The Effect of Osteoporosis on Healing of Distal Radius Fragility Fractures




Although the decision for operative versus nonoperative treatment of distal radius fractures remains subjective and is performed on a case-by-case basis, evaluation and treatment of patients with concomitant osteoporosis requires understanding of the behavior of this injury as a distinct subset of distal radius fractures. Age, infirmity, and osteoporosis affect every aspect of the fracture. Understanding what makes these fractures unique assists surgeons in more effective and efficient treatment. The authors present the current understanding of osteoporotic fragility fractures of the distal radius, focusing on epidemiology, biomechanics of bone healing, and its implication on strategies for management.


Key points








  • Distal radius fractures are among the most common fractures seen and are increasing in incidence because of increased prevalence of osteoporosis and increasing age of our population.



  • The osteoporotic distal radius is deficient in both cortical and trabecular bone, but early changes in cortical bone most predispose to fragility fractures.



  • The fracture callus formed around an osteoporotic fracture is less stiff than a normal fracture callus, but it is unclear how this affects long-term function or biomechanics.



  • Nonoperative management of osteoporotic distal radius fractures in low-demand patients remains well indicated and can lead to long-term clinical outcomes similar to operative management.



  • There are multiple acceptable methods for operative management of osteoporotic distal radius fractures; but volar locking plates are most commonly used, safely and readily applied, allowing for early motion, and have an acceptable complication profile.






Introduction


Fractures of the distal radius are among the most common fragility fractures seen in clinical practice, with estimates of annual incidence ranging as high as 86,000 in the United States alone. Given the aging population, this number is only expected to increase.


Although the surgical treatment of distal radius fractures has advanced significantly since the advent of the volar locking plate, recent studies, including Arora and colleagues, Koval and colleagues, and Young and Rayan, have challenged the trend toward operative management and have prompted increased interest in nonoperative treatment of these fractures. Although the decision for operative versus nonoperative treatment still remains subjective and is performed on a case-by-case basis, evaluation and treatment of patients with a distal radius fragility fracture requires understanding of the behavior of this injury as a distinct subset of distal radius fractures. Age, infirmity, and osteoporosis affect every aspect of the fracture, from epidemiology and injury biomechanics to fixation mechanics and the biology of healing. Understanding what makes these fractures unique assists the surgeon in more effective and efficient treatment.




Introduction


Fractures of the distal radius are among the most common fragility fractures seen in clinical practice, with estimates of annual incidence ranging as high as 86,000 in the United States alone. Given the aging population, this number is only expected to increase.


Although the surgical treatment of distal radius fractures has advanced significantly since the advent of the volar locking plate, recent studies, including Arora and colleagues, Koval and colleagues, and Young and Rayan, have challenged the trend toward operative management and have prompted increased interest in nonoperative treatment of these fractures. Although the decision for operative versus nonoperative treatment still remains subjective and is performed on a case-by-case basis, evaluation and treatment of patients with a distal radius fragility fracture requires understanding of the behavior of this injury as a distinct subset of distal radius fractures. Age, infirmity, and osteoporosis affect every aspect of the fracture, from epidemiology and injury biomechanics to fixation mechanics and the biology of healing. Understanding what makes these fractures unique assists the surgeon in more effective and efficient treatment.




Epidemiology


Most distal radius fractures in the elderly are attributable to osteoporosis, with a correspondingly higher incidence in the female versus male population. A 2004 study of the French National Hospital Database found an incidence of 7.5 per 1000 in women and 2.3 per 1000 in men older than 45 years. A later single-center British study estimated that these fractures compose 17.5% of adult fractures. Other studies have confirmed the strong correlation between fracture incidence and displacement and patient age, especially for female patients, in whom incidence increases from 8.9 per 10,000 in patients aged 19 to 49 years to 119 per 10,000 in patients older than 80 years.


Several risk factors for occurrence and severity of distal radius fragility fracture have been elucidated, with most relating directly or indirectly to bone quality. Known osteoporosis or decreased bone mineral density (BMD) as measured by a dual-energy x-ray absorptiometry (DEXA) scan is well established to increase the risk for distal radius fragility fracture ; but other studies have examined nutritional, lifestyle, and genetic predisposing factors. A case-control study demonstrated lower serum 25-hydroxyvitamin levels in fracture patients versus matched controls, independently of measured BMD, indicating a qualitative as well as quantitative bone deficit. Although this has been posited as a potential explanation for prior studies finding increased incidence of distal radius fractures in the elderly during winter months, the studies have been unable to differentiate between vitamin D levels and variations in patient activity as causative factors.




Biomechanics


Osteoporotic and normal distal radii differ in structural and mechanical properties. A cadaver study by Spadaro and colleagues attempted to determine whether cortical or trabecular properties are the main contributors to biomechanical load to failure. The ultimate compressive strength of 21 osteopenic cadaver radii was found to correlate strongly with cortical cross-sectional area, indicating a major contribution by the cortical shell to the ultimate strength of distal radii. A correlation was also noted, however, between trabecular density (as opposed to area) and strength, leading to the conclusion that axial distal radius strength is affected by both quantity of cortex and quality of trabecular bone.


More recent studies have used high-resolution quantitative computed tomography (HR-QCT) to reveal in vivo changes associated with postmenopausal distal radius. A recent study of 51 women over 1 year by Kawalilak and colleagues used this method and found that postmenopausal women experience a decrease in total density, accompanied by a reduction in number and an increase in thickness of trabeculae. Another recent study of 117 postmenopausal women by Stein and colleagues demonstrated significantly altered trabecular morphology in women with fractures, including rodlike rather than platelike trabecular microarchitecture, and loss of axial trabecular orientation. Although BMD was lost in both cortex and trabeculae in this group, there were no measureable differences in cortical structure.


The difficulty in parsing these data is in determining the relative contribution of cortical and trabecular bone to total strength in the distal radius; although both are correlated to increase fracture risk, causality and contribution to weakness are difficult to determine. Among the studies that attempted to isolate cortical contribution is a case-control study of 138 postmenopausal women by Bala and colleagues , which found that dense cortical porosity of the distal radius as measured by HR-QCT is predictive of fracture independent of BMD. Although this study was unable to make a strong statement of cortical porosity’s effect in osteoporotic individuals because of the high prevalence of this finding (approximately 90%) in this population, it did demonstrate that cortical architecture has an independent effect (odd ratio 4.00, confidence interval 1.15–13.90) on fracture risk in osteopenic women.


A more focused study by Bjørnerem and colleagues in 2013 examined 345 women aged 40 to 61 years. Each 1-SD increase in cortical porosity of the distal radius, as measured by HR-QCT, was found to correlate with an increased risk of fracture, although the association was weak in the distal radius as compared with the tibia and fibula.


Taken as a whole, these studies make a convincing argument that, at least in the early stages of osteopenia, cortical rather than trabecular bone provides the most significant contribution to distal radius fracture resistance. Although further studies are certainly required to test this conclusion, it can inform our methods of treatment of these fractures.

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Feb 23, 2017 | Posted by in ORTHOPEDIC | Comments Off on The Effect of Osteoporosis on Healing of Distal Radius Fragility Fractures

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