Objectives: To investigate the effects of a device-assisted muscle strengthening exercise program on the surgically traumatized multifidus musculature and on the intact longissimus and iliocostal muscles and to assess the possible relationship between patients' reported pain symptoms and changes in muscle strength or changes in cross-sectional area (CSA) of the musculature.
Design: Open, prospective noncontrolled prepost intervention study.
Setting: University-affiliated center for ambulant physiotherapy.
Participants: Fifteen patients who had undergone dorsal osteosynthesis for treatment of thoracolumbar vertebral fracture and who complained of persistent back pain.
Intervention: Twelve-week device-assisted training exercise program.
Main outcome measures: Patients' pain score, muscle strength, and the CSA of the paravertebral musculature determined by magnetic resonance imaging (MRI) were assessed before and after the exercise program.
Results: MRI findings revealed no increase in the CSA of the multifidus muscle in any patient (median change, -.27 cm 2 ). All patients, however, exhibited hypertrophy of both the longissimus and iliocostal muscles (median change, 1.39 cm 2 ). Significant increase in muscle strength was observed in 14 of 16 patients (median increase, 56%; range, 0.7%-126.4%). The median overall pain score improved from 19 (range, 7-24) to 16 (range, 5-27). The change in muscle strength and muscle CSA, however, showed no correlation. There was also no correlation between increase in muscle strength and changes in pain scores.
Conclusions: The device-assisted training program resulted in hypertrophy of the iliocostal and longissimus muscles and an increase in muscle strength in patients with surgically stabilized vertebral fractures. About half of the patients reported relief of pain. No correlation was found between hypertrophy, increase in muscle strength, and relief of pain. The surgically damaged multifidus musculature, however, did not show any change in CSA and was not accessible to rehabilitative measures.