Intravenous versus oral acetaminophen for pain and quality of recovery after ambulatory spine surgery: a randomized controlled trial.

INTRODUCTION: As ambulatory spine surgery increases, efficient recovery and discharge become essential. Multimodal analgesia is superior to opioids alone. Acetaminophen is a central component of multimodal protocols and both intravenous and oral forms are used. While some advantages for intravenous acetaminophen have been touted, prospective studies with patient-centered outcomes are lacking in ambulatory spine surgery. A substantial cost difference exists. We hypothesized that intravenous acetaminophen would be associated with fewer opioids and better recovery. METHODS: Patients undergoing ambulatory spine surgery were randomized to preoperative oral placebo and intraoperative intravenous acetaminophen or preoperative oral acetaminophen. All patients received general anesthesia and multimodal analgesia. The primary outcome was 24-hour opioid use in intravenous morphine milligram equivalents (MMEs), beginning with arrival to the postanesthesia care unit (PACU). Secondary outcomes included pain, Quality of Recovery (QoR)-15 scores, postoperative nausea and vomiting, recovery time, and correlations between pain catastrophizing, QoR-15, and pain. RESULTS: A total of 82 patients were included in final analyses. Demographics were similar between groups. For the primary outcome, the median 24-hour MMEs did not differ between groups (12.6 (4.0, 27.1) vs 12.0 (4.0, 29.5) mg, p=0.893). Postoperative pain ratings, PACU MMEs, QoR-15 scores, and recovery time showed no differences. Spearman's correlation showed a moderate negative correlation between postoperative opioid use and QoR-15. CONCLUSION: Intravenous acetaminophen was not superior to the oral form in ambulatory spine surgery patients. This does not support routine use of the more expensive intravenous form to improve recovery and accelerate discharge. TRIAL REGISTRATION NUMBER: NCT04574778.

Modulating hemoglobin allostery for treatment of sickle cell disease: current progress and intellectual property.

INTRODUCTION: Sickle cell disease (SCD) is a debilitating inherited disorder that affects millions worldwide. Four novel SCD therapeutics have been approved, including the hemoglobin (Hb) modulator Voxelotor. AREAS COVERED: This review provides an overview of discovery efforts toward modulating Hb allosteric behavior as a treatment for SCD, with a focus on aromatic aldehydes that increase Hb oxygen affinity to prevent the primary pathophysiology of hypoxia-induce erythrocyte sickling. EXPERT OPINION: The quest to develop small molecules, especially aromatic aldehydes, to modulate Hb allosteric properties for SCD began in the 1970s; however, early promise was dogged by concerns that stalled support for research efforts. Persistent efforts eventually culminated in the discovery of the anti-sickling agent 5-HMF in the 2000s, and reinvigorated interest that led to the discovery of vanillin analogs, including Voxelotor, the first FDA approved Hb modulator for the treatment of SCD. With burgeoning interest in the field of Hb modulation, there is a growing landscape of intellectual property, including drug candidates at various stages of preclinical and clinical investigations. Hb modulators could provide not only the best chance for a highly effective oral therapy for SCD, especially in the under-developed world, but also a way to treat a variety of other human conditions.

The Penn State Protein Ladder system for inexpensive protein molecular weight markers.

We have created the Penn State Protein Ladder system to produce protein molecular weight markers easily and inexpensively (less than a penny a lane). The system includes plasmids which express 10, 15, 20, 30, 40, 50, 60, 80 and 100 kD proteins in E. coli. Each protein migrates appropriately on SDS-PAGE gels, is expressed at very high levels (10-50 mg per liter of culture), is easy to purify via histidine tags and can be detected directly on Western blots via engineered immunoglobulin binding domains. We have also constructed plasmids to express 150 and 250 kD proteins. For more efficient production, we have created two polycistronic expression vectors which coexpress the 10, 30, 50, 100 kD proteins or the 20, 40, 60, 80 kD proteins. 50 ml of culture is sufficient to produce 20,000 lanes of individual ladder protein or 3750 lanes of each set of coexpressed ladder proteins. These Penn State Protein Ladder expression plasmids also constitute useful reagents for teaching laboratories to demonstrate recombinant expression in E. coli and affinity protein purification, and to research laboratories desiring positive controls for recombinant protein expression and purification.

Risk of Gastrointestinal Bleeding With Extended Use of Nonsteroidal Anti-Inflammatory Drug Analgesia After Joint Arthroplasty.

BACKGROUND: Chronic nonsteroidal anti-inflammatory drug (NSAID) use is associated with gastrointestinal bleeding via inhibition of endogenous mucosal protection and platelet aggregation. This study aimed to determine whether extended NSAIDs after joint arthroplasty is associated with increased risk of gastrointestinal bleeding. METHODS: This was a retrospective study examining 28,794 adults who underwent joint arthroplasty by one of 50 surgeons from 2016 to 2018. Episodes of gastrointestinal bleeding within 90 days postoperatively were identified prospectively. Postoperative medications were reported directly by patients with electronic questionnaires. The primary analysis was performed using binary logistic regression. RESULTS: A total of 74 (0.26%) episodes of gastrointestinal bleeding occurred within 90 days (median 8 days) postoperatively. Of 5086 patients with complete data included in the primary analysis, 59.6% had used NSAIDs with median duration of 2 weeks (interquartile range, 0-6 weeks). Patients with gastrointestinal bleeding were significantly older (71.3 vs 67.0 years), required longer hospitalizations (2.1 vs 1.5 days), and more commonly had a history of peptic ulcers (10.8% vs 0.9%). However, there was no positive association between NSAID use and gastrointestinal bleeding. In fact, the odds of gastrointestinal bleeding were lower in patients taking NSAIDs. Gastrointestinal bleeding was associated with anticoagulants, antiplatelet agents, and, to a lesser extent, aspirin. CONCLUSION: NSAIDs were not associated with gastrointestinal bleeding and may be prescribed safely for a majority of patients after joint arthroplasty. The greatest odds of gastrointestinal bleeding occurred in patients with peptic ulcer disease and those who received antiplatelet and anticoagulation agents. Increasing age and bilateral surgery were also associated with gastrointestinal bleeding. LEVEL OF EVIDENCE: Level III.

General vs Spinal Anesthesia for Total Joint Arthroplasty: A Single-Institution Observational Review.

BACKGROUND: Total joint arthroplasty (TJA) can be successfully carried out under general (GA) or spinal anesthesia (SA). The existing literature does not adequately illustrate which technique is optimal. The purpose of this study is to prospectively compare the effects of anesthesia technique on TJA outcomes. METHODS: This 2-year, prospective, observational study was conducted at a single institution where patients receiving primary TJA were consecutively enrolled. Patients were contacted postoperatively to assess for any 90-day complications. The primary outcome of the study was the overall complication rate. RESULTS: A total of 2242 patients underwent total hip arthroplasty (n = 656; 29.26%) or total knee arthroplasty (n = 1586; 70.74%) between 2015 and 2017. Of these procedures, 1325 (59.10%) were carried out under SA and 917 (40.90%) were carried out under GA. Patients in the GA cohort had higher mean Charlson Comorbidity Index scores (0.05 SA vs 0.09 GA; P < .05) and higher average body mass index (29.35 SA vs 30.24 GA; P < .05). On multivariate analysis, patients in the SA cohort had a significantly lower overall complication rate relative to their GA counterparts (7.02% vs 10.14%; odds ratio, 0.66; 95% confidence interval, 0.49-0.90; P < .05). In addition, length of stay in the GA cohort was significantly longer (2.43 [SD, 1.62] vs 2.18 [SD, 0.88] days; P < .01) and a larger percentage of GA patients were discharged to a nursing facility (32.28% vs 25.06%; odds ratio, 0.55; 95% confidence interval, 0.44-0.70; P < .05). CONCLUSION: Our study demonstrates that SA for TJA is associated with a decrease in overall complications and healthcare resource utilization.

Cluster-Randomized Trial of Opiate-Sparing Analgesia after Discharge from Elective Hip Surgery.

BACKGROUND: Surgeons have traditionally relied on opiates after hip replacement, despite a growing epidemic of abuse. This study assessed the efficacy of multimodal analgesia and impact of conservative opiate prescribing after discharge from hip surgery. STUDY DESIGN: In this cluster-randomized trial, 235 patients undergoing hip replacement (5 surgeons) received 1 of 3 discharge pain regimens: scheduled-dose multimodal analgesia with a minimal opiate supply (group A), scheduled-dose multimodal analgesia with a traditional opiate supply (group B), or a traditional pro re nata (as needed) opiate regimen alone (group C). Each of the surgeons comprised a distinct cluster and alternated in a randomized sequence between interventions. The multimodal regimen comprised fixed-schedule doses of acetaminophen, meloxicam, and gabapentin. Primary outcomes were daily visual analogue scale pain and opiate use for 30 days. Secondary outcomes included satisfaction, sleep quality, opiate-related symptoms, hip function, and adverse events. The primary intent-to-treat analysis was performed using linear mixed models. RESULTS: Daily pain was significantly lower in group A (coefficient [Coeff] -0.81; p = 0.003) and group B (Coeff -0.61; p = 0.021) relative to group C. Although daily opiate use in group A (Coeff -0.77; p < 0.001) and group B (Coeff -0.30; p = 0.04) was lower than group C, opiate use for group A was also lower than group B (Coeff -0.46; p = 0.002). Duration of opiate use was significantly shorter for group A (1.14 weeks) and group B (1.39 weeks) compared with group C (2.57 weeks). There were fewer opiate-related symptoms, most commonly fatigue, in group A compared with C, but groups B and C were not significantly different. Both multimodal regimens improved satisfaction and sleep, and there were no differences in hip function or adverse events. CONCLUSIONS: Multimodal analgesia with minimal opiates improved pain control while significantly decreasing opiate use and opiate-related adverse effects. It is time to rethink our reliance on opiates after elective operations.

Unicompartmental Knee Arthroplasty Provides Significantly Greater Improvement in Function than Total Knee Arthroplasty Despite Equivalent Satisfaction for Isolated Medial Compartment Osteoarthritis.

BACKGROUND: While some advocate for unicompartmental knee arthroplasty (UKA) for isolated medial compartment osteoarthritis (OA), others favor total knee arthroplasty (TKA). The purpose of this study was to compare the functional outcomes of UKA and TKA performed for patients with unicompartmental arthritis (OA). METHODS: A study was performed on 133 patients that met strict criteria for UKA, but who underwent either medial UKA or TKA for isolated medial compartment OA based upon physician equipoise. The primary outcome-New Knee Society Score (KSS)-was assessed preoperatively and at 2 years postoperatively. A propensity score weighted regression was used to balance the groups on several key covariates, including age, gender, body mass index, and baseline KSS. RESULTS: After propensity weighting, there were no significant differences between UKA and TKA in overall baseline KSS or KSS after 2 years postoperatively. While TKA patients had demonstrated a significantly greater improvement in the symptoms KSS subscale, UKA patients had a significantly greater improvement in the function subscale. Expectations were significantly more likely to be met after UKA, but there were no differences in patient satisfaction. CONCLUSION: UKA and TKA are both highly successful options for treating patients with medial compartment OA, although functionality increased more, and expectations were more likely to be met, after UKA in this study. Given equivalent patient satisfaction after both TKA and UKA, surgeons should consider factors such as clinical experience, individual preference, cost of care, surgical risk, and recovery needs, when making treatment decisions regarding this clinical entity.

Mechanical Complications Following Total Hip Arthroplasty Based on Surgical Approach: A Large, Single-Institution Cohort Study.

BACKGROUND: The influence of surgical approach on risk of early postoperative mechanical complications after total hip arthroplasty (THA) continues to be a focus of debate. We performed the first single-institution study on risk of early operative and nonoperative mechanical complications after THA based on approach, with the hypothesis that there would be no clinically significant difference with modern surgical methods. METHODS: A retrospective study was conducted on 16,186 consecutive THA performed from 2010 to 2016. Revision or conversion THA and cases performed for hip fracture, with recalled prostheses, or during a surgeon's learning period were excluded. THAs were performed using direct anterior (DA; n = 5465), direct lateral (DL; n = 8561), or posterolateral approach with soft tissue repair (PL; n = 2160). All mechanical complications within the first 2 years were identified. The primary analysis was a time to event Cox regression, accounting for both patient and surgeon characteristics. RESULTS: Compared with the DL approach, risk of mechanical complications was higher for both DA and PL. Adjusted risk of instability within 2 years was 0.17%, 0.74%, and 1.74% for DL, DA, and PL, respectively. While occurring at similar rates with the PL and DL approaches, the risk of periprosthetic fracture and loosening increased with DA. Consequently, femoral failure, including fracture or loosening, occurred more frequently for DA, with an adjusted incidence of 1.20% vs 0.58% and 0.47%, with DL and PL. CONCLUSION: Even with soft tissue repair, instability continues to occur with increased frequency with the PL approach. While reducing dislocation, a higher risk of femoral failure with DA must also be considered. Nevertheless, the DL approach appears to confer the lowest overall risk of mechanical complications.

Higher Prevalence of Concomitant Shoulder Labral Tears in Patients With Femoroacetabular Impingement.

PURPOSE: To examine the prevalence of concomitant symptomatic glenoid labral tears in patients with femoroacetabular impingement (FAI) in comparison to a control group of patients undergoing anterior cruciate ligament (ACL) reconstruction. METHODS: We retrospectively identified 1,644 patients who underwent femoroacetabular osteoplasty (FAO) and labrum repair from January 2007 to September 2016 and 1,055 patients who underwent arthroscopic ACL reconstruction from January 2012 to December 2014, which acted as our control group. An electronic questionnaire, including 8 questions regarding history of shoulder pathology, was sent to all patients in both groups. Symptomatic shoulder labral tears were identified on the basis of a positive magnetic resonance imaging scan or history of labral repair by reviewing patients' medical records and the filled questionnaire. Continuous variables were compared by use of a Mann-Whitney U test, and categorical variables were compared using Fisher's exact test. The Holm-Bonferroni sequential correction method was used to adjust P values for multiple comparisons of the presence of shoulder pathology. RESULTS: A total of 443 patients (405 cam lesion) in the FAO group and 307 patients in the ACL reconstruction group completed the prepared questionnaire and were included in the study. Patients in the FAO group were slightly older (36.3 years [range, 15.4-61.7] vs 32.3 years [range, 16.3-75.7]) and more commonly female in the FAO group (58.0%, n = 257) compared with those in the ACL group (48.9%, n = 150). The prevalence of shoulder labral tear was 12.0% (95% confidence interval [CI], 9.3%-15.3%) for the FAO group compared with only 3.3% (95% CI, 1.8%-5.9%) for the ACL group. This represents a 3.7-fold (95% CI, 1.9-7.1) increase in the risk of shoulder labral tear for patients in the FAO group. Furthermore, shoulder labral tears were reported to be traumatic in only 43.4% of patients in the FAO group compared with 80.0% of patients in the ACL group. A similar proportion of patients in both groups (66.0% for FAO vs 60.0% for ACL) underwent a shoulder labral repair procedure. CONCLUSION: There appears to be an association between acetabular labral tear caused by FAI and shoulder labral lesions. Patients in the FAI group had a 3.7-fold increase in the risk of shoulder labral tear compared with the ACL group. Future studies are needed to examine a possible cause behind the current findings. LEVEL OF EVIDENCE: Level III, comparative trial study.

2018 John N. Insall Award: Recovery of Knee Flexion With Unsupervised Home Exercise Is Not Inferior to Outpatient Physical Therapy After TKA: A Randomized Trial.

BACKGROUND: Concerns about the cost and convenience of postsurgical physical therapy (PT) have sparked interest in unsupervised, home-based rehabilitation. However, the effectiveness of unsupervised home exercise after primary TKA has not been previously evaluated. QUESTIONS/PURPOSES: (1) Can unsupervised home exercise after surgery provide noninferior recovery of passive knee flexion compared with formal outpatient PT? (2) Does a web-based platform for home-based exercise provide an advantage compared with a printed PT manual? METHODS: We conducted a randomized, noninferiority trial involving 290 patients (20% of the 1464 eligible patients who could be contacted) who underwent primary TKA from March 2016 to April 2018. We included patients > 18 years old who were undergoing primary, unilateral TKA and provided written consent. We excluded patients with preoperative knee flexion < 90°, patients considering surgical intervention in a hip or the contralateral knee, patients discharged to an extended care facility, and revision or conversion TKA. We randomized patients to one of three groups: outpatient PT, unsupervised home exercise using a web-based platform (web PT), or unsupervised home exercise using a printed paper manual (paper PT). We also implemented a "delayed recovery intervention" within the home exercise program, in which patients were obliged to begin outpatient PT if knee flexion was < 70° at 2 weeks or < 90° at 4 weeks. The primary outcome was change in knee flexion from preoperative baseline after 4 to 6 weeks and 6 months. Secondary outcomes included Knee Injury and Osteoarthritis Outcome Score (KOOS), time back to activities of daily living, and time off narcotics. All analyses were intention to treat, and the noninferiority margin was 5% with maximum flexion as the outcome of interest for this parameter. RESULTS: Adjusted differences in change in passive flexion for web PT +3° (95% confidence interval [CI], -1.2° to 6.4°) and paper PT +5° (95% CI, 0.99°-8.6°) were not inferior to outpatient PT based on a predefined 5° margin. Change in knee flexion from baseline was 0° for outpatient PT, -2° for web PT, and -1° for paper PT after 4 to 6 weeks and 8°, 8°, and 12° for the three groups, respectively, after 6 months. Additionally, there was no difference in the change in KOOS from baseline at 4 to 6 weeks or 6 months postoperatively as well as time back to work, driving, and walking without an assistive device. CONCLUSIONS: Unsupervised home exercise is an effective rehabilitation strategy after primary TKA and was noninferior to formal outpatient PT in selected patients. It is worthwhile to reconsider the current practice of automatically designating patients for outpatient PT after primary TKA, because appropriately selected patients with adequate clinical support can achieve similar results at home. LEVEL OF EVIDENCE: Level I, therapeutic study.

Managing Superficial Distal Medial Collateral Ligament Insufficiency in Primary Total Knee Arthroplasty Using Bone Staples.

Superficial medial collateral ligament (MCL) injury is an occasional intraoperative complication during total knee arthroplasty (TKA) that can lead to failure. Although previous studies have recommended complex repair or conversion to a constrained implant, the authors evaluated results of superficial distal MCL reapproximation using bone staples. Records of 31 patients who underwent staple reapproximation for superficial MCL avulsion from the tibial attachment during primary TKA from 2005 to 2015 were reviewed. They were compared with 685 patients who underwent uncomplicated TKA (primary control) and 18 who underwent revision TKA for instability (secondary control). Subjective knee instability was assessed with a patient questionnaire, and other end points included revision for instability or stiffness and manipulations under anesthesia. The authors prospectively collected Knee injury and Osteoarthritis Outcome Score (KOOS) and visual analog scale satisfaction scores. The mean follow-up was 2.6 years. No patients treated with staple repair required revision for instability, whereas two patients were revised in the primary control. Subjective instability was reported in 19.2% of staple repair patients compared with 24.2 and 46.2% of patients in the primary and secondary controls. The mean KOOS for the staple group was 71.7 points, 77.3 for the primary control, and 49.3 for the secondary. KOOSs for the staple group were 5.6 points lower than the primary control, but 22.4 points higher than the secondary. Staple reapproximation is a simple and effective method for repairing the superficial distal MCL in primary TKA. The rate of instability and functional outcomes was comparable to uncomplicated primary TKA.

Use of Intrawound Antibiotics in Orthopaedic Surgery.

Intrawound antibiotics have been used in orthopaedic surgery procedures to prevent the development of surgical site infections. Local delivery of antibiotic powder has demonstrated a notable reduction in surgical site infection in rabbit and rodent in vivo models, as well as in other surgical fields, including vascular, colorectal, cardiothoracic, and dermatologic surgery. Intrawound antibiotic powder has been used in many orthopaedic applications, including spine surgery, total joint arthroplasty, trauma, foot and ankle reconstruction, and elbow surgery. Although the theory behind the use of intrawound antibiotic powder is promising, it has potential adverse effects, including antibiotic resistance, circulatory collapse, and decreased bone healing. In addition, most studies in the orthopaedic literature on the use of intrawound antibiotic powder are retrospective in nature.

The Role of Perioperative Surveillance in 90-Day Total Joint Arthroplasty Care.

BACKGROUND: With the recent implementation of a bundled payment model for total joint arthroplasty, healthcare providers are financially responsible for management of complications throughout the 90-day perioperative period. Our aim was to assess the effectiveness of a surveillance system that was implemented to enhance communication during this period. METHODS: A retrospective study was conducted using a prospectively collected database of patients who underwent primary total joint arthroplasty from January 2015 to April 2016. Surveillance was performed using electronic messages and telephone calls. The use of this system in response to several clinical scenarios was measured by the total number of messages and calls exchanged. RESULTS: Communication was greater among patients who experienced a complication (median 8), went to the emergency department (ED; median 9), and were readmitted to the hospital (median 8), relative to patients who had an uncomplicated course (median 5). Additionally, communication was greater among patients who presented to outside facilities for ED visits (median 11) and readmissions (median 9) relative to those who returned to the index hospital for ED visits (median 7) and readmissions (median 6). More distant patients had decreased follow-up attendance but did not have a compensatory increase in use of the surveillance system. CONCLUSION: Patients used the surveillance system to relay information about clinically significant events when such events arose. Additionally, patients who returned to outside facilities used the surveillance system to remain engaged with their original provider. However, more distant patients did not appear to use the surveillance system to compensate for decreased follow-up attendance.

The "Bundle Busters": Incidence and Costs of Postacute Complications Following Total Joint Arthroplasty.

BACKGROUND: Recently, a bundled payment model was implemented in the United States to improve quality and reduce costs. While hospitals may be rewarded for lowering costs, they may be financially exposed by high cost complications, the so-called bundle busters. We aimed at determining the incidence, etiology, and costs of postacute complications after total joint arthroplasty (TJA). METHODS: A retrospective study was conducted using a prospectively collected database of patients who underwent primary total hip arthroplasty (THA) or total knee arthroplasty (TKA) from January 2015 to April 2016. Nurse navigators performed postoperative surveillance to identify patients with complications and unplanned clinical events in the 90-day postoperative period. This was combined with episode-of-care costs provided by third-party payers to derive the mean and per capita costs of postacute complications and clinical events. RESULTS: Among 3018 THA and 5389 TKA patients, 3.35% of THA and 2.62% of TKA patients sought emergency department or urgent care services, 2.62% of THA and 3.69% of TKA patients required hospital readmission, and 3.99% of TKA patients required manipulation. Joint-related complications were more common following THA, whereas medical complications were more frequent after TKA. The most costly complications after THA were periprosthetic fracture, dislocation, and myocardial infarction, compared to deep infection, myocardial infarction, and pulmonary embolism after TKA. CONCLUSION: Joint-related complications were among the most costly events after TJA, and given their higher incidence after THA, had a larger impact on per capita costs. Medical complications were more common after TKA and more costly. Despite these events, postacute complications made up less than 5% of the total 90-day costs of TJA.

Patients Living Alone Can Be Safely Discharged Directly Home After Total Joint Arthroplasty: A Prospective Cohort Study.

BACKGROUND: Despite the expense and potential hazards of inpatient rehabilitation, there is a prevailing belief that patients living alone cannot be safely discharged directly home after total joint arthroplasty. The purpose of this study was to assess the safety and efficacy of direct home discharge for patients living alone during convalescence after primary total joint arthroplasty. METHODS: We prospectively studied 910 consecutive patients undergoing primary, unilateral total hip arthroplasty or total knee arthroplasty over an 8-month period. Patients discharged directly home who were living alone for the first 2 weeks after the surgical procedure were identified as the investigational group and those discharged to home and living with others constituted the control group. The primary outcomes were 90-day complications and unplanned clinical events, including readmissions, emergency department or urgent care visits, and office visits. Functional outcomes, patient satisfaction, pain relief, and return to daily function were also assessed. RESULTS: During the study period, 874 patients (96%) were discharged directly home and only 36 patients (4%) were discharged to a rehabilitation facility. Of those discharged home, 769 patients were included in the final analysis, including 138 patients living alone and 631 patients living with others, and 105 patients were excluded as they opted not to participate. Patients living alone more commonly stayed an additional night in the hospital and utilized more home health services. There was no increase in complications or unplanned clinical events for patients living alone compared with those living with others. Further, no significant differences in functional outcomes or pain relief were detected, and satisfaction scores were equivalent after 90 days. CONCLUSIONS: Patients living alone had a safe and manageable recovery when discharged directly home after total joint arthroplasty. Extending the initial hospitalization and providing home health services on a selected basis may be a more cost-effective approach than routine discharge to an inpatient rehabilitation facility. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Weighing in on Body Mass Index and Infection After Total Joint Arthroplasty: Is There Evidence for a Body Mass Index Threshold?

BACKGROUND: Although morbid obesity is considered a modifiable risk factor for periprosthetic joint infection (PJI), there is no consensus regarding an appropriate threshold for body mass index (BMI) above which a high risk for infection may outweigh the benefits of surgery. QUESTIONS/PURPOSES: (1) Is there a BMI cutoff threshold that is associated with increased risk for PJI? (2) Is the risk of PJI increased in higher obesity classes? METHODS: A retrospective study was conducted of all primary THAs and TKAs performed at one institution between 2006 and 2015. Overall 19,226 patients were eligible to be included in the study; 1053 patients were excluded as a result of incomplete data, resulting in a final cohort of 18,173 patients (8757 TKAs and 9416 THAs). PJI was defined using the International Consensus Meeting criteria. To ensure accurate followup, and because there is evidence to support the association between obesity and early infection, we identified PJI within 90 days of the index surgery. This relationship was examined separately for BMI as a continuous variable and for each BMI category as defined by the Centers for Disease Control and Prevention (underweight ≤ 18.49 kg/m; normal 18.5-24.9 kg/m; overweight 25-29.9 kg/m; obese class I 30-34.9 kg/m; obese class II 35-39.9 kg/m; obese class III ≥ 40 kg/m). Analyses were performed with logistic regression, accounting for both patient and surgical risk factors. A BMI threshold was evaluated with a receiver operating characteristic (ROC) curve and the Youden index. RESULTS: The area under the ROC curve for BMI and risk of PJI within 90 days was only 0.58 (confidence interval [CI], 0.52-0.63) suggesting such a cutoff was not much better than random chance. Among the BMI classes, patients with class III obesity (≥ 40 kg/m) were the only ones showing a higher risk for PJI within 90 days (odds ratio [OR], 3.09 [1.46-6.54]; p = 0.003). The risk of developing PJI was not greater for overweight (OR, 0.72; 95% CI, 0.38-1.4), class I obese (OR, 1.06; 95% CI, 0.57-2.0), or class II obese (OR, 1.08; 95% CI, 0.52-2.2) patients. Underweight patients also demonstrated no increased risk for PJI (OR, 1.80; 95% CI, 0.23-13.9). CONCLUSIONS: The risk for infection increases gradually throughout the full range of BMI, but no threshold exists. Weight reduction before surgery may mitigate risk for infection for all patients with a BMI above normal. Of note, patients with a BMI > 40 kg/m carried a threefold higher risk for PJI and for these patients, the risks of surgery must be carefully weighed against its benefits. LEVEL OF EVIDENCE: Level III, therapeutic study.