Multiple regression analysis of the factors influencing the results of expansive open-door laminoplasty for cervical myelopathy due to ossification of the posterior longitudinal ligament

We conducted a multiple regression analysis on the surgical results (minimum follow-up of 5 years) of 55 patients who underwent expansive open-door laminoplasty (open-door ELAP) for cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL) in order to determine statistically the impact of factors influencing the results. Duration of myelopathy was found to be a significant factor indicating poor results, while progression of ossification and age at the time of surgery were significant factors indicating deterioration. Three other factors (preoperative severity of myelopathy, degree of spinal canal expansion and changes of the curve indices before and after surgery did not have a significant influence on the results. To improve the surgical results, it is thus essential to operate on patients as soon as they develop symptoms of myelopathy. There exists a certain limitation in posterior decompression for OPLL including open-door ELAP until prevention of the progression of ossification becomes possible.