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DOI:    [Accepted]
Published online October 15, 2018.
Trunk Muscle Strength After Lumbar Spine Fusion: A 12-Month Follow-up
Outi Elina Ilves1  , Marko Henrik Neva2, Keijo Häkkinen3, Joost Dekker4, William J. Kraemer5, Sami Tarnanen1, Kati Kyrölä6, Jari Ylinen2,7, Kirsi Piitulainen1,7, Salme Järvenpää7, Tiina Kaistila2, Arja Häkkinen1,7
1Health Sciences, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
2Department of Orthopedics and Trauma, Tampere University Hospital, Tampere, Finland
3Biology of Physical Activity, Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Finland
4Departments of Rehabilitation Medicine and Psychiatry, VU University Medical Center, Amsterdam, The Netherlands
5Department of Human Sciences, The Ohio State University, Columbus, OH, USA
6Department of Orthopedics and Traumatology, Central Finland Health Care District, Jyväskylä, Finland
7Department of Physical Medicine and Rehabilitation, Central Finland Health Care District, Jyväskylä, Finland
Corresponding Author:  Outi Elina Ilves
Tel: +358408054946   Fax: +35814617422    Email:
Received: June 6, 2018   Revised: July 20, 2018   Accepted: September 30, 2018
The aim of this study was to investigate the changes in trunk muscle strength 12 months after LSF, compared to preoperative strength.
Materials and Methods
Altogether 194 patients (mean age 61 [SD 21] years) who underwent LSF, participated in this prospective longitudinal study. Participants had physical measurements before surgery and 12 months postoperatively. Isometric trunk extension and flexion strength was measured by strain-gauge dynamometer in standing position. Strength changes were calculated. Regression analysis was performed to explore, which factors predicts the strength-levels 12 months postoperatively.
The preoperative mean (SD) extension strength was 205 (144) Newtons (N) and it increased to 258 (142) N (p<0.001) in the 12-month follow up. Correspondingly, flexion strength increased from 295 (172) N to 364 (164) N (<0.001). Preoperative extension/flexion (E/F) strength ratio was 0.75 (0.38) and it remained at 0.73 (0.26) 12 months postoperatively (p=0.39).
Although the trunk muscle strength increased 26% in extension and 23% at 12-month follow-up after surgery, they both remained low. In addition, flexion strength remained higher than extension strength, which indicates imbalance between those muscle groups. Age, severe back pain, and low trunk muscle strength before surgery predicts low trunk muscle strength one year after spinal fusion.
Keywords: spine; spinal fusion; muscle strength; isometric strength; low back pain; surgery

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