Radiological Evaluation of the Initial Fixation between Cortical Bone Trajectory and Conventional Pedicle Screw Technique for Lumbar Degenerative Spondylolisthesis

STUDY DESIGN: Retrospective study. PURPOSE: To compare initial fixation using the cortical bone trajectory (CBT) technique versus conventional pedicle screws (PS) in radiographs of postsurgical lumbar degenerative spondylolisthesis. OVERVIEW OF LITERATURE: Few reports have documented the holding strength of CBT technique for spondylolisthesis cases. METHODS: From October 2009 to June 2014, 21 cases of degenerative spondylolisthesis were surgically treated in our institution. Ten were treated with conventional PS technique and 11 of with CBT technique. Mean lumbar lordosis and percent slippage were evaluated preoperatively, immediately after surgery, and 6 months and 1 year postoperatively using radiographs. We also investigated percent loss of slip reduction. RESULTS: There were statistically significant differences between preoperative percent slippage and postoperative slippage in both PS and CBT procedures over 1 year, and both techniques showed good slip reduction. On the other hand, lumbar lordosis did not change significantly in either the PS or CBT groups over 1 year. CONCLUSIONS: CBT technique showed similarly good initial fixation compared with the PS procedure in the treatment of lumbar degenerative spondylolisthesis.

Significance of the Pars Interarticularis in the Cortical Bone Trajectory Screw Technique: An In Vivo Insertional Torque Study

STUDY DESIGN: Retrospective study. PURPOSE: Cortical bone trajectory (CBT), a more medial-to-lateral and shorter path than the traditional one for spinal fusion, is thought to be effective for severely degenerated vertebrae because screws are primarily stabilized at the posterior elements. We evaluated the efficacy of this approach through in vivo insertional torque measurement. OVERVIEW OF LITERATURE: There has been only one prior in vivo study on CBT insertional torque. METHODS: Between January 2013 and April 2014, a total of 22 patients underwent posterior lumbar fusion using the CBT technique. The maximum insertional torque, which covers the radial strength needed for insertion, was measured for 113 screws, 8 of which were inserted for L5 spondylolysis. The insertional torque for cases with (n=8) and without (n=31) spondylolysis of L5 were compared using one-way analysis of variance (ANOVA). To evaluate vertebral degeneration, we classified 53 vertebrae without spondylolysis by lumbar radiography using semiquantitative methods; the insertional torque for the 105 screws used was compared on the basis of this classification. Additionally, differences in insertional torque among cases grouped by age, sex, and lumbar level were evaluated for these 105 screws using ANOVA and the Tukey test. RESULTS: The mean insertional torque was significantly lower for patients with spondylolysis than for those without spondylolysis (4.25 vs. 8.24 in-lb). There were no statistical differences in insertional torque according to vertebral grading or level. The only significant difference in insertional torque between age and sex groups was in men <75 years and women ≥75 years (10 vs. 5.5 in-lb). CONCLUSIONS: Although CBT should be used with great caution in patient with lysis who are ≥75 years, it is well suited for dealing with severely degenerated vertebrae because the pars interarticularis plays a very important role in the implementation of this technique.

Clear Zone Formation around Screws in the Early Postoperative Stages after Posterior Lumbar Fusion Using the Cortical Bone Trajectory Technique

STUDY DESIGN: Retrospective study. PURPOSE: To evaluate the initial fixation using the cortical bone trajectory (CBT) technique for posterior lumbar fusion through assessment of the clear zones around the screws and the risk factors involved. OVERVIEW OF LITERATURE: Postoperative radiolucent zones (clear zones) are an indicator of poor conventional pedicle screw fixation. METHODS: Between January 2013 and April 2014, 19 patients (8 men and 11 women) underwent posterior lumbar interbody fusion or posterior lumbar fusion using the CBT technique. A total of 109 screws were used for evaluation with measurement of the maximum insertional torque of last two screw rotations. Clear zone-positivity on plain radiographs was investigated 6 months after surgery. The relation between intraoperative insertional torque and clear zone-positivity was investigated by one-way analysis of variance. In addition, the correlation between clear zone-positivity and gender, age (75 years old), or operative stabilization level (3 vertebral levels) was evaluated using the chi-square test. RESULTS: Clear zones were observed around six screws (5.50%) in five patients (26.3%). The mean insertional torque (4.00+/-2.09 inlbs) of clear zone-positive screws was lower than that of clear zone-negative screws (8.12+/-0.50 in-lbs), but the difference was not significant. There was a significant correlation between clear zone-positivity and operative level of stabilization. CONCLUSIONS: The low incidence of clear zone-positive screws indicates good initial fixation using the CBT technique. Multilevel fusions may be risk factors for clear zone generation.

Differences between Cervical Schwannomas of the Anterior and Posterior Nerve Roots in Relation to the Incidence of Postoperative Radicular Dysfunction

STUDY DESIGN: A retrospective study. PURPOSE: To assess the case files of patients who underwent surgery for cervical dumbbell schwannoma for determining the differences between schwannomas of the anterior and posterior nerve roots with respect to the incidence of postoperative radicular dysfunction. OVERVIEW OF LITERATURE: The spinal roots giving origin to schwannoma are frequently nonfunctional, but there is a risk of postoperative neurological deficit once these roots are resected during surgery. METHODS: Fifteen patients with cervical dumbbell schwannomas were treated surgically. Ten men and 5 women, who were 35-79 years old (mean age, 61.5 years), presented with neck pain (n=6), radiculopathy (n=10), and myelopathy (n=11). RESULTS: Fourteen patients underwent gross total resection and exhibited no recurrence. Follow-ups were performed for a period of 6-66 months (mean, 28 months). Preoperative symptoms resolved in 11 patients (73.3%) but they persisted partially in 4 patients (26.7%). Six patients had tumors of anterior nerve root origin, and 9 patients had tumors of posterior nerve root origin. Two patients who underwent total resection of anterior nerve root tumors (33.3%) displayed minor postoperative motor weakness. One patient who underwent total resection of a posterior nerve root tumor (11.1%) showed postoperative numbness. CONCLUSIONS: Appropriate tumor removal improved the neurological symptoms. In this study, the incidence of radicular dysfunction was higher in patients who underwent resection of anterior nerve root tumors than in patients who underwent resection of posterior nerve root tumors.

Intradural Extramedullary Spinal Ependymoma: A Case Report of Malignant Transformation Occurring

Intradural extramedullary spinal ependymomas are extremely rare. Herein, we describe a lesion-type spinal ependymoma that followed a malignant course, and discuss its clinical presentation, etiopathogenesis, and treatment. We present a patient who was diagnosed with an intradural extramedullary spinal tumor at T4-T6. The patient underwent gross total resection of the tumor without damage to the spinal cord. Histological examination, classified the lesion as a World Health Organization (WHO)-grade 2 ependymoma. One and a half years later, magnetic resonance imaging detected a recurring tumor at T4-T5. The tumor was removed and classified as a WHO-grade 3 anaplastic ependymoma. The patient was started on a course of regional spinal cord radiotherapy. The patient achieved tumoral control and clinical stabilization after the recurrence. We must consider the differential diagnosis of intradural extramedullary spinal tumors. The best treatment for this lesion is gross total resection and adjunctive radiotherapy is necessary in cases of malignant-change.

Entrapment of the Fifth Lumbar Spinal Nerve by Advanced Osteophytic Changes of the Lumbosacral Zygapophyseal Joint: A Case Report

A 54-year-old female patient had a 6-year history of backache and left sciatica. Five years earlier, she had undergone surgery in another hospital for left L4-5 disc herniation. Computed tomography revealed the ossified wall that enclosed the left L5 nerve root. There were also osteophytic changes in the left L5-S zygapophyseal joint. These osteophytes developed rostrally, along the left L5 nerve root, throug h the intervertebral foramina. We performed decompression surgery for the left L5 nerve root, and surgery resulted in symptomatic relief. We experienced a rare clinical presentation of osteophytic formation, with a specific configuration in relation to the nerve root. Surgeons should be aware of entrapment of the lumbar spinal nerve by advanced osteophytic changes occurring in the zygapophyseal joint after lumbar surgery.