Given that sarcopenia promotes functional decline, loss of independence, and earlier mortality among elderly individuals (3), screening for patients with sarcopenia is imperative. The present study found that 68.5% of the included patients with hip fracture had sarcopenia (91.0% in males and 63.1% in females) and that male sex, underweight, undernutrition, and femoral neck fractures were associated with sarcopenia. Several studies have reported a higher prevalence of sarcopenia in men with hip fractures (6,19). Considering that males have more muscle mass than females, they may be more susceptible to the effects of age-related loss of muscle mass.
Underweight and undernutrition have been known risk factors for sarcopenia (3,20). Furthermore, while the type of hip fracture has been associated with age, sex, and bone mineral density (21-23), no study has yet investigated the relationship between the type of hip fracture and sarcopenia. Moreover, sarcopenia can be a negative prognostic predictor for patients with cancer (24). However, little is known regarding the impact of sarcopenia on hip fracture management. Previous studies have reported that sarcopenia promotes poor functional outcomes after surgery and increases the risk of five-year mortality in patients with hip fractures (13-15). Indeed, the present study found that patients with sarcopenia had a lower Barthel index, lower hospital discharge rate, and higher one-year mortality rate, which remains consistent with those presented in previous studies. These findings can potentially help clinicians make better treatment decisions and provide more information regarding surgical management to the patients and their families.
Our study found that the type of hip fracture was related to sarcopenia. Notably, one study showed that patients with trochanteric fractures had lower bone mineral densities than those with femoral neck fractures (23), while another found a correlation between muscle mass and bone mass (12). Therefore, we expected higher rates of trochanteric fractures among the sarcopenia group. However, the sarcopenia group had higher rates of femoral neck fractures than trochanteric fractures. Only a few studies have investigated the relationship between body composition and type of hip fracture. Among them, Di Monaco et al. reported that patients with femoral neck fractures had higher body fat mass than those with trochanteric fractures (25). The difference between femoral neck and trochanteric fractures lies within muscle attachment considering that the magnitude of the reaction force applied to the bone caused by muscle contractions may affect the type of fracture. Nonetheless, further studies are needed to determine the relationship between muscle mass and type of hip fracture.
No consensus has been established regarding the treatment for low muscle mass. However, studies have shown that the combination of exercise training and nutritional supplementation can effectively improve muscle mass (26). Exercise training, even at low intensity, has been shown to reduce mortality among elderly individuals (27). As such, patients with hip fractures should continue to exercise as much as possible after discharge. While no therapeutic agents are currently available for the treatment of low muscle mass, drugs utilized for the treatment of osteoporosis, such as alendronate and alfacalcidol, have been reported to have positive effects on muscle volume (28,29). However, given that these studies were conducted in the general population, it remains unclear whether similar results would be obtained in patients with hip fractures. Furthermore, gaining muscle mass does not prevent aging-related loss of muscle strength (30). Bimagrumab (BYM338; Novartis), a fully human monoclonal antibody that prevents ligand binding and promotes differentiation of human myoblasts (31), has shown promising results in the treatment of sarcopenia. Studies have shown that although bimagrumab promoted greater muscle mass compared to placebo, no improvements in physical function were noted (32). Further studies are therefore needed to develop an effective drug for the treatment of sarcopenia.
The presented study has several limitations worth noting. First, walking speed and grip strength could not be measured given the difficultly of evaluating physical function in patients during the acute phase of fractures. Although the diagnosis of sarcopenia requires assessing walking speed and grip strength, the current diagnostic criteria are controversial given that they exclude patients with locomotor disease (e.g., osteoarthritis, osteoporosis, and lumbar spinal stenosis). Sakai et al. reported that sarcopenia among elderly patients with locomotor disease (osteoarthritis, spondylosis, and osteoporosis) should be evaluated using muscle mass alone without physical performance (33). Considering that most cases of fractures in elderly individuals are caused by falls and that most patients with hip fractures have osteoporosis, it may be reasonable to conclude that patients with hip fractures have impaired physical function. Second, the current study did not assess comorbidities (e.g., cancer, cardiac diseases, endocrine diseases, and neurological disease). Given that some patients had dementia or no relatives, a common occurrence in actual clinical practice, accurate medical histories could not be obtained. These comorbidities may have affected the treatment outcomes. However, given that these comorbidities also affect muscle mass loss (secondary sarcopenia), the diagnosis of sarcopenia may help assess the severity of these comorbidities.