Sage Journals: Discover world-class research

Abstract

Study Design

Narrative Review.

Objectives

Recent studies have separated assessment of sarcopenia into two main categories within spine surgery: (1) general sarcopenia assessing systemic muscle degeneration and (2) spine-specific sarcopenia assessing muscle degeneration within the more localized paraspinal musculature. We sought to highlight challenges in optimizing outcomes for adult spinal deformity (ASD) patients with sarcopenia and evaluate the effectiveness of using general and spine-specific sarcopenia metrics for prognostication.

Methods

We evaluated the relationship between sarcopenia and surgical outcomes in ASD, explored methods for assessing sarcopenia, and provided recommendations for managing ASD patients with consideration of sarcopenia based on literature review. Global and spine-specific sarcopenia assessment approaches were compared, emphasizing the impact of diagnostic methods, such as MRI and clinical performance tests, on outcome prediction.

Results

The large variability in sarcopenia measurement methods significantly affected its prognostic utility in ASD treatment. Studies using the psoas muscle to define global sarcopenia revealed mixed results for prediction. Meanwhile, assessments focusing on fatty infiltration of paraspinal muscles showed stronger correlations with complications than general sarcopenia markers.

Conclusion

Standardizing sarcopenia assessment in ASD is essential to facilitating its integration into clinical practice. Assessments focusing on paraspinal muscle quality demonstrated stronger associations with complications than general sarcopenia markers, underscoring the dissociation between systemic and spine-specific muscle health. Hence, future studies should refine sarcopenia metrics for spine-specific assessment as opposed to global metrics. Research should also be done to optimize interventions specifically targeting spinal sarcopenia to potentially enhance surgical outcomes. Adopting consistent, targeted sarcopenia evaluation can contribute to safer, more effective treatment pathways for ASD patients.

Keywords

adult spinal deformity sarcopenia frailty complications proximal junctional kyphosis reoperation spine paraspinal muscle

Introduction to Sarcopenia in Adult Spinal Deformity

Adult spinal deformity (ASD) surgery is challenged by high rates of postoperative complications and unplanned reinterventions, becoming unacceptable in value-driven healthcare systems. ASD is defined as structural spinal abnormalities in adults that cause physical distress.¹ Its high prevalence, cost of surgery, and rate of morbidity are straining healthcare systems worldwide.

Predictive ASD models are used to supplement clinical practice, largely driven by the massive physiological burden of deformity correction.^2,3 Traditionally, these models have incorporated data on patient demographics, medical co-morbidities, and spinal alignment.^4,5 Recently, hip axis measurements have been used to guide optimal sagittal alignment and minimize post-operative mechanical failures.⁶ Use of artificial intelligence (AI), deep learning (DL), and incorporation of the paraspinal soft tissue have further increased the predictive power of these models.^7,8 For example, positive soft-tissue injury findings per magnetic resonance imaging (MRI) predicted the need for surgery in pediatric cervical trauma patients.⁹ Further incorporation of machine learning yielded improved predictive accuracy of proximal junction kyphosis (PJK) when using models incorporating raw MRIs compared to similar models fed radiographic data.¹⁰ Analogous studies evaluating pre-operative soft tissue compromise in the form of senescent degeneration within relevant paraspinal muscles to predict operative outcomes would hold great utility.

Sarcopenia is degenerative loss of skeletal muscle mass and function resulting in adverse outcomes.¹¹ Despite association with falls, disability, and physical limitations leading to increased injury and mortality, details of how sarcopenia should be measured and used in clinical practice are contentiously debated.¹¹ On a pathophysiologic scale, complex relationships between catabolic pathways have been cited to contribute to sarcopenia.^11,12 Common biomarkers have been identified in age-related insulin resistance, obesity, and muscle degeneration, hinting at a connection between sarcopenia and other catabolic systems (Table 1).¹²

Table 1.

Several Possible Molecular Causes of Sarcopenia (Non-Exhaustive)^11-13

System	Proposed etiology or mechanism
Insulin resistance/obesity	Increased leptin, causing increased IL6, TNF, and GH secretion
	Decreased IGF1 effectiveness
	Decreased sex hormone (estrogen in women, testosterone in men)
	Rapamycin alterations
	Increased Forkhead box protein transcription factors
Osteoporosis	Decreased bone-to-muscle hormones such as myostatin, irisin, and osteocalcin
	Altered Wnt-β-catenin signaling
	Vitamin D receptor polymorphisms
	GH, IGF-1, and sex hormone alterations
Muscle (myocellular)	Myofiber size and quantity reduction
	Reduction in motor neurons
	Age-related transition from type II to type I fibers
	Fat infiltration (myosteatosis)
	Decreased myocyte mitochondrial integrity and increased oxidative stress
	Epigenetic changes via microRNA
	Myostatin upregulation

Abbreviations: IL6, interleukin 6; TNF, tumor necrosis factor; GH, growth hormone; IGF1, insulin growth factor 1.

For example, the co-existence of sarcopenia and osteoporosis, or “osteosarcopenia,” has been associated with increased falls, fractures, hospital/skilled nursing facility admission, and mortality risks.¹³ Concurrent sarcopenia and obesity, or “sarcopenic obesity,” has been implicated with clinical consequences like cardiovascular disease, metabolic syndromes, falls, cognitive impairment, and overall mortality.¹⁴ In an aging population with increasingly sedentary lifestyles, a multifactorial approach considering relevant comorbidities is crucial to the management of multifactorial sarcopenia. With the rising popularity of weight-loss medications like GLP-1 agonists promoting weight loss at the expense of lean muscle mass, more research is required to elucidate the relative benefits and dangers of these single-pronged approaches.¹⁵

A distinction between “general” and “spine-specific” sarcopenia has been proposed.¹⁶ General, or global, sarcopenia refers to a metric of low muscle strength, quantity, and/or physical performance. Notably, this definition does not specify muscle group but instead reports systemic muscle patency. Alternatively, the spine-specific or spinal sarcopenia distinction was implemented to narrow the scope of muscle patency to that of paraspinal musculature.¹⁶ While this grouping of sarcopenia has not been adopted widely, early studies have distinguished between their respective associations to spinal parameters in facet-joint arthropathy, foraminal stenosis, and lumbar spinal stenosis.¹⁶ These two conditions are frequently dissociated; significant spinal sarcopenia may be present despite preserved systemic muscle mass. Recognition of this distinction is essential for accurate prognostication in ASD.

Clinical definition of sarcopenia is also ill-defined. Various measurement modalities have been applied to diagnosing sarcopenia, ranging from functional examination of patient mobility via whole body performance to radiographic analysis of representative muscles.^12,17 These efforts have evolved over time, and several modifiable characteristics have been identified to improve perioperative outcomes in ASD correction.¹²

Large financial incentives exist for sarcopenia management. 10%-16% of elderly people are affected by general sarcopenia globally, with even greater prevalence among diabetic patients.¹⁸ The total annual cost of hospitalization in the United States in 2014 was $40.4 billion for patients with sarcopenia.¹⁹ The average cost per person was $260, with greatest burden for Hispanic women ($548/person) and elderly patients (>65 years; $375/person).¹⁹ A nearly 2-fold greater odds of hospitalization was found for individuals with sarcopenia with an average 0.18 more hospital stays, costing an additional $2316.¹⁹ Greater understanding of sarcopenia may serve to alleviate not only the total societal financial burden of treating sarcopenic patients, but also the financial discrepancies between different racial and age groups.

In 2023, the Scoliosis Research Society (SRS) developed a senescence task force to evaluate the current knowledge of sarcopenia: tools of assessment, potential avenues of treatment, and how sarcopenia may contribute to ASD complications. In response, we discuss the variability between sarcopenia and surgical outcomes for ASD, propose methods to assess global and spine-specific sarcopenia assessment, provide recommendations for optimization of ASD patients with sarcopenia undergoing surgery, and opine about the future of spine-specific sarcopenia.

Screening, Diagnosis and Quantification

No standardized approach to measuring sarcopenia has been universally implemented within clinical research, though several operational definitions have been proposed by different research groups.²⁰ Consequently, different methods have been published with correspondingly inconsistent results when examining its prognostic effectiveness, obscuring the true relationship between sarcopenia and spinal deformity. To address this variability, a consensus on the definition and diagnosis of sarcopenia was proposed in 2010, revised in 2018, by the European Working Group on Sarcopenia in Older People (EWGSOP2) (Table 2).¹⁷

Table 2.

EWGSOP2 Definition of Sarcopenia: Table Reproduced From Cruz-Jentoft et al 2018 With Permission¹⁷

1. Low muscle strength

2. Low muscle quantity or quality

3. Low physical performance

Fulfillment of criterion 1 suggests probable sarcopenia; additional fulfillment of criterion 2 suggests confirmed sarcopenia, and fulfillment of all 3 criteria suggests severe sarcopenia.

The EWGSOP2 shifted the defining characteristics of sarcopenia to emphasize muscle function. While the decision for this revision was influenced by the measurability of sarcopenia as a research parameter, the group also proposed that strength more effectively predicted patient outcomes than muscle mass or muscle quality.¹⁷ Subsequently, threshold measurements representative of muscle strength and mass for diagnosis of sarcopenia were proposed with several validated tools.¹⁷ These measurements served as proxies for senescent muscle atrophy (Table 3). Pathology for these tests were defined as ≥2 standard deviations from healthy reference 17.

Table 3.

Commonly Used Tools/Modalities for Measuring General Sarcopenia^{12,17,21-23,26,27}

Criteria	Tools/modalities
Muscle strength	Hand grip strength (HGS) – calibrated dynamometer
Muscle strength	Performance metrics – chair stand test
Muscle Mass	Skeletal/appendicular muscle mass or CSA of relevant muscle group – MRI, CT, DEXA, or BIA
Physical performance	Performance metrics – SPPB, gait speed, TUG

Abbreviations: HGS, hand-grip strength; CSA, cross-sectional area; MRI, magnetic resonance imaging; CT, computed tomography; DEXA, dual-energy X-ray absorptiometry; BIA, bioelectrical impedance analysis; SPPB, short physical performance battery; TUG, timed up-and-go.

Muscle Strength

Measured via hand grip strength (HGS) or the “chair stand test.”^12,17,21-23 HGS is measured with a calibrated dynamometer, while the “chair stand test” measures the time required for a patient to stand five times from a seated position without use of their arms.

Muscle Mass (Normalized for BMI)

Reported as total skeletal muscle mass, appendicular muscle mass, or as a cross-sectional area of relevant muscle groups. These values are measured primarily by MRI or CT but can also be reported from dual-energy X-ray absorptiometry (DEXA) or Bioelectrical Impedance Analysis (BIA) with various frequency settings/calculations (SF, MF, BIA_Sergi).^12,17,24,25

Physical Performance

Assessed by a series of timed tests measuring the completion of standardized tasks, including gait speed, the Short Physical Performance Battery (SPPB), and the Timed Up-and-Go test (TUG).^12,17,26,27 Gait speed is recorded as with ambulation of 4 meters. Alternatively, the SPPB accounts for a combination of gait speed, balance, and chair stand. The TUG test measures a similar combination of activities, including rising from a chair, walking 3 meters to a defined object, returning to the chair, and returning to a seated position. Conveniently, each of these performance tests may be readily performed in most clinical settings.

Considerable variation in rates of patients meeting diagnostic criteria for sarcopenia among different measurement modality choices were identified in a study applying EWGSOP2 criteria in a single population of colorectal cancer patients.²⁵ Specifically, 3.8% and 7.5% of this cohort had low muscle strength based on HGS and chair-stand test respectively. Low muscle mass prevalence was noted in 12.5% of patients with CT, 9.1% by DEXA, 98.6% by MF-BIA, 48.6% by MF-BIA_Sergi, and 17.5% by SF-BIA_Sergi. As such, the proportions of confirmed sarcopenia ranged from 0.3% (chair-stand test and DEXA) to 11.4% (HGS and MF-BIA). Weak agreement was found among different diagnostic modalities (Cohens Kappa = 0-0.6) except for SF-BIA_Sergi and MF-BIA_Sergi (Kappa = 1.0).²⁵ Sensitivities and specificities, with DEXA as the reference, for each modality were identified (Table 4).²⁵

Table 4.

Rate of Low (Positive) Criteria for Sarcopenia, and Sensitivity/Specificity Among the Same Cohort of 503 Colorectal Cancer Patients by Different Measurement Modalities as Reported by Berg et al, 2024²⁵

Measurement modality	Patients meeting criteria for sarcopenia (%)	Sensitivity^a	Specificity^a
HGS^b	3.8	—	—
Chair-stand^c	7.5	—	—
MF-BIA	98.6	1.0	0.02
MF-BIA_Sergi	48.6	1.0	0.6
SF-BIA_Sergi	17.5	0.8	0.9
CT	12.5	0.6	0.9
DEXA	9.1	—	—

Abbreviations: HGS, hand-grip strength; CT, computed tomography; DEXA, dual-energy X-ray absorptiometry; BIA, bioelectrical impedance analysis; SF, single frequency; MF, multifrequency.

^aDEXA used as reference standard for sensivity and specificity calculations.

^bHGS data used with DEXA measurements for confirmed sarcopenia diagnosis calculation.

^cChair-Stand data used with MF-BIA measurements for confirmed sarcopenia diagnosis calculation.

Screening tools, while not possessing the same sensitivity as EWGSOP2 criteria, are convenient for daily practice.^28,29 For example, the SARC-F screening tool is a questionnaire eliciting subjective information about strength (S), walking assistance (A), rising from a chair (R), climbing stairs (C), and falls (F) with good internal reliability and positive correlations to parallel sarcopenia criteria, instrumental activity of daily living (IADL) deficits, and mortality.^28,30 Alternatively, the d₃-isotope creatine dilution test may be used to screen sarcopenia, in which methyl-d₃ creatine concentrations are measured after an oral dose of d₃ creatine A.¹¹ This test accurately estimated whole-body muscle mass in strength training and has predicted disability and mortality of older adults.^31,32 Although these initial results are promising, they have yet to be translated into clinical decision-making.

To fully appreciate the impact of sarcopenia on ASD, elucidating a reliable and accurate diagnostic parameter of sarcopenia that is derived from imaging modalities that are part of standard clinical care is paramount.

Predictive and Prognostic Value

An analysis of 235 patients who underwent thoracolumbar fusions for ASD found that patients with sarcopenia had similar outcomes to patients without sarcopenia.²³ Patients with sarcopenia, defined as the lowest quartile psoas muscle cross-sectional area at L3 and L4 (normalized for height), did not differ from controls when examining global balance, levels of fusion, mechanical failures, anesthetic duration, estimated blood loss, blood transfusion requirements, initiation of walking, hospital length of stay, aggregate complications, disposition, readmission rates, mortality, and revision surgeries.²³

In contrast, other studies have reported results suggesting direct correlations between sarcopenia and poor clinical outcomes in ASD patients. A study of 196 patients found that the lowest quartile sarcopenic patients (defined by the total psoas surface area at L3 divided by the total L3 vertebral body area) had longer ICU length of stay (1.2 ± 1.5 days vs 0.8 ± 1.1 days) and greater total postoperative blood transfusion volumes (573 ± 715 mL vs 269 ± 453 mL).³³ Another study of 73 patients who underwent pedicle subtraction osteotomy (PSO) found that sarcopenia, as defined by the psoas-lumbar vertebral index (PLVI) (Figure 1), was associated with increased total complication rate.³⁴ Specifically, a dose response between sarcopenia magnitude and complication rate was reported. Furthermore, PLVI below threshold values were associated with significantly elevated rates of PJK (34% for PLVI <1.1), wound infections (12% for PLVI <0.8), and dural tears (14% for PLVI <0.8).³⁴

Figure 1.

Psoas-Lumbar Vertebral Index (PLVI) Equation Based on the Cross-Sectional Areas (CSA) of the Psoas and L4 Vertebral Body

An association between spinal sarcopenia and PJK after long thoracolumbar fusion to the pelvis was found in a cohort of 29 ASD patients >50 years old.²⁴ Greater average fatty infiltration percentage was found in the regions above the upper instrumented vertebra in patients with PJK (25.0 ± 6.5%) compared to patients without PJK (15.3 ± 4.8%). Hounsfield units and bone mineral density of the vertebral body at the same levels were not significantly different between PJK and non-PJK populations, suggesting that sarcopenia may be a better metric for predicting PJK than osteopenia.²⁴ Similar analyses of adjacent segment disease following spinal fusions with pelvic fixation in ASD patients consistently found positive correlations between metrics of sarcopenia and development of adjacent segment disease. Two retrospective studies found that the strongest predictor of PJK and proximal junction failure was psoas CSA in ASD patients after thoraco-pelvic fusions and short posterior lumbar fusions.^35,36 Similarly, CSA (L3-4) and fatty infiltration (L4-5) of the lower lumbar multifidus was correlated with development of adjacent segment disease in a study of patients with posterior lumbar fusion.³⁷ Another correlation was revealed between adjacent segment disease and the combined lean muscle CSA (FCSA) of the multifidus, erector spinae, and psoas. Patients with adjacent segment disease were found to have a smaller FCSA (3681 mm² vs 4268 mm²) and smaller FCSA/total CSA ratio (53.3% vs 58.6%).³⁸ These studies demonstrate the potential value of using spinal muscular mass and quality metrics to predict underlying bony disease in spine surgery.

One study found that only the degree of fatty infiltration of the erector spinae (and not that of the multifidus and psoas muscles at L4/L5) differed between patients who suffered PJK and those who did not.³⁹ A separate study contrarily found that patients with scoliosis had a smaller CSA of both multifidus and psoas muscles compared to patients with lumbar spinal stenosis.⁴⁰ Interestingly, it also found that HGS and DXA-measured whole-body composition were not different among these patients, which further calls into question the accuracy of global strength as a measure of sarcopenia.⁴⁰ These examples highlight how varying definitions and diagnostic tools for sarcopenia within and between the studies can result in a mixed picture regarding sarcopenia’s relationship with ASD. Future studies may be needed to help elucidate whether fatty infiltration or total muscle area have a greater contribution to the negative effect.

Beyond prognostication for operative complications in ASD correction, spinal sarcopenia has been implicated as a causative variable for ASD development. A cohort study found a smaller CSA index (CSA/height²; 12.6 cm²/m² vs 15.1 cm²/m²), decreased lumbar extensor strength index (lumbar extensor strength/body weight; 0.5 Nm/kg vs 0.8 Nm/kg), and greater fat infiltration rate (20.1% vs 16.3%) in ASD patients with sagittal imbalance compared to non-ASD controls.⁴¹ Interestingly, there was no difference in global sarcopenia metrics such as total appendicular skeletal muscle mass and HGS. These results suggest that correction of sarcopenia components specific to spinal musculature (CSA index, lumbar extensor strength, or lumbar fat infiltration) may prevent development of deformity in non-ASD patients as well as increase prognostic outcomes for ASD correction.

This sample of studies demonstrated marked heterogeneity among definition and prognostic value of sarcopenia in ASD (Table 5).

Table 5.

Summary of Studies Evaluating Predictive and Prognostic Value of Sarcopenia in ASD

Study (author, year)	Patient population	Sarcopenia metric	Sarcopenia classification	Key findings
Akbik, 2023	235 patients undergoing ≥4 level ASD surgery	Psoas CSA at L3 and L4, grouped by quartiles	General	No difference in outcomes found between patients with and without sarcopenia
Pernik, 2023	196 patients undergoing thoracolumbar spinal surgery	Psoas CSA at L3, grouped by quartiles	General	Sarcopenic patients had longer ICU length of stay, and post-operative blood transfusion volumes
Babu, 2023	73 patients undergoing ≥5 level ASD surgery with PSO	Psoas CSA at L4	General	Sarcopenic patients had significantly elevated rates of PJK, wound infection, and dural tears
Tsutsui, 2023	29 patients >50 years old undergoing T9 or T10 to pelvis ASD surgery	Fat infiltration percentage of erector spinae and multifidus at UIV to UIV+2	Spine-specific	PJK was associated with greater sarcopenia, but not bone mineral density, in the UIV
Eleswarapu, 2022	32 patients undergoing thoracic to pelvis fusion with 2-year follow-up	Psoas CSA at L4	General	Sarcopenia was the most powerful predictor of PJK and PJF when compared with traditional spinopelvic parameters
Ruffilli, 2023	308 patients age 50-85 years undergoing ≤3 level posterior lumbar fusion	Psoas CSA at L4	General	Sarcopenia was an independent risk factor for both PJK and PJF.
Gong, 2022	66 patients, 33 with adjacent segment disease and 33 matched controls	CSA of multifidus at L3-4 and fat infiltration percentage of multifidus at L4-5	Spine-specific	Sarcopenia was correlated with development of adjacent segment disease
Chang, 2019	50 patients with adjacent segment disease and 50 matched controls	CSA of combined multifidus, erector spinae, and psoas at L4-5	Spine-specific and general^a	Patients with adjacent segment disease tended to have more sarcopenia than healthy controls
Park, 2024	57 patients undergoing ≥4 level fusion ASD surgery	Fat infiltration percentage of separate erector spinae, multifidus, and psoas muscles	Spine-specific and general	Fat infiltration of erector spinae alone differed between patients with PJK and patients without PJK.
Yagi, 2016	120 patients, 60 lumbar spinal stenosis patients matched with 60 degenerative lumbar scoliosis patients treated with surgery	Spine-specific: CSA of multifidus at L5-S1	Spine-specific and general	Sarcopenia via CSA metrics differed between scoliosis patients and those with isolated lumbar spinal stenosis
Yagi, 2016		Generalized: CSA of psoas at L5-S1, HGS, and DEXA body composition	Spine-specific and general
Kim, 2021	108 patients with either degenerative adult spinal deformity with sagittal imbalance or degenerative spinal disease (without imbalance)	Spine-specific: CSA of multifidus and erector spinae at L2-L5, lumbar extensor strength, and fat infiltration of multifidus and erector spinae at L2-L5	Spine-specific and general	Patients with ASD and sagittal imbalance had more spine-specific sarcopenia than non-ASD controls. These same groups did not differ in generalized sarcopenia metrics
Kim, 2021		Generalized: Total skeletal muscle mass and hand grip strength	Spine-specific and general

Abbreviations: ASD, adult spinal deformity; CSA, cross sectional area; HGS, hand grip strength; PJK, proximal junctional kyphosis; PJF, proximal junctional failure.

^aSarcopenia in this study was represented as a combined metric with components from both general and spine-specific sarcopenia.

Modifiable Targets

A multi-disciplinary approach may be taken to limit and/or reverse sarcopenia to decrease its associated complications. Several approaches have collectively endorsed that (1) consuming high-quality protein may limit loss of muscle strength and function in sarcopenia; (2) resistance exercise may slow loss of skeletal muscle oxidative capacity and stimulate hypertrophy to prevent and/or reverse sarcopenia.^12,20 Other interventions are explored in research but require further development before incorporation into clinical care.¹² It should be noted that the following interventions are directed at general sarcopenia and may not adequately address localized spinal muscle degeneration (eg, fatty infiltration of paraspinal muscle). Further research must investigate targeted management of spinal sarcopenia before sufficient evidence is available for clinical recommendation.

A review published in 2021 consolidated interventions from evidence-based guidelines and systematic reviews, stratified by treatment setting (Table 6).²⁰

Table 6.

General Sarcopenia Treatment Modalities and Quality of Evidence, Stratified by Treatment Setting. Table Reproduced From Dent et al 2021 With Permission²⁰

Intervention	Community	Hospital
Exercise: Resistance-based training	First-line treatment, consider for routine use	First-line treatment, consider for routine use
Nutritional intervention: Protein supplementation/protein-rich diet	Second-line or adjunctive treatment option	Second-line or adjunctive treatment option
Exercise + nutritional (protein) intervention	Second-line or adjunctive treatment option	Insufficient evidence
Vitamin D supplementation	Limited use in selected patients	Limited use in selected patients
Anabolic hormone supplementation	Insufficient evidence	Insufficient evidence
Other pharmacologic interventions	Insufficient evidence	Insufficient evidence
Education: Discussion with patients regarding adequate calorie/protein intake	Insufficient evidence	Insufficient evidence

Only resistance exercise has been consistently shown to increase muscle performance and body composition in sarcopenic patients.^{11,20,26,27,42} 2018 guidelines strongly recommended physical activity as first-line treatment for and primary prevention of general sarcopenia.^11,20 A published trial measured various sarcopenic biomarkers and functional abilities in elderly patients undergoing an 8-week body weight resistance program without further supplementation.²⁶ Improvements in functional tests for the training cohort were found compared to the control group. Muscle specific biomarker concentrations also changed for the training group compared to the control group to suggest decreased sarcopenic burden.²⁶ A separate study further explored the effects of resistance training with additional supplementation on sarcopenia.²⁷ After 12 weeks of training and β-hydroxy-β-methyl butyrate supplementation in post-acute care geriatric patients, improvements were noted in performance [+1.8 points on short physical performance battery (SPPB) test], balance (+1.0 points), and chair stand (+0.7 points) when compared to a control group with a placebo supplement. While HGS significantly improved at 12 weeks for both the intervention (+3.7 kg) and placebo (+1.0 kg) groups, only the intervention group sustained increased strength at 1 year follow-up (+4.2 kg).²⁷ A 12 week resistance training program with collagen peptide supplement in sarcopenic subjects also found benefit.⁴² After normalization by diet, the authors found supplemented and placebo cohorts significantly differed with respect to increased fat-free mass (FFM) (4.2 kg vs 2.9 kg) fat loss (5.5 kg vs 3.5 kg), and muscle strength increase (16.1 Nm vs 7.4 Nm).⁴²

Optimizing nutrition decrease muscle atrophy in aging populations has also shown promising results as a second-line treatment option.²⁰ An association of diet quality with handgrip weakness as a proxy for sarcopenia had been found in a multiethnic Asian human cohort.²¹ Applying the dietary quality index-international (DQI-I) scale for grading diet variety, adequacy, moderation, and balance, researchers found increased HGS in patients within higher quartile DQI-I’s (+1.1 kg HGS in highest vs lowest quartile). A 15% lower odds ratio of handgrip weakness for each quartile increase in DQI-I was identified. Diet adequacy in the DQI-I was most correlated to strength. Interestingly, a caloric restriction has also been found to improve muscle function while attenuating age-related decline. Through molecular mechanisms like that of muscle activation, caloric restriction activates enzymes involved in lipid, protein, and mitochondrial function to decrease oxidant emission and hence decrease oxidative damage to DNA and proteins.⁴³ The balance between sufficient, diverse nutrients and caloric restriction reiterates a complicated, multifactorial network contributing to development of sarcopenia.

Pharmacologic supplementation actively researched for sarcopenia management but has yet to demonstrate consistent benefit in practice, despite promising initial results.¹¹ In one study, patients supplemented with L-carnitine had improvements of 12.4% greater HGS and 31.5% smaller frailty index scores compared to controls with no improvement at 10 weeks, though with no differences in frailty biomarkers (IL-6, TNF-α, and IGF-1).⁴⁴ A similar study found that diets with high vitamin D, E, and whey protein content improved skeletal muscle mass (+0.2 kg/m²), HGS (+2.7 kg), and favorable biomarkers such as IGF-1 (+14.3 ng/mL) and IL-2 (−575.3 pg/mL) in adults with sarcopenia after 6 months.⁴⁵ Other investigated drugs in literature have found minor benefits in older patients.¹¹

In summary, these experiments suggest that pre- and post-operative physical rehabilitation with a focus primarily on resistance exercise, and situationally nutritional fortification, may improve outcomes for adults with spinal deformity undergoing surgical intervention.

Surgical Decision-Making Considerations

Implementing the ideal corrective strategy for ASD patients remains challenging. Lower surgical invasiveness may yield lower surgical costs, decreased risks of complications and morbidity, and earlier postoperative mobilization than longer-segment fusions.⁴⁶ Alternatively, greater surgical invasiveness may facilitate greater deformity correction while yielding higher overall complication rates, longer operative and recovery times, and increased financial burdens.⁴⁶ The utility of accurate preoperative assessment of sarcopenia may lie in guiding surgeon’s decisions with respect to appropriate degree of surgical invasiveness. Consideration of global sarcopenia could tip the decision-making scale towards less invasive operations due to the larger physiologic stress associated with more invasive operations. Meanwhile muscle degeneration above the desired upper-instrumented vertebrae (UIV) or otherwise limited paraspinal function could influence the surgeon to proceed with different UIV based on stability potential and decreased risk of PJK at levels with robust paraspinal musculature.³⁹

Future Steps to Standardize Sarcopenia

Sarcopenia diagnosis is performed with many tools in both imaging and functional tests.^12,17,25 The variability of the reported relationship between degree of sarcopenia and adverse outcomes of ASD correction suggests that modality selection is not as arbitrary as initially purported. A natural next step would be to optimize definition of sarcopenia using easily evaluated and readily available tools in clinical practice.⁴⁷ Furthermore, the relatively new distinction of spinal sarcopenia may benefit from an appropriate quantitative measure of function analogous to HGS for global sarcopenia. One possible measure is through muscular extension capacity tests. A published study found peak torque and static hold time in isometric lumbar extension, and measurement of repetitions in dynamic lumbar extension were all reliable assessments of lumbar muscle endurance.⁴⁸ They may therefore reliably capture decreased paraspinal muscle function in spinal sarcopenia. Hence, we propose the following diagnostic tools: (1) HGS for assessment of global sarcopenia; (2) muscular extension capacity for evaluation of paraspinal-specific functional sarcopenia; and (3) MRI to assess paraspinal muscle mass (Table 7). MRI was chosen as the preferred imaging modality over DEXA because DEXA was found to be less effective than high-resolution imaging in distinguishing spinal deformity types (such as between degenerative lumbar scoliosis and lumbar spinal stenosis).⁴⁰ While MRIs are limited in their ability to assess the natural variation in body morphology given measurements of muscle are taken from a single section at the L3 level, it still maintained a relatively high sensitivity and specificity in general sarcopenia diagnosis.²⁵ A narrower focus for image analysis may be considered, as demonstrated in the aforementioned analysis that specifically measured the erector spinae to produce the best predictions of PJK and proximal junctional failure when compared to the multifidus and psoas muscles at the L4-L5 level.³⁹ In addition to muscle-specific assessments, different grading systems (eg, Goutallier classification) may refine the ability to define sarcopenia at relevant spinal levels and predict outcomes more accurately.⁸ Initial insight into this possibility may be gleaned from two studies showing qualitative Goutallier analysis of paraspinal fatty infiltration to be a stronger predictor of patient-reported outcomes following spinal fusion than cross-sectional area of the same muscles.^49,50 There is exciting potential in Goutallier grading for future optimization and quantitative analysis using automated 3-dimensional renders.⁵¹

Table 7.

Recommendations for the Next Steps in Advancing the Use of Sarcopenia in ASD

General	Distinguish general and spine-specific sarcopenia in clinical research. Report both metrics, when possible, for clarity
[1]	Global sarcopenia measurements should include HGS testing as a metric for muscle strength
[2]	Muscular extension capacity should be explored as a metric for functional capacity in spinal sarcopenia
[3]	MRI should be the preferred imaging modality for assessing paraspinal muscle mass

Abbreviations: ASD, adult spinal deformity; HGS, hand-grip strength; MRI, magnetic resonance imaging.

The relationship between global sarcopenia and spine-specific sarcopenia is less closely related than previously considered.¹⁶ Patients undergoing lumbar spinal fusion for degenerative spinal pathologies had poorly correlated measures of general sarcopenia (tested with SPPB, HGS, and psoas index) compared to spine-specific sarcopenia (measured with fatty infiltration of the multifidus and erector spinae).¹⁶ A separate study found that HGS could not distinguish between spinal deformity and spinal stenosis as opposed to spine-specific cross-sectional measurements, which were capable. Therefore, specific tests of spine-related muscles such as maximal voluntary exertion (MVE) and endurance time (ET) of paravertebral muscles may more accurately elucidate the degree of sarcopenia relevant to spinal deformity.⁵² It is possible that global sarcopenia may be used as a parameter to indicate general frailty in patient selection while spine-specific sarcopenia is used in construct length planning.

Despite the relatively weak prognosticating evidence for general sarcopenia, proposed interventions are relatively safe and may provide benefits with minimal risks. Resistance exercise, supplemented by properly balanced nutrition, has consistently demonstrated significantly improved performance.^26,27,42 Supplements like collagen, L-carnitine, vitamin D/E, whey protein and HMB are commercially available at an affordable rate with relatively benign side effect profiles.^53,54 Additionally, a protein-rich diet with sufficient nutrients and food groups with variety, moderation, and adequacy have several beneficial outcomes, including reduced risk of metabolic syndrome and reduced sarcopenia prevalence.²¹ Thus, we recommend providing a formal nutritional assessment and consult to safely implement proper dietary and supplement targets as part of a preoperative optimization strategy for ASD patients screened positive for sarcopenia. We do not currently recommend magnesium supplementation for prevention and/or treatment of sarcopenia given its potential adverse side effects and limited data in humans.⁵⁵

Other considerations for the limited clinical utility of sarcopenia in ASD may include (1) the heterogeneity of ASD, (2) unconsidered sarcopenia magnitude, and (3) unexplored sarcopenia types. Spinal deformity encompasses a wide variety of etiologies that may differ in pathophysiology.¹ The studies in this review that have found inconclusive relationships between sarcopenia and surgical outcomes have selected patients based on surgical procedures. Analysis based on distinct pathophysiology of ASD may elucidate currently obscured relationships. For example, the relationship between sarcopenia and ASD from hereditary degenerative features may differ from that between sarcopenia and ASD from trauma/iatrogenic causes. Sarcopenia has also been commonly reported categorically, so an analysis of sarcopenia as a continuous variable may also reveal correlations lost in discrete analysis. Finally, as the intersections of sarcopenia with other pathologies such as sarcopenic obesity, osteosarcopenia and spinal sarcopenia are increasingly studied, their potential correlations in adult spinal deformity must also be explored.

Limitations

By nature of narrative reviews, the authors’ viewpoints are expressed, which increased subjectivity with interpretation of the literature used in this study. Additionally, this study did not employ a systematic review protocol to ensure a comprehensive overview of the evidence regarding sarcopenia and spinal deformity. Instead, it relied on the authors’ collective experiences to compile references (Figure 2). This approach may decrease the study’s reproducibility and introduce selection biases, potentially favoring pre-existing viewpoints. Relevant studies may have been missed, particularly if published in other languages or less prominent journals.

Figure 2.

Modified PRISMA Diagram Illustrating How Articles Were Gathered for This Review. Articles Were Subjectively Selected by Relevance as Nature of a Narrative Review

Conclusions

Sarcopenia is a nascent framework for studying ASD with no universal standard in clinical and research use. Previous attempts to define the phenomenon were highly variable, obscuring the true relationship between sarcopenia and ASD and stunting its implementation. Despite this variability, certain groups have successfully shown significant relationships between paraspinal atrophy and adverse outcomes following ASD correction. Pre-operative prevention and reversal of muscle atrophy in general sarcopenia seems prudent through a combination of resistance exercising and nutritional supplementation. Future studies should distinguish between general and spine specific sarcopenia and determine if more accurate sarcopenia assessment and pre-operative optimization would dictate surgical decision making, decrease complications, and improve patient outcomes following operations for ASD.

Footnotes

Acknowledgments

Scoliosis Research Society Senescence Task Force.

ORCID iDs

Tim T. Bui

Karan Joseph

Alexander T. Yahanda

Javier Pizones

Elizabeth Lord

Robert K. Eastlack

Ferran Pellisé

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Tim Bui, Karan Joseph, and Camilo Molina. The first draft of the manuscript was written by Tim Bui and all authors commented on previous versions of the manuscript. All authors read and approved of the final manuscript.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Disclosure

No financial support was provided for this study; this study was conceived in response to the Scoliosis Research Society’s call for research, so it may include implicit biases aligned with those of the society. CAM (corresponding author) serves as a consultant for Kuros, Augmedics, SMAIO, Baxter Health, and SI-Bone.

References

Kim

Yang

Chang

, et al. Adult spinal deformity: current concepts and decision-making strategies for management. Asian Spine J. 2020;14(6):886-897. doi:10.31616/asj.2020.0568

Dalton

Mohamed

Akioyamen

Schwab

Lafage

. PreOperative planning for adult spinal deformity goals: level selection and alignment goals. Neurosurg Clin. 2023;34(4):527-536. doi:10.1016/j.nec.2023.06.016

Arora

Demb

Cummins

Callahan

Clark

Theologis

. Predictive models to assess risk of extended length of stay in adults with spinal deformity and lumbar degenerative pathology: development and internal validation. Spine J. 2023;23(3):457-466. doi:10.1016/j.spinee.2022.10.009

Pellisé

Serra-Burriel

Smith

, et al. Development and validation of risk stratification models for adult spinal deformity surgery. J Neurosurg Spine. 2019;31(4):587-599. doi:10.3171/2019.3.SPINE181452

Schwab

Blondel

Bess

, et al. Radiographical spinopelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis. Spine. 2013;38(13):E803-E812. doi:10.1097/BRS.0b013e318292b7b9

Hills

Lenke

Sardar

, et al. The T4-L1-Hip axis: defining a normal sagittal spinal alignment. Spine. 2022;47(19):1399-1406. doi:10.1097/brs.0000000000004414

Loftus

Tighe

Filiberto

, et al. Artificial intelligence and surgical decision-making. JAMA Surg. 2020;155(2):148-158. doi:10.1001/jamasurg.2019.4917

Mandelli

Nüesch

Zhang

, et al. Assessing fatty infiltration of paraspinal muscles in patients with lumbar spinal stenosis: goutallier classification and quantitative MRI measurements. Front Neurol. 2021;12:656487. doi:10.3389/fneur.2021.656487

Hect

McDowell

Fields

Greene

. Relationship of cervical soft tissue injury and surgical predication following pediatric cervical spinal trauma and its sequelae on long-term neurologic outcome. World Neurosurg X. 2023;20:100235. doi:10.1016/j.wnsx.2023.100235

10.

Johnson

Chanbour

Ali

, et al. Artificial intelligence to preoperatively predict proximal junction kyphosis following adult spinal deformity surgery: soft tissue imaging may be necessary for accurate models. Spine. 2023;48(23):1688-1695. doi:10.1097/brs.0000000000004816

11.

Cruz-Jentoft

Sayer

. Sarcopenia. The Lancet. 2019;393(10191):2636-2646. doi:10.1016/S0140-6736(19)31138-9

12.

Kuo

Y-K

Lin

Y-C

Lee

C-Y

, et al. Novel insights into the pathogenesis of spinal sarcopenia and related therapeutic approaches: a narrative review. Int J Mol Sci. 2020;21(8):3010. doi:10.3390/ijms21083010

13.

Clynes

Gregson

Bruyère

Cooper

Dennison

. Osteosarcopenia: where osteoporosis and sarcopenia collide. Rheumatology. 2021;60(2):529-537. doi:10.1093/rheumatology/keaa755

14.

Prado

Batsis

Donini

Gonzalez

Siervo

. Sarcopenic obesity in older adults: a clinical overview. Nat Rev Endocrinol. 2024;20(5):261-277. doi:10.1038/s41574-023-00943-z

15.

Ida

Kaneko

Imataka

, et al. Effects of antidiabetic drugs on muscle mass in type 2 diabetes mellitus. Curr Diabetes Rev. 2021;17(3):293-303. doi:10.2174/1573399816666200705210006

16.

Schönnagel

Chiaparelli

Camino-Willhuber

, et al. Spine-specific sarcopenia: distinguishing paraspinal muscle atrophy from generalized sarcopenia. Spine J. 2024;24(7):1211-1221. doi:10.1016/j.spinee.2024.02.021

17.

Cruz-Jentoft

Bahat

Bauer

, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing 2019;48(1):16-31. doi:10.1093/ageing/afy169

18.

Yuan

Larsson

. Epidemiology of sarcopenia: prevalence, risk factors, and consequences. Metabolism. 2023;144:155533. doi:10.1016/j.metabol.2023.155533

19.

Goates

Arensberg

Gaillard

Guralnik

Pereira

. Economic impact of hospitalizations in US adults with sarcopenia. J Frailty Aging. 2019;8(2):93-99. doi:10.14283/jfa.2019.10

20.

Dent

Woo

Scott

Hoogendijk

. Toward the recognition and management of sarcopenia in routine clinical care. Nat Aging. 2021;1(11):982-990. doi:10.1038/s43587-021-00136-1

21.

Huang

Shanmugam

Huang

van Dam

Hilal

. Association of diet quality with hand grip strength weakness and asymmetry in a multi-ethnic Asian cohort. Br J Nutr. 2024;131(7):1236-1243. doi:10.1017/S0007114523002647

22.

Yin

Cheng

Wang

Guan

Yin

. Influence of sarcopenia on surgical efficacy and mortality of percutaneous kyphoplasty in the treatment of older adults with osteoporotic thoracolumbar fracture. Exp Gerontol. 2024;186:112353. doi:10.1016/j.exger.2023.112353

23.

Akbik

Al-Adli

Pernik

, et al. A comparative analysis of frailty, disability, and sarcopenia with patient characteristics and outcomes in adult spinal deformity surgery. Glob Spine J. 2022;13(8):2345-2356. doi:10.1177/21925682221082053

24.

Tsutsui

Hashizume

Iwasaki

, et al. Sarcopenia at the upper instrumented vertebra is more significantly associated with proximal junctional kyphosis after long fusion for adult spinal deformity surgery than osteopenia. J Clin Neurosci. 2023;116:13-19. doi:10.1016/j.jocn.2023.08.012

25.

Berg

Alavi

Beichmann

, et al. The choice of diagnostic modality influences the proportion of low muscle strength, low muscle mass, and sarcopenia in colorectal cancer patients. Clin Nutr ESPEN. 2024;60:17-23. doi:10.1016/j.clnesp.2024.01.001

26.

Rezaei

Eslami

Tartibian

. The effects of TRX suspension training on sarcopenic biomarkers and functional abilities in elderlies with sarcopenia: a controlled clinical trial. BMC Sports Sci Med Rehabil. 2024;16(1):58. doi:10.1186/s13102-024-00849-x

27.

Meza-Valderrama

Sánchez-Rodríguez

Messaggi-Sartor

, et al. Supplementation with β-hydroxy-β-methylbutyrate after resistance training in post-acute care patients with sarcopenia: a randomized, double-blind placebo-controlled trial. Arch Gerontol Geriatr. 2024;119:105323. doi:10.1016/j.archger.2023.105323

28.

Nishikawa

Asai

Fukunishi

, et al. Screening tools for sarcopenia. Vivo. 2021;35(6):3001-3009. doi:10.21873/invivo.12595

29.

Krzymińska-Siemaszko

Deskur-Śmielecka

Kaluźniak-Szymanowska

Murawiak

Wieczorowska-Tobis

. Comparison of diagnostic value of the SARC-F and its four modified versions in polish community-dwelling older adults. Clin Interv Aging. 2023;18:783-797. doi:10.2147/cia.S408616

30.

Malmstrom

Miller

Simonsick

Ferrucci

Morley

. SARC-F: a symptom score to predict persons with sarcopenia at risk for poor functional outcomes. J Cachexia Sarcopenia Muscle 2016;7(1):28-36. doi:10.1002/jcsm.12048

31.

Balachandran

Evans

Cawthon

, et al. Comparing D3-Creatine dilution and dual-energy X-ray absorptiometry muscle mass responses to strength training in low-functioning older adults. J Gerontol A Biol Sci Med Sci. 2023;78(9):1591-1596. doi:10.1093/gerona/glad047

32.

Cawthon

Blackwell

Cummings

, et al. Muscle mass assessed by the D3-creatine dilution method and incident self-reported disability and mortality in a prospective observational study of community-dwelling older men. J Gerontol A Biol Sci Med Sci. 2021;76(1):123-130. doi:10.1093/gerona/glaa111

33.

Pernik

Hicks

Akbik

, et al. Psoas muscle index as a predictor of perioperative outcomes in geriatric patients undergoing spine surgery. Glob Spine J. 2022;13(7):2016-2024. doi:10.1177/21925682211072626

34.

Babu

Wang

Jami

Durand

Neuman

Kebaish

. Sarcopenia as a risk factor for complications following pedicle subtraction osteotomy. Clin Spine Surg. 2023;36(5):190-194. doi:10.1097/bsd.0000000000001455

35.

Eleswarapu

O'Connor

Rowan

, et al. Sarcopenia is an independent risk factor for proximal junctional disease following adult spinal deformity surgery. Glob Spine J. 2022;12(1):102-109. doi:10.1177/2192568220947050

36.

Ruffilli

Barile

Cerasoli

, et al. Sarcopenia and osteopenia are independent risk factors for proximal junctional disease after posterior lumbar fusion: results of a retrospective study. J Craniovertebral Junction Spine. 2023;14(1):65-70. doi:10.4103/jcvjs.jcvjs_140_22

37.

Gong

Zou

Liu

Wang

. Low lumbar multifidus muscle status and bone mineral density are important risk factors for adjacent segment disease after lumbar fusion: a case-control study. J Orthop Surg Res. 2022;17(1):490. doi:10.1186/s13018-022-03388-8

38.

Chang

Park

, et al. Paraspinal lean muscle mass measurement using spine MRI as a predictor of adjacent segment disease after lumbar fusion: a propensity score-matched case-control analysis. AJR Am J Roentgenol. 2019;212(6):1310-1317. doi:10.2214/ajr.18.20441

39.

Park

Cho

Kim

Park

Baek

. Sarcopenia in paraspinal muscle as a risk factor of proximal junctional kyphosis and proximal junctional failure after adult spinal deformity surgery. J Neurosurg Spine. 2024 2024;40(3):324-330. doi:10.3171/2023.9.SPINE23531

40.

Yagi

Hosogane

Watanabe

Asazuma

Matsumoto

Keio Spine Research Group . The paravertebral muscle and psoas for the maintenance of global spinal alignment in patient with degenerative lumbar scoliosis. Spine J. 2016;16(4):451-458. doi:10.1016/j.spinee.2015.07.001

41.

Kim

Shin

Lee

, et al. Sarcopenia and back muscle degeneration as risk factors for degenerative adult spinal deformity with sagittal imbalance and degenerative spinal disease: a comparative study. World Neurosurg. 2021;148:e547-e555. doi:10.1016/j.wneu.2021.01.053

42.

Zdzieblik

Oesser

Baumstark

Gollhofer

König

. Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men: a randomised controlled trial. Br J Nutr. 2015;114(8):1237-1245. doi:10.1017/S0007114515002810

43.

Larsson

Degens

, et al. Sarcopenia: aging-related loss of muscle mass and function. Physiol Rev. 2019;99(1):427-511. doi:10.1152/physrev.00061.2017

44.

Badrasawi

Shahar

Zahara

Nor Fadilah

Singh

. Efficacy of L-carnitine supplementation on frailty status and its biomarkers, nutritional status, and physical and cognitive function among prefrail older adults: a double-blind, randomized, placebo-controlled clinical trial. Clin Interv Aging. 2016;11:1675-1686. doi:10.2147/cia.S113287

45.

Liu

, et al. A high whey protein, vitamin D and E supplement preserves muscle mass, strength, and quality of life in sarcopenic older adults: a double-blind randomized controlled trial. Clin Nutr. 2019;38(1):159-164. doi:10.1016/j.clnu.2017.12.020

46.

Ledesma

Tran

Lambrechts

, et al. Short-Segment versus Long-Segment Spinal Fusion Constructs for the Treatment of Adult Degenerative Scoliosis: A Comparison of Clinical Outcomes. World Neurosurg 2023;171:e611-e619. doi:10.1016/j.wneu.2022.12.069

47.

Harada

Siyaji

Younis

Louie

Samartzis

. Imaging in spine surgery: current concepts and future directions. Spine Surg Relat Res. 2020;4(2):99-110. doi:10.22603/ssrr.2020-0011

48.

Udermann

Mayer

Graves

Murray

. Quantitative assessment of lumbar paraspinal muscle endurance. J Athl Train. 2003;38(3):259-262.

49.

Pinter

Wagner

Fredericks

Jr. , et al. Cervical paraspinal muscle fatty degeneration is not associated with muscle cross-sectional area: qualitative assessment is preferable for cervical sarcopenia. Clin Orthop Relat Res. 2021;479(4):726-732. doi:10.1097/corr.0000000000001621

50.

Zavras

Sullivan

Federico

, et al. Preoperative multifidus muscle quality is associated with patient reported outcomes after lateral lumbar interbody fusion. Glob Spine J. 2022;14(2):647-656. doi:10.1177/21925682221120400

51.

Tamai

Chen

Stone

, et al. The evaluation of lumbar paraspinal muscle quantity and quality using the goutallier classification and lumbar indentation value. Eur Spine J. 2018;27(5):1005-1012. doi:10.1007/s00586-018-5485-4

52.

Chen

Yang

Tang

, et al. Correlation between strength/endurance of paraspinal muscles and sagittal parameters in patients with degenerative spinal deformity. BMC Muscoskelet Disord. 2023;24(1):643. doi:10.1186/s12891-023-06747-6

53.

Wang

. A review of the effects of collagen treatment in clinical studies. Polymers. 2021;13(22):3868. doi:10.3390/polym13223868

54.

Wilson

Manninen

. Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: a review. Nutr Metab. 2008;5:1. doi:10.1186/1743-7075-5-1

55.

Liu

Wang

Zhang

, et al. Magnesium supplementation enhances mTOR signalling to facilitate myogenic differentiation and improve aged muscle performance. Bone. 2021;146:115886. doi:10.1016/j.bone.2021.115886

General and Spine-Specific Sarcopenia in Adult Spinal Deformity: a Narrative Overview of Current Strengths and Limitations

Abstract

Study Design

Objectives

Methods

Results

Conclusion

Keywords

Introduction to Sarcopenia in Adult Spinal Deformity

Screening, Diagnosis and Quantification

Muscle Strength

Muscle Mass (Normalized for BMI)

Physical Performance

Predictive and Prognostic Value

Modifiable Targets

Surgical Decision-Making Considerations

Future Steps to Standardize Sarcopenia

Limitations

Conclusions

Footnotes

Acknowledgments

ORCID iDs

Author Contributions

Funding

Declaration of Conflicting Interests

Disclosure

References