Metabolic activity of osteoarthritic knees correlates with BMI

The influence of chondrocyte source on the manufacturing reproducibility of human tissue engineered cartilage

Multiple human tissue engineered cartilage constructs are showing promise in advanced clinical trials but identifying important measures of manufacturing reproducibility remains a challenge. FDA guidance suggests measuring multiple mechanical properties prior to implantation, because these properties could affect the long term success of the implant. Additionally, these engineered cartilage mechanics could be sensitive to the autologous chondrocyte source, an inherently irregular manufacturing starting material. If any mechanical properties are sensitive to changes in the autologous chondrocyte source, these properties may need to be measured prior to implantation to ensure manufacturing reproducibility and quality. Therefore, this study identified variability in the compressive, friction, and shear properties of a human tissue engineered cartilage constructs due to the chondrocyte source. Over 200 constructs were created from 7 different chondrocyte sources and tested using 3 distinct mechanical experiments. Under confined compression, the compressive properties (aggregate modulus and hydraulic permeability) varied by orders of magnitude due to the chondrocyte source. The friction coefficient changed by a factor of 5 due to the chondrocyte source and high intrapatient variability was noted. In contrast, the shear modulus was not affected by changes in the chondrocyte source. Finally, measurements on the local compressive and shear mechanics revealed variability in the depth dependent strain fields based on chondrocyte source. Since the chondrocyte source causes large amounts of variability in the compression and local mechanical properties of engineered cartilage, these mechanical properties may be important measures of manufacturing reproducibility. STATEMENT OF SIGNIFICANCE: Although the FDA recommends measuring mechanical properties of human tissue engineered cartilage constructs during manufacturing, the effect of manufacturing variability on construct mechanics is unknown. As one of the first studies to measure multiple mechanical properties on hundreds of human tissue engineered cartilage constructs, we found the compressive properties are most sensitive to changes in the autologous chondrocyte source, an inherently irregular manufacturing variable. This sensitivity to the autologous chondrocyte source reveals the compressive properties should be measured prior to implantation to assess manufacturing reproducibility.

A Microarray Study of Articular Cartilage in Relation to Obesity and Severity of Knee Osteoarthritis

OBJECTIVE

To query the transcript-level changes in the medial and lateral tibial plateau cartilage in tandem with obesity in patients with end-stage osteoarthritis (OA).

DESIGN

Cartilage was obtained from 23 patients (20 obese [body mass index > 30 kg/m²], 3 overweight [body mass index < 30 kg/m²]) at the time of total knee replacement. Cartilage integrity was assessed using Outerbridge scale, while radiographic changes were scored on preoperative X-rays using Kellgren-Lawrence (K-L) classification. RNA was probed for differentially expressed transcripts between medial and lateral compartments using Affymetrix Gene 2.0 ST Array and validated via real-time polymerase chain reaction. Gene ontology and pathway analyses were also queried.

RESULTS

Scoring of cartilage integrity by the Outerbridge scale indicated that the medial and lateral compartments were similar, while scoring by the K-L classification indicated that the medial compartment was more severely damaged than the lateral compartment. We observed a distinct transcript profile with >50% of transcripts unique between medial and lateral compartments. MMP13 and COL2A1 were more highly expressed in medial versus lateral compartment. Polymerase chain reaction confirmed expression of 4 differentially expressed transcripts. Numerous transcripts, biological processes, and pathways were significantly different between overweight and obese patients with a differential response of obesity on medial and lateral compartments.

CONCLUSIONS

Our findings support molecular differences between medial and lateral compartments reflective of the greater severity of OA in the medial compartment. The K-L system better reflected the molecular results than did the Outerbridge. Moreover, the molecular effect of obesity was different between the medial and lateral compartments of the same knee plausibly reflecting the molecular effects of differential biomechanical loading.

Regional Differences Between Perisynovial and Infrapatellar Adipose Tissue Depots and Their Response to Class II and Class III Obesity in Patients With Osteoarthritis

OBJECTIVE

Obesity is associated with an increased risk of developing osteoarthritis (OA), which is postulated to be secondary to adipose tissue-dependent inflammation. Periarticular adipose tissue depots are present in synovial joints, but the association of this tissue with OA has not been extensively explored. The aim of this study was to investigate differences in local adipose tissue depots in knees with OA and characterize the changes related to class II and class III obesity in patients with end-stage knee OA.

METHODS

Synovium and the infrapatellar fat pad (IPFP) were collected during total knee replacement from 69 patients with end-stage OA. Histologic changes, changes in gene and protein expression of adiponectin, peroxisome proliferator-activated receptor γ (PPARγ), and Toll-like receptor 4 (TLR-4), and immune cell infiltration into the adipose tissue were investigated.

RESULTS

IPFP and synovium adipose tissue depots differed significantly and were influenced by the patient's body mass index. Compared to adipocytes from the IPFP and synovium of lean patients, adipocytes from the IPFP of obese patients were significantly larger and the synovium of obese patients displayed marked fibrosis, increased macrophage infiltration, and higher levels of TLR4 gene expression. The adipose-related markers PPARγ in the IPFP and adiponectin and PPARγ in the synovium were expressed at lower levels in obese patients compared to lean patients. Furthermore, there were increased numbers of CD45+ hematopoietic cells, CD45+CD14+ total macrophages, and CD14+CD206+ M2-type macrophages in both the IPFP and synovial tissue of obese patients.

CONCLUSION

These differences suggest that IPFP and synovium may contain 2 different white adipose tissue depots and support the theory of inflammation-induced OA in patients with class II or III obesity. These findings warrant further investigation as a potentially reversible, or at least suppressible, cause of OA in obese patients.

Analysis of Risk Factors for Lower-limb Deep Venous Thrombosis in Old Patients after Knee Arthroplasty

Background:

Deep venous thrombosis (DVT) is a common complication of arthroplasty in old patients. We analyzed risk factors for lower-limb DVT after arthroplasty in patients aged over 70 years to determine controllable risk factors.

Methods:

This was a retrospective study of 1,025 patients aged >70 years treated with knee arthroplasty at our hospital between January 2009 and December 2013. Of 1,025 patients, 175 had postoperative lower-limb DVT. We compared medical history, body mass index (BMI), ambulatory blood pressure, preoperative and postoperative fasting blood glucose (FBG), preoperative blood total cholesterol, triglyceride, high- and low-density lipoprotein cholesterol, and preoperative homocysteine (Hcy) between thrombus and non-thrombus groups. B-mode ultrasonography was used to detect lower-limb DVT before the operation and 7 days after the operation in all patients. Logistic regression analysis was used to determine risk factors for DVT.

Results:

Incidence of diabetes (P = 0.014), BMI (P = 0.003), preoperative FBG (P = 0.004), postoperative FBG (P = 0.012), and preoperative Hcy (P < 0.001) were significantly higher in the thrombus group. A significantly greater proportion of patients in the non-thrombus group had early postoperative activity (P < 0.001) and used a foot pump (P < 0.001). Operative duration was significantly longer in the thrombus group (P = 0.012). Within the thrombus group, significantly more patients had bilateral than unilateral knee arthroplasty (P < 0.01). Multivariate logistic analysis revealed BMI, preoperative Hcy, postoperative FBG, long operative duration, bilateral knee arthroplasty, and time to the activity after the operation to be predictive factors of DVT. At 6-month follow-up of the thrombus group, 4.7% of patients had pulmonary embolism and 18.8% had recurrent DVT; there were no deaths.

Conclusions:

Obesity, inactivity after operation, elevated preoperative Hcy and postoperative FBG, long operative duration, and bilateral knee arthroplasty were risk factors for DVT in patients aged over 70 years.

Changes in bone mineral density of the distal femur after total knee arthroplasty: a 7-year DEXA follow-up comparing results between obese and nonobese patients

BACKGROUND AND PURPOSE

Periprosthetic femoral bone mineral density (BMD, g/cm2) decreases after total knee arthroplasty (TKA) as a result of the stress-shielding phenomenon. It is not known whether obesity has an effect on this phenomenon or not. The aim of this study was to assess long-term periprosthetic BMD changes after TKA and compare whether there is a difference between obese and nonobese patients.

METHODS

A total of 69 TKAs in 61 patients were performed, and BMD measurements of the distal femur were followed up to 7 years postoperatively. The patients were divided into two study groups according to their body mass index, and the groups were compared in relation to BMD and functional outcome.

RESULTS

The mean of periprosthetic bone loss during the 7-year follow-up varied from 10.3% to 30.6% depending on the region of interest (p<0.0005). The highest bone-loss rates were detected during the first three postoperative months. A total of 26 patients were categorized as obese with a body mass index value of ≥30 kg/m2. The obese patients' total periprosthetic BMD was higher at both baseline (8.6%) and 7 years after operation (p=0.05) (15.2%).

CONCLUSION

Periprosthetic bone loss around the femoral component continued for up to 7 years postoperatively. The loss of bone density was not associated with any negative clinical outcome in this study, but periprosthetic bone loss was of a smaller quantity in the obese which is probably due to higher weight induced stresses on bone.

Musculoskeletal pain in overweight and obese children

This review seeks to provide a current overview of musculoskeletal pain in overweight and obese children. Databases searched were Academic Search Complete, CINAHL, Medline, Proquest Health and Medical Complete, Scopus, Google Scholar, SPORTDiscuss and Trove for studies published between 1 January 2000 and 30 December 2012. We used a broad definition of children within a 3- to 18-year age range. The search strategy included the following terms: obesity, morbid obesity, overweight, pain, musculoskeletal pain, child, adolescent, chronic pain, back pain, lower back pain, knee pain, hip pain, foot pain and pelvic pain. Two authors independently assessed each record, and any disagreement was resolved by the third author. Data were analysed using a narrative thematic approach owing to the heterogeneity of reported outcome measures. Ninety-seven records were initially identified using a variety of terms associated with children, obesity and musculoskeletal pain. Ten studies were included for thematic analysis when predetermined inclusion criteria were applied. Bone deformity and dysfunction, pain reporting and the impact of children being overweight or obese on physical activity, exercise and quality of life were the three themes identified from the literature. Chronic pain, obesity and a reduction in physical functioning and activity may contribute to a cycle of weight gain that affects a child's quality of life. Future studies are required to examine the sequela of overweight and obese children experiencing chronic musculoskeletal pain.

Obesity has a negative impact on clinical outcome after total knee arthroplasty

BACKGROUND AND AIMS

Obesity has been linked to the development of osteoarthritis of the knee and since the incidence of obesity is increasing, the need for total knee arthroplasty (TKA) is likely to increase. Conflicting findings have been reported concerning the relationship between obesity and TKA. It has been shown in several studies, that obese patients have poorer clinical results after operation. On the other hand it has also been reported similar results for obese and non-obese patients. The purpose of this study was to analyze clinically and radiologically the results of total knee artrhoplasty in obese patients.

MATERIAL AND METHODS

The study consisted of 48 patients who had a TKA. The patients were divided in two groups according their body mass index. Patients of BMI over 30 were regarded as obese.

RESULTS

The obese patients had poorer clinical success at the final follow-up, their WOMAC scores were significantly higher compared to non-obese (pain 20.7 vs. 11.6; p = 0.021, stiffness 26.9 vs. 13.4; p = 0.006, physical function 26.5 vs. 14.4; p = 0.003). Differences were also found in the Knee (KS) and Function (FS) scores and a long-term postoperative ROM and (KS: 83.6 vs. 88.9; p = 0.01, FS: 63.6/76.3; p = 0.051, ROM: 104.6 vs. 109.6; p = 0.016). Non-obese patients reached better percentage improvement in the KSS compared to obese patients (KS change + 194.5% vs. + 59.5%, p = 0.03; FS change + 51.5% vs. + 14.9%, p = 0.19).

CONCLUSIONS

Obesity has a negative impact on the outcome of TKA, assessed by patients' clinical function and satisfaction level.

All-polyethylene tibial components in obese patients are associated with low failure at midterm followup

BACKGROUND

In the United States, the obese population has increased markedly over the last four decades, and this trend continues. High patient weight places additional stress on TKA components, which may lead to increased polyethylene wear, osteolysis, radiolucencies, and clinical failure. Metal-backed tibial components and all-polyethylene tibial components in the general population have comparable osteolysis and failure, but it is unclear whether these components yield similar osteolysis and failure in obese patients.

QUESTIONS/PURPOSES

We therefore determined the (1) function, (2) occurrence of osteolysis, and (3) complications in a cohort of obese patients receiving all-polyethylene tibial components.

PATIENTS AND METHODS

Between September 17, 1996, and December 19, 2002, we implanted all-polyethylene tibial components in 90 obese patients (125 knees); 24 patients (33 knees) died and 13 patients (17 knees) were lost to followup, leaving 53 patients (59%) with 75 knees. All surgeries were cruciate-retaining, tricompartmental TKAs. We evaluated patients with Knee Society Scores and serial radiographs. Minimum followup was 7 years (mean, 10.4 years; range, 7-14 years).

RESULTS

At latest followup, mean Knee Society Score was 92 points. There were five tibial radiolucencies, all less than 1 mm and characterized as nonprogressive. We observed minimal, nonprogressive osteolysis in one knee. One patient required reoperation after a traumatic event. There were no implant-related failures and no implants at risk of failure.

CONCLUSIONS

At an average 10-year followup, all-polyethylene tibial components were functioning well in this obese group. These findings confirm the effectiveness of all-polyethylene tibial components in obese patients.

Outcomes of unicompartmental knee arthroplasty stratified by body mass index

Patients who have high body mass indices can have disabling medial compartment knee osteoarthritis, which might benefit from unicompartmental knee arthroplasty (UKA). The purpose of this study was to compare clinical and radiographic outcomes of UKAs in patients with body mass indices (BMIs) greater and less than 35 kg/m(2). Thirty-four patients (40 knees) had BMIs of 35 kg/m(2) or greater, whereas the remaining 33 patients (40 knees) had BMIs below 35 kg/m(2), with 2-year minimum follow-up. In the high-BMI group, 5 knees were revised to total knee arthroplasty, compared with none in the lower BMI group. Knee Society scores were lower in the surviving high-BMI knees. All surviving components were radiographically stable. The results suggest that UKA should be approached with caution in patients who have high BMIs.

Treatment of knee arthrosis in the morbidly obese patient

The purpose of this article is to present the challenges of dealing with the morbidly obese patient suffering from degenerative knee arthrosis. Surgery should only be undertaken when conservative management has failed and comorbidities optimized. Owing to risks related to comorbidities, diligence is necessary before proceeding with surgery to lessen the chance of complications-especially infection. Evaluation, conservative treatments, preoperative optimization, and surgical options are discussed.