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Extradural tethering effect as one mechanism of radiculopathy complicating posterior decompression of the cervical
1Department of Orthopaedic Surgery, Saitama Medical Center, Saitama Medical School, Kawagoe, Japan.
Study Design:
This study used anatomical and clinical data to analyze the postoperative tension-status of cervical roots after posterior decompression of the cervical spinal cord. The efficacy of longitudinal durotomy with regard to prevention of postoperative palsy was investigated in a controlled study.
Objectives:
To elucidate the mechanism of postoperative radiculopathy and to prevent its occurrence.
Summary Of Background Data:
Previous anatomical studies by the authors revealed that the posteromedial shift of the dura-root junction following posterior bulging of the cervical dural sac exerted a traction force on the portion of the roots outside the dural sac and reduced the tension on the rootlets inside the dural sac. These traction-related phenomena disappear after longitudinal durotomy.
Methods:
Lengths of various parts of an anterior root were measured in 20 Japanese adult cadavers. The shortest pre- and postoperative distances between the anterolateral mid-edge of the spinal cord and dura-root junction were compared, using computed tomography-myelograms of postoperative C5 radiculopathies. The effects of longitudinal durotomy were also investigated in a controlled study involving 118 patients with laminoplasty.
Results:
The length ratio between the longest and shortest anterior rootlet in each cervical root showed fairly constant values. Clinically, the length of the shortest rootlet could be calculated using a myelogram. Radiographical findings in cases of postoperative radiculopathies suggested increased tension on roots outside the dural sac but not on rootlets inside the dural sac. Application of longitudinal durotomy in a type of lateral opening laminoplasty resulted in the disappearance of postoperative radiculopathy.
Conclusions:
An extradural tethering effect was suggested as one mechanism leading to postoperative radiculopathy. Durotomy may be useful in the treatment of postoperative palsy.