Orthopedics

Review Article 

Predictors of Hospital Readmission After Total Shoulder Arthroplasty

Philip J. Belmont Jr, MD; Nicholas A. Kusnezov, MD; John C. Dunn, MD; Julia O. Bader, PhD; Kelly Kilcoyne, MD; Brian R. Waterman, MD

Abstract

The study was conducted to determine the incidence rate, risk factors, and postoperative conditions associated with 30-day readmission after total shoulder arthroplasty (TSA). A total of 3547 patients who underwent primary TSA were identified from the 2011–2013 American College of Surgeons National Surgical Quality Improvement Program. The 30-day readmission rate was 2.9%. The only preoperative predictors of hospital readmission were American Society of Anesthesiologists classification of 3 or greater (odds ratio, 2.16; 95% confidence interval, 1.30–3.61) and a history of cardiac disease (odds ratio, 2.13; 95% confidence interval, 1.05–4.31). Of patients with any perioperative complications, 42 (34%) were readmitted, and the presence of any complication increased the risk of readmission (odds ratio, 28.95; 95% confidence interval, 18.44–45.46). Periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, and pneumonia were significant predictors of hospital readmission after TSA (P<.0001). The incidence of hospital readmission after TSA peaked within the first 5 days after discharge, and 26%, 32%, and 55% of all hospital readmissions occurred by postoperative days 5, 7, and 14, respectively. Pre-operative medical optimization to reduce the rates of postoperative complications, such as periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, pneumonia, and urinary tract infection, are likely to decrease the need for subsequent readmission. Patients should be counseled about these risk factors preoperatively. [Orthopedics. 2017; 40(1):e1–e10.]

Abstract

The study was conducted to determine the incidence rate, risk factors, and postoperative conditions associated with 30-day readmission after total shoulder arthroplasty (TSA). A total of 3547 patients who underwent primary TSA were identified from the 2011–2013 American College of Surgeons National Surgical Quality Improvement Program. The 30-day readmission rate was 2.9%. The only preoperative predictors of hospital readmission were American Society of Anesthesiologists classification of 3 or greater (odds ratio, 2.16; 95% confidence interval, 1.30–3.61) and a history of cardiac disease (odds ratio, 2.13; 95% confidence interval, 1.05–4.31). Of patients with any perioperative complications, 42 (34%) were readmitted, and the presence of any complication increased the risk of readmission (odds ratio, 28.95; 95% confidence interval, 18.44–45.46). Periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, and pneumonia were significant predictors of hospital readmission after TSA (P<.0001). The incidence of hospital readmission after TSA peaked within the first 5 days after discharge, and 26%, 32%, and 55% of all hospital readmissions occurred by postoperative days 5, 7, and 14, respectively. Pre-operative medical optimization to reduce the rates of postoperative complications, such as periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, pneumonia, and urinary tract infection, are likely to decrease the need for subsequent readmission. Patients should be counseled about these risk factors preoperatively. [Orthopedics. 2017; 40(1):e1–e10.]

In the era of growing health care expenditures, policymakers are increasingly seeking measures to reduce preventable medical costs and optimize administrative efficiency. Hospital readmissions are a burden on the health care system, contributing as much as $20 billion in costs per year.1–9 In response to this issue, the Patient Protection and Affordable Care Act established the Hospital Readmission Reduction Program to curtail costs incurred as a result of unplanned readmissions.10–14 Hospital readmission rates have quickly become a metric for evaluating hospital performance by the Centers for Medicare & Medicaid Services and the National Quality Forum.10,14 Financial penalties are imposed for rates exceeding normative values.15 Among the fields affected by these programs, orthopedic surgery has received significant focus because of its heavy reliance on ambulatory procedures and inpatient surgery.16

The use of total shoulder arthroplasty (TSA) in the US health care system has risen dramatically over the past few decades, with a nearly 250% increase to 47,000 TSA procedures performed in 2008.17 Despite the increasing prevalence of TSA procedures, limited broad-based data are available on their cost and epidemiology.17–19 As a significant contributor to elective orthopedic surgical hospital readmissions, TSA is likely to become a major contributor to mounting health care expenses. Although factors that affect length of stay after TSA are well delineated,20 literature on readmission after TSA is limited to either single-institution21,22 or registry data.23–26 Readmission rates after TSA have been reported at 4.5% to 6.0% at 90 days,21,25 and rates are significantly lower than after total knee arthroplasty or total hip arthroplasty.23 However, pre- and postoperative in-hospital patient characteristics that herald an increased likelihood of readmission are largely unexamined, with only 1 known retrospective, single-state registry exploring variables that predict readmission after TSA.25

This study was conducted to identify factors associated with postoperative readmission after TSA. The authors used the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database, with the goal of reducing unplanned readmissions and associated costs. A model for reducing readmissions would provide a basis for early intervention and provide strategies to reduce adverse events and secondary health care costs associated with readmission. To replicate the interval used by existing quality control programs, this study evaluated patient characteristics and surgical variables leading to 30-day postoperative readmission after TSA.

Materials and Methods

This study was exempted from institutional review board approval because it was a publicly available, deidentified database review study. The American College of Surgeons NSQIP database was queried. The NSQIP is a data repository that receives records from 374 participating medical centers across several US health care settings. Patients enrolled in the NSQIP are prospectively followed for 30 days postoperatively and are monitored for hospital readmission, postoperative complications, and mortality. The ACS stringently maintains NSQIP, and it has shown excellent interrater reliability, with a 1.6% disagreement rate for all variables.27 The use of the NSQIP database and its methods are well documented28–32 and can be referenced in the program's participant user guide.33

The Current Procedural Terminology (CPT) code 23472 for total shoulder arthroplasty was used to identify patients who underwent this procedure and had their data registered with the NSQIP from 2011 to 2013. In the existing classification, CPT code 23472 includes both anatomic TSA and reverse TSA prosthesis. Independent analysis of anatomic TSA and reverse TSA prosthesis was not possible because of the shared CPT code. Patient-specific factors, including demographic data, medical comorbidities, and selected laboratory values, were recorded (Table 1). In addition, surgical characteristics were obtained, including total operative time, mode of anesthesia, and postoperative blood transfusion within 72 hours of the procedure.


Patient Demographics and Preoperative Characteristics
Patient Demographics and Preoperative Characteristics

Table 1:

Patient Demographics and Preoperative Characteristics

Systemic and local complications were classified as either major or minor, based on the categories used in previous reports (Tables 23).34,35 Major systemic complications were recognized as those requiring complex medical intervention. Major local complications included periprosthetic joint infection, peripheral nerve injury, and implant failure. Periprosthetic joint infections included all deep wound and organ or space surgical site infections. Deep surgical site infections were defined as those occurring within 30 days after the principal operative procedure and involving deep soft tissues as well as either purulent drainage, spontaneous dehiscence with signs or symptoms of infection, or abscess. Hospital readmission within 30 days of the index TSA was the primary outcome measure.


Complications (Current Procedural Terminology Code 23472)

Table 2:

Complications (Current Procedural Terminology Code 23472)


Univariate and Chi-square Analysis of the Influence of Risk Factors on 30-Day Readmission Rate
Univariate and Chi-square Analysis of the Influence of Risk Factors on 30-Day Readmission Rate

Table 3:

Univariate and Chi-square Analysis of the Influence of Risk Factors on 30-Day Readmission Rate

Bivariate logistic regression analysis was used to determine the effect of patient variables, surgical factors, and complications on hospital readmission. Principal patient-based predictors included medical comorbidities, wound classification (clean vs clean contaminated/contaminated/dirty/infected), age (<60 years, 60–69 years, 70–79 years, and ≥80 years), sex, body mass index (≤29.9, 30.0–39.9, and ≥40 kg/m2), hospital discharge status (admitted from home vs admitted from acute care hospital/nursing home/outside emergency department/other), American Society of Anesthesiologists (ASA) classification (1 or 2 vs 3 or 4), designated preoperative laboratory values, and functional status (independent vs dependent). Patients were determined to have a history of cardiac disease if they had 1 or more of the following: new diagnosis or exacerbation of chronic congestive heart failure within 30 days of surgery, history of angina within 30 days of surgery, history of myocardial infarction within the past 6 months, or any percutaneous cardiac intervention or other history of cardiac surgery. Surgical risk factors incorporated were mode of anesthesia (general vs spinal/epidural/regional), operative time, and blood transfusion within 72 hours postoperatively. Operative time was characterized as being greater or less than the average procedural time plus 1 SD. Surgical outcomes included those specified within the NSQIP data set by the surgical clinical reviewers and were indexed as mortality, all complications, major systemic complications, major local complications, minor systemic complications, and minor local complications.

For all factors with P<.2 and with frequencies greater than 10 on initial bivariate testing, multivariate logistic regression analysis was used.36,37 To minimize model distortion, any variable that was absent in more than 20% of the cohort was excluded from multivariate analysis. Both odds ratio (OR) and 95% confidence interval (CI) were reported. Significant independent predictor variables were identified as those that maintained P<.05 with OR and 95% CI exclusive of 1.0 after multivariate analysis. The C-statistic was used to measure discriminative capacity, and the Hosmer and Lemeshow goodness of fit test was used to assess model calibration.

Results

There were 3547 patients who underwent TSA. Mean age of the entire cohort was 70.1 (±9.9) years (Table 1). A substantial number of patients had comorbidities that included ASA classification of 3 or greater (51.8%), diabetes (16.7%), and body mass index of 40 or greater (9.0%). Within the 30-day postoperative period, 8 patients (0.23%) died and 122 (3.4%) had 1 or more complications (Table 2). A total of 46 major systemic complications occurred in 44 (1.2%) patients, and 75 minor systemic complications occurred in 70 (2.0%) patients. Of the major systemic complications, 52% were cardiovascular. Pulmonary embolism was the most prevalent (0.4%), followed by myocardial infarction (0.3%). Transfusion was required in 5.4% of patients. Urinary tract infection (1.0%), pneumonia (0.5%), and deep venous thrombosis (0.5%) were the most common minor systemic complications. There were 13 patients (0.4%) who had a major local complication and 11 patients (0.3%) who had a minor local complication. Deep wound infection was the most common major local complication (0.4%). Average length of stay was 2.2 (±2.2) days, and 103 patients (2.9%) were readmitted within 30 days of discharge after TSA.

Of the patients who had any complication, 42 (34%) were readmitted. Perioperative complications were strongly associated with increased risk of readmission (OR, 28.95; 95% CI, 18.44–45.46). Complications with readmission rates that approximated or exceeded 50% included pulmonary embolism, postoperative sepsis, cardiac arrest requiring cardiopulmonary resuscitation, deep venous thrombosis, progressive renal insufficiency, periprosthetic infection, and wound dehiscence (Table 2).

Bivariate analysis identified multiple risk factors for readmission, and these were analyzed in multivariate testing (Table 3). Multivariate logistic regression analysis showed that ASA classification of 3 or greater (OR, 2.16; 95% CI, 1.30–3.61) and a history of cardiac disease (OR, 2.13; 95% CI, 1.05–4.31) were the only preoperative surgical characteristics that predicted hospital readmission (Table 4). Preoperative demographics, including age, sex, body mass index, functional status, and remaining medical comorbidities, as well as surgical variables, such as operative time, type of anesthesia, and need for blood transfusion, were no longer significant. Individual postoperative complications that were significantly associated with hospital readmission included periprosthetic joint infection (OR, 268.93; 95% CI, 57.43–1001.00), myocardial infarction (OR, 29.32; 95% CI, 7.34–117.49), pulmonary embolism (OR, 21.18; 95% CI, 4.85–92.48), deep venous thrombosis (OR, 21.10; 95% CI, 6.41–69.44), pneumonia (OR, 11.99; 95% CI, 3.52–40.80), and urinary tract infection (OR, 6.35; 95% CI, 2.33–17.35). The C-statistic (0.79) for the final regression model indicated good discriminative capacity, and the goodness of fit test showed no statistically significant lack of fit, which indicates good calibration between the model and the source data.


Significant Risk Factors for 30-Day Readmission

Table 4:

Significant Risk Factors for 30-Day Readmission

Information on the timing of hospital readmission was available for 71.8% (74 of 103) of cases. The incidence of hospital readmissions after TSA peaked within the first 5 days after discharge, and 26%, 32%, and 55% of all hospital readmissions occurred by postoperative days 5, 7, and 14, respectively.

Discussion

The overall 30-day readmission rate after TSA was 2.9%, which is comparable to the rate of 2.7% for anatomic and reverse TSA reported in the only other study with a similar period of postoperative surveillance.21 In this previous single-center review of 556 TSA procedures, the readmission rate after TSA increased to 4.5% at 60 days and 5.2% at 90 days postoperatively. In comparison, the overall 30-day readmission rate after total hip arthroplasty or total knee arthroplasty with the NSQIP data set was 3.7% to 4.6%.30,31 To the authors' knowledge, the current study is the first to evaluate the effect of patient-based variables, surgical risk factors, and postoperative complications on hospital readmission after TSA. Contemporary patients undergoing TSA have significant medical comorbidities, and the current study cohort had an ASA classification of 3 or greater (51.8%), age 70 years or older (54.7%), diabetes (16.7%), and morbid obesity (9.0%). As a result, recognition of pertinent patient-based and surgical risk factors for stratifying individual surgical outcomes and the incidence of hospital readmission is essential. The current study found that ASA classification of 3 or greater (OR, 2.16; 95% CI, 1.30–3.61) and a history of cardiac disease (OR, 2.13; 95% CI, 1.05–4.31) were the only preoperative surgical characteristics that predicted readmission after multivariate analysis. The remaining preoperative demographic and surgical variables identified on univariate analysis were no longer significant on multivariate analysis after controlling for the influence of the remaining risk factors. In contrast, the role of patient factors and surgical characteristics in hospital readmission after TSA in single-state24–26 or single-institution investigations21 is limited because these studies did not provide the same level of detail on medical comorbidities, laboratory values, and surgical characteristics as the NSQIP data set. Additionally, the current study found no difference for factors previously shown to predict increased 60- to 90-day readmission rates after TSA, such as age,25 race,26 or increasing number of medical comorbidities.25

After TSA, 3.4% of patients had a complication that significantly increased the likelihood of readmission (OR, 28.95; 95% CI, 18.44–45.46). Systemic complications accounted for three-fourths of patients with major complications (77%) and minor complications (86%). Multivariate analysis showed that medical complications that were significant risk factors for readmission included myocardial infarction, pulmonary embolism, deep venous thrombosis, pneumonia, and urinary tract infection. Further, periprosthetic joint infection was the strongest predictor of hospital readmission and the only statistically significant local complication. Medical complications rather than surgical complications were responsible for most readmissions after TSA, and this finding corroborates previous studies that showed that 80% to 82% of complications leading to readmission after TSA were medical.25,26

The identification of pertinent complications that contribute to hospital readmission after primary TSA can lead to targeted interventions to mitigate these complications in high-risk patients during the perioperative period. In the absence of reliable evidence, the American Academy of Orthopaedic Surgeons offered a consensus statement advocating for perioperative mechanical or chemical venous thromboembolic prophylaxis for patients undergoing TSA. Although deep venous thrombosis and pulmonary embolism were among the most common and significant complications associated with readmission, few clinical studies have investigated these complications38–42 and their appropriate treatment. This finding underscores the importance of postoperative surveillance for venous thromboembolic disease and careful consideration of chemoprophylaxis in patients undergoing TSA. Additionally, in patients with a history of cardiac disease, cardiology consultation and medical optimization and moderation of risk factors for postoperative urinary tract infection, such as prolonged catheterization, may decrease readmissions after TSA. Finally, hospitals may be pressured to use evidence-based algorithms that have been shown to improve clinical outcomes and reduce length of stay after total joint arthroplasty, independent of hospital or procedure volume,43 to recoup financial incentives.44

Studies of overall 30-,21 60-,21 and 90-day21,25,26 TSA readmission rates have not provided a detailed analysis of trends in readmission within the first 30 days. When patients are followed for a 90-day period, the plurality of TSA readmissions occur within the first 30 days after hospital discharge.21 The current study found that among patients with a known time line for readmission, 26% occurred within 5 days and 55% occurred within 14 days. Average length of stay was 2.2 days in the TSA cohort. Most preventable hospital readmissions occur in the days immediately after discharge and are related to coordination of care.45 These data suggest that efforts to decrease readmissions after TSA should be directed toward patients with ASA classification of 3 or greater or with a history of cardiac disease as well as those with a postoperative complication, including periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, pneumonia, and urinary tract infection. Careful preoperative screening and discharge planning, with close postoperative surveillance, may be considered in patients with these risk factors, especially within the first 2 weeks after discharge.

Limitations

The strength of the NSQIP data set is its prospective multi-institutional data collection of patient-based and surgical characteristics as well as postoperative complications among more than 3500 TSA procedures. Within the NSQIP infrastructure, rigid protocols dictate close oversight to limit errors in reporting adverse outcomes and maintain the fidelity of data.27,32 The study had several methodologic limitations. First, the NSQIP does not include information on potential variables, such as hospital volume, insurance status, discharge destination, and standardized comorbidity scores.24–26 The study attempted to account for comorbid disease with the use of ASA classification as a proxy risk factor for overall health status.27 Second, the study did not stratify rates of readmission by operative indication and surgical technique (eg, anatomic TSA and reverse TSA) because these procedures were classified under a common CPT code during the study period. Based on previous studies that showed an increased risk of complications in patients undergoing reverse TSA, the 2.9% readmission rate in the current study may be an overestimate of the TSA readmission rate and an underestimate of the reverse TSA readmission rate. However, more recent prospective case-control studies showed no difference in major complications or revision surgery at 2 years when TSA and reverse TSA were compared.46 Third, the NSQIP data set relates readmissions and the causative condition. Thus, it was not possible to determine the exact cause of readmission or to determine whether readmission events were directly related to the TSA procedure or to complications of surgery.

Despite these limitations, this investigation offers the most comprehensive evaluation of 30-day readmission rates in a large volume of patients undergoing TSA in the United States. Measures to decrease hospital readmission rates must focus on clinically relevant perioperative variables that inform composite risk stratification and reduce medical costs across the continuum of care.47 Optimized pre-operative and perioperative management of patients undergoing TSA with ASA classification of 3 or greater or a history of cardiac disease may include preoperative screening, in-depth surgical counseling, and referral for medical management. Medical interventions to minimize the potential for postoperative complications, such as periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, pneumonia, and urinary tract infection, are likely to decrease the need for hospital readmission.

Conclusion

Risk factors that increase the likelihood of readmission after TSA include ASA classification of 3 or greater and a history of cardiac disease. Preoperative medical optimization to reduce rates of postoperative complications, such as periprosthetic joint infection, myocardial infarction, pulmonary embolism, deep venous thrombosis, pneumonia, and urinary tract infection, are likely to decrease the need for hospital readmission. Patients should be counseled on these risk factors preoperatively.

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  47. Kansagara D, Englander H, Salanitro A, et al. Risk prediction models for hospital readmission: a systematic review. JAMA. 2011; 306(15):1688–1698. doi:10.1001/jama.2011.1515 [CrossRef]

Patient Demographics and Preoperative Characteristics

CharacteristicValueTotal No. of PatientsNo.

No ReadmissionReadmission
Age, mean±SD, y70.1±9.935473444103
  <60 y, No. (%)495 (14.0)-48213
  60–69 y, No. (%)1114 (31.4)-109321
  70–79 y, No. (%)1301 (36.7)-126239
  ≥80 y, No. (%)637 (18.0)-60730
Sex, No. (%)-35443441103
  Male1540 (43.4)-149248
  Female2004 (56.6)-194955
Body mass index, mean±SD, kg/m230.7±6.735363433103
  ≤29.9 kg/m2, No. (%)1841 (52.1)-178655
  30.0–39.9 kg/m2, No. (%)1377 (38.9)-133839
  ≥40.0 kg/m2, No. (%)318 (9.0)-3099
Functional status, No. (%)-35133411102
  Independent3415 (97.2)-332095
  Partially or totally dependent98 (2.8)-917
Transfer status, No. (%)-35453443102
  From acute care hospital/inpatient9 (0.3)-81
  Not transferred (admitted from home)3505 (98.9)-340897
  Nursing home/chronic care/intermediate care25 (0.7)-223
  Outside emergency department4 (0.1)-31
  Transfer from other2 (0.1)-20
Wound classification, No. (%)-35473444103
  Clean3489 (98.4)-3388101
  Clean/contaminated, contaminated, dirty/infected58 (1.6)-562
American Society of Anesthesiologists classification, No. (%)-35423439103
  1–21710 (48.3)-168030
  3–41832 (51.8)-175973
Preoperative laboratory values, mean±SD-
  Hematocrit40.2%±4.4%3189309693
  Platelets, ×103/µL241.5±69.63130303991
  Creatinine, mg/dL1.0±0.63130303496
  Serum albumin, g/dL4.0±0.41315127738
Medical comorbidities, No. (%)-
  Smokinga337 (9.5)35473444103
  All diabetesb591 (16.7)35473444103
  Dyspnea244 (6.9)35473444103
  Hypertension2407 (67.9)35473444103
  Any cardiac issuec154 (4.3)35473444103
  Previous myocardial infarction within 6 mo2 (0.1)35473444103
  Percutaneous cardiac intervention86 (2.4)35473444103
  Previous cardiac surgery71 (2.0)35473444103
  History of revascularization/amputation for peripheral vascular disease/rest pain/gangrene7 (0.2)35473444103
  Previous transient ischemic attack/cerebrovascular accident/stroke with neurologic deficit/cerebrovascular accident/stroke without neurologic deficit76 (2.1)35473444103
  Dialysis use/renal failure18 (0.5)35473444103
  Systemic sepsis (yes/no)16 (0.5)35473444103
  Previous operation within 30 d5 (0.1)35473444103
Operative time, mean±SD, min117.4±46.835463443103
  ≤117 min, No. (%)3080 (86.9)-299288
  >117 min, No. (%)466 (13.1)-45115
Type of anesthesia, No. (%)35473444103
  General3408 (96.1)-3307101
  All others139 (3.9)-1372
Occurrence of bleeding transfusions (≥1 unit packed/whole red blood cells given within 72 h postoperatively), No. (%)35473444103
  None3354 (94.6)-326193
  ≥1 unit193 (5.4)-18310
Time from operation to discharge, mean±SD, d2.1±2.135473444103

Complications (Current Procedural Terminology Code 23472)

CharacteristicNo. (%)No.Readmission <30 DaysaP

No ReadmissionReadmission
Overall complications122 (3.4)804228.95 (18.44–45.46)<.0001
Major systemic complications44 (1.2)261827.84 (14.71–52.72)<.0001
  Pulmonary embolism13 (0.4)7630.37 (10.02–92.07)<.0001
  Unplanned intubation4 (0.1)3114.41 (1.68–123.32).01
  Postoperative sepsis/septic shock8 (0.2)26106.41 (21.21–533.86)<.0001
  Stroke/cerebrovascular accident5 (0.1)418.43 (0.93–76.11).06
  Acute renal failure1 (0.03)10--
  Cardiac arrest requiring cardiopulmonary resuscitation2 (0.1)1133.54 (2.08–539.90).01
  Myocardial infarction11 (0.3)7420.74 (6.02–71.44)<.0001
  Coma0 (0)00--
Minor systemic complications70 (2.0)482219.22 (11.08–33.33)<.0001
  Urinary tract infection37 (1.0)2989.92 (4.42–22.27)<.0001
  Deep venous thrombosis16 (0.5)8836.18 (13.30–98.43)<.0001
  Pneumonia19 (0.5)13616.33 (6.08–43.86)<.0001
  Progressive renal insufficiency3 (0.1)1268.12 (6.13–757.19)0
Major local complications13 (0.4)310123.33 (33.39–455.52)<.0001
  Deep wound infection/organ or space surgical site infection12 (0.4)210185.03 (39.98–856.23)<.0001
  Peripheral nerve injury1 (0.03)10--
  Graft/prosthesis failure0 (0)00--
Minor local complications11 (0.3)6529.24 (8.77–97.42)<.0001
  Superficial wound infection7 (0.2)5213.63 (2.61–71.07)0
  Wound disruption4 (0.1)1379.83 (9.33–693.33)<.0001
Mortality or major complication61 (1.7)342735.63 (20.48–62.01)<.0001

Univariate and Chi-square Analysis of the Influence of Risk Factors on 30-Day Readmission Rate

Risk FactoraReadmission <30 DaysbP
Age, y
  Age, continuous1.03 (1.01–1.06).0037
Sex
  Female vs male1.14 (0.77–1.69).5133
Body mass index, mean, kg/m2
  Body mass index, continuous0.98 (0.95–1.01).2931
Functional status
  Dependent vs independent2.69 (1.21–5.96).0148
Wound classification
  All other vs clean1.20 (0.29–4.98).8035
American Society of Anesthesiologists classification
  ≥3 (severe or life-threatening disturbance) vs ≤2 (no or mild disturbance)2.32 (1.51–3.57).0001
Preoperative laboratory values
  Platelets, mean±SD, ×103/µL0.997 (0.993–1.000).0403
  Serum albumin, mean±SD, g/dL0.44 (0.22–0.89).0213
  Prealbumin (≤3.5 g/dL vs >3.5 g/dL)2.40 (1.12–5.18).0251
Medical comorbidities
  Dyspnea2.39 (1.36–4.21).0024
  Hypertension1.88 (1.16–3.05).0107
  Any cardiac issue3.07 (1.64–5.73).0004
  Percutaneous cardiac intervention3.11 (1.40–6.91).0054
  Previous cardiac surgery3.85 (1.72–8.62).001
  History of revascularization/amputation for peripheral vascular disease/rest pain/gangrene7.76 (1.15–52.22)
  Sepsis within 48 h before surgery4.86 (1.09–21.64).0382
  Previous surgery <30 d earlier11.19 (1.47–85.53).0199
Comorbidities, total
  3 vs 05.02 (2.53–9.96).0016
Operative time, min
  Operative time, continuous1.002 (0.998–1.006).3753
Type of anesthesia
  General vs spinal/epidural/regional2.84 (0.39–20.51).3019
Bleeding transfusions
  Yes vs no1.92 (0.98–3.74).0567
Time from operation to discharge1.03 (0.99–1.08).1871
Length of stay (≥5 d vs <5 d)2.64 (1.34–5.17).0049

Significant Risk Factors for 30-Day Readmission

Risk FactorReadmission <30 DaysaP
American Society of Anesthesiologists classification ≥3 (severe or life-threatening disturbance) vs ≤2 (no or mild disturbance)1.84 (1.14–2.96).012
Sepsis within 48 h before surgery8.99 (2.16–37.48).0026
Pulmonary embolism15.36 (3.45–68.42).0003
Myocardial infarction24.44 (6.17–96.76)<.0001
Urinary tract infection7.38 (2.92–18.67)<.0001
Deep venous thrombosis20.87 (6.47–67.31)<.0001
Pneumonia10.85 (3.36–34.99)<.0001
Authors

The authors are from the Department of Orthopaedic Surgery (PJB, NAK, JCD, KK, BRW) and the Department of Clinical Investigations (JOB), William Beaumont Army Medical Center, El Paso, Texas.

The authors have no relevant financial relationships to disclose.

The views expressed in this manuscript are those of the authors and do not reflect the official policy of the William Beaumont Army Medical Center, the Department of the Army, the Department of Defense, or the US Government. All authors are employees of the US Government. This work was prepared as part of their official duties, and as such, there is no copyright to be transferred. The American College of Surgeons National Surgical Quality Improvement Program and the hospitals participating in the ACS NSQIP are the source of the data used herein; they have not verified and are not responsible for the statistical validity of the data analysis or the conclusions derived by the authors.

Correspondence should be addressed to: Brian R. Waterman, MD, Department of Orthopaedic Surgery, William Beaumont Army Medical Center, Texas Tech University Health Sciences Center, 5005 N Piedras St, El Paso, TX 79920 ( brian.r.waterman@gmail.com).

Received: August 23, 2015
Accepted: January 21, 2016
Posted Online: September 21, 2016

10.3928/01477447-20160915-06

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