Inpatient temporal trends in open and minimally invasive sacroiliac joint fusions

INTRODUCTION

Lower back pain is the leading cause of activity limitation and the inability to work worldwide.¹ Studies suggest that 15% to 30% of chronic low back pain cases are attributed to dysfunction of the sacroiliac joint (SIJ).² The SIJ is a key anatomical region in the spine that facilitates shock absorption and stability during weight-bearing activities.³ Sacroiliac joint dysfunction (SIJD) can arise due to trauma, aging, and structural abnormalities, often leading to symptoms such as localized and radiating pain, stiffness, and compensatory mobility changes that may affect activities of daily living.^3,4 Importantly, SIJD has now been shown to be a common outcome after lumbosacral fusions.⁵

Initial strategies for SIJD treatment often involve conservative treatments, such as the use of cold therapy, NSAIDs, and muscle relaxers for acute management. Physical therapy and core strengthening exercises are considered first-line treatments by many clinicians, as they provide stability and alleviate symptoms.^2,6 More advanced interventions may include local anesthetics, which play a role in both diagnosing and relieving pain associated with SIJ dysfunction.⁷ Radiofrequency denervation is considered when conservative treatments fail to provide long-term relief, but there has been significant variability in outcomes with this approach.⁸ Intra-articular steroid injections decrease inflammation and pain in the short term but numerous studies have shown poor long-term resolution of symptoms.^9,10

For pain that is refractory, a sacroiliac joint fusion (SIJF) may be indicated to alleviate these issues.¹¹ Within this procedure the sacrum and ilium are fused, effectively eliminating movement within the SIJ joint.¹² This procedure has already shown promising results by demonstrating greater clinical outcomes, decreased opioid use and better work status when compared to conservative treatment.¹³ There are two primary approaches to SIJF: the traditional open technique, and the minimally invasive surgery (MIS) approach, with the later gaining popularity due to its favorable outcomes.^14,15 With growing literature supporting the use of MIS SIJF, its nationwide utilization has been difficult to understand due to the absence of unique current procedural terminology (CPT) codes for the respective SIJF procedures.

However, on January of 2015, this issue was solved facilitating a more systematic approach to diagnosing, processing insurance claims, and making clinical decisions. Most importantly, these developments allow us to now gain a comprehensive understanding of the different SIJF approaches, providing surgeons with valuable information regarding the utilization and outcomes. While SIJF is routinely performed in the outpatient setting, our study focused on understanding variables on the inpatient use of SIJF.

In this study, we evaluated patients who had undergone inpatient SIJF from 2016-2020 using the national inpatient sample (NIS) database. The purpose of this study is to analyze the temporal trends in utilization for both open and MI inpatient SIJF. We hypothesize that inpatient MI SIJF procedure volume will increase over time.

METHODS

NIS database

The NIS of the healthcare cost and utilization project, sponsored by the Agency for Healthcare Research and Quality, was used for this study. This administrative database is the largest inpatient hospitalization-related healthcare dataset in the United States. This database includes hospitalized inpatient data from all states taking part in HCUP, which approximates to roughly 95% of the US population. The patients within this database compose a 20% stratified sample of all discharges from hospitals across the nation. The dataset captures approximately 8 million hospital stays annually from more than 100 hospitals. After applying sampling weights, the data estimate over 35 million hospitalizations nationwide, providing a representation of the entire United States.¹⁶ The database utilizes billing CPT codes to confer inpatient clinical and nonclinical data for each hospital stay.

Study patients

A retrospective analysis was conducted using data from the NIS database spanning from 2016 to 2020. Patient inclusion for the study was based on the presence of CPT codes for open SIJF (CPT code: 27280) and MIS SIJF (CPT code: 27279). These codes were converted into ICD-10 PCS codes for inpatient identification. Patients were further dividing patients into two groups: open and MIS. Open included the following ICD-10 PCS codes, 0SG704Z, 0SG707Z, 0SG70JZ, 0SG70KZ, 0SG70ZZ, 0SG804Z, 0SG807Z, 0SG80JZ, 0SG80KZ, 0SG80ZZ. These codes include both right and left sided procedures and the use of autologous, non-autologous and synthetic substitutes for SIJF fusions. MIS included the following ICD-10 PCS codes 0SG734Z, 0SG737Z, 0SG73JZ, 0SG73KZ, 0SG73ZZ, 0SG744Z, 0SG747Z, 0SG74JZ, 0SG74KZ, 0SG74ZZ, 0SG834Z, 0SG837Z, 0SG83JZ, 0SG83KZ, 0SG83ZZ, 0SG844Z, 0SG847Z, 0SG84JZ, 0SG84KZ, 0SG84ZZ. These codes include, both left and right sided procedures, percutaneous and endoscopic approaches, internal fixations procedures and the use of autologous, nonautologous and synthetic substitutes for MIS fusions.

Data and outcomes

Data collection included patient demographics such as gender (female, male), age, insurance type (Medicare, Medicaid, private insurance, self-pay, no charge, other), race (White, Black, Hispanic, Asian/Pacific Islander, Native American, other), region (Northeast, Midwest, South, West), and location/teaching status of the hospital (rural, urban non-teaching, urban teaching). Procedural volumes for open and MIS during each year obtained for temporal analysis. As the NIS database contains no patient identifiers and complies with the Health Insurance Portability and Accountability Act (HIPAA) regulations, this study was exempt from IRB approval and the requirement for informed consent, in accordance with 45 CFR 46.104(d)(4).

Statistical analysis

Statistical significance was determined using p values, with a threshold set at p<0.05. Trends and comparisons were analyzed over the five-year span using Mann-Kendall test, t-tests were used for continuous variables and chi-square tests for categorical variables. All statistical analyses were performed using statistical package for the social science (SPSS) version 27.

RESULTS

A total of 38,660 inpatient SIJF procedures were included in this study. From these 34,590 were open SIJF procedures and 3,890 were MIS. The average age of patients increased slightly over the study period, from 58.46 years in 2016 to 60.75 years in 2020.

Overall, the procedures were predominantly performed on female patients (p<0.001), with this distribution remaining stable throughout the study period as well.

When comparing patient demographics, insurance coverage for SIJF procedures predominantly consisted of Medicare payers (p<0.001). The surgeries were predominantly conducted in urban teaching hospitals (p<0.001). As for the racial demographics, the majority patient population identified as White (p<0.001) (Table 1). These differences remained stable across the study period.

A statistically significant difference was seen between open and MIS procedure volumes, with the majority of procedures being open (p<0.001). Temporal analysis using Mann-Kendall test on the open and MIS procedure volumes from 2016 to 2020 showed no statistically significant difference over the years (p=0.806, 0.462 respectively) (Table 2) (Figure 1). Regional analysis revealed significant disparities in the distribution of procedure volume (p<0.001), with the highest number of procedures performed in the South (41.6%) (Table 3).

DISCUSSION

Our study provides critical insights into the temporal trends of inpatient SIJF procedures from 2016 to 2020. We observed no statistically significant difference in both open and MIS SIJF inpatient procedures during the studied timeframe, but a significant difference was seen geographically with most procedures being performed in the South. These findings provide valuable insight on the trajectory of open and MIS SIJF utilization in the inpatient setting.

Our study observed a higher prevalence of sacroiliac joint issues in women, along with an increase in the mean age compared to previous research. This directly contradicts a study by Irwin et al which suggests that age and gender may not have a strong correlation with sacroiliac joint pathology.²² The disparities found in our study align with others that also found a higher prevalence of SIJF in women.¹⁸ The higher prevalence of SIJF in women may be associated with pregnancy related SIJ pain, as illustrated by in a study conducted by Fiani et al which showed that MIS procedures have proven effective in addressing pain and improving function in postpartum women.²³

With recent advancements in SIJF techniques, MIS is emerging with far more favorable outcomes than the open approach.¹⁴ Despite these advancements, our study found no statistical significant difference in inpatient MIS and open procedure volumes from 2016-2020, which contrasts with previous reports of increasing SIJF volumes during this same time frame. For instance, an analysis conducted by Federico et al using Medicare data indicated a rise in SIJF procedures over time, with the majority of procedures being the MIS from 2015 onwards.¹⁷ Similarly, Ton et al using the Pearldiver database reported an increase in SIJF procedural volume during the same time period.¹⁸ We believe this difference to be in the patient population being analyzed as the Pearldiver and Medicare data include patient procedures that are both inpatient and outpatient, while the NIS database strictly only includes hospitalized inpatient procedures. These findings add to the growing body of evidence of the shift in clinical practice toward outpatient settings for MIS procedures, as highlighted in previous studies.

Hersh et al, when analyzing MIS SIJF trends across the same time period reported over 75% of all SIJF procedures were MIS, with over 50% being done by non-surgical specialties and an increased number offered in the outpatient and ambulatory surgical setting.¹⁹

Regional analysis revealed significant disparities in the distribution of procedure volume, with the highest number of procedures performed in the South (41.57%). These findings align with those of previous studies that analyzed the temporal trends of SIJF during a similar timeframe.^18,20 The rapid growth of spinal procedures performed in the south is well documented by Moore et al.²¹

Limitations

Our study does not come without its limitations. First, the NIS database is retrospective and does not include outpatient procedures, post-operative follow-up, and associated co-morbidities following discharge. Thus, data on associated procedural co-morbidities are only those reported while the patient is hospitalized post-operatively. Patient identifiers are removed; as a result, readmissions cannot be tracked. Second, the retrospective nature of the analysis limits the ability to establish causality. Lastly, the reliance on the NIS database may introduce selection bias and inaccuracies due to coding errors.

CONCLUSION

Our findings suggest that inpatient SIJF volumes remained stable from 2016-2020, with most procedures performed in the South. These findings align with the increasing shift toward outpatient MIS SIJF, as inpatient volumes did not rise despite greater MIS adoption. Future studies should examine outpatient trends to further characterize this shift.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

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