A new concept for making decisions regarding the surgical approach for cervical ossification of the posterior longitudinal ligament: the K-line.
METHODS
To report a new index, the K-line, for deciding the surgical approach for cervical ossification of the posterior longitudinal ligament (OPLL).


OBJECTIVE
To analyze the correlation between the K-line-based classification of cervical OPLL patients and their surgical outcome.


BACKGROUND
Previous studies showed that kyphotic alignment of the cervical spine and a large OPLL are major factors causing poor surgical outcome after laminoplasty for cervical OPLL patients. However, no report has evaluated these 2 factors in 1 parameter.


METHODS
The K-line was defined as a line that connects the midpoints of the spinal canal at C2 and C7. Twenty-seven patients who had cervical OPLL and underwent posterior decompression surgery were classified into 2 groups according to their K-line classification. OPLL did not exceed the K-line in the K-line (+) group and did exceed it in the K-line (-) group. By intraoperative ultrasonography, we evaluated the posterior shift of the spinal cord after the posterior decompression procedure. The Japanese Orthopedic Association scores before surgery and 1 year after surgery were evaluated, and the recovery rate was calculated.


RESULTS
Eight patients were classified as K-line (-), and 19 patients were classified as K-line (+). The mean recovery rate was 13.9% in the K-line (-) group and 66.0% in the K-line (+) group (P < 0.01). Ultrasonography showed that the posterior shift of the spinal cord was insufficient in the K-line (-) group.


CONCLUSIONS
The present results demonstrate that a sufficient posterior shift of the spinal cord and neurologic improvement will not be obtained after posterior decompression surgery in the K-line (-) group. Our new index, the K-line, is a simple and practical tool for making decisions regarding the surgical approach for cervical OPLL patients.
Fujiyoshi
Takayuki
T
Spine Section, Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan.
Yamazaki
Masashi
M
Kawabe
Junko
J
Endo
Tomonori
T
Furuya
Takeo
T
Koda
Masao
M
Okawa
Akihiko
A
Takahashi
Kazuhisa
K
Konishi
Hiroaki
H
D000368:Aged; D000369:Aged, 80 and over; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D019299:Decompression, Surgical / Q000379:methods* / Q000639:trends; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017887:Ossification of Posterior Longitudinal Ligament / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D011859:Radiography