OPLL颈椎后纵韧带骨化

OPLL经典综述讲读,王雪鹏杭州市骨科研究所杭州市第一人民医院骨科,Ossification of the posterior longitudinal ligament (OPLL) results from pathologic replacement of the PLL with lamellar bone, potentially causing spinal cord compression and neurologic deteriorationOPLL was first described in Japanese patients and has classically been considered a cause of myelopathy in patients of East Asian origin,spondylosismyelopathyradiculopathystenosisdisc herniation,Among patients in Japan with cervical spine disorders, the incidence has been estimated at 1.9% to 4.3% and, in other Asian countries, up to 3.0%OPLL has been recognized as an etiology of myelopathy regardless of ethnicity, with an estimated incidence rate of 0.1% to 1.7% among North Americans and Europeans,Pathoanatomy,The PLL runs along the dorsal surface of the C1 anterior arch and cervical vertebral bodies and consists of longitudinal fibers confluent with the tectorial membrane cranially and ending at the sacrum caudallyfunctionally,the PLL resists spine hyperflexion,Pathophysiology,The pathologic process leading to OPLL begins with chondroblast- and fibroblast-like spindle cell proliferation, along with vascular infiltration leading to PLL degeneration and hypertrophy. Endochondral ossification follows, resulting in its replacement with mature lamellar boneGenetics,local tissue characteristics, and associated medical comorbidities have all been implicated in this final common pathway,Medical comorbidities are also associated with the development of OPLLUp to 50% of Caucasian patients with OPLL also have diffuse idiopathic skeletal hyperostosisHypoparathyroidism,hypophosphatemic rickets,hyperinsulinemia, and obesity have been identified as risk factors,Natural History,Patients with OPLL commonly present in their fifth and sixth decades,with men affected twice as often as women.Most patients have some neurologic symptoms at diagnosis, with 28% to 39% fulfilling diagnostic criteria for myelopathy,In patients with myelopathy, 64% had deteriorated,however, and 89% of patients with Nurick grade 3 or 4 myelopathy who refused surgery had progressed to a wheelchair- or bed-bound state,Risk factors for the development of myelopathy include 60% spinal canal stenosis,6 mm of space available for the cord, increased cervical range of motion, and OPLL that is laterally deviated within the spinal canalAge, gender, and the number of levels affected by OPLL do not affect the prognosis,Clinical Presentation,Changes in gait or balance, loss of fine motor control, and upper extremity weakness,numbness, or paresthesias are suggestive of myelopathyEarly muscular fatigue or worsening symptoms at the extremes of cervical motion are also concerning,Patients with OPLL are at an increased risk of acute spinal cord injury with trauma,and rapid neurologic deterioration in association association with even a minor trauma or whiplash injury should raise concern for the development of central cord syndrome,Physical Examination,Radiologic Evaluation,The lateral radiograph is also used to determine the relationship of the OPLL to the kyphosis line (K-line),which is drawn from the center of the canal at C2 to the center of the canal at C7A large OPLL mass or loss of cervical lordosis causes the OPLL to protrude posterior to the K-line (referred to as K-line negative). This is a negative prognostic factor for posterior surgery alone,CT with sagittal and coronal reformatting has emerged as the benchmark for radiographic evaluation of OPLL and is necessary to reliably characterize it,Greater than 60% canal occupancy at any level and a laterally deviated mass are associated with high rates of myelopathyThis “double layer sign” on axial or sagittal CT images is associated with dural tear rates 50% with anterior decompression versus 13% when the sign is absent,Nonsurgical Management,Prophylactic surgery is neither necessary nor recommended Management includes temporary immobilization with a neck brace, steroidal or nonsteroidal anti-inflammatory medications, activity modification,and physical therapy,patients should be advised to avoid activities that may result in sudden or excessive cervical spine motion because OPLL is associated with a high rate of acute spinal cord injury, even in patients who do not meet surgical criteria,Surgical Treatment,Surgical decompression is the treatment of choice for patients with Nurick grade 3 or 4 myelopathy or severe radiculopathy caused by OPLL via either an anterior or posterior approach,Anterior Decompression and Fusion,Proponents argue that it allows for a superior decompression and is more effective at maintaining or restoring cervical lordosis than is posterior surgery. Associated anterior pathology, such as disk herniations,can also be addressed,Disadvantages include technical difficulty, inability to decompress cranial to C2, and high rates of pseudarthrosis and dysphagia when three or more levels require treatment Dural tears are also much more common with an anterior approach, given that anterior dural ossification occurs in 13% to 15%,Exposure is provided by the standard Smith-Robinson approach, and diskectomy, hemicorpectomy,or subtotal corpectomy sufficient to allow exposure of the underlying OPLL mass is performedCorpectomies of up to five levels have been performed with success,but removal of three or more contiguous levels is associated with increased complication and reoperation rates,Complications occur as part of the approach (eg, dysphagia, dysphonia), the decompression (eg, C5 palsy, dural tears), or the fusion (eg,graft subsidence, pseudarthrosis),Nerve root palsies occur in 4% to 17% of patients through either direct trauma or traction.Patients present with weakness, numbness,pain, or paresthesias, most commonly in the C5 distribution,Dural tears occur in 4% to 20% of patients, often because of dural ossification or attenuation.Cerebrospinal fluid leakage may result in pseudomeningocele or fistula formation, leading to neural damage, airway compression,meningitis, or wound complications,Tears recognized intraoperatively are treated by direct repair or by application of autogenous fascial or synthetic collagen grafts. Closure of pinhole defects or augmentation of repairs is done with thrombogenic sealants, such as fibrin glue or gelatin foam. Postoperatively, diverting lumbar drains and bed rest can be used,In an effort to reduce dural tear rates, Yamaura et al introduced the“anterior floating method” for cervical decompression, consisting of subtotal vertebral body resection and thinning, but not removal, of the OPLL. The posterior vertebral body is not reconstructed, allowing the OPLL to “float” anteriorly and away from the spinal canal. At 5-year follow-up, the authors achieved a mean recovery rate of 68.5% and improvement in Japanese Orthopaedic Association scores from 8.3 to 14.2. No leaks of cerebrospinal fluid occurred, but 14% of patients were left with an inadequate decompression. In these patients,or with OPLL progression, the authors recommended subsequent posterior decompression.,When addressing more than two or three levels, fibular strut grafts are preferred for their structural support. For one or two levels, structural grafts of tricortical iliac crest, fibula, and vertebral bodies have all been described.More recently,interbody cages with nonstructural bone graft or bone graft substitutes have been used.Overall rates of pseudarthrosis vary from 3% to 15%, with the highest rates occurring in patients undergoing fusion of three or more levels.,Posterior Decompression,When more than two or three cervical levels are affected by OPLL, posterior surgery (ie, laminoplasty, or laminectomy and fusion) is preferred because of the technical ease and lower rate of complications. Disadvantages include the risk of postoperative disease progression, inability to correct cervical kyphosis, and poor results in K-line negative patients.,Laminoplasty accomplishes this by hinging open the laminae with either an “open door” or “French door” technique, resulting in a 30% to 40% increase in the size of the spinal canalLaminectomy and fusion entails removal of the laminae followed by instrumented posterolateral fusion,resulting in a 70% to 80% increase in canal volume,A full analysis of the advantages and disadvantages between laminoplasty compared with laminectomy and fusion has been discussed elsewhereOur preference is to use laminectomy and fusion for OPLL because the retained cervical motion with laminoplasty may allow disease progression,and the risk for progression to kyphosis at the affected levels is eliminated with fusion,For severe disease, recovery rates after posterior decompression appear to be lower than those following anterior decompression, but with a lower complication rate,Iwasaki et al retrospectively compared the results of anterior decompression and fusion with those of laminoplasty; they reported better outcomes after anterior surgery in patients with an OPLL mass occupying 60% of the canal; however,it results in a reoperation rate of 26% versus 2% in the laminoplasty group. With60% canal occupancy,recovery rates were equivalent.,A prospective comparison of anterior decompression and fusion versus laminoplasty found similar results. Patients with 50% canal occupancy had superior recovery rates with anterior surgery but equivalentrates with 50% involvementPatients with 5of cervical lordosis also had significantly worse outcomes from laminoplasty, and 50% lost lordosis versus none in the fusion group.Half of the laminoplasty patients experienced OPLL progression versusonly one after anterior surgeryHowever, surgical complications heavily favored laminoplasty, with a 23% complication rate and a 14% reoperation rate in the anterior group and none in the laminoplasty patients,Only one study to date has examined the results of laminectomy and fusion for OPLL.,Chen et al reported a mean recovery rate of 62% at 5 years among 83 patients who underwent instrumented laminectomy and fusion from C2 or C3 to C7. Patients with a good outcome had significantly more postoperative lordosis (16.1 versus10.4). No other factors, including occupying ratio, were significant between groups. The reoperation rate was 4%, all the result of epidural hematoma formation. Whether posterior fusion had an effect on disease progression was not evaluated, although the authors noted no longterm decline in neur