Posterior movement and enlargement of the spinal cord after cervical laminoplasty

Abstract

We performed CT myelography in 38 patients with cervical myelopathy before and after laminoplasty to enlarge the canal. The sagittal and transverse diameters, the cross-sectional area, and the central point of the spinal cord were measured.After cervical laminoplasty, the mean sagittal diameter of the spinal cord at C5 increased by 0.8 mm, but the mean transverse diameter decreased by 0.9 mm. The mean cross-sectional area of the cord increased by 7.4% and that of the dural sac and its contents by 33.8% at C5. The centre of the spinal cord moved a mean 2.8 mm posteriorly at this level.Enlargement of the spinal canal is sufficient to decompress the spinal cord, but posterior movement may be the limiting factor in determining the decompressive effect of laminoplasty. [Br] 1998;80-B:33-7. Received 28 April 1997; Accepted after revision 8 July 1997 In patients with cervical myelopathy, anterior interbody fusion or laminoplasty is performed to expand the canal. In some cases, both anterior and posterior operations are done at the same time. We usually undertake laminoplasty for patients who have developmental spinal stenosis. There are many variations of the technique 1-7 and good clinical results have been reported for all of them. Our method is the 'open-door' type which uses the spinous processes as bone blocks, thereby requiring no additional theatre time for taking grafts from the iliac crest and avoiding the complications of iliac-crest bone donor sites. Moreover, central laminar osteotomies to enlarge the spinal canal are very safe since the spinous processes have been previously resected. J Bone Joint SurgAfter laminoplasty, the spinal cord is decompressed and also moves posteriorly (Fig. 1) Patients and MethodsWe performed laminoplasty in 38 patients, 26 men and 12 women. Their mean age was 56 years (29 to 85) at the time of the operation. Nineteen patients had cervical myelopathy and 17 had ossification of the posterior longitudinal ligament. The remaining two had hypertrophy of the posterior longitudinal ligament and calcification of the ligamentum flavum.The laminoplasty was performed from C3 to C7 in 36 patients, from C3 to T2 in one, and from C2 to T2 in one. Operative technique (Fig. 2). The patient is placed prone and a straight midline skin incision is used. The paravertebral muscles are resected from the spinous processes and the posterior surfaces of the laminae are exposed. The insertion of the semispinalis muscle to C2 is preserved.The spinous processes are resected so that their bases are longer than 5 mm, and their remnants are split with a highspeed drill. At the transitional portion of the laminae and facet joints, the laminae are thinned enough to allow them to be pushed laterally, the 'open-door' technique. The widths of the lateral gutters are determined by CT myelography (CTM) before the operation.The laminae are opened and any adhesions to the dura mater are dissected off. Bone blocks approximately 10 to 15 mm long from the spinous processes are then inserted at the site of the lamin...

The relationship between laminoplasty opening angle and increased sagittal canal diameter and the prediction of spinal canal expansion following double-door cervical laminoplasty

“…In addition, except for the case which has main compressive factor at C6/7, it does not have to expand the sagittal canal diameter at C4 and C7 to same degree because C4 is the midpoint of the arc of cervical lordosis, whereas C7 is the endpoint of that arc. In the literature, the average opening size varied from 10 to 20 mm for DDCL [11,[23][24][25][26], which is consistent with our study.…”

Factors affecting the surgical results of expansive laminoplasty for cervical spondylotic myelopathy

“…Patients with cervical kyphosis were treated with either an anterior procedure alone or by a combined anterior and posterior approach in order to restore cervical lordosis. Published papers suggest that a significant neurological improvement is associated with posterior cord migration and that this, in turn, shows a significant correlation with the extent of pre-operative cervical lordosis [1,2,11,19]. In our series, patients with kyphosis were excluded because we wanted to exclude the effect of the type of surgery on the surgical results.…”

“…There are many reports on the factors affecting the prognosis of surgery for patients with cervical myelopathy [1,2,4,3,5,6,7,11,12,13,14,15,16,17,19,21,22]. Some factors have been said to influence the results, but not all have been proved to be of prognostic value.…”

“…Some factors have been said to influence the results, but not all have been proved to be of prognostic value. The presence of a significant cervical kyphosis seems to affect prognosis adversely if the patient is treated by laminoplasty alone, as there may be no significant neurological improvement when the posterior cord is involved [1,2,19]. Accurate prediction of the likely surgical results is difficult in older patients but in general it seems to be worse than in the younger age group [4,11,15,21].…”

Recent Surgical Methods of Double-door Laminoplasty of the Cervical Spine (Kurokawa's Method)

“…Various materials are used to maintain the enlarged spinal canal such as thread 3) , autogeneous bone (spinous process 4,5) , iliac bone 2,6) ), hydroxyapatite spacer [7][8][9][10][11][12][13][14][15][16][17] , and titanium plate and screw 18,19) . Double-door type was first developed by Kurokawa in the late 1970s and reported in 1982 2) .…”