Subcutaneous Fat Thickness Is Associated With Early Reoperation and Infection After Total Knee Arthroplasty in Morbidly Obese Patients

The role of subcutaneous fat and BMI in predicting surgical outcomes and patient reported outcomes in robotic-assisted total hip arthroplasty

Background

The purpose of this study was to assess if subcutaneous fat (SCF) or BMI is a predictor of surgical complications and patient reported outcomes in patients undergoing robotic-assisted total hip arthroplasty (THA).

Methods

Patients who underwent robotic-assisted primary THAs at one institution between 2018 and 2020 were included in this retrospective cohort study. Prior to surgery, computed tomography (CT) was used to measure SCF in the posterolateral quadrant of the hip. SCF was measured 3 centimeters (cm) proximal to the greater trochanter (PGT) and 3 cm inferior to the distal tip of the greater trochanter (DGT).Measurements were normalized to the size of the patient's bony anatomy by dividing the subcutaneous fat area measurement by the transverse diameter of the femur 10 cm inferior to the tip of the greater trochanter. Patients were divided into quintiles determined by SCF distribution around the mean (groups 1-5) and BMI (BMI<25, BMI 25-29.9, BMI 30-34.9, BMI 35-39.9, and >40). Ninety day outcomes and PROMIS (Patient Reported Outcome Measures Information System) scores were acquired from the Michigan Arthroplasty Registry Collaborative Quality Initiative (MARCQI) database preoperatively, at 14-112 days post-operative and at the latest follow up.

Results

There were 175 patients identified with a mean age of 63.83 years (range 27-89) and a mean BMI of 30.73kg/m2 (range 18.2-48.4). Interclass correlation coefficient was greater than 0.9 in all PGT, DGT, and GT measurements. Analysis of Variance (ANOVA) found there was a significantly shorter time from incision to closure in quintiles 1 and 3 when compared to the SCF quintile 5 (p<0.05) and that there was a significantly shorter time from incision to closure in BMI categories 1, 2, and 3 when compared to BMI category 5 (BMI > 40). There were no differences between SCF and BMI as predictive of length of stay, transfusion status, infection, or PROMIS scores.

Conclusion

It can be concluded that hip SCF on axial CT images can reliably measure SCF and is predictive of time from incision to closure, but it does not show a significant difference in predicting the length of stay, infection, or PROMIS scores when compared to BMI.

Body Mass Index Improvement Reduces Total Knee Arthroplasty Complications Among Patients Who Have Extreme, But Not Severe, Obesity

BACKGROUND

While morbid obesity has been associated with increased complication risk in primary total knee arthroplasty (TKA), limited evidence is available to attribute decreased surgical complication rates with body mass index (BMI) reduction.

METHODS

We retrospectively assessed 464 unilateral TKAs performed in morbidly obese patients, including 158 extremely obese (BMI > 45) and 306 severely obese patients (BMI 40 to 44.9). A detailed medical record review identified concurrent modifiable risk factors and successful preoperative BMI reduction, reaching either a contemporary risk target (BMI < 40) or an institutionally accepted threshold (BMI < 45). Postoperative blood glucose levels and one-year adverse outcomes (periprosthetic joint infection (PJI), wound dehiscence, knee manipulation, periprosthetic fracture) were compared to 557 contemporary control subjects with expected slightly lower (moderate obesity, BMI 35 to 39.9) or sufficiently lower complication risk (overweight, BMI 25 to 29.9).

RESULTS

PJI and postoperative hyperglycemia were identified more frequently among morbidly obese patients in comparison with a moderately obese control group. Extremely obese patients (BMI > 45) whose BMI improved below 45 had no measurable difference in infection risk from the control group (OR [odds ratio] 0.84, 95% CI [confidence interval] 0.04 to 16.88), while those with a non-improved BMI had a significantly higher risk (OR 7.70, 95% CI 1.89 to 31.41). No significant differences in the risk for infection were observed between severely obese patients (BMI 40 to 44.9) with preoperative BMI improvement (1.5% rate, OR 1.70, 95% CI 0.17 to 16.57) or non-improvement (1.7% rate, OR 1.87, 95% CI 0.41 to 8.43).

CONCLUSIONS

Preoperative medical optimization may decrease postoperative TKA complications. The findings of this study support BMI improvement for extremely obese patients (BMI > 45). The assignment of 40 BMI as a threshold for otherwise healthy patients may exclude patients from potential surgical benefits without realizing risk reduction.

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.

Acute Surgical Site Complications in Direct Anterior Total Hip Arthroplasty: Impact of Local Subcutaneous Tissue Depth and Body Mass Index

Background

Body mass index (BMI) is an imperfect measure of patients' adiposity and operative risk. Radiographic and direct subcutaneous measurements have been utilized in attempts to more accurately characterize the risk of postoperative complications, including surgical site infection. This study aims to evaluate whether direct tissue depth measurement is a more accurate predictor of skin complication following direct anterior total hip arthroplasty (THA).

Methods

A retrospective chart review of patients who underwent elective THA between April 30, 2020, and January 31, 2023, was performed. Baseline demographics, antibiotics, anticoagulation, and intraoperatively measured tissue depths at proximal, middle, and distal portions of the incision were recorded. Patient follow-up was reviewed to assess the development of skin complication in the acute postoperative period.

Results

Data were collected from 280 patients who underwent THA via direct anterior approach by a single surgeon. The mean age was 66.0 years, and 52.1% were female. A total of 18/280 (6.4%) patients developed an abrasion (5/18) or superficial surgical site infection (13/18) within the first 60 days postoperatively. Patients who developed skin complications had a significantly higher BMI (33.7 kg/m2 vs 29.9 kg/m2; P = .0021). Patients with a BMI >30 kg/m2 had more than 5 times increased odds of developing a superficial skin complication in the acute 60-day postoperative period compared to those with a BMI <30 kg/m2 (Odds ratio = 5.318, P = .0059). None of the measured tissue depths, nor their average together, were shown to be significant predictors of skin complications.

Conclusions

This study showed that BMI is a significant predictor of acute skin complications in direct anterior THA patients. No other significant predictors were found to be associated with increased risk, including proximal, middle, and distal tissue depths.

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.

Association between radiographic soft-tissue thickness and increased length of stay, operative time, and infection rate after reverse shoulder arthroplasty

BACKGROUND

Reverse shoulder arthroplasty (RSA) is a widely performed surgical procedure to address various shoulder pathologies. Several studies have suggested that radiographic soft-tissue thickness may play a role in predicting complications after orthopedic surgery, but there have been limited studies determining the use of radiographic soft-tissue thickness in RSA. The purpose of this study was to evaluate whether radiographic soft-tissue thickness could predict clinical outcomes after RSA and compare the predictive capabilities against body mass index (BMI). We hypothesized that increased radiographic shoulder soft-tissue thickness would be a strong predictor of operative time, length of stay (LOS), and infection in elective RSA.

MATERIAL AND METHODS

A retrospective review of patients undergoing RSA at an academic institution was conducted. Preoperative radiographic images were evaluated including measurements of the radius from the humeral head center to the skin (HS), deltoid radius-to-humeral head radius ratio (DHR), deltoid size, and subcutaneous tissue size. Different correlation coefficients were used to analyze various types of relationships, and the strength of these associations was classified based on predefined boundaries. Subsequently, multivariable linear and logistic regressions were performed to determine whether HS, DHR, deltoid size, and subcutaneous tissue size could predict LOS, operative time, or infection while controlling for patient factors.

RESULTS

HS was the most influential factor in predicting both operative time and LOS after RSA, with strong associations indicated by standardized β coefficients of 0.234 for operative time and 0.432 for LOS. Subcutaneous tissue size, deltoid size, and DHR also showed stronger predictive values than BMI for both outcomes. In terms of prosthetic joint infection, HS, deltoid size, and DHR were significant predictors, with HS demonstrating the highest predictive power (Nagelkerke R2 = 0.44), whereas BMI did not show a statistically significant association with infection. Low event counts resulted in wide confidence intervals for odds ratios in the infection analysis.

CONCLUSION

Greater shoulder soft-tissue thickness as measured with concentric circles on radiographs is a strong predictor of operative time, LOS, and postoperative infection in elective primary RSA patients.

Does local fat thickness correlate with post-operative infection in open reduction and internal fixation of acetabulum fractures?

PURPOSE

Obesity is an epidemic which increases risk of many surgical procedures. Previous studies in spine and hip arthroplasty have shown that fat thickness measured on preoperative imaging may be as or more reliable in assessment of risk of post-operative infection and/or wound complications than body mass index (BMI). We hypothesized that, similarly, increased local fat thickness at the surgical site is a predictor of wound complication in acetabulum fracture surgery.

METHODS

Patients who underwent open reduction and internal fixation (ORIF) of an acetabulum fracture through a Kocher-Langenbeck (K-L) approach at a single institution from 2013 to 2020 were identified. Pre-operative CT scans were used to measure fat thickness from the skin to the greater trochanter in line with the surgical approach. Post-operative infections and wound complications were recorded and associated with fat thickness and BMI.

RESULTS

238 patients met inclusion criteria. 12 patients had either infection or a wound complication (5.0%). There was no significant association with BMI or preoperative fat thickness on post-operative infection or wound complication (p-value 0.73 and 0.86).

CONCLUSIONS

There is no statistically significant association of post-operative infection or wound complications in patients with increased soft tissue thickness or increased BMI. ORIF of acetabulum fractures through a K-L approach can be performed safely in patients with large subcutaneous fat thickness and high BMI with low risk of infection or wound complications.

Microvascular free flap coverage of complex soft tissue defects after revision total knee arthroplasty: a cross-sectional observation study

BACKGROUND AND PURPOSE

Soft tissue defects after total knee arthroplasties (TKA) represent a major orthopedic challenge with amputation as a feared outcome. Microvascular free flap coverage (FFC) can increase limb salvage rates, but complications related to the procedure are yet to be explored further. We aimed to review a single-center experience with FFC for soft tissue defects related to revision total knee arthroplasty.

METHODS

Through a retrospective chart review from 2006 to 2021, we identified all patients who had FFC of a knee with an existing TKA. Typically, patients underwent 2-stage revision arthroplasty. To identify areas of intervention, we divided the entire regimen into 2 phases divided by the free flap surgery (pre- and post-free flap).

RESULTS

We identified 18 patients with a median age at free flap surgery of 69 years (range 39-85), who were followed for a median of 5.1 years (range 2 months to 10.6 years). The median duration from primary TKA to their final operation was 17.5 months (range 19 days to 7 years). Patients underwent a mean of 7.6 surgical procedures on their knee with 3.6 orthopedic revisions prior to the FFC and 0.6 after. Soft tissue coverage was achieved in all patients and no patients underwent amputation. One-third of patients experienced early complications at recipient site after free flap surgery. There were no donor site complications.

CONCLUSION

Microvascular FFC of complex soft tissue defects after revision total knee arthroplasty proved achievable in all patients with successful limb salvage in all patients.

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.

Accurate surgical posterior tibial slope alteration can be achieved in total knee arthroplasty regardless of surgeon skill level or local soft tissue thickness-A retrospective radiograph-based study

PURPOSE

To retrospectively report on the impact of local soft tissue thickness and surgeon skill level on the accuracy of surgical posterior tibial slope (PTS) alteration achieved in patients undergoing total knee arthroplasty (TKA) utilising lateral knee radiographs.

METHODS

Pre- and postoperative radiographs of 82 patients undergoing primary TKA using conventional mechanical alignment technique were measured by two observers and subjected to quality criteria for accurate measurement of the PTS. All patients underwent a standardised surgical approach for PTS alteration: cruciate-retaining (CR) cases with preoperative PTS ≤ 10° were set for reconstruction of the preoperative PTS. Cases indicated for posterior-stabilised (PS) design and/or with a preoperative PTS > 10° were set for 3° of postoperative PTS. Pretibial subcutaneous fat (PSF) and surgeon skill level were analysed for their predictive quality regarding the accuracy of surgical PTS alteration achieved.

RESULTS

The overall mean postoperative PTS was significantly lower than the preoperative values (6.2°, SD 2.7 vs. 7.7°, SD 3.2; p = 0.002103). Neither local soft tissue thickness, namely PSF, nor surgeon skill level was found to be a predictor of the accuracy of surgical PTS alteration achieved. Among cases set for PTS reconstruction, 25.9% and 42.6% achieved a postoperative PTS within ±1° and ±2° of preoperative values, respectively. In patients with a PTS > 10° or those indicated for PS design, slope reduction was achieved with a mean postoperative PTS of 6.5°. Furthermore, 14.3% and 32.1% of cases were within ±1° and ±2° of 3, respectively.

CONCLUSION

This study demonstrates that accurate surgical alteration of the PTS is possible in TKA regardless of local knee soft tissue thickness or surgeon skill level. This proves the clinical feasibility of both targeted reduction as well as reconstruction of the PTS in TKA.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

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.

An Update on the Management and Optimization of the Patient with Morbid Obesity Undergoing Hip or Knee Arthroplasty

The prevalence of obesity in the United States is at a record high of 42%. In 1999, the Centers for Disease Control and Prevention recognized the obesity epidemic as a national problem, spurring the first generation of interventions for obesity prevention and control. Despite billions of dollars in funding, legislative changes, and public health initiatives, the trajectory of American obesity has not waivered. Obesity is also strongly associated with the development of osteoarthritis. The growing population of young, obese, and sick patients presents a unique dilemma for orthopedic surgeons performing joint replacement, as obesity levels and the demand for joint replacement are only expected to rise further.

A Radiographic Abdominal Pannus Sign is Associated With Postoperative Complications in Anterior THA

BACKGROUND

Numerous studies have shown that elevated BMI is associated with adverse outcomes in THA; however, BMI alone does not adequately represent a patient's adipose and soft tissue distribution, especially when the direct-anterior approach is evaluated. Local soft tissue and adipose, especially in the peri-incisional region, has an unknown impact on patient outcomes after direct-anterior THA. Moreover, there is currently no known evaluation method to estimate the quantity of local soft tissue and adipose tissue. The current study introduced a new radiographic parameter that is measurable on supine AP radiographs: the abdominal pannus sign.

QUESTION/PURPOSE

Are patients who have an abdominal pannus extending below the upper (cephalad) border of the symphysis pubis more likely to experience problems after anterior-approach THA that are plausibly associated with that finding, including infections resulting in readmission, wound complications resulting in readmission, fractures, or longer surgical time, than patients who do not demonstrate this radiographic sign?

METHODS

Between 2015 and 2020, five surgeons performed 727 primary direct-anterior THAs. After exclusion criteria were applied, 596 procedures were included. Of those, we obtained postoperative radiographs in the postanesthesia care unit in 100% of procedures (596 of 596), and 100% of radiographs (596) were adequate for review in this retrospective study. The level of the pannus in relation to the pubic symphysis was assessed on immediate supine postoperative AP radiographs of the pelvis: above (pannus sign 1), between the upper and lower borders (pannus sign 2), or below the level of the pubic symphysis (pannus sign 3). In this study, we combined pannus signs 2 and 3 into a single group for analysis not only because there was a limited number of patients in each group, but also because there was no statistically significant difference between the two groups. Pannus sign 1 was identified in 82% of procedures (486 of 596), and pannus sign ≥ 2 was identified in 18% (110). We compared the groups (pannus sign 1 versus pannus sign ≥ 2) in terms of the percentage of patients who experienced problems within 90 days of THA that might be associated with that physical finding, including infections resulting in readmission including subcutaneous, subfascial, and prosthetic joint infections; wound complications resulting in readmission, defined as dehiscence or delayed healing; and all fractures, and we compared the groups in terms of surgical time-that is, the cut-to-close time.

RESULTS

Patients with a pannus sign of ≥ 2 were more likely than those with a pannus sign of 1 to have a postoperative infection (6.4% [seven of 110 procedures] versus 0.6% [three of 486], odds ratio 10.96 [95% confidence interval (CI) 2.83 to 42.38]; p < 0.01), wound complications (0.9% [one of 110] versus 0% [0 of 486] with an infinite odds ratio [95% CI indeterminate]; p = 0.18), and fractures (4.5% [five of 110] versus 0% [0 of 486], with an infinite odds ratio [95% CI indeterminate]; p < 0.01). The mean surgical time was longer in patients with a pannus sign of ≥ 2 than it was in those with a pannus sign of 1 (128 ± 25.3 minutes versus 118 ± 27.5 minutes, mean difference 10 minutes; p < 0.01).

CONCLUSION

Based on these findings, patients who have an abdominal pannus that extends below the upper (cephalad) edge of the pubic symphysis are at an increased risk of experiencing serious surgical complications. If THA is planned in these patients, an approach other than the direct-anterior approach should be considered. Surgeons performing THA who do not obtain supine radiographs preoperatively should use a physical examination to evaluate for this finding, and if it is present, they should use an approach other than the direct-anterior approach to minimize the risk of these complications. Future studies might compare the abdominal pannus sign using standing radiographs, which are used more often, with other well-documented associated risk factors such as elevated BMI or higher American Society of Anesthesiologists classification.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

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.

Sarcopenia is an independent risk factor for failure to achieve the 1-year MCID of the KOOS, JR and PROMIS PF-SF10a after TKA

BACKGROUND

Sarcopenia, which is a progressive and multifactorial condition of decreased muscle strength, has been identified as an independent predictor for falls, revision, infection, and readmissions following total knee arthroplasty (TKA), but its association to patient reported outcomes (PROMs) is less studied. The aim of this study is to determine if sarcopenia and other measures of body composition are correlated with ability to achieve the 1-year minimal clinically important difference (MCID) of the KOOS JR and PROMIS-PF-SF10a following primary TKA.

METHODS

A multicenter retrospective case-control study was performed. Inclusion criteria consisted of patients over the age of 18 undergoing primary TKA, body composition metrics determined by computed tomography (CT), and available pre- and post-operative PROM scores. Predictors of achievement of the 1-year MCID of the KOOS JR and PROMIS PF-SF-10a were determined through a multivariate linear regression.

RESULTS

140 primary TKAs met inclusion criteria. 74 (52.85%) patients achieved the 1-year KOOS, JR MCID and 108 (77.41%) patients achieved the 1-year MCID for the PROMIS PF-SF10a. Sarcopenia was independently associated with decreased odds of achieving the MCID of both the KOOS, JR (OR 0.31, 95%CI 0.10-0.97, p = 0.04) and the PROMIS-PF-SF10a (OR 0.32, 95%CI 0.12-0.85, p = 0.02) CONCLUSIONS: In our study, sarcopenia was independently associated with increased odds of failure to achieve the 1-year MCID of the KOOS, JR and PROMIS PF-SF10a after TKA. Early identification of sarcopenic patients may be beneficial for arthroplasty surgeons so that targeted nutritional counseling and exercises can be recommended prior to TKA.

The role of spine adipose index in predicting the risk for septic spondylodiscitis after lumbar percutaneous laser disc decompression

The aim. To analyze the role of the spine adipose index (SAI) in predicting the risk of septic spondylodiscitis after lumbar percutaneous laser disk decompression (PLDD).

Material and methods. A retrospective observational single-center study was performed. Various clinical and instrumental parameters have been studied, including the spine adipose index, which are potential risk factors for the development of postprocedural septic spondylodiscitis.

Results. The study included 219  patients who underwent PLDD for degenerative lumbar disk disease. The average period of postoperative observation was  30.8  ±  13.3  months. Signs of septic spondylodiscitis were detected in 5 (2.28%) cases. Multivariate analysis showed that III degree of anesthesiological risk by the American Society of Anesthesiologists (ASA) scale (p = 0.021), a high value of body mass index (more than 25 kg/m2) (p = 0.043) and a high value of SAI (over 0.7) (p = 0.037) are statistically significantly associated with the development of septic spondylodiscitis in patients who underwent lumbar PLDD.

Conclusion. The value of SAI is statistically significantly associated with the development of spondylodiscitis in patients who underwent PLDD for degenerative lumbar disk disease. 

Radiographic Findings in Flexion Instability after Total Knee Arthroplasty

Flexion instability (FI) is one of the leading causes of knee pain and revision surgery. Generally, the biomechanical etiology is considered to be a larger flexion than extension gap. This may be due to mismatch of components sizes to the bone or malalignment. Other factors such as muscle weakness may also play a role, and the diagnosis of FI after total knee arthroplasty (TKA) relies on a combination of patient's complaints during stair descent or walking and physical examination findings. Our study examines the role of implant positioning and sizes in the diagnosis of FI. A retrospective review of 20 subjects without perceived FI and 13 patients diagnosed with FI after TKA was conducted. Knee injury and osteoarthritis outcome scores (KOOS) were documented, and postoperative radiographs were examined. Measurements including included tibial slope, condylar offset, femoral joint line elevation along with surrogate soft-tissue measures for girth and were compared between groups. The FI group was found to have a significantly lower KOOS score compared with the non-FI group (55.6 vs. 73.5; p = 0.009) as well as smaller soft-tissue measurements over the pretubercle region (6.0 mm vs. 10.6 mm; p = 0.007). Tibial slope, condylar offset ratios, and femoral joint line elevation were not significantly different between the FI and non-FI groups. We noted a significant difference in tibial slope in posterior-stabilized implants in subjects with and without FI (6.4° vs. 1.5°; p = 0.003). Radiographic measurements consistent with malalignment were not indicative of FI. X-ray measurements alone are not sufficient to conclude FI as patient symptoms, and clinical examinations remain the key indicators for diagnosis. Radiographic findings may aid in surgeon determination of an underlying cause for an already identified FI situation and help in planning revision surgery.

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.

Goals, challenges and strategies for wound and bleeding management in total knee arthroplasty: A modified Delphi method

BACKGROUND

Surgical techniques related to soft tissue management play critical roles in optimizing surgical outcomes and patient satisfaction in total knee arthroplasty (TKA). Despite the importance of wound closure and bleeding management approaches, no published guidelines/consensus are available.

METHODS

Twelve orthopedic surgeons participated in a modified Delphi panel consisting of 2 parts (each part comprising two rounds) from September-October 2018. Questionnaires were developed based on published evidence and guidelines on surgical techniques/materials. Questionnaires were administered via email (Round 1) or at a face-to-face meeting (subsequent rounds). Panelists ranked their agreement with each statement on a five-point Likert scale. Consensus was achieved if ≥70% of panelists selected 4/5, or 1/2. Statements not reaching consensus in Round 1 were discussed and repeated or modified in Round 2. Statements not reaching consensus in Round 2 were excluded from the final consensus framework.

RESULTS

Consensus was reached on 13 goals of wound management. Panelists agreed on 38 challenges and 71 strategies addressing surgical techniques or wound closure materials for each tissue layer, and management strategies for blood loss reduction or deep vein thrombosis prophylaxis in TKA. Statements on closure of capsular and skin layers, wound irrigation, dressings and drains required repeat voting or modification to reach consensus.

CONCLUSION

Consensus from Asia-Pacific TKA experts highlights the importance of wound management in optimizing TKA outcomes. The consensus framework provides a basis for future research, guidance to reduce variability in patient outcomes, and can help inform recommendations for wound management in TKA.

Comparison of silver-embedded occlusive dressings and negative pressure wound therapy following total joint arthroplasty in high BMI patients: a randomized controlled trial

INTRODUCTION

High body mass index (BMI) and wound drainage following total joint arthroplasty (TJA) can lead to wound healing complications and periprosthetic joint infection. Silver-embedded occlusive dressings and negative pressure wound therapy (NPWT) have been shown to reduce these complications. The purpose of this prospective trial was to compare the effect of silver-embedded dressings and NPWT on wound complications in patients with BMI ≥ 35 m/kg2 undergoing TJA.

METHODS

We conducted a randomized control trial of patients who had a BMI > 35 m/kg² and were undergoing primary TJA between October 2017 and February 2020. Patients who underwent revision surgery, or those with an active infection, previous scar, history of wound healing complications, post-traumatic degenerative joint disease with hardware, or inflammatory arthritis were excluded. Patients were randomized to receive either a silver-embedded occlusive dressing (control) or NPWT. Frequency distributions, means, and standard deviations were used to describe patient demographics, postoperative complications, 90-day readmissions, and reoperations. T-test and chi-squared tests were used to test for significant differences between continuous and categorical variables, respectively.

RESULTS

Two hundred-thirty patients with 3-month follow-up were included. One-hundred-fifteen patients received the control and 115 patients received NPWT. There were six patients (5.2%) in the control group with wound complications (drainage: n = 5, non-healing wound: n = 1) and two patients (1.7%) in the NPWT with complications (drainage: n = 2). There were no 90-day readmissions in the control group versus two (1.8%) 90-day readmissions in the NPWT group. Finally, three patients (2.6%) in the control group underwent reoperations (irrigation and debridement [I&D], I&D with modular implant exchange, and implant revision), while none in the NPWT group had undergone reoperation. The two groups showed insignificant differences in wound complications (p = 0.28), 90-day readmissions (p = 0.50), and reoperations (p = 0.25).

CONCLUSION

Patients with BMI ≥ 35 m/kg2 undergoing TJA have no statistical difference in early wound complications, readmissions, or reoperations when treated with either silver-embedded dressings or NPWT.

Predictors of Reinfection in Prosthetic Joint Infections Following Two-Stage Reimplantation

BACKGROUND

Two-stage reimplantation is an effective treatment for periprosthetic joint infection (PJI). Many factors are involved in the variable success of this procedure. The purpose of this study is to examine the relationship between patient risk factors, comorbidities, and the pathogen on reinfection rates following two-stage reimplantation.

METHODS

We evaluated 158 patients treated for PJI from 2008-2019. Only patients who had completed a two-stage exchange were included. Patient demographics, comorbidities, laboratory values, time-to-reimplantation, pathogen, antibiotic sensitivities, host status, and reinfection rates were assessed. Multivariate analysis was performed to identify correlation between risk factors and reinfection. A P-value < .05 was considered statistically significant.

RESULTS

31 patients experienced a reinfection (19.6%). There was a statistically significant association between infection with Methicillin Sensitive Staphylococcus Aureus (MSSA) and reinfection (P = .046). Patients with a reinfection also had a significantly greater median serum C-reactive protein (CRP) level (12.65 g/dL) at the time of diagnosis compared to patients without a reinfection (5.0 g/dL) (P = .010). Median Erythrocyte Sedimentation Rate (ESR) (56 in no re-infection and 69 in re-infection) and time-to-reimplantation (101 days in no reinfection and 141 days in reinfection) demonstrated a trend toward an association with re-infection but were not statistically significant (P = .055 and P = .054 respectively).

CONCLUSION

As the number of arthroplasties continue to rise, PJIs are increasing proportionately and represent a significant revision burden. Elevated C-reactive protein (CRP) levels and Methicillin Sensitive Staphylococcus aureus (MSSA) infection were strongly associated with failure of a two-stage reimplantation. While not statistically significant with our numbers, there were strong trends toward an association between elevated Erythrocyte Sedimentation Rate (ESR), longer time-to-reimplantation, and reinfection.

The radiographic soft tissue thickness is associated with wound complications after open reduction and internal fixation of patella fractures

Background

Displaced patella fracture is commonly treated with open reduction and internal fixation (ORIF). Wound complications after surgery often lead to prolonged hospitalization and dissatisfaction of patients. Periarticular adiposity and swelling may be associated with wound complications. The purpose of this study is to determine the relationship between periarticular soft tissue thickness and wound complications after ORIF of patella fractures.

Methods

We retrospectively studied 237 patients undergoing ORIF for patella fractures from June 2017 to February 2021 at our institution. We established periarticular soft tissue thickness ratio (PSTTR) to evaluate soft tissue status on lateral knee X-ray radiographs. Univariate analysis was performed to identify the association between PSTTR and postoperative wound complication. A receiver-operating characteristic (ROC) curve analysis was performed to evaluate the predictive value of PSTTR.

Results

The incidence of postoperative wound complication was 10.5%. Minor wound complication occurred in 24 patients, and major wound complication occurred in one patient. The average femoral PSTTR (fPSTTR) was 0.94 ± 0.17 and the average tibial PSTTR (tPSTTR) was 0.66 ± 0.16. fPSTTR proved to be associated with postoperative wound complication. In the ROC analysis of fPSTTR predicting postoperative wound complication, the area under curve (AUC) was 0.676, which indicated a moderate predictive value.

Conclusions

PSTTR was a feasible method to assess periarticular soft tissue. The increased fPSTTR was associated with wound complications after ORIF of patella fractures.

What is the Impact of Body Mass Index Cutoffs on Total Knee Arthroplasty Complications?

BACKGROUND

Body mass index (BMI) cutoffs are commonly used to decide whether to offer obese patients elective total knee arthroplasty (TKA). However, weight loss goals may be unachievable for many patients who are consequentially denied complication-free surgery. The purpose of this study was to assess the impact of different BMI cutoffs on the rates of complication-free surgery after TKA.

METHODS

Patients undergoing elective, primary TKA from 2015 to 2018 were identified in the American College of Surgeons National Surgical Quality Improvement Program database using Common Procedural Terminology code 27447. The BMI and rates of any thirty-day complication were collected. BMI cutoffs of 30, 35, 40, 45, and 50 kg/m² were applied to model the incidence of complications if TKA would have been allowed or denied based on the BMI.

RESULTS

A total of 314,719 patients underwent TKA, and 46,386 (14.7%) had a BMI ≥40 kg/m². With a BMI cutoff of 40 kg/m², 268,333 (85.3%) patients would have undergone TKA. A total of 282,552 (94.8%) would experience complication-free surgery, and 17.3% of all complications would be prevented. TKA would proceed for 309,479 (98.3%) patients at a BMI cutoff of 50 kg/m². A total of 293,108 (94.7%) would not experience a complication, and 2.8% of complications would be prevented. A BMI cutoff of 35 kg/m² would prevent 36.6% of all complications while allowing 94.8% of complication-free surgeries to proceed.

CONCLUSION

Lower BMI cutoffs can reduce complications, but will limit access to complication-free TKA for many patients. These data do not indicate TKA should be performed without consideration of risks from obesity; however, a holistic assessment and shared decision-making may be more valuable when deciding on appropriate goal weight reduction.

Thickness of the Subcutaneous Fat as a Risk Factor for Surgical Site Infection Following Fragility Hip Fracture Surgery

INTRODUCTION

Surgical site infection (SSI) following fragility hip fracture (FHF) surgery is associated with increased morbidity and mortality.

SIGNIFICANCE

Prediction of patients at risk for SSI is fundamental. We aimed to determine whether subcutaneous radiographic fat measurement (SRM) is associated with increased SSI risk.

METHODS

A retrospective case-control comparison of SRMs at 3 locations around the hip. Patients diagnosed with SSI in the first post-operative year were matched with age, gender, surgical year, Charlsons' co-morbidity index score, and surgical type controls, not diagnosed with SSI, at a 1:2 ratio. Measurements included the distance between (1) the sourcil to skin surface (SS), (2) the tip of the greater trochanter to skin surface (TGTS), and (3) the most prominent lateral aspect of the greater trochanter to skin surface.

RESULTS

1430 patients were operated during the study period, of whom 45 patients presented with a diagnosis of SSI and compared to 90 controls. Infections occurred 27.4 ( ± 24.8) days following surgery. SRM significantly differed between groups, and all were higher in the study group; SS, 86.8 ± 25.5 cm vs 74.2 ± 15.3 cm; TGTS, 59.8 ± 26.3 cm vs 47.0 ± 15.8 cm; and LGTS, 45.4 ± 25.1 cm vs 33.2 ± 15.1 cm (P = .003, .004, and .004, respectively). Intraclass correlation coefficients (intra-rater) were high for all measurements (.999 for all). Intraclass correlation coefficients (inter-rater) for SS, TGTS and LGTS were high, .749 (.663.815), .792 (.719.847) and .817 (.751.866), respectively.

CONCLUSIONS

SRMs were found to be a valid and reproducible tool for predicting high risk of SSI in geriatric patients sustaining FHFs.

LEVEL OF EVIDENCE

III.

Lymphedema Is a Significant Risk Factor for Failure After Primary Total Hip Arthroplasty

BACKGROUND

Lymphedema is a chronic disease characterized by fluid buildup and swelling that can lead to skin and soft-tissue fibrosis and recurring soft-tissue infections. Literature with regard to the increased risk of complications following a surgical procedure in patients with lymphedema is emerging, but the impact of lymphedema in the setting of primary total hip arthroplasty (THA) remains unknown. The purpose of this study was to review outcomes following primary THA performed in patients with lymphedema compared with a matched cohort without lymphedema.

METHODS

Using our institutional total joint registry and medical records, we identified 83 patients (57 were female and 26 were male) who underwent THA with ipsilateral lymphedema. For comparison, these patients were matched 1:6 (based on sex, age, date of the surgical procedure, and body mass index [BMI]) to a group of 498 patients without lymphedema who underwent primary THA for osteoarthritis. Subsequently, postoperative complications and implant survivorship were evaluated for each group. The mean follow-up for each group was 6 years. Survivorship was compared between cohorts using Kaplan-Meier methodology and included both survivorship free of infection and survivorship free of reoperation or revision. Univariate Cox regression analysis was utilized to assess the association between patient factors for the time to event outcomes noted above.

RESULTS

In patients with a history of lymphedema, there was an increased risk of complications (hazard ratio [HR], 1.97; p < 0.01), including reoperation for any cause (HR, 3.16; p < 0.01) and postoperative infection (HR, 4.48; p < 0.01). The 5-year infection-free survival rate was 90.3% for patients with lymphedema compared with 97.7% for patients without lymphedema (p < 0.01).

CONCLUSIONS

Patients with lymphedema are at increased risk for complications, including reoperation and infection, following primary THA. These data emphasize the importance of appropriate preoperative counseling in this population and should encourage efforts to identify methods to improve outcomes, including further investigation of the effects of preoperative optimization of lymphedema prior to THA and methods for improved perioperative management.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

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.

Novel radiographic hip fat thickness ratio correlates with early re-operation following total hip arthroplasty

INTRODUCTION

Obesity is thought to lead to increased failure rates following total hip arthroplasty (THA). Site-specific fat distribution has been suggested to be a better indicator of risk, compared to body mass index. Fat thickness measurement methods were developed for total knee arthroplasty, however, there is limited data on the methods for THA. The aim of this study was to assess the interobserver and intraobserver reliability of a newly defined radiographic subcutaneous fat thickness ratio and investigate the correlation of this ratio with early failure following THA.

METHODS

321 patients who underwent primary THA at a single institution between 2014 and 2017, with at least 1-year of follow-up and a preoperative pelvis anteroposterior x-ray radiograph were included in this study. A high hip fat thickness ratio (HFTR) was arbitrarily defined as ⩾2. Early failure was defined as revision or re-operation for any reason and death related to operation first year following THA.

RESULTS

The HFTR was shown to have excellent intraobserver and interobserver reliability. High HFTR was associated with higher risk of early failure following THA (odds ratio 3.8, [95% confidence interval, 1.2-12.1], p < 0.05). The same association persisted when HFTR was analysed as a continuous variable (p < 0.01) and in multivariate analysis (p < 0.05).

CONCLUSIONS

HFTR can be used to assess periarticular soft tissue distribution and may be regarded as a useful and reproducible tool for assessing risk of early failure following THA.

Radiographic spine adipose index: an independent risk factor for deep surgical site infection after posterior instrumented lumbar fusion

BACKGROUND CONTEXT

Surgical site infections (SSIs) after spinal fusion surgery increase healthcare costs, morbidity and mortality. Routine measures of obesity fail to consider site specific fat distribution.

PURPOSE

To assess the association between the spine adipose index and deep surgical site infection and determine a threshold value for spine adipose index that can assist in preoperative risk stratification in patients undergoing posterior instrumented lumbar fusion (PILF).

STUDY DESIGN/SETTING

Multicenter retrospective case-control study.

PATIENT SAMPLE

We reviewed patients who underwent PILF from January 1, 2010 to December 31, 2018.

OUTCOME MEASURES

All patients developing a deep primary incisional or organ-space SSI within 90 days of surgery as per US Center for Disease Control and Prevention criteria were identified. We gathered potential pre-operative and intra-operative deep infection risk factors for each patient. A 1:1 match was performed using the following criteria: gender, age (±3 y), ethnicity, date of surgery (± 1 y), and hospital location of surgery. Spine adipose index was measured on pre-operative mid-sagittal cuts of T2 weighted MRI scans. Each measurement was repeated twice by three authors in a blinded fashion, with each series of measurement separated by a period of at least six weeks.

METHODS

Stepwise binary logistic regression analysis was used to assess the association between SAI and the development of deep SSI. Separate logistic regression models were used for body mass index (BMI) and direct measures of subcutaneous fat thickness. Receiver Operating Characteristic analysis was used to determine the optimal value for SAI, and subsequent risk ratios were calculated using the identified threshold. Intra- and inter-observer reliabilities were assessed using intra-class coefficients.

RESULTS

Forty-two patients were included in final analysis, with twenty-one cases and twenty-one matched controls. The spine adipose index was significantly greater in patients developing deep SSI (p=.029), and this relationship was maintained after adjusting for confounders (p=.046). Risk of developing deep SSI following PILF surgery was increased 2.0-fold when the spine adipose index was ≥0.51. The spine adipose index had excellent (ICC >0.9; p<.001) inter- and intra-observer reliabilities.

CONCLUSION

The spine adipose index is a novel radiographic measure and an independent risk factor for developing deep SSI, with 0.51 being the ideal threshold value for pre-operative risk stratification in patients undergoing PILF surgery.

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.

Novel clinical and radiological measures of lower limb obesity

Osteoarthritis of the knee is strongly associated with central obesity, and the prevalence of obesity in patients undergoing knee arthroplasty procedures is expected to increase. Central obesity is associated with multiple adverse outcomes after knee arthroplasty, but the impact of obesity specifically around the operated knee is poorly understood. One reason for this is the absence of a standardized measure, analogous to BMI for central obesity, to facilitate research. The aim of this study was to develop a radiological limb obesity scoring system which reliably corresponds with anthropometric measurements. Detailed anthropometric and radiological measurements were taken from patients undergoing total and unicompartmental knee replacement. Anthropometric measurements were combined into a composite score using principal components analysis. Different radiological scoring methods were evaluated against the anthropometric measure using correlation and regression analyses. Intraclass correlation coefficients were used to evaluate intra- and inter-observer reliability of the radiographic measurements. Measurements were obtained from fifty patients. There was a significant correlation between the composite anthropometric score and unadjusted radiological soft tissue width at the level of the femoral condyles (p < 0.001). There was also a significant correlation with the ratio of tissue to bone widths at the same level (p < 0.001), and fit was improved by including variables coding for soft tissues overlapping the medial or lateral boundaries of the radiograph. We have demonstrated a methodology for producing standardized radiological limb obesity scores which are strongly correlated with anthropometric measurements, and which can be easily applied in diverse clinical and research settings.

Predictive value of adipose to muscle area ratio based on MRI at knee joint for postoperative functional outcomes in elderly osteoarthritis patients following total knee arthroplasty

BACKGROUND

The current research used a new index-adipose to muscle area ratio (AMR)-to measure fatness compared with body mass index (BMI) in elderly osteoarthritis (OA) patients following total knee arthroplasty. Our study aimed to test the relationship between the two indexes (AMR and BMI) and to examine whether AMR was a predictive factor of patient-reported outcome measures (PROMS) for elderly OA patients following total knee arthroplasty (TKA).

METHODS

The retrospective data of 78 OA patients (older than 60 years) following TKA was included in our study. Clinical features of patients included age, BMI, sex, AMR, side of the implant, time of follow-up, complications, the Knee Society Score (KSS score), and the Hospital for Special Surgery knee score (HSS score). The area of adipose tissue and muscle tissue was measured on the cross section (supra-patella, midline of the patella, joint line of the knee) of the knee magnetic resonance imaging (MRI). AMR was calculated as the average of adipose to muscle area ratio at the three levels. The Pearson correlation analysis, simple linear regression, and multiple linear regression were used to study the relationship between BMI, AMR, and PROMS (KSS total-post score and HSS-post score) in the study.

RESULTS

Of all patients, the mean (± standard deviations (SD)) of age was 67.78 ± 4.91 years. For BMI and AMR, the mean (± SD) were 26.90 ± 2.11 and 2.36 ± 0.69, respectively. In Pearson correlation analysis, BMI had a good correlation with AMR (r = 0.56, p = 0.000), and AMR (r = - 0.37, p = 0.001, HSS-post score; r = - 0.43, p = 0.000, KSS total-post score) had better correlations with PROMS postoperatively compared with BMI (r = - 0.27, p = 0.019, HSS-post score; r = - 0.33, p = 0.003, KSS total-post score). In multivariate linear regression analysis, AMR was negatively correlated with KSS total-post score as well as HSS-post score, while BMI was not. As for patients with complications, AMR values were between the 3rd quartile and 4th quartile of the AMR value in the entire study cohort.

CONCLUSIONS

In this study, the new obesity evaluation indicator-AMR, which was well related with BMI, was found to be a predictor of PROMS (KSS total-post score and HSS-post score) in elderly OA patients following TKA.

Increased fat depth is not associated with increased risk of surgical complications following total hip arthroplasty

AIMS

Previous research has demonstrated increased early complication rates following total hip arthroplasty (THA) in obese patients, as defined by body mass index (BMI). Subcutaneous fat depth (FD) has been shown to be an independent risk factor for wound infection in cervical and lumbar spine surgery, as well as after abdominal laparotomy. The aim of this study was to investigate whether increased peritrochanteric FD was associated with an increased risk of complications in the first year following THA.

METHODS

We analyzed prospectively collected data on a consecutive series of 1,220 primary THAs from June 2013 until May 2018. The vertical soft tissue depth from the most prominent part of the greater trochanter to the skin was measured intraoperatively using a sterile ruler and recorded to the nearest millimetre. BMI was calculated at the patient's preoperative assessment. All surgical complications occuring within the initial 12 months of follow-up were identified.

RESULTS

Females had a significantly greater FD at the greater trochanter in comparison to males (median 3.0 cm (interquartile range (IQR) 2.3 to 4.0) vs 2.0 cm (IQR 1.7 to 3.0); p < 0.001) despite equivalent BMI between sexes (male median BMI 30.0 kg/m² (IQR 27.0 to 33.0); female median 29.0 kg/m² (IQR 25.0 to 33.0)). FD showed a weak correlation with BMI (R² 0.41 males and R² 0.43 females). Patients with the greatest FD (upper quartile) were at no greater risk of complications compared with patients with the lowest FD (lower quartile); 7/311 (2.3%) vs 9/439 (2.1%); p = 0.820 . Conversely, patients with the highest BMI (≥ 40 kg/m²) had a significantly increased risk of complications compared with patients with lower BMI (< 40 kg/m²); 5/60 (8.3% vs 18/1,160 (1.6%), odds ratio (OR) 5.77 (95% confidence interval (CI) 2.1 to 16.1; p = 0.001)).

CONCLUSION

We found no relationship between peritrochanteric FD and the risk of surgical complications following primary THA. Cite this article: Bone Joint J 2020;102-B(9):1146-1150.

Greater Knee Soft Tissue Thickness Predisposes Patients to Subsequent Periprosthetic Joint Infection After Total Knee Arthroplasty

BACKGROUND

Although obesity is a risk factor for periprosthetic joint infection (PJI) after total knee arthroplasty (TKA), the role of soft tissue thickness (STT) at the surgical site has not been well studied. This study examined if increased STT in the medial and anterior aspects of the knee are independent risk factors for PJI.

METHODS

A retrospective study was conducted on 206 patients who underwent 2-stage exchange arthroplasty for PJI from 2000 to 2015. They were matched 1:3 to a control group of primary, noninfected TKA patients with minimum 2 years infection-free survival by age, gender, age-adjusted Charlson Comorbidity Index, date of surgery, and body mass index (BMI). Two blinded orthopedic surgeons measured the medial STT from the medial aspect of the knee at the level of the joint line on an anteroposterior radiograph, and anterior STT 8 cm above the joint line on a lateral radiograph from the skin to the quadriceps tendon.

RESULTS

Increased STT was significantly associated with a higher risk for PJI. The mean anterior STT was 29.74 ± 13.76 mm in the PJI group and 24.88 ± 9.76 mm in the control group. The mean medial STT was 42.42 ± 14.66 mm for PJI and 37.27 ± 12.51 mm for control. Both STT measurements were significantly higher in PJI cases with BMI <30 kg/m² vs control patients with BMI <30 kg/m².

CONCLUSION

Anterior and medial knee STT was an independent risk factor for PJI after primary TKA and represents a simple radiographic method to assess postoperative infection risk. Excess adipose tissue around the surgical site can predispose patients to PJI after TKA regardless of BMI.

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

BACKGROUND

Both body mass index (BMI) and local measures of adiposity at the surgical site have been identified as independent risk factors for periprosthetic joint infection (PJI) (periprosthetic joint infection) after total knee arthroplasty (TKA). We aimed to 1) evaluate previously used measures of assessing knee adiposity and 2) determine the best measure for predicting both surgical duration and PJI after TKA.

METHODS

We performed a multicentre retrospective review of 4745 patients who underwent primary TKA between January 2013 and December 2016. Patient demographic information, surgical duration and postoperative infection status within one year were obtained. Preoperative weight-bearing AP and lateral x-rays were analyzed to determine prepatellar adipose thickness, bony width of the tibial plateau, and total soft tissue knee width. The knee adipose index (KAI) was calculated from the ratio of bone to total knee width.

RESULTS

We observed substantial variability in both local measures of adiposity compared with BMI. Neither measure of local knee adipose showed a significant correlation with PJI risk. By contrast, there was a strong correlation between PJI risk and BMI >35 (odds ratio 2.9, 95% CI 1.4-6.1). Surgical duration increased with both BMI and measures of local adipose tissue (KAI and prepatellar fat thickness).

CONCLUSION

Local adipose deposition varies greatly for any given BMI. In this study, BMI was a better predictor of PJI after TKA than local measures of knee adipose tissue.

Pretubercular Subcutaneous Thickness Is a Protective Factor for Superficial Wound Complications After Total Knee Arthroplasty in Nonmorbidly Obese Patients

BACKGROUND

Anterior knee subcutaneous thickness has been associated with increased risk of early reoperation for surgical site infection after primary total knee arthroplasty (TKA) in morbidly obese patients. However, most patients undergoing TKA are not morbidly obese. The aims of this study were to (1) assess the association between anterior knee subcutaneous thickness and early superficial wound complications and (2) determine a threshold value for anterior knee subcutaneous thickness measures that can assist in preoperative risk stratification in nonmorbidly obese TKA patients.

METHODS

Using retrospective analysis, we reviewed 494 primary TKAs performed in patients with a body mass index <40 kg/m² at our institution from January 1, 2010 to December 31, 2017. All patients developing a superficial surgical site infection within 90 days of index arthroplasty requiring treatment with antibiotics or reoperation were identified. Prepatellar thickness and pretubercular thickness were measured on preoperative lateral radiographs and associated with 90-day superficial wound complications.

RESULTS

Sixty-two of the 494 patients developed a superficial wound complication within 90 days of index arthroplasty. TKA patients in the superficial wound complication group had significantly less pretubercular thickness (P = .027). Risk of developing 90-day superficial wound complication was 1.85-fold lower when pretubercular thickness was ≥12 mm (P = .028). Prepatellar thickness (P = .895) was not significantly associated with superficial wound complications.

CONCLUSION

Increased pretubercular thickness is a protective factor for developing superficial wound complications, with 12 mm being an ideal threshold value for preoperative risk stratification in nonmorbidly obese patients undergoing primary TKA surgery.

Does peritrochanteric fat thickness increase the risk of early reoperation for infection or wound complications following total hip arthroplasty?

Background

Radiographically measured subcutaneous peri-incisional tissue depth has been correlated with post-operative surgical site infection after cardiac, cervical spine, and total knee surgery. Its impact following primary total hip arthroplasty (THA) has not been studied. We compare the interobserver reliability of measuring peritrochanteric fat thickness on pre-operative radiographs and hypothesize that these measurements are a reproducible way to predict acute post-operative wound complications and infection in patients undergoing THA.

Methods

A retrospective case-control analysis was performed at a single institution. Patients taken to the operating room within 90 days of their primary THA for a wound complication or deep infection between 2008 and 2016 were identified. Patients <18 years old, those with history of open surgery on the affected hip, or with inadequate radiographs were excluded. Patients were matched 1:1 for gender, age, BMI, and ASA score to THA patients without early wound complications.

Results

All radiographic measurements performed were found to have excellent inter-rater reliabilities (range 0.96-0.98). There was no difference in peritrochanteric fat thickness measurements between the two groups including the sourcil to skin surface (89.5 mm vs. 91.9 mm, p = 0.5), tip of greater trochanter to skin surface (52.9 mm vs. 53.7 mm, p = 0.8), and lateral greater trochanter to skin surface (36.0 mm vs. 37.8 mm, p = 0.6) measurements.

Conclusion

Contrary to other previously reported surgical procedures, radiographic measurement of subcutaneous depth is not a valid tool for predicting a return to the OR for wound complications in the early post-operative period following primary total hip arthroplasty.

Internal Validation of a Predictive Model for Satisfaction After Primary Total Knee Arthroplasty

BACKGROUND

As the number of total knee arthroplasty (TKA) procedures continues to rise in the context of bundled payment models, patients dissatisfied postoperatively that require additional care will impose additional cost to the healthcare system. The purpose of this study is to internally validate a predictive model for postoperative patient satisfaction after TKA.

METHODS

In total, 484 consecutive primary TKA patients between January 2014 and January 2016 were included. Patients were stratified into 4 risk tiers based on scores of a retrospectively applied, 11-component novel knee survey for postoperative satisfaction: low risk (>96.5), mild risk (75-96.4), moderate risk (60-74.9), and high risk (<60). Binary logistic and multivariate linear regression models were constructed to determine whether the survey was predictive of satisfaction. A receiver operator curve was constructed to determine a threshold score below which patients were likely to experience postoperative dissatisfaction.

RESULTS

The mean (±standard deviation) age was 66.3 ± 9.2 years (range 31.7-100.1) and mean body mass index was 34.2 ± 8.2 kg/m² (range 16.2-68.4). A knee survey score of 96.5 conferred a 97.5% sensitivity and 95.7% negative predictive value for satisfaction. Patients with higher knee survey scores had greater odds (odds ratio 1.03, 95% confidence interval 1.01-1.06, P = .003) of postoperative satisfaction. Increasing risk tier was significantly associated with decreased satisfaction (low risk 95.7%, mild risk 93.8%, moderate risk 86.4%, and high risk 80.4%; P = .007). The knee survey was not significantly correlated with complications (r = -0.43, P = .32).

CONCLUSION

This novel knee survey conferred a 97.5% sensitivity and 95.7% negative predictive value in identifying at-risk patients for postoperative dissatisfaction after primary TKA.

Modifiable and Nonmodifiable Predictive Factors Associated with the Outcomes of Total Knee Arthroplasty

Total knee arthroplasty (TKA) is a valuable treatment option for advanced osteoarthritis in patients unresponsive to conservative treatments. Despite overall satisfactory results, the rate of unsatisfied patients after TKA remains high, ranging from 5 to 40%. Different modifiable and nonmodifiable prognostic factors associated with TKA outcomes have been described. The correction, whenever possible, of modifiable factors is fundamental in preoperative patients' optimization protocols. Nonmodifiable factors can help in predicting the outcomes and creating the right expectations in the patients undergoing TKA. The goal of this review is to summarize the modifiable and nonmodifiable prognostic factors associated with TKA outcomes.

Internal Validation of a Predictive Model for Complications After Total Hip Arthroplasty

BACKGROUND

Total hip arthroplasty (THA) is projected to increase in prevalence and associated complications will impose significant cost on the US healthcare system. The purpose of this study is to validate a predictive model for postoperative complications utilizing a novel 11-component hip-specific questionnaire encompassing preoperatively available clinical and radiographic data.

METHODS

Consecutive primary THA patients between January 2014 and January 2016 were included. Exclusion criteria included patients without questionnaire scoring variables and less than 1-year follow-up. Patients were stratified into 4 tiers based on their questionnaire score: low risk (>74), mild risk (57-73), moderate risk (41-56), and high risk (<40). A binary logistic regression was performed to determine if the questionnaire predicted complications. Receiver-operator curves were constructed to determine the threshold score below which there was a high likelihood of experiencing a complication.

RESULTS

Four hundred fifty patients were included in the final analysis with a mean (range) follow-up of 2.1 years (1.0-5.9), age of 63.1 years (25.7-9.17), and body mass index of 31.7 kg/m² (17.8-64.5). The complication rate was 13.6%. A hip questionnaire score of 73.8 conferred a 98.5% sensitivity and 98.5% negative predictive value for complications. The questionnaire score was the strongest predictor of a decreased complication likelihood (odds ratio 0.94, 95% confidence interval 0.90-0.97, P < .001). Risk tier was significantly associated with complications (low risk: 0; mild risk: 12; moderate risk: 25; and high risk: 24; P < .001).

CONCLUSION

This novel hip questionnaire demonstrated a high sensitivity and negative predictive value to identify patients at risk for postoperative complications. Future studies should attempt to prospectively validate the use of this questionnaire.

Prospective Study of Central versus Peripheral Obesity in Total Knee Arthroplasty

PURPOSE

Body mass index (BMI) is often used to predict surgical difficulty in patients receiving total knee arthroplasty (TKA); however, BMI neglects variation in the central versus peripheral distribution of adipose tissue. We sought to examine whether anthropometric factors, rather than BMI alone, may serve as a more effective indication of surgical difficulty in TKA.

MATERIALS AND METHODS

We prospectively enrolled 67 patients undergoing primary TKA. Correlation coefficients were used to evaluate the associations of tourniquet time, a surrogate of surgical difficulty, with BMI, pre- and intraoperative anthropometric measurements, and radiographic knee alignment. Similarly, Knee Injury and Osteoarthritis Outcome Score (KOOS) was compared to BMI.

RESULTS

Tourniquet time was significantly associated with preoperative inferior knee circumference (p=0.025) and ankle circumference (p=0.003) as well as the intraoperative depth of incision at the quadriceps (p=0.014). BMI was not significantly associated with tourniquet time or any of the radiographic parameters or KOOS scores.

CONCLUSIONS

Inferior knee circumference, ankle circumference, and depth of incision at the quadriceps (measures of peripheral obesity) are likely better predictors of surgical difficulty than BMI. Further study of alternative surgical indicators should investigate patients that may be deterred from TKA for high BMI, despite relatively low peripheral obesity.

Lower Extremity Geometry in Morbid Obesity-Considerations for Total Knee Arthroplasty

BACKGROUND

Obesity has been associated with varying adverse outcomes related to total knee arthroplasty (TKA) and has long been associated with various mechanical complications. Computational modeling holds promise for investigating biomechanical aberrations related to TKA in obese patients. However, basic anthropometric information regarding the shape of the lower extremity in obese patients is lacking. We, therefore, developed a method to determine lower extremity shape both generally and subject specific as a function of body mass index (BMI) and sex.

METHODS

A unique set of 4 radiographs (knee anteroposterior/lateral; EOS long-leg alignment anteroposterior/lateral) were reviewed for patients with BMI exceeding 30 kg/m² before undergoing TKA. Soft tissue thickness in both the coronal and sagittal planes, including anterior adipose tissue thickness overlying the tibial tubercle and patella, was measured. Elliptical parameters were then determined for any distance along the lower extremity. Additional measurements were obtained, including prepatellar thickness and pretubercular thickness and anteroposterior and mediolateral dimensions of the proximal tibia. A total of 232 obese subjects were analyzed.

RESULTS

Girth increased as a function of BMI. Anterior prepatellar and pretubercular subcutaneous fat thickness in females exceeded that in males for all values of BMI. Wide variation was seen with regard to overall patterns of adiposity among same-sex subjects with similar BMI. Proximal tibial osseous dimensions did not demonstrate an association with BMI; however, males were found to have deeper and wider tibias compared with females.

CONCLUSIONS

BMI and sex influence lower extremity shape. The prediction algorithms developed here holds implications for future biomechanical studies of TKA in obese patients.

Complications and Obesity in Arthroplasty-A Hip is Not a Knee

BACKGROUND

Obesity has previously been demonstrated to be an independent risk factor for increased complications after total hip and knee arthroplasties (THA and TKA). The purpose of this study was to compare the effects of obesity and body mass index (BMI) to determine whether the magnitude of the effect was similar for both procedures.

METHODS

We queried the American College of Surgeons National Surgical Quality Improvement Program database to identify patients who underwent primary THA or TKA between 2010 and 2014. Patients were stratified by procedure and classified as nonobese, obese, or morbidly obese according to BMI. Thirty-day rates of wound complications, deep infection, total complications, and reoperation were compared using univariate and multivariate logistic regression analyses.

RESULTS

We identified 64,648 patients who underwent THA and 97,137 patients who underwent TKA. Obese THA patients had significantly higher rates of wound complications (1.53% vs 0.96%), deep infection (0.31% vs 0.17%), reoperation rate (2.11% vs 1.02%), and total complications (5.22% vs 4.63%) compared with TKA patients. Morbidly obese patients undergoing THA were also found to have significantly higher rates of wound complications (3.25% vs 1.52%), deep infection (0.84% vs 0.23%), reoperation rate (3.65% vs 1.60%), and total complications (7.36% vs 5.57%). Multivariate regression analysis identified increasingly higher odds of each outcome measure as BMI increased.

CONCLUSION

This study demonstrates that the impact of obesity on postoperative complications is more profound for THA than TKA. This emphasizes the importance of considering patient comorbidities in the context of the specific procedure when assessing risks of surgery.

The Radiographic Prepatellar Fat Thickness Ratio Correlates With Infection Risk After Total Knee Arthroplasty

BACKGROUND

Obesity has been associated with complications after a total knee arthroplasty (TKA). Surgical site infection (SSI) after TKA is one of the feared complications as it increases revision rates, costs, and stress to the patient. There is conflicting evidence in the literature regarding body mass index (BMI) and risk of infection after TKA, and some studies have suggested that site-specific fat distribution may be a better metric for determining risk of postoperative infections. Here, we investigate the correlation of soft tissue distribution about the knee to SSI after TKA.

METHODS

We retrospectively review 572 patients who underwent primary TKA at a single institution from 2006 to 2010. We introduce the prepatellar fat thickness ratio (PFTR) as a radiographic means to quantitatively assess fat distribution about the knee and evaluate this measurement's ability to assess the risk of developing an SSI after TKA.

RESULTS

The PFTR was shown to be a better predictor of SSI than BMI in both the univariate (P = .05) and multivariate (P = .01) analyses.

CONCLUSION

Although BMI cannot fully account for variations in adipose distribution, the PFTR may account for this variability and may be a helpful tool for assessing a patient's preoperative risk of SSI after TKA.

Periarticular Soft Tissue Envelope Size and Postoperative Wound Complications Following Total Knee Arthroplasty

BACKGROUND

Periprosthetic joint infection following total knee arthroplasty (TKA) is a serious complication often related to obesity which leads to poor patient outcomes and increased resource utilization. A periarticular soft tissue index (PASTI) may help predict postoperative wound complications than BMI alone.

METHODS

Three hundred seventy-six TKA patients with a preoperative, lateral knee X-ray radiograph and 1 year of follow up were analyzed. We used 2 pairs of soft tissue and bony measurements, one referencing the femur and the other the tibia. A high PASTI was defined as a ratio >3.0. Minor complications involved clinical interventions related to the surgical wound. Major complications involved return to the operating room.

RESULTS

More minor complications occurred in high PASTI for both tibial (20.9% vs 6.4%; odds ratio 3.89, 95% confidence interval 1.94-7.79, P < .001) and femoral measurements (15.3% vs 7.2%; odds ratio 2.09, 95% confidence interval 1.06-4.15, P = .013). Major complications were also more frequent in high PASTI, though not statistically significant. The proportion of obesity (BMI > 30) in both minor (12.4% vs 7.7%, P = .140) and major complications (2.8% vs 3.3%, P = .788) was not statistically different.

CONCLUSION

More wound complications occurred in patients with high PASTI, while no difference was seen using BMI. BMI has traditionally approximated patient size, but does not describe variations in body habitus. PASTI is a more reliable and direct way to assess the periarticular soft tissue envelope size, which is associated with postoperative wound complications in the knee.