[Original Article]Skeletal muscle mass and clinical findings to evaluate the effectiveness of one-stage surgery in tandem spinal stenosis

[ABSTRACT]【Purpose】The incidence of Tandem Spinal Stenosis (TSS) is increasing rapidly with population aging, though its pathophysiology and pathogenesis are not clear. There is no consensus whether a one-stage or two-stage procedure is better. We compared preoperative skeletal muscle mass, clinical symptoms, and surgical results between TSS patients who underwent simultaneous cervical and lumbar decompression and lumbar spinal stenosis (LSS) patients who underwent lumbar decompression. The characteristics of the TSS patients and the surgical outcomes of one-stage surgery were evaluated.【Methods】There were 118 patients (mean age 66.3 years, 71 men) who received surgical treatment. Of these, 9 patients had TSS (mean age 74.3 years, 4 men) and 109 had LSS (mean age 65.7 years, 67 men). A bioelectric impedance analyzer (BIA) was used to measure systemic skeletal muscle mass and phase angle, an index of cell membrane aging. The visual analog scale (VAS) score for low back pain (LBP) and leg pain and leg numbness, the Japanese Orthopaedic Association scoring system (JOA score), the Roland-Morris Disability Questionnaire (RDQ), the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ), and the Oswestry Disability Index (ODI) were used to evaluate clinical symptoms. Preoperative skeletal muscle mass, phase angle, clinical symptoms, and surgical results were compared between the groups. 【Results】Operative time was significantly longer in the TSS group than in the LSS group (p < 0.05), but the amount of bleeding was not significantly different between the groups. The height, trunk muscle mass, and phase angle of the trunk and both lower limbs were significantly lower in the TSS group than in the LSS group (p < 0.05). JOA scores were significantly lower in the TSS group (p < 0.05), and 88% of TSS patients had difficulty in climbing stairs, significantly more than in the LSS group (28%, p < 0.05). Although clinical symptoms in both groups improved after surgery, there was no significant difference in the degree of clinical improvement (p > 0.05). 【Discussion】TSS was associated with decreased trunk muscle mass and decreased phase angle of the trunk and both lower limbs, suggesting the progression of trunk muscle atrophy due to decreased activity. In addition, about 90% of TSS patients had difficulty in climbing stairs. A one-stage minimally invasive operation was performed for TSS and the amount of intraoperative bleeding was equivalent to that of LSS alone. The one-stage approach seems to be effective.