Discordance in Published 30-Day Readmission Rates Following Primary Total Hip and Total Knee Arthroplasty: Centers for Medicare and Medicaid Services (CMS) Versus the National Surgical Quality Improvement Program (NSQIP).

Background: 30-day readmission is an important quality metric evaluated following primary total joint arthroplasty (TJA) that has implications for hospital performance and reimbursement. Differences in how 30-day readmissions are defined between Centers for Medicare and Medicaid Services (CMS) and other quality improvement programs (i.e., National Surgical Quality Improvement Program [NSQIP]) may create discordance in published 30-day readmission rates. The purpose of this study was to evaluate 30-day readmission rates following primary TJA using two different temporal definitions. Methods: Patients undergoing primary total hip and primary total knee arthroplasty at a single academic institution from 2015-2020 were identified via common procedural terminology (CPT) codes in the electronic medical record (EMR) and institutional NSQIP data. Readmissions that occurred within 30 days of surgery (consistent with definition of 30-day readmission in NSQIP) and readmissions that occurred within 30 days of hospital discharge (consistent with definition of 30-day readmission from CMS) were identified. Rates of 30-day readmission and the prevalence of readmission during immortal time were calculated. Results: In total, 4,202 primary TJA were included. The mean hospital length of stay (LOS) was 1.79 days. 91% of patients were discharged to home. 30-day readmission rate using the CMS definition was 3.1% (130/4,202). 30-day readmission rate using the NSQIP definition was 2.7% (113/4,202). Eight readmissions captured by the CMS definition (6.1%) occurred during immortal time. Conclusion: Differences in temporal definitions of 30-day readmission following primary TJA between CMS and NSQIP results in discordant rates of 30-day readmission. Level of Evidence: III.

Observed Differences in Patient Comorbidities and Complications Undergoing Primary Total Joint Arthroplasty Between Non-orthopaedic and Orthopaedic Referral Patients.

BACKGROUND: Value-based total joint arthroplasty (TJA) has resulted in decreasing surgeon reimbursement which has created concern that surgeons are being incentivized to avoid medically complex patients. The purpose of this study was to determine if patients who underwent primary total knee (TKA) and total hip arthroplasty (THA) had different comorbidities and complication rates based on referral type: 1) non-orthopaedic referral (NOR), 2) outside orthopaedic referral (OOR) or 3) self-referral (SR). METHODS: At a single tertiary care centre, patients undergoing primary TJA between July 2019 and January 2020 were identified using current procedural codes. Data were abstracted from the Institutional National Surgical Quality Improvement Program (NSQIP) along with electronic medical records which included referral type, primary insurance, demographics, comorbidities, and comorbidity scores, including an American Society of Anesthesiology (ASA) score. Complications and outcomes were tracked for 90 days post-operatively. Referral groups were compared using Chi-square exact tests for categorical variables and t-tests or Wilcoxon Rank Sum tests for continuous variables, as appropriate. RESULTS: Of the 393 patients included in this study, there were 249 (63%) NOR, 104 (26%) OOR, and 40 (10%) SR. The OOR versus NOR group had a significantly greater proportion of patients with obesity (79 vs 64%, p=0.047) and an ASA score ≥3 (59 vs 43%, p=0.007). There was a significantly greater proportion of patients with wound complications (10 vs 4%, p=0.023) and ≥2 complications (14 vs 3%, p<0.001) in OOR versus NOR, respectively. CONCLUSION: Patients who underwent primary TJA and were referred by an orthopaedic surgeon tended to have more comorbid conditions and higher rates of severe complications. The observed difference in referrals may be explained by monetary incentivization in the context of current reimbursement trends. Organizations utilizing bundled payment programs to reimburse surgeons should use a risk-stratification model to mitigate incentivizing surgeons to avoid medically complex patients.

Clinical and Computational Evaluation of an Anatomic Patellar Component.

INTRODUCTION: Anatomic patellar components for total knee arthroplasty (TKA) have demonstrated favorable in vivo kinematics. A novel failure mechanism in patients implanted with anatomic patella components was observed, prompting a clinical and computational investigation to identify patient and implant-related factors associated with suboptimal performance. METHODS: A retrospective evaluation was performed comparing 100 TKA patients implanted with anatomical versus 100 sex-, age-, and BMI-matched patients implanted with dome patellar components. All were implanted with the same posterior-stabilized (PS) TKA system with a minimum 1-year follow-up duration. Several radiographic parameters were assessed. A separate computational evaluation was performed using finite-element analysis, comparing components. Bone strain energy density was measured at the proximal and distal patellar poles. RESULTS: Patients who had anatomic patellar components had a significantly higher prevalence of anterior knee pain (AKP; 18 versus 2%, P < 0.001), chronic effusions (18 versus 2%, P < 0.001), and superior patellar pole fragmentation (36 versus 13%, P < 0.001) versus those who had dome patellar components. The anatomic group also demonstrated more lateral patellar subluxation (2.3 versus 1.1 mm, P < 0.001) and lateral tilt (5.4 versus 4.0 mm, P = 0.013). There was a higher, but not significant, number of revisions in the anatomic group (7 versus 3, P = 0.331). In computational evaluation, all simulations demonstrated increased bone strain energy density at the superior patellar pole for the anatomic patella. Resection thickness < 13 mm resulted in an over 2-fold increase in strain energy density, while a negative 7° resection angle resulted in a 6-fold higher superior pole strain energy. CONCLUSION: Patients who had this design of anatomic patellar component showed higher rates of AKP, effusion, and superior pole fragmentation than patients who had dome patellae, with higher superior patella pole strain energy confirmed on computational evaluation. Avoiding higher resection angles and excessive patellar resection may improve the performance and survivorship of the anatomic patella.

Resident Synovial Macrophages in Synovial Fluid: Implications for Immunoregulation in Infectious and Inflammatory Arthritis.

Objectives: Resident synovial macrophages (RSM) provide immune sequestration of the joint space and are likely involved in initiation and perpetuation of the joint-specific immune response. We sought to identify RSM in synovial fluid (SF) and demonstrate migratory ability, in additional to functional changes that may perpetuate a chronic inflammatory response within joint spaces. Methods: We recruited human patients presenting with undifferentiated arthritis in multiple clinical settings. We used flow cytometry to identify mononuclear cells in peripheral blood and SF. We used a novel transwell migration assay with human ex-vivo synovium obtained intra-operatively to validate flow cytometry findings. We used single cell RNA-sequencing (scRNA-seq) to further identify macrophage/monocyte subsets. ELISA was used to evaluate the bone-resorption potential of SF. Results: We were able to identify a rare population of CD14dim, OPG+, ZO-1+ cells consistent with RSM in SF via flow cytometry. These cells were relatively enriched in the SF during infectious processes, but absolutely decreased compared to healthy controls. Similar putative RSM were identified using ex vivo migration assays when MCP-1 and LPS were used as migratory stimulus. scRNA-seq revealed a population consistent with RSM transcriptionally related to CD56+ cytotoxic dendritic cells and IDO+ M2 macrophages. Conclusion: We identified a rare cell population consistent with RSM, indicating these cells are likely migratory and able to initiate or coordinate both acute (septic) or chronic (autoimmune or inflammatory) arthritis. RSM analysis via scRNA-seq indicated these cells are M2 skewed, capable of antigen presentation, and have consistent functions in both septic and inflammatory arthritis.

Non-Linear Optics at Twist Interfaces in h-BN/SiC Heterostructures.

Understanding the emergent electronic structure in twisted atomically thin layers has led to the exciting field of twistronics. However, practical applications of such systems are challenging since the specific angular correlations between the layers must be precisely controlled and the layers have to be single crystalline with uniform atomic ordering. Here, an alternative, simple, and scalable approach is suggested, where nanocrystallinetwo-dimensional (2D) film on 3D substrates yields twisted-interface-dependent properties. Ultrawide-bandgap hexagonal boron nitride (h-BN) thin films are directly grown on high in-plane lattice mismatched wide-bandgap silicon carbide (4H-SiC) substrates to explore the twist-dependent structure-property correlations. Concurrently, nanocrystalline h-BN thin film shows strong non-linear second-harmonic generation and ultra-low cross-plane thermal conductivity at room temperature, which are attributed to the twisted domain edges between van der Waals stacked nanocrystals with random in-plane orientations. First-principles calculations based on time-dependent density functional theory manifest strong even-order optical nonlinearity in twisted h-BN layers. This work unveils that directly deposited 2D nanocrystalline thin film on 3D substrates could provide easily accessible twist-interfaces, therefore enabling a simple and scalable approach to utilize the 2D-twistronics integrated in 3D material devices for next-generation nanotechnology.

Phase Stability of Hexagonal/Cubic Boron Nitride Nanocomposites.

Boron nitride (BN) is an exceptional material, and among its polymorphs, two-dimensional (2D) hexagonal and three-dimensional (3D) cubic BN (h-BN and c-BN) phases are most common. The phase stability regimes of these BN phases are still under debate, and phase transformations of h-BN/c-BN remain a topic of interest. Here, we investigate the phase stability of 2D/3D h-BN/c-BN nanocomposites and show that the coexistence of two phases can lead to strong nonlinear optical properties and low thermal conductivity at room temperature. Furthermore, spark-plasma sintering of the nanocomposite shows complete phase transformation to 2D h-BN with improved crystalline quality, where 3D c-BN possibly governs the nucleation and growth kinetics. Our demonstration might be insightful in phase engineering of BN polymorph-based nanocomposites with desirable properties for optoelectronics and thermal energy management applications.

'Tis Time 'Tis Time: The Importance of Operative Time, Thoroughness, and Shakespeare in Dair Procedures in Total Joint Arthroplasty.

Background: Prosthetic joint infections (PJIs), while rare, are a devasting complication of both total joint arthroplasty (TJA). With most patients undergoing surgical treatment for PJI, options vary between one-stage or two-stage (the gold standard) procedures. Debridement, antibiotics, and implant retention (DAIR) procedures are a common, less morbid alternative to two-stage revisions, but patients undergoing DAIR procedures more often experience reinfections. This is likely in part due to non-standardized irrigation and debridement (I&D) methods within these procedures. Furthermore, DAIR procedures are often desired due to their cost effectiveness and lesser operative times, but no investigations have occurred regarding operative-time-based outcomes. This study aimed to compare reinfection incidence with procedure time in DAIR procedures. In addition, this study aimed to introduce the novel Macbeth Protocol for the I&D portion of DAIR procedures and assess its efficacy. Methods: Records of unilateral DAIR procedures for primary TJA PJI performed by arthroplasty surgeons from 2015-2022 were retrospectively reviewed for patient demographics, select medical history, body mass index (BMI), joint, microbiology, and follow-up data. In addition, a single surgeon's DAIR procedures (for primary and revision TJA) were reviewed and use of The Macbeth Protocol was noted. Results: A total of 71 patients (mean age 64.00 ± 12.81 years) who underwent unilateral DAIR were included. Patients with reinfections following their DAIR procedure had significantly (p = 0.034) lower procedure times (93.72 ± 15.01 min) compared to those without reinfections (105.87 ± 21.91 min). Twenty-two patients underwent 28 DAIR procedures by the senior author, where 11 (39.3%) DAIR procedures utilized The Macbeth Protocol. The use of this protocol did not significantly affect reinfection rate (p = 0.364). Conclusion: This study concluded that increased operative time led to less reinfections for DAIR procedures treating unilateral primary TJA PJIs. Additionally, this study introduced The Macbeth Protocol, which demonstrated promising potential as an I&D technique despite not showing statistical significance. Arthroplasty surgeons should not sacrifice patient outcomes determined by reinfection rate for decreased operative time. Level of Evidence: III.

Projected Prevalence of Obesity in Aseptic Revision Total Hip and Knee Arthroplasty.

Background: The purpose of this study was to develop projections of the prevalence of obesity in aseptic revision THA and TKA patients through the year 2029. Methods: The National Surgical Quality Improvement Project (NSQIP) was queried for years 2011-2019. Current procedural terminology (CPT) codes 27134, 27137, and 27138 were used to identify revision THA and CPT codes 27486 and 27487 were used to identify revision TKA. Revision THA/TKA for infectious, traumatic, or oncologic indications were excluded. Participant data were grouped according to body mass index (BMI) categories: underweight/normal weight, <25 kg/m2; overweight, 25-29.9 kg/m2; class I obesity, 30.034.9 kg/m2; class II obesity, 35.0-39.9 kg/m2; morbid obesity ≥ 40 kg/m2. Prevalence of each BMI category was estimated from year 2020 to year 2029 through multinomial regression analyses. Results: 38,325 cases were included (16,153 revision THA and 22,172 revision TKA). From 2011 to 2029, prevalence of class I obesity (24% to 25%), class II obesity (11% to 15%), and morbid obesity (7% to 9%) increased amongst aseptic revision THA patients. Similarly, prevalence of class I obesity (28% to 30%), class II obesity (17% to 29%), and morbid obesity (16% to 18%) increased in aseptic revision TKA patients. Conclusion: Prevalence of class II obesity and morbid obesity demonstrated the largest increases in revision TKA and THA patients. By 2029, we estimate that approximately 49% of aseptic revision THA and 77% of aseptic revision TKA will have obesity and/or morbid obesity. Resources aimed at mitigating complications in this patient population are needed. Level of Evidence: III.

Bridge Plate Fixation of Distal Femur Fractures: Defining Deficient Radiographic Callus Formation and Its Associations.

OBJECTIVE: To determine whether deficient early callus formation can be defined objectively based on the association with an eventual nonunion and specific patient, injury, and treatment factors. METHODS: Final healing outcomes were documented for 160 distal femur fractures treated with locked bridge plate fixation. Radiographic callus was measured on postoperative radiographs until union or nonunion had been declared by the treating surgeon. Deficient callus was defined at 6 and 12 weeks based on associations with eventual nonunion through receiver-operator characteristic analysis. A previously described computational model estimated fracture site motion based on the construct used. Univariable and multivariable analyses then examined the association of patient, injury, and treatment factors with deficient callus formation. RESULTS: There were 26 nonunions. The medial callus area at 6 weeks <24.8 mm 2 was associated with nonunion (12 of 39, 30.8%) versus (12 of 109, 11.0%), P = 0.010. This association strengthened at 12 weeks with medial callus area <44.2 mm 2 more closely associated with nonunion (13 of 28, 46.4%) versus (11 of 120, 9.2%), P <0.001. Multivariable logistic regression analysis found limited initial longitudinal motion (OR 2.713 (1.12-6.60), P = 0.028)) and Charlson Comorbidity Index (1.362 (1.11-1.67), P = 0.003) were independently associated with deficient callus at 12 weeks. Open fracture, mechanism of injury, smoking, diabetes, plate material, bridge span, and shear were not significantly associated with deficient callus. CONCLUSION: Deficient callus at 6 and 12 weeks is associated with eventual nonunion, and such assessments may aid future research into distal femur fracture healing. Deficient callus formation was independently associated with limited initial longitudinal fracture site motion derived through computational modeling of the surgical construct but not more routinely discussed parameters such as plate material and bridge span. Given this, improved methods of in vivo assessment of fracture site motion are necessary to further our ability to optimize the mechanical environment for healing. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Unravelling the room temperature growth of two-dimensional h-BN nanosheets for multifunctional applications.

The room temperature growth of two-dimensional van der Waals (2D-vdW) materials is indispensable for state-of-the-art nanotechnology. Low temperature growth supersedes the requirement of elevated growth temperatures accompanied with high thermal budgets. Moreover, for electronic applications, low or room temperature growth reduces the possibility of intrinsic film-substrate interfacial thermal diffusion related deterioration of the functional properties and the consequent deterioration of the device performance. Here, we demonstrated the growth of ultrawide-bandgap boron nitride (BN) at room temperature by using the pulsed laser deposition (PLD) process, which exhibited various functional properties for potential applications. Comprehensive chemical, spectroscopic and microscopic characterizations confirmed the growth of ordered nanosheet-like hexagonal BN (h-BN). Functionally, the nanosheets show hydrophobicity, high lubricity (low coefficient of friction), and a low refractive index within the visible to near-infrared wavelength range, and room temperature single-photon quantum emission. Our work unveils an important step that brings a plethora of potential applications for these room temperature grown h-BN nanosheets as the synthesis can be feasible on any given substrate, thus creating a scenario for "h-BN on demand" under a frugal thermal budget.

Component Rotation in Well-Functioning, Gap Balanced Total Knee Arthroplasty Without Navigation.

BACKGROUND: Malalignment of total knee arthroplasty (TKA) components is a potential cause of clinical failure following TKA. Since the goal of a gap balancing (GB) technique is equal flexion and extension gaps secondary to soft-tissue balancing, and not necessarily component alignment, variation in component placement may exist. Our purpose was (1) to evaluate precision of component alignment in well-functioning GB TKAs performed without the aid of navigation using computed tomographic evaluation and (2) to determine any relationship between femoral version and/or tibial torsion and TKA component positioning. METHODS: There were 93 well-functioning TKAs performed with an extension gap first GB technique with a minimum 2-year follow-up evaluated using computed tomography to assess component rotational alignment, as well as osseous femoral version and tibial torsion. Femoral and tibial rotational alignment was assessed by previously described methods. RESULTS: The mean Knee Society Score was 185.7 ± 21.7. The mean range of motion was 128.5 ± 7.8°. Femoral posterocondylar axis (relative to the transepicondylar axis) values ranged from -8.3 to 4.1° with a mean of -0.78 ± 2.7° (internal rotation). Mean tibial rotation was 17.2 ± 7.9° internal rotation relative to the tibial tubercle. No correlation was found between native femoral version and femoral component rotational alignment (Pearson's correlation coefficient, r, 0.007). Weak correlation was found between native tibial torsion and tibial component alignment (r = 0.24). CONCLUSION: Despite being only a secondary objective with the GB technique, most components evaluated were within the desired range of rotation. Alignment was not influenced by native osseous rotational geometry. LEVEL OF EVIDENCE: Level III, Retrospective Cohort Study.

What Is the Fate of Total Joint Arthroplasty Patients Who Are Asked to Quit Smoking Prior to Surgery?

Background: Smoking is a known risk factor for complications following primary total joint arthroplasty (TJA). Little is known regarding the fate of patients who are asked to quit smoking before surgery. The purpose of this study was to evaluate the success of smoking cessation prior to primary TJA and the impact of smoking cessation on perioperative outcomes. Methods: This is a retrospective review of patients who presented between 2008 and 2020 to a single academic medical center with a documented smoking history and were asked to quit smoking prior to receiving a date for primary TJA. The cohort was surveyed about smoking cessation, smoking history, use of quit aids, seeking surgery elsewhere due to the cessation policy, and postoperative complications. Descriptive statistics evaluated the relationship between demographics, smoking cessation, and postoperative complications. Results: A total of 101 patients completed the survey with an overall response rate of 48%. Sixty-two percent of patients quit smoking before surgery, and 51% of these patients reported remaining smoke-free at 6 months postoperatively. The average time to quit before TJA was 45 days (range: 1-365 days), and 62% quit without quit aids. The wound complication/infection rate was significantly higher for patients who did not stop smoking prior to TJA (4 of 16; 27%) than for those who did quit prior to surgery (3 of 63; 5%; P = .02). Conclusions: This study demonstrates that most patients (62%) will stop smoking, if required, prior to primary TJA. Furthermore, 51% of patients reported abstinence from smoking at 6 months following TJA. TJA appears to be an effective motivator for smoking cessation. Level of Evidence: III (retrospective cohort study).

Whole-body phase angle correlates with pre-operative markers in total joint arthroplasty.

Background: Bioimpedance derived whole body phase angle (ϕ), a measure of cellular integrity, has been identified as an independent marker of morbidity and mortality in many medical and surgical specialties. While similar measures of water homeostasis like extracellular edema (EE) have been associated with pre-operative risk, ϕ has not been studied in orthopaedics, despite potential to serve as a pre-operative marker. This study aims to identify relationships between ϕ, EE, and body composition metrics, laboratory values, patient reported outcomes, and comorbidities. Methods: Multi-frequency bioimpedance analysis (BIA) records, laboratory values, and patient reported outcomes of adult patients presenting to an academic arthroplasty clinic were retrospectively reviewed. Correlation coefficients between ϕ, EE, and reviewed information were conducted. Results: ϕ was significantly correlated (p<0.001) most positively with measures of lean tissue such as skeletal muscle mass (r=0.48), appendicular skeletal muscle index (r=0.39), lean body mass (r=0.43), and dry lean mass (r=0.47), while it held negative correlations (p<0.001) with age (r= -0.55), and body fat mass (r= -0.11). ϕ was not correlated with body mass index (BMI, p = 0.204). In contrast, EE demonstrated its strongest positive correlations (p<0.001) with body fat mass (r=0.32), age (r=0.50), and BMI (r=0.26), and its strongest negative correlations (p<0.001) with serum albumin (r= -0.37) and total protein (r= -0.23). Conclusions: Based on their associations with markers of health and fitness, BIA determined ϕ and EE demonstrate relationships to markers currently implemented in orthopaedic practice. This likely indicates that ϕ has potential as a comprehensive surrogate for several commonly used markers to quantify pre-operative risk. In the future, ϕ may aid in developing risk-stratifications for intervention and prevention of complications.

Did Rapid Expansion of Same Day Discharge Hip and Knee Arthroplasty During the COVID-19 Pandemic Increase Early Complications?

Background: The COVID-19 pandemic has had a lasting impact on patients seeking total hip and knee arthroplasty (THA, TKA) including more patients undergoing same day discharge (SDD) following total joint arthroplasty (TJA). The purpose of this study was to assess whether expansion of SDD TJA during the COVID-19 pandemic resulted in more early complications following TJA. We anticipated that as many institutions quickly launched SDD TJA programs there may be an increase in 30-day complications. Methods: We retrospectively queried the ACS-NSQIP database for all patients undergoing primary elective TJA from January 1, 2018, to December 31, 2020. Participants who underwent THA or TKA between January 1, 2018 and March 1, 2020 were grouped into pre-COVID and between March 1, 2020 and December 31, 2020 were grouped into post-COVID categories. Patients with length of stay greater than 0 were excluded. Primary outcome was any complication at 30 days. Secondary outcomes included readmission and re-operation 30 days. Results: A total of 14,438 patients underwent TKA, with 9,580 occurring pre-COVID and 4,858 post-COVID. There was no difference in rates of total complication between the pre-COVID (3.55%) and post-COVID (3.99%) groups (p=0.197). Rates of readmissions for were similar for the pre-COVID (1.75%) and post-COVID (1.98%) groups (p=0.381). There was no statistically significant difference in respiratory complications between the pre-COVID (0.41%) and post-COVID group (0.23%, p=0.03). A total of 12,265 patients underwent THA, with 7,680 occurring pre-COVID and 4,585 post-COVID. There was no difference in rates of total complication between the pre-COVID (3.25%) and post-COVID (3.49%) groups (p=0.52). Rates of readmissions for were similar for the pre-COVID (1.77%) and post-COVID (1.68%) groups (p=0.381). There was no statistically significant difference in respiratory complications between the pre-COVID (0.16%) and post-COVID group (0.07%, p=0.26). Combined data to include THA and TKA patients did not find a statistical difference in the rate of complications or readmission but did note a decrease in the rate of combined respiratory complications in the post-COVID group (0.15% vs. 0.30%, p=0.028). Conclusion: Rapid expansion of SDD TJA during the COVID-19 pandemic did not increase overall complication, readmission, or re-operation rates. Level of Evidence: IV.

Body Composition Changes in the Immediate Peri-operative Period Following Total Joint Arthroplasty.

Background: Bioimpedance analysis (BIA) is a readily available tool to assess body composition in a clinical setting. BIA has received little attention in orthopaedics and namely joint arthroplasty. This study aims to quantify changes in body composition in the immediate peri-operative period following total joint arthroplasty. Methods: Adults scheduled for elective total joint arthroplasty were recruited to participate. Patients underwent BIA scans in the immediate peri-operative period: pre-operative on their day of surgery, post-operative day 0, and post-operative day 1. Results: 67 patients were enrolled to undergo BIA scans. Mean age was 62.64 ± 10.28 years old, and 49.2% were females. The all-supine cohort exhibited a 0.36 ± 0.61 kg increase in dry lean mass (p < 0.001) and 1.30 ± 2.14 kg increase in lean body mass on postoperative day 0 (p < 0.001). Patients received to 1.16 ± 0.58 kg of fluid mass, on average. Conclusion: BIA is a rapid, portable tool that allows for body composition analysis of an inpatient surgical population. This study demonstrated that BIA can detect net fluid changes and may approximate implant mass following total joint arthroplasty. This may aid surgeons in interpreting post-operative body composition changes.

Does Isolated Unilateral Hip or Knee Osteoarthritis Lead to Adverse Changes in Extremity Composition?

Background: While muscle atrophy is a function of normal aging, loss of muscle in the setting of hip and knee osteoarthritis (OA) has been observed using radiographic studies. There is limited data available regarding changes in extremity composition using bioimpedance (BIA). The purpose of this study was to assess the changes in extremity composition in patients with isolated, unilateral hip or knee OA using BIA. Methods: Patients presenting to our institution's adult reconstruction clinic from February 2020 to April 2021 were retrospectively reviewed to identify those with isolated, unilateral hip and knee OA. The InBody 770 Body Composition Analyzer (InBody USA, Cerritos, California) was used to perform a complete body composition assessment, per protocol. Lean extremity mass (LEM), fat mass (FM), intracellular water (ICW), extremity body water (EBW = ICW + extracellular water (ECW)) and phase angle (PA) were determined. Differences between the affected (OA) and unaffected (no OA) extremities were compared using t-tests. Results: 38 patients had isolated hip OA. The mean age was 60.8 (±11.7) years, mean BMI was 31.7 (±6.8) kg/m2, and 39.5% were female. LEM, FM, EBW, ICW, and PA were significantly decreased in the hip OA extremity (LEM: 20.0 vs. 20.4 kg, p=0.0008, FM: 8.8 vs. 8.9 kg, p=0.0049, EBW: 15.7 vs 16.0, p=0.0011, ICW: 9.5 vs. 9.7 L, p=0.0004, PA: 4.5 vs 4.9º, p<0.0001). There were 25 patients with isolated knee OA. Mean age was 62.8 (±11.3) years, mean BMI was 33.6 (±6.9) kg/m2, and 52.0% were female. FM and PA were significantly lower in the knee OA extremity (11.3 vs 11.4 kg, p=0.0291, 4.5 vs 4.9º, p<0.0001). There were no significant differences in LEM, EBW, and ICW between the knee OA extremity and the unaffected extremity. Conclusion: Patients with isolated, unilateral hip OA had decreased LEM, FM, EBW, and ICW in the affected extremity. Both unilateral hip and knee OA was associated with decreased PA, suggestive of greater underlying dysfunction in muscle or cellular performance. Further study is needed to better define when these abnormalities develop, how they progress over time, and the impact of targeted interventions in reversing these changes. Level of Evidence: III.

The Impact of Orthopaedic Surgical Training on Body Composition.

Background: Residency is known to consist of rigorous training that has contributed to increased rates of resident burn out, depression, and suicide. There have been recent efforts to attempt to combat and solve the rising levels of mental health concerns amongst physicians and physicians in training. While studies have examined the adverse effects of medical training on mental health, few have examined the associated changes in physical health. This study aimed to identify and compare baseline body composition and hand grip strength of orthopaedic surgery residents. The second aim was to identify and compare changes that may occur over the course of the training program. Methods: First year orthopaedic surgery residents ("interns") were recruited to undergo body composition measurements via bioimpedance analysis (BIA) during their first, third, and twelfth month of post-graduate training. At each interval, three hand-grip-strength measurements per hand were captured. Additionally, orthopaedic surgery residents who had already completed their first year ("non-interns") were recruited to undergo baseline and 12-month BIA for comparison. Results: Six interns and six non-interns were recruited. The interns lost 2.88 ± 4.26 kg (-3.31% ± 4.75%) of their initial body mass with most of the loss being body fat mass (1.97 ± 2.62 kg) by three months. Interns recovered a fair amount of mass loss by 12 months with a net change of -0.78 ± 3.14 kg (-1.09% ± 3.90%). Non-interns experienced an overall net weight gain (1.20 ± 3.64 kg; 1.68% ± 5.55%) over the same period. Intern HGS changed by -1.92 ± 2.49 kg and 3.39 ± 2.34 kg at 3- (n=6) and 12-months (n=3), respectively. Conclusion: This study demonstrates that there is an appreciable decrease in overall body mass, lean tissue mass, and body fat throughout the orthopaedic resident's intern year. The results demonstrate an initial fall in each body metric and strength by 3-months followed by partial recovery by 12-months. This pattern contrasts the average gain of body mass in each measured metric by non-interns. This study is limited by population sizes and by incompleteness of HGS data. Level of Evidence: II.

Prevalence of Sarcopenia and Sarcopenic Obesity in an Academic Total Joint Arthroplasty Practice.

Background: Body mass index (BMI) is routinely used for preoperative risk stratification; however, it does not provide a detailed assessment of body composition and intentional weight loss alone may not decrease complications. Sarcopenia-a disorder involving low muscle mass, quality, or performance-has been associated with an increased risk for postoperative complications and is treatable through nutritional supplementation or resistance training. It, counterintuitively, may occur with obesity as "sarcopenic obesity"; however, the prevalence is not widely known. The purpose of this study was to assess the prevalence of sarcopenia and sarcopenic obesity. Material and methods: Patients underwent body composition assessment using multifrequency bioimpedance testing (InBody 770, InBody USA, California). They were classified as sarcopenic based on the appendicular skeletal muscle index and obese by percent body fat. Body composition parameters were compared between obesity or sarcopenia groups and traditional BMI-based obesity definitions. Results: A total of 219 patients underwent body composition assessment. The mean age was 62.1 years, BMI was 34.3 kg/m2, and 53.8% were female. Fifty-seven (26.0%) patients were not obese or sarcopenic, 130 (59.4%) were obese not sarcopenic, 18 (8.2%) were sarcopenic nonobese, and 14 (6.4%) were sarcopenic obese. There was heterogeneity in body composition between groups. Sarcopenic patients were older than those without sarcopenia. Skeletal muscle mass, body fat mass, and appendicular skeletal muscle index increased with increasing BMI. Conclusion: Sarcopenia and sarcopenic obesity were found in nearly 15% of patients. Measures of muscle quantity increased with higher BMI may influence the prevalence of sarcopenia in the morbidly obese, and these patients may require specialized criteria accounting for increased body mass.

Projected Prevalence of Obesity in Primary Total Knee Arthroplasty: How Big Will the Problem Get?

BACKGROUND: Obesity is a well-established risk factor for complications following primary total knee arthroplasty (TKA). The purpose of this study is to utilize 3 national databases to develop projections of obesity within the general population and primary TKA patients in the United States through 2029. METHODS: Data from the National Surgical Quality Improvement Program (NSQIP), the Behavior Risk Factor Surveillance System (BRFSS), and the National Health and Nutrition Examination Survey were queried for years 1999-2019. Current Procedural Terminology code 27447 was used to identify primary TKA patients in NSQIP. Individuals were categorized according to body mass index (kg/m2) by year: normal weight (≤24.9); overweight (25.0-29.9); obese (30.0-39.9); and morbidly obese (≥40). Multinomial logistic regression was used to project categorical body mass index data for years 2020-2029. RESULTS: A total of 8,372,221 individuals were included (7,986,414 BRFSS, 385,807 NSQIP TKA). From 2011 to 2019, the prevalence of normal weight and overweight individuals declined in the general population (BRFSS) and in primary TKA. Prevalence of obese/morbidly obese individuals increased in the general population from 31% to 36% and in primary TKA from 60% to 64%. Projection models estimate that by 2029, 46% of the general population will be obese/morbidly obese and 69% of primary TKA will be obese/morbidly obese. CONCLUSION: By 2029, we estimate ≥69% of primary TKA to be obese/morbidly obese. Increased resources dedicated to care pathways and research focused on improving outcomes in obese arthroplasty patients will be necessary as this population continues to grow. LEVEL OF EVIDENCE: Level III, Retrospective Cohort Study.

Not all Total Hip and Knee Arthroplasties Are the Same: What Are the Implications in Large Database Studies?

BACKGROUND: The use of claims databases for research after total hip and knee arthroplasty (THA, TKA) has increased exponentially. These studies rely on accurate coding, and inadvertent inclusion of patients with nonroutine indications may influence results. The purpose of this study was to evaluate the complexity of THA and TKA captured by CPT code and determine if complication rates vary based on the indication. METHODS: The NSQIP database was queried using CPT codes 21730 and 27447 to identify patients undergoing THA and TKA from 2018 to 2019. The surgical indication was classified based on the ICD-10 diagnosis code as routine primary, complex primary, inflammatory, fracture, oncologic, revision, infection, or indeterminant. Patient factors and 30-day complications, readmission, reoperation, and wound complications were compared. RESULTS: A total of 86,009 THA patients had 703 ICD-10 diagnosis codes and 91.4% were routine primary indications. Complication rates were: routine primary 7.4%, complex primary 11.3%, inflammatory 12.5%, fracture 23.9%, oncologic 32.4%, revision 26.9%, infection 38.7%, and indeterminant 10.3% (P < .0001). 137,500 TKA patients had 552 ICD-10 diagnosis codes and 96.1% were routine primary cases. Complication rates were: routine primary 5.9%, complex primary 8.0%, inflammatory 7.2%, fracture 38.9%, oncologic 32.7%, revision 13.3%, infection 37.7%, and indeterminant 9.6% (P < .0001). Routine primary arthroplasty had significantly lower rates of reoperation, readmission, and wound complications. CONCLUSION: Using CPT code alone captures 10% of THA and 4% of TKA patients with procedures for nonroutine primary indications. It is essential to recognize identification of patients simply by CPT code has the potential to inadvertently introduce bias, and surgeons should critically assess methods used to define the study populations.