Hip Fractures and Vitamin D: 2021-2022

Ray Marks

Department of Health and Behavior Studies, Columbia University, Teachers College, New York, USA

*Correspondence to: Dr. Ray Marks, Department of Health and Behavior Studies, Columbia University, Teachers College, New York, USA.

Copyright © 2022 Dr. Ray Marks. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction
Hip fractures, which are mostly injury derived, rather than pathologically derived pose an extremely serious and ongoing public health problem as well as excessive personal costs to the older adult, even if they survive surgery or the injury, in general [1,2]. As well as affecting various degrees of disability, and immense hardships for many, these negative hip fracture outcomes, along with persistent post hip fracture surgical mortality rates that remain high will probably continue to ensue for some time to come in light of the numbers of older adults living to higher ages [3], and especially in the face of COVID-19 social isolation impacts [4], and the fact that most patients who sustain a hip fracture will have significant co-morbid health conditions, and may also suffer from cognitive impairments to a high degree [2], and with excess peri-operative complications and adverse outcomes in the presence of COVID-19 [5]. Moreover, those who survive surgery and incur excess disability may have a high risk of incurring a subsequent second or third hip fracture, especially if they have self-management challenges and others, such as following instructions or having to remain socially isolated in response to pandemic public health rulings. Indeed, factors contributing to the unrelenting numbers of older adults sustaining a hip fracture currently include but are not limited to osteoporosis, depression, and falls injuries that all imply there may be some approaches that can be harnessed readily to avert this highly deleterious crisis among the elderly [6], especially if there are persistent service restrictions. Of specific interest is thus regard, include approaches that might not only attenuate if not completely eliminate hip fracture risk and injury, but can also foster better bone health, cognitive health, immunity, falls injuries and sarcopenia [6,7]. To this end, this narrative overview highlights the most recent publications and their findings as regards vitamin D, a controversial realm of inquiry, but one with some observations that may yet prove clinically relevant.

The focus here on vitamin D, a fat soluble vitamin is not novel and has been pursued for some time, and is a one either absorbed into the skin in the presence of sunlight and converted to an active form thereafter, or ingested as a nutrient analogue. However, where its presence occurs at an insufficient level (25(OH)D < 50nmol/l (i.e., 20ng/mL)) or a deficient level (25(OH)D < 25nmol/l (i.e., 10ng/mL), the likelihood of fragility fractures is raised significantly and especially in those many elderly who sustain COVID-19 and/or one or more chronic health conditions. Thus even though the evidence on the effects of vitamin D deficiency and/or vitamin D supplementation on fracture healing and material osseointegration is still limited, and frequently discordant, it appears that vitamin D would be expected to have a positive influence on several physiological processes essential to bone and neuromuscular health, including its possible benefit on muscle strength, bone mass, balance and immune system functioning [8-10].

As well, in addition to evidence that COVID-19 is an independent risk factor for hip fracture mortality, mounting evidence shows taking a vitamin D supplement to maintain a serum concentration of 25(OH)D of at least 30ng/mL (preferred range 40-60ng/mL), can help reduce the risk of COVID-19 and its severe outcomes, including mortality [11]. In parallel research it is also evident that inadequate serum vitamin D levels are increasingly being linked to common chronic conditions that heighten hip fracture risk, such as depression, dementia, frailty, and poor cardiovascular health [9], thus providing more support than not for the importance of not neglecting to consider efforts to routinely assess prevailing levels of serum vitamin D among older adults at risk for hip fracture, as well as those who have sustained a hip fracture, and are recovering and intervening as indicated.

Methods
After searching the PUBMED, GOOGLE SCHOLAR, and Web of Science Consolidated databases to identify works published predominantly from February 1 2021-February 28 2022, items discussing either some relevant hip fracture statistic as well as articles related to Vitamin D and hip fractures and hip fracture determinants were sought and carefully examined.

The search was limited however, by excluding studies prior to 2021 and those that currently did not directly address the present topic of interest. All forms of study that were deemed acceptable were classified as representing basic information about hip fractures, vitamin D and its influence in the realm of hip fracture risk factors, and studies directly examining or reviewing vitamin D in the context of hip fractures directly.

Results

General
The current literature search revealed 87 PUBMED articles [of a possible 2572 discussing hip fractures and 5346 vitamin D related articles] using: Hip fracture and Vitamin D. However, almost half of the 87 articles listed on PUBMED for the years of February 2021-February 2022, and even among the 41 articles listed on Web of Science only some were relevant, while many were unrelated to this present discourse. Those listed on Google Scholar were generally represented in PUBMED or the Web of Science. As a whole, and despite any possible bias favoring the publication of articles with positive conclusions, most current reports that were deemed salient appeared to show persistently high rates of hip fracture mortality, and a linkage between this risk and the patient’s pre fracture health status [12,13], as well as multiple post fracture factors that may implicate vitamin D [14]. See summary findings in below.

Hip Fractures

Among the salient articles published recently that pertain to hip fractures and their ongoing challenges are those listed in Table 1.

Vitamin D
Key findings indicate vitamin D is related to bone health, dementia, acute respiratory infections, fractures, frailty [23-27].

To optimize bone health among those older adults with poor sunlight exposure or access to vitamin D containing foods, use of a vitamin D supplement of 400-1000 IU/day should be considered [28].

Hip Fractures and Vitamin D
A summary of most of the current conclusions reached by authors as regards observations linking vitamin D to some aspect of hip fracture is shown in Table 2.

As outlined in the above highlighted and current body of research, and which represents a high percentage of available publications listed on PUBMED and the additionally reviewed electronic data bases over the time periods February 2021-2022 these tend to imply vitamin D is a potentially relevant and possibly noteworthy factor in explaining hip fracture incidence, severity, and outcomes. It also appears there is some support for considering vitamin D supplementation among vulnerable older adults, in the event food associated vitamin D intake or sunlight exposure produces insufficient serum vitamin D levels, especially in the realm of: 1) primary and secondary fracture prevention efforts [29,45,46], 2) minimizing post-operative hip fracture surgery mortality risk, while maximizing recovery efforts, especially intermediate outcomes such as hip bone mineral density in vitamin D deficient cases [39] and walking or functional ability [47], fewer surgical complications, new fractures, or medical readmissions [35] and life quality [40] given the possible direct impact on either severe preoperative vitamin D deficiency [40] and/or the reactive depletion of prevailing vitamin D levels due to the inflammation caused by the fracture and/or surgical intervention [33]. Moreover, even though disputed in a meta analysis conducted by Chakhtoura et al. [48], these authors point to other evidence showing that vitamin D does appear to play a critical role in musculoskeletal health [48] and its common deficiency in older adults is a strong hip fracture correlate [49] that increases the length of hospital stays and reduces functional recovery [37]. Accordingly, a meta analysis by Bischoff-Ferrari concluded that in the realm of the geriatric ‘at risk’ older adult suffering from a vitamin D deficiency, implementing vitamin D supplementation of 800-1000IU per day is yet strongly recommended for purposes of minimizing falls and hip fracture risk and injury [29]. The current impact of low vitamin D serum levels and COVID-19 risk, an independent hip fracture mortality correlate as well as a potent fracture risk factor also warrants attention [8,38,41,44].

Indeed, most prevailing 2021-2022 published articles remain favorable to the idea that a sufficient vitamin D level is beneficial to the health status of older adults, and by analogy to a lower risk of fragility or osteoporotic hip fractures in post menopausal women [45]. Hence, in addition to its possible wide ranging health benefits, vitamin D supplementation is strongly recommended for protecting older vulnerable adults during this persistent pandemic period of social isolation by those wishing to mitigate fragility fractures, infections and pulmonary dysfunction [50], while reducing hip fracture mortality outcomes as well as hip fracture risk [51]. Other evidence suggests attention to resolving this current lack of consistent vitamin D associated impacts despite years of study should still assume a high research priority for purposes of advancing geriatric well-being and care, as well as for delineating sound evidence based clinical and post surgical hip fracture initiatives and practices. This is because, apart from the persistent risk of fragility fractures, and their high mortality rates observed among older hip fractures patients, many who survive may yet develop an additional or secondary fragility fracture [52].

Discussion
One of the most pervasive problematic health issues facing older adults is the fact they are often highly prone to falls and falls injuries, bone mass deficits, muscle weakness, and cognitive challenges that can threaten their very existence. However, according to Zhao et al. [44] vitamin D along with femoral neck bone mineral density and height are significantly associated with the occurrence of hip fractures in elderly women even after adjustment for confounding factors. Other evidence implies exposure to vitamin D-in sufficient quantities may greatly help to mitigate one or more hip fracture determinants such as low bone mineral density or mass or both, thus possibly limiting the extent of low energy fractures that commonly produce adverse outcomes [10]. As well, the post-surgical use of vitamin D supplements, although not discussed by Kim et al. [1], but where indicated, appears to offer the possibility of more favorable bone repair than its absence [10]. Accordingly, these latter authors called for routine assays of vitamin D in the context of bone fracture services, a call supported by Lim et al. [37] in both the post and pre surgical contexts, even if not concluded by Chakhtoura et al. [49].

Factors that might impact the presence of vitamin D negatively include:

 Malnutrition
 Poor nutrition [42,53]
 Lack of sunlight exposure
 No supplement usage/irregular usage
 Limited calcium usage/presence [49]

At the same time, a failure to routinely test for and remediate lower vitamin D levels in a timely manner may be an additional hip fracture determinant, especially if a present deficiency is reversible and is affecting bone as well as muscle function in some way [54]. However, since confusion still reigns in this regard, it seems reasonable to proceed with caution and to only advocate vitamin D supplementation if this is clearly indicated.

To advance this line of inquiry, it is possible that efforts to collate data from all available historic records, studies employing multiple research designs, diverse samples, and vitamin D status definitions will be helpful.

Until then, despite the lack of any solid consensus, it appears the most up to date literature on vitamin D shows its deficiency can have enormous ramifications for the older adult and may predictably result in immense excess personal as well as societal health costs and increases in hospitalization rates due to excess ground level falls incurred by the elderly [54], as well as osteoporotic fractures [12]. For example, by starting to simply target older adults and their families and health providers, and especially identifying older adults at high risk for vitamin D deficits early on in adult life, including those who have previously suffered from hip fractures, it appears that when all factors are considered the delivery of vitamin D to recovering hip fracture patients may impact both mortality, as well as desired functional outcomes favorably [46], and may provide benefits as far as fostering bone mineral density through its timely and appropriately targeted fortification [39] and its apparent ability to boost the Alendronate tail effect on bone density in osteoporotic women [55]. This includes those suffering from multiple co-morbid health conditions, and providing these adults all necessary resources to offset any vitamin D deficiency in the future [10]. In particular, as discussed by Downey et al. [56], since the number of fragility hip fractures in adults 60 years of age or older is estimated to triple or quadruple by 2050, with an estimated global cost of hip fractures in the year 2050 of $ 130 billion [57], the possible favorable role of vitamin D supplements in mitigating this to some degree, as indicated, must surely warrant widespread consideration.

In this regard, individuals living in the community and who might benefit most are-

 Those who are sedentary with mobility problems
 Those with multiple co-morbid health conditions
 Previous fallers/those who previously fractures a hip [30]
 Those who live alone/and don’t venture out of doors
 Frail adults older than 80 years of age [58]
 Those who are depressed
 Those who are weak and deemed to have fragile bones [30]

To this end, carefully tailored prevention programs are strongly indicated, even if these are only able to produce modest bone building benefits, as well as possible reductions in COVID-19 infection rates, fragility fractures, and lower post surgical complications [See Figure 1].

In sum, despite obvious limitations to the above discourse such as its focus solely on data for the past year derived from various observational studies and others, and the fact the quality of the evidence may be lower than desired, and may not include a broad enough spectrum of adults who have suffered hip fractures during the pandemic period, vitamin D and its association with hip fracture risk and recovery clearly warrants further study.

In particular, a clear exploration of the role of sunlight, diet, and exercise and vitamin D serum levels on bone health and bone healing across the lifespan is highly recommended and may yield far reaching benefits.

Conclusions
On the basis of this snapshot of the past years’ hip fracture/vitamin D publications we conclude:

 Many hip fracture cases are found to have deficient serum vitamin D levels.
 Early screening and possible vitamin D supplementation should be considered for at risk older adults living in the community.
 Restoring or helping hip fracture patients to maintain a sufficient vitamin D level is likely to be beneficial in multiple ways.
 More research to examine this issue remains desirable.

Bibliography

1. Kim, S. M., Moon, Y. W., Lim, S. J., Yoon, B. K., Min, Y. K., Lee, D. Y. & Park, Y. S. (2012). Prediction of survival, second fracture, and functional recovery following the first hip fracture surgery in elderly patients. Bone., 50(6), 1343-1350.
2. Li, L., Bennett-Brown, K., Morgan, C. & Dattani, R. (2020). Hip fractures. Brit J Hosp Med., 81(8), 1-10.
3. Hagino, H. (2021). Current and future burden of hip and vertebral fractures in Asia. Yonago Acta Med., 64(2), 147-154.
4. Ronel, D., Keren, Y., Muallem, A. & Elboim-Gabyzon, M. (2022). The effect of physical and social isolation due to the COVID-19 pandemic on the incidence of hip fractures among senior citizens. Geriatric Nurs., 43, 21-25.
5. Galivanche, A. R., Mercier, M. R., Schneble, C. A., Brand, J., Pathak, N., Varthi, A. G., et al. (2021). Clinical characteristics and perioperative complication profiles of COVID-19-positive patients undergoing hip fracture surgery. JAAOS Global Res & Rev., 5(10).
6. Tarazona-Santabalbina, F. J., Ojeda-Thies, C., Figueroa Rodríguez, J., Cassinello-Ogea, C. & Caeiro, J. R. (2021). Orthogeriatric management: improvements in outcomes during hospital admission due to hip fracture. Int J Environment Res Pub Hlth., 18(6), 3049.
7. Yoo, J. I., Chung, H. J., Kim, B. G., Jung, Y. K., Baek, K. W., Song, M. G. & Cho, M. C. (2021). Comparative analysis of the association between various serum vitamin D biomarkers and sarcopenia. J Clin Lab Anal., 35 ,(9), e23946.
8. Skuladottir, S. S., Ramel, A., Eymundsdottir, H., Hjaltadottir, I., Launer, L. J., Cotch, M. F., et al. (2021). Serum 25-hydroxy-vitamin D status and incident hip fractures in elderly adults: Looking beyond bone mineral density. J Bone Min Res., 36(12), 2351-2360.
9. Sizar, O., Khare, S., Goyal, A., Bansal, P. & Givler, A. (2021). Vitamin D Deficiency. In: StatPearls [Internet]
10. Chevalley, T., Brandi, M. L., Cavalier, E., Harvey, N. C., Iolascon, G., Cooper, C., et al. (2021). How can the orthopedic surgeon ensure optimal vitamin D status in patients operated for an osteoporotic fracture? Osteoporos Int., 32(10), 1921-1935.
11. Bae, J. H., Choe, H. J., Holick, M. F. & Lim, S. (2022). Association of vitamin D status with COVID-19 and its severity. Rev Endocrine Metab Dis., 1-21.
12. Baidoo, P. K., Odei, J. B., Ansu, V., Segbefia, M. & Holdbrook-Smith, H. (2021). Predictors of hip fracture mortality in Ghana: A single-center prospective study. Arch Osteoporos., 16(1), 35.
13. Liow, M., Ganesan, G., Chen, J., Koh, J., Howe, T. S., Yong, E. L., et al. (2021). Excess mortality after hip fracture: Fracture or pre-fall comorbidity? Osteoporos Int., 32(12), 2485-2492.
14. Blanco, J. F., da Casa, C., Pablos-Hernández, C., González-Ramírez, A., Julián-Enríquez, J. M. & Díaz-Álvarez, A. (2021). 30-day mortality after hip fracture surgery: Influence of postoperative factors. PloS one., 16(2), e0246963.
15. Gong, X. F., Li, X. P., Zhang, L. X., Center, J. R., Bliuc, D., Shi, Y., et al. (2021). Current status and distribution of hip fractures among older adults in China. Osteoporos Int., 32(9), 1785-1793.
16. Kawaji, H., Ishii, M., Sasaki, K., Takakubo, Y., Ishikawa, H. & Takagi, M. (2022). Decennial trends in hip fractures over 20 years in Yamagata Prefecture, Japan. J Orthop Sci., S0949-2658.
17. Lorentzon, M., Johansson, H., Harvey, N. C., Liu, E., Vandenput, L., McCloskey, E. V. & Kanis, J. A. (2022). Osteoporosis and fractures in women: The burden of disease. Climacteric., 25(1), 4-10.
18. Meyer, A. C., Ek, S., Drefahl, S., Ahlbom, A., Hedström, M. & Modig, K. (2021). Trends in hip fracture incidence, recurrence, and survival by education and comorbidity: A Swedish register-based study. Epidemiol (Cambridge, Mass.)., 32(3), 425-433.
19. Park, H. Y., Han, K., Kim, Y., Kim, Y. H. & Sur, Y. J. (2021). The risk of hip fractures in individuals over 50 years old with prediabetes and type 2 diabetes-a longitudinal nationwide population-based study. Bone., 142, 115691.
20. Schemitsch, E., Adachi, J. D., Brown, J. P., Tarride, J. E., Burke, N., Oliveira, T. & Slatkovska, L. (2022). Hip fracture predicts subsequent hip fracture: A retrospective observational study to support a call to early hip fracture prevention efforts in post-fracture patients. Osteoporos In., 33(1), 113-122.
21. Shimizu, A., Maeda, K., Fujishima, I., Kayashita, J., Mori, N., Okada, K., et al. (2022). Hospital Frailty Risk Score predicts adverse events in older patients with hip fractures after surgery: Analysis of a nationwide inpatient database in Japan. Arch Gerontol Geriatr., 98, 104552.
22. Zhang, Y. W., Lu, P. P., Li, Y. J., Dai, G. C., Chen, M. H., Zhao, Y. K., et al. (2021). Prevalence, characteristics, and associated risk factors of the elderly with hip fractures: A cross-sectional analysis of NHANES 2005-2010. Clin Interventions Aging., 16, 177-185.
23. Emadzadeh, M., Mehdizadeh, A., Sharifan, P., Khoshakhlagh, M., Sahebi, R., Sadeghi, R., et al. (2022). The effects of vitamin D fortified products on bone biomarkers: A systematic review and meta-analysis. Iran J Pub Hlth., 51(2), 278-291.
24. Geng, T., Lu, Q., Wan, Z., Guo, J., Liu, L., Pan, A. & Liu, G. (2022). Association of serum 25-hydroxyvitamin D concentrations with risk of dementia among individuals with type 2 diabetes: A cohort study in the UK Biobank. PLoS Med., 19(1), e1003906.
25. Ganmaa, D., Enkhmaa, D., Nasantogtokh, E., Sukhbaatar, S., Tumur‐Ochir, K. E. & Manson, J. E. (2022). Vitamin D, respiratory infections, and chronic disease: Review of meta‐analyses and randomized clinical trials. J Int Med., 291(2), 141-164.
26. Göçer, Ş. & Balbaloğlu, Ö. (2021). Association of frailty with serum vitamin D and parathyroid hormone levels. Acıbadem Üniversitesi Sağlık Bilimleri Dergisi, 13(1), 119-125.
27. Tański, W., Kosiorowska, J. & Szymańska-Chabowska, A. (2021). Osteoporosis - risk factors, pharmaceutical and non-pharmaceutical treatment. European Rev Med Pharmacol Sci., 25(9), 3557-3566.
28. Reid, I. R. (2022). Bone-friendly lifestyle and the role of calcium or vitamin D supplementation. Climacteric, 25(1), 37-42.
29. Bischoff-Ferrari H. A. (2020). Vitamin D beim geriatrischen Patienten [Vitamin D in geriatric patients]. Der Internist, 61(6), 535-540.
30. Arshad, A., Ibrahim, M. T., Arshad, H., Hammad, M. B., Sheikh, S. A., Khan, A. H., et al. (2021). Clinical characteristics and outcomes of patients presenting with hip fractures at a tertiary care hospital in Pakistan. Arch Osteoporos., 16(1), 1-10.
31. Li, S., Xi, C., Li, L., Long, Z., Zhang, N., Yin, H., et al. (2021). Comparisons of different vitamin D supplementation for prevention of osteoporotic fractures: A Bayesian network meta-analysis and meta-regression of randomised controlled trials. Int J Food Sci Nutr., 72(4), 518-528.
32. Ginsberg, C., Katz, R., de Boer, I. H., Kestenbaum, B. R., Chonchol, M., Shlipak, M. G., et al. (2018). The 24,25 to 25-hydroxyvitamin D ratio and fracture risk in older adults: The cardiovascular health study. Bone., 107, 124-130.
33. Giordano, S., Proietti, A., Bisaccia, T., Caso, P., Martocchia, A., Falaschi, P. & Tafaro, L. (2018). Hypovitaminosis D: Comparison between patients with hip fracture and patients with vertebral fractures. Osteoporos int., 29(9), 2087-2091.
34. Hershkovitz, A., Maydan, G., Ben Joseph, R. & Nissan, R. (2021). Vitamin D levels in post-acute hip fractured patients and their association with rehabilitation outcomes. Disabil Rehabil., 1-8.
35. Ingstad, F., Solberg, L. B., Nordsletten, L., Thorsby, P. M., Hestnes, I. & Frihagen, F. (2021). Vitamin D status and complications, readmissions, and mortality after hip fracture. Osteoporos int., 32(5), 873-881
36. Jamal, A. B., Hasan Khan, M. N. & Sadiq, M. (2021). Intertrochanteric hip fractures and vitamin D deficiency; a significant association. J Ayub Med Coll Abbottabad., 33(2), 257-261.
37. Lim, C., Roh, Y. H., Kim, S. & Nam, K. W. (2021). Preoperative vitamin D deficiency is associated with postoperative functional recovery and complications after hip fracture surgery. J Bone Metab., 28(4), 333-338.
38. Mahmood, A., Rashid, F., Limb, R., Cash, T., Nagy, M. T., Zreik, N., et al. (2021). Coronavirus infection in hip fractures (CHIP) study. The Bone & JointJ., 103-B(4), 782-787.
39. Scragg, R. & Sluyter, J. D. (2021). Is there proof of extraskeletal benefits from vitamin D supplementation from recent mega trials of vitamin D? JBMR Plus., 5(1), e10459.
40. Sim, D. S., Tay, K., Howe, T. S. & Koh, S. (2021). Preoperative severe vitamin D deficiency is a significant independent risk factor for poorer functional outcome and quality of life 6 months after surgery for fragility hip fractures. Osteoporos Int., 32(11), 2217-2224.
41. Seshadri, M. S., Gopi, M., Murali, P. & Kumar, K. (2021). Osteoporosis in a rural community-long-term effects of a community level program of calcium and vitamin D supplementation-A prospective observational study. Indian J Endocrinol Metab., 25(4), 305-312.
42. Thorpe, D. L., Beeson, W. L., Knutsen, R., Fraser, G. E. & Knutsen, S. F. (2021). Dietary patterns and hip fracture in the Adventist Health Study 2: Combined vitamin D and calcium supplementation mitigate increased hip fracture risk among vegans. Am J Clin Nutr., 114(2), 488-495.
43. Valle, C., Pedri, L., Pires, G. B., Blanco, M. S., Paula, B. S. & Araújo, C. (2021). Influence of hypovitaminosis D on the ocurrence of fractures. Revista Brasileira de Ortopedia, 56(6), 784-789.
44. Yu, S. J., Yang, Y., Zang, J. C., Li, C., Wang, Y. M. & Wang, J. B. (2021). Evaluation of serum 25-hydroxyvitamin D3 and bone mineral density in 268 patients with hip fractures. Orthop Surg., 13(3), 892-899.
45. Zhao, J. H., Shi, H. P., Jiang, D. J., Wang, L. T., Chen, S. B. & Jia, W. T. (2021). Analysis of combined indicators for risk of osteoporotic hip fracture in elderly women. Orthop Surg., 13(4), 1205-1212.
46. Conley, R. B., Adib, G., Adler, R. A., Åkesson, K. E., Alexander, I. M., Amenta, K. C., Blank, R. D., et al. (2020). Secondary fracture prevention: consensus clinical recommendations from a Multistakeholder Coalition. J Bone Mineral Res., 35(1), 36-52.
47. Feskanich, D., Willett, W. C. & Colditz, G. A. (2003). Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. The American Journal of Clinical Nutrition, 77(2), 504-511.
48. Koutalos, A. A., Chalatsis, G. I., Varsanis, G., Malizos, K. N. & Karachalios, T. (2021). The effect of zoledronic acid and high-dose vitamin D on function after hip fractures. A prospective cohort study. Eur J Orthop Surg & Traumatol.
49. Hao, L., Carson, J. L., Schlussel, Y., Noveck, H. & Shapses, S. A. (2020). Vitamin D deficiency is associated with reduced mobility after hip fracture surgery: A prospective study. Am J Clin Nutr., 112(3), 613-618.
50. Chakhtoura, M., Bacha, D. S., Gharios, C., Ajjour, S., Assaad, M., Jabbour, Y., et al. (2021). Vitamin D supplementation and fractures in adults: A systematic umbrella review of meta-analyses of controlled trials. J Clin Endocrinol Metab., 107(3), 882-898.
51. Larrosa, M., Gomez, A., Casado, E., Moreno, M., Vázquez, I., Orellana, C., et al. (2012). Hypovitaminosis D as a risk factor of hip fracture severity. Osteoporos Int., 23(2), 607-614.
52. Dos Santos, R. N., Maeda, S. S., Jardim, J. R. & Lazaretti-Castro, M. (2021). Reasons to avoid vitamin D deficiency during COVID-19 pandemic. Arch Endocrinol Metab., 64(5), 498-506.
53. Lim, M. A. & Pranata, R. (2021). Coronavirus disease 2019 (COVID-19) markedly increased mortality in patients with hip fracture-a systematic review and meta-analysis. J Clinical Orthop and Trauma., 12(1), 187-193.
54. Bugeja, M., Curmi, A., Desira, D., Bologna, G. A., Galea, F. & Esposito, I. (2021). Hip Fractures in Malta: Are we missing an opportunity? Surgery Journal (New York, N.Y.), 7(3), e184-e190.
55. Rizzoli, R., Biver, E. & Brennan-Speranza, T. C. (2021). Nutritional intake and bone health. The Lancet. Diabetes & Endocrinol., 9(9), 606-621.
56. Kupisz-Urbańska, M., Płudowski, P. & Marcinowska-Suchowierska, E. (2021). Vitamin D deficiency in older patients-problems of sarcopenia, drug interactions, Management in Deficiency. Nutrients., 13(4), 1247.
57. Catalano, A., Bellone, F., Santoro, D., Schwarz, P., Gaudio, A., Basile, G., et al. (2021). Vitamin D boosts alendronate tail effect on bone mineral density in postmenopausal women with osteoporosis. Nutrients., 13(6), 1878.
58. Downey. C., Flannery, S., Abd Wahab, E. H., Askin, D., O'Kelly, P., Shortt, C. P., et al. (2020). The patient's second hip fracture - one in ten. Ir Med J. 113(6), 93.
59. Nguyen, M. H. & Lui, S. K. (2020). Holistic management of older patients with hip fractures. Orthop Nurs. 39(3), 183-191.
60. Lips, P., Bilezikian, J. P. & Bouillon, R. (2020). Vitamin D: giveth to those who needeth. JBMR Plus., 4(1), e10232.
61. Neale, R. E., Wilson, L. F., Black, L. J., Waterhouse, M., Lucas, R. M. & Gordon, L. G. (2021). Hospitalisations for falls and hip fractures attributable to vitamin D deficiency in older Australians. Brit J Nutr., 126(11), 1682-1686.
62. Shi, T. T., Min, M., Zhang, Y., Sun, C. Y., Liang, M. M. & Sun, Y. H. (2019). Depression and risk of hip fracture: a systematic review and meta-analysis of cohort studies. Osteoporos Int., 30(6), 1157-1165.