Maya Hioki

Effect of arthroscopic partial meniscectomy on the function of quadriceps femoris

The purpose of this study was to investigate the functional characteristics of the quadriceps femoris (QF) muscle group after the effect of presurgery disuse, surgery, and postsurgery disuse using surface electromyography and muscle functional magnetic resonance imaging (mfMRI). A total of 20 individuals (11 men and nine women) who underwent arthroscopic knee surgery participated in this study. Maximum voluntary contraction (MVC) of the QF muscle group was measured in the legs that received surgery and those that did not. To acquire the functional properties of the QF muscle group, electromyographic (EMG) activity during repetitive dynamic knee extension exercises (five sets of ten repetitions; load 30% MVC) and mfMRI before and after the exercises were obtained. EMG activity was evaluated in three phases depending on the knee joint angle: concentric and eccentric phases (Con/Ecc), concentric (Con) phase only, and eccentric (Ecc) phase only. The mean MVC of the legs that received surgery was significantly lower (22%) than that of the legs that did not. Regarding the EMG activity during the Con/Ecc and Con phases, there were significant leg and set effects but no significant leg-by-set interactions; however, during the Ecc phase, there was a significant set effect. Regarding changes in the mfMRI signal, leg and exercise had significant effects, but there was no significant leg-by-exercise interaction. These results suggest that presurgery disuse, partial meniscectomy, and postsurgery disuse induce dysfunction of the QF muscle group that is dependent on a decrease in MVC. Thus, these patients need maximal muscle-force improvement for effective rehabilitation after surgery.

Intramuscular adipose tissue determined by T1-weighted MRI at 3T primarily reflects extramyocellular lipids.

PURPOSE The purpose of this study was to assess relationships between intramuscular adipose tissue (IntraMAT) content determined by MRI and intramyocellular lipids (IMCL) and extramyocellular lipids (EMCL) determined by (1)H magnetic resonance spectroscopy ((1)H MRS) or echo intensity determined by B-mode ultrasonography of human skeletal muscles. METHODS Thirty young and elderly men and women were included. T1-weighted MRI was taken from the right mid-thigh to measure IntraMAT content of the vastus lateralis (VL) and biceps femoris (BF) using a histogram shape-based thresholding technique. IMCL and EMCL were measured from the VL and BF at the right mid-thigh using (1)H MRS. Ultrasonographic images were taken from the VL and BF of the right mid-thigh to measure echo intensity based on gray-scale level for quantitative analysis. RESULTS There was a significant correlation between IntraMAT content by MRI and EMCL of the VL and BF (VL, r=0.506, P<0.01; BF, r=0.591, P<0.001) and between echo intensity and EMCL of the VL and BF (VL, r=0.485, P<0.05; BF, r=0.648, P<0.01). IntraMAT content was also significantly correlated with echo intensity of the VL and BF (VL, r=0.404, P<0.05; BF, r=0.493, P<0.01). CONCLUSION Our study suggests that IntraMAT content determined by T1-weighted MRI at 3T primarily reflects extramyocellular lipids, not intramyocellular lipids, in human skeletal muscles.

Estimation of muscle atrophy based on muscle thickness in knee surgery patients

The purpose of this study was to establish an accurate estimation of muscle atrophy in the quadriceps femoris (QF) muscle group. Eighteen individuals who underwent meniscectomy participated in the study (nine men and nine women, mean age 44·4 years). Both operated and non‐operated thighs were scanned by magnetic resonance imaging to determine the volume and thickness of the QF muscle group. Muscle volume was estimated using eleven axial images, and muscle thickness was measured at the anterior, lateral and medial regions of the proximal, mid‐ and distal thigh, respectively. A stepwise linear regression analysis was performed to obtain the relationship between the difference in muscle volume and the difference in muscle thickness between operated and non‐operated limbs. There was no significant difference in muscle volume of the QF between operated (806·6 ± 220·0 cm3) and non‐operated (913·7 ± 241·5 cm3) limbs. Based on the stepwise linear regression analysis, the difference in muscle volume was significantly correlated with the difference in muscle thickness at the anterior proximal thigh and lateral mid‐thigh and anterior mid‐thigh (R = 0·93, P<0·01). In conclusion, the difference in muscle volume between operated and non‐operated limbs can be estimated accurately by measuring muscle thickness of the QF at three sites: the anterior proximal thigh, the lateral mid‐thigh and anterior mid‐thigh. Muscle thickness can be measured easily using imaging techniques such as ultrasonography. We propose that this method provides an easy and accurate estimate of knee surgery‐induced muscle atrophy in clinical medicine.

Associations of intramyocellular lipid in vastus lateralis and biceps femoris with blood free fatty acid and muscle strength differ between young and elderly adults

The present study aimed to determine relationships between intramyocellular lipid and biochemical profiles or muscle strength in elderly (n = 15; mean age, 71 years) and young (n = 15; mean age, 21 years) male and female adults. Levels of intramyocellular lipid in the vastus lateralis and biceps femoris muscles were determined using 1H‐magnetic resonance spectroscopy. Fasting blood samples were collected to measure levels of glucose, insulin, haemoglobin A1c, total cholesterol, high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol, free fatty acid, triglyceride, adiponectin, and high‐sensitivity C‐reactive protein. Muscle strength was assessed as maximal voluntary contraction during isometric knee extension. Muscle cross‐sectional area in the vastus lateralis was measured using magnetic resonance imaging. Specific force (N cm−2) indicating force generation capacity was calculated as muscle strength (N) divided by the muscle cross‐sectional area of the vastus lateralis (cm2). The intramyocellular lipid content was similar in both muscles in both groups. The intramyocellular lipid content in the biceps femoris significantly correlated with serum free fatty acid levels (r = 0·62, P<0·05), and that in the vastus lateralis significantly and inversely correlated with specific force (r = −0·58, P<0·05) in the young, but not in the elderly adults. The relationship between the intramyocellular lipid content in the thigh muscles and biochemical profiles, or specific force differed between elderly and young adults. Age‐associated changes in morphology, function and metabolic factors apparently influence intramyocellular lipid metabolism in the thigh muscles.