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Object The authors undertook this study to evaluate curve progression, risk factors for curve progression, and outcomes after decompression surgery in patients with degenerative lumbar scoliosis with minimal to moderate curvature. Methods Of 852 patients with lumbar canal stenosis treated by posterior decompression surgery, 50 patients had a lumbar curve greater than 10° at final follow-up. These patients were divided into 2 groups according to curve progression during the follow-up period: the P group (11 patients), with a curve progression of more than 5°, and the NP group (39 patients), with a curve progression of 5° or less. The authors compared preoperative parameters in these 2 groups to elucidate risk factors associated with curve progression and other surgical outcomes. Results The average lumbar curve progression in the total group of 50 patients was 3.4° ± 3.9° (range −2.0° to 22.0°). In the P group the average curve progression was 8.5°, and in the NP group it was 2.0°. Multivariate logistic regression analysis showed no significant association between curve progression and any of the potential risk factors evaluated (including curve magnitude, decompression method, and degenerative intervertebral disc changes). Spur formation, evaluated with the Nathan classification at the concave side of the curve, tended to be greater in the P group, although the difference was not statistically significant. There was no significant difference in revision surgery rate, and none of the patients required arthrodesis due to curve progression. Clinical outcomes, evaluated with the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire and the Scoliosis Research Society 22-question questionnaire, were also similar in the 2 groups. Conclusions Surgical outcomes did not deteriorate in the P group. While curve progression after decompression surgery could not be predicted from the preoperative factors considered, spur formation at the concave side of the curve may be a candidate factor. The results of this study indicate that spinal fixation to halt deformity progression is not always necessary if the patient's pathological condition derives mainly from canal stenosis.

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To clarify the mechanism of osteoporosis in adolescent idiopathic scoliosis (AIS), we investigated radiological and histological changes in the cervical vertebrae of a chicken thoracic scoliosis model. Forty newly hatched broiler chicks were randomly divided into four equal groups: sham-operated chickens serving as control (CON), pinealectomized chickens (PNX), sham-operated (CON + MLT) and pinealectomized chickens (PNX + MLT) that received intraperitoneal administration of melatonin. Pinealectomy was performed at the age of 3 days, and the chickens were killed at 2 months of age. Postmortem X-rays were examined for the presence of scoliosis, and micro-computed tomography (micro-CT) images were taken to evaluate the microstructure of the cervical vertebrae. Histological specimens of the scanned cervical vertebra were prepared, and a midsagittal section was stained with hematoxylin and eosin and tartrate-resistant acid phosphatase to evaluate the numbers of osteoblasts and osteoclasts, respectively. Scoliosis developed at the thoracic spine in all chickens of the PNX and in two of the PNX + MLT group. Micro-CT data revealed that chickens in the PNX group had a greater degree of generalized osteoporosis compared with the other birds. The number of osteoblasts was significantly decreased in the PNX group, while no significant difference was observed among chickens in the numbers of osteoclasts. Our results suggest that melatonin deficiency reduces osteoblast proliferation and leads to the development of scoliosis and osteoporosis. The restoration of melatonin prevented the development of scoliosis and osteoporosis, indicating that melatonin levels may be crucial to the development of deformity and osteoporosis in AIS.