Study Design. A retrospective multi-institutional study. Objective. To clarify the distribution of intraoperative blood loss during cervical laminoplasty for ossification of the posterior longitudinal ligament (OPLL), and to identify the radiographical risk factors for the occurrence of major blood loss in patients with OPLL undergoing laminoplasty. Summary of Background Data. The incidence of major intraoperative blood loss during laminoplasty for OPLL is unknown. Methods. All patients who underwent cervical laminoplasty for OPLL between April 2005 and March 2008 at 27 institutions across Japan were included in this analysis. We investigated the patients' characteristics and surgical data, and compared the radiographical characteristics of OPLL in patients with and without major blood loss. Results. The estimated intraoperative blood loss was reported for 545 patients (429 male and 116 female; mean age, 62.7 yr). The mean intraoperative blood loss was 223 g (median, 130 g; range, minimal to 3350 g). Excluding 1 patient with intraoperative vertebral artery injury, major blood loss greater than 500 g was reported in 45 patients (8.3%). Patients with major blood loss were more likely to have neurological complications (5/45 vs. 12/499) and a longer hospital stay (29.5 d vs. 28.8 d) in comparison with those without major blood loss. The occupying ratio of OPLL was greater in the major blood loss group (48.3% vs. 42.2%; P = 0.02). A multivariate analysis revealed an occupying ratio of 60% or greater to be associated with an increased risk of major intraoperative blood loss (odds ratio, 2.4; 95% confidence interval, 1.1-5.3). Conclusion. Laminoplasty for OPLL is associated with a risk of major intraoperative blood loss, which can potentially give rise to devastating postoperative complications. An occupying ratio of 60% or greater is a risk factor for major blood loss during laminoplasty in patients with OPLL.
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