Extensive Type II Muscle Fiber Atrophy in Elderly Female Hip Fracture Patients.
BACKGROUND
Sarcopenia, or the loss of muscle mass and strength, is known to increase the risk for falls and (hip) fractures in older people. The objective of this study was to assess the skeletal muscle fiber characteristics in elderly female hip fracture patients.


METHODS
Percutaneous needle biopsies were collected from the vastus lateralis muscle in 15 healthy young women (20 ± 0.4 years), 15 healthy elderly women (79 ± 1.7 years), and 15 elderly women with a fall-related hip fracture (82 ± 1.5 years). Immunohistochemical analyses were performed to assess Type I and Type II muscle fiber size, and myonuclear and satellite cell content.


RESULTS
Type II muscle fiber size was significantly different between all groups (p < .05), with smaller Type II muscle fibers in the hip fracture patients (2,609 ± 185 µm2) compared with healthy elderly group (3,723 ± 322 µm2) and the largest Type II muscle fibers in the healthy young group (4,755 ± 335 µm2). Furthermore, Type I muscle fiber size was significantly lower in the hip fracture patients (4,684 ± 211 µm2) compared with the healthy elderly group (5,842 ± 316 µm2, p = .02). The number of myonuclei per Type II muscle fiber was significantly lower in the healthy elderly and hip fracture group compared with the healthy young group (p = .011 and p = .002, respectively). Muscle fiber satellite cell content did not differ between groups.


CONCLUSIONS
Elderly female hip fracture patients show extensive Type II muscle fiber atrophy when compared with healthy young or age-matched healthy elderly controls. Type II muscle fiber atrophy is an important hallmark of sarcopenia and may predispose to falls and (hip) fractures in the older population.
Department of Human Movement Sciences.|Department of Surgery, Division of Trauma Surgery.
Irene Fleur
IF
Kramer
Department of Human Movement Sciences.
Tim
T
Snijders
Department of Human Movement Sciences.
Joey S J
JSJ
Smeets
Department of Human Movement Sciences.
Marika
M
Leenders
Department of Human Movement Sciences.
Janneau
J
van Kranenburg
Department of Human Biology, Maastricht University Medical Centre+, Maastricht, the Netherlands.|Department of Medical Sciences, Molecular Epidemiology and Science for Life Laboratory, Uppsala University, Sweden.
Marcel
M
den Hoed
Department of Human Movement Sciences.
Lex B
LB
Verdijk
Department of Surgery, Division of Trauma Surgery.
Martijn
M
Poeze
Department of Human Movement Sciences.
Luc J C
LJC
van Loon
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001707:Biopsy, Needle; D003430:Cross-Sectional Studies; D005260:Female; D006620:Hip Fractures / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology*; D012307:Risk Factors; D055948:Sarcopenia / Q000473:pathology*
Falls; Hip fracture; Muscle; Sarcopenia