Split Spinous Processes Research Articles

Comparison of the effect of 3 different approaches to the lumbar spinal canal on postoperative paraspinal muscle damage

Background To assess the effect of 3 different surgical approaches on paraspinal muscle atrophy in patients undergoing lumbar back surgery, we compared their pre- and postoperative CT scans and their serum Hb, CRP, and CPK levels. Methods The study population consisted of 71 patients who had undergone lumbar back surgery with microscopic posterior decompression without fusion. We examined the effect on paraspinal muscle atrophy of 3 different approaches to the spinal canal. Group 1 (n = 19) underwent unilateral paraspinal dissection from the spinous process with cutting of the spinous process. In group 2 (n = 24), we used modified bilateral decompression via hemilaminectomy, and group 3 (n = 28) was treated by modified bilateral decompression via spinous process splitting. We measured the levels of CPK, Hb, and CRP preoperatively and on the first postoperative day, and compared the preoperative volume of the paraspinal muscle with the volume measured 1 year after the operation. Results Age, sex, operative time, and CRP and Hb levels were not statistically different among the 3 groups. The postoperative elevation of CPK was significantly lower in groups 2 and 3 than in group 1. Group 3 manifested a significantly lower degree of atrophic changes of the paraspinal muscle than groups 1 and 2. Conclusions We found that among the 3 approaches evaluated, modified bilateral decompression via spinous process splitting is less invasive, facilitates preservation of the paraspinal muscle, and is a useful approach to posterior spinal elements resulting in decreased muscle damage.

Delayed dural laceration by hydroxyapatite spacer causing tetraparesis following double-door laminoplasty

The authors describe 4 cases of delayed dural laceration by hydroxyapatite (HA) spacer causing tetra-paresis following double-door laminoplasty. There are few reports of iatrogenic spinal cord lesions developing after double-door laminoplasty, although some complications such as postoperative C-5 paralysis or axial symptoms have been reported. The purpose of this report is to draw attention to the possibility of delayed dural laceration and its triggering mechanism. One hundred thirty patients treated for cervical myelopathy were followed up for an average of 2 years and 9 months after laminoplasty. Four patients experienced aggravation of cervical myelopathy. Anterior dislodgement of HA spacers was shown on plain lateral radiographs. Follow-up T2-weighted magnetic resonance imaging demonstrated that the dislodged HA spacers were surrounded by cerebrospinal fluid at the time of aggravation. The dislodged HA spacers were removed and the dural membrane defects were repaired by patching with the fascia of the gluteus maximus muscle. The preoperative symptoms improved after the second operation in all patients. It is hypothesized that the loosening of the HA spacer in split spinous processes could occur with the movement of the cervical spine and/or the breakage of the suture before bone bonding. Anterior dislodgement of the HA spacer toward the spinal canal would cause dural laceration by direct friction between the dural membrane and the dislodged HA spacer, resulting in clinical aggravation. Despite the well-documented advantages of using HA spacers for double-door laminoplasty, possible laceration due to a dislodged HA spacer should be considered as a late complication.

Clinical results of cervical laminectomy by spinous-process splitting approach

Clinical results of cervical laminectomy by spinous-process splitting approach

Split–spinous process laminotomy and discectomy for degenerative lumbar spinal stenosis: a preliminary report

The authors evaluated a new minimally invasive spinal surgery technique to correct degenerative lumbar spinal stenosis involving a split-spinous process laminotomy and discectomy (also known as the "Marmot operation"). This prospective study randomized 70 patients with lumbar stenosis to undergo either a Marmot operation (40 patients), or a conventional laminectomy (30 patients), with or without discectomy. Spinal anteroposterior diameter, cross-sectional area, lateral recess distance, spinal stability, postoperative back pain, functional outcomes, and muscular trauma were evaluated. The follow up ranged from 10 to 18 months, with a mean of 15.1 months for the Marmot operation group and 14.8 months for the conventional laminectomy group. Compared with patients in the conventional laminectomy group, patients who received a Marmot operation had a shorter mean postoperative duration until ambulation without assistance, a reduced mean duration of hospital stay, a lower mean creatine phosphokinase-muscular-type isoenzyme level, a lower visual analog scale score for back pain at 1-year follow up, and a better recovery rate. These patients also had a longer mean duration of operative time and a greater mean blood loss compared with the conventional group. Satisfactory neurological decompression and symptom relief were achieved in 93% of these patients. Most of the patients (66%) in this group needed discectomy for decompression. The postoperative mean lateral recess width, spinal anteroposterior diameter, and cross-sectional area were all significantly increased. There was no evidence of spinal instability in any patient. One patient with insufficient lateral recess decompression and recurrent disc herniation needed additional conventional laminectomy and discectomy, and one patient with mild superficial wound infection was successfully treated with antibiotics and frequent dressing changes. A Marmot operation may provide effective spinal decompression. Although this method requires more operative time than a conventional method, it may involve only minimal muscular trauma, spinal stability maintenance, and early mobilization; shorten the duration of hospital stay; reduce postoperative back pain; and provide satisfactory neurological and functional outcomes.

Lumbar spinous process—splitting laminectomy for lumbar canal stenosis

In conventional laminectomy for lumbar canal stenosis (LCS), intraoperative damage of posterior supporting structures can lead to irreversible atrophy of paraspinal muscles. In 2001, the authors developed a new procedure for lumbar laminectomy, the lumbar spinous process-splitting laminectomy (LSPSL). In this new procedure, the spinous process is split longitudinally in the middle and then divided at its base from the posterior arch, leaving the bilateral paraspinal muscles attached to the lateral aspects. Ample working space for laminectomy is obtained by retracting the split spinous process laterally together with its attached paraspinal muscles. After successfully decompressing nerve tissues, each half of the split spinous process is reapproximated using a strong suture. Thus, the supra- and interspinous ligaments are preserved, as is the spinous process, and damage to the paraspinal muscles is minimal. Eighteen patients with LCS underwent surgery in which this new technique was used. Twenty patients in whom conventional laminectomy was undertaken were chosen as controls. At 2 years, the clinical outcomes (as determined using the Japanese Orthopaedic Association [JOA] scores and recovery rate) and the rate of measured magnetic resonance imaging-documented paravertebral muscle atrophy were evaluated and compared between the two groups. The mean JOA score recovery rates were 67.6 and 59.2%, respectively, for patients treated with LSPSL and conventional laminectomy; the mean rates of paravertebral muscle atrophy were 5.3 and 23.9%, respectively (p = 0.0005). Preservation of posterior supporting structures and satisfactory recovery rate after 2 years indicated that this technique can be a useful alternative to conventional decompression surgery for lumbar canal stenosis.

Cervical posterior laminoplasty operation using coralline hydroxyapatite

To study the results of using coralline hydroxyapatite (CHA) in cervical posterior laminoplasty operation. Two hundred and fifty-six patients underwent cervical spinous process-splitting laminoplasty using CHA. All patients had been followed up over 3 months. One hundred and forty-two patients were followed up at least 2 years. All patients had spinal stenosis at least at 3 levels or OPLL. The average follow up time was 34.6 months. The CHA grafts were stable between the split spinous processes. The union rate of CHA was 83.5%. After operation, the spinal cord moved dorsally, and the anteroposterior compression ratio had been improved from 0.19 to 0.42. No apparent kyphosis occurred. The JOA score improvement rate was 58.3%. There were 24 patients (17%) with axial symptom. Cervical posterior laminoplasty operation using coralline hydroxyapatite may achieve good results.

Finite Element Analysis of the Space Created by Split Spinous Processes in Double-Door Laminoplasty to Optimize Shape of an Artificial Spacer

In double-door laminoplasty, several types of artificial spinous process spacers have been used instead of grafted bone from the iliac crest. However, inadequate contact between the spacer and the spinous process has recently been reported. From the observation during operation, we suspect that the main cause of the inadequate contact is the difference in shape between the spacer and the widened space created by the split spinous processes. The purpose of this study was to investigate the shape of the widened space by means of a finite element analysis in order to confirm our observation objectively and to provide a shape design of a spacer adapting to the space. Half-sectioned finite element models of the second cervical (C2) vertebra and the C6 vertebra were made from both the computed tomography (CT) of a clinical case and a plastic model of a cervical spine. The finite element model was designed to have almost the same size and shape as those of the genuine vertebra in the clinical case. Since cancellous bone and soft tissues were thought not to meaningfully influence the rigidity of the model, the model was made of only cortical bone with a thickness of 1.5 mm. The x-axis was defined as the lateral direction of the vertebral body, the y-axis as the anteroposterior direction of the vertebral body and the z-axis as the craniocaudal direction along the posterior margin of the vertebral body. The boundary conditions were fixed at the inner surface of the half-sectioned vertebral body. A force of 100 N was applied to the inner surface of the half-sectioned spinous process (to the cranial side and the caudal side, 50 N each) in the direction of the x-axis. The lateral deviation of each split spinous process was defined as the degree of deviation in the x-axis direction. The degree of lateral deviation of each split spinous process was analyzed in two types of models with and without making a lateral gutter 4 mm wide along the z-axis direction. The lateral deviation at the cranial side was larger than that at the caudal side in both the C2 and C6 vertebrae. The difference between the lateral deviation at the cranial side and the caudal side of each vertebra was larger in the type of model with the lateral gutter than in the type of model without it. It was confirmed that the shape of the widened space is trapezoidal in not only the axial but also frontal sections. In conclusion, the optimal shape of a spacer adapting to the widened space in double-door laminoplasty is trapezoidal in not only the axial but also frontal sections.

FINITE ELEMENT ANALYSIS OF THE SPACE CREATED BY SPLIT SPINOUS PROCESSES IN DOUBLE-DOOR LAMINOPLASTY TO OPTIMIZE SHAPE OF AN ARTIFICIAL SPACER

In double-door laminoplasty, several types of artificial spinous process spacers have been used instead of grafted bone from the iliac crest. However, inadequate contact between the spacer and the spinous process has recently been reported. From the observation during operation, we suspect that the main cause of the inadequate contact is the difference in shape between the spacer and the widened space created by the split spinous processes. The purpose of this study was to investigate the shape of the widened space by means of a finite element analysis in order to confirm our observation objectively and to provide a shape design of a spacer adapting to the space. Half-sectioned finite element models of the second cervical (C2) vertebra and the C6 vertebra were made from both the computed tomography (CT) of a clinical case and a plastic model of a cervical spine. The finite element model was designed to have almost the same size and shape as those of the genuine vertebra in the clinical case. Since cancellous bone and soft tissues were thought not to meaningfully influence the rigidity of the model, the model was made of only cortical bone with a thickness of 1.5 mm. The x-axis was defined as the lateral direction of the vertebral body, the y-axis as the anteroposterior direction of the vertebral body and the z-axis as the craniocaudal direction along the posterior margin of the vertebral body. The boundary conditions were fixed at the inner surface of the half-sectioned vertebral body. A force of 100 N was applied to the inner surface of the half-sectioned spinous process (to the cranial side and the caudal side, 50 N each) in the direction of the x-axis. The lateral deviation of each split spinous process was defined as the degree of deviation in the x-axis direction. The degree of lateral deviation of each split spinous process was analyzed in two types of models with and without making a lateral gutter 4 mm wide along the z-axis direction. The lateral deviation at the cranial side was larger than that at the caudal side in both the C2 and C6 vertebrae. The difference between the lateral deviation at the cranial side and the caudal side of each vertebra was larger in the type of model with the lateral gutter than in the type of model without it. It was confirmed that the shape of the widened space is trapezoidal in not only the axial but also frontal sections. In conclusion, the optimal shape of a spacer adapting to the widened space in double-door laminoplasty is trapezoidal in not only the axial but also frontal sections.

Contact of hydroxyapatite spacers with split spinous processes in double-door laminoplasty for cervical myelopathy

We developed a new type of spacer made of hydroxyapatite (the STSS spacer) for double-door laminoplasty, and evaluated the contact of 93 STSS spacers with the split spinous processes in 20 patients with double-door laminoplasty. Contact was assessed by measuring the extent of touch of the spacer to the spinous processes, classified into four categories based on computed tomography (CT) images: excellent, complete touch on both sides of the spacer to the spinous process; good, complete touch on one side and more than half touch on the other side; fair, more than half touch on both sides; poor, half or less touch on at least one side. Excellent contact was achieved in 65 spacers (69.9%); good, in 13 (14.0%); fair, in 11 (11.8%); and poor, in 4 (4.3%). The percentages of excellent or good categories were 75.0% at the C3 level, 73.7% at the C4 level, 78.9% at the C5 level, 90.0% at the C6 level, and 100% at the C7 level. The contact rate of the STSS spacer with the spinous process was better than that achieved with other spacers, probably because the characteristic shape of the STSS spacer was compatible with the widened space between the bilateral spinous processes; i.e., it is trapezoidal on both the axial and the frontal sections. However, the appropriate size of the spacer must be selected in accordance with the size of the spinous process to obtain higher percentages of excellent or good contact.

Expansive Midline T-Saw Laminoplasty (Modified Spinous Process-Splitting) for the Management of Cervical Myelopathy

The authors developed a method of spinous process-splitting laminoplasty using a threadwire saw in a prospective study of 25 patients with cervical myelopathy. This report describes the surgical technique and the results of the expansive midline laminoplasty performed with an threadwire saw. To compare the efficacy of midline, threadwire-saw laminoplasty with that of the original spinous process-splitting laminoplasty. The spinous process-splitting laminoplasty was described by Kurokawa in 1982. Although the procedure has a number of theoretical and practical advantages, it has not been widely used because of technical difficulties. Twenty-five patients who underwent expansive, midline, threadwire-saw laminoplasty from C3 to C7 for cervical myelopathy were studied. The threadwire saw was used to split the spinous processes. The mean follow-up period was 34 months. Neurologic results were evaluated with pre- and postoperative scores, and recovery rates were evaluated by methods described in previous reports using the Japanese Orthopaedic Association scoring system. Radiographic data analyzed included plain radiographs and computed tomography scans. The duration of surgery and the amount of blood lost during this procedure using the threadwire saw were compared with the duration and blood loss that occurred during the original Kurokawa's procedure using a burr. In all cases, good enlargement of the cervical canal was achieved. The mean increase in cervical cross-sectional area was 36.1%, according to computed tomography scans. No dural tears occurred, and no patients experienced any decrease in neurologic function. The neurologic recovery rate was 72%, which was almost same as the neurologic recovery rate in the original procedure. Using the threadwire saw, the mean duration of surgery was 63 minutes shorter and the mean blood loss was 70 cc less than in procedures using burrs. The application of the threadwire saw to split the spinous processes made Kurokawa's procedure simpler, faster, and safer.

THE PATHOLOGY OF NEURAL-ARCH DEFECTS

In discussing the relative significance of neural-arch defects and split spinous processes (bifid spines), Willis stated: When the defect destroys the integrity of that portion of the bony arch between the vertebral body and the inferior articular processes as in the case of a bilaterally separate neural arch the condition is much more serious. Here we have the anchorage of the spine depending merely upon a fibrocartilaginous union with ligamentous and muscular support. Again, Rupture of the synchondrosis [defect] is more serious than the ligamentous injury which accompanies it. The separated bone ends are covered with cartilaginous material and, therefore, show no tendency to reunite. In this particular specimen, the defect in the isthmus on the right was united not by fibrocartilage, but by unusually strong fibrous ligaments, and was ensheathed in a fibrous capsule. The isthmus on the left was completely absent, and there was no evidence of fibrocartilaginous replacement. The pseudo-articulations between the pedicles, and the abnormal prolongations of the cephalad portions of the laminae, were effected by ligaments and not by cartilage. Findings in this specimen were: (a) the complete absence of an isthmus on one side, and, on the other side, a defective isthmus strongly fixed by ligaments and three times the length of the normal isthmus above; (b) the abnormal conformations of the laminae and their pseudo-articulations with the pedicles; (c) the structural variations noted in the ligamentum flavum on each side; and (d) the associated presence of a partial developmental lumbarization of the first sacral segment and a sacralization of the first coccygeal segment.

SPINA BIFIDA OCCULTA CERVICALIS

Hypertrichosis over a dimpled area in any region of the vertebral column is suggestive of spina bifida occulta. It is considered almost pathognomonic for those types of spina bifida in which a protruding cystic tumor is absent. The hairy area usually covers a defect in the vertebra in the form of an absent or split spinous process, a cleft in the arch of the vertebra, or, as Beck 1 asserts, even a mere depression in the spinous process. Some even go so far as to include with spina bifida occulta conditions in which the anomaly is not in the bony structures, but presumably in the spinal cord itself. On purely clinical grounds, Fuchs 2 has described such conditions as myelodysplasia. He considers spina bifida occulta as the most severe form or stage of what he terms myelodysplasia. Few cases of the latter are mentioned in the literature. Spiller 3 recently