30-day morbidity and mortality after elective shoulder arthroscopy: a review of 9410 cases

J Shoulder Elbow Surg (2013) 22, 1667-1675

www.elsevier.com/locate/ymse

SHOULDER

30-day morbidity and mortality after elective shoulder arthroscopy: a review of 9410 cases Christopher T. Martin, MD*, Yubo Gao, PhD, Andrew J. Pugely, MD, Brian R. Wolf, MD Department of Orthopaedic Surgery and Rehabilitation, University of Iowa Hospitals and Clinics, Iowa City, IA, USA Background: Few studies have reported incidence of or risk factors for morbidity and mortality after elective shoulder arthroscopy. Methods: We used Current Procedural Terminology (CPT) billing codes to query the National Surgical Quality Improvement Program database and identified 9410 cases of elective shoulder arthroscopy. Univariate and multivariate analyses were used to identify risk factors for complication. Results: Among 9410 patients, 109 complications occurred in 93 (0.99%). Major morbidity was 0.54% (51 patients), which included 4 patients (0.04%) with a mortality, and minor morbidity was 0.44% (42 patients). The most common complication was a return to the operating room (29 cases, 0.31%). Superficial surgical site infections occurred in 15 cases (0.16%), deep infections in 1 (0.01%), deep venous thrombosis or thrombophlebitis in 8 (0.09%), peripheral nerve injury in 1 (0.01%), and pulmonary embolism in 6 (0.06%). The multivariate analysis showed smoking history (odds ratio [OR], 1.91; 95% confidence interval [CI], 1.12-3.27), history of chronic obstructive pulmonary disease (OR, 3.25; 94% CI, 1.38-7.66), operative time of longer than 1.5 hours (OR, 2.1; 95% CI, 1.32-3.36), and American Society of Anesthesia class of 3 or 4 compared with 1 or 2 (OR, 1.82; 95% CI, 1.03-3.21) as risk factors for complication. Conclusions: Morbidity and mortality are rare events after elective shoulder arthroscopy, and the procedure should generally be considered safe. Surgeons should offer smoking cessation to active users of tobacco and should be efficient with operative time whenever possible. Level of evidence: Level II, Prospective Cohort Design, Treatment Study. Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Arthroscopy; shoulder; complications; risk factors; morbidity; mortality

Shoulder arthroscopy is among the most common of orthopaedic procedures, with marked increases in utilization noted within the last 10 years,13,16,29 and it is generally regarded as safe. Early reports on morbidity after shoulder arthroscopy first appeared in the 1980s, with complication This study received an exemption by the institutional review board at the University of Iowa. *Reprint requests: Christopher T. Martin, MD, Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242, USA. E-mail address: [email protected] (C.T. Martin).

rates ranging from 0.76% to 5.3%,23,24 and some more recent series have reported overall complication rates of up to 10.6%.19 However, the majority of these studies have been based on surgeon responses to surveys or on small retrospective case series.1,2,5,7,9-11,19,27 To the best of our knowledge, there have been no large, prospectively collected series of complications after shoulder arthroscopy. As a result, the incidence of complications and the risk factors for morbidity and mortality are not well defined. Clarification on the incidence of morbidity and mortality after shoulder arthroscopy should be useful for obtaining

1058-2746/$ - see front matter Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2013.06.022

1668 informed consent and for comparing results across institutions. Furthermore, identification of modifiable risk factors should be useful for preoperative risk stratification and medical optimization. The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) prospectively collects 30-day morbidity and mortality data from more than 480 hospitals around the United States. In this study, our goal was to retrospectively query this database and to identify the incidence of 30-day morbidity and mortality after shoulder arthroscopy, with an emphasis on the identification of risk factors.

Methods Data acquisition and patient selection NSQIP methodology has been well publicized elsewhere.4,6,8 Study institutions prospectively collect patient data, and data collection spans more than 480 hospitals throughout the United States, with a roughly equal mix of academic and private hospitals. The database does not include stand-alone surgical centers, but it does include outpatient procedures performed in the hospital setting. Surgical clinical reviewers (SCRs) are responsible for the data collection.11 The SCR prospectively collects complication data during a 30-day period through chart review of postoperative progress notes and clinic visits in the outpatient setting. Patients who have not had a clinic visit within 30 days are called by the SCR directly to verify the presence or absence of complications or admissions at outside institutions. If the medical record is unclear, the SCR directly calls the treating surgeon for clarification. In this way, complications that occur both in the hospital setting and after discharge are captured with high quality. Routine data audits have shown an interobserver disagreement of only 1.56%.22 We retrospectively surveyed the database using Current Procedural Terminology (CPT) billing codes for shoulder arthroscopy performed during the 6-year period between January 1, 2005, and December 31, 2011. The included CPT codes were 29806 (capsulorrhaphy, 731 cases), 29807 (superior labrum anterior to posterior [SLAP] repair, 980 cases), 29819 (loose body removal, 38 cases), 29820 (partial synovectomy, 29 cases), 29821 (complete synovectomy, 46 cases), 29824 (distal claviculectomy, 540 cases), 29825 (lysis of adhesions, 147 cases), 29826 (subacromial decompression, 3355 cases), 29827 (rotator cuff repair, 3438 cases), and 29828 (biceps tenodesis, 106 cases). Of these 9410 cases, the primary anesthetic type was general anesthesia in 8533 (90.7%), regional anesthesia in 662 (7%), and monitored anesthesia care with other local pain control modalities in 215 (2.3%). Our goal was to include only patients undergoing elective arthroscopy. The database does not include patients undergoing surgery for acute trauma. We additionally sought to intentionally exclude any patient with preoperative sepsis or with a preoperative wound infection (wound class 2, 3, or 4). However, zero patients met these criteria. Thus, we excluded zero patients. In total, this search identified 9410 cases of elective shoulder arthroscopy, which formed our study group. Our study group contains procedures of varying complexity. To determine if surgical complexity contributed to morbidity rates, we conducted a separate analysis. Procedures were assigned into major or minor on the basis of level of invasiveness and if reconstruction or repair was involved. Major procedures included

C.T. Martin et al. capsulorrhaphy, SLAP repair, cuff repair, and biceps tenodesis. The remaining procedures were considered minor. Some patients had both major and minor procedures performed. If a patient had any major procedure, the patient was counted in the major procedure group and was not also counted in the minor group.

Outcomes We defined three separate outcome categories: any complication; major morbidity and mortality; and minor morbidity. In general, we considered a complication major if it involved a systemic lifethreatening event or posed a substantial threat to a vital organ. We considered a complication minor if it localized to the operative extremity and did not pose a substantial systemic threat to the patient. Complication groups are consistent with previously published methods (Table I).20,28 Mortality was included with major morbidity because the patient numbers were not sufficient for separate analysis. For the outcome of any complication, we included all of the morbidities listed under both major and minor morbidity and also included mortality. Hospital readmission was recorded in the NSQIP database only for the year 2011. Because large numbers of patients did not have this data point available, we did not include it in the multivariate statistical analysis. Numbers of patients who developed a complication and had an American Society of Anesthesia (ASA) class of 3 or 4 were also very low. Thus, ASA classes 3 and 4 were combined into a single category and compared against classes 1 and 2. Patients who developed both a major and minor morbidity were included only in the major morbidity analysis and were not counted twice.

Comorbidity data inclusion Strict definitions exist for each comorbidity, and the full listing is in the NSQIP user file.4 Some data points had incomplete data. A complete listing of all data points and the number of patients with each is in the appendix (Table E1, available on the journal’s website at www.jclinepi.com).

Statistical analysis and identification of risk factors We conducted separate analyses for each level of complication severity. First, we identified unadjusted differences between patients with and without complications. A Student t-test was used for continuous variables, and a c2 test was used for categorical variables. Second, we attempted to control for confounders by conducting a multivariate logistic regression analysis. The outcome variable was any complication, major morbidity or mortality, or minor morbidity. Our goal was to avoid excluding potentially important predictors of complication, and thus we included any variable in this model if it had P < .2 in the univariate analysis and had at least 60% complete patient data. Some variables were included at the authors’ discretion if they had been identified as significant risk factors for complication in previous studies. A complete listing of the variables used in each model is available in the appendix (Table E2, available on the journal’s website at www. jclinepi.com). Our multivariate models required complete patient data. Therefore, patients with a missing data point were excluded in the multivariate analysis.

Morbidity risk after shoulder arthroscopy

1669

Table I Frequency of complications among 9410 patients who underwent elective shoulder arthroscopy Frequency Major complication Organ space infection 2 Sepsis 1 Septic shock 2 Deep SSI 1 Wound dehiscence 1 Pulmonary embolism 6 Ventilator >48 h 1 Unplanned intubation 3 Acute renal failure 1 Cardiac arrest requiring CPR 2 Myocardial infarction 4 Stroke 1 Coma >24 h 0 Graft, prosthesis, or flap failure 0 Return to operating room 29 Total incidence of 54 major complications 51 Total number of patients with a major complication Minor complication Superficial SSI 15 Pneumonia 7 Urinary tract infection 15 DVT or thrombophlebitis 8 Bleeding transfusions 5 Peripheral nerve injury 1 Renal insufficiency 0 Total incidence of 51 minor complications Total number of patients with 42 a minor complication Mortality 4 Total incidence of any complication 109 Total number of patients with 93 any complication Incidence of readmission) 29 of 2831)

Percentage 0.02 0.01 0.02 0.01 0.01 0.06 0.01 0.03 0.01 0.02 0.04 0.01 0 0 0.31 0.57 0.54

0.16 0.07 0.16 0.09 0.05 0.01 0 0.54 0.44 0.04 1.1 0.99 1.02

CPR, cardiopulmonary resuscitation; DVT, deep venous thrombosis; SSI, surgical site infection. ) Readmission data were collected only for 2011, and only 2831 patients had this data point available.

Statistical significance in all models was considered to be P < .05. Statistical analysis was performed with use of SAS (version 9.2; SAS Institute, Cary, NC, USA). Model quality was evaluated by calibration and C value (or C index or C statistic) for discrimination. The calibration test yields a modified c2 statistic, and a P value > .05 indicates that the model fits the data well. The C value relating to the accuracy of a model is termed discrimination, and good discrimination is commonly reported to be between 0.65 and 0.85.

Results Among 9410 patients undergoing elective shoulder arthroscopy, there were a total of 109 complications occurring

in 93 patients. The overall incidence of having any complication was 0.99% (93 patients); major morbidity was 0.54% (51 patients), which included 4 patients (0.04%) with a mortality; and minor morbidity was 0.44% (42 patients). The most common complication was a return to the operating room (29 cases, 0.31%). Superficial surgical site infections occurred in 15 cases (0.16%), deep infections in 1 (0.01%), deep venous thrombosis or thrombophlebitis in 8 (0.09%), and pulmonary embolism in 6 (0.06%). Data for readmission from 2011 were available for 2831 patients, and 29 (1.01%) of those were readmitted (Table I). There was no difference in the overall incidence of complications between major procedures (51 of 5255 patients, 0.97%) and minor procedures (42 of 4155 patients, 1.01%) (P ¼ .84). There was also no difference in the incidence of major morbidity or mortality (0.49% vs 0.60%; P ¼ .48) or minor morbidity (0.48% vs 0.41%; P ¼ .63) between the two groups. For the outcome of any complication, the univariate analysis identified age (P ¼ .002), body mass index (P ¼ .048), chronic obstructive pulmonary disease (COPD; P < .0001), hypertension (P ¼ .008), diabetes (P ¼ .012), peripheral vascular disease (P ¼ .044), preoperative white blood cell count (P ¼ .037), ASA class (P < .0001), operative time longer than 1.5 hours (P < .0001), and the absence of resident involvement (P ¼ .033) as risk factors for complication (Table II). The subsequent multivariate analysis showed smoking history (odds ratio [OR], 1.91; 95% confidence interval [CI], 1.12-3.27), history of COPD (OR, 3.25; 94% CI, 1.38-7.66), operative time longer than 1.5 hours (OR, 2.1; 95% CI, 1.32-3.36), and ASA class of 3 or 4 compared with 1 or 2 (OR, 1.82; 95% CI, 1.03-3.21) as independent predictors of any complication (Table III). For the outcome of major morbidity or mortality, the univariate analysis identified COPD (P ¼ .018), diabetes (P ¼ .011), disseminated cancer (P ¼ .032), preoperative international normalized ratio (P ¼ .041), ASA class (P ¼ .0002), operative time (P ¼ .021), and the absence of resident involvement (P ¼ .02) as risk factors for complication (Table IV). The subsequent multivariate analysis showed a history of COPD (OR, 3.39; 95 % CI, 1.12-10.25) and the absence of resident involvement (OR, 2.99; 95% CI, 1.07-8.41) as independent risk factors for major morbidity or mortality (Table III). For the outcome of minor morbidity, the univariate analysis identified patient age (P ¼ .012), body mass index (P ¼ .028), COPD (P ¼ .0013), hypertension (P ¼ .041), ASA class (P < .0001), and operative time longer than 1.5 hours (P ¼ .001) as risk factors for complication (Table V). The subsequent multivariate analysis showed ASA class of 3 or 4 compared with 1 or 2 (OR, 2.31; 95% CI, 1.04-5.15) and operative time longer than 1.5 hours (OR, 2.82; 95% CI, 1.39-5.72) as independent risk factors for minor morbidity (Table III). The three multivariate models fit the data well with Hosmer-Lemeshow goodness-of-fit P value from .16 for

1670 Table II

C.T. Martin et al. Univariate analysis of patients with and without any complication

Characteristic Age (years) <40 (%) 40-65 (%) >65 (%) Gender Male (%) Female (%) Race Black (%) White (%) Other (%) BMI (kg/m2) <35 (%) 35 (%) Current alcohol abuse (%) Current smoker (%) Recent weight lossy (%) Dyspnea (%) COPD (%) CHF (%) Hypertension (%) Diabetes (%) Peripheral vascular disease (%) Esophageal varices (%) Disseminated cancer (%) Steroid use (%) Bleeding disorder (%) Dialysis (%) Chemotherapy within 30 days (%) Radiation therapy within 90 days (%) Prior operation within 30 days (%) Mean (SD) pre-op sodium Mean (SD) pre-op BUN Mean (SD) pre-op albumin Mean (SD) pre-op WBC Mean (SD) pre-op HCT Mean (SD) pre-op platelets Mean (SD) pre-op INR ASA class 1 or 2: no or mild disturbance 3 or 4: severe or life-threatening disturbance Blood transfusion None (%) 1 (%) Operative time 1.5 h >1.5 h Resident involvement (%) Functional status Independent (%) Totally or partially dependent (%)

Without any complication (n ¼ 9317)

With any complication (n ¼ 93)

Unadjusted P value .0022)

99.38 99.11 98.30

0.62 0.89 1.70

99.02 98.99

0.98 1.01

99.13 98.92 99.23

0.87 1.08 0.77

.8822

.4113

99.09 98.53 2.12 18.61 0.10 3.59 1.91 0.09 37.11 11.91 0.42 0.01 0.05 0.94 1.33 0.05 0.01 0.04 0.23 139.5 (2.58) 16.49 (6.12) 4.20 (0.41) 7.03 (2.22) 41.44 (4.12) 243.7 (66.62) 1.06 (0.37)

0.91 1.47 1.30 25.81 0.00 5.38 9.68 0.00 50.54 20.43 2.60 0.00 1.08 1.08 2.15 0.00 0.00 0.00 0.00 139.7 (2.57) 17.73 (8.80) 4.11 (0.42) 7.91 (3.21) 41.18 (4.41) 249.1 (79.84) 1.04 (0.12)

99.33 97.95

0.67 2.05

98.95 1.00

1.05 0.00

99.27 98.39 23.59

0.73 1.61 13.16

99.03 96.67

0.97 3.33

.0481)

1.0000 .0765 1.0000 .3900 <.0001) 1.0000 .0077) .0119) .0441) 1.0000 .0579 .5886 .3547 1.0000 1.0000 1.0000 1.0000 .4454 .2678 .2433 .0374) .6155 .5967 .6468 <.0001)

1.0000 <.0001) .0328) .0601

ASA, American Society of Anesthesia; BMI, body mass index; BUN, blood urea nitrogen; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; HCT, hematocrit; INR, international normalized ratio; pre-op, preoperative; WBC, white blood cell count. ) Significant (P < .05). y More than 10% loss of body mass in the last 6 months.

Morbidity risk after shoulder arthroscopy Table III Predictors of morbidity as identified through multivariate regression analysis Adjusted odds ratio (95% confidence interval) Risk of any complication (n ¼ 7039) Smoking history History of COPD ASA class of 3 or 4 compared with 1 or 2 Operative time >1.5 h vs <1.5 h Risk of major morbidity or mortality (n ¼ 7097) History of COPD Absence of resident involvement Risk of minor morbidity (n ¼ 7053) ASA class of 3 or 4 compared with 1 or 2 Operative time >1.5 h vs <1.5 h

1.91 (1.12-3.27) 3.25 (1.38-7.66) 1.82 (1.03-3.21) 2.10 (1.32-3.36)

3.39 (1.12-10.25) 2.99 (1.07-8.41)

2.31 (1.04-5.15) 2.82 (1.39-5.72)

ASA, American Society of Anesthesia; COPD, chronic obstructive pulmonary disease.

any complication, .53 for major, and .32 for minor. The three models discriminate well with C value from 0.735 for any complication, 0.705 for major, and 0.731 for minor.

Discussion Few prospective studies have reported on morbidity after elective shoulder arthroscopy, and the currently available data are mostly derived from surgeon-reported surveys or retrospective case series. Clarification of the incidence of postoperative morbidity would thus be useful for performing informed consents and for benchmarking results across institutions. Furthermore, the identification of risk factors for morbidity may be useful for preoperative medical optimization. Therefore, the purpose of this study was to report the incidence of 30-day morbidity and mortality from a large, prospectively collected database and to identify predictors of postoperative complication. To the best of our knowledge, no similar large database study on complication data exists for shoulder arthroscopy.12,27 The majority of previous studies have been retrospective case series and have reported surgical site infection rates ranging from 0% to 3.4%,27 neurologic injury of up to 30%,14 and deep venous thrombosis rates of up to 0.31%.9 Mortality has been reported, but only as case reports.2 Small et al24 in 1986 used a survey sent to members of the North American Arthroscopy Association to collect data on 14,329 cases of shoulder arthroscopy.

1671 Overall surgeon-reported complication rates in that study ranged from 0.76% after subacromial procedures to 5.3% after anterior staple capsulorrhaphy. Here, we have reported an overall 30-day complication rate of 0.99% and a major morbidity rate of 0.54%. Infections and thromboembolic events were rare in our series. Notably, our data were prospectively collected by SCR staff at each participating center.22 Thus, our data are not dependent on retrospective chart review or surgeon recollection of complication incidence for accuracy. Overall, we think that the 0.99% overall complication rate and 0.54% major morbidity rate should be viewed as low and that elective shoulder arthroscopy is likely to be safe in appropriately selected patients. Furthermore, in addition to reporting overall complication rates, we have reported an exhaustive listing of 30-day incidences of postoperative morbidity data. The majority of previous studies have focused on complications specific to the operative extremity, and the incidence of systemic events, such as stroke, myocardial infarction, renal failure, and mortality, is poorly defined in the literature.12,21,27 The incidence of systemic morbidity was low in our series, with each of these appearing in less than 0.05% of cases and mortality occurring in only 0.04%. Patients can be reliably informed that major adverse events after elective shoulder arthroscopy are rare. Increasing complexity of surgical procedures has previously been correlated with increased risk of complication.27 Our analysis includes arthroscopic procedures of varying complexity, and we attempted to assess for this by comparing morbidity rates across procedures on the basis of the level of invasiveness. To our surprise, there was no significant difference between major and minor procedures in our analysis. However, operative time longer than 1.5 hours was found to be a significant predictor for development of any complication or minor morbidity in our multivariate analyses. It is possible that the greater complexity of the more invasive procedures is primarily reflected in their increased operative time. Smoking has been correlated with worse outcomes across a variety of orthopaedic procedures.3,15,26 In this study, both smoking history and a history of COPD were found to be correlated with increased risk for development of any complication in our multivariate analysis, and history of COPD was also identified as an independent factor in the multivariate analysis for major morbidity risk. These findings are likely to be related, and the patients with a smoking history are probably the same as those with a history of COPD. The estimated effect of smoking history in our multivariate model was substantial, representing a nearly 2-fold increase in risk of any complication (OR, 1.91; 95% CI, 1.12-3.27). Surgeons should be encouraged to offer smoking cessation help when appropriate. The absence of resident involvement appeared as a risk factor for major morbidity in our multivariate analysis. This would seem to imply that having a resident present decreased the major morbidity rates. The data are

1672 Table IV

C.T. Martin et al. Univariate analysis of patients with and without major morbidity or mortality

Characteristic Age (years) <40 (%) 40-65 (%) >65 (%) Gender Male (%) Female (%) Race Black (%) White (%) Other (%) BMI (kg/m2) <35 (%) 35 (%) Current alcohol abuse (%) Current smoker (%) Recent weight lossy (%) Dyspnea (%) COPD (%) CHF (%) Hypertension (%) Diabetes (%) Peripheral vascular disease (%) Esophageal varices (%) Disseminated cancer (%) Steroid use (%) Bleeding disorder (%) Dialysis (%) Chemotherapy within 30 days (%) Radiation therapy within 90 days (%) Prior operation within 30 days (%) Mean (SD) pre-op sodium Mean (SD) pre-op BUN Mean (SD) pre-op albumin Mean (SD) pre-op WBC Mean (SD) pre-op HCT Mean (SD) pre-op platelets Mean (SD) pre-op INR ASA class 1 or 2: no or mild disturbance 3 or 4: severe disturbance or life-threatening disturbance Blood transfusion None (%) 1 (%) Operative time 1.5 h >1.5 h Resident involvement (%) Functional status Independent (%) Totally or partially dependent (%)

Without major morbidity or mortality (n ¼ 9359)

With major morbidity or mortality (n ¼ 51)

Unadjusted P value .1302

99.61 99.51 99.15

0.39 0.49 0.85

99.40 99.55

0.60 0.45

99.83 99.39 99.55

0.17 0.61 0.45

.3221

.3133

.5010 99.47 99.33 2.12 18.65 0.10 3.60 1.96 0.09 37.18 11.94 0.43 0.01 0.05 0.94 1.32 0.05 0.01 0.04 0.23 139.5 (2.58) 16.50 (6.12) 4.20 (0.41) 7.03 (2.23) 41.44 (4.12) 243.7 (66.61) 1.06 (0.37)

0.53 0.67 0.00 25.49 0.00 3.92 7.84 0.00 49.02 23.53 2.22 0.00 1.96 1.96 3.92 0.00 0.00 0.00 0.00 139.5 (2.58) 18.14 (10.36) 4.13 (0.46) 7.45 (2.23) 40.82 (4.26) 246.0 (89.59) 1.02 (0.07)

99.61 98.95

0.39 1.05

99.32 1.00

0.68 0.00

99.58 99.18 23.57

0.42 0.82 9.09

99.46 98.89

0.54 1.11

1.0000 .2110 1.0000 .7065 .0183) 1.0000 .0834 .0110) .1791 1.0000 .0321) .3849 .1488 1.0000 1.0000 1.0000 1.0000 .9458 .3440 .4528 .2807 .3840 .8840 .0414) .0002)

1.0000 .0158) .0203) .3898

ASA, American Society of Anesthesia; BMI, body mass index; BUN, blood urea nitrogen; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; HCT, hematocrit; INR, international normalized ratio; pre-op, preoperative; WBC, white blood cell count. ) Significant (P < .05). y More than 10% loss of body mass in the last 6 months.

Morbidity risk after shoulder arthroscopy Table V

1673

Univariate analysis of patients with and without minor morbidity

Characteristic Age (years) <40 (%) 40-65 (%) >65 (%) Gender Male (%) Female (%) Race Black (%) White (%) Other (%) BMI (kg/m2) <35 (%) >35 (%) Current alcohol abuse (%) Current smoker (%) Recent weight lossy (%) Dyspnea (%) COPD (%) CHF (%) Hypertension (%) Diabetes (%) Peripheral vascular disease (%) Esophageal varices (%) Disseminated cancer (%) Steroid use (%) Bleeding disorder (%) Dialysis (%) Chemotherapy within 30 days (%) Radiation therapy within 90 days (%) Prior operation within 30 days (%) Mean (SD) pre-op sodium Mean (SD) pre-op BUN Mean (SD) pre-op albumin Mean (SD) pre-op WBC Mean (SD) pre-op HCT Mean (SD) pre-op platelets Mean (SD) pre-op INR ASA class 1 or 2: no or mild disturbance 3 or 4: severe disturbance or life-threatening disturbance Blood transfusion None (%) 1 (%) Operative time 1.5 h >1.5 h Resident involvement (%) Functional status Independent (%) Totally or partially dependent (%)

Without minor morbidity (n ¼ 9317)

With minor morbidity (n ¼ 42)

99.77 99.61 99.14

0.23 0.39 0.86

99.62 99.44

0.38 0.56

99.30 99.52 99.68

0.70 0.48 0.32

Unadjusted P value .0117)

.1917

.4154

99.61 99.20 2.12 18.61 0.10 3.59 1.91 0.09 37.11 11.91 0.42 0.01 0.05 0.94 1.33 0.05 0.01 0.04 0.23 139.5 (2.58) 16.49 (6.12) 4.20 (0.41) 7.02 (2.22) 41.44 (4.12) 243.7 (66.62) 1.05 (0.37)

0.39 0.80 3.13 26.19 0.00 7.14 11.90 0.00 52.38 16.67 3.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 140.0 (2.59) 17.18 (6.21) 4.07 (0.32) 8.49 (4.10) 41.59 (4.62) 253.1 (67.04) 1.09 (0.16)

99.72 98.99

0.28 1.01

99.63 100.00

0.37 0.00

99.70 99.21 23.59

0.30 0.79 18.75

99.57 97.75

0.43 2.25

.0280)

.4968 .2083 1.0000 .1917 .0013) 1.0000 .0411) .3431 .1280 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 .2844 .5656 .3261 .0781 .8422 .4635 .5146 <.0001)

1.0000 .0012)

.5194 .0608

ASA, American Society of Anesthesia; BMI, body mass index; BUN, blood urea nitrogen; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; HCT, hematocrit; INR, international normalized ratio; pre-op, preoperative; WBC, white blood cell count. ) Significant (P < .05). y More than 10% loss of body mass in the last 6 months.

1674 somewhat contradictory to those of previously published studies in the general surgical literature, which have shown slightly increased morbidity rates with resident involvement in cases but no increase in mortality.18,25 It is not clear why the absence of a resident would increase complications for elective arthroscopy. During our preoperative workup visits, patients will occasionally express concern about the possibility that a resident will be involved in their case. We think that these data should be interpreted to mean that resident involvement in elective arthroscopic cases is generally safe, and patients can be counseled that resident involvement does not appear to place them at higher risk for an adverse event.30 Our group has previously used similar methodology to report incidence of and risk factors for complications after elective knee arthroscopy. Overall complication rates were slightly higher in that study, at 1.6%. Major morbidity was 0.76%, which included 1 patient (0.0008%) with mortality, and minor morbidity was 0.86%. The lower complication rates reported in this study for shoulder arthroscopy are consistent with the findings of Small et al, who reported an overall complication rate of 0.76% in shoulder procedures compared with 1.84% in the knee.23 Our prior study showed black race, prior operation within 30 days, operative time longer than 1.5 hours, and age of 40 to 65 years compared with age younger than 40 years as risk factors for any complication after knee arthroscopy. Of those variables, only operative time appears again in this analysis. It is not clear why the analyses differed. Presumably, the systemic threat to the patient from an arthroscopic incision should be similar in both the shoulder and the knee. Positioning is different for shoulder arthroscopy, which is frequently done in a beach chair or lateral decubitus position, as opposed to knee arthroscopy, which is done supine, and previous studies have shown that positioning is related to unique complication types.17 Alternatively, the incidence of morbidity in each of these studies is low, and it is possible that important risk factors could vary slightly across studies by chance alone in spite of our large patient numbers. Overall, our results, which are consistent with prior studies, indicate that shoulder and knee patients should be considered separately when postoperative outcomes after arthroscopy are discussed and that incidence of and risk factors for complication may differ across the 2 populations. Our study has several weaknesses. First, our follow-up is limited to 30 days, and some orthopaedic complications, such as deep venous thrombosis or pulmonary embolism, can certainly occur beyond 30 days. Longer term follow-up studies would be likely to have higher complication rates than what is reported here. Second, the NSQIP database does not contain information about orthopaedic-specific outcomes, such as postoperative pain and range of motion or patient-reported outcome scores. Inclusion of negative outcomes from these categories would also likely increase the complication rates reported here. In addition, the database does not include information from stand-alone

C.T. Martin et al. ambulatory surgical centers. Many shoulder arthroscopies are performed in stand-alone centers, and it is possible that care processes differ between the stand-alone centers and hospital-based ambulatory surgical suites. We also do not know the number of cases performed at each center, and it is possible that outcomes differ between high- and lowvolume centers. Furthermore, the database does not record some variables that are specific to arthroscopic shoulder surgery, such as use of pressurized inflow pumps or patient positioning, and we cannot comment specifically on those factors. Third, we have included arthroscopic procedures of varying invasiveness in the same analysis. We attempted to account for this variation by performing a separate analysis in which we compared morbidity incidence across procedure types, and there was no significant difference between major and minor arthroscopic procedures. It is possible that the effect of invasiveness is primarily represented by a longer operative time, which we did include in each of the analyses. Fourth, our multivariate models require complete patient data, and as a result we were forced to exclude more than 2000 patients who had at least one missing data point from the multivariate analyses, and this is a possible source of bias. Finally, our study did not include a power analysis and instead analyzed all eligible subjects. It is possible that in spite of our large patient numbers, we are not powered to show statistically significant differences across some variables. However, we think that any small differences that might exist, but went undetected, may be unlikely to be clinically significant.

Conclusion Overall, we have shown low incidences of overall complication rates and of both major and minor morbidity after elective shoulder arthroscopy, as reported from a large series of prospectively collected data. These data should be useful in providing morbidity information to patients during informed consent and may be useful for benchmarking results across institutions. Furthermore, our multivariate analysis identified several risk factors for any complication, including smoking history, history of COPD, elevated ASA class of 3 or 4, and operative times longer than 1.5 hours. Shoulder arthroscopy surgeons should offer smoking cessation aid to active users of tobacco and should be efficient with operative time whenever possible.

Disclaimer The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

Morbidity risk after shoulder arthroscopy

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Table E1 Number and percentage of 9410 patients with each variable in the univariate analyses Variable

Number

Percentage

Age Gender Race BMI Current alcohol abuse Current smoker Recent weight loss) Dyspnea COPD CHF Hypertension Diabetes Peripheral vascular disease Esophageal varices Disseminated cancer Steroid use (%) Bleeding disorder Dialysis Chemotherapy within 30 days Radiation therapy within 90 days Prior operation within 30 days Pre-op sodium Pre-op BUN Pre-op albumin Pre-op WBC Pre-op HCT Pre-op platelets Pre-op INR ASA class Blood transfusion Operative time Resident involvement Functional status

9410 9399 9355 9294 8019 9410 9410 9409 9410 9410 9410 9410 8020 8020 9410 9410 9410 9410 8020 8020 7992 4989 4607 2205 5027 5306 5018 1655 9390 3522 9410 7281 9362

100 100 99 99 85 100 100 100 100 100 100 100 85 85 100 100 100 100 85 85 85 53 49 23 53 56 53 18 100 37 100 77 99

ASA, American Society of Anesthesia; BMI, body mass index; BUN, blood urea nitrogen; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; HCT, hematocrit; INR, international normalized ratio; Pre-op, preoperative; WBC, white blood cell count. ) More than 10% loss of body mass in the last 6 months.

Table E2

Variables included in the multivariate model

Any complication Age Body mass index Race) Gender) Smoking history History of chronic obstructive pulmonary disease History of peripheral vascular disease Hypertension Diabetes Resident involvement American Society of Anesthesia class Functional status Operative time Major morbidity Age Body mass index) Race) Gender) Diabetes Resident involvement American Society of Anesthesia class Functional status) Operative time Minor morbidity Age Body mass index Race) Gender American Society of Anesthesia class Functional status History of chronic obstructive pulmonary disease Resident involvement) Operative time )

Variable added at authors’ discretion.