Stephanie Valentin

Age and side-related morphometric MRI evaluation of trunk muscles in people without back pain

This study evaluated lumbar spine muscle volume and Muscle Fatty Infiltrate (MFI) across two age groups of healthy adults. Twenty-four participants (young group - YG: age 18-25, n = 12; mature group - MG: age 45-60, n = 12) without low back pain underwent T1-weighted axial MRI. Muscle volume and MFI were obtained from the left and right lumbar erector spinae (ES), multifidus (M), rectus abdominis (RA) and psoas (PS) muscles. For MFI, mean pixel intensity (MPI) of muscles was reported as a percentage of subcutaneous fat MPI. Within-group comparison of left and right side muscle volume was not significantly different in the YG. In the MG, right RA and ES were significantly smaller than left (RA p = 0.049; ES p = 0.03). In both groups, left PS, M and ES MFI was significantly smaller compared to the right side and left RA MFI was significantly greater compared to right side (all p ≤ 0.001). For M volume, 81.7-84.6% of variance was explained by age, height and Body Mass Index (BMI). For ES volume, 81.6-82.8% of variance was explained by height and BMI. Age explained 18.1%-36.0% of variance in M and ES right MFI. Therefore, age and BMI are relevant factors for extensor muscle volume, but not for flexor muscle volume. Also, age significantly influences MFI for right-sided extensors only. The age effect is apparently independent of full subjective back functionality. For future spinal muscle research, the side-and muscle-specific effect of age on muscle morphology should be considered.

Inter-rater reliability of trunk muscle morphometric analysis

BACKGROUND Inter-rater reliability of generalised lumbar extensor muscle CSA has been identified, however, more detailed reliability metrics of individual trunk muscles are lacking. OBJECTIVE To report muscle volume and muscle fatty infiltrate (MFI) inter-rater reliability of individual trunk muscles between two novice assessors. METHODS Lumbar axial MRI scans from 10 healthy male participants were analysed. The muscles erector spinae (ES), multifidus (M), rectus abdominis (RA), and psoas (PS) were manually traced, region of interest quantified and muscle volume and MFI determined by both assessors. Agreement between the assessors was determined using intraclass correlation coefficients (3,1), Bland-Altman plots and Lins concordance coefficient. RESULTS Good to excellent agreement was found for volume (ICC 0.77-0.96) and MFI (0.84-0.96) for all muscles on first evaluation, except for M volume, which required a second evaluation. Best agreement for muscle volume and MFI was found for ES (ICC 0.96). CONCLUSIONS First evaluation of muscle volume and MFI yields high to excellent inter-rater agreement, except for M, where further training and/or experience is required to achieve acceptable reliability outcomes. This may have clinical implications due to the relevance of M atrophy reported in patients with low back pain.

The presence of long spinal muscles increases stiffness and hysteresis of the caprine spine in-vitro

Long muscle-tendon-units are known to contribute to spinal stiffness and hysteresis in-vivo, yet their contribution as a passive structure in-vitro is less well defined. Twelve full length caprine spines including the head, pelvis and all spinal muscles were tested during displacement in Flexion-Extension (FE) and coupled Lateral and Rotational (LR) motion in a material testing machine. Hysteresis and modified stiffness (modST), i.e. mean force divided by the total displacement, were calculated. This was repeated following removal of dorsal muscles (longissimus dorsi and gluteus) and ventral muscles (iliopsoas), in a random order. ModST and hysteresis in the different dissection stages were identified. Correlations between modST, hysteresis, body mass, spine length and longissimus muscle thickness were calculated. Removal of dorsal musculature reduced extension modST significantly by 23%, and flexion modST by 40%. Ventral muscle removal reduced extension modST by 1% and flexion modSt by 13%. Hysteresis was reduced by 27% after dorsal and 2% after ventral muscle removal in FE hysteresis. Out of 105 correlation coefficients, five values were significantly correlated (p<0.05, range r(2): 0.61-0.71) and 10 values were highly significantly correlated (p<0.01, range r(2): 0.75-0.97). Strongest correlations were between hysteresis and modST for the same movement direction and dissection state. The results of this study demonstrate that the presence of muscles stiffens the spine with dorsal muscles showing more effect. This supports the concept that muscle volume even in a non-contractile state provides a stabilising function to the spine.

Kinematic parameters of sheep walking on a treadmill

Ovine locomotion studies are rare, despite their relevance for medical research. The aim of this preliminary study was to investigate habituation and temporospatial parameters during treadmill walking of seven Austrian Mountain sheep. Sheep were naïve to treadmill exercise. During five treadmill sessions, movement cycle duration (MCD), vertical trunk movement (VTM), stride height (SH), stride length (SL), and percentage of movement cycle at stance (%St) were assessed. Two sheep were excluded from the study because they would not walk on the treadmill. From the end measurement session, MCD (0.95 s) and %St (62%) were similar to reported kinetics of sheep walking over ground, although stride length (1.05 m) was longer in this study. These findings suggest that sheep may require more than five sessions to become habituated to treadmill walking.

Surface electromyography in animal biomechanics: A systematic review.

The study of muscle activity using surface electromyography (sEMG) is commonly used for investigations of the neuromuscular system in man. Although sEMG has faced methodological challenges, considerable technical advances have been made in the last few decades. Similarly, the field of animal biomechanics, including sEMG, has grown despite being confronted with often complex experimental conditions. In human sEMG research, standardised protocols have been developed, however these are lacking in animal sEMG. Before standards can be proposed in this population group, the existing research in animal sEMG should be collated and evaluated. Therefore the aim of this review is to systematically identify and summarise the literature in animal sEMG focussing on (1) species, breeds, activities and muscles investigated, and (2) electrode placement and normalisation methods used. The databases PubMed, Web of Science, Scopus, and Vetmed Resource were searched systematically for sEMG studies in animals and 38 articles were included in the final review. Data on methodological quality was collected and summarised. The findings from this systematic review indicate the divergence in animal sEMG methodology and as a result, future steps required to develop standardisation in animal sEMG are proposed.

Spinal Motion and Muscle Activity during Active Trunk Movements - Comparing Sheep and Humans Adopting Upright and Quadrupedal Postures

Sheep are used as models for the human spine, yet comparative in vivo data necessary for validation is limited. The purpose of this study was therefore to compare spinal motion and trunk muscle activity during active trunk movements in sheep and humans. Three-dimensional kinematic data as well as surface electromyography (sEMG) of spinal flexion and extension was compared in twenty-four humans in upright (UR) and 4-point kneeling (KN) postures and in 17 Austrian mountain sheep. Kinematic markers were attached over the sacrum, posterior iliac spines, and spinous and transverse processes of T5, T8, T11, L2 and L5 in humans and over the sacrum, tuber sacrale, T5, T8, T12, L3 and L7 in sheep. The activity of erector spinae (ES), rectus abdominis (RA), obliquus externus (OE), and obliquus internus (OI) were collected. Maximum sEMG (MOE) was identified for each muscle and trial, and reported as a percentage (MOE%) of the overall maximally observed sEMG from all trials. Spinal range of motion was significantly smaller in sheep compared to humans (UR / KN) during flexion (sheep: 6–11°; humans 12–34°) and extension (sheep: 4°; humans: 11–17°). During extension, MOE% of ES was greater in sheep (median: 77.37%) than UR humans (24.89%), and MOE% of OE and OI was greater in sheep (OE 76.20%; OI 67.31%) than KN humans (OE 21.45%; OI 19.34%), while MOE% of RA was lower in sheep (21.71%) than UR humans (82.69%). During flexion, MOE% of RA was greater in sheep (83.09%) than humans (KN 47.42%; UR 41.38%), and MOE% of ES in sheep (45.73%) was greater than KN humans (14.45%), but smaller than UR humans (72.36%). The differences in human and sheep spinal motion and muscle activity suggest that caution is warranted when ovine data are used to infer human spine biomechanics.

Cincinnati Orthopaedic Disability Index in canines

General description: The Cincinnati Orthopaedic Disability Index (CODI) is a case-specific questionnaire completed by owners of dogs with orthopaedic disease, to measure individual functional status of the dog (Gingerich and Strobel 2003). Owners are asked to describe activities which are restricted in their dog due to the orthopaedic condition and each activity is categorised for severity by the owner.

Comparative need for spinal stabilisation between quadrupedal and bipedal locomotion

Sheep are commonly used as an animal model for the human lumbar spine, but similarities in trunk muscle activity of humans and sheep during functional tasks such as locomotion have not been investigated. Therefore, the aim of the study was to evaluate trunk and pelvic limb muscle activity during walk and run/trot gaits in man and sheep. Electromyography of the muscles erector spinae (ES), gluteus maximus (GM), rectus abdominis (RA), obliquus externus (OE) and obliquus internus (OI) were collected in 24 humans and 15 sheep during treadmill walk and run/trot. Kinematic data from the tarsus (human) or metatarsus (sheep) were obtained to define motion cycles and determine stride characteristics. Mean and range of normalised muscle activity were calculated. In phasic muscles, the occurrence of the maximum was reported. At walk, mean activity was greater in humans for all three abdominal muscles (all p<0.01). At the run/trot, mean activity of ES was significantly greater in sheep (p<0.05) and mean activity of right OI was greater in humans (p=0.016). At the walk, range of ES activity was significantly greater in humans compared to sheep (p<0.01), but significantly smaller in humans in RA and right OE (p<0.05). At the run/trot, range of activity was significantly greater in humans compared to sheep in all muscles (p<0.05), except right RA and OI. Compared to humans, occurrence of maximum activity was earlier in sheep for ES right during walk (p=0.005), and later for GM during walk and run/trot (p<0.001). The results suggest that numerous differences in trunk muscle activity exist between man and sheep during treadmill walk and run/trot, and that these differences are muscle-and gait-specific. Trunk muscle activity should therefore be regarded as species-specific which suggests differences in stabilization strategies. This should be taken into consideration when extrapolating animal model findings to the human spine.

In vivo magnetic resonance imaging features of spinal muscles in the ovine model

Summary Background Muscle fatty infiltration (MFI) has been identified in patients with spinal pain using magnetic resonance imaging (MRI). Even though sheep are a commonly used animal model for the human spine, comparative sheep MFI data from MRI is not available. Determining MFI in sheep spinal muscles using acquisition protocols commonly used in man will identify the applicability of this approach in future sheep model studies, such that the effects of spinal interventions on muscle can be assessed prior to their use in a human (clinical) population. Objective To quantify ovine lumbar spine MFI using three-dimensional two-point Dixon and T1-weighted sequences. Methods T1-weighted and Dixon lumbar spine axial sequences were collected in 14 healthy Austrian mountain sheep using a 1.5-T MRI. At each vertebrae, the region of interest of psoas major and minor (PS), multifidus (M), and longissimus (L) were identified. To determine MFI from the T1-weighted images, the mean pixel intensity (MPI) was calculated as a percentage of subcutaneous or intermuscular fat. For the Dixon images, fat sequence MPI was calculated as a percentage of the summed fat and water sequence MPIs. Spinal degeneration was graded and correlated to MFI. Dixon MFI was compared to T1-weighted MFI obtained from subcutaneous and intermuscular fat. Results For every muscle, T1-weighted MFI calculated using subcutaneous fat scored significantly lower than Dixon MFI and T1-weighted MFI calculated using intermuscular fat (p < 0.001). There were no significant MFI differences between T1-weighted images calculated using intermuscular fat and Dixon images for M and L (p > 0.05), although significant differences were found for PS. Conclusion In sheep, Dixon sequences provide an acceptable comparison to T1-weighted sequences for lumbar extensor MFI based on intermuscular fat. However, compared to the human literature, ovine lumbar musculature contains greater MFI, making interspecies comparisons more complex.

MRI-determined lumbar muscle morphometry in man and sheep: potential biomechanical implications for ovine model to human spine translation

The sheep is a commonly used animal model for human lumbar spine surgery, but only in vitro investigations comparing the human and ovine spine exist. Spinal musculature has previously not been compared between man and sheep. This additional knowledge could further indicate to what extent these species are biomechanically similar. Therefore, the purpose of the study was to investigate spinal muscle morphometric properties using magnetic resonance imaging (MRI) in different age groups of healthy human participants and sheep in vivo. Healthy human participants (n = 24) and sheep (n = 17) of different age groups underwent T1‐weighted MRI of the lumbar spine. Regions of interest of the muscles erector spinae (ES), multifidus (M) and psoas (PS) were identified. The ratio of flexor to extensor volume, ratio of M to ES volume, and muscle fat relative to an area of intermuscular fat were calculated. Sheep M to ES ratio was significantly smaller than in the human participants (sheep 0.16 ± 0.02; human 0.37 ± 0.05; P < 0.001), although flexor to extensor ratio was not significantly different between species (human 0.39 ± 0.08; sheep 0.43 ± 0.05; P = 0.06). Age did not influence any muscle ratio outcome. Sheep had significantly greater extensor muscle fat compared with the human participants (M left human 40.64%, sheep 53.81%; M right human 39.17%, sheep 51.33%; ES left human 40.86%, sheep 51.29%; ES right human 35.93%, sheep 44.38%; all median values; all P < 0.001), although PS did not show any significant between‐species differences (PS left human 36.89%, sheep 33.67%; PS right human 32.78%, sheep 30.09%; P < 0.05). The apparent differences in the size and shape of sheep and human lumbar spine muscles may indicate dissimilar biomechanical and functional demands, which is an important consideration when translating to human surgical models.