Singh et al. BMC Musculoskeletal Disorders (2017) 18:8 DOI 10.1186/s12891-016-1385-0
RESEARCH ARTICLE
Open Access
An underlying diagnosis of osteonecrosis of bone is associated with worse outcomes than osteoarthritis after total hip arthroplasty Jasvinder A. Singh1,2,3*, Jason Chen4, Maria C. S. Inacio4, Robert S. Namba5 and Elizabeth W. Paxton4
Abstract Background: Well-designed studies of complications and readmission rates in patients undergoing total hip arthroplasty (THA) with osteonecrosis are lacking. Our objective was to examine if a diagnosis of osteonecrosis was associated with complications, mortality and readmission rates after THA. Methods: We analyzed prospectively collected data from an integrated healthcare system’s Total Joint Replacement Registry of adults with osteonecrosis vs. osteoarthritis (OA) undergoing unilateral primary THA during 2001–2012, in an observational cohort study. We examined mortality (90-day), revision (ever), deep (1 year) and superficial (30-day) surgical site infection (SSI), venous thromboembolism (VTE, 90-day), and unplanned readmission (90-day). Age, gender, race, body mass index, American Society of Anesthesiologists class, and diabetes were evaluated as confounders. We used logistic or Cox regression to calculate odds or hazard ratios (OR, HR) with 95% confidence intervals (CI). Results: Of the 47,523 primary THA cases, 45,252 (95.2%) had OA, and 2,271 (4.8%) had osteonecrosis. Compared to the OA, patients with osteonecrosis were younger (median age 55 vs. 67 years), and were less likely to be female (42.5% vs. 58.3%) or White (59.8% vs. 77.4%). Compared to the OA, the osteonecrosis cohort had higher crude incidence of 90-day mortality (0.7% vs. 0.3%), SSI (1.2% vs. 0.8%), unplanned readmission (9.6% vs. 5.2%) and revision (3.1% vs. 2.4%). After multivariable-adjustment, patients with osteonecrosis had a higher odds/hazard of mortality (OR: 2.48; 95% CI:1.31–4.72), SSI (OR: 1.67, 95%CI:1.11–2.51), unplanned 90-day readmissions (OR: 2.20; 95% CI:1.67–2.91) and a trend towards higher revision rate 1-year post-THA (HR: 1.32; 95% CI: 0.94–1.84), than OA patients. Conclusions: Compared to OA, a diagnosis of osteonecrosis was associated with worse outcomes post-THA. A detailed preoperative discussion including the risk of complications is needed for informed consent from patients with osteonecrosis. Keywords: Total hip replacement, Readmission, Osteoarthritis, Osteonecrosis, Arthroplasty, Joint replacement, Diagnosis, Risk factor
* Correspondence: [email protected] “The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs or the United States government.” 1 Medicine Service, Birmingham VA Medical Center, Birmingham, AL, USA 2 Department of Medicine at School of Medicine, and Division of Epidemiology at School of Public Health, University of Alabama, Faculty Office Tower 805B, 510 20th Street S, Birmingham, AL 35294, USA Full list of author information is available at the end of the article © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Singh et al. BMC Musculoskeletal Disorders (2017) 18:8
Background Total hip arthroplasty (THA) is a successful surgical treatment for end stage arthritis [1]. The most common underlying diagnosis in patients undergoing elective THA is osteoarthritis (OA), followed by osteonecrosis, congenital hip disorders, and inflammatory arthritis [2]. A systematic review of 67 studies with 2,593 patients with 3,277 hips concluded that osteonecrosis was not associated with higher revision rates after THA compared to the other underlying diagnoses [3], with minor exceptions. A small single-site retrospective study of 31 patients with glucocorticoid-induced osteonecrosis undergoing THA reported improvement in pain and function with THA but high complication and reoperation rates [4]; however, there were no controls. Post-THA complications and associated hospital readmissions are undesirable THA outcomes of great interest clinically, due to associated morbidity. Post-arthroplasty complications, such as surgical site infections (SSI) and thromboembolic complications, are responsible for most surgically related readmissions [5–7]. Overall, 90-day readmission rates range 7–8% after primary THA or primary total knee arthroplasty [7–9]. Readmission rate can have a significant impact on health care resources, especially given the high volume of these procedures. Mortality is rare after THA (mostly elective) and is extremely undesirable. We recently showed that an underlying diagnosis of RA was associated with higher readmission rate compared to OA [10]. To our knowledge, studies of complications and readmission rates in patients undergoing THA with osteonecrosis are lacking. It is possible that outcomes in patients with osteonecrosis undergoing THA have improved over time due to the improvement in bearing surfaces and ubiquitous use of cementless fixation [11]. The objective of our study was to examine whether compared to OA, an underlying diagnosis of osteonecrosis was associated with a higher adjusted risk of complications and readmissions after primary THA (study hypothesis). We also performed exploratory analyses to assess the association of the cause of osteonecrosis with complications and readmissions post-primary THA. Methods We described study methods and results as recommended in the Strengthening of Reporting in Observational studies in Epidemiology (STROBE) statement [12]. Study design, data source, and patient sample
We performed a cohort study of patients who had undergone an elective unilateral primary THA using the Kaiser Permanente (KP) Total Joint Replacement Registry (TJRR). We identified a cohort of patients
Page 2 of 9
who underwent elective unilateral primary THA between 04/01/2001 and 12/31/2012. The KP is a integrated healthcare system that covers over 9.5 million members in 7 US geographical areas. We have previously reported details on the KP TJRR data collection procedures, structure, and participation [13, 14]. The KP TJRR uses paper and electronic data capture tools to collect information by surgeons and other healthcare providers at the point of care, as well as data from other databases (including the electronic medical records) using electronic screening algorithms. The information from different data sources of the registry is linked using the integrated healthcare system’s unique patient identifiers. The data repository for the registry is a SQL database. A quarterly quality control check of these data ensures high accuracy. Specifically, the KP TJRR prospectively collects outcomes (i.e. readmissions, revision, SSI, venous thromboembolism (VTE)). Several outcomes including revision, SSI and VTE are adjudicated by review of charts by trained research associates [13, 14]. In a chart review of random sample of osteonecrosis and OA cases (n = 60; 30 cases each of osteonecrosis and OA) performed by an abstractor blinded to the database diagnosis, we found that the true positive rate of diagnoses (OA vs. osteonecrosis) was 88%. All registered cases in the KP TJRR are tracked until outcome and/or end of their lives. The voluntary participation of the KP TJRR in 2011 was 95% [14]. This study included all unilateral primary elective THA procedures, in patients aged 18 years old or older, with surgery indication for OA and/or osteonecrosis registered during the study period (N = 47,523). Patients who had a diagnosis of both OA and osteonecrosis (N = 563) were not included in the study. Patients who underwent revision THA, partial THA, or conversion procedures, as the index procedure, were not included in the study. This was done for two reasons: (1) the majority of THA are elective primary THA, our condition of interest; and (2) to keep the population homogeneous and allow easy interpretation of results. Cases from the geographical regions where the organization owns the hospitals (Southern California, Northern California, and Hawaii), covering 92% of the KP TJRR registered cases, were included. The final sample had cases from 50 hospitals and 362 surgeons. Outcome measures
The outcomes of interest in this study were mortality within 90 days, SSI (30 days for superficial and 1 year for deep infections), VTE within 90 days, unplanned readmissions within 90 days of the index primary elective THA, and revision (ever and for any reason). All outcome measures were obtained from the KP TJRR using
Singh et al. BMC Musculoskeletal Disorders (2017) 18:8
2001–12 data; timing of outcome assessment was chosen based on clinical relevance, based on feedback from an expert surgeon (R.N.). SSIs, which can be either deep or superficial were defined according to the Centers for Disease Control and Prevention/National Healthcare Safety Network criteria [15]. Superficial and deep SSI were also combined into one measure in this study since we anticipated a small number of events for these two components individually. The VTE measure, which included symptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE) in this study due to the small number of events, were identified using the Agency for Healthcare Research and Quality patient safety indicators technical specifications [16] and further confirmed by chart review validation by trained clinical research associates. Readmissions are captured by the KP TJRR using quarterly extracts from the institutional electronic medical records of all hospital readmissions post discharge from the original joint arthroplasty procedure, available from 2009. Only unplanned readmissions, which were determined based on the 2014 Centers for Medicare and Medicaid Services Procedure-Specific Readmission Measures Updates and Specification Report for Elective Primary THA [17] were included in the analysis. Planned admissions such as those likely for subsequent hip arthroplasty procedures (e.g. International Classifications of Disease, 9th Revision, code (ICD-9) 715.34, Osteoarthrosis, localized, pelvic region and thigh and ICD-9: 733.42, aseptic necrosis of head and neck of femur) were not included in the reported readmissions. Revisions were defined as any re-operation of the index procedure where a component was replaced.
Page 3 of 9
increment); American Society of Anesthesiologists (ASA) class (10% and p < 0.10 or deemed clinically important for the relationship studied. Odds ratios (OR), hazard ratios (HR), 95% confidence internals (CI), and p-values are reported. A sensitivity analysis was conducted to evaluate the robustness of estimations accounting for missing data. We also performed sensitivity analyses that adjusted for the competing risk of death. No formal sample size calculations were done for this observational cohort study. Data were analyzed using SAS (Version 9.2, SAS Institute, Cary, NC, USA) and p-value
RESEARCH ARTICLE
Open Access
An underlying diagnosis of osteonecrosis of bone is associated with worse outcomes than osteoarthritis after total hip arthroplasty Jasvinder A. Singh1,2,3*, Jason Chen4, Maria C. S. Inacio4, Robert S. Namba5 and Elizabeth W. Paxton4
Abstract Background: Well-designed studies of complications and readmission rates in patients undergoing total hip arthroplasty (THA) with osteonecrosis are lacking. Our objective was to examine if a diagnosis of osteonecrosis was associated with complications, mortality and readmission rates after THA. Methods: We analyzed prospectively collected data from an integrated healthcare system’s Total Joint Replacement Registry of adults with osteonecrosis vs. osteoarthritis (OA) undergoing unilateral primary THA during 2001–2012, in an observational cohort study. We examined mortality (90-day), revision (ever), deep (1 year) and superficial (30-day) surgical site infection (SSI), venous thromboembolism (VTE, 90-day), and unplanned readmission (90-day). Age, gender, race, body mass index, American Society of Anesthesiologists class, and diabetes were evaluated as confounders. We used logistic or Cox regression to calculate odds or hazard ratios (OR, HR) with 95% confidence intervals (CI). Results: Of the 47,523 primary THA cases, 45,252 (95.2%) had OA, and 2,271 (4.8%) had osteonecrosis. Compared to the OA, patients with osteonecrosis were younger (median age 55 vs. 67 years), and were less likely to be female (42.5% vs. 58.3%) or White (59.8% vs. 77.4%). Compared to the OA, the osteonecrosis cohort had higher crude incidence of 90-day mortality (0.7% vs. 0.3%), SSI (1.2% vs. 0.8%), unplanned readmission (9.6% vs. 5.2%) and revision (3.1% vs. 2.4%). After multivariable-adjustment, patients with osteonecrosis had a higher odds/hazard of mortality (OR: 2.48; 95% CI:1.31–4.72), SSI (OR: 1.67, 95%CI:1.11–2.51), unplanned 90-day readmissions (OR: 2.20; 95% CI:1.67–2.91) and a trend towards higher revision rate 1-year post-THA (HR: 1.32; 95% CI: 0.94–1.84), than OA patients. Conclusions: Compared to OA, a diagnosis of osteonecrosis was associated with worse outcomes post-THA. A detailed preoperative discussion including the risk of complications is needed for informed consent from patients with osteonecrosis. Keywords: Total hip replacement, Readmission, Osteoarthritis, Osteonecrosis, Arthroplasty, Joint replacement, Diagnosis, Risk factor
* Correspondence: [email protected] “The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs or the United States government.” 1 Medicine Service, Birmingham VA Medical Center, Birmingham, AL, USA 2 Department of Medicine at School of Medicine, and Division of Epidemiology at School of Public Health, University of Alabama, Faculty Office Tower 805B, 510 20th Street S, Birmingham, AL 35294, USA Full list of author information is available at the end of the article © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Singh et al. BMC Musculoskeletal Disorders (2017) 18:8
Background Total hip arthroplasty (THA) is a successful surgical treatment for end stage arthritis [1]. The most common underlying diagnosis in patients undergoing elective THA is osteoarthritis (OA), followed by osteonecrosis, congenital hip disorders, and inflammatory arthritis [2]. A systematic review of 67 studies with 2,593 patients with 3,277 hips concluded that osteonecrosis was not associated with higher revision rates after THA compared to the other underlying diagnoses [3], with minor exceptions. A small single-site retrospective study of 31 patients with glucocorticoid-induced osteonecrosis undergoing THA reported improvement in pain and function with THA but high complication and reoperation rates [4]; however, there were no controls. Post-THA complications and associated hospital readmissions are undesirable THA outcomes of great interest clinically, due to associated morbidity. Post-arthroplasty complications, such as surgical site infections (SSI) and thromboembolic complications, are responsible for most surgically related readmissions [5–7]. Overall, 90-day readmission rates range 7–8% after primary THA or primary total knee arthroplasty [7–9]. Readmission rate can have a significant impact on health care resources, especially given the high volume of these procedures. Mortality is rare after THA (mostly elective) and is extremely undesirable. We recently showed that an underlying diagnosis of RA was associated with higher readmission rate compared to OA [10]. To our knowledge, studies of complications and readmission rates in patients undergoing THA with osteonecrosis are lacking. It is possible that outcomes in patients with osteonecrosis undergoing THA have improved over time due to the improvement in bearing surfaces and ubiquitous use of cementless fixation [11]. The objective of our study was to examine whether compared to OA, an underlying diagnosis of osteonecrosis was associated with a higher adjusted risk of complications and readmissions after primary THA (study hypothesis). We also performed exploratory analyses to assess the association of the cause of osteonecrosis with complications and readmissions post-primary THA. Methods We described study methods and results as recommended in the Strengthening of Reporting in Observational studies in Epidemiology (STROBE) statement [12]. Study design, data source, and patient sample
We performed a cohort study of patients who had undergone an elective unilateral primary THA using the Kaiser Permanente (KP) Total Joint Replacement Registry (TJRR). We identified a cohort of patients
Page 2 of 9
who underwent elective unilateral primary THA between 04/01/2001 and 12/31/2012. The KP is a integrated healthcare system that covers over 9.5 million members in 7 US geographical areas. We have previously reported details on the KP TJRR data collection procedures, structure, and participation [13, 14]. The KP TJRR uses paper and electronic data capture tools to collect information by surgeons and other healthcare providers at the point of care, as well as data from other databases (including the electronic medical records) using electronic screening algorithms. The information from different data sources of the registry is linked using the integrated healthcare system’s unique patient identifiers. The data repository for the registry is a SQL database. A quarterly quality control check of these data ensures high accuracy. Specifically, the KP TJRR prospectively collects outcomes (i.e. readmissions, revision, SSI, venous thromboembolism (VTE)). Several outcomes including revision, SSI and VTE are adjudicated by review of charts by trained research associates [13, 14]. In a chart review of random sample of osteonecrosis and OA cases (n = 60; 30 cases each of osteonecrosis and OA) performed by an abstractor blinded to the database diagnosis, we found that the true positive rate of diagnoses (OA vs. osteonecrosis) was 88%. All registered cases in the KP TJRR are tracked until outcome and/or end of their lives. The voluntary participation of the KP TJRR in 2011 was 95% [14]. This study included all unilateral primary elective THA procedures, in patients aged 18 years old or older, with surgery indication for OA and/or osteonecrosis registered during the study period (N = 47,523). Patients who had a diagnosis of both OA and osteonecrosis (N = 563) were not included in the study. Patients who underwent revision THA, partial THA, or conversion procedures, as the index procedure, were not included in the study. This was done for two reasons: (1) the majority of THA are elective primary THA, our condition of interest; and (2) to keep the population homogeneous and allow easy interpretation of results. Cases from the geographical regions where the organization owns the hospitals (Southern California, Northern California, and Hawaii), covering 92% of the KP TJRR registered cases, were included. The final sample had cases from 50 hospitals and 362 surgeons. Outcome measures
The outcomes of interest in this study were mortality within 90 days, SSI (30 days for superficial and 1 year for deep infections), VTE within 90 days, unplanned readmissions within 90 days of the index primary elective THA, and revision (ever and for any reason). All outcome measures were obtained from the KP TJRR using
Singh et al. BMC Musculoskeletal Disorders (2017) 18:8
2001–12 data; timing of outcome assessment was chosen based on clinical relevance, based on feedback from an expert surgeon (R.N.). SSIs, which can be either deep or superficial were defined according to the Centers for Disease Control and Prevention/National Healthcare Safety Network criteria [15]. Superficial and deep SSI were also combined into one measure in this study since we anticipated a small number of events for these two components individually. The VTE measure, which included symptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE) in this study due to the small number of events, were identified using the Agency for Healthcare Research and Quality patient safety indicators technical specifications [16] and further confirmed by chart review validation by trained clinical research associates. Readmissions are captured by the KP TJRR using quarterly extracts from the institutional electronic medical records of all hospital readmissions post discharge from the original joint arthroplasty procedure, available from 2009. Only unplanned readmissions, which were determined based on the 2014 Centers for Medicare and Medicaid Services Procedure-Specific Readmission Measures Updates and Specification Report for Elective Primary THA [17] were included in the analysis. Planned admissions such as those likely for subsequent hip arthroplasty procedures (e.g. International Classifications of Disease, 9th Revision, code (ICD-9) 715.34, Osteoarthrosis, localized, pelvic region and thigh and ICD-9: 733.42, aseptic necrosis of head and neck of femur) were not included in the reported readmissions. Revisions were defined as any re-operation of the index procedure where a component was replaced.
Page 3 of 9
increment); American Society of Anesthesiologists (ASA) class (10% and p < 0.10 or deemed clinically important for the relationship studied. Odds ratios (OR), hazard ratios (HR), 95% confidence internals (CI), and p-values are reported. A sensitivity analysis was conducted to evaluate the robustness of estimations accounting for missing data. We also performed sensitivity analyses that adjusted for the competing risk of death. No formal sample size calculations were done for this observational cohort study. Data were analyzed using SAS (Version 9.2, SAS Institute, Cary, NC, USA) and p-value
