Femoral head osteonecrosis: detection and grading by using a rapid MR imaging protocol

Long-Term Results of a Phase I/II Clinical Trial of Autologous Mesenchymal Stem Cell Therapy for Femoral Head Osteonecrosis

(1) Background: Osteonecrosis of the femoral head (ONFH) is characterized by impaired vascularization with ischemia resulting in bone cell death, leading to the deterioration of the hip joint. Mesenchymal stem/stromal cells (MSCs) are an attractive potential therapeutic approach in this setting. The aim of this study is to evaluate the clinical improvement in terms of pain and quality of life, as well as the safety of the procedure during the follow-up of patients. (2) Methods: A Phase I-II Open-Label Non-Randomized Prospective clinical trial was conducted. Eight patients with idiopathic ONFH and stage < IIC in the ARCO classification were included. Four weeks before therapy, 40 mL of autologous bone marrow was obtained, and MSCs were expanded under Good-Manufacturing-Practice (GMP) standards. Study medication consisted of a suspension of autologous BM-derived MSCs (suspended in a solution of 5-10 mL of saline and 5% human albumin) in a single dose of 0.5-1 × 10⁶ cells/kg of the patient, administered intraosseously with a trocar and under radioscopic control. Per-protocol monitoring of patients included a postoperative period of 12 months, with a clinical and radiological assessment that included the visual analog scale (VAS), the Harris scale, the SF-36, and the radiological evolution of both hips. In addition, all patients were further followed up for eight years to assess the need for long-term total hip replacement (THR) surgery. (3) Results: Median age of patients included was 48.38 ± 7.38 years, and all patients were men. Autologous MSCs were expanded in all cases. There were no adverse effects related to cell administration. Regarding efficacy, both VAS and ODI scores improved after surgery. Radiologically, 12.5% of patients improved at the end of follow-up, whereas 50% improved clinically. No adverse effects related to the procedure were recorded, and none of the patients needed THR surgery within the first year after MSC therapy. (4) Conclusions: The use of autologous MSCs for patients with ONFH disease is feasible, safe in the long term, and potentially effective.

Optimization of MRI Protocol for the Musculoskeletal System

자기공명영상(magnetic resonance imaging; 이하 MRI)은 다른 영상 기법에 비해 연부 조직 대조도와 해상력이 높아 근골격계 영역에서 중요한 진단 기기로 이용되고 있다. 최근 MRI 관련 기술이 발달함에 따라 빠른 영상 촬영 및 다양한 영상면 재구성이 가능해짐으로써 입체적인 근골격계 해부학적 구조와 병변을 더욱 잘 평가할 수 있게 되었다. 또한, MRI는 최적화 정도에 따라 영상의 질, 진단 정확도 및 촬영 시간 등이 달라지며, MRI 장치의 효율적 인 운용과도 관련이 있어, 이를 관리하는 것은 영상의학과 의사의 중요한 역할이다. 본 종설에서는 6개 주요 관절에 따른 환자 자세, radiofrequency 코일 선택, 권장 펄스열, 영상면 구성 및 스캔 파라미터에 대한 지침을 제시함으로써 근골격계 MRI의 최적화에 도움이 되고자 한다.

Acute hip pain: mimics of a femoral neck fracture

Acute hip pain is a common presenting complaint among patients attending Emergency Departments particularly following a traumatic event. A proximal femoral fracture is the main consideration, which requires urgent confirmation and treatment; however, there are a number of conditions, which could mimic neck of femur fracture and the causes may not be directly related to the hip, so systematic and careful observation of pelvic MRI could shed light on the true culprit of acute hip pain.

Long-term Outcome of Multiple Small-diameter Drilling Decompression Combined with Hip Arthroscopy versus Drilling Alone for Early Avascular Necrosis of the Femoral Head

BACKGROUND

Avascular necrosis of femoral head (AVNFH) typically presents in the young adults and progresses quickly without proper treatments. However, the optimum treatments for early stage of AVNFH are still controversial. This study was conducted to evaluate the therapeutic effects of multiple small-diameter drilling decompression combined with hip arthroscopy for early AVNFH compared to drilling alone.

METHODS

This is a nonrandomized retrospective case series study. Between April 2006 and November 2010, 60 patients (98 hips) with early stage AVNFH participated in this study. The patients underwent multiple small-diameter drilling decompression combined with hip arthroscopy in 26 cases/43 hips (Group A) or drilling decompression alone in 34 cases/55 hips (Group B). Patients were followed up at 6, 12, and 24 weeks, and every 6 months thereafter. Radiographs were taken at every follow-up, Harris scores were recorded at the last follow-up, the paired t-test was used to compare the postoperative Harris scores. Surgery effective rate of the two groups was compared using the Chi-square test.

RESULTS

All patients were followed up for an average of 57.6 months (range: 17-108 months). Pain relief and improvement of hip function were assessed in all patients at 6 months after the surgery. At the last follow-up, Group A had better outcome with mean Harris' scores improved from 68.23 ± 11.37 to 82.07 ± 2.92 (t = -7.21, P = 0.001) than Group B with mean Harris' scores improved from 69.46 ± 9.71 to 75.79 ± 4.13 (t = -9.47, P = 0.037) (significantly different: t = -2.54, P = 0.017). The total surgery effective rate was also significantly different between Groups A and B (86.0% vs. 74.5%; χ2 = 3.69, P = 0.02).

CONCLUSION

For early stage of AVNFH, multiple small-diameter drilling decompression combined with hip arthroscopy is more effective than drilling decompression alone.

ACR Appropriateness Criteria Osteonecrosis of the Hip

Osteonecrosis of the hip (Legg-Calvé-Perthes) is a common disease, with 10,000-20,000 symptomatic cases annually in the United States. The disorder affects both adults and children and is most frequently associated with trauma and corticosteroid usage. The initial imaging evaluation of suspected hip osteonecrosis is done using radiography. MRI is the most sensitive and specific imaging modality for diagnosis of osteonecrosis of the hip. The clinical significance of hip osteonecrosis is dependent on its potential for articular collapse. The likelihood of articular collapse is significantly increased with involvement of greater than 30%-50% of the femoral head area, which is optimally evaluated by MRI, often in the sagittal plane. Contrast-enhanced MRI may be needed to detect early osteonecrosis of the hip in pediatric patients, revealing hypoperfusion. In patients with a contraindication for MRI, use of either CT or bone scintigraphy with SPECT (single-photon emission CT) are alternative radiologic methods of assessment. Imaging helps guide treatment, which may include core decompression, osteotomy, and ultimately, need for joint replacement. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

The use of core track endoscopy to document accurate decompression of the femoral head

The aim of this study is to evaluate the role of endoscopy as diagnostic and prognostic method for Ficat and Steinberg stage IIIA and IIIB lesions by assessing the efficacy, risks and complications of this method. In a prospective study from January 2008 until September 2013, nine patients (13 hips) were assessed. In nine hips the disease was stage II, in three hips stage III and in one hip stage IV. Evaluation included x-rays, magnetic resonance and bone scintigraphy. After femoral head decompression, the borders of the removed necrotic area were investigated under direct visualisation by means of endoscopy in order to assess the vitality status of the surrounding bone. Endoscopic evaluation was successful in nine hips. The visualisation of healthy bone borders after removing the necrotic bone was not possible in four cases. The preoperative MRI findings were in correlation to our endoscopic findings in five out of nine cases. There were no cases of cartilage perforation, femoral neck fracture and other intra and postoperative complications. Endoscopic evaluation of the removed necrotic bone can greatly improve the therapeutic effect by visualising the borders of the decompressed bone area and provide information regarding the necessity for bone graft and the type of graft required.

Differentiation, diagnosis, and treatment of osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis

Osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis are hip arthropathies that result in marked pain and disability. Although these diseases share features of arthritis-like symptoms and are all treated with total hip arthroplasty, they are separate diseases with distinct epidemiologic, radiographic, and histopathologic findings. In this article, the authors present clinical tips and techniques that will aid the surgeon in diagnosing and treating these different entities.

Accuracy and limitations of diagnostic methods for avascular necrosis of the hip

INTRODUCTION

Femoral head avascular necrosis (FHAVN) is the result of irreversible anoxia of the subchondral bone. The death of bone cells can cause articular collapse and pain, and in turn usually leads to degenerative arthritis. FHAVN is a common disorder, affecting mainly young male adults. Reliability, accuracy and prognostic value of any classification system are important in evaluation and treatment of FHAVN.

AREAS COVERED

Although in the past, scintigraphy and CT and more recently PET have been used for diagnosing AVN, currently the most important imaging methods included in the most widely used classification systems, consist of radiographs and magnetic resonance imaging (MRI). The latter is used in major classification systems for early detection (pre-radiographic stage) of FHAVN and for assessing lesion size and location before collapse of the articular surface occurs. The purpose of this review is to present the current data regarding the accuracy of the X-rays and MRI in diagnosing, monitoring and postoperative evaluation of FHAVN.

EXPERT OPINION

The author's opinion is that MRI may contribute to improve staging, investigate radiologically occult collapse, depict other causes of disability and pain, assess prognosis and evaluate treatment. Newer MRI techniques, such as diffusion-weighted imaging and perfusion imaging, have not yet provided additional and clinically useful information.

Value of sagittal fat-suppressed proton-density fast-spin-echo of the knee joint as a limited protocol in evaluating internal knee derangements

PURPOSE

The aim of the study was to determine the accuracy and observer agreement in the assessment of internal knee derangement using sagittal fat-suppressed proton-density fast-spin-echo (FS PD-FSE) compared with combined sagittal T1-weighted spin-echo, dual-proton-density, and T2-weighted spin-echo sequences and with arthroscopy.

METHODS

One hundred eighteen patients undergoing routine knee magnetic resonance (MR) imaging had additional imaging with sagittal FS PD-FSE sequences. Menisci, cruciate ligaments, extensor tendons (ETs), bone marrow, osteoarthritic changes, soft tissue edema, joint effusion, and incidental tumors were analyzed. Magnetic resonance images were independently reviewed by 2 radiologists. Fifty patients underwent knee arthroscopy. Statistical analysis compared both imaging protocols with each other and with arthroscopy. Intrareader and interreader agreements were evaluated using κ analysis. Both protocols were compared with arthroscopy.

RESULTS

Intrareader agreement was very high except for readings of the posterior cruciate ligament, ETs, and cartilage. Intrareader agreement did not differ significantly between the 2 readers except for ETs, bone marrow, and cartilage. Interreader percent agreements were high using both protocols and were not significantly different between the 2 readers except for posterior cruciate ligament. Compared with arthroscopy, both methods showed almost identical results regarding sensitivity, specificity, positive predictive value, and negative predictive value, except for cartilage where FS PD-FSE had increased sensitivity, whereas the combined protocol had increased specificity.

CONCLUSIONS

Sagittal FS PD-FSE is comparable to our regular MR protocol in assessing internal knee derangement with an overall agreement of at least 93% on all sites except cartilage. It was also comparable to arthroscopy in assessing the cruciate ligaments and menisci, but had a low specificity for cartilaginous derangements. It can replace our 3 sagittal series comprising T1- and T2-weighted and proton-density-spin-echo sequences, hence saving time and cost.

Osteonecrosis in children after therapy for malignancy

OBJECTIVE

Osteonecrosis in the growing population of childhood cancer survivors results from disease and treatment. Imagers must be knowledgeable about patient groups at risk for its development, patterns of involvement and potential implications. This review will focus on implications of this potentially life-altering toxicity.

CONCLUSION

Childhood cancer survivors are at increased risk for developing osteonecrosis. Because osteonecrosis is often asymptomatic until late in the process, imaging is critical for its detection and characterization when interventions may be most effective to ameliorate its progression.

Osteonecrosis in human immunodeficiency virus (HIV)-infected patients: a multicentric case-control study

Osteonecrosis (ON) is a rare disabling complication occurring in patients with human immunodeficiency virus (HIV) infection at a higher frequency than in the general population despite effective combination antiretroviral therapy being made available, as recently documented by several retrospective studies. We designed a multicentric case-control study among HIV-infected patients cared for at institutions in the Italian CISAI group (Italian Study Group for Adverse Events in HIV Infection) to search for additional predictors of ON in this special population. All centers which observed at least one case of ON were requested to report data for central re-evaluation. Parallel HIV-positive, ON-free controls were randomly selected and matched with confirmed cases of ON for sex, age and CD4 T-cell counts at the time of HIV diagnosis. Fifteen cases and controls were included in the final sample. Univariate statistical analyses revealed a significant association between ON and exposure to steroids (P = 0.001), exposure to one or more drugs in addition to HAART (Highly Active Anti-Retroviral Therapy) (P = 0.03), high titers of total serum IgE (P = 0.02), loss of working ability (P = 0.03), triglycerides levels over 200 mg/dL before antiretrovirals (P = 0.03) and cholesterol levels over 200 mg/dL before and after antiretrovirals (P = 0.03 and 0.05, respectively). High serum IgE levels and loss of working ability in advance of ON appeared for the first time as possible predictors of ON in HIV patients, while long-term exposure to steroids, combined hyperlipemia and chronic treatment with other drugs in addition to antiretrovirals were confirmed. Predicting and preventing ON in the individual HIV-infected patient is therefore a clinically challenging opportunity.

Osteonecrosis of the femoral head: etiology, imaging and treatment

Osteonecrosis of the femoral head is a disabling clinical entity affecting young adults that usually leads to destruction of the hip joint. A high index of suspicion is necessary for the diagnosis due to the insidious onset of the bone infarcts and the lack of specific clinical signs at the early stages. Many etiology-associated factors have been identified reducing thus the number of idiopathic cases. A number of joint salvaging treatment options are available if early diagnosis can be achieved. MR imaging has been proved to be a highly accurate method both for early diagnosis and for staging of the disease. Replacement of the hip joint is the last resort for pain relief and function, although non-desirable because of the young age of the affected population.

Imaging the complications of bone marrow transplantation in children

Bone marrow transplantation is frequently performed to restore hematologic and immunologic competence after chemotherapy and radiation therapy for a range of childhood malignancies, as well as to treat various congenital conditions in which hematologic and immunologic functions are depressed or absent. Potentially devastating complications may occur during the pre-engraftment period after bone marrow transplantation, when marrow aplasia may supervene for several weeks until engraftment occurs, as well as during the post-engraftment period (the 3 months after engraftment) and in subsequent months and years. Complications of bone marrow transplantation may be classified either according to the time interval between transplantation and the occurrence of the complication or according to the organ system affected. The range of complications that may affect the central nervous system and the rest of the body may be detected with ultrasonography, computed tomography, and magnetic resonance imaging. Neurologic, paranasal sinus, pulmonary, and abdominopelvic complications all may be seen after bone marrow transplantation. Graft-versus-host disease and lymphoproliferative disorders also may occur. The increasing use of bone marrow transplantation mandates that the radiologist be familiar with the full range of potential complications and their imaging appearances.

The incidence and natural history of osteonecrosis in HIV-infected adults

BACKGROUND

Osteonecrosis is increasingly recognized as a debilitating complication of human immunodeficiency virus (HIV) infection, but the natural history has not been well described. We previously documented a high prevalence (4.4%) of magnetic resonance imaging (MRI)-documented osteonecrosis of the hip in a cohort of 339 asymptomatic HIV-infected patients. The present study was designed to determine the incidence of newly diagnosed osteonecrosis in this cohort and to describe the natural history of osteonecrosis in HIV-infected patients.

METHODS

Asymptomatic HIV-infected patients with a previous hip MRI negative for osteonecrosis underwent follow-up MRI. Patients with asymptomatic or symptomatic osteonecrosis were enrolled in a natural history study, which included serial MRIs and a physiotherapy follow-up.

RESULTS

Two hundred thirty-nine patients underwent a second MRI a median of 23 months after the initial MRI. Osteonecrosis of the femoral head was diagnosed in 3 patients (incidence, 0.65 cases per 100 person-years). During the period of January 1999 through April 2006, symptomatic hip osteonecrosis developed in 13 clinic patients (incidence, 0.26 cases per 100 person-years). Among 22 patients enrolled with symptomatic hip osteonecrosis, 18 had bilateral involvement of the femoral heads, and 7 had osteonecrosis involving other bones. Two (11%) of 18 asymptomatic patients and 13 (59%) of 22 symptomatic patients underwent total hip replacement. The percentage of involvement of the weight-bearing surface of the femoral head and the rate of progression to total hip replacement was significantly greater (P<.001) in symptomatic patients than in asymptomatic patients.

CONCLUSIONS

HIV-infected patients are at approximately 100-fold greater risk of developing osteonecrosis than the general population. Disease progression is slower in asymptomatic patients than in symptomatic patients. Given the high frequency of total hip replacement in symptomatic patients, studies to assess preventive and treatment strategies are essential.

Systematic analysis of classification systems for osteonecrosis of the femoral head

BACKGROUND

Multiple classification systems for osteonecrosis of the hip have been developed to assist physicians in the diagnosis and treatment of this potentially debilitating disorder. The purpose of this analysis was to delineate the classification systems utilized in reports published since 1985 and, through a comparison of the most commonly used systems, to identify consistent factors that would allow for cross-publication comparisons to be made.

METHODS

We performed a PubMed search for reports of outcome studies concerning treatment methods for osteonecrosis of the hip. All studies of reported outcomes with greater than ten patients were included in the analysis. Various classification systems were tabulated to determine usage frequencies. The four most commonly used systems were then analyzed to determine common factors used for classification.

RESULTS

One hundred and fifty-seven studies were available for analysis. Sixteen major classification systems that made use of more than one radiographic factor were identified, and nine of these systems had one to five modifications reported throughout the literature. Additionally, eleven other systems made use of single factors obtained from either magnetic resonance imaging or anatomic data. The review revealed that four classification systems accounted for greater than 85.4% of the reported studies. Parameters for these four systems were stratified to allow for uniformity of patient or study evaluation.

CONCLUSIONS

This analysis of the reported classification systems for osteonecrosis of the femoral head revealed several similarities between the most commonly used systems. An analysis of patients can be made with any of the four major systems if specific data are collected according to various magnetic resonance imaging and radiographic findings. This approach will allow for easier comparison of studies across different centers.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

Nontraumatic osteonecrosis of the femoral head: ten years later

The etiology of osteonecrosis of the hip may have a genetic basis. The interaction between certain risk factors and a genetic predisposition may determine whether this disease will develop in a particular individual. The rationale for use of joint-sparing procedures in the treatment of this disease is based on radiographic measurements and findings with other imaging modalities. Early diagnosis and intervention prior to collapse of the femoral head is key to a successful outcome of joint-preserving procedures. The results of joint-preserving procedures are less satisfactory than the results of total hip arthroplasty for femoral heads that have already collapsed. New pharmacological measures as well as the use of growth and differentiation factors for the prevention and treatment of this disease may eventually alter our treatment approach, but it is necessary to await results of clinical research with long-term follow-up of these patients.

Osteonecrosis of Hip and Knee in Patients with Severe Acute Respiratory Syndrome Treated with Steroids

PURPOSE

To evaluate whether there is a relationship between steroid treatment and risk for osteonecrosis of the hip and knee in patients with severe acute respiratory syndrome (SARS).

MATERIALS AND METHODS

The hospital ethics committee approved the study, and all patients provided written informed consent. A total of 254 patients with confirmed SARS treated with steroids underwent evaluation with magnetic resonance (MR) imaging for osteonecrosis. Clinical profiles, joint symptoms, relevant past medical and drug history, steroid dose, and radiographic and MR imaging evidence of osteonecrosis and other bone abnormalities were evaluated. Mann-Whitney, Kruskal-Wallis, and Pearson exact chi(2) tests were performed, and univariate and multivariate logistic regression analyses were applied.

RESULTS

One hundred thirty-four (53%) of 254 patients had recent onset of large joint pain, but 211 (80%) of 264 painful joints were not associated with abnormality on MR images. MR images in 12 (5%) of 254 patients showed evidence of subchondral osteonecrosis in the proximal femur (n = 9), distal femur (n = 2), and proximal and distal femora and proximal tibiae (n = 1). Additional nonspecific subchondral and intramedullary bone marrow abnormalities were present in 77 (30%) of 254 patients. Results of multiple logistic regression analysis confirmed cumulative prednisolone-equivalent dose to be the most important risk factor for osteonecrosis. The risk of osteonecrosis was 0.6% for patients receiving less than 3 g and 13% for patients receiving more than 3 g prednisolone-equivalent dose. No relationship was found between additional nonspecific bone marrow abnormalities and steroid dose.

CONCLUSION

An appreciable dose-related risk was found for osteonecrosis in patients receiving steroid therapy for SARS. Additional nonspecific bone marrow abnormalities were frequent. Joint pain was common after SARS infection and was not a useful clinical indicator of osteonecrosis.

Pharmacogenetic Risk Factors for Osteonecrosis of the Hip Among Children With Leukemia

Purpose

One of the adverse effects of therapy for acute lymphoblastic leukemia (ALL) is osteonecrosis of the hip. Putative risk factors for osteonecrosis have included being female, white race, and older age. Our goal was to define possible genetic risk factors for osteonecrosis among children treated for newly diagnosed ALL.

Methods

Using a candidate gene approach, we determined the genotypes for 16 common polymorphisms in genes likely to affect the pharmacokinetics or pharmacodynamics of antileukemic medications in 64 children with ALL. Therapy included glucocorticoids and antifolates. Magnetic resonance imaging of both hips was used to diagnose osteonecrosis, and was performed at similar times from the start of ALL therapy (P = .61) in the 25 patients with and the 39 patients without osteonecrosis (median, 447 days and 443 days, respectively).

Results

In addition to age older than 10 years (odds ratio [OR], 24.2; P = .0001) and white race (OR, 11.1; P = .037), host factors for osteonecrosis included the vitamin D receptor FokI start site CC genotype (OR, 4.5; P = .045), and the thymidylate synthase low activity 2/2 enhancer repeat genotype (OR, 7.4; P = .049).

Conclusion

Because folate-related and vitamin D–receptor genetic variants have been associated with bone and vasculature morbidity, these pharmacogenetic associations likely reflect the interaction of antileukemic medications with germline sensitivity to drug actions, and might identify ALL patients at highest risk to develop osteonecrosis.

Avascular necrosis and bone marrow edema syndrome

MR imaging is the most accurate modality for the diagnosis of AVN, bone marrow edema syndrome, and femoral head insufficiency fractures. When the particular demographics of the patient are considered, the specificity of this examination is high. The reported success rates of joint-sparing operative intervention are variable. When compared with conservative management, the outcome of joint-sparing operative intervention in patients who have early (stage I, II) AVN lesions is improved. This is impetus for screening programs for patients who are known to be at high risk for AVN, such as patients who have undergone renal transplants and others who are on long-term, high-dose corticosteroid treatment. There is strong evidence that bone marrow edema syndrome (TO) is a distinct entity with demonstrable unique histopathology and well-defined demographics. Increased spatial resolution revealed typical subchondral findings of AVN in lesions that were once believed to represent irreversible TO. SIF of the femoral head is a new concept with a seemingly distinct population and with clinical presentation and imaging characteristics that should permit its differentiation from AVN.

Subchondral fractures in osteonecrosis of the femoral head: comparison of radiography, CT, and MR imaging

OBJECTIVE

Our objective was to compare the sensitivity of unenhanced radiography, CT, and MR imaging in revealing subchondral fractures.

SUBJECTS AND METHODS

Forty-five subjects with stage I and stage II osteonecrosis of the femoral head were included in the study as part of a multicenter clinical trial to evaluate the effectiveness of recombinant human bone morphogenetic protein as an adjuvant treatment to core decompression. Patients were evaluated with radiography, CT, and MR imaging 6 and 12 months after surgery.

RESULTS

At 6 months, 18 fractures were shown on CT scans, but only 12 were detected on radiographs and six, on MR images. At 12 months, 20 subchondral fractures were detected on CT scans, but only 17 were seen on radiographs and 11, on MR images. Compared with CT, MR imaging has a sensitivity and specificity of 38% and 100%, and unenhanced radiography has a sensitivity and specificity of 71% and 97%, respectively. On T2-weighted MR images, the subchondral fractures were visualized as crescentic high-signal-intensity lines, and in all patients, on the corresponding CT scans, the fracture clearly breached the femoral cortex.

CONCLUSION

CT reveals more subchondral fractures in osteonecrosis of the femoral head than unenhanced radiography or MR imaging. The high-signal-intensity line seen on T2-weighted MR images appears to represent fluid accumulating in the subchondral fracture, which may indicate a breach in the overlying articular cartilage.

Association of plasminogen activator inhibitor-1 genotype with avascular osteonecrosis in steroid-treated renal allograft recipients

BACKGROUND

The mechanism of avascular osteonecrosis (AVN) is controversial. Besides an increased bone marrow pressure with reduced blood supply, an enhanced coagulation has been considered. We hypothesize that a genetic variant of the plasminogen activator inhibitor-1 (PAI-1) determines the risk of AVN in glucocorticoid-treated patients.

METHODS

Genotyping for the 4G/5G PAI-1 polymorphism was performed in 228 glucocorticoid-treated renal transplant patients. AVN of the hip was present in 26 patients. Magnetic resonance imaging (MRI) of the hips was obtained in 81 of the remaining renal transplant patients without clinical symptoms of AVN.

RESULTS

The presence of the homozygous 4G/4G PAI-1 genotype was higher in patients with AVN (60.3%) as compared with patients without either clinical (20.6%, P<0.007) or radiological signs of AVN (17.3%, P<0.002). The prevalence of AVN by genotype was 1.8% with the 5G/5G, 7.7% with the 5G/4G, and 30.3% with the 4G/4G alleles (P<0.001 vs. 5G/4G and 5G/5G). The prevalence of AVN increased with increasing body mass index (BMI) (P=0.04). The prevalence of AVN by genotype in subjects with persistent hyperparathyroidism was 4.2% with the 5G/5G, 15.2% with the 5G/4G, and 55.5% with the 4G/4G alleles (P<0.003 vs. 5G/4G and P<0.001 vs. 5G/5G).

CONCLUSIONS

Hypofibrinolysis conferred by the 4G/4G PAI-1 gene variant is a major predisposing factor for AVN in renal transplant patients. The risk is particularly high in obese subjects or patients with persistent hyperparathyroidism. A prospective intervention study of early anticoagulation after renal transplantation is needed to assess whether glucocorticoid-associated AVN can be prevented.