Backbone fractures and HIV

Breaks (fractures) in the bones that make up the spine are relatively common in people with osteoporosis. According to doctors in Milan, Italy, affected people may not initially notice such fractures. This lack of recognition tends to occur because at first such fractures may be minor and symptom free. However, even a person with an initially symptom-free spine fracture is at increased risk for future fractures, both in the spine and hips. Furthermore, a growing number of fractures in the spine can cause pain, severe difficulty with movement and posture and, eventually, an increased risk of death.

To explore the presence of backbone fractures in HIV-positive people, doctors in Milan analysed health-related information collected from a fracture-screening program at their clinic. Among 194 participants who underwent assessments of bone density and had X-ray scans of their spine, doctors found that 12% had fractures in their backbone and 9% had deformities arising because of fractures in the spine. People aged 51 and older were significantly more likely to have backbone fractures than younger participants. Unexpectedly, most fractures (70%) were diagnosed in people who did not have osteoporosis.

While most studies of fracture risk in populations deal with the issue of the density of bones, the Milan (and other) researchers also raise the issue of the micro architecture of bone. Another study in HIV-positive people has also raised this issue, and bone micro architecture is likely an issue that requires further research in people with HIV.

Study details

Doctors in the infectious disease clinic at the University of Milan conducted an extensive screening program for bone thinning and fracture among HIV-positive people. In addition to undergoing low-dose X-ray scans called DEXA (dual-energy X-ray absorptiometry), used for assessing bone density, participants had X-ray scans of their spine and extensive blood tests.

People who had a history of backbone fractures and/or were using medicines to increase bone density were not enrolled.

The average profile of participants was as follows:

• 73% male, 27% women
• age – 49 years
• body mass index (BMI) – 24
• CD4+ count – 460 cells/mm³
• taking ART – 71%
• co-infection with hepatitis B or C – 25%
• current smokers –58%
• used corticosteroids – 15%
• used street drugs – 19%
• lower-than-ideal levels of vitamin D in their blood – 56%
• 33% of female participants had undergone menopause

Results—Bone density

DEXA scans revealed the following:

• 42% had normal bone density
• 43% had osteopenia (moderately thin bones)
• 15% had osteoporosis (severely thin bones)

Fractures

Analysis of the X-ray scans of the spine revealed that 12% of participants had fractures in their backbones. These fractures were distributed among different age ranges as follows:

• 39 years and younger – 2% had spine fractures
• 41 to 50 years – 12% had spine fractures
• 51 years and older – 24% had spine fractures

Fractures were distributed among people with different bone densities in the following ways:

• normal bone density – 10% had fractures (eight out of 81 participants)
• osteopenia – 11% had fractures (nine out of 84 participants)
• osteoporosis – 24% had fractures (seven out of 29 participants)

These differences were not statistically significant.

Risk factors for backbone fractures

Taking all of the health-related data they collected into account, researchers found that the following factors were statistically linked to an increased risk of backbone fractures:

• being older than 50 years of age
• having used corticosteroids

There were statistical trends that approached but did not reach significance, suggesting that perhaps a larger study might have found the following to also be risk factors:

• injection of street drugs
• excess alcohol drinking

However, in the present study these were not significantly linked to bone loss.

Bear in mind

The present study was done with data captured at one point in time. Such studies are cross-sectional in nature and can only provide a snapshot of what was happening at that time. Long-term observational studies of larger numbers of HIV-positive people may be needed to capture a more detailed picture of changes in bone health and the impact of drugs used to treat low bone density.

What is interesting about the Milan study was that many backbone fractures (70%) occurred in participants who did not have osteoporosis, suggesting that backbone fractures may be more common than expected among people with HIV.

A deeper look

The Milan study also suggests that, regardless of bone density, unfavourable changes are occurring deep within the bones (the microstructure or micro architecture) of some HIV-positive people. Such changes in micro architecture are only partially revealed by DEXA scans. More sophisticated assessments, such as high-resolution peripheral CT scans, would be needed to gain insight into the changes in the bones’ micro architecture.

A Swiss study

Researchers in the Swiss city of Geneva using high-resolution CT scans have confirmed changes in the micro architecture of the bones of some HIV-positive men aged 60 and older. These researchers analysed data from 28 HIV-positive men and compared them to data from 112 HIV-negative men of similar age. In this study the following factors were statistically linked to unfavourable changes in bone micro architecture:

• low levels of physical activity
• lower-than-normal levels of estrogen
• higher-than-normal levels of proteins in the blood linked to bone thinning

There was no connection between poor bone micro architecture and the following:

• the use of the anti-HIV drug tenofovir (Viread and found in Truvada, Atripla, Complera and Stribild)
• testosterone levels in the blood
• vitamin D levels in the blood

Furthermore, none of the HIV-positive men were taking treatment for low bone density.

The Swiss study was small but innovative in its use of high-resolution CT scans.

The combined results of the studies from Italy and Switzerland should pave the way for further investigation into the underlying reasons for the unfavourable changes to bone micro architecture.

—Sean R. Hosein

REFERENCES:

1. Gazzola L, Savoldi A, Bai F, et al. Assessment of radiological vertebral fractures in HIV-infected patients: clinical implications and predictive factors. HIV Medicine. 2015; in press.
2. Biver E, Calmy A, Delhumeau C, et al. Microstructural alterations of trabecular and cortical bone in long-term HIV-infected elderly men on successful antiretroviral therapy. AIDS. 2014 Oct 23;28(16):2417-27.