Nobuyuki Tsuzuki

extradural Tethering Effect as One Mechanism of Radiculopathy Complicating Posterior Decompression of the Cervical Spinal Cord

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.

Tension-band laminoplasty of the cervical spine.

Summary. A new laminoplasty of the cervical spine has been developed using preserved ligaments as a tension-band. The laminae were enlarged in an open-door fashion and spacers inserted to maintain the spinolaminoligamentous complex intact. The stretched ligaments exerted a tension-band effect on the spacers and stabilised them so that neck movements could be started as soon as bleeding stopped. The spacers were iliac grafts, or were made of a bioactive ceramic which proved more satisfactory. The results of 102 cases with ceramic spacers showed an average preservation of preoperative movement between C2 and C7 to be 79% in cervical spondylotic myelopathy and 67% in ossification of the posterior longitudinal ligament at 3 years after operation. No spacer became displaced. CT showed new bone formation in the lamina-ceramic gap in 59% of the spacers used in cervical spondylotic myelopathy by sixth months and in 63% in cases of ossification of the posterior longitudinal ligament by the third month. Neurological recovery was comparable to that after other types of laminoplasty, but the new method allows better function of the neck and more new bone formation around the spacers.Résumé. Nous avons développé une nouvelle laminoplastie des vertèbres cervicales utilisant les ligaments comme facteurs de compression. Les lames ont étéélargies en feuillets de livre et des entretoises ont été insérées pour conserver le complexe spino-lamino-ligamentaire. La tension sur ces entretoises est exercée par les ligaments lors des mouvements du cou dont la mobilisation a débuté dès l’arrêt des saignements opératoires. Comme entretoises, des greffons iliaques et une céramique bio-active ont été mis à l’essai, c’est celle-ci qui a donné les meilleurs résultats. Dans les 102 cas utilisant la céramique, suivis en moyenne 27 mois (12 à 46 mois), on note une conservation de la mobilité pré-opératoire entre C2 et C7; 79% en cas de myélopathie cervicale d’origine osseuse; 67% en cas de myélopathie dûe à l’ossification du ligament longitudinal postérieur à la 3ème année post-opératoire. Il n’y a pas eu de déplacement des entretoises en céramique. L’étude scannographique montre l’existence d’une néoformation osseuse dans l’espace lame-céramique au 6ème mois post-opératoire dans 59% des cas de myélopathie d’origine osseuse et dans 63% des cas au 3ème mois post-opératoire en cas de myélopathie par ossification du ligament postérieur. Le degré des récupérations neurologiques est comparable aux autres types de laminoplastie mais avec cette méthode, on note comme avantage une meilleure fonction post-opératoire et un degré plus important d’ossification au niveau des entretoises.

Staged spinal cord decompression through posterior approach for thoracic myelopathy caused by ossification of posterior longitudinal ligament

Study Design. Prospective clinical study of the effect of staged elimination of anatomic factors inhibiting posterior shift of the thoracic spinal cord on the degree of posterior shift of the thoracic spinal cord and its significance in augmenting the safety of ossification of posterior longitudinal ligament (OPLL) manipulation in thoracic OPLL myelopathy. Objectives. To develop a comprehensive method that enables safe and sufficient decompression of the spinal cord for thoracic OPLL myelopathy. Summary of Background Data. Decompression of the spinal cord by direct manipulations of thoracic OPLLs, via either anterior or posterior approach, caused some iatrogenic catastrophic spinal cord injuries, and methods to prevent such injuries during surgery have not yet been developed. Methods. Procedures of elimination of anatomic factors inhibiting posterior shift of the thoracic spinal cord were performed in stages at intervals of between 1 month and 11 years depending on patients’ neurologic status. The first stage operation consisted of extensive cervicothoracic laminoplastic decompression with or without posterior longitudinal durotomy, and if the decompression were insufficient, measures for OPLL–spinal cord separation with or without OPLL manipulation were added. Results. All 17 patients with thoracic OPLL myelopathy showed improvements of neurology comparable with those with successful anterior approaches after decompression. The mean follow-up period was 42 months (range 6–101 months). Neurologic improvements persisted for the entire follow-up period in all patients except one patient who developed arachnoid cyst compressing the dorsum of the once-decompressed spinal cord 30 months after surgery. Conclusions. Staged posterior decompression to eliminate anatomic factors inhibiting posterior shift of the thoracic spinal cord is the safest and the most reliable method of spinal cord decompression to treat thoracic OPLL myelopathy, so far. However, long-term results are required before the methods can be established.

Surgical anatomy of the nerves and muscles in the posterior cervical spine: A guide for avoiding inadvertent nerve injuries during the posterior approach

Study Design. An anatomic study investigated the cervical dorsal rami and major cervical paravertebral muscles. Objective. To provide a detailed description of the cervical dorsal rami and important paravertebral muscles as a way of avoiding inadvertent injuries during the posterior approach. Summary of Background Data. No detailed anatomic studies of the nerves and the muscles in the posterior neck useful for the posterior approach have been reported previously. Methods. Running courses of the cervical dorsal rami of spinal nerves and the morphology of cervical major paravertebral muscles were studied using 14 cadavers. In four posterior approaches of cervical laminoplasty, subcutaneous facial exits of cutaneous nerves and the running course of the right C3 medial branches around facet joint were exposed for observation of living anatomy. Results. Every medial branch from the dorsal rami of the C3–C8 spinal nerves passed through an anatomic tunnel dorsolateral to the facet joint. The base of the tunnel was a bony gutter between neighboring facet joint capsules, and the roof was the tendon of the semispinalis capitis. In this tunnel, the medial branch had a little laxity in moving, and was assumed to be the most susceptible to iatrogenic injury during the operation. The semispinalis cervicis was composed with long muscle bundles. Each of these had only one or two innervating nerves from the dorsal rami of cervical spinal nerves. Cutaneous branches from the dorsal rami were found adjacent to every spinous process below the C2 spinous process in cadaveric studies. However, only two or three larger cutaneous nerves were discernible below the C5 or C6 spinous process in surgical approaches. Conclusions. With the posterior approach to the cervical spine, a precise knowledge of the cervical dorsal rami anatomy and the innervating patterns of the paravertebral muscles is necessary for avoidance of inadvertent injuries to the nerves.

Topographic anatomy of the posterior ramus of thoracic spinal nerve and surrounding structures.

Study Design. Cadaver dissection. Objective. To examine the potential points of spinal nerve entrapment and the articular branches in the thoracic spine. Summary of Background Data. Despite many cadaver studies focused on the cervical and lumbar spinal nerves, detailed anatomy of the thoracic nerve branches is missing from the viewpoint of painful neuropathy on the thoracic region. Methods. A total of 120 pairs of thoracic spinal nerves out of 10 donated cadavers were dissected. Detailed anatomy of the posterior ramus and medial/lateral branches and their fine branches in the entire thoracic region was investigated by both macroscopic and stereomicroscopic dissections. Results. The posterior ramus of the thoracic nerve passed through the narrow space between the bony structures and adjacent fibrous tissue. It is sent to the first branch, which is called “the descending branch,” before bifurcating into medial and lateral branches. The medial branch runs posterolaterally, then turns medially along the edge of multifidus, and passes between that and semispinalis, whereas the lateral branch runs underneath the intertransverse ligament. Both medial and lateral cutaneous branches penetrated the thoracolumbar fascia, and the medial cutaneous branch penetrated the tendinous portion of back muscles. Conclusion. Several points might be listed as potential sites of entrapment along the course of the posterior ramus of the thoracic nerve and its branches, leading to the cause of thoracic back pain. In addition, the articular branch entering the facet (zygapophyseal) joint originated from the descending branch, which was the first branch of the posterior ramus.

The value of a new method for assessing the separate functions of the long tracts and involved segments in patients with cervical myelopathy.

Abstract In order to assess accurately lesions of the spinal cord in patients with cervical myelopathy we have developed a new method of examination, which is based on the Japanese Orthopaedic Association (JOA) scoring system. The method attempts to assess separately the functions of the long tract and any involved cord segments in respect to the period after treatment. It was used in 117 consecutive patients who were divided into 2 groups based on whether or not there was a T2-high- intensity lesion within the spinal cord, as revealed by a preoperative magnetic resonance imaging scan (MRI). The results of this method correlated well with the MRI findings. It was assumed that the degree of function of the upper limbs in patients with a T2-high-intensity lesion revealed more about a segment than about the long tract.Résumé Pour évaluer les lésions médullaires dans la myélopathie cervicale, nous avons développé une méthode d’examen basée sur la classification de l’Association Orthopédique Japonaise (JOA). La méthode essaie d’évaluer les fonctions de l’ensemble médullaire et du segment concerné après une période de traitement. 117 malades consécutifs ont été divisés en deux groupes selon qu’il y avait ou non un signal d’hyper-intensité en T2 sur l’IRM pré-opératoire. Les résultats selon cette méthode ont été en corrélation avec les résultats IRM.

Extensive Cervicothoracic Laminoplastic Decompression of the Spinal Cord: A New Method of Posterior Decompression for Thoracic Myelopathy Caused by Ossification of the Posterior Longitudinal Ligament

Ossification of the posterior longitudinal ligament (OPLL) at the thoracic level tends to be multiple or extensive, depending on the degree and number of impingements on the spinal cord. In the case of thoracic myelopathy caused by OPLL, excision of OPLL is the most effective method of relieving pressure on the spinal cord, but the anterior approach for OPLL excision is technically demanding. Moreover, in the case of highly impinging OPLL, postoperative neurological deterioration resulting in complete paraplegia, although infrequent, has been reported [1-3]. So far, thoracic OPLL has remained a challenge to the spinal surgeon in Japan. Postoperative neurological catastrophes are thought to arise from inadvertent trauma of the spinal cord, resulting from the excision maneuvers in an OPLL-narrowed spinal canal. Moreover, the spinal cord has probably lost its vital resistance to trauma following severe and long-standing compression by OPLL.

Tension-Band Laminoplasty: A Laminoplasty with Minimal Surgical Intervention to the Spinoligamentous Complex for Better Postoperative Neck Function

The development of surgical techniques for cervical laminoplasty in Japan has shown that the key issue in obtaining better postoperative function of the neck is preserving the integrity of the spinoligamentous (SL) complex in lamina-enlarging procedures [1]. The characteristic structural changes after laminoplasty, namely, loss of lordosis with a mild anterior tilt of the cervical spine accompanied by neck stiffness [2], result from damage to the SL complex. These structural changes produce fatigue in the neck with axial pain, a reduction in the range of motion (ROM) of the neck, and a loss of smoothness in neck movements. All of these dysfunctions cause considerable inconvenience in the activities of daily living [3,4]. The loss of a posterior supporting force by cutting the spinous processes and/or spinous ligaments causes a forward inclination of the neck and the outflow of osteoblastic substances from inside the bone through the exposed bone marrow of the spinous processes and laminae. This might be a major cause of both the stiffness of the healed soft tissue and the posterior segmental fusion between laminae or spinous processes [5]. All these facts indicate that surgical intervention in the SL complex should be minimal for the best possible postoperative neck function. In 1989 [6], we developed a tension-band laminoplasty (TBL) which allowed sufficient spinal cord decompression while maintaining the maximal integrity of the SL complex. In TBL, the tension-band effect of the preserved ligaments allowed early postoperative neck mobilization, facilitated the union of spacers, and prevented postoperative soft tissue contracture. The operative procedures and results are described below.

Paralysis of the Arm Occurring After Decompression of the Cervical Spinal Cord

Paralysis of the arm has been known to occur occasionally after both posterior and anterior decompression of the cervical spinal cord without apparent mechanical trauma to the spinal cord or roots during the operation. It usually occurs as minor neurological symptoms of segmental deterioration in generally improved neurologies. Such paralysis can include both motor and sensory disturbances. The nature of the motor involvement is a lesion of the secondary motor neuron, i.e., involving the motor cell and/or anterior root, but not the long tracts of the spinal cord. This type of paralysis occurs predominantly in the C5 region and has been called C5 paralysis representatively. The primary lesions of this paralysis, i.e., whether it is of root or spinal cord origin, and the nature of the factors inducing the paralysis are not clear [1-3]. Trauma-induced paralysis, e.g., by drill penetration or laminar-edge impingement, is not discussed here.