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Complications, demographics and hospital stay in organ transplant patients undergoing total hip arthroplasty - A national database study between 2016 and 2019
, Vibhu Krishnan Viswanathanc, Vishaal Sakthivelnathand, Varatharaj Mounasamye, Senthil Sambandamf,
∗Corresponding author: Senthil Sambandam. vibhukviswanathan@gmail.com
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
The purpose of this study was to analyze the post-operative complications following THA in organ transplant patients; and compare the outcome with general population undergoing THA.
In this retrospective study using the National Inpatient Sample (NIS) database, 813 cases of THA (both primary and revision THA) in organ transplant patients (OT) were reviewed. ICD-10 codes were used to assess post-operative variables including the length of stay, cost of care, medical and surgical complications among OT patients undergoing THA. A comparison of all these variables was made with the non-OT (NOT) control population.
Among 367,894 patients undergoing THR between 2016 and 2019 on NIS database, 813 were OT patients. There was significantly greater proportion of males in the OT group (p < 0.001). Patients in the OT group were also significantly younger (mean age: 61.08 ± 11.95 in OT versus 65.87 ± 11.39 years in NOT; p < 0.001). The OT group had significantly higher prevalence of anemia (p < 0.001), acute renal failure (ARF; p < 0.001), and transfusion rates (p < 0.001). The OT patients also had significantly greater dislocation rates (p = 0.010), wound dehiscence (p = 0.03) and deep surgical-site infections (SSI; p = 0.002). The mean length of hospital stay (3.55 ± 4.89 days in OT vs 2.32 ± 2.52 days in NOT; p < 0.001), cost of care ($82,567.89 ± 74,505.54 vs $66,845.18 ± 47,761.39 for OT and NOT groups, respectively; p < 0.001) and mortality (p = 0.04) were significantly greater in the OT population, as compared to controls.
Organ transplant patients have significantly greater risk for developing post-operative complications like anemia, ARF, need for higher transfusion rates, prosthetic dislocations, wound dehiscence, and deep SSI following THA. The length of stay, total expenditure incurred and mortality were also higher in OT patients undergoing THA.
Keywords
Organ transplant
Demographics
Hospital stay
Total hip arthroplasty
Complications
Database study
1 Introduction
Organ transplant (OT) rates are increasing over the years world-wide and the number of organ transplants will continue to grow as the population of baby boomers gets older across the US and world. In 2021, in the United States alone, there were 41,354 organ transplants, which represented a 5.9% increase over 2020.1
Organ transplants lead to an increased risk for osteoporosis, fractures and avascular necrosis. Osteoporosis is increased due to pre-transplant bone loss, post-transplant risk due to bed rest, steroids, calcineurin inhibitors, and poor nutrition.1 In renal transplant patients, a 22.5% (ranging between 6% and 45%) increased risk of fractures has been reported after 5 years.2 Certain other studies in the literature have reported approximately 22%–42% enhanced risk of fractures following other visceral transplants.3 These statistics show that there is an overwhelmingly increased need for joint replacements in these patients. Several authors have reported that OT patients undergoing arthroplasty procedures have substantially higher complication rates and expenditure, in comparison with non-OT patients.4,5 Based on a retrospective cross-sectional data involving 1998 to 2011 National Inpatient Sample (NIS) data on patients undergoing total hip arthroplasty (THA), Navale et al.4 reported that OT patients exhibited higher rates of inpatient complications, longer hospital stay and greater admission costs. In another NIS data-based study,5 it was concluded that OT patients undergoing shoulder arthroplasty had substantially greater prevalence of co-morbidities, higher complication rates, longer length of hospital stay and inherently increased inpatient resource utilization.
Nevertheless, a majority of studies, published hitherto, have either involved a small sample size or are based on single-institution data. The studies, which have reported expenditure or complication rates, have also focused on specific types of organ transplants. In this study, we therefore utilized a large National Inpatient Sample (NIS) database to analyze the OT patients undergoing total hip arthroplasty (THA), with regard to patient demographics, length of stay, costs and complication rates.
2 Methods and Materials
2.1 Patient data
The study was conducted using the data from National Inpatient Sample Database (NIS) Healthcare Cost and Utilization Project (HCUP) Agency for Healthcare Research and Quality.6 We included data from 2016 to 2019. NIS is the largest all-payer inpatient care database within the United States, containing data from more than 7 million hospital stays, which encompasses 20% of the hospitals in the United States. This study was exempted from Institutional Review Board (IRB) approval (and need for consent from patients), since all the data are de-identified and publicly available.
Data elements within the NIS database include demographic data, length of stay, source of payment, hospital charges, discharge status, comorbidities, and more. The database utilizes the ICD-10-CM/PCS since 2015. The patients who underwent THR were identified using the ICD-10 procedural codes listed for primary or secondary procedure codes (Appendix 1). Using this search strategy, a total of 367,894 patients with THR (both primary and revision THA) were identified. Of the total, 813 were organ transplant patients, and the remaining were included as control (NOT) subjects.
Obesity, age, and sex were three pre-operative variables recorded. Post-operative medical and surgical outcomes studied from the NIS database included elective procedure, dislocation, mortality/death, hematoma, wound disruption, infection, anemia, acute renal failure (ARF), hypotension, pulmonary embolism (PE), myocardial infarction (MI), pneumonia, blood transfusions, intra-operative complications, deep venous thrombosis (DVT), stroke, peri-prosthetic fractures, prosthetic hip dislocations, prosthetic loosening, length of stay, and health care-related expenditure. A detailed comparison of all these demographic, clinical, outcome and hospital stay-related parameters was made between these two groups (OT versus NOT). The charge/costs were calculated in accordance with the methodology devised by Healthcare Cost and Utilization Project (HCUP) for calculating the Cost-to-charge ratios (CCR) (https://www.hcup-us.ahrq.gov/reports/methods/MS2021-05-CCR-Methodologies.pdf; https://www.hcup-us.ahrq.gov/db/ccr/ed-ccr/EDCCR-UserGuide-2012-2019.pdf).
2.2 Data analysis
Statistical analyses were conducted using SPSS version 27.0.7 Descriptive statistics were used to aggregate the patient demographic data. Analytical statistics were used to assess if there was any association between pre-operative and post-operative risk factors in organ transplant patients versus controls. T-tests were used for analyzing numerical variables like age, length of stay, and total hospital-related expenditure. Chi-squared analyses were used to analyze binomial variables.
Fischer Exact tests were used when the incidence values were less than 5; and Pearson chi-square for values greater than 5. A p-value ≤ 0.05 was considered statistically significant. Odds ratios and corresponding 95% confidence intervals for the surgical outcomes and complications were measured as a ratio of the incidence in the control group to the incidence in OT patients.
3 Results
Based on the NIS database, a total of 367,894 patients undergoing THR between 2016 and 2019, were identified. Among them, 813 were OT patients; and the remaining (367,894 patients) were included as controls (NOT group). Patients undergoing both primary and revision THA were included in this study.
3.1 Patient characteristics
OT patients were significantly younger (61.08 ± 11.95) than the control (65.87 ± 11.39) population (p < 0.001). There was substantially greater proportion of males in OT, as compared to NOT group (61% in OT versus 43.9% in NOT group; p < 0.001). There was substantially greater proportion of patients belonging to African-American, Hispanic or Asian ethnicity in the OT group; while patients of Caucasian background were more common in the NOT group (p < 0.001). The patients belonging to NOT group had substantially greater prevalence of emergent admissions, as compared with the OT patients (p < 0.001; Table 1). Since the data was retrieved from NIS database using ICD-10 codes for specific diagnoses, the details regarding the indications for undergoing THA, prior history of surgical procedures (including previous hips surgeries), previous anesthesia- or surgery-related complications, history of immunosuppressant medications, time interval between organ transplant and THA etc. could not be evaluated in the current study.
| Organ Transplant (N = 813) | Control (N = 367,894) | p value | |
| Male | 496 (61%) | 161,618 (43.9%) | <0.001 |
| Age (in years) | 61.08 ± 11.95 | 65.87 ± 11.39 | <0.001 |
| Elective vs emergent admissions | 114 (14.02%) vs 698 (85.98%) | 31,720 (8.62%) vs 334,855 (91.38%) | <0.001 |
| Race | |||
| Caucasian | 577 (72.95%) | 314,917 (85.6%) | <0.001 |
| African-American | 125 (15.80%) | 28,549 (7.76%) | |
| Hispanic | 50 (6.32%) | 13,502 (3.67%) | |
| Asian or Pacific Islander | 23 (2.91%) | 3531 (0.96%) | |
| Native American | *** | 1140 (0.31%) | |
| Other | 13 (1.64%) | 6255 (1.70%) | |
| Patient Disposition Following Discharge | |||
| Routine (home) | 270 (33.21%) | 143,331 (38.96%) | <0.001 |
| Short term hospital stays | *** | 883 (0.24%) | |
| Another type of facility | 208 (25.58%) | 67,472 (18.34%) | |
| Home health care | 327 (40.22%) | 155,619 (42.3%) | |
| LAMA | 0 (0%) | 258 (0.07%) | |
| Death | *** | 331 (0.09%) | |
3.2 Length of stay and cost of care
There was a statistically significant difference in the mean length of hospital stay between the two groups (3.55 ± 4.89 days in OT versus 2.32 ± 2.52 days in NOT patients; p < 0.001). The total reported expenditure was significantly higher in OT patients ($82,567.89 ± 74,505.54), in comparison with the control group ($66,845.18 ± 47,761.39; p < 0.001; Table 2).
| OT group | NOT group | p value | |
| Length of Stay (years) | 3.55 ± 4.89 | 2.32 ± 2.52 | <0.001 |
| Total Charge | $82,567.89 ± 74,505.54 | $66,845.18 ± 47,761.39 | <0.001 |
3.3 Systemic complications
There was a significantly higher (four times greater rate) mortality rate in OT (0.36%), as compared to NOT (0.09%) group (p = 0.04). Anemia was the most commonly reported systemic complication. 28.5% of OT patients had postoperative anemia, as compared to 19.5% in NOT patients (p < 0.001). There was also a significantly greater need for blood transfusions in the OT group (7.63% in OT group versus 3.5% in NOT control group; p=<0.001). The prevalence of ARF was 5.37 times higher in the OT group, as compared to the control group (11.93% in OT group vs 2.5% in control population; p=<0.001). There was no statistically significant difference between the two groups with respect to other systemic complications like MI, pneumonia, DVT and PE.
3.4 Local complications
The prosthetic dislocation rate was significantly higher in OT patients, in comparison with the control group (2.4% dislocation rate in OT vs 1.4% in control group; p = 0.01; Table 3). Wound dehiscence following THA was also significantly higher among OT, in comparison with the controls [0.37% (OT) vs 0.08 (NOT); OR = 4.47; p = 0.03]. The incidence of deep SSI was also substantially higher in OT group (OR = 32.38, p < 0.001). On the other hand, there was no statistically significant difference in the peri-prosthetic mechanical complication rates or peri-prosthetic fractures between the two groups.
| Number in NOT Group (N = 367,894) | Number in OT Group (N = 813) | Odds Ratio (95% CI) | p value | |
| Death/Mortality | 331 (0.09%) | *** (0.36%) | 4.13 (1.32/12.89) | 0.038 |
| Anemia | 71,886 (19.54%) | 235 (28.91%) | 1.67 (1.44/1.95) | <0.001 |
| Acute Renal failure (ARF) | 9197 (2.5%) | 97 (11.93%) | 5.37 (4.34/6.65) | <0.001 |
| Deep Venous Thrombosis (DVT) | 560 (0.15%) | *** | 1.61 (0.40/6.48) | 0.35 |
| Pulmonary embolism (PE) | 4819 (1.31%) | 0 | *** | |
| Myocardial infarction (MI) | 147 (0.04%) | *** | 3.21 (0.45/22.94) | 0.27 |
| Pneumonia | 957 (0.26%) | *** | 1.87 (0.69/5.00) | 0.17 |
| Blood Transfusions | 12,840 (3.5%) | 62 (7.63%) | 2.28 (1.76/2.95) | <0.001 |
| Periprosthetic Fractures | 4413 (1.2%) | 12 (1.48%) | 1.23 (0.69/2.18) | 0.47 |
| Dislocations | 5150 (1.4%) | 20 (2.46%) | 1.78 (1.14/2.78) | 0.01 |
| Peri-prosthetic mechanical complications | 2848 (0.77%) | *** | 1.27 (0.63/2.55) | 0.49 |
| Peri-prosthetic infections | 3820 (1.04%) | 11 (1.35%) | 1.30 (0.72/2.37) | 0.38 |
| Wound dehiscence | 304 (0.08%) | *** (0.37%) | 4.47 (1.43/13.96) | 0.03 |
| Deep SSI | 28 (0.008%) | *** | 32.33 (7.69/135.93) | 0.002 |
| Superficial SSI | 43 (0.011%) | 0 | *** |
3.5 Discharge disposition
With regard to the disposition of the patients following discharge, a significantly greater proportion of patients in NOT group were discharged home following surgery; while a substantial proportion of OT patients required to be transferred to alternate health care facilities (p < 0.001).
4 Discussion
Our study observed that OT patients had a significantly different demographic profile, as compared to NOT patients. These patients also had a significantly longer length of hospital stay and incurred greater health care-related costs. We could also observe that OT patients were at a substantially higher risk for mortality, multiple systemic (anemia, ARF) and local complications (wound dehiscence, prosthetic dislocations and deep SSI) as compared to the non-OT patients. Thus, based on our study, the OT patients had a significantly more adverse and complicated post-surgical phase, in comparison with the general population.
The length of stay for OT patients was 1.22 days longer than the control population. Certain previous studies in the literature involving OT patients undergoing THA also made similar observations. In the study by Navale et al.,4 organ transplant patients undergoing hip arthroplasty required 4.47 days of mean peri-operative hospital stay.4 Similar studies have reported longer hospital stays in OT patients undergoing joint arthroplasties: 0.27 days longer following shoulder arthroplasty, 0.44 days longer following knee arthroplasty, and 4.2 days longer after hip arthroplasty.5,8,9 The reasons underlying the longer length of stay in organ transplant patients are multifactorial; and include higher incidence of complication rates, need for extended antibiotic prophylaxis, and a multidisciplinary team approach with specialists to address associated co-morbidities.
Additionally, the expenditure incurred by the organ transplant patients in our cohort was also approximately $15,000 higher than the control group. These findings were in agreement with the observations made by previous researchers. Navale et al.,4 in his cohort of OT undergoing THA, had reported $887 additional charges in comparison with the control population. Klika et al.9 showed that OT patients undergoing total knee arthroplasty (TKA) incurred approximately $962 higher expenditure. This difference in the admission costs could be attributed to the need for higher quality of care, involvement of greater number of specialist physicians involved in the patient care, requirement for more investigations, medications (both for infection prophylaxis and failure of transplant rejection); and longer length of hospital stay.
In our study, organ transplant patients who underwent THA tended to be younger. Brown et al.10 reported that OT patients undergoing hip or knee replacement had a significantly lower mean age of 61 years (as compared with a mean age of 65 years in the control population). Sayeed Noor,11 in his study, also observed that OT patients required arthroplasty procedures at a substantially younger age (mean age of 49 years). The possible reasons underlying the need for hip replacement in the OT patients at a relatively younger age include higher prevalence of osteoporosis, osteonecrosis, and fractures secondary to bone loss resulting from immunosuppressive treatments.
In our patient cohort, 61% of organ transplant patients were males (which was significantly higher than the control population). Similar trends of male predominance have also been reported by previous studies on organ transplant patients undergoing joint arthroplasties.5,12 In a previous study on shoulder arthroplasty procedures in OT patients, 53% of patients were males. In general, the visceral transplant rates have been reported to be more common in males, which could possibly explain the male predominance observed in our study too. In a study published in 2015 on the annual kidney transplant report, greater than 60% of transplant recipients were reported to be males.12
The overall rates of systemic and local complications were significantly higher in the OT patients. The organ transplant patients had 1.67 times greater chance of developing anemia in our patient cohort. On a similar note, Agarwal et al.13 reported a significantly higher incidence of anemia following hip replacement in organ transplant patients. In general, the enhanced risk of anemia in organ transplant patients can be attributed to the poor general systemic condition of the patients due to poor kidney function, iron deficiency anemia, transplant rejection, chronic inflammation, and immunosuppressive medications. Blood transfusion rates were also 2.28 times more likely in OT patients than in the control cohort. In another study involving patients undergoing shoulder arthroplasty, a significantly higher rate of blood transfusion was reported in OT patients. A significantly lower pre-operative hematocrit value and chronic use of immunosuppressive medications in the OT group could be contributory to such high transfusion rates.13,14
There was a 5.37-fold increase in ARF in the organ transplant group after hip arthroplasty This finding was also supported by the report by Cavanaugh et al.,15 where the incidence of post-operative ARF was 3.48% in kidney transplant patients and 4.48% in liver transplant patients undergoing joint replacements. In the study by Han et al. too,16 liver transplant patients had greater chances of developing ARF after joint replacements (OR: 5.40 and 4.35 after hip and knee replacements, respectively). This finding could be attributed to poor renal perfusion due to a history of CKD, nephrotoxic anti-rejection drugs, and overall negative, peri-operative fluid balance in these complicated scenarios.17
We could also observe a significantly higher risk of local complications in OT patients following THA. The risk of deep SSI was significantly higher in organ transplant cohort. Similarly, the rate of wound dehiscence was also substantially higher in the organ transplant patients. This relatively higher rates of infectious complications in organ transplant patients following arthroplasty procedures is quite understandable, considering the high association with systemic comorbidities, need for chronic immunosuppressive medications and higher need for blood product transfusions peri-operatively.14,17 Dislocation rates were also 1.78 times more likely in OT patients of our cohort. In a previously published meta-analysis, there was a significantly higher risk of hip dislocations (6%) in renal transplant patients.18,19 Such higher dislocation rates may be attributed to the poor soft tissue quality, need for complicated surgical procedures and poor bone density in this complicated patient cohort.20
In our patient cohort, mortality was 4.13 times higher in the organ transplant patients. In a single-institution study by Brown et al.10 too, mortality rates following joint replacement surgeries were substantially higher (with OR of 7.42; p < 0.001) in individuals who had previously undergone organ transplants. The increased mortality in this group of patients is not surprising, considering that they are high-risk, immunocompromised patients (in view of all the aforementioned reasons).
4.1 Limitations of the study
The current study suffers from the inherent weaknesses related to use of NIS data. This database only records the administrative data for the duration of initial hospitalization of the patients. Such administrative databases carry the liability of variable levels of reliability. Details regarding the long-term patient outcome after discharge, which are crucial factors in patients undergoing arthroplasty surgeries, cannot be evaluated with NIS database. In addition, even though the details and variables coded in NIS are reasonably accurate (specificity of at least 92%), it can be incomplete. The major advantage of this data is this is the largest available database involving all payers in the United States. This makes it an ideal sample to study rare cohorts of patients, such as OT patients in our study.
5 Conclusion
Organ transplant patients are at substantially greater risk for developing several post-operative systemic and local complications including anemia, ARF, need for higher transfusion rates, prosthetic dislocations, wound dehiscence, and deep SSI following THA. The length of stay, total expenditure incurred and mortality rates are also significantly higher in OT patients undergoing THA.
Ethical (IRB) approval and consent to participate
Not applicable since data base is commercially available and HIPAA compliant.
Consent for publication
All authors consent for publication of this manuscript.
Availability of supporting data
No other supporting data available.
Funding
No external source of funding received for this project.
CRediT authorship contribution statement
Sushrruthi Varatharaj: Data analysis, writing up manuscript, reviewing and language editing. Tejas Senthil: Data processing, data analysis, preparing tables, language editing, proof reading. Vibhu Krishnan Viswanathan: Data processing, data analysis, reviewing manuscript content, overseeing manuscript preparation and language editing. Vishaal Sakthivelnathan: Data procurement and processing, data analysis, reviewing manuscript content and language editing. Varatharaj Mounasamy: Formulating research methodology, reviewing manuscript content and overseeing manuscript preparation. Senthil Sambandam: Conceptualization, formulating research methodology, data procurement and processing, data analysis, reviewing manuscript, proof reading and submitting.
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