Steroid-Induced Avascular Necrosis in the Foot and Ankle-Pathophysiology, Surgical, and Nonsurgical Therapies: Case Study and Literature Review

Steroid-induced avascular necrosis (AVN) of the lower extremity is a destructive process of the bone found in patients who have been treated with these medications for a variety of medical conditions. There are several proposed etiologies for development of this condition, however much debate still remains for the exact pathophysiology. The main clinical characteristics include edema, arthralgias, and restricted joint range of motion. Diagnostic imaging is a key aspect in the analysis of this pathologic process. When steroid-induced AVN affects multiple bones, this atypical presentation is difficult to treat due to its diffuse nature, therefore surgical options are limited. In these cases, conservative therapy is targeted toward pain relief and preserving joint range of motion. This review aims to provide an overview on the presentation of steroid-induced AVN in the foot and ankle, outline the pathophysiology of the process, and describe a variety of both conservative and surgical treatment options. A case study is provided to showcase a patient presentation of diffuse steroid-induced AVN of the foot and ankle and their course of treatment.Levels of Evidence: Level V: Expert opinion.

The association of an elevated Th/Ts ratio and lupus anticoagulant with symptomatic osteonecrosis in systemic lupus erythematosus patients

Objective

This study aimed to assess the risk factors for symptomatic osteonecrosis (ON) in systemic lupus erythematosus (SLE) and identify clinical characteristics and laboratory markers for predicting symptomatic ON occurrence in SLE patients.

Methods

Seventy (6.0%) of 1175 SLE patients diagnosed with symptomatic ON were included in this study. An equal number of SLE patients without symptomatic ON, matched in terms of age and gender, were enrolled in the control group. Clinical symptoms, routine laboratory examinations, lymphocyte subsets, and treatments of these patients were retrospectively reviewed and compared between the two groups. Logistic regression analysis was employed to identify risk factors associated with symptomatic ON in SLE.

Results

Among the 70 cases in the symptomatic ON group, 62 (88.6%) patients experienced femoral head necrosis, with bilateral involvement observed in 58 patients. Bone pain was reported in 32 cases (51.6%), and 19 cases (30.6%) presented with multiple symptoms. Univariate analysis revealed significant differences between the two groups in various factors, including disease duration (months), cumulative steroid exposure time, history of thrombosis, neurological involvement, the number of affected organs, myalgia/myasthenia, and the use of medications such as glucocorticoids, immunosuppressants, aspirin, and statins (P<0.05). Moreover, lupus anticoagulant (LA) levels were significantly higher in the symptomatic ON group than in the control group (P<0.05). Furthermore, notable distinctions were observed in peripheral blood immune cells, including an elevated white blood cell count (WBC), a decreased percentage of Ts cells (CD3+CD8+), and an elevated Th/Ts ratio. Logistic regression analysis revealed that a history of thrombosis, LA positivity, and an elevated Th/Ts ratio remained positive factors associated with symptomatic ON (P<0.05).

Conclusion

Decreased Ts cells and changes in the T lymphocyte subset play an important regulatory role in the development of symptomatic ON. A history of thrombosis and LA are associated with an increased probability of symptomatic ON in SLE and may serve as potential predictors.

Periprosthetic joint infection and immunity: Current understanding of host-microbe interplay

Periprosthetic joint infection (PJI) is a major complication of total joint arthroplasty. Even with current treatments, failure rates are unacceptably high with a 5-year mortality rate of 26%. Majority of the literature in the field has focused on development of better biomarkers for diagnostics and treatment strategies including innovate antibiotic delivery systems, antibiofilm agents, and bacteriophages. Nevertheless, the role of the immune system, our first line of defense during PJI, is not well understood. Evidence of infection in PJI patients is found within circulation, synovial fluid, and tissue and include numerous cytokines, metabolites, antimicrobial peptides, and soluble receptors that are part of the PJI diagnosis workup. Macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs) are initially recruited into the joint by chemokines and cytokines produced by immune cells and bacteria and are activated by pathogen-associated molecular patterns. While these cells are efficient killers of planktonic bacteria by phagocytosis, opsonization, degranulation, and recruitment of adaptive immune cells, biofilm-associated bacteria are troublesome. Biofilm is not only a physical barrier for the immune system but also elicits effector functions. Additionally, bacteria have developed mechanisms to evade the immune system by inactivating effector molecules, promoting killing or anti-inflammatory effector cell phenotypes, and intracellular persistence and dissemination. Understanding these shortcomings and the mechanisms by which bacteria can subvert the immune system may open new approaches to better prepare our own immune system to combat PJI. Furthermore, preoperative immune system assessment and screening for dysregulation may aid in developing preventative interventions to decrease PJI incidence.

Efficacy and safety of total glucosides of paeony in the treatment of systemic lupus erythematosus: A systematic review and meta-analysis

Background: Total glucosides of paeony (TGP), extracted from the Chinese medicine Paeonia lactiflora Pall., have been proven to be effective in various autoimmune diseases. We aim to systematically evaluate the efficacy and safety of TGP combined with different conventional therapeutic agents in the treatment of systemic lupus erythematosus (SLE). Methods: Eight databases were searched for randomized controlled studies of TGP for SLE. The search time was set from the establishment of the databases to March 2022. The risk of bias was assessed by the Cochrane Evaluation Manual (5.1.0), RevMan 5.3 software was used for meta-analysis, and the certainty of the evidence was assessed by the GRADE methodology. Results: A total of 23 articles were included, including 792 patients overall in the treatment group and 781 patients overall in the control group. The meta-analysis results showed that TGP combined with conventional treatments was superior to the conventional treatments in reducing the SLE disease activity and the incidence of adverse reactions (SMD_TGP+GC+CTX = -1.98, 95% Cl = [-2.50, -1.46], p < 0.001; SMD_TGP+GC+HCQ = -0.65, 95% Cl = [-1.04, -0.26], p <0.001; SMD_TGP+GC+TAC = -0.94, 95% Cl = [-1.53, -0.34], p < 0.05; SMD_TGP+GC = -1.00, 95% Cl = [-1.64, -0.36], p < 0.05; and RR_TGP+GC+CTX = 0.37, 95% Cl = [0.21, 0.64], p < 0.001). The results also showed that TGP helped improve other outcomes related to SLE disease activity, such as complement proteins (C3 and C4), immunoglobulins (IgA, IgM and, IgG), ESR, CRP, 24 h urine protein, and recurrence rate. In addition, TGP may also be effective in reducing the average daily dosage of glucocorticoids (GCs) and the cumulative dosage of cyclophosphamide (CTX). The certainty of the evidence was assessed as moderate to low. Conclusion: TGP is more effective and safer when used in combination with different conventional therapeutic agents. It helped reduce the disease activity of SLE and the incidence of adverse reactions. However, we should be cautious about these conclusions as the quality of the evidence is poor. Future studies should focus on improving the methodology. High-quality randomized controlled trials (RCTs) will be necessary to provide strong evidence for the efficacy of TGP for SLE. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO, identifier CRD42021272481.

Enhanced tendon healing by a tough hydrogel with an adhesive side and high drug-loading capacity

Hydrogels that provide mechanical support and sustainably release therapeutics have been used to treat tendon injuries. However, most hydrogels are insufficiently tough, release drugs in bursts, and require cell infiltration or suturing to integrate with surrounding tissue. Here we report that a hydrogel serving as a high-capacity drug depot and combining a dissipative tough matrix on one side and a chitosan adhesive surface on the other side supports tendon gliding and strong adhesion (larger than 1,000 J m^-2) to tendon on opposite surfaces of the hydrogel, as we show with porcine and human tendon preparations during cyclic-friction loadings. The hydrogel is biocompatible, strongly adheres to patellar, supraspinatus and Achilles tendons of live rats, boosted healing and reduced scar formation in a rat model of Achilles-tendon rupture, and sustainably released the corticosteroid triamcinolone acetonide in a rat model of patellar tendon injury, reducing inflammation, modulating chemokine secretion, recruiting tendon stem and progenitor cells, and promoting macrophage polarization to the M2 phenotype. Hydrogels with 'Janus' surfaces and sustained-drug-release functionality could be designed for a range of biomedical applications.

A systematic review and meta-analysis comparing complications following total hip arthroplasty for systemic lupus erythematosus versus for non-systemic lupus erythematosus

Background

Osteonecrosis of the femoral head is one of the most severe complications in systemic lupus erythematosus (SLE) patients. Total hip arthroplasty (THA) is an effective treatment for femoral head necrosis. However, there is no consensus on the specific effect of THA on SLE patients. The objective of the present study was to review the current evidence regarding rates of THA complications and postoperative function in systemic lupus erythematosus.

Methods

Two independent reviewers searched PubMed, Cochrane Library, and EMBASE from January 1, 2000, to December 29, 2021. The primary outcomes were postoperative complications, including deep vein thrombosis (DVT), hematoma, wound infection, dislocation, periprosthetic fracture, revision, mortality.

Results

A total of 179 articles yielded 28 studies eligible for inclusion with 10 studies used for meta-analysis. This study found a statistically significant difference in DVT, dislocation, wound infection, periprosthetic fracture, and revision.

Conclusions

This meta-analysis shows that SLE patients with THA are at an increased risk of DVT, wound infection, dislocation, periprosthetic fracture, revision, periprosthetic joint infection, following THA in comparison with non-SLE patients with THA. There was no adequate evidence to support the notion that the risk of seroma or hematoma following THA is increased in SLE. Also, there was no significant difference in HHS scores between SLE patients and non-SLE patients after THA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03075-8.

Total Glucosides of Paeonia lactiflora for Safely Reducing Disease Activity in Systemic Lupus Erythematosus: A Systematic Review and Meta-Analysis

Background: Total glucosides of paeony (TGP), extracted from the dried roots of Paeonia lactiflora Pall., are proven to regulate immune function in various rheumatic diseases. We aim to systematically evaluate the efficacy and safety of TGP in reducing disease activity in systemic lupus erythematosus (SLE).

Methods: We searched trials in seven electronic databases and two clinical trail registries. Randomized controlled trials (RCTs) evaluating efficacy and safety of TGP for SLE were identified. The Cochrane Risk of Bias Tool 2.0 was used for quality assessment of the included trials, and RevMan 5.4 software was used for meta-analysis.

Results: A total of 14 RCTs were included, including 978 participants, 492 in the intervention group and 486 in the control group. Regarding the efficacy of TGP for SLE, results showed that TGP plus conventional treatments (CTs) was superior to CTs alone in reducing disease activity (MD_SLEDAI-1m = −3.54, 95% CI = −4.08 to −3.00, p < 0.00001; MD_SLEDAI-2m = −3.80, 95% CI = −4.51 to −3.09, p < 0.00001; MD_SLEDAI-3m = −1.62, 95% CI = −2.60 to −0.64, p < 0.0001; MD_SLEDAI-6m = −1.97, 95% CI = −3.18 to −0.76, p = 0.001). The results also showed that TGP contributed to a betterment in improving other outcomes related to lupus activity, such as ESR, CRP, complement proteins (C3, C4), and immunoglobulins (IgA, IgM). In addition, TGP significantly decreased average daily glucocorticoid dosage and cumulative cyclophosamide dosage, as well as disease recurrence rate. In terms of safety, TGP may reduce the incidence of adverse reactions (RR = 0.51, 95% CI = 0.29 to 0.88, p = 0.01). The certainty of the evidence were assessed as moderate to low.

Conclusion: TGP appears potentially effective and generally safe in reducing disease activity in SLE. However, in view of high risk of bias, the findings need to be confirmed in high-quality trials.

Systematic Review Registration: https://www.crd.york.ac.uk/prospero, identifier CRD42021274850

Impact of glucocorticoids on the incidence of lupus-related major organ damage: a systematic literature review and meta-regression analysis of longitudinal observational studies

OBJECTIVE

In systemic lupus erythematosus (SLE), disease activity and glucocorticoid (GC) exposure are known to contribute to irreversible organ damage. We aimed to examine the association between GC exposure and organ damage occurrence.

METHODS

We conducted a literature search (PubMed (Medline), Embase and Cochrane January 1966-October 2021). We identified original longitudinal observational studies reporting GC exposure as the proportion of users and/or GC use with dose information as well as the occurrence of new major organ damage as defined in the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index. Meta-regression analyses were performed. Reviews, case-reports and studies with <5 years of follow-up, <50 patients, different outcomes and special populations were excluded.

RESULTS

We selected 49 articles including 16 224 patients, 14 755 (90.9%) female with a mean age and disease duration of 35.1 years and of 37.1 months. The mean follow-up time was 104.9 months. For individual damage items, the average daily GC dose was associated with the occurrence of overall cardiovascular events and with osteoporosis with fractures. A higher average cumulative dose adjusted (or not)/number of follow-up years and a higher proportion of patients on GC were associated with the occurrence of osteonecrosis.

CONCLUSIONS

We confirm associations of GC use with three specific damage items. In treating patients with SLE, our aim should be to maximise the efficacy of GC and to minimise their harms.

Glucocorticoid-induced osteonecrosis in systemic lupus erythematosus patients

Osteonecrosis (ON) is a complex and multifactorial complication of systemic lupus erythematosus (SLE). ON is a devastating condition that causes severe pain and compromises the quality of life. The prevalence of ON in SLE patients is variable, ranging from 1.7% to 52%. However, the pathophysiology and risk factors for ON in patients with SLE have not yet been fully determined. Several mechanisms for SLE patients' propensity to develop ON have been proposed. Glucocorticoid is a widely used therapeutic option for SLE patients and high-dose glucocorticoid therapy in SLE patients is strongly associated with the development of ON. Although the hips and knees are the most commonly affected areas, it may be present at multiple anatomical locations. Clinically, ON often remains undetected until patients feel discomfort and pain at specific sites at which point the process of bone death is already advanced. However, strategies for prevention and options for treatment are limited. Here, we review the epidemiology, risk factors, diagnosis, and treatment options for glucocorticoid-induced ON, with a specific focus on patients with SLE.

Predictors of avascular necrosis in a cohort of Egyptian systemic lupus erythematosus patients: Retrospective two centers study

BACKGROUND

Avascular necrosis is a common complication in patients with SLE.

OBJECTIVE

This study aimed to investigate the risk factors for occurrence of avascular necrosis among SLE patients receiving steroid therapy at various doses, in combination with immunosuppressants.

METHODS

In this retrospective study, the medical records of all SLE patients under follow-up at the outpatient clinics of Cairo and kafr Elsheikh University hospitals through the period from November 2014 to August 2019, were included. The avascular necrosis was diagnosed by the findings of different imaging modalities.

RESULTS

We retrieved the medical records of 770 SLE patients during the study period; of them, 55 patients (7.1%) had avascular necrosis. There was significant higher usage of cyclophosphamide (p = 0.003), total cumulative dose of steroids 15-35g plus immunosuppressants (p < 0.001), and steroids >35g plus Immunosuppressants (p = 0.016) in avascular necrosis cohort. Based on the univariate analysis, disease duration more than five years and cumulative use of steroids were statistically significant predictors for the evolvement of avascular necrosis. Multivariate logistic regression analysis revealed that disease duration more than five years was associated independently with avascular necrosis.

CONCLUSION

Our data seem to show a role of the association of immunosuppressant plus steroid on the risk to develop avascular necrosis.

The Categorization of Pain in Systemic Lupus Erythematosus

Systemic lupus erythematous is a systemic autoimmune disease that can cause severe pain and impair quality of life. Pain in lupus can arise from a variety of mechanisms and is usually assessed in terms of activity and damage. In contrast, categorization of symptoms as type 1 and type 2 manifestations encompasses a broader array of symptoms, including widespread pain, fatigue, and depression that may track together. The categorization of symptoms as type 1 and type 2 manifestations can facilitate communication between patient and provider as well as provide a framework to address more fully the complex symptoms experienced by patients.

Associations between glucocorticoids, antiphospholipid antibodies and femur head necrosis in patients with SLE: a directed acyclic graph-based multicentre study

Background

Osteonecrosis of the femoral head (ONFH) remains a major cause of disability in patients with systemic lupus erythematosus (SLE) and seriously impairs quality of life. This study aimed to investigate associations between glucocorticoids (GCs), antiphospholipid antibodies (aPLs), and ONFH in patients with SLE.

Methods

We conducted a multicentre cohort study on patients with SLE and used a directed acyclic graph-based analysis strategy. Details of GC therapy, aPLs status, other drug administration and other SLE-related characteristics were collected. ONFH occurrence during follow-up was determined by magnetic resonance imaging. Multivariable logistic regression and generalized estimating equation models were performed to assess their effects on ONFH, and a simplified scoring system comprising these factors for short- and medium-term SLE-ONFH prediction was developed by receiver operating characteristic curve analysis.

Results

Of 449 SLE patients with a median follow-up duration of 5.3 years, 41 (9.1%) developed ONFH. Independently risk factors of SLE-ONFH including: average daily GC dose with an adjusted odds ratio (aOR) of 1.1 and 95% confidence interval (CI) of 1.0-1.1; GC therapy duration (3-5 years: aOR 3.3, 95% CI 1.4-7.8; >5 years: aOR 8.0, 95% CI 3.3-19.4); initial intravenous GC (aOR 4.4, 95% CI 1.9-10.1); positive aPLs (aOR 2.8, 95% CI 1.4-5.8); and Arterial hypertension secondary to GC usage (aOR 5.2, 95% CI 1.4-19.1). And we successfully developed the simplified scoring system (SCORE model) with an area under the curve of 0.88 (95% CI 0.82-0.94).

Conclusion

Based on the risk factors involved in the development of SLE-ONFH, a novel SCORE model was developed, which might be helpful for risk stratification of SLE-ONFH in clinical practice.

Avascular Necrosis of Bone in Patients with Uveitis Treated with Systemic Corticosteroids

Purpose: To identify the prevalence, risk factors and outcomes of avascular necrosis (AVN) in patients with chronic uveitis.Methods: A retrospective study of patients with corticosteroid-induced AVN treated at Manchester Uveitis Clinic between 1991 and 2019.Results: From a cohort of 4478 patients, 1698 had been treated with systemic corticosteroids. Five patients with AVN were identified (prevalence 0.29%). The mean age at diagnosis of AVN was 49 years. All 5 patients were using systemic immunosuppression. Four patients developed femoral head AVN in 7 joints, one had bilateral knee osteonecrosis. The mean duration of corticosteroid before AVN was 38 months; the mean dose at onset was 17mg/day and the mean cumulative dose was 18,860mg. Three patients required total hip replacements but management was conservative for others. There was no permanent disability.Conclusions: AVN is a rare but severe complication of corticosteroid therapy. Clinicians should be vigilant for symptoms of bone pain as early detection and cessation of corticosteroids can reverse incipient AVN and avoid surgery.

Juvenile-onset multifocal osteonecrosis in systemic lupus erythematosus: A case report

RATIONALE

Osteonecrosis (ON) is a devastating illness that leads to bone ischemia and potential joint destruction. Systemic lupus erythematosus (SLE) is a chronic, autoimmune disease, with multi-system involvement which is closely associated with occurrence of ON. Multifocal ON, with an estimated morbidity of 3% in SLE patients, is extremely rare in juvenile subjects.

PATIENT CONCERNS

A 13.3-year-old female SLE patient was admitted to hospital 20 months following the SLE diagnosis because of a sudden aggravation of sore knees. She suffered from double knee joint pain and her left knee joint showed typical signs of inflammation including redness, swelling, heat, and pain.

DIAGNOSES

The SLE patient was diagnosed with multifocal ON of her knee joint based on magnetic resonance imaging findings of bone destruction and osteoproliferation at the bilateral distal femur and proximal tibia.

INTERVENTIONS

The patient received high-dose methylprednisolone and intravenous cyclophosphamide pulse therapies for controlling active lupus and nephritis. Oral calcitriol and dipyridamole were administered to alleviate knee pain and inhibit thrombi formation, thereby suppressing ON progress.

OUTCOMES

Three weeks following the treatment, the swelling in patient's left knee subsided. Her self-reporting pain score decreased from 9 to 4 and walking time increased from 45minutes to 90minutes per day. Nearly 5 weeks later, the pain in bilateral knee joints disappeared and the patient could walk without difficulties.

LESSONS

This patient is the youngest SLE patient who developed multifocal ON based on the reported literature. It suggests that ON can occur in young SLE patients. A combination of internal and external risk factors can promote the development of ON. The balanced approach to the application of corticosteroids and immunosuppressors in the treatment of SLE and prevention of ON is a challenging problem that deserves further exploration.

The impact of systemic lupus erythematosus on the risk of infection after total hip arthroplasty: a nationwide population-based matched cohort study

BACKGROUND

We aimed to assess the impact of systemic lupus erythematosus (SLE) on the risk of infection after total hip arthroplasty (THA).

METHODS

We identified patients undergoing primary THA (1996-2013) in Taiwan National Health Insurance Research Database (NHIRD). Patients were then divided into the SLE and control groups according to the diagnosis of SLE. We used 1:1 propensity score to match the control to the SLE group by age, sex, and comorbidities. The primary outcome was infection, including early and late superficial wound infection and periprosthetic joint infection (PJI). The secondary outcome was in-hospital complications.

RESULTS

We enrolled 325 patients in each group. In the primary outcome, the incidence of early superficial wound infection and PJI was comparable between the SLE and matched-control group. However, the incidence of late superficial wound infection and PJI in the SLE group was higher than that in matched-control group (11.4% vs. 5.5%, P = 0.01; 5.2% vs 2.2%, P = 0.04, respectively). Furthermore, the SLE group had a higher risk for late superficial wound infection and PJI (hazard ratio = 2.37, 95% confidence interval (CI) 1.35-4.16; HR = 2.74, 95% CI 1.14-6.64, respectively) than the matched-control. Complications other than infection and in-hospital mortality cannot be compared because of very low incidence.

CONCLUSIONS

SLE is a risk factor for developing late superficial wound infection and PJI, but not for early postoperative complications following THA. Clinical presentations should be monitored to avoid misdiagnosis of PJI in SLE patients after THA.

Systemic Lupus Erythematosus: Targeted literature review of the epidemiology, current treatment and disease burden in the Asia Pacific region

OBJECTIVE

To understand the epidemiology, current treatment and disease burden of systemic lupus erythematosus (SLE) in the Asia Pacific region (APAC).

METHODS

A targeted literature review of published evidence on SLE in APAC was conducted, using the MEDLINE® database (2008-2018), conference proceedings and other supplementary sources.

RESULTS

The review identified 70 studies conducted in China (n=15), Japan (n=13), Taiwan (n=12), Korea (n=9), Australia (n=7), Hong Kong (n=6), Singapore (n=4), and multiple places within the APAC region (n=4). Incidence rates (per 100,000 per year) ranged from 0.9-8.4, while prevalence rates ranged from 3.7-127 (per 100,000); however, recent data was limited. Asian SLE patients were reported to have higher disease severity, activity (higher SLE disease activity index scores) and organ damage accrual; along with increased morbidity, mortality, and susceptibility to renal involvement compared with other ethnicities in APAC. The risk of developing SLE is higher in the Asian population. Routinely used SLE therapies included belimumab, hydroxychloroquine, cyclophosphamide, tacrolimus, azathioprine, mycophenolate mofetil, and corticosteroids; however, prescribing patterns varied across the region. Increased disease activity was associated with high economic burden and poor quality of life for SLE patients in APAC.

CONCLUSION

SLE remains a disease with a significant unmet medical need for an innovative therapy that is well-tolerated and effective for patients in APAC. Further evidence is required to better characterize the disease and fully capture the burden and impact of SLE in APAC. This review has highlighted where there is a paucity of data from patients across the APAC region.

Symptomatic multifocal avascular necrosis in an adolescent with neuropsychiatric systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by malar rash, oral ulcers, arthralgia, photosensitivity and nephritis. Herein, we report a rare comorbidity, multiple avascular necrosis (AVN), in an adolescent SLE patient and also highlight the importance of risk factors for this comorbidity with a brief literature review. A 13-year-old female patient was admitted with severe headache, visual plus auditory hallucinations, polyarthritis and a history of recurrent oral ulcers. Acneiform malar rash, arthritis, cytopenia, low complement levels and autoantibody positivity yielded SLE diagnosis. We diagnosed her as having multifocal AVN after the 4th dose of cyclophosphamide, with bilateral knee pain and swelling and typical geographical lesions on magnetic resonance imaging. Avascular necrosis is a rare comorbidity of SLE and neuropsychiatric involvement, cyclophosphamide administration and severe disease may be the possible risk factors in addition to corticosteroid use. Further multicenter studies investigating the possible risk factors of AVN with a large number of patients are needed.

Biomaterials to Mimic and Heal Connective Tissues

Connective tissue is one of the four major types of animal tissue and plays essential roles throughout the human body. Genetic factors, aging, and trauma all contribute to connective tissue dysfunction and motivate the need for strategies to promote healing and regeneration. The goal here is to link a fundamental understanding of connective tissues and their multiscale properties to better inform the design and translation of novel biomaterials to promote their regeneration. Major clinical problems in adipose tissue, cartilage, dermis, and tendon are discussed that inspire the need to replace native connective tissue with biomaterials. Then, multiscale structure-function relationships in native soft connective tissues that may be used to guide material design are detailed. Several biomaterials strategies to improve healing of these tissues that incorporate biologics and are biologic-free are reviewed. Finally, important guidance documents and standards (ASTM, FDA, and EMA) that are important to consider for translating new biomaterials into clinical practice are highligted.