Kei Watanabe1, Masayuki Ohashi2, Toru Hirano2, Keiichi Katsumi3, Hirokazu Shoji2, Tatsuki Mizouchi2, Yuya Ishikawa2, Kazuhiro Hasegawa4, Naoto Endo2, Hideaki E Takahashi5. 1. Division of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi Dori, Chuo-ku, Niigata City, 951-8510, Niigata, Japan. keiwatanabe_39jp@live.jp. 2. Division of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi Dori, Chuo-ku, Niigata City, 951-8510, Niigata, Japan. 3. Department of Orthopedic Surgery, Uonuma Kikan Hospital, 4132 Urasa, Minami-Uonuma City, 949-7302, Niigata, Japan. 4. Niigata Spine Surgery Center, 2-5-22 Nishimachi, Konanku, Niigata City, 950-0165, Niigata, Japan. 5. Niigata Bone Science Institute, 761 Kizaki, Kitaku, Niigata City, 950-3304, Niigata, Japan.
Abstract
PURPOSE: To determine whether posterior implant removal prevents stress-shielding-induced vertebral osteopenia within the posterior fusion area in surgically treated patients with adolescent idiopathic scoliosis (AIS). METHODS: Eighteen patients with major thoracic AIS (mean age, 43.3 years; range, 32-56 years; mean follow-up, 28.8 years, range, 20-39 years) who underwent posterior spinal fusion (PSF) alone between 1973 and 1994 were included. Participants were divided into implant removal (group R, n = 10, mean interval until implant removal, 50 months) and implant non-removal groups (group NR, n = 8). Bone mineral density was evaluated using the Hounsfield units (HU) of the computed tomography image of the full spine. The HU values of the UIV-1 (one level below the uppermost instrumented vertebra), apex, LIV+1 (one level above the lowermost instrumented vertebra), and LIV-1 (one level below the lowermost instrumented vertebra; as a standard value) were obtained. Stress-shielding-induced osteopenia was assessed as the UIV-1/LIV-1, apex/LIV-1, and LIV+1/LIV-1 HU ratios (× 100). RESULTS: Overall (median, 25th-75th percentile), the apex (144.7, 108.6-176.0) and LIV+1 (159.4, 129.7-172.3) demonstrated lower HU values than LIV-1 (180.3, 149.2-200.2) (both comparisons, p < .05). Comparison of groups R and NR showed no significant differences in the scoliosis correction rate, bone mineral density of the proximal femur, the HU absolute values of all investigated vertebrae, or in the HU ratios of the investigated vertebrae to LIV-1. CONCLUSION: Instrumented PSF causes stress-shielding-induced osteopenia of the vertebral body within the fusion area in adulthood, which cannot be prevented by posterior implant removal, probably due to firm fusion mass formation. These slides can be retrieved under Electronic Supplementary Material.
PURPOSE: To determine whether posterior implant removal prevents stress-shielding-induced vertebral osteopenia within the posterior fusion area in surgically treated patients with adolescent idiopathic scoliosis (AIS). METHODS: Eighteen patients with major thoracic AIS (mean age, 43.3 years; range, 32-56 years; mean follow-up, 28.8 years, range, 20-39 years) who underwent posterior spinal fusion (PSF) alone between 1973 and 1994 were included. Participants were divided into implant removal (group R, n = 10, mean interval until implant removal, 50 months) and implant non-removal groups (group NR, n = 8). Bone mineral density was evaluated using the Hounsfield units (HU) of the computed tomography image of the full spine. The HU values of the UIV-1 (one level below the uppermost instrumented vertebra), apex, LIV+1 (one level above the lowermost instrumented vertebra), and LIV-1 (one level below the lowermost instrumented vertebra; as a standard value) were obtained. Stress-shielding-induced osteopenia was assessed as the UIV-1/LIV-1, apex/LIV-1, and LIV+1/LIV-1 HU ratios (× 100). RESULTS: Overall (median, 25th-75th percentile), the apex (144.7, 108.6-176.0) and LIV+1 (159.4, 129.7-172.3) demonstrated lower HU values than LIV-1 (180.3, 149.2-200.2) (both comparisons, p < .05). Comparison of groups R and NR showed no significant differences in the scoliosis correction rate, bone mineral density of the proximal femur, the HU absolute values of all investigated vertebrae, or in the HU ratios of the investigated vertebrae to LIV-1. CONCLUSION: Instrumented PSF causes stress-shielding-induced osteopenia of the vertebral body within the fusion area in adulthood, which cannot be prevented by posterior implant removal, probably due to firm fusion mass formation. These slides can be retrieved under Electronic Supplementary Material.
Entities:
Keywords:
Adolescent idiopathic scoliosis; Body mass index; Body weight; Bone metabolism; Bone mineral density; Long-term follow-up; Osteopenia; Osteoporosis; Spinal fusion; Spinal instrumentation; Surgery
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