Abstract. Introduction. There is a longstanding presumed association between obesity, complications, and revision surgery in primary knee arthroplasty. This has more recently been called into question, particularly in centres where a high volume of arthroplasty is performed. We investigated the correlation between Body Mass Index (BMI), mortality, and revision surgery. Method. This was a cohort study of at least 10 years following primary knee arthroplasty from a single high volume arthroplasty unit. Mortality and revision rates were collected from all patients who underwent primary knee arthroplasty between 2009 and 2010. Kaplan Meier analysis was performed. Results. There were 1161 female and 948 male patients with a mean age of 69 (21 to 97). All cause survivorship excluding mortality was 97.2% up to 13yrs with a minimum of 10 years. The revision rate in this series was 2.8% with no significant difference in revision rates after 10 year between patients with BMI above and below 40 (p=0.438). There was no significant difference in 10-year mortality between patients above and below a BMI of 40 (p=0.238). Conclusion. This study shows no significant difference in the long term survival of total knee replacement between patients with normal and high BMI. Careful consideration should be given before rationing surgery based on BMI alone

There is a longstanding presumed association between obesity, complications, and revision surgery in primary knee arthroplasty. This has more recently been called into question, particularly in centres where a high volume of arthroplasty is performed. We investigated the correlation between Body Mass Index (BMI), mortality, and revision surgery. This was a cohort study of at least 10 years following primary knee arthroplasty from a single high volume arthroplasty unit. Mortality and revision rates were collected from all patients who underwent primary knee arthroplasty between 2009 and 2010. Kaplan Meier analysis was performed. There were 1161 female and 948 male patients with a mean age of 69 (21 to 97). All cause survivorship excluding mortality was 97.2% up to 13yrs with a minimum of 10 years. The revision rate in this series was 2.8% with no significant difference in revision rates after 10 year between patients with BMI above and below 40 (p=0.438). There was no significant difference in 10–year mortality between patients above and below a BMI of 40 (p=0.238). This study shows no significant difference in the long term survival of total knee replacement between patients with normal and high BMI. Careful consideration should be given before rationing surgery based on BMI alone

While obesity is associated with an increased risk of complications after total hip arthroplasty (THA) the relationship between body mass index (BMI) and the risk of early postoperative complications has not been fully characterized. This study sought to describe the relationship between BMI and the risk of early postoperative complications, including periprosthetic joint infection (PJI), composite surgical, and composite medical complications. Primary, elective THAs performed from 2016–2021 were identified using the Premier Healthcare Database (PHD). The study's primary outcome was the diagnosis of PJI within 90 days of THA. Using BMI as a continuous variable, logistic regression was used to develop restricted cubic splines (RCSs) to determine the impact of BMI on PJI risk. Bootstrap simulation was used to identify an inflection point in the final RCS model. The same technique was used to characterize the effects of BMI on composite medical and surgical complications. We found that PJI risk increased exponentially beyond a BMI cutpoint of 37.4 kg/m. 2. Relative to the cutpoint, patients with a BMI of 40 or 50 kg/m. 2. were at a 1.22- and 2.55-fold increased risk of developing PJI, respectively. Surgical complications increased at a BMI of 32 kg/m. 2. and medical complications increased at a BMI of 39 kg/m. 2. Relative to these cutpoints, patients with a BMI of 50 kg/m. 2. were at a 1.36- and 2.07-fold increased risk of developing medical and surgical complications, respectively. The results of this study indicate a non-linear relationship between patient BMI and early postoperative risk of PJI, composite medical complications, and composite surgical complications following THA. The identified cutpoints with associated odds ratios can serve as tools to help risk-stratify and counsel patients seeking primary THA

The need for hip and knee replacement surgery is increasing. Enhanced recovery programmes, where patients mobilise quickly and safely after surgery, have been adopted now in many hospitals. There are anecdotal reports of Primary Care Trusts raising thresholds for referral for surgery based on patients' Body Mass Index (BMI). The aim of this study was to evaluate the early outcome of hip and knee arthroplasty in obese patients (BMI>30) enrolled in the enhanced recovery programme. Between March 2010 and January 2011, 672 patients were enrolled in our enhanced recovery programme. 316 patients (47%) were classified as obese (BMI>30, range 30-39). There was no significant difference in the length of stay: 4.58 days in the obese patients and 4.44 days in the non-obese. There was also no difference in the rates of superficial infections or oozy wounds. Knee replacements was performed more commonly than hip replacements in the obese group. There was no significant difference in the early outcome of hip and knee replacement surgery in patients with a higher Body Mass Index when undergoing lower limb arthroplasty through the enhanced recovery programme. These patients should continue to be offered surgery when clinically indicated

Introduction. Obesity has been considered a relative contra-indication in unicompartmental knee arthroplasty (UKA) due to fear of high wear rates, loosening and tibial collapse. The aim of this study was to investigate the impact of high body mass index (BMI) on ten-year survivorship and five-year functional outcome after Oxford UKA, a fully congruous mobile bearing design with large contact area and low wear rate. Methods. This prospective study examines a consecutive series of 595 knees (mean age 66 years, range: 33-88) undergoing Oxford UKA with a minimum 5-year follow-up. Patients were divided into three groups; Group I (Normal body weight), BMI <25 (n=171), Group II (overweight), BMI 25- 30 (n=264), and Group III (Obese), BMI ≥30 (n=160). The survivorship and functional outcome (as assessed by change in Oxford Knee Score [DeltaOKS]) and Knee Society Score (KSS) for all three groups were compared. Results. The mean follow-up was 6.3 years. There was no significant difference in the 10-year survivorship between groups (96% for all groups). Although numbers were small there was no significant difference in revision rates for patients with BMI ≥35 (n=1/38). Group III patients had a lower pre-operative OKS and lower post-operative OKS compared to groups I and II, although DeltaOKS was similar (p= .977). At last follow-up the Functional KSS was lower in group III (p=.11), although Objective KSS was not significantly different between groups (p=.954). Conclusion. Oxford UKA can be safely used in obese and morbidly-obese patients. Design features of congruous bearing and large contact area ensure low wear rates. Summary. No significant difference in revision rates noted between groups of increasing body mass index in this prospective study of outcome in patients undergoing medial Oxford unicondylar knee replacement

Background: The purpose of this study was to evaluate the relationship between body mass index and early complications following total knee joint replacement surgery. Methods: 527 patients who underwent a primary knee replacement were included in this study. All these patients were subjected to a pre-operative assessment and then followed up at six weeks and one year following surgery. Any complication that occurred during this period was recorded. Complications were grouped into systemic and local, each group being subdivided into minor and major. Collected data were analysed by the SPSS version 12. Chi-square tests, t-test analysis, univariate logistic regression studies and multivariate analysis were performed. Results: 64 patients (12,1%) were found to have an early complication following knee replacement surgery. 36 patients (6.8%) were found to have a major local complication. Overall BMI did not seem to influence the rate of complication. After stratification of patients per BMI, there appeared to be a weak correlation between BMI and early complications but this was not statistically significant. A stronger correlation was found between the surgeon and presence of complication. Conclusions: BMI has a weak correlation to early complications following joint replacement surgery. The operating surgeon seems to have a stronger correlation to early complications as compared to BMI

Introduction. Implementing operative eligibility thresholds based on body mass index (BMI) alone risks restricting access to improved pain, function, and quality-of-life. The purpose of this study was to: 1) investigate the relationship between BMI and improvements in 1-year patient reported outcome measures (PROMs), and 2) determine how many patients would have been denied 1-year improvements with specific BMI cut-offs. Methods. Data were collected on a prospective cohort of 3,214 TKA patients from 2015–2018. Clinically meaningful 1-year improvements were defined as 15 points for Knee Injury and Osteoarthritis Outcome Scores (KOOS) pain and Physical Function Shortform (PS), and 14 points for Knee-Related Quality-of-Life (KRQOL). For specific BMI cut-offs, the positive predictive value for predicting a failure to improve and number of patients denied surgery to avoid one failed improvement was calculated. Results. PROMs improvements were greater with increasing BMI. Patients with BMI ≥40 kg/m. 2. had median (Q1, Q3) KOOS pain improvements of 47.2 points (33.3, 58.3) and those with BMI 18.5–24.9 kg/m. 2. had median improvements of 41.7 (27.8, 55.6). Similar findings were observed for KOOS PS (28.4 vs. 26.3) and KRQOL (50.0 vs. 43.8). With a BMI cut-off of 30 kg/m. 2. , 9 patients would have been denied improvements from surgery for each failed improvement avoided whereas with a BMI cut-off of 50 kg/m. 2. , 15 patients would have been denied improvements from surgery. Implementing BMI thresholds alone did not influence the rate of improvements in KOOS-PS or KRQOL. Conclusion. Patients with higher BMI were observed to have greater improvements in PROMs after primary TKA. Enforcing arbitrary BMI cut-offs would deprive pain and functional improvements from patients who would benefit the most. Moreover, there appears to be no increase in the rate of PROMs improvements by enforcing BMI thresholds. This study demonstrates that determining TKA eligibility should involve a holistic approach rather than limiting to BMI measurements alone

Perioperative blood management remains a challenge during total hip and total knee arthroplasty (THA and TKA, respectively). The purpose of this study was to determine the impact of body mass index (BMI) on blood transfusion in THA and TKA. We retrospectively evaluated 2399 patients, of whom 896 underwent THA and 1503 had TKA. A variety of outcome variables were assessed for their relationship to BMI which was stratified using the World Health Organization (WHO) classification scheme (Normal <25 kg/m2, Overweight 25–30, and Obese >30). Increased BMI was found to be protective of blood transfusion in both THA and TKA patients. Among THA patients, transfusion rates were 34.8%, 27.6% and 21.9% for normal, overweight and obese categories respectively (p = 0.002). TKA transfusion rates were 17.3%, 11.4% and 8.3% for the same categorization of BMI (p = 0.002). No trends were identified for a relationship between BMI and deep vein thrombosis, pulmonary embolism, myocardial infarction, discharge location, length of stay, 30-day readmission rate and preoperative hemoglobin level. Elevated BMI was significantly associated with decreased age, increased Hemoglobin A1c, increased baseline creatinine, increased OR time, increased American Society of Anesthesiologists (ASA) score and increased estimated blood loss in both THA and TKA patients. There was a statistically significant trend toward increased deep surgical site infection in THA patients (p = 0.043)

There is little evidence describing the influence of body mass index on the outcome of Total Hip Replacement (THR). There are concerns that an increasing BMI may lead to increased blood loss, infection and venous thromboembolism. 800 consecutive patients undergoing primary cemented THR were followed for a minimum of 18 months. The Harris Hip Score (HHS) and SF-36 were recorded pre-operatively and at 6 and 18 months post-operatively. In addition other significant events were noted, namely death, dislocation, re-operation, superficial and deep infection and blood loss. Multiple regression analysis was performed to identify whether BMI was an independently significant predictor of the outcome of THR. No relationship was seen between the BMI of an individual and the development of any of the complications noted. The HHS was seen to increase dramatically post-operatively in all patients. BMI did predict for a lower HHS at 6 and 18 months, and a lower physical functioning component of the SF-36 at 18 months. This effect was small when compared with the overall improvements in these scores. Conclusion: THR provides good symptomatic relief irrespective of BMI. On the basis of this study we can find no justification for withholding THR solely on the grounds of BMI

Introduction. Maximizing efficiency in total knee replacement surgery is desirable and one of the key aspects is optimum utilization of available theatre time allocation. The level of complexity of the pathology is often one of the determinants of the length of operative time. Body mass index (BMI) has also been positively correlated with operative time. However, two patients with the same BMI but different body habitus (central obesity vs generalized obesity) may present different challenges during surgery. An index focusing on the anthropometry of the lower limb (supra-patella index SPI) has been proposed and we hypothesize that it correlates more closely with operative time than BMI. Method. BMI and SPI were determined in all patients recruited into a prospective trial of a specific knee implant. All patients were operated on by one of two surgeons in a standardized manner. Data including operative time and tourniquet time were determined. Results. Data for BMI was available on 50 patients and 46 patients had SPI values. The mean BMI was 34, 3 (sd 7.6) and 74% of patients were obese. The mean SPI was 2, 3 (sd 3.2). Both the BMI and SPI correlated with operative time and tourniquet time using the Spearman rank-order correlation coefficient. The BMI correlated marginally better with the operative time and the SPI correlated marginally better with the tourniquet time. Conclusion. Both BMI and SPI correlated with operative time. Both indices can be used as predictors of operative time. ONE DISCLOSURE

Introduction: There is little evidence describing the influence of Body Mass Index (BMI) on the outcome of Total Hip Replacement (THR). There are concerns that an increasing BMI may increase complication rates such as superficial and deep infection, blood loss, operation time and aseptic loosening. There is evidence that obese patients receive good symptomatic relief from THR and so it is important that the advisability of surgery is made on good evidence. Methods: 800 patients undergoing primary Charnley total hip replacement were followed prospectively for a minimum of 18 months. The Harris Hip Score (HHS) and SF-36 were recorded pre-operatively and at 6 and 18 months post-operatively. Other significant events were noted, namely death, dislocation, re-operation, superficial and deep infection and blood loss. Stepwise multiple regression analysis was performed to identify whether BMI was an independently significant predictor of the outcome of THR. Results: The mean age of patients was 68 years, with 61% females. At 18 months 31 patients (39 hips) had died. There were 15 re-operations, 13 dislocations and 7 deep infections. No relationship was seen between the BMI of an individual and the development of post-operative complications. The HHS was seen to increase dramatically postoperatively in all patients (mean 43 points at 18 months). BMI did predict for a lower HHS at 6 and 18 months and a lower physical functioning score on the SF-36. Discussion: THR produces a significant improvement in symptoms in patients, irrespective of BMI. An increasing BMI does not result in an increase in the early complication rate following THR. There is a reduction in the HHS and physical function component of SF-36 with increasing BMI, although this effect is small. On the basis of this study we do not think that THR should be withheld solely on the grounds of BMI

Aim. Computer-navigated total knee arthroplasty has been shown to improve the outcome in outliers with consistent results. The aim of this study is to evaluate the clinical and radiographic outcomes of computer-navigated knee arthroplasty with respect to deformity and body mass index (BMI). Materials and Methods. Data was prospectively collected for 117 consecutive patients undergoing primary computer-navigated total knee arthroplasty using Ci Brainlab system with J&J PFC PS implants by a single surgeon utilising a tibia cut first, gap-balancing technique. Pre-operative and post-operative long-leg films, weight-bearing, films were taken and the long-axis was measured by a single observer. Intra-operative computer navigation long-axis values were stored as screenshots intra-operatively after registration and after implant was cemented. BMI, range of motion (ROM), SF 36 and Oxford knee scores were recorded both before surgery and on follow-up. Minimum 2-year follow-up. Eight patients were lost to follow-up and 8 had incomplete 2 year data. Data was analysed using the Chi-squared test for categorical variables and the t-test for continuous variables. Results. Eighty-four (83.2%) female, 17 (16.8%) male patients age 65.3±6.9 years with a pre-operative BMI of 27.2±4.1 (18.6 to 40.0). Eighty-eight (87.1%) met the Singapore definition of overweight with BMI>23 kg/m2. Forty-two (41.6%) had a BMI>27.5 kg/m2 indicative of obesity in Singapore. Pre-operative radiographic axis was 9.3±10.6° varus. Thirty (29.7%) patients had a pre-operative coronal plane deformity of more than 15°. Meanoperative duration 96.0±10.7 mins. Post-operative radiographic axis was 0.05±3.0° valgus. Significant improvement was seen in knee extension, knee flexion, SF 36 and Oxford knee scores at 2 years. No significant improvement in extensor lag and straight leg-raising at 2 years. Pre-operative axis >15° was not significantly related to operative duration. BMI>23 kg/m2 was significantly related to longer operative time (88.8±10.8 vs. 97.1±10.3 min, p<0.021). BMI >27.5 kg/m2 not significantly related to operative duration, pre-operative SF36 or Oxford knee scores. Post-operative axis deviation of more than 3° not significantly related to BMI > 23 or 27.5 kg/m2, similar to post-implant navigation axis. BMI >23 kg/m2 not significantly related to 2 year SF36, Oxford knee score and range of motion at 2 years. BMI >27.5 kg/m2 not significantly related to 2 year SF36 or Oxford knee scores. Conclusion. Although restoration of coronal alignment even in deformity >15° is possible with computer navigation, post-operative extensor lag and weakness is still a problem determined by pre-operative extensor lag and weakness in straight leg raising. Computer navigation is useful when exposure and landmarks to assess alignment are difficult such as in obesity where the standard external tibia jig doesn't sit well with the thick subcutaneous layer and for determining the epicondylar axis of the femur in a deep wound. Despite the technical challenges of performing a total knee arthroplasty with obesity, BMI is not a determinant of functional scores when computer navigation is used

All over the world, obesity rates are on the rise. Medical complications and increased health risks are often associated with being overweight or obese, but a thorough understanding of in vivo motions for obese, overweight and normal weight subjects does not exist. Therefore, the objective of this study was to compare knee kinematics in TKA subjects by body mass index (BMI). In vivo knee kinematics were determined for 253 TKA subjects during a Deep Knee Bend (DKB) from full extension to maximum flexion using a 3D to 2D image registration technique. Each of these subjects was then classified into one of three BMI categories: obese (BMI greater than or equal to 30), overweight (BMI greater than or equal to 25 and less than 30) and normal weight (BMI less than 25 and greater than or equal to 18.5). Subjects were provided by 11 surgeons using ten different TKA devices. All subjects were deemed clinically successful. On average, weight bearing range of motion (ROM) for the obese (n=79), overweight (n=113) and normal weight (n=61) groups were 107.7° (range: 74° to 136°, standard deviation (σ) =14.9°), 109.6° (60° to 150°, σ=17.5°) and 114.1° (72° to 147°, σ=14.4), respectively. ROM of 90° or less was seen in 16.5% of the obese subjects, 14.2% of the overweigh subjects and 6.6% of the normal weight subjects. ROM of 125° or more was seen in 15.2% of the obese subjects, 16.8% of the overweight subjects and 23.0% of the normal weight subjects. From full extension to maximum flexion the obese, overweight and normal weight groups averaged 8.65° (−5.14° to 22.51°, σ=6.22°), 7.58° (−2.85° to 24.72°, σ=5.71°) and 5.72° (−4.84° to 19.43°, σ=5.65°) of axial rotation. Axial rotation of 3° or less was seen in 20.25% of the obese subjects, 23.01% of the overweight subjects and 39.34% of the normal weight subjects. Axial rotation of greater than 9° was seen in 51.90% of the obese subjects, 35.40% of the overweight subjects and 26.23% of the normal weight subjects. Opposite axial rotation was seen in 8.86% of the subjects in the obese group, 9.73% of the overweight group and 9.84% of the normal weight group. On average, from full extension to maximum flexion, the medial condyle for the obese, overweight and normal weight groups experienced −5.44mm (−22.20mm to 8.04mm, σ=7.9mm), −6.30mm (−25.22mm to 5.35mm, σ=7.36mm) and −4.78mm (−20.79mm to 5.49mm, σ=6.68mm) of posterior femoral rollback (PFR), respectively. The obese, overweight and normal weight groups averaged −12.66 mm (−34.57mm to 0.34mm, σ=9.32mm), −12.38mm (−36.72mm to 1.83mm, σ=10.33mm) and −9.39 mm (−34.55mm to 0.35mm, σ=8.98mm) of lateral PFR, respectively. Condylar lift-off of greater than 1mm was seen in 16.46% of obese subjects, 10.62% of overweight subjects and 11.48% of normal weight subjects. Various statistical differences were seen across the groups. The normal weight subjects had significantly higher ROM that the obese subjects (p=0.0184), while there was no difference seen between the normal weight and overweight groups or the overweight and obese groups. The obese and the overweight groups had significantly more axial rotation than the normal weight group from 0° to 90°, 0° to maximum flexion, 30° to 90°, 30° to maximum flexion and 60° to 90°. There were a significantly higher number of cases of condylar lift-off for obese subjects when compared to both normal weight and overweight groups. It can be concluded that body mass index does play a factor in TKA kinematics

Purpose: Osteoarthritis (OA) is the most common form of arthritis in the United States and according to the National Institutes of Health, affects over 21 million people. This degenerative joint disease has repeatedly been linked to obesity. It is hypothesized that obesity, defined as a body mass index (BMI) over 30 kg/m2, increases the incidence of OA through increased joint pressure and disruption of normal metabolism. The actual changes in metabolism resulting from obesity and possibly preceding OA have not been thoroughly investigated. The purpose of this study was to identify the relationship between chondrocyte metabolism and BMI in osteoarthritic tissue. Method: Grade 0 or 1 cartilage was removed from the medial and/or lateral femoral condyles after total knee arthroplasty. Isolated chondrocytes were then resus-pended in alginate beads at 2×106 cells/mL. The beads were equilibrated in media containing 10% fetal bovine serum for 7 days (37°C) and then separated into wells (8 beads/well) with 1 mL media. Media was replaced every 48 hours. At day 5, 9, and 13 days, glycosamino-glycan (GAG) content was measured in the cell pellet, alginate, and saved media using the dimethylmethylene blue (DMMB) assay. The DMMB results were normalized to DNA content. All procedures were approved by the University of Wisconsin – Madison, Institutional Review Board. Results: At day 5, the average normalized GAGs from the obese group (BMI > 30 kg/m2) was > 4-fold higher than the average normalized GAGs in the non-obese group (BMI < 30 kg/m2). The 4-fold difference in normalized GAGs continued at day 9 with significance (p=0.0087) and widened at day 13, without significance. Some osteoarthritic knees had less tissue quality, therefore GAG testing was limited to earlier study days resulting in variable sample numbers for each study day. Conclusion: The study results reveal a significant relationship between normalized GAGs and BMI in this population of osteoarthritic patients, supporting the connection between osteoarthritis and obesity previously reported. Higher patient BMI (> 30 kg/m2) may be similar to dynamic compression injuries that cause increased GAG synthesis in response to cartilage damage. In conclusion, elevated normalized GAGs in obese patients’ chondrocytes suggests increased cartilage damage

The aim of this study was to determine if patient reported outcome scores for arthroscopic meniscectomy are adversely affected by the degree of knee osteoarthritis or patient body mass index (BMI). All patients who underwent arthroscopic meniscectomy within the NHS in Scotland between 6th February and 29th April 2012 were audited as part of the Scottish Government Musculoskeletal Knee Arthroscopy Audit and were eligible for inclusion within this study. A total of 270 patients returned both their pre-operative and post-operative EuroQol 5Q5D5L descriptive questionnaire and Knee injury and Osteoarthritis Outcomes Scores. Patients were stratified according to BMI, degree of osteoarthritis, history of injury, and duration of knee symptoms. Pre-operative to post-operative EuroQol index scores [0.642±0.253 to 0.735±0.277, median±SD] and Knee injury and Osteoarthrtis Outcome Scores [44.63±18.78 to 62.28±24.94, median±SD] improved across all patients (p<0.0001). This was irrespective of degree of BMI, history of injury, or duration of symptoms. There was no such improvement in patients with moderate to severe osteoarthritis. Those patients with a BMI >35 kg/m2 had lower post-operative scores than the pre-operative scores of those of BMI <30 kg/m2. Arthroscopic meniscectomy is beneficial regardless of patient BMI, duration of symptoms, history of injury, or in the presence of mild arthritis

Introduction. Obesity is known to influence surgical risk in total hip replacement (THR), with increased Body Mass Index (BMI) leading to elevated risk of complications and poorer outcome scores. Using a multinational trial data of a single implant, we assess the impact of BMI and regional variations on Harris Hip scores (HHS). Method. We assessed BMI in 11 regional centres and associations with HHS at one year. Data were collected from 744 patients prospectively from 11 centres in the UK, Germany, Switzerland, Austria, New Zealand and Netherlands as part of a multicentre outcome trial. All Arthroplasties used RM Pressfit vitamys components (Mathys, Switzerland). Demographic, operative data and HHS were analysed with General Linear Model Anova, Minitab 16 (Minitab Inc, Pennsylvania). Results. 744 patients were included with mean age 70.0yrs (30.5–93.1, SD 10yrs) with 58.3% female distribution. Mean BMI was 27.7 (16.7–47.1 SD 4.7). The most frequent approach was Posterior in 48.5% cases, Anterior 18.1%, Anterolateral 16.9% and Lateral 15.7%. The study included patients from Austria 6.4%, Germany 20.2%, Netherlands 34.6%, NZ 6.9%, Switzerland 24.2% and UK 39.5%. The greatest proportion of high risk BMI >40 were performed in the UK 4.4% and NZ 5.9% with Germany and the Netherlands operating on high BMI patients <1% of the time. The UK had the highest proportion of overweight (BMI >30) patients at 39%. The greatest proportion of BMI <25 patients were found in the Netherlands, NZ and Switzerland at over one third. Higher BMI was associated with improvements in HHS (p=0.043). Age and Approach had no influence on outcome scores. Discussion. Higher BMI positively correlates with a greater improvement in Harris Hip score showing that obese patients benefit more from THR. No differences were observed with age, approach or gender. Conclusion. Although higher risk, this study shows obese patients benefit more from THR

Obesity is an increasing public health concern associated with increased perioperative complications and expense in lumbar spine fusions. While open and mini-open fusions such as transforaminal lumbar interbody fusion (TLIF) and minimally invasive TLIF (MIS-TLIF) are more challenging in obese patients, new MIS procedures like oblique lateral lumbar interbody fusion (OLLIF) may improve perioperative outcomes in obese patients relative to TLIF and MIS-TLIF. The purpose of this study is to determine the effects of obesity on perioperative outcomes in OLLIF, MIS-TLIF, and TLIF. This is a retrospective cohort study. We included patients who underwent OLLIF, MIS-TLIF, or TLIF on three or fewer spinal levels at a single Minnesota hospital after conservative therapy had failed. Indications included in this study were degenerative disc disease, spondylolisthesis, spondylosis, herniation, stenosis, and scoliosis. We measured demographic information, body mass index (BMI), surgery time, blood loss, and hospital stay. We performed summary statistics to compare perioperative outcomes in MIS-TLIF, OLLIF, and TLIF. We performed multivariate regression to determine the effects of BMI on perioperative outcomes controlling for demographics and number of levels on which surgeries were operated. OLLIF significantly reduces surgery time, blood loss, and hospital stay compared to MIS-TLIF, and TLIF for all levels. MIS-TLIF and TLIF do not differ significantly except for a slight reduction in hospital stay for two-level procedures. On multivariate analysis, a one-point increase in BMI increased surgery time by 0.56 ± 0.47 minutes (p = 0.24) in the OLLIF group, by 2.8 ± 1.43 minutes (p = 0.06) in the MIS-TLIF group, and by 1.7 ± 0.43 minutes (p < 0.001) in the TLIF group. BMI has positive effects on blood loss for TLIF (p < 0.001) but not for OLLIF (p = 0.68) or MIS-TLIF (p = 0.67). BMI does not have significant effects on length of hospital stay for any procedure. Obesity is associated with increased surgery time and blood loss in TLIF and with increased surgery time in MIS-TLIF. Increased surgery time may be associated with increased perioperative complications and cost. In OLLIF, BMI does not affect perioperative outcomes. Therefore, OLLIF may reduce the disparity in outcomes and cost between obese and non-obese patients

Introduction. Obesity has been associated with higher complication rates and poorer outcomes following joint replacement surgery. Body mass index (BMI) is a simple index of body composition and forms part of preoperative assessment. It does not take into account the proportion of lean mass and body fat and can give a false impression of body composition in healthy manual workers. A more accurate measure of body composition is available using non-invasive bioimpedance methods. This study aims to identify whether BMI provides an accurate measure of body fat composition in patients awaiting lower limb arthroplasty surgery. Methods. Consecutive patients attending for pre-assessment clinic prior to total knee and hip replacement surgery were examined. All patients had their BMI calculated and underwent bioimpedance testing using a bedside Bodystat 1500 scanner (Bodystat, UK). Results. 83 patients (28 male) were included. Mean age was 68 years (range 16 to 92). All were awaiting lower limb arthroplasty surgery (39 primary total hip replacement, 4 revision total hip replacement, 38 primary total knee replacement, one unicompartmental knee replacement and one patellofemoral joint replacement). Mean BMI was 30.8 (range 20.8 to 48.9). Mean body fat percentage was 37.4% (range 17% to 53.9%). A weak correlation was seen between the calculated BMI and the measured body fat percentage (r=0.42, Pearson's correlation coefficient). Mean body fat percentage in obese patients (BMI > 30; mean BMI 34.9; n=42) was 42% while in the non-obese patients (BMI < 30; mean BMI 26.6; n=41) was 32.8%. This difference was significant (p<0.001). Conclusion. In patients undergoing lower limb arthroplasty the calculated BMI has a weak correlation with the measured body fat percentage. Bedside, non-invasive bioimpedance analysis provides a quick and accurate measure of body composition and can be used during preoperative assessment. Future correlation of outcome against body composition and BMI will validate the use of body composition in these patients. Care should be taken when relying on BMI alone to assess body fat composition

Abstract

Unicompartment knee replacement (UKR) has been an effective treatment of isolated medial compartment osteoarthritis (OA). There has been several studies which suggest that patellofemoral (PFJ) wear may not be a relative contraindication for UKR with no statistical difference in failure rates. There is currently conflicting evidence on the role of BMI.

We will review if BMI and PFJ wear impacts on the post operative functional scores following UKR.

A retrospective review of a prospectively collected database was performed. Data was collected between 26/6/2014 and 25/8/2022. 159 UKR procedures were identified. BMI and PFJ cartilage wear were collected. Oxford knee scores (OKS) were collected at > 2 years. PFJ wear was split into International Cartilage Research Society (ICRS) grades I&II and III&IV.

159 UKR procedures were identified, of these 115 had 2 year follow up. There were 77 who had OKS recorded at 2 years. For PFJ wear there was no statistical difference in the median OKS at 2 years 45 vs 43.5 (p=0.408). Assessing the BMI the median was 29kg/m², range 20–43kg/m². Spearman's rank was performed to assess the correlation between BMI and >2 year OKS, this demonstrated a moderately negative correlation p(df)=−0.339 (CI 95% −0.538, −0.104) p=0.004.

There is no statistically significant difference in >2 year OKS following UKR regardless of PFJ wear. There is a moderately negative correlation between BMI and >2 year OKS which was significant p=0.004. Therefore BMI is a more important consideration when counselling patients for UKR.

Cemented total hip replacements (THR) are widely used and are still recognized as the gold standard by which all other methods of hip replacements are compared. [. 1. ]. Long-term results of cemented total hip replacements show that the revision rate due to aseptic loosening could be as high as 75.4% [. 2. ]. Moreover, high stresses developed in the cement mantle of reconstructed hips can lead to premature failure of the constructs [. 3. ]. Surgical fixation techniques vary considerably [. 4. ]. The aim of this study was to investigate the performances of different surgical fixation techniques of hip implants for patients with different body mass indices, bone morphology and bone quality, using finite element (FE) methods. Anatomically correct reconstructed hemi-pelves were created, using CT-Scan data of the Visible Human Data set, downloaded to Mimics V8.1 software, where poly-lines of cancellous and cortical bones were created, and exported to I-Deas 11.0 FE package, where the econstructed hemi-pelvis was simulated. Accurate 3D model of the hemi-pelvis was scaled up and down to create hemi-pelves of acetabular sizes of the following diameters: 46 mm, 52 mm, and 58 mm. Following sensitivity analyses, element sizes ranging from 1–3 mm were used. Material properties of the bones, implants and cement were taken from literature [. 5. –. 7. ]. Bones of poor quality were simulated by a reduction in the elastic modulii of the cortical bone by 50%, the cancellous bone by 10 % and the subchondral bone by 50% [. 5. ]. The nodes at the sacro-iliac joint areas and the pubic support areas were fixed. A compressive force of 3 times body weight was simulated at the hip joint. The nodes between the cancellous and subchondral bones were merged. Contact elements were used at the subchondral bone and cement mantle interface and between the femoral head implant and acetabular component. Dynamic in vitro tests, simulating forces acting on a hip joint during a gait cycle, were carried out on reconstructed synthetic bones, positioned on an Instron 8874 hydraulic machine, to verify the FE models. The volume of cement stressed at different levels in groups of 0–1 MPa, 1–2 MPa and up to 11 and above MPa were calculated. Results of FE analyses showed that. an increase in the body mass index from 20 to 30 generated an increase in the tensile stress level in the cement mantle;. lower tensile and shear stresses developed in thicker cement mantles. For a 46mm acetabular size, peak tensile stresses decreased from 10.32MPa to 8.14MPa and peak shear stresses decreased from 5.36MPa to 3.67MPa when cement mantle thickness increased from 1mm to 4mm. A reduction in the bone quality would result in an increase of approximately 45% in the cement mantle stresses. Results of in-vitro tests show that an increase in the cement mantle thickness improved fixation, corroborating with the FE results. Performances of fixation techniques depend on the patient’s bone mass index, bone quality, bone morphology