Dislocation of a primary total hip arthroplasty is more common in patients with a lumbar spinal fusion

Spinopelvic Motion: A Simplified Approach to a Complex Subject

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

Patients with Hip Osteoarthritis Have a Higher Rate of Spinal Reoperation Following Lumbar Spinal Fusion

BACKGROUND

Lumbar spinal pathology is known to affect outcomes following total hip arthroplasty (THA). However, the effect of hip osteoarthritis (OA) on outcomes following lumbar fusion has not been well studied. The purpose of this study was to determine the association between hip OA and spinal reoperation following lumbar spinal fusion.

METHODS

The 5% Medicare Part B claims database was queried for all patients who underwent primary elective lumbar fusion from 2005 to 2019. Patients were divided into 2 groups: those who underwent elective THA within 1 year after primary lumbar fusion, indicating that they had severe hip OA at the time of lumbar fusion, and those who underwent lumbar fusion with no diagnosed hip OA and no THA during the study period. Exclusion criteria included THA as a result of trauma, revision THA or primary THA in the 5-year period before primary lumbar fusion, <65 years of age, and no enrollment in the database for 5 years before and 1 year after primary lumbar fusion. The primary outcome was spinal reoperation within 1, 3, and 5 years. Multivariable Cox regression was performed with age, sex, diabetes, heart disease, obesity, smoking status, osteoporosis, number of levels fused, use of posterior instrumentation, use of an interbody device, use of bone graft, and surgical approach as covariates.

RESULTS

Overall, 1,123 patients (63.4% female; 91.3% White; mean age, 76.8 ± 4.1 years) were included in the hip OA group and 8,893 patients (56.2% female; 91.3% White; mean age, 74.8 ± 4.9 years) were included in the control group. After multivariable analysis, patients with severe hip OA had significantly greater rates of revision surgery at 3 years (odds ratio [OR], 1.61; p < 0.001) and 5 years (OR, 1.87; p < 0.001) after the index lumbar fusion.

CONCLUSIONS

Patients with severe hip OA at the time of primary lumbar fusion had a significantly increased risk of spinal reoperation at 3 and 5 years postoperatively. These data provide further evidence to support performing THA prior to lumbar fusion in the unsettled debate regarding which surgery should be prioritized for patients with simultaneous degenerative diseases of the hip and lumbar spine.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The outcome of revision total hip arthroplasty for instability

Aims

Instability is a common indication for revision total hip arthroplasty (THA). However, even after the initial revision, some patients continue to have recurrent dislocation. The aim of this study was to assess the risk for recurrent dislocation after revision THA for instability.

Methods

Between 2009 and 2019, 163 patients underwent revision THA for instability at Stanford University Medical Center. Of these, 33 (20.2%) required re-revision due to recurrent dislocation. Cox proportional hazard models, with death and re-revision surgery for periprosthetic infection as competing events, were used to analyze the risk factors, including the size and alignment of the components. Paired t-tests or Wilcoxon signed-rank tests were used to assess the outcome using the Veterans RAND 12 (VR-12) physical and VR-12 mental scores, the Harris Hip Score (HHS) pain and function, and the Hip disability and Osteoarthritis Outcome score for Joint Replacement (HOOS, JR).

Results

The median follow-up was 3.1 years (interquartile range 2.0 to 5.1). The one-year cumulative incidence of recurrent dislocation after revision was 8.7%, which increased to 18.8% at five years and 31.9% at ten years postoperatively. In multivariable analysis, a high American Society of Anesthesiologists (ASA) grade (hazard ratio (HR) 2.72 (95% confidence interval (CI) 1.13 to 6.60)), BMI between 25 and 30 kg/m2 (HR 4.31 (95% CI 1.52 to 12.27)), the use of specialized liners (HR 5.39 (95% CI 1.97 to 14.79) to 10.55 (95% CI 2.27 to 49.15)), lumbopelvic stiffness (HR 6.03 (95% CI 1.80 to 20.23)), and postoperative abductor weakness (HR 7.48 (95% CI 2.34 to 23.91)) were significant risk factors for recurrent dislocation. Increasing the size of the acetabular component by > 1 mm significantly decreased the risk of dislocation (HR 0.89 (95% CI 0.82 to 0.96)). The VR-12 physical and HHS (pain and function) scores improved significantly at mid term.

Conclusion

Patients requiring revision THA for instability are at risk of recurrent dislocation. Higher ASA grades, being overweight, a previous lumbopelvic fusion, the use of specialized liners, and postoperative abductor weakness are significant risk factors.

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.

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.

Does Surgical Approach Affect Dislocation Rate After Total Hip Arthroplasty in Patients Who Have Prior Lumbar Spinal Fusion? A Retrospective Analysis of 16,223 Cases

BACKGROUND

Lumbar spinal fusion (LSF) is a risk factor for dislocation following total hip arthroplasty (THA). The effect of the surgical approach on this association has not been investigated. This study examined the association between the surgical approach and dislocation following THA in patients who had prior LSF.

METHODS

We retrospectively reviewed 16,223 primary elective THAs at our institution from June 2011 to September 2022. Patients who had LSF prior to THA were identified using International Classification of Diseases (ICD) codes. Patients were stratified by LSF history, surgical approach, and intraoperative robot or navigation use to compare dislocation rates. There were 8,962 (55.2%) posterior, 5,971 (36.8%) anterior, and 1,290 (8.0%) laterally based THAs. Prior LSF was identified in 323 patients (2.0%). Binary logistic regressions were used to assess the association of patient factors with dislocation risk.

RESULTS

There were 177 dislocations identified in total (1.1%). In nonadjusted analyses, the dislocation rate was significantly higher following the posterior approach among all patients (P = .003). Prior LSF was associated with a significantly higher dislocation rate in all patients (P < .001) and within the posterior (P < .001), but not the anterior approach (P = .514) subgroups. Multivariate regressions demonstrated anterior (OR [odds ratio] = 0.64, 95% CI [confidence interval] 0.45 to 0.91, P = .013), and laterally based (OR = 0.42, 95% CI 0.18 to 0.96, P = .039) approaches were associated with decreased dislocation risk, whereas prior LSF (OR = 4.28, 95% CI 2.38 to 7.69, P < .001) was associated with increased dislocation risk. Intraoperative technology utilization was not significantly associated with dislocation in the multivariate regressions (OR = 0.72, 95% CI 0.49 to 1.06, P = .095).

CONCLUSIONS

The current study confirmed that LSF is a significant risk factor for dislocation following THA; however, anterior and laterally based approaches may mitigate dislocation risk in this population. In multivariate analyses, including surgical approach, LSF, and several perioperative variables, intraoperative technology utilization was not found to be significantly associated with dislocation risk.

Dislocation Following Anterior and Posterior Total Hip Arthroplasty in the Setting of Spinal Deformity and Stiffness: Evolving Trends Using a High-Risk Protocol at a Single Tertiary Center

BACKGROUND

Patients who have spinal stiffness and deformity are at the highest risk for dislocation after total hip arthroplasty (THA). Previous reports of this cohort are limited to antero-lateral and postero-lateral (PL) approaches. We investigated the dislocation rate after direct anterior (DA) and PL approach THA with a contemporary high-risk protocol to optimize stability.

METHODS

We investigated patients undergoing THA who had preoperative biplanar imaging from January-December 2019. Patients were identified using radiographic criteria of spinal-stiffness (<10-degree change in sacral slope from standing to seated) and deformity (flatback deformity with >10-degree difference in pelvic incidence and lumbar lordosis). There were 367 patients identified (181 DA, 186 PL). The primary outcome was dislocation rate at 2-years postoperatively. Risk-factors for dislocation were evaluated using logistic regressions (significance level of 0.05).

RESULTS

There were 6 (1.6%) dislocations in the entire cohort, with low dislocation rates for both DA (0.6%) and PL-THA (2.7%). We observed increased utilization of dual mobility with larger outer head bearings (>38 mm) with PL-THA (34.4 versus 5.0%, P < .01) and conversely increased utilization of 32-mm femoral-heads with DA-THA (39.4 versus 7.0%, P < .001). Surgical approach (PL) was not a significant risk-factor for dislocation (odds ratio: 5.03, P = .15). Patients who had a history of lumbar-fusion had 8-times higher odds for dislocation (OR: 8.20, P = .020).

CONCLUSIONS

To the best of our knowledge, this is the largest series to date evaluating DA and PL-THA in the hip-spine 2B-group. Our results demonstrate lower dislocation rate than expected with either surgical approach using a high-risk protocol.

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.

Impact of prior spinal fusion surgery on complications and functional outcomes following total hip arthroplasty: an updated systematic review and meta-analysis

PURPOSE

This study aimed to compare the complication rates and functional outcomes between patients with and without a history of spinal fusion undergoing THA.

METHODS

A systematic search was conducted across PubMed, EMBASE, Scopus, and Cochrane databases. Studies that compared adults with and without a history of spinal fusion after primary THA were included. The methodological quality of the studies was evaluated using MINORS criteria. Meta-analyses were performed utilizing mean differences (MD), standardized mean differences (SMD), and odds ratios (OR), along with 95% confidence intervals (CI).

RESULTS

Seventeen studies involving 1,789,356 patients (31,786 in the SF group and 1,757,570 in the Non-SF group) were analyzed. The spinal fusion group exhibited significantly higher rates of dislocation (OR 2.50, 95% CI 1.78-3.52), periprosthetic fracture (OR 1.96, 95% CI 1.39-2.77), overall complications (OR 1.73, 95% CI 1.10-2.71), and revision rates (OR 1.86, 95% CI 1.74-1.99). Furthermore, within the first three months, there was an increased risk of dislocation (OR 4.38, 95% CI 1.36-14.14) and revisions (OR 3.87, 95% CI 1.63-9.18). Longer spinal fusions were significantly associated with a higher risk of dislocations (OR 0.62, 95% CI 0.53-0.71). Additionally, prior spinal fusion was linked to higher levels of pain (SMD 0.11, 95% CI 0.02-0.19) and poorer functional outcomes (MD - 0.09, 95% CI - 0.18 to - 0.00).

CONCLUSIONS

Patients with a history of spinal fusion undergoing THA exhibit increased complication rates, higher levels of pain, and greater functional limitations than those without prior fusion. These findings have significant clinical implications for optimizing perioperative care in high-risk patient populations.

Spinal fusion and total hip arthroplasty: why timing is important

BACKGROUND

There is increasing debate among orthopaedic surgeons over the temporal relationship between lumbar spinal fusion (LSF) and total hip arthroplasty (THA) for patients with hip-spine syndrome. Few large studies have directly compared the results of patients who undergo LSF prior to THA (LSF-THA) to those who undergo LSF after THA (THA-LSF). The current study matched THA patients with a prior LSF to patients who underwent LSF after THA to assess: 90-day and 1-year (1) medical/surgical complications; and (2) revisions.

METHODS

We queried a national, all-payer database to identify all patients undergoing THA between 2010 and 2018 (n = 716,084). The LSF-THA patients and THA-LSF patients were then matched 1:1 on age, sex, Charleson Comorbidity Index, and obesity. Medical/surgical complications and revisions at 90 days and 1 year were recorded. Categorical and continuous variables were analysed utilising t-tests and chi-square, respectively.

RESULTS

LSF-THA patients experienced significantly more postoperative dislocations at 90 days and 1 year compared to THA-LSF patients (p = 0.048 and p < 0.001). There were a similar number of revisions performed for LSF-THA and THA-LSF patients at both 90 days and 1 year (p = 0.183 and p = 0.426). Furthermore, at 1 year, LSF-THA patients experienced more pneumonia (p = 0.005) and joint infection (p = 0.020).

CONCLUSIONS

Prior LSF has been demonstrated to increase the risk of postoperative dislocation in patients undergoing THA. The results of the present study demonstrate increased dislocations with LSF-THA compared to THA-LSF. For "hip spine syndrome" patients requiring both LSF and THA, it may be more beneficial to undergo THA prior to LSF. Arthroplasty surgeons may wish to collaborate with spinal surgeons to ensure optimal outcomes for this group of patients.

Superior outcomes of total hip arthroplasty without prior lumbar arthrodesis: a systematic review and meta-analysis

PURPOSE

The number of patients undergoing total hip arthroplasty (THA) surgery after previous lumbar arthrodesis (LA) is rising. Literature suggests that LA may significantly impact pelvic biomechanics and potentially compromise the success of prosthetic hip replacement. This study aims to evaluate complication rates, dislocation rates, and revision rates in patients with prior LA undergoing THA surgery compared to those undergoing THA surgery without prior LA.

METHODS

A systematic review and meta-analysis were conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A PICOS template was developed to ensure a structured approach. The search for relevant studies was performed across five databases, including Pubmed, Scopus, Embase, Medline, and Cochrane. The selected articles were evaluated based on the Levels of Evidence (LoE) criteria. The Coleman Methodology Score (mCMS) was employed to analyze the retrospective studies. This systematic review and meta-analysis were registered in the International Prospective Register of Systematic Reviews (PROSPERO). For the outcomes that allowed for a meta-analysis performed using R software, a p < 0.05 was considered statistically significant.

RESULTS

The final analysis included seventeen studies comprising a total of 3,139,164 cases of THA. Among these cases, 3,081,137 underwent THA surgery alone, while 58,027 patients underwent THA with a previous LA. The study investigated various factors, including dislocation rates, revision rates, and complication, as well as the surgical approach and type of implant used, for both the THA-only group and the group of patients who underwent THA with prior LA. The analysis revealed a statistically significant difference (p < 0.05) for all variables studied, favoring the group of patients who underwent THA alone without prior LA.

CONCLUSIONS

This systematic review and meta-analysis demonstrated a statistically significant superiority in all analyzed outcomes for patients who underwent THA-only without prior LA. Specifically, patients with isolated THA implants experienced significantly lower incidences of THA dislocation, wound complications, periprosthetic joint infection, revision, and mechanical complications.

LEVEL OF EVIDENCE

Level IV.

Scoliosis Without Fusion and Increased Risk of Early Medical and Surgery-Related Complications After Total Hip Arthroplasty: A Propensity-score Analysis

INTRODUCTION

There is a paucity of literature that examines how the abnormal spinopelvic alignment of scoliosis affects outcomes after total hip arthroplasty (THA) in the absence of a lumbar fusion.

METHODS

Patients with a history of scoliosis (idiopathic, adolescent, degenerative, or juvenile) without fusion and those without a history of scoliosis who underwent primary THA were identified using a large national database. Ninety-day incidence of various medical complications, emergency department (ED) visit, and readmission and 1-year incidence of surgery-related complications and cost of care were evaluated in both the scoliosis and control cohorts. Propensity score matching was used to control for patient demographic factors and comorbidities as covariates.

RESULTS

After propensity matching, 21,992 and 219,920 patients were identified in the scoliosis and control cohorts, respectively. Patients with scoliosis were at increased risk of several 90-day medical complications, including pulmonary embolism (odds ratio [OR] 1.96; P < 0.001), deep vein thrombosis (1.49; P < 0.001), transfusion (OR, 1.13; P < 0.001), pneumonia (OR, 1.37; P < 0.001), myocardial infarction (OR, 1.38; P = 0.008), sepsis (OR, 1.59; P < 0.001), acute anemia (OR, 1.21; P < 0.001), and urinary tract infection (OR, 1.1; P = 0.001). Patients with a history of scoliosis were at increased 1-year risk of revision (OR, 1.31; P < 0.001), periprosthetic joint infection (OR, 1.16; P = 0.0089), dislocation (OR, 1.581; P < 0.001), and aseptic loosening (OR, 1.39; P < 0.001) after THA. Patients with scoliosis without a history of fusion were more likely to return to the emergency department (OR, 1.26; P < 0.001) and be readmitted (OR, 1.78; P < 0.001) within 90 days of THA.

DISCUSSION

Patients with even a remote history of scoliosis without fusion are at increased risk of 90-day medical and surgery-related complications after hip arthroplasty. Hip and spine surgeons should collaborate in future studies to best understand how to optimize these patients for their adult reconstructive procedures.

The Hip-spine Assessment of a Novel Surgical Planning Software Provides Acetabular Component Targets That Are Reliable and in Agreement With Current Clinical Recommendations

Background

Spinopelvic immobility has been reported to increase dislocation risk following total hip arthroplasty. Surgically placing acetabular components in a functional orientation has been shown to mitigate risk. The aim of this study was to evaluate the validity and reliability of novel surgical planning software to generate clinically recommended cup targets.

Methods

Hip-spine assessments were performed retrospectively on 40 patients. Five reviewers, including 3 arthroplasty-trained surgical fellows and 2 clinical research scientists performed the assessments. Hip-spine assessments consisted of measuring anterior pelvic plane tilt, sacral slope, pelvic incidence, and lumbar lordosis on standing anteroposterior pelvis and lateral standing and seated hip-spine images. Generated cup targets and a control group (40°/20° relative to the anterior pelvic plane) were compared to clinically recommended cup targets. Agreement was defined as a cup position within the recommended range or within 3° of a specific target (eg, 40° inclination) when no range was provided. Intraclass correlation coefficients were used to assess interrater and intrarater reliability, and McNemar's chi-square test was used to measure success relative to the control group.

Results

The intraclass correlation coefficient was 0.88 for delta sacral slope and 0.92 for pelvic incidence-lumbar lordosis mismatch. For patients with spinopelvic risk factors, the generated targets matched the clinical recommendations in 81% of patients compared to only 16% in the control group.

Conclusions

Excellent interrater and intrarater reliability was achieved using the novel surgical planning software. The resultant target values agreed with clinical recommendations to a greater extent than the control group.

Spinal surgery and the risk of reoperation after total hip arthroplasty: a cohort study based on Swedish spine and hip arthroplasty registers

BACKGROUND AND PURPOSE

Studies suggest increased revision risk of total hip arthroplasty (THA) in individuals with lumbar spinal fusion, but studies including non-fused individuals are lacking. We aimed to investigate whether individuals undergoing lumbar spinal stenosis surgery with or without fusion are at an increased risk of reoperation before or after THA.

PATIENTS AND METHODS

The Swedish Spine Register and the Swedish arthroplasty register were searched from 2000 through 2021. Chi-square, Kaplan-Meier and binary multivariate logistic regression were used to compare reoperation rates up to 10 years after THA surgery.

RESULTS

7,908 individuals had undergone lumbar spinal stenosis surgery (LSSS) (fusion n = 1,281) and THA. LSSS before THA compared with THA-only controls was associated with a higher risk of THA reoperations: 87 (2%) out of 3,892 vs. 123 (1%) out of 11,662 (P < 0.001). LSSS after THA compared with THA-only controls was not associated with a higher risk of reoperation, confirmed by Kaplan- Meier analyses and binary multivariate logistic regression. Mortality was lower in individuals undergoing both LSSS and THA, regardless of procedure order. There was no difference in THA reoperations in individuals who had undergone LSSS before THA without fusion or with fusion. The individuals who had undergone LSSS after THA with fusion had an increased risk of THA reoperation compared with those without fusion.

CONCLUSION

LSSS with or without fusion before THA is associated with an increased risk of THA reoperation. Spinal fusion increased the risk of reoperation of THA when performed after THA.

How to Screen for Lumbar Spine Stiffness in Patients Awaiting Total Hip Arthroplasty

BACKGROUND

This study aimed to (1) define the prevalence of spinopelvic abnormalities among patients who have hip osteoarthritis (OA) and controls (asymptomatic volunteers) and (2) identify factors that reliably predict the presence of lumbar spine stiffness.

METHODS

This is a prospective, cross-sectional, case-cohort study of patients who have end-stage primary hip OA, who underwent primary total hip arthroplasty (THA). Patients were compared with a cohort of asymptomatic volunteers, matched for age, sex, and body mass index (BMI), serving as a control group. Spinopelvic pathologies were defined as: lumbar spine flatback deformity (difference of 10 or more degrees for pelvic incidence minus lumbar lordosis angle), a standing sagittal pelvic tilt of 19° or more and lumbar spine stiffness (lumbar flexion of less than 20° between both postures).

RESULTS

The prevalence of spinopelvic pathologies was similar between patients and controls (flatback deformity: 16% versus 10%, P = .209; standing pelvic tilt >19°: 17% versus 24%, P = .218; lumbar spine stiffness: 6% versus 5%, P = .827). Age over 65 years-old and standing lumbar lordosis angle less than 45° were associated with high sensitivity and specificity for identifying lumbar spine stiffness (age >65 years: 82% and 66%; standing lumbar lordosis angle <45°: 85% and 73%).

CONCLUSION

The presence of end-stage hip osteoarthritis was not associated with increased prevalence of adverse spinopelvic characteristics compared to matched, asymptomatic volunteers. Age and LLstanding are the strongest predictors of lumbar spine flexion and can guide clinical practice on when to obtain additional radiographs for patients who have hip OA before arthroplasty to identify at-risk patients.

LEVEL OF EVIDENCE

II (prospective, cohort study).

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

BACKGROUND

Patients with ankylosing spondylitis (AS) experience abnormal spinopelvic motion due to chronic inflammation of the axial skeleton, predisposing them to impingement and dislocation. The purpose of this study was to evaluate total hip arthroplasty (THA) dislocation rates in AS patients and evaluate the effects of age and gender on dislocation risk.

METHODS

Patients who underwent primary THA from 2005 to 2014 were identified using the PearlDiver database. AS patients were compared to age- and gender-matched controls without AS. Patients with a history of spine pathology or spine surgery were excluded. Univariate analyses were performed based on age and sex to evaluate dislocation rates at 90 days, 6 months, 1 year, and 5 years postoperatively.

RESULTS

A total of 2792 THA patients (59.6% male) with AS were identified and compared to an age- and gender-matched control group of 5582 THA patients (59.5% male) without AS or known spine pathology. At final follow-up, there were 96 dislocations (3.4%) in the AS group and 138 (2.5%) dislocations in the control group (OR 1.40; 95% CI, 1.08-1.83; p = 0.0118). AS patients ⩾70 years old had higher dislocation rates at all time points (OR range, 1.75-2.09; p < 0.05) compared to controls. At 5-year follow-up, dislocation-free survivorship was 95.7% (95% CI, 94.5-96.9%) for AS patients ⩾70 years old compared to 97.3% (95% CI, 96.6-98.0%) for patients ⩾70 years old without AS.

CONCLUSIONS

Older AS patients have higher dislocation rates following THA. This effect is likely related to decreased spinopelvic motion in the sagittal plane, predisposing patients to impinge and dislocate.

Hemiarthroplasty Versus Total Hip Arthroplasty for Femoral Neck Fracture in Elderly Patients: Twelve-Month Risk of Revision and Dislocation in an Instrumental Variable Analysis of Medicare Data

BACKGROUND

There is practice variation in the selection of a total hip arthroplasty (THA) or a hemiarthroplasty (HA) for the treatment of displaced femoral neck fractures in elderly patients. Large data sets are needed to compare the rates of rare complications following these procedures. We sought to examine the relationship between surgery type and secondary hip surgery (revision or conversion arthroplasty) at 12 months following the index arthroplasty, and that between surgery type and dislocation at 12 months, among elderly Medicare beneficiaries who underwent THA or HA for a femoral neck fracture, taking into account the potential for selection bias.

METHODS

We performed a population-based, retrospective study of elderly (>65 years of age) Medicare beneficiaries who underwent THA or HA following a femoral neck fracture. Two-stage, instrumental variable regression models were applied to nationally representative Medicare medical claims data from 2017 to 2019.

RESULTS

Of the 61,695 elderly patients who met the inclusion criteria, of whom 74.1% were female and 92.2% were non-Hispanic White, 10,268 patients (16.6%) underwent THA and 51,427 (83.4%) underwent HA. The findings from the multivariable, instrumental variable analyses indicated that treatment of displaced femoral neck fractures with THA was associated with a significantly higher risk of dislocation at 12 months compared with treatment with HA (2.9% for the THA group versus 1.9% for the HA group; p = 0.001). There was no significant difference in the likelihood of 12-month revision/conversion between THA and HA.

CONCLUSIONS

The use of THA to treat femoral neck fractures in elderly patients is associated with a significantly higher risk of 12-month dislocation, as compared with the use of HA, although the difference may not be clinically important. A low overall rate of dislocation was found in both groups. The risk of revision/conversion at 12 months did not differ between the groups.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Direct anterior approach associated with lower dislocation risk after primary total hip arthroplasty in patients with prior lumbar spine fusion

BACKGROUND

While there has been much interest in the increased dislocation rate in total hip arthroplasty (THA) patients with a lumbar spine fusion (LSF), there is minimal literature comparing the risk based on surgical approach. The purpose of this study was to determine if a direct anterior (DA) approach was protective against dislocation when compared to the anterolateral and posterior approaches in this high-risk patient population.

METHODS

A retrospective review was performed of 6554 THAs performed at our institution from January 2011 to May 2021. 294 (4.5%) patients had a prior LSF and were included in the analysis. The surgical approach, timing of LSF in relation to THA, vertebral levels fused, timing of THA dislocation, and the need for revision surgery were recorded for statistical analysis.

RESULTS

In total, 39.7.3% of patients underwent a DA approach (n = 117), 25.9% underwent an anterolateral approach (n = 76), and 34.3% underwent a posterior approach (n = 101). There was no difference in number of vertebral levels fused between groups (mean 2.5, all p > 0.05). There was a total of 13 (4.4%) THA dislocation events, with an average time from surgery to dislocation of 5.6 months (0.3-30.5 months). There were fewer dislocations in the DA cohort (0.9%) in comparison to both the anterolateral (6.6%, p = 0.036) and posterior groups (6.9%, p = 0.026).

CONCLUSIONS

The DA approach demonstrated a significantly lower THA dislocation rate compared to both the anterolateral and posterior approaches in patients with a concomitant LSF.

Is Timing of Total Hip Arthroplasty and Lumbar Spine Fusion Associated With Risk of Hip Dislocation?

Background

In patients with concomitant hip and lumbar spine disease, the question of which surgery-total hip arthroplasty (THA) or lumbar spine fusion (LSF)-to address first has not been adequately answered. We aimed to evaluate the risk of dislocation after THA in patients with LSF first or after THA.

Methods

Retrospective review utilizing the PearlDiver database querying Current Procedural Terminology codes for LSF in the year prior (LSF first) or in the year after primary or revision THA (THA first). International Classification of Disease codes identified postoperative hip dislocation as our primary outcome variable. Demographic data collected included age, sex, and obesity. Dislocation rates were described as a proportion of the cohort and compared with chi-square tests.

Results

We identified 280,857 primary THA and 42,314 revision THA cases from 2012-2019. Of these, 2090 underwent primary THA and LSF, and 283 underwent revision THA and LSF within a year of each procedure. No differences in age, sex, or obesity between groups were noted. No difference in rate of all-time dislocation for primary THA was noted for the LSF first 51/1429 (3.6%) compared to the THA first 30/661 (4.0%) groups (P = .34), or for revision THA with LSF first 48/204 (23.5%) compared to THA first 27/117 (23.1%) groups (P = 1.0).

Conclusions

There was no difference in the risk of dislocation after primary or revision THA if LSF occurred prior to or after the THA. These findings can help surgeons as they counsel patients with concomitant lumbar spine and hip degeneration.

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.

Hip offset and leg-length restoration in revision hip arthroplasty with a monoblock, hydroxyapatite-coated stem

AIMS

Restoration of normal hip biomechanics in arthroplasty surgery is important in order to achieve good muscle function and joint stability.

METHODS

In this retrospective cohort study, we examined the postoperative radiographs of 131 femoral revision arthroplasty procedures using a monoblock, fully hydroxyapatite (HA)-coated titanium stem. Femoral offset, modified-global offset and leg length were measured of the operated and contralateral hips.

RESULTS

Femoral offset was restored to ±10 mm in 108 cases (82%), modified-global offset was restored ±10 mm in 93 cases (71%) and leg length was restored to ±10 mm in 102 cases (81%). There were 4 dislocations with a mean follow-up period of 38 months.

CONCLUSIONS

Restoration of hip biomechanics is achievable with a monoblock stem and thus is a viable option in revision hip arthroplasty.

It is the Opioids Not the Spine Surgeon; Dislocation After Total Hip Arthroplasty is Associated With Opioid Use in Patients Who Have Prior Lumbar Spine Fusion

BACKGROUND

Patients who have prior lumbar spine fusion (LSF) have an increased risk for dislocation after total hip arthroplasty (THA). These patients also have elevated rates of opioid use. We aimed to evaluate the associated risk of dislocation after THA in patients who have prior LSF comparing those who have opioid use to those who do not.

METHODS

This was a retrospective review using a large national database of 246,617 primary and 34,083 revision THA cases from 2012 to 2019. There were 1,903 primary THA and 288 revision THA cases identified with LSF prior to THA. Postoperative hip dislocation was our primary outcome variable and patients were stratified to use or nonuse of opioid at THA. Demographic data including age, sex, and obesity were collected. Multivariate analyses evaluated association of opioid use and dislocation after adjusting for demographics.

RESULTS

There was increased odds of dislocation for opioid use at THA for both primary (adjusted Odds Ratio [aOR] = 2.29, 95% Confidence Interval [CI] 1.46 to 3.57, P < .0003) and revision THA (aOR = 1.92, 95% CI 1.62 to 3.08, P < .0003), in patients who have prior LSF. Prior LSF without opioid use was associated with increased odds of dislocation (aOR = 1.38, 95% CI 1.01 to 1.88, P = .04), but this was lower than the associated risk of opioid use without LSF (aOR 1.72, 95% CI 1.63 to 1.81, P < .001).

CONCLUSION

Increased odds of dislocation were noted with opioid use at time of THA in patients who have prior LSF. Associated risk of dislocation was higher for opioid use than prior LSF. This suggests that dislocation risk is multifactorial and we should look to strategies to reduce opioid use prior to THA.

Did the dislocation risk after primary total hip arthroplasty decrease over time? A meta-analysis across six decades

BACKGROUND

While continuous optimization is attempted to decrease the incidence of dislocation after total hip arthroplasty (THA), dislocation remains a major complication. This meta-analysis aims to analyze the evolution of the dislocation risk after primary THA over the decades and to evaluate its potential publication bias.

PATIENTS AND METHODS

A systematic search was performed according to the PRISMA guidelines for this meta-analysis in the literature published between 1962 and 2020. MEDLINE, Cochrane and Embase databases were searched for studies reporting the dislocation risk and length of follow-up. Studies that reported on revision rates only and did not mention separate dislocations were excluded. All study designs were eligible. Study quality was assessed by existing quality assessment tools adjusted for arthroplasty research. Overall risk and yearly dislocation rates were calculated and related to historical time frame, study design, sample size and length of follow-up.

RESULTS

In total, 174 studies were included with an overall moderate quality. In total there were 85.209 dislocations reported in 5.030.293 THAs, showing an overall dislocation risk of 1.7%, with a median follow-up of 24 months. The overall dislocation risk classified per decade decreased from 3.7% in 1960-1970 to 0.7% in 2010-2020. The yearly dislocation rate decreased from 1.8 to 0.7% within these same decades. There was no significant correlation between the reported dislocation risk and the duration of follow-up (p = 0.903) or sample size (p = 0.755). The reported dislocation risk was higher in articles with registry data compared to other study designs (p = 0.021).

CONCLUSION

The dislocation risk in THA has been decreasing over the past decades to 0.7%. Non-selective registry studies reported a higher dislocation risk compared to studies with selective cohorts and RCTs. This indicates that the actual dislocation risk is higher than often reported and 'real-world data' are reflected better in large-scale cohorts and registries.

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.

Revision hip arthroplasty dislocation risk calculator: when to select dual mobility, large heads, constrained liners, or a standard head size? Testing one hundred thousand hip revisions with artificial intelligence

PURPOSE

Preventing dislocation with large head (≥ 36 mm), dual mobility, or constrained acetabular liner is another option than a standard (≤ 32 mm). Many other dislocations risk factors than size of the femoral head exist after hip arthroplasty revision. Predicting dislocation with a calculator according to the implant, to the indication of revision, and to patient's risks could allow a better surgery decision.

METHODS

Our search method covers the period from 2000 to 2022. A total of 470 relevant citations on hip major revision (cup or stem or both revisions) were identified with artificial intelligence comprising 235 publications of 54,742 standard heads comprising 142 publications of 35,270 large heads, comprising 41 publications of 3945 constrained acetabular components, and 52 publications of 10,424 dual mobility implants. We considered four implant types (standard, large head, dual mobility, or constrained acetabular liner) as the entry layer of the artificial neural network (ANN). Indication for revision THA was the second hidden layer. Demographics, spine surgery, and neurologic disease were the third layer. Implant revision, reconstruction process as next input (hidden layer). Surgery-related factors, and so on. The output was a postoperative dislocation or not.

RESULTS

Of the 104,381 hips that underwent a major revision, a second revision for dislocation was performed for 9234 hips. In each implant group, dislocation remained the first cause of revision. The rate of second revision for dislocation as a percentage of first revision procedures was significantly higher in the standard head group (11.8%) than in the constrained acetabular liner group (4.5%), the dual mobility group (4.1%), and the large head group (6.1%). Instability of a previous THA, infection, or periprosthetic fracture as the indication for revision was increased risk factors as compared with aseptic loosening. One hundred variables were used to create the calculator with the best parameter combination of data and ranking the different factors, according to the four implant types (standard, large head, dual mobility, or constrained acetabular liner).

CONCLUSION

The calculator can be used as a tool to identify patients at risk for dislocation after hip arthroplasty revision and individualize recommendations to select another option than a standard head size.

Anteroposterior pelvic radiograph findings correlate with sagittal spinopelvic motion

It has been well documented in the arthroplasty literature that lumbar degenerative disc disease (DDD) contributes to abnormal spinopelvic motion. However, the relationship between the severity or pattern of hip osteoarthritis (OA) as measured on an anteroposterior (AP) pelvic view and spinopelvic biomechanics has not been well investigated. Therefore, the aim of the study is to examine the association between the severity and pattern of hip OA and spinopelvic motion. A retrospective chart review was conducted to identify patients undergoing primary total hip arthroplasty (THA). Plain AP pelvic radiographs were reviewed to document the morphological characteristic of osteoarthritic hips. Lateral spine-pelvis-hip sitting and standing plain radiographs were used to measure sacral slope (SS) and pelvic femoral angle (PFA) in each position. Lumbar disc spaces were measured to determine the presence of DDD. The difference between sitting and standing SS and PFA were calculated to quantify spinopelvic motion (ΔSS) and hip motion (ΔPFA), respectively. Univariate analysis and Pearson correlation were used to identify morphological hip characteristics associated with changes in spinopelvic motion. In total, 139 patients were included. Increased spinopelvic motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.05). Loss of hip motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.001). A decreased joint space was associated with a decreased ΔPFA (p = 0.040). The presence of disc space narrowing, disc space narrowing > two levels, and disc narrowing involving the L5-S1 segment were associated with decreased spinopelvic motion (all p < 0.05). Preoperative hip OA as assessed on an AP pelvic radiograph predicts spinopelvic motion. These data suggest that specific hip osteoarthritic morphological characteristics listed above alter spinopelvic motion to a greater extent than others.

Does Individualization of Cup Position Affect Prosthetic or Bone Impingement Following THA?

INTRODUCTION

Spinopelvic (SP) mobility patterns during postural changes affect three-dimensional acetabular component position, the incidence of prosthetic impingement, and total hip arthroplasty (THA) instability. Surgeons have commonly placed the acetabular component in a similar "safe zone" for most patients. Our purpose was to determine the incidence of bone and prosthetic impingement with various cup orientations and determine if a preoperative SP analysis with individualized cup orientation lessens impingement.

METHODS

A preoperative SP evaluation of 78 THA subjects was performed. Data was analyzed using a software program to determine the prevalence of prosthetic and bone impingement with a patient individualized cup orientation versus six commonly selected cup orientations. Impingement was correlated with known SP risk factors for dislocation.

RESULTS

Prosthetic impingement was least with the individualized choice of cup position (9%) vs. preselected cup positions (18 to 61%). The presence of bone impingement (33%) was similar in all groups and not affected by cup position. Factors associated with impingement in flexion were age, lumbar flexion, pelvic tilt (stand to flexed seated), and functional femoral stem anteversion. Risk factors in extension included standing pelvic tilt, standing SP tilt, lumbar flexion, pelvic rotation (supine to stand and stand to flexed seated), and functional femoral stem anteversion.

CONCLUSION

Prosthetic impingement is reduced with individualized cup positioning based on SP mobility patterns. Bone impingement occurred in one-third of patients and is a noteworthy consideration in preoperative THA planning. Known SP risk factors for THA instability correlated with the It dependspresence of prosthetic impingement in both flexion and extension.

"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.

Validation of a preoperative formula to estimate postoperative pelvic sagittal alignment and mobility before performing total hip arthroplasty for patients with hip osteoarthritis

BACKGROUND

Although it is important to consider pelvic alignment and mobility in the standing and sitting positions before THA, it is not known how to preoperatively predict individual postoperative pelvic alignment and mobility. The purpose of this study was to investigate the pelvic alignment and mobility before and after THA, and to develop a predictive formula using preoperative factors to calculate postoperative sagittal alignment and mobility.

METHODS

One hundred seventy patients were assessed. The 170 patients were randomly divided into a prediction model analysis group (n = 85) and an external validation group (n = 85). In the prediction model analysis group, preoperative spinopelvic parameters were used to develop the predictive formulas to predict the postoperative sacral slope (SS) in standing and sitting positions and ΔSS. These were applied to the external validation group and assessed.

RESULTS

R² in multiple linear regression models for postoperative SS in standing, SS in sitting and ΔSS were 0.810, 0.672, and 0.423, respectively. The values of predicted and postoperative parameters were very close with no significant difference: SS in standing (33.87 vs. 34.23, P = 0.834), SS in sitting (18.86 vs. 19.51, P = 0.228), and ΔSS (15.38 vs. 14.72, P = 0.619).

CONCLUSION

The present study showed that the pelvic alignment and mobility after THA can be predicted using preoperative factors. Although a model with higher accuracy is needed, it is important to use a predictive formula to estimate the postoperative condition before performing THA.

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.

High Prevalence of Spinopelvic Risk Factors in Patients With Post-Operative Hip Dislocations

BACKGROUND

Excessive standing posterior pelvic tilt (PT), lumbar spine stiffness, low pelvic incidence (PI), and severe sagittal spinal deformity (SSD) have been linked to increased dislocation rates. We aimed to determine the prevalence of these 4 parameters in a cohort of unstable total hip arthroplasty (THA) patients and compare these to a large representative control population of primary THA patients.

METHODS

Forty-eight patients with instability following primary THA were compared to a control cohort of 9414 THA patients. Lateral X-rays in standing and flexed-seated positions were used to assess PT and lumbar lordosis (LL). Computed tomography scans were used to measure PI and acetabular cup orientation. Thresholds for "at risk" spinopelvic parameters were standing posterior PT ≤ -15°, lumbar flexion (LL_stand-LL_seated) ≤ 20°, PI ≤ 41°, PI ≥ 70°, and SSD (PI-LL_stand mismatch ≥ 20°).

RESULTS

There were significant differences in mean spinopelvic parameters between the dislocating and control cohorts (P < .001). There were no differences in mean PI (58° versus 56°, respectively, P = .29) or prevalence of high and low PI between groups. 67% of the dislocating patients had one or more significant risk factors, compared to only 11% of the control. A total of 71% of the dislocating patients had cup orientations within the traditional safe zone.

CONCLUSION

Excessive standing posterior PT, low lumbar flexion, and a severe SSD are more prevalent in unstable THAs. Pre-op screening for these parameters combined with appropriate planning and implant selection may help identify at risk patients and reduce the prevalence of dislocation.

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 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 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.

The Top Three Burning Questions in Total Hip Arthroplasty

Total hip arthroplasty (THA) for end-stage osteoarthritis is one of the most effective surgical treatments in medicine. Impressive outcomes have been well documented in the literature with patients gaining ambulation and recovery of hip joint function. Nevertheless, there are still debatable issues and controversies that the orthopedic community has not been able to provide a definitive answer for. This review is focused on the current three most debatable issues surrounding the THA procedure: (1) new cutting-edge technology, (2) spinopelvic mobility, and (3) fast-track protocols. The scope of the herein narrative review is to analyze the debatable issues surrounding the three aforementioned topics and conclude the best contemporary clinical approaches regarding each issue.

Increased Dislocation Rates After Total Hip Arthroplasty in Patients With Prior Isolated Sacroiliac Joint Arthrodesis

BACKGROUND

While stiffness of the lumbosacral spine is a known predictor of instability following total hip arthroplasty (THA), little is known about the medical- and surgical-related outcomes following THA in patients who have prior isolated sacroiliac (SI) joint arthrodesis.

METHODS

197 patients who had a history of isolated SI joint arthrodesis who subsequently underwent elective primary THA for a diagnosis of osteoarthritis (THA-SI) from 2015 to 2021 were identified in a national administrative database. Using propensity score matching and logistic regression analyses, this cohort was compared to two groups of patients: patients who did not have any history of lumbar or SI arthrodesis and patients undergoing primary THA who had a history of lumbar arthrodesis without extension into the SI joint (THA-LF).

RESULTS

The THA-SI group had a significantly higher incidence of dislocation (odds ratio 2.06, 95% confidence interval 1.04-4.04, P = .037) with no increased incidence of medical complications or other surgical complications when compared to patients without a history of SI or lumbar arthrodesis. There were no significant differences in any complications in THA-SI patients when compared to THA-LF patients.

CONCLUSION

Patients who had prior isolated SI joint arthrodesis undergoing primary THA demonstrated a two-fold increased incidence of dislocation when compared to those who did not have prior SI arthrodesis, although the risk of complications in this population was similar to that observed in patients who had prior isolated lumbar spine arthrodesis.

Prosthetic Hip Dislocations in Direct Anterior versus Posterior Approach in Patients with Instrumented Lumbar Fusion

BACKGROUND

Instrumented Posterior Lumbar Spinal Fusion (IPLSF) has been demonstrated to contribute to instability following Total Hip Arthroplasty (THA). It is unclear whether a supine Direct Anterior (DA) approach reduces the risk of instability.

METHODS

A retrospective review of 1,773 patients who underwent THA through either a DA approach or a posterior approach at our institution over a 7-year period. Radiographic and chart review were then used to identify our primary group of interest comprised of 111 patients with previous IPLSF. Radiographic review, chart review, and phone survey was performed. Dislocation rates in each approach group were then compared within this cohort of patients with IPLSF.

RESULTS

Within the group of patients with IPLSF, 33.3% (n=37) received a DA approach while 66.6% (n=74) received a posterior approach. None of the 9 total dislocations in the DA group had IPLSF, whereas 4 of the 16 total dislocations in the posterior approach group had IPLSF (p=0.78). When examining the larger group of patients, including those without IPLSF, patients undergoing a DA approach had a lower BMI and were likely have a smaller head size implanted (p<0.001 for both). Using Fischer's exact test, fusion was associated with dislocation in the posterior approach group (p<0.01), whereas fusion was not associated with dislocation in the anterior approach group (p=1.0).

CONCLUSIONS

While there was no significant difference in dislocation rates between posterior and anterior approach groups, in patients with IPLSF, the anterior approach had a lower percentage of dislocation events compared to the posterior approach.

Dislocation Rates of Primary Total Hip Arthroplasty in Patients With Prior Lumbar Spine Fusion and Lumbar Degenerative Disk Disease With and Without Utilization of Dual Mobility Cups: An American Joint Replacement Registry Study

INTRODUCTION

Patients undergoing primary total hip arthroplasty (THA) with a previous history of lumbar spine fusion (LSF) are at increased risk of dislocation. The purpose of this study was to compare the 90-day and 1-year dislocation rates of patients with LSF or lumbar degenerative disk disease who underwent primary THA with and without dual mobility (DM) constructs.

METHODS

An American Joint Replacement Registry data set of patients aged 65 years and older undergoing primary THA with minimum 1-year follow-up with a history of prior LSF or a diagnosis of lumbar degenerative disk disease was created. DM status was identified, and dislocation and all-cause revision at 90 days and 1 year were assessed.

RESULTS

A total of 15,572 patients met study criteria. The overall dislocation rates for the non-DM and DM groups were 1.17% and 0.68%, respectively, at 90 days, and 1.68% and 0.91%, respectively, at 1 year ( P = 0.005). The odds of 90-day (OR = 0.578, [ P = 0.0328]) and 1-year (OR = 0.534, [ P = 0.0044]) dislocation were significantly less with DM constructs, compared with non-DM constructs. No statistically significant difference was observed in revision rates between groups.

DISCUSSION

This large registry-based study identified a reduced risk of dislocation in patients at risk for spinal stiffness when a DM compared with non-DM construct was used in primary THA at 90-day and 1-year follow-up intervals. Our data support the use of DM constructs in high-risk patients with stiff spines and altered spinopelvic mobility as a promising option to mitigate the risk of postoperative hip instability after primary THA.

LEVELS OF EVIDENCE

Level III. Therapeutic retrospective cohort.

Failure of a Highly Cross-Linked Polyethylene Liner After Spine Fusion

A 73-year-old woman, 11 years after total hip arthroplasty and 2 years after a multilevel lumbar spine fusion, presented with a 2-month history of anterior hip and gluteal pain. She was diagnosed with an acetabular liner fracture that occurred through the high wall, likely related to repetitive impingement on the neck of the femoral implant, as notable burnishing was observed on the explanted femoral head. The acetabulum was successfully revised to a dual-mobility articulation. Spinal fusion after total hip arthroplasty can alter the acetabular implant position and was seen in our patient whose previously functional high-walled liner failed. Surgeons may consider alternative techniques, including a change in acetabular implant's anteversion to mitigate the need for a high-walled liner or the use of a dual-mobility bearing.

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.

Large Femoral Heads and Select Dual-Mobility Bearings Are Associated With Reduced Instability in Contemporary Posterior Approach Total Hip Arthroplasty

BACKGROUND

Postoperative dislocation is considered the main drawback of posterior approach total hip arthroplasty (THA). Thinner highly cross-linked polyethylene and dual-mobility bearings allow maximizing femoral head diameter per a given cup size. This study evaluated dislocation rates as large femoral head bearings were introduced into a practice over an 11-year period.

METHODS

A total of 1,511 consecutive primary THAs were retrospectively reviewed. Demographics, implant sizes, femoral head-acetabular cup ratio, and dislocation status were collected from the electronic medical record. Data were evaluated using time series analysis techniques as larger femoral heads, thinner polyethylene liners, and dual-mobility bearings were introduced. The cohort was 57% women with mean age and body mass index of 62 years (range, 13 to 93) and 31 kg/m² (range, 13 to 54), respectively.

RESULTS

The overall dislocation rate was 0.98%. Use of femoral head sizes ≥ 40 millimeters increased from 4% in the years 2010 to 2016 to 51% in the years 2017 to 2021, correlating with a 50% reduction in dislocation rate from 1.4% to 0.7% (P = .279). Also, no dislocations occurred in patients who had dual-mobility bearings or ≥ 40-millimeter femoral heads (P = .007). Twelve of 14 dislocations occurred in cases with head-cup ratio < 0.7 (P = .013). Thirteen of 14 dislocations were in women (P = .005).

CONCLUSION

Maximizing the femoral head diameter per given cup size correlated with a decrease in dislocation rate in modern posterior approach THA. Furthermore, these results suggest that dual-mobility articulations should be reserved for high-risk patients or patients in whom a 40-millimeter femoral head is not possible.

LEVEL OF EVIDENCE

IV-consecutive case series; no control group.

Patients With Low-Grade Lumbosacral Transitional Vertebrae Demonstrate No Difference in Achievement of Clinical Thresholds After Hip Arthroscopy for Femoroacetabular Impingement Syndrome

PURPOSE

To compare clinical outcomes at 2 years following primary hip arthroscopy (HA) for femoroacetabular impingement syndrome (FAIS) between patients with and without low-grade lumbosacral transitional vertebra (LSTV).

METHODS

We performed a retrospective matched-cohort analysis of patients who underwent primary HA for FAIS from 2011 to 2018 with minimum 2-year follow-up. LSTV was graded on preoperative radiographs using the Castellvi classification. Patients with grades I and II LSTV were matched 1:1 with controls on age, sex, and body mass index. Radiographic markers of FAIS morphology were measured. Pre- to postoperative improvement in the modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS) as well as 2-year achievement rates for the minimum clinically-important difference, substantial clinical benefit, and patient acceptable symptom state were compared between patients with versus without LSTV. The Wilcoxon signed-rank test was used for intergroup mean comparisons and the Cochran-Mantel-Haenszel test for categorical variables.

RESULTS

In total, 58 patients with LSTV were matched to 58 controls. Among LSTV patients, 48 were Castellvi type 1 (82.8%) and 32 (55.2%) had bilateral findings. No significant differences were found between groups with respect to radiographic markers of FAIS, including alpha angle (P = .88), lateral center edge angle (P = .42), or crossover sign (P = .71). Although patients with LSTV had greater improvement in NAHS at 2-year follow-up compared with control patients (P = .04), there were no significant differences in modified Harris Hip Score improvement (P = .31) or achievement of the minimum clinically-important difference (P = .73), substantial clinical benefit (P = .61), or patient acceptable symptom state (P = .16).

CONCLUSIONS

Patients with low-grade LSTV had greater 2-year improvement in NAHS than controls, whereas no significant differences were observed in achievement of clinical thresholds at 2-year follow-up. There were no differences between groups with respect to any measured radiographic markers of FAIS morphology. Importantly, the findings of this study are underpowered and should be viewed with caution in the greater context of the LSTV literature.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Hip arthroplasty dislocation risk calculator: evaluation of one million primary implants and twenty-five thousand dislocations with deep learning artificial intelligence in a systematic review of reviews

PURPOSE

This paper aims to provide an overview of the possibility regarding the artificial intelligence application in orthopaedics to predict dislocation with a calculator according to the type of implant (hemiarthroplasty, standard total hip arthroplasty, dual mobility, constrained cups) after primary arthroplasty.

MATERIAL AND METHODS

Among 75 results for primary arthroplasties, 26 articles were reviews on dislocation after hemiarthroplasty, 40 after standard total hip arthroplasty, seven about primary dual-mobility arthroplasty (DM THA), and two reviews about constrained implants. Although our search method for systematic reviews covers ten years (2012-2022), none for dual mobility was published before 2016, showing a recent explosion of original articles on this subject. A total of 1,069,565 implants and 26,488 dislocations in primary arthroplasties are included in these 75 reviews. We used a supervised learning model in which models assign objects to groups as input and artificial neural network (ANN) with nodes, hidden layers, and output layers. We considered only four implant types as the input layer. We considered the patient's factors (indication for THA, demographics, spine surgery, and neurologic disease) as the second input values (hidden layer). We considered the implant position as the third input (hidden layer) property including head size, combined anteversion, or spinopelvic alignment. Surgery-related factors, approach, capsule repair, etc. were the fourth input values (hidden layer). The output was a post-operative dislocation or not within three months.

RESULTS

The accuracy for predicting dislocation with this systematic review was 95%. Dislocation risk, based on the type of implant, was wide-ranging, from 0 to 3.9% (mean 0.31%) for the 3045 DM THA, from 0.2 to 1.2% (overall 0.91%) for the 457 constrained liners, from 1.76 to 4.2% (mean 2.1%) for 895,734 conventional total hip arthroplasties, and from 0.76 to 12.2% (mean 4.5%) for 170,329 hemiarthroplasties. In the conventional THA group, many factors increase the risk of dislocation according to the calculator, and only a few (big head, anterior approach) decrease the risk, but not very significantly. In the hemiarthroplasty group, many factors can increase the risk of dislocation until 30%, but none could decrease the risk. According to the calculator, the DM THA and the constrained liner markedly decreased the risk and were not affected by implant position, spine surgery, and spinopelvic position.

CONCLUSION

To our knowledge, this study is the first to yield an implant-specific dislocation risk calculator that incorporates the patient's comorbidities, the position of components, and surgery factors affecting instability risk.

Complications following total hip arthroplasty and hemiarthroplasty for femoral neck fractures in patients with a history of lumbar spinal fusion

INTRODUCTION

The purpose of this study was to examine whether previous lumbar spinal fusion (LSF) was an independent risk factor for complications in patients undergoing total hip arthroplasty (THA) or hemiarthroplasty for displaced femoral neck fractures.

METHODS AND MATERIALS

An administrative database was queried from 2010 to Q2 of 2019 to analyze and compare complications in patients undergoing either THA or hemiarthroplasty for femoral neck fracture with a history of LSF versus no history of LSF. Joint complications including periprosthetic fracture, prosthetic joint infection (PJI), prosthetic joint dislocation (PJD), aseptic loosening, and prosthetic revision were examined at 90 days and 1 year post-operatively.

RESULTS

In the THA cohort, patients with prior LSF had significantly higher likelihood of aseptic loosening at 90 days and 1 year post-operatively in comparison to those without prior LSF (90-day: OR 2.22; 1-year: OR 1.95). Patients in the hemiarthroplasty cohort with prior LSF had significantly higher likelihood of PJI (90-day: OR 2.18; 1-year: OR 2.37), aseptic loosening (90-day: OR 3.42; 1-year: OR 4.68), and prosthetic revision (90-day: OR 2.27; 1-year: OR 2.25) in both the 90-day and 1-year postoperative period in comparison to those without prior LSF. Additionally, for the same cohort, periprosthetic fracture (1-year: OR 2.32) and PJD (1-year: OR 2.31) were significantly higher at 1-year postoperative.

CONCLUSION

Presence of LSF was found to be an independent risk factor for increased joint complications in patients undergoing either a THA or hemiarthroplasty for displaced femoral neck fractures.

Influence of kinematics of the lumbopelvic complex in hip arthroplasty dislocation: from assessment to recommendations

INTRODUCTION

In total hip arthroplasty (THA), misplacement of the implant can provide instability. Adequate orientation of the acetabular cup is a challenge due to variations in inter-individual anatomy and kinematics of the pelvis in everyday life. The aim of this study was to characterize the kinematic factors influencing the risk of dislocation in order to give recommendations for optimal placement of the cup. We hypothesized that the lack of pelvic adaptation would influence the risk of prosthetic instability and motivate adapted.

MATERIALS AND METHODS

Eighty patients with primary unilateral THA were included in a matched case-control study. Seventy-four patients were divided into two groups: group 1 (G1) consisting of patients with postoperative THA dislocation (37 patients) and group 2 (G2), without episodes of dislocation within two years postoperatively (37 patients). In both groups, spino-pelvic parameters and cup orientation were measured in standing and sitting positions with EOS^® X-ray imaging and compared to each other between 12 and 24 months post-operatively.

RESULTS

No significant difference between the two groups was found for static parameters. In a sitting position, a lack of pelvic retroversion with a significant lower variation in sacral slope was observed in group 1 (8.0° ± 9.3 for G1 versus 14.7° ± 6.2 for G2, p < 0.01). Twenty-two (59%) patients with THA instability had sacral slope variations of less than 10° versus eight (21% of patients) with stable THA (p < 0.01). Cup orientation in the Lewinnek safe zone was not significantly different (59% vs 67%, p = 0.62), and the spino-pelvic parameters and cup orientation measured did not change between the standing and sitting positions. However, only 14 (37%) cups in G1 were in the functional safe zone versus 24 (67%) in G2 (p = 0.03).

CONCLUSION

Static parameters of the sagittal spinopelvic balance have a low predictive value for prosthetic instability. Dynamic analysis is essential. Kinematic parameters must be taken into account in determining the ideal position of the cup or stem. Stiffness with locked standing or sitting pelvis must be integrated in order to determine a personalized safe zone.

LEVEL OF EVIDENCE

Level III (matched case-control study).

Evaluating Outcomes of Spinopelvic Fixation for Patients Undergoing Long Segment Thoracolumbar Fusion with a Prior Total Hip Arthroplasty

INTRODUCTION

Understanding the relationship between spinal fusion and its effects on relative spinopelvic alignment in patients with prior total hip arthroplasty (THA) is critical. However, limited data exist on the effects of long spinal fusions on hip alignment in patients with a prior THA. Our objective was to compare clinical outcomes and changes in hip alignment between patients undergoing long fusion to the sacrum versus to the pelvis in the setting of prior THA.

METHODS

Patients with a prior THA who underwent elective thoracolumbar spinal fusion starting at L2 or above were retrospectively identified. Patients were placed into one of two groups: fusion to the sacrum or pelvis. Preoperative, six-month postoperative, one-year postoperative, and delta spinopelvic and acetabular measurements were measured from standing lumbar radiographs.

RESULTS

A total of 112 patients (55 sacral fusions, 57 pelvic fusions) were included. Patients who underwent fusion to the pelvis experienced longer length of stay (LOS) (8.31 vs. 4.21, P < 0.001) and less frequent home discharges (30.8% vs. 61.9%, P = 0.010), but fewer spinal revisions (12.3% vs. 30.9%, P = 0.030). No difference was observed in hip dislocation rates (3.51% vs. 1.82%, P = 1.000) or hip revisions (5.26% vs. 3.64%, P = 1.000) based on fusion construct. Fusion to the sacrum alone was an independent predictor of an increased spine revision rate (odds ratio: 3.56, P = 0.023). Patients in the pelvic fusion group had lower baseline lumbar lordosis (LL) (29.2 vs. 42.9, P < 0.001), six-month postoperative LL (38.7 vs. 47.3, P = 0.038), and greater 1-year ∆ pelvic incidence-lumbar lordosis (-7.98 vs. 0.21, P = 0.032).

CONCLUSION

Patients with prior THA undergoing long fusion to the pelvis experienced longer LOS, more surgical complications, and lower rate of spinal revisions. Patients with instrumentation to the pelvis had lower LL preoperatively with greater changes in LL and pelvic incidence-lumbar lordosis postoperatively. No differences were observed in acetabular positioning, hip dislocations, or THA revision rates between groups.