Variability of outcome after lumbar disc surgery.

STUDY DESIGN: A prospective, consecutive study of patients' outcome at three subsequent follow-up times after lumbar disc surgery.

OBJECTIVES: To evaluate how consistent outcome remained in a group of patients after lumbar disc surgery.

SUMMARY OF BACKGROUND DATA: Despite similar results concerning the overall outcome, results in most studies show different prognostic factors for lumbar disc surgery at different follow-up times. A reason for this observation could be that patients shift to a different outcome group during the observation period.

METHODS: Before surgery and at the three follow-ups (3, 12, and 28 months after surgery) the Low Back Outcome Score was calculated. Groups with favorable and unfavorable outcome were determined after each follow-up according to the scores.

RESULTS: Ninety-eight patients were studied. Forty percent showed an unstable outcome at different follow-up times. For each follow-up, three prognostic factors were determined. No prognostic factor showed significance at all follow-up examinations.

CONCLUSIONS: Patients whose outcome after lumbar disc surgery does not remain stable present a major problem in the calculation of prognostic factors.