Statistics in Brief: An Introduction to the Use of Propensity Scores

Safety of Outpatient Single-level Cervical Total Disc Replacement: A Propensity-Matched Multi-institutional Study

STUDY DESIGN

A retrospective cohort comparison study.

OBJECTIVE

The aim of this study was to investigate the perioperative adverse event profile of cervical total disc replacement (CTDR) performed as an outpatient relative to inpatient procedure.

SUMMARY OF BACKGROUND DATA

Recent reimbursement changes and a push for safe reductions in hospital stay have resulted in increased interest in performing CTDRs in the outpatient setting. However, there has been a paucity of studies investigating the safety of outpatient CTDR procedures, despite increasing frequency.

METHODS

Patients who underwent single-level CTDR were identified in the 2005 to 2016 National Surgical Quality Improvement Program database. Outpatient versus inpatient procedure status was defined by length of stay, with outpatient being less than 1 day. Patient baseline characteristics and comorbidities were compared between the two groups. Propensity score matched comparisons were then performed for 30-day perioperative complications and readmissions between the two cohorts. In addition, perioperative outcomes of outpatient single-level CTDR versus matched outpatient single-level anterior cervical discectomy and fusion (ACDF) cases were compared.

RESULTS

In total, 373 outpatient and 1612 inpatient single-level CTDR procedures were identified. After propensity score matching was performed to control for potential confounders, statistical analysis revealed no significant difference in perioperative complications between outpatient versus matched inpatient CTDR. Notably, the rate of readmissions was not different between the two groups. In addition, there was no difference in rates of perioperative adverse events between outpatient single-level CTDR versus matched outpatient single-level ACDF.

CONCLUSION

The perioperative outcomes evaluated in the current study support the conclusion that, for appropriately selected patients, single-level CTDR can be safely performed in the outpatient setting without increased rates of 30-day perioperative complications or readmissions compared with inpatient CTDR or outpatient single-level ACDF.

LEVEL OF EVIDENCE

3.

No Difference in Morbidity and Mortality After Total Joint Arthroplasty in Liver Transplant Recipients: A Propensity Score-Matched Analysis of a Nationwide, Population-Based Study Using Universal Healthcare Data

BACKGROUND

Controversy remains regarding the outcomes after total joint arthroplasty (TJA) among patients with or without liver transplantation (LT). This study aimed at investigating the prevalence of TJA in patients after LT and comparing the morbidity and mortality with the non-LT group.

METHODS

We conducted a nationwide, population-based study, with data extracted from a universal health insurance database, based on the International Classification of Disease, Ninth Revision, Clinical Modification. Patients who underwent TJAs between January 2001 and December 2014 were included. Patients who had bilateral TJAs or a TJA before LT were excluded. A total of 43 patients with LT and 350,337 patients without LT were included. The analysis was implemented using data from all patients and those matched by 1-to-10 propensity score matching. Multivariable logistic regression was used to control confounding variables.

RESULTS

The prevalence of patients undergoing TJA after LT was 1.3% (43/3276). After propensity score matching, patients with LT were not associated with 30-day complications (adjusted odds ratio [aOR], 0.98; 95% confidence interval [CI], 0.93-1.03; P = .35), 30-day readmission rates (aOR, 0.93; 95% CI, 0.92-1.08; P = .87), 90-day complication rates (aOR, 0.95; 95% CI, 0.88-1.02; P = .16), 1-year infection rates (aOR, 1.04; 95% CI, 0.96-1.12; P = .35), reoperation rates (aOR, 1.06; 95% CI, 0.92-1.23; P = .41), or mortality (aOR, 0.91; 95% CI, 0.80-1.04; P = .18).

CONCLUSION

The morbidity and mortality seem to be comparable whether TJA is performed in patients with or without LT. Methods for risk assessment would be feasible in liver transplant recipients.

Outpatient elective posterior lumbar fusions appear to be safely considered for appropriately selected patients

BACKGROUND CONTEXT

There has been growing interest in performing posterior lumbar fusions (PLFs) in the outpatient setting to optimize patient satisfaction and reduce cost. Although still done in only a small percentage of cases, this has been more possible because of advances in surgical techniques and anesthesia. However, data on the perioperative course of outpatient compared with inpatient PLF in a large sample size are scarce.

PURPOSE

This study aimed to compare perioperative complications between outpatient and inpatient PLF in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database.

STUDY DESIGN/SETTING

A retrospective cohort comparison study was carried out.

PATIENT SAMPLE

Patients undergoing PLF with or without interbody fusion from the 2005 to 2015 NSQIP database comprised the sample.

OUTCOME MEASURES

Outcome measures were postoperative complications within 30 days and readmission within 30 days.

METHODS

Patients who underwent PLF with or without interbody fusion were identified in the 2005-2015 NSQIP database. Outpatient procedures were defined as cases that had hospital length of stay (LOS)=0 days, whereas inpatient procedures were defined as LOS=1-30 days. Patient characteristics, comorbidities, and procedural variables (inclusion of interbody fusion, instrumentation, and number of levels fused) were compared between the two cohorts. Propensity score-matched comparisons were then performed for postoperative complications and 30-day readmissions between the two groups.

RESULTS

The current study included 360 outpatient and 36,610 inpatient PLF cases. After propensity matching to control potential confounding factors, statistical analysis revealed no significant difference in postoperative adverse events other than significantly lower blood transfusions in the outpatient group (2.78% vs. 10.83%, p<.001). Notably, the rate of readmissions was not different between the groups.

CONCLUSIONS

Based on the lack of differences in rates of most perioperative complications and 30-day readmissions between the outpatient and inpatient cohorts, it seems that outpatient PLF may be appropriately considered for select patients. However, extremely careful patient selection should be exercised.

Discharge to Inpatient Rehab Does Not Result in Improved Functional Outcomes Following Primary Total Knee Arthroplasty

BACKGROUND

Monitored rehabilitation has long been considered an essential part of the recovery process in total knee arthroplasty (TKA). However, the optimal setting for rehabilitation remains uncertain. We sought to determine whether inpatient rehabilitation settings result in improved functional and patient-reported outcomes after primary TKA.

METHODS

All patients undergoing primary TKA from May 2007 to February 2011 were identified from our institutional total joint registry. Propensity score matching was then performed, resulting in a final cohort of 1213 matched pairs for discharge destination to either home or a rehabilitation facility (inpatient rehab or skilled nursing facility). Length of stay, need for manipulation, 6-month complications, and 2-year Western Ontario and McMaster Universities Osteoarthritis Index, Lower Extremity Activity Scale, 12-item Short Form Health Survey, and Hospital for Special Surgery knee expectations surveys were compared.

RESULTS

Patients discharged to a rehab facility were noted to have a shorter hospital length of stay (5.0 vs 5.4 days). Patients discharged to inpatient rehabilitation reported more fractures at 6 months postoperatively. However, no differences in manipulation rates, 2-year outcome scores, or changes in outcome scores were found between the 2 groups.

CONCLUSION

Inpatient rehabilitation settings did not result in lower complications at 6 months or improved functional or patient-reported outcomes at 2 years compared to discharge directly to home when patients are propensity matched for age, living situation, comorbidities, baseline functional status, and insurance status. This finding has important cost implications and calls into question whether the healthcare system should allow otherwise healthy patients to use inpatient rehabilitation services postoperatively after primary TKA.

Comparison of Short-term Complications After Rotator Cuff Repair: Open Versus Arthroscopic

PURPOSE

To define and compare the incidence and risk factors for short-term complications after arthroscopic and open rotator cuff repair (RTCR), and to identify independent risk factors for complications after RTCR.

METHODS

All patients who underwent open or arthroscopic RTCR from 2005 to 2013 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Short-term complications were categorized as surgical, medical, mortality, and unplanned 30-day readmission. Univariate analysis allowed the comparison of patient demographics and comorbidities. Propensity score matching was used to control for demographic differences between arthroscopic and open RTCR patient groups. Independent risk factors for complication were identified using multivariate logistic regression.

RESULTS

Overall, 11,314 RTCRs were identified (24% open, 76% arthroscopic). The mean operative time for open RTCR was 78 minutes compared with 91 minutes for arthroscopic repairs (P < .001). The overall complication rate was 1.3%, with the highest complication unplanned return to the operating room (41 patients, 0.36%). The 30-day readmission was 1.16% (76/6,560 patients) and the mortality rate was 0.03% (3 patients). Total 30-day complications in the propensity-score-matched patient group were higher after open versus arthroscopic repair (1.79% vs 1.17%; P = .006). The overall infection rate after RTCR was 0.56%, with deep wound infection higher in the open repair patient group (P = .003). Multivariate analysis identified age >65 years (odds ratio [OR] 1.6; 95% confidence interval [CI] 1.2-2.3), operative time >90 minutes (OR 1.5; CI 1.1-2.1), and open RTCR (OR 1.6; CI 1.1-2.3) as independent risk factors for complications.

CONCLUSIONS

Short-term complications after RTCR are rare. Total complications are higher after open RTCR in propensity-matched patient groups and in multivariate analysis. Risk factors for complications include patient age >65, operative time >90 minutes, and open repair. Open RTCR is associated with an increased risk of surgical infections.

LEVEL OF EVIDENCE

Level III, retrospective comparative trial.

Comparison of 30-Day Complications Between Navigated and Conventional Single-level Instrumented Posterior Lumbar Fusion: A Propensity Score Matched Analysis

STUDY DESIGN

Retrospective cohort comparison study.

OBJECTIVE

To compare perioperative outcomes between navigated and conventional single-level instrumented posterior lumbar fusions in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database.

SUMMARY OF BACKGROUND DATA

Although multiple studies have investigated the accuracy of pedicle screw placement and radiation exposure with navigation, no study has compared perioperative complications between navigated and conventional posterior lumbar fusion. The potential benefits of navigation include improved accuracy of screw placement and reduced surgeon radiation exposure, but this is balanced by potential operative time and surgical site contamination/infection related to this bulky technology.

METHODS

Patients who underwent navigated or conventional single-level posterior instrumented lumbar fusions were identified in the 2010-2015 NSQIP database. The usage of navigation was characterized. Patient characteristics and comorbidities were compared between the two treatment groups. Propensity score matching was done and comparisons were made for operative time, hospital length of stay, postoperative complications, and 30-day readmissions between the two cohorts.

RESULTS

The percentage of navigated cases tended to increase over years studied to approximately 10%. After propensity matching to control potential confounding factors, statistical analysis revealed no significant difference in operative time and for most adverse events including wound infection, return to the operating room, and readmission. There were significantly lower blood transfusions in the navigated cohort (2.84% vs. 7.15%, P < 0.001). Patients who underwent navigated surgery also had a shorter mean hospital length of stay (0.2 day difference, P = 0.016).

CONCLUSION

The reduced blood loss and mildly reduced hospital length of stay identified for the navigated cases are probably markers of more minimally invasive surgery in the navigated cohort. The current study could not identify other differences in operative time, wound infection, or return to the operating room/readmission between navigated and conventional single level posterior instrumented lumbar cases.

LEVEL OF EVIDENCE

3.

Definitional Differences of 'Outpatient' Versus 'Inpatient' THA and TKA Can Affect Study Outcomes

BACKGROUND

There has been great interest in performing outpatient THA and TKA. Studies have compared such procedures done as outpatients versus inpatients. However, stated "outpatient" status as defined by large national databases such as the National Surgical Quality Improvement Program (NSQIP) may not be a consistent entity, and the actual lengths of stay of those patients categorized as outpatients in NSQIP have not been specifically ascertained and may in fact include some patients who are "observed" for one or more nights. Current regulations in the United States allow these "observed" patients to stay more than one night at the hospital under observation status despite being coded as outpatients. Determining the degree to which this is the case, and what, exactly, "outpatient" means in the NSQIP, may influence the way clinicians read studies from that source and the way hospital systems and policymakers use those data.

QUESTIONS/PURPOSES

The purposes of this study were (1) to utilize the NSQIP database to characterize the differences in definition of "inpatient" and "outpatient" (stated status versus actual length of stay [LOS], measured in days) for THA and TKA; and (2) to study the effect of defining populations using different definitions.

METHODS

Patients who underwent THA and TKA in the 2005 to 2014 NSQIP database were identified. Outpatient procedures were defined as either hospital LOS = 0 days in NSQIP or being termed "outpatient" by the hospital. The actual hospital LOS of "outpatients" was characterized. "Outpatients" were considered to have stayed overnight if they had a LOS of 1 day or longer. The effects of the different definitions on 30-day outcomes were evaluated using multivariate analysis while controlling for potential confounding factors.

RESULTS

Of 72,651 patients undergoing THA, 529 were identified as "outpatients" but only 63 of these (12%) had a LOS = 0. Of 117,454 patients undergoing TKA, 890 were identified as "outpatients" but only 95 of these (11%) had a LOS = 0. After controlling for potential confounding factors such as gender, body mass index, functional status before surgery, comorbidities, and smoking status, we found "inpatient" THA to be associated with increased risk of any adverse event (relative risk, 2.643, p = 0.002), serious adverse event (relative risk, 2.455, p = 0.011), and readmission (relative risk, 2.775, p = 0.010) compared with "outpatient" THA. However, for the same procedure and controlling for the same factors, patients who had LOS > 0 were not associated with any increased risk compared with patients who had LOS = 0. A similar trend was also found in the TKA cohort.

CONCLUSIONS

Future THA, TKA, or other investigations on this topic should consistently quantify the term "outpatient" because different definitions, stated status or actual LOS, may lead to different assignments of risk factors for postoperative complications. Accurate data regarding risk factors for complications after total joint arthroplasty are crucial for efforts to reduce length of hospital stay and minimize complications.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Outpatient and Inpatient Unicompartmental Knee Arthroplasty Procedures Have Similar Short-Term Complication Profiles

BACKGROUND

Advances in surgical techniques and anesthesia have made performing unicompartmental knee arthroplasty (UKA) in the outpatient setting a possibility. The touted benefits of outpatient surgery include higher patient satisfaction and reduced costs. However, detailed information on the perioperative outcomes of outpatient compared with inpatient UKA in a large, national patient population in the United States has never been reported. The present study compares perioperative complications between outpatient and inpatient UKAs in the National Surgical Quality Improvement Program database.

METHODS

Patients who underwent UKA were identified in the 2005-2015 National Surgical Quality Improvement Program database. Outpatient procedures were defined as those with length of hospital stay = 0 days, whereas inpatient procedures were defined as those with length of hospital stay = 1-4 days. Patients' characteristics and comorbidities were compared between the two groups. Propensity score matched comparisons were performed for 30-day perioperative complications and readmissions between the two cohorts.

RESULTS

This study included 568 outpatient and 5312 inpatient UKA cases. After propensity matching to control potential confounding factors, statistical analysis revealed no significant difference in any perioperative complications or any postdischarge complications between the outpatient and inpatient cohorts. Notably, the rate of 30-day readmissions between the two cohorts was not statistically different.

CONCLUSION

Based on the perioperative outcome measures assessed in this study, outpatient UKA can be appropriately considered in carefully selected patients based on the lack of differences in rates of 30-day perioperative complications and readmissions between the outpatient and matched inpatient groups.

Continued Inpatient Care After Primary Total Knee Arthroplasty Increases 30-Day Post-Discharge Complications: A Propensity Score-Adjusted Analysis

BACKGROUND

Discharge destination, either home or skilled care facility, after total knee arthroplasty (TKA) may be associated with significant variation in postacute care outcomes. The purpose of this study was to characterize the 30-day postdischarge outcomes after primary TKA relative to discharge destination.

METHODS

All primary unilateral TKAs performed for osteoarthritis from 2011-2014 were identified in the National Surgical Quality Improvement Program database. Propensity scores based on predischarge characteristics were used to adjust for selection bias in discharge destination. Propensity-adjusted multivariable logistic regressions were used to examine associations between discharge destination and postdischarge complications.

RESULTS

Among 101,256 primary TKAs identified, 70,628 were discharged home and 30,628 to skilled care facilities. Patients discharged to facilities were more frequently were female, older, higher body mass index class, higher Charlson comorbidity index and American Society of Anesthesiologists scores, had predischarge complications, received general anesthesia, and classified as nonindependent preoperatively. Propensity adjustment accounted for this selection bias. Patients discharged to skilled care facilities after TKA had higher odds of any major complication (odds ratio = 1.25; 95% confidence interval, 1.13-1.37) and readmission (odds ratio = 1.81; 95% confidence interval, 1.50-2.18). Skilled care was associated with increased odds for respiratory, septic, thromboembolic, and urinary complications. Associations with death, cardiac, and wound complications were not significant.

CONCLUSION

After controlling for predischarge characteristics, discharge to skilled care facilities vs home after primary TKA is associated with higher odds of numerous complications and unplanned readmission. These results support coordination of care pathways to facilitate home discharge after hospitalization for TKA whenever possible.

Comparison of Outpatient vs Inpatient Total Knee Arthroplasty: An ACS-NSQIP Analysis

BACKGROUND

There has been a recent surge of interest in performing primary total knee arthroplasty (TKA) in the outpatient setting to reduce cost and increase patient satisfaction. Detailed information on the safety of outpatient TKA in large sample sizes is scarce.

METHODS

Patients who underwent primary, elective TKA were identified in the 2005-2014 American College of Surgeons National Surgical Quality Improvement Program database. Outpatient procedure was defined as having a hospital length of stay of 0 days, whereas inpatient procedure was defined as having a length of stay ≥1 days. To reduce the effect of confounding factors and nonrandom assignment of treatment, propensity score matching was used. Multivariate analyses on the matched samples were used to compare the rates of adverse events that happened any time during the 30-day postoperative period, postdischarge adverse events, and readmissions between the outpatient and inpatient cohorts.

RESULTS

A total of 112,922 TKA patients met the inclusion criteria. Of these, only 642 (0.57%) were outpatient procedures. Outpatients tended to be men, slightly younger, and have less comorbidity. After propensity matching, multivariate analysis revealed a higher rate of postdischarge blood transfusions (P < .001) in the outpatient cohort. There were no other significant differences in 30-day postoperative individual adverse events or readmissions.

CONCLUSION

Based on the perioperative outcome measures studied here, outpatient TKA can be appropriately considered in select patients based on rates of overall perioperative adverse events and readmissions. However, higher surveillance of these patients postdischarge may be warranted.

Outcomes of Ceramic Bearings After Primary Total Hip Arthroplasty in the Medicare Population

BACKGROUND

The purpose of this study was to analyze the outcomes of ceramic bearings used in primary total hip arthroplasty (THA) in the Medicare population.

METHODS

A total of 315,784 elderly Medicare patients (65+) who underwent primary THA between 2005 and 2014 were identified from the United States Medicare 100% national administrative hospital claims database. Outcomes of interest included infection, dislocation, revision, or mortality at any time point after primary surgery. Propensity scores were developed to adjust for selection bias in the choice of bearing type at index primary surgery.

RESULTS

For primary THA patients treated with ceramic-on-polyethylene (C-PE) bearings and ceramic-on-ceramic (COC) bearings, there was significantly reduced risk of infection relative to metal-on-polyethylene (M-PE) bearings (C-PE hazard ratio [HR]: 0.86, P = .001; COC HR: 0.74, P = .01). For the C-PE cohort, we also observed reduced risk of dislocation (HR: 0.81, P < .001) and mortality (HR: 0.92, P < .001). There was no significant difference in risk of revision for either the C-PE or COC bearing cohorts when compared with M-PE. For the COC cohort, there was no significant difference in dislocation or mortality risk.

CONCLUSION

As in previous studies, we found that ceramic bearings have similar overall revision risk as M-PE bearings in primary THA at 8-9 years of follow-up. The results indicate that, after adjusting for selection bias and various confounding patient-, surgeon-, and hospital-related factors, Medicare primary THA patients treated with ceramic bearings exhibit lower risk of infection than those treated with M-PE bearings. In addition, C-PE bearings were associated with lower risk of dislocation and mortality.

Prognostic value of right upper mediastinal lymphadenectomy in Sweet procedure for esophageal cancer

BACKGROUND

The prognostic value of the right upper mediastinal lymph node dissection (RUMLND) for patients with middle or lower thoracic esophageal squamous cell carcinoma (ESCC-MLT) is still not well established yet. Our objective is to evaluate the prognostic role of the Sweet procedure plus right upper mediastinal lymph node dissection (MS) by comparing with the Sweet procedure with standard lymph node dissection (SS) in terms of long-term survival.

METHODS

Totally 1,477 ESCC-MLT patients underwent radical intent surgery (186 with MS, 1,291 with SS) at our department between January 2007 and September 2013. After propensity score matching (PSM), 186 patients from each group were matched and analyzed. The 5-year survival rates in two groups were compared by detailed stratifications in terms of clinical characteristics.

RESULTS

As for the prognostic role of RUMLND, patients treated with MS tended to obtain higher 5-year survival rate than patients treated with SS in univariate analysis (48.1% vs. 37.4%). Moreover, in multivariate analysis, MS yielded significant higher 5-year survival rate compared with SS (P=0.041). In addition, subgroup analyses of the survival between the MS and SS patients by detailed stratifications demonstrated the survival superiority in the MS group with age <60 years old, TNM stage III, number of lymph node dissection (LND) ≥15, as well as no using of postoperative adjuvant treatment.

CONCLUSIONS

The RUMLND in Sweet procedure is an independent prognostic factor for ESCC-MLT patients, especially for those with thoracic middle segment-located tumor, stage III or younger.

Left thoracotomy for middle or lower thoracic esophageal carcinoma: still Sweet enough?

BACKGROUND

Esophagectomy via left thoracotomy (the Sweet procedure) has long been the conventional route for resection of esophageal carcinoma, especially in China. However, this procedure is being increasingly critiqued, mainly regarding the lymphadenectomy. The objective of this study was to compare the Sweet procedure with the right upper mediastinal lymph node resection (MS) and Ivor-Lewis (IL) procedure in the treatment of middle or lower thoracic esophageal squamous cell carcinoma (OSCC-MLT) in terms of lymphadenectomy, postoperative complications, and long-term survival.

METHODS

A total of 336 OSCC-MLT patients underwent radical intent surgery (188 with MS and 148 with IL procedure) between January 2007 and September 2013 in our hospital. After propensity score matching, 129 patients from each procedure were included. The efficacy of lymph node dissection at each station was estimated by the index of estimated benefit from lymph node dissection (IEBLD).

RESULTS

IEBLD is relatively high in stations 2L, 2R, 8, 16 and 17. The metastasis rates and ratios were similar between the MS and IL procedures at each station. The MS procedure significantly outperformed the IL procedure with a shorter operating time (212 vs. 317 min), shorter in-hospital stay (10.7 vs. 15.3 days), and fewer postoperative complications (30.2% vs. 43.4%). However, the 5-year survival rates were not significantly different between the two procedures (46.9% vs. 44.0%).

CONCLUSIONS

The MS procedure of esophagectomy is not inferior to the IL procedure in efficiency, moreover the MS procedure is safer.

Outcomes of Ceramic Bearings After Revision Total Hip Arthroplasty in the Medicare Population

BACKGROUND

The purpose of this study was to analyze the utilization and outcomes of ceramic bearings used in revision total hip arthroplasty (R-THA) in the Medicare population.

METHODS

A total of 31,809 patients aged >65 years at the time of revision surgery who underwent R-THA between 2005 and 2013 were identified from the United States Medicare 100% national administrative claims database. Outcomes of interest included relative risk of readmission (90 days) or infection, dislocation, rerevision, or mortality at any time point after revision. Propensity scores were developed to adjust for selection bias in the choice of bearing type at revision surgery.

RESULTS

The utilization of ceramic-on-polyethylene (C-PE) and ceramic-on-ceramic (COC) bearings in R-THA increased from 5.3% to 26.6% and from 1.8% to 2.5% in between 2005 and 2013, respectively. For R-THA patients treated with C-PE bearings, there was reduced risk of 90-day readmission (hazard ratio, HR: 0.90, P = .007). We also observed a trend for reduced risk of infection with C-PE (HR: 0.88) that did not reach statistical significance (P = .14). For R-THA patients treated with COC bearings, there was reduced risk of dislocation (HR: 0.76, P = .04). There was no significant difference in risk of rerevision or mortality for either the C-PE or COC bearing cohorts when compared with the metal-on-polyethylene bearing cohort.

CONCLUSION

Medicare patients treated in a revision scenario with ceramic bearings exhibit similar risk of rerevision, infection, or mortality as those treated with metal-on-polyethylene bearings. Conversely, we found an association between the use of specific ceramic bearings in R-THA and reduced risk of readmission (C-PE) and dislocation (COC).

Hyaluronic Acid Injections in Medicare Knee Osteoarthritis Patients Are Associated With Longer Time to Knee Arthroplasty

BACKGROUND

Few nonoperative treatment options for knee osteoarthritis (OA) are available, but there is ongoing debate about the effectiveness of intra-articular (IA) hyaluronic acid (HA) injections. We investigated whether the formulation of IA HA, or its combined use with IA corticosteroid (CS), may be contributing to some of the reported variation in clinical outcomes.

METHODS

The 5% Part B Medicare data (2005-2012) were used to identify knee OA patients who underwent knee arthroplasty (KA). The time from diagnosis of OA to KA was compared between patients with (HA) and without (no HA) IA HA use, using quantile regression with propensity score adjustment. These were further stratified by type of IA HA. Patient factors associated with time to KA were also assessed using Cox regression.

RESULTS

The "HA" cohort was associated with a longer time to KA of 8.7 months (95% confidence interval: 8.3-9.1 months; P < .001) compared with the "no HA" cohort, with extended time to KA in the bioengineered Euflexxa IA HA cohort. Patient factors associated with longer time to KA included women, younger patients, minority patients, patients with fewer comorbidities, and IA CS injection use. Patients with both IA HA and IA CS had an additional 6.3 months (95% confidence interval: 5.5-7.0 months; P < .001) to KA over those with only IA HA.

CONCLUSION

In a large cohort of elderly patients undergoing KA, there was a significant longer time from diagnosis of OA to KA in those receiving IA HA. It is unclear if the extended time may lead to less KA utilization.