We enrolled a large sample size to identify the OVCF patients with different stages of sarcopenia according to EWGSOP sarcopenia classification by assessing muscle strength, muscle mass and physical performance. The cut-off values of handgrip strength and 6-meter usual gait speed were according to AWGS because of the eastern people generally have a smaller physique and a lower BMI than the western people. To avoid the effects of pain and movement restriction, handgrip strength and 6-meter usual gait speed were measured post-operation.
The relationship between sarcopenia and vertebral compression fractures has been preliminarily explored. Iolascon et al. [13] confirmed that the rate of sarcopenia increasing along with the number of vertebral fragility fractures in women. A cross-sectional study examined 216 women with fresh OVCF, the result showed sarcopenia were independent risk factors for acute OVCF [14]. However, both two studies definition of sarcopenia only included skeletal muscle mass as the unique parameter. Thus, the sarcopenic patients identified by these studies could have presarcopenia, sarcopenia, or severe sarcopenia. One study in community-dwelling elderly subjects showed that elderly subjects with sarcopenia had a greater risk of falls compared with normal elderly subjects, but those with presarcopenia did not [15]. Another study in women with a hip fracture showed that sarcopenic women had a lower ability to function in their activities of daily living than presarcopenic women [16]. These results demonstrated the value of sarcopenia classification for a better risk stratification. A total of 72 (21.9%) recurrent OVCF occurred during our 1-year follow-up and the refracture rate was increased in advancing sarcopenia patients (20.9% vs 32.6% vs 54.2%, respectively). Our multivariate analysis also demonstrated that sarcopenia, severe sarcopenia were independent risk factors for OVCRF, whereas presarcopenia was not.
The reasons why OVCF recurrence rate increased in advanced sarcopenia stage remain uncertain, the following reasons can be hypothesized. First, a large proportion of fragility fractures in patients with osteoporosis are reported to be caused by falls [17]. Muscle mass and strength as critical components in maintaining physical function, mobility, and vitality [18]. Low muscle quality would lead to physical disability and frailty, and subsequently increase the risk of falls. Previous studies have reported patients with sarcopenia over 80 - year - old were approximate three times to have a fall than non-sarcopenia patients within two years [19]. Second, advanced sarcopenia stage was associated with a lower BMD in the present study(Table 1,P = 0.007). Two large sample data study confirmed sarcopenia was associated with osteopenia and osteoporosis in Asian area [20, 21]. For patients with low BMD, the quality of the vertebral bodies was poor, resulting in a greater probability of OVCRF. Bone and muscle are not only adjacent to each other in anatomy, but also indispensable in basic metabolism. Recently, it has become clear that bone and muscle share genetic determinants [22]. The close interaction between bone loss and muscle wasting results in the co-occurrence of osteoporosis and sarcopenia, named osteosarcopenia [23]. Furthermore, some researchers have found a synergistic effect between osteoporosis and sarcopenia, lead to the occur of fragility fracture [24].
Low bone mineral density is another risk factor for recurrent fractures in this study. The average T-score was − 3.4 in patients with subsequent fractures and − 2.8 in patients without subsequent fractures group. Young-Joon Rho et al. [25] regard osteoporosis as the most important risk factor for additional fracture. However, Compared with BMD (OR 1.736; 95% CI 1.294–2.328, p = 0.000), sarcopenia (OR 2.536; 95% CI 1.130–5.692, p = 0.024) and severe sarcopenia (OR 4.579; 95% CI 1.615–12.968, p = 0.004) had greater odds ratio in the multivariate model. We therefore concluded that sarcopenia, severe sarcopenia had much stronger prediction power for the occurrence of postoperative OVCRF than BMD.
Advanced sarcopenia stage was associated with lower BMI (P = 0.000), lower serum albumin level (P = 0.008) and higher NRS 2002 scores (P = 0.000) in the present study(Table 1), both of which are common index to evaluate nutritional status. Lin WC et al reported that low BMI was a significant predictor of new VCFs after vertebroplasty, especially if the BMI was less than 22 kg/m [26]. However, none of the traditional nutritional indices, such as BMI, albumin levels and NRS 2002 scores, were associated with OVCRF. We speculated that sarcopenia is a more comprehensive parameter than these traditional nutritional indices, reflecting not only the nutritional status but also the functional status. Moreover, skeletal muscle mass has been reported to be a new index for nutritional assessment [27]. Existing research has focused more on anti-osteoporosis treatment to prevent recurrence of fractures [28, 29], the present study indicated that anti-sarcopenia could be regarded as a potential therapeutic target in the future. We think resistance training program such as knee extension/flexion and leg presses to offset sarcopenia could be carried out at the appropriate time after surgery. Adequate nutritional intake and certain nutritional supplements, such as leucine and omega-3 polyunsaturated fatty acids, could have a synergistic effect with resistance training in maintaining muscle mass [30].
Age and sex were statistically significant difference between the OVCRFs group and non-OVCRFs group in univariate analysis. Other risk factors like treated vertebral level, vacuum clefts, intradiscal cement leakage, and AP ratio showed no difference between the two groups, which were still controversial [25, 31, 32]. Meanwhile, multivariate analysis revealed that female (OR 6.325; 95% CI 2.176–18.368, p = 0.001) and older age (OR 1.863; 95% CI 1.002–3.464, p = 0.049) were related to OVCRFs after PKP in our study. As people getting older, the quantity and mass of trabeculae will decrease simultaneously. The absorption of calcium in the digestive system decreases at the same time, leading to the loss of bone mass in elderly patients, especially postmenopausal women [33, 34]. Lidsay et al. [35] observed that almost 20% of women would experience another fracture within 1 year of an incident vertebral fracture.
The present study was strengthened by its large sample retrospective study design, the strict inclusion and exclusion criteria, and rigorous follow-up strategy. Our department is one of the largest spine centers in China, performing > 400 OVCF operations annually, which enabled the study to be finished within a short time range. However, there are still several limitations. First, this is a single-center study, the conclusions of this study need to be validated in multicenter studies in the future. Second, only symptomatic subsequent fractures were included. The actual subsequent fractures rate would be higher than the observed rate. Third, there were differences in the use of anti-osteoporosis drugs during postoperative follow-up, which may resulted in a biased refracture rate.