Neck muscle strength before and after cervical laminoplasty: relation to axial symptoms.

STUDY DESIGN

A prospective study to investigate serial changes in neck muscle strength before and after cervical laminoplasty.

OBJECTIVES

To examine the correlation between neck muscle strength and axial symptoms, and to clarify the risk factors for axial symptoms.

SUMMARY OF BACKGROUND DATA

Axial symptoms are common complications after posterior cervical spinal surgery. Although several technical considerations have reduced axial symptoms, the causes of axial symptoms are still largely unknown. Previous studies have indicated that neck muscle strength is reduced in patients with neck pain.

MATERIALS AND METHODS

Nineteen consecutive patients underwent cervical expansive laminoplasty for cervical spondylotic myelopathy. Age, sex, operative time, blood loss, clinical results, cervical curvature, range of motion, visual analog scale (VAS) for axial symptoms, and manual muscle strengths were examined before and after surgery. At 3 and 12 months, these factors were compared statistically between the no pain (NP) group (VAS <3) and the pain (P) group (VAS >or=3). The correlation between VAS and neck muscle strength, and the reduction in neck muscle strength in extension were analyzed statistically.

RESULTS

Six patients (31.5%) complained of axial symptoms at 3 months, and the symptoms continued in 3 patients (15.8%) at 12 months. At 3 months, cervical lordosis was 15.7 degrees in the NP group and 5.0 degrees in the P group, and neck strength in extension was 104.9% and 61.8%, respectively. At 12 months, neck strength in extension was 124.3% and 62.2%, respectively. These differences were statistically significant. The correlation between neck pain VAS and neck muscle strength, and the reduction in neck muscle strength in extension were statistically significant.

CONCLUSIONS

Neck muscle strength recovered to the preoperative value by 3 months and increased to 120% by 12 months in the NP group, whereas in the P group, neck muscle strength remained reduced by 60% and did not recover. Neck muscle strength and axial symptoms were strongly correlated.