Risk factors for avascular bone necrosis after renal transplantation

Management of Posttraumatic Avascular Necrosis of the Proximal Humerus

The etiology of avascular necrosis (AVN) of the proximal humerus can be classified as idiopathic or posttraumatic, the latter being mainly due to proximal humerus fractures. Evidence suggests that posttraumatic AVN may require surgical intervention more often than idiopathic AVN of the proximal humerus. This article provides a comprehensive review of the management of posttraumatic AVN of the proximal humerus. Early stage AVN (stages 1 to 3) is commonly treated with nonoperative intervention or core decompression of the humeral head, whereas later stage disease (stages 4 and 5) may require hemiarthroplasty or total shoulder arthroplasty to restore function. [Orthopedics. 2021;44(6):367-375.].

Outcomes of total hip arthroplasty in haemodialysis and renal transplant patients: systematic review

BACKGROUND

Chronic renal failure is increasing in prevalence and reported to have deleterious effects on the outcome of total hip arthroplasty (THA).

AIM

To investigate the clinical and functional outcomes of THA in patients receiving haemodialysis or who have previously undergone renal transplantation.

METHODS

Systematic review of the literature using bibliographic databases up to July 2018 to determine the functional outcome, complications and revision rates of THA in patients receiving haemodialysis for end-stage renal failure and those with a previous renal transplant.

RESULTS

25 studies were identified with a total of 797 THAs. 166 patients (20.8%) were receiving haemodialysis and 631 patients (79.2%) had undergone transplantation. All studies reported a marked improvement in hip function following THA. There were 27 failures (15.7% revision rate) in the haemodialysis group and 101 failures (16.0% revision rate) in the transplant group. The revision rate for cemented implants was higher in haemodialysis versus transplant patients (23% vs. 15%), with the converse being true for uncemented implants (3.8% vs. 6.9%). The deep infection rate was higher in the haemodialysis group (10.8% vs. 2.1%).

CONCLUSIONS

Patients receiving haemodialysis or with a history of renal transplantation can expect good functional outcome following THA. However, the revision rate and deep infection rate are higher than would be expected in patients receiving THA for primary OA. Aseptic loosening is the most common reason for revision. Uncemented implants appear to be associated with lower failure rates both in haemodialysis patients and those who have had a transplant.

Incidence and risk factors for osteonecrosis of the hip in renal transplant patients: a prospective single-centre study

BACKGROUND

There is a lack of evidence about the risk factors associated with osteonecrosis of the femoral head (ONFH).

PURPOSES

To determine the incidence and risk factors for ONFH following renal transplantation (RT).

METHODS

In total, data of 681 RT patients (mean age at surgery, 49.5 ± 13.6 years; 249 women and 432 men) were evaluated to determine the incidence of ONFH. Hip magnetic resonance imaging (MRI) was performed six months after RT. The following potential predictors of ONFH were evaluated: (1) patient's condition at RT; laboratory test results including calcium (Ca), phosphorus (P), calcium-phosphorus product (Ca × P), and intact parathyroid hormone before RT; blood relationship between the patient and donor; and mismatching number of human leukocyte antigens (HLAs), especially HLA class I and class II and (2) dosages of steroids after RT, immunosuppressive regimen, and incidence of acute rejection.

RESULTS

ONFH was observed in 30 hips (21 cases, 3.1%). We successfully matched 63 patients without ONFH. Multivariate logistic regression analysis, adjusted for cumulative dosages of steroids, revealed that mismatching number of HLA (hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.10-2.36; p = 0.014), HLA class II (HR, 3.73; 95% CI, 1.46-9.56; p = 0.001), P before RT (HR, 1.62; 95% CI, 1.02-2.58; p = 0.041), and Ca × P  before RT (HR, 1.06; 95% CI, 1.01-1.11; p = 0.024) were risk factors for ONFH.

CONCLUSION

A greater number of HLA mismatches, HLA class II, serum P, and serum Ca × P were risk factors for ONFH after RT. Therefore, these factors should be evaluated in order to predict ONFH after RT.

Osteonecrosis of Femoral Head, An Overlooked Long-Term Complication after Paraquat Intoxication: A Retrospective Cohort Study

With increasing numbers of patients surviving acute intoxication phase, long-term complication after paraquat intoxication is a topic worth exploring, such as osteonecrosis (ON) of femoral head. We reviewed 86 paraquat-intoxicated survivors between 2000 and 2012 in Chang Gung Memorial Hospital, a 3700-bed tertiary hospital in Taiwan. With all the patients underwent same detoxification protocol in the acute stage, 17.4% of paraquat poisoning survivors developed ON of femoral head requiring surgery during follow up. Most of ON episodes occurred within 2 to 4 years after paraquat intoxication and then plateau after 6 years. ON patients exhibited higher SOFA scores than non-ON patients (2.80 ± 2.14 vs. 1.76 ± 1.52, p = 0.028). Furthermore, AKIN scores are also higher in the ON patients than non-ON patients (0.87 ± 1.13 vs. 0.38 ± 0.74, p = 0.040). Multivariate logistic regression showed higher AKIN score and higher partial pressure of carbon dioxide in the blood 48 hours after admission significantly predicted ON of femoral head after paraquat intoxication (p = 0.002 and p = 0.006 respectively). Larger studies with longer follow-up durations are warranted to confirm our finding.

Avascular osteonecrosis in kidney transplant recipients: Risk factors in a recent cohort study and evaluation of the role of secondary hyperparathyroidism

Avascular osteonecrosis (AVN) is a bone complication that indicates poor functional prognosis. Modern immunosuppressive and steroid-sparing drugs have significantly lowered the occurrence of AVN after kidney transplantation (KT). However, recent data on its incidence rates and risk factors are lacking. Using a large, recent cohort, we sought to investigate AVN incidence and risk factors, with a special focus on mineral and bone disorders. We conducted a cohort study in 805 patients who underwent KT between 2004 and 2014. AVN was identified in 32 patients (4%): before KT in 15 (1.8%) and after KT in 18 (2.2%) cases, including one patient with both. In the group with post-KT AVN, the median time intervals from KT to 1) first symptoms and 2) AVN diagnosis were 12 months [1–99] and 20 months [4–100], respectively. Being overweight/obese, having pre-transplant diabetes or hyperparathyroidism at transplantation, developing acute rejection, and receiving higher cumulative corticosteroid doses were associated with AVN occurrence. Multivariate analysis revealed that BMI ≥ 26 kg/m² and higher cumulative corticosteroid doses were predictive of AVN. In conclusion, overweight/obesity is a strong risk factor for AVN. Despite a low maintenance dose, the use of corticosteroids—mostly for treatment of acute rejection—remains an independent risk factor.

Calcineurin-inhibitor induced pain syndrome - Magnetic resonance imaging and scintigraphic findings illustrated through two cases

Calcineurin-inhibitor induced pain syndrome (CIPS) is a condition characterized by lower extremity pain in patients receiving tacrolimus or cyclosporine therapy following organ transplantation. Through two cases, we demonstrate key imaging findings in CIPS with bone scintigraphy and magnetic resonance imaging (MRI), which are those of increased scintigraphic activity and marrow edema in the lower extremities, respectively. CIPS is an important condition that has characteristic imaging findings, but is unfortunately underappreciated in the radiology literature. To our knowledge, this is the first article in the radiology literature presenting two cases of CIPS, as well as the first to present both scintigraphic and MRI findings in this condition.

High-Dose Corticosteroid Use and Risk of Hip Osteonecrosis: Meta-Analysis and Systematic Literature Review

The effect of varying corticosteroid regimens on hip osteonecrosis incidence remains unclear. We performed a meta-analysis and systematic literature review to determine osteonecrosis occurrences in patients taking corticosteroids at varying mean and cumulative doses and treatment durations, and whether medical diagnoses affected osteonecrosis incidence. Fifty-seven studies (23,561 patients) were reviewed. Regression analysis determined significance between corticosteroid usage and osteonecrosis incidence. Osteonecrosis incidence was 6.7% with corticosteroid treatment of >2 g (prednisone-equivalent). Systemic lupus erythematosus patients had positive correlations between dose and osteonecrosis incidence. Each 10 mg/d increase was associated with a 3.6% increase in osteonecrosis rate, and >20 mg/d resulted in a higher osteonecrosis incidence. Clinicians must be wary of osteonecrosis in patients on high corticosteroid regimens, particularly in systematic lupus erythematosus.

Corticosteroid administration within 2 weeks after renal transplantation affects the incidence of femoral head osteonecrosis

BACKGROUND AND PURPOSE

It has been suggested that avascular osteonecrosis (AVN) of the femoral head occurs early after systemic steroid administration. The purpose of this study was to investigate the risks regarding development of AVN at a very early stage after renal transplantation.

METHODS

The presence or absence of AVN was determined by MRI at 4 weeks, at 6-12 weeks, at 24 weeks, and at 12 months after renal transplantation in 286 patients (183 males) with a mean age of 39 (16-65) years. The relationship between AVN and age, sex, absence or presence of acute rejection (AR), type of transplanted kidney (living or cadaveric), type of immune suppressor, and total dose of orally administered steroids given in the 2-week period after transplantation was investigated.

RESULTS

There were no statistically significant correlations between the development of AVN and age, sex, absence or presence of AR, type of transplanted kidney, or type of immune suppressor. A significant dose-response relationship was found between development of AVN and the total dose of steroid administered in the first 2 weeks after surgery.

INTERPRETATION

We found a relationship between AVN development and steroid dose in the early postoperative period, and we also showed a dose-response relationship.

Metabolic bone diseases in kidney transplant recipients

Metabolic bone disease after kidney transplantation has a complex pathophysiology and heterogeneous histology. Pre-existing renal osteodystrophy may not resolve completely, but continue or evolve into a different osteodystrophy. Rapid bone loss immediately after transplant can persist, at a lower rate, for years to come. These greatly increase the risk of bone fracture and vertebral collapse. Each patient may have multiple risk factors of bone loss, such as steroids usage, hypogonadism, persistent hyperparathyroidism (HPT), poor allograft function, metabolic acidosis, hypophosphatemia, vitamin D deficiency, aging, immobility and chronic disease. Clinical management requires a comprehensive approach to address the underlying and ongoing disease processes. Successful prevention of bone loss has been shown with vitamin D, bisphosphonates, calcitonin as well as treatment of hypogonadism and HPT. Novel approach to restore the normal bone remodeling and improve the bone quality may be needed in order to effectively decrease bone fracture rate in kidney transplant recipients.

Glucocorticoid-induced avascular bone necrosis: diagnosis and management

Glucocorticoid use is one of the most important causes of avascular bone necrosis (AVN). The pathogenesis of glucocorticoid-induced AVN is not fully understood but postulated mechanisms include fat hypertrophy, fat emboli and intravascular coagulation that cause impedance of blood supply to the bones. Data regarding the relationship between AVN and dosage, route of administration and treatment duration of glucocorticoids are conflicting, with some studies demonstrating the cumulative dose of glucocorticoid being the most important determining factor. Early recognition of this complication is essential as the prognosis is affected by the stage of the disease. Currently, there is no consensus on whether universal screening of asymptomatic AVN should be performed for long-term glucocorticoid users. A high index of suspicion should be exhibited for bone and joint pain at typical sites. Magnetic resonance imaging (MRI) or bone scintigraphy is more sensitive than plain radiograph for diagnosing early-stage AVN. Conservative management of AVN includes rest and reduction of weight bearing. Minimization of glucocorticoid dose or a complete withdrawal of the drug should be considered if the underlying conditions allow. The efficacy of bisphosphonates in reducing the rate of collapse of femoral head in AVN is controversial. Surgical therapy of AVN includes core decompression, osteotomy, bone grafting and joint replacement. Recent advances in the treatment of AVN include the use of tantalum rod and the development of more wear resistant bearing surface in hip arthroplasty.

NCI, NHLBI/PBMTC first international conference on late effects after pediatric hematopoietic cell transplantation: endocrine challenges-thyroid dysfunction, growth impairment, bone health, & reproductive risks

The endocrine system is highly susceptible to damage by high-dose chemotherapy and/or irradiation before hematopoietic cell transplantation (HCT) during childhood. The specific endocrine organs most affected by HCT include the thyroid gland, the pituitary, and the gonads. In addition, hormones that support development and stability of the skeletal system are also affected. Insufficiency of thyroid hormone is 1 of the most common late sequelae of HCT, and occurs more often in young children. Deficiency in the pituitary's production of growth hormone is a problem of unique concern to the pediatric population. The reproductive risks of HCT depend on the patient's gender and pubertal status at the time of HCT. Pubertal or gonadal failure frequently occurs, especially in females. Infertility risks for both genders remain high, whereas methods of fertility preservation are limited in all but postpubertal males. Bone health post-HCT can be compromised by low bone mineral density as well as avascular necrosis, but the data on both problems in the pediatric HCT population are limited. In this paper, the current state of knowledge, gaps in that knowledge, and recommendations for future research are addressed in detail for each of these systems.

Kienböck's disease: unusual cause of acute onset wrist pain in a dialysis patient

Kienböck's disease is a rare disorder that presents with wrist pain and limitation of motion and is caused by avascular necrosis of the lunate bone. Dialysis patients occasionally present with wrist pain. However, Kienböck's disease is rarely reported in dialysis patients. We report a case of 52-year-old woman with a 28-year history of hemodialysis who presented with acute wrist pain. T1-weighted magnetic resonance imaging showed diffuse low intensity of the lunate bone, consistent with the diagnosis of Kienböck's disease. Because this disease can lead to chronic debilitating wrist pain, prompt diagnosis, accurate staging, and provision of appropriate treatment is mandatory.

Steroid induced osteonecrosis: An analysis of steroid dosing risk

Osteonecrosis is a serious condition involving bone destruction that frequently requires surgical treatment to rebuild the joint. While there is an abundance of literature documenting corticosteroid related osteonecrosis, there is no consensus as to the relative risk of osteonecrosis after administration of steroids via parenteral, oral, topical, inhaled and other routes. This risk is an important prognostic indicator because identification and conservative intervention can potentially reduce morbidity associated with aggressive surgical treatment of osteonecrosis. This paper provides insight into establishing guidelines related to the risk of developing osteonecrosis as a result of corticosteroid use. Case studies, retrospective studies and prospective studies in humans on different corticosteroids and varied dosages were assessed. Most cases of osteonecrosis are secondary to systemically administered corticosteroids and/or high dose daily therapy, particularly in patients with underlying comorbidities including connective tissue diseases, hyperlipidemia, or previous trauma. Previous case reports of osteonecrosis related to inhaled or topical use of steroids are complicated by the fact that in the great majority of cases, the patients are also treated with systemic steroids prior to the development of osteonecrosis. Based on the literature, a set of recommendations regarding the risk of osteonecrosis in patients on steroids was formulated.

Curative effect and safety of vascularized fibula grafting in renal transplant recipients with osteonecrosis of the femoral head: three case reports

Osteonecrosis of the femoral head is a common and severe complication after renal transplantation. It is characterized by deterioration of hip joint function, which impairs quality of life. We present 3 renal transplant case reports of patients with osteonecrosis of the femoral head who underwent free vascularized fibular grafting at our hospital. Follow-up was from 1(1/2) to 2 years. All 3 patients exhibited good recovery with substantial improvement in joint function. Intraoperative and postoperative findings demonstrated the safety of this surgical procedure.

Predictors of avascular necrosis of bone in long-term survivors of hematopoietic cell transplantation

BACKGROUND

Avascular necrosis (AVN) is a debilitating condition reported after chronic steroid use. The purpose of this study was to describe the magnitude of risk in individuals who survived >or=1 years after hematopoietic cell transplantation (HCT), and to investigate the role of immunosuppressive agents such as prednisone, tacrolimus (FK506), mycophenolate mofetil (MMF), and cyclosporine (CSA) in the development of AVN after HCT.

METHODS

Using a retrospective study design, the authors followed 1346 eligible patients for the development of AVN. Cumulative incidence was calculated taking into consideration competing risk from death and disease recurrence. Cox proportional regression techniques were used to identify associated risk factors.

RESULTS

The median age at HCT was 34 years (range, 7 months-69 years), and median length of follow-up for those surviving was 8.2 years. Seventy-five patients developed AVN of 160 joints. The cumulative incidence of AVN at 10 years was 2.9% after autologous HCT, 5.4% after allogeneic matched related donor HCT, and 15% after unrelated donor HCT (P<.001 compared with autologous HCT recipients). For allogeneic transplant recipients, male sex (relative risk [RR], 2.1; 95% confidence interval [95% CI], 1.1-4.0); presence of chronic graft-versus-host disease (RR, 2.2); and exposure to CSA, FK506, prednisone, and MMF rendered patients at increased risk, especially in patients with a history of exposure to >or=3 drugs (RR, 9.2; 95% CI, 2.42-35.24).

CONCLUSIONS

Future studies examining the pathogenetic mechanism underlying AVN should help develop targeted interventions to prevent this chronic debilitating condition.

Degree of corticosteroid treatment within the first 2 months of renal transplantation has a strong influence on the incidence of osteonecrosis of the femoral head

BACKGROUND AND PURPOSE

It has been suggested that avascular osteonecrosis (AVN) of the femoral head develops early after renal transplantation. We evaluated the relationship between risk of AVN and dose of steroids administered in different time periods.

METHODS

Development of AVN was determined using MRI at 3-6 weeks, 9-12 weeks, 24 weeks, and 12 months after transplantation in 150 patients (96 males). We investigated possible associations between acute rejection reactions, the dose of cyclosporine, tacrolimus use, total steroid dose by the second, fourth, sixth, or eighth weeks after transplantation, and incidence of AVN.

RESULTS

There was no statistically significant difference between incidence of AVN and presence or absence of an acute rejection reaction. We found a statistically significant association between AVN incidence and the total dose of steroids administered during the first 2 months after transplantation, and there was a doseresponse relationship. No other statistically significant associations were found.

INTERPRETATION

Our findings confirm that the total dose of steroids given within the first 2 months after renal transplantation has a great influence on the incidence of AVN.

Management of metabolic bone disease in kidney transplant recipients

Bone disease after kidney transplantation has a complex pathophysiology and heterogeneous histology. Pre-existing renal osteodystrophy may not resolve completely, but continue or evolve into a different osteodystrophy. Rapid bone loss immediately after transplant can persist, at a lower rate, for years to come. These greatly increase the risk of bone fracture and vertebral collapse. Hypovitaminosis D, hyperparathyroidism and hyperaluminemia may resolve after kidney transplant, but many patients have other risk factors of bone loss, such as steroids usage, hypogonadism, persistent hyperparathyroidism, poor allograft function, aging, and chronic diseases. Clinical management requires a comprehensive approach to address the underlying and ongoing disease processes. Successful prevention of bone loss has been shown with vitamin D analogues, bisphosphonates and calcitonin. Novel approaches to restore the normal bone remodeling and improve the bone quality may be needed in order to effectively decrease bone fractures in kidney transplant recipients.

Study of rotating permanent magnetic field to treat steroid-induced osteonecrosis of femoral head

Sixty New Zealand rabbit models with steroid-induced necrosis of femoral head were exposed to a rotating permanent magnetic field (RPMF) (group A1-2 h/d for one month and group A2-2 h/d for two months), and the changes of femoral head, blood viscosity, serum cholesterol, triglyceride, and pressure within the hip joint cavity were measured and statistically analysed compared to that of control group (B1 and B2) and sham group (C1 and C2). After RPMF treatment, the osteogenesis regeneration of the necrotic femoral head was markedly improved, as was shown by micro-CT. Blood viscosity, serum cholesterol, triglyceride, and pressure in the hip joint cavity were found significantly reduced. RPMF could affect various critical aspects in the course of femoral head necrosis, which will be a promising measure in the prevention and treatment of steroid-induced necrosis of femoral head, especially in the early stage.

Avascular osteonecrosis after renal transplantation

Avascular osteonecrosis (AVN) is a serious osseous complication after renal transplantation. Its prevalence clearly decreased from 20% to 4% after introduction of cyclosporine and reduction of steroid doses. The aim of our study was to evaluate the frequency of AVN among kidney transplant recipients and to determine the risk factors by comparing them with a population without AVN. Among 326 kidney transplant recipients between June 1986 and December 2004, 15 patients developed AVN with mean age of 40.86 years, including 11 men and 4 women. Fifteen kidney transplant recipients without AVN were selected to be matched for age, gender, and date of transplantation (control group). Cases of symptomatic AVN were diagnosed by hip X-ray, radioisotope bone scan, or magnetic resonance imaging. AVN was diagnosed at a mean of 3.5 years after transplantation (range, 0.5-13 years). The main localization of AVN was the femoral head in 12 cases and the femoral condyle in 3 cases. We studied the following risk factors: the type of donor (cadaver or living donor), the duration on dialysis before transplantation, the cumulative steroid dose, the acute rejection rate, and the posttransplantation weight gain. Statistical analysis showed that the cumulative steroid dose and the acute rejection rate were higher among the AVN group than the control group (P=.04 and P=.058, respectively). The prevalence of AVN in our population is 4.6%, which is probably an underestimate since these were symptomatic cases. The reduction or early withdrawal of steroids remains the only efficient preventive treatment for AVN.

From marrow oedema to osteonecrosis: common paths in the development of post-transplant bone pain

Osteonecrosis, the calcineurin-inhibitor-induced pain syndrome and transient marrow oedema may occur after renal transplantation, are generally painful and can be diagnosed by X-ray, radionuclide scan or magnetic resonance imaging. They share features of increased intraosseous pressure, compromised vascular supply, marrow oedema and the development of a 'bone compartment syndrome'. Glucocorticoid dosage is the most commonly implicated risk factor for osteonecrosis. Mechanisms may include the differentiation of mesenchymal stem cells to adipocytes causing increased intraosseous pressure and collapse of marrow sinusoids, as well as increased osteoblast and osteocyte apoptosis. Some of these effects may be ameliorated by lipid lowering drugs. Calcineurin-inhibitors, particularly cyclosporine, may increase the risk of osteonecrosis because of vasoconstrictive effects and sirolimus may influence the development of osteonecrosis by potentiating the effects of calcineurin inhibitors or by influencing the lipid profile. For osteonecrosis, early stages are generally managed conservatively or with core decompression sometimes accompanied by bone grafting and more recently the injection of bone morphogenic protein. The use of iloprost to improve blood flow and bisphosphonates and RANK-ligand inhibition to reduce osteoclastic resorption of remaining trabecular structures are as yet unproven strategies. Unfortunately, the rate of total hip arthroplasty remains high. For the calcineurin-inhibitor-induced pain syndrome and transient marrow oedema, calcium channel blockers, the reduction or withdrawal of calcineurin-inhibitors and core decompression have been used. Although a lack of randomized controlled trials makes management decisions difficult, early recognition of these bone pain syndromes affords the best opportunity for avoiding prolonged pain or joint replacement surgery.

Association of corticosteroids and factor V, prothrombin, and MTHFR gene mutations with avascular osteonecrosis in renal allograft recipients

The mechanism of posttransplantation avascular osteonecrosis (AVN) is controversial. Besides an increased bone marrow pressure due to reduced blood supply, enhanced coagulation has been considered. We investigated the associations of factor V Leiden, prothrombin G20210A, and MTHFR C677T mutations as well as cumulative corticosteroid doses with AVN in renal allograft recipients. The records of 39 volunteer patients and 11 patients in whom osteonecrosis was previously identified were reviewed for cumulative corticosteroid dosages during the first year. All patients were screened for factor V Leiden, prothrombin G20210A, and MTHFR C677T mutations by direct sequencing of genomic DNA. The cumulative corticosteroid dosages at 3, 6, and 12 months in the osteonecrotic group (5033.5 +/- 1565.3, 7164.9 +/- 2063.1, 8835.1 +/- 2216.8 mg) were significantly higher than in the control group (3629 +/- 1504.1, 4784.5 +/- 1568.7, 6322.4 +/- 1686.6 mg; P = .013, P = .001, P = .001, respectively). No significant difference in factor V Leiden, prothrombin G20210A, and MTHFR C677T mutations was observed between the osteonecrotic and control groups (P > .05). In conclusion, an association between the first year (3, 6, and 12 month) cumulative corticosteroid dosages and AVN was demonstrated in renal transplant recipients. However, no correlation was determined between factor V Leiden, prothrombin G20210A, and MTHFR C677T mutations and osteonecrosis.

Diffusion-weighted MR study of femoral head avascular necrosis in severe acute respiratory syndrome patients

PURPOSE

To evaluate the apparent diffusion coefficient (ADC) of femoral head avascular necrosis (AVN) in severe acute respiratory syndrome (SARS).

MATERIALS AND METHODS

Seventy-nine SARS patients with hip pain underwent both conventional and diffusion-weighted MRI (b-value=0-1000 seconds/mm(2)). The abnormal regions on the diffusion-weighted images were outlined by using the conventional images as guides, and the ADCs were calculated. The ADC differences between normal and AVN femoral heads were compared.

RESULTS

Of the 158 hips examined, 28 had AVN (11 with bilateral hip AVN, three with right hip AVN, and three with left hip AVN). The mean ADC was markedly greater in the AVN femoral head (1.66 x 10(-3) mm(2)/second+/-0.20) than in the normal femoral head (0.47 x 10(-3) mm(2)/second+/-0.082; P<0.0001). There was no overlap between the normal and AVN femoral heads.

CONCLUSION

DWI can provide valuable information regarding the diffusion properties of femoral head AVN, and markedly increased diffusion was identified in AVN.

Maintenance immunosuppression use and the associated risk of avascular necrosis after kidney transplantation in the United States

BACKGROUND

Avascular necrosis (AVN) after renal transplantation has been largely attributed to the use of corticosteroids. However, other risk factors such as microvascular thrombosis and hyperlipidemia have been well described and may be of increased importance in the era of early steroid cessation and avoidance. We hypothesized that maintenance immunosuppressive medications known to be associated with these risk factors for AVN would also be associated with a higher risk of AVN.

METHODS

By using the U.S. Renal Data System database, we studied 27,772 primary patients on Medicare who received a solitary kidney transplant between January 1, 1996, and July 31, 2000. Cox proportional hazards regression models were used to calculate adjusted hazard ratios (AHRs) for patient- and transplant-related factors (including allograft rejection) with Medicare claims for AVN. The intensity and duration of corticosteroid use could not be assessed.

RESULTS

Among patients who were prescribed sirolimus at discharge, 3.5% of patients who received the combination of sirolimus-cyclosporine A (CsA) demonstrated AVN, compared with 1.4% of patients who received the combination of sirolimus-tacrolimus (P=0.06 by chi). In Cox regression, CsA use (vs. tacrolimus) (AHR 1.36, 95% confidence interval, 1.09-1.71) was independently associated with an increased risk of AVN. Sirolimus use showed a trend toward significance (AHR 1.59, 95% confidence interval, 0.99-2.56), with no significant interaction with CsA.

CONCLUSIONS

Compared with other maintenance immunosuppression, AVN was significantly more common after use of CsA prescribed at the time of discharge for renal transplantation. Whether this increased risk of AVN was directly attributable to hyperlipidemia, microvascular thrombosis, or differences in corticosteroid dosing could not be determined.

Avascular necrosis of bone in severe acute respiratory syndrome

AIM: To report the incidence of avascular osteonecrosis (AVN) in severe acute respiratory syndrome (SARS) patients.

MATERIALS AND METHODS: Sixty-seven SARS patients who had large joint pain between March 2003 and May 2003 underwent both plain radiographs and magnetic resonance imaging (MRI) examination on the same day. All patients received steroids and ribavirin treatment. All plain radiographs and MR images were analysed by two experienced musculoskeletal radiologists. Any abnormalities, location, extent, morphology, the number, size and signal intensity of lesions were evaluated.

RESULTS: Twenty-eight patients were identified with AVN, The mean time to diagnosis of AVN was 119 days after the onset of SARS, or 116 days after steroid use. Three patients had early bilateral AVN of the femoral head, four patients of one femoral head, five patients of the bilateral hips and knees, four patients of the ipsilateral hip and knees, 10 patients of the knee(s), one patient of the right proximal fibula, and one patient of the knees and talus. Results of hip, knee and ankle plain radiographs were negative.

CONCLUSION: AVN can occur in the patients with SARS. AVN had a strong association with steroid use. More studies are required to confirm whether the virus itself can also lead to AVN.

Bone disease after renal transplantation

Bone disease is common after renal transplantation. The main syndromes are bone loss with a consequent fracture rate of 3% per year, osteonecrosis of the hip, and bone pain. The causes of disease include preexisting uremic osteodystrophy (hyperparathyroidism, aluminum osteomalacia, beta2-associated amyloidosis, and diabetic osteopathy), postoperative glucocorticoid therapy, poor renal function, and ongoing hyperparathyroidism, as the result of either autonomous transformation of the parathyroid gland or ongoing physiologic stimuli. Cyclosporine A treatment, hyperphosphaturia, and a pathogenic vitamin D allele have also been implicated. Bone loss is particularly pronounced during the first year after operation, amounting to up to 9% of bone mass. The clinical and biochemical picture is consistent with a high turnover bone disease, but histomorphometric studies do not completely support this. Principal prophylactic options include preoperative osteodystrophy prophylaxis; postoperative calcium, vitamin D, or calcitriol therapy; estrogen therapy for postmenopausal women; and parathyroidectomy for medically intractable hyperparathyroidism. Recently, prophylactic biphosphonate treatment has shown promise, but the exact indications for treatment remain to be determined.