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

Systematic measurement of spino-pelvic alignment as a simple strategy to reduce the dislocation rate in primary hip arthroplasties

BACKGROUND

The incorporation of spinopelvic alignment measurement in the planning of primary hip arthroplasties is a simple and low-cost method whose isolated impact on reducing dislocation rates has not been clearly established.

AIM

The objective was to estimate the probability of dislocation and its occurrence rate by comparing 2 demographically similar populations, 1 with the measurement incorporated and the other without it. Additionally, the modification and distribution of surgical practices and indications aimed at reducing the risk of dislocations were compared.

METHODS

A before-and-after study with prospective registry and retrospective control group was designed. We compared 693 patients (prospective registry) with the incorporation of spinopelvic alignment measurement in preoperative planning versus 341 from a previous period who constituted the control group (retrospective registry). All had a minimum follow-up of 2 years.

RESULTS

The dislocation rate significantly decreased from 3.2% to 0.7%, with an OR of 0.22 for dislocation in the intervention group. There was a significant increase in the use of dual-mobility components in patients with complete misalignment and stems with extended offset in patients with partial misalignment.

CONCLUSIONS

In conclusion, the incorporation of spinopelvic alignment measurement in preoperative planning is an accessible method for any medical centre that contributed to modifying surgical practices, ultimately leading to a significant reduction in the dislocation rate.

Increasing Limb Length During Stage 1 Revision Leads to Higher Rates of Instability Following Stage 2 Revision Total Hip Arthroplasty

BACKGROUND

Currently, two-stage revision total hip arthroplasty is the gold standard in managing periprosthetic joint infection (PJI) of the hip; however, complications are common, including instability. The purpose of this study was to determine how alterations in limb length during a stage 1 articulating spacer affect dislocation rates of the stage 2 revision.

METHODS

A retrospective study of consecutive patients who underwent two-stage revision total hip arthroplasty for PJI between December 2013 and December 2022 was performed. We measured limb length as the perpendicular distance from the trans-teardrop line to the apex of the lesser trochanter after stage 1 articulating spacer implantation. Independent t-tests and logistic regression were used to compare limb lengths following stage 1 spacers between patients who did and did not dislocate after stage 2 implantation. Overall, 147 patients who underwent staged revisions for the treatment of PJI were identified. The cohort was 59% women who had a mean age of 60 years (range, 25 to 84 years) and an average follow-up time of 2.7 years (range, 1.0 to 9.1 years).

RESULTS

The dislocation rates after stage 1 and stage 2 were 3.0 and 11.7%, respectively. Limb length did not impact dislocation rates of the articulating stage 1 spacers (P = 0.71), but patients who sustained a dislocation following stage 2 were lengthened significantly more at stage 1 implantation (8.5 ± 15.9 versus 0.8 ± 11.8 mm, P = 0.033). Additionally, the odds of dislocation after stage 2 increased by 7% with each mm lengthened during stage 1 (odds ratio = 1.07, 95% confidence interval: 1.01 to 1.13).

CONCLUSIONS

During a stage 1 articulating spacer of the hip, limb length restoration is often disregarded, which can result in overlengthening that may necessitate subsequent shortening during stage 2 reconstruction. This study demonstrates that overlengthening of an articulating stage 1 hip spacer can place the patient at an increased risk of dislocation following stage 2 reconstruction.

Efficacy of a novel, fluoroscopy-based robotic-assisted total hip arthroplasty system in restoring limb length and offset

INTRODUCTION

Optimizing leg length discrepancy (LLD) and restoring global and femoral offset (GO, FO) are integral to improving the stability and longevity of total hip arthroplasty (THA). A novel robotic-assisted THA (RA-THA) platform has been developed to utilize pre-operative templating and intraoperative fluoroscopic imaging to guide the restoration of native biomechanics. We sought to evaluate the effectiveness of this novel, pin-less, fluoroscopy-based RA-THA system to restore templated LLD and offset parameters.

MATERIALS AND METHODS

We performed a retrospective analysis on a consecutive series of 98 patients who underwent fluoroscopy-based RA-THA at our institution. The primary outcomes were the differences between preoperatively templated LLD, GO, and FO parameters with intraoperatively achieved parameters measured by the robotic system and with postoperatively achieved parameters measured from postoperative radiographs.

RESULTS

The mean difference between achieved and preoperatively templated values of LLD (-1.5 ± 5.5 mm), GO (-0.1 ± 5.5 mm), and FO (-0.1 ± 5.4 mm) were all within - 1.5 mm of establishing equalized leg length and offset. The proportion of patients with a difference in achieved and templated values < 10 mm were 92% for LLD, 91% for GO, and 93% for FO. For 43 of the 98 (44%) patients in this study, the surgeon referenced intraoperative robotic data to adjust femoral components from the preoperative plan in order to optimize LLD and offset parameters.

CONCLUSIONS

The results of our present study demonstrated that fluoroscopy-based RA-THA is associated with high levels of accuracy in restoring key biomechanics of the hip. In a large number of patients, the surgeon used intraoperative robotic data to more closely achieve LLD and offset goals. This demonstrates the ability of this system to merge preoperative data with intraoperative, actionable data provided by the robotic software to restore leg length and global/femoral offset parameters. Words: 279/ 300.

The Impact of Leg Length and Offset Change on Dislocation Risk Following Primary Total Hip Arthroplasty

BACKGROUND

Soft tissue management in total hip arthroplasty includes appropriate restoration and/or alteration of leg length (LL) and offset to re-establish natural hip biomechanics. The purpose of this study was to evaluate the effect of LL and offset-derived variables in a multivariable survival model for dislocation.

METHODS

Clinical, surgical, and radiographic data was retrospectively acquired for 12,582 patients undergoing primary total hip arthroplasty at a single institution from 1998 to 2018. There were twelve variables derived from preoperative and postoperative radiographs related to LL and offset that were measured using a validated automated algorithm. These measurements, as well as other modifiable and nonmodifiable surgical, clinical, and demographic factors, were used to determine hazard ratios for dislocation risk.

RESULTS

None of the LL or offset variables conferred significant risk or protective benefit for dislocation risk. By contrast, all other variables included in the multivariable model demonstrated a statistically significant effect on dislocation risk with a minimum effect size of 28% (range 0.72 to 1.54) (sex, surgical approach, acetabular liner type, femoral head size, neurologic disease, spine disease, and prior spine surgery).

CONCLUSIONS

Contrary to traditional teaching and our hypothesis, operative changes in LL and offset did not demonstrate any clinically or statistically significant effect in this large and well-characterized cohort. This does not imply that these variables are not important in individual cases, but rather suggests the overall impact of LL and offset changes is relatively minor for dislocation risk compared to other variables that were found to be highly clinically and statistically significant in this population. These results may also suggest that surgeons do a good job of restoring native LL and offset for patients, which may mitigate their analyzed impact.

Adverse spinopelvic mobility in patients undergoing total hip arthroplasty is associated with high mobility of the hip in a flexed seated position

PURPOSE

Adverse spinopelvic mobility from a standing to a flexed seated position of more than 20° of the spinopelvic tilt (∆SPT) has been shown to have a high risk of dislocation. If hypermobility of the hip analysed with the pelvic femoral angle (∆PFA) has a high risk of impingement, the correlation between the range of motion of the hip from a standing to a flexed seated position and its implication in adverse spinopelvic mobility has not been described.

METHODS

A series of 337 patients treated with primary THA underwent lateral x-ray in standing and flexed seated positions to analyse ∆SPT, ∆PFA and spinopelvic parameters. The objectives were to establish a ∆PFA threshold associated with a ∆SPT ⩾20° and to subsequently investigate its influence in conjunction with spinopelvic risk factors on the occurrence of adverse spinopelvic mobility.

RESULTS

The area under the curve was 0.904 (95%CI, 0.864-0.945) for ∆PFA to predict ∆SPT ⩾ 20°; it was predicted by ∆PFA ⩾ 95° with a sensitivity of 91.7% and a specificity of 74.4% at the Youden optimal threshold. Patients with a ∆SPT < 20° (277 patients) had a mean ∆PFA of 83° compared to 110° if ∆SPT ⩾ 20° (60 patients) (p < 0.001). Patients with a ∆PFA < 95° (203 patients) had a mean ∆SPT of -6° compared to 18° if ∆PFA ⩾ 95° (134 patients) (p < 0.001). ∆PFA ⩾ 95° rates were 95% (57/60) and 27.8% (77/200) in patients with ∆SPT ⩾ 20° and ∆SPT < 20°, respectively (OR 49.35; CI, 15.01-162.28; p < 0.001).

CONCLUSIONS

High mobility of the hip (∆PFA ⩾ 95°) seems to be a necessary condition for adverse spinopelvic mobility. A preoperative analysis of patients with lower hip mobility, associated with spinopelvic risk factors, might identify patients with abnormal spinopelvic mobility after the restoration of femoral flexion.

TRIAL REGISTRATION

IDRCB 2023-A01390, CNIL MR004 2225508 (07/06/2023), retrospectively registered.

Contemporary insights into spinopelvic mechanics

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.

Offset Considerations in Total Hip Arthroplasty

To perform total hip arthroplasty (THA) successfully, a surgeon must be able to place the implants in a position that will restore and duplicate the patient's baseline anatomy and soft-tissue tension. One of the critical factors is the restoration of femoral offset. It is the goal of this review to precisely define measurement of offset in THA, describe its role in hip joint biomechanics, outline alterations that can be performed intraoperatively, and explain how it can create potential pathologic states. If there is a lack of offset restoration, it can result in a host of complications, including bony impingement with pain, edge loading or prosthetic joint instability, and alterations in the muscle length-tension relationship leading to reduced motor performance. Excessive femoral offset can increase hip abductor muscle and iliotibial band tension resulting in greater trochanteric pain regardless of the surgical approach. The purpose of this review was to analyze intraoperative surgical factors, choice of prosthetic implant type and position that are required to maximize stability, and dynamic motor performance after THA.

Archetype analysis of the spine-hip relationship identifies distinct spinopelvic profiles

INTRODUCTION

The position of the pelvis in the sagittal plane can vary considerably between different functional positions. Adapting the position of the acetabular cup in relation to the alignment between the spine and the hip of each individual, prior to prosthesis placement, can prevent the risk of prosthetic impingement. Taken individually, risk factors for unfavorable spinopelvic kinematics can be difficult to interpret when trying to precisely predict which patients are at risk. Furthermore, the use of classifications or algorithms can be complex, most often associated with limited values and often difficult to apply in current practices of risk assessment.

HYPOTHESIS

We hypothesized that the deconstruction of the data matrix including age and spinopelvic parameters (SPT, LL, PI, LF and PI-LL) correlated with the analysis of spinopelvic kinematics could be used to define an individualized hip-spine relationship.

MATERIAL AND METHOD

We applied archetypal analysis, which is a probabilistic, data-driven and unsupervised approach, to a complete phenotype cohort of 330 patients before total hip arthroplasty to define the spinopelvic profile of each individual using the spinopelvic parameters without threshold value. For each archetype, we analyzed the spinopelvic kinematics, not implemented in the creation of the archetypes.

RESULTS

An unsupervised learning method revealed seven archetypes with distinct spinopelvic kinematic profiles ranging from -8.9 ° to 13.15 ° (p = 0.0001) from standing to sitting and -5. 35 ° to -10.81 ° (p = 0.0001) from supine to standing. Archetype 1 represents the "ideal" patient (A1); young patients without spinopelvic anomaly and the least at risk of mobility anomaly. Followed by 3 archetypes without sagittal imbalance according to their lumbar lordosis and pelvic incidence, from the highest to the lowest (archetypes 2-4), archetype 4 exposing a greater risk of spinopelvic kinematic anomaly compared to others. Then 2 archetypes with sagittal imbalance: archetype 5, with an immobile pelvis in the horizontal plane from standing to sitting position in anterior tilt and archetype A6, with significant posterior pelvic tilt standing, likely compensating for the imbalance and associated with the greatest anomaly of spinopelvic kinematics. Finally, archetype 7 with the stiffest lumbar spine without sagittal imbalance and significant unfavorable kinematics from standing to sitting.

CONCLUSION

An archetypal approach to patients before hip replacement can refine diagnostic and prognostic features associated with the hip-spine relationship and reduced heterogeneity, thereby improving spinopelvic characterization. This risk stratification of spinopelvic kinematic abnormalities could make it possible to target patients who require adapted positioning or types of implants before prosthetic surgery.

LEVEL OF EVIDENCE

IV retrospective study.

Worse Patient-Reported Outcomes and Spino-Pelvic Parameters After Total Hip Arthroplasty for Rapidly Progressive Osteoarthritis of the Hip Compared to Osteoarthritis: A Propensity-Matched Cohort Study

BACKGROUND

This study aimed to assess the association between the disease process of hip osteoarthritis and total hip arthroplasty (THA) outcomes; this is a critical issue, as rapid progression has been postulated to be responsible for patient dissatisfaction after THA.

METHODS

This retrospective case-control study included 255 patients who underwent THA and completed a mean follow-up duration of 42.1 months (range, 24.0 to 77.0). We classified patients into those who had (n = 26) and did not have (n = 229) rapidly progressive osteoarthritis of the hip (RPOA), defined as a narrowing rate of joint space ≥ 2 mm yearly or a ≥ 50% loss within 12 months, excluding any other cause of a destructive arthropathy. Propensity score-matched cohorts for age, sex, body mass index, and spino-pelvic measures were created, and the outcomes were compared between the 2 groups.

RESULTS

After successfully matching RPOA (n = 25) and non-RPOA patients (n = 50), there were significant differences in minimum clinically important difference (P = .009 for European Quality of Life 5-Dimension, and P < .001 for low back pain), patient acceptable symptom state (P = .015 for European Quality of Life 5-Dimension, and P < .001 for Hip Disability and Osteoarthritis Outcome Score Joint Replacement score), patient satisfaction (P = .028), and T1 pelvic angle as an indicator of global sagittal spinal deformity (P = .017). There was a correlation between T1 pelvic angle and low back pain in the RPOA group (R = 0.628, P < .001).

CONCLUSIONS

Patients who exhibited RPOA before undergoing THA showed worse patient-reported outcomes compared with those who did not have rapid progression. Our study highlights the critical role of the disease process in influencing THA outcomes, advocating for a paradigm shift toward more meticulous preoperative evaluations, including global spinal deformity, standardized diagnostic criteria, and tailored interventions.

Is it feasible to develop a supervised learning algorithm incorporating spinopelvic mobility to predict impingement in patients undergoing total hip arthroplasty?

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.

Methods

This international, multicentre prospective cohort study across two centres encompassed 157 adults undergoing primary robotic arm-assisted THA. Impingement during specific flexion and extension stances was identified using the virtual range of motion (ROM) tool of the robotic software. The primary AI model, the Light Gradient-Boosting Machine (LGBM), used tabular data to predict impingement presence, direction (flexion or extension), and type. A secondary model integrating tabular data with plain anteroposterior pelvis radiographs was evaluated to assess for any potential enhancement in prediction accuracy.

Results

We identified nine predictors from an analysis of baseline spinopelvic characteristics and surgical planning parameters. Using fivefold cross-validation, the LGBM achieved 70.2% impingement prediction accuracy. With impingement data, the LGBM estimated direction with 85% accuracy, while the support vector machine (SVM) determined impingement type with 72.9% accuracy. After integrating imaging data with a multilayer perceptron (tabular) and a convolutional neural network (radiograph), the LGBM's prediction was 68.1%. Both combined and LGBM-only had similar impingement direction prediction rates (around 84.5%).

Conclusion

This study is a pioneering effort in leveraging AI for impingement prediction in THA, utilizing a comprehensive, real-world clinical dataset. Our machine-learning algorithm demonstrated promising accuracy in predicting impingement, its type, and direction. While the addition of imaging data to our deep-learning algorithm did not boost accuracy, the potential for refined annotations, such as landmark markings, offers avenues for future enhancement. Prior to clinical integration, external validation and larger-scale testing of this algorithm are essential.

Does Artificial Intelligence Outperform Humans Using Fluoroscopic-Assisted Computer Navigation for Total Hip Arthroplasty?

Background

Successful total hip arthroplasty (THA) relies on the correct implant position. THA accuracy can be improved with the use of intraoperative fluoroscopic-assisted computer navigation. Artificial intelligence (AI) software may enhance fluoroscopic navigation; however, the accuracy of the AI compared to human-controlled software in assessing acetabular component position and leg length discrepancy (LLD) has not been studied.

Methods

We analyzed 420 consecutive primary THAs performed by a single surgeon using fluoroscopic-assisted computer navigation software. The first cohort of 211 patients required inputs from a human technician (manual), while the second cohort of 209 patients used an automated version of the software controlled by AI. The intraoperative acetabular component placement (inclination and anteversion) and LLD were recorded and compared to the 2-week postoperative standing anterior-posterior pelvis radiograph.

Results

Ninety-four percent (199/211) of cups in the manual cohort and 95% (198/209) of cups in the AI cohort were within the Lewinnek "safe-zone" (P = 1.0). In the manual cohort, 69% (146/211) of THAs had a final LLD within ±2 mm of the intraoperatively navigated LLD (ie, ΔLLD ≤2 mm). In the AI cohort, 66% (137/209) of THAs had a final LLD within ±2 mm of the intraoperatively navigated LLD (P = .47). Ninety-nine percent (209/211) of hips in the manual cohort and 98% (205/209) of hips in the AI cohort had a final LLD within ±5 mm of the intraoperatively navigated LLD (P = .45).

Conclusions

Both AI and human-controlled versions of the same navigation platform were similarly accurate for navigating cup position within the Lewinnek "safe zone" and LLD accuracy.

Medullary-Sparing Antibiotic Cement Articulating Spacer Reduces the Rate of Mechanical Complications in Advanced Septic Hip Arthritis: A Retrospective Cohort Study

Antibiotic cement articulating spacers eradicate infection during a two-stage revision for advanced septic hip arthritis (ASHA); however, mechanical complications have been reported. We hypothesized that the rate of mechanical complications would be lower in medullary-sparing (MS) than in non-medullary-sparing (n-MS) articulating spacers. A retrospective study of ASHA using n-MS or MS spacers was conducted between 1999 and 2019. The rate of mechanical complications and reoperation and risk factors for mechanical complications were analyzed. The cohort included 71 n-MS and 36 MS spacers. All patients were followed up for 2 years. The rate of spacer dislocation was lower in MS (0%) than in n-MS spacers (14.1%; p = 0.014). The reoperation rate for mechanical complications was lower in MS (0%) than in n-MS spacers (12.7%; p = 0.019). The rate of a diaphyseal stem during reimplantation was lower in MS (0%) than in n-MS spacers (19.4%; p = 0.002). The identified risk factors for n-MS spacer dislocation were postoperative under-restored femoral head diameter ≥3 mm, femoral offset ≥3 mm, and surgical volume (≤6 resection arthroplasties per year). Both spacers controlled infection. However, MS spacers had a lower spacer dislocation and reoperation rate and avoided the diaphyseal stem during reimplantation. We recommend using MS spacers to restore native femoral head diameter and femoral offset when ASHA is treated by surgeons with lower surgical volumes.

Low pelvic incidence with low lordosis and distal apex of lumbar lordosis associated with higher rates of abnormal spinopelvic mobility in patients undergoing THA

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.

Functional Component Positioning in Total Hip Arthroplasty and the Role of Robotic-Arm Assistance in Addressing Spinopelvic Pathology

Hip, spine, and pelvis function as a unified kinetic chain. Any spinal pathology, results in compensatory changes in the other components to accommodate for the reduced spinopelvic motion. The complex relationship between spinopelvic mobility and component positioning in total hip arthroplasty presents a challenge in achieving functional implant positioning. Patients with spinal pathology, especially those with stiff spines and little change in sacral slope, are at high instability risk. In this challenging subgroup, robotic-arm assistance enables the execution of a patient specific plan, avoiding impingement and maximizing range of motion; especially utilizing virtual range of motion to dynamically assess impingement.

The incidence of hip dislocation after posterior approach primary total hip arthroplasty: comparison of two different posterior repair techniques

INTRODUCTION

Total hip arthroplasty (THA) remains one of the most successful orthopedic surgical procedures. The posterior approach is associated with a higher incidence of post-operative dislocations than others. Adequate posterior soft tissue repair techniques, including capsulorrhaphy and transosseous bone sutures in the greater trochanter effectively reduce the dislocation rate. Post-operative "posterior hip precautions" were historically believed to reduce dislocation risks, although not clearly proven. The first protocol consists of capsulorrhaphy with the prescription of post-operative posterior hip precautions (TT) and the second, transosseous bone sutures without precautions (TB). This study aims to determine the optimal protocol to decrease the dislocation rate following posterior approach primary THA.

MATERIALS AND METHODS

A 10-year retrospective case-control chart review analyzed demographic, pre-, intra-, and post-surgical parameters. Primary outcomes were the difference in dislocation and revision surgery rates between protocols. Secondary outcomes included the incidence of recurrent dislocations and the identification of predictors of dislocation.

RESULTS

2,242 THAs were reviewed and 26 (1.2%) resulted in dislocation. Increased age (p = 0.04) ASA score (p = 0.03) and larger acetabular cup size (p < 0.001) were associated with heightened risk. Tendon to tendon (TT) repair saw a 1.62% dislocation rate versus 0.98% for tendon-to-bone (TB) repair, although statistically insignificant (p = 0.2). Transosseous repair resulted in recurrent dislocations for 8/16 (50%) patients compared to 6/10 (60%) in the suture group (p ≤ 0.001). No significance was found for prescription of posterior hip precautions.

CONCLUSIONS

To our knowledge, this is the first study to perform a direct comparison of TT repair with posterior precautions to TB repair without posterior precautions. Similarity in dislocation rate, decreased recurrent events and the alleviated patient burden from precautions leads the authors to recommend the TB repair without precautions for a successful THA.