0 evaluation of the adequacy of decompression. However, this is a complication we have seen in patients referred to us after failure to improve following laminoplasty. The incidence of this occurrence is unknown but it is not nil. On the other hand, failure to achieve adequate decompression rarely occurs in patients undergoing laminectomy. In a series of patients we evaluated postoperatively with MRI after undergoing laminectomy and posterior instrumentation, every patient was

adequately decompressed and no patient developed loss of lordosis or a kyphotic deformity. Neurological outcome in patients undergoing laminoplasty or laminectomy and posterior instrumentation is comparable. The recovery rate using the JOA score in a large number of laminoplasty series ranged between 5060% The recovery rate in our series of patients treated with laminectomy and

Cervical stenosis : treatment strategy, surgical approach and technique PAUL R. COOPER,MD I PROFESSOROF NEUROSURGERY,NEW YORKUNIVERSITYMEDICALCENTER

! Indications for Operation Radiographic demonstration of cervical spondylosis is present in 25-50% of patients by the age of 50 and in 75-850/0 of patients by the age of 65. Nevertheless only a small minority of patients present with signs and symptoms of cervical spondylotic myelopathy. Thus the imaging findings of cervical spondylosis by themselves are not an indication for operation. In order to be considered as a candidate for operative decompression, patients must have motor and sensory symptoms or objective deficit as well as evidence of spinal cord compression on imaging studies. While patients who are neurologically intact with imaging findings of spondylosis are frequently advised that prophylactic operation is indicated to prevent catastrophic spinal cord injury after a fall or a motor vehicle accident there is no data on the risks versus benefits of this strategy. Once patients develop myelopathic signs or symptoms operation is indicated but the choice of operative approach depends on the number of spinal segments involved, whether compression is predominantly from anterior or posterior, the extent of compression above and below the disc space, and the sagittal alignment of the cervical spine.

spondylotic compression or two level adjacent spondylosis, or ossification of the posterior longitudinal ligament [OPLL) extending no more than two vertebral bodies. Vertebrectomy is appropriate for patients with OPLL or patients with osteophytes at adjacent levels. In patients with osteophytes from spondylosis at adjacent levels, either two level osteophytectomy or vertebrectomy may be performed although there is some evidence that lordosis is better maintained with two level excision of osteophytes. In patients with extensive OPLL, multilevel vertebrectomy will be effective in decompressing the spinal cord but the greater the number of vertebrae removed [without supplemental posterior instrumentation) the higher the chance of graft and plate failure. Anterior plate and screw design have advanced greatly in the past two decades from unlocked to locked rigid screw-plate systems, semi-rigid systems and most recently to systems which allow for translation of the plate in relation to the screws. This allows for settling of the graft and maintenance of shared load between the graft and plate minimizing stress on the screws or plate and is particularly useful in multilevel vertebrectomies.

I The Anterior Approach

)~ Neurological outcome

- Choice of

procedure

The anterior approach is ideal for single level

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Neurological outcome after anterior decompressive outcome in our patients

posterior instrumentation was 65o/0 (Neurosurgery 52 ' 1081-1088, 2003). In summary neurological outcome is similar when laminectomy and laminoplasty are compared. Loss of alignment occurs after laminoplasty but not in patients undergoing laminectomy and posterior instrumentation. Posterior instrumentation prevents movement against residual compressive lesions and fusion likely prevents growth of osteophytes at instrumented levels. I.I

in a series which has been published previously has been gratifying. Between 79 and 890/0 of muscle groups with abnormal function preoperatively improved, mean mJOA score improved from 12.4 to 14.9. Using the Cooper Scale which evaluated upper and lower extremities separately 47% of patients with abnormal upper extremity function improved and 75% of patients with abnormal lower extremity function improved.

| The Posterior Approach )) Indications

The posterior approach is technically easier than the anterior approach and is ideal for patients with a lordotic spine with compression at more than two disc spaces or two vertebral bodies [in the case of OPLL). It is contraindicated in patients with kyphosis as the spinal cord will not move posteriorly away from anterior compressive lesions. It is also contraindicated in patients with midline soft cervical discs compressing the spinal cord. ~ Choice of procedure

In considering the posterior approach, the surgeon has the choice of laminectomy alone, laminectomy with posterior instrumentation, or laminoplasty. All of the posterior approaches have the disadvantage of not removing the offending pathology but if the spinal cord moves posteriorly away from the compressive lesion this is of little consequence. A certain percentage of patients who have laminectomy will develop kyphotic deformity. This is more likely to occur if the facets are resected, and if preexisting instability is present. - Laminectomy and posterior Instrumentation

By combining laminectomy with interfacet

fusion and posterior instrumentation utilizing screw/plate or screw/rod constructs, the spine is stabilized and kyphotic deformity will not occur. It is also advantageous because osteophyte progression likely ceases once the spine is fused. If anterior operation should become necessary at a future time for residual compression or growth of OPLL the spine is stable and anterior graft or instrumentation failure is unlikely. For OPLL in particular, the posterior approach avoids the complications of long anterior decompression : graft extrusion, plate loosening, esophageal dysfunction, and dural tears and cerebrospinal fluid fistulae. Posterior fixation of the cervical spine was revolutionized by Roy-Camille who developed plates and screws for the fixation at the lateral masses. The original plates were rudimentary, could not be bent, were limited in length and had a fixed inter-hole distance making them difficult to use for multilevel fixation. Subsequent development of lateral mass plates by others produced plates that could be bent to the contour of the spine and were sufficient in length for stabilizing the entire cervical spine with

holes spaced from 11 to 15 mm apart. Subsequent development of polyaxial screw/rod devices allowed more versatility and more accurate placement of screws in the lateral masses.

patients had at least some improvement in sensory function.

~) Laminoplasty

Occasional patients require a combined anterior and posterior approach. Patients with spondylotic myelopathy and kyphotic deformity who require a multilevel vertebrectomy to achieve adequate decompression may also require posterior instrumentation to further stabilize the spine and prevent anterior graft and plate failure.

Laminoplasty has been advocated as a preferred means of posterior decompression. Advocates claim that it is superior in maintaining normal alignment, maintains normal motion, and prevents postoperative spinal cord compression by a "laminectomy membrane". To the contrary there is no data in the literature supporting any of these claims as will be discussed in a subsequent session of this meeting. ~) Outcome

We have reviewed our results with laminectomy and posterior instrumentation in a series of 38 patients with OPLL or cervical spondylotic myelopathy. The mean mJOA score improved from 12.9 to 15.6, 96% of muscle groups with less than 5/5 strength improved, gait improved in 940/0 of patients and all

Combined Anterior and Posterior Approach

Conclusions In summary anterior operation is indicated for compression by soft disc, osteophyte or OPLL at one or two vertebral levels. For greater than two levels of compression by osteophyte or OPLL in a patient with a lordotic spine posterior decompression and stabilization will achieve excellent results. Anterior operation is indicated for decompression and correction of kyphotic deformities and should be combined with posterior instrumentation after multilevel vertebrectomies to minimize the incidence of plate and graft complications, toJ

Does l a m i n e c t o m y still hold a place in the treatment of cervical stenosis ? When is it necessary to add a fixation after and or laminoplasty ? KAZUMASA UEYAMA I MEDICAL CORPORATIONSEIYUKAI. HIROSAKI MEMORIAL HOSPITAL.JAPAN

Introduction - ~

ervical laminop!asty was developed in Japan in the early 1970s to resolve postoperative problems after conventional laminectomy for instability and deformity which caused a

recurrence of myelopathy ; there have since been many modifications. The aim of laminoplasty is to expand the spinal canal, to preserve the posterior structure of the cervical spine and assure stability, and to prevent the formation of postlaminectomy

membrane. From ]986 to 2004 in our department, 206 patients with cervical myelopathy due to cervical spondylosis or ossification of the longitudinal ligament (OPLL) underwent laminoplasty. Only 2 cases with OPLL and straight sagittal alignment were necessary to add anterior fixation because of neurological deterioration. Although sagittal curvature of the cervical spine has been suggested to be one of the factors affecting the outcome of laminoplasty for the treatment of cervical myelopathy, no general consensus has been reached on this issue. In our experience with cervical laminoplasty, o

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