Expansive laminoplasty for ossification of the posterior longitudinal ligament (OPLL) has had favorable outcomes. Many modifications of expansive laminoplasty have been developed, including expansive laminoplasty with and without spinous process spacers (SPS). The purpose of this study was to determine whether surgical outcomes were similar between expansive laminoplasty surgeries with and without SPS.Of 109 consecutive patients undergoing surgery for OPLL, 68 patients undergoing expansive laminoplasty were included in the study after excluding patients with other conditions affecting their functional status. The patients were divided into 2 groups based on their K-line, which connects the midpoints of the spinal canal at C2 and C7. Patients were further divided into 2 subgroups: those undergoing expansive laminoplasty without SPS (without SPS group) and those undergoing expansive laminoplasty with SPS (with SPS group). Surgical outcomes were evaluated between K-line (+) and K-line (-) groups. After dividing those groups further into the with SPS and without SPS groups, the differences in surgical outcomes were evaluated again.No significant difference existed in the recovery rate between the with SPS and without SPS groups and between the K-line (+) and K-line (-) groups. When the surgical outcome was only evaluated in the K-line (+) group, the recovery rate 1 year postoperatively was higher in patients without SPS than in those with SPS. Therefore, for patients with K-line (+), the possibility exists that SPS can restrict the posterior shift of the spinal cord and affect the surgical outcome.
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