Fast track and outpatient surgery in total knee arthroplasty: beneficial for patients, doctors and hospitals

Perioperative non-opioid analgesia strategies after high tibial osteotomy: a systematic review of prospective studies

PURPOSE

Little is known about the optimal analgesia regimen after HTO. Thus, this study systematically reviewed the literature on clinical and patient-reported outcomes of pain management strategies for patients after HTO.

METHODS

A comprehensive search of the PubMed, Cochrane CENTRAL, and CINAHL databases was conducted from inception through September 2023. Studies were included if they evaluated pain reduction with analgesia strategies after HTO and were excluded if they did not report pain control outcomes.

RESULTS

Five studies with 217 patients were included. Patients with a multimodal intraoperative injection cocktail to the knee, femoral nerve block (FNB), or adductor canal block (ACB) for HTO had significant improvement in visual analog scale (VAS) and numerical rating scale (NRS) scores in the first 12 h postoperatively compared to controls. Patients on duloxetine had significantly lower NRS scores at 1, 7, and 14 days postoperatively and significantly lower nonsteroidal anti-inflammatory drug (NSAID) usage throughout the two-week postoperative period than the control group. Patients receiving an ACB had significantly lower opioid consumption than controls at 12 h postoperative. In patients with an FNB or ACB, no significant difference in quadriceps strength or time to straight leg raise postoperatively was observed compared to controls.

CONCLUSION

A multimodal periarticular injection cocktail, FNB, or an ACB effectively reduces pain on the first day after HTO, with an ACB able to reduce opioid consumption on the first postoperative day. Duloxetine combined with an ACB effectively decreases pain for two weeks postoperatively while reducing NSAID consumption in patients after HTO.

LEVEL OF EVIDENCE

IV.

Severe genu varus deformity does not affect enhanced recovery after surgery total knee arthroplasty outcomes

INTRODUCTION

Enhanced recovery after surgery (ERAS) has been increasingly adopted in orthopaedic surgery. Although not an exclusion criterion, patients undergoing total knee arthroplasty (TKA) with preoperative severe varus deformity may be less likely to be enrolled for ERAS. This study aimed to compare the success of ERAS TKA between patients with severe preoperative varus deformities (≥ 15° varus) and the control group (< 15° varus to 14° valgus). Our secondary aim was to compare postoperative complications and functional outcomes between the two groups.

MATERIALS & METHODS

310 TKAs performed from August 2019 to February 2021 were analyzed with a follow-up of 6 months postoperatively. The primary outcome, ERAS TKA success, was defined as length of hospital stay of < 24 h. Other parameters included 30-day postoperative complications and clinical outcomes such as the original Oxford Knee Score (OKS), the Knee Society Knee (KSKS) and Function Score (KSFS), Visual Analog Scale for Pain (VAS-P), 36-Item Short-Form Health Survey (SF-36) Physical Component Summary (PCS) and SF-36 Mental Component Summary (MCS).

RESULTS

There were 119 patients in the severe deformity group and 191 patients in the control group. There were no significant differences in ERAS success between the severe deformity group and control group, with both groups achieving similarly high rates (> 90%) of ERAS success. There were also no differences in 30-day postoperative complications and 6-month postoperative clinical outcomes.

CONCLUSION

Patients with severe preoperative varus deformity undergoing ERAS TKA achieved high ERAS success rates (> 90%). Genu varum is not a contraindication for ERAS TKA.

Outcomes of Lateral Transfibular Approach for Total Ankle Replacement

Total ankle replacement through a lateral transfibular approach with trabecular metal implants was introduced in 2012 and originally was advertised as a safer approach in terms of wound healing issues. Further studies showed no significant difference comparing anterior and lateral approach for infections and would healing issues, whereas the main advantage is deformity correction, acting on coronal, sagittal, and rotational deformities and on fibular length issues. It showed a survival rate of 97.7% at 5 years follow-up.

Fast-Track for Total Ankle Replacement: A Novel Enhanced Recovery Protocol for Select Patients

BACKGROUND

Enhanced recovery after surgery programs, also called fast-track protocols, were developed and successfully applied in the last decade for hip and knee reconstruction. Specific fast-track protocols have not yet been applied to ankle prostheses. The aim of the study was to develop and validate an enhanced recovery protocol for total ankle replacement (TAR) evaluating the clinical and radiographic results. We hypothesize that on the basis of well-defined pre- and postoperative characteristics, the current knowledge on ankle replacement, and referring to hip and knee reconstruction, it is possible to identify a "patient type" to be safely eligible to a Fast-Track Protocol with at least comparable results and without increasing the complications risk.

METHODS

We identified 8 predictive variables that might affect the outcome of TAR. Those variables were the body mass index, the state of anxiety or depression, the functional preoperative status, ankle equinus, the coronal malalignment, the surgical time, the surgical accessory procedures, and the bone quality. These characteristics were evaluated for each patient with almost validated outcome tools attributing a specific score. Based on the score obtained, the patients were divided into 2 groups: the Standard Protocol group (Control Group) and the Fast-Track Protocol group (Study Group). The main difference between treatment of the 2 groups relates to the use of postoperative plaster casts: in the Fast-Track group the cast was removed the first day after surgery and walking was allowed in sports shoes assisted with crutches, whereas in the Standard Protocol group, the cast was removed after 3 weeks. Clinical and radiographic evaluation was performed for all patients preoperatively and postoperatively every 6 months.

RESULTS

A total of 163 patients received a score between 1 and 5 and were included in the control group (Standard Protocol); 47 patients received a score of 0 and were allocated to the study group (Fast-Track Protocol). Clinically, except for the preoperative American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot scale score, no statistically significant differences were recorded in the multiple comparisons between the 2 groups. No significant differences were found regarding complications.

CONCLUSION

In selected patients, it is possible to apply an enhanced recovery protocol of rehabilitation, focused on immediate weightbearing and mobilization without any plaster or boot.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Comparative Analysis of Outcomes in Medicare-Eligible Patients with a Hospital Stay Less than Two-Midnights versus Longer Length of Stay following Total Knee Arthroplasty: Implications for Inpatient-Outpatient Designation

The Centers for Medicaid and Medicare Services (CMS) removed primary total knee arthroplasty (TKA) from the inpatient-only list in January 2018. This study aims to compare outcomes in Medicare-aged patients who underwent primary TKA and had an in-hospital stay spanning less than two-midnights to those with a length of stay greater than or equal to two-midnights. We retrospectively reviewed 4,138 patients ages ≥65 who underwent primary TKA from 2016 to 2020. Two cohorts were established based on length of stay (LOS), those with an LOS <2 midnights were labeled outpatient and those with an LOS ≥2 midnights were labeled inpatient as per CMS designation. Demographic, clinical data, knee injury and osteoarthritis outcome score for joint replacement (KOOS, JR), and veterans RAND 12 physical and mental components (VR-12 PCS & MCS) were collected. Demographic differences were assessed with Chi-square and independent sample t-tests. Clinical data and KOOS, JR and VR-12 PCS and MCS scores were compared by using multilinear regression analysis, controlling for demographic differences. There were 841 (20%) patients with a LOS < 2 midnights and 3,297 (80%) patients with a LOS ≥ 2 midnights. Patients with a LOS < 2 midnights were significantly younger (71.70 vs. 73.06; p < 0.001), more likely male (42.1 vs. 25.7%; p < 0.001), Caucasian (68.8 vs. 57.7%; p <0.001), have lower BMI (30.80 vs. 31.92; p < 0.001), Charlson Comorbidity Index (CCI; 4.62 vs. 4.96; p < 0.001), and American Society of Anesthesiologists (ASA) class II or higher (p < 0.001). These patients were more likely to be discharged home compared to patients with LOS ≥ 2 midnights (95.8 vs. 73.1%; p < 0.001). Patients who stayed ≥ 2 midnights reported lower patient-reported outcome scores at all time-periods (preoperatively, 3 months and 1 year), but these differences did not exceed the minimum clinically important difference. Mean improvement preoperatively to 1 year postoperatively in KOOS, JR (22.53 vs. 25.89; p < 0.001), and VR-12 PCS (12.16 vs. 11.49; p = 0.002) was statistically higher for patients who stayed < 2 midnights, though these differences were not clinically significant. All-cause ED visits (p = 0.167), 90-day all-cause readmissions (p = 0.069) and revision (p = 0.277) did not statistically differ between the two cohorts. TKA patients classified as outpatient had similar quality metrics and saw similar clinical improvement following TKA with respect to most patient reported outcome measures, although they were demographically different. Outpatient classification is more likely to be assigned to younger males with higher functional scores, lower BMI, CCI, and ASA class compared with inpatients. This Retrospective Cohort Study shows level III evidence.

Outpatient total knee and hip arthroplasty present comparable and even better clinical outcomes than inpatient operation

Background

The purpose of this study was to compare total complications, complications stratified by type, readmissions, and reoperations at 30 and 90 days after outpatient and standard inpatient total knee and total hip arthroplasty (TKA, THA).

Methods

A literature search was conducted from the PubMed, Cochrane Library, and Embase databases for articles published before 20 August 2021. The types of studies included prospective randomized controlled trials, prospective cohort studies, retrospective comparative studies, retrospective reviews of THA and TKA registration databases, and observational case-control studies. Comparisons of interest included total complications, complications stratified by type, readmissions, and reoperations at 30 and 90 days. The statistical analysis was performed using Review Manager 5.3.

Results

Twenty studies with 582,790 cases compared relevant postoperative indicators of outpatient and inpatient total joint arthroplasty (TJA) (TKA and THA). There was a significant difference in the total complications at 30 days between outpatient and inpatient THA (p = 0.001), readmissions following TJA (p = 0.03), readmissions following THA (p = 0.001), stroke/cerebrovascular incidents following TJA (p = 0.01), cardiac arrest following TJA (p = 0.007), and blood transfusions following TJA (p = 0.003). The outcomes showed an obvious difference in 90-day total complications between outpatient and inpatient TJA (p = 0.01), readmissions following THA (p = 0.002), and surgical-related pain following TJA (p < 0.001). We did not find significant differences in the remaining parameters.

Conclusion

Outpatient procedures showed comparable and even better outcomes in total complications, complications stratified by type, readmissions, and reoperations at 30 and 90 days compared with inpatient TJA for selected patients.

Risk Factors for Delayed Discharge and Adverse Outcomes Following Outpatient Billed Total Knee Arthroplasty

BACKGROUND

The volume of outpatient total knee arthroplasty (TKA) has increased with advances in perioperative protocols, patient selection, and recent policy changes regarding insurance authorization. This study analyzed 30-day outcomes from a national database to better understand risk factors for delayed discharge (length of stay [LOS] ≥1), readmission, and reoperation after outpatient TKA.

METHODS

The National Surgical Quality Improvement Program (NSQIP) database was utilized to collect TKA (CPT 27447) billed as outpatient surgery performed from 2013 to 2018. Patient demographics, comorbidities, and short-term outcomes were collected and compared in LOS 0 versus LOS ≥1 cohorts. Subgroup analysis was completed for TKA performed in 2018, after the Center for Medicare Services removal of TKA from the inpatient-only list.

RESULTS

A total of 13,669 patients had outpatient TKA performed from 2013 to 2018. Most patients had LOS ≥1 day (77.1%). The LOS 0 cohort demonstrated a lower 30-day readmission rate (1.8%) compared to LOS ≥1 (2.8%), P > .01. Both groups demonstrated a low 30-day reoperation rate, LOS 0 (0.7%) and LOS ≥1 (1.1%), P = .05. Regression analysis demonstrated risk factors for LOS ≥1 day included COPD, ASA ≥3, age >75, and BMI >35 kg/m². Regression analysis demonstrated male gender, age >75, ASA ≥3, and albumin <3.5 g/dL were risk factors for readmission. Hypertension was a risk factor for 30-day reoperation.

CONCLUSION

Risk factors for LOS ≥1 day include age >75, ASA ≥3, BMI >35 kg/m². In addition, BMI >35 kg/m² was a risk factor for readmission and reoperation. These findings reinforce appropriate patient selection when considering outpatient TKA.

Influence of outpatient total knee arthroplasty compared to inpatient surgery on medical and economic outcomes

Firstly, this study compared the rate of readmission after a total knee arthroplasty between selected out- patients (no hospitalization, directly sent home after surgery) and inpatients (3 days hospitalization) at 6 weeks. Secondly, it examined the mobility and the complications in the two groups after the same period of time. The rate of readmission, complications and knee mobility of 32 outpatients (M-age : 61 years ± 10 ; 10 females), were compared against those of 32 birth- matched inpatients (M-age : 64 years ± 8.6 ; 10 females). No patient was re-admitted in either group. Post- surgical complications included one hematoma resorbed at 6 weeks in the outpatient group and three joint effusions in the inpatient group. There were no instances of deep venous thrombosis, failure of primary fixation, infection, or wound dehiscence. Knee mobility was identical between the two groups. This is the first study to compare inpatient and outpatient total knee arthroplasty in a Belgian setting. Our study suggests that day-care total knee arthroplasty in selected patients is possible without increasing the rate of re-admission and complications, and without affecting the mobility at 6 weeks. However, the Belgian financial incentives do not seem to currently promote this surgical approach. These results should be confirmed with a larger sample to define the adequate length of stay after a total knee arthroplasty.

Clinical efficacy of adductor canal block in medial open wedge high tibial osteotomy

BACKGROUND

To evaluate the effect of adductor canal block (ACB) on short-term postoperative outcomes in patients who underwent medial open-wedge high tibial osteotomy (MOWHTO) compared to that of a placebo.

METHODS

35 patients who underwent unilateral MOWHTO between 2017 and 2019 were prospectively reviewed and randomly divided into two groups: 19 patients who received a single-shot ACB and 16 patients who received a saline injection (a placebo group). Primary outcomes were (1) pain measured using the visual analog scale and range of motion, (2) patient satisfaction, (3) postoperative need for additional opioids, (3) quadriceps strength (the time to straight leg raising [SLR]), (4) clinical outcomes, and (5) complications.

RESULTS

The pain score was lower in the ACB group than in the placebo group in the first 12 h (p = 0.04). ACB did not exhibit significantly less quadriceps strength weakness postoperatively. There was no statistical difference in the time to SLR (23.5 ± 17.7 h in ACB vs. 27.6 ± 11.4 in placebo, p = 0.520). The opioid consumption rate within postoperative 12 h was significantly decreased after ACB (16.7% in ACB, 70% in placebo, p = 0.017). The proportion of patients with more than 5 opioid injections within 72 h postoperatively was lower in the ACB group (8.3% in ACB, 50% in placebo, p = 0.043). Both groups did not show any localized and systemic complications.

CONCLUSION

ACB following MOWHTO exhibited better outcomes than a placebo with respect to opioid consumption with no changes in the quadriceps strength and complications.

LEVEL OF EVIDENCE

II, Prospectively comparative study.

Prevention of Periprosthetic Joint Infection (PJI): A Clinical Practice Protocol in High-Risk Patients

Background: Periprosthetic joint infection (PJI) represents 25% of failed total knee arthroplasties (TKA). The European Knee Associates (EKA) formed a transatlantic panel of experts to perform a literature review examining patient-related risk factors with the objective of producing perioperative recommendations in PJI high-risk patients. Methods: Multiple databases (Pubmed/MEDLINE, EMBASE, Scopus, Cochrane Library) and recommendations on TKA PJI prevention measures from the International Consensus Meetings on PJI from the AAOS and AAHKS were reviewed. This represents a Level IV study. Results: Strong evidence was found on poor glycemic control, obesity, malnutrition, and smoking being all associated with increased rates of PJI. In the preoperative period, patient optimization is key: BMI < 35, diet optimization, Hemoglobin A1c < 7.5, Fructosamine < 292 mmol/L, smoking cessation, and MRSA nasal screening all showed strong evidence on reducing PJI risk. Intraoperatively, a weight-based antibiotic prophylaxis, accurate fluid resuscitation, betadine and chlorhexidine dual skin preparation, diluted povidone iodine solution irrigation, tranexamic acid administration, and monofilament barbed triclosan-coated sutures for soft tissues closure all represented effective prevention measures. In the postoperative period, failure to reach normalization of ESR, CRP, D-dimer, and IL-6 six weeks postoperatively suggested early PJI. Conclusion: The current recommendations from this group of experts, based on published evidence, support risk stratification to identify high-risk patients requiring implementation of perioperative measures to reduce postoperative PJI.

Outpatient total knee arthroplasty leads to a higher number of complications: a meta-analysis

Background

Careful pre- and post-operative management can allow surgeons to perform outpatient TKA, making this a more affordable procedure. The aim of the present meta-analysis is to compare outpatient and inpatient TKA.

Methods

A systematic search of the literature was performed in July 2020 on PubMed, Web of Science, Cochrane library, and on the grey literature databases. The papers collected were used for a meta-analysis comparing outpatient and inpatient TKA in terms of complication and readmission rates. Risk of bias and quality of evidence were defined according to Cochrane guidelines.

Results

The literature search resulted in 4107 articles; of these, 8 articles were used for the meta-analysis. A total of 212,632 patients were included, 6607 of whom were TKA outpatients. The overall complication rate for outpatient TKAs was 16.1%, while inpatient TKAs had an overall lower complication rate of 10.5% (p = 0.003). The readmission rate was 4.9% in outpatient TKAs and 5.9% in inpatient TKAs. Only 3 studies reported the number of deaths, which accounted for 0%. The included studies presented a moderate risk of bias, and according to GRADE guidelines, the level of evidence for complications and readmissions was very low.

Conclusions

This meta-analysis documented that outpatient TKA led to an increased number of complications although there were no differences in the number of readmissions. However, future high-level studies are needed to confirm results and indications for the outpatient approach, since the studies currently available have a moderate risk of bias and a very low quality of evidence.

Validation of a Novel Device for the Knee Monitoring of Orthopaedic Patients

Fast-track surgery is becoming increasingly popular, whereas the monitoring of postoperative rehabilitation remains a matter of considerable debate. The aim of this study was to validate a newly developed wearable system intended to monitor knee function and mobility. A sensor system with a nine-degree-of-freedom (DOF) inertial measurement unit (IMU) was developed. Thirteen healthy volunteers performed five 10-meter walking trials with simultaneous sensor and motion capture data collection. The obtained kinematic waveforms were analysed using root mean square error (RMSE) and correlation coefficient (CC) calculations. The Bland–Altman method was used for the agreement of discrete parameters consisting of peak knee angles between systems. To test the reliability, 10 other subjects with sensors walked a track of 10 metres on two consecutive days. The Pearson CC was excellent for the walking data set between both systems (r = 0.96) and very good (r = 0.95) within the sensor system. The RMSE during walking was 5.17° between systems and 6.82° within sensor measurements. No significant differences were detected between the mean values observed, except for the extension angle during the stance phase (E1). Similar results were obtained for the repeatability test. Intra-class correlation coefficients (ICCs) between systems were excellent for the flexion angle during the swing phase (F1); good for the flexion angle during the stance phase (F2) and the re-extension angle, which was calculated by subtracting the extension angle at swing phase (E2) from F2; and moderate for the extension angle during the stance phase (E1), E2 and the range of motion (ROM). ICCs within the sensor measurements were good for the ROM, F2 and re-extension, and moderate for F1, E1 and E2. The study shows that the novel sensor system can record sagittal knee kinematics during walking in healthy subjects comparable to those of a motion capture system.

Effects of Enhanced Recovery After Surgery in Total Knee Arthroplasty for Patients Older Than 65 Years

OBJECTIVES

To explore the safety and efficacy of the enhanced recovery after surgery (ERAS) program for elderly total knee arthroplasty (TKA) patients.

METHODS

A prospective controlled study was conducted for patients older than 65 years, who would undergo unilateral TKA with a minimum follow-up of 2 years. Patients were divided into an ERAS group (n = 106) and a traditional group (n = 141) based on the patients' willingness to participate in the ERAS program. Baseline parameters of American Society of Anesthesiologists classification and comorbidity were recorded. Complication, mortality, knee function assessment using knee society score and knee range of motion, and perioperative clinical outcomes were compared between the two groups.

RESULTS

There were no significant differences between the two groups in terms of baseline parameters. Although no significant differences were found in postoperative nausea and vomiting, urinary tract infection, deep venous thrombosis, pulmonary embolism, wound delayed healing, superficial infection, and deep infection, there were significantly fewer total complications in the ERAS group (26/106 vs 52/141; P = 0.039). No significant difference was found in short-term mortality (1/106 vs 3/141; P = 0.836) between the two groups. There were no significant differences in preoperative visual analogue scale (VAS), knee society score (KSS), and range of motion (ROM) between the two groups. Lower VAS scores were found in the ERAS group at time of postoperative day (POD) 1 (P = 0.012) and POD 5 (P = 0.020); no significant differences were observed at time of postoperative month (POM) 1 and final follow-up. Higher KSS scores were found in the ERAS group at time of POD 1 (P = 0.013), and POD 5 (P = 0.011), no significant differences were observed at time of POM 1 and final follow-up. Increased ROM degree was found in the ERAS group at time of POD 1 (P = 0.021); no significant differences were observed at time of POD 5, POM 1 and final follow-up. Decreased intraoperative blood loss (P < 0.001), total blood loss (P < 0.001), transfusion rate (P = 0.004), and length of stay (P < 0.001) were found in the ERAS group; no significant differences were found in operative time and hospitalization costs between the two groups.

CONCLUSION

The ERAS program is safer and more efficacious in elderly TKA patients compared to the traditional pathway. It could effectively relieve perioperative pain and improve joint function, and reduce blood transfusion, length of stay, and total complications without increasing short-term mortality.

Outpatient total knee arthroplasty: Readmission and complication rates on day 30 in 61 patients

BACKGROUND

Total knee arthroplasty (TKA) on an outpatient basis is controversial due to concerns about patient safety. In France, only 1.1% of TKAs performed in 2017 were outpatient procedures. Nevertheless, recent advances in the multi-modal and multidisciplinary management of TKA patients combined with optimisation of the various components of perioperative care are increasing the use of outpatient TKA. However, studies on outcomes remain scarce. The primary objective of this work was to compare readmission rates within 30 days after TKA between patients managed as outpatients and as inpatients. The secondary objectives were to compare complication rates and patient satisfaction between the two groups.

HYPOTHESIS

After outpatient TKA, the day-30 rates of readmission and complications are similar to those seen after inpatient TKA.

MATERIAL AND METHODS

A retrospective single-centre study of consecutive patients who underwent TKA between April 2014 and July 2017 was performed. Readmissions, complications, and patient satisfaction were collected.

RESULTS

Of 574 patients, 61 were selected to undergo outpatient TKA and 513 had inpatient TKA. The day-30 readmission rate was 2/61 (3.3%) in the outpatient group and 25/513 (4.9%) in the inpatient group. The overall complication rate was 8% in the outpatients and 7.2% in the inpatients. The satisfaction rate was high in the outpatient group, with 80% very satisfied and 20% satisfied patients.

CONCLUSION

When performed in appropriately selected patients, outpatient TKA is not associated with a higher readmission rate compared to inpatient TKA.

LEVEL OF EVIDENCE

IV, retrospective comparative study.

Can Total Knee Arthroplasty Be Performed Safely as an Outpatient in the Medicare Population?

BACKGROUND

The Centers for Medicare and Medicaid Services has solicited public comments for the 2017 Proposed Rule to consider removing total knee arthroplasty (TKA) from the Inpatient Only List. The purpose of this study is to compare the complication rates between outpatient (same-day discharge), short-stay (discharge within 1 day), and inpatient TKA and to identify the ideal candidates for a short-stay or outpatient procedure.

METHODS

We queried the American College of Surgeons-National Surgical Quality Improvement Program database for patients over age 65 years who underwent TKA from 2014 to 2015. Demographics, comorbidities, 30-day complications, and readmission rates were compared between patients after outpatient, short-stay, and inpatient procedures. A multivariate regression analysis was then performed to identify at-risk patients who should not be candidates for outpatient or short-stay TKA.

RESULTS

Of the 49,136 Medicare-aged TKA patients, 365 (0.7%) were outpatient, 3033 (6%) were short-stay and 45,738 (93%) were inpatient. Short-stay patients had a lower complication rate than both the outpatient and inpatient groups (2% vs. 8% vs. 8%, P < .001). Independent risk factors (all P < .05) for experiencing a complication or requiring an inpatient stay include female gender (odds ratio [OR] 1.655), general anesthesia (OR 1.282), diabetes mellitus (OR 1.171), chronic obstructive pulmonary disease (OR 1.579, P < .001), hypertension (OR 1.144), kidney disease (OR 1.425), American Society of Anesthesiologists Score 4 (OR 1.748), body mass index >35 kg/m² (OR 1.265), and age >75 years (OR 1.429).

CONCLUSION

TKA can be performed safely as an outpatient in a subset of healthy Medicare patients with a complication rate similar to an inpatient stay. A 23-hour stay, however, may be the "sweet spot" that minimizes complications in this population.