 95% CI 1.53-12.53, P= .006) compared to THA patients. Lumbar degenerative disease and under-restoration of hip offset were present in a high proportion of patients with hip instability. Although multiple factors may contribute to THA instability, these data suggest that restoration of offset is essential, particularly in patients with spinopelvic pathology, and may be more important than historically described acetabular targets. Level III.

Does spinopelvic motion change after total hip arthroplasty?

Spinopelvic motion plays an important role in functional acetabular cup position after total hip arthroplasty (THA). Sacral slope (SS) has been a useful surrogate for spinopelvic motion. The present study aimed to investigate statistical characteristics of spinopelvic motion before and after THA using changes in SS in supine, standing, and sitting positions. A total of 76 patients (88 hips) were assessed. To classify spinopelvic mobility, defined as a change in SS from standing to sitting position (ΔSSstand/sit), 10° ≤ ΔSSstand/sit ≤ 30°, ΔSSstand/sit < 10°, and ΔSSstand/sit > 30° were considered normal, stiff, and hypermobile, respectively. Over ± 7° changes in SS between before and oneyear after THA were observed in 39 (44.3%) hips in the sitting position, 19 (21.6%) hips in the supine position, seven (7.9%) in the standing position. Percentages of hips with stiff spinopelvic mobility (11.4% vs. 22.7%) and hypermobile spinopelvic mobility (23.9% vs. 12.5%) between before THA and oneyear after THA were significantly different (p = 0.034 and p = 0.016, McNemar's test). At oneyear after THA, 40.0% (4/10) of hips with stiff spinopelvic mobility and 57.1% (12/21) of hips with hypermobile spinopelvic mobility shifted to normal spinopelvic mobility. Change in SS between before THA and oneyear after THA had a high inter-subject variability especially in the sitting position. In addition, there was a distinct shift to normal spinopelvic mobility postoperatively in hips with stiff and hypermobile spinopelvic mobility pre-operatively.

Instability in Patients with Lumbar Spine Disease or Fusion Undergoing Posterior Approach vs. Lateral Approach Primary Total Hip Arthroplasty

Background and Hypothesis: &#x0D; Dislocation rates after total hip arthroplasty (THA) in patients with fixed spinopelvic motion due to lumbar spine disease or fusion have been reported as high as 20%. Few studies exist that compare dislocation rates in patients with spine pathology undergoing THA via different surgical approaches. The purpose of this study was to compare postoperative dislocation rates in patients with lumbar spine disease or fusion between those undergoing a primary THA using a posterior versus direct lateral surgical approach. &#x0D; &#x0D; Experimental Design or Project Methods: &#x0D; With IRB approval, 1,205 primary THAs performed by two surgeons were retrospectively reviewed. One surgeon routinely performs THAs with a posterior approach while the other surgeon routinely uses a direct lateral approach. Chart review from the electronic medical record was conducted to identify patients who have lumbar spine disease or a lumbar spine fusion. Dislocations for patients with and without lumbar spine disease were compared by posterior approach and direct lateral approach. &#x0D; &#x0D; Results: &#x0D; 767 posterior approach and 431 direct lateral approach THAs were available for analysis. 43.6% of all THAs had lumbar spine pathology (337/767 posterior and 185/431 direct lateral). The overall dislocation rate was 1.26% (15/1195). The main predictors of dislocation in binary logistic regression were the presence of lumbar spine pathology (OR 5.24, 95% CI: 1.47–18.69, p=0.018) and posterior surgical approach (OR 7.93, 95% CI: 1.04–60.6, p=0.046). The dislocation rate for direct lateral approach THAs with lumbar spine pathology was significantly lower compared to posterior approach THAs with lumbar spine pathology (0.0% vs 3.6%, p=0.011). &#x0D; &#x0D; Conclusion and Potential Impact: &#x0D; Although there were few dislocations, the study results suggest a direct lateral approach for primary THA may be beneficial to reduce postoperative dislocation for patients with limited spinopelvic motion due to lumbar spine pathology.

Paradoxical spinopelvic motion: does global balance influence spinopelvic motion in total hip arthroplasty?

BackgroundRecent research has proposed a classification of spinopelvic stiffness according to pelvic spatial orientation for risk stratification in patients who undergo total hip arthroplasty (THA). However, the influence of global alignment was not investigated, and this study evaluated the effect of global balance (sagittal vertical axis [SVA]) on spinopelvic motion.MethodsWe conducted a retrospective review of consecutive primary THA patients. We measured SVA, spinopelvic parameters (pelvic tilt [PT], pelvic incidence, and sacral slope), thoracic kyphosis (TK), lumbar lordosis (LL), proximal femur angle (PFA), and cup version using functional radiographs of patients in the standing and upright sitting positions. Linear regression was performed to identify parameters related to global trunk alignment change (∆SVA). Spinopelvic stiffness was defined as PT position change < 10°, and a subset of patients with PT change < 0° was categorized into a paradoxical spinopelvic motion group.ResultsOne hundred twenty-four patients were analyzed (mean age: 65 years, 61% female). In univariate regression analysis, ∆TK, ∆LL, and ∆PFA were correlated to ∆SVA. In multivariate regression analysis, ΔLL (p < 0.001) and ΔPFA (p < 0.001) were found to be correlated to ΔSVA (ΔSVA = − 11.97 + 0.05ΔTK – 0.23ΔLL – 0.17ΔPFA; adjusted R2 = 0.558). Spinopelvic stiffness was observed in 40 patients (32%), including five (4%) with paradoxical motion (∆PT = − 3° ± 1°, p < 0.001) with characteristics of balanced standing global trunk alignment (standing SVA = − 1.0 ± 5.1 cm), similar stiffness of the lumbosacral spine (∆LL = − 7° ± 5°), higher hip motion (∆PFA = − 78° ± 6°, p = 0.017), and higher anterior trunk shift (∆SVA = 6.2 ± 2.0 cm, p = 0.003) from standing to sitting as compared to the stiffness group. Two of these five patients experienced dislocation events after THA.ConclusionsThe lumbosacral and hip motions were the major contributors to global alignment postural change. Paradoxical motion is a rare but dangerous clinical condition in THA that might be related to a disproportionally large trunk shift in the stiff lumbosacral spine causing excessive hip motion. In paradoxical motion, diminishing functional acetabular clearance during position change might pose the prosthesis at higher risk of impingement and instability than spinopelvic stiffness.

Spinopelvic Hypermobility Corrects After Staged Bilateral Total Hip Arthroplasty.

Background: Spinopelvic hypermobility may be secondary to a stiff osteoarthritic hip with a compliant spine. Purpose: We sought to determine if spinopelvic hypermobility resolves after total hip arthroplasty (THA) and when it resolves in patients with bilateral hip osteoarthritis (OA) undergoing staged bilateral THA. We also sought to analyze the change in spinopelvic parameters before and after the second THA. Methods: We conducted a retrospective review of 2047 THAs that were performed by 2 fellowship-trained arthroplasty surgeons from 2014 to 2018. Patients with preoperative spinopelvic hypermobility undergoing staged bilateral THA were identified. Radiographic spinopelvic parameters, including sacral slope (SS), pelvic incidence (PI), lumbar lordosis (LL), PI-LL mismatch, anterior pelvic plane tilt (APPt), and spinopelvic tilt (SPT), were measured on preoperative, 6-week postoperative, and 1-year postoperative lateral standing and sitting radiographs. Bilateral hip OA was graded using Kellgren-Lawrence criteria. Results: We identified 42 patients with preoperative spinopelvic hypermobility who underwent staged bilateral THA. Mean time (standard deviation) between surgeries was 9.4 months (±10.0). After the first THA, spinopelvic hypermobility resolved in 29% of the patients. After the second THA, it resolved in 67% at 6 weeks, increasing to 98% at 1 year postoperatively. Conclusion: Spinopelvic hypermobility resolves after staged bilateral THA in 98% of the patients, occurring most often only after the second THA. Less than one-third of the patients had resolution after the first THA, suggesting that contralateral hip OA continues to drive hip-driven spinopelvic motion. Acetabular component position targets based on functional pelvic position should incorporate these changes in spinopelvic motion with the understanding that resolution of hypermobility usually occurs after the second THA.

P96. Pelvic morphometry for the spine and hip surgeon: Pelvic incidence is correlated to sacro-acetabular angle

<h3>BACKGROUND CONTEXT</h3> Alterations in spinopelvic motion and position following spinopelvic fusion may lead to impingement, increased wear, and dislocation in total hip arthroplasty (THA). Pelvic morphometry is critical in determining appropriate spinal alignment and acetabular position. <h3>PURPOSE</h3> Understanding the relationship between pelvic and acetabular morphometry and changes in postoperative position may enable more synergy between cup placement and spinal fusion. <h3>STUDY DESIGN/SETTING</h3> Single center, retrospective, case series. <h3>PATIENT SAMPLE</h3> Consecutive sample of patients from a single institution. <h3>OUTCOME MEASURES</h3> Radiographic spinopelvic parameters. <h3>METHODS</h3> This was a retrospective study of adult patients following spinopelvic fusion between 2012 and 2020. Patients with neuromuscular disease, active infections, trauma or tumors were excluded. Demographic data and operative details were recorded. Pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), acetabular ante-inclination (AI) and sacro-acetabular angle (SAA) were measured. Similar to PI, SAA is a fixed morphometric parameter. Measurements were made on preoperative and most recent postoperative standing sagittal spine radiographs. Analysis was performed with paired t-test and linear regression. <h3>RESULTS</h3> A total of 124 patients met inclusion criteria with mean follow-up time 17.6 months. PI-LL mismatch improved postoperatively from 19.6° to 5.7° (P < 0.001) and PT decreased from 27° to 25° (P = 0.008). PI and SAA were correlated with a 1° increase in PI corresponding to a 0.6° increase in SAA (P < 0.001, R2 = 0.446). Preoperative and postoperative spinopelvic parameters were not correlated with preoperative or postoperative AI. However, regression analysis revealed a 1° increase in AI postoperatively was correlated with a 0.9° increase in PT (P < 0.001, R2 = 0.81) and 1.6° decrease in LL (P < 0.001, R2 = 0.54). <h3>CONCLUSIONS</h3> Radiographic morphometric measurements of the acetabulum and pelvis are closely related. Changes in pelvic tilt and lumbar lordosis to restore sagittal spine balance following spinopelvic fusion appear to be linked to changes in acetabular position. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Spinopelvic Biomechanics and Total Hip Arthroplasty: A Primer for Clinical Practice.

Abnormal spinopelvic motion from spine pathology is associated with inferior outcomes after total hip arthroplasty, including inferior patient-reported outcomes, increased rates of instability, and higher revision rates. Identifying these high-risk patients preoperatively is important to conduct the appropriate workup and formulate a surgical plan. Standing and sitting lateral spinopelvic radiographs are able to identify and quantify abnormal spinopelvic motion. Depending on the type of spinopelvic deformity, some patients may require increased anteversion, increased offset, and large diameter heads or dual mobility articulations to prevent dislocation. This review article will provide the reader with practical information that can be applied to patients regarding the terminology, pathophysiology, evaluation, and management of total hip arthroplasty patients with spinopelvic pathology.

Applying the Hip-Spine Relationship: What X-Rays and Measurements Are Important?

Understanding spinopelvic motion and the dynamic relationship of the hip, spine, and pelvis is essential in decreasing the risk of instability after total hip arthroplasty. The hip-spine relationship is complex, and a detailed analysis of each patient’s spinopelvic mobility is warranted to help guide safe acetabular component positioning. Through the use of a standing anteroposterior pelvis X-ray, lateral spinopelvic radiographs in the standing and seated position, and advanced functional imaging, key spinopelvic parameters can be obtained. A systematic preoperative workup can help to identify hip-spine pathology that predisposes patients to instability, and can help in planning and establishing a patient-specific “safe zone.” Based on the presence of concomitant hip-spine pathology, patients must be evaluated thoroughly with preoperative imaging to plan for the optimal target acetabular cup position. This paper guides readers through important parameters and imaging associated to spinopelvic motion as it relates to total hip arthroplasty stability.