SARS‐CoV‐2 infection causes inflammation that can lead to significant changes in bone structure, according to a study in mice.
The study, published in the Journal of Orthopaedic Research, is the first to suggest that people with Covid‐19 may experience long‐term orthopaedic issues, such as decreased bone mass, increased fracture risk, and other musculoskeletal complications.
“Our study provides direct evidence that SARS‐CoV‐2 infection leads to acute bone loss, an increased number of osteoclast bone cells, and thinner growth plates,” said Dominik Haudenschild, Professor in the Department of Orthopaedic Surgery at University of California-Davis Health.
In the study, mice who had Covid-19 showed significant bone loss. This loss decreased the bone mechanical strength and increased the risk of fractures.
If similar bone loss occurs in human patients following their Covid‐19 recovery, it could leave them with a long‐term — even permanent — increased risk of fractures due to fragile bones. This is especially true in elderly patients.
The study suggested that the higher risk of fragility fractures, when a person falls from standing height or less, may be one of the underreported long-haul symptoms of Covid.
“This study has profound clinical implications,” said R. Lor Randall, professor and chair of the Department of Orthopaedic Surgery. “Musculoskeletal ramifications of Covid may not be the first medical issue that comes to mind when one thinks about the pandemic. Nevertheless, many people suffer from fragile bones and Covid can put them at an even greater risk for fracture.”
The study examined the bone structure of SAR-CoV-2 infected (12 male and 12 female) and non-infected (four male and four female) mice. They found that bone and joint tissues are susceptible to viral infection. A protein linked to SARS‐CoV‐2 infection was also identified in cells in the joint’s connective tissue (synovium), bone marrow, and the distal femoral growth plate. It was also found in the lungs.
The study also showed that SARS‐CoV‐2 infection was associated with significant changes to the trabecular bone microstructure in infected male and female mice.
“The data from the study are the first confirmation of the harmful effect of SARS‐CoV‐2 infection on the bones, from resorption (tissue breakdown) to growth plate thinning,” Haudenschild said.
“This means that bone loss and growth disturbances may be serious complications of Covid‐19.”
The researchers suggested multiple ways that Covid-19 may affect the bones. For example, the SARS-CoV-2 virus triggers the immune system to produce proinflammatory proteins known as cytokines. These cytokines can lead to hyperinflammation that may contribute to various bone and joint diseases.
Long‐term bed rest and decreased physical ability could lead to bone loss due to lack of use. In addition, Covid patients treated with corticosteroids could also experience significant bone loss during their treatment.
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