Unilateral Versus Bilateral Pedicle Screw Fixation in Lumbar Spinal Fusion

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Study Design.

A prospective study of 87 patients who underwent unilateral or bilateral pedicle screw fixation.


To determine whether unilateral pedicle screw fixation is comparable with bilateral fixation in one- or two-segment lumbar spinal fusion.

Summary of Background Data.

Clinical results for unilateral variable screw placement instrumentation in isolated L4–L5 fusion have been reported to be as good as those for bilateral instrumentation. However, unilateral instrumentation may not be recommended for multilevel fusion.


Eighty-seven patients were assigned to either unilateral (n = 47) or bilateral (n = 40) pedicle screw instrumentation groups. Two kinds of pedicle screw system (Moss Miami, DePuy, Warsaw, IN, and Steffee VSP, AcroMed, Cleveland, OH) were used. Operating time, blood loss, duration of hospital stay, clinical outcomes, fusion rates, complication rates, and medical expenses were studied and tested with independent sample t test and χ2 test.


There were no significant differences between the two groups in blood loss, clinically satisfactory results, fusion rate, and complication rate. There were significant differences in duration of operating time, duration of hospital stay, and medical expenses. The number of fusion segments or kinds of instrumentation did not affect the fusion rate or clinical outcomes.


Unilateral pedicle screw fixation was as effective as bilateral pedicle screw fixation in lumbar spinal fusion independent of the number of fusion segments (one or two segments) or pedicle screw systems. Based on the results of this study, unilateral fixation could be used in two-segment lumbar spinal fusion.

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