Biomedical subjects
Publications and source records attributed to J Willén.
The entire concept of spinal stenosis is based on the assumption that there is a minimal space necessary for the function of the neural content of the spinal canal, and this space, under certain circumstances, gets too small. This may seem self evident, but it was not until the middle of the previous century that there was sufficient focus on this concept to establish the diagnosis of lumbar spine stenosis.
STUDY DESIGN: An experimental study on patients undergoing posterior lumbar spine surgery. OBJECTIVES: To study the relation between external compression and muscle strain induced by spinal retractors and intramuscular pressure in the dorsolumbar compartment during posterior spinal surgery. SUMMARY OF BACKGROUND DATA: Pressures were studied as a function of the distance between the retractor blades during surgery. METHODS: Intramuscular pressure was measured bilaterally in the erector spinae muscle with intermittent microcapillary infusion technique in 12 patients undergoing posterior lumbar spine surgery during 271 (range 90-420) minutes. Three self-retaining retractors were tested; the McCulloch, the Viking, and the Richard retractors. RESULTS: Intramuscular pressure was 7.7 mm Hg before surgery. It varied between 35 mm Hg and 69 mm Hg during surgical exposure of the laminas and facet joints. Intramuscular pressure varied between 61 mm Hg and 158 mm Hg depending on which retractor was used and on the distance between the retractor blades. Intramuscular pressure never exceeded 30 mm Hg at rest after the operation. CONCLUSIONS: External compression and muscle strain from retractor blades during surgery increased intramuscular pressure in the paravertebral muscles to levels that, according to other studies, induce ischemia in the muscles.
PURPOSE: To evaluate the effect of compressive axial loading in imaging of the lumbar spine in patients with clinically suspected spinal stenosis. MATERIAL AND METHODS: A total of 84 patients were examined, 50 with CT (after intrathecal contrast administration) and 34 with MR. First the dural sac cross-sectional area (CSA) was determined with the patient in the supine psoas relaxed position (PRP). Then the CSA was determined during supine axial compression in slight extension (ACE), obtained with a specially designed loading device. A measurement error study was performed. RESULTS: A minimum difference in CSA of 15 mm2 between PRP and ACE was found to be significant. In 40/50 (80%) of CT-examined patients and in 26/34 (76%) of MR-examined patients a significant difference in CSA was found. In 25/84 (30%) of the patients there was a significant difference at more than one level. CONCLUSION: For an adequate evaluation of the CSA, CT or MR studies should be performed with axial loading in patients who have symptoms of lumbar spinal stenosis.
STUDY DESIGN: In patients with sciatica or neurogenic claudication, the structures in and adjacent to the lumbar spinal canal were observed by computed tomographic myelography or magnetic resonance imaging in psoas-relaxed position and during axial compression in slight extension of the lumbar spine. OBJECTIVES: To determine the mechanical effects on the lumbar spinal canal in a simulated upright position. SUMMARY OF BACKGROUND DATA: For years, functional myelographic investigation techniques were shown to be of value in the evaluation of suspected encroachment of the spinal canal. Since the advent of computed tomography and magnetic resonance imaging, there have been few clinical and experimental attempts that have imitated these techniques. The data indicate that the space within the canal is posture dependent. METHODS: Portable devices for axial loading of the lumbar spine in computed tomographic and magnetic resonance examinations were developed. Fifty patients (94 sites) were studied with computed tomographic myelography, and 34 patients (80 sites) with magnetic resonance in psoas-relaxed position followed by axial compression in slight extension. The dural sac cross-sectional area at L2 to S1, the deformation of the dural sac and the nerve roots, and the changes of the tissues surrounding the canal were observed. RESULTS: In 66 of the investigated 84 patients, there was a statistically significant reduction of the dural sac cross-sectional area in at least one site during axial compression in slight extension. Of the investigated patients, 29 passed the borderlines for relative (100 mm2) or absolute stenosis (75 mm2) in 40 sites. In 30 patients, there was deformation of the dural sac in 46 sites. In 11 of the patients investigated with magnetic resonance imaging, there was a narrowing of the lateral recess in 13 sites, during axial compression in slight extension. CONCLUSIONS: Axial loading of the lumbar spine in computed tomographic scanning and magnetic resonance imaging is recommended in patients with sciatica or neurogenic claudication when the dural sac cross-sectional area at any disc location is below 130 mm2 in conventional psoas-relaxed position and when there is a suspected narrowing of the dural sac or the nerve roots, especially in the ventrolateral part of the spinal canal in psoas-relaxed position. The diagnostic specificity of the spinal stenosis will increase considerably when the patient is subjected to an axial load.
The treatment of thoracolumbar fractures was traditionally conservative. With increasing demands for early mobilization, operative reduction and stabilization has become more popular, even in less severe injuries. The Harrington instrumentation is still useful and efficient. However, in fractures with posterior element ruptures, the internal fixator is superior in stabilizing the fracture. Early mobilization in a body cast is an equivalent treatment to surgery in less severe burst fractures if the neurology is intact. A treatment program for different fractures is presented.
Conservative management of 54 patients with thoracolumbar (T12 and/or L1) burst fractures was investigated. The fractures were subdivided according to the Denis classification and a modification was suggested. Most type A and B fractures showed good results regarding reduction and neurological improvement. However, severe type B (with anterior column compression and spinal canal narrowing exceeding 50%), D, and E fractures were to a large extent complicated by intractable low back pain, neurological involvement, and signs of instability. This study suggests predictors for complications in patients with burst fractures in the thoracolumbar junction. These are (a) compression rate of the anterior column exceeding 50%, (b) narrowing of the spinal canal exceeding 50%, (c) signs of rotational malalignment in fracture level, and (d) level of the injury (L1 fractures).
The variation in the dimensions of the lumbar spinal canal under both flexion-extension and axial compression-distraction was studied using computerized tomography (CT) scans in human cadaver lumbar spine specimens. In 3-mm-thick CT slices through the disk at L3-L4, the cross-sectional area of the spinal canal was reduced by around 40 mm2, corresponding to a 16% reduction of the initial area when the lumbar spines were moved both from flexion to extension and from distraction to compression. A corresponding reduction in the midsagittal diameter of the canal of 2 mm was found. During these motions, the ligamentum flavum did not appear to be a significant factor for the dynamic changes affecting the dimensions of the canal. This held true even after the disk had been excised in order to produce a total collapse of the disk space.
Fifty patients (14-55 years of age) with unstable thoracolumbar fractures were studied: 24 patients treated conservatively 1971-1977 and 26 patients treated surgically with Harrington instrumentation 1977-1981. The treatment groups were comparable in all respects. Radiologic evaluation showed that Harrington distraction rods restored the fractured vertebra almost to its original shape, and the gibbus and scoliosis were significantly reduced. However, at the follow-up examination at least 2 years after the injury, the gibbus angle had recurred almost to the value at admission in patients with the rods removed. The conservatively treated patients showed a continuous increase of the gibbus angle and of the anterior and central vertebral compression. At the follow-up evaluation, all fractures in both treatment groups were healed. There was no difference between the treatment groups regarding neurologic improvement. Thirteen of 14 patients with severe or moderate paraparesis considerably improved their neurological status. A rehabilitation index with special reference to paraparetic patients showed no difference between the treatment groups already three months after the injury. Thoracolumbar fatigue, thoracolumbar pain and stiffness, skin problems, and pain at direct pressure at the fracture site occurred equally in the conservative and Harrington groups. The overall complications were few. The aseptic intermittent catheterization method introduced in 1977 considerably diminished the frequency of upper urinary tract infections. The treatment with open reduction, fusion, and stabilization with Harrington rods considerably reduced the immobilization and hospitalization times. The average immobilization time was reduced from 67 to 18 days. The hospitalization time in neurologically intact patients was reduced from 80 to 30 days.
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Fourteen patients with unstable thoracolumbar fractures were examined with conventional roentgenologic technique and CT before and after operation with Harrington instrumentation. CT was superior in evaluating posterior elements, bone fragments in the spinal canal, and degree of narrowing of the spinal canal. Harrington rods restored the general spinal alignment. However, even after surgery, the midsagittal diameter, as well as the cross-sectional area of the spinal canal were still diminished by 26%. The reduction of the spinal canal improved significantly by early surgical intervention. Open reduction and stabilization with Harrington rods and fusion within three days after injury is recommended.
Seven vertebral preparations of L1, with surrounding discs, facet joints, and ligaments were exposed to an instant axial dynamic force in order to produce a burst or crush fracture. The resulting fractures were similar to fractures observed clinically and showed a comminuted vertebral body with fractured vertebral end-plates, dislocated disc nucleus, bone fragments severely encroaching upon the spinal canal, and facet joint laxity. The flexion-extension range was increased considerably. This implies that this fracture type should be regarded as unstable with a risk of progressive flexion deformity, neurologic deterioration and pain. The fracture could be reduced by an axial distraction force of 400 N simulating the effect of Harrington distraction rods. However, the distraction resulted in an "empty" vertebral body with small areas of spongious bone mixed with fragments of the disc nucleus and fragments of the vertebral end-plate.
Among 14 patients with unstable thoracolumbar fractures examined by both conventional radiography and CT, we found seven patients with a "new" common fracture pattern. This fracture pattern consisted of (1) superior disc injury, (2) crush fracture of the upper half of the vertebral body, (3) sagittal fracture (cleavage fracture) of the lower half of the vertebral body, (4) bone fragments in the spinal canal, and (5) laminar fracture. Five of the seven patients had sustained their injuries in vertical falls; all five had primary neurological deficit symptoms. We consider this fracture to be unstable.
Thirty-seven patients with unstable thoracolumbar fractures and paraplegia were studied: 11 patients were given exclusively conservative treatment, 14 patients were treated conservatively after laminectomy with or without fusion, and 12 patients were treated with Harrington instrumentation. None of the 12 cases with complete paraparesis at admission to the hospital improved their neurological status. In patients with moderate and severe but not complete paraparesis one month after injury, the neurological improvement continued for several years and in many the neurological restitution was complete. There was no difference between the three treatment groups regarding the neurological improvement. A new Rehabilitation Index was constructed with special reference to paraplegic patients. One month after the injury the Rehabilitation Score in the Harrington group was considerably higher than in the other groups. After three months the score was equalized in the conservatively treated group and the Harrington group whereas the score of the laminectomy-fusion group remained lower as long as two years after injury. Thirty-two patients were followed-up two years after the injury. Irrespective of the treatment, 30 of 32 patients had reached their maximal ADL scores at the follow-up. In 19 patients the bladder function was satisfactory. Eleven patients could walk independently. Twelve patients used wheel-chairs. Twenty-eight patients managed outdoor transportation without help. Twenty-four patients (75 per cent) had returned to work. Complaints about back deformity, skin problems and pain at direct pressure over the fracture site were significantly more frequent in the conservative and laminectomy-fusion groups. The treatment with open reduction, fusion and stabilization with Harrington rods considerably reduced the immobilization and hospitalization time. The complications were few. - The Harrington operation resulted in an early rehabilitation, which is of great psychological importance for the patient. - Our study confirms the disadvantages of laminectomy followed by conservative treatment reported by other authors.
Thirty-eight patients were followed up 13 to 17 years after sustaining a fracture of the tibia. The aim was to establish the frequency of post-thrombotic venous insufficiency. All patients were examined clinically and with a modified ultrasound technique. In addition some were studied using phlebography. Fifteen patients had symptoms of venous insufficiency in the fractured leg. Seven had only local symptoms, while in the other eight the venous insufficiency was verified objectively. The following factors predisposed to the development of venous insufficiency: Age above 45 years at the time of trauma, a high energy trauma resulting in comminuted fractures, and a long immobilization period.
Two comparable groups with unstable thoracolumbar fractures have been studied: one consisting of 23 patients treated conservatively and one consisting of 20 patients treated surgically with Harrington instrumentation. The vertebral injuries have been analysed radiologically at the time of injury as well as after completion of conservative and surgical treatment and at follow-up on average 6 years and 3 months after injury in the conservatively treated group and 2 years and 2 months after injury in the operated group. The vertebral fractures were often solitary at the L1 level with a characteristic radiologic appearance and mainly caused by flexion-rotation injuries. There were indirect signs of associated ligament injuries in most cases. Indirect signs of associated disc injury were found in 77 per cent of the cases, most of them related to the superior disc. The signs of disc injury were accentuated at the two follow-up examinations. In the operated group, the radiologic appearance of the vertebral body normalised after Harrington instrumentation. A preoperative gibbus angle of 19.4 degrees was reduced to 6.8 degrees on average postoperatively. In 13 of the operated cases the rods were removed. Among these patients the gibbus angle increased to 17.6 degrees at the final follow-up examination, compared with 11.9 degrees in the patients who had their rods retained. This difference in gibbus angle was significant. In the conservatively treated group, the initial gibbus angle of 19.5 degrees continuously increased to 27.6 degrees at the follow-up examination. All vertebral fractures had healed at the follow-up examination.