A 90-day Bundled Payment for Primary Single-level Lumbar Discectomy/Decompression: What Does "Big Data" Say?

Reimbursement of Lumbar Fusion at an Orthopaedic Specialty Hospital Versus Tertiary Referral Center

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVE

To explore the differences in Medicare reimbursement for lumbar fusion performed at an orthopaedic specialty hospital (OSH) and a tertiary referral center and to elucidate drivers of Medicare reimbursement differences.

SUMMARY OF BACKGROUND DATA

To provide more cost-efficient care, appropriately selected patients are increasingly being transitioned to OSHs for lumbar fusion procedures. There are no studies directly comparing reimbursement of lumbar fusion between tertiary referral centers (TRC) and OSHs.

METHODS

Reimbursement data for a tertiary referral center and an orthopaedic specialty hospital were compiled through the Centers for Medicare and Medicaid Services. Any patient with lumbar fusions between January 2014 and December 2018 were identified. OSH patients were matched to TRC patients by demographic and surgical variables. Outcomes analyzed were reimbursement data, procedure data, 90-day complications and readmissions, operating room times, and length of stay (LOS).

RESULTS

A total of 114 patients were included in the final cohort. The tertiary referral center had higher post-trigger ($13,554 vs. $8,541, P <0.001) and total episode ($49,973 vs. $43,512, P <0.010) reimbursements. Lumbar fusion performed at an OSH was predictive of shorter OR time (β=0.77, P <0.001), shorter procedure time (β=0.71, P <0.001), and shorter LOS (β=0.53, P <0.001). There were no significant differences in complications (9.21% vs. 15.8%, P =0.353) or readmission rates (3.95% vs. 7.89%, P =0.374) between the 2 hospitals; however, our study is underpowered for complications and readmissions.

CONCLUSION

Lumbar fusion performed at an OSH, compared with a tertiary referral center, is associated with significant Medicare cost savings, shorter perioperative times, decreased LOS, and decreased utilization of post-acute resources.

LEVEL OF EVIDENCE

3.

Lumbar Laminotomy: Variables Affecting 90-day Overall Reimbursement

INTRODUCTION

Lumbar laminotomy/diskectomy is a common procedure performed to address radiculopathy that persists despite conservative treatment. Understanding cost/reimbursement variability and its drivers has the potential to help optimize related healthcare delivery. The goal of this study was to assess variability and factors associated with reimbursement through 90 days after single-level lumbar laminotomy/diskectomy.

METHODS

Lumbar laminotomies/diskectomies were isolated from the 2010 to 2021 PearlDiver M151 data set. Exclusion criteria included patients younger than 18 years; other concomitant spinal procedures; and indications of trauma, oncologic, or infectious diagnoses. Patient, surgical, and perioperative data were abstracted. These variables were examined using a multivariable linear regression model with Bonferroni correction to determine factors independently correlated with reimbursement.

RESULTS

A total of 28,621 laminotomies/diskectomies were identified. The average ± standard deviation 90-day postoperative reimbursement was $9,453.83 ± 19,343.99 and, with a non-normal distribution, the median (inner quartile range) was $3,314 ($5,460). By multivariable linear regression, variables associated with greatest increase in 90-day postoperative reimbursement were associated with admission (with the index procedure [+$11,757.31] or readmission [+$31,248.80]), followed by insurance type (relative to Medicare, commercial +$4,183.79), postoperative adverse events (+$2,006.60), and postoperative emergency department visits (+$1,686.89) ( P < 0.0001 for each). Lesser associations were with Elixhauser Comorbidity Index (+$286.67 for each point increase) and age (-$24.65 with each year increase) ( P < 0.001 and P = 0.003, respectively).

DISCUSSION

This study assessed a large cohort of lumbar laminotomies/diskectomies and found substantial variations in reimbursement/cost to the healthcare system. The largest increase in reimbursement was associated with admission (with the index procedure or readmission), followed by insurance type, postoperative adverse events, and postoperative emergency department visits. These results highlight the need to balance inpatient versus outpatient surgeries while limiting postoperative readmissions to minimize the costs associated with healthcare delivery.

Patient-specific Risk Factors Increase Episode of Care Costs After Lumbar Decompression

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

To determine, which patient-specific risk factors increase total episode of care (EOC) costs in a population of Centers for Medicare and Medicaid Services beneficiaries undergoing lumbar decompression.

SUMMARY OF BACKGROUND DATA

Lumbar decompression is an effective option for the treatment of central canal stenosis or radiculopathy in patients unresponsive to nonoperative management. Given that elderly Americans are more likely to have one or more chronic medical conditions, there is a need to determine, which, if any, patient-specific risk factors increase health care costs after lumbar decompression.

METHODS

Care episodes limited to lumbar decompression surgeries were retrospectively reviewed on a Centers for Medicare and Medicaid Service reimbursement database at our academic institution between 2014 and 2019. The 90-day total EOC reimbursement payments were collected. Patient electronic medical records were then matched to the selected care episodes for the collection of patient demographics, medical comorbidities, surgical characteristics, and clinical outcomes. A stepwise multivariate linear regression model was developed to predict patient-specific risk factors that increased total EOC costs after lumbar decompression. Significance was set at P <0.05.

RESULTS

A total of 226 patients were included for analysis. Risk factors associated with increased total EOC cost included increased age (per year) (β = $324.70, P < 0.001), comorbid depression (β = $4368.30, P = 0.037), revision procedures (β = $6538.43, P =0.012), increased hospital length of stay (per day) (β = $2995.43, P < 0.001), discharge to an inpatient rehabilitation facility (β = $14,417.42, P = 0.001), incidence of a complication (β = $8178.07, P < 0.001), and readmission (β = $18,734.24, P < 0.001) within 90 days.

CONCLUSIONS

Increased age, comorbid depression, revision decompression procedures, increased hospital length of stay, discharge to an inpatient rehabilitation facility, and incidence of a complication and readmission within 90 days were all associated with increased total episodes of care costs.

Risk stratification of patients undergoing outpatient lumbar decompression surgery

BACKGROUND CONTEXT

Reimbursement has slowly transitioned from a fee-for-service model to a bundled payment model after introduction of the United States Centers for Medicare and Medicaid Services bundled payment program. To minimize healthcare costs, some surgeons are trying to minimize healthcare expenditures by transitioning appropriately selected lumbar decompression patients to outpatient procedure centers.

PURPOSE

To prepare a risk stratification calculator based on machine learning algorithms to improve surgeon's preoperative predictive capability of determining whether a patient undergoing lumbar decompression will meet inpatient vs. outpatient criteria. Inpatient criteria was defined as any overnight hospital stay.

STUDY DESIGN/SETTING

Retrospective single-institution cohort.

PATIENT SAMPLE

A total of 1656 patients undergoing primary lumbar decompression.

OUTCOME MEASURES

Postoperative outcomes analyzed for inclusion into the risk calculator included length of stay.

METHODS

Patients were split 80-20 into a training model and a predictive model. This resulted in 1,325 patients in the training model and 331 into the predictive model. A logistic regression analysis ensured proper variable inclusion into the model. C-statistics were used to understand model effectiveness. An odds ratio and nomogram were created once the optimal model was identified.

RESULTS

A total of 1,656 patients were included in our cohort with 1,078 dischared on day of surgery and 578 patients spending ≥ 1 midnight in the hospital. Our model determined older patients (OR=1.06, p<.001) with a higher BMI (OR=1.04, p<0.001), higher back pain (OR=1.06, p=.019), increasing American Society of Anesthesiologists (ASA) score (OR=1.39, p=.012), and patients with more levels decompressed (OR=3.66, p<0.001) all had increased risks of staying overnight. Patients who were female (OR=0.59, p=.009) and those with private insurance (OR=0.64, p=.023) were less likely to be admitted overnight. Further, weighted scores based on training data were then created and patients with a cumulative score over 118 points had a 82.9% likelihood of overnight. Analysis of the 331 patients in the test data demonstrated using a cut-off of 118 points accurately predicted 64.8% of patients meeting inpatient criteria compared to 23.0% meeting outpatient criteria (p<0.001). Area under the curve analysis showed a score greater than 118 predicted admission 81.4% of the time. The algorithm was incorporated into an open access digital application available here: https://rothmanstatisticscalculators.shinyapps.io/Inpatient_Calculator/?_ga=2.171493472.1789252330.1671633274-469992803.1671633274 CONCLUSIONS: Utilizing machine-learning algorithms we created a highly reliable predictive calculator to determine if patients undergoing outpatient lumbar decompression would require admission. Patients who were younger, had lower BMI, lower preoperative back pain, lower ASA score, less levels decompressed, private insurance, lived with someone at home, and with minimal comorbidities were ideal candidates for outpatient surgery.

Langerhans cell histiocytosis involving only the thymus in an adult: A case report

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare disease of unknown etiology. LCH involving the thymus is mainly seen in pediatric patients and is extremely rare in adults. In this report, we describe a rare case of LCH originating from the thymus in an adult.

CASE SUMMARY

A 56-year-old man was admitted in April 2022 with complaints of intermittent dizziness since 2020, which had worsened in the previous 10 d. The physical chest examination was negative, and there was a history of hypertension for > 2 years. Chest computed tomography showed a nodular soft tissue density shadow in the anterior mediastinum measuring approximately 13 mm × 9 mm × 8 mm. Postoperative pathological findings confirmed the diagnosis of LCH.

CONCLUSION

It is challenging to differentiate LCH involving the thymus from thymoma in imaging features. Pathological biopsy remains the gold standard when an anterior mediastinal occupying lesion is found.

Demographics and Medical Comorbidities as Risk Factors for Increased Episode of Care Costs Following Lumbar Fusion in Medicare Patients

The objective was to evaluate medical comorbidities and surgical variables as independent risk factors for increased health care costs in Medicare patients undergoing lumbar fusion. Care episodes limited to lumbar fusions were retrospectively reviewed on the Centers of Medicare and Medicaid Innovation (CMMI) Bundled Payment for Care Improvement (BPCI) reimbursement database at a single academic institution. Total episode of care cost was also collected. A multivariable linear regression model was developed to identify independent risk factors for increased total episode of care cost, and logistic models for surgical complications and readmission. A total of 500 Medicare patients were included. Risk factors associated with increased total episode of care cost included transforaminal interbody fusion (TLIF) and anterior lumbar interbody fusion (ALIF) (β = $5,399, P < 0.001) and ALIF+PLF (AP) fusions (β = $24,488, P < 0.001), levels fused (β = $3,989, P < 0.001), congestive heart failure (β = $6,161, P = 0.022), hypertension with end-organ damage (β = $10,138, P < 0.001), liver disease (β = $16,682, P < 0.001), inpatient complications (β = $4,548, P = 0.001), 90-day complications (β = $10,012, P = 0.001), and 90-day readmissions (β = $15,677, P < 0.001). The most common surgical complication was postoperative anemia, which was associated with significantly increased costs (β = $18,478, P < 0.001). Female sex (OR = 2.27, P = 0.001), AP fusion (OR = 2.59, P = 0.002), levels fused (OR = 1.45, P = 0.005), cerebrovascular disease (OR = 4.19, P = 0.003), cardiac arrhythmias (OR = 2.32, P = 0.002), and fluid electrolyte disorders (OR = 4.24, P = 0.002) were independent predictors of surgical complications. Body mass index (OR = 1.07, P = 0.029) and AP fusions (OR = 2.87, P = 0.049) were independent predictors of surgical readmission. Among medical comorbidities, congestive heart failure, hypertension with end-organ damage, and liver disease were independently associated with a significant increase in total episode of care cost. Interbody devices were associated with increased admission cost.

Reimbursement of Lumbar Decompression at an Orthopedic Specialty Hospital Versus Tertiary Referral Center

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to investigate the differences in Medicare reimbursement for one- to three-level lumbar decompression procedures performed at a tertiary referral center versus an orthopedic specialty hospital (OSH).

SUMMARY OF BACKGROUND DATA

Lumbar decompression surgery is one of the most commonly performed spinal procedures. Lumbar decompression also comprises the largest proportion of spinal surgery that has transitioned to the outpatient setting.

METHODS

Patients who underwent a primary one- to three- level lumbar decompression were retrospectively identified. Reimbursement data for a tertiary referral center and an OSH were compiled through Centers for Medicare and Medicaid Services. Demographic data, surgical characteristics, and time cost data were collected through chart review. Multivariate regression models were used to determine independent factors associated with total episode of care cost, operating room (OR) time, procedure time, and length of stay (LOS), and to determine independent predictors of having the decompression performed at the OSH.

RESULTS

Total episode of care, facility, and non-facility payments were significantly greater at the tertiary referral center than the OSH, as were OR time for one- to three-level procedures, procedure time of all pooled levels, and LOS for one- and two-level procedures. Three-level procedure was independently associated with increased OR time, procedure time, and LOS. Age and two-level procedure were also associated with increased LOS. Procedure at the OSH was associated with decreased OR time and LOS. Charlson Comorbidity Index was a negative predictor of decompression being performed in the OSH setting.

CONCLUSION

Significant financial savings to health systems can be expected when performing lumbar decompression surgery at a specialty hospital as opposed to a tertiary referral center. Patients who are appropriate candidates for surgery in an OSH can in turn expect faster perioperative times and shorter LOS.Level of Evidence: 3.

Burden of preoperative opioid use and its impact on healthcare utilization after primary single level lumbar discectomy

BACKGROUND CONTEXT

The complication profile and higher cost of care associated with preoperative opioid use and spinal fusion is well described. However, the burden of opioid use and its impact in patients undergoing lumbar discectomy is not known. Knowledge of this, especially for a relatively benign and predictable procedure will be important in bundled and value-based payment models.

PURPOSE

To study the burden of pre-operative opioid use and its effect on postoperative healthcare utilization, cost, and opioid use in patients undergoing primary single level lumbar discectomy.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

A 29,745 patients undergoing primary single level lumbar discectomy from the IBM MarketScan (2000-2018) database.

OUTCOME MEASURES

Ninety-day and 1-year utilization of lumbar epidural steroid injections, emergency department (ED) services, lumbar magnetic resonance imaging, hospital readmission, and revision lumbar surgery. Continued opioid use beyond 3-months postoperatively until 1-year was also studied. We have reported costs associated with healthcare utilization among opioid groups.

METHODS

Patients were categorized in opioid use groups based on the duration and number of oral prescriptions before discectomy (opioid naïve, < 3-months opioid use, chronic preoperative use, chronic preoperative opioid use with 3-month gap before surgery, and other). The risk of association of preoperative opioid use with outcome measures was studied using multivariable logistic regression analysis with adjustment for various demographic and clinical variables.

RESULTS

A total of 29,745 patients with mean age of 45.3±9.6 years were studied. Pre-operatively, 29.0% were opioid naïve, 35.0% had < 3-months use and 12.0% were chronic opioid users. There was a significantly higher rate of post-operative lumbar epidural steroid injections, magnetic resonance imaging , ED visits, readmission and revision surgery within 90-days and 1-year after surgery in chronic pre-operative opioid users as compared with patients with < 3-months use and opioid naïve patients (p<.001). Chronic post-operative opioid use was present in 62.6% of the preoperative chronic opioid users as compared with 5.6% of patients with < 3-months opioid use. A 3-month prescription free period before surgery in chronic pre-operative opioid users cut the incidence of chronic post-operative opioid use by more than half, at 25.7%. Cost of care and adjusted analysis of risk have been described.

CONCLUSION

Chronic preoperative opioid use was present in 12% of a national cohort of lumbar discectomy patients. Such opioid use was associated with significantly higher post-operative healthcare utilization, risk of revision surgery, and costs at 90-days and 1-year postoperatively. Two-third of chronic preoperative opioid users had continued long-term postoperative opioid use. However, a 3-month prescription free period before surgery in chronic opioid users reduces the risk of long-term postoperative use. This data will be useful for patient education, pre-operative opioid use optimization, and risk-adjustment in value-based payment models.

Outpatient Versus Inpatient Surgical Fixation of Isolated Ankle Fractures: An Analysis of 90-Day Complications, Readmissions, and Costs

Despite increasing interest toward managing isolated ankle fractures in an outpatient setting, evidence of its safety remains largely limited. The 2007 to 2014 Humana Administrative Claims database was queried to identify patients undergoing open reduction internal fixation for unimalleolar, bimalleolar, or trimalleolar isolated closed ankle fractures. Two cohorts (outpatient versus inpatient) were then matched on the basis of age, sex, race, region, fracture type (uni-/bi-/trimalleolar) and Elixhauser Comorbidity Index to control for selection bias. Multivariate regression analyses were performed to report independent impact of outpatient-treated ankle fracture surgery on 90-day complications, readmission, and emergency department visit rates. Independent-samples t test was used to compare global 90-day costs between cohorts. A total of 5317 inpatient-treated and 6941 outpatient-treated closed ankle fractures were included in the final cohort. After matching and multivariate analyses, patients with outpatient ankle fractures, compared with patients with inpatient ankle fractures, had statistically lower rates of pneumonia (2.3% versus 4.0%; p < .001), myocardial infarction (0.9% versus 1.8%; p = .005), acute renal failure (2.2% versus 5.3%; p < .001), urinary tract infections (7.4% versus 12.3%; p < .001), and pressure ulcers (0.9% versus 2.0%; p = .001). Outpatient ankle fractures also had lower rates of 90-day readmissions (9.7% versus 14.1%; p < .001) and emergency department visits (13.8% versus 16.2%; p = .028). Last, overall 90-day costs for outpatient ankle fractures were nearly $9000 lower than costs for inpatient ankle fractures ($12,923 versus $21,866; p < .001). Based on our findings, it appears that outpatient treatment of ankle fractures can be deemed safe and feasible in a select cohort of patients.

Lumbar disc herniation surgery: Is it worth adding interspinous spacer or instrumented fusion with regard to disc excision alone?

BACKGROUND

Discectomy is sometimes associated with recurrence of disc herniation and pain after surgery. The evidence to use an interspinous dynamic stabilization system or instrumented fusion in association with disc excision to prevent pain and re-operation remains controversial. In this study, we analyzed if adding interspinous spacer or fusion, offers advantages in relation to microdiscetomy alone.

METHODS

Patients with lumbar disc herniation were divided in 3 groups; microdiscectomy alone (MD), microdiscectomy plus interspinous spacer (IS) and open discectomy plus posterior lumbar interbody fusion (PLIF). The clinical efficacy was measured using the Owestry Disability Index (ODI). Other outcome parameters including visual analogue scale for pain (VAS) back and legs, length of stay, direct in-hospital cost, 90-day complication rate, and 1-year re-operation rate were also evaluated.

RESULTS

A total of 103 patients whose mean age was 39.1 (±8.5) years were included. A significant improvement of the ODI and VAS back and legs pain baseline score was detected in the 3 groups. After 1 year, no significant differences in ODI, VAS back and legs pain were found between the 3 groups. There was an increase of 169% of the total direct in- hospital cost in IS group and 287% in PLIF group, in relation to MD (p < 0.001). Length of stay was 86% higher in the IS group and 384% longer in the PLIF group compared to MD (p < 0.001). The 1 year re-operation rates were 5.6%, 10% and 16.2% (p = 0.33). Discectomy seems to be the main responsible for the clinical improvement, without the interspinous spacer or fusion adding any benefit. The addition of interspinous spacer or fusion increased direct in-hospital cost, length of stay, and did not protect against re-operation.

Reduction of direct costs in high-risk lumbar discectomy patients during the 90-day post-operative period through annular closure

Purpose

Despite being an extremely successful procedure, recurrent disc herniation is one of the most common post-discectomy complications in the lumbar spine and contributes significant health care and socioeconomic costs. Patients with large annular defects are at a high risk for reherniation, but an annular closure device (ACD) has been designed to reduce reherniation risk in this population and may, in turn, help control direct health care costs after discectomy.

Patients and methods

This analysis examined the 90-day post-discectomy cost estimates among ACD-treated (n=272) and control (discectomy alone; n=278) patients in a randomized controlled trial (RCT). Direct medical costs were estimated based on 2017 Humana and Medicare claims. Index discectomies were assumed to occur in an outpatient (OP) setting, whereas repeat discectomies were assumed to be 60% in OP and 40% in inpatient (IP). A sensitivity analysis was performed on this assumption. The device cost was not included in the analysis in order to focus on costs in the 90-day post-operative period.

Results

Within 90 days of follow-up, post-operative complications occurred in 3.3% of the ACD patients and 8.6% of the control patients (P=0.01). The average 90-day cost to treat an ACD patient was $10,257 compared to $11,299 per control patient for a 80:20 distribution of Commercial:Medicare coverage ($1,042 difference). This difference varied from $687 with 100% Medicare to $1,132 with 100% Commercial coverage. Varying the IP vs OP distribution resulted in a cost difference range of $968 to $1,156 with the ACD.

Conclusion

Augmenting discectomy with an ACD in high-risk patients with a large annular defect reduced reherniation and reoperation rates, which translated to a reduction of direct health care costs between $687 and $1,156 per patient during the 90-day post-operative period. Large annular defect patients are an easily identifiable high-risk population. Operative strategies that reduce complication risks in these patients, such as the ACD, could be advantageous from both patient care and economic perspectives.

Trends of postoperative length of stay in spine surgery over 10 years in Japan based on a prospective multicenter database

OBJECTIVES

To identify factors associated with prolonged length of stay (LOS) in spine surgery, with the goal of establishing details of LOS for multiple diseases and surgical procedures.

PATIENTS AND METHODS

The subjects were patients who underwent spine surgery at 10 facilities in the Nagoya Spine Group from January 2005 to December 2015. Data were collected for patient background, primary spinal pathology, anatomical location of the lesion, and surgical methods. The primary outcome was LOS, which was defined as the calendar days from surgery to hospital discharge.

RESULTS

A total of 10,829 patients (5953 males, 4876 females; age 5-93 years, mean 60.2 ± 28.8 years) were identified in the database. Average follow-up was 61 months (range: 13-120 months). Average LOS was 22.3 ± 21.3 days, and there was a gradual decrease in LOS over the study period. LOS was significantly correlated with age, and prolonged LOS was significantly associated with thoracic spine surgery and significantly longer after surgery with instrumentation. Average LOS was >30 days for intramedullary tumor resection and posterior cervical fusion, but only 10.2 days for microendoscopic discectomy. Reoperation was performed in 210 patients (1.9%) and these patients had a significantly higher average LOS of 43.1 days.

CONCLUSION

These results will assist quality improvement in spine surgery. The identified risk factors for prolonged LOS will also assist in planning of surgery, postoperative care, and discharge, with the goal of reducing health care costs.

What are the Rates, Reasons, and Risk Factors of 90-day Hospital Readmission After Lumbar Discectomy?: An Institutional Experience

STUDY DESIGN

This is a retrospective cohort study.

OBJECTIVE

To report the rate, reasons, and risk factors for 90-day readmissions after lumbar discectomy at an academic medical center.

SUMMARY OF BACKGROUND DATA

Several studies have reported complications and readmissions after spine surgery; however, only one previous study has focused specifically on lumbar discectomy. As the patient profile and morbidity of various spine procedures is different, focus on procedure-specific complications and readmissions will be beneficial.

MATERIALS AND METHODS

Patients who underwent lumbar discectomy for unrelieved symptoms of prolapsed intervertebral disk and had at least 90 days of follow-up at an academic institution (2013-2014) were included. Retrospective review of electronic medical record was performed to record demographic and clinical profile of patients. Details of lumbar discectomy, index hospital stay, discharge disposition, hospital readmission within 90 days, reason for readmission and treatment given have been reported. Risk factors for hospital readmission were analyzed by multivariate logistic regression analysis.

RESULTS

A total of 356 patients with a mean age of 45.0±13.8 years were included. The 90-day readmission rate was 5.3% (19/360) of which two-third patients were admitted within 30 days giving a 30-day readmission rate of 3.7% (13/356). The top 2 primary reasons for readmission included back and/or leg pain, numbness, or tingling (42.9%), and persistent cerebrospinal fluid leak or seroma (25.0%). On adjusted analysis, risk factors associated with higher risk of readmission included incidental durotomy [odds ratio (OR), 26.2; 95% confidence interval (CI), 5.3-129.9] and discharge to skilled nursing facility/inpatient rehabilitation (OR, 25.2; 95% CI, 2.7-235.2). Increasing age was a negative predictor of readmission (OR, 0.95; 95% CI, 0.91-0.99).

CONCLUSIONS

Incidental durotomy, younger age, and discharge to nursing facility were associated with higher risk of 90-day hospital readmission after lumbar discectomy. As compared with extensive spine procedures, patient comorbidity burden may not be as significant in predicting readmission after this relatively less invasive procedure.