STATIC AND DYNAMIC MODIFICATIONS OF THE C ERVICAL-SPINE AFTER LAMINECTOMY IN CERVICARTHROSIC MYELOPATHY

Purpose of the study Extensive cervical laminectomy has been widely us ed in the treatment of progressive myelopathies secondary to stenotic conditions. Complications of this procedure such as spinal instability , accelerated spondylotic changes, postoperative spinal deformity and constriction of the dura mater by extradural scar tissue formation hav e been recognized. However, the frequency of these complications is pr obably overestimated and their consequences on the clinical outcome re main unknown. The purpose of this report was to describe the incidence and consequences of cervical spinal deformity and instability after m ultilevel laminectomy in adult patients with myelopathy caused by cerv ical spondylosis and to determine the usefulness of preoperative dynam ic films in the prevention of postoperative destabilization. Materials and methods 30 patients older than 30 years who underwent a laminecto my of more than 3 levels without fusion for myelopathy secondary to ce rvical spondylosis were reviewed retrospectively with an average follo w-up of 5 years. Functional results were evaluated according to the Ja panese Orthopaedic Association scoring system. Lateral views in neutra l position, in flexion and in extension of the preoperative cervical r oentgenograms were analyzed in comparison with the last follow-up one in order to identify the changes in the curvature of the cervical colu mn, in the range of motion of the neck, in the intervertebral angular mobility and antero-posterior displacement of the vertebral bodies, an d finally to identify the incidence of spinal instability. Results 18 patients (31 per cent) developed postoperative changes in cervical spi ne curvature. 15 patients (25 per cent) had one or more destabilized l evels. Deformities of the cervical spine occuring after surgery do not appear to cause any symptom or neurologic abnormalities. Destabilizat ion required repeat surgery in 3 patients. All the levels found destab ilized on the postoperative films were hypermobile on the preoperative dynamic radiographs. A preoperative olisthesis without hypermobility was not a risk factor for postoperative destabilization. Conclusion Th e use of preoperative dynamic radiographs should improve the selection of patients undergoing laminectomy for the treatment of multilevel ce rvical cord compression. Dynamic X-rays may also reinforce the need fo r possible adjunctive procedures such as fusion and instrumentation, i n order to prevent a postoperative destabilization. A preoperative oli sthesis with a hypermobility in sagittal or horizontal planes must be fused and instrumented.