Paraspinal muscle involvement in FSHD



Supplemental Appendix, appendix e-1MRI - Scan positions and assessments of muscle compartments The quantitative fat fractions were analyzed on five cross-sectional Dixon slices, three spinal and two lower extremity slices. Spinal scan positions: The cervical scan position was defined at the level of C7, the thoracic at T12 and the lumbar at L4. At all three positions, the paraspinal muscles were mapped. In addition, the psoas muscles were mapped at the lumbar position (figure 1A-C).Thigh scan position: The femoral length was measured in cranial-caudal direction, and the scan position was determined as the midpoint of the distance between the head and the medial condyle of the femur. The three compartments of the thigh were mapped: the anterior compartment (rectus femoris, sartorius, and the vastus lateralis, medialis and intermedius muscles); the medial compartment (the adductor muscles and the gracilis muscle); and the posterior compartment (the biceps, semitendinosus and semimembranosus muscles) (figure 1D).Calf scan position: The tibial length was measured in cranial-caudal direction, and the scan position was determined as 1/3 of the distance between the medial condyle and the inferior articular surface of the tibia. The superficial posterior compartment of the lower leg was divided into two groups: the medial superficial posterior compartment (the medial gastrocnemius muscle) and the lateral superficial posterior compartment (the lateral gastrocnemius and the soleus muscles). The remaining three compartments were also mapped: the anterior compartment (the tibialis anterior and extensor digitorum longus muscles); the lateral compartment (the peroneus longus and brevis muscles); and the deep posterior compartment (the tibialis posterior, flexor digitorum longus and flexor hallucis longus muscles) (figure 1E).Muscle strength testingThe CITEC hand-held dynamometer (C.I.T. Technics, Centre for Innovative Technics, Netherlands) was used to quantify the maximum voluntary contraction in the paraspinal muscles, the pelvic girdle and the lower extremities of all subjects. Neck extension was evaluated with the dynamometer placed posterior to the occipital bone, and was measured with the subject in both sitting and prone position. Back strength was evaluated with the subject in prone position with fixated legs and with the dynamometer positioned between the scapulas. Hip flexion was examined in supine position with hip and knee flexed at 90° and the dynamometer placed distally anterior on the thigh. Knee flexion and extension were evaluated with the subject in prone position with the knee flexed 90°. The dynamometer was placed distally on the lower leg, anteriorly when measuring extension, and posteriorly when measuring flexion. Ankle plantar and dorsal flexions were investigated with the subject placed in supine position. The dynamometer was placed dorsal to the metatarsals to measure dorsal flexion and plantar to the metatarsals to measure plantar flexion. Three strength measures were obtained, and the highest score was recorded. A maximum score of 350 Newton was set for ankle plantar flexion. All other strength tests had a maximum score of 400 Newton. The same examiner (CV) evaluated muscle strength in all subjects.Muscle strength of the back was also examined with a static back extension endurance test. The subject was placed in a prone position with fixated legs and arms resting on the back. The subject was instructed to lift the chest from the bench and hold the position for as long as possible. The test was stopped after 5 minutes. ................
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