Transforaminal Lumbar Interbody Fusion with Double Banana Cages: Clinical Evaluations and Finite Element Model Analysis.

STUDY DESIGN: Clinical and basic study. OBJECTIVES: This study aimed to investigate whether transforaminal lumbar interbody fusion (TLIF) using 2 banana-shaped cages leads to good clinical outcomes. METHODS: First, we conducted a clinical study to compare outcomes among patients who underwent TLIF using different types or numbers of cages. Propensity matched patients in each group were reviewed. Thirty-four patients who underwent surgery with 2 bullet-shaped cages (group A), 34 with a banana-shaped cage (group B), and 34 with 2 banana-shaped cages (group C) were compared. Twelve months after the surgery, bony fusion and cage subsidence were evaluated. RESULTS: The mean amount of cage subsidence was 14.9% in group A, 19.9% in group B, and 11.8% in group C. Subsidence in group B was significantly greater than that in group C (P < .01). Radiological bony fusion was not achieved in 2 cases in group B. Second, we performed a finite element model (FEM) analysis to determine the biomechanical stress of the vertebral endplate by comparing the single-banana cage construct with a double banana-shaped cage construct. FEM analysis showed that the maximum stress of the endplate in the single-cage model was 1.72-times greater than the maximum stress in the double-cage model. Furthermore, the maximal stress in the single-cage model was significantly higher than in the double-cage model during lumbar extension and side bending. CONCLUSION: This study showed that TLIF with double banana-shaped cages led to good clinical outcomes with less cage subsidence, probably because of decreased mechanical stress on the vertebral endplate.

Alterations in axial curvature of the cervical spine with a combination of rotation and extension in the conventional anterior cervical approach.

PURPOSE: Alterations of three-dimensional cervical curvature in conventional anterior cervical approach position are not well understood. The purpose of this study was to evaluate alignment changes of the cervical spine in the position. In addition, simulated corpectomy was evaluated with regard to sufficiency of decompression and perforation of the vertebral artery canal. METHODS: Fifty patients with cervical spinal disorders participated. Cervical CT scanning was performed in the neutral and supine position (N-position) and in extension and right rotation simulating the conventional anterior approach position (ER-position). Rotation at each vertebral level was measured. With simulation of anterior corpectomy in a vertical direction with a width of 17 mm, decompression width at the posterior wall of the vertebrae and the distance from each foramen of the vertebral artery (VA) were measured. RESULTS: In the ER-position, the cervical spine was rotated rightward by 37.2° ± 6.2° between the occipital bone and C7. While the cervical spine was mainly rotated at C1/2, the subaxial vertebrae were also rotated by several degrees. Due to the subaxial rotation, the simulated corpectomy resulted in smaller decompression width on the left side and came closer to the VA canal on the right side. CONCLUSIONS: In the ER-position, the degrees of right rotation of subaxial vertebrae were small but significant. Therefore, preoperative understanding of this alteration of cervical alignment is essential for performing safe and sufficient anterior corpectomy of the cervical spine.

Lower incidence of adjacent segment degeneration after anterior cervical fusion found with those fusing C5-6 and C6-7 than those leaving C5-6 or C6-7 as an adjacent level.

STUDY DESIGN: Retrospective analysis of adjacent disc degeneration (ADD) after anterior cervical decompression and fusion (ADF). OBJECTIVES: To elucidate the influence of the number of levels fused in ADF on the incidence of ADD. SUMMARY OF BACKGROUND DATA: ADD is known as a complication associated with ADF. However, how the number of levels fused affects the incidence of ADD is not well understood. METHODS: One hundred and two patients with cervical degenerative disease, who underwent ADF and were followed for more than 24 months, were retrospectively analyzed. They were classified into 2 groups, a long group (L group) consisting of 50 cases with ADF of 4 or more disc levels, and a short group (S group) consisting of 52 cases with ADF of 3 or fewer disc levels. Furthermore, the patients were also divided into 2 groups according to inclusion or exclusion of C5-6 and C6-7 (C group: including both, NC group: not including both). The incidence of ADD, and that of symptomatic ADD (sADD), was compared between the 2 classifications. RESULTS: In the L group, there were 13 cases of ADD (26.0%), including 1 case of sADD (2.0%), whereas in the S group, there were 22 cases of ADD (42.3%), including 11 cases of sADD (21.2%). The incidence of sADD was significantly lesser in the L group (P=0.024). Three cases with sADD in the S group required revision surgery, whereas no additional surgery related to ADD was performed on patients in the L group. In addition, in the C group, ADD occurred in 20 of 71 cases (28.2%) and sADD occurred in 4 of 71 cases (5.6%), whereas in the NC group, ADD occurred in 15 of 31 cases (48.4%) and sADD occurred in 8 of 31 cases (25.8%). The incidence of ADD and sADD were significantly lesser in the C group (P=0.048). CONCLUSIONS: ADD occurs less frequently among patients in whom C5-6 and C6-7 are fused than among those in whom C5-6 or C6-7 is left at an adjacent level, irrespective of the length of the fusion.

Surgical outcome of 2-stage (posterior and anterior) surgical treatment using spinal instrumentation for tuberculous spondylitis.

STUDY DESIGN: A prospective study on the clinical outcomes in patients with tuberculous spondylitis treated by a 2-stage operation (posterior and anterior) using posterior spinal instrumentation. OBJECTIVE: To evaluate the clinical outcomes of the 2-stage surgical treatment (first stage: placement of posterior instrumentation and second stage: anterior debridement and bone grafting) for tuberculous spondylitis. SUMMARY OF BACKGROUND DATA: There have been few reports describing the effects of 2-stage surgical treatment for tuberculous spondylitis. METHODS: Ten patients (5 men and 5 women) with tuberculous spondylitis were treated by 2-stage operations. Age at the initial operation was 64.6+/-14.8 years (average+/-SD) (range: 47 to 83 y). The clinical outcomes were evaluated before and after the surgery in terms of hematologic examination, pain level, and neurologic status. Bone fusion and changes in sagittal alignment were examined radiographically. RESULTS: All patients showed suppression of infection, bony fusion, relief of pain, and recovery of neurologic function. No significant changes were observed in kyphosis angle at the final follow-up. There were no incidences of severe complications or recurrence. CONCLUSIONS: Our results showed that posterior and anterior 2-stage surgical treatment for tuberculous spondylitis is a viable surgical option for cases in which conservative treatment has failed. However, the changes in sagittal alignment showed that this strategy provides limited kyphosis correction.

Postsurgical recurrence of osteophytes causing dysphagia in patients with diffuse idiopathic skeletal hyperostosis.

Although cervical anterior osteophytes accompanying diffuse idiopathic skeletal hyperostosis (DISH) are generally asymptomatic, large osteophytes sometimes cause swallowing disorders. Surgical resection of the osteophyte has been reported to be an effective treatment; however, little study has been given to the recurrences of osteophytes. A prospective study was performed for seven patients who underwent surgical resection of cervical anterior osteophytes for the treatment of recalcitrant dysphagia caused by osteophytes that accompanied DISH. The seven patients were six men and one woman ranging in age from 55 to 78 years (mean age = 65 years). After a mean postoperative follow-up period of 9 years (range: 6-13 years), surgical outcomes were evaluated by symptom severity and plain radiographs of the cervical spine. On all operated intervertebral segments, the effect of postoperative intervertebral mobility (range of movement > 1 degree) on the incidence of recurrent osteophytic formation (width > 2 mm) was analyzed by Fisher's exact test. Complete relief of the dysphagia was obtained within one month postoperatively in five patients, while it was delayed for 3 months in two patients. All of the patients developed recurrent cervical osteophytic formation, with an average increase rate of approximately 1 mm/year following surgical resection. Of the 20 operated intervertebral segments, the incidence of recurrent osteophytes was significantly higher (P = 0.0013) in the 16 segments with mobility than in the four segments without mobility. Five of the seven patients remained asymptomatic, although radiological recurrence of osteophytes was seen at the final follow-up. The two remaining patients complained of moderate dysphagia 10 and 11 years after surgery, respectively; one of these two required re-operation due to progressive dysphagia 11 years postoperatively. In patients with cervical DISH and dysphagia, surgical resection of osteophytes resulted in a high likelihood of the recurrence of osteophytes. Therefore, attending surgeons should continue to follow these patients postoperatively for more than 10 years in order to assess the regrowth of osteophytes that may contribute to recurrent symptoms.

Effects of abdominal belts on the cross-sectional shape of the trunk during intense contraction of the trunk muscles observed by computer tomography.

BACKGROUND: Several mechanisms of how abdominal belts affect the trunk have been postulated, but very little is known about how the belts affect the cross-sectional shape of the trunk during trunk muscle exertions. METHODS: To evaluate the effects of abdominal belts on the cross-sectional shape of the trunk during contraction of the trunk muscles, CT images at the third lumbar vertebra level of 20 healthy males (age: 23-45 years) under 8 different conditions (combinations of performing or not performing the Valsalva maneuver after full inhalation or at neutral respiratory state, while wearing or not wearing a 100-mm-wide abdominal belt) were evaluated. The cross-sectional shapes of the trunk seen on CT images taken at the level of the 3rd lumbar vertebra were compared using three-way ANOVA. FINDINGS: Wearing the belt decreased the cross-sectional area of the trunk, and wearing it while performing the Valsalva maneuver and during inhalation compressed the postero-lateral part of the trunk and made the trunk nearly round by increasing the ratio of the anterior-posterior width to the right-left width. INTERPRETATION: A wide belt cinched around the abdomen exerts external hoop tension on the trunk and stiffens the trunk. When the belt is worn during the Valsalva maneuver after deep inhalation, the posterolateral portion of the trunk is compressed and the trunk becomes circular.

Segmental wire fixation for lumbar spondylolysis associated with spina bifida occulta.

INTRODUCTION: The effectiveness of segmental wire fixation technique in repairing lumbar spondylolysis has already been reported. However, whether the technique can be indicated for spondylolysis associated with spina bifida, which is occasionally found with spondylolysis, is not well known. In this study, the authors report the mid-term clinical outcome of the procedure performed in patients with symptomatic lumbar spondylolysis associated with spina bifida occulta. MATERIALS AND METHODS: Among 20 patients with symptomatic lumbar spondylolysis who underwent segmental wire fixation between 1996 and 2001, four patients associated with spina bifida occulta were evaluated with an average of 32 months follow-up. Bony union at spondylolysis sites and spina bifida was evaluated using plain X-rays and computed tomography (CT) scans. Clinical symptoms were assessed using Japanese Orthopedic Association scores for back pain (JOA scores) and Henderson's evaluation of functional capacity. RESULTS: The radiographic examinations of the latest follow-ups revealed the following results. Pars defect; in three cases with bilateral defect, one case healed bilaterally and two healed only unilaterally. One case with unilateral defect healed. Spina bifida; two cases showed bony union and two showed no union. Of the four patients operated, two were rated excellent with the remaining two good according to Henderson's evaluation. The recovery rate of JOA score was averaged at 69.7 +/- 23.5%. No serious complications were noted. CONCLUSIONS: In four cases associated with lumbar spondylolysis and spina bifida, segmental wire fixation provided satisfactory clinical outcomes.

Surgical treatment for cervical myelopathy in patients aged > 80 years.

The surgical outcomes of 13 patients who were diagnosed with cervical spondylotic myelopathy were reviewed retrospectively. Mean patient age at surgery was 83 years. The severity of cervical spondylotic myelopathy was evaluated using the Japanese Orthopaedic Association score. Daily activities were evaluated using the Barthel index. The preoperative JOA score and Barthel index were 7.8 and 63.5, respectively. The mean JOA score and Barthel index maximum recovery rate were 35% and 24%, respectively. The results of this study imply that surgery for patients with cervical spondylotic myelopathy aged > 80 years is warranted.