This scoping review provides a reconnoitering mapping of the available original literature elaborating on clinical outcome categories in defined sarcopenic and orthogeriatic patients. Through our investigation, we have identified several research gaps related to geographic and demographic subpopulations, the assessment and definition of sarcopenia, and the adverse events associated with sarcopenia in orthogeriatrics.

To the best of our knowledge, this study is the first scoping review conducted to investigate the available evidence on the assessment of sarcopenia and comprehensive evaluation of adverse outcomes in older patients in orthopedic and trauma care who are hospitalized. Previous systematic reviews on sarcopenia in orthopedic patients have included younger patients and focused on mortality or postoperative functional recovery after hip, spine, or distal radius surgeries [7, 33,34,35,36,37,38,39].

More than half of the current body of research on sarcopenia in older patients in orthopedic and trauma care is derived from populations in eastern Asia. Thus, according to the origin of most of the studies included, it is not surprising that the assessment criteria and reference values of the AWGS were used in most of the studies included in this review.

The published working group consensus criteria exhibit notable discrepancies. For instance, the EWGSOP2 algorithm requires the presence of both low muscle strength and low muscle mass for a sarcopenia diagnosis, while the EWGSOP1 criteria consider either low muscle mass or low muscle strength. Moreover, there are variations in the reference values across the working group criteria. For example, in women, low muscle strength according to the FNIH2 criteria corresponds to only 80% of the low muscle strength defined by the EWGSOP1 criteria (Table 1). Consequently, Stuck et al. demonstrated that the prevalence of sarcopenia varies significantly (1%—17%) in a cohort of 1495 community-dwelling participants based on the sarcopenia definition employed [40]. Similarly, Kim et al. reported a disparity in sarcopenia prevalence (2%—28%) depending on the underlying definition [41]. As highlighted by Bischoff-Ferrari et al., these discrepancies in prevalence may introduce biases in causal relationship analyses, as different sarcopenia definitions do not equally predict sarcopenia-related complications [42]. Considering the diverse age groups, procedural interventions (trauma vs. elective cases), anatomical regions assessed, and the geographic diversity of study populations, the heterogeneous nature of sarcopenia diagnostics precludes a robust meta-analysis.

Interestingly, despite well-established elements for sarcopenia assessments, four studies did not use such consensus criteria. Instead, three studies calculated a psoas vertebral muscle index. The ratio of patients identified with sarcopenia in these studies was similar compared to those using consensus criteria (24–51%). In their study of 450 older trauma patients, Kaplan et al. used the total cross-sectional psoas muscle area at the L3 level and used reference values to define sarcopenia (male < 52.4 cm2/m2; female < 38.6 cm2/m2) [19]. Similarly, among 196 spine patients, Pernik et al. assessed a psoas lumbar vertebral index (cross-sectional area of the psoas muscle on axial CT images at L3 versus area of the L3 vertebra on axial CT images)), based on which patients were divided into quartiles [26]. The patients ranging in the lowest psoas lumbar vertebral index quartile were defined as sarcopenic. Sim et al. used a psoas lumbar vertebral index at the L4 level and assigned patients according to the median to a ‘low’ or ‘high’ group among 615 patients with hip fractures [28]. Wiedl et al. measured the maximum calf circumference and defined 83% of their patients with less than 33 cm calf circumference as sarcopenic [8]. In summary, the heterogeneity of the underlying sarcopenia definitions precludes from a meta-analysis of outcome parameters.

Previous studies have demonstrated a clear association between sarcopenia and prolonged length of hospital stay, particularly in individuals below the age of 65 [43]. Our review indicates a potential trend towards prolonged hospital stays in orthogeriatric patients with sarcopenia. Nevertheless, the clinical relevance of this extension is uncertain, given that only four studies reported statistically significant findings and most of the differences were only marginal. Only Gonzalez-Montalvo et al. found a slightly shorter hospital stay in sarcopenic patients with hip fractures compared to non-sarcopenic patients [13]. However, this study was conducted in a specialized orthogeriatric unit providing a high standard of care including nutrition and physical exercise aimed at reducing length of hospital stay and may therefore not be comparable to studies conducted in other environments.

Non-home discharge may reflect negative outcomes such as declining overall health, which can be caused by conditions like delirium, dementia, or secondary diseases such as pneumonia. In addition, it may be secondary to (surgical) treatment failure, inadequate pain management, and the inability to walk independently. The potential link between institutionalization and sarcopenia in geriatric patients receiving orthopedic and trauma care could not be substantiated in this scoping review as the literature indicated high rates of re-institutionalization to nursing homes, rehabilitation units, and long-term care for both sarcopenic and non-sarcopenic groups (77% and 68%, respectively).However, in the orthogeriatric population specifically, the acute hospitalization may simply reveal an existing inability to live independently for both patients and their families. Therefore, non-home discharge may be seen as a symptom associated with the progression of sarcopenia rather than a direct consequence.

In their systematic review on sarcopenia and its correlation with falls and fractures in older adults, Yeung et al. found a heightened risk of falls in sarcopenic individuals (OR 1.60; 95%CI 1.37–1.86) [39]. While their study encompassed older adults without a lower age limit but with a mean or median age of over 65 years, it did not specifically focus on patient populations undergoing orthopedic or trauma surgeries. In the context of orthopedic and trauma care, patients are often instructed to adhere to postoperative weight-bearing restrictions, sometimes necessitating the use of assistive devices for walking. Despite efforts by orthopedic and trauma surgeons to minimize these restrictions in older patients, they may be unavoidable in certain cases. In addition to factors such as coordination ability, cognitive function, and physical decline, older patients undergoing orthopedic and trauma care may have to significantly higher rates of falls and subsequent fractures compared to non-orthopedic patient populations.

Refracture rates within a time frame of 12 to 36 months following hip fracture have been documented to vary between 6 and 15% [44]. The observed 10% overall refracture rate after hip fractures among sarcopenic older patients in orthopedic and trauma care does not indicate an elevated refracture risk in this population [13]. After percutaneous vertebroplasty of spine fractures, there is a possibility of spinal refractures occurring in up to 52% of patients within a period of 7 years [45]. Chen et al. conducted a multivariate analysis to account for confounding variables and determined that sarcopenia was associated with a significantly increased risk of spinal refracture following kyphoplasty, with a prevalence rate of 84% [12]. They attribute this finding to the reduction in stability and the increase in pressure on the vertebral body as a result of muscle atrophy and degeneration associated with sarcopenia.

Multiple systematic reviews portray sufficient evidence regarding the association of sarcopenia and mortality in orthopedic patients [7, 34, 37]. Our scoping review suggests such a similarly consistent association between sarcopenia and mortality in the orthogeriatric population. The wide range of the published 1-year mortality rates (1–73%) may be secondary to the respective studies’ study populations and sarcopenia assessment criteria. Such heterogeneity precludes from a meta-analysis based on the existing literature.

Using various tools (patient related outcome measurement, PROMs), many studies evaluated the quality of life among their patients. Our review suggests that sarcopenia is associated with a decreased general functional outcome and quality of life compared to non-sarcopenic orthogeriatric populations. However, it is important to note that the heterogeneity of the PROMs used in these studies makes it difficult to determine the exact extent of this association.

Our scoping review reveals that the rates of refractures and subsequent falls have been insufficiently investigated in older patients in orthopedic and trauma care. The possible association of refractures and subsequent falls to sarcopenia can neither be expected nor excluded.

One major drawback of the literature review approach is always the potential for incomplete retrieval of relevant studies. However, this risk is mitigated by the involvement of two independent reviewers who conducted the systematic literature screening. Further limitations of this review’s methodology include language and age restrictions. This may explain some of the low variation regarding the geographic distribution of the included studies. Although we only included studies investigating patients over the age of 65 years, the mean age varied significantly among the different studies. This may be an important confounder regarding some of the results presented in our review. However, by exclusively including patients aged 65 years and above, we ensure a specific focus on the orthogeriatric population. In conclusion, caution should be exercised in all interpretations and deductions due to the heterogeneity of study populations, sarcopenia definitions, injury and disease modalities and localizations, follow-up periods, and outcome assessment tools discussed in this review.