Hospitalizations for fractures after renal transplantation in the United States

Postoperative Care and Outcomes in Solid-Organ Transplant Patients Undergoing Lower Extremity Fracture Treatment

OBJECTIVES

To determine the postoperative outcomes in solid-organ transplant (SOT) patients undergoing operative treatment of lower extremity fractures.

METHODS

DESIGN

Retrospective comparative study.

SETTING

Academic Level 1 trauma center.

PATIENT SELECTION CRITERIA

Patients who underwent SOT and operative treatment of lower extremity fracture from 2013 to 2021 were identified, excluding pathologic fractures.

OUTCOME MEASURES AND COMPARISONS

Postoperative complications, length of stay, time to death, 90-day and 1-year readmission rates, readmission causes, discharge location, and immunosuppressive regiments.

RESULTS

Sixty-one patients with an average age of 67 years (range 29-88) were included. The mortality rate was 37.7%. The average follow-up was 15.2 months (range of 2 weeks-10 years). The majority of patients (32.8%) had received a liver transplant, and femoral neck fractures constituted the largest fracture group. The average length of stay was 10 days, with the shortest being 1 day and the longest being 126 days (SD 18). The majority of patients (57.3%) were not discharged home. Only 2 suffered from a postoperative complication requiring another procedure: hardware removal and liner exchange for periprosthetic joint infection, respectively. There was a 27.9% 90-day readmission rate with 2 deaths within that period with the most common being altered mental status (29.4%), genitourinary infections (17.6%), repeat falls (11.8%), and low hemoglobin requiring transfusion (11.8%). The longest average time to death analyzed by transplant type was found among lung transplant patients (1076 days, 62.5% mortality), followed by liver transplant patients (949 days, 35.0% mortality), and then kidney transplant patients (834 days, 38.9% mortality). The shortest time to death was 71 days from index procedure.

CONCLUSIONS

Family members of SOT patients undergoing operative treatment of lower extremity fractures should be made aware of the high risk for 90-day readmission postoperatively (27.9%) and overall mortality (12.5%). Providers should be aware of the need for multidisciplinary involvement for inpatient care, monitoring postoperative complications, and facilitating discharge planning.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Pretransplant Parathyroidectomy in Patients with Severe Secondary Hyperparathyroidism and Long-Term Effectiveness After Kidney Transplantation

Kidney transplantation (KT) is the best option for patients with end-stage renal disease, but recipients still have legacy bone mineral disease from the pretransplant period, especially patients with severe secondary hyperparathyroidism (sHPT). Patients who had severe sHPT and underwent KT were analyzed retrospectively. Two groups were identified (patients with severe sHPT who had parathyroidectomy or calcimimetic before KT). Bone mineral density (BMD) was measured in the first year and last follow-up at the femoral neck, total hip, and lumbar spine using the dual-energy X-ray absorptiometry (DXA). Persistent hyperparathyroidism (perHPT) incidence was significantly higher in the calcimimetic group (75% vs. 40%, p=0.007). In patients with parathyroidectomy, BMDs were higher at femoral neck (0.818±0.114 vs. 0.744±0.134, p=0.04) and lumbar spine (1.005±0.170 vs. 0.897±0.151, p=0.01) at the first assessment. The BMD comparison between patients treated with parathyroidectomy and calcimimetic found a significant difference only in the femoral neck at second evaluation (0.835±0.118 vs. 0.758±0.129; p=0.03). In multivariate, linear regression revealed a positive association between the last BMD of the femoral neck with body mass index (CC: 0.297, 95% CI, 0.002-0.017) and parathyroidectomy (CC: 0.319, 95% CI, 0.021-0.156). Parathyroidectomy is associated with a significantly better femoral neck BMD and a lower incidence of perHPT in patients with severe sHPT.

The comprehensive incidence and risk factors of fracture in kidney transplant recipients: A meta-analysis

AIM

Kidney transplant recipients are at high risk of fracture due to many factors such as nutritional status, hyperparathyroidism, acidosis and steroid administration. The current meta-analysis aimed to comprehensively analyse the incidence and risk factors of fracture in kidney transplant recipients.

METHODS

A systematic search on Embase, Web of Science, PubMed and Cochrane Library until November 2023 was performed. RStudio software was used to analyse data.

RESULTS

Twenty-eight eligible studies containing 310 530 kidney transplant recipients were included in the analysis. The pooled incidence of fracture was 10% (95% confidence interval [CI]: 7%-13%) generally. When divided by regions, it was further observed that the pooled incidence of fracture was 13% (95% CI: 9%-17%) in Europe, 11% (95% CI: 6%-16%) in North America, 7% (95% CI: 3%-11%) in Asia. Regarding the risk factors, pooled analysis revealed that age of recipient (hazard ratio [HR] = 1.50, 95% CI: 1.17-1.91), female sex (HR = 1.45, 95% CI: 1.36-1.53), pretransplantation diabetes (HR = 1.76, 95% CI: 1.58-1.97), pretransplantation fracture history (HR = 2.28, 95% CI: 1.86-2.78), dialysis duration (HR = 1.09, 95% CI: 1.01-1.17) and deceased donor (HR = 1.21, 95% CI: 1.05-1.39) related to higher risk of fracture. The general quality of included studies was acceptable, and no publication bias existed except for the analysis between age of recipient and fracture incidence; further trim and fill method indicated age of recipient showed a correlation trend with the fracture incidence without the statistical significance.

CONCLUSION

The pooled incidence of fracture reaches 10% in kidney transplant recipients, which relates to age of recipient, female sex, pretransplantation diabetes or fracture history, dialysis duration and decease donor.

Risk Factors for Fractures in Renal Transplantation: A Population-Based Cohort Study

INTRODUCTION

Kidney transplant recipients are at an increased risk of fractures, and targeted preventive strategies are needed. Therefore, in this retrospective cohort study, we investigated a large population-based cohort to identify the transplant recipient-specific risk factors for fractures in Taiwanese kidney transplant recipients.

METHODS

We conducted a retrospective cohort study using the National Health Insurance Research Database. Patients who underwent renal transplantation between 2003 and 2015 were identified and followed until December 31, 2015, to observe the development of fractures. Variables associated with the development of post-transplant fractures were identified by calculating hazard ratios in a Cox regression model.

RESULTS

5,309 renal transplant recipients were identified, of whom 553 (10.4%) were diagnosed with post-transplant fractures. Independent predictors of post-transplant fractures included an age at transplant ≥65 years (p < 0.001), female sex (p < 0.001), fractures within 3 years prior to transplantation (p < 0.001), and diabetes mellitus (p < 0.001). In addition, daily prednisolone doses >2.9–5.3 mg/day (p < 0.001), >5.3–8.7 mg/day (p < 0.001), and >8.7 mg/day (p < 0.001) were also independent predictors of post-transplant fractures. Conversely, the use of peritoneal dialysis before renal transplantation (p = 0.021), hypertension (p = 0.005), and the use of tacrolimus (p < 0.001), azathioprine (p = 0.006), mycophenolate mofetil/mycophenolic acid (p = 0.002), mTOR inhibitors (p = 0.004), and calcium supplements (p = 0.009) were inversely correlated with post-transplant fractures.

CONCLUSION

We recommend minimizing daily glucocorticoids as early and as far as possible in conjunction with immunosuppressive regimens such as tacrolimus, azathioprine, mycophenolate mofetil/mycophenolic acid, mTOR inhibitors, and calcium supplements, especially in older female recipients and in recipients with diabetes and a history of prior fractures.

High risk of osteoporosis and fracture following solid organ transplantation: a population-based study

Background

Osteoporosis and fractures increase morbidity and mortality rates after solid organ transplantation (SOT), but few studies have analyzed the risk of osteoporosis and related fractures after SOT. In this retrospective cohort study, we investigated the risk of osteoporosis and fractures in different SOT recipients.

Methods

This study was a retrospective cohort study using a nationally representative database in Taiwan. We collected the data of SOT recipients and used the propensity score matching method to obtain a comparison cohort. To reduce bias, we excluded patients who had been diagnosed with osteoporosis or fracture before inclusion. All participants were followed up until the date of diagnosis as having a pathological fracture, death, or the end of 2018, whichever occurred first. The Cox proportional hazards model was used to investigate the risk of osteoporosis and pathological fracture in SOT recipients.

Results

After adjustment for the aforementioned variables, SOT recipients were observed to have a higher risk of osteoporosis (hazard ratio (HR) = 1.46, 95% confidence interval (CI): 1.29-1.65) and fracture (HR: 1.19, 95% CI: 1.01-1.39) than the general individuals. Among the different SOT recipients, the highest risk of fractures was noted in heart or lung transplant recipients, with a HR of 4.62 (95% CI: 2.05-10.44). Among the age groups, patients aged >61 years had the highest HRs for osteoporosis (HR: 11.51; 95% CI, 9.10-14.56) and fracture (HR: 11.75, 95% CI: 8.97-15.40).

Conclusion

SOT recipients had a higher risk of osteoporosis and related fractures than the general population, with the highest risks observed in patients receiving heart or lung transplants, older patients, and patients with CCI scores of >3.

Time-Varying Risk Factors for Incident Fractures in Kidney Transplant Recipients: A Nationwide Cohort Study in South Korea

Little is known about the time-varying risk factors for fractures in kidney transplant recipients (KTRs). Using the Korea Organ Transplantation Registry, a nationwide cohort study of KTRs, the incidence, locations, and time-varying predictors of fractures were analyzed, including at baseline and post-transplant 6-month variables in KTRs who underwent KT between January 2014 and June 2019. Among 4134 KTRs, with a median follow-up of 2.94 years (12,441.04 person-years), 63 patients developed fractures. The cumulative 5-year incidence was 2.10%. The most frequent locations were leg (25.40%) and foot/ankle (22.22%). In multivariable analysis, older recipient age at baseline (hazard ratio [HR], 1.035; 95% confidence interval [CI], 1.007–1.064; p = 0.013) and higher tacrolimus trough level (HR, 1.112; 95% CI, 1.029–1.202; p = 0.029) were associated with higher risks for fractures. Pretransplant diabetes mellitus had a time-dependent impact on fractures, with increasing risk as time elapses (HR for diabetes mellitus 1.115; 95% CI, 0.439–2.832; HR for diabetes mellitus × time, 1.049; 95% CI, 1.007–1.094; p = 0.022). In conclusion, KTRs had a high risk of peripheral skeletal fractures in the first 5 years. At baseline recipient age, pretransplant diabetes mellitus and tacrolimus trough level after KT were responsible for the fractures in KTRs.

Kidney Transplantation, Immunosuppression, and Fracture Risk: Clinical and Economic Implications

Rationale & Objective

Disorders of bone and mineral metabolism frequently develop with advanced kidney disease, may be exacerbated by immunosuppression after kidney transplantation, and increase the risk of fractures.

Study Design

Retrospective database study.

Setting & Participants

Kidney-only transplant recipients aged ≥18 years from 2005 to 2016 in the United States captured in US Renal Data System records, which integrate Organ Procurement and Transplantation Network/United Network for Organ Sharing records with Medicare billing claims.

Exposures

Various immunosuppression regimens in the first 3 months after kidney transplantation.

Outcomes

The development of fractures, as ascertained using diagnostic codes on Medicare billing claims.

Analytical Approach

We used multivariable Cox regression with inverse propensity weighting to compare the incidence of fractures >3 months-to-3 years after kidney transplantation associated with various immunosuppression regimens compared to a reference regimen of antithymocyte globulin (TMG) or alemtuzumab (ALEM) with tacrolimus + mycophenolic acid + prednisone using inverse probability treatment weighting.

Results

Overall, fractures were identified in 7.5% of kidney transplant recipients (women, 8.8%; men, 6.7%; age < 55 years, 5.9%; age ≥ 55 years, 9.3%). In time-varying regression, experiencing a fracture was associated with a substantially increased risk of subsequent death within 3 months (adjusted hazard ratio [aHR], 3.06; 95% confidence interval [CI], 2.45-3.81). Fractures were also associated with increased Medicare spending (first year: $5,122; second year: $10,890; third year: $11,083; [P < 0.001]). Induction with TMG or ALEM and the avoidance or early withdrawal of steroids significantly reduced the risk of fractures in younger (aHR, 0.63; 95% CI, 0.54-0.73) and older (aHR, 0.83; 95% CI, 0.74-0.94) patients. The avoidance or early withdrawal of steroids with any induction was associated with a reduced risk of fractures in women.

Limitations

This was a retrospective study which lacked data on immunosuppression levels.

Conclusions

Fractures after kidney transplantation are associated with significantly increased mortality risk and costs. The early avoidance or early withdrawal of steroids after induction with TMG or ALEM reduces the risk of fractures after kidney transplantation and should be considered for patients at high-risk of this complication, including older adults and women.

Secondary Osteoporosis

Osteoporosis is a global public health problem, with fractures contributing to significant morbidity and mortality. Although postmenopausal osteoporosis is most common, up to 30% of postmenopausal women, > 50% of premenopausal women, and between 50% and 80% of men have secondary osteoporosis. Exclusion of secondary causes is important, as treatment of such patients often commences by treating the underlying condition. These are varied but often neglected, ranging from endocrine to chronic inflammatory and genetic conditions. General screening is recommended for all patients with osteoporosis, with advanced investigations reserved for premenopausal women and men aged < 50 years, for older patients in whom classical risk factors for osteoporosis are absent, and for all patients with the lowest bone mass (Z-score ≤ -2). The response of secondary osteoporosis to conventional anti-osteoporosis therapy may be inadequate if the underlying condition is unrecognized and untreated. Bone densitometry, using dual-energy x-ray absorptiometry, may underestimate fracture risk in some chronic diseases, including glucocorticoid-induced osteoporosis, type 2 diabetes, and obesity, and may overestimate fracture risk in others (eg, Turner syndrome). FRAX and trabecular bone score may provide additional information regarding fracture risk in secondary osteoporosis, but their use is limited to adults aged ≥ 40 years and ≥ 50 years, respectively. In addition, FRAX requires adjustment in some chronic conditions, such as glucocorticoid use, type 2 diabetes, and HIV. In most conditions, evidence for antiresorptive or anabolic therapy is limited to increases in bone mass. Current osteoporosis management guidelines also neglect secondary osteoporosis and these existing evidence gaps are discussed.

Safety of shoulder arthroplasty in lung transplant recipients

PURPOSE

Although shoulder arthroplasty is relatively safe in general population, it remains unclear in transplant recipient. Aim of this study was to determine outcomes and morbidity after shoulder arthroplasty in lung transplant recipients.

METHODS

A retrospective analysis was performed at our university hospital center from 2001 to 2015. Main inclusion criterion was all lung transplant recipient who underwent shoulder arthroplasty. Clinical outcomes including Constant score, visual analogue scale (VAS), American Shoulder and Elbow Surgeons score (ASES) were determined in pre-operative period and a minimum follow-up of 36 months. Special attention was taken about complications.

RESULTS

Among 700 lung transplant recipients, we identified 12 patients who underwent 14 shoulder arthroplasties. Arthroplasties were performed after proximal humeral avascular necrosis (n = 10), degenerative osteoarthritis (n = 1) and non-union of proximal humeral fracture (n = 1). 8 anatomical total shoulder arthroplasties and 6 reversed shoulder arthroplasties were performed. Mean follow-up was 61.4 months (± 22.1). Mean age was 47.1 (± 9.3) years. All patients had immunosuppression therapy at the time of surgery. Mean Constant score was improved at last follow-up [43(± 9.7) vs 94(± 4), p < 0.001]. VAS decreased from 6.4 (± 1.2) to 0.4 (± 0.8), p < 0.001. Mean ASES was improved from 33 (± 6) to 91 (± 5) at last follow-up (p < 0.001). Range of motion were improved between early post-operative evaluation and last follow-up: forward flexion: 85° (± 8°) vs 119°(± 13°); abduction: 83° (± 14°) vs 106°(± 23°); external rotation (RE1): 26° (± 7°) vs 36°(± 10°). At last follow-up, one revision was required for humeral prothesis loosening at 2 years post-surgery. One patient died due to acute pulmonary decompensation on chronic rejection 66 months after shoulder arthroplasty.

CONCLUSION

Shoulder arthroplasty is a safe procedure in this vulnerable population of lung transplant recipients. Such results encourage us to continue arthroplasty surgery when required.

LEVEL OF EVIDENCE

IV.

Mineral Bone Disorders in Kidney Transplantation

Bone disease after kidney transplantation is associated with an increased risk of fractures, morbidity, and mortality. Its pathophysiology is complex, involving multiple contributors including pretransplant bone disease, immunosuppressive medications, and changes in the parathyroid-bone-kidney axis. Risk scores, bone turnover markers, and noninvasive imaging modalities are only able to partially predict the fracture risk in kidney transplant recipients. The optimal management of bone disease after kidney transplantation has not yet been established, with only a limited number of randomized clinical trials evaluating the efficacy of treatment regimens in kidney transplant recipients. This review focuses on the pathophysiology, evaluation, prevention, and treatment of post-kidney transplant mineral and bone disease as guided by recent evidence.

Fractures after kidney transplantation: Incidence, predictors, and association with mortality

BACKGROUND

Major fractures (MF) are associated with increased mortality in the general population and represent an even higher risk in patients with chronic kidney disease. We investigated incidence, predictors and clinical outcomes associated with first MF (MF_first) following kidney transplantation (KT).

METHODS

We used the Swedish National Renal Registry of 3992 first KT recipients (2005-2016) (median age 53 years, 65% men) and identified all MF_first in hip, spine, humerus and forearm following KT. We estimated incidence rates and predictors of MF_first using flexible parametric hazard models and Fine-Gray analysis accounting for competing risk of death, and risk of all-cause mortality following MF_first using Cox proportional hazards models with fracture as time-varying exposure.

RESULTS

During median follow-up of 4.8 years (IQR 2.2-7.9 years), there were 279 fractures of which 139 were forearm fractures. The crude incidence rate of MF_first (n = 279) was 13.5/1000 patient-years and that of hip fractures (n = 69) 3.4/1000 patient-years. The multivariate-adjusted fracture incidence rates were highest during the first 6 months following KT, and 86% higher in women than in men. High age, female sex, previous history of MF, diabetes nephropathy, pretransplant dialysis therapy and acute rejection were associated with increased risk for MF_first, whereas pre-emptive KT was associated with lower risk of MF_first. Spline curves showed markedly higher impact of higher age on risk of MF_first in women than in men. MF_first (n = 279) independently predicted increased all-cause mortality risk (hazard ratio, HR, 1.78(95%CI 1.35-2.36)). Among MF_first, with humerus fracture as reference, hip fracture (HR, 4.68(95%CI 1.56-14.06)) and spine fracture (HR, 4.02(95%CI 1.19-13.54)), but not forearm fracture (HR, 1.17 (95%CI 0.38-3.53)), were associated with increased all-cause mortality risk.

CONCLUSIONS

The initial 6 months following kidney transplantation is a high-risk period for MF. Among MF, hip fracture and spine fracture associate with substantially increased all-cause mortality risk.

Natural history of mineral metabolism, bone turnover and bone mineral density in de novo renal transplant recipients treated with a steroid minimization immunosuppressive protocol

The skeletal effects of renal transplantation are not completely understood, especially in patients managed with a steroid minimization immunosuppressive protocol and long term. We enrolled 69 adult transplant recipients (39 males; ages 51.1 ± 12.2 years), free of antiresorptive therapy and managed with a steroid minimization immunosuppressive protocol, into a 5-year prospective observational study to evaluate changes in areal bone mineral density (aBMD), mineral metabolism and bone remodelling. Dual energy X-ray absorptiometry, laboratory parameters of mineral metabolism (including parathyroid hormone, sclerostin and fibroblast growth factor 23) and non-renal cleared bone turnover markers (BTMs) (bone-specific alkaline phosphatase, trimeric N-terminal propeptide and tartrate-resistant acid phosphatase 5b) were assessed at baseline and 1 and 5 years post-transplantation. The mean cumulative methylprednisolone exposure at 1 and 5 years amounted to 2.5 ± 0.8 and 5.8 ± 3.3 g, respectively. Overall, bone remodelling activity decreased after transplantation. Post-transplant aBMD changes were minimal and were significant only in the ultradistal radius during the first post-operative year {median -2.2% [interquartile range (IQR) -5.9-1.2] decline, P = 0.01} and in the lumbar spine between Years 1 and 5 [median 1.6% (IQR -3.2-7.0) increase, P = 0.009]. BTMs, as opposed to mineral metabolism parameters and cumulative corticosteroid exposure, associated with aBMD changes, both in the early and late post-transplant period. Most notably, aBMD changes inversely associated with bone remodelling changes. In summary, in de novo renal transplant recipients treated with a steroid minimization immunosuppressive protocol, BMD changes are limited, highly variable and related to remodelling activity rather than corticosteroid exposure.

Bone fracture risk factors in prevalent hemodialysis patients

Bone fractures are an important cause of morbidity and mortality in hemodialysis (HD) patients. The aim of this study was to quantify the incidence of fractures in a cohort of prevalent HD patients and evaluate its relationship with possible risk factors. We performed a retrospective analysis of 341 patients, since they started HD (median of 51 months). Demographic, clinical, and biochemical parameters as well as vascular calcifications (VC) were evaluated. Fifty-seven episodes of fracture were identified with a median HD vintage of 47 months (incidence rate of 31 per 1000 person-years). Age (p < 0.001), female gender (p < 0.001), lower albumin (p = 0.02), and higher VC score (p < 0.001) were independently associated with increased risk of fracture, while active vitamin D therapy (p = 0.03) was associated with decreased risk. A significantly higher risk of incident fracture was also associated with higher values of bone-specific alkaline phosphatase (bALP) (p = 0.01) and intact parathyroid hormone (iPTH) levels either < 300 pg/mL (p = 0.02) or > 800 pg/mL (p < 0.001) compared with 300-800 pg/mL. In conclusion, bone fracture incidence in HD patients is high and its risk increases with age, female gender, lower serum albumin, and with the presence of more VC. Prevalent HD patients with low or high iPTH levels or increased bALP also had a higher fracture risk. Therapy with active vitamin D seems to have a protective role. Assessment of fracture risk and management in dialysis patients at greatest risk requires further study.

Interventions for preventing bone disease in kidney transplant recipients

BACKGROUND

People who have chronic kidney disease (CKD) have important changes to bone structure, strength, and metabolism. Children experience bone deformity, pain, and delayed or impaired growth. Adults experience limb and vertebral fractures, avascular necrosis, and pain. The fracture risk after kidney transplantation is four times that of the general population and is related to Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) occurring with end-stage kidney failure, steroid-induced bone loss, and persistent hyperparathyroidism after transplantation. Fractures may reduce quality of life and lead to being unable to work or contribute to community roles and responsibilities. Earlier versions of this review have found low certainty evidence for effects of treatment. This is an update of a review first published in 2005 and updated in 2007.

OBJECTIVES

This review update evaluates the benefits and harms of interventions for preventing bone disease following kidney transplantation.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 16 May 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

RCTs and quasi-RCTs evaluating treatments for bone disease among kidney transplant recipients of any age were eligible.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial risks of bias and extracted data. Statistical analyses were performed using random effects meta-analysis. The risk estimates were expressed as a risk ratio (RR) for dichotomous variables and mean difference (MD) for continuous outcomes together with the corresponding 95% confidence interval (CI). The primary efficacy outcome was bone fracture. The primary safety outcome was acute graft rejection. Secondary outcomes included death (all cause and cardiovascular), myocardial infarction, stroke, musculoskeletal disorders (e.g. skeletal deformity, bone pain), graft loss, nausea, hyper- or hypocalcaemia, kidney function, serum parathyroid hormone (PTH), and bone mineral density (BMD).

MAIN RESULTS

In this 2019 update, 65 studies (involving 3598 participants) were eligible; 45 studies contributed data to our meta-analyses (2698 participants). Treatments included bisphosphonates, vitamin D compounds, teriparatide, denosumab, cinacalcet, parathyroidectomy, and calcitonin. Median duration of follow-up was 12 months. Forty-three studies evaluated bone density or bone-related biomarkers, with more recent studies evaluating proteinuria and hyperparathyroidism. Bisphosphonate therapy was usually commenced in the perioperative transplantation period (within 3 weeks) and regardless of BMD. Risks of bias were generally high or unclear leading to lower certainty in the results. A single study reported outcomes among 60 children and adolescents. Studies were not designed to measure treatment effects on fracture, death or cardiovascular outcomes, or graft loss.Compared to placebo, bisphosphonate therapy administered over 12 months in transplant recipients may prevent fracture (RR 0.62, 95% CI 0.38 to 1.01; low certainty evidence) although the 95% CI included the possibility that bisphosphonate therapy might make little or no difference. Fracture events were principally vertebral fractures identified during routine radiographic surveillance. It was uncertain whether any other drug class decreased fracture (low or very low certainty evidence). It was uncertain whether interventions for bone disease in kidney transplantation reduce all-cause or cardiovascular death, myocardial infarction or stroke, or graft loss in very low certainty evidence. Bisphosphonate therapy may decrease acute graft rejection (RR 0.70, 95% CI 0.55 to 0.89; low certainty evidence), while it is uncertain whether any other treatment impacts graft rejection (very low certainty evidence). Bisphosphonate therapy may reduce bone pain (RR 0.20, 95% CI 0.04 to 0.93; very low certainty evidence), while it was very uncertain whether bisphosphonates prevent spinal deformity or avascular bone necrosis (very low certainty evidence). Bisphosphonates may increase to risk of hypocalcaemia (RR 5.59, 95% CI 1.00 to 31.06; low certainty evidence). It was uncertain whether vitamin D compounds had any effect on skeletal, cardiovascular, death, or transplant function outcomes (very low certainty or absence of evidence). Evidence for the benefits and harms of all other treatments was of very low certainty. Evidence for children and young adolescents was sparse.

AUTHORS' CONCLUSIONS

Bisphosphonate therapy may reduce fracture and bone pain after kidney transplantation, however low certainty in the evidence indicates it is possible that treatment may make little or no difference. It is uncertain whether bisphosphonate therapy or other bone treatments prevent other skeletal complications after kidney transplantation, including spinal deformity or avascular bone necrosis. The effects of bone treatment for children and adolescents after kidney transplantation are very uncertain.

Closed Fracture Diagnosed by Bedside Ultrasonography During Hemodialysis: A Report of Seven Cases and Relevant Clinical Characteristics

BACKGROUND

Patients undergoing dialysis have a high incidence of fracture, and early diagnosis is important. We report seven cases of closed rib or upper-limb fractures diagnosed by bedside ultrasonography during maintenance hemodialysis sessions and describe relevant clinical characteristics.

CASE PRESENTATION

We identified seven patients who were injured by falls in their homes. No injuries occurred on the day of dialysis. Five of the 7 patients did not visit the emergency room. All patients complained of persistent unexplained pain during a regular hemodialysis session. Ultrasonography (US) was performed during dialysis sessions, without any reports of pain. Before US evaluation, the sensitivity of radiography for diagnosis of fracture was 25%, while the sensitivity of US was 100%. Compared with other patients in our clinic, these patients were significantly older and had lower serum albumin concentrations and lower hemodialysis efficiency as determined by Kt/V. They also had a higher incidence of diabetes and a greater need for vasopressors during dialysis. These findings were consistent with the results of previous studies of the characteristics of fractures in dialysis patients. However, blood levels of creatinine, corrected calcium, phosphate, intact parathyroid hormone, and hemoglobin, as well as bone density and blood pressure, after the previous dialysis session were not different.

CONCLUSIONS

To our knowledge, this is the first report of closed fracture of superficial bone diagnosed by bedside ultrasonography during a hemodialysis session. Ultrasonography is especially useful for diagnosis in these cases because it is noninvasive and highly accurate. Doctors should determine the differential diagnosis for closed fracture in patients undergoing dialysis, especially in those who are older, have diabetes, and are malnourished, and in those with recent contusions and persistent pain.

Fractures and Subsequent Graft Loss and Mortality among Older Kidney Transplant Recipients

OBJECTIVES

Older adults who undergo kidney transplantation (KT) are living longer with a functioning graft and are at risk for age-related adverse events including fractures. Understanding recipient, transplant, and donor factors and the outcomes associated with fractures may help identify older KT recipients at increased risk. We determined incidence of hip, vertebral, and extremity fractures; assessed factors associated with incident fractures; and estimated associations between fractures and subsequent death-censored graft loss (DCGL) and mortality.

DESIGN

This was a prospective cohort study of patients who underwent their first KT between January 1, 1999, and December 31, 2014.

SETTING

We linked data from the Scientific Registry of Transplant Recipients to Medicare claims through the US Renal Data System.

PARTICIPANTS

The analytic population included 47 815 KT recipients aged 55 years or older.

MEASUREMENTS

We assessed the cumulative incidence of and factors associated with post-KT fractures (hip, vertebral, or extremity) using competing risks models. We estimated risk of DCGL and mortality after fracture using adjusted Cox proportional hazards models.

RESULTS

The 5-year incidence of post-KT hip, vertebral, and extremity fracture for those aged 65 to 69 years was 2.2%, 1.0%, and 1.7%, respectively. Increasing age was associated with higher hip (adjusted hazard ratio [aHR] = 1.37 per 5-y increase; 95% confidence interval [CI] = 1.30-1.45) and vertebral (aHR = 1.31; 95% CI = 1.20-1.42) but not extremity (aHR = .97; 95% CI = .91-1.04) fracture risk. DCGL risk was higher after hip (aHR = 1.34; 95% CI = 1.12-1.60) and extremity (aHR = 1.30; 95% CI = 1.08-1.57) fracture. Mortality risk was higher after hip (aHR = 2.31; 95% CI = 2.11-2.52), vertebral (aHR = 2.80; 95% CI = 2.44-3.21), and extremity (aHR = 1.85; 95% CI = 1.64-2.10) fracture.

CONCLUSION

Our findings suggest that older KT recipients are at higher risk for hip and vertebral fracture but not extremity fracture; and those with hip, vertebral, or extremity fracture are more likely to experience subsequent graft loss or mortality. These findings underscore that different fracture types may have different underlying etiologies and risks, and they should be approached accordingly. J Am Geriatr Soc 67:1680-1688, 2019.

Bone health in chronic kidney disease-mineral and bone disorder: a clinical case seminar and update

The metabolic abnormalities affecting bone in the setting of chronic kidney disease (CKD) are complex with overlapping and interacting aetiologies and have challenging diagnostic and management strategies. Disturbances in calcium, phosphate, fibroblast growth factor 23, parathyroid hormone concentrations and vitamin D deficiency are commonly encountered and contribute to the clinical syndromes of bone disorders in CKD, including hyperparathyroidism, osteomalacia, osteoporosis and adynamic bone disease. Mineral and bone abnormalities may also persist or arise de novo post-renal transplantation. The Kidney Disease Improving Global Outcomes organisation describes these mineral metabolism derangements and skeletal abnormalities as 'CKD Mineral and Bone Disorder'. Patients with this disorder have an increased risk of fracture, cardiovascular events and overall increased mortality. In light of the recently updated 2017 guidelines from the Kidney Disease Improving Global Outcomes, we present a clinical case-based discussion to highlight the complexities of investigating and managing the bone health of patients with CKD with a focus on these updates.

Effects of denosumab on bone metabolism and bone mineral density in kidney transplant patients: a systematic review and meta-analysis

OBJECTIVE

The use of immunosuppressive agents, especially glucocorticoids, are associated with increased risks of bone loss in kidney transplant patients. Denosumab, a potent antiresorptive agent, has been shown to increase bone mineral density (BMD) in patients with CKD. However, its effects on bone metabolism and BMD in kidney transplant patients remain unclear.

METHODS

A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through April 2018 to identify studies evaluating denosumab's effect on changes in bone metabolism and BMD from baseline to post-treatment course in kidney transplant patients. Study results were pooled and analyzed utilizing random-effects model. The protocol for this systematic review is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42018095055).

RESULTS

Five studies (a clinical trial and four cohort studies) with a total of 162 kidney transplant patients were identified. The majority of patients had a baseline eGFR ≥ 30 mL/min/1.73 m². After treatment (≥ 6 to 12 months), there were significant increases in BMD with standardized mean differences (SMDs) of 3.26 (95% CI 0.88-5.64) and 1.83 (95% CI 0.43 to 3.22) for lumbar spine and femoral neck, respectively. There were also significant increases in T scores with SMDs of 0.92 (95% CI 0.58 to 1.25) and 1.14 (95% CI 0.17 to 2.10) for lumbar spine and femoral neck, respectively. After treatment, there were no significant changes in serum calcium (Ca) or parathyroid hormone (PTH) from baseline to post-treatment course (≥ 6 months) with mean differences (MDs) of 0.52 (95% CI, - 0.13 to 1.16) mmol/L and - 13.24 (95% CI, - 43.85 to 17.37) ng/L, respectively. The clinical trial data demonstrated more asymptomatic hypocalcemia in the denosumab (12 episodes in 39 patients) than in the control (1 episode in 42 patients) group. From the cohort studies, the pooled incidence of hypocalcemia following denosumab treatment was 1.7% (95% CI 0.4 to 6.6%). All reported hypocalcemic episodes were mild and asymptomatic, but the majority of patients required Ca and vitamin D supplements.

CONCLUSION

Among kidney transplant patients with good allograft function, denosumab effectively increases BMD and T scores in the lumbar spine and femur neck. From baseline to post-treatment, there are no differences in serum Ca and PTH. However, mild hypocalcemia can occur following denosumab treatment, requiring monitoring and titration of Ca and vitamin D supplements.

Association between malnutrition-inflammation score and risk of subsequent self-reported bone fractures in prevalent kidney transplant recipients

Chronic inflammation and protein energy wasting (PEW) syndrome are common in kidney transplant recipients (KTR). The presence of inflammation and PEW syndrome can directly affect bone resorption and bone formation, leading to bone loss and fractures. We showed PEW is independently associated with new clinically detected bone fractures in prevalent KTR.

INTRODUCTION

Kidney transplant recipients (KTR) have a 4-fold higher risk of fracture compared to the general population. Chronic inflammation and PEW syndrome are common in KTR and are associated with poor outcomes. We hypothesized that the Malnutrition-Inflammation Score (MIS), a validated measure of PEW, is associated with higher risk of bone fractures in KTR.

METHODS

This prospective cohort study included 839 prevalent KTR from a Central European academic center. MIS, a semiquantitative instrument of PEW, was calculated at the study entry. Self-reported history of fractures was recorded during the 2-year follow-up period. The association between MIS and bone fractures was examined in logistic regression analyses with adjustment for age, gender, eGFR, smoking habits, history of pre-transplant bone fractures, and acute rejection.

RESULTS

Mean age was 51 ± 13 years, and 56% of patients were males with median (interquartile range) transplant vintage 69 (38-112) months, estimated glomerular filtration rate 55 ± 21 ml/min/1.73 m², and calculated MIS 3 (2-4) at enrollment. Fifty-five (7%) patients experienced self-reported bone fractures during the 2-year follow-up period. Higher MIS score showed linear association with increased risk of fracture. Each one-point higher MIS was associated with 23% higher risk of bone fractures (odds ratio (OR) and 95% CI 1.23, 1.12-1.34), which remained significant after multivariable adjustments (OR 1.17, 95% CI 1.06-1.29).

CONCLUSION

The MIS is independently associated with new clinically detected bone fractures in prevalent KTR.

Fracture Risk in Dialysis and Kidney Transplanted Patients: A Systematic Review

Chronic kidney disease is associated with an increased risk of fracture and cardiovascular mortality. The risk of fracture in hemodialysis (HD), peritoneal dialysis (PD) and kidney transplant (KT) patients is higher when compared with the general population. However, there exists a knowledge gap concerning which group has the highest risk of fracture. We aimed to compare the risk of fracture in HD, PD, and KT populations. We conducted a systematic review of observational studies evaluating the risk of fracture in HD, PD, or KT patients. Eligible studies were searched using MEDLINE, Embase, Web of Science, and Cochrane Library from their inception to January 2016, and in grey literature. Incidences (cumulative and rate) of fracture were described together using the median, according to fracture sites, the data source (administrative database or cohort and clinical registry), and fracture diagnosis method. Prevalence estimates were described separately. We included 47 studies evaluating the risk of fracture in HD, PD, and KT populations. In administrative database studies, incidence of hip fracture in HD (median 11.45 per 1000 person-years [p-y]), range: 9.3 to 13.6 was higher than in KT (median 2.6 per 1000 p-y; range 1.5 to 3.8) or in PD (median 5.2 per 1000 p-y; range 4.1 to 6.3). In dialysis (HD+PD), three studies reported a higher incidence of hip fracture than in KT. Prevalent vertebral fracture (assessed by X-rays or questionnaire) reported in HD was in a similar range as that reported in KT. Incidence of overall fracture was similar in HD and KT, from administrative databases studies, but lower in HD compared with KT, from cohorts or clinical registry studies. This systematic review suggests an important difference in fracture risk between HD, PD, and KT population, which vary according to the diagnosis method for fracture identification. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Mineral and Bone Disease in Kidney Transplant Recipients

PURPOSE OF REVIEW

Despite metabolic improvements following kidney transplantation, transplant recipients still often suffer from complex mineral and bone disease after transplantation.

RECENT FINDINGS

The pathophysiology of post-transplant disease is unique, secondary to underlying pre-transplant mineral and bone disease, immunosuppression, and changing kidney function. Changes in modern immunosuppression regimens continue to alter the clinical picture. Modern management includes reducing cumulative steroid exposure and correcting the biochemical abnormalities in mineral metabolism. While bone mineral density screening appears to help predict fracture risk and anti-osteoporotic therapy appears to have a positive effect on bone mineral density, more data regarding specific treatment is necessary. Patients with mineral and bone disease after kidney transplantation require special care in order to properly manage and mitigate their mineral and bone disease. Recent changes in clinical management of transplant patients may also be changing the implications on patients' mineral and bone disease.

Rethinking Bone Disease in Kidney Disease

Renal osteodystrophy (ROD) is the bone component of chronic kidney disease mineral and bone disorder (CKD-MBD). ROD affects bone quality and strength through the numerous hormonal and metabolic disturbances that occur in patients with kidney disease. Collectively these disorders in bone quality increase fracture risk in CKD patients compared with the general population. Fractures are a serious complication of kidney disease and are associated with higher morbidity and mortality compared with the general population. Furthermore, at a population level, fractures are at historically high levels in patients with end-stage kidney disease (ESKD), whereas in contrast the general population has experienced a steady decline in fracture incidence rates. Based on these findings, it is clear that a paradigm shift is needed in our approach to diagnosing and managing ROD. In clinical practice, our ability to diagnose ROD and initiate antifracture treatments is impeded by the lack of accurate noninvasive methods that identify ROD type. The past decade has seen advances in the noninvasive measurement of bone quality and strength that have been studied in kidney disease patients. Below we review the current literature pertaining to the epidemiology, pathology, diagnosis, and management of ROD. We aim to highlight the pressing need for a greater awareness of this condition and the need for the implementation of strategies that prevent fractures in kidney disease patients. Research is needed for more accurate noninvasive assessment of ROD type, clinical studies of existing osteoporosis therapies in patients across the spectrum of kidney disease, and the development of CKD-specific treatments. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Changes in bone microarchitecture following kidney transplantation-Beyond bone mineral density

Bone disease in kidney transplant recipients (KTRs) is characterized by bone mineral density (BMD) loss but bone microarchitecture changes are poorly defined. In this prospective cohort study, we evaluated bone microarchitecture using non-invasive imaging modalities; high-resolution magnetic resonance imaging (MRI), peripheral quantitative computed tomography (pQCT), dual energy X-ray absorptiometry (DXA), and the trabecular bone score (TBS) following kidney transplantation. Eleven KTRs (48.3 ± 11.2 years) underwent MRI (tibia), pQCT (radius) and DXA at baseline and 12 months post-transplantation. Transiliac bone biopsies, performed at transplantation, showed 70% of patients with high/normal bone turnover. Compared with baseline, 12-month MRI showed deterioration in indices of trabecular network integrity-surface to curve ratio (S/C; -15%, P = 0.03) and erosion index (EI; +19%, P = 0.01). However, cortical area increased (+10.3%, P = 0.04), with a non-significant increase in cortical thickness (CtTh; +7.8%, P = 0.06). At 12 months, parathyroid hormone values (median 10.7 pmol/L) correlated with improved S/C (r = 0.75, P = 0.009) and EI (r = -0.71, P = 0.01) while osteocalcin correlated with CtTh (r = 0.72, P = 0.02) and area (r = 0.70, P = 0.02). TBS decreased from baseline (-5.1%, P = 0.01) with no significant changes in BMD or pQCT. These findings highlight a post-transplant deterioration in trabecular bone quality detected by MRI and TBS, independent of changes in BMD, underlining the potential utility of these modalities in evaluating bone microarchitecture in KTRs.

Symptomatic fracture risk in the renal replacement therapy population

Background

Bone fractures are an important cause of morbidity and mortality in patients on renal replacement therapy (RRT). The aim of this multicentre observational study was to quantify the incidence of radiologically proven bone fracture by anatomical site in prevalent RRT groups and study its relationship to potential risk factors.

Methods

We performed a retrospective analysis of electronic records of all 2096 adults prevalent on RRT in the West of Scotland on 7 July 2010 across all hospitals (except one where inception was 1 August 2011) to identify all subsequent radiologically proven fractures during a median 3-year follow-up.

Results

There were 340 fractures, with an incidence of 62.8 per 1000 patient-years. The incidences were 37.6, 99.2 and 57.6 per 1000 patient-years in the transplant, haemodialysis (HD) and peritoneal dialysis (PD) groups, respectively (P < 0.05). In the multivariable model, age and HD (relative to transplant or PD) were independently associated with increased risk of fractures, while primary glomerular disease, increasing serum albumin and taking alfacalcidol or lanthanum were associated with decreased risk. In a multivariable model of only HD patients, age was independently associated with an increased risk of fractures, while glomerular disease, high serum albumin and being on alfacalcidol and lanthanum were associated with decreased risk. In a multivariable model in transplant patients, there were no significant independent predictors of fracture.

Conclusions

The risk of symptomatic bone fracture is high in RRT patients and is ∼2.5 times higher in HD than in renal transplant patients, with the increased risk being independent of baseline factors. Fracture risk increases with age and lower serum albumin and is reduced if the primary renal diagnosis is glomerular disease. The possible protective role of alfacalcidol and lanthanum in HD patients deserves further exploration.

Raising awareness on the therapeutic role of cholecalciferol in CKD: a multidisciplinary-based opinion

Vitamin D is recognized to play an essential role in health and disease. In kidney disease, vitamin D analogs have gained recognition for their involvement and potential therapeutic importance. Nephrologists are aware of the use of oral native vitamin D supplementation, however, uncertainty still exists with regard to the use of this treatment option in chronic kidney disease as well as clinical settings related to chronic kidney disease, where vitamin D supplementation may be an appropriate therapeutic choice. Two consecutive meetings were held in Florence in July and November 2016 comprising six experts in kidney disease (N = 3) and bone mineral metabolism (N = 3) to discuss a range of unresolved issues related to the use of cholecalciferol in chronic kidney disease. The panel focused on the following six key areas where issues relating to the use of oral vitamin D remain controversial: (1) vitamin D and parathyroid hormone levels in the general population, (2) cholecalciferol in chronic kidney disease, (3) vitamin D in cardiovascular disease, (4) vitamin D and renal bone disease, (5) vitamin D in rheumatological diseases affecting the kidney, (6) vitamin D and kidney transplantation.

Fractures in Kidney Transplant Recipients: A Comparative Study Between England and New York State

OBJECTIVES

Fractures are associated with high morbidity and are a major concern for kidney transplant recipients. No comparative analysis has yet been conducted between countries in the contemporary era to inform future international prevention trials.

MATERIALS AND METHODS

Data were obtained from the Hospital Episode Statistics and the Statewide Planning and Research Cooperative databases on all adult kidney transplants performed in England and New York State from 2003 to 2013, respectively, and on posttransplant fracture-related hospitalization from 2003 to 2014.

RESULTS

Our analysis included 18 493 English and 11 602 New York State kidney transplant recipients. Overall, 637 English recipients (3.4%) and 398 New York State recipients (3.4%) sustained a fracture, giving an unadjusted event rate of 7.0 and 5.9 per 1000 years, respectively (P = .948). Of these, 147 English (0.8%) and 101 New York State recipients (0.9%) sustained a hip fracture, giving an unadjusted event rate of 1.6 and 1.5 per 1000 years, respectively (P = .480). There were no differences in the cumulative incidence of all fractures or hip fractures. One-year mortality rates after any fracture (9% and 11%) or after a hip fracture (15% and 17%) were not different between cohorts.

CONCLUSIONS

Contemporaneous English and New York State kidney transplant recipients have similar fracture rates and mortality rates postfracture.

Advances in the evaluation of bone health in kidney transplant patients

Bone disease related to chronic kidney disease and, particularly, to kidney transplant patients is a common cause or morbidity and mortality, especially due to a higher risk of osteoporotic fractures. Despite the fact that this has been known for decades, to date, an appropriate diagnostic strategy has yet to be established. Apart from bone biopsy, which is invasive and scarcely used, no other technique is available to accurately establish the risk of fracture in kidney patients. Techniques applied to the general population, such as bone densitometry, have not been subjected to sufficient external validation and their use is not systematic. This means that the identification of patients at risk of fracture and therefore those who are candidates for preventive strategies is an unmet need. Bone strength, defined as the ability of the bone to resist fracture, is determined by bone mineral density (measured by bone densitometry), trabecular architecture and bone tissue quality. The trabecular bone score estimates bone microarchitecture, and low values have been described as an independent predictor of increased fracture risk. Bone microindentation is a minimally invasive technique that measures resistance of the bone to micro-cracks (microscopic separation of mineralised collagen fibres), and therefore bone tissue biomechanical properties. The superiority over bone densitometry of the correlation between the parameters measured by trabecular bone score and microindentation with the risk of fracture in diverse populations led us to test its feasibility in chronic kidney disease and kidney transplant patients.

Serum phosphorus levels and fracture following renal transplantation

PURPOSE

Increased fracture rates are observed in renal transplant recipients (RTRs) compared with the general population. Risk factors include age, diabetes, dialysis vintage, immunosuppression and mineral and bone disorders.¹ Low serum phosphorus levels occur post-transplantation; however, its relationship with fracture risk has not been evaluated. The purpose of this study was to evaluate risk factors for fracture in RTRs at a single tertiary referral centre.

METHODS

A retrospective cross-sectional analysis of 146 patients (75 M, 71 F) who had been referred for dual energy X-ray densitometry (DXA) post-renal transplantation was performed. Aetiology of end stage kidney disease (ESKD), duration of dialysis, parathyroidectomy history, immunosuppression regimen, bone mineral density (BMD), biochemistry and fractures were documented. Statistical analyses included univariable and multivariable regression.

RESULTS

The mean age of patients was 54 years and mean time post-transplantation 6.7 years. A total of 79 fractures occurred in 52 patients (35%), with 40 fractures occurring post-transplantation. Ankle/foot fractures were most common (48%). Lower serum phosphorus levels and declining femoral neck (FN) T-score and were associated with fractures in both univariable and multivariable regression analyses after adjusting for age, gender, weight, estimated glomerular filtration rate and pre-transplant history of fracture (P=.011 and P=.042 respectively). The relationship between serum phosphorus and fracture remained significant independent of FN T-score, parathyroid hormone levels, parathyroidectomy status and prednisolone use.

CONCLUSION

Fracture was common post-renal transplantation. Lower serum phosphorus levels and declining FN T-scores were associated with fractures. The mechanism of this previously unreported observation requires further evaluation in prospective studies.

Bone Quality in Chronic Kidney Disease: Definitions and Diagnostics

PURPOSE OF REVIEW

In this paper, we review the epidemiology, diagnosis, and pathogenesis of fractures and renal osteodystrophy.

RECENT FINDINGS

The role of bone quality in the pathogenesis of fracture susceptibility in chronic kidney disease (CKD) is beginning to be elucidated. Bone quality refers to bone material properties, such as cortical and trabecular microarchitecture, mineralization, turnover, microdamage, and collagen content and structure. Recent data has added to our understanding of the effects of CKD on alterations to bone quality, emerging data on the role of abnormal collagen structure on bone strength, the potential of non-invasive methods to inform our knowledge of bone quality, and how we can use these methods to inform strategies that protect against bone loss and fractures. However, more prospective data is required. CKD is associated with abnormal bone quality and strength which results in high fracture incidence.

Spine Trabecular Bone Score as an Indicator of Bone Microarchitecture at the Peripheral Skeleton in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

Studies using high-resolution peripheral quantitative computed tomography showed progressive abnormalities in cortical and trabecular microarchitecture and biomechanical competence over the first year after kidney transplantation. However, high-resolution peripheral computed tomography is a research tool lacking wide availability. In contrast, the trabecular bone score is a novel and widely available tool that uses gray-scale variograms of the spine image from dual-energy x-ray absorptiometry to assess trabecular quality. There are no studies assessing whether trabecular bone score characterizes bone quality in kidney transplant recipients.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

Between 2009 and 2010, we conducted a study to assess changes in peripheral skeletal microarchitecture, measured by high-resolution peripheral computed tomography, during the first year after transplantation in 47 patients managed with early corticosteroid-withdrawal immunosuppression. All adult first-time transplant candidates were eligible. Patients underwent imaging with high-resolution peripheral computed tomography and dual-energy x-ray absorptiometry pretransplantation and 3, 6, and 12 months post-transplantation. We now test if, during the first year after transplantation, trabecular bone score assesses the evolution of bone microarchitecture and biomechanical competence as determined by high-resolution peripheral computed tomography.

RESULTS

At baseline and follow-up, among the 72% and 78%, respectively, of patients having normal bone mineral density by dual-energy x-ray absorptiometry, 53% and 50%, respectively, were classified by trabecular bone score as having high fracture risk. At baseline, trabecular bone score correlated with spine, hip, and ultradistal radius bone mineral density by dual-energy x-ray absorptiometry and cortical area, density, thickness, and porosity; trabecular density, thickness, separation, and heterogeneity; and stiffness and failure load by high-resolution peripheral computed tomography. Longitudinally, each percentage increase in trabecular bone score was associated with increases in trabecular number (0.35%±1.4%); decreases in trabecular thickness (-0.45%±0.15%), separation (-0.40%±0.15%), and network heterogeneity (-0.48%±0.20%); and increases in failure load (0.22%±0.09%) by high-resolution peripheral computed tomography (all P<0.05).

CONCLUSIONS

Trabecular bone score may be a useful method to assess and monitor bone quality and strength and classify fracture risk in kidney transplant recipients.

Osteoporosis in patients with diabetes after kidney transplantation

Preexisting diabetes increases risk of fractures after kidney transplantation (KT). However, little is known about mechanisms and prevention of increased fragility in these patients. Pathophysiology of osteoporosis after KT is complex and characterized by high prevalence of adynamic bone disease. Despite high prevalence of preexisting diabetes in KT recipients, diabetes patients were underrepresented in the studies that explored mechanisms and treatments of osteoporosis after KT. Therefore, caution should be exercised before considering conventional fracture prevention strategies in this unique group of patients. Many traditional osteoporosis medications reduce bone turnover and, hence, can be ineffective or even harmful in diabetic patients after KT. Contrary to predictions, evidence from the studies conducted in mostly non-diabetic subjects demonstrated that bisphosphonates failed to reduce fracture rates after KT. Therefore, bisphosphonates use should be limited in diabetic patients until more evidence supporting their post-transplant efficacy is available. We recommend the following strategies that may help reduce fracture risk in diabetes subjects after KT such as adequate management of calcium, parathyroid hormone, and vitamin D levels, optimization of glycemic control, use of steroid-sparing immunosuppressive regimens, and fall prevention.

Outcomes of bisphosphonate therapy in kidney transplant recipients: a systematic review and meta-analysis

Mineral and bone disorders that precede kidney transplantation are exacerbated in the post-transplant setting by tertiary hyperparathyroidism and immunosuppressive regimens. Bone mineral density (BMD) decreases following transplantation, leading to increased fracture risk. The effect of bisphosphonates on fracture is unknown. The aim of this study was to update estimates of change in BMD and fracture rates in bisphosphonate-treated kidney transplant recipients through meta-analysis. Studies comparing bisphosphonate therapy to standard of care were included if follow-up duration was more than 6 months. We performed random-effects meta-analysis to determine the effect of bisphosphonates on lumbar spine and femoral neck BMD and fracture rates. Bisphosphonates improved femoral neck and lumbar spine BMD compared with controls (0.055 g/cm(2) , 95% CI 0.012-0.099 and 0.053 g/cm(2) , 95% CI 0.032-0.074, respectively) without adversely affecting serum creatinine or calcium. This corresponded to an unweighted improvement in BMD of 6.0% and 7.4%, respectively. There was no difference in fracture incidence in the two groups. Bisphosphonate therapy in kidney transplant recipients is associated with a statistically significant improvement in BMD at the lumbar spine and femoral neck. There was no difference in fracture incidence. Bisphosphonates did not adversely affect allograft dysfunction or serum calcium levels.

Is total hip arthroplasty safely performed in lung transplant patients? Current experience from a retrospective study of the Zurich lung transplant cohort

Background

In recent years, the number of lung transplants has increased rapidly, with higher quality of life and improved survival rates in transplant recipients, including patients with advanced age. This, in turn, means that more transplant recipients will seek musculoskeletal care to treat degenerative joint disease and also trauma incidents. Safety concerns regarding elective and posttraumatic hip arthroplasty in transplant patients include an increased risk of infection, wound healing problems, periprosthetic fractures and loosening of the implants.

Methods

Clinical outcomes and safety aspects were retrospectively reviewed for five primary total hip arthroplasties (THA) in lung transplant recipients with minimal follow-up of two years at average of 2.6 (2–11) years. Patients were recruited from the Zurich Lung Transplant Center comprising of a cohort of 253 patients between January 1st, 2004 and December 31st, 2013.

Results

All five patients subjectively reported excellent outcomes after THA with a final average Harris Hip Score of 97 (86–100). One 71-year-old patient died 26 months after THA unrelated to arthroplasty. One superficial wound healing disturbance was documented. No periprosthetic fractures, no dislocations, no periprosthetic infections, no further revision surgery, no implant loosening was observed.

Conclusions

In conclusion, THA can be safely and successfully performed even in lung transplant patients under long-term immunosuppressive therapy and polymedication, provided a multidisciplinary approach can be granted.

Risk factors for fracture in adult kidney transplant recipients

AIM: To determine the general and transplant-specific risk factors for fractures in kidney transplant recipients.

METHODS: We conducted a cohort study of all adults who received a kidney-only transplant (n = 2723) in Ontario, Canada between 2002 and 2009. We used multivariable Cox proportional hazards regression to determine general and transplant-specific risk factors for major fractures (proximal humerus, forearm, hip, and clinical vertebral). The final model was established using the backward elimination strategy, selecting risk factors with a P-value ≤ 0.2 and forcing recipient age and sex into the model. We also assessed risk factors for other fracture locations (excluding major fractures, and fractures involving the skull, hands or feet).

RESULTS: There were 132 major fractures in the follow-up (8.1 fractures per 1000 person-years). General risk factors associated with a greater risk of major fracture were older recipient age [adjusted hazard ratio (aHR) per 5-year increase 1.11, 95%CI: 1.03-1.19] and female sex (aHR = 1.81, 95%CI: 1.28-2.57). Transplant-specific risk factors associated with a greater risk of fracture included older donor age (5-year increase) (aHR = 1.09, 95%CI: 1.02-1.17) and end-stage renal disease (ESRD) caused by diabetes (aHR = 1.72, 95%CI: 1.09-2.72) or cystic kidney disease (aHR = 1.73, 95%CI: 1.08-2.78) (compared to glomerulonephritis as the reference cause). Risk factors across the two fracture locations were not consistent (major fracture locations vs other). Specifically, general risk factors associated with an increased risk of other fractures were diabetes and a fall with hospitalization prior to transplantation, while length of time on dialysis, and renal vascular disease and other causes of ESRD were the transplant-specific risk factors associated with a greater risk of other fractures.

CONCLUSION: Both general and transplant-specific risk factors were associated with a higher risk of fractures in kidney transplant recipients. Results can be used for clinical prognostication.

Fracture Incidence in Adult Kidney Transplant Recipients

BACKGROUND

It remains uncertain whether kidney transplant recipients are a high-risk group for fracture.

METHODS

We conducted a cohort study using Ontario, Canada health care databases to estimate the 3-, 5- and 10-year cumulative incidence of nonvertebral fracture (proximal humerus, forearm, hip) in adult kidney transplant recipients between 1994 and 2009, stratifying by sex and age (<50 versus ≥50 years) at transplant. We also assessed the 3-year cumulative incidence of all fracture locations (excluding skull, toes, and fingers) and falls, 10-year cumulative incidence of hip fracture alone, and nonvertebral fracture incidence in recipients compared to nontransplant reference groups matched on age, sex, and cohort entry year. We studied 4821 recipients (median age, 50 years).

RESULTS

Among the age and sex strata, female recipients aged 50 years or older had the highest 3-year cumulative incidence of nonvertebral fracture (3.1%; 95% confidence interval [95% CI], 2.1-4.4%). Recipients had a higher 3-year cumulative incidence of nonvertebral fracture (1.6%; 95% CI, 1.3-2.0%) compared to the general population with no previous nonvertebral fracture (0.5%; 95% CI, 0.4-0.6%; P < 0.0001) and nondialysis chronic kidney disease (1.1%; 95% CI, 0.9-1.2%; P = 0.03), but a lower fracture incidence than the general population with a previous nonvertebral fracture (2.3%; 95% CI, 1.9-2.8%; P = 0.007). The 10-year cumulative incidence of hip fracture in all recipients was 1.7% (≥3% defined as high risk in clinical guidelines).

CONCLUSIONS

Kidney transplant recipients may have a lower fracture risk than previously suggested in the literature. Results inform our understanding of fracture incidence after kidney transplantation and how it compares to nontransplant populations.

Trabecular bone score in kidney transplant recipients

SUMMARY

It is uncertain whether bone mineral density (BMD) can accurately predict fracture in kidney transplant recipients. Trabecular bone score (TBS) provides information independent of BMD. Kidney transplant recipients had abnormal bone texture as measured by lumbar spine TBS, and a lower TBS was associated with incident fractures in recipients.

INTRODUCTION

Trabecular bone score (TBS) is a texture measure derived from dual energy X-ray absorptiometry (DXA) lumbar spine images, providing information independent of bone mineral density. We assessed characteristics associated with TBS and fracture outcomes in kidney transplant recipients.

METHODS

We included 327 kidney transplant recipients from Manitoba, Canada, who received a post-transplant DXA (median 106 days post-transplant). We matched each kidney transplant recipient (mean age 45 years, 39% men) to three controls from the general population (matched on age, sex, and DXA date). Lumbar spine (L1-L4) DXA images were used to derive TBS. Non-traumatic incident fracture (excluding hand, foot, and craniofacial) (n = 31) was assessed during a mean follow-up of 6.6 years. We used multivariable linear regression models to test predictors of TBS, and multivariable Cox proportional hazard regression was used to estimate hazard ratios (HRs) per standard deviation decrease in TBS to express the gradient of risk.

RESULTS

Compared to the general population, kidney transplant recipients had a significantly lower lumbar spine TBS (1.365 ± 0.129 versus 1.406 ± 0.125, P < 0.001). Multivariable linear regression revealed that receipt of a kidney transplant was associated with a significantly lower mean TBS compared to controls (-0.0369, 95% confidence interval [95% CI] -0.0537 to -0.0202). TBS was associated with fractures independent of the Fracture Risk Assessment score including BMD (adjusted HR per standard deviation decrease in TBS 1.64, 95% CI 1.15-2.36).

CONCLUSION

Kidney transplant recipients had abnormal bone texture as assessed by TBS and a lower lumbar spine TBS was associated with fractures in recipients.

Efficacy and Safety of Bisphosphonates for Low Bone Mineral Density After Kidney Transplantation: A Meta-Analysis

In patients with low bone mineral density (BMD) after kidney transplantation, the role of bisphosphonates remains unclear. We performed a systematic review and meta-analysis to investigate the efficacy and safety of bisphosphonates.We retrieved trials from PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) from inception through May 2015. Only randomized controlled trials that compared bisphosphonate-treated and control groups of patients with low bone mineral density after kidney transplantation were included. The primary outcomes were the percent change in BMD, the absolute change in BMD, and the BMD at the end of study at the lumbar spine. The results were expressed as the mean difference (MD) or relative risk (RR) with the 95% confidence interval (CI). We used a random-effects model to pool the outcomes.We included 17 randomized controlled trials with 1067 patients. Only 1 included trial was found to be at low risk of bias. The rest of the included studies were found to have high to uncertain risk of bias. Compared with the control group, those who received bisphosphonates had a significant increase in percent change in BMD (mean difference [MD] = 5.51, 95% confidence interval [CI] 3.22-7.79, P < 0.00001) and absolute change in BMD (MD = 0.05, 95% CI 0.04-0.05, P < 0.00001), but a nonsignificant increase in BMD at the end of the study (MD = 0.02, 95% CI -0.01 to 0.05, P = 0.25) at the lumbar spine. Bisphosphonates resulted in a significant improvement in percent change in BMD (MD = 4.95, 95% CI 2.57-7.33, P < 0.0001), but a nonsignificant improvement in absolute change in BMD (MD = 0.03, 95% CI -0.00 to 0.06, P = 0.07) and BMD at the end of the study (MD = -0.01, 95% CI -0.04 to 0.02, P = 0.40) at the femoral neck. No significant differences were found in vertebral fractures, nonvertebral fractures, adverse events, and gastrointestinal adverse events.Bisphosphonates appear to have a beneficial effect on BMD at the lumbar spine and do not significantly decrease fracture events in recipients. However, the results should be interpreted cautiously due to the lack of robustness and the heterogeneity among studies.

Frequency of bone mineral density testing in adult kidney transplant recipients from Ontario, Canada: a population-based cohort study

BACKGROUND

We lack consensus on the clinical value, frequency, and timing of bone mineral density (BMD) testing in kidney transplant recipients. This study sought to determine practice patterns in BMD testing across kidney transplant centres in Ontario, Canada, and to compare the frequency of testing in kidney transplant recipients to non-transplant reference groups.

METHODS

Using healthcare databases from Ontario, Canada we conducted a population-based cohort study of adult kidney transplant recipients who received a transplant from 1994-2009. We used logistic regression to determine if there was a statistically significant difference across transplant centres in the decision to perform at least one BMD test after transplantation, adjusting for covariates that may influence a physician's decision to order a BMD test. We used the McNemar's test to compare the number of recipients who had at least one BMD test to non-transplant reference groups (matching on age, sex, and date of cohort entry).

RESULTS

In the first 3 years after transplant, 4821 kidney transplant recipients underwent 4802 BMD tests (median 1 test per recipient, range 0 to 6 tests), costing $600,000 (2014 CAD equivalent dollars). Across the six centres, the proportion of recipients receiving at least one BMD test varied widely (ranging from 15.6 to 92.1 %; P < 0.001). Over half (58 %) of the recipients received at least one BMD test post-transplant, a value higher than two non-transplant reference groups (general population with a previous non-vertebral fracture [hip, forearm, proximal humerus], 13.8 %; general population with no previous non-vertebral fracture, 8.5 %; P value <0.001 for each of the comparisons).

CONCLUSIONS

There is substantial practice variability in BMD testing after transplant. New high-quality information is needed to inform the utility, optimal timing, and frequency of BMD testing in kidney transplant recipients.

Fifty shades of gray: Bone disease in renal transplantation

Kidney transplantation is the renal replacement therapy of choice for patients with end stage renal disease. Advances in technology, surgical techniques and pharmacotherapy have improved renal allograft survival. Increasingly, we are seeing long term side effects related to renal transplantation, bone disease being a major one amongst them. Renal transplant patients have a higher risk of fragility fractures even when compared to those who remain on dialysis. This is likely to be related to pre-existing underlying bone disease and the emergence of new metabolic bone problems post-transplant. Conditions such as persistent hyperparathyroidism and the use of certain immunosuppressive agents have a deleterious effect on the post renal transplant bone.

Remarkable advances in the field of metabolic bone research have been made in the last decade and newer imaging techniques, biomarkers and therapeutic options are now available for osteoporosis in the general population. Interest is being focused on attempting to extrapolate these new discoveries to the management of bone disease post renal transplant. This review will briefly describe the metabolic bone changes that occur after transplantation and will provide an update on the currently available investigative options and therapeutic strategies for the management of post renal transplant bone disease.

Comparison of single CT scan assessment of bone mineral density, vascular calcification and fat mass with standard clinical measurements in renal transplant subjects: the ABC HeART study

Background

Despite limitations of routine methods, Clinical Practice Guidelines support the assessment of bone mineral density (BMD) and vascular calcification in renal transplant recipients. Changes in fat mass also occur post-transplantation, although they are traditionally difficult to measure accurately. We report the feasibility, convenience and accuracy of measuring the above 3 parameters using a novel CT protocol.

Methods

We conducted a cross-sectional study of 64 first renal allograft recipients (eGFR > 30 ml/min/1.73 m²). Quantitative CT (QCT) BMD analysis was conducted using CT lumbar spine (GE Medical Systems Lightspeed VCT & Mindways QCT Pro Bone Mineral Densitometry System Version 4.2.3) to calculate spinal volumetric BMD and compared with standard DXA calculated areal BMD at the spine, hip and distal forearm. Abdominal aortic calcification was assessed by semi-quantitative Aortic Calcification Index (ACI) method and compared with lateral lumbar x-ray Kappuila score and pulse wave velocity (PWV). Visceral and subcutaneous adipose tissue volume (Osirix 16 Ver 3.7.1) was compared with BMI.

Results

Participants were 61 % male, had a mean age of 47 years, median ESKD duration of 5.4 years and a mean eGFR of 54 ml/min. iDXA median T-score at proximal femur was −1.2 and at lumbar spine was −0.2. Median QCT Trabecular T-score at lumbar spine was −1.2. The percent of subjects with a T-score of <2.5 by site and method was DXA Proximal Femur: 7 %, DXA distal radius: 17 %, DXA spine: 9 %, QCT (American College of Radiology cutoffs): 9 %. CT derived ACI correlated with PWV (r = 0.29, p = 0.02), pulse wave pressure (r = 0.51, p < 0.001), QCT Trabecular (−0.31, p = 0.01) and cortical volumetric BMD and history of cardiovascular events (Mann–Whitney U, p = 0.02). Both visceral and subcutaneous adipose tissue correlated with BMI (r = 0.63 & 0.64, p < 0.001).

Conclusions

Single CT scan triple assessment of BMD, vascular calcification and body composition is an efficient, accurate and convenient method of risk factor monitoring post renal transplantation.

Fracture risk and mortality post-kidney transplantation

BACKGROUND

Fractures are associated with high morbidity and economic costs. There is a paucity of information on fractures after kidney transplantation outside the United States.

METHODS

Data were obtained from the Hospital Episode Statistics database on kidney transplants performed in England between 2001 and 2013 and post-transplant fracture-related hospitalization. Mortality data were obtained from the Office for National Statistics.

RESULTS

In total, 21 769 first kidney transplant procedures were analyzed with 112 512 patient-years follow-up. Overall, 836 (3.8%) kidney allograft recipients developed a fracture requiring hospitalization. Event rate was 9.99 for any fracture and 1.54 for a hip fracture per 1000 patient-years. Accounting for the competing risk of mortality, increasing age, female gender, white ethnicity, and a history of pre-transplant diabetes mellitus or previous fracture were associated with increased fracture risk post-kidney transplantation. Death occurred in 2407 (11.1%) kidney allograft recipients, with 173 deaths occurring post-fracture. In an extended Cox model, hip fracture as a time-varying factor was independently associated with an increased risk of death (hazard ratio, 3.288; 95% confidence intervals, 2.513-4.301; p < 0.001).

CONCLUSIONS

Fracture rates in English kidney transplant recipients are lower than previously reported in US cohorts. Sustaining a hip fracture is associated with an increased mortality risk. Our results can be used to power future fracture prevention trials.

Bone imaging and fracture risk assessment in kidney disease

Fractures are more common and are associated with greater morbidity and morality in patients with kidney disease than in members of the general population. Thus, it is troubling that in chronic kidney disease (CKD) patients there has been a paradoxical increase in fracture rates over the past 20 years compared to the general population. Increased fracture incidence in CKD patients may be driven in part by the lack of screening for fracture risk. In the general population, dual energy X-ray absorptiometry (DXA) is the clinical standard to stratify fracture risk, and its use has contributed to decreases in fracture incidence. In contrast, in CKD, fracture risk screening with DXA has been uncommon due to its unclear efficacy in predicting fracture and its inability to predict type of renal osteodystrophy. Recently, several prospective studies conducted in patients across the spectrum of kidney disease have demonstrated that bone mineral density measured by DXA predicts future fracture risk and that clinically relevant information regarding fracture risk is provided by application of the World Health Organization cutoffs for osteopenia and osteoporosis to DXA measures. Furthermore, novel high-resolution imaging tools, such as high-resolution peripheral quantitative computed tomography (HR-pQCT), have been used to elucidate the effects of kidney disease on cortical and trabecular microarchitecture and bone strength and to identify potential targets for strategies that protect against fractures. This review will discuss the updated epidemiology of fractures in CKD, fracture risk screening by DXA, and the utility of state-of-the art imaging methods to uncover the effects of kidney disease on the skeleton.