A Preoperative Workup of a "Hip-Spine" Total Hip Arthroplasty Patient: A Simplified Approach to a Complex Problem

Effect of Spinopelvic Parameters on Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome

BACKGROUND

Spinopelvic parameters, including pelvic tilt (PT), sacral slope (SS), and pelvic incidence, have been developed to characterize the relationship between lumbar spine and hip motion, but a paucity of literature is available characterizing differences in spinopelvic parameters among patients with femoroacetabular impingement syndrome (FAIS) versus patients without FAIS, as well as the effect of these parameters on outcomes of arthroscopic treatment of FAIS.

PURPOSE

To (1) identify differences in spinopelvic parameters between patients with FAIS versus controls without FAIS; (2) identify associations between spinopelvic parameters and preoperative patient-reported outcomes (PROs); and (3) identify differences in PROs between patients with stiff spines (standing-sitting ΔSS ≤10°) versus those without.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

The study enrolled patients ≥18 years of age who underwent primary hip arthroscopy for treatment of FAIS with cam, pincer, or mixed (cam and pincer) morphology. Participants underwent preoperative standing-sitting imaging with a low-dose 3-dimensional radiography system and were matched on age and body mass index (BMI) to controls without FAIS who also underwent EOS imaging. Spinopelvic parameters measured on EOS films were compared between the FAIS and control groups. Patients with FAIS completed the modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS) before surgery and at 1-year follow-up. Outcome scores were compared between patients with stiff spines versus those without. Associations between spinopelvic parameters and baseline outcome scores were assessed with Pearson correlations. Continuous variables were compared with Student t test and/or Mann-Whitney U test, and categorical variables were compared with Fisher exact test.

RESULTS

A total of 50 patients with FAIS (26 men; 24 women; mean age, 36.1 ± 10.7 years; mean BMI, 25.6 ± 4.2) were matched to 30 controls without FAIS (13 men; 17 women; mean age, 36.6 ± 9.5 years; mean BMI, 26.7 ± 3.6). Age, sex, and BMI were not significantly different between the FAIS and control groups (P > .05). Standing PT was not significantly different between stiff and non-stiff cohorts (P = .73), but sitting PT in the FAIS group was more than double that of the control group (36.5° vs 15.0°; P < .001). Incidence of stiff spine was significantly higher in the FAIS group (62.0% vs 3.3%; P < .001). Among FAIS patients, those with stiff spines had a significantly higher prevalence of cam impingement, whereas those with non-stiff spines had a higher prevalence of mixed impingement (P = .04). No significant differences were seen in preoperative mHHS or NAHS scores or pre- to postoperative improvement in scores between FAIS patients with stiff spines versus those without (P > .05), but a greater sitting SS was found to be positively correlated with a higher baseline mHHS (r = 0.36; P = .02).

CONCLUSION

Patients with FAIS were more likely to have a stiff spine (standing-sitting ΔSS ≤10°) compared with control participants without FAIS. FAIS patients with stiff spines were more likely to have isolated cam morphology than patient without stiff spines. Although sitting SS was positively correlated with baseline mHHS, no significant differences were seen in 1-year postoperative outcomes between FAIS patients with versus without stiff spine.

Mobility of the lumbo-pelvic-hip complex (spinopelvic mobility) and sagittal spinal alignment - implications for surgeons performing hip arthroplasty

INTRODUCTION

The optimal positioning of the hip prosthesis components is influenced by the mobility and balance of the spine. The present study classifies patients with pathology of the spino-pelvic-hip complex, showing possible methods of preventing hip dislocations after arthroplasty.

HYPOTHESIS

Hip-Spine Classification helps arthroplasty surgeons to implant components in more patient-specific position.

MATERIALS AND METHODS

The group of 100 patients treated with total hip arthroplasty. Antero-posterior (AP) X-rays of the pelvis in a standing position, lateral spine (standing and sitting) and AP of the pelvis (supine after the procedure) were analyzed. We analyzed a change in sacral tilt value when changing from standing to sitting (∆SS), Pelvic Incidence (PI), Lumbar Lordosis (LL) Mismatch, sagittal lumbar pelvic balance (standing position). Patients were classified according to the Hip-Spine Classification. Postoperatively, the inclination and anteversion of the implanted acetabular component were measured.

RESULTS

In our study 1 A was diagnosed in 61% of all cases, 1B in 18%, 2 A in 16%, 2B in 5%. 50 out of 61 (82%) in group 1 A were placed within the Levinnek "safe zone". In 1B, 2 A, 2B, the position of the acetabular component was influenced by both the spinopelvic mobility and sagittal spinal balance. The mean inclination was 43.35° and the anteversion was 17.4°.

CONCLUSIONS

Categorizing patients according to Hip-Spine Classification one can identify possible consequences the patients at risk. Pathology of the spino-pelvic-hipcomplex can lead to destabilization or dislocation of hip after surgery even though implanted according to Lewinnek's indications. Our findings suggest that Lewinnek safe zone should be abandoned in favor of the concept of functional safe zones.

Patients Requiring Both Total Hip Arthroplasty and Lumbar Spinal Fusion Have Lower Hip Functional Outcome Scores: A Matched Case-Control Study

BACKGROUND

While patients who undergo both lumbar spinal fusion (LSF) and total hip arthroplasty (THA) have increased complication rates compared to patients who have not undergone LSF, there is a paucity of literature evaluating THA functional outcomes in patients with a history of LSF. This study was conducted to determine whether patients undergoing THA with a history of LSF have inferior functional outcomes compared to patients having no history of LSF.

METHODS

A retrospective matched case-control study was conducted at an academic center. Patients who underwent both THA and LSF (cases) were matched with controls who underwent THA without LSF. Inclusion criteria required a minimum of 1-year follow-up for the Hip Disability and Osteoarthritis Outcome Score Joint Replacement [HOOS-JR]. Following propensity matching for age, sex, race, body mass index, and comorbidities, 291 cases and 1,164 controls were included, with no demographic differences.

RESULTS

Patients who underwent both THA and LSF had a significantly lower preoperative HOOS-JR (47 versus 50; P < .001), postoperative HOOS-JR (77 versus 85; P < .001), a significant lower rate of achieving the patient acceptable symptom state (55 versus 67%; P < .001), with no significant difference in delta HOOS-JR (34 versus 34; P = .834). When comparing patients undergoing THA before LSF or LSF before THA, no differences existed for preoperative HOOS-JR (50 versus 47; P = .304), but patients undergoing THA before LSF had lower postoperative HOOS-JR scores (74 versus 81; P = .034), a lower-delta HOOS-JR (27 versus 35; P = .022), and a lower rate of reaching the HOOS-JR minimal clinically important difference (62 versus 76%; P = .031).

CONCLUSIONS

Patients who have a history of LSF experience a similar improvement in hip function when undergoing THA compared to patients who do not have a history of LSF. However, due to lower preoperative function, they may have a lower postoperative functional outcome ceiling. Additionally, patients undergoing THA before LSF have worse hip functional outcomes than patients undergoing LSF before THA.

Impact of the hip-spine relationship and patient-perceived leg length discrepancy after total hip arthroplasty: A retrospective study

PURPOSE

Patient-perceived leg length discrepancy (PLLD) is one of the major postoperative complications of total hip arthroplasty (THA). This study aimed to identify factors that cause PLLD following THA.

MATERIALS AND METHODS

This retrospective study included a series of consecutive patients who underwent unilateral THA between 2015 and 2020. Ninety-five patients who underwent unilateral THA with postoperative radiographic leg length discrepancy (RLLD) ≤1 cm were classified into two groups according to the direction of preoperative pelvic obliquity (PO). Standing radiographs of the hip joint and whole spine were obtained before and one year after THA. The clinical outcomes and the presence or absence of PLLD was confirmed one year after THA.

RESULTS

Sixty-nine patients were classified as having type 1 PO (rising toward the unaffected side) and 26 were classified as having type 2 PO (rising toward the affected side). Eight patients with type 1 PO and seven with type 2 PO had PLLD postoperatively. In the type 1 group, patients with PLLD had larger preoperative and postoperative PO values and larger preoperative and postoperative RLLD than those without PLLD (p = 0.01, p < 0.001, p = 0.01, and p = 0.007, respectively). In the type 2 group, patients with PLLD had larger preoperative RLLD, larger amount of leg correction, and a larger preoperative L1-L5 angle than those without PLLD (p = 0.03, p = 0.03, and p = 0.03, respectively). In type 1, postoperative PO was significantly associated with postoperative PLLD (p = 0.005), but spinal alignment was not an indicator of postoperative PLLD. The area under the curve (AUC) for postoperative PO was 0.883 (good accuracy) with a cut-off value was 1.90° CONCLUSION: Rigidity of the lumbar spine might lead to postoperative PO as a compensatory movement, resulting in PLLD after THA in type 1. Further research on the relationship between flexibility of the lumbar spine and PLLD is needed.

Decreased Instability in High-Risk (Hip-Spine 2B) Patients After Modifications of Surgical Planning and Technique

BACKGROUND

Patients undergoing primary total hip arthroplasty (THA) who have spinal deformity and a stiff spine are the highest-risk group for instability. Despite the increasing use of dual-mobility cups and large femoral heads, dislocation remains a major complication after THA. Preoperative planning becomes a critical aspect of ensuring precise component positioning within a safe zone. The purpose of this study was to investigate dislocation rates over a 9-year period.

METHODS

A retrospective review of 4,731 THAs performed by 3 orthopaedic surgeons between January 2014 and March 2023 was performed. Spinopelvic measurements were conducted to determine the hip-spine classification group for each patient. Only patients classified as 2B (pelvic incidence-lumbar lordosis > 10° and Δsacral slope < 10°) were eligible. Both absolute and relative dislocation frequencies were then analyzed using time-series analysis techniques and Fisher's exact tests.

RESULTS

A total of 281 hip-spine 2B patients undergoing primary THA were eligible for analysis (57% women; mean age, range: 66 years, 23 to 87; mean body mass index, range: 28, 16 to 45). The overall dislocation rate was 4.3%. Use of femoral head sizes ≥ 40 mm increased from 4% in 2014 to 2019 to 37% in 2020 to 2023 (P < .001), while the use of dual-mobility cups decreased from 100% in 2014 to 2019 to 37% in 2020 to 2023 (P < .001). Acetabular component planning was changed from the supine plane to the standing plane in February 2020. Those changes in surgical practice were notably correlated with a significant decrease in dislocation rates from 6.8% in 2014 to 2019 to 1.5% in 2020 to 2023 (P = .03).

CONCLUSIONS

Our study demonstrates that the introduction of advanced preoperative THA planning to the standing plane, coupled with precise intraoperative technology for implant placement, can significantly reduce the risk of instability in high-risk THA patients. Notably, we observed a significant decrease in dislocation rates, which aligned with the shift in surgical practice.

LEVEL OF EVIDENCE

IV.

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

INTRODUCTION

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.

METHODS

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.

RESULTS

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).

DISCUSSION

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.

Outcomes and complications of Total Hip Arthroplasty in patients with a pre-existing pathologic spine-hip relation. A systematic review of the literature

BACKGROUND

There has been a growing interest in pathologic spine-hip relations (PSHR) in current literature, with the aim of reducing the risk of prosthetic impingement, dislocation, and edge loading in total hip arthroplasty (THA). The primary objective of this review is to determine the effect of different PSHR on primary THA outcomes and complication profile. The secondary objective is to stratify the risk of different subgroups of PSHR patients.

METHODS

A systematic review of the literature was performed in accordance with PRISMA guidelines. Randomised controlled trials, comparative cohort studies and case-control studies comparing outcomes and complication rates of primary THA in patients with and without a PSHR (spinal fusion; degenerative spinal conditions determining stiff spine and/or spinal misalignment) were included. The quality of the included studies and the risk of bias were assessed. The revision rate, complications, and clinical and radiological data were analysed. Complications included: aseptic loosening (AL), periprosthetic joint infections (PJI), hip dislocations and periprosthetic fractures (PF).

RESULTS

Fifteen articles were included with 3.306.342 THAs. The mean follow-up (FU) was 31.4 ± 21.7 months. The population was divided into three subgroups: spinal fusion patients (48.315 THAs); non-fused patients with spinal stiffness (106.110 THAs); non-fused patients with normal spines (3.151.917 THAs). A statistically significant risk stratification was observed about dislocation rate (5.98 ± 6.9% SF, 3.0 ± 1.9% non-SF Stiff and 2.26 ± 1.4% non-SF; p = 0.028). Similarly, about THA revision rate, a statistically significant risk stratification was also observed (7.3 ± 6.8% SF, 6.4 ± 3.1% non-SF Stiff and 2.7 ± 1.7% non-SF; p = 0.020). No statistically significant difference was observed when analysing AL, PJI and PF.

CONCLUSION

A statistically significant risk stratification of dislocation and revision rate was observed in the different PHSR, as theorised by the Bordeaux classification. Fused patients present a higher risk, degenerated and/or stiff spine an intermediate risk and mobile spines a lower risk profile. A standardised approach to THA candidate patients must consider the possible PSHR to improve clinical outcomes and reduce adverse events of THA.

Hip-spine relationship: clinical evidence and biomechanical issues

The hip-spine relationship is a critical consideration in total hip arthroplasty (THA) procedures. While THA is generally successful in patient, complications such as instability and dislocation can arise. These issues are significantly influenced by the alignment of implant components and the overall balance of the spine and pelvis, known as spinopelvic balance. Patients with alteration of those parameters, in particular rigid spines, often due to fusion surgery, face a higher risk of THA complications, with an emphasis on complications in instability, impingement and dislocation. For these reasons, over the years, computer modelling and simulation techniques have been developed to support clinicians in the different steps of surgery. The aim of the current review is to present current knowledge on hip-spine relationship to serve as a common platform of discussion among clinicians and engineers. The offered overview aims to update the reader on the main critical aspects of the issue, from both a theoretical and practical perspective, and to be a valuable introductory tool for those approaching this problem for the first time.

The Empty Ischial Fossa Sign: A Visual Representation of Relative Inadequate Anteversion in the Posteriorly Tilted Pelvis

Background

Instability is a known complication following total hip arthroplasty (THA) and is influenced by spinopelvic alignment. Radiographic markers have been investigated to optimize the acetabular cup position. This study evaluated if the empty ischial fossa (EIF) sign and the position of the trans-teardrop line were predictive of postoperative instability.

Methods

All patients who underwent THA from 2011 to 2018 at a single institution were retrospectively reviewed. Pelvic tilt was measured using a trans-teardrop line compared to the superior aspect of the pubic symphysis on standing anteroposterior pelvis radiographs. Postoperative dislocations were identified through chart review and radiographic review. The EIF sign was determined by the presence of uncovered bone below the posterior inferior edge of the acetabular component at the level of the native ischium and posterior wall on standing postoperative anteroposterior radiographs.

Results

One thousand seven hundred fifty patients (952 anterior approach and 798 posterior approach) were included. The EIF sign was present in 458 patients (26.2%) and associated with an increased dislocation rate (3.9% vs 0.9%, P < .0001). Patients with spondylosis/instrumented fusion, and positive EIF sign had a dislocation risk of 5.1% vs 1.3% (P = .001). A postoperative outlet pelvis was not significant for increased dislocation risk (odds ratio 2.16, P = .058). Patients with combined spondylosis/fusion, posterior approach, outlet pelvis, and EIF sign had a dislocation rate of 14.5%.

Conclusions

The EIF sign was an independent risk factor for postoperative instability and may represent failure to account for pelvic tilt. Avoidance of the EIF sign during cup positioning may help reduce dislocations following THA.

Acetabular cup positioning in primary routine total hip arthroplasty-a review of current concepts and technologies

INTRODUCTION

Total hip arthroplasty (THA) has revolutionized the treatment of hip joint arthritis. With the increased popularity and success of the procedure, research has focused on improving implant survival and reducing surgical complications. Optimal component orientation has been a constant focus with various philosophies proposed. Regardless of the philosophy, achieving an accurate acetabular position for each clinical scenario is crucial. In this paper, we review the recent developments in improving the accuracy and ideal positioning of the acetabular cup in routine primary THA.

METHODOLOGY

A review of the recent scientific literature for acetabular cup placement in primary THA was performed, with available evidence for safe zones, spinopelvic relationship, preoperative planning, patient-specific instrumentation, navigation THA and robotic THA.

CONCLUSION

Though the applicability of Lewinnek safe zones has been questioned with an improved understanding of spinopelvic relationships, its role remains in positioning the acetabular cup in a patient with normal spinopelvic alignment and mobility. Evaluation of spinopelvic relationships and accordingly adjusting acetabular anteversion and inclination can significantly reduce the incidence of dislocation in patients with a rigid spine. In using preoperative radiography, the acetabular inclination, anteversion and intraoperative pelvic position should be evaluated. With improving technology and the advent of artificial intelligence, superior and more accurate preoperative planning is possible. Patient-specific instrumentation, navigated and robotic THA have been reported to improve accuracy in acetabular cup positioning as decided preoperatively but any significant clinical advantage over conventional THA is yet to be elucidated.

Defining and measuring objective and subjective spinal stiffness: a scoping review

PURPOSE

Examine and identify the breadth of definitions and measures of objective and subjective spinal stiffness in the literature, with a focus on clinical implications.

METHODS

A scoping review was conducted to determine what is known about definitions and measures of the specific term of spinal stiffness. Following the framework by Arksey and O'Malley, eligible peer-reviewed studies identified using PubMed, Ebsco health, and Scopus were included if they reported definitions or measures of spinal stiffness. Using a data abstraction form, the studies were classified into four themes: biomechanical, surgical, pathophysiological, and segmental spinal assessment. To identify similarities and differences between studies, sixteen categories were generated.

RESULTS

In total, 2426 records were identified, and 410 met the eligibility criteria. There were 350 measures (132 subjective; 218 objective measures) and 93 indicators of spinal stiffness. The majority of studies (n = 69%) did not define stiffness.

CONCLUSION

This review highlights the breadth of objective and subjective measures that are both clinically and methodologically diverse. There is no consensus regarding a standardised definition of stiffness in the reviewed literature.

Outcomes of Hip Arthroscopy in the Setting of Concomitant Symptomatic Lumbosacral Spine Pathology: A Matched Control Study With Minimum 24-Month Follow-up

BACKGROUND

The overlapping biomechanical relationship between the lumbosacral spine and pelvis poses unique challenges to patients with concomitant pathologies limiting spinopelvic range of motion.

PURPOSE

To assess the influence of concomitant, symptomatic lumbosacral spine pathology on patient-reported outcome measures (PROMs) after hip arthroscopy for the treatment of femoroacetabular impingement (FAI) and symptomatic labral tears.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective query of prospectively collected data identified patients aged ≥18 years with a minimum 24-month follow-up who underwent hip arthroscopy by a single surgeon for the treatment of symptomatic labral tears secondary to FAI. Patients were stratified into cohorts based on the presence (hip-spine [HS]) or absence (matched control [MC]) of symptomatic lumbosacral spine pathology. Inclusion within the HS cohort required confirmation of lower back pain/symptoms on preoperative surveys plus a diagnosis of lumbosacral spine pathology verified by radiology reports and correlating clinical documentation. Patients with previous spine surgery were excluded. PROMs were compared between groups, along with rates of achieving minimal clinically important difference (MCID) thresholds, Patient Acceptable Symptom State (PASS) thresholds, revision arthroscopy, and conversion to total hip arthroplasty (THA).

RESULTS

A total of 70 patients with lumbosacral pathology were coarsened exact matched to 87 control patients without spinal pathology. The HS cohort had preoperative baseline scores that were significantly worse for nearly all PROMs. Follow-ups at 3, 6, 12, and 24 months displayed similar trends, with the HS cohort demonstrating significantly worse scores for most collected outcomes. However, at every time point, HS and MC patients exhibited similar magnitudes of improvement across all PROM and pain metrics. Furthermore, while significantly fewer HS patients achieved PASS for nearly all PROMs at 12- and 24-month follow-ups, MCID thresholds were reached at similar or greater rates across all PROMs relative to the MC cohort. Finally, there were no significant differences in rates of revision or THA between cohorts at maximum available follow-up.

CONCLUSION

After hip arthroscopy to address labral tears in the setting of FAI, patients with symptomatic lumbosacral pathologies and no history of spine surgery were found to exhibit inferior pre- and postoperative PROMs but achieved statistically similar clinical benefit and rates of PROM improvement through 24-month follow-up compared with the MC cohort with isolated hip disease. These findings aid in providing a realistic recovery timeline and evidence that coexisting hip and spine disorders are not a contraindication for arthroscopic hip preservation surgery.

Increased Cup Anteversion May Not Prevent Posterior Dislocation in Patients With Abnormal Spinopelvic Characteristics in Total Hip Arthroplasty

Background

The aims of this study were to (1) assess the degree of variation in acetabular component placement and combined anteversion in a large cohort of dislocating total hip arthroplasties; (2) assess the spinopelvic characteristics of the cohort; and (3) examine the association between cup anteversion and reported direction of instability.

Methods

A commercial database of 245 dislocating total hip arthroplasties referred for postoperative computed tomography and functional radiographic imaging and analysis were reviewed. Spinopelvic parameters and cup and stem positions were measured in the supine, standing, flex-seated, and anterior pelvic plane (APP) positions. Spinopelvic characteristics were stratified by high, neutral, and low cup anteversion using thresholds of >35° and <15° anteversion in standing, respectively.

Results

In the dislocation cohort, 62%, 45%, and 42% of cups were within the safe zone in supine, standing, and the APP, respectively (P < .001). Patients with high vs neutral or low cup anteversion had significantly stiffer spines, more posterior pelvic tilt in standing, greater changes in pelvic tilt, and higher sagittal imbalance. Of the 45 patients with high cup anteversion and reported instability direction, 60% and 40% were reported to have posterior and anterior instability, respectively, with no differences in spinopelvic characteristics.

Conclusions

In this dislocating cohort, there is a decreased percentage of cups within the safe zone in the APP and standing position compared to the supine reference. In addition, we found that patients having poor spinopelvic characteristics and high cup anteversion can still dislocate, suggesting that adjusting cup anteversion alone may not be sufficient for preventing instability.

Current Concepts in Diagnosis and Management of Patients Undergoing Total Hip Replacement with Concurrent Disorders of Spinopelvic Anatomy: A Narrative Review

Despite the high success rate of primary total hip replacement (THR), a significant early revision rate remains, which is largely attributed to instability and dislocations. Despite the implants being placed according to the safe zone philosophy of Lewinnek, occurrence of THR dislocation is not an uncommon complication. Large diagnostic and computational model studies have shown variability in patients' mobility based on the individual anatomic and functional relationship of the hip-pelvis-spine complex. The absolute and relative position of hip replacement components changes throughout motion of the patient's body. In the case of spinopelvic pathology such as spine stiffness, the system reaches abnormal positional states, as shown with computerized models. The clinical result of such pathologic hip positioning is edge loading, implant impingement, or even joint dislocation. To prevent such complications, surgeons must change the dogma of single correct implant positioning and take into account patients' individualized anatomy and function. It is essential to broaden the standard diagnostics and their anatomical interpretation, and correct the pre-operative surgical planning. The need for correct and personalized implant placement pushes forward the development and adaptation of novel technologies in THR, such as robotics. In this current concepts narrative review, we simplify the spinopelvic biomechanics and pathoanatomy, the relevant anatomical terminology, and the diagnosis and management algorithms most commonly used today.

An Analysis of the Preoperative Factors, Spinopelvic Mobility and Sagittal Spinal Alignment in Pre-THA Patients

Hip arthroplasty is a very effective medical procedure. The optimal positioning of the components and the functioning of the endoprosthesis are influenced, among other things, by the mobility and balance of the spine. The aim of the study was to analyze the factors influencing the mobility of the lumbar-pelvic-iliac complex (spinopelvic mobility) together with the assessment of sagittal spinal alignment in patients prior to THA (total hip arthroplasty). Patients who underwent hip replacement surgery due to advanced osteoarthritis of the hip were enrolled in the study (n = 103). The sociodemographic characteristics, BMI, radiological advancement of the degenerative disease, quality of life, and range of joint mobility were completed using a proprietary questionnaire, the EQ-5D-5L questionnaire, and a clinical examination. X-ray images were analyzed: AP of the pelvis standing up, lateral of the spine standing and sitting. Key parameters were measured as ∆SS-change in sacrum angle value when changing from standing to sitting position and pelvic incidence (PI)-lumbar lordosis (LL) mismatch-sagittal lumbar pelvic balance measured in standing position. The patients were assigned to the appropriate groups according to the Hip-Spine Classification: normal group: 1A (n = 65; 63.1%), abnormal groups: 1B (n = 17; 16.5%), 2A (n = 16; 15.5%), 2B (n = 5; 4.9%). A correlation was shown between the abnormal groups and the individual components of PROMs in the scope of the self-service and normal activities categories (EQ-5D and EQ-VAS). However, the strength of the relationship turned out to be moderate, and the remaining components of the survey were statistically insignificant. The remaining factors analyzed, i.e., age, BMI, the range of hip motion, the presence of contracture in the joint in a clinical examination, and the radiological advancement of osteoarthritis on the Tonnis scale, do not predict abnormal relationships between the spine and the pelvis in our patients waiting for THA. Therefore, further investigations are needed to evaluate the correlation between preoperative factors and the lumbar-pelvic-iliac complex in patients prior to planned hip arthroplasty.

Patients Who Have Had Three or More Levels Fused During Lumbar Spinal Fusion Have Worse Functional Outcomes After Total Hip Arthroplasty

BACKGROUND

Lumbar spinal fusion (LSF) and total hip arthroplasty (THA) are commonly performed in patients who have concomitant spine and hip pathology. While patients who have three or more levels fused during LSF have increased postoperative opioid consumption after undergoing THA, it is unknown whether the number of levels fused during LSF affects THA functional outcomes.

METHODS

A retrospective study was conducted at a tertiary academic center for patients who underwent LSF first and then had a primary THA performed with a minimum of one-year follow-up for the Hip Disability and Osteoarthritis Outcome Score Joint Replacement (HOOS-JR). Operative notes were reviewed to determine the number of levels fused during LSF. There were 105 patients who underwent one-level LSF, 55 patients underwent two-level LSF, and 48 patients underwent three-or-more-level LSF. No significant differences existed in age, race, body mass index, and comorbidities between the cohorts.

RESULTS

While preoperative HOOS-JR was similar among the three cohorts, patients who had three-or-more-level LSF had significantly lower HOOS-JR scores than patients who had two-level or one-level LSF (71.4 versus 82.4 versus 78.2; P = .010) and a lower delta HOOS-JR (27.2 versus 39.4 versus 35.9; P = .014). Patients who had three-or-more-level LSF had a significantly lower rate of achieving minimal clinically important difference (61.7% versus 87.2% versus 78.7%; P = .011) and the patient acceptable symptom state (37.5% versus 69.1% versus 59.0%; P = .004) for the HOOS-JR, compared to patients who had two-level or one-level LSF, respectively.

CONCLUSIONS

Surgeons should counsel patients who have had three-or-more-level LSF that they may have a lower rate of hip function improvement and symptom acceptability after THA, compared to patients who have had a less number of levels fused during LSF.

Creating Consensus in the Definition of Spinopelvic Mobility

INTRODUCTION

The term "spinopelvic mobility" is most often applied to motion within the spinopelvic segment. It has also been used to describe changes in pelvic tilt between various functional positions, which is influenced by motion at the hip, knee, ankle and spinopelvic segment. In the interest of establishing a consistent language for spinopelvic mobility, we sought to clarify and simplify its definition to create consensus, improve communication, and increase consistency with research into the hip-spine relationship.

METHODS

A literature search was performed using the Medline (PubMed) library to identify all existing articles pertaining to spinopelvic mobility. We reported on the varying definitions of spinopelvic mobility including how different radiographic imaging techniques are used to define mobility.

RESULTS

The search term "spinopelvic mobility" returned a total of 72 articles. The frequency and context for the varying definitions of mobility were reported. 41 papers used standing and upright relaxed-seated radiographs without the use of extreme positioning, and 17 papers discussed the use of extreme positioning to define spinopelvic mobility.

DISCUSSION

Our review suggests that the definitions of spinopelvic mobility is not consistent in the majority of published literature. We suggest descriptions of spinopelvic mobility independently consider spinal motion, hip motion, and pelvic position, while recognizing and describing their interdependence.

"Incidence of Instability Following Primary Total Hip Arthroplasty Continues to Decline in the Medicare Population"

BACKGROUND

Instability has been the primary cause of failure following primary total hip arthroplasty (THA) leading to revision hip surgery. The purpose of this study was to determine if instability rates have further declined following advances in primary THA including dual mobility articulations, direct anterior approaches, advanced technologies, and improved knowledge of the hip-spine relationships.

METHODS

Using the 5% Medicare Part B claims data from 1999 to 2019, we identified 81,573 patients who underwent primary THA for osteoarthritis. Patients who experienced instability at 3 months, 6 months, 1 year, and 2 years were identified. Multivariate cox regression analyses evaluated the effect of patient and procedure characteristics on the risk for instability.

RESULTS

Instability at 1 year following primary THA declined from approximately 4% in 2000 to 2.3% in 2010 and 1.6% in 2018. The leading cause of revision surgery was infection (18.6%), followed by peri-prosthetic fracture (14%), mechanical loosening (11.5%), and instability (9.4%). High risk groups for instability continue to include increased age, higher Charlson index, obesity, lumbar spine pathology, and neurocognitive disorders.

CONCLUSION

Instability is no longer the leading etiology of failure following primary THA with a decline of approximately 40% over the past decade. Infection, periprosthetic fracture, mechanical loosening, and then instability are now the leading causes of failure. Multiple factors may play a role in the decline of instability including increased use of dual mobility articulations, direct anterior approaches, improved knowledge of the hip-spine relationships, and use of advanced technologies.

Sacral Slope Change From Standing to Relaxed-Seated Grossly Overpredicts the Presence of a Stiff Spine

BACKGROUND

Several authors propose that a change in sacral slope of ≤10° between the standing and relaxed-seated positions (ΔSS_{standing→relaxed-seated}) identifies a patient with a stiff lumbar spine and has suggested the use of dual-mobility bearings for such patients undergoing a total hip arthroplasty (THA). The aim of this study was to assess how accurately ΔSS_{standing→relaxed-seated} can identify patients with a stiff spine.

METHODS

A prospective, multicentre, consecutive cohort series of 312 patients had standing, relaxed-seated, and flexed-seated lateral radiographs prior to THA. ΔSS_{standing→relaxed-seated} was determined by the change in sacral slope between the standing and relaxed-seated positions. Lumbar flexion (LF) was defined as the difference in lumbar lordotic angle between standing and flexed-seated. LF ≤20° was considered a stiff spine. The predictive value of ΔSS_{standing→relaxed-seated} for characterizing a stiff spine was assessed.

RESULTS

A weak correlation between ΔSS_{standing→relaxed-seated} and LF was identified (r² = 0.13). Eighty six patients (28%) had ΔSS_{standing→relaxed-seated} ≤10° and 19 patients (6%) had a stiff spine. Of the 86 patients with ΔSS_{standing→relaxed-seated} ≤10°, 13 had a stiff spine. The positive predictive value of ΔSS_{standing→relaxed-seated} ≤10° for identifying a stiff spine was 15%.

CONCLUSION

In this cohort, ΔSS_{standing→relaxed-seated} ≤10° was not correlated with a stiff spine. Using this simplified approach could lead to a 7-fold overprediction of patients with a stiff lumbar spine and abnormal spinopelvic mobility, unnecessary use of dual-mobility bearings, and incorrect component alignment targets. Referring to patients with ΔSS_{standing→relaxed-seated} ≤10° as being stiff is misleading. The flexed-seated position should be used to effectively assess a patient's spine mobility prior to THA.

Risk of Dislocation and Revision Following Primary Total Hip Arthroplasty in Patients With Prior Lumbar Fusion With Spinopelvic Fixation

BACKGROUND

The effect of spinopelvic fixation in addition to lumbar spinal fusion (LSF) on dislocation/instability and revision in patients undergoing primary total hip arthroplasty (THA) has not been reported previously.

METHODS

The PearlDiver Research Program was used to identify patients aged 30 and above undergoing primary THA who received (1) THA only, (2) THA with prior single-level LSF, (3) THA with prior 2-5 level LSF, or (4) THA with prior LSF with spinopelvic fixation. The incidence of THA revision and dislocation/instability was compared through logistic regression and Chi-squared analysis. All regressions were controlled for age, gender, and Elixhauser Comorbidity Index (ECI).

RESULTS

Between 2010 and 2018, 465,558 patients without history of LSF undergoing THA were examined and compared to 180 THA patients with prior spinopelvic fixation, 5,299 with prior single-level LSF, and 1,465 with prior 2-5 level LSF. At 2 years, 7.8% of THA patients with prior spinopelvic fixation, 4.7% of THA patients with prior 2-5 level LSF, 4.2% of THA patients with prior single-level LSF, and 2.2% of THA patients undergoing only THA had a dislocation event or instability (P < .0001). After controlling for length of fusion, pelvic fixation itself was associated with higher independent risk of revision (at 2 years: 2-5 level LSF + spinopelvic fixation: aHR = 3.15, 95% CI 1.77-5.61, P < .0001 vs 2-5 level LSF with no spinopelvic fixation: aOR = 1.39, 95% CI 1.10-1.76, P < .0001).

CONCLUSION

At 2 years, spinopelvic fixation in THA patients were associated with a greater than 3.5-fold increase in hip dislocation risk compared to those without LSF, and an over 2-fold increase in THA revision risk compared to those with LSF without spinopelvic fixation.

LEVEL OF EVIDENCE

III.

Total knee arthroplasty in patients with lumbar spinal fusion leads to significant changes in pelvic tilt and sacral slope

BACKGROUND

The knee-hip-spine syndrome has been well elucidated in the literature in recent years. The aim of this study was to evaluate the effect of total knee arthroplasty (TKA) on spinopelvic sagittal alignment in patients with and without pre-TKA lumber spinal fusion.

METHODS

This is a retrospective cohort study of 113 patients who underwent TKA for primary osteoarthritis. Patients were stratified into the following three groups: (1) patients who had pre-TKA spinal fusion (SF, n = 19), (2) patients who had no spinal fusion but experienced pre-TKA flexion contracture (FC, n = 20), and (3) patients without flexion contracture or spinal fusion before TKA (no SF/FC, n = 74). Spinopelvic sagittal alignment parameters, including pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and plumb line-sacrum distance (SVA) were measured preoperatively and 3 months postoperatively on lateral standing full-body low-dose images.

RESULTS

TKA resulted in significant pre- to postoperative changes in pelvic tilt (average ∆ PT = - 8.6°, p = 0.018) and sacral slope (average ∆ SS = 8.6°, p = 0.037) in the spinal fusion (SF) group. Non-significant changes in spinopelvic sagittal alignment parameters (PT, SS, LL, TK, SVA) were noted postoperatively in all patients in the FC and the no SF/FC groups.

CONCLUSIONS

TKA can lead to meaningful changes in spinopelvic alignment in patients with prior lumbar fusion compared to those without spinal fusion. Patients with spinal fusion who are candidates for both hip and knee replacements should consider undergoing TKA first since changes in spinopelvic sagittal alignment can increase the risk of future complications.

LEVEL III EVIDENCE

Retrospective Cohort Study.

Functional safe zone for THA considering the patient-specific pelvic tilts: An ultrasound-based approach

The usual Lewinnek orientation for cup positioning in total hip arthroplasty is not suitable for all patients as it does not consider the patient mobility. We propose an ultrasound-based approach to compute a Functional Safe Zone (FSZ) considering daily positions. Our goal was to validate it, and to evaluate how the input parameters impact the FSZ size and barycentre. The accuracy of the FSZ was first assessed by comparing the FSZ computed by the proposed approach and the true FSZ determined by 3D modelling. Then, the input parameters' impact on the FSZ was studied using a principal component analysis. The FSZ was estimated with errors below 0.5° for mean anteversion, mean inclination, and at edges. The pelvic tilts and the neck orientation were found correlated to the FSZ mean orientation, and the target ROM and the prosthesis dimensions to the FSZ size. Integrated into the clinical workflow, this non-ionising approach can be used to easily determine an optimal patient-specific cup orientation minimising the risks of dislocation.

The Correlation Between Pelvic Motion and Lumbar Motion in Patients Presenting With a Lumbar Spinal Pathology: Implications for Assessing Dislocation Risk in Total Hip Arthroplasty

Background

Arthroplasty surgeons use the change in sacral slope (ΔSS) from sitting to standing as a measure of spinal motion. The relationship between ΔSS and the change in lumbar lordosis (ΔLL), an established spinal motion measure, has not been well studied. This study aims to determine the correlation between ΔSS and ΔLL.

Methods

Consecutive patients presenting to a spine clinic from 2020 to 2021 at a single institution were retrospectively studied. Standing and sitting lateral radiographs were measured for SS and LL. Patients were divided using ΔSS and ΔLL into stiff (0°-9°), normal (10°-30°), or hypermobile (>30°) category. Patients with a ΔSS-determined normal or hypermobile spine but a ΔLL-determined stiff spine were compared to the rest of the cohort.

Results

Overall, 100 patients were included. Of these patients, 47% had the same classification when looking at ΔSS and ΔLL, whereas 53% had conflicting classifications. Twenty percent of patients had a ΔSS-determined normal or hypermobile spine but ΔLL-determined stiff spine. The correlation between ΔSS and ΔLL was 0.510 (P < .001). When isolating patients who underwent lumbar fusion, the correlation between ΔSS and ΔLL was 0.345 (P < .001).

Conclusions

ΔSS has a moderate correlation with ΔLL in patients presenting for evaluation of their lumbar spine but low correlation in patients with lumbar fusion. In our cohort, 20% of patients had a ΔSS-determined normal or hypermobile spine but a ΔLL-determined stiff spine, representing a potential high-risk dislocation cohort not captured by ΔSS alone. Arthroplasty surgeons should revisit classifying spinal motion based solely on ΔSS.

Posterior Approach Total Hip Arthroplasty Utilizing a Monoblock Dual-Mobility Construct Without Posterior Hip Precautions: A Series of 580 Hips with One Dislocation

BACKGROUND

Instability remains a devastating complication following total hip arthroplasty (THA). Here we describe a mini-posterior approach with a monoblock dual-mobility implant without "traditional posterior hip precautions" yielding excellent results.

METHODS

There were 580 consecutive hips in 575 patients who underwent THA utilizing a monoblock dual-mobility implant and a mini-posterior approach. With this technique, the acetabular component positioning does not rely on tradition intra-operative radiographic abduction and anteversion goals, but rather uses patient-specific anatomic landmarks (anterior acetabular rim and, when visible, the transverse acetabular ligament) to set cup position; stability is assessed with a significant, dynamic intra-operative test of range of motion. Patients' mean age was 64 years (range, 21 to 94) and 53.7% were women.

RESULTS

Mean abduction was 48.4° (range, 29° to 68°) and mean anteversion was 24.7° (range, -1 to 51°). Patient Reported Outcomes Measurement Information System scores improved in every measured domain from preoperative to final postoperative visit. There were seven (1.2%) patients who required reoperation, with mean time to reoperation of 1.3 months (range, one to 176 days). Only one patient (0.2%) who had a pre-operative history of spinal cord injury and Charcot arthropathy dislocated.

CONCLUSION

A posterior approach hip surgeon may want to consider using a monoblock dual-mobility construct and avoidance of traditional posterior hip precautions to achieve early hip stability with an extremely low dislocation rate and high patient satisfaction scores.

Association of age and spinopelvic function in patients receiving a total hip arthroplasty

Restricted spinopelvic mobility received attention as a contributing factor for total hip arthroplasty (THA) instability. However, it is still unknown, how the spinopelvic function is influenced by age. In identifying the patients at highest risk for altered spinopelvic mechanics the study aimed to determine the association of age on the individual segments of the spinopelvic complex and global spinal sagittal alignment in patients undergoing THA. 197 patients were included in the prospective observational study conducting biplanar stereoradiography (EOS) in standing and sitting position pre-and postoperatively. Two independent investigators assessed C7-sagittal vertical axis (C7-SVA), cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), anterior plane pelvic tilt (APPT), and pelvic femoral angle (PFA). Key segments of the spinopelvic complex are defined as lumbar flexibility (∆ LL = LL_standing - LL_sitting), pelvic mobility (∆ SS = SS_standing - SS_sitting) and hip motion (∆ PFA = PFA_standing - PFA_sitting). Pelvic mobility was further defined based on ∆ SS = SS_standing - SS_sitting as stiff (∆ SS < 10°), normal (∆ SS ≥ 10°-30°) and hypermobile (∆ SS > 30°). The patient collective was classified into three groups: (1) < 60 years (n = 56), (2) ≥ 60-79 years (n = 112) and (3) ≥ 80 years (n = 29). Lumbar flexibility (∆ LL) was decreased with increasing age between all groups (36.1° vs. 23.1° vs. 17.2°/p₁₊₂ < 0.000, p₂₊₃ = 0.020, p₁₊₃ < 0.000) postoperatively. Pelvic mobility (∆ SS) was decreased in the groups 2 and 3 compared to group 1 (21.0° and 17.9° vs. 27.8°/p₁₊₂ < 0.000, p₂₊₃ = 0.371, p₁₊₃ = 0.001). Pelvic retroversion in standing position (APPT) was higher in group 2 and 3 compared to group 1 (1.9° and - 0.5° vs 6.9°/p₁₊₂ < 0.000, p₂₊₃ = 0.330, p₁₊₃ < 0.000). Global sagittal spinal balance (C7-SVA) showed more imbalance in groups 2 and 3 compared to group 1 (60.4 mm and 71.2 mm vs. 34.5 mm/p₁₊₂ < 0.000, p₂₊₃ = 0.376, p₁₊₃ < 0.000) postoperatively. The preoperative proportion of patients with stiff pelvic mobility in group 1 was distinctly lower than in group 3 (23.2% vs. 35.7%) and declined in group 1 to 1.8% compared to 20.7% in group 3 after THA. Changes after THA were reported for groups 1 and 2 representing spinopelvic complex key parameter lumbar flexibility (∆ LL), pelvic mobility (∆ SS) and hip motion (∆ PFA), but not for group 3. This is the first study to present age-adjusted normative values for spinopelvic mobility. The subgroups with increased age were identified as risk cohort for altered spinopelvic mechanics and enhanced sagittal spinal imbalance and limited capacity for improvement of mobility after THA. This valuable information serves to focus in the preoperative screening on the THA candidates with the highest risk for abnormal spinopelvic function.

Pubic Symphysis to Sacrococcygeal Joint: A Poor Correlate to Other Spinopelvic Measurements

BACKGROUND

The hip-spine relationship is increasingly recognized as critical for optimizing stability following total hip arthroplasty (THA). However, these measurements are not routinely obtained during THA workup. It has been suggested that insight can be gained from supine antero-posterior pelvis radiograph, measuring the distance from the superior border of the pubic symphysis to the sacro-coccygeal joint (PSCD). This study assessed the correlation between PSCD and lateral lumbar radiographic metrics in a cohort of preoperative THA patients.

METHODS

We retrospectively evaluated 250 consecutive patients who underwent THA with preoperative supine antero-posterior pelvis and lateral lumbar radiographs. The mean age was 68 years (range, 42 to 89), 61% were women, and the mean body mass index was 30 kg/m² (range, 19 to 52). Two reviewers measured PSCD, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), and lumbar lordosis (LL). Inter-observer reliability was calculated for all measurements, and correlation coefficients were calculated for PSCD with respect to PT, SS, PI, and LL.

RESULTS

Correlations between PSCD and lumbar radiographic metrics were all statistically significant, except for PI in men but graded as "weak" or "very weak" for men and women, respectively, as follows: PT = -0.30 (P < .01) and -0.46 (P < .01); SS = 0.27 (P < .01) and 0.22 (P < .01); PI = -0.04 (P = .70) and -0.19 (P = .02); and LL = 0.45 (P < .01) and 0.30 (P < .01). Inter-observer reliability was graded as "strong" for every metric.

CONCLUSION

The PSCD was weakly correlated with all evaluated lateral lumbar radiographic metrics in both sexes, despite strong inter-observer reliability. Therefore, PSCD cannot reliably serve as a proxy for evaluating the hip-spine relationship.

Functional implant positioning in total hip arthroplasty and the role of robotic-arm assistance

INTRODUCTION

Accurate implant positioning, tailored to the phenotype and unique biomechanics of each patient is the single most important objective in achieving stability in THA and maximise range of motion. The spine-pelvis-hip construct functions as a single unit adapting to postural changes. It is widely accepted in the literature that no universaltarget exists and variations in spinopelvic mobility mandate adjustments to the surgical plan; thus bringing to the fore the concept of personalised, functional component positioning.

METHODS

This manuscript aims to outline the challenges posed by spinopelvic imbalance and present a reproducible, stepwise approach to achieve functional-component positioning. We also present the one-year functional outcomes and Patient Reported Outcome Measures of a prospective cohort operated with this technique.

RESULTS AND CONCLUSION

Robotic-arm assisted Total Hip Arthroplasty has facilitated enhanced planning based on the patient's phenotype and evidence suggests it results in more reproducible and accurate implant positioning. Preservation of offset, avoiding leg-length discrepancy, accurate restoration of the centre of rotation and accomplishing the combinedversion target are very important parameters in Total Hip Arthroplasty that affect post-operative implant longevity, patient satisfaction and clinical outcomes.

Perioperative management of leg-length discrepancy in total hip arthroplasty: a review

Leg-length discrepancy (LLD) presents a significant management challenge to orthopedic surgeons and remains a leading cause of patient dissatisfaction and litigation after total hip arthroplasty (THA). Over or under-lengthening of the operative extremity has been shown to have inferior outcomes, such as dislocation, exacerbation of back pain and sciatica, and general dissatisfaction postoperatively. The management of LLD in the setting of THA is multifactorial, and must be taken into consideration in the pre-operative, intra-operative, and post-operative settings. In our review, we aim to summarize the best available practices and techniques for minimizing LLD through each of these phases of care. Pre-operatively, we provide an overview of the appropriate radiographic studies to be obtained and their interpretation, as well as considerations to be made when templating. Intra-operatively, we discuss several techniques for the assessment of limb length in real time, and post-operatively, we discuss both operative and non-operative management of LLD. By providing a summary of the best available practices and strategies for mitigating the impact of a perceived LLD in the setting of THA, we hope to maximize the potential for an excellent surgical and clinical outcome.

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

OBJECTIVE

We sought to correlate various spinopelvic and lower limb alignments, and to examine the current spinopelvic theories on a Chinese cohort.

METHODS

We 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.

RESULTS

PT, 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).

CONCLUSION

THA 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 KNOWLEDGE

This study provides new insights into the clinical relevance of lower limb alignments to spinopelvic motion after THA in a relatively young Chinese population.

Spinal pathology and outcome post-THA: does segment of arthrodesis matter?

INTRODUCTION

The presence of lumbar spine arthrodesis (SA) is associated with abnormal spinopelvic characteristics and inferior outcome post total hip arthroplasty (THA). However, whether patients with upper segment SA are also at increased risk of complications is unknown. This study aims to (1) determine if upper segment SA is associated with inferior THA outcomes; (2) assess spino-pelvic characteristics; and (3) test whether static or dynamic spinopelvic characteristics correlate with outcome post-THA.

MATERIALS AND METHODS

In this retrospective, case-matched, cohort study from a tertiary referral centre, 40 patients (59 hips) that had undergone both THA and any level of spinal arthrodesis (49 THA-Lumb and 10 THA-Cerv) were compared with 41 patients (59 hips) who had THA-only without known spinal pathology. Spino-pelvic characteristics [including severity of Degenerative-Disc-Disease (DDD); spinal balance and stiffness] and outcome, including patient reported outcome measures (PROMs), at minimum of 1-year post-THA were assessed.

RESULTS

THA-Lumb and THA-Cerv groups had greater number of complications and inferior hip and spinal PROMs compared to THA-Only (p < 0.001). Similar spinopelvic characteristics were seen between the THA-Cerv and THA-Lumb, which were significantly different to the THA-only group. The presence of DDD and unbalanced or stiff spine was associated with increased dislocation and inferior PROMs in the whole cohort.

CONCLUSIONS

THA in the presence of SA, regardless of level, is associated with inferior outcomes and an increased risk for dislocation. The presence of a SA is associated with increased risk of adverse spinopelvic characteristics. Such characteristics were strongly associated with increased dislocation-risk and inferior PROMs. It is likely that these adverse characteristics are the most important adverse predictor, rather than segment of SA per se.

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.

Does Total Hip Arthroplasty Affect Spinopelvic and Spinal Alignment?: A Prospective Observational Investigation

STUDY DESIGN

A prospective observational study, level of evidence 3.

OBJECTIVES

The study with patients undergoing unilateral total hip arthroplasty (THA) aimed to evaluate the following hypotheses: (1) the spinal sagittal and coronal alignment alters due to THA, (2) the spinopelvic parameter changes after THA, (3) the spinopelvic alignment differs between sagittal balanced and imbalanced patients.

SUMMARY OF BACKGROUND DATA

Surgical correction of spinal sagittal misalignment affects the spinopelvic alignment and pelvic tilt. It is not yet known to what extent THA affects spinopelvic, spinal sagittal, and coronal alignment.

MATERIALS AND METHODS

A total of 153 patients undergoing THA were assessed with biplanar stereoradiography in standing position preoperatively and postoperatively. Two independent investigators examined C7-sagittal vertical axis (C7-SVA), pelvic incidence-lumbar lordosis (PI-LL) mismatch, lumbar lordosis (LL), C7-central sacral vertical line, pelvic oblique angle lumbosacral, intra-pelvic oblique angle, pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), anterior plane pelvic tilt (APPT), and pelvic femoral angle (PFA). An analysis of the sagittal misaligned subgroups of C7-SVA and PI-LL on the influence of the spinopelvic alignment was performed.

RESULTS

A significant difference in spinopelvic parameters was detected in the preoperative to postoperative comparison (SS, PT, APPT, and PFA; P <0.000) ( d =-0.394; d =0.609; d =-0.481; d =0.431). The coronal alignment and pelvic obliquity revealed no significant differences. The misaligned groups (C7-SVA; PI-LL) demonstrated significant increases in PI and PT and decreased in LL compared with the groups with normal sagittal alignment. Preoperatively, 66/153 (C7-SVA) and 46/153 (PI-LL) of the THA patients presented sagittal misalignment, respectively.

CONCLUSIONS

The results suggest an effect of THA on sagittal spinal and spinopelvic alignment, with a significant reduction of PT postoperatively and no effect on coronal alignment. Particularly striking are the significant differences in the misaligned groups, which may be classified as risk population and potentially can contribute biomechanically to a higher risk of posterior impingement and anterior THA dislocation. The substantial proportion of sagittal misaligned patients in the THA collective illustrates the crucial need for interdisciplinary collaboration.

Does spinopelvic motion change after total hip arthroplasty?

PURPOSE

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.

METHODS

A total of 76 patients (88 hips) were assessed. To classify spinopelvic mobility, defined as a change in SS from standing to sitting position (ΔSS_stand/sit), 10° ≤ ΔSS_stand/sit ≤ 30°, ΔSS_stand/sit < 10°, and ΔSS_stand/sit > 30° were considered normal, stiff, and hypermobile, respectively.

RESULTS

Over ± 7° changes in SS between before and one year 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 one year after THA were significantly different (p = 0.034 and p = 0.016, McNemar's test). At one year 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.

CONCLUSIONS

Change in SS between before THA and one year 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.

Periprosthetic joint infection rates across primary total hip arthroplasty surgical approaches: a systematic review and meta-analysis of 653,633 procedures

INTRODUCTION

Evidence demonstrates comparable clinical outcomes across the various surgical approaches to primary total hip arthroplasty (THA). However, high-quality contemporary data regarding periprosthetic joint infection (PJI) risk between direct anterior approach (DAA) and other (THA) approaches is lacking. This systematic review and meta-analysis evaluated PJI rates reported in the literature between the DAA and other approaches.

MATERIALS AND METHODS

Five online databases were queried for all studies published from January 1st, 2000 through February 17th, 2021 that reported PJI rates between DAA and other surgical approaches. Studies reporting on primary THAs for osteoarthritis (OA) and that included PJI rates segregated by surgical approach were included. Articles reporting on revision THA, alternative THA etiologies, or minimally invasive techniques were excluded. Mantel-Haenszel (M-H) models were utilized to evaluate the pooled effect of surgical approach on infection rates. Validated risk of bias and methodological quality assessment tools were applied to each study. Multiple sensitivity analyses were conducted to evaluate the robustness of analyses.

RESULTS

28 articles reporting on 653,633 primary THAs were included. No differences were found between DAA cohorts and combined other approaches (OR: 0.95; 95% CI 0.74-1.21; p = 0.67) as well as segregated anterolateral approach cohorts (OR: 0.82, 95% CI 0.64-1.06; p = 0.13). However, DAA patients had a significantly reduced risk of infection compared to those undergoing posterior (OR: 0.66, 95% CI 0.58-0.74; p < 0.0001) and direct lateral (OR: 0.56, 95% CI 0.48-0.65; p < 0.00001) approaches.

CONCLUSION

The DAA to primary THA had comparable or lower PJI risk when compared to other contemporary approaches. The results of the most up-to-date evidence available serve to encourage adult reconstruction surgeons who have already adopted the DAA. Additionally, orthopaedic surgeons considering adoption or use of the direct anterior approach for other reasons should not be dissuaded over theoretical concern for a general increase in the risk of PJI.

LEVEL OF EVIDENCE

Level III.

Relationship Between Sacroiliac Joint-related Pain and Spinopelvic Mobility

STUDY DESIGN

A case-control study.

OBJECTIVE

To evaluate the relationship between sacroiliac joint-related pain (SIJ-RP) and spinopelvic mobility.

SUMMARY OF BACKGROUND DATA

No specific radiological findings are available for the diagnosis of SIJ-RP. A previous study reported that a higher pelvic incidence and sacral slope (SS) values were significantly associated with sacroiliac joint pain. The concept of spinopelvic mobility, which is evaluated by the differences between SS in the standing and sitting positions, has been the focus of hip and spine surgeries in recent years.

MATERIALS AND METHODS

The SIJ-RP group comprised patients diagnosed with SIJ-RP based on physical findings and their response to analgesic injections. No other lumbar or hip joint diseases were observed. The non-SIJ-RP group comprised patients with lower back pain for reasons other than SIJ-RP. Radiographs of the lateral view of the pelvis in the standing and sitting positions were evaluated for all patients. We compared and analyzed the backgrounds, SS in the two positions, and difference in SS between the two positions in both groups.

RESULTS

In total, 245 patients were included in the study, with 49 and 196 patients in the SIJ-RP and non-SIJ-RP groups, respectively. More female patients experienced SIJ-RP than male patients ( P =0.0361). There were significant differences between the groups for SS in standing ( P =0.0076), sitting ( P =0.0005), and those with a difference between sitting and standing of <5° ( P =0.0278) in the univariate analyses. Logistic regression analyses, after adjustment for age and sex, revealed significant differences between the groups with an SS difference <5° ( P =0.0088; 95% confidence interval, 1.280-5.519), with an odds ratio of 2.7.

CONCLUSION

On evaluating spinopelvic mobility, we found that SIJ-RP was related to hypomobility of the sacrum, which could indicate the hypermobility of the sacroiliac joint.

Occupational Hazards to the Joint Replacement Surgeon: How Can Technology Help Prevent Injury?

Occupational hazards pose varying threats to the joint replacement surgeon. Musculoskeletal pain due to the repetitive nature of performing joint arthroplasty is felt daily by most surgeons. The purpose of this paper is to offer a basic introduction and demonstrate the many ways technology utilized during total joint arthroplasty can help mitigate common occupational hazards for the arthroplasty surgeon. This paper guides readers through the evolution and drivers behind technology in joint arthroplasty, describes several technologies currently available, and discusses how certain aspects of this technology may work to improve surgeon and patient outcomes. We review how advanced technologies in arthroplasty may reduce physical and mental demand, improve reproducibility, and decrease complications. The decision to utilize advanced technology in joint arthroplasty is ultimately made on an individual level after careful consideration of available literature.

Association between sagittal spinal alignment and mechanical complications after primary total hip arthroplasty: a systematic review

Objective

Total hip arthroplasty (THA) affects pelvic posture and spinal alignment. These postural changes may further predispose patients to mechanical complications (MCs) after THA. The aim of this study was to conduct a systematic review to investigate whether any high-quality studies have assessed the association between sagittal spinal alignment and MCs after primary THA.

Methods

Inclusion criteria for studies were adult patients (age ≥18 years), primary THA, pre- and postoperative spinopelvic standing sagittal radiographs acquired preoperatively and at a minimum of 6-month follow-up, measurements of spinopelvic parameters, and reporting of possible MCs after THA. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Results

Six articles met the inclusion criteria. Although several studies confirmed the importance of spinal alignment when planning THA, these mainly investigated pelvic mobility as a risk factor for THA dislocation. Radiological follow-up imaging practices varied, and studies focused on different individual spinopelvic parameters.

Conclusion

Based on our study findings, no conclusions can be drawn regarding the association between sagittal spinal alignment and MCs after primary THA. Further research is needed to improve our knowledge of the connection between MCs after THA and sagittal spinal alignment.

Does Low Back Pain Improve Following Total Hip Arthroplasty?

BACKGROUND

Frequently, patients indicated for total hip arthroplasty (THA) present with low back pain (LBP) and hip pain. The purpose of this study was to compare patients whose back pain resolved after THA with those where back pain did not resolve and identify how to predict this using spinopelvic parameters.

METHODS

We reviewed a series of 500 patients who underwent THA for unilateral hip osteoarthritis by 2 surgeons. Patients underwent biplanar standing and sitting EOS radiographs pre-operatively. Patients with previous spine surgery or femoral neck fracture were excluded. Demographic data was analyzed at baseline. The Oswestry Disability Index (ODI) scores were calculated pre-operatively and at 1 year postoperatively. Spinopelvic parameters included, pelvic incidence and sacral slope (SS) change from standing to sitting.

RESULTS

Two hundred and four patients (41%) had documented LBP before THA. The Oswestry Disability Index (ODI) for patients improved from 38.9 ± 17.8 pre-operatively to 17.0 ± 10.6 at 1 year post-operatively (P < .001). At 1- and 2-year follow-up, resolution of back pain occurred in 168 (82.4%) and 187 (91.2%) patients, respectively. Pelvic incidence was not predictive of back pain resolution. All patients whose back pain resolved had a sacral slope change from standing to sitting of >10°, while those patients whose back pain did not resolve had a change of <10°.

CONCLUSION

This study demonstrates that symptomatic low back pain (LBP) resolves in 82% of patients after THA. The results of this study may be used to counsel patients on back pain and its resolution following total hip replacement.

Spinopelvic Mobility Pattern and Acetabular Anteversion in Stiff Hips With Ankylosing Spondylitis After Total Hip Arthroplasty

BACKGROUND

Fused hips with spine stiffness in ankylosing spondylitis (AS) reduce spinopelvic mobility. We aimed to assess spinopelvic mobility pattern and acetabular anteversion in AS after total hip arthroplasty (THA).

MATERIAL AND METHODS

Ninety-four stiff hips in 58 AS individuals (mean age: 37.05) who underwent THA between 2012 and 2018 with a modified lateral approach were included. Twenty-three hips were fused, and 71 hips had mean flexion of 37.67°. Pelvic tilt, pelvic inclination, sacral slope (SS), and lumbar lordosis were correlated with THA, and functional outcomes were assessed at 34.6-month mean follow-up.

RESULTS

Thirty-seven had a stuck sitting pattern with stuck standing seen in 4 individuals. SS standing before and after THA were 25.08° and 27.30°. SS sitting was 8.99° compared to 16.80°. SS from sitting to standing was reduced (17.7°) in 17 individuals. Spine stiffness in extension was seen in 4 out of 37. Mean acetabular inclination after THA was 42.67°, and acetabular anteversion was 17.48°. Flexion after THA improved to mean 98.47°. Changes in SS from sitting to standing were correlated with THA (r-value: 0.93, P-value: .0001). The Harris Hip Score improved from 25.31 to 82.39 (P-value <.05), and the mean 12-item Short Form Survey at review was 52.18 and 59.55 (physical and mental components). The mean Western Ontario and Mc Master Universities Arthritis Index score was 17.56.

CONCLUSIONS

Spinopelvic mobility change was <10° after THA in AS, stuck sitting was seen in 37 of 58 (63.8%), and stuck standing was seen in 4 of 58 (6.9%), including spine stiffness in flexion or extension. Acetabular anteversion assessed was 17.48° (standard deviation: 4.41), with significant functional improvement.

LEVEL OF EVIDENCE

Level 4.

Total hip arthroplasty has higher complication rates in stiff spine patients: a systematic review and network meta-analysis

Background

Ankylosing spondylitis (AS) and spinal fusion (SF) classified as stiff spines have been associated with the increased rate of complications following total hip arthroplasty (THA). However, the differences between the two cohorts have inconsistent evidence.

Methods

We searched for studies comparing complications among stiff spine patients, including SF and AS, who underwent THA in PubMed/MEDLINE, Embase, Cochrane CENTRAL, Web of Science, and Scopus until March 2021. Studies detailing rates of mechanical complications, aseptic loosening, dislocation, infection, and revisions were included. We performed network meta-analyses using frequentist random-effects models to compare differences between cohorts. We used P-score to rank the better exposure with the lowest complications.

Results

Fourteen studies were included in the final analysis. A total of 740,042 patients were included in the systematic review and network meta-analysis. Mechanical complications were highest among SF patients (OR 2.33, 95% CI 1.86, 2.92, p < 0.05), followed by AS patients (OR 1.18, 95% CI 0.87, 1.61, p = 0.82) compared to controls. Long Spinal Fusions had the highest aseptic loosening (OR 2.33, 95% CI 1.83, 2.95, p < 0.05), dislocations (OR 3.25, 95% CI 2.58, 4.10, p < 0.05), infections (OR 2.14, 95% CI 1.73, 2.65, p < 0.05), and revisions (OR 5.25, 95% CI 2.23, 12.32, p < 0.05) compared to AS and controls. Our results suggested that SF with longer constructs may be associated with higher complications in THA patients.

Conclusions

THAs following SFs have higher mechanical complications, aseptic loosening, dislocations, and infections, especially with longer constructs. AS patients may have fewer complications compared to this cohort.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03237-8.

Effect of Coronal and Sagittal Spinal Malalignment on Spinopelvic Mobility in Patients Undergoing Total Hip Replacement: A Prospective Observational Study

STUDY DESIGN

This was a prospective observational study.

OBJECTIVE

This investigation aimed (1) to determine the impact of sagittal spinal alignment with C7-sagittal vertical axis (SVA), pelvic incidence-lumbar lordosis (PI-LL) mismatch and Roussouly classification on individual segments of spinopelvic mobility represented by lumbar flexibility [∆lumbar lordosis (LL)], pelvic mobility [∆pelvic tilt (PT)], and hip motion [∆pelvic femoral angle (PFA)] and (2) to assess the influence of coronal spinal balance on the spinopelvic complex in patients undergoing total hip arthroplasty (THA) preoperatively and postoperatively.

SUMMARY OF BACKGROUND DATA

Restricted spinopelvic mobility gained attention as a contributing factor for THA instability. However, it remains unclear what influence the coronal and sagittal spinal alignment has on spinopelvic mobility.

MATERIALS AND METHODS

A total of 197 THA patients were included in the investigation conducting biplanar stereoradiography in standing and sitting position preoperatively and postoperatively. Two independent investigators assessed C7-SVA (≤50 mm balanced, >50 mm imbalanced), PI-LL (≤10 degrees balanced, >10 degrees imbalanced), refounded Roussouly classification, coronal spinal balance with C7-central sacral vertical line, LL, pelvic incidence (PI), PT, PFA. Individual segments of spinopelvic mobility based on the change from standing to sitting were defined as ∆LL, ∆PT, and ∆PFA. Unpaired t test or Welch t test for comparison between groups of 2 was applied. Analysis of variance and post hoc analysis according to Bonferroni or Games-Howell was used to determine differences between groups of >2. The Spearman rank correlation coefficient was used to determine the interrater reliability of the radiographic measurements.

RESULTS

Significant differences were demonstrated for ∆LL (SVA balanced/imbalanced: 24.7 degrees/19.1 degrees, P =0.001; PI-LL balanced/imbalanced: 24.4 degrees/16.4 degrees, P <0.000), PT (SVA balanced/imbalanced: 12.5 degrees/15.2 degrees, P =0.029; PI-LL balanced/imbalanced: 10.8 degrees/20.5 degrees, P <0.000), PI (SVA balanced/imbalanced: 52.9 degrees/56.9 degrees, P =0.001; PI-LL balanced/imbalanced: 52.1 degrees/61.0 degrees, P <0.000), LL (SVA balanced/imbalanced: 54.8 degrees/47.8 degrees, P =0.029; PI-LL balanced/imbalanced: 55.3 degrees/42.6 degrees, P <0.000). The coronal spinal balance (central sacral vertical line) indicated no significant differences regarding spinopelvic mobility between positive, neutral, or negative balanced groups. Significant differences with decreased pelvic mobility (∆PT) and lumbar flexibility (∆LL) in low-grade PI types 1 and 2 compared with high-grade PI type 4 according to the Roussouly classification were observed.

CONCLUSIONS

This is the first study to investigate spinal sagittal alignment using 3 different classifications in association to the spinopelvic complex in THA patients preoperatively and postoperatively. The significantly altered spinopelvic mechanics with decreased lumbar flexibility and increased pelvic retroversion in sagittal imbalanced patients clearly indicate the need for a separate consideration of the global spinal sagittal alignment. Our findings emphasize the importance of risk stratification for THA candidates in terms of sagittal imbalance attempting to mitigate the THA instability risk with accurate preoperative planning.

LEVEL OF EVIDENCE

Level III.

Intraoperative Technology Use Improves Accuracy of Functional Safe Zone Targeting in Total Hip Arthroplasty

BACKGROUND

Targets of acetabular inclination and anteversion have been suggested based on a patient's spinopelvic mobility. Current methods in total hip arthroplasty (THA) include manual instrumentation, computer-assisted navigation, and robotic-assisted surgery. This study aims to compare the accuracy of these 3 methods in targeting the functional safe zone.

METHODS

This is a prospective multicenter study including a series of 251 consecutive primary posterior THA patients from April 2019 to January 2021. Preoperative lateral standing and sitting spinopelvic radiographs were obtained. Each patient was classified using the Hip-Spine Classification. A functional safe zone plan was determined. Surgeons used their preferred method (manual instrumentation, computer-assisted, or robotic-assisted). Postoperative anteversion and inclination was measured and compared to the preoperative plan. Mean differences between preoperative and postoperative values were calculated. Welch's t-test was used to assess significant between-group differences with P < .05 considered significant.

RESULTS

Of the 249 patients, there were 63 manual instrumentation, 68 computer-assisted navigation, and 118 robotic-assisted surgery. Robotic-assisted surgery (rTHA) was significantly more accurate in targeting anteversion (1 ± 2) compared to manual instrumentation (mTHA; 7 ± 6, P < .001) and computer-assisted navigation (cTHA; 6 ± 6, P < .001). rTHA was also significantly more accurate in targeting inclination (1 ± 1) compared to mTHA (8 ± 7, P < .001) and cTHA (6 ± 7, P < .001). Although cTHA had greater accuracy in targeting both inclination and anteversion compared to mTHA, these differences were not statistically significant.

CONCLUSION

Robotic-assisted surgery was more accurate than both computer-assisted navigation and manual instrumentation in targeting the functional safe zone in primary THA. Further research is needed to evaluate the effect of improved accuracy on dislocation rates.

Is the Rate of Change in Posterior Pelvic Tilt After Total Hip Arthroplasty Constant?

Background

The purpose of this study was to evaluate the age-related change in pelvic sagittal inclination in the standing position after total hip arthroplasty (THA). This study hypothesized that the rate of progression of posterior tilt is not constant.

Material and methods

We measured sacral slope and pelvic tilt in 36 patients who were followed up for more than 10 years after unilateral primary THA.

Results

The posterior pelvic tilt in the standing position progressed significantly in the first year after THA and then progressed slowly. However, there was a tendency to accelerate again for those older than 75 years. Posterior pelvic tilt tended to progress rapidly after surgery in patients with femoral neck fractures and subchondral fractures of the femoral head.

Conclusions

In patients older than 75 years and those with fragility fractures, postoperative pelvic tilt in the standing position tends to be greater, suggesting that the use of a large head or dual mobility system should be considered.

Hip-spine relationship in total hip arthroplasty - Simplifying the concepts

Total hip arthroplasty (THA) has been described as the operation of the century. Despite significant advancement in the field of technology, hip instability remains second most common cause of revision hip surgery after infection. There is garning interest to identify role of hip-spine relationship in order to identify high-risk patients for instability after THA. Acetabular component position varies according to spinal alignment and mobility in order to decrease risk of impingement and instability. Preoperative work up includes standing pelvis anteroposterior radiograph and lateral spino-pelvic radiograph in standing and sitting position. The focus of this review is to develop an algorithm to address the spino-pelvic pathology and guide the treatment on the basis of sagittal movement of the spine-pelvis-hip complex and to minimise the rate of dislocation following THA.

The accuracy in determining pelvic tilt from anteroposterior pelvic radiographs in patients awaiting hip arthroplasty

Spinopelvic mobility affects outcome after THA. Whether the sacro-femoral-pubic (SFP) angle, measured on AP radiographs, can be reliably used to estimate pelvic tilt (PT) in hip osteoarthritis patients is unknown. This study aimed to (1) validate the use of the SFP angle in the calculation of PT from AP radiographs, and (2) identify individual patient factors affecting the estimation of PT. A cohort of 100 patients awaiting THA for end-stage hip osteoarthritis was prospectively studied. AP and lateral radiographs, taken in the standing and relaxed-seated positions were evaluated for spinopelvic measurements (SFP, PT, and pelvic incidence [PI]). To validate the SFP angle, estimated PT values using the formula [PT = 75°-SFP] were compared to the true, measured values from the lateral radiographs. Despite good agreement for the estimated and true PT (16.2 ± 5.9° vs. 15.5 ± 8.6°; p = .315), a significantly poorer agreement could be found between the two methods at high or low values of PT. Patient-specific PI correlated with the difference between the two measurement methods (Pearson's r = -0.644; p < .001). However, the change in SFP angle equaled approximately the change in pelvic tilt (∆PT = 2°-∆SFP; Pearson's r = -0.934; p < .001). Absolute values for the sagittal PT should not be estimated from AP pelvic radiographs in patients awaiting total hip arthroplasty. However, the relative change in PT between different positions equals approximately the change in SFP angle. This may allow functional cup orientation after THA to be determined between different postures from an AP radiograph of the pelvis. The SFP angle has moderate accuracy in determining a patient's pelvic tilt; however, it can accurately determine a patient's change in pelvic tilt in different positions.

Personalized Hip Joint Replacement with Large Diameter Head: Current Concepts

Hip arthroplasty is a common procedure in elective orthopaedic surgery that has excellent outcomes. Hip replacement surgery aims to create a “forgotten” joint, i.e., a pain-free joint akin to a native articulation. To achieve such goals, hip arthroplasty must be personalised. This is achieved by restoring: the centre of rotation of the native hip; leg length equality; femoral offset; femoral orientation; soft tissue tension; joint stability with an unrestricted hip range of motion; and having appropriate stress transfer to the bone. In addition, the whole pathway should provide an uneventful and swift postoperative recovery and lifetime implant survivorship with unrestricted activities. At our institution, the preferred option is a personalized total hip arthroplasty (THA) with a large diameter head (LDH) using either monobloc or dual-mobility configuration for the acetabular component. LDH THA offers an impingement-free range of motion and a reduced risk of dislocation. The larger head-neck offset allows for a supraphysiologic range of motion (ROM). This can compensate for a patient’s abnormal spinopelvic mobility and surgical imprecision. Additionally, LDH bearing with a small clearance exerts a high suction force, which provides greater hip micro-stability. With appropriate biomechanical reconstruction, LDH THA can restore normal gait parameters. This results in unrestricted activities and higher patient satisfaction scores. We use LDH ceramic on ceramic for our patients with a life expectancy of more than 20 years and use LDH dual mobility bearings for all others.

Can Abnormal Spinopelvic Relationships be Identified by Anteroposterior Pelvic Radiographs?

BACKGROUND

Abnormal spinopelvic relationships may place patients at an increased risk for instability after primary total hip arthroplasty. The purpose of this study was to determine if radiographic markers on a standing anteroposterior (AP) pelvis radiograph could identify patients with sagittal spinopelvic imbalance or spinal stiffness.

METHODS

Patients undergoing primary total hip arthroplasty at a single institution from 2017 to 2020 with standing AP pelvis radiographs and sitting/standing lateral radiographs were identified. AP pelvis radiographs were assessed for the following: lumbosacral hardware, spine osteophytes, disc space narrowing, scoliosis>5°, pelvic obliquity>5°, and overlap of the sacrococcygeal junction/pubic symphysis. Patients with spinopelvic imbalance and/or spinopelvic stiffness were identified. Univariate and multivariate analyses were performed. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Four hundred eighty-six patients were included. Prevalence of isolated sagittal spinopelvic imbalance and isolated spinopelvic stiffness was 12% and 21%, respectively; 11% of patients had sagittal imbalance and stiffness. Overlap of the sacrococcygeal junction/pubic symphysis (OR = 10.2, 95% CI = 5.3-19.8) and presence of lumbosacral hardware (OR = 4.4, 95% CI = 2.0-9.4) were markers of an increased risk of combined sagittal imbalance and stiffness. Seventy-nine percent of patients with overlap of the sacrococcygeal junction and pubic symphysis and 82% of patients with lumbosacral hardware had an abnormal spinopelvic relationship.

CONCLUSION

Isolated sagittal imbalance and stiffness were difficult to predict on standing AP pelvis radiographs. Overlap of the sacrococcygeal junction/pubic symphysis and presence of lumbosacral hardware associated with a higher risk of combined sagittal imbalance/stiffness and were present in ≥79% of patients with an abnormal spinopelvic relationship.

LEVEL OF EVIDENCE

IV; retrospective cohort study.