Serum 1alpha,25-dihydroxyvitamin D3 accumulates into the fracture callus during rat femoral fracture healing

A decrease in serum 1,25(OH)2D after elective hip replacement and during bone healing is associated with changes in serum iron and plasma FGF23

OBJECTIVE

Although calcitriol is essential for bone healing, its serum concentrations are low after hip surgery, and they continue to decline during bone healing. This study aimed to test the hypothesis of an association of changes in calcitriol production with the status of fibroblast growth factor 23 (FGF23) and iron deficiency after elective hip replacement for coxarthrosis.

METHODS

In this prospective study, we measured the biomarkers of 17 patients undergoing elective hip replacement on admission, on the first day after surgery, and at the regular check-up after 48 ± 8 days. The serum concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, transferrin, ferritin, parathyroid hormone, intact plasma FGF23 (iFGF23) and C-terminal FGF23 (cFGF23) were determined.

RESULTS

In our patients who underwent elective hip replacement, significant correlations existed between the percent change in the conversion rate of 25(OH)D to 1,25(OH)₂D, plasma intact to C-terminal FGF23 ratio, and serum iron.

CONCLUSIONS

The production of calcitriol is compromised after elective hip replacement surgery, leading to reduced levels of active vitamin D in the serum. Significant correlations between the percent change in the conversion rate of 25(OH)D to 1,25(OH)₂D, plasma intact to C-terminal FGF23 ratio, and serum iron on the first day as well as 7 weeks after surgery could inspire future studies to determine whether and how calcitriol deficiency should be corrected, especially in fracture cases.

Decrease in serum calcitriol (but not free 25-hydroxyvitamin D) concentration in hip fracture healing

OBJECTIVE

To assess the decrease in serum calcitriol concentrations after hip fracture.

METHODS

Serum concentrations of calcitriol, 25(OH)D, parathyroid hormone (PTH), directly measured free 25(OH)D, and indices of bone formation were measured in elderly patients with hip fracture (HF) and patients with elective hip replacement (EHR) at admission and after 7 weeks.

RESULTS

A total of 45 patients with HF and 17 patients with EHR completed this prospective study. Baseline serum calcitriol levels were ≤ 60 pmol/l in 26% of the HF patients. After 7 weeks, they significantly decreased (p < 0.001). In patients with EHR, serum calcitriol was within the reference range in all but one patient and did not change during the 7-week recovery phase. Seven weeks after HF, a significant positive relationship was observed between the change in calcitriol and serum 25(OH)D concentration (r = 0.385, p = 0.009) and free 25(OH)D (r = 0.296, p = 0.048), and a decrease in calcitriol during recovery was associated with a decrease in serum PTH (p = 0.038). Seven weeks after HF, changes in both serum PTH and serum 25(OH)D concentrations contributed to the prediction of changes in serum calcitriol (R² = 0.190, p = 0.012).

CONCLUSIONS

Unlike patients with EHR, subjects with HF had low serum 25(OH)D and low free 25(OH)D concentrations at admission, while their serum 1,25D levels were relatively elevated. Decreases in circulating calcitriol levels in the 7 weeks following hip surgery were associated with a resolution of secondary hyperparathyroidism and low availability of free 25(OH)D.

Fixation Using Alternative Implants for the Treatment of Hip Fractures (FAITH-2): The Clinical Outcomes of a Multicenter 2 × 2 Factorial Randomized Controlled Pilot Trial in Young Femoral Neck Fracture Patients

OBJECTIVE

To assess whether the fixation method and vitamin D supplementation affect the risk of patient-important outcomes within 12 months of injury in nongeriatric femoral neck fracture patients.

DESIGN

A pilot factorial randomized controlled trial.

SETTING

Fifteen North American clinical sites.

PARTICIPANTS

Ninety-one adults 18-60 years of age with a femoral neck fracture requiring surgical fixation.

INTERVENTION

Participants were randomized to a surgical intervention (sliding hip screw or cancellous screws) and a vitamin D intervention (vitamin D3 4000 IU daily vs. placebo for 6 months).

MAIN OUTCOME MEASUREMENTS

The primary clinical outcome was a composite of patient-important complications (reoperation, femoral head osteonecrosis, severe femoral neck malunion, and nonunion). Secondary outcomes included fracture-healing complications and radiographic fracture healing.

RESULTS

Eighty-six participants with a mean age of 41 years were included. We found no statistically significant difference in the risk of patient-important outcomes between the surgical treatment arms (hazard ratio 0.90, 95% confidence interval 0.40-2.02, P = 0.80) and vitamin D supplementation treatment arms (hazard ratio 0.96, 95% confidence interval 0.42-2.18, P = 0.92).

CONCLUSIONS

These pilot trial results continue to describe the results of current fixation implants, inform the challenges of improving outcomes in this fracture population, and may guide future vitamin D trials to improve healing outcomes in young fracture populations. Although the pilot trial was not adequately powered to detect treatment effects, publishing these results may facilitate future meta-analyses on this topic.

LEVEL OF EVIDENCE

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

The Impact of Vitamin D Levels in Foot and Ankle Surgery

Hypovitaminosis D has been established as a global health problem. As an important regulator of skeletal health homeostasis throughout one's life, optimal levels are presumed. Debate, however, still exists surrounding the definition of normal vitamin D levels and what affect hypovitaminosis D has on fracture prevention, fracture healing, and successful arthrodesis. A literature search failed to show any level 1 studies examining hypovitaminosis D and union rates in foot and/or ankle arthrodesis procedures. Several retrospective studies do point to some sort of association between nonunion and hypovitaminosis D. Because of lack of high-level studies, a potential study design is proposed.

Tobacco and bone fractures: A review of the facts and issues that every orthopaedic surgeon should know

Objectives

The aim of this study was to review the impact of smoking tobacco on the musculoskeletal system, and on bone fractures in particular.

Methods

English-language publications of human and animal studies categorizing subjects into smokers and nonsmokers were sourced from MEDLINE, The Cochrane Library, and SCOPUS. This review specifically focused on the risk, surgical treatment, and prevention of fracture complications in smokers.

Results

Smokers have an increased risk of fracture and experience more complications with delayed bone healing, even if they have already stopped smoking, because some adverse effects persist for a prolonged period. Some risks can be reduced during and after surgery by local and general prevention, and smoking cessation is an important factor in lessening this risk. However, if a patient wants to stop smoking at the time of a fracture, the cessation strategies in reducing tobacco use are not easy to implement. The patient should also be warned that using e-cigarettes or other tobaccos does not appear to reduce adverse effects on health.

Conclusion

The evidence reviewed in this study shows that smoking has a negative effect in terms of the risk and treatment of fractures.

Cite this article: J. Hernigou, F. Schuind. Tobacco and bone fractures: A review of the facts and issues that every orthopaedic surgeon should know. Bone Joint Res 2019;8:255–265. DOI: 10.1302/2046-3758.86.BJR-2018-0344.R1.

Optimizing the Host in Fracture Surgery

Multiple factors impact fracture healing; thus, endocrine optimization and nutritional optimization warrant investigation in the acute fracture and nonunion patient. This article presents current evidence regarding the role of the endocrinologists and the dietician in the fracture patient as well as the most recent data assessing the vitamin D axis in these populations. Similarly, the most recent information regarding the use and risks of NSAIDs in fracture healing are presented. The fracture surgeon must consider each individual patient and weigh the benefits versus the costs of host optimization.

Fixation using alternative implants for the treatment of hip fractures (FAITH-2): design and rationale for a pilot multi-centre 2 × 2 factorial randomized controlled trial in young femoral neck fracture patients

BACKGROUND

Femoral neck fractures in patients ≤ 60 years of age are often very different injuries compared to low-energy, hip fractures in elderly patients and are difficult to manage because of inherent problems associated with high-energy trauma mechanisms and increased functional demands for recovery. Internal fixation, with multiple cancellous screws or a sliding hip screw (SHS), is the most common treatment for this injury in young patients. However, there is no clinical consensus regarding which surgical technique is optimal. Additionally, there is compelling rationale to use vitamin D supplementation to nutritionally optimize bone healing in young patients. This pilot trial will determine feasibility and provide preliminary clinical data for a larger definitive trial.

METHODS

We will conduct a multicenter, concealed randomized controlled pilot study, using a 2 × 2 factorial design in 60 patients aged 18-60 years with a femoral neck fracture. Eligible patients will be randomized in equal proportions to one of four groups: 1) SHS and vitamin D supplementation (4000 international units (IU) daily dose) for 6 months, 2) cancellous screws and vitamin D supplementation (4000 IU daily dose) for 6 months, 3) SHS and placebo, and 4) cancellous screws and placebo. Participants will be followed for 12 months post-fracture. Feasibility outcomes include initiation of clinical sites, recruitment, follow-up, data quality, and protocol adherence. Clinical outcomes, for both the pilot and planned definitive trials, include a composite of patient-important outcomes (re-operation, femoral head osteonecrosis, severe femoral neck malunion, and nonunion), health-related quality of life and patient-reported function, fracture healing complications, and radiographic fracture healing. A priori success criteria have been established. If the pilot study is deemed successful, study participants will be included in the definitive trial and clinical outcomes for the pilot will not be analyzed. If the pilot study is not deemed successful, clinical outcome data will be analyzed.

DISCUSSION

Results of this study will inform the feasibility of a definitive trial. If clinical outcome data are analyzed, they will be disseminated through a publication and presentations.

TRIAL REGISTRATION

The FAITH-2 trial, described as a definitive trial, was registered at ClinicalTrials.gov (NCT01908751) prior to enrollment of the first participant.

Effect of modulating dietary vitamin D on the general bone health of rats during posterolateral spinal fusion

Vitamin D plays a significant role in musculoskeletal health by regulating calcium, phosphate, and promoting new bone mineralization. The purpose of this study was to understand the effect of dietary vitamin D on general bone health during peri-operative bone healing via an in vivo dosing study of vitamin D in a rat posterolateral fusion model using autograft. Vitamin D Deficient (DD), vitamin D Insufficient (ID), Control vitamin D (CD), and Hyper-vitamin D (HD) groups were studied. Increasing dietary vitamin D improved quantitative measures of femoral geometry, including femoral strength, stiffness, and density. Femoral biomechanics, cortical thickness, moment of inertia, cross-sectional area, and measures from bone ashing were all greater in the HD group versus the CD. This suggests that additional dietary vitamin D above normal levels during spinal fusion may lead to improvement in bone health. Serum vitamin D levels were also observed to decrease during fusion healing. These results demonstrate that dietary vitamin D improves general bone health in the femur of a rat model during posterolateral spinal fusion. This suggests a role for further clinical evaluation of vitamin D dietary intake during the peri-operative period, with the possibility of avoiding adverse consequences to general bone health. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1435-1443, 2018.

Paracrine interactions between mesenchymal stem cells and macrophages are regulated by 1,25-dihydroxyvitamin D3

Mesenchymal stem cells (MSC) modulate the macrophage-mediated inflammatory response through the secretion of soluble factors. In addition to its classical effects on calcium homeostasis, 1,25-dihydroxyvitamin D3 (1,25D3) has emerged as an important regulator of the immune system. The present study investigates whether 1,25D3 modulates the paracrine interactions between MSC and macrophages. 1,25D3 stimulated MSC to produce PGE₂ and VEGF and regulated the interplay between macrophages and MSC toward reduced pro-inflammatory cytokine production. Conditioned media (CM) from co-cultures of macrophages and MSC impaired MSC osteogenesis. However, MSC cultured in CM from 1,25D3-treated co-cultures showed increased matrix maturation and mineralization. Co-culturing MSC with macrophages prevented the 1,25D3-induced increase in RANKL levels, which correlated with up-regulation of OPG secretion. MSC seeding in three-dimensional (3D) substrates potentiated their immunomodulatory effects on macrophages. Exposure of 3D co-cultures to 1,25D3 further reduced the levels of soluble factors related to inflammation and chemotaxis. As a consequence of 1,25D3 treatment, the recruitment of monocytes toward CM of 3D co-cultures decreased, while the osteogenic maturation of MSC increased. These data add new insights into the pleiotropic effects of 1,25D3 on the crosstalk between MSC and macrophages and highlight the role of the hormone in bone regeneration.

Effect of osteoporosis medications on fracture healing

Antiosteoporotic medications are often used to concurrently treat a patient's fragility fractures and underlying osteoporosis. This review evaluates the existing literature from animal and clinical models to determine these drugs' effects on fracture healing. The data suggest that these medications may enhance bone healing, yet more thorough prospective studies are warranted. Pharmacologic agents that influence bone remodeling are an essential component of osteoporosis management. Because many patients are first diagnosed with osteoporosis when presenting with a fragility fracture, it is critical to understand how osteoporotic medications influence fracture healing. Vitamin D and its analogs are essential for the mineralization of the callus and may also play a role in callus formation and remodeling that enhances biomechanical strength. In animal models, antiresorptive medications, including bisphosphonates, denosumab, calcitonin, estrogen, and raloxifene, do not impede endochondral fracture healing but may delay repair due to impaired remodeling. Although bisphosphonates and denosumab delay callus remodeling, they increase callus volume and result in unaltered biomechanical properties. Calcitonin increases cartilage formation and callus maturation, resulting in improved biomechanical properties. Parathyroid hormone, an anabolic agent, has demonstrated promise in animal models, resulting in accelerated healing with increased callus volume and density, more rapid remodeling to mature bone, and improved biomechanical properties. Clinical data with parathyroid hormone have demonstrated enhanced healing in distal radius and pelvic fractures as well as postoperatively following spine surgery. Strontium ranelate, which may have both antiresorptive and anabolic properties, affects fracture healing differently in normal and osteoporotic bone. While there is no effect in normal bone, in osteoporotic bone, strontium ranelate increases callus bone formation, maturity, and mineralization; forms greater and denser trabeculae; and improves biomechanical properties. Further clinical studies with these medications are needed to fully understand their effects on fracture healing in order to simultaneously treat fragility fractures and underlying osteoporosis.

Prescription of Vitamin D to Fracture Patients: A Lack of Consensus and Evidence

OBJECTIVES

We conducted a survey to explore practice patterns regarding the assessment of hypovitaminosis D and the prescription of vitamin D in acute fracture patients. Our secondary objective was to determine whether practice patterns differed between fragility and nonfragility fracture patients.

DESIGN

Cross-sectional survey.

SETTING

All surveys were completed using SurveyMonkey.

PATIENTS/PARTICIPANTS

We surveyed surgeon members of the Canadian Orthopaedic Association and the Orthopaedic Trauma Association.

INTERVENTION

Survey.

MAIN OUTCOME MEASUREMENTS

The proportion of surgeons who routinely prescribe vitamin D to fracture patients.

RESULTS

A total of 397 surveys were completed. Of total, 65.8% of surgeons indicated that they routinely prescribe vitamin D to fragility fracture patients and 25.7% routinely prescribe vitamin D to nonfragility fracture patients. We identified considerable variability in dosing regimens, as 45 different dosing regimens were prescribed in fragility fracture patients and 29 in nonfragility fracture patients. They ranged from daily doses of 400 IU to loading doses of 600,000 IU. The most frequently prescribed doses were 1000 IU daily (14.6%), 2000 IU daily (13.4%), and 50,000 IU weekly (8.7%). Respondents indicated that they heavily relied on clinical experience to guide their decisions to prescribe vitamin D to fracture patients.

CONCLUSIONS

The results of this survey demonstrate multiple areas of uncertainty and a lack of consensus in the prescription of vitamin D to fracture patients. Fragility patients frequently receive vitamin D supplementation, whereas most surgeons do not prescribe vitamin D to young fracture patients. High-quality clinical research is needed to determine whether vitamin D supplementation is beneficial to fracture patients.

LEVEL OF EVIDENCE

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

What Is the Role of Vitamin D Supplementation in Acute Fracture Patients? A Systematic Review and Meta-Analysis of the Prevalence of Hypovitaminosis D and Supplementation Efficacy

OBJECTIVES

The objectives of this systematic review and meta-analyses are (1) to estimate the prevalence of hypovitaminosis D in fracture patients and (2) to summarize the available evidence on the efficacy of vitamin D supplementation in fracture patients.

DATA SOURCES

A comprehensive search of the MEDLINE, Embase, PubMed, and Cochrane Central Register of Controlled Trials databases was conducted. Conference abstracts from relevant meetings were also searched.

STUDY SELECTION

We included studies that investigate vitamin D insufficiency or examine the effect of vitamin D supplementation on 25-hydroxy-vitamin D (25(OH)D) serum levels in fracture patients.

DATA EXTRACTION

Two authors independently extracted data using a predesigned form.

DATA SYNTHESIS

We performed a pooled analysis to determine the prevalence of postfracture hypovitaminosis D and mean postfracture 25(OH)D levels. We present detailed summaries of each of the studies evaluating the impact of vitamin D supplementation.

RESULTS

The weighted pooled prevalence of hypovitaminosis D was 70.0% (95% confidence interval: 63.7%-76.0%, I = 97.7). The mean postfracture serum 25(OH)D was 19.5 ng/mL. The studies that evaluated the efficacy of vitamin D supplementation suggest that vitamin D supplementation safely increases serum 25(OH)D levels. Only 1 meeting abstract showed a trend toward reduced risk of nonunion after a single large loading dose of vitamin D.

CONCLUSIONS

This review found a high prevalence of hypovitaminosis D in fracture patients and that vitamin D supplementation at a range of doses safely increases 25(OH)D serum levels. To date, only 1 pilot study published as a meeting abstract has demonstrated a trend toward improved fracture healing with vitamin D supplementation.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Functional Improvement in Geriatric Hip Fractures: Does Vitamin D Deficiency Affect the Functional Outcome of Patients With Surgically Treated Intertrochanteric Hip Fractures

Introduction:

The “Integrated Care Pathway” for geriatric intertrochanteric (IT) fractures in Singapore’s Tan Tock Seng Hospital has shown significant functional recovery in patients’ activities of daily living. However, the influence of preoperative vitamin D on functional recovery remains equivocal. This retrospective study therefore aims to determine whether patients with preoperative vitamin D deficiency have poorer functional outcomes.

Method:

A total of 171 patients who had surgical treatment for IT fractures were recruited in the study. They were categorized into group A (vitamin D deficient) and group B (normal vitamin D). Charlson Comorbidity Index (CCI) score and nutritional parameters including hemoglobin, albumin, and adjusted calcium levels on admission were recorded. The Modified Barthel Index (MBI) score was used to measure functional recovery at the following time intervals: at pre-fall, at discharge after surgery, at 6 months, and at 1-year follow-up.

Results:

The mean age of both the groups (A: 79.7 years, n = 45; B: 83.0 years, n = 126) was statistically different (P < .05). However, the mean CCI (A: 9.42 and B: 10.13), hemoglobin (A: 12.4 and B 11.1), adjusted calcium (A: 2.39 and B: 2.38), and mean albumin (A: 33.6 and B: 33.0) of the groups were not significantly different. Furthermore, the MBI scores were not significantly different for both groups at preinjury (A: 91.5 and B: 89.4), at discharge (A: 55.2 and B: 58.9), at 6 months (A: 70.9 and B: 75.1), and at 1 year (A: 75.8 and B: 79.4).

Conclusion:

In our cohort, patients with vitamin D deficiency were younger. However, vitamin D deficiency at time of injury had no significant influence on functional recovery in patients with surgically treated hip fracture in our Integrated Care Pathway. In addition, patients who had a normal vitamin D levels had similar functional scores and improvement postoperatively and at 1 year (A: 82.8% and B: 88.9%).

Intact bone vitality and increased accumulation of nonmineralized bone matrix in biopsy specimens of juvenile osteochondritis dissecans: a histological analysis

BACKGROUND

Although commonly proposed to be the starting point of juvenile osteochondritis dissecans (JOCD), avascular osteonecrosis (AVN) has been an inconsistent finding in histological studies. Analysis of early-stage lesions is required to elucidate the origins of OCD and justify proper treatment.

PURPOSE

To analyze histological sections of JOCD lesions with special emphasis on bone vitality.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Of 64 patients with 74 JOCD lesions (20 females, mean age, 11.4 years; 44 males, mean age, 12.7 years), 34 required surgery because of lesion instability or failed nonoperative treatment. From 9 patients, 11 histological specimens were obtained. Lesions were classified according to the International Cartilage Repair Society (ICRS). Two additional histological control sections were harvested from children without JOCD manifestation. Undecalcified histological sections were histomorphometrically analyzed. To analyze the skeletal health of the patients, biochemical analyses with special emphasis on bone metabolism were performed.

RESULTS

Histologically, no osteonecrosis was visible in any of the cases. Osteocyte distribution was similar among OCD lesions and controls. ICRS OCD I lesions (n = 6) showed no intralesional separation. In ICRS OCD II and III lesions (n = 5), there was a subchondral fracture concomitant with histological characteristics of active repair mechanism (increased bone formation: osteoid volume P = .008, osteoblast number P = .046; resorption: osteoclast number P = .005; and tissue fibrosis compared with controls). Instead, in ICRS OCD I lesions, subchondral osteoid volume (P = .010) and osteoblast number (P = .046) were significantly increased compared with controls; however, no active repair mechanisms (no increased bone resorption or fibrous tissue) were detected, suggesting a focal lack of mineralization. Fifty-seven of 64 patients (89.1%) showed a vitamin D deficiency. The median vitamin D serum level of the patients with ICRS OCD I lesions was 13.6 µg/L.

CONCLUSION

In the present study, osteonecrosis was not found in histological specimens of JOCD. As a secondary finding, focal accumulations of nonmineralized bone matrix indicating a lack of mineralization in ICRS OCD I lesions were revealed. This finding correlated with a low level of vitamin D in the affected children.

Alveolar bone regeneration in response to local application of calcitriol in vitamin D deficient rats

AIM

Vitamin D deficiency is considered to diminish bone regeneration. Yet, raising the serum levels takes months. A topic application of the active vitamin D metabolite, calcitriol, may be an effective approach. Thus, it becomes important to know the effect of vitamin D deficiency and local application on alveolar bone regeneration.

MATERIAL AND METHODS

Sixty rats were divided into three groups; two vitamin depletion groups and a control group. Identical single defects (2 mm diameter) were created in the maxilla and mandible treated with calcitriol soaked collagen in one deficiency group while in the other two groups not. Histomorphometric analysis and micro CTs were performed after 1 and 3 weeks. Serum levels of 25(OH)D3 and PTH were determined.

RESULTS

Bone formation rate significantly increased within the observation period in all groups. Bone regeneration was higher in the maxilla than in the mandible. However, bone regeneration was lower in the control group compared to vitamin depletion groups, with no significant effects by local administration of calcitriol (micro CT mandible p = 0.003, maxilla p < 0.001; histomorphometry maxilla p = 0.035, mandible p = 0.18).

CONCLUSION

Vitamin D deficiency not necessarily impairs bone regeneration in the rat jaw and a single local calcitriol application does not enhance healing.

Vitamin D and bone fracture healing

AIM: To examine whether vitamin D is of potential relevance in the healing process of fractures.

METHODS: The present narrative review examined the bulk of the evidence based literature on the topic of vitamin D and bone healing in key electronic data bases from 1980 onwards using the terms vitamin D and bone healing, callus, fracture healing. All data were examined carefully and categorized according to type of study. A summary of the diverse terms and approaches employed in the research, as well as the rationale for hypothesizing vitamin D has a role in fracture healing was detailed.

RESULTS: The results show very few human studies have been conducted to examine if vitamin D is effective at promoting post fracture healing, and the different animal models that have been studied provide no consensus on this topic. The terms used in the related literature, as well as the methods used to arrive at conclusions on this clinical issue are highly diverse, there is no standardization of either of these important terms and methodologies, hence no conclusive statements or clinical guidelines can be forthcoming. There is a strong rational for continuing to examine if vitamin D supplements should be administered post-fracture, and ample evidence vitamin D is an essential hormone for functioning in general, as well as bone health and muscle as this relates to bone density.

CONCLUSION: Whether those with low vitamin D levels can benefit from supplements if their nutritional practices do not cover recommended daily amounts, remains in question.

The role of vitamin D in human fracture healing: a systematic review of the literature

INTRODUCTION

Vitamin D is essential for bone mineralization and for the subsequent maintenance of bone quality. Mineralization is part of hard callus formation and bone remodelling, processes, which are part of fracture healing. We provide a comprehensive review of the literature to summarize and clarify if possible, the cellular effects of vitamin D and its clinical involvement in the process of fracture healing in human.

MATERIAL AND METHODS

We conducted a literature search in PubMed, Embase (OVID version), and Web of Science.

RESULTS

A total of 75 in vitro and 30 in vivo studies were found with inconsistent results about the cellular effect of vitamin D on fracture involved inflammatory cells, cytokines, growth factors, osteoblasts, osteoclasts and on the process of mineralization. With only five in vitro studies performed on material derived from a fracture site and one in vivo study in fracture patients, the exact cellular role remains unclear. Seven studies investigated the circulating vitamin D metabolites in fracture healing. Although it appears that 25(OH)D and 24,25(OH)2D3 are not affected by the occurrence of a fracture, this might not be the case with serum concentrations of 1,25(OH)2D3. The potential clinical effect of vitamin D deficiency is only described in one case series and three case controlled studies, where the results tend to show no effect of a vitamin D deficiency. No clinical studies were found investigating solely vitamin D supplementation. Two clinical studies found a positive effect of vitamin D supplementation and calcium, of increased bone mineral density or respectively increased fracture callus area at the fracture site. One study found indirect evidence that vitamin D and calcium promoted fracture healing.

CONCLUSION

Despite these results, and the presumed beneficial effect of vitamin D supplementation in deficient patients, clinical studies that address the effects of vitamin D deficiency or supplementation on fracture healing are scarce and remain inconclusive. We conclude that vitamin D has a role in fracture healing, but the available data are too inconsistent to elucidate how and in what manner.

Vitamin D supplementation enhances the fixation of titanium implants in chronic kidney disease mice

Vitamin D (Vit D) deficiency is a common condition in chronic kidney disease (CKD) patients that negatively affects bone regeneration and fracture healing. Previous study has shown that timely healing of titanium implants is impaired in CKD. This study aimed to investigate the effect of Vit D supplementation on implant osseointegration in CKD mice. Uremia was induced by 5/6 nephrectomy in C57BL mice. Eight weeks after the second renal surgery, animals were given 1,25(OH)2D3 three times a week intraperitoneally for four weeks. Experimental titanium implants were inserted into the distal end of femurs two weeks later. Serum measurements confirmed decreased 1,25(OH)2D levels in CKD mice, which could be successfully corrected by Vit D injections. Moreover, the hyperparathyroidism observed in CKD mice was also corrected. X-ray examination and histological sections showed successful osseointegration in these mice. Histomorphometrical analysis revealed that the bone-implant contact (BIC) ratio and bone volume (BV/TV) around the implant were significantly increased in the Vit D-supplementation group. In addition, resistance of the implant, as measured by a push-in method, was significantly improved compared to that in the vehicle group. These results demonstrate that Vit D supplementation is an effective approach to improve the fixation of titanium implants in CKD.

Influence of diabetic state and vitamin D deficiency on bone repair in female mice

Type 1 diabetes is associated with an increased fracture risk, an impaired fracture healing, and an increased vitamin D insufficiency. However, the role of vitamin D in diabetic bone repair process remains unclear. We therefore examined the effects of vitamin D deficiency on the impaired bone repair in streptozotocin (STZ)-induced diabetes using female mice. Diabetes was induced by STZ injection into female mice after feeding with normal or vitamin D-deficient diet for 6weeks from the age of 4weeks. A femoral bone defect was induced in mice 4 weeks after induction of diabetes. The repair of damaged site on the femur was significantly delayed at days 7 and 10 after bone defect by diabetic state in mice, as assessed by quantitative computed tomography, while vitamin D deficiency did not affect the bone repair both in mice with normal and diabetic state. The decreases in bone mineral density (BMD) at cortical and trabecular bone by diabetic state were significantly augmented by vitamin D deficiency in tibia at the undamaged side in mice. Diabetic state blunted the levels of osteogenic and chondrogenic genes enhanced by vitamin D deficiency. Moreover, vitamin D deficiency significantly aggravated the decreases in osteocalcin and IGF-1 mRNA by diabetic state. In conclusion, our study showed that vitamin D deficiency aggravates the decrease in BMD by diabetic state in female mice, although vitamin D deficiency did not affect bone repair delayed by diabetic state.

Changes in the serum level of vitamin d during healing of tibial and femoral shaft fractures

BACKGROUND

Several systemic factors and hormones are thought to regulate the fracture healing process. Vitamin D has emerged as a compound or hormone that actively participates in the regulation of calcium homeostasis and bone metabolism.

OBJECTIVES

The aim of this study is to determine the serum changes in the level of vitamin D during the acute healing period of tibial and femoral shaft fractures.

PATIENTS AND METHODS

This cross-sectional study included of 73 patients with tibial and femoral shaft fractures referred to the Poursina Hospital between February 2011 and February 2012. Changes in the serum levels of vitamin D were assessed three times in a period of three weeks (at the first visit, end of first week, and end of the third week). Variables such as age, gender, fractured bone, concomitant fracture of tibia and fibula, type of fracture, time of measurement and serum levels of 25-hydroxyvitamin D were assessed. All statistical analyses were performed using the SPSS software.

RESULTS

Forty tibial fractures and 33 femoral fractures were recorded. Mean vitamin D levels at the time of admission, after one week and at the end of the third week for the 73 participants included in the study were 39.23, 31.49, and 28.57 ng/mL, respectively. The overall reduction of vitamin D level was significantly more evident in the first week versus the following (P < 0.0001).

CONCLUSIONS

Serum levels of vitamin D in patients with tibial or femoral fractures were reduced during the curative period of the fracture. This can be related the role of vitamin D in the formation and mineralization of the callus. Patients with tibial or femoral shaft fractures may benefit from the administration of vitamin D supplements during the fracture healing process.

UV photoactivation of 7-dehydrocholesterol on titanium implants enhances osteoblast differentiation and decreases Rankl gene expression

Vitamin D plays a central role in bone regeneration, and its insufficiency has been reported to have profound negative effects on implant osseointegration. The present study aimed to test the in vitro biological effect of titanium (Ti) implants coated with UV-activated 7-dehydrocholesterol (7-DHC), the precursor of vitamin D, on cytotoxicity and osteoblast differentiation. Fourier transform infrared spectroscopy confirmed the changes in chemical structure of 7-DHC after UV exposure. High-pressure liquid chromatography analysis determined a 16.5±0.9% conversion of 7-DHC to previtamin D(3) after 15min of UV exposure, and a 34.2±4.8% of the preD(3) produced was finally converted to 25-hydroxyvitamin D(3) (25-D(3)) by the osteoblastic cells. No cytotoxic effect was found for Ti implants treated with 7-DHC and UV-irradiated. Moreover, Ti implants treated with 7-DHC and UV-irradiated for 15min showed increased 25-D(3) production, together with increased ALP activity and calcium content. Interestingly, Rankl gene expression was significantly reduced in osteoblasts cultured on 7-DHC-coated Ti surfaces when UV-irradiated for 15 and 30min to 33.56±15.28% and 28.21±4.40%, respectively, compared with the control. In conclusion, these findings demonstrate that UV-activated 7-DHC is a biocompatible coating of Ti implants, which allows the osteoblastic cells to produce themselves active vitamin D, with demonstrated positive effects on osteoblast differentiation in vitro.

Impact of dietary vitamin D on osseointegration in the ovariectomized rat

AIM

Vitamin D deficiency is highly prevalent in the population and associated with impaired peri-implant bone regeneration. Yet, there is a gap in understanding the impact of vitamin D supplementation on the process of osseointegration. In this study, the effect of vitamin D supplementation on peri-implant bone regeneration was investigated.

METHODS

Fifty ovariectomized Sprague-Dawley rats were divided into three groups. The depletion group was fed a vitamin D-free diet for 8 weeks. The repletion group received vitamin D-free diet for 6 weeks, before animals were switched to standard diet containing 2400 IU/kg vitamin D. The control group was fed the standard diet. Two titanium mini-implants were placed in the tibia. All groups remained on their previous diet until sacrifice. Blood sample testing and histomorphometric analysis were performed.

RESULTS

Vitamin D depletion caused a significant reduction in 25-hydroxvitamin D in rat serum that returned to control levels in the repletion group. This vitamin deficiency was associated with a decrease in bone-to-implant contact in the cortical area, which was leveled to controls in the repletion group. No significant changes by vitamin D depletion were noticed in the medullar compartment. Moreover, also the peri-implant bone area and the mineral apposition rate remained unchanged upon vitamin D depletion.

CONCLUSION

These results indicate that vitamin D deficiency has a negative impact on cortical peri-implant bone formation in ovariectomized rats, which can be compensated by vitamin D supplementation. This study provides first insight into the potential beneficial effect of vitamin D supplementation in implant dentistry.

Effect of 1,25-dihydroxy vitamin D3 on fracture healing and bone remodeling in ovariectomized rat femora

Osteoporosis is a major health problem characterized by compromised bone strength that predisposes patients to an increased risk of fracture, more and more investigations are focusing on the treatment of osteoporotic fracture healing. However, there are few studies elucidating the efficacy of vitamin D, 1,25-dihydroxy vitamin D(3) (1,25(OH)(2)D(3)), on osteoporotic fracture healing. In the present study we have established an osteoporotic fracture rat model to evaluate the effects of 1,25(OH)(2)D(3) on fracture healing. Female SD rats of six-month-old (n=40) allocated randomly into two groups were given ovariectomy. Bilateral midshaft femoral osteotomy was performed 12 weeks post-ovariectomy. Then treatment was begun at the second day after osteotomy and continued until sacrifice at 6 and 16 weeks post-fracture with middle chain triglyceride (MCT) vehicle and 1,25(OH)(2)D(3) at 0.1 microg/kg/day by oral gavage. Fracture callus was evaluated by soft X-ray radiography, micro-computed tomography (micro-CT), biomechanical testing and histology. Soft X-ray radiography, at 6 weeks post-fracture, showed a less distinct fracture line in the 1,25(OH)(2)D(3) group compared with the MCT-vehicle group, however, the fracture line was invisible in both groups at 16 weeks post-fracture. Micro-CT based histomorphometric data, at 6 weeks post-fracture, showed that the total volume of callus (TV) was approximately 23% higher in the 1,25(OH)(2)D(3) group than that in the MCT-vehicle group (P<0.001), and the new bone volume (BV), BV/TV, the trabecular number (Tb.N), and density of TV also showed the same trend. At 16 weeks post-fracture, the increment still existed as shown by Tb.Th and density of TV (P<0.001, vs control). Biomechanical testing data, at 6 weeks post-fracture, showed that the ultimate load at failure and energy absorption of the 1,25(OH)(2)D(3) group were nearly one fold higher than that of the MCT-vehicle group (P<0.001). At 16 weeks post-fracture, the ultimate load and energy absorption were also higher with the treatment of 1,25(OH)(2)D(3) (P<0.01 vs control). Histology showed that the fracture callus in the 1,25(OH)(2)D(3) group was remodeled better compared to the control group. In conclusion, 1,25(OH)(2)D(3) could promote fracture healing by improving the histomorphometric parameters, mechanical strength and tendency to increase transformation of woven bone into lamellar bone in an ovariectomized rat model.

Expression of connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) during fracture healing

Localization and expression of connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) during fracture healing in mouse ribs were investigated. In situ hybridization demonstrated that CTGF/Hcs24 mRNA was remarkably expressed, especially in hypertrophic chondrocytes and proliferating chondrocytes, in the regions of regenerating cartilage on days 8 and 14 after fracture. CTGF/Hcs24 mRNA was also expressed in proliferating periosteal cells in the vicinity of the fracture sites on days 2 and 8, and in cells in fibrous tissue around the callus on day 8. Northern blot analysis showed that expression of CTGF/Hcs24 mRNA was 3.9 times higher on day 2 of fracture healing than that on day 0. On day 8, it reached a peak of 8.6 times higher than that on day 0. It then declined to a lower level. Immunostaining showed that CTGF/Hcs24 was localized in hypertrophic chondrocytes and proliferating chondrocytes in the regions of regenerating cartilage, and in active osteoblasts in the regions of intramembranous ossification. Although CTGF/Hcs24 was abundant in the proliferating and differentiating cells (on days 8 and 14), immunostaining decreased as the cells differentiated to form bone (on day 20). CTGF/Hcs24 was also detected in cells in fibrous tissue, vascular endothelial cells in the callus, and periosteal cells around the fracture sites. These results suggest that CTGF/Hcs24 plays some role in fracture healing.