Differences in Type 2 Fiber Composition in the Vastus Lateralis and Gluteus Maximus of Patients with Hip Fractures

Abstract

Backgruound: Aging leads to sarcopenia, which is characterized by reduced muscle mass and strength. Many factors, including altered muscle protein turnover, diminished neuromuscular function, hormonal changes, systemic inflammation, and the structure and composition of muscle fibers, play a crucial role in age-related muscle decline. This study explored differences in muscle fiber types contributing to overall muscle function decline in aging, focusing on individuals with hip fractures from falls.

Methods: A pilot study at Chungnam National University Hospital collected muscle biopsies from hip fracture patients aged 20 to 80 undergoing surgical treatment. Muscle biopsies from the vastus lateralis and gluteus maximus were obtained during hip arthroplasty or internal fixation. Handgrip strength, calf and thigh circumference, and bone mineral density were evaluated in individuals with hip fractures from falls. We analyzed the relationships between each clinical characteristic and muscle fiber type.

Results: In total, 26 participants (mean age 67.9 years, 69.2% male) were included in this study. The prevalence of sarcopenia was 53.8%, and that of femoral and lumbar osteoporosis was 19.2% and 11.5%, respectively. Vastus lateralis analysis revealed an age-related decrease in type IIx fibers, a higher proportion of type IIa fibers in women, and an association between handgrip strength and type IIx fibers in men. The gluteus maximus showed no significant correlations with clinical parameters.

Conclusion: This study identified complex associations between age, sex, handgrip strength, and muscle fiber composition in hip fracture patients, offering insights crucial for targeted interventions combating age-related muscle decline and improving musculoskeletal health.

Keywords: Aging; Fracture; Muscles; Sarcopenia.

Fig. 1.

Study design. We obtained muscle tissue samples from the vastus lateralis and gluteus maximus of patients with hip fractures, analyzed the composition of muscle fiber types, and endeavored to establish correlations between fiber types and clinical indices. BMD, bone mineral density.

Fig. 2.

Relationship between fiber types in the vastus lateralis and age or handgrip strength in patients with femur fractures. (A) Correlation analysis of the proportion of type IIa fibers and age. (B) Correlation analysis of the proportion of type IIa fibers and handgrip strength. (C) Correlation analysis of the proportion of type IIx fibers and age. (D) Correlation analysis of the proportion of type IIx fibers and handgrip strength. (E) Correlation analysis of the proportion of type IIx/IIa fibers and age. (F) Correlation analysis of the proportion of type IIx/IIa fibers and handgrip strength. The data were evaluated using Pearson and Spearman correlation analysis. r_p, Pearson correlation coefficient; r_s, Spearman rank correlation coefficient.

Fig. 3.

Differences in fiber types in the vastus lateralis based on age, sex, and handgrip strength in patients with femur fracture. The fasttwitch muscle fibers were evaluated using immunostaining in the vastus lateralis. (A) The proportion of type IIa and IIx fibers was compared between the young and old groups. (B) The proportion of type IIa and IIx fibers was compared between men and women. (C) The proportion of type IIa and IIx fibers was compared between the top 50% and bottom 50% of handgrip strength. Data are expressed as mean±standard error of the mean. ^aP<0.05 compared with the corresponding controls.

Fig. 4.

Differences in fiber types in the vastus lateralis based on body weight, body mass index, and calf or thigh circumference in patients with femur fractures. The disparities in the proportions of type IIa and IIx fibers according to (A) body weight, (B) body mass index (BMI), (C) calf circumference, and (D) thigh circumference were assessed. Data are expressed as mean±standard error of the mean. ^aP<0.05 compared with the corresponding controls.