Characteristics of Back Muscle Strength in Patients with Scheduled for Lumbar Fusion Surgery due to Symptomatic Lumbar Degenerative Diseases

STUDY DESIGN: Cross sectional study. PURPOSE: To evaluate characteristics of back muscle strength in patients scheduled for lumbar fusion surgery. OVERVIEW OF LITERATURE: Little is known regarding muscle strength in patients with symptomatic lumbar degenerative diseases who require fusion surgery. METHODS: Consecutive 354 patients scheduled for posterior lumbar interbody fusion due to symptomatic degenerative diseases were approached for participation. 316 patients were enrolled. Before surgery, muscle strength was assessed by measuring maximal isometric extension strength at seven angular positions (0°, 12°, 24°, 36°, 48°, 60°, and 72°) and mean isometric strength was calculated. The Oswestry Disability Index (0-100) and visual analogue scale (0-100) for back pain were recorded. Muscle strength was compared according to gender, age (<60, 60-70, and ≥70 years) and scheduled fusion level (short, <3; long, ≥3). RESULTS: Isometric strength was significantly decreased compared with previously reported results of healthy individuals, particularly at extension positions (0°-48°, p<0.05). Mean isometric strength was significantly lower in females (p<0.001) and older patients (p<0.05). Differences of isometric strength between short and long level fusion were not significantly different (p>0.05). Isometric strengths showed significant, but weak, inverse correlations with age and Oswestry Disability Index (r<0.4, p<0.05). CONCLUSIONS: In patients with symptomatic lumbar degenerative diseases, back muscle strength significantly decreased, particularly at lumbar extension positions, and in females and older patients.