BMI is a Better Predictor of Periprosthetic Joint Infection Risk Than Local Measures of Adipose Tissue After TKA

Surgical site soft tissue thickness as a predictor of complications following arthroplasty

Appreciation of soft-tissue thickness (STT) at surgical sites is an increasingly recognized aspect of arthroplasty procedures as it may potentially impacting postoperative outcomes. Recent research has focused on the predictive value of preoperative STT measurements for complications following various forms of arthroplasty, particularly infections, across procedures such as total knee, hip, shoulder, and ankle replacements. Several studies have indicated that increased STT is associated with a higher risk of complications, including infection and wound healing issues. The assessment of STT before surgery could play a crucial role in identifying patients at a higher risk of complications and may be instrumental in guiding preoperative planning to optimize outcomes in arthroplasty procedures. Standardized measurement techniques and further research are essential to enhance the reliability and clinical utility of STT assessment for arthroplasty surgery.

The association of anterior soft tissue depth (ASTD) with wound dehiscence following total ankle arthroplasty

Total ankle arthroplasty (TAA) is a common intervention for the treatment of end-stage ankle arthritis. Unfortunately, use of a longitudinal anterior incision to gain access to the ankle is commonly associated with postoperative wound dehiscence. In this retrospective cohort study the incidence of postoperative anterior wound dehiscence following TAA in 100 consecutive patients was 21 %, and 7 (33.33 %) of the dehiscence cases were serious enough to require additional operative treatment. The anterior soft tissue depth (ASTD) at the level of the tibiotalar joint was measured from the anterior margin of the skin to the anterior margin of the ankle as viewed on the standard lateral radiograph. The overall median ASTD for the entire cohort was 21.79 (range 5.7 to 37.3) mm, whereas that in the non-dehiscence group was 22.06 (5.7, 37.3) mm and that in the dehiscence group was 18.6 (12.78, 35.9) mm, and this difference was statistically significant (p = 0.0240). Receiver operating characteristic (ROC) curve analyses showed that a preoperative ASTD ≤ 16 mm maximized diagnostic sensitivity and specificity and predicted dehiscence.

Predicting periprosthetic joint infection in primary total knee arthroplasty: a machine learning model integrating preoperative and perioperative risk factors

BACKGROUND

Periprosthetic joint infection leads to significant morbidity and mortality after total knee arthroplasty. Preoperative and perioperative risk prediction and assessment tools are lacking in Asia. This study developed the first machine learning model for individualized prediction of periprosthetic joint infection following primary total knee arthroplasty in this demographic.

METHODS

A retrospective analysis was conducted on 3,483 primary total knee arthroplasty (81 with periprosthetic joint infection) from 1998 to 2021 in a Chinese tertiary and quaternary referral academic center. We gathered 60 features, encompassing patient demographics, operation-related variables, laboratory findings, and comorbidities. Six of them were selected after univariate and multivariate analysis. Five machine learning models were trained with stratified 10-fold cross-validation and assessed by discrimination and calibration analysis to determine the optimal predictive model.

RESULTS

The balanced random forest model demonstrated the best predictive capability with average metrics of 0.963 for the area under the receiver operating characteristic curve, 0.920 for balanced accuracy, 0.938 for sensitivity, and 0.902 for specificity. The significant risk factors identified were long operative time (OR, 9.07; p = 0.018), male gender (OR, 3.11; p < 0.001), ASA > 2 (OR, 1.68; p = 0.028), history of anemia (OR, 2.17; p = 0.023), and history of septic arthritis (OR, 4.35; p = 0.030). Spinal anesthesia emerged as a protective factor (OR, 0.55; p = 0.022).

CONCLUSION

Our study presented the first machine learning model in Asia to predict periprosthetic joint infection following primary total knee arthroplasty. We enhanced the model's usability by providing global and local interpretations. This tool provides preoperative and perioperative risk assessment for periprosthetic joint infection and opens the potential for better individualized optimization before total knee arthroplasty.

Body Mass Index is Not an Appropriate Proxy for the Condition of Peri-Incisional Adiposity in Primary Total Joint Arthroplasty Patients

BACKGROUND

The American Academy of Orthopaedic Surgeons defined the acceptable threshold for elective safe surgery as a body mass index (BMI) under 40 due to the increased risk of complications. A consequence of this recommendation has been a hard cutoff based on BMI, which restricts access to care for an increasingly large and diverse population. There is an improved understanding that excess adipose tissue confers additional risk for postoperative complications, including infection, through mechanical and physiologic mechanisms. But, it is unclear if BMI is an accurate indicator of adiposity in total joint arthroplasty (TJA) patients and, thus, whether BMI is capturing clinically relevant information in obese patients. Our objective was to determine the relationship between peri-incisional adiposity (PIA) and BMI in a consecutive series of diverse primary TJA patients.

METHODS

A consecutive series of patients indicated for primary TJA were preoperatively evaluated. For each patient, the following variables were collected: BMI and measures of PIA on radiographs and ultrasounds.

RESULTS

In THA patients (N = 99), Pearson's correlation coefficient (r) = 0.436, which indicates a moderate correlation between BMI and adiposity. In total knee arthroplasty patients (N = 271), r = 0.395 for femoral PIA (FPIA) and r = 0.249 for tibial PIA, which indicates a weak correlation between BMI and adiposity measured on radiography. In total knee arthroplasty patients, r = 0.560 for femoral PIA and r = 0.544 for tibial PIA, which indicates a moderate correlation between BMI and adiposity measured on ultrasound.

CONCLUSIONS

Quantification of obesity has become a common practice in the preoperative evaluation of primary TJA patients. The intent is to determine the magnitude of adipose tissue, which is one of the main drivers of postoperative complications in obesity. The BMI is ubiquitously used as a proxy for obesity due to its simplicity of attainment and calculation. We report that BMI has a weak-to-moderate association with PIA in this population. These findings indicate that BMI may not accurately represent the condition of peri-incisional adipose tissue and, thus, is not capturing the relevant obesity data for preoperative risk stratification in primary TJA patients.

LEVEL OF EVIDENCE

III.

Radiographic soft tissue thickness is not a risk factor for infection after primary total ankle arthroplasty

As the incidence of total ankle arthroplasty (TAA) for the management of end-stage arthritis is on the rise, identification of risk factors for periprosthetic joint infection (PJI) is essential. There has been limited research exploring the use of radiographic soft tissue thickness in TAA despite its predictive value in other forms of arthroplasty. This study evaluated the predictive capabilities of radiographic soft-tissue thickness for PJI following TAA. A retrospective analysis of 323 patients at a single institution who underwent primary TAA from 2003 to 2019 was conducted. Patient demographics, comorbidities, indication for surgery, prosthesis type and tourniquet time were recorded. Tibial-Tissue and Talus-Tissue distances were measured on preoperative lateral radiographic imaging. Logistic regression was utilized to determine the Odds Ratio (OR) of risk factors for the occurrence of PJI. Of the 323 patients, 6 patients (1.86 %) developed a PJI. Average duration of follow-up was 8.42 ± 2.52 years. Neither Tibial-Tissue (OR = 0.975; 95 % CI [0.947 - 1.004]; p = 0.09) nor Talus-Tissue thickness (OR = 0.976; 95 % CI [0.940 - 1.012]; p = 0.18) were significant predictors of PJI. Although not statistically significant, the infected cohort had smaller average Tibial-Tissue (2.20 vs. 2.53 cm; p = 0.05) and Talus-Tissue thickness (2.19 vs. 2.44 cm; p = 0.36) compared to the non-infected cohort. Measurements such as Tibial-Tissue length and Talus-Tissue length were not significant predictors of PJI following primary TAA. These findings underscore the necessity for additional research to identify modifiable risk factors aimed at reducing PJI rates and enhancing patient outcomes. LEVEL OF EVIDENCE: III, Retrospective Comparative Study.

Phase angle and extracellular edema predict risk of postoperative complications in total joint arthroplasties

Intro

Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are common procedures that improve mobility but carry a risk of postoperative complications, particularly in patients with obesity. Body Mass Index (BMI) is traditionally used for risk assessment but does not account for muscle mass or fat distribution. Bioelectrical impedance analysis (BIA) provides a more detailed body composition evaluation. This study investigates the association between BIA-derived metrics and postoperative complications in TKA and THA, hypothesizing that these metrics are superior predictors compared to BMI.

Methods

A retrospective cohort study was performed on 567 adult patients who underwent primary THA or TKA from January 2020 to December 2023. The data collected included demographic characteristics, comorbidities, preoperative laboratory values, preoperative BIA measurements and postoperative complications. Multivariate logistic regression models were developed to identify independent predictors of postoperative complications. Receiver operating characteristic (ROC) curves assessed the predictive accuracy of BIA-metrics models compared to BMI model.

Results

In a cohort of 567 patients (55.7% female, median age 66), no significant difference in BMI was found between the complication and non-complication groups. However, the complication group had a higher ECW/TBW ratio (0.396 vs. 0.393, p = 0.011), higher ECW/ICW ratio (0.657 vs. 0.647, p = 0.012), and a lower phase angle (4.65 vs. 4.80, p = 0.039). Multivariate logistic regression analysis revealed that higher standardized ECW/TBW (OR 1.65, 95% CI 1.17-2.31, p = 0.004) and ECW/ICW z-scores (OR 1.61, 95% CI 1.15-2.23, p = 0.005) were associated with increased odds of postoperative complications, while a lower phase angle was protective (OR 0.58, 95% CI 0.37-0.91, p = 0.018). ROC analysis showed moderate predictive accuracy for ECW/TBW (AUC 0.71, 95% CI 0.62-0.79), ECW/ICW (AUC 0.70, 95% CI 0.62-0.79), and phase angle (AUC 0.69, 95% CI 0.60-0.79). In contrast, BMI was not significantly associated with complications, and BMI model demonstrated inferior predictive accuracy (AUC 0.61).

Conclusion

ECW/TBW, ECW/ICW and phase angle are associated with postoperative complications in patients undergoing primary TKA or THA. These metrics provide better predictive accuracy than BMI enhancing preoperative risk stratification.

How reliable is the soft tissue radiological knee index in predicting superficial surgical site infection following total knee arthroplasty?

INTRODUCTION

The purpose of this study was to evaluate the association between the Soft Tissue Radiological Knee (SToRK) Index and the risk of developing a superficial surgical site infection (SSSI) following primary total knee arthroplasty (TKA).

METHODS

The SToRK Index was measured using calibrated long leg radiographs (LLR) in 174 patients undergoing TKA.

RESULTS

A moderate correlation was found between the SToRK Index and body mass index (BMI) (rs=0.574; p < 0.001). The SToRK Index was a better predictor of SSSI in females than males. In females, a SToRK Index cutoff of 2.01 had a sensitivity and specificity of 41.3% and 74.6% for developing SSSI, respectively, with a positive likelihood ratio of 1.63.

CONCLUSION

The SToRK Index can be used as an additional tool in assessing the risk for SSSI after TKA. It might be more predictive in females due to the different fat distribution compared to males.

Consistent Factors Influence Body Mass Index Thresholds for Total Joint Arthroplasty Across Health-Care Systems: A Qualitative Study

BACKGROUND

Body mass index (BMI) thresholds are used as eligibility criteria to reduce complication risk in total joint arthroplasty (TJA). This approach oversimplifies preoperative risk assessment and inadvertently restricts access to effective surgical treatment for osteoarthritis. A prior survey of orthopaedic surgeons in the United States identified complex underlying factors that influence BMI considerations. To understand whether similar factors exist and influence surgeons in a different health-care system setting, we investigated Canadian surgeons' views and use of BMI criterion thresholds for TJA access.

METHODS

A cross-sectional online qualitative survey was conducted with orthopaedic surgeons performing TJA in the Canadian health-care system. Responses were anonymous and questions were open-ended to allow for candid perspectives. Survey data were coded and a systematic process was followed to identify major themes. Findings were compared with U.S. surgeon perspectives.

RESULTS

Sixty-nine respondents had a mean age of 49.0 ± 11.4 years (range, 33 to 79 years), with a mean surgical experience duration of 15.7 ± 11.4 years (range, 2 to 50 years). Surgeons reported variable use of BMI thresholds in practice. Twelve interconnected factors that influence BMI considerations were identified: (1) variable evidence interpretation, (2) surgical challenge, (3) surgeon beliefs and biases, (4) hospital differences, (5) access to resources, (6) health system bias, (7) patient health status, (8) patient body fat distribution, (9) patient decisional burden (to lose weight or accept risk), (10) evidence gaps and uncertainties, (11) need for innovation, and (12) societal views. Nine themes matched with findings from U.S. surgeons.

CONCLUSIONS

Parallel to the United States, complex, interconnected factors influence Canadian orthopaedic surgeons' variable use of BMI restrictions for TJA eligibility. Despite different health-care systems and reimbursement models, similar technical and personal factors were identified. With TJA practice guidelines advising against hard BMI criteria, attention regarding access to resources, surgical training, and innovations to address TJA complexity in patients with large bodies are critically needed. Future advancements in this sphere must balance barrier removal with risk reduction to ensure safe and equitable surgical care.

CLINICAL RELEVANCE

This study may influence surgeon behaviors with regard to hard BMI cutoffs for TJA and encourage critical thought about factors that influence decisions about surgical eligibility for patients with high BMI.

Greater Risk of Periprosthetic Joint Infection Associated with Prolonged Operative Time in Primary Total Knee Arthroplasty: Meta-Analysis of 427,361 Patients

Background/Objectives: Periprosthetic joint infection (PJI) is a severe complication in total knee arthroplasty (TKA) with catastrophic outcomes. The relationship between prolonged operative times and PJI remains debated. This meta-analysis investigated the link between prolonged operative times and the risk of PJI in primary TKA. Methods: A comprehensive search of the MEDLINE/PubMed, Cochrane Library, and EMBASE databases was conducted to identify studies comparing the incidence of PJI in TKAs with prolonged versus short operative times, as well as those comparing operative times in TKAs with and without PJI. Pooled standardized mean differences (SMD) in operative times between groups with and without PJI or surgical site infections (SSI), including superficial SSIs and PJIs, were analyzed. Additionally, the pooled odds ratios (OR) for PJI in TKAs with operative times exceeding 90 or 120 min were examined. Results: Seventeen studies involving 427,361 patients were included. Significant differences in pooled mean operative times between the infected and non-infected TKA groups were observed (PJI, pooled SMD = 0.38, p < 0.01; SSI, pooled SMD = 0.72, p < 0.01). A higher risk of PJI was noted in surgeries lasting over 90 or 120 min compared to those of shorter duration (90 min, pooled OR = 1.50, p < 0.01; 120 min, pooled OR = 1.56, p < 0.01). Conclusions: An association between prolonged operative time and increased risk of PJI in primary TKA has been established. Strategies for infection prevention should encompass thorough preoperative planning aimed at minimizing factors that contribute to prolonged operative times.

Association of Radiographic Soft Tissue Thickness With Revision Total Ankle Arthroplasty Following Primary Total Ankle Arthroplasty: A Minimum of 5-year Follow-up

Background

The incidence of primary total ankle arthroplasty (TAA) is rising, with a corresponding increase in revision surgeries. Despite this, research on risk factors for revision TAA following primary TAA remains limited. Radiographic soft tissue thickness has been explored as a potential predictor for outcomes in hip, knee, and shoulder arthroplasty, but its role in TAA has not been assessed. This study aimed to assess the predictive value of radiographic soft tissue thickness for identifying patients at risk of requiring revision surgery following primary TAA.

Methods

A retrospective study was conducted on 323 patients who underwent primary TAA between 2003 and 2019. Radiographic measurements of soft tissue thickness were obtained from preoperative radiographs. Two novel radiographic measures of soft tissue thickness were developed and assessed (tibial tissue thickness and talus tissue thickness). Clinical variables including age, gender, body mass index (BMI), American Society of Anesthesiologists (ASA) classification, diabetes, smoking status, primary diagnosis, and implant type were recorded. Logistic regression analysis was used to assess the predictive value of soft tissue thickness and BMI for revision TAA.

Results

The rate of revision surgery was 4.3% (14 of 323 patients). Patients requiring revision had significantly greater tibial tissue (3.54 vs 2.48 cm; P = .02) and talus tissue (2.79 vs 2.42 cm; P = .02) thickness compared with those not requiring revision. Both the tibial tissue thickness (odds ratio 1.16 [1.12-1.20]; P < .01) and the talus tissue thickness (odds ratio: 1.10 [1.05-1.15]; P < .01) measurements were significant predictors of revision TAA in multivariable logistic regression models. However, BMI was not a significant predictor of revision TAA. The two metrics demonstrated excellent interrater reliability.

Conclusion

Greater soft tissue thickness was a better predictor of revision TAA compared with BMI. These findings suggest that radiographic soft tissue thickness may be a valuable tool for assessing the risk of the need for revision TAA following primary TAA. Further research is needed to validate and explore the potential impact on clinical practice.

Level of Evidence

Level III, comparative study.

Effect of Taiwan's Diabetes Shared Care Program on the risk of periprosthetic joint infection after total joint arthroplasty in patients with type 2 diabetes mellitus: an eight-year population-based study

BACKGROUND

Periprosthetic joint infection (PJI) is a significant post-arthroplasty complication for diabetic patients, with uncontrolled diabetes identified as a PJI risk factor. Taiwan's Diabetes Shared Care Program (DSCP) was established for holistic diabetes care.

AIM

To evaluate the DSCP's impact on PJI incidence and patients' medical costs.

METHODS

Data were analysed from Taiwan's National Health Insurance Research Database from 2010 to 2020, focusing on type 2 diabetes mellitus (DM) patients who had undergone arthroplasty. The study group involved DSCP participants, while a comparison group comprised non-participants with matched propensity scores for age, sex, and comorbidities. The primary outcome was the PJI incidence difference between the groups; the secondary outcome was the medical expense difference.

FINDINGS

The study group consisted of 11,908 type 2 DM patients who had arthroplasty and joined the DSCP; PJI occurred in 128 patients. Among non-participants, 184 patients had PJI. The PJI incidence difference between the groups was statistically significant (1.07% vs 1.55%). The study group's medical costs were notably lower, regardless of PJI incidence. Multivariate regression showed higher PJI risk in patients in comparison group, aged >70 years, male, or who had obesity, anaemia.

CONCLUSION

The study indicates that DSCP involvement reduces PJI risks and decreases annual medical costs for diabetic patients after arthroplasty. Consequently, the DSCP is a recommendable option for such patients who are preparing for total joint arthroplasty.

Local adiposity may be a more reliable predictor for infection than body mass index following total knee arthroplasty: a systematic review

PURPOSE

Improved understanding of the factors that predispose TKA patients to infection has considerable economic and medical impact. BMI is commonly used as a proxy for obesity to determine the risk of postoperative infection. However, this metric appears to be fraught with inconsistency in this application. BMI is a simple calculation which provides general insight into body habitus. But it fails to account for anatomic distribution of adipose tissue and the proportion of the mass that is skeletal muscle. Our objective was to review the literature to determine if local adiposity was more predictive than BMI for infection following TKA.

METHODS

A database search was performed for the following PICO (Population, Intervention, Comparison, and Outcome) characteristics: local measurements of adiposity (defined as soft tissue thickness or fat thickness or soft tissue envelope at the knee) in patients over 18 years of age treated with total knee arthroplasty used to determine the relationship between local adiposity and the risk of infection (defined as prosthetic joint infection or wound complication or surgical site infection). Quality was assessed using the GRADE framework and bias was assessed using ROBINS-I .

RESULTS

Six articles (N=7081) met the inclusion criteria. Four of the six articles determined that adiposity was more associated with or was a better predictor for infection risk than BMI. One of the six articles concluded that increased adiposity was protective for short term infection and that BMI was not associated with the outcome of interest. One of the six articles determined that BMI was more strongly associated with PJI risk than soft tissue thickness.

CONCLUSION

The use of adiposity as a proxy for obesity in preoperative evaluation of TKA patients is an emerging concept. Although limited by heterogeneity, the current literature suggests that local adiposity may be a more reliable predictor for infection than BMI following primary TKA.

LEVEL OF EVIDENCE

IV systematic review.

Local Soft-Tissue Thickness vs. Body Mass Index as Predictors of Complications After Total Knee or Hip Arthroplasty: A Literature Review

» Body mass index (BMI) is a nonspecific measure of general fat composition that demonstrates little conclusive or definitive association with surgical site complications after total knee and total hip arthroplasty.» Quantifying soft-tissue thickness (STT) around the joint of interest has shown positive correlations with complications and is arguably a better predictor than BMI.» In this literature review, 14 articles (7 discussing hips and 7 discussing knees) discussing the association of STT, BMI, and surgical site complications after total hip and knee arthroplasty were scrutinized and summarized to present relevant information necessary to compare STT with BMI.» Five of the 7 studies involving hips and 4 of the 7 studies involving knees show a positive relationship between STT and outcomes including complications and infection, with some claiming STT as a stronger predictor of surgery site problems than BMI.» Since many variables, such as STT measurement technique, surgical outcomes, sample sizes, and surgical approach, varied between the studies, definitive inferences are difficult to make and future studies of bigger sample size and higher power should focus on the described measurement techniques.

Visceral Fat as a Risk Factor for Periprosthetic Joint Infection After Total Hip and Knee Arthroplasty

BACKGROUND

Visceral obesity, a strong indicator of chronic inflammation and impaired metabolic health, has been shown to be associated with poor postoperative outcomes and complications. This study aimed to evaluate the relationship between visceral fat area (VFA) and periprosthetic joint infection (PJI) in total joint arthroplasty (TJA) patients.

METHODS

A retrospective study of 484 patients who had undergone a total hip or knee arthroplasty was performed. All patients had a computed tomography scan of the abdomen/pelvis within two years of their TJA. Body composition data (ie, VFA, subcutaneous fat area, and skeletal muscle area) were calculated at the Lumbar-3 vertebral level via two fully automated and externally validated machine learning algorithms. A multivariable logistic model was created to determine the relationship between VFA and PJI, while accounting for other PJI risk factors. Of the 484 patients, 31 (6.4%) had a PJI complication.

RESULTS

The rate of PJI among patients with VFA in the top quartile (> 264.1 cm2) versus bottom quartile (< 82.6 cm2) was 5.6% versus 10.6% and 18.8% versus 2.7% in the total hip arthroplasty and total knee arthroplasty cohorts, respectively. In the multivariate model, total knee arthroplasty patients with a VFA in the top quartile had a 30.5 times greater risk of PJI than those in the bottom quartile of VFA (P = .0154).

CONCLUSION

VFA may have a strong association with PJI in TJA patients. Using a standardized imaging modality like computed tomography scans to calculate VFA can be a valuable tool for surgeons when assessing risk of PJI.

Total Hip and Knee Arthroplasty Surgery in the Morbidly Obese Patient: A Critical Analysis Review

»

Obesity, defined as body mass index (BMI) ≥30, is a serious public health concern associated with an increased incidence of stroke, diabetes, mental illness, and cardiovascular disease resulting in numerous preventable deaths yearly.

»

From 1999 through 2018, the age-adjusted prevalence of morbid obesity (BMI ≥40) in US adults aged 20 years and older has risen steadily from 4.7% to 9.2%, with other estimates showing that most of the patients undergoing hip and knee replacement by 2029 will be obese (BMI ≥30) or morbidly obese (BMI ≥40).

»

In patients undergoing total joint arthroplasty (TJA), morbid obesity (BMI ≥40) is associated with an increased risk of perioperative complications, including prosthetic joint infection and mechanical failure necessitating aseptic revision.

»

The current literature on the role that bariatric weight loss surgery before TJA has on improving surgical outcomes is split and referral to a bariatric surgeon should be a shared-decision between patient and surgeon on a case-by-case basis.

»

Despite the increased risk profile of TJA in the morbidly obese cohort, these patients consistently show improvement in pain and physical function postoperatively that should be considered when deciding for or against surgery.

Risk Factors for Periprosthetic Joint Infection after Primary Total Knee Arthroplasty

Periprosthetic joint infection (PJI) is a major adverse event of primary total knee arthroplasty (TKA) from the patient's perspective, and it is also costly for health care systems. In 2010, the reported incidence of PJI in the first 2 years after TKA was 1.55%, with an incidence of 0.46% between the second and tenth year. In 2022, it has been published that 1.41% of individuals require revision TKA for PJI. The following risk factors have been related to an increased risk of PJI: male sex, younger age, type II diabetes, obesity class II, hypertension, hypoalbuminemia, preoperative nutritional status as indicated by prognostic nutritional index (PNI) and body mass index, rheumatoid arthritis, post-traumatic osteoarthritis, intra-articular injections prior to TKA, previous multi-ligament knee surgery, previous steroid therapy, current tobacco use, procedure type (bilateral), length of stay over 35 days, patellar resurfacing, prolonged operative time, use of blood transfusions, higher glucose variability in the postoperative phase, and discharge to convalescent care. Other reported independent risk factors for PJI (in diminishing order of importance) are congestive heart failure, chronic pulmonary illness, preoperative anemia, depression, renal illness, pulmonary circulation disorders, psychoses, metastatic tumor, peripheral vascular illness, and valvular illness. Preoperative intravenous tranexamic acid has been reported to diminish the risk of delayed PJI. Knowing the risk factors for PJI after TKA, especially those that are avoidable or controllable, is critical to minimizing (ideally preventing) this complication. These risk factors are outlined in this article.

Do TKAs in Patients with Higher BMI Take Longer, and is the Difference Associated with Surgeon Volume? A Large-database Study from a National Arthroplasty Registry

BACKGROUND

Increased surgical time in TKA may impact economic costs and clinical outcomes. Prior work has found that TKAs in patients with high BMI take longer, and these patients may be at greater risk for postoperative complications like infection. However, these studies included small numbers of patients and surgeons from single institutions and they did not consider surgeon volume.

QUESTIONS/PURPOSES

Using the New Zealand Joint Registry (NZJR), we asked: (1) Is there a relationship between increasing patient BMI and TKA operative time? (2) Is the effect of BMI on surgical time less pronounced among surgeons who perform more TKAs per year than those who perform fewer?

METHODS

Data were collected from the NZJR between January 2010 and December 2018 as it is the only national registry that records both BMI and surgical time. Primary TKA performed for osteoarthritis by surgeons with more than 50 TKAs over the period of the study were identified. BMI and operative time (skin incision to closure in minutes) were recorded. Patients with the following were excluded: lateral parapatellar or minimally invasive approaches; navigated, patient-specific instrumentation, or robot-assisted TKA; uncemented or hybrid fixation; those with procedures performed by a trainee (all or part); or a nonosteoarthritic indication. Of 64,108 TKAs performed during the study period, a total of 42% (27,057) met our inclusion criteria. The primary outcome was the effect of BMI on operative time. Operative time is expressed in minutes as a mean for each single-unit BMI increase across all surgeons, controlled for other variables that might influence operative time such as patella resurfacing and cruciate-retaining versus posterior-stabilized designs. Overall, the mean operative time (skin incision to closure) was 79 ± 22 minutes. Surgical experience was assessed by subdividing surgeons into six groups according to the number of TKAs performed annually (< 10, 10 to 24, 25 to 49, 50 to 74, 75 to 99, and > 100). Statistical analyses were performed including a general linear model to assess the independent association between BMI and operative time, allowing for the effects of other patient and surgical features. In addition, linear regression analyses explored the associations between BMI and operative time in the whole group and within surgical volume groups.

RESULTS

There was an association between increasing BMI and increasing surgical duration. The mean operative time increased from 75 ± 22 minutes in patients with a normal BMI of 25 kg/m2 to 87 ± 24 minutes in patients with a BMI of 40 kg/m2 to 94 ± 28 minutes in patients with a BMI > 50 kg/m2 (p < 0.001). Surgeons performing fewer than 25 TKAs per year took 14% longer to perform a TKA on a patient with a BMI of 40 kg/m2 than on a patient with a normal BMI of 25 kg/m2. However, surgeons performing greater than 25 TKAs per year took 10% longer.

CONCLUSION

In this study, an increase BMI was associated with increased surgical time in TKA. Surgical duration for high-volume surgeons appears less influenced by increases in BMI than lower volume surgeons. Although the absolute increase in duration was small, prolonged surgical time may reduce theater productivity. Even though the issues around managing patients with high BMI are multifactorial and complex, considerations from these findings include ensuring appropriate theater scheduling and possibly referring patients with high BMI to specialist centers. Further studies should focus on assessing the effectiveness of such measures in reducing complications and improving outcomes in patients with elevated BMI.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Prognostic nutritional index as a risk factor for aseptic wound complications after total knee arthroplasty

BACKGROUND

Patients with malnutrition have a high risk of postoperative complications in total knee arthroplasty (TKA). Previously, serum albumin and total lymphocyte count were considered preoperative nutritional assessment measures. Prognostic nutritional index (PNI) is calculated by a combination of serum albumin and total lymphocyte count. This study aimed to identify the risk factors for postoperative complications after TKA, including preoperative nutritional assessment, and evaluated preoperative PNI as a predictor of postoperative complications.

METHODS

One-hundred and sixty patients (234 knees) who underwent primary TKA were enrolled consecutively from 2010 to 2018. The serum albumin (g/dL) and total lymphocyte count (/mm³) were examined within 3 months before TKA; thereafter, the PNI was calculated. Postoperative aseptic wound problems, such as skin erosion and dehiscence within 2 weeks and periprosthetic joint infection after TKA were examined.

RESULTS

Periprosthetic joint infections occurred in 14 knees (6.0%). Postoperative aseptic wound problems within 2 weeks were significant risk factors of periprosthetic joint infection (odds ratio; 5.10, 95% confidence interval [CI]; 1.438-18.093, p = 0.012). No significant differences were noted in the patient demographics, such as age, sex, body mass index (BMI), and comorbidities between the positive and negative groups for periprosthetic joint infection, except for the rate of aseptic operative wound problems. Furthermore, postoperative aseptic wound problems were influenced by high BMI (odds ratio; 1.270, 95% CI; 1.111-1.453, p = 0.000) and low PNI (odds ratio; 0.858, 95% CI; 0.771-0.955, p = 0.015).

CONCLUSIONS

Preoperative nutritional status, indicated by PNI and BMI, was associated with postoperative wound problems within 2 weeks. Periprosthetic joint infection after TKA was associated with early postoperative aseptic wound problems.

Do Extended Oral Postoperative Antibiotics Prevent Early Periprosthetic Joint Infection in Morbidly Obese Patients Undergoing Primary Total Joint Arthroplasty?

BACKGROUND

Extended oral antibiotic prophylaxis after primary total knee arthroplasty (TKA) and total hip arthroplasty (THA) in patients with body mass index (BMI) ≥40 kg/m² may reduce the rate of early periprosthetic joint infection (PJI); however, existing data are limited. The purpose of this study was to examine rates of wound complications and PJI in patients with BMI ≥40 kg/m² treated with and without extended oral antibiotic prophylaxis after surgery.

METHODS

We retrospectively identified all primary THA and TKA performed since 2015 in patients with a BMI ≥40 kg/m² at a single institution. Extended oral antibiotic prophylaxis for 7-14 days after surgery was prescribed at the discretion of each surgeon. Wound complications and PJI were examined at 90 days postoperatively.

RESULTS

In total, 650 cases (205 THA and 445 TKA) were analyzed. Mean age was 58 years and 62% were women. Mean BMI was 44 kg/m². Extended oral antibiotic prophylaxis was prescribed in 177 cases (27%). At 90 days, there was no difference between prophylaxis and nonprophylaxis groups in rate of wound complications (11% vs 8%; P = .41) or PJI (1.7% vs 0.6%; P = .35). The univariate analysis demonstrated increased operative time (odds ratio (OR) 1.01; 95% confidence interval (95% CI) 1.01-1.02) and diabetes mellitus (OR 1.88; 95% CI 1.03-3.46) to be associated with increased risk of 90-day wound complications. No patient factors were associated with increased risk of PJI at 90 days postoperatively.

CONCLUSION

Extended oral antibiotic prophylaxis after primary THA and TKA did not reduce rates of wound complications or early PJI in a morbidly obese patient population.

Lower Extremity Girth Does Not Predict Complications in TKA

BACKGROUND

Obese patients have increased complications after total knee arthroplasty (TKA). A body mass index (BMI) cutoff of 40 is frequently used to determine eligibility for TKA. Patients with a BMI <40 and extremely large legs which may predispose them to complications are approved for surgery because they fall below this cutoff. Alternatively, patients with truncal obesity and a BMI >40 are accepted because they have thin legs. We sought to determine whether BMI or girth should be used to determine eligibility.

METHODS

453 patients who underwent TKA were included. A lower extremity girth (LEG) ratio was calculated dividing the width of the soft tissue envelope by bone width on lateral radiographs. Receiver operator curves were generated to predict 90-day complications.

RESULTS

There was no difference in median LEG ratio between patients with or without a complication (P = .08). Receiver operator curves indicated that size of the soft tissue envelope had no utility in predicting complications. There was no correlation between LEG ratio and specific complications such as infection, malalignment, or wound complications. Using a LEG ratio threshold of 4.834, the sensitivity and specificity for predicting complications were 48% and 64%, respectively. The median BMI for patients with no complication was 32.3 and 35 for patients with a complication (P = .07).

CONCLUSION

Complications are not necessarily associated with size of the soft tissue envelope in TKA.Decisions concerning TKA should not be made solely on the size of a patient's leg.

LEVEL OF EVIDENCE

Level III (retrospective comparative study).

Soft-tissue thickness radiographic measurement: a marker to evaluate acute periprosthetic joint infection risk in total hip replacement

The objective of our study was to evaluate the association between acute periprosthetic joint infection (APJI) and radiographic measurement of soft-tissue thickness in elective total hip replacement surgery. A case-control study was conducted to compare the soft-tissue thickness radiographic measurement (SRM) at the hip in patients diagnosed with APJI based on Tsukayama et al. (2003) criteria after total hip replacement with patients that were not infected, at a single institution from 2013 to 2019. To minimize selection bias, each case was matched with two controls using the following methodology: patients of the same sex, with an age variation of ± 5 years, and nearest in surgery date to the cases were selected. All postoperative radiographs were performed in the first 24 h after total hip arthroplasty (THA) surgery as it is protocolized in our institution. Soft-tissue thickness radiographic measurement was defined as the distance from the tip of the greater trochanter to the skin following a perpendicular line to the femoral diaphysis in postoperative anteroposterior hip radiographs. In total, 78 patients were included (26 cases and 52 controls). The SRM median of the cases was 76.19 mm (SD: 26.518) and 53.5 mm (SD: 20.47) in controls. A multivariate logistic regression model showed an independent association between APJI and SRM (odds ratio (OR) = 1.033, 95 % confidence interval (CI) 1.007–1.059, p=0.012). Patients with an SRM greater than 60 mm had a 7-fold increase in the odds of APJI (OR = 7.295, 95 % CI = 2.364–22.511, p<0.001). The results of our study suggest an association between large SRM at the hip and the risk of APJI in patients with primary total hip arthroplasty. SRM may be a helpful and easy tool for evaluating the risk of APJI before elective primary total hip replacement surgery.

Prevention of Prosthetic Joint Infection: From Traditional Approaches towards Quality Improvement and Data Mining

A projected increased use of total joint arthroplasties will naturally result in a related increase in the number of prosthetic joint infections (PJIs). Suppression of the local peri-implant immune response counters efforts to eradicate bacteria, allowing the formation of biofilms and compromising preventive measures taken in the operating room. For these reasons, the prevention of PJI should focus concurrently on the following targets: (i) identifying at-risk patients; (ii) reducing “bacterial load” perioperatively; (iii) creating an antibacterial/antibiofilm environment at the site of surgery; and (iv) stimulating the local immune response. Despite considerable recent progress made in experimental and clinical research, a large discrepancy persists between proposed and clinically implemented preventative strategies. The ultimate anti-infective strategy lies in an optimal combination of all preventative approaches into a single “clinical pack”, applied rigorously in all settings involving prosthetic joint implantation. In addition, “anti-infective” implants might be a choice in patients who have an increased risk for PJI. However, further progress in the prevention of PJI is not imaginable without a close commitment to using quality improvement tools in combination with continual data mining, reflecting the efficacy of the preventative strategy in a particular clinical setting.