Search

This review discusses the correction of coronal deformity and intercompartmental imbalance through bone resection in total knee arthroplasty (TKA). To achieve functional knee balance, coronal, rotational, and sagittal alignment are critical to successful patient outcomes. Though variations in coronal alignment are debated as a correlate to positive results, advancements in utilizing implant position, alignment, and soft tissue balance to improve patient outcomes and function are an evolving discussion. This study draws upon existing literature, clinical studies, and surgical techniques related to TKA, including advancements in navigation and robotics. The study highlights the importance of individualized alignment strategies for varus and valgus knees. While mechanical neutral alignment has shown excellent long-term data, reevaluating the anatomic recreation of the patient's joint line obliquity is now being studied extensively. Sensor data and navigation systems contribute to improved outcomes and patient satisfaction. The evolution of navigation and robotics has led surgeons to achieve their target angles consistently and accurately; now, the discussion is around the most effective alignment targets. The classification of various phenotypes assists in the proposed starting points for implant position, but soft tissue tension is required in the input data to achieve global balance and stable motion. Each approach's advantages and limitations are considered. In conclusion, achieving optimal coronal alignment, joint line obliquity, and soft tissue balance is crucial for successful TKA outcomes. Personalized alignment philosophies, supported by three-dimensional data and sensor technology, are evolving to minimize critical errors and enhance functional results. Robotic assistance and future advancements in artificial intelligence and machine learning hold promise for further improving TKA outcomes in the quest for soft tissue stabilization., Competing Interests: None declared., (Thieme. All rights reserved.)

Improper alignment and implant positioning following unicompartmental knee arthroplasty (UKA) has been shown to lead to postoperative pain and increase the incidence of revision procedures. The use of robotic-arm assistance for UKA (RAUKA) has become an area of interest to help overcome these challenges. The accuracy of intraoperative alignment compared with standing long-leg X-rays postoperatively following medial RAUKA has been in question. Therefore, the purpose of this study was to (1) determine final mean intraoperative coronal alignment in extension utilizing an image based intraoperative navigation system, and (2) compare final intraoperative alignment to 6-week weight-bearing (WB) long-leg X-rays. Patients who underwent RAUKA for medial compartmental osteoarthritis were identified from January 1, 2018, to August 31, 2019, through our institution's joint registry. The query yielded 136 (72 right and 64 left) patients with a mean age of 72.02 years and mean body mass index (BMI) of 28.65 kg/m 2 who underwent RAUKA. Final intraoperative alignment was compared with WB long leg X-rays 6 weeks postoperatively by measuring the mechanical alignment. Statistical analysis was primarily descriptive. Pearson's correlation coefficient was used to determine the relationship between intraoperative alignment to 6-week alignment. A p- value of <0.05 was considered statistically significant. Mean intraoperative coronal alignment after resections and trialing was 4.39 varus ± 2.40 degrees for the right knee, and 4.81 varus ± 2.29 degrees for the left knee. WB long-leg X-rays 6 weeks postoperatively demonstrated mechanical axis alignment for the right and left knees to be 3.01 varus ± 2.10 and 3.7 varus ± 2.38 degrees, respectively. This resulted in a change in alignment of 1.36 ± 1.76 and 1.12 ± 1.84 degrees for the right and left knees, respectively ( p   <  0.05). Pearson's correlation coefficient demonstrated a correlation of 0.69 between intraoperative to long-leg-X-ray alignment. RAUKA demonstrates excellent consistency when comparing postoperative WB long-leg X-rays to final intraoperative image-based non-WB alignment., Competing Interests: None declared., (Thieme. All rights reserved.)

Chronic venous insufficiency (CVI) is extraordinarily prevalent in our aging population with over 30 million people in the United States suffering from the disease. There is a paucity of data analyzing the effects of CVI on outcomes following total knee arthroplasty (TKA). The purpose of this study was to utilize a nationwide administrative claims database to determine whether patients with CVI undergoing TKA have higher rates of: (1) in-hospital lengths of stay (LOS); (2) readmission rates; (3) medical complications; (4) implant-related complications; and (5) costs of care compared to controls. Using a nationwide database, we matched patients with CVI undergoing TKA to controls without CVI undergoing TKA in a 1:5 ratio by age, sex, and medical comorbidities associated with CVI. Primary outcomes analyzed within the study included LOS, 90-day readmission rates, 90-day medical complications, 2-year implant-related complications, in addition to 90-day total global episode of care costs. The query yielded 1,265,534 patients with ( n  = 210,926) and without ( n  = 1,054,608) CVI undergoing primary TKA. Patients with CVI had significantly longer LOS (4 vs. 3 days, p <  0.0001), higher 90-day readmission rates (20.96 vs. 15.34%; odds ratio [OR]: 1.46, 95% confidence interval [CI]: 1.44-1.48, p  < 0.0001), and higher odds of medical complications (2.27 vs. 1.30%; OR: 1.76, 95% CI: 1.70-1.83, p   <  0.0001) compared to matched controls. Patients with CVI also had higher odds of periprosthetic joint infections (2.23 vs. 1.03%; OR: 2.18, p  < 0.0001) and implant-related complications in general (4.27 vs. 2.17%; OR: 2.01, 95% CI: 1.96-2.06, p <  0.0001). Additionally, patients with CVI had higher total global 90-day episode of care costs ($15,583.07 vs. $14,286.95, p  < 0.0001). Patients with CVI undergoing TKA have increased LOS, higher odds of medical and implant complications, and increased costs of care compared to those without CVI. The study can be utilized by orthopaedic surgeons to counsel patients on the potential complications following this procedure. This is a level III, retrospective cohort study., Competing Interests: V.H.H. reports other from Stryker, other from Consensus, other from Pfizer, outside the submitted work. M.R. reports grants and other from Stryker, grants and other from Orthosensor, grants from Smith and Nephew, outside the submitted work. All other authors reported no conflict of interest., (Thieme. All rights reserved.)

Well-powered studies evaluating the effects of Paget's disease on patient outcomes following primary total knee arthroplasty (TKA) are limited. The objective of this study was to determine whether Paget's disease patients undergoing primary TKA have higher rates of complications. A query of an administrative database was performed identifying Paget's disease patients undergoing primary TKA as the study cohort. Patients who did not have Paget's disease served as a matching cohort. Study group patients were matched in a 1:5 ratio by age, sex, and comorbidities. The query yielded 34,284 patients in the study ( n  = 5,714) and matched ( n  = 28,570) cohorts. Outcomes analyzed included length of stay (LOS), costs of care, 90-day medical and surgical complications, and 2-year implant-related complications. Multivariate logistic regression analyses were used to calculate the odds ratios (ORs) of complications. Paget's disease patients undergoing primary TKA were found to have significantly longer in-hospital LOS (4 vs. 3 days, p  < 0.0001). Study group patients incurred significantly higher 90-day episode-of-care costs ($15,124.55 vs. $14,610.01, p  < 0.0001). Additionally, Paget's disease patients were found to have higher incidences and odds of medical/surgical (25.93 vs. 13.58%; OR: 1.64, p  < 0.0001) and implant-related complications (8.97 vs. 5.02%; OR: 1.71, p  < 0.0001). Specifically, Paget's disease patients were more likely to have periprosthetic fractures, mechanical loosening, and revision TKAs ( p  < 0.0001). This study demonstrated that Paget's disease was associated with longer in-hospital LOS, increased costs, and higher rates of complications. The study can be utilized by physicians to adequately educate patients with Paget's disease concerning potential complications following their primary TKA., Competing Interests: T.M.S. reports other from AAHKS social media, other from TJO, Smith & Nephew, Hereaus, Next Science, other from Zimmer Biomet, KCl, Reflexion Health, other from Depuy, Stryker, Exactech, outside the submitted work. M.P.B. reports other from TJO, Zimmer Biomet, other from Amedica, other from Depuy, Synthes, Exactech, PCORI, Stryker, Smith & Nephew, DJO, EOA, AAHKS, AAOS, JOA, JSOA, Arthroplasty Today, outside the submitted work. M.A.M. reports other from Microport, Stryker, other from Merz, Medical Compression Systems, DJ Orthopaedics, J&J, OrthoSensor, Pacira, Sage products, TissueGene, U.S. Medical Innovations, DJ Orthopaedics, NIH, Ongoing Care Solutions, other from JOA, JKS, Surgical Techniques International, American Journal of Orthopedics, Orthopedics, other from AAOS, outside the submitted work. M.W.R. reports other from Stryker, Smith & Nephew, Zimmer, other from AAOS, AAHKS, outside the submitted work. All the other authors report no conflict of interest., (Thieme. All rights reserved.)

The impact of gender on total knee arthroplasty (TKA) postoperative complications, readmission rates, and costs of care has not been often evaluated. Therefore, the purpose of this study was to investigate which sex had higher rates of: (1) medical complications; (2) implant complications; (3) lengths of stay (LOSs); (4) readmission rates; and (5) costs after TKA. A query was performed using an administrative claims database from January 1, 2005, to March 31, 2015. Patients who had TKAs were identified using International Classification of Diseases, Ninth Revision and Current Procedural Terminology codes. Males and females were filtered separately and matched according to age and various medical comorbidities leading to 1,590,626 patients equally distributed. Primary outcomes analyzed included 90-day medical complications, LOSs, 90-day readmission rates, in addition to day of surgery and total global 90-day episode of care costs. Pearson's chi-square analyses were used to compare medical complications and readmission rates. Welch's t- tests were used to test for significance in matching outcomes and costs. A p- value of less than 0.01 was considered statistically significant. Males had a smaller risk of complications than women (1.35 vs. 1.40%, p  < 0.006) and higher rates of implant-related complications (2.28 vs. 1.99%, p  < 0.0001). Mean LOSs were lower for males: 3.16 versus 3.34 days ( p  < 0.0001). The 90-day readmission rates were higher in men (9.67 vs. 8.12%, p  < 0.0001). This study demonstrated that males undergoing primary TKA have lower medical complications and shorter LOSs then their female counterparts. However, males have higher implant-related complications, readmission rates, and costs of care., Competing Interests: None declared., (Thieme. All rights reserved.)

Gout is the most common inflammatory arthritis and affects approximately 4% of the U.S. population. As the prevalence of gout and the number of total knee arthroplasties (TKAs) performed continue to increase, the literature on TKA in patients with gout remains scant. The purpose of this study was to evaluate the outcomes of patients with gout following TKA at a population level, that is, how patient with gout fair after TKA. We hypothesized that patients with gout have higher rates of complications and higher costs compared with controls. A case-control study was designed to evaluate two cohorts of Medicare patients who underwent TKA whose only distinguishing feature was the presence or absence of gout. Matching was performed to decrease confounding at a 1:1 ratio based on age, gender, and Charlson comorbidity index (CCI), (10-year survival predictor). The Medicare standard analytical files were queried through International Classification of Disease and current procedural terminology codes. A total of 15,238 patients were evaluated with 7,619 in each cohort. There were no age, gender, or CCI differences and 57.4% were females. Day of surgery and 90-day post-surgery costs were both significantly greater in those with gout ( p  < 0.001 for both). Multivariate analysis revealed that gout patients had increased odds of infection (odds ratio [OR] 1.229, p  = 0.019), cardiac arrest (OR 1.354, p  = 0.002), pneumonia (OR 1.161, p  < 0.001), hematoma (OR 1.204, p  = 0.002), and development of capsulitis (OR 1.208, p  = 0.012). Nonetheless these patients had a decreased risk of pulmonary emboli (OR 0.835, p  = 0.016). Our results support our hypothesis that patients with gout have higher rates of postoperative complications and increased day of surgery and 90-day costs of care after TKA. Given the high prevalence of gout in the United States, additional study on the utility of preoperative gout optimization for TKA patients is warranted. The level of evidence of this study is III, and it is a retrospective case-control study., Competing Interests: C.L.E. reports personal fees from Surgical Care Affiliates LLC, personal fees from Northeast Orthopaedic Resident STEPP Summit, other from IlluminOss Medical, other from Heron Therapeutics, outside the submitted work; and Musculoskeletal Transplant Foundation, Medical Board of Trustees Coding and Reimbursement Committee, American Academy of Orthopaedic Surgeons Own. The Bone Steering Committee, American Orthopaedic Association Board of Councilors, Nominating Committee, Southern Orthopaedic Association Board Member, Eastern Orthopaedic Association Professional Development Committee, Ruth Jackson Orthopaedic Society Membership Committee, Musculoskeletal Tumor Society Executive Committee (Vice President), and North Carolina Orthopaedic Association., (Thieme. All rights reserved.)

Large-scale studies evaluating the effects of Parkinson's disease (PD) on primary total knee arthroplasty (TKA) are limited. The purpose of this study was to determine if PD patients undergoing primary TKA have increased: (1) medical complications; (2) implant-related complications; (3) readmission rates; and (4) costs. A query was performed using an administrative claims database. The study group consisted of all patients undergoing primary TKA who had a history of PD. Matched non-PD patients undergoing primary TKA served as a control group. The query yielded 72,326 patients (PD = 18,082; matching cohort = 54,244). Pearson's chi-square tests, logistic regression analyses, and Welch's t- tests were used to test for significance between the cohorts. Primary TKA patients who had PD were found to have greater incidences and odds of medical complications (4.21 vs. 1.24%; odds ratio [OR]: 3.50, 95% confidence interval [CI]: 3.15-3.89, p <  0.0001) and implant-related complications (5.09 vs. 3.15%; OR: 1.64, 95% CI: 1.51-1.79, p <  0.0001) compared with the matching cohort. Additionally, the rates and odds of 90-day readmission were higher (16.29 vs. 12.66%; OR:1.34, p <  0.0001) and episodes of care costs were significantly greater ($17,105.43 vs. $15,252.34, p   <  0.0001) in patients who had PD. Results demonstrate that PD patients undergoing primary TKA had higher incidences of medical and implant-related complications. They also had increased 90-day readmission rates and costs compared with controls. The findings of this study should be used in risk stratification and should inform physician-patient discussion but should not be arbitrarily used to deny access to care., Competing Interests: M.A.M. reports other from The Journal of Knee Surgery, outside the submitted work. The rest authors declare no conflict of interest., (Thieme. All rights reserved.)

Despite the high incidence of sarcopenia in the orthopaedic community, studies evaluating the influence of sarcopenia following primary total knee arthroplasty (TKA) are limited. Therefore, the purpose of this study is to determine if sarcopenic patients undergoing primary TKA have higher rates of (1) in-hospital lengths of stay (LOS); (2) medical complications; (3) implant-related complications; (4) fall risk; (5) lower extremity fracture risk; and (6) costs of care. Sarcopenia patients were matched to controls in a 1:5 ratio according to age, sex, and medical comorbidities. The query yielded 90,438 patients with ( n  = 15,073) and without ( n  = 75,365) sarcopenia undergoing primary TKA. Primary outcomes analyzed included: in-hospital LOS, 90-day medical complications, 2-year implant-related complications, fall risk, lower extremity fracture risk, and costs of care. A p -value of less than 0.05 was considered statistically significant. Patients with sarcopenia undergoing primary TKA had greater in-hospital LOS (4 vs. 3 days, p  < 0.0001). Sarcopenic patients were also found to have increased incidence and odds of 90-day medical complications (2.9 vs. 1.1%; odds ratio [OR] = 2.83, p  < 0.0001), falls (0.9 vs. 0.3%; OR = 3.54, p  < 0.0001), lower extremity fractures (1.0 vs. 0.2%; OR = 5.54, p  < 0.0001), and reoperation (0.9 vs. 0.5%; OR = 1.87, p  < 0.0001). Additionally, sarcopenic patients had greater 2-year implant-related complications (4.3 vs. 2.4%; OR = 1.80, p  < 0.0001), as well as day of surgery ($52,900 vs. 48,248, p  < 0.0001), and 90-day ($68,303 vs. $57,671, p  < 0.0001) costs compared with controls. This analysis of over 90,000 patients demonstrates that patients with sarcopenia undergoing primary TKA have greater in-hospital LOS, increased odds of 90-day medical complications, falls, lower extremity fractures, and reoperations. Additionally, sarcopenia was associated with greater 2-year implant-related complications, day of surgery costs, and 90-day costs. The study is useful as it can allow orthopaedic surgeons to properly educate these patients of the potential complications which may occur following their surgery., Competing Interests: M.W.R. reports other from stryker, other from smith and nephew, other from stryker, other from orthosensor, other from American Academy of orthopaedic surgeon, other from American Academy of Hip and Knee surgeons, outside the submitted work; in addition, M.W.R. has a patent orthosensor with royalties paid. The rest authors declare no conflict of interest., (Thieme. All rights reserved.)

A greater number of medically complex patients with multiple comorbidities are now more readily considered for total knee arthroplasty (TKA). Therefore, the purpose of this study was to determine whether comorbidity burden, measured with the Elixhauser Comorbidity Index (ECI), correlated with 90-day medical complications and longer in-hospital lengths-of-stay (LOS) in TKA patients. The PearlDiver supercomputer was queried for all primary TKA patients in the Medicare Standard Analytic Files from 2005 to 2014 using International Classification of Disease, 9th edition codes. Patients were included based on ECI scores, ranging from 1 to 5. ECI 1 patients served as the control cohort, while ECI 2, 3, 4, and 5 patients were considered study cohorts. Each study cohort was matched based on age and gender to the control cohort, resulting in a total of 715,398 patients included for analysis (ECI 1, n  = 144,072; ECI 2, n  = 144,072; ECI 3, n  = 144,072; ECI 4, n  = 144,072; ECI 5, n  = 139,110). Logistic regression analyses were performed to compare 90-day medical complications and Welch's t -tests were performed to compare LOS between the cohorts. Patients with higher ECI scores were more likely to develop medical complications and have longer LOS compared with matched patients in the control cohort. Compared with matched ECI 1 patients, patients with ECI scores of 2 (odds ratio [OR]: 1.19, 95% confidence interval [CI]: 1.14-1.24), 3 (OR: 1.27, 95% CI: 1.21-1.32), 4 (OR: 1.32, 95% CI: 1.27-1.38), and 5 (OR: 1.33, 95% CI: 1.27-1.39) were significantly more likely to develop 90-day medical complications. Additionally, the mean LOS of patients in the ECI 2 (2.59 ± 1.49 vs. 2.73 ± 1.52 days), ECI 3 (2.59 ± 1.49 vs. 2.88 ± 1.51 days; p  < 0.001), ECI 4 (2.59 ± 1.49 vs. 3.01 ± 1.56 days; p  < 0.001), and ECI 5 (2.61 ± 1.49 vs. 3.14 ± 1.61 days; p  < 0.001) groups were significantly longer than the mean LOS in the control ECI 1 group. In an increasingly complex patient population, associations between comorbidities and outcomes after TKA procedures can guide providers on how to modify their pre- and postoperative care. These results demonstrate that higher ECI scores are associated with a greater likelihood of 90-day medical complications and longer in-hospital LOS., Competing Interests: M.A.M. reports other from Stryker, other from Microport, other from DJ Orthopaedics, other from Johnson and Johnson, other from Medical Compression Systems, other from Merz, other from Orthosensor, other from Pacira, other from Sage Products, other from Tissue Gene, other from US Medical Innovations, other from National Institutes of Health (NIAMS and NICHD), other from Ongoing Care Solutions, other from American Journal of Orthopaedics, other from Journal of Arthroplasty, other from Journal of Knee Surgery, other from Orthopedics, other from Surgical Technology International, other from American Academy of Orthopaedic Surgeons, outside the submitted work. M.R. reports other from Stryker, other from Orthosensor, other from Smith & Nephew, outside the submitted work. All the other authors report no conflict of interest., (Thieme. All rights reserved.)

Robotic-assisted unicompartmental knee arthroplasty (RAUKA) is an emerging area of interest. The purpose of this study was to compare (1) different patient demographic profiles; (2) annual primary and revision utilization rates; (3) risk factors for revision procedures; and (4) survivorship between RAUKA and manual UKA (MUKA). Using the PearlDiver database, patients who underwent RAUKA or MUKA between 2005 and 2014 within the Medicare database were identified, yielding a total of 35,061 patients (RAUKA = 13,617; manual = 21,444). Patient demographics (age, gender, comorbidities, Charlson-Comorbidity Index, and geographic region) were compared between cohorts. Annual primary and revision utilization rates as well as risk factors for revision procedures were also compared. Kaplan-Meier survivorship was also calculated. The Pearson χ 2 test was used to test for significance in patient demographics, whereas the Welch t -test was used to compare the incidence of revisions as well as the revision burden (proportion of revisions to total sum of primary and revision procedures). Multivariate binomial logistic regression analysis was performed to compare risk factors for revision procedures. There were statistically significant differences in RAUKA versus MUKA patients with respect to age ( p <  0.001), gender ( p <  0.001), and region ( p <  0.001). RAUKA procedures performed increased over 12-fold compared with manual, which increased only 4.5-fold. RAUKA procedures had significantly lower revision incidence (0.99 vs. 4.24%, p  = 0.003) and revision burden (0.91 vs. 4.23%, p  = 0.005) compared with manuals. For patients undergoing RAUKA, normal (19-24 kg/m 2 ) and obese (30-39 kg/m 2 ) body mass index ( p  < 0.05), congestive heart failure ( p  = 0.004), hypothyroidism ( p <  0.001), opioid dependency ( p  = 0.002), and rheumatoid arthritis ( p <  0.001) were risk factors for a revision procedure. Kaplan-Meier survival curve 3 years following the index procedure to all-cause revisions demonstrated that RAUKA patients maintained nearly 100% survivorship compared with manual patients who had 97.5% survivorship. The data demonstrate increased utilization of RAUKA in the United States. The current data indicated that RAUKA has significantly lower revision rates and improved survivorship compared with patients undergoing non-RAUKA within Medicare patients., Competing Interests: None declared., (Thieme. All rights reserved.)

The effort to reduce overall healthcare costs may affect more complex patients, as their pre- and postoperative care can be substantially involved. Therefore, the purpose of this study was to use a large nationwide insurance database to compare (1) costs, (2) reimbursements, and (3) net losses of 90-day episodes of care (EOC) for total knee arthroplasty (TKA) patients according to Elixhauser's Comorbidity Index (ECI) scores. All TKAs performed between 2005 and 2014 in the Medicare Standard Analytic Files were extracted from the database and stratified based on ECI scores, ranging from 1 to 5. ECI 1 patients served as the control cohort, while ECI 2, 3, 4, and 5 patients were considered study cohorts. Each study cohort and control cohort were matched based on age and sex, resulting in a total of 715,398 patients included for analysis. Total EOC costs, reimbursements, and total net losses (defined as total EOC costs minus total EOC reimbursements) were compared between the cohorts. Overall, total EOC costs increased with ECI. For example, compared with the matched ECI 1 cohorts, the total EOC costs for ECI 5 patients ($56,589.19 vs. $51,747.54) were significantly greater ( p  < 0.01). Although reimbursements increased with increasing ECI, so did net losses. The net losses for ECI 5 patients were greater than that for ECI 1 patients ($42,309.39 vs. $40,007.82). The bundled payments for care improvement (BPCI) and comprehensive care for joint replacement (CJR) are alternative payment models that might de-incentivize treatment of more complex patients. Our study found that despite increasing reimbursements, overall costs, and therefore net losses, were greater for more complex patients with higher ECI scores., Competing Interests: G.S. reports other from Convatec, Acelity, Biomet, Medtronic, Pacira, Zimmer, Force Therapeutics, Springer, Elsevier, Thieme, World Scientific, and Operation Walk USA, outside the submitted work. A.M. reports other from Stryker, Journal of Arthroplasty, and American Academy of Orthopedic Surgeons, outside the submitted work. M.R. reports other from Stryker, Orthosensor, Smith and Nephew, outside the submitted work. M.A.M. reports other from Stryker, Microport, DJ Orthopedics, Johnson and Johnson, Medical Compression Systems, Merz, Orthosensor, Pacira, Sage Products, Tissue Gene, US Medical Innovations, National Institutes of Health (National Institute of Arthritis and Musculoskeletal and Skin Diseases [NIAMS] and National Institute of Child Health and Human Development [NICHD]), Ongoing Care Solutions, American Journal of Orthopedics, Journal of Arthroplasty, Journal of Knee Surgery, Orthopedics, Surgical Technology International, American Academy of Orthopedic Surgeons, outside the submitted work., (Thieme. All rights reserved.)

The potential added costs of managing fibromyalgia patients after total knee arthroplasty (TKA) have not been assessed. Therefore, the purpose of this study was to perform a cost analysis of fibromyalgia versus nonfibromyalgia patients who underwent TKA. Specifically, we evaluated the following episodes of care: (1) readmission rates, (2) total costs, (3) total reimbursements, and (4) net losses for surgical and medical complications. Patients who underwent TKAs between 2005 and 2014 from the Medicare Standard Analytical Files of the PearlDiver supercomputer were propensity score matched by patients with and without fibromyalgia in a 1:1 ratio based on age, sex, and the Charlson Comorbidity Index, yielding a total of 305,510 patients distributed equally between the cohorts for analysis. Odds ratios (ORs), 95% confidence intervals (CIs), and p -values were calculated. Mean costs, total costs, and total reimbursements were assessed as along with total net losses, which were defined as total costs minus total reimbursements. Fibromyalgia patients had similar 90-day readmission rates compared with nonfibromyalgia patients (OR: 1.03; 95% CI: 1.00-1.06; p  = 0.06) but incurred lower readmission costs (US$2,318,384,295 vs. US$2,534,482,404; p  < 0.001). Although fibromyalgia patients had higher total reimbursements for medical complications ($27,758,057 vs. US$18,780,610; p  < 0.001), the increased management costs (US$106,049,870 vs. US$66,080,469; p  < 0.001) led to greater net losses (US$78,291,813 vs. US$47,299,859; p  < 0.001). Similarly, although fibromyalgia patients had higher total reimbursements for surgical complications (US$94,192,334 vs. US$73,969,026; p  < 0.001), the increased surgical costs (US$382,122,613 vs. US$306,359,910; p  < 0.001) led to greater net losses (US$287,930,279 vs. US$232,390,884; p  < 0.001). This study highlights some of the potential financial discrepancies of managing patients with fibromyalgia. Our findings suggest medical and surgical complication costs to be greater than reimbursement, resulting in overall net financial losses. These findings need to be considered in the light of health care reform and cost structuring., Competing Interests: Dr. Mont reports other from AAOS, other from American Association of Hip and Knee Surgeons, other from Cymedica, other from DJ Orthopaedics, other from Flexion Therapeutics, other from Johnson & Johnson, other from Journal of Arthroplasty, other from Journal of Knee Surgery, other from Knee Society, other from Medicus Works LLC, other from MicroPort, other from National Institutes of Health (National Institute of Arthritis and Musculoskeletal and Skin Diseases and Eunice Kennedy Shriver National Institute of Child Health and Human Development), other from Ongoing Care Solutions, other from Orthopedics, other from Orthosensor, other from Pacira, other from Peerwell, other from Performance Dynamics, other from Pfizer, other from Skye Biologics, other from Stryker, other from Surgical Techniques International, other from Kolon TissueGene, other from UpToDate, other from US Medical Innovations, and other from Wolters Kluwer Health - Lippincott Williams & Wilkins outside the submitted work., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

There are conflicting results regarding the impact of rheumatoid arthritis (RA) on total knee arthroplasty (TKA) outcomes. Therefore, the purpose of this study was to compare outcomes of patients with and without RA undergoing primary TKA. Specifically, we assessed (1) 90-day medical complications, (2) 90-day readmission rates, (3) short-term implant-related complications, (4) 1-year mortality, and (5) total global 90-day episode-of-care costs. The authors of the study hypothesize that RA would increase the rate of medical- and implant-related complications, readmission rates, and costs. A retrospective level of evidence III study was conducted using the Medicare standard analytical files from the PearlDiver database. Patients were queried using the International Classification of Disease, ninth revision codes. Patients with RA were randomly matched 1:1 to controls according to age, gender, and Charlson's comorbidity index. Two mutually exclusive cohorts were formed. Medical- and implant-related complications, readmission rates, and costs were analyzed and compared between the cohorts. Statistical analysis using logistic regression was performed calculating odds ratios (OR), 95% confidence intervals (95% CI), and their respective p- values. The query returned 102,898 patients with ( n  = 51,449) and without ( n  = 51,449) RA undergoing primary TKA within the Medicare database from 2005 to 2014. Patients with RA had greater odds of medical complications (OR: 2.08, 95% CI: 1.98-2.20, p  < 0.001), implant complications (OR: 1.30, 95% CI: 1.24-1.36, p  < 0.001), 1-year mortality (OR: 1.35, 95% CI: 0.68-2.70, p  = 0.39), total 90-day episode-of-care costs ($16,605 vs. 15,716.53; p  < 0.001), and 90-day readmission rates were similar between cohorts (OR: 1.08, 95% CI: 1.05-1.12, p  < 0.001). RA increases postoperative complications and costs following primary TKA within Medicare patients. Comprehensive preoperative optimization for patients with a diagnosis of RA may mitigate perioperative complications, thus improving patient outcomes, and ultimately reducing episode-of-care costs., Competing Interests: None declared., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Medical comorbidities have been shown to cause an increase in peri-and postoperative complications following total knee arthroplasty (TKA). However, the increase in cost associated with these complications has yet to be determined. Factors that influence cost have been of great interest particularly after the initiation of bundled payment initiatives. In this study, we present and quantify the influence of common medical comorbidities on the cost of care in patients undergoing primary TKA. A retrospective level of evidence III study was performed using the PearlDiver supercomputer to identify patients who underwent primary TKA between 2007 and 2015. Patients were stratified by medical comorbidities and compared using analysis of variance for reimbursements for the day of surgery and over 90 days postoperatively. A cohort of 137,073 US patients was identified as having undergone primary TKA between 2007 and 2015. The mean entire episode-of-care reimbursement was $23,701 (range: $21,294-26,299; standard deviation [SD] $2,611). The highest reimbursements were seen in patients with chronic obstructive pulmonary disease (mean $26,299; SD $3,030), hepatitis C (mean $25,662; SD $2,766), morbid obesity (mean $25,450; SD $2,154), chronic kidney disease (mean $25,131, $3,361), and cirrhosis (mean $24,890; SD $2,547). Medical comorbidities significantly impact reimbursements, and therefore cost, after primary TKA. Comprehensive preoperative optimization for patients with medical comorbidities undergoing TKA is highly recommended and may reduce perioperative complications, improve patient outcome, and ultimately reduce cost., Competing Interests: None declared., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Risk factors for adverse events after total knee arthroplasty (TKA) relating to malignancy have not been well studied. Thus, the purpose of this study was to conduct a retrospective case-control outcome and cost analysis after TKA in this population. Patients with a history of breast cancer (BrCa) were identified based on the International Classification of Disease 9th revision codes. An age- and sex-matched cohort was also identified of patients without a history of BrCa. Complications, length of stay, comorbidity burden, and reimbursements were tracked at 90 days. Each cohort comprised 92,557 patients. Length of stay was similar between cohorts ( p  = 0.627). Comorbidity status and incidence of pulmonary embolism (PE), lower extremity ultrasound, and chest computed tomography (CT) use were higher in patients with a history of BrCa ( p  < 0.05 for all). Control patients had a lower incidence of acute myocardial infarction (0.14 vs. 0.21%; p  < 0.001). Surgical complications were similar. The 90-day reimbursements were greater in patients with a history of BrCa (US$13,990 vs. US$13,033 for controls; p  = 0.021). Surgeons should be aware of the increased risk of PE after TKA in patients with a history of BrCa as well as increased 90-day costs, which warrant great attention., Competing Interests: None., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Substance abuse can have strong negative impacts on surgical outcomes. Therefore, this study assessed the effects of drug abuse in total knee arthroplasty (TKA) patients. Specifically, we identified revision TKA (RTKA): (1) incidence, (2) causes, (3) time to revision, and (4) patient demographics in patients with a history of drug abuse. The Medicare database within the PearlDiver Supercomputer (Warsaw, IN) was queried to identify 2,159,221 TKAs performed between 2005 and 2012. Drug abuse was subdivided into cocaine, cannabis, opioids, sedatives/hypnotics/anxiolytics (SHA), amphetamines, and alcohol abusers. The effect of drug use on the incidence and cause for RTKA, time to revision, as well as patient demographics were correlated using multivariate, analysis of variance, and regression analyses. There was a significant increase in the number of primary TKAs in cocaine ( p  = 0.011), cannabis ( p  < 0.001), opioid ( p  < 0.001), SHA ( p  < 0.001), amphetamine ( p  < 0.001), and alcohol ( p  < 0.001) users. Amphetamine users had the fastest mean time to revision (691 days, standard deviation: 679 days). At 30-, 90-day, and 6-month postoperative, cocaine had the highest proportion of patients requiring RTKA (7, 12, and 20%, respectively), and at 1-year alcohol abusers (38%, p  < 0.001). Infection was the most common cause of revision in all drug abuse/dependent cohorts. Age distributions varied significantly by group for primary TKA ( p  < 0.001). Comorbidity status was similar in all RTKA patients as determined by comparison of the mean Charlson comorbidity index scores ( p  = 0.091). Based on these results, drug abuse patients are at increased risk for RTKA. These high-risk patients should, therefore, be appropriately risk stratified and receive comprehensive postoperative pain management., Competing Interests: M.R.: Stryker, Orthosensor; T.Y.L.: Smith & Nephew, Stryker; M.A.M.: AAOS, Abbott, Cymedica, DJ Orthopaedics, Johnson & Johnson, Journal of Arthroplasty, Journal of Knee Surgery, Mallinckrodt Pharmaceuticals, Microport, National Institutes of Health (NIAMS & NICHD), Ongoing Care Solutions, Orthopedics, Orthosensor, Pacira, Peerwell, Performance Dynamics Inc., Sage, Stryker, Surgical Technologies International, Kolon TissueGene. The remaining authors report no conflict of interest., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Nutritional status has become increasingly important in optimizing surgical outcomes and preventing postoperative infection and wound complications. However, currently, there is a paucity in the orthopaedics literature investigating the relationship between nutritional status and wound complications following total knee arthroplasty (TKA). Therefore, the purpose of this study was to determine the prevalence of (1) postoperative infections, (2) wound complications, (3) concomitant infection with wound (CoIW) complication, and (4) infection followed by wound complication by using (1) albumin, (2) prealbumin, and (3) transferrin levels as indicators of nutritional status. These four different outcome measures were chosen as they are encountered commonly in daily clinical practice. A retrospective review of a national private payer database for patients who underwent TKA with postoperative infections and wound complications stratified by preoperative serum albumin (normal: 3.5-5 g/dL), prealbumin (normal: 16-35 mg/dL), and transferrin levels (normal: 200-360 mg/dL) between 2007 and 2015 was conducted. Patients were identified by Current Procedural Terminology (CPT), International Classification of Disease, ninth revision (ICD-9) codes, and Logical Observation Identifiers Names and Codes (LOINC). Linear regression was performed to evaluate changes over times. Yearly rates of infection, as well as a correlation and odds ratio analysis of nutritional laboratory values to postoperative complications, were also performed. Our query returned a total of 161,625 TKAs, of which 11,047 (7%) had postoperative wound complications, 18,403 (11%) had infections, 6,296 (34%) had CoIW, and 4,877 (4%) patients with infection developed wound complications. Albumin was the most commonly ordered laboratory test when assessing complications (96%). Wound complications, infections, CoIW, and infection with wound complications after were higher in those below the normal range: albumin <3.5 g/dL (9, 14, 6, and 5%), prealbumin <15 mg/dL (20, 23, 13, and 12%), and transferrin <200 mg/dL (12, 17, 6, and 6%). Preoperative albumin, prealbumin, and transferrin values falling below the normal range represented an increased risk for postoperative complications. Those patients who were in the normal range, however, did not have an increased risk. Therefore, our results suggest that preoperative nutritional optimization can play an important role in reducing the risk for postoperative complications., Competing Interests: None., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

As the use of disease modifying antirheumatic drugs have increased, it remains unclear whether or not this has affected the rates of total knee arthroplasty (TKA) in rheumatoid arthritis (RA) patients. Therefore, the purpose of this study was to evaluate the annual trends of RA patients who underwent TKA. Specifically, we evaluated: (1) the annual trends of TKAs due to RA in the United States population; and (2) the annual trends in the proportion of TKAs due to RA in the United States. The Nationwide Inpatient Sample was used to identify all patients who underwent TKA between 2002 and 2013 ( n  = 6,492,873). Then, we identified TKA patients who had a diagnosis of RA, defined by the International Classification of Diseases, Ninth Revision (ICD-9) code 714.0. The incidence of TKAs with a diagnosis of RA in the United States was calculated using the U.S. population as the denominator. Regression models were used to analyze the annual trends of RA in patients who underwent TKA. A total of 209,332 RA patients were identified who underwent TKA. The annual prevalence of RA in patients who underwent TKA slightly increased, from 33.2 per 1,000 TKAs in 2002 to 35 per 1,000 TKAs in 2013 ( R 2  = 0.254, p  = 0.095). The annual number of TKAs with a diagnosis of RA increased by 93.1% from 11,618 to 22,430. After normalizing for the U.S. population, the incidence of TKAs with RA increased from 5.4 to 9.2 TKAs per 1 million U.S. adults (incidence rate ratio [IRR] = 1.05; 95% confidence interval [CI], 1.05-1.05; p  < 0.001). In 2002, 11,618 (3.31%) TKAs, and in 2013, 22,430 (3.50%) TKAs were due to RA. The prevalence of RA in those who underwent TKA remained the same from 2002 to 2013 (coefficient = 0.02; 95% CI, -0.01 to 0.05; p  = 0.095). The results of this study demonstrated that the rates of TKA performed in RA patients have remained relatively stable. Furthermore, there may have been a decline in the rate of RA patients undergoing TKA, due to an increase in the U.S. population by approximately 28.8 million during the study period., Competing Interests: The authors would like to acknowledge the following disclosures: M.W.R. is a consultant for, or has received institutional or research support from the following companies: Stryker, Orthosensor, not related to this study. M.A.M. is a consultant for, or has received institutional or research support from the following companies: Stryker, DJO Global, Sage Products, TissueGene, OnGoing Care Solutions, Microport, Orthosensor, National Institutes of Health, Johnson & Johnson, Pacira Pharmaceuticals, Cymedica, Peerwell, Performance Dynamics Inc. He is on the editorial/governing board of the American Journal of Orthopedics, Journal of Arthroplasty, Journal of Knee Surgery, and Surgical Technology International, not related to this study., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

As surgical techniques and pharmacology advance, the management of postoperative pain in patients undergoing total knee arthroplasty (TKA) continues to evolve. The current standards of care are composed of multimodal pain management including opioids, nonsteroidal anti-inflammatory drugs and gabapentinoids, peripheral nerve blocks, and periarticular injections. Newer modalities are composed of delayed release local anesthetics and cryoneurolysis. To summarize the current evidence-based treatment modalities and forecast changes in the management of patients having TKAs, we reviewed available data on: (1) oral analgesics; (2) periarticular injections; (3) peripheral nerve blocks; (4) multimodal regimens; and (5) newer modalities in post-TKA pain management. Multimodal analgesic regimens that target numerous pain pathways may provide the best pain management, rehabilitation, patient satisfaction, and reduce opioid use and related side effects. Periarticular injections of delayed-release local anesthetics may further enhance pain management., Competing Interests: Dr. Mont, Dr. Kelly, and Dr. Elmallah are paid consultants for Pacira Pharmaceuticals Inc., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Cellular therapies are emerging as potentially promising treatments for numerous musculoskeletal conditions, such as knee osteoarthritis (OA). As orthopaedic surgeons represent a sizable portion of the providers who deliver these therapies, it is particularly essential for them to understand their fundamental principles. One major principle is to identify the appropriate sources for obtaining these cells, with bone marrow being most common. Therefore, the purpose of this review was to provide an overview of cell-based therapies available for the treatment of knee OA with a focus on bone marrow-derived cellular therapies. Specifically, we discuss (1) bone marrow aspiration technique, (2) processing to bone marrow aspirate concentrate, and (3) the rational and clinical evidence for the use of bone marrow cellular therapies for the treatment of knee OA., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

An increasing number of total knee arthroplasties (TKAs) are performed on obese patients. It is imperative to remain up to date on the effect of obesity on surgical outcomes and reimbursement trends. The purpose of this study was to evaluate the impact different severities of obesity have on primary and revision TKA, specifically: (1) incidence and trends over time; (2) annual growth rate; and (3) admission costs from 2010 to 2014. A retrospective review of a large commercial private payer database within the PearlDiver Supercomputer application (Warsaw, IN) of TKA procedures was conducted. Patients who underwent TKA and subsequent revision were identified by Current Procedural Terminology (CPT) and ninth revision International Classification of Disease (ICD-9) codes. The index procedure was linked with ICD-9 codes for body mass indexes (BMIs) from <19 to >70. Statistical analysis was primarily descriptive to demonstrate the revision incidence and reimbursement deviations due to BMI. Compound annual growth rate (CAGR) was also calculated. Our query returned a total of 87,607 TKA patients within the study BMI ranges. The majority of patients had a BMI of 40 to 44.9 (12.2%) and least in the BMI >70 (0.2%) range. BMI of 40 to 44.9 had the highest overall 5-year mean reimbursement of $11,521 and the highest overall mean 5-year deviation from normal BMI (19-24) patients of $3,300. The incidence and burden of TKA revision was highest in patients with a BMI of 60 to 69.9 (21 and 17.3%, respectively). Average 5-year revision reimbursement and deviation from normal BMI (19-24) was highest in patients with a BMI of 40 to 44.9 ($13,883 and $4,030, respectively). The number of obese patients receiving TKA is steadily rising. The cost of treating obese patients rises as BMI deviates from normal, as does the incidence of revision surgery. Therefore, surgeons must be active in counseling patients on weight optimization as part of preoperative standard of care., Competing Interests: Conflict of Interest: None., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)