Masao Koda, Takeo Furuya, Junya Saito, Yasushi Ijima, Mitsuhiro Kitamura, Seiji Ohtori, Sumihisa Orita, Kazuhide Inage, Tetsuya Abe, Hiroshi Noguchi, Toru Funayama, Hiroshi Kumagai, Kosei Miura, Katsuya Nagashima, Masashi Yamazaki

May 2018, Volume 27, Issue 6, pp 1393 - 1400 Original Article Read Full Article 10.1007/s00586-018-5505-4

First Online: 14 February 2018


Addition of posterior instrumented fusion to laminoplasty (posterior decompression with instrumented fusion: PDF) can improve the surgical outcome of patients with K-line (−) cervical ossification of the longitudinal ligament (OPLL) compared with laminoplasty alone. We sought to elucidate the factors that are significantly associated with a better outcome after PDF for K-line (−) OPLL.


The present study included 38 patients who underwent PDF for K-line (−) OPLL and were followed up for at least 1 year after surgery. Clinical outcome was assessed using Japanese Orthopedic Association (JOA) scores for cervical myelopathy and the recovery rate was calculated. Patients who belonged to the upper quartile of all the patients according to rank order of the JOA score recovery rate were considered to have a good outcome. The correlations between good outcome, patient factors and imaging assessments were analyzed statistically.


Univariate analyses showed that postoperative conversion of K-line from (−) to (+) (p = 0.004), no increase in the sagittal vertical axis from the center of gravity of the head to C7 (p = 0.07), and a lower grade of preoperative intramedullary T2-signal intensity (p = 0.03) were candidates for the association. Stepwise logistic regression analysis revealed that postoperative K-line conversion from (−) to (+) is an independent factor that is significantly associated with a better surgical outcome (p = 0.04).


Postoperative K-line conversion from (−) to (+) is a factor independently associated with a better surgical outcome.

Graphical abstract

These slides can be retrieved under Electronic Supplementary material.[Figure not available: see fulltext.]

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