Risk Factors and Consequences of Lower Extremity Fracture Nonunions in Veterans With Spinal Cord Injury

Impact of osteoporosis and osteoporosis medications on fracture healing: a narrative review

Antiresorptive medications do not negatively affect fracture healing in humans. Teriparatide may decrease time to fracture healing. Romosozumab has not shown a beneficial effect on human fracture healing.

BACKGROUND

Fracture healing is a complex process. Uncertainty exists over the influence of osteoporosis and the medications used to treat it on fracture healing.

METHODS

Narrative review authored by the members of the Fracture Working Group of the Committee of Scientific Advisors of the International Osteoporosis Foundation (IOF), on behalf of the IOF and the Société Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT).

RESULTS

Fracture healing is a multistep process. Most fractures heal through a combination of intramembranous and endochondral ossification. Radiographic imaging is important for evaluating fracture healing and for detecting delayed or non-union. The presence of callus formation, bridging trabeculae, and a decrease in the size of the fracture line over time are indicative of healing. Imaging must be combined with clinical parameters and patient-reported outcomes. Animal data support a negative effect of osteoporosis on fracture healing; however, clinical data do not appear to corroborate with this. Evidence does not support a delay in the initiation of antiresorptive therapy following acute fragility fractures. There is no reason for suspension of osteoporosis medication at the time of fracture if the person is already on treatment. Teriparatide treatment may shorten fracture healing time at certain sites such as distal radius; however, it does not prevent non-union or influence union rate. The positive effect on fracture healing that romosozumab has demonstrated in animals has not been observed in humans.

CONCLUSION

Overall, there appears to be no deleterious effect of osteoporosis medications on fracture healing. The benefit of treating osteoporosis and the urgent necessity to mitigate imminent refracture risk after a fracture should be given prime consideration. It is imperative that new radiological and biological markers of fracture healing be identified. It is also important to synthesize clinical and basic science methodologies to assess fracture healing, so that a convergence of the two frameworks can be achieved.

A moderate spinal contusion injury in rats alters bone turnover both below and above the level of injury with sex-based differences apparent in long-term recovery

Spinal cord injury (SCI) leads to significant sublesional bone loss and high fracture rates. While loss of mechanical loading plays a significant role in SCI-induced bone loss, animal studies have demonstrated mechanical loading alone does not fully account for loss of bone following SCI. Indeed, we have shown that bone loss occurs below the level of an incomplete moderate contusion SCI, despite the resumption of weight-bearing and stepping. As systemic factors could also impact bone after SCI, bone alterations may also be present in bone sites above the level of injury. To examine this, we assessed bone microarchitecture and bone turnover in the supralesional humerus in male and female rats at two different ages following a moderate contusion injury in both sub-chronic (30 days) and chronic (180 days) time points after injury. At the 30-day timepoint, we found that both young and adult male SCI rats had decrements in trabecular bone volume at the supralesional proximal humerus (PH), while female SCI rats were not different from age-matched shams. At the 180-day timepoint, there were no statistical differences between SCI and sham groups, irrespective of age or sex, at the supralesional proximal humerus. At the 30-day timepoint, all SCI rats had lower BFR and higher osteoclast-covered trabecular surfaces in the proximal humerus compared to age-matched sham groups generally matching the pattern of SCI-induced changes in bone turnover seen in the sublesional proximal tibia. However, at the 180-day timepoint, only male SCI rats had lower BFR at the supralesional proximal humerus while female SCI rats had higher or no different BFR than their age-matched counterparts. Overall, this preclinical study demonstrates that a moderate contusion SCI leads to alterations in bone turnover above the level of injury within 30-days of injury; however male SCI rats maintained lower BFR in the supralesional humerus into long-term recovery. These data further highlight that bone loss after SCI is not driven solely by disuse. Additionally, these data allude to potential systemic factors exerting influence on bone following SCI and highlight the need to consider treatments for SCI-induced bone loss that impact both sublesional and systemic factors.

Malunions following lower extremity fractures in veterans with a spinal cord injury/disorder

BACKGROUND

Nearly 50% of all persons with a spinal cord injury/disorder (SCI/D) will sustain an osteoporotic fracture sometime in their life, with lower extremity fractures being the most common. There are a number of complications that can occur post fracture, including fracture malunion. To date, there have been no dedicated investigations of malunions among persons with SCI/D.

OBJECTIVES

The primary objective of this study was to identify risk factors associated with fracture malunion among fracture-related (type of fracture, fracture location, initial fracture treatment) and SCI/D-related factors. Secondary objectives were to describe treatment of fracture malunions and complications following these malunions.

METHODS

Veterans with SCI/D with an incident lower extremity fracture and subsequent malunion from Fiscal Year (FY) 2005-2015 were selected from the Veteran Health Administration (VHA) databases using International Classification of Diseases, 9th edition (ICD-9) codes for lower extremity fractures and malunion. These fracture malunion cases underwent electronic health record (EHR) review to abstract information on potential risk factors, treatments and complications for malunion. Twenty-nine cases were identified with a fracture malunion with 28 of them successfully matched with Veterans with a lower extremity fracture during FY2005-FY2014 without a malunion (matched 1:4) based on having an outpatient utilization date of care within 30 days of the fracture case. There was trend towards more nonsurgical treatment in the malunion group (n = 27, 96.43%) compared to the control group (n = 101, 90.18%) (P = 0.05), though fracture treatment proved not to be not associated with developing a malunion in univariate logistic regression analyses (OR = 0.30; 95% CI: 0.08-1.09). In multivariate analyses, Veterans with tetraplegia were significantly less likely (approximately 3-fold) to have a fracture malunion (OR = 0.38; 95% CI: 0.14-0.93) compared to those with paraplegia. Fracture malunion was significantly less likely to occur for fractures of the ankle (OR = 0.02; 95% CI: 0-0.13) or the hip (OR = 0.15; 95% CI: 0.03-0.56) compared to femur fractures. Fracture malunions were rarely treated. The most common complications following malunions were pressure injuries (56.3%) followed by osteomyelitis (25.0%).

CONCLUSIONS

Persons with tetraplegia as well as fractures of the ankle and hip (compared to the femur) were less likely to develop a fracture malunion. Attention to prevention of avoidable pressure injuries following a fracture malunion is important.

The Pathophysiology, Identification and Management of Fracture Risk, Sublesional Osteoporosis and Fracture among Adults with Spinal Cord Injury

BACKGROUND

The prevention of lower extremity fractures and fracture-related morbidity and mortality is a critical component of health services for adults living with chronic spinal cord injury (SCI).

METHODS

Established best practices and guideline recommendations are articulated in recent international consensus documents from the International Society of Clinical Densitometry, the Paralyzed Veterans of America Consortium for Spinal Cord Medicine and the Orthopedic Trauma Association.

RESULTS

This review is a synthesis of the aforementioned consensus documents, which highlight the pathophysiology of lower extremity bone mineral density (BMD) decline after acute SCI. The role and actions treating clinicians should take to screen, diagnose and initiate the appropriate treatment of established low bone mass/osteoporosis of the hip, distal femur or proximal tibia regions associated with moderate or high fracture risk or diagnose and manage a lower extremity fracture among adults with chronic SCI are articulated. Guidance regarding the prescription of dietary calcium, vitamin D supplements, rehabilitation interventions (passive standing, functional electrical stimulation (FES) or neuromuscular electrical stimulation (NMES)) to modify bone mass and/or anti-resorptive drug therapy (Alendronate, Denosumab, or Zoledronic Acid) is provided. In the event of lower extremity fracture, the need for timely orthopedic consultation for fracture diagnosis and interprofessional care following definitive fracture management to prevent health complications (venous thromboembolism, pressure injury, and autonomic dysreflexia) and rehabilitation interventions to return the individual to his/her pre-fracture functional abilities is emphasized.

CONCLUSIONS

Interprofessional care teams should use recent consensus publications to drive sustained practice change to mitigate fracture incidence and fracture-related morbidity and mortality among adults with chronic SCI.

LncRNA RMRP Contributes to the Development and Progression of Spinal Cord Injury by Regulating miR-766-5p/FAM83A Axis

Spinal cord injury (SCI) is known as a central nervous system disorder. Previous studies suggested that long-non-coding RNA RMRP (LncRNA RMRP) was abnormally expressed in SCI, but the potential underlying mechanism remains to be further explored. To explore the regulatory roles of LncRNA RMRP/miR-766-5p/FAM83A axis in SCI. Spinal T9 hemisection was performed on healthy adult male Sprague Dawley (SD) rats to establish the SCI rat models. The expressions of LncRNA RMRP in spinal cord of rats in different groups were examined by RT-qPCR. Moreover, AGE1.HN and PC12 cells were treated with hypoxic condition, and expression of LncRNA RMRP was examined by RT-qPCR methods. Furthermore, hypoxic PC12 cells were transfected with LncRNA RMRP OE, and the cell viability, proliferation, and apoptosis were examined. Next, the direct targeting relationship between LncRNA RMRP and miR-766-5p, as well as miR-766-5p and FAM83A, was confirmed by dual-luciferase reporter and RNA pull-down assays. Finally, the effects of LncRNA RMRP/miR-766-5p/FAM83A axis on cell viability, proliferation, and apoptosis were examined. LncRNA RMRP was downregulated in SCI rats and over-expression of LncRNA RMRP alleviated the SCI condition. LncRNA RMRP over-expression increased the viability and proliferation, and inhibited the apoptosis of hypoxic PC12 cells in vitro. miR-766-5p was confirmed as a target of LncRNA RMRP, and FAM83A was confirmed as a target of miR-766-5p. LncRNA RMRP could regulate the proliferation and apoptosis of hypoxic PC12 cells via regulating miR-766-5p/FAM83A axis in vitro. LncRNA RMRP may contribute to the pathogenesis of SCI via regulating miR-766-5p/FAM83A axis.