What is most related to spinal malalignment among various muscle evaluation indices? -The Wakayama Spine Study — The International Society for the Study of the Lumbar Spine
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What is most related to spinal malalignment among various muscle evaluation indices? -The Wakayama Spine Study (#1216)

Hiroshi Hashizume 1 2 , Hiroyuki Oka 3 , Shunji Tsutsui 1 , Masanari Takami 1 , Keiji Nagata 1 , Yuyu Ishimoto 1 , Masatoshi Teraguchi 1 4 , Yoshiki Asai 1 , Hiroki Iwahashi 1 , Takahide Sasaki 1 , Shizumasa Murata 1 , Sakae Tanaka 5 , Noriko Yoshimura 3 , Munehito Yoshida 1 6 , Hiroshi Yamada 1
  1. Dept. of Orthopaedic Surgery, Wakayama Medical University, Wakayama City, Wakayama, Japan
  2. School of Health and Nursing Science, Wakayama Medical University, Wakayama, Japan
  3. 22nd Century Medical and Research Center, The University of Tokyo Hospital, Tokyo, Japan
  4. Spine Care Center, Wakayama Medical University Kihoku Hospital, Katsuragi, Wakayama, Japan
  5. Dept. of Orthopaedic Surgery, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
  6. Dept. of Orthopedic Surgery, Sumiya Orthopedic Hospital, Wakayama City, Wakayama, Japan

Purpose: Sarcopenia is attracting attention as a cause of spinal malalignment (forward leaning posture) associated with aging. We examined what is most related to spinal malalignment among various muscle evaluation indices.

Method: A cross-sectional analysis was conducted on 737 residents (215 males, 522 females, mean age 63.5 ± 13.1 years old) who participated in the second survey of Wakayama Spine Study conducted in a seacoast town. Evaluation items were C7 SVA of standing X-ray lateral image, existence of low back pain within one month, Oswestry disability index (ODI), trunk muscle mass and limb skeletal muscle mass by impedance method, paraspinal muscle (PVM = multifidus + erector spinae muscle) and psoas major muscle cross-sectional area (CSA) and the fat infiltration ratio (FIR) of lumbar MRI. In addition, grip strength, walking speed, and 5 times chair rise time were also measured, and sarcopenia was judged according to the criteria of the Asian Working Group for Sarcopenia (2019). In this study, C7 SVA ≥ 50 mm was defined as the "spinal malalignment".

Statistics: We examined (1) the relationship between spinal malalignment and low back pain / ODI, (2) the relationship between spinal misalignment and sarcopenia using a multiple logistic model, (3) the correlation between trunk muscle mass and CSAs of paraspinal muscle / psoas major muscle (both non-fat areas). Finally, we created multiple regression models with C7 SVA as the objective variable, sex, age, BMI, and one of the muscle evaluation indices (alternately input) as the explanatory variable and determined which muscle evaluation index has the greatest influence by comparing the standardized β.

Results: The spinal malalignment was significantly related with the existence of low back pain and ODI. Age, obesity, and sarcopenia were all significantly associated with the spinal malalignment. Trunk muscle mass and CSAs of paraspinal muscle / psoas major muscle showed a strong correlation. On the other hand, the degree of influence on C7 SVA is in the order of “L1/2 PVM FIR (β 0.33) > L1/2 PVM CSA (0.24) ≒ L4/5 PVM FIR (0.24) > L4/5 PVM CSA (0.20) ≒ trunk muscle mass (0.20) > psoas major muscle FIR (0.10). Limb skeletal muscle mass was not a significant factor for C7 SVA.

Conclusion: From the results of the cross-sectional survey, we believe that the muscle evaluation index most related to the spinal malalignment is the FIR of PVM at the upper lumbar region. Since limb skeletal muscle mass and C7 SVA did not correlate, it is necessary to establish diagnostic criteria for "paraspinal muscle sarcopenia" in order to predict spinal malalignment.

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