JBJS | Curvature and Range of Motion of the Cervical Spine After Laminaplasty*

The Journal of Bone & Joint Surgery, Volume 82, Issue 12

Articles | December 01, 2000

Curvature and Range of Motion of the Cervical Spine After Laminaplasty*

Ikuo Aita, M.D.†; Yasuyoshi Wadano, M.D.‡; Takeshi Yabuki, M.D.§

Investigation performed at the Department of Orthopaedic Surgery, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Department of Orthopaedic Surgery, Institute of Clinical Medicine, University of Tsukuba, Tennohdai 1-1-1, Tsukuba-shi, Ibaraki, 305-8575, Japan.
‡Department of Orthopaedics, Center for Medical Sciences, Ibaraki Prefectural University of Health Science, 4669-2 Ami-Mati, Inashiki-Gun, Ibaraki, 300-0394, Japan.
Â§Yabuki Orthopaedic Clinic, 2-12-18, Keyakidai, Moriya-Mati, Mitasouma-Gun, Ibaraki, 302-0128, Japan.

The Journal of Bone & Joint Surgery. 2000; 82:1743-1743

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Abstract

Background: The curvature and range of motion of the cervical spine decrease after laminaplasty. However, to our knowledge these changes have not been studied prospectively. Also, the effect of laminaplasty on the mobility of the occipito-atlanto-axial joints has not been studied in detail. The purpose of our study was to prospectively evaluate the range of motion and curvature of the cervical spine, including the occipito-atlanto-axial joints, following laminaplasty.

Methods: We conducted a prospective study of twenty-six patients who underwent cervical laminaplasty. They were followed for a mean of 6.7 years (range, five to nine years). Radiographs were made before the operation and at one, three, and five years after the operation. The curvature index, the angle of each vertebra in the neutral position from the occiput to the seventh cervical vertebra, and the range of motion in the sagittal plane were measured.

Results: The curvature index, the angle of the axis and the sixth cervical vertebra, and the angle of the axis and the seventh cervical vertebra in the neutral position were reduced after the operation. The rate of reduction declined between the third and fifth postoperative years. On the other hand, the mean distance between the occiput and the atlas as well as the mean angle of the axis and the atlas did not change significantly. The range of motion of the axis and the seventh cervical vertebra was decreased after the operation, and it continued to decrease slowly over the study period. The range of motion of the occipito-atlanto-axial complex increased slightly, which may represent a compensation for the decreased mobility of the middle and caudad parts of the cervical spine.

Conclusions: Laminaplasty diminishes lordosis and straightens the cervical spine. The range of motion and lordosis continued to decrease, though at a diminishing rate, between the third and fifth postoperative years.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

Cervical myelopathy can be treated with anterior interbody arthrodesis or laminaplasty. In some cases, both are performed concomitantly. Laminaplasty is usually indicated for patients who have stenosis of the spinal canal, and its clinical results have been excellent^5,6,10,14,17.

The curvature and range of motion of the cervical spine decrease after laminaplasty^4,8-10,13,16. However, these postoperative changes have not been studied longitudinally, to our knowledge. Moreover, the changes in the mobility of the cephalad part of the cervical spine (the occipito-atlanto-axial complex) following this procedure have been examined in few studies¹⁶. The purpose of the present study was to prospectively evaluate the range of motion and curvature of the cervical spine, including the occipito-atlanto-axial joints, following laminaplasty.

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Fig. 1:: Diagram of the laminaplasty. The spinous process is cut at the base and is used as a bone block. Lateral gutters are made at the medial border of the facet joint to open the laminae bilaterally.

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Fig. 2:: Diagram showing measurement of the curvature index. We modified the method of Ishihara7. On a lateral radiograph, E is the baseline that connects the inferior corner of the axis (C2) and the superior corner of the seventh cervical vertebra (C7). A, B, C, and D are the perpendicular lines joining line E to the middle of each vertebra.

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Fig. 3:: Diagram showing that lines parallel to the posterior surfaces of the vertebral bodies create an angle between each pair of vertebrae.

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Fig. 4-A: Diagram showing measurement of the distance between the inferior surface of the occiput and the posterior arch of the atlas (C1). The distance is expressed in millimeters.

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Fig. 4-B: Diagram showing measurement of the angle of the atlanto-axial joint (C1 and C2).

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Table I: Curvature in Neutral Position in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

*The values are given as the mean and standard deviation, with the range in parentheses.†Significantly different from the preoperative value (paired t test, p < 0.01).‡Significantly different from the preoperative value (paired t test, p < 0.05).

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	17.9 ± 11.9 (-9.7-36.2)	10.5 ± 12.9 (-7.5-33.9)†	9.1 ± 13.2 (-15.7-30.8)†	8.6 ± 13.2 (-15.4-35.3)†
C2-C7 (n = 22) (degrees)	20.2 ± 13.1 (-1.9-44.4)	12.6 ± 13.8 (-7.1-40.2)†	11.9 ± 13.6 (-7.8-41.3)†	11.0 ± 12.8 (-9.0-43.8)†
Curvature index (n = 25) (percent)	14.1 ± 11.8 (-9.8-39.1)	7.6 ± 10.4 (-11.4-26.5)†	7.9 ± 11.0 (-16.6-28.3)†	6.8 ± 10.6 (-11.2-27.7)†
Occiput-C1 (n = 25) (mm)	7.5 ± 3.4 (0.0-15.2)	6.3 ± 4.2 (0.0-19.5)†	6.9 ± 4.7 (0.0-19.5)‡	7.4 ± 4.4 (0.0-19.5)
C1-C2 (n = 26) (degrees)	27.5 ± 7.1 (13.5-41.1)	29.0 ± 6.5 (10.5-41.2)	28.3 ± 7.1 (10.5-39.7)	28.8 ± 6.9 (10.5-38.8)

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Table I: Curvature in Neutral Position in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	17.9 ± 11.9 (-9.7-36.2)	10.5 ± 12.9 (-7.5-33.9)†	9.1 ± 13.2 (-15.7-30.8)†	8.6 ± 13.2 (-15.4-35.3)†
C2-C7 (n = 22) (degrees)	20.2 ± 13.1 (-1.9-44.4)	12.6 ± 13.8 (-7.1-40.2)†	11.9 ± 13.6 (-7.8-41.3)†	11.0 ± 12.8 (-9.0-43.8)†
Curvature index (n = 25) (percent)	14.1 ± 11.8 (-9.8-39.1)	7.6 ± 10.4 (-11.4-26.5)†	7.9 ± 11.0 (-16.6-28.3)†	6.8 ± 10.6 (-11.2-27.7)†
Occiput-C1 (n = 25) (mm)	7.5 ± 3.4 (0.0-15.2)	6.3 ± 4.2 (0.0-19.5)†	6.9 ± 4.7 (0.0-19.5)‡	7.4 ± 4.4 (0.0-19.5)
C1-C2 (n = 26) (degrees)	27.5 ± 7.1 (13.5-41.1)	29.0 ± 6.5 (10.5-41.2)	28.3 ± 7.1 (10.5-39.7)	28.8 ± 6.9 (10.5-38.8)

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Table II: Curvature in Neutral Position in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

*The non-OPLL group includes patients with cervical spondylotic myelopathy and hypertrophy of the posterior longitudinal ligament. Repeated-measures analysis of variance revealed no significant differences between the non-OPLL and OPLL groups.†The values are given as the mean and standard deviation, with the range in parentheses.

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	16.7 ± 12.6 (-9.7-34.8)	8.8 ± 12.3 (-7.5-32.4)	8.4 ± 13.1 (-15.7-29.6)	7.0 ± 12.9 (-15.4-32.9)
OPLL (n = 10)	19.9 ± 11.0 (6.6-36.2)	13.2 ± 14.0 (-4.3-33.9)	10.2 ± 13.9 (-11.0-30.8)	11.0 ± 14.0 (-5.9-35.3)
C2-C7 (degrees)
Non-OPLL (n = 15)	20.0 ± 12.7 (-1.9-40.6)	9.9 ± 11.6 (-7.1-27.7)	9.5 ± 11.6 (-7.8-27.1)	8.3 ± 10.3 (-9.0-28.4)
OPLL (n = 7)	20.6 ± 14.8 (0.4-44.4)	18.5 ± 17.0 (-1.3-40.2)	17.1 ± 17.1 (-2.7-41.3)	16.7 ± 16.4 (1.6-43.8)
Curvature index (percent)
Non-OPLL (n = 16)	13.1 ± 13.5 (-9.8-38.1)	6.0 ± 10.3 (-11.4-26.5)	7.0 ± 11.8 (-16.69-28.3)	5.5 ± 11.0 (-11.2-27.7)
OPLL (n = 9)	15.9 ± 8.5 (5.8-29.0)	10.5 ± 10.5 (-5.8-21.9)	9.5 ± 9.7 (-5.6-19.6)	9.2 ± 10.2 (-6.8-22.0)
Occiput-C1 (mm)
Non-OPLL (n = 15)	7.0 ± 3.8 (0.0-13.2)	7.1 ± 5.0 (0.0-19.5)	7.5 ± 5.0 (1.1-19.5)	7.7 ± 4.9 (0.0-19.5)
OPLL (n = 10)	8.2 ± 2.8 (4.9-15.2)	5.0 ± 2.4 (0.0-7.7)	5.9 ± 4.4 (0.0-1.3)	7.0 ± 3.6 (1.5-13.1)
C1-C2 (degrees)
Non-OPLL (n = 16)	26.4 ± 6.5 (13.5-39.6)	28.0 ± 6.5 (10.5-35.5)	27.3 ± 7.0 (10.5-38.6)	27.7 ± 7.4 (10.5-37.8)
OPLL (n = 10)	29.1 ± 8.1 (16.4-41.1)	30.6 ± 6.5 (21.4-41.2)	29.9 ± 7.3 (16.8-39.7)	30.6 ± 6.0 (18.2-38.8)

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Table II: Curvature in Neutral Position in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	16.7 ± 12.6 (-9.7-34.8)	8.8 ± 12.3 (-7.5-32.4)	8.4 ± 13.1 (-15.7-29.6)	7.0 ± 12.9 (-15.4-32.9)
OPLL (n = 10)	19.9 ± 11.0 (6.6-36.2)	13.2 ± 14.0 (-4.3-33.9)	10.2 ± 13.9 (-11.0-30.8)	11.0 ± 14.0 (-5.9-35.3)
C2-C7 (degrees)
Non-OPLL (n = 15)	20.0 ± 12.7 (-1.9-40.6)	9.9 ± 11.6 (-7.1-27.7)	9.5 ± 11.6 (-7.8-27.1)	8.3 ± 10.3 (-9.0-28.4)
OPLL (n = 7)	20.6 ± 14.8 (0.4-44.4)	18.5 ± 17.0 (-1.3-40.2)	17.1 ± 17.1 (-2.7-41.3)	16.7 ± 16.4 (1.6-43.8)
Curvature index (percent)
Non-OPLL (n = 16)	13.1 ± 13.5 (-9.8-38.1)	6.0 ± 10.3 (-11.4-26.5)	7.0 ± 11.8 (-16.69-28.3)	5.5 ± 11.0 (-11.2-27.7)
OPLL (n = 9)	15.9 ± 8.5 (5.8-29.0)	10.5 ± 10.5 (-5.8-21.9)	9.5 ± 9.7 (-5.6-19.6)	9.2 ± 10.2 (-6.8-22.0)
Occiput-C1 (mm)
Non-OPLL (n = 15)	7.0 ± 3.8 (0.0-13.2)	7.1 ± 5.0 (0.0-19.5)	7.5 ± 5.0 (1.1-19.5)	7.7 ± 4.9 (0.0-19.5)
OPLL (n = 10)	8.2 ± 2.8 (4.9-15.2)	5.0 ± 2.4 (0.0-7.7)	5.9 ± 4.4 (0.0-1.3)	7.0 ± 3.6 (1.5-13.1)
C1-C2 (degrees)
Non-OPLL (n = 16)	26.4 ± 6.5 (13.5-39.6)	28.0 ± 6.5 (10.5-35.5)	27.3 ± 7.0 (10.5-38.6)	27.7 ± 7.4 (10.5-37.8)
OPLL (n = 10)	29.1 ± 8.1 (16.4-41.1)	30.6 ± 6.5 (21.4-41.2)	29.9 ± 7.3 (16.8-39.7)	30.6 ± 6.0 (18.2-38.8)

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Table III: Cervical Range of Motion in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

*The values are given as the mean and standard deviation, with the range in parentheses.†Significantly different from the preoperative value (paired t test, p < 0.01).

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	40.0 ± 11.4 (21.3-63.0)	17.1 ± 10.1 (2.0-42.6)†	14.0 ± 11.5 (0.0-42.0)†	13.2 ± 11.1 (0.0-38.8)†
C2-C7 (n = 18) (degrees)	46.5 ± 12.9 (23.5-70.1)	24.5 ± 14.6 (1.7-52.3)†	23.0 ± 15.1 (0.0-49.7)†	20.5 ± 15.5 (0.0-47.8)†
Occiput-C1 (n = 24) (mm)	5.3 ± 4.0 (0.4-14.9)	6.8 ± 3.3 (0.2-14.7)	7.0 ± 3.4 (0.0-14.3)	6.4 ± 4.1 (0.8-14.5)
C1-C2 (n = 25) (degrees)	7.6 ± 4.2 (0.2-16.2)	9.1 ± 4.3 (1.5-16.1)	9.0 ± 4.6 (1.5-19.7)	9.3 ± 5.3 (1.4-22.3)

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Table III: Cervical Range of Motion in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

*The values are given as the mean and standard deviation, with the range in parentheses.†Significantly different from the preoperative value (paired t test, p < 0.01).

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	40.0 ± 11.4 (21.3-63.0)	17.1 ± 10.1 (2.0-42.6)†	14.0 ± 11.5 (0.0-42.0)†	13.2 ± 11.1 (0.0-38.8)†
C2-C7 (n = 18) (degrees)	46.5 ± 12.9 (23.5-70.1)	24.5 ± 14.6 (1.7-52.3)†	23.0 ± 15.1 (0.0-49.7)†	20.5 ± 15.5 (0.0-47.8)†
Occiput-C1 (n = 24) (mm)	5.3 ± 4.0 (0.4-14.9)	6.8 ± 3.3 (0.2-14.7)	7.0 ± 3.4 (0.0-14.3)	6.4 ± 4.1 (0.8-14.5)
C1-C2 (n = 25) (degrees)	7.6 ± 4.2 (0.2-16.2)	9.1 ± 4.3 (1.5-16.1)	9.0 ± 4.6 (1.5-19.7)	9.3 ± 5.3 (1.4-22.3)

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Table IV: Range of Motion in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	43.7 ± 11.1 (23.5-63.0)	18.5 ± 9.8 (2.0-42.6)	16.2 ± 12.6 (0.0-42.0)	15.1 ± 12.3 (0.0-38.8)
OPLL (n = 10)	34.0 ± 9.5 (21.3-50.0)	14.7 ± 10.7 (2.9-32.1)	10.3 ± 8.9 (0.0-25.4)	10.2 ± 8.7 (0.0-24.8)
C2-C7 (degrees)
Non-OPLL (n = 11)	49.8 ± 11.9 (32.8-70.1)	27.9 ± 14.1 (5.6-52.3)	25.7 ± 16.0 (0.0-49.7)	24.3 ± 16.1 (0.0-47.8)
OPLL (n = 7)	41.5 ± 13.5 (23.5-57.5)	19.2 ± 14.8 (1.7-42.1)	18.8 ± 13.5 (0.0-38.8)	14.6 ± 13.6 (0.0-38.0)
Occiput-C1 (mm)
Non-OPLL (n = 14)	4.0 ± 2.8 (0.7-8.2)	6.2 ± 3.2 (0.2-9.7)	6.9 ± 3.3 (0.0-11.8)	6.2 ± 4.2 (0.8-14.5)
OPLL (n = 10)	7.1 ± 4.9 (0.4-14.9)	7.8 ± 3.5 (4.3-14.7)	7.2 ± 3.8 (2.7-14.3)	6.7 ± 4.2 (2.0-14.4)
C1-C2 (degrees)
Non-OPLL (n = 15)	7.9 ± 4.4 (0.2-16.2)	9.7 ± 3.8 (4.1-15.9)	9.9 ± 3.9 (3.9-19.7)	9.7 ± 5.8 (1.4-22.3)
OPLL (n = 10)	7.2 ± 4.1 (0.2-13.7)	8.1 ± 5.0 (1.5-16.1)	7.7 ± 5.4 (1.5-16.7)	8.8 ± 4.6 (2.7-15.0)

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Table IV: Range of Motion in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	43.7 ± 11.1 (23.5-63.0)	18.5 ± 9.8 (2.0-42.6)	16.2 ± 12.6 (0.0-42.0)	15.1 ± 12.3 (0.0-38.8)
OPLL (n = 10)	34.0 ± 9.5 (21.3-50.0)	14.7 ± 10.7 (2.9-32.1)	10.3 ± 8.9 (0.0-25.4)	10.2 ± 8.7 (0.0-24.8)
C2-C7 (degrees)
Non-OPLL (n = 11)	49.8 ± 11.9 (32.8-70.1)	27.9 ± 14.1 (5.6-52.3)	25.7 ± 16.0 (0.0-49.7)	24.3 ± 16.1 (0.0-47.8)
OPLL (n = 7)	41.5 ± 13.5 (23.5-57.5)	19.2 ± 14.8 (1.7-42.1)	18.8 ± 13.5 (0.0-38.8)	14.6 ± 13.6 (0.0-38.0)
Occiput-C1 (mm)
Non-OPLL (n = 14)	4.0 ± 2.8 (0.7-8.2)	6.2 ± 3.2 (0.2-9.7)	6.9 ± 3.3 (0.0-11.8)	6.2 ± 4.2 (0.8-14.5)
OPLL (n = 10)	7.1 ± 4.9 (0.4-14.9)	7.8 ± 3.5 (4.3-14.7)	7.2 ± 3.8 (2.7-14.3)	6.7 ± 4.2 (2.0-14.4)
C1-C2 (degrees)
Non-OPLL (n = 15)	7.9 ± 4.4 (0.2-16.2)	9.7 ± 3.8 (4.1-15.9)	9.9 ± 3.9 (3.9-19.7)	9.7 ± 5.8 (1.4-22.3)
OPLL (n = 10)	7.2 ± 4.1 (0.2-13.7)	8.1 ± 5.0 (1.5-16.1)	7.7 ± 5.4 (1.5-16.7)	8.8 ± 4.6 (2.7-15.0)

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

We prospectively reviewed the radiographs of twenty-six patients who underwent cervical laminaplasty at the Tsukuba University Hospital. All of the patients underwent laminaplasty only. Patients who underwent both an anterior and a posterior operation were excluded from this study. All of the operations were performed by, or under the supervision of, one of the authors (I. A., Y. W., or T. Y.). The mean duration of follow-up was 6.7 years (range, five to nine years). Twenty-one patients were men and five were women, with ages ranging from thirty-four to seventy-six years (mean, fifty-seven years) at the time of the operation. Cervical spondylotic myelopathy was the diagnosis in sixteen patients, and ossification of the posterior longitudinal ligament was the diagnosis in nine. One patient had hypertrophy of the posterior longitudinal ligament.

We performed a French-door laminaplasty, in which the spinous process is used as a bone block (Fig. 1). The operation was performed on the third through seventh cervical vertebrae in sixteen patients, on the third through seventh cervical vertebrae with a domed laminotomy of the axis in five patients, on the third through sixth cervical vertebrae in three patients, on the second through seventh cervical vertebrae in one patient, and on the second cervical through second thoracic vertebrae in one patient.

Plain lateral radiographs of the cervical spine were made before the operation and at one, three, and five years after the operation, with the patient in the upright position. The tube-to-film distance was 150 centimeters. Using a Speedy Particle Image Color and Computer Analysis-II machine (Nippon Avionics, Minato-ku, Tokyo, Japan), we measured the curvature index (Fig. 2), the angle of the axis and the sixth cervical vertebra, the angle of the axis and the seventh cervical vertebra, and the angles of each vertebra from the axis to the seventh cervical vertebra in the neutral position (Fig. 3). We also measured the range of motion in the sagittal plane. We believe that the curvature index as described by Ishihara⁷ represents the curvature better than the angle of the axis and the seventh cervical vertebra because it incorporates the position of the other vertebrae. Because the inferior corner of the seventh cervical vertebra was sometimes difficult to identify on lateral radiographs, we modified the measurement technique. For the same reason, the angle of the axis and the sixth cervical vertebra was measured in addition to the angle of the axis and the seventh cervical vertebra. Since it was difficult to measure the angle between the occiput and the atlas (the first cervical vertebra), we measured the distance between the inferior surface of the occiput and the posterior arch of the atlas (Fig. 4-A) in millimeters. The angle of the atlanto-axial joint (the first and second cervical vertebrae) was also measured (Fig. 4-B). All radiographic analysis was performed by one of the authors (I. A.). We also measured these values in active flexion and extension. The difference between flexion and extension was calculated as the range of motion.

Preoperative and postoperative values were compared with use of the paired t test. Repeated-measures analysis of variance was used to determine significance between groups. Correlations between findings before the operation and those five years after the operation were evaluated with the Pearson correlation coefficient.

Results

Introduction | Materials and Methods | Results | Discussion | References

According to the Japanese Orthopaedic Association scale for cervical spondylotic myelopathy⁴, the mean preoperative score was 10.8 ± 2.4 points and the mean postoperative score was 12.5 ± 2.5 points; the mean recovery rate was 26.9 ± 32.3 percent.

The curvature index, the angle of the axis and the sixth cervical vertebra, and the angle of the axis and the seventh cervical vertebra in the neutral position were reduced after the operation (p < 0.01) (Table I). The rate of reduction declined between the third and fifth postoperative years. The angles between adjacent levels, from the axis to the seventh cervical vertebra, were similarly reduced (p < 0.01). On the other hand, the mean distance between the occiput and the atlas and the mean angle of the atlas and the axis did not change significantly.

The patients were divided into two groups: those without ossification of the posterior longitudinal ligament and those with ossification of the ligament. The group with no ossification included all of the patients with cervical spondylotic myelopathy or hypertrophy of the posterior longitudinal ligament. There were no significant differences between the groups (Table II). However, the group with ossification of the posterior longitudinal ligament had less of a decrease in the lordotic curvature than the other group did. At five years after the operation, the angle of the axis and the sixth cervical vertebra and the curvature index in the group with no ossification were 41.9 and 42 percent of the preoperative values, respectively. In the group with ossification, these values were 55.3 and 57.9 percent, respectively.

There were linear correlations between the preoperative and five-year angles of the axis and the sixth cervical vertebra (r = 0.88; p < 0.01) and between the preoperative and five-year curvature indices (r = 0.87; p < 0.01).

The range of motion of the axis and the seventh cervical vertebra after laminaplasty decreased and continued to decrease slowly over the study period (Table III). The range of motion of the occipito-atlanto-axial joints increased slightly but not significantly.

The group with ossification of the posterior longitudinal ligament had less spinal mobility before and after the operation than did the group with no ossification of the ligament (Table IV). However, these differences were not significant.

There was a linear relationship between the preoperative and five-year angles of the axis and the sixth cervical vertebra (p < 0.01). The correlation coefficient, however, was low (r = 0.48).

Neither the curvature nor the range of motion of the cervical spine had a significant relationship with the clinical outcome.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Cervical laminaplasty enlarges the spinal canal and decompresses the spinal cord. The curvature and the range of motion of the cervical spine have been reported to decrease after laminaplasty^4,8-10,13,16. However, in those studies postoperative data from only one time-point were measured. Since the data were not obtained longitudinally, it is not known whether these postoperative changes in the cervical spine were progressive. In the present study, we evaluated the changes in the cervical spine over a period of at least five years.

A decrease in the lordosis was obvious at one year after the operation. The curvature continued to decrease, although to a lesser degree, between the third and fifth postoperative years. At five years after the operation, the angle of the axis and the sixth cervical vertebra and the curvature index were about 60 percent of the preoperative values.

The main cause of this change in curvature could be destruction of the facet joint by the lateral gutters formed as part of the laminaplasty (Fig. 1), or the change could be the result of damage of the paravertebral muscles and their attachments to the spinous processes. Lateral gutters are made between the facet joints and the laminae. They protrude into the medial portion of the facet joint, which could lead to a limitation of extension and a decrease in lordosis. Moreover, it appears to be difficult for an opened lamina to lie on top of another lamina in extension. Postoperative weakness of the posterior structure of the cervical spine may also be an etiological factor. During the operation, the paravertebral muscles are dissected off the spinous processes from the third to the seventh cervical vertebra. The insertion of the semispinalis cervicis onto the spinous process of the axis is partially resected, although it is repaired at the end of the procedure. The decrease in the curvature may continue until there is union of the facet joints.

Diminished lordosis may cause clinical problems. If the curvature straightens, residual ossification of the posterior longitudinal ligament or disc herniation may compress the spinal cord. Therefore, an effort should be made to maintain the lordosis of the cervical spine after laminaplasty. We now perform laminaplasty without resecting the insertion of the semispinalis cervicis onto the spinous process of the axis. We believe that another important step is to suture the posterior muscles and the ligamentum nuchae tightly. If the bilateral paravertebral muscles are not sutured closely in the center, the function of the posterior muscles will decrease.

Only a few studies have addressed the curvature of the occipitocervical region after laminaplasty. The curvature of the occipito-atlanto-axial complex is thought to become more lordotic in compensation for the decreased lordosis of the axis and the seventh cervical vertebra. Yonezawa et al.¹⁶ reported that the distance between the occiput and the lamina of the atlas decreased after laminaplasty. However, we found no significant change in this distance after laminaplasty. When thinking about the curvature of the cervical spine, one must consider the curvature of other spinal regions, including the cervicothoracic junction, in the standing posture. Compensation for the decreased lordosis of the cervical spine may occur in any region of the spine.

Except for the occipito-atlanto-axial joints, the cervical spine had a decreased range of motion after laminaplasty. This decrease may have resulted from the creation of the lateral gutters at the medial border of the facet joints. Mobility may continue to decrease until the facet joints fuse.

Movement of the spine may cause trauma to the spinal cord in some patients with myelopathy. In these instances, decreased mobility in and of itself may have a salutary effect¹⁷.

The increased mobility of the occipito-atlanto-axial joints may represent compensation for the decreased mobility of the axis and the seventh cervical vertebra, which is consistent with the findings of Yonezawa et al.¹⁶.

In the present study, neither the curvature nor the range of motion of the cervical spine had a significant relationship with the clinical outcome. A number of factors affect the clinical outcome in cervical myelopathy. Although decreased lordosis and mobility may have some effect on the spinal cord, patient age¹, duration of symptoms^1-3,11,12,15, and severity of spinal compression^11,12 may be more important predictors of outcome.

References

Introduction | Materials and Methods | Results | Discussion | References

Bertalanffy, H., and Eggert, H. R.: Clinical long-term results of anterior discectomy without fusion for treatment of cervical radiculopathy and myelopathy. A follow-up of 164 cases. Acta Neurochir.,90: 127-135, 1988.90127 1988

Ebersold, M. J.; Pare, M. C.; and Quast, L. M.: Surgical treatment for cervical spondylitic myelopathy. J. Neurosurg.,82: 745-751, 1995.82745 1995 [PubMed]

Fukui, K.; Kataoka, O.; Sho, T.; and Sumi, M.: : Pathomechanism, pathogenesis, and results of treatment in cervical spondylotic myelopathy caused by dynamic canal stenosis. Spine,,15: 1148-1152, 1990.151148 1990

Hase, H.; Watanabe, T.; Hirasawa, Y.; Hashimoto, H.; Miyamoto, T.; Chatani, K.; Kageyama, N.; and Mikami, Y.: Bilateral open laminoplasty using ceramic laminas for cervical myelopathy. Spine,,16: 1269-1276, 1991.161269 1991

Hirabayashi, K.; Watanabe, K.; Wakano, K.; Suzuki, N.; Satomi, K.; and Ishii, Y. : Expansive open-door laminoplasty for cervical spinal stenotic myelopathy. Spine,8: 693-699, 1983.8693 1983 [PubMed]

Hirabayashi, K., and Satomi, K.: Operative procedure and results of expansive open-door laminoplasty. Spine,13: 870-876, 1988.13870 1988 [PubMed]

Ishihara, A.: Roentgenographic studies on the normal pattern of the cervical curvature. Nippon Seikeigeka Gakkai Zasshi,42: 1033-1044, 1968.421033 1968 [PubMed]

Itoh, T.: Clinical studies on the significance of en bloc laminoplasty for cervical compressive myelopathy. Nippon Seikeigeka Gakkai Zasshi,,60: 1109-1123, 1986.601109 1986

Kamioka, Y.; Yamamoto, H.; Tani, T.; Ishida, K.; and Sawamoto, T.: : Postoperative instability of cervical OPLL and cervical radiculomyelopathy. Spine,,14: 1177-1183, 1989.141177 1989

Kawai, S.; Sunago, K.; Doi, K.; Saika, M.; and Taguchi, T.: Cervical laminoplasty (Hattori's method). Procedure and follow-up results. Spine,13: 1245-1250, 1988.131245 1988 [PubMed]

Koyanagi, T.; Hirabayashi, K.; Satomi, K.; Toyama, Y.; and Fujimura, Y.: Predictability of operative results of cervical compression myelopathy based on preoperative computed tomographic myelography. Spine,18: 1958-1963, 1993.181958 1993 [PubMed]

Matsuyama, Y.; Kawakami, N.; and Mimatsu, K.: : Spinal cord expansion after decompression in cervical myelopathy. Investigation by computed tomography myelography and ultrasonography. Spine,20: 1657-1663, 1995.201657 1995 [PubMed]

Sato, T.: Radiological follow-up of motion in the cervical spine after surgery. Nippon Seikeigeka Gakkai Zasshi,66: 607-620, 1992.66607 1992 [PubMed]

Tsuji, H.: Laminoplasty for patients with compressive myelopathy due to so-called spinal canal stenosis in cervical and thoracic regions. Spine,,7: 28-34, 1982.728 1982

Yang, K. C.; Lu, X. S.; Cai, Q. L.; Ye, L. X.; and Lu, W. Q.: Cervical spondylotic myelopathy treated by anterior multilevel decompression and fusion. Follow-up report of 214 cases. Clin. Orthop.,221: 161-164, 1987.221161 1987 [PubMed]

Yonezawa, T.; Katoh, Y.; Kitagawa, H.; Tsuji, H.; and Itoh, T.: Long-term results of en bloc laminoplasty of the cervical spine. Rinshou Seikei Geka,27: 281-286, 1992.27281 1992

Yoshida, M.; Otani, K.; Shibasaki, K.; and Ueda, S.: Expansive laminoplasty with reattachment of spinous process and extensor musculature for cervical myelopathy. Spine,17: 491-497, 1992.17491 1992 [PubMed]

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Fig. 3:: Diagram showing that lines parallel to the posterior surfaces of the vertebral bodies create an angle between each pair of vertebrae.

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Fig. 4-A: Diagram showing measurement of the distance between the inferior surface of the occiput and the posterior arch of the atlas (C1). The distance is expressed in millimeters.

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Fig. 4-B: Diagram showing measurement of the angle of the atlanto-axial joint (C1 and C2).

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Table I: Curvature in Neutral Position in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	17.9 ± 11.9 (-9.7-36.2)	10.5 ± 12.9 (-7.5-33.9)†	9.1 ± 13.2 (-15.7-30.8)†	8.6 ± 13.2 (-15.4-35.3)†
C2-C7 (n = 22) (degrees)	20.2 ± 13.1 (-1.9-44.4)	12.6 ± 13.8 (-7.1-40.2)†	11.9 ± 13.6 (-7.8-41.3)†	11.0 ± 12.8 (-9.0-43.8)†
Curvature index (n = 25) (percent)	14.1 ± 11.8 (-9.8-39.1)	7.6 ± 10.4 (-11.4-26.5)†	7.9 ± 11.0 (-16.6-28.3)†	6.8 ± 10.6 (-11.2-27.7)†
Occiput-C1 (n = 25) (mm)	7.5 ± 3.4 (0.0-15.2)	6.3 ± 4.2 (0.0-19.5)†	6.9 ± 4.7 (0.0-19.5)‡	7.4 ± 4.4 (0.0-19.5)
C1-C2 (n = 26) (degrees)	27.5 ± 7.1 (13.5-41.1)	29.0 ± 6.5 (10.5-41.2)	28.3 ± 7.1 (10.5-39.7)	28.8 ± 6.9 (10.5-38.8)

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Table I: Curvature in Neutral Position in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	17.9 ± 11.9 (-9.7-36.2)	10.5 ± 12.9 (-7.5-33.9)†	9.1 ± 13.2 (-15.7-30.8)†	8.6 ± 13.2 (-15.4-35.3)†
C2-C7 (n = 22) (degrees)	20.2 ± 13.1 (-1.9-44.4)	12.6 ± 13.8 (-7.1-40.2)†	11.9 ± 13.6 (-7.8-41.3)†	11.0 ± 12.8 (-9.0-43.8)†
Curvature index (n = 25) (percent)	14.1 ± 11.8 (-9.8-39.1)	7.6 ± 10.4 (-11.4-26.5)†	7.9 ± 11.0 (-16.6-28.3)†	6.8 ± 10.6 (-11.2-27.7)†
Occiput-C1 (n = 25) (mm)	7.5 ± 3.4 (0.0-15.2)	6.3 ± 4.2 (0.0-19.5)†	6.9 ± 4.7 (0.0-19.5)‡	7.4 ± 4.4 (0.0-19.5)
C1-C2 (n = 26) (degrees)	27.5 ± 7.1 (13.5-41.1)	29.0 ± 6.5 (10.5-41.2)	28.3 ± 7.1 (10.5-39.7)	28.8 ± 6.9 (10.5-38.8)

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Table II: Curvature in Neutral Position in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	16.7 ± 12.6 (-9.7-34.8)	8.8 ± 12.3 (-7.5-32.4)	8.4 ± 13.1 (-15.7-29.6)	7.0 ± 12.9 (-15.4-32.9)
OPLL (n = 10)	19.9 ± 11.0 (6.6-36.2)	13.2 ± 14.0 (-4.3-33.9)	10.2 ± 13.9 (-11.0-30.8)	11.0 ± 14.0 (-5.9-35.3)
C2-C7 (degrees)
Non-OPLL (n = 15)	20.0 ± 12.7 (-1.9-40.6)	9.9 ± 11.6 (-7.1-27.7)	9.5 ± 11.6 (-7.8-27.1)	8.3 ± 10.3 (-9.0-28.4)
OPLL (n = 7)	20.6 ± 14.8 (0.4-44.4)	18.5 ± 17.0 (-1.3-40.2)	17.1 ± 17.1 (-2.7-41.3)	16.7 ± 16.4 (1.6-43.8)
Curvature index (percent)
Non-OPLL (n = 16)	13.1 ± 13.5 (-9.8-38.1)	6.0 ± 10.3 (-11.4-26.5)	7.0 ± 11.8 (-16.69-28.3)	5.5 ± 11.0 (-11.2-27.7)
OPLL (n = 9)	15.9 ± 8.5 (5.8-29.0)	10.5 ± 10.5 (-5.8-21.9)	9.5 ± 9.7 (-5.6-19.6)	9.2 ± 10.2 (-6.8-22.0)
Occiput-C1 (mm)
Non-OPLL (n = 15)	7.0 ± 3.8 (0.0-13.2)	7.1 ± 5.0 (0.0-19.5)	7.5 ± 5.0 (1.1-19.5)	7.7 ± 4.9 (0.0-19.5)
OPLL (n = 10)	8.2 ± 2.8 (4.9-15.2)	5.0 ± 2.4 (0.0-7.7)	5.9 ± 4.4 (0.0-1.3)	7.0 ± 3.6 (1.5-13.1)
C1-C2 (degrees)
Non-OPLL (n = 16)	26.4 ± 6.5 (13.5-39.6)	28.0 ± 6.5 (10.5-35.5)	27.3 ± 7.0 (10.5-38.6)	27.7 ± 7.4 (10.5-37.8)
OPLL (n = 10)	29.1 ± 8.1 (16.4-41.1)	30.6 ± 6.5 (21.4-41.2)	29.9 ± 7.3 (16.8-39.7)	30.6 ± 6.0 (18.2-38.8)

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Table II: Curvature in Neutral Position in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	16.7 ± 12.6 (-9.7-34.8)	8.8 ± 12.3 (-7.5-32.4)	8.4 ± 13.1 (-15.7-29.6)	7.0 ± 12.9 (-15.4-32.9)
OPLL (n = 10)	19.9 ± 11.0 (6.6-36.2)	13.2 ± 14.0 (-4.3-33.9)	10.2 ± 13.9 (-11.0-30.8)	11.0 ± 14.0 (-5.9-35.3)
C2-C7 (degrees)
Non-OPLL (n = 15)	20.0 ± 12.7 (-1.9-40.6)	9.9 ± 11.6 (-7.1-27.7)	9.5 ± 11.6 (-7.8-27.1)	8.3 ± 10.3 (-9.0-28.4)
OPLL (n = 7)	20.6 ± 14.8 (0.4-44.4)	18.5 ± 17.0 (-1.3-40.2)	17.1 ± 17.1 (-2.7-41.3)	16.7 ± 16.4 (1.6-43.8)
Curvature index (percent)
Non-OPLL (n = 16)	13.1 ± 13.5 (-9.8-38.1)	6.0 ± 10.3 (-11.4-26.5)	7.0 ± 11.8 (-16.69-28.3)	5.5 ± 11.0 (-11.2-27.7)
OPLL (n = 9)	15.9 ± 8.5 (5.8-29.0)	10.5 ± 10.5 (-5.8-21.9)	9.5 ± 9.7 (-5.6-19.6)	9.2 ± 10.2 (-6.8-22.0)
Occiput-C1 (mm)
Non-OPLL (n = 15)	7.0 ± 3.8 (0.0-13.2)	7.1 ± 5.0 (0.0-19.5)	7.5 ± 5.0 (1.1-19.5)	7.7 ± 4.9 (0.0-19.5)
OPLL (n = 10)	8.2 ± 2.8 (4.9-15.2)	5.0 ± 2.4 (0.0-7.7)	5.9 ± 4.4 (0.0-1.3)	7.0 ± 3.6 (1.5-13.1)
C1-C2 (degrees)
Non-OPLL (n = 16)	26.4 ± 6.5 (13.5-39.6)	28.0 ± 6.5 (10.5-35.5)	27.3 ± 7.0 (10.5-38.6)	27.7 ± 7.4 (10.5-37.8)
OPLL (n = 10)	29.1 ± 8.1 (16.4-41.1)	30.6 ± 6.5 (21.4-41.2)	29.9 ± 7.3 (16.8-39.7)	30.6 ± 6.0 (18.2-38.8)

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Table III: Cervical Range of Motion in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

*The values are given as the mean and standard deviation, with the range in parentheses.†Significantly different from the preoperative value (paired t test, p < 0.01).

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	40.0 ± 11.4 (21.3-63.0)	17.1 ± 10.1 (2.0-42.6)†	14.0 ± 11.5 (0.0-42.0)†	13.2 ± 11.1 (0.0-38.8)†
C2-C7 (n = 18) (degrees)	46.5 ± 12.9 (23.5-70.1)	24.5 ± 14.6 (1.7-52.3)†	23.0 ± 15.1 (0.0-49.7)†	20.5 ± 15.5 (0.0-47.8)†
Occiput-C1 (n = 24) (mm)	5.3 ± 4.0 (0.4-14.9)	6.8 ± 3.3 (0.2-14.7)	7.0 ± 3.4 (0.0-14.3)	6.4 ± 4.1 (0.8-14.5)
C1-C2 (n = 25) (degrees)	7.6 ± 4.2 (0.2-16.2)	9.1 ± 4.3 (1.5-16.1)	9.0 ± 4.6 (1.5-19.7)	9.3 ± 5.3 (1.4-22.3)

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Table III: Cervical Range of Motion in Twenty-six Patients Who Had Laminaplasty for the Treatment of Cervical Myelopathy

*The values are given as the mean and standard deviation, with the range in parentheses.†Significantly different from the preoperative value (paired t test, p < 0.01).

	Preoperative*	Postoperative*
1 yr.	3 yrs.	5 yrs.
C2-C6 (n = 26) (degrees)	40.0 ± 11.4 (21.3-63.0)	17.1 ± 10.1 (2.0-42.6)†	14.0 ± 11.5 (0.0-42.0)†	13.2 ± 11.1 (0.0-38.8)†
C2-C7 (n = 18) (degrees)	46.5 ± 12.9 (23.5-70.1)	24.5 ± 14.6 (1.7-52.3)†	23.0 ± 15.1 (0.0-49.7)†	20.5 ± 15.5 (0.0-47.8)†
Occiput-C1 (n = 24) (mm)	5.3 ± 4.0 (0.4-14.9)	6.8 ± 3.3 (0.2-14.7)	7.0 ± 3.4 (0.0-14.3)	6.4 ± 4.1 (0.8-14.5)
C1-C2 (n = 25) (degrees)	7.6 ± 4.2 (0.2-16.2)	9.1 ± 4.3 (1.5-16.1)	9.0 ± 4.6 (1.5-19.7)	9.3 ± 5.3 (1.4-22.3)

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Table IV: Range of Motion in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	43.7 ± 11.1 (23.5-63.0)	18.5 ± 9.8 (2.0-42.6)	16.2 ± 12.6 (0.0-42.0)	15.1 ± 12.3 (0.0-38.8)
OPLL (n = 10)	34.0 ± 9.5 (21.3-50.0)	14.7 ± 10.7 (2.9-32.1)	10.3 ± 8.9 (0.0-25.4)	10.2 ± 8.7 (0.0-24.8)
C2-C7 (degrees)
Non-OPLL (n = 11)	49.8 ± 11.9 (32.8-70.1)	27.9 ± 14.1 (5.6-52.3)	25.7 ± 16.0 (0.0-49.7)	24.3 ± 16.1 (0.0-47.8)
OPLL (n = 7)	41.5 ± 13.5 (23.5-57.5)	19.2 ± 14.8 (1.7-42.1)	18.8 ± 13.5 (0.0-38.8)	14.6 ± 13.6 (0.0-38.0)
Occiput-C1 (mm)
Non-OPLL (n = 14)	4.0 ± 2.8 (0.7-8.2)	6.2 ± 3.2 (0.2-9.7)	6.9 ± 3.3 (0.0-11.8)	6.2 ± 4.2 (0.8-14.5)
OPLL (n = 10)	7.1 ± 4.9 (0.4-14.9)	7.8 ± 3.5 (4.3-14.7)	7.2 ± 3.8 (2.7-14.3)	6.7 ± 4.2 (2.0-14.4)
C1-C2 (degrees)
Non-OPLL (n = 15)	7.9 ± 4.4 (0.2-16.2)	9.7 ± 3.8 (4.1-15.9)	9.9 ± 3.9 (3.9-19.7)	9.7 ± 5.8 (1.4-22.3)
OPLL (n = 10)	7.2 ± 4.1 (0.2-13.7)	8.1 ± 5.0 (1.5-16.1)	7.7 ± 5.4 (1.5-16.7)	8.8 ± 4.6 (2.7-15.0)

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Table IV: Range of Motion in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL) and without Ossification (Non-OPLL)*

	Preoperative	Postoperative†
1 yr.	3 yrs.	5 yrs.
C2-C6 (degrees)
Non-OPLL (n = 16)	43.7 ± 11.1 (23.5-63.0)	18.5 ± 9.8 (2.0-42.6)	16.2 ± 12.6 (0.0-42.0)	15.1 ± 12.3 (0.0-38.8)
OPLL (n = 10)	34.0 ± 9.5 (21.3-50.0)	14.7 ± 10.7 (2.9-32.1)	10.3 ± 8.9 (0.0-25.4)	10.2 ± 8.7 (0.0-24.8)
C2-C7 (degrees)
Non-OPLL (n = 11)	49.8 ± 11.9 (32.8-70.1)	27.9 ± 14.1 (5.6-52.3)	25.7 ± 16.0 (0.0-49.7)	24.3 ± 16.1 (0.0-47.8)
OPLL (n = 7)	41.5 ± 13.5 (23.5-57.5)	19.2 ± 14.8 (1.7-42.1)	18.8 ± 13.5 (0.0-38.8)	14.6 ± 13.6 (0.0-38.0)
Occiput-C1 (mm)
Non-OPLL (n = 14)	4.0 ± 2.8 (0.7-8.2)	6.2 ± 3.2 (0.2-9.7)	6.9 ± 3.3 (0.0-11.8)	6.2 ± 4.2 (0.8-14.5)
OPLL (n = 10)	7.1 ± 4.9 (0.4-14.9)	7.8 ± 3.5 (4.3-14.7)	7.2 ± 3.8 (2.7-14.3)	6.7 ± 4.2 (2.0-14.4)
C1-C2 (degrees)
Non-OPLL (n = 15)	7.9 ± 4.4 (0.2-16.2)	9.7 ± 3.8 (4.1-15.9)	9.9 ± 3.9 (3.9-19.7)	9.7 ± 5.8 (1.4-22.3)
OPLL (n = 10)	7.2 ± 4.1 (0.2-13.7)	8.1 ± 5.0 (1.5-16.1)	7.7 ± 5.4 (1.5-16.7)	8.8 ± 4.6 (2.7-15.0)