Effect of anular repair on the healing strength of the intervertebral disc: a sheep model.

STUDY DESIGN: The intervertebral disc, in a sheep model, was used to assess the effect of directly repairing three different anular incisions on the subsequent healing strength of the intervertebral disc. OBJECTIVES: To assess whether directly repairing an anular defect, made at the time of lumbar discectomy, could influence the healing rate and strength of the anulus fibrosus. METHODS: Twenty-four sheep underwent a retroperitoneal approach to five lumbar disc levels. An anular incision, followed by partial discectomy was done at each exposed level. Anular incisions used in this study consisted of 1) a straight transverse slit, 2) a cruciate incision, and 3) a window or box excision. Healing strength was measured at three time intervals: 2 weeks, 4 weeks, and 6 weeks. Each anular incision type was performed on 30 lumbar discs, 10 discs in each time interval. Five discs in each time interval underwent direct repair, and five discs were left unrepaired to heal as controls. The sheep were killed at 2, 4, and 6 weeks after surgery. The lumbar spines were removed en bloc, and the intervertebral discs were subjected to pressure-volume testing to assess the anular strength of repaired versus unrepaired disc injuries at each time interval. RESULTS: Statistical analysis was performed to evaluate the effects of healing time, incision technique, and repair on the pressure-volume characteristics of the involved discs. Pressure-volume testing showed trends of stronger healing for repaired discs, but at no time interval was any significant difference found between repaired and nonrepaired anular strength. Of the nonrepaired discs, the box incision was only 40 to 50% as strong as the slit or cruciate incised discs during early healing. CONCLUSION: Direct repair of anular incisions in the lumbar spine does not significantly alter the healing strength of the intervertebral disc after lumbar discectomy.

Anterior C1-C2 screw fixation and bony fusion through an anterior retropharyngeal approach.

We present a case that demonstrates an occasion where an alternative method of C1-C2 fusion may be used when a posterior approach limited to the atlantoaxial level is not desirable. A 22-year-old man presented with a symptomatic nonunited Brooks posterior atlantoaxial fusion following a chronically displaced type II odontoid fracture with a two-part fracture of the posterior arch of C1. An anterior retropharyngeal approach was used to perform an anterior C1-C2 fusion with screw fixation. The surgical technique, as well as the merits and indications of this infrequently used procedure, are discussed.

Cervical Radiculopathy.

This article discusses the relevant anatomy, clinical presentation, diagnosis and surgical treatment for cervical radiculopathy. The etiology of cervical radiculopathy can play a role in the subsequent treatment of this problem. Both anterior and posterior surgical management is discussed.

Current management of cervical spine instability.

Instability of the cervical spine is a frequently occurring problem in a number of rheumatologic conditions. The importance of recognizing cervical instability lies in its close association with severe, sometimes irreversible, neurologic compromise that can lead to paralysis or even death. Operative stabilization of cervical instability prior to the onset of irreversible neurologic changes has been advocated. The problem, however, has been that no reliable method has accurately predicted which patients with cervical instability are at risk for spinal cord compression. It has been determined in recent studies that specific measurements of radiographic instability are strongly associated with worsening neurologic compromise. These measurements assess the space available for the spinal cord, and recommendations can be made for surgical stabilization in patients with cervical instability, prior to the onset of neurologic changes.

A modified posterolateral approach to the thoracic spine.

We describe a modified technique for posterolateral approach to the thoracic spine and report the use of this procedure in 21 patients. The technique is safe and effective for selected indications. The evolution of the posterolateral or costotransversectomy approach to the thoracic spine has in large part focused on enlarging the exposure to the vertebral bodies and epidural space by resecting an increasing number of ribs and removing a wider portion of those ribs resected. In this modified approach to the thoracic spine, the costovertebral articulation is preserved, and no rib resection is necessary to gain adequate exposure to the thoracic vertebral body and epidural space. We did a retrospective review of 21 patients undergoing 22 modified posterolateral approaches to the thoracic spine. Sixteen patients had biopsies of thoracic vertebral lesions through this approach; 3 underwent decompression of the thoracic spinal cord; 2 approaches were done for the removal of a herniated thoracic disc; and in one, the pedicle was removed. This modified posterolateral approach allowed adequate exposure for selected indications. One complication, a wound infection, developed after biopsy for suspected osteomyelitis. This modified posterolateral approach is well suited to provide access for biopsy of thoracic spinal lesions; for decompression of a paraspinal abscess; and for decompression of the thoracic spinal cord by anterolateral compressive lesions such as herniated thoracic disc or epidural tumor when resection of the vertebral body is not necessary; or the approach may be used for patients who are debilitated or at poor risk to undergo thoracotomy.

Anular incision technique on the strength and multidirectional flexibility of the healing intervertebral disc.

STUDY DESIGN: This study used a sheep model to biomechanically analyze the healing strength of the anulus fibrosus after two types of anular incisions. OBJECTIVE: This study evaluated whether the type of anular incision made at the time of lumbar discectomy plays a role in the subsequent healing strength of the anulus and the biomechanical flexibility of the corresponding motion segment. METHODS: Two types of anular incision, a full thickness removal of a box or window of anulus and a full thickness straight transverse slit through the anulus, were made in the intervertebral discs of 18 adult sheep. After healing times of 2, 4, and 6 weeks, the intervertebral discs were tested versus control levels for strength of anular healing and biomechanical flexibility of the corresponding motion segment. RESULTS: The box incised discs showed a significantly greater loss in strength during the early healing phase (2 to 4 weeks) and a longer response before recovering anular strength when compared with the slit-incised discs. The type of incision also affected the multidirectional flexibility of the motion segments in a differentiated manner. Larger amounts of motion were seen with the box incision when compared with the slit incision at all time periods and in all pure moments. CONCLUSION: The technique of anular incision plays a definite role in the timing and strength of subsequent anular healing. The box incision through the anulus led to significantly weaker healing than did the slit incision in the early healing phase (2-4 weeks). Also, larger amounts of motion were seen in the vertebral motion segments of those discs undergoing box incision when compared with slit or control levels.