Addressing Osteosarcopenia Can Help Mitigate Risk of Hip Fracture in Older Adults

Osteopenia, osteoporosis, and sarcopenia are age-related changes in the musculoskeletal system. They lead to transformations in body composition and strength that can decrease mobility and independence and increase fall and fracture risk. The conditions create a large clinical and economic burden on the healthcare system and will impact virtually all persons in some form during their lifetimes. Orthopaedic surgeons are uniquely positioned to diagnose and treat these conditions, which can have a lasting and considerable impact on patient’s lives.

Defining ‘osteosarcopenia’
Osteopenia and osteoporosis are well-studied conditions with defined criteria for diagnosis, but sarcopenia has been less recognized. All share common risk factors and have recently been combined to into a term called “osteosarcopenia.” This term applies to a subset of persons affected by both osteoporosis and sarcopenia. The prevalence of osteosarcopenia increases with age, estimated at roughly 14.3 percent of men and 20.3 percent of women aged 60 to 64 years; the rate increases to 59.4 percent of men and 48.3 percent of women aged 75 years or older.

Sarcopenia is a generalized disorder of skeletal muscle involving loss of muscle mass and function. It typically occurs with advancing age, at a rate of roughly 1 percent per year in the sixth decade. It may also result from secondary conditions. It has not been well-recognized in the past but is garnering more attention as the aging population grows, given its progressive nature and the range of possible adverse effects it has on health. Sarcopenia can lead to impaired mobility and increased adverse health outcomes and mortality. This often increases fall and fracture risk; impairs ability to perform activities of daily living; contributes to lower quality of life; can lead to loss of independence or need for long-term care placement or hospitalization; and can be associated with cardiac disease, respiratory disease, and cognitive impairment.

Although sarcopenia has long been associated with aging and elderly patients, it is now recognized that sarcopenia can begin earlier in life. There are many contributing causes beyond aging. Contributing factors or secondary causes of sarcopenia include lack of activity, age-related decline in testosterone, genetic factors, and insufficient energy or protein intake because of anorexia or malabsorption.

Impact on muscle strength
Initial definitions of sarcopenia focused on low muscle mass, but it was discovered that muscle function was a better predictor of outcomes. Newer definitions include muscle strength and physical performance. Muscle strength is currently the most reliable measure of muscle function. Recommendations for diagnosis start with patient screening for risk factors. Diagnosis is suspected based on presence of low muscle strength but confirmed by the addition of low muscle quantity or quality. When low physical performance is also present, sarcopenia is considered severe.

A simple method to assess muscle strength in the clinical setting is by measuring grip strength with a handheld dynamometer. Skeletal muscle mass or quality can be evaluated with dual-energy X-ray absorptiometry, CT, or MRI. Physical performance measures include gait speed, the Timed Up and Go test, and 400-meter walk test.

Pharmacotherapy
Early detection and treatment of osteosarcopenia will hopefully reduce morbidity and mortality and improve quality of life for patients. Current treatment is supported by limited evidence and includes dietary supplementation with calcium, vitamin D, and essential amino acids, in addition to increased protein intake, activity modifications, and resistance exercise (Fig. 1).

There are no FDA-approved pharmacologic interventions for sarcopenia. However, several drugs exist for treatment of osteoporosis, including bisphosphonates, hormone-replacement therapy (including estrogen and testosterone), selective estrogen receptor modulators, denosumab, and anabolic drugs (e.g., teriparatide).

Benefits of exercise
Evidence-based clinical practice guidelines typically recommend increased physical activity as the primary treatment for osteosarcopenia. However, evidence is conflicting regarding the most effective type of exercise (e.g., resistance, aerobic, balance, multicomponent exercises).

Several randomized, controlled trials (RCTs) have demonstrated the efficacy of resistance training in treating osteosarcopenia. This stimulates osteoblastogenesis and muscle protein synthesis, leading to improvements in bone microarchitecture, muscle mass, strength, and functional capacity in osteoporotic and sarcopenic older adults. There have been studies investigating the role of stretching and balance exercises, including yoga and tai chi. Although these programs have been found to be beneficial, there is not enough evidence to make strong recommendations at this time.

A recent meta-analysis of 43 RCTs investigating the effect of exercise on sarcopenia in older people found improvements in quality of life, muscle strength, and physical performance at 12-week follow-up after patients initiated an exercise protocol. Moreover, 3,728 patients with a median age of 72.9 years were randomized to exercise programs versus lifestyle modifications alone, and resistance exercise was found to have the largest impact on outcome measures, although balance and aerobic exercise were found to be beneficial as well.

Hip fracture rates continue to rise, with the incidence expected to nearly double by 2050 compared with 2018. Therefore, it is beneficial to both surgeons and patients to address underlying conditions leading to falls and fractures. Two of the biggest risk factors include osteoporosis and sarcopenia.

In addition to encouraging a healthy lifestyle and activity modifications, a routine exercise program that includes resistance training has strong evidence in the medical literature to support its use in delaying the onset of or treating osteosarcopenia. Further research is needed to determine the specific type, intensity, and frequency of exercise.

Leslie Schwindel, MD, FAAOS, is a general orthopaedic surgeon at Lake Cumberland Regional Hospital in Somerset, Kentucky, and a member of the AAOS Now Editorial Board.

References

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